阅读说明：本技术 波动齿轮装置及波动发生器 (Wave gear device and wave generator ) 是由 金山尚树 于 2017-04-28 设计创作，主要内容包括：波动齿轮装置(1)的波动发生器(4)将外齿齿轮(3)挠曲成沿椭圆状闭合曲线(C0)的形状,在长轴(Lmax)两端的2处,形成外齿齿轮(3)的与内齿齿轮(2)啮合的啮合部分(5a、5b),使啮合部分(5a、5b)沿圆周方向进行移动。椭圆状闭合曲线(C0)呈非点对称的形状。例如,椭圆状闭合曲线(C0)是不以短轴(Lmin)为对称轴而仅以长轴(Lmax)为对称轴的线对称的闭合曲线。在非点对称的状态下在长轴方向的两端形成啮合部分(5a、5b)。通过在长轴的2处啮合部分选择不同的形状,能够减少由伴随波动发生器(4)的旋转产生的二次角度传递误差成分所导致的振动。(A wave generator (4) of a wave gear device (1) bends an external gear (3) into a shape along an elliptical closed curve (C0), forms meshing parts (5a, 5b) of the external gear (3) that mesh with an internal gear (2) at 2 positions on both ends of a major axis (Lmax), and moves the meshing parts (5a, 5b) in the circumferential direction. The elliptical closed curve (C0) is non-point symmetrical in shape. For example, the elliptical closed curve (C0) is a line-symmetric closed curve that does not have the minor axis (Lmin) as the axis of symmetry but has only the major axis (Lmax) as the axis of symmetry. Engaging portions (5a, 5b) are formed at both ends in the longitudinal direction in a non-point-symmetric state. By selecting different shapes of the meshing parts at the position 2 of the major axis, the vibration caused by the secondary angle transmission error component generated along with the rotation of the wave generator (4) can be reduced.)

1. A wave gear device having:

A rigid gear;

A flexible gear engageable with the rigid gear; and

A wave generator that bends the flexible gear into a non-circular shape to form an engagement portion that engages with the rigid gear, and moves the engagement portion in a circumferential direction of the rigid gear,

Wherein the content of the first and second substances,

The wave generator flexes the flex gear into: engaging portions are formed at 2 or more places at equal angular intervals in the circumferential direction of the flexible gear,

The shapes of the engaging portions are different from each other for at least 2 positions.

2. the wave gear device according to claim 1,

The rigid gear is an internal gear, and the flexible gear is an external gear.

3. the wave gear device according to claim 2,

the wave generator flexes the external gear into a shape along an elliptic closed curve so that the meshing portion is formed at 2,

The ellipse-shaped closed curve is a closed curve which is not point-symmetrical.

4. The wave gear device according to claim 3,

The elliptical closed curve is a line-symmetric closed curve that does not have the minor axis of the elliptical closed curve as the axis of symmetry but has only the major axis of the elliptical closed curve as the axis of symmetry.

5. the wave gear device according to claim 2,

The wave generator flexes the external gear into a shape along a non-circular closed curve so that the meshing portion is formed at 3,

On the closed curve, the shapes of 3 curved line portions defining the respective engaging portions are different from each other.

6. the wave gear device according to claim 2,

the wave generator has a rigid wave plug and a wave bearing mounted between a plug outer peripheral surface of the wave plug and an inner peripheral surface of the external gear,

The non-circular deflection shape of the external gear is defined by the contour shape of the plug outer peripheral surface.

7. The wave gear device according to claim 2,

The wave generator includes a plurality of rollers that come into contact with an inner peripheral surface of the external gear to deflect the external gear into a non-circular shape.

8. A wave generator of a wave gear device, wherein an external gear is bent into a shape along an elliptical closed curve, meshing parts of the external gear which mesh with an internal gear are formed at 2 positions on both ends of a major axis of the elliptical closed curve, and the meshing parts are moved in a circumferential direction of the internal gear,

Wherein the content of the first and second substances,

the wave generator has:

A rigid wave plug; and

a wave bearing mounted between a plug outer peripheral surface of the wave plug and an inner peripheral surface of the external gear,

The contour shape of the plug outer peripheral surface is defined based on the elliptical closed curve,

The elliptical closed curve is a line-symmetric closed curve that does not have the minor axis of the elliptical closed curve as the axis of symmetry but has only the major axis as the axis of symmetry.

9. A wave generator of a wave gear device, wherein an external gear is bent into a shape along an elliptical closed curve, meshing parts of the external gear which mesh with an internal gear are formed at 2 positions on both ends of a major axis of the elliptical closed curve, and the meshing parts are moved in a circumferential direction of the internal gear,

Wherein the content of the first and second substances,

The wave generator has:

A plurality of rollers that contact an inner peripheral surface of the external gear and flex the external gear into a shape that follows the elliptical closed curve; and

a roller holding member that holds the plurality of rollers at different positions along the elliptical closed curve so that the plurality of rollers are inscribed in the elliptical closed curve,

The elliptical closed curve is a line-symmetric closed curve that does not have the minor axis of the elliptical closed curve as the axis of symmetry but has only the major axis as the axis of symmetry.

Technical Field

The present invention relates to a wave gear device, and more particularly to a wave generator that causes an external gear to flex into a non-circular shape and mesh with an internal gear at 2 or more locations.

background

In the wave gear device, a flexible externally toothed gear is flexed into a non-circular shape by a wave generator so as to mesh with the internally toothed gear at 2 or more places at equal angular intervals in the circumferential direction. For example, the external gear is bent into an elliptical shape, and meshing portions with the internal gear are formed at 2 positions on both ends of the major axis in the elliptical shape. In the case where the external gear is flexed into a three-lobed shape (3-lobed shape), meshing portions with the internal gear are formed at 3 at intervals of 120 ° in the circumferential direction.

If the wave generator is rotated by a motor or the like in this state, the meshing portion of the two gears moves in the circumferential direction of the internal gear. For each revolution of the meshing parts of the two gears, a relative rotation occurs between the two gears by the difference in their numbers of teeth. If one gear is fixed so as not to rotate, the decelerated rotation is obtained from the other gear. The difference in the number of teeth of the two gears is set to an integral multiple of the number of meshing portions.

in the external-tooth gear that is deflected into a non-circular shape by the wave generator, the shapes of the respective meshing portions are the same. For example, when the external gear is flexed into an ellipsoidal shape and meshed with the internal gear at 2, the external gear is flexed into a point-symmetric ellipsoidal shape with its center as a symmetric point. The shape of the meshing portions of the external gear formed at both ends of the long shaft is the same. In the case of meshing the external gear with the internal gear at 3, the external gear is flexed into a 3-fold symmetrical shape in which the shape becomes uniform every 120 ° rotation around the center thereof. The shapes of the 3-place meshing portions in the external gear are the same.

Patent documents 1 and 2 propose wave gear devices in which an external gear is deformed into an elliptical shape by a wave generator, and the external gear and the internal gear are meshed at 2 positions. Patent document 1 describes that an oval curve, a hybrid arc, a 4-force shape, and the like composed of a cosine component are used as a contour shape of a wave plug that defines a deflection shape of an external gear. In patent document 2, an elliptical shape of a wavy plug expressed by a tangential polar coordinate expression having a fourier expansion term of 4 terms or more is proposed.

Patent document

patent document 1: japanese patent No. 4067037

Patent document 2: japanese patent No. 2916012

Disclosure of Invention

Here, since the external gear flexed into an ellipsoidal shape is meshed with the internal gear at 2 positions at both ends of the major axis thereof, the major axis (meshed portion) passes 2 times from the same position every 1 rotation of the wave generator. Each portion in the circumferential direction of the externally toothed gear performs a wave motion in which the portion is repeatedly flexed at a constant amplitude in the radial direction. The wave motion is 2 cycles of vibration per 1 revolution of the wave generator. Therefore, in the wave gear device in which the external gear is flexed into an ellipsoidal shape, the angular transmission error generated by the wave gear device includes a vibration component of 2 cycles when the wave generator rotates for 1 cycle, and the secondary vibration component is larger than the vibration components of other times.

Likewise, since the external gear flexed into a trefoil shape is meshed with the internal gear at 3 angular intervals of 120 °, the meshing portion passes 3 times from the same position every 1 revolution of the wave generator. Each portion in the circumferential direction of the externally toothed gear performs a wave motion in which the portion is repeatedly flexed at a constant amplitude in the radial direction. The wave motion is a 3 cycle vibration per 1 revolution of the wave generator. In this case, the angular transmission error generated by the wave gear device includes a vibration component of 3 cycles when the wave generator rotates 1 cycle, and the third vibration component is larger than the vibration components of the other times.

The angle transmission error of the wave gear device is caused by a machining error of the tooth portions of both gears, an assembly error such as an eccentricity or an inclination of the wave generator and both gears, and the like. The secondary or tertiary vibration component causes resonance of the device to which the wave gear device is attached, and causes a positioning failure of a drive system such as a conveyance system. In applications where a highly accurate motion trajectory such as a robot arm is required, there are cases where driving with maintaining accuracy satisfying a required level cannot be achieved due to such vibration components.

such a problem also occurs in a wave gear device having a rigid external gear and a flexible internal gear, and having a structure in which the internal gear is bent into a non-circular shape and partially meshes with the external gear.

the present invention aims to provide a wave gear device and a wave generator capable of reducing vibration caused by an angle transmission error component generated in a period corresponding to the number of positions of an engagement portion per 1 rotation of an input rotation.

In order to solve the above problem, a wave gear device according to the present invention includes: a rigid gear; a flexible gear engageable with the rigid gear; and a wave generator which bends the flexible gear into a non-circular shape to form an engagement portion which engages with the rigid gear, and moves the engagement portion in a circumferential direction of the rigid gear. The wave generator flexes the flex gear as: in the circumferential direction of the flexible gear, engaging portions that engage with the rigid gear are formed at 2 or more places at equal angular intervals. In addition, the shapes of at least 2 engaging portions are different from each other.

Each meshing portion of the flexible gear, which is flexed into a non-circular shape, passes through the same position in the circumferential direction of the rigid gear for every 1 rotation of the input rotation. The meshing state with the rigid gear is also different between the meshing parts having different shapes. In the case where one engaging portion passes and the case where the other engaging portion passes, the engaging state is different, and therefore the manner of occurrence (timing, magnitude) of the angle transfer error is also different. As a result, it is possible to reduce the vibration caused by the angular transmission error component generated in a cycle corresponding to the number of positions of the engagement portion per 1 rotation of the input.

For example, a wave gear device has: a rigid internally toothed gear; a flexible external gear engageable with the internal gear; and a wave generator that flexes the external gear into a non-circular shape so that a meshing portion where the external gear meshes with the internal gear is formed at 2 or more positions at equal angular intervals in a circumferential direction of the external gear, the meshing portion being moved in a circumferential direction of the internal gear.

in the case where the external gear is flexed into a shape along an elliptical closed curve by the wave generator so that meshing portions of different shapes are formed at 2, the elliptical closed curve may be made to be a closed curve that is not point-symmetrical. For example, the elliptical closed curve may be a closed curve that is not symmetrical about the minor axis of the elliptical closed curve but is symmetrical about only the major axis.

The external gear is sometimes flexed into a shape along a non-circular closed curve by the wave generator so that a meshing portion is formed at 3. In this case, for example, on a closed curve defining the deflection shape of the external gear, 3 curved portions defining the respective meshing portions are different from each other.

As the wave generator, a wave generator having a rigid wave plug and a wave bearing installed between a plug outer peripheral surface of the wave plug and an inner peripheral surface of the externally toothed gear may be used. In this case, the non-circular deflection shape of the external gear is defined by the contour shape of the plug outer peripheral surface. Further, as the wave generator, a wave generator having a plurality of rollers which come into contact with the inner peripheral surface of the external gear to bend the external gear into a non-circular shape may be used.

The present invention also relates to a wave generator for a wave gear device, which bends an external gear into a shape along an elliptical closed curve, forms meshing portions of the external gear that mesh with an internal gear at 2 positions on both ends of a major axis of the elliptical closed curve, and moves the meshing portions in a circumferential direction of the internal gear. A wave generator of the present invention has a rigid wave plug and a wave bearing installed between the plug outer peripheral surface of the wave plug and the inner peripheral surface of an externally toothed gear. The contour shape of the plug outer peripheral surface is defined based on an elliptical closed curve. The elliptical closed curve is a line-symmetric closed curve that does not have the minor axis of the elliptical closed curve as the axis of symmetry but has only the major axis as the axis of symmetry.

In addition, a wave generator of a wave gear device of the present invention includes: a plurality of rollers that contact an inner peripheral surface of the external gear and flex the external gear into a shape that follows an elliptical closed curve; and a roller holding member that holds the plurality of rollers at different positions along the elliptical closed curve so that the plurality of rollers are inscribed in the elliptical closed curve. The elliptical closed curve is a line-symmetric closed curve that does not have the minor axis of the elliptical closed curve as the axis of symmetry but has only the major axis as the axis of symmetry.

in the present specification, the term "elliptic closed curve" represents a closed curve composed of a combination of a plurality of elliptic curves having different shapes, a combination of curves such as circular arcs approximating an elliptic curve, a combination of an elliptic curve and a curve approximating an elliptic curve, or the like.

For example, a curved portion on one side of the minor axis and a curved portion on the other side of the minor axis on the elliptical closed curve are defined by ellipses having different shapes. Both ends of these curved portions are smoothly connected at both end positions of the minor axis to define an elliptical closed curve. In a more specific example, an elliptical closed curve is formed by defining a curve portion on one side of the minor axis on the elliptical closed curve by the curve described in patent document 1, defining a curve portion on the other side by the curve described in patent document 2, and smoothly connecting both ends of the curves at both end positions of the minor axis.

The external gear is bent into, for example, a shape of an elliptic closed curve symmetrical along a line having only the long axis as the symmetry axis, not a shape of point symmetry having the rotation center thereof as the symmetry point. The meshing portions of the two gears are formed at both ends in the long axis direction. I.e. the engagement portion is formed at 2. Therefore, the meshing portion passes 2 times from the same position in the circumferential direction of the internal gear during 1 rotation of the wave generator. When one engaging portion passes through the other engaging portion, the engaging state is different from the other engaging portion, and the occurrence manner (timing, magnitude) of the angle transfer error is different from each other. As a result, it is possible to reduce the vibration caused by the quadratic error component of the angular transfer error generated in 2 cycles per 1 rotation of the wave generator.

Drawings

Fig. 1(a) is a schematic end view of a wave gear device according to embodiment 1, and fig. 1(b) is an explanatory view showing an elliptical closed curve that defines a deflection shape of an external gear.

Fig. 2 is a schematic longitudinal cross-sectional view of the wave gear device of fig. 1.

Fig. 3(a) is a schematic end view of a wave gear device according to embodiment 2, and fig. 3(b) is an explanatory view showing an elliptical closed curve that defines the deflection shape of an external gear.

fig. 4 is a schematic longitudinal cross-sectional view of the wave gear device of fig. 3.

Fig. 5 is an explanatory diagram illustrating a wave gear device according to embodiment 3 of the present invention.

Fig. 6 is an explanatory diagram showing a wave gear device according to embodiment 4 of the present invention.

Fig. 7 is an explanatory diagram showing a wave gear device according to embodiment 5 of the present invention.

Detailed Description

An embodiment of a wave gear device to which the present invention is applied will be described below with reference to the drawings. The following embodiments relate to a cup-type wave gear device. However, the present invention is also equally applicable to a top hat-type wave gear device and a flat-type wave gear device.

[ embodiment 1]

Fig. 1(a) is a schematic end view of a wave gear device according to embodiment 1, and fig. 1(b) is an explanatory view showing an elliptical closed curve that defines the deflection shape of the external gear. Fig. 2 is a schematic longitudinal sectional view of the wave gear device. As shown in these drawings, the wave gear device 1 includes: an annular rigid internally toothed gear 2 (rigid gear); a cup-shaped flexible external gear 3 (flexible gear) coaxially disposed inside the internal gear 2; and a wave generator 4 embedded inside the external gear 3.

The external gear 3 is flexed by the wave generator 4 into a shape following an elliptical closed curve C0. On the external gear 3 deflected by the wave generator 4, meshing portions that mesh with the internal gear 2 are formed at 2 on both ends of the major axis Lmax on the elliptical closed curve C0. In fig. 1(a), portions surrounded by dotted lines are the engaging portions 5a, 5 b.

If the wave generator 4 is rotated by a motor or the like (not shown), the meshing portions 5a, 5b of the two gears 2, 3 move in the circumferential direction of the internal gear 2. If the meshing parts 5a, 5b rotate once, relative rotation by the amount of difference in the number of teeth of the two gears 2, 3 occurs between the two gears 2, 3. The difference in the number of teeth between the internal gear 2 and the external gear 3 is 2n (n: a positive integer), for example, 2 (n is 1). For example, if the internal gear 2 is fixed so as not to rotate, the rotation of the wave generator 4 can be obtained as decelerated rotation that is greatly decelerated from the external gear 3 side.

The internally toothed gear 2 has an annular member 6 having a substantially rectangular cross section and internal teeth 7 formed on a circular inner peripheral surface of the annular member 6. The external gear 3 has: a cylindrical barrel part 11 which can be bent in a radial direction; a disc-shaped diaphragm 12 extending radially inward from the rear end of the cylindrical body 11; an annular boss 13 which is a rigid body connected to the inner peripheral edge of the diaphragm 12; and external teeth 14 formed on the outer peripheral surface portion of the cylindrical barrel portion 11 on the opening end side.

The wave generator 4 has: a cylindrical sleeve 21; a wave plug (cam plate) 22 attached to the outer peripheral surface of the sleeve 21; and a wave bearing 23 attached to the outer peripheral surface 22a of the wave plug 22. The outer peripheral surface 22a has a contour shape similar to an elliptical closed curve C0. The outer ring outer peripheral surface 23a of the wave bearing 23 attached to the outer peripheral surface 22a is flexed into a contour shape corresponding to the elliptical closed curve C0. The external-teeth-formed portion 15 of the cylindrical barrel part 11 in the external-teeth gear 3, on which the external teeth 14 are formed, is flexed into a shape following an elliptical closed curve C0 corresponding to the contour shape of the outer-ring outer peripheral surface 23 a.

Here, the elliptical closed curve C0 that defines the deflection shape of the external gear 3 due to the wave generator 4 is composed of 2 elliptical curves, for example, as shown in fig. 1 (b).

The elliptical closed curve C0 is defined by a 1 st curve portion C1 defining one side (upper half in fig. 1 b) of the minor axis Lmin thereof and a 2 nd curve portion C2 defining the other side (lower half in fig. 1 b) of the minor axis Lmin. In fig. 1(b), a curve in which the 1 st curve portion C1 is line-symmetrical with respect to the minor axis Lmin is shown by a chain line, and a difference between the 1 st curve portion C1 and the 2 nd curve portion C2 is exaggeratedly shown.

the 1 st curved portion and the 2 nd curved portion C2 are elliptic curves having different shapes from each other, but having the same circumference and the same length as the minor axis. For example, the curvature of the major axis Lmax of the 1 st curved line portion C1 and its vicinity is larger than the curvature of the major axis Lmax of the 2 nd curved line portion C2 and its vicinity. At both ends of the minor axis Lmin, the ends of the 1 st curved line portion and the 2 nd curved line portion C2 are smoothly connected to each other, forming an elliptical closed curve C0. The elliptical closed curve C0 has the major axis Lmax as the axis of symmetry (line symmetry with respect to the major axis Lmax), but does not have the minor axis Lmin as the axis of symmetry (non-line symmetry with respect to the minor axis Lmin).

The external gear 3 of this example is flexed into a shape following an elliptical closed curve C0 by the wave generator 4. The flexed external gear 3 meshes with the internal gear 2 at both ends of the major axis Lmax. That is, the meshing portions 5a, 5b of the gears 2, 3 are formed at both ends of the major axis Lmax. Since the meshing portion is formed at 2, the meshing portion of the two gears 2, 3 passes 2 times from the same position in the circumferential direction of the internal gear 2 during 1 rotation of the wave generator 4.

At the engaging portion formed by the 1 st curve portion C1 of the elliptic closed curve C0 (in fig. 1(a), the engaging portion 5a) and the engaging portion formed by the 2 nd curve portion C2 (in fig. 1(a), the engaging portion 5b), the engaging state is different, and the appearance manner (timing, magnitude) of the angle transfer error is also different. Therefore, it is possible to reduce the vibration caused by the quadratic error component generated in 2 cycles per 1 rotation of the input rotation (rotation of the wave generator 4) included in the angle transmission error of the wave gear device 1.

embodiment 2 (example of roller-type wave generator)

fig. 3(a) is a schematic end view showing a wave gear device according to embodiment 2, and fig. 3(b) is an explanatory view showing an elliptical closed curve defining a deflection shape of the external gear. Fig. 4 is a schematic longitudinal sectional view of the wave gear device. The wave gear device 31 of embodiment 2 includes: an annular rigid internally toothed gear 32 (rigid gear); a cup-shaped flexible external gear 33 (flexible gear) disposed inside the internal gear 32; and a six-roller wave generator 34 disposed inside the flexible externally toothed gear 33. The external gear 33 is flexed into a shape along an elliptical closed curve by the wave generator 34, and at 2 of both ends of its major axis Lmax, meshing portions that mesh with the internal gear 32 are formed. The portions surrounded by the chain line in fig. 3(a) are meshing portions 35a, 35b of the external gear 33 that mesh with the internal gear 32.

the six-roller wave generator 4 has: a hollow input shaft 41; a support disc 42 which is a roller holding member fixed coaxially to the outer peripheral surface of the hollow input shaft 41 or formed as an integral member with the hollow input shaft 41; and 6 rollers 51 to 56 mounted on the support disk 42. The rollers 51 to 56 contact the inner peripheral surface of the external-tooth-formation portion of the external gear 33 from the inside, and flex the external gear 33 into a shape along an elliptical closed curve C10. The rollers 51 to 56 are arranged along an elliptical closed curve C10 centered on the rotation center (device center axis) 31a at positions inscribed in the elliptical closed curve C10.

As shown in fig. 3 b, the elliptical closed curve C10 is defined by a 1 st curve portion C11 defining one side (upper half in the figure) of the minor axis Lmin and a 2 nd curve portion C12 defining the other side (lower half in the figure) of the minor axis Lmin. In fig. 3(b), a line-symmetric curve of the 1 st curve portion C11 with respect to the minor axis Lmin is shown by a chain line, and the difference of the 1 st curve portion C11 and the 2 nd curve portion C12 is exaggeratedly shown.

For example, the 1 st curved line portion C11 and the 2 nd curved line portion C12 are elliptical curves having different shapes from each other, but have the same circumference and the same length as the minor axis. The curvature at and near the position of the major axis Lmax of the 1 st curved line portion C11 is greater than the curvature at and near the position of the major axis Lmax of the 2 nd curved line portion C12. At both ends of the minor axis Lmin, the corresponding ends of the 1 st curved line portion C11 and the 2 nd curved line portion C12 are smoothly connected to each other, forming an elliptical closed curve C10. Therefore, the elliptical closed curve C10 has the major axis Lmax as the symmetry axis (line symmetry with respect to the major axis Lmax), but does not have the minor axis Lmin as the symmetry axis (line asymmetry with respect to the minor axis Lmin).

Of the rollers 51 to 56, the rollers 51, 52, and 53 are disposed on one side (upper side in the drawing) with respect to the short axis Lmin, and the rollers 54, 55, and 56 are disposed on the other side. The roller 51 is positioned on the major axis Lmax, and the rollers 52 and 53 are rollers having the same size and are disposed at positions that are line-symmetrical with respect to the major axis Lmax. Similarly, the roller 54 is positioned on the major axis Lmax, and the rollers 55 and 56 are rollers having the same size and are disposed at positions line-symmetrical with respect to the major axis Lmax.

For example, although the rollers 51 and 54 have the same size, the roller centers are located at positions that are not point-symmetrical with respect to the rotational center (device center axis) 31a with a slightly different distance therebetween. Although the rollers 52 and 55 have the same size, the roller centers are slightly different from the rotation center (device center axis) 31a in distance, and are disposed at positions that are not point-symmetrical. Similarly, although the rollers 53 and 56 have the same size, their roller centers are slightly different in distance from the rotation center (device center axis) 31a and are disposed at positions that are not point-symmetrical. By changing the roll size, it is also possible to define an elliptical closed curve C10 that is not point-symmetric.

The elliptical closed curve C10 defined by the rollers 51 to 56 is, as described above, non-point-symmetrical with respect to the rotation center 31 a. That is, the shape is line-symmetric with the major axis Lmax as the symmetry axis, but is not line-symmetric with respect to the minor axis Lmin.

In the wave gear device 31 of this example, at the meshing portion formed by the 1 st curve portion C11 of the elliptical closed curve C10 (the meshing portion 35a in fig. 3 (a)) and the other meshing portion formed by the 2 nd curve portion C12 (the meshing portion 35b in fig. 3 (a)), the meshing state is different, and the occurrence manner (timing, magnitude) of the angle transmission error is also different. Therefore, it is possible to reduce the vibration of the wave gear device 31 caused by the quadratic error component of the angular transmission error generated in 2 cycles per 1 rotation of the input rotation (rotation of the wave generator 34).

[ embodiment 3]

Fig. 5 is an explanatory diagram showing a wave gear device according to embodiment 3 to which the present invention is applied. The wave gear device 120 is provided with a rigid externally toothed gear 122 (rigid gear) at the innermost side. An annular flexible internal gear 123 (flexible gear) is disposed so as to concentrically surround the external gear 122. The ring-shaped wave generator 124 is disposed so as to concentrically surround the internal gear 123.

the internal gear 123 is flexed by the wave generator 124, for example, into a shape along an elliptical closed curve C30 that is the same as the elliptical closed curve C0 in the case of embodiment 1. On the internal gear 123 deflected by the wave generator 124, at 2 of both ends of the minor axis Lmin on the elliptical closed curve C30, meshing portions 125a, 125b that mesh with the external gear 122 are formed. In fig. 5, portions surrounded by dotted lines are the engaging portions 125a, 125 b.

The wave generator 124 has an annular rigid cam plate 126 and a wave bearing 127 mounted on the inside thereof. Further, in the illustrated example, the outer race of the wave bearing 127 is formed integrally with the rigid cam plate 126. The non-circular inner peripheral surface 126a of the rigid cam plate 126 is defined by an elliptical closed curve C0.

The wave generator 124 causes the inner internally-toothed gear 123 to flex into an elliptical shape, and the internal teeth at both ends of the minor axis Lmin of the elliptical shape mesh with the external teeth of the inner externally-toothed gear 122. For example, if the wave generator 124 is rotated by a rotation drive source such as a motor and the external gear 122 is fixed so as not to rotate, the meshing position of the two gears 122 and 123 moves in the circumferential direction, and relative rotation corresponding to the difference in the number of teeth between the two gears occurs between the two gears. This rotation can be taken from the internal gear 123.

The shapes of the curved portions of the short-axis both end portions on the elliptical closed curve C30 are different from each other. The shapes of the meshing portions 125a, 125b of the internal gear 123 deflected by these curved portions are also different from each other. As a result, the meshing state with the external gear 122 differs between the meshing portions 125a and 125b, and the appearance mode (timing and magnitude) of the angle transmission error differs. Therefore, it is possible to reduce the vibration caused by the quadratic error component generated in 2 cycles per 1 rotation of the input rotation included in the angle transmission error of the wave gear device 120.

[ embodiment 4]

Fig. 6 is an explanatory diagram illustrating a wave gear device according to embodiment 4. The wave gear device 140 has: a rigid internal gear 142 (rigid gear); a flexible external gear 143 (flexible gear) disposed inside the internal gear 142; and a wave generator 144 of a non-circular profile embedded inside the external gear 143. The portion of the external gear 143 where external teeth are formed is deflected into a non-circular shape by the wave generator 144.

the wave generator 144 has a rigid cam plate 146 of non-circular profile and a wave bearing 147 mounted at its outer periphery. The non-circular outer peripheral surface 146a of the rigid cam plate 146 is defined by a closed curve that can be inscribed in a perfect circle at equally spaced plural places in the circumferential direction of the perfect circle. In this example, the non-circular outer peripheral surface 146a has a three-lobed shape (3-lobed shape), and is defined by a closed curve C40 that can be inscribed in a perfect circle at 3 equally spaced positions in the circumferential direction of the perfect circle. The non-circular outer peripheral surface may be defined by a closed curve that can be inscribed in a perfect circle at a plurality of 4 or more places at equal intervals in the circumferential direction of the perfect circle.

with the wave generator 144 of this shape, the external gear 143 is flexed into a shape following the non-circular contour of the wave generator 144, and meshing portions 145a, 145b, 145c that mesh with the internal gear 142 are formed at 3 angular intervals of 120 °. On a closed curve C40 defining a non-circular outer peripheral surface 146a of a rigid cam plate 146 of the wave generator 144, 3-point curved portions C40a, C40b, C40C forming the engaging portions 145a to 145C are set to shapes different from each other. Accordingly, the meshing states of the 3-position meshing portions 145a to 145c with the internal gear 142 are also different from each other.

The wave generator 144 is connected to a high-speed rotation input shaft such as a motor shaft. If the wave generator 144 rotates, the meshing position of the two gears 142, 143 moves in the circumferential direction, and relative rotation is generated between the two gears 142, 143 due to the difference in their tooth numbers. For example, the internal gear 142 is fixed so as not to rotate, the external gear 143 is coupled to a member on the load side, and the external gear 143 receives the decelerated rotation and transmits the rotation to the member on the load side. The difference in the number of teeth between the gears 142 and 143 in this case is set to 3n (n is a positive integer).

The 3-point meshing portions 145a to 145c of the external gear 143 with the internal gear 142 are different from each other in meshing state, and the occurrence modes (timing and magnitude) of the angular transmission errors are also different. Therefore, it is possible to reduce the vibration caused by the error component of three times, which is generated in 3 cycles per 1 rotation of the input, included in the angle transmission error of the wave gear device 140.

(embodiment 5)

Fig. 7 is an explanatory diagram illustrating a wave gear device according to embodiment 5. In the wave gear device 160 shown in the figure, a flexible internal gear 163 (flexible gear) is disposed outside a rigid external gear 162 (rigid gear), and a wave generator 164 having an inner peripheral surface with a non-circular contour is disposed on the outer peripheral side of the internal gear 163.

The wave generator 164 includes a rigid cam plate 166 having a non-circular inner peripheral surface 166a, and a wave bearing 167 attached to the non-circular inner peripheral surface 166 a. The non-circular inner peripheral surface 166a of the rigid cam plate 166 is defined by a closed curve that can circumscribe a perfect circle at equally spaced plural places in the circumferential direction of the perfect circle. In this example, the non-circular inner peripheral surface 166a has a three-lobed shape (3-lobed shape), and is defined by a closed curve C50 that can be circumscribed on a perfect circle at equal intervals 3 in the circumferential direction of the perfect circle. The non-circular inner peripheral surface may be defined by a closed curve that can circumscribe a circle at equal intervals in the circumferential direction of the circle at 4 or more points.

With the wave generator 164 of this shape, the internal gear 163 is flexed into a shape following the non-circular contour of the wave generator 164, and at 3 angular intervals of 120 °, meshing portions 165a, 165b, 165c that mesh with the external gear 162 are formed. On a closed curve C50 defining the non-circular inner peripheral surface 166a of the wave generator 164, 3-point curved portions C50a, C50b, C50C forming the engaging portions 165a to 165C are set to shapes different from each other. Accordingly, the meshing states of the 3-position meshing portions 165a to 165c with the external gear 162 are different from each other.

For example, if the wave generator 164 is rotated by a rotation drive source such as a motor and the external gear 162 is fixed so as not to rotate, the meshing position of the gears 162 and 163 moves in the circumferential direction, and relative rotation corresponding to the difference in the number of teeth between the gears occurs between the gears. This rotation can be obtained from the internal gear 163. The difference in the number of teeth between the gears 162 and 163 in this case is set to 3n (n is a positive integer).

The 3-point meshing portions 165a to 165c of the internal gear 163 with the external gear 162 are different from each other in meshing state, and the occurrence modes (timing and magnitude) of the angular transfer error are also different. Therefore, it is possible to reduce the vibration caused by the error component of three times, which is generated in 3 cycles per 1 rotation of the input, included in the angle transmission error of the wave gear device 160.

[ other embodiments ]

As described above, the present invention is not limited to the cup-type wave gear device, and can be applied to a silk hat-type wave gear device and a flat-type wave gear device as well.

In embodiments 1, 2, and 3 described above, since the elliptical closed curve may have a non-point-symmetric shape, various shapes can be used as the 1 st and 2 nd curve portions defining the elliptical closed curve. For example, a combination of the plug shape proposed in patent document 1 and the plug shape proposed in patent document 2 can be adopted. Further, 2 kinds of plug shapes selected from the conventional plug shapes described in patent document 1 can be used.