阅读说明：本技术 齿轮箱 (Gear box ) 是由 詹姆斯·布伦特·克拉森 里查德·博斯 于 2020-03-27 设计创作，主要内容包括：本发明提供了一种行星齿轮箱,在内座圈和同轴外座圈之间有两排行星轮。输入齿轮也可以与内行星轮或外行星轮啮合。为了避免由于施加的扭矩产生的扭曲而造成所述齿轮的分离啮合,可以使用凸轮效应,其中施加的扭矩产生径向预载。与所述输入齿轮啮合的所述齿轮可以在也与所述内座圈或所述外座圈中对应的一个啮合的所述齿轮的部分处啮合。行星轮可以与具有不同螺旋角的轴向部分齿轮接合。所述内座圈或所述外座圈可以由以不同螺旋角齿轮接合的两个部件形成,以与所述行星轮的所述不同轴向部分啮合。通过使用这些不同的部件,组装变得容易,因为所述部件可以轴向地滑动到所述行星轮上。(The invention provides a planetary gearbox with two rows of planet wheels between an inner race and a coaxial outer race. The input gear may also be in mesh with the inner or outer planet gears. To avoid disengaging the gears due to distortion from the applied torque that creates the radial preload, a camming effect may be used. The gear that meshes with the input gear may mesh at a portion of the gear that also meshes with a corresponding one of the inner race or the outer race. The planet wheels may be engaged with axial part gears having different helix angles. The inner or outer race may be formed of two parts geared at different helix angles to mesh with the different axial portions of the planet. By using these different parts, assembly is facilitated, since the parts can be slid axially onto the planet wheels.)

1. A gearbox assembly comprising:

a sun gear defining an inner race on an outer surface of the sun gear, wherein the sun gear defines an axis between a first end and an opposite second end of the sun gear;

a ring gear defining an outer race on an inner surface of the sun gear, wherein the ring gear is coaxial with the sun gear;

an inner set of planet gears in contact with the inner race gear of the sun gear;

an outer set of planet gears in contact with the outer race gear of the ring gear;

wherein each planet in the inner set of planets is in contact with at least two planet gears in the outer set of planets and each planet in the outer set of planets is in contact with at least two planet gears in the inner set of planets; and

an intermediate gear defining an intermediate race in gear contact with one of: (a) the inner set of planet gears or (b) the outer set of planet gears; and is

Wherein one of the sun gear, the ring gear, and the intermediate gear remains stationary.

2. The gear box assembly of claim 1, wherein:

the inner set of planet gears each have a first axial length measured parallel to the axis of the sun gear; and is

The outer set of planets each having a second axial length measured parallel to the axis of the sun, wherein the second axial length is different than the first axial length; and is

Wherein the intermediate race is in gear contact with a longer axial gear set of: (a) the inner set of planet gears or (b) the outer set of planet gears.

3. The gear box arrangement of claim 1, wherein the inner set of planet gears and the outer set of planet gears have a length that is in gear contact, and the inner set of planet gears, the outer set of planet gears, the inner race, the outer race, and the intermediate race have respective diameters selected to enable torque to be provided via one of the sun gear, the ring gear, or the intermediate gear such that an increased radial load of the inner set of planet gears and the outer set of planet gears is sufficient to overcome a separating force created by the torque.

4. The gearbox arrangement of claim 3, wherein at least one of the following each has an aspect ratio greater than 1: (a) the inner set of planet gears or (b) the outer set of planet gears.

5. The gear case arrangement of claim 1, where the inner set of planet gears and the outer set of planet gears each include two differently tapered portions.

6. The gear case arrangement of any of claims 1-4, wherein the inner set of planet gears and the outer set of planet gears each define a helical gear.

7. The gear case arrangement of claim 6 wherein the inner set of planet gears and the outer set of planet gears each define a helical gear having a constant helix angle.

8. The gear case arrangement of claim 6, wherein the inner set of planet gears and the outer set of planet gears each define helical gears with different helix angles along an axial length.

9. The gear case arrangement of claim 8, wherein the inner set of planet gears and the outer set of planet gears each define a herringbone gear pattern.

10. A gearbox arrangement according to claim 9, wherein said intermediate gear comprises two axially adjacent members each having a respective angled gear surface corresponding to a portion of said herringbone gear pattern, wherein said two axially adjacent members are fastened to each other.

11. A gearbox arrangement according to any one of claims 9 or 10, wherein said ring gear comprises two axially adjacent members each having a respective angled gear surface corresponding to a portion of said herringbone gear pattern, wherein said two axially adjacent members are fastened to each other.

12. A gearbox arrangement according to any of claims 9-11, wherein said sun gear comprises two axially adjacent members each having a respective angled gear surface corresponding to a portion of said herringbone gear pattern, wherein said two axially adjacent members are fastened to each other.

13. A gearbox arrangement according to claim 1, further comprising at least one inner shield configured to axially constrain the inner set of planet wheels.

14. A gearbox arrangement according to any of claims 1 or 13, further comprising at least one outer shield configured to axially constrain the outer set of planet wheels.

15. The gear box arrangement of any of claims 1-14, wherein an outer surface of each of the inner and outer sets of planet gears defines a plurality of gear teeth that are separated from adjacent gear teeth by a gear root, and wherein at least a portion of the gear root defines a radial slot.

16. The gear case arrangement of any of claims 1-15, where each planet in the inner set of planets and each planet in the outer set of planets is hollow.

17. A multi-stage gearbox arrangement comprising a plurality of gearbox arrangements according to any of claims 1-16, wherein the plurality of gearbox arrangements are arranged in stages such that a first ring gear of a first gearbox arrangement is connected to and drives a second intermediate gear of a second gearbox arrangement.

18. A gearbox assembly comprising:

a sun gear defining an inner race on an outer surface of the sun gear, wherein the sun gear defines an axis between a first end and an opposite second end of the sun gear;

a ring gear defining an outer race on an inner surface of the sun gear, wherein the ring gear is coaxial with the sun gear;

an inner set of planet gears in contact with the inner race gear of the sun gear;

an outer set of planet gears in contact with the outer race gear of the ring gear;

wherein each planet in the inner set of planets is in contact with at least two planet gears in the outer set of planets and each planet in the outer set of planets is in contact with at least two planet gears in the inner set of planets; and

an intermediate gear defining an intermediate race in gear contact with one of: (a) the inner set of planet gears or (b) the outer set of planet gears; and is

Wherein the outer surface of the inner race, the outer race, the middle race, and each planet in the inner set of planets and each planet in the outer set of planets each define a plurality of gear teeth having a continuous helix angle.

19. The gearbox arrangement of claim 18, further comprising at least one inner shield attached to the sun gear and configured to constrain axial motion of the inner set of planet gears.

20. The gear box assembly of claim 19 wherein said at least one inner boot comprises two inner boots each secured to opposite axial ends of said sun gear.

21. A gearbox arrangement according to any of claims 18-20, further comprising at least one outer shield attached to the ring gear and configured to constrain axial movement of the outer set of planet wheels.

22. The gear box assembly of claim 21 wherein said at least one outer shroud comprises two outer shrouds each secured to opposite axial ends of said ring gear.

23. The gear case arrangement of any one of claims 19-20 wherein each of the axial ends of the inner set of planet gears has a hemispherical shape and the at least one inner shield has a curved shape corresponding to the hemispherical shape of the axial ends of the inner set of planet gears.

24. The gearbox arrangement of any one of claims 18-23, wherein the intermediate gear is an output ring and one of the sun gear or the ring gear is driven by an input motor.

25. The gearbox arrangement according to any of claims 18-24, wherein:

the inner set of planet gears each have a first axial length measured parallel to the axis of the sun gear; and is

The outer set of planets each having a second axial length measured parallel to the axis of the sun, wherein the second axial length is different than the first axial length; and is

Wherein the intermediate race is in gear contact with a longer axial gear set of: (a) the inner set of planet gears or (b) the outer set of planet gears.

26. The gear box arrangement of claim 25, wherein at least one of the following each have an aspect ratio greater than 1: (a) the inner set of planet gears or (b) the outer set of planet gears.

27. The gear case arrangement of any of claims 18-26, where each planet in the inner set of planets and each planet in the outer set of planets is hollow.

28. A gearbox assembly comprising:

a sun gear defining an inner race on an outer surface of the sun gear, wherein the sun gear defines an axis between a first end and an opposite second end of the sun gear;

a ring gear defining an outer race on an inner surface of the sun gear, wherein the ring gear is coaxial with the sun gear;

an inner set of planet gears in contact with the inner race gear of the sun gear;

an outer set of planet gears in contact with the outer race gear of the ring gear;

wherein each planet in the inner set of planets is in contact with at least two planet gears in the outer set of planets and each planet in the outer set of planets is in contact with at least two planet gears in the inner set of planets; and

an intermediate gear defining an intermediate race in gear contact with one of: (a) the inner set of planet gears or (b) the outer set of planet gears;

at least one inner shield attached to the sun gear and configured to axially constrain the inner set of planets; and

at least one outer shield attached to the ring gear and configured to axially constrain the outer set of planets.

29. The gear case arrangement of claim 28 wherein each of the axial ends of the inner set of planet gears has a hemispherical shape and the at least one inner shield has a curved shape corresponding to the hemispherical shape of the axial ends of the inner set of planet gears.

30. The gearbox arrangement of any of claims 28-29, wherein each of the axial ends of the outer set of planets has a hemispherical shape, and the at least one outer shield has a curved shape that corresponds to the hemispherical shape of the axial ends of the outer set of planets.

31. The gearbox arrangement according to any of claims 28-30, wherein:

the inner set of planet gears each have a first axial length measured parallel to the axis of the sun gear; and is

The outer set of planets each having a second axial length measured parallel to the axis of the sun, wherein the second axial length is different than the first axial length; and is

Wherein the intermediate race is in gear contact with a longer axial gear set of: (a) the inner set of planet gears or (b) the outer set of planet gears.

32. The gearbox arrangement of any one of claims 28-31, wherein the intermediate gear is an output gear and one of the sun gear or the ring gear is driven by an input motor.

33. The gear box arrangement of claim 31, wherein at least one of the following each have an aspect ratio greater than 1: (a) the inner set of planet gears or (b) the outer set of planet gears.

34. The gear case arrangement of any of claims 28-33, where the inner set of planet gears and the outer set of planet gears each define a helical gear.

35. The gear box arrangement of any of claims 28-34, wherein an outer surface of each of the inner and outer sets of planet gears defines a plurality of gear teeth that are separated from adjacent gear teeth by a gear root, and wherein at least a portion of the gear root defines a radial slot.

36. The gear case arrangement of any of claims 28-35, where each planet in the inner set of planets and each planet in the outer set of planets is hollow.

37. A gearbox assembly comprising:

a sun gear defining an inner race on an outer surface of the sun gear, wherein the sun gear defines an axis between a first end and an opposite second end of the sun gear;

a ring gear defining an outer race on an inner surface of the sun gear, wherein the ring gear is coaxial with the sun gear;

an inner set of planet gears in contact with the inner race gear of the sun gear;

an outer set of planet gears in contact with the outer race gear of the ring gear;

wherein each planet in the inner set of planets is in contact with at least two planet gears in the outer set of planets and each planet in the outer set of planets is in contact with at least two planet gears in the inner set of planets; and

an intermediate gear defining an intermediate race in gear contact with one of: (a) the inner set of planet gears or (b) the outer set of planet gears; and is

Wherein each planet in the inner set of planets and each planet in the outer set of planets is stiffer than each of the sun, the ring, and the intermediate gear such that one or more of the sun, the ring, or the intermediate gear is deformed to balance radial loads on the inner set of planets and the outer set of planets.

38. The gear case arrangement of claim 37, where each planet in the inner set of planets and each planet in the outer set of planets comprises a metallic material.

39. A gearbox arrangement according to claim 38, wherein one or more of said sun gear, said ring gear and said intermediate gear comprises a plastics material.

40. The gearbox assembly of any one of claims 37-39, wherein:

the inner set of planet gears each have a first axial length measured parallel to the axis of the sun gear; and is

The outer set of planets each having a second axial length measured parallel to the axis of the sun, wherein the second axial length is different than the first axial length; and is

Wherein the intermediate race is in gear contact with a longer axial gear set of: (a) the inner set of planet gears or (b) the outer set of planet gears.

41. The gearbox arrangement of claim 40, wherein at least one of the following each has an aspect ratio greater than 1: (a) the inner set of planet gears or (b) the outer set of planet gears.

42. The gear case arrangement of any of claims 37-41, where the inner set of planets and the outer set of planets each include two differently tapered portions.

43. The gear case arrangement of any of claims 37-41, wherein the inner set of planet gears and the outer set of planet gears each define a helical gear.

44. The gear case arrangement of claim 43 wherein said inner set of planet gears and said outer set of planet gears each define a helical gear having a constant helix angle.

45. The gear case arrangement of claim 43, wherein the inner set of planet gears and the outer set of planet gears each define helical gears with different helix angles along an axial length.

46. The gear case arrangement of claim 45, wherein the inner set of planet gears and the outer set of planet gears each define a herringbone gear pattern.

47. The gearbox arrangement of claim 46, wherein said intermediate gear comprises two axially adjacent members each having a respective angled gear surface corresponding to a portion of said herringbone gear pattern, wherein said two axially adjacent members are fastened to each other.

48. The gearbox arrangement of claim 46, wherein said ring gear comprises two axially adjacent members each having a respective angled gear surface corresponding to a portion of said herringbone gear pattern, wherein said two axially adjacent members are secured to one another.

49. A gearbox arrangement according to claim 46, wherein said sun gear comprises two axially adjacent members each having a respective angled gear surface corresponding to a portion of said herringbone gear pattern, wherein said two axially adjacent members are fastened to each other.

50. A gearbox arrangement according to claim 37, further comprising at least one inner shield configured to axially constrain the inner set of planet wheels.

51. A gearbox arrangement according to any of claims 37 or 50, further comprising at least one outer shield configured to axially constrain the outer set of planet wheels.

52. The gear box arrangement of any of claims 37-51, wherein an outer surface of each of the inner and outer sets of planet gears defines a plurality of gear teeth that are separated from adjacent gear teeth by a gear root, and wherein at least a portion of the gear root defines a radial slot.

53. The gear case arrangement of any of claims 37-52, where each planet in the inner set of planets and each planet in the outer set of planets is hollow.

54. A gearbox assembly comprising:

a sun gear defining an inner race on an outer surface of the sun gear, wherein the sun gear defines an axis between a first end and an opposite second end of the sun gear;

a ring gear defining an outer race on an inner surface of the sun gear, wherein the ring gear is coaxial with the sun gear;

an inner set of planet gears in contact with the inner race gear of the sun gear;

an outer set of planet gears in contact with the outer race gear of the ring gear;

wherein each planet in the inner set of planets is in contact with at least two planet gears in the outer set of planets and each planet in the outer set of planets is in contact with at least two planet gears in the inner set of planets; and

an intermediate gear defining an intermediate race in gear contact with one of: (a) the inner set of planet gears or (b) the outer set of planet gears; and is

Wherein each planet in the inner set of planets and each planet in the outer set of planets is less stiff than each of the sun, ring, and intermediate gears such that one or more of the sun, ring, or intermediate gears is deformed to balance radial loads on the inner and outer sets of planets.

55. The gear case arrangement of claim 54, where each planet in the inner set of planets and each planet in the outer set of planets comprises a metallic material.

56. The gear case arrangement of claim 55, where each planet in the inner set of planet wheels and each planet in the outer set of planet wheels is hollow.

57. The gear case arrangement of claim 54, where each planet in the inner set of planets and each planet in the outer set of planets comprises a plastic material.

58. The gearbox arrangement of any one of claims 54-57, wherein:

the inner set of planet gears each have a first axial length measured parallel to the axis of the sun gear; and is

The outer set of planets each having a second axial length measured parallel to the axis of the sun, wherein the second axial length is different than the first axial length; and is

Wherein the intermediate race is in gear contact with a longer axial gear set of: (a) the inner set of planet gears or (b) the outer set of planet gears.

59. The gearbox device of claim 58, wherein at least one of the following each has an aspect ratio greater than 1: (a) the inner set of planet gears or (b) the outer set of planet gears.

60. The gear case arrangement of claim 54, where the inner set of planet gears and the outer set of planet gears each include two differently tapered portions.

61. The gear case arrangement of claim 54, wherein the inner set of planet gears and the outer set of planet gears each define a helical gear.

62. The gear case arrangement of claim 61, wherein the inner set of planet gears and the outer set of planet gears each define a helical gear with a constant helix angle.

63. The gear case arrangement of claim 61, wherein the inner set of planet gears and the outer set of planet gears each define a helical gear with a different helix angle along an axial length.

64. The gear case arrangement of claim 63, wherein the inner set of planet gears and the outer set of planet gears each define a herringbone gear pattern.

65. The gearbox arrangement of claim 64, wherein said intermediate gear comprises two axially adjacent members each having a respective angled gear surface corresponding to a portion of said herringbone gear pattern, wherein said two axially adjacent members are fastened to each other.

66. The gearbox arrangement of claim 64, wherein said ring gear comprises two axially adjacent members each having a respective angled gear surface corresponding to a portion of said herringbone gear pattern, wherein said two axially adjacent members are secured to one another.

67. A gearbox arrangement according to claim 64, wherein said sun gear comprises two axially adjacent members each having a respective angled gear surface corresponding to a portion of said herringbone gear pattern, wherein said two axially adjacent members are fastened to each other.

68. The gearbox arrangement of claim 54, further comprising at least one inner shield configured to axially constrain the inner set of planet gears.

69. A gearbox arrangement according to any of claims 54 or 68, further comprising at least one outer shield configured to axially constrain the outer set of planet wheels.

70. The gearbox arrangement of any of claims 54-69, wherein an outer surface of each of the inner and outer sets of planet gears defines a plurality of gear teeth that are separated from adjacent gear teeth by a gear root, and wherein at least a portion of the gear root defines a radial slot.

71. The gear case arrangement of any of claims 54-70, where each planet in the inner set of planet wheels and each planet in the outer set of planet wheels is hollow.

72. A method of assembling a gearbox assembly, the method comprising:

placing a set of outer planet gears in gear contact with an inner surface of the outer race;

placing a set of inner planet gears in contact with the outer set of planet gears, each inner planet gear in contact with two outer planet gears, and each outer planet gear in contact with two inner planet gears;

placing a first part of an inner race in contact with the inner planetary gear and coaxial with the outer race, the first part having a first angled gear surface;

placing a second part of an inner race in contact with the inner planetary gear and coaxial with the outer race, the second part having a second angled gear surface, the first and second angled gear surfaces having different helix angles; and

placing an input gear in contact with the outer planetary gear and coaxial with the outer race.

73. The method of claim 72, wherein the first and second angled gear surfaces have opposing helix angles that collectively form a herringbone gear surface.

74. A method according to claim 72 or claim 73, wherein the input gear includes a first input gear member having a first angled input gear surface and a second input gear member having a second angled input gear surface, and the step of placing an input gear in contact with the outer set of planet gears and coaxially with the outer race includes placing the first input gear member coaxially with the outer planet gears and with the first angled input gear surface in contact with the outer set of planet gears, and placing the second input gear member coaxially with the outer set of planet gears and with the second angled input gear surface in contact with the outer set of planet gears, the first angled input gear surface and the second angled input gear surface have different helix angles.

75. The method of claim 74, wherein the first and second angled input gear surfaces have opposite helix angles to together form a herringbone input gear surface.

76. The method of claim 74 or claim 75, wherein the first angled input gear surface is placed in contact with the outer planet gear prior to the step of placing the inner set of planet gears in contact with the outer set of planet gears, and the second angled input gear surface is placed in contact with the outer set of planet gears after the step of placing the first input gear member and the second input gear member of the inner race in contact with the inner planet gears.

77. A method of assembling a gearbox assembly, the method comprising the steps of:

placing a set of inner planet gears in gear contact with an outer surface of the inner race;

placing a set of outer planet gears in contact with the inner set of planet gears, each outer planet gear in contact with two inner planet gears, and each inner planet gear in contact with two outer planet gears;

placing a first member of an outer race in contact with the inner planetary gear and coaxial with the inner race, the first member having a first angled gear surface;

placing a second member of an outer race in contact with an outer set of planet gears and coaxial with the inner race, the second member having a second angled gear surface, the first and second angled gear surfaces having different helix angles; and placing an input gear in contact with the inner set of planet gears and coaxial with the inner race.

78. The method of claim 77, wherein the first and second angled gear surfaces have opposing helix angles that collectively form a herringbone gear surface.

79. A method according to claim 77 or claim 78, wherein the input gear includes a first input gear member having a first angled input gear surface and a second input gear member having a second angled input gear surface, and said step of placing an input gear in contact with said inner planet gear and coaxial with said inner race comprises placing said first input gear member coaxial with said inner set of planet gears and wherein said first angled input gear surface is in contact with said inner planet gear, and placing the second input gear member coaxial with the inner set of planet gears and with the second angled input gear surface in contact with the inner planet gears, the first angled input gear surface and the second angled input gear surface have different helix angles.

80. The method of claim 79, wherein the first and second angled input gear surfaces have opposite helix angles to together form a herringbone input gear surface.

81. The method of claim 79 or claim 80, wherein the first angled input gear surface is placed in contact with the inner set of planet gears before the step of placing the outer set of planet gears in contact with the inner set of planet gears, and the second angled input gear surface is placed in contact with the inner set of planet gears after the step of placing the first input gear member and the second input gear member of the outer race in contact with the outer planet gears.

Background

In published patent application number WO2013173928a1, a device is shown that increases torque with two rows of roller-based planets, all of which are in contact with the other two roller-based planets, and the number of planets is sufficient to achieve a low cam angle. Below this angle, the cam action that occurs when the device is loaded increases the force between the gear engagement or rolling members and the contact pressure at the contact between the inner planet and the outer planet, the inner planet and the inner race, and the outer planet and the outer race.

Achieving a sufficiently high coefficient of friction to allow such camming to occur is a challenge because many common material combinations, such as steel-steel combinations, have a lower Coefficient of Friction (CF) than is required for typical camming angles of such devices. Therefore, materials such as nickel alloys or other material combinations must be used to achieve a sufficiently high CF to allow the cam angle geometry to provide a traction pressure proportional to the torque transmitted.

Another challenge of the rolling contact type is to keep all the planets equally circumferentially spaced. The rolling contact itself is not "circumferentially staggered" relative to the other planets, and the two rows of planets are inherently unstable if the circumferential spacing of the planets is uncontrolled. By unstable is meant that the inner race will not remain concentric with the outer race if the planets become unequally spaced.

Another challenge with embodiments of roller-based gearboxes is the need for bearings to keep the outer race axially aligned with the inner race.

A gear arrangement such as a conventional gear reducer will typically use a planet gear carrier with a shaft and bearings to position the planet gears. The planet carrier adds rotational mass, cost and complexity.

Disclosure of Invention

A gearbox assembly is provided having an inner race having an outer surface and defining an axis, and an outer race having an inner surface and being coaxial with the inner race. The gearbox arrangement has a set of orbital planet wheels comprising an inner planet wheel in gear contact with the outer surface of the inner race and an outer planet wheel in gear contact with the inner surface of the outer race, each inner planet wheel being in gear contact with two outer planet wheels and each outer planet wheel being in gear contact with two inner planet wheels. There may be an input ring coaxial with the inner and outer races and in contact with the inner planet wheels or with the outer planet wheel gears.

In one embodiment, there is one of a or B, where a is the outer planet wheels being longer than the inner planet wheels, and each outer planet wheel has a respective first portion that meshes with the inner planet wheel with which it is in contact, and the input ring has an outer surface that meshes with a respective second portion of each outer planet wheel with which it is in contact, both the first and second portions of the outer planet wheels meshing with the outer race; and B is that the inner planet wheels are longer than the outer planet wheels and each inner planet wheel has a respective first portion which meshes with the outer planet wheel with which it is in contact, and the input ring has an inner surface which meshes with a respective second portion of each inner planet wheel with which it is in contact, both the first and second portions of the inner planet wheels meshing with the inner race.

In another embodiment, the inner and outer planets have lengths of gear contact and the gears and races have respective diameters selected to produce torque on the input ring such that the increased radial load of the inner and outer planets is sufficient to overcome the separation force between the gears produced by the torque on the input ring.

In another embodiment, at least one of the outer surface of the inner race and the inner surface of the outer race is formed by two angled gear surfaces having different helix angles. The two angled gear surfaces may be positioned on axially adjacent components. This arrangement can be used to enable the components to be moved axially into meshing contact with the planet gear pinions, thereby facilitating assembly.

Various embodiments relate to a gearbox comprising: a sun gear defining an inner race on an outer surface thereof, wherein the sun gear defines an axis between a first end and an opposite second end of the sun gear; a ring gear defining an outer race on an inner surface of the sun gear, wherein the ring gear is coaxial with the sun gear; an inner set of planet gears in contact with the inner race gear of the sun gear; an outer set of planet gears in contact with the outer race gear of the ring gear; wherein each planet in the inner set of planets is in contact with at least two planet gears in the outer set of planets and each planet in the outer set of planets is in contact with at least two planet gears in the inner set of planets; and an intermediate gear defining an intermediate race in gear contact with one of: (a) the inner set of planet gears or (b) the outer set of planet gears; and wherein one of the sun gear, the ring gear, and the intermediate gear remains stationary.

In some embodiments, the inner set of planet gears each have a first axial length measured parallel to the axis of the sun gear; and the outer set of planets each having a second axial length measured parallel to the axis of the sun, wherein the second axial length is different than the first axial length; and wherein the intermediate race is in gear contact with a longer axial gear set of: (a) the inner set of planet gears or (b) the outer set of planet gears. In various embodiments, the inner set of planet gears and the outer set of planet gears have a length that is in gear contact, and the inner set of planet gears, the outer set of planet gears, the inner race, the outer race, and the intermediate race have respective diameters selected to enable torque to be provided via one of the sun gear, the ring gear, or the intermediate gear such that an increased radial load of the inner set of planet gears and the outer set of planet gears is sufficient to overcome a separating force generated by the torque. Further, in certain embodiments, at least one of the following each have an aspect ratio greater than 1: (a) the inner set of planet gears or (b) the outer set of planet gears. In some embodiments, the inner set of planet wheels and the outer set of planet wheels each include two portions that taper in different ways.

In various embodiments, the inner set of planet gears and the outer set of planet gears each define a helical gear. In some embodiments, the inner set of planet gears and the outer set of planet gears each define a helical gear with a constant helix angle. Further, the inner set of planet gears and the outer set of planet gears can each define helical gears having different helix angles along the axial length. In various embodiments, the inner set of planet gears and the outer set of planet gears each define a herringbone gear pattern. Further, the intermediate gear may comprise two axially adjacent components each having a respective angled gear surface corresponding to a portion of the herringbone gear pattern, wherein the two axially adjacent components are fastened to each other. In certain embodiments, the ring gear includes two axially adjacent components each having a respective angled gear surface corresponding to a portion of the herringbone gear pattern, wherein the two axially adjacent components are secured to each other. Further, the sun gear may include two axially adjacent components each having a respective angled gear surface corresponding to a portion of the herringbone gear pattern, wherein the two axially adjacent components are secured to each other.

In certain embodiments, the gearbox assembly further comprises: at least one inner shield configured to axially constrain the inner set of planet gears. In various embodiments, the gearbox further comprises at least one outer shield configured to axially constrain the outer set of planets. In various embodiments, an outer surface of each planet wheel of the inner, outer, middle, and inner sets of planet wheels and each planet wheel of the outer set of planet wheels each defines a plurality of gear teeth that are separated from adjacent gear teeth by a gear root, and wherein at least a portion of the gear root defines a radial slot. In some embodiments, each planet in the inner set of planet gears and each planet in the outer set of planet gears is hollow.

Various embodiments relate to a multi-stage gearbox arrangement comprising a plurality of gearbox arrangements as discussed herein, wherein the plurality of gearbox arrangements are arranged in stages such that a first ring gear of a first gearbox arrangement is connected to and drives a second intermediate gear of a second gearbox arrangement.

Certain embodiments relate to a gearbox arrangement comprising: a sun gear defining an inner race on an outer surface thereof, wherein the sun gear defines an axis between a first end and an opposite second end of the sun gear; a ring gear defining an outer race on an inner surface of the sun gear, wherein the ring gear is coaxial with the sun gear; an inner set of planet gears in contact with the inner race gear of the sun gear; an outer set of planet gears in contact with the outer race gear of the ring gear; wherein each planet in the inner set of planets is in contact with at least two planet gears in the outer set of planets and each planet in the outer set of planets is in contact with at least two planet gears in the inner set of planets; and an intermediate gear defining an intermediate race in gear contact with one of: (a) the inner set of planet gears or (b) the outer set of planet gears; and wherein the outer surface of the inner race, the outer race, the middle race, and each planet in the inner set of planet wheels and each planet in the outer set of planet wheels each define a plurality of gear teeth having a continuous helix angle.

In various embodiments, the gearbox also includes at least one inner shield attached to the sun gear and configured to constrain axial motion of the inner set of planets. In certain embodiments, the at least one inner shield comprises two inner shields each secured to opposite axial ends of the sun gear. In various embodiments, at least one outer shield is attached to the ring gear and is configured to constrain axial movement of the outer set of planets. In certain embodiments, the at least one outer shield comprises two outer shields each secured to opposite axial ends of the ring gear. Further, each of the axial ends of the inner set of planet gears can have a hemispherical shape and the at least one inner shield can have a curved shape corresponding to the hemispherical shape of the axial ends of the inner set of planet gears. In various embodiments, the intermediate gear is an output ring and one of the sun gear or the ring gear is driven by an input motor. In some embodiments, the inner set of planet gears each have a first axial length measured parallel to the axis of the sun gear; and the outer set of planets each having a second axial length measured parallel to the axis of the sun, wherein the second axial length is different than the first axial length; and wherein the intermediate race is in gear contact with a longer axial gear set of: (a) the inner set of planet gears or (b) the outer set of planet gears. Further, at least one of the following each have an aspect ratio greater than 1: (a) the inner set of planet gears or (b) the outer set of planet gears. In some embodiments, each planet in the inner set of planet gears and each planet in the outer set of planet gears is hollow.

Various embodiments relate to a gearbox arrangement comprising: a sun gear defining an inner race on an outer surface thereof, wherein the sun gear defines an axis between a first end and an opposite second end of the sun gear; a ring gear defining an outer race on an inner surface of the sun gear, wherein the ring gear is coaxial with the sun gear; an inner set of planet gears in contact with the inner race gear of the sun gear; an outer set of planet gears in contact with the outer race gear of the ring gear; wherein each planet in the inner set of planets is in contact with at least two planet gears in the outer set of planets and each planet in the outer set of planets is in contact with at least two planet gears in the inner set of planets; and an intermediate gear defining an intermediate race in gear contact with one of: (a) the inner set of planet gears or (b) the outer set of planet gears; at least one inner shield attached to the sun gear and configured to axially constrain the inner set of planets; and at least one outer shield attached to the ring gear and configured to axially constrain the outer set of planets.

In various embodiments, each of the axial ends of the inner set of planet gears has a hemispherical shape and the at least one inner shield has a curved shape that corresponds to the hemispherical shape of the axial ends of the inner set of planet gears. Further, each of the axial ends of the outer set of planet gears has a hemispherical shape, and the at least one outer shield has a curved shape corresponding to the hemispherical shape of the axial end of the outer set of planet gears. In some embodiments, the inner set of planet gears each have a first axial length measured parallel to the axis of the sun gear; and the outer set of planets each having a second axial length measured parallel to the axis of the sun, wherein the second axial length is different than the first axial length; and wherein the intermediate race is in gear contact with a longer axial gear set of: (a) the inner set of planet gears or (b) the outer set of planet gears.

In certain embodiments, the intermediate gear is an output gear and one of the sun gear or the ring gear is driven by an input motor. In various embodiments, at least one of the following each have an aspect ratio greater than 1: (a) the inner set of planet gears or (b) the outer set of planet gears. In addition, the inner set of planet gears and the outer set of planet gears each define a helical gear. In some embodiments, an outer surface of each planet wheel of the inner, outer, middle, and inner sets of planet wheels and each planet wheel of the outer set of planet wheels defines a plurality of gear teeth that are separated from adjacent gear teeth by a gear root, and wherein at least a portion of the gear root defines a radial slot. In some embodiments, each planet in the inner set of planet gears and each planet in the outer set of planet gears is hollow.

Certain embodiments relate to a gearbox arrangement comprising: a sun gear defining an inner race on an outer surface thereof, wherein the sun gear defines an axis between a first end and an opposite second end of the sun gear; a ring gear defining an outer race on an inner surface of the sun gear, wherein the ring gear is coaxial with the sun gear; an inner set of planet gears in contact with the inner race gear of the sun gear; an outer set of planet gears in contact with the outer race gear of the ring gear; wherein each planet in the inner set of planets is in contact with at least two planet gears in the outer set of planets and each planet in the outer set of planets is in contact with at least two planet gears in the inner set of planets; and an intermediate gear defining an intermediate race in gear contact with one of: (a) the inner set of planet gears or (b) the outer set of planet gears; and wherein each planet in the inner set of planet wheels and each planet in the outer set of planet wheels is stiffer than each of the sun gear, the ring gear, and the intermediate gear, such that one or more of the sun gear, the ring gear, or the intermediate gear deforms to balance radial loads on the inner set of planet wheels and the outer set of planet wheels.

In some embodiments, each planet in the inner set of planets and each planet in the outer set of planets comprises a metallic material. Further, one or more of the sun gear, the ring gear, and the intermediate gear comprise a plastic material.

In various embodiments, the inner set of planet gears each have a first axial length measured parallel to the axis of the sun gear; and the outer set of planets each having a second axial length measured parallel to the axis of the sun, wherein the second axial length is different than the first axial length; and wherein the intermediate race is in gear contact with a longer axial gear set of: (a) the inner set of planet gears or (b) the outer set of planet gears. In certain embodiments, at least one of the following each have an aspect ratio greater than 1: (a) the inner set of planet gears or (b) the outer set of planet gears. In various embodiments, the inner set of planet wheels and the outer set of planet wheels each include two portions that taper in different ways. In some embodiments, the inner set of planet gears and the outer set of planet gears each define a helical gear. In some embodiments, the inner set of planet gears and the outer set of planet gears each define a helical gear with a constant helix angle. In various embodiments, the inner set of planet gears and the outer set of planet gears can each define helical gears having different helix angles along the axial length. Further, the inner set of planet gears and the outer set of planet gears each define a herringbone gear pattern. In certain embodiments, the idler gear includes two axially adjacent components each having a respective angled gear surface corresponding to a portion of the herringbone gear pattern, wherein the two axially adjacent components are secured to each other.

In various embodiments, the ring gear includes two axially adjacent components each having a respective angled gear surface corresponding to a portion of the herringbone gear pattern, wherein the two axially adjacent components are secured to each other. In various embodiments, the sun gear includes two axially adjacent components each having a respective angled gear surface corresponding to a portion of the herringbone gear pattern, wherein the two axially adjacent components are secured to each other. Further, the gear box may further include: at least one inner shield configured to axially constrain the inner set of planet gears. In various embodiments, the gearbox arrangement further comprises at least one outer shield configured to axially constrain the outer set of planet wheels. In some embodiments, an outer surface of each planet wheel of the inner, outer, middle, and inner sets of planet wheels and each planet wheel of the outer set of planet wheels defines a plurality of gear teeth that are separated from adjacent gear teeth by a gear root, and wherein at least a portion of the gear root defines a radial slot. In addition, each planet in the inner set of planet wheels and each planet in the outer set of planet wheels can be hollow.

Various embodiments relate to a gearbox arrangement comprising: a sun gear defining an inner race on an outer surface thereof, wherein the sun gear defines an axis between a first end and an opposite second end of the sun gear; a ring gear defining an outer race on an inner surface of the sun gear, wherein the ring gear is coaxial with the sun gear; an inner set of planet gears in contact with the inner race gear of the sun gear; an outer set of planet gears in contact with the outer race gear of the ring gear; wherein each planet in the inner set of planets is in contact with at least two planet gears in the outer set of planets and each planet in the outer set of planets is in contact with at least two planet gears in the inner set of planets; and an intermediate gear defining an intermediate race in gear contact with one of: (a) the inner set of planet gears or (b) the outer set of planet gears; and wherein each planet in the inner set of planet wheels and each planet in the outer set of planet wheels is stiffer than each of the sun gear, the ring gear, and the intermediate gear, such that one or more of the sun gear, the ring gear, or the intermediate gear deforms to balance radial loads on the inner set of planet wheels and the outer set of planet wheels.

In some embodiments, each planet in the inner set of planets and each planet in the outer set of planets comprises a metallic material. In addition, each planet in the inner set of planet wheels and each planet in the outer set of planet wheels is hollow. In various embodiments, each planet in the inner set of planets and each planet in the outer set of planets comprises a plastic material. Further, in some embodiments, the inner set of planet gears each have a first axial length measured parallel to the axis of the sun gear; and the outer set of planets each having a second axial length measured parallel to the axis of the sun, wherein the second axial length is different than the first axial length; and wherein the intermediate race is in gear contact with a longer axial gear set of: (a) the inner set of planet gears or (b) the outer set of planet gears. In various embodiments, at least one of the following each have an aspect ratio greater than 1: (a) the inner set of planet gears or (b) the outer set of planet gears. In some embodiments, the inner set of planet wheels and the outer set of planet wheels each include two portions that taper in different ways. In some embodiments, the inner set of planet gears and the outer set of planet gears each define a helical gear. In various embodiments, the inner set of planet gears and the outer set of planet gears each define a helical gear with a constant helix angle. In some embodiments, the inner set of planet gears and the outer set of planet gears can each define helical gears having different helix angles along the axial length. In some embodiments, the inner set of planet gears and the outer set of planet gears each define a herringbone gear pattern. Further, the intermediate gear may comprise two axially adjacent components each having a respective angled gear surface corresponding to a portion of the herringbone gear pattern, wherein the two axially adjacent components are fastened to each other. In certain embodiments, the ring gear includes two axially adjacent components each having a respective angled gear surface corresponding to a portion of the herringbone gear pattern, wherein the two axially adjacent components are secured to each other. Further, the sun gear may include two axially adjacent components each having a respective angled gear surface corresponding to a portion of the herringbone gear pattern, wherein the two axially adjacent components are secured to each other.

In some embodiments, the gearbox arrangement further comprises at least one inner shield configured to axially constrain the inner set of planet wheels. In certain embodiments, the gearbox arrangement further comprises at least one outer shield configured to axially constrain the outer set of planet wheels. In various embodiments, an outer surface of each planet wheel of the inner, outer, middle, and inner sets of planet wheels and each planet wheel of the outer set of planet wheels each defines a plurality of gear teeth that are separated from adjacent gear teeth by a gear root, and wherein at least a portion of the gear root defines a radial slot. In various embodiments, each planet in the inner set of planet wheels and each planet in the outer set of planet wheels is hollow.

Various embodiments relate to a method of assembling a gearbox assembly, the method comprising: placing a set of outer planet gears in gear contact with an inner surface of the outer race; placing a set of inner planet gears in contact with the outer set of planet gears, each inner planet gear in contact with two outer planet gears, and each outer planet gear in contact with two inner planet gears; placing a first member of an inner race in contact with the inner planetary gear and coaxial with the outer race, the first member having a first angled gear surface; placing a second part of an inner race in contact with the inner planetary gear and coaxial with the outer race, the second part having a second angled gear surface, the first and second angled gear surfaces having different helix angles; and placing an input gear in contact with the outer planet gear and coaxial with the outer race. In certain embodiments, the first angled gear surface and the second angled gear surface have opposing helix angles that collectively form a herringbone gear surface. In various embodiments, the input gear includes a first input gear member having a first angled input gear surface and a second input gear member having a second angled input gear surface, and the step of placing the input gear in contact with the outer set of planet gears and coaxially with the outer race includes placing the first input gear member coaxially with the outer planet gears and wherein the first angled input gear surface is in contact with the outer set of planet gears, and placing the second input gear member coaxially with the outer set of planet gears and wherein the second angled input gear surface is in contact with the outer set of planet gears, the first angled input gear surface and the second angled input gear surface having different helix angles.

In some embodiments, the first angled input gear surface and the second angled input gear surface have opposite helix angles to together form a herringbone input gear surface. Further, the first angled input gear surface may be placed in contact with the outer planet gear prior to the step of placing the inner set of planet gears in contact with the outer set of planet gears, and the second angled input gear surface may be placed in contact with the outer set of planet gears after the step of placing the first input gear member and the second input gear member of the inner race in contact with the inner planet gears.

Further, certain embodiments relate to a method of assembling a gearbox assembly, the method comprising the steps of: placing a set of inner planet gears in gear contact with an outer surface of the inner race; placing a set of outer planet gears in contact with the inner set of planet gears, each outer planet gear in contact with two inner planet gears, and each inner planet gear in contact with two outer planet gears; placing a first member of an outer race in contact with the inner planetary gear and coaxial with the inner race, the first member having a first angled gear surface; placing a second part of the outer race in contact with the outer set of planet gears and coaxial with the inner race, the second part having a second angled gear surface, the first and second angled gear surfaces having different helix angles; and placing an input gear in contact with the inner set of planet gears and coaxial with the inner race.

In certain embodiments, the first angled gear surface and the second angled gear surface have opposing helix angles that collectively form a herringbone gear surface. Further, according to certain embodiments, the input gear includes a first input gear member having a first angled input gear surface and a second input gear member having a second angled input gear surface, and the step of placing the input gear in contact with the inner planet gear and coaxial with the inner race includes placing the first input gear member coaxial with the inner set of planet gears and wherein the first angled input gear surface is in contact with the inner planet gears, and placing the second input gear member coaxial with the inner set of planet gears and wherein the second angled input gear surface is in contact with the inner planet gears, the first angled input gear surface and the second angled input gear surface having different helix angles. In various embodiments, the first angled input gear surface and the second angled input gear surface have opposite helix angles to together form a herringbone input gear surface. Further, in some embodiments, the first angled input gear surface is placed in contact with the inner set of planet gears before the step of placing the outer set of planet gears in contact with the inner set of planet gears, and the second angled input gear surface is placed in contact with the inner set of planet gears after the step of placing the first input gear member and the second input gear member of the outer race in contact with the outer planet gears.

Drawings

Reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

fig. 1 is a simplified schematic axial end view of a portion of a motor including a gearbox with magnetic planet wheels.

Fig. 2 is a simplified schematic axial end view of a portion of the motor of fig. 1, also showing electromagnetic stator poles/posts represented by dashed lines.

Fig. 3 is a schematic circumferential cross-sectional view of the exemplary embodiment of fig. 2, with partially assembled stators located on both axial ends of the planet.

Fig. 4 is a schematic cross section of an exemplary embodiment of a gearbox with outer planet wheels larger than inner planet wheels, 16 planet wheels per row, and the larger planet wheel row with magnets.

Fig. 5 is a schematic cross section of an exemplary embodiment of a gearbox with larger outer planets than inner planets, 14 planets in each row, and the larger row of planets with magnets.

FIG. 6 is a schematic cross section of an exemplary embodiment of a gearbox with outer planet wheels larger than inner planet wheels.

Fig. 7 is a schematic side view of two planets showing an exemplary gear pattern.

FIG. 8 is a diagram illustrating a simplified example of a low angle lobe profile.

Fig. 9 is a schematic cross section of an exemplary gearbox with hollow planet wheels, showing the path between the inner and outer rings.

FIG. 10 is a front isometric view of an embodiment of a gearbox.

FIG. 11 is a rear isometric view of the gearbox of FIG. 10.

FIG. 12 is an isometric cross-sectional view of a gearbox with an asymmetric sun gear input.

FIG. 13 is an exploded view of the gearbox of FIG. 12.

FIG. 14 is a cross-sectional view of the gearbox of FIG. 12, illustrating an exemplary assembly step.

FIG. 15 is a schematic diagram of a profile offset concept that may be implemented for a gear tooth profile.

FIG. 16 is an isometric view of a test system for a gearbox.

FIG. 17 is a cross-sectional view of an exemplary gearbox showing an idler ring.

FIG. 18 is an isometric view of an exemplary symmetric gearbox.

FIG. 19 is an isometric cross-sectional view of the symmetric gearbox of FIG. 14.

FIG. 20 is an isometric cutaway view of an exemplary gearbox with an asymmetric sun input.

Fig. 21-22 are alternative views of a symmetric gearbox according to certain embodiments.

Fig. 23-24 are alternative views of alternative gearboxes according to certain embodiments.

Fig. 25-28 are alternative views of a gearbox according to certain embodiments.

Fig. 29-35 are alternative views of various components of a complete gearbox disposed within a housing, according to certain embodiments.

Fig. 36A to 36C schematically show a part of a gear, which is formed of a soft material into a normal shape, a thin shape, and a shape having a cutout at a gear root, respectively.

FIG. 37 is an isometric cross-sectional view of a two-stage gearbox.

FIG. 38 is an isometric cross-sectional view of an actuator including the two-stage gearbox of FIG. 37.

Fig. 39 is a side cross-sectional view of the actuator of fig. 38.

Fig. 40 is a schematic side section view of a gearbox with tapered planet wheels.

Fig. 41 is an exploded isometric view of a gearbox with tapered planets.

FIG. 42 is a side cross-sectional view of the gearbox of FIG. 41.

FIG. 43 is an isometric view of the gearbox of FIG. 41.

Detailed Description

The present disclosure describes various embodiments more fully with reference to the accompanying drawings. It should be understood that some, but not all embodiments are shown and described herein. Indeed, the embodiments may take many different forms and the disclosure should not be construed as limited to the embodiments set forth herein. Insubstantial modifications of the embodiments described herein are possible without departing from what is intended to be covered by the claims. Rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

Embodiments of the present device eliminate the need for a planet carrier by transmitting torque from the inner fixed ring to the outer output ring directly through the two rows of planet gears. The gear reduction ratio is determined by the difference between the outer diameter of the inner ring and the inner diameter of the outer ring, the inner and outer planets serving as torque transfer load paths between them. When the planet is made to orbit, the outer ring will rotate with a gear ratio such as about 3: 1 or possibly lower or up to about 6: 1 or possibly higher. The reduction ratio is larger as the outer diameter of the inner ring is closer to the inner diameter of the outer output ring.

Embodiments of the devices disclosed herein use a combination of features to provide equal circumferential spacing and axial alignment of the planets and races, and because the interaction of the planets and races provides axial alignment from the inner race to the outer race, in some applications the need for or reduction in strength (and therefore cost and weight) of additional bearings is eliminated. Further, embodiments of the apparatus disclosed herein provide a structure that applies magnetic force directly to the planets to eliminate the need for a separate motor rotor, where the planets themselves act as a rotor with a reduction ratio because they orbit at a higher speed than the output ring. This eliminates the need for a sun ring input, simplifying the manufacture and assembly of the motor-gearbox combination. The fact that the planets (and hence the magnets contained) spin is not considered a significant detriment because they still provide magnetic flux to the air gap and stator.

Embodiments of the device use gears or lobes that are small enough and numerous enough to provide a motion and feel that is more like rolling contact than a gear. In the claims, the term "lobe" also encompasses the term "gear". Lobes have the advantage of providing a high surface area in the radial direction (as opposed to gears having gear teeth that act like wedges). In one example, the pressure angle of the lobe or gear may be greater than 20, 30, or 40 degrees. In an alternative configuration, high angle gears may be used instead of lobes. By configuring the gears or lobes in a herringbone configuration, a number of characteristics may be achieved, including: the circumferential planet wheel spacing due to the specified circumferential positioning of the planet wheel gears; due to the herringbone helical gears, the planet wheels are axially aligned with the races and the inner and outer planet wheels; and the ability to eliminate or reduce the need for bearings between the inner and outer races, since the herringbone gears on the planets provide multi-axis (i.e., radial and axial position) constraints. The use of Permanent Magnets (PM) in the planets allows one or more (e.g., two) electromagnetic stators positioned on the axial ends of the device to be commutated in such a way as to apply rotational torque and motion to the planets and by doing so generate torque on the outer ring (the inner ring is used as a fixed reference in these non-limiting examples, although it is understood that the outer ring may be used as a fixed reference and the inner ring may be the output ring.

Embodiments including permanent magnets

A typical conventional differential gear with a planet gear carrier cannot include permanent magnets in the planet gears because the differential gearbox requires bearings and shafts in the planet gears. Furthermore, if a conventional planetary gear (with a single circular array of planet gears) uses permanent magnets in the planet gears along with a fixed sun gear, it will act as a speed increaser rather than a speed reducer.

In fig. 1, a simplified schematic diagram of a portion of a non-limiting exemplary embodiment of an apparatus 10 is shown. The inner race 12 acts as a fixed or reference race, the outer race 14 acts as an output member, and the respective arrays of inner and outer planet wheels 16, 18 apply torque from the inner race 12 to the outer race 14 as the inner and outer planet wheels 16, 18 orbit. In order to make the planets orbit, an embodiment of the device has permanent magnets 20 embedded in one or more of the planets and preferably (as shown in fig. 1) in all of the inner and outer planets (e.g. placed within their axial inner openings).

Fig. 2 shows a simplified schematic of an embodiment of the apparatus 10, wherein the electromagnetic stator poles/columns 22 are represented by dashed lines. A range of numbers of planets and columns may be used, such as may be used in a conventional electric motor and stator, such as 72 stator columns and 68 planets. In this non-limiting example, the number of planets includes 34 inner planets and 34 outer planets. The stator may have electromagnets with posts or air coils. Also shown in FIG. 2 is section line A-A, which shows where the section view of FIG. 3 is cut. The section line cuts through the outer planet, but between the inner planet. If air coils are used, it is preferable to have a back iron 26 of soft magnetic material to transfer the magnetic flux from each air coil 22 to each adjacent air coil 22.

Fig. 3 shows a schematic cross section of the non-limiting exemplary embodiment of fig. 2, in which the partially assembled stator is located on both axial ends of the planet. (the coil on the electromagnetic element is not shown). The placement of the permanent magnets 20 is such that two magnets are used and placed in the outer planet 18 from either end such that they are drawn together across the split or axial positioning member 24. This allows the magnets to be retained in the planet wheel without the need for additional fixing means. This provides the entire end of the magnet for propulsion when interacting with the electromagnetic stator pole 22. Other means of inserting and securing the magnets may also be used. The inner planet wheels may use the same or a different arrangement than the outer planet wheels. A stator element comprising poles (embodied as air coils in the illustrated embodiment) 22 and back iron 26 is schematically shown. As shown, the stator elements may be on both axial sides of the device 10. The stator may be attached to a stationary element, here an inner race 12. Here, spacers 28 are used to connect back iron 26 to inner race 12.

The axial positioning member 24 does not require a separate magnet. The member 24 simply prevents the magnets from moving together. If separated, such as for two simple cylindrical permanent magnets separated by a plastic ring (if plastic gears are used) for forming the axial positioning member 24, then a disk 112 of soft magnetic material (e.g., steel) is required between them.

The axial positioning member 24 is preferably molded or manufactured in one piece with at least one inner portion 114 (inner diameter) of the planet. The entire planet may be formed as a single piece, or the gear face of the planet may be one or more separate pieces into which the inner portion 114 is inserted. A soft magnetic member, such as a steel disc 112, is preferably used as the flux connection path between the two magnets. In some embodiments, the permanent magnet may have a cylindrical end portion with a smaller diameter than the disk of soft magnetic material. Simple cylindrical magnets are considered to be less expensive to manufacture and use steel disc spacers between them for the flux connection so that the discs can be easily adjusted to the desired thickness (whereas permanent magnets are more difficult to machine to the same tolerances).

The embodiment shown in fig. 1-3 has 2 rows of similarly sized planets (rollers, planets, and/or the like) with magnets in each row. The magnet is oriented to have: a first polarity arrangement (when viewed from one axial side), such as north (N) poles in an array; and a second polarity arrangement, such as a south (S) pole in another array, as seen in fig. 1 and 2. Some configurations use planets that are much smaller in one array than in another. In such embodiments, the magnets may be located only in the larger planets (rather than in the smaller planets), however it should be understood that in various embodiments, the magnets may be placed in other planet orientations. Placing the magnets only in the larger planets provides benefits such as providing a lighter stator due to the smaller radial size. Regardless of the size of the planet, the magnets may be limited to one row. The examples shown in fig. 4-5 in the version with 16 and 14 planets per row, respectively, have larger outer planets 18 with magnets 20 only in the outer array.

This single row magnet configuration has alternating polarities of magnets in a single array of permanent magnet planets.

The stator may have a plurality of poles. Each pole may be embodied as an electromagnet with a pole or an air coil, for example. For a conventional three-phase motor, the stator has a number of poles that is divisible by 3 (the term "pole" or "limb" when referring to the stator refers to each individual limb and coil, or coil if air coils are used). It may also be useful for the number of poles to be divisible by 4, so if the number of poles can be divided by both 3 and 4, the number of poles can be divided by 12.

The number of rotor posts (here rotor posts refers to the number of planets with permanent magnets of alternating polarity with respect to adjacent planets with magnets) is then based on the number of stator posts, and for concentrated windings the number of rotor posts is greater or less than the number of stator posts. For example, -2 or +2, but-4 or +4 is preferred as this distributes the magnetic forces around the air gap to reduce the bending load on the stator. Other differences will also apply.

Here, the number of rotor columns is the number of planets with magnets therein, which is typically the total number of planets or the number of planets in one of the rows of planets.

In an embodiment with magnets in a row of planets, an example of a suitable number of planets in a row is 16, as shown in fig. 4.

The embodiment shown in fig. 1-5 is referred to herein as a sunless self-energizing gearbox. Each of these embodiments has only one (usually fixed) inner ring and one outer ring (usually connected to the output). The planet wheels act as bearings, which reduces or eliminates the need for conventional bearings. Such actuators may be useful for implementations that utilize high speed actuation, such as exoskeletons. Embodiments disclosed in this application may be used with exoskeletons such as that disclosed in U.S. patent application publication No. 2017/0181916, the contents of which are incorporated herein by reference in their entirety.

Fig. 6 shows an embodiment with 14 planets per row, with a range of planet wheel sizes smaller than fig. 5. The magnets are not shown. All of these embodiments may be used with or without magnets. In the absence of magnets, the input force/torque may be provided by an external source (such as an input gear powered by an external motor), as described and illustrated below.

Gear or lobe configuration

Fig. 7 shows a non-limiting example of an inner chevron gear or lobe 30 on the inner planet wheel 16 and an outer chevron gear or lobe 32 on the outer planet wheel 18. Gears or lobes 30 and 32 are schematically illustrated by lines. The gears or lobes 30 and 32 will mesh, although the gears appear slightly separated in this view. The herringbone gears or lobes help constrain the axial positioning of the planets. Axial positioning may be constrained by any use of gears or lobes having different helix angles at different portions of the planet that are in simultaneous contact with the surface or another planet. The chevron shape shown in fig. 7 is but one example of this. To distinguish from the "pressure angle" defined below, the angles referred to in this paragraph (i.e., the angles at which the lobes peaks or valleys are away from the axial direction) will be referred to as helix angles. In this embodiment, the helix angles 34 (represented by arcs connecting the lines showing the lobes 30 to dashed lines parallel to the axis of the inner planet wheels 16) are opposite on different axial portions of the planet wheels. This opposite non-zero angle is an example of different helix angles on different axial portions.

While the device may be configured to work with a traction surface, the use of a lobe such as that shown in fig. 8 will have the effect of increasing the apparent coefficient of friction by preventing slippage at larger angles between the gears. Thus, high effective pressure angle lobes, such as sinusoidal profiles, may be used as long as the average maximum pressure angle under load is low enough to prevent the lobe or gear face from disengaging.

The pressure angle of certain device 10 embodiments may significantly affect the loading of the gears/lobes 30, 32. Because there is a self-camming action (as discussed herein) when the device 10 (gearbox) is loaded and designed according to certain embodiments, it places a radial load on the planets 16, 18. In case the pressure angle is smaller than the lower threshold, there is a risk of gear tooth engagement, so that the device 10 does not rotate or generates high friction. In the event that the pressure angle is greater than the upper threshold, the gears/lobes 30, 32 become too shallow to withstand significant loads, which may cause the gears/lobes 30, 32 to hop under load. The lower and upper thresholds are influenced by the cam angles of the inner and outer planetary gears 16, 18.

Adjusting the pressure angle may increase or decrease the radial force in order to improve load sharing between multiple planets 16, 18, or increase the life of the planets 16, 18 or other gears in the apparatus 10 (e.g., by reducing the load experienced by the gears). For example, in a device 10 incorporating planets having a low stiffness (e.g., comprising a low stiffness material or low stiffness construction), the material stiffness alone provides a significant amount of deflection to allow load sharing between the planets 16, 18 of the device 10. Providing gears/lobes 30, 32 with high pressure angles will increase the radial load on the planet wheels 16, 18, but reduce the bending load on the planet wheels 16, 18. In implementations where root bending is identified as a severe failure mode, this configuration may increase the life of the planets 16, 18. More typically, it may be desirable to reduce the radial load on the less rigid planets 16, 18 and to utilize the lower pressure angle of the gears/lobes 30, 32 to maximize the overall stiffness of the apparatus 10. In an arrangement 10 having high stiffness planets 16, 18, additional radial loads may be utilized to ensure that there is sufficient deflection of the planets 16, 18 (or other gears/rings as discussed herein) to ensure load sharing between the planets 16, 18. For example, using a higher pressure angle may provide sufficient deflection of the planets 16, 18 to increase load sharing between the planets 16, 18.

It may be beneficial for the planets 16, 18 to have a higher pressure angle due to the reduced stress concentration at the root of the tooth. This will translate into lower stresses in the tooth root, which may increase the life of the planet wheels 16, 18.

A simplified example of a high effective pressure angle lobe profile is shown in fig. 8. The high effective pressure angle lobe geometry is believed to allow for high rolling contact capability by increasing the radial effective surface area. The combination of the self-camming effect, which increases the radial contact force with increasing torque, and this low effective pressure angle lobe geometry is expected to result in minimal slip and therefore low rolling friction.

High effective pressure angle-in conventional gearboxes, high pressure angles can result in high separating forces between gears during torque transfer. In embodiments of the device, the lobe pressure angle is sufficiently low to increase the effective coefficient of friction of the contact area, thereby establishing the cam angle. Once this critical effective coefficient of friction (EFC) is established, the self-excitation effect will cause the planets to increase traction pressure rather than slip or jump. Fig. 8 depicts lobe contact between the planet and the race. The dotted lines represent the pitch diameter of the planets on the bottom and the larger diameter races on the top. The long dashed line a represents the actual contact angle if the contact between the planet and the raceway is a non-geared interface and the contact angle for this particular implementation is in the radial direction with respect to the planet axis. Line B represents the maximum pressure angle during lobe engagement when the planet (shown with lobe 30) rolls on the race (shown with corresponding lobe 32) and is perpendicular to the surface of the lobe. Line C represents the minimum pressure angle during load engagement when the planet (with lobe 30 as shown) rolls on the race (with corresponding lobe 32 as shown) and is perpendicular to the surface of lobe 30. During torque transmission, the contact pressure is biased in one direction, so there is no effective contact in the opposite direction of contact line B. Due to this contact pattern, the average effective pressure angle is along line D, approximately midway between lines B and C.

Each of the inner and outer races may be circular and centered on an axis, as described in WO2013173928a1 (the contents of which are incorporated herein by reference). Traction angleThe following can be defined: for each pair of first inner planet wheels 16 contacting the first outer planet wheels 18, the traction angleDefined as the angle between a first line extending outward from the axis through the center of the first inner planet wheel 16 and a second line extending from the point of contact of the first outer planet wheel 18 with the outer race 14 and the point of contact of the first inner planet wheel 16 with the inner race 12. The orbital motion of the planet gears 16, 18 results in differential motion between the inner race 12 and the outer race 14, so torque forces are transmitted between the inner race 12 and the outer race 14 via the planet gears 16, 18. The torque forces are transmitted between the contact points of adjacent planet wheels 16, 18 and thus at a traction angle, the traction angle beingThe ratio of the circumferential component to the radial component being equal to the draft angleThe tangent of (c). Thus, as described in WO2013173928a1, for the traction surface, if the coefficient of friction between the inner race 12 and the inner planet 16 is greater than the tangent of this angle, the torque will produce a radial component sufficient to maintain traction between the inner planet 16 and the outer planet 18 as the torque increases, without requiring a large preload or any additional mechanism to increase the radial load. This is referred to herein as the "cam effect"; devices 10 exhibiting such a cam effect may also be referred to herein as "self-energizing" (e.g., self-energizing gearboxes).

With the gears or lobes 30, 32 on the planet gears 16, 18, the coefficient of friction between the surfaces of the planet gears 16, 18 is independent of creating a self-energizing effect to prevent the planet gears 16, 18 from rotationally slipping on each other. Instead, gears or lobes 30, 32 are used to synchronize the planets 16, 18 with each other and their respective races.

In the embodiment shown in fig. 7, the lobes 30, 32 cover substantially the entire radial surface of the planet wheels 16, 18, and the inner planet lobe 30 meshes with both the outer planet lobe 32 and the inner race 12 lobe, and the outer planet lobe 32 meshes with both the inner planet lobe 30 and the outer race 14 lobe. However, certain embodiments may have lobes on only a portion of the planet gears 16, 18. Further, other embodiments may provide: different portions of the planet wheels 16, 18 and thus possibly different lobes 30, 32 are in contact with the corresponding races than adjacent planet wheels. Different options for lobes, gears or traction surfaces are also possible for different contacts.

Gear tooth profile

Embodiments of the present device 10 incorporate gear contact between the two rows of planet gears 16, 18 and between the planet gears and the races. This gear contact allows for a larger cam angle and potentially higher torque transmission. One challenge to be solved by gear contact is that radial compression between gear components can result in non-conjugate motion, and high friction and cogging due to the wedging effect of the teeth of one planet acting as a wedge that is pressed between the receiving teeth of the meshing planet. This wedging effect results in a high mechanical gain of radial forces between the planets coplanar with the gear contact face, resulting in high friction and wear. Radial crowding of gears together also produces variable friction forces due to the variation in mechanical advantage during the different phases of gear tooth contact during rotation of the planet. This variable friction can lead to cogging and irregular wear.

The new gear tooth profile for the device provides a combination of rolling contact at traction coefficient and an involute gear tooth profile that provides the remainder of the torque transfer not provided by rolling contact.

Cylindrical rolling contact surfaces are used between the gear teeth and, if used with spur gears, will reduce the amount of gear contact (i.e., it will reduce the contact ratio). At a sufficiently high percentage of cylindrical rolling contact, a gear contact ratio of less than 1 will occur. Before this ratio, it was difficult or impossible to achieve a rolling contact ratio of greater than 1. The use of a helical tooth pattern as described herein may provide continuous rolling contact between gears, as well as continuous gear contact for smooth rolling contact and uninterrupted gear torque transmission. Helical teeth having helical directions at different axial portions of the planet wheel may form a herringbone tooth.

It should be noted that embodiments may use a cam angle and coefficient of friction that allows the rolling surface to transmit a high percentage of torque. In other applications, it may be preferable to use a cam angle and CF that does not result in a self-energizing effect. In this case, the gear teeth may provide a greater percentage of the total torque.

Gear with convex angle

The use of a relatively simple gear tooth profile in the form of a sine wave gear shows reasonable performance. This shape may be a pure sine wave or an approximate sine wave, such as a series of connected arcs forming a convex angle. For a high enough number of lobes, the tooth height is short enough to reduce sliding motion between gear teeth while providing sufficient surface area in the radial direction at the tips and roots of the lobes for smooth rolling contact. For example, the lobe height may be less than 1/20, 1/30, or 1/40 of the gear radius, such as the inner planet gears 16 or the outer planet gears 18. The use of a high helix angle provides consistent radial contact and consistent torque transmission surface area in the tangential direction. When such a lobed shape is used with the self-camming geometry of the present apparatus 10, the draft angle will determine how much torque transmission is provided by tangential contact and how much draft is provided via the tooth root in half rolling contact with the toe end.

Torque transmission

Embodiments of the device 10 provide rigid torque transmission even when constructed of plastic. The rotational stiffness potential of the embodiment of the device 10 is believed to be much higher than the potential of a conventional planetary gear train. This is because torque is transmitted from the inner gear 16 to the outer gear 18 along an almost straight line of the inner gear 16 and the outer gear 18. This linear torque transfer is shown in the simplified finite element analysis of FIG. 9. Arrows have been added to mark stress lines 110, which are shown in lighter shading in fig. 9.

Increasing the radial preload may increase stiffness but also increase rolling friction. Increased rolling friction is not always beneficial, but there are also situations where increased rolling friction may be beneficial. For example, in machining, it is desirable to prevent back-driving of the gearbox due to tool loads or vibrations. In other applications, such as applications requiring safety braking, a high preload may be used to render the gearbox non-back drivable at a certain back-drive torque. This reduces the cost, complexity and power consumption of, for example, the brake, which must be separated from the current.

Embodiments with input ring

In one example, the self-energizing portion of the device includes a stationary inner sun gear that meshes with a plurality of spaced-apart inner planets 16 (e.g., 17 equally spaced-apart inner planets 16) that in turn mesh with a corresponding number of spaced-apart outer planets 18 (e.g., 17 equally spaced-apart outer planets 18). The outer planet wheels 18 then mesh with the races of the outer ring. The input to this stage is the orbiting of the planet wheels 16, 18, and the output is the motion of the outer ring. The input stage drives the planet wheels 16, 18 at the self-excitation stage by using planet gears. This stage uses the sun gear as input, the planet wheel rotation as output, and the idler outer ring. In an exemplary embodiment, a 45 ° helix angle is used in the herringbone configuration of each of the gears, although other helix angles exist (whether provided in the herringbone configuration, continuous helical configuration, varying helix angle configuration, spur gear configuration, and/or the like).

The diameter and number of gear teeth used in the embodiment having a helix angle of 45 are the embodiments shown in table 1.

TABLE 1

	Diameter of	Number of teeth
			Sun of the sun	105.4	170
Inner planet wheel	19.85	32
			Outer planet wheel	12.40	20
Outer ring	158.10	255
			Input sun gear	124.89	102
Input planet wheel	20.81	17
			Idler ring	166.51	136

The traction and gear configuration of an embodiment of the device is described in published patent application No. wo 2013173928a1. Various embodiments as discussed herein include configurations that use gear inputs and gear tooth profiles and configurations that provide benefits including an efficient way to keep the planets equally spaced (circumferentially and axially), a way to minimize part count through asymmetric inputs, and a simplified way to increase reduction ratios through asymmetric sun ring inputs to the inner or outer planetary arrays.

Fig. 10 and 11 show front and rear isometric views, respectively, of an embodiment of a gearbox 40. It can be seen that there is an inner gear 42 and an outer gear 44 with chevron gear teeth 46 on the inner gear 42 and meshing chevron gear teeth 48 on the outer gear. In this embodiment, only the inner gear 42 extends to the rear of the gearbox. The outer race 50 drives the planetary gears and the internal gear 42 contacts inner races 52 and 54 of different sizes to drive one inner race 52 relative to the other inner race 54.

Axially outward sun gear input

The use of geared contact between the planet gears and the ring gear causes them to be equally circumferentially spaced. Furthermore, according to certain embodiments, the use of herringbone gears or lobe teeth prevents movement of the gears in the axial direction. This allows the gears to act as bearings for the relative positions of the inner fixed gear and the outer output gear in both the radial and axial (thrust bearing) directions.

Furthermore, this combination of herringbone gears or lobes provides the ability to drive the inner or outer planet wheels from only one side of the gearbox without significant twisting of the planet wheels about the radial axis of the device 10. By using gear 90 in fig. 12, the reduction ratio (or speed ratio if reversed) can be increased by using a sun gear 96 input, where gear 90 is fixed to either the outer planet gear 92 (as shown in this partial assembly schematic here) or the inner planet gear 94, which inner planet gear 94 has the same or a different pitch diameter than the planet gear to which it is fixed. This side drive also facilitates assembly as it allows the use of a single gear array rather than two or more arrays in helical alignment. These helical gears must be screwed together during assembly, so only one set of planets in the axial direction allows the inner fixed ring gear and/or the outer output gear to be manufactured in two pieces and screwed together from opposite axial ends of the device 10.

In an example of how a non-limiting exemplary embodiment of a device may be assembled, one way in which a device may be assembled when formed into a geometric shape according to the principles described herein is described below.

Assembly

Fig. 13 is an exploded view and fig. 14 is a cross-sectional view of the device of fig. 12. The features shown in fig. 12 are also present in fig. 13. Furthermore, there are: a pin 98 for temporary alignment of the outer planet; an outer output gear 100 having a bore 102 for receiving a pin; an input sun ring 104 coupled to the input sun gear 96, and a stationary sun ring 106 coupled to a stationary sun gear 108.

The assembly sequence is as follows and is indicated by the box with step numbers in fig. 14. In step 1, the outer planetary gear 92 is inserted into the outer output gear 100. Since they are the first components to be installed, there is sufficient space in the radial direction to place the outer planet gears 92 into the outer output gear 100 via radial motion, so despite the herringbone mesh, the outer output gear and the outer planet gears can each be constructed as a single-piece component. In step 1A, a pin 98 is inserted through a hole in the outer planet gear 92 and a hole 102 in the outer output gear 100. These pins are used for temporary alignment and can be removed when no longer needed. In step 2, the input sun ring 104 is inserted and meshed with the first half of the gear 90 fixed to the outer planetary gears 92. In step 3, the inner planet 94 is installed. They may also be inserted radially. In step 4, the stationary sun ring 106 is installed and meshed with portions of the inner planet gears 94. In step 5, the stationary sun gear 108 is inserted into and meshed with the other portions of the inner planet gears 94. The stationary sun ring 106 and the stationary sun gear 108 may be fixed together. In step 6, the input sun gear 96 is inserted and may be fixed to the input sun ring 104.

To operate this non-limiting exemplary embodiment, rotating the sun gear and holding the inner ring will cause the outer ring to spin at a reduced ratio of about 7: 1.

If the outer planet gears are driven by a sun gear, as shown here, and are input by a gear of larger diameter than the outer planet gears shown here, then it is preferred that the smallest dimension of the larger sun input ring gear be larger than the outer diameter of the fixed ring gear. In this way, assembly of the gearbox can be achieved, as the two halves of the inner fixed ring (4, 5) can be "screwed" together from either side of the inner row of planet wheels, after the inner sun ring member (2) has been screwed onto the larger sun input planet gears from the inner plane outwards as described above. Furthermore, if the outer diameter of the inner stationary ring is less than half of the sun input ring, the sun input ring gear assembly can be chevron contoured so it does not require bearings. The inner half of the sun input ring can be "screwed" into engagement with the sun input planet gears from the inside of the assembly before the yellow inner planet gears are inserted, and then after the inner (yellow) row of planet gears are inserted and the two halves of the inner fixed herringbone gears are assembled from both axial ends, the other half of the herringbone sun gears can be screwed to the first half of the sun gears from the outside.

This configuration will leave the assembly fully constrained in the axial direction, however this configuration does not necessarily balance the axial loads as shown on the planet because it is not a symmetrical herringbone arrangement.

To minimize the axial load on the planet, one of three design constraints can be implemented:

in embodiments where the helix angle of the gears is held constant along the axial length of each gear, the gear mesh between the inner planet gears and the stationary sun gear is of a different length relative to the gear mesh between the inner planet gears and the stationary sun ring; and the gear mesh between the outer planet gears and the input sun gear is of a different length than the gear mesh between the outer planet gears and the input sun ring. These lengths may be selected to reduce axial forces.

In embodiments where the axial length remains constant, the gear mesh between the inner planet gears and the stationary sun gear has a different helix angle relative to the gear mesh between the inner planet gears and the stationary sun ring; and the gear mesh between the outer planet gears and the input sun gear has a different helix angle to the gear mesh between the outer planet gears and the input sun ring. These lengths may be selected to reduce axial forces.

In embodiments where neither the helix angle nor the axial length remains constant, the gear mesh between the inner planet gears and the stationary sun gear will have a different length and helix angle relative to the gear mesh between the inner planet gears and the stationary sun ring; and the gear mesh between the outer planet gears and the input sun gear is of a different length and helix angle to the gear mesh between the outer planet gears and the input sun ring. These lengths may be selected to reduce axial forces.

Gear combination

While such a device 10 has many potential benefits, in this regard, the inventors have shown that no known gear combination provides perfect gear engagement. Each solution has a certain amount of error in one or more parameters, such as gear diameter, module, meshing contact, and/or the like.

Some gear solutions have errors that will be less than the manufacturing tolerances of the various gear components. However, the number of solutions with such low errors is limited and it is desirable to have additional solutions.

So far, more than 1 hundred million planet wheels and the combination of the number of planet wheels on the ring gear and the number of gear teeth have been tested, but no perfect solution exists. This requires the possibility of limiting the possibilities to a minimum of imperfections.

Constraints for selecting the available combinations include the following:

the difference in the diameters of the sun and outer rings is large enough that the reduction ratio between the inner fixed ring and the outer output ring is greater than 2: 1 (2 orbits of the planet wheels result in 1 or more revolutions of the output ring). The number of planets ranges from a minimum of 5 to a maximum of 30, although there are other solutions outside this planet range.

The gear tooth pitch is greater than 0.7mm (which allows for manufacture by common gear production methods including injection molding).

Given that the gear diameter can be scaled to a larger or smaller diameter as desired, an outer ring diameter of about 89.25mm is set constant. By this application. This diameter is selected to be a useful size in the robotic market.

Only imperfect solutions have been found. Imperfections in the gear combination manifest as imperfect alignment of the gear teeth or mismatches in the meshing gear module. Typically, the inner row of planets will mesh well with the inner fixed gear and the outer row of planets will mesh well with the outer output ring gear, but the inner planet gear teeth will be misaligned with the outer planet row gears. Some misalignment can be tolerated due to the consistency/flexibility of the material (and the resulting consistency/flexibility of the components being constructed), but the more misalignment, the lower the torque transmission capability of the gearbox, and the greater the friction due to interference between gears.

The use of more, smaller teeth increases the number of potential options, but pinion teeth make manufacturing and assembly more difficult, and in some cases may also reduce torque transmission.

Using fewer planets increases the manufacturability of the planets, but more planets allows for greater torque capacity, assuming that the load is shared between the planets and provides an additional solution.

The number of available combinations is surprisingly small, taking all these factors into account. An inaccuracy index is used to compare different options, the index indicating the degree of misalignment of the planet wheels to the planet wheel mesh for a given option.

The potentially usable configurations are limited to those solutions with root mean square error coefficients less than 0.0004 and are shown in the following table. Error coefficients higher than those shown are suitable for some applications. Furthermore, the illustrated configuration can be scaled geometrically while keeping the number of teeth constant.

The error coefficients reflected in the data shown in table 2 below account for angular and diameter errors. The ratios given assume that the input is the rotation of the input sun gear, the inner ring remains stationary, and the outer ring serves as the output.

TABLE 2

Selecting at least 1mm of gear/lobe teeth (which allows for manufacturing such as by 3D printing) and minimizing the error factor, the discovery analysis according to this algorithm yields only hundreds of positive options from hundreds of millions of possibilities for inspection

Other less desirable options are displayed.

The gear combination includes both in-phase and out-of-phase gears. The inclusion of out-of-phase gears significantly increases the number of solutions when compared to an in-phase only solution. Furthermore, in out-of-phase solutions, the error coefficients tend to be lower. Out-of-phase refers to a configuration in which, for a given rotational position of the output, one pinion gear meshes with one ring gear at a different phase of gear tooth meshing than the other pinion gear meshes with the same ring gear.

In certain embodiments, a higher error coefficient may be accommodated to provide a functional gearbox with components that move appropriately relative to each other by providing gear teeth on various gear surfaces that experience profile shifting. Using the concept of profile offset, gears can be designed with an adjusted center distance between two meshing gears, with an adjusted design that encompasses undercuts in gears with too few teeth, and/or with an adjusted amount of slippage in gear meshing. In this case, the same tool can be used to manufacture the gear, but its placement relative to the central axis of the gear is changed. This results in a slightly different tooth form as shown in fig. 15.

By utilizing profile shifting, a higher error threshold can be used to create a gearbox solution for a device as discussed herein while maintaining the functionality of the device, even with a combination of gears that could otherwise render the device inoperative.

Profile shifting is also used to optimize efficiency in gear meshing by adjusting the amount of slip that occurs in the gear mesh. By minimizing the specific slippage, each gear tooth will have a minimal amount of slippage in the mesh, thereby improving efficiency and minimizing potential problems of wear failure. Typically, this will shift the profile of one gear of a pair inwardly (-x) while shifting the mating gear profile outwardly (+ x). In most applications, the sum of these offsets tends to be very close to zero so that the system as a whole works well.

In the arrangement of the self-energizing gearbox provided according to the embodiments discussed herein, the sum of these offsets is related to the amount of error in the gearbox solution. However, the magnitude of the sum of the profile offsets of the gears within the design may be increased to accommodate the increased error factor while providing a functional self-energizing gearbox. The gear mesh between adjacent gears maintains its optimum point for a particular slip in a typical gearbox, taking into account the included offset. In the embodiments as discussed herein, there is significantly more gear mesh than a typical planetary gearbox of similar dimensions, meaning that once the error is accounted for in the profile offset, any additional offset in one gear will correspond to a complementary offset in every other gear. Thus, the gear mesh is not optimized individually for a specific slip, but as a whole. This has the added benefit of allowing profile shifting as errors in gear engagement are spread between multiple gear engagements.

In certain exemplary embodiments, the planet gears may be provided with a positive profile offset to effectively increase the pressure angle of each included gear tooth and reduce stress concentrations at the root of each tooth in order to extend the life of the planet gears.

Test board

Separate components were designed and 3D printed as stationary and input components fixed to the gearbox in order to test the output torque capability. FIG. 16 shows a torque testing apparatus for connecting a mass on a lever arm to a gearbox and measuring the torque required to lift the mass. As shown in fig. 16, a1 foot lever arm 112 is connected to the output outer ring to load the output of the gearbox, and the output torque is calculated as the mass (not shown) attached to attachment point 114 multiplied by the length of the arm. A wrench (not shown) is attached to the arm input 116 for transmitting torque through the device.

Idler ring

As shown in fig. 17, an idler ring 118 can be inserted around the larger diameter outer planet gear teeth on the larger gear wheel 90 to prevent separation between the planet gears and the input sun gear teeth when the gear is energized.

Symmetrical structure

To prevent the planet from bending, the self-energizing gears can be positioned on either side of the input, as shown in fig. 18 and 19. This configuration ensures that the planet wheels remain parallel to the central axis of the gearbox. The outer input ring 120 is surrounded on both sides by a stationary ring 122 and meshes with inner planet gears 124 to drive the inner planet gears 124. The inner and outer planet gears 124, 126 form a two-row planetary gear system to drive an output sun ring 128 relative to the stationary ring 122.

Input ring meshing at the diameter of the main planet wheels

FIG. 20 illustrates a cross-sectional isometric view of a non-limiting exemplary embodiment of a single-sided input self-energizing gearbox. An inner ring 130 (here a fixed ring) is in contact with an array of in-gear planet wheels 132. The outer ring 134 (here the output ring) is also in contact with an array of outer gear planets 136, and each of the outer gear planets 136 is in contact with two inner gear planets 132. Input torque is provided using the gear input ring 138. In the embodiment shown, the gear input ring 138 has a radially outward facing portion that is in contact with the outer planet gears. In this embodiment, the outer planet gears 136 have the same diameter in a first portion 140 that meshes with the inner planet gears 132 and a second portion 142 that meshes with the input ring 138. Both the first portion 140 and the second portion 142 engage the outer ring 134. Here, the first and second portions comprise respective ends of the planet wheels 136, but a symmetrical arrangement such as that shown in fig. 19 may also be used. The engagement of the outer planet with the outer ring gear along all of its length helps to maintain the alignment of the planet. In the embodiment shown, a single gear mesh covers both the first portion 140 and the second portion 142, but these portions may also have separate gear meshes. The embodiment shown has straight cut gears, but helical gears, as well as herringbone gears as described above, may also be used. Helical gears in which all of the helices on the gear surface of an embodiment are identical enable the gear components to be threaded into the assembly relative to one another. As discussed herein, if helical gears are used, the axial force is not generated in the same manner as a conventional planetary gearbox.

In certain embodiments, the gearbox may have a single-sided input and a single helical tooth pattern (no herringbone pattern is required). In this embodiment, the input drives the outer planets, and the planets cause differential motion of the inner and outer rings, one of which is fixed and the other of which is the output.

Helical gears typically require thrust bearings or opposing helix angles (herringbone patterns) to maintain axial positioning of the gears. However, these require space and weight. Embodiments that encompass axially floating helical gears as discussed herein have been found to exhibit axial positional stability during use. The inventors have found that a self-exciting gearbox configuration with a double row of planet gears without planet shafts creates a situation where the axial force on one gear mesh on the planet gears is cancelled (opposed) by the opposing helical interface on the other gear mesh on each planet gear. That is, the axial force on the outer planet from the inner planet cancels the axial force on the outer planet from the outer ring, and the axial force on the inner planet from the outer planet cancels the axial force on the inner planet from the inner ring. The result is that the axial force on the planet wheels is much lower than in the case of a planetary gearbox with a single row of planet wheels.

While the axial forces on the planets cancel, the axial forces on the input, inner and outer rings do not cancel and other elements (such as, for example, thrust bearings) may be used to carry the axial loads on these elements.

A significant advantage of a single angle helix is that the gearbox can be assembled. Herringbone patterns are very difficult, if not impossible, to assemble. A single helix angle allows the gears to slide axially together and the cancellation of the axial forces allows them to operate without a shaft or bearing.

When torque is applied to the input ring 138, there is a torsional load transmitted to the outer planet gears 136 in addition to the rotational torque transmitted to each of the planet gears about their single axis. Due to the self-energizing (or cam) effect between the inner ring 130 and the outer ring 134 through the two rows of planet gears, as the torque output of the device increases, the gears on the two rows of planet gears and the inner ring 130 and outer ring 134 are forced to engage more proportionally. At a particular length and a particular reduction ratio of the outer planet gears, the straightening effect of the self-energising effect of meshing the gears together on the outer planet gears will be greater than the twisting effect of the input from the input sun gear 138. The length of the longest planet may correspond to the total width of the device in the axial direction. Those skilled in the art can calculate this combination of width and reduction ratio to ensure that when torque is applied to the input gear 138, the engagement of the outer planet wheels 136 with the outer ring 134 straightens the outer planet wheels 136 due to the cam effect that the output torque transmitted from the inner ring 130 to the outer ring 134 causes the gears to be pushed into engagement rather than the separating force that would disengage them (which would allow them to twist). Due to the gear ratio of the gearbox, the input torque on the input gear 138 will be significantly lower than the torque transmitted through the planet wheels 136 and 132. At the 7: 1 ratio, the input torque is approximately 1/7 of the output torque. As a result, the dominant force in the outer planet wheels 136 will be the load due to the transfer of torque from the inner ring 130 to the outer ring 134. The radial load component from the cam effect ensures that the contacting gear teeth of the outer planet 136 are pressed radially into the corresponding gear teeth in the outer ring 134. This radial load results in a straightening effect that counteracts the twisting effect due to the input torque from the input gear 138. This effect is all the greater the pressure angle in the gear teeth or the greater the cam angle due to the resulting increase in radial load in the gear.

The larger the aspect ratio of pinion length to planet diameter, the less likely the planet will twist due to torque from the sun input. There are two reasons for this relationship. Generally, for a given gear box outer diameter and width, the larger the aspect ratio, the smaller the pinion diameter and, therefore, the higher the reduction ratio. The general trend is that the higher the reduction ratio, the greater the radial force on the pinion, which can be used to create deeper meshing between the pinion and the ring than the reduced torque force created by the input to the sun, because the reduction ratio is increased, which requires lower torque at the sun ring input, and therefore greater alignment effects. To this end, it is believed that planet wheel ratio ratios greater than 1: 1, 1.5: 1, 2: 1, 2.5: 1, 3: 1, 3.5: 1, 4: 1 are suitable for self-aligning the pinions when the gearbox is transmitting torque from the sun input to the output ring.

Furthermore, the high aspect ratio between the planet length and the planet diameter allows a low helix angle of the gear teeth on the planet while still achieving a high contact ratio (gear mesh overlap). A lower helix angle further reduces the axial force.

The aspect ratio can be greater than 2: 1, and can be 3: 1 or higher, 4: 1 or higher, 5: 1 or higher, 6: 1 or higher, 7: 1 or higher, 8: 1 or higher, 9: 1 or higher, or 10: 1 or higher. In one embodiment, the planet comprises an aspect ratio of at least 4: 1.

In a typical planetary gearbox with a single row of planets, the high aspect ratio will be decreasingly beneficial as the gears will twist and lose torque transmission capability. Longer gears in a typical gearbox are subject to a "knock down factor" because the planet carrier, for example, will twist and bias the torque transfer to one end of the planet. In contrast, the self-exciting gearbox provided according to embodiments herein transmits torque purely radially, making the length of the gears relatively unpractical and enabling longer planet lengths without knock-down problems.

The fact that there is no twisting or twisting of the gears in this gearbox enables the use of extra long planets without significantly reducing the expected torque output. FIG. 21 illustrates an exemplary gearbox configuration with extended outer planetary gear length and including dual motor inputs.

The embodiment shown in fig. 21-22 encompasses sun input at both ends of longer planets. This allows two motors to drive one gearbox symmetrically. The motor has an outer rotor design and the stator is fixed to an ultra wide inner ring. Specifically, as shown in fig. 21, the gearbox includes a motor stator 301 defining a gearbox interior. A motor rotor 302 surrounds the motor stator 301 and is fixedly secured to an input ring 303 which drives outer planet wheels 304. The outer planet wheels 304 in turn drive inner planet wheels 305 that engage and move relative to a fixed inner ring 306. The outer planet 304 additionally drives an outer ring output 307.

As mentioned above, the gearbox with the included motor may also be formed in a single sided configuration, e.g., with one or more motors located within the inner diameter of the small inner ring gear.

Other embodiments include only one sun ring at one end. In this configuration, there are two sun rings driven by two separate motors. The motor stator is fixed to an inner ring, which in this configuration is fixed. The motor rotor is fixed to the input sun ring.

In another embodiment shown in fig. 23-24, there is an outboard motor, where the stator 310 defines the fixed outer diameter of the device, and the motor rotor 311 is inboard of the stator 310 and is embodied as the outer ring of the device. In the illustrated embodiment of fig. 23-24, the device includes two outer rings on opposite axial ends of the device, with each outer ring having an integrated motor rotor 311. The outer ring (including the motor rotor 311) drives outer planet wheels 312 which orbit and drive an inner output ring 314. As particularly shown in fig. 24, it should be understood that in certain embodiments, the outer planetary wheels 312 may drive multiple output rings 314 or a single output ring 314. This embodiment provides an increased speed configuration. The outer planet wheels 312 are additionally engaged with and rotate with inner planet wheels 313 which operate together with the outer planet wheels 312 to provide the self-energising function of the gearbox. The inner planet 313 orbits around a fixed inner ring 315.

Both the inboard and outboard motor configurations may also encompass an inner rotor at both axial ends of the device rather than an outer rotor that surrounds the device and forms the outer diameter of the device.

Fig. 25-28 show an alternative embodiment in which the input ring 322 drives the inner planets 323. In a reducer such as the embodiment shown in fig. 25-28, the inner ring 324 or the outer ring 320 may be the output. Further, as shown in fig. 25-28, various embodiments may include a single input ring 321 or multiple input rings 321 (e.g., two input rings 321 each positioned on opposite axial ends of the device).

In the illustrated embodiment of fig. 25-28, the stationary output ring 320 (which may be embodied as a motor stator) defines an outer diameter of the device. One or more input rings 321 rotate relative to the stationary output ring 320 and drive the inner planets 323. The inner planet 323 rotates relative to and with the outer planet 322, providing the self-energizing function of the device. Those outer planet gears 322 rotate relative to the stationary output ring 320. The inner planet 323 drives the inner output ring 324.

In another embodiment, specifically shown in fig. 26, there is only a single input ring 321, which provides an output on one side. The side without the input ring is shown in isometric view in fig. 26, and the side with the input ring is shown in fig. 27. Fig. 28 shows an exemplary embodiment configured for use with two input rings 321, however the input rings 321 are removed to show the configuration of the planet wheels 322, 323 of the device.

Any of the inner ring 324, the outer ring 320, and the intermediate ring, such as the input ring 321 shown in fig. 25-28, may be an input or an output. The remaining rings, which are neither input nor output rings, may be fixed.

In embodiments with many small planets, the relative motion of the inner ring 324 and the outer ring 320 is much less than the relative motion of the intermediate ring (e.g., the input ring 321) with respect to the inner ring 324 and the outer ring 320. Thus, while the intermediate ring may be fixed with one of the inner and outer rings being the input and the other being the output, this configuration will result in a small (close to 1) rate of change of speed with faster internal moving parts than the input and output, and is generally not preferred. In the case of the intermediate ring as an input or an output, the device will be a speed increaser if the intermediate ring is an output and a speed decreaser if the intermediate ring is an input.

In the case of a plurality of intermediate rings, it is also possible to have one intermediate ring as input and one intermediate ring as output. Of the inner and outer rings, one may be fixed and the other may be free spinning. With this arrangement, a gear ratio different from 1 can be obtained if one of the intermediate rings is connected to the inner planet wheels and the other is connected to the outer planet wheels. This gear ratio can be varied by varying the size of the planets. It is noted that further variations can be obtained by allowing the planet wheels to change size along their axial length so that the intermediate ring contacts the planet wheels with a different diameter.

In addition, both the outer and inner rings may be movable and the gearbox will provide the difference between them as an output, the gear ratio being dependent on the movement of the inner and outer rings.

Another possibility is to use a self-energizing gearbox as the tool output. In particular, if the motor is attached to the sun gear input, and if the inner ring is attached to a shaft that rotates clockwise in the outer output ring, which is attached to a shaft that must rotate counterclockwise, a reverse differential joint may be formed.

It will be appreciated that the same principle will apply if in one embodiment the input ring meshes with the outer side of the inner planet, for example having a first and second portion meshing with the outer planet and the input ring respectively, both portions meshing with the inner ring.

Such designs may utilize straight cut gear teeth, helical gear teeth, lobes, friction surfaces, or other profiles.

The straight cut gear tooth design described above may be advantageous for assembly, with a significantly lower part count when compared to the herringbone design, and allows the gear to be inserted into the assembly from one side.

The straight cut gear tooth design does not have the axial constraint on the planet as the herringbone design does, so some mechanism is required to axially constrain the planet. This design uses a shield (nonce) (not shown in fig. 20) on either axial end to prevent the planets from floating axially out of the gearbox. By crowning the axial ends of the planets and adding lubricant, losses due to friction are minimized.

Bearings and shafts may be used in some configurations of the device to axially position the planet gears. For some configurations, especially smaller devices, it is preferable to eliminate any bearings or shafts in the planets.

In this case, an axial positioning strategy is required, whether the gears are helical or straight cut. Fig. 29-36 illustrate one possible configuration for providing an axial positioning strategy for a gear via a device. The embodiment of fig. 29-36 incorporates the relative curvature between the ends of the planets 332, 333 and the shields (e.g., inner shields 337, 338 and/or outer shields 339, 340) at the ends of one or more ring gears (e.g., outer ring 330, inner ring 334, input ring 331). The ends of the planets 332, 333 have a spherical or semi-spherical cross-section on their axial ends, and the shields (e.g., inner shields 337, 338 and outer shields 339, 340) have corresponding semi-spherical shapes. The axial ends of the planets 332, 333 or the shrouds (inner shrouds 337, 338 and/or outer shrouds 339, 340) may provide a tapered cross-section, however curved profiles on the axial ends of the planets and the shrouds may provide the desired function. This configuration provides a circular line of contact on the planet gears 332, 333 as their axial ends contact the shrouds (inner shrouds 337, 338 and/or outer shrouds 339, 340), which approximates the pitch diameter of the gear teeth. This configuration prevents high sliding speeds and wear when axial forces are encountered, such as when the device is positioned on an end (e.g., such that the central axis of the device is positioned vertically) and gravity is pulling the planets 332, 333 downward toward one of the shields (e.g., the inner and outer shields 337, 339 or the inner and outer shields 338, 340 on the input side). In some configurations, the planets 332, 333 are hollow, and thus this circle of contact on the planets 332, 333 can be between the inner diameter of the through-holes of the planets 332, 333 and the roots of the teeth of the planets 332, 333.

The embodiment shown here uses straight cut gears, however in alternative embodiments the guards 337 to 340 may operate with spiral cut gears.

The illustrated embodiment of fig. 29-36 encompasses a device enclosed within a housing comprising the outer surfaces of the input-side housing portion 343, the output-side housing portion 342, and the outer housing 344, as well as the stationary outer ring 330. Fig. 29 shows in detail an exploded view of the device shown in fig. 30. Fig. 31 shows a partial cross-sectional view of the interior of the device, and fig. 32 shows a cross-sectional view with the housing components removed. Fig. 33 shows a partially exploded view of the gear component (shown assembled in fig. 34 and in cross-section in fig. 35). The arrangement of fig. 29 to 36 comprises a sun input ring 331 having an input connector 335 attached thereto. The sun input ring 331 is centrally located within the device and has an outer gear surface. The sun input ring 331 drives outer planet wheels 332 which orbit around the sun input ring 331 and drive inner planet wheels 333. The outer planets 332 engage and rotate relative to the fixed outer ring 330. In addition, the inner planet gears 333 orbit around and drive an inner ring 334, the inner ring 334 providing an output for the device. The inner ring 334 has an output 336 connected thereto which rotates relative to the housing via the bearing formation (encompassing the bearing race 341). The output of the illustrated embodiment is also connected to an output plate 345 that, together with the outer housing 344, constrains the movement of the bearing race 341. As particularly shown in the cross-sectional view, the device additionally comprises: inner shields 337, 338 configured to axially constrain movement of the inner planet 333; and outer shrouds 339, 340 configured to axially constrain the motion of the outer planet 332.

Further, as shown in the figureThe arrangement has planet gears arranged in two rows, in this embodiment the outer planet gears 332 are axially longer than the inner planet gears 333. An inner shield 338 contacting the inner planet 333 may be fixed to the inner ring 334 and an outer shield 340 contacting the outer planet 332 may be fixed to the outer ring 330. In the exemplified embodiment, the protective caps are provided at both axial ends of the device. In the illustrated embodiment, where the planets 332, 333 extend to different axial locations on the input axial end, the inner 337 and outer 339 shrouds on the input axial side may be at different axial locations to contact planets in the respective row of planets.

The shields 337 to 340 and the planet wheels 332, 333 may have curved surfaces that contact each other. The curvature on the axial ends of the planet wheels 332, 333 contact the curvature on the shields 337 to 340, so that the contact circles on the ends of the planet wheels 332, 333 are located outside the planet wheel through holes and inside the roots of the planet gear teeth. Such embodiments provide contact between the planet wheels 332, 333 and shields 337-340 proximate the pitch diameter of the planet wheels 332, 333 proximate the location where the planet wheels 332, 333 contact the shields 337-340 relative to their fixed or stationary elements, thus minimizing sliding speed. Here, the shrouds 337 to 340 are fixed to the inner ring 334 and the outer ring 330, and the planets 332, 333 contact the inner ring 334 and the outer ring 330.

Load sharing

In a typical planetary gearbox, it is expected that a number of planets greater than 3 will not share the load evenly without very precise tolerances. The self-exciting gearbox has more than 3 planetary wheel pairs and must have some mechanism to ensure that there is load sharing to make best use of the strength of the other planetary wheels. There are several mechanisms that such gearboxes can utilize, and several non-limiting mechanisms described herein take advantage of the unusual load distribution of such gearboxes.

One non-limiting mechanism for load sharing in a self-energizing gearbox is the radial compliance of the planet, inner or outer ring, or any combination thereof. Due to the cam effect of the planet wheels, there is a strong radial load component in the gearbox, which is transmitted between the outer ring, the planet wheels and the inner ring. If any of these gears have radial compliance, the gears will be able to compress under the radial load of the cam effect. Due to this flexibility, the tolerance band of a large number of planets can be occupied, allowing the planets to share the load. This radial flexibility may come from a number of features or parameters including, but not limited to, thin walls, lower material stiffness, or gear tooth root extension, such as radial slots between teeth.

To ensure that there is load sharing between a large number of planets, the previous document relates to the need to allow some degree of deflection of the planets of the gearbox. This deflection may be due to geometry, such as undercuts in thin-walled gears or gear teeth, or may be due to material stiffness in one or more gears.

In certain embodiments, the overall size of the planets of various embodiments, and the ability to provide relatively thin walls (and hollow interiors) for such planets to achieve radial flexibility of the planets, provides sufficient planet flexibility to achieve load sharing. The planets may be made of a rigid material (such as steel), but have thin walls (and a hollow interior) and deflect under load so that the remaining planets may contact the associated gear and carry the load. Alternatively or in addition, the planets are made of a less rigid material and have a solid construction, but still deflect sufficiently to allow the other planets to begin sharing the load. It has been found that relatively small differences in the design of the planet wheels can create significant differences in the load share shown in the gearbox.

It should be appreciated that the design and manufacture of the planets may be configured to withstand high stresses and/or high cycle counts. In some device designs, the planets will maintain the highest stress concentration for all components of the device. Thus, in some implementations, high strength and/or long life materials may be used for the planets.

In order to maintain high strength in the planet wheels, load sharing may instead be achieved by reducing the stiffness of the other gears (outer ring, inner ring and/or sun gear), wherein the strength can be reduced to some extent without affecting the critical safety margin of the gearbox. It has been shown that load sharing can be achieved by making the planet gears from a rigid material (such as steel) and making the remaining gears from a less rigid material (such as carbon fibre filled PEEK).

Interestingly, the stiffness reduction required for this approach is significantly higher than that required to change only the material of the planet. In one simulation, the planet has 1/2 stiffness of the remaining gears and is shown to be able to adequately share the load. To achieve the same amount of load sharing in a configuration with fully stiff planets, the remaining gears must have a planet stiffness of about 1/7.

Regardless of the load sharing mechanism, the higher the radial (cam) load, the more similar the planet loads due to the greater load sharing effect. Higher radial loads are accompanied by higher pressure angles of the gear tooth geometry and higher cam angles of the planetary contacts.

Another load sharing mechanism comes from the 2-stage planetary gear structure of the gearbox. The unloaded planet-planet mesh between the inner planet and the outer planet acts to stabilise the loaded planet-planet mesh when the planet cams move onto each other. Thus, it is believed that there will be a small amount of shift in the planet position before a sufficiently high radial load is generated to "lock" into place. This effect is expected to increase load sharing between the planets and has a stronger effect at lower pressure angles.

The distribution of stresses on the self-energizing gearbox under load causes radial loads on the planet and gear members. This radial load may further deform one or more of these components and allow the planet to effectively share the load by making the self-exciting component more easily deformable. This can be achieved by reducing the overall stiffness of the self-exciting components (i.e. the outer ring, the planet and the inner ring). Three different methods may be implemented to achieve this type of stiffness variation (fig. 36A-36C). The first method utilizes changes in material stiffness to reduce the overall stiffness of these components; this means that the component will deform more under the same radial load and become susceptible to deformation under the same tangential load to which the gear teeth are subjected. The deformation caused by radial and tangential loads will contribute to a more efficient load sharing and an overall stiffer gearbox. The degree to which the stiffness is sufficiently low will depend on the gear tolerances. Fig. 36A shows an exemplary portion of a nominal thickness gear 150, which may be formed from a lower stiffness material. The second method uses geometric methods (e.g., thin walls) to change the overall stiffness of these components. This will make the component less stiff and more easily deformable under a certain radial load. Fig. 36B shows an exemplary portion of the thin-walled gear 152. The third method uses another geometry method in which the wall thickness is maintained at nominal dimensions, but the tooth geometry is modified to have radial slots on the root. In this approach, both radial and tangential loads have an effect on gear compliance, which allows for more efficient load sharing. Fig. 36C shows an exemplary portion of a nominal thickness gear 154 having a radial slot 156 on the root.

The disclosed design may eliminate the need for a planet carrier and bearings, as the input is provided by the input ring, the circumferential positioning is provided by the gears, and the axial positioning may be provided by, for example, a shield, tapered planet gears, or portions with different angle gears.

By eliminating the need for a planet carrier and bearings, tolerance stack-up of these positioning elements is eliminated. This allows more than three planet gears to mesh more consistently with the ring gear.

The eliminated tolerance stack-up element includes the position of the planet carrier pin. The concentricity of the planet carrier, the runout of the bearing, and the eccentricity of the bearing hole in each planet with the pitch circle of the gear.

In addition to eliminating these tolerance stack-up factors, radial flexibility can be introduced into the design in a number of different ways. The effect of introducing radial flexibility is to reduce the variation in load between the planets due to the variation in planet size.

In addition, because the planet carrier is eliminated, for example, the planet can be hollow and therefore radially flexible.

Two-stage gearbox

The gearbox as described above can be made as a two-stage gearbox as shown in figures 37 to 39. FIG. 37 is an isometric cutaway view of an exemplary two-stage gearbox 160. As shown in fig. 37, the outer housing 162 acts as a common outer stationary gear in two stages. The input ring 164 has an outer surface 166 that meshes with a first stage external gear 168. The first stage internal gear 170 meshes with the first stage inner ring 172 to drive the inner ring 172 relative to the outer shell 162. The first stage inner ring is connected to a second stage input gear 174 and may be integrally formed with the second stage input gear 174, the second stage input gear 174 having an outer surface 176 that meshes with a second stage outer gear 178. The second stage annulus gear 180 meshes with the inner output gear 182 to drive the inner output gear 182 relative to the outer housing 162, the differential motion providing the two stage gearbox output.

FIG. 38 illustrates an actuator using the two-stage gearbox shown in FIG. 37. In addition to the components shown in FIG. 37, FIG. 38 shows a flange 184 connected to the input ring 164 and an inner housing member 163 connected to the outer housing 162. An electric motor rotor and stator, not shown, may be connected to the flange 184 and the inner housing 163 to drive the flange 184 relative to the inner housing member 163 to drive the two-stage gearbox. Also shown in fig. 38 is an output cover 186 connected to the inner output gear 182 and a stationary outer cover 188 connected to the outer housing 162. Fig. 39 shows a side cross-sectional view of the embodiment of fig. 38.

If the outer ring gear of the first stage has the same pitch circle diameter and number of teeth as the other outer ring gear of the second stage and is one body, the inner ring gear of the first stage is connected to the input gear of the second stage and the inner ring gear of the second stage becomes the output of the second stage.

If the inner ring gear is shared by two stages, the outer ring gear of the first stage is linked to the input gear of the second stage, and the outer ring gear of the second stage becomes the output of the device. More than two stages can be connected in this way.

Tapered embodiments

Another exemplary embodiment of a single-sided self-energizing gearbox is a tapered design as shown in fig. 40-43. In this design, the spur gear teeth of the more basic single sided gearbox design are replaced by tapered gears, the gear contact remaining the same as described above, but being tapered.

By tapering the gears, the planet becomes axially constrained and backlash can be reduced or eliminated by adjusting the shims to the position shown in fig. 25. Otherwise, the gearbox would work in the same way as the non-tapered version.

Tapered gear profiles are currently difficult to manufacture by conventional gear manufacturing methods such as hobbing or skiving. Thus, it would be possible to use another method such as, but not limited to, injection molding, surface milling, powder metallurgy, or gear rolling. The number of parts may also increase due to manufacturing limitations of these tapers.

Tapered or non-tapered tooth profiles may use straight or helical gears or lobes. The use of a helix angle on a tapered gear may be beneficial due to manufacturing methods or to optimize strength or noise.

Fig. 40 shows a schematic cross section of a tapered helical self-energizing gearbox, showing how the gear components are separated due to manufacturing and assembly considerations, and where shims may be inserted. Note that this is not a true cross-section, as typically the inner and outer gears do not mesh with the inner and outer races at the same circumferential location. The outer race 200 in this embodiment is divided into a first part 202 that contacts the outer gear 206 at an axial position corresponding to the inner gear 208, and a second part 204 that contacts the outer gear 206 at an axial position corresponding to the input gear 210. Inner race 212 is also shown as being divided into parts 214 and 216. An outer shim 218 is shown between the parts 202 and 204 of the outer race 200 and an inner shim 220 is shown between the parts 214 and 216 of the inner race.

If injection molding is chosen as the manufacturing method, the longer (outer) gear may also have a split (not shown) at its neck 222 to facilitate manufacturing using injection molding.

Fig. 41 shows an isometric exploded view of a gearbox as schematically shown in fig. 40 with the further variation that the first part 202 of the outer race is here shown divided into two further parts 202A and 202B.

FIG. 42 is a side cross-sectional view of the gearbox of FIG. 41 with the outer planetary gear removed. FIG. 43 is an isometric view of the gearbox of FIG. 41.

The tapered gears may be used for spur or helical gears, including herringbone gears. In addition to providing some axial positioning, the taper also allows for backlash adjustment using shims. The chevron teeth allow for more precise axial positive positioning of the planet and ring gears. Where used together, all benefits are achieved, but some applications will benefit from one of them.

As shown, for example, in fig. 20, unilateral (asymmetric) input is possible without chevron or tapered teeth due to self-excitation effects that cause the teeth to engage and thus eliminate distortion of the gear axis.

In the claims, the word "comprising" is used in its inclusive sense and does not exclude the presence of other elements. The indefinite articles "a" and "an" preceding a feature of a claim do not exclude the presence of more than one of the feature. Each of the various features described herein may be used in one or more embodiments and, as described only herein, should not be construed as essential to all embodiments defined by the claims.

Conclusion

Many modifications and other embodiments will come to mind to one skilled in the art to which this disclosure pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosure is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.