阅读说明：本技术 机器人、齿轮装置以及齿轮装置的制造方法 (Robot, gear device, and method for manufacturing gear device ) 是由 坂田正昭 于 2019-06-04 设计创作，主要内容包括：本发明提供机器人、齿轮装置以及齿轮装置的制造方法,其能够实现长寿命化。一种机器人,具备第一构件、第二构件、传递使上述第二构件相对转动的驱动力的齿轮装置以及向上述齿轮装置输出上述驱动力的驱动源,上述齿轮装置具有：内齿齿轮；外齿齿轮,具有柔性,并且局部与上述内齿齿轮啮合；以及波动发生器,与上述外齿齿轮的内周面接触,使上述内齿齿轮与上述外齿齿轮的啮合位置在周向上移动,上述内齿齿轮、上述外齿齿轮以及上述波动发生器中之一连接到上述第一构件,另一连接到上述第二构件,上述外齿齿轮以镍铬钼钢为主材料,上述内齿齿轮以实施了淬火和回火处理的球状石墨铸铁或者实施了奥氏体回火处理的球状石墨铸铁为主材料。(The invention provides a robot, a gear device and a method for manufacturing the gear device, which can realize long service life. A robot comprising a first member, a second member, a gear device for transmitting a driving force for relatively rotating the second member, and a driving source for outputting the driving force to the gear device, wherein the gear device comprises: an internal gear; an external gear having flexibility and partially meshing with the internal gear; and a wave generator that contacts an inner peripheral surface of the external gear to move a meshing position of the internal gear and the external gear in a circumferential direction, wherein one of the internal gear, the external gear, and the wave generator is connected to the first member, and the other is connected to the second member, wherein the external gear is made of nickel-chromium-molybdenum steel, and the internal gear is made of spheroidal graphite cast iron subjected to quenching and tempering or spheroidal graphite cast iron subjected to austenite tempering.)

1. A robot is characterized by comprising:

A first member;

A second member that rotates relative to the first member;

A gear device that transmits a driving force that relatively rotates the second member; and

A drive source that outputs the drive force to the gear device,

The gear device has:

An internal gear;

An external gear having flexibility and partially meshing with the internal gear; and

A wave generator that contacts an inner peripheral surface of the external gear to move a meshing position of the internal gear and the external gear in a circumferential direction,

One of the internal gear, the external gear, and the wave generator is connected to the first member, and the other is connected to the second member,

The external gear is mainly made of nickel-chromium-molybdenum steel, and the internal gear is mainly made of spheroidal graphite cast iron subjected to quenching and tempering treatment or spheroidal graphite cast iron subjected to austenite tempering treatment.

2. The robot of claim 1,

The Vickers hardness of the surface of the internal gear is equal to or less than the Vickers hardness of the surface of the external gear.

3. Robot according to claim 1 or 2,

The Vickers hardness of the surface of the external gear is in the range of 400 to 520.

4. Robot according to claim 1 or 2,

The Vickers hardness of the surface of the internal gear is in a range of 300 or more and 450 or less.

5. The robot of claim 1,

The residual stress of the external gear is in the range of-950 MPa or more and-450 MPa or less.

6. The robot of claim 1,

The external teeth of the external gear have a surface roughness Ra of 0.2 [ mu ] m or more and 1.6 [ mu ] m or less.

7. The robot of claim 1,

The surface roughness Ra of the internal teeth of the internal gear is within the range of 0.1-0.8 [ mu ] m.

8. The robot of claim 1,

The surface roughness Ra of the outer teeth of the external gear is larger than the surface roughness Ra of the inner teeth of the internal gear.

9. the robot of claim 1,

The average crystal grain size of the external gear is smaller than the average crystal grain size of the internal gear.

10. the robot of claim 1,

The external gear contains a group IV element or a group V element in a range of 0.01 to 0.5 mass%.

11. The robot of claim 1,

A lubricant is provided between the internal gear and the external gear,

The lubricant contains a base oil, a thickener, and an organic molybdenum compound, and has an oil separation degree in a range of 4 mass% or more and 13.8 mass% or less.

12. The robot of claim 1,

The spheroidal graphite cast iron as a main material of the internal gear includes a sorbite structure or a bainite structure.

13. A gear device, comprising:

An internal gear;

An external gear having flexibility and partially meshing with the internal gear; and

A wave generator that contacts an inner peripheral surface of the external gear to move a meshing position of the internal gear and the external gear in a circumferential direction,

the external gear is made of nickel-chromium-molybdenum steel, and the internal gear is made of spheroidal graphite cast iron subjected to quenching and tempering treatment or spheroidal graphite cast iron subjected to austenite tempering treatment.

14. A method of manufacturing a gear device, the gear device comprising:

An internal gear;

An external gear having flexibility and partially meshing with the internal gear; and

A wave generator that contacts an inner peripheral surface of the external gear to move a meshing position of the internal gear and the external gear in a circumferential direction,

The method for manufacturing the gear device comprises the following steps:

preparing an internal gear member made of spheroidal graphite cast iron as a main material; and

the member for internal gear is subjected to quenching and tempering treatment or austempering treatment to obtain the internal gear.

15. The method of manufacturing a gear device according to claim 14,

The spheroidal graphite cast iron contained in the member for internal gears comprises graphite and a matrix,

The matrix comprises a pearlitic structure.

Technical Field

the invention relates to a robot, a gear device and a method for manufacturing the gear device.

Background

In a robot including a manipulator configured to include at least 1 arm, for example, a joint portion of the manipulator is rotated by driving a motor, and at this time, rotation of a driving force from the motor is decelerated by a speed reducer (gear device) and transmitted to the manipulator.

As such a speed reducer, for example, a wave gear device described in patent document 1 is known. The wave gear device described in patent document 1 includes: a rigid internally toothed gear in the shape of a ring; a cup-shaped flexible external gear disposed inside the internal gear; and a wave generator of an elliptical profile embedded inside the external gear.

Patent document 1: japanese patent laid-open No. 2002-349681

However, in the wave gear device described in patent document 1, the constituent material of the internal gear is a high-strength aluminum alloy or a copper alloy, and the constituent material of the external gear is structural steel or stainless steel. Therefore, there is a problem that the mechanical characteristics of the internal gear and the external gear are insufficient, and the life of the gear device is short. The life of the gear device is a cause of, for example, a reduction in the work efficiency of the robot.

disclosure of Invention

a robot according to an application example of the present invention includes: a first member; a second member that rotates relative to the first member; a gear device that transmits a driving force that relatively rotates the second member; and a drive source that outputs the drive force to the gear device, the gear device having: an internal gear; an external gear having flexibility and partially meshing with the internal gear; and a wave generator that contacts an inner peripheral surface of the external gear to move a meshing position of the internal gear and the external gear in a circumferential direction, one of the internal gear, the external gear, and the wave generator being connected to the first member, and the other thereof being connected to the second member, wherein the external gear is made of nickel-chromium-molybdenum steel, and the internal gear is made of spheroidal graphite cast iron subjected to quenching and tempering or spheroidal graphite cast iron subjected to austempering.

A gear device according to an application example of the present invention includes: an internal gear; an external gear having flexibility and partially meshing with the internal gear; and a wave generator that contacts an inner peripheral surface of the external gear to move a meshing position between the internal gear and the external gear in a circumferential direction, wherein the external gear is mainly made of nickel-chromium-molybdenum steel, and the internal gear is mainly made of spheroidal graphite cast iron subjected to quenching and tempering or spheroidal graphite cast iron subjected to austenite tempering.

A method of manufacturing a gear device according to an application example of the present invention is characterized by comprising: an internal gear; an external gear having flexibility and partially meshing with the internal gear; and a wave generator that is in contact with an inner peripheral surface of the external gear and moves a meshing position of the internal gear and the external gear in a circumferential direction, the method for manufacturing the gear device including: preparing an internal gear member made of spheroidal graphite cast iron as a main material; and subjecting the member for internal gear to quenching and tempering treatment or austempering treatment to obtain the internal gear.

Drawings

Fig. 1 is a side view showing a schematic configuration of a robot according to an embodiment of the present invention.

Fig. 2 is a longitudinal sectional view showing a gear device according to a first embodiment of the present invention.

Fig. 3 is a front view (view when viewed from the axis a direction) of the gear device main body shown in fig. 2.

fig. 4 is a cross-sectional view showing a surface state of external teeth of a flexible gear provided in the gear device shown in fig. 2.

Fig. 5 is a longitudinal sectional view showing a gear device according to a second embodiment of the present invention.

Fig. 6 is a process diagram showing an embodiment of a method for manufacturing a gear device according to the present invention.

fig. 7 is an observation image of the polished surface of the rigid gear of example 4 under a scanning electron microscope.

Fig. 8 is an observation image of the polished surface of the rigid gear according to example 26 under a scanning electron microscope.

Fig. 9 is an observation image of the polished surface of the rigid gear in comparative example 1 under a scanning electron microscope.

description of the reference numerals

1 … gear device body, 1B … gear device body, 2 … rigid gear, 3 … flexible gear, 3B … flexible gear, 4 … wave generator, 5 … housing, 5B … housing, 10 … gear device, 10B … gear device, 11 … cover, 11B … cover, 12 … body, 13 … bearing, 14 … bearing, 15 … inner wheel, 16 … outer wheel, 17 … roller, 18 … cross roller bearing, 23 … inner teeth, 31 … body, 32 … bottom, 32B … flange, 33 … outer teeth, 36 … opening, 41 … cam, 42 … bearing, 61 … shaft, 62 … shaft, 80 …, 100 … reduction ratio, 110 …, 111 … inner wall surface, 111B … inner wall surface, 120B … first arm, 121, …, 36130 second arm, … working line portion, 36140 working line portion 150, … working line portion 141, … working line portion, … working line portion, … end working line portion 151, 170 … motor, 190 … control device, 411 … shaft part, 412 … cam part, 421 … inner wheel, 422 … ball, 423 … outer wheel, G … lubricant, J1 … first shaft, J2 … second shaft, J3 … third shaft, La … long shaft, Lb … short shaft, S1 … component preparation process, S2 … heat treatment process, S3 … assembling process and a … axis.

Detailed Description

Hereinafter, a robot, a gear device, and a method for manufacturing the gear device according to the present invention will be described in detail based on preferred embodiments shown in the drawings.

1. Robot

first, an embodiment of the robot according to the present invention will be briefly described.

fig. 1 is a side view showing a schematic configuration of a robot according to an embodiment of the present invention. Hereinafter, for convenience of explanation, the upper side in fig. 1 is referred to as "upper" and the lower side is referred to as "lower". The base side in fig. 1 is referred to as a "base end side", and the opposite side (end effector side) is referred to as a "tip end side". In fig. 1, the vertical direction is a "vertical direction", and the horizontal direction is a "horizontal direction".

The robot 100 shown in fig. 1 is a robot used for operations such as feeding, discharging, transporting, and assembling of precision equipment or parts (objects) constituting the precision equipment, for example. As shown in fig. 1, the robot 100 includes a base 110, a first arm 120, a second arm 130, a working head 140, an end effector 150, and a wiring line portion 160. Hereinafter, each part of the robot 100 will be briefly described in order.

The base 110 is fixed to a floor, not shown, by bolts or the like, for example. A control device 190 for controlling the robot 100 as a whole is provided inside the base 110. The first arm 120 is coupled to the base 110, and the first arm 120 is rotatable about a first axis J1 (pivot axis) along the vertical direction with respect to the base 110. That is, the first arm 120 rotates relative to the base 110.

Here, the base 110 includes: a motor 170 (driving source) as a first motor, such as a servo motor, which generates a driving force for rotating the first arm 120; and a gear device 10 as a first speed reducer that reduces the rotation of the driving force of the motor 170. An input shaft of the gear device 10 is coupled to a rotation shaft of the motor 170, and an output shaft of the gear device 10 is coupled to the first arm 120. Therefore, when the motor 170 is driven and the driving force thereof is transmitted to the first arm 120 via the gear device 10, the first arm 120 relatively rotates in the horizontal plane about the first axis J1 with respect to the base 110. That is, the motor 170 is a driving source that outputs a driving force to the gear device 10.

The second arm 130 is connected to a distal end portion of the first arm 120, and the second arm 130 is rotatable about a second axis J2 (a rotation axis) along the vertical direction with respect to the first arm 120. Although not shown, a second motor that generates a driving force for rotating the second arm 130 and a second speed reducer that reduces the rotation of the driving force of the second motor are provided in the second arm 130. Then, the driving force of the second motor is transmitted to the second arm 130 via the second reduction gear, whereby the second arm 130 rotates in the horizontal plane about the second shaft J2 with respect to the first arm 120.

A working head 140 is disposed at the distal end of the second arm 130. The working head 140 has a spline shaft 141 through which a spline nut and a ball screw nut (both not shown) coaxially disposed at the distal end portion of the second arm 130 are inserted. The spline shaft 141 is rotatable about a third axis J3 shown in fig. 1 with respect to the second arm 130, and is movable (raised and lowered) in the up-down direction.

a rotating motor and a lifting motor are disposed in the second arm 130, although not shown. The driving force of the rotating electric machine is transmitted to the spline nut via a driving force transmission mechanism, not shown, and when the spline nut rotates forward and backward, the spline shaft 141 rotates forward and backward about the third shaft J3 along the vertical direction.

On the other hand, the driving force of the elevator motor is transmitted to the ball screw nut via a driving force transmission mechanism, not shown, and the spline shaft 141 moves up and down when the ball screw nut rotates forward and backward.

An end effector 150 is connected to a tip end portion (lower end portion) of the spline shaft 141. The end effector 150 is not particularly limited, and examples thereof include an end effector for gripping a conveyed object, an end effector for processing a processed object, and the like.

A plurality of wires connected to each electronic component (for example, a second motor, a rotary motor, a lift motor, etc.) disposed in the second arm 130 are routed into the base 110 through a tubular wiring routing portion 160 connecting the second arm 130 and the base 110. Further, such a plurality of wires are collected in the base 110 and routed to the control device 190 provided in the base 110 together with wires connected to the motor 170 and an encoder not shown.

As described above, the robot 100 includes: a base 110 as a first member; a first arm 120 as a second member provided rotatably with respect to the base 110; a gear device 10 that transmits a driving force from one side of the base 110 and the first arm 120 to the other side; and a motor 170 as a driving source that outputs a driving force to the gear device 10.

In addition, the first arm 120 and the second arm 130 may be collectively understood as "second member". In addition, the "second member" may include the working head 140 and the end effector 150 in addition to the first arm 120 and the second arm 130.

In the present embodiment, the first reduction gear includes the gear device 10, but the second reduction gear may include the gear device 10, or both the first reduction gear and the second reduction gear may include the gear device 10. In the case where the second reduction gear includes the gear device 10, the first arm 120 may be regarded as the "first member" and the second arm 130 may be regarded as the "second member". Instead of the gear device 10, a gear device 10B described later may be used.

In the present embodiment, the motor 170 and the gear device 10 are provided on the base 110, but the motor 170 and the gear device 10 may be provided on the first arm 120. In this case, the output shaft of the gear device 10 may be coupled to the base 110.

2. Gear device

Hereinafter, embodiments of the gear device of the present invention will be described.

< first embodiment >

Fig. 2 is a longitudinal sectional view showing a gear device according to a first embodiment of the present invention. Fig. 3 is a front view (view when viewed from the axis a direction) of the gear device main body shown in fig. 2. Fig. 4 is a cross-sectional view showing a surface state of external teeth of a flexible gear provided in the gear device shown in fig. 2. In the drawings, the dimensions of the respective portions are exaggerated as necessary for convenience of explanation, and the dimension ratio between the portions does not necessarily match the actual dimension ratio.

The gear device 10 shown in fig. 2 is a wave gear device, and is used as a speed reducer, for example. The gear device 10 includes a gear device body 1 and a housing 5 in which the gear device body 1 is housed, and these are integrated. Here, the lubricant G is disposed in the housing 5 of the gear device 10. Hereinafter, each part of the gear device 10 will be described. The housing 5 may be provided as needed or omitted.

(Gear device body)

the gear device main body 1 includes: a rigid gear 2 as an internal gear; a flexible gear 3 as an external gear, which is cup-shaped and is disposed inside the rigid gear 2; and a wave generator 4 disposed inside the flexible gear 3.

In the present embodiment, the rigid gear 2 is fixed (connected) to the base 110 (first member) of the robot 100 via the housing 5, the flexible gear 3 is connected to the first arm 120 (second member) of the robot 100, and the wave generator 4 is connected to the rotating shaft of the motor 170 disposed on the base 110 of the robot 100.

When the rotating shaft of the motor 170 rotates (i.e., generates a driving force), the wave generator 4 rotates at the same rotational speed as the rotating shaft of the motor 170. Then, since the rigid gear 2 and the flexible gear 3 have different numbers of teeth, the positions of meshing with each other move in the circumferential direction and rotate relative to each other around the axis a. In the present embodiment, the number of teeth of the rigid gear 2 is greater than the number of teeth of the flexible gear 3, and therefore the flexible gear 3 can be rotated at a rotational speed lower than the rotational speed of the rotational shaft of the motor 170. That is, a speed reducer having the wave generator 4 as an input shaft side and the flexible gear 3 as an output shaft side can be realized.

Further, even if the flexible gear 3 is fixed (connected) to the base 110 and the rigid gear 2 is connected to the first arm 120 according to the form of the housing 5, the gear device 10 can be used as a speed reducer. In addition, even if the rotation shaft of the motor 170 is connected to the flexible gear 3, the gear device 10 can be used as a speed reducer, and in this case, the wave generator 4 may be fixed (connected) to the base 110 and the rigid gear 2 may be connected to the first arm 120. When the gear device 10 is used as a speed-increasing gear (when the flexible gear 3 is rotated at a rotation speed higher than the rotation speed of the rotation shaft of the motor 170), the relationship between the input side and the output side may be reversed.

As shown in fig. 2 and 3, the rigid gear 2 is a gear made of a rigid body that does not substantially flex in the radial direction, and is an annular internal gear having internal teeth 23. In the present embodiment, the rigid gear 2 is a flat gear. That is, the internal teeth 23 have a tooth trace parallel to the axis a. Further, the tooth trace of the internal teeth 23 may be inclined with respect to the axis a. That is, the rigid gear 2 may be a helical gear or a herringbone gear.

As shown in fig. 2 and 3, the flexible gear 3 is inserted to the inside of the rigid gear 2. The flexible gear 3 is a gear having flexibility capable of being deformed in a radial direction, and is an external gear having external teeth 33 (teeth) that mesh with a part of the internal teeth 23 of the rigid gear 2. The flexible gear 3 has fewer teeth than the rigid gear 2. Since the number of teeth of the flexible gear 3 and the rigid gear 2 is different from each other as described above, a reduction gear can be realized.

In the present embodiment, the flexible gear 3 has a cup shape having an opening portion 36 in which one end (the end portion on the right side in fig. 2) in the axis line a direction is opened, and the external teeth 33 are formed from the opening portion 36 to the other end. Here, the flexible gear 3 has: a cylindrical body portion 31 (tube portion) having a cylindrical shape (more specifically, a cylindrical shape) about an axis a, and a bottom portion 32 connected to the other end portion of the body portion 31 in the direction of the axis a. This makes it easier for the end of the opening 36 to flex in the radial direction than the bottom 32 of the body 31, and therefore, it is possible to achieve good flexing engagement between the flexible gear 3 and the rigid gear 2. Further, the rigidity of the bottom portion 32 connected to the shaft 62 (e.g., output shaft) can be improved. Accordingly, the gear device 10 is suitable for use in repeated reverse rotation because the backlash is very small, and the ratio of the number of meshing teeth is large, so that the force applied to 1 tooth is small, and a high torque capacity can be obtained. Further, since the lubricant can be used for such a severe application, a high lubricating performance is required for the lubricant.

As shown in fig. 2 and 3, the wave generator 4 is disposed inside the flexible gear 3 and is rotatable about an axis a. Then, the wave generator 4 causes the external teeth 33 of the flexible gear 3 to mesh with the internal teeth 23 of the rigid gear 2 by deforming the cross section of the opening portion 36 of the flexible gear 3 into an elliptical or oblong shape having the major axis La and the minor axis Lb. Here, the flexible gear 3 and the rigid gear 2 are engaged with each other inside and outside so as to be rotatable about the same axis a.

In the present embodiment, the wave generator 4 has a cam 41 and a bearing 42 fitted to the outer periphery of the cam 41. The cam 41 has a shaft 411 rotating around the axis a and a cam portion 412 protruding outward from one end of the shaft 411.

A shaft 61 (e.g., an input shaft) is connected to the shaft 411. The outer peripheral surface of the cam portion 412 is elliptical or oblong when viewed from the direction along the axis a. The bearing 42 includes a flexible inner ring 421 and an outer ring 423, and a plurality of balls 422 disposed therebetween. Here, the inner ring 421 is fitted into the outer peripheral surface of the cam portion 412 of the cam 41, and is elastically deformed into an elliptical shape or an oval shape along the outer peripheral surface of the cam portion 412. Along with this, the outer ring 423 is also elastically deformed into an elliptical shape or an oblong shape. The outer peripheral surface of the inner ring 421 and the inner peripheral surface of the outer ring 423 have track surfaces for guiding and rolling the plurality of balls 422 in the circumferential direction. The plurality of balls 422 are held by a retainer, not shown, so as to keep a constant interval in the circumferential direction. Grease, not shown, is disposed in the bearing 42. This grease may be the same as or different from lubricant G described later.

As the cam 41 rotates about the axis a, the wave generator 4 changes the direction of the cam portion 412, and accordingly, the outer peripheral surface of the outer ring 423 is also deformed, and the meshing position between the rigid gear 2 and the flexible gear 3 is moved in the circumferential direction.

The rigid gear 2, the flexible gear 3, and the wave generator 4 are each made of a metal material such as an iron-based material.

In particular, the flexible gear 3 (external gear) is mainly made of nickel-chromium-molybdenum steel. The nickel-chromium-molybdenum steel is a tough steel obtained by an appropriate heat treatment, and is excellent in mechanical properties (particularly fatigue strength), and therefore can be said to be suitable as a constituent material of the flexible gear 3 on which repetitive stress acts.

Examples of the nickel-chromium-molybdenum steel include those described in JIS G4053: 2016. Specifically, the numbers specified in the JIS standard include SNCM220, SNCM240, SNCM415, SNCM420, SNCM431, SNCM439, SNCM447, SNCM616, SNCM625, SNCM630, SNCM815 and the like. Among them, SNCM439 is particularly preferably used as the nickel-chromium-molybdenum steel used as the constituent material of the flexible gear 3, from the viewpoint of excellent mechanical properties.

The material of the flexible gear 3 may include a material other than nickel-chromium-molybdenum steel. That is, the flexible gear 3 may be made of a composite material in which nickel-chromium-molybdenum steel and other materials are combined. However, the nickel-chromium-molybdenum steel may be a main material as long as it occupies a larger proportion (% by mass) in the entire material than other materials.

On the other hand, the material constituting the rigid gear 2 (internal gear) is mainly spheroidal graphite cast iron. Spheroidal graphite cast iron is also called spheroidal graphite cast iron, and is cast iron in which spheroidal graphite is crystallized. In such spheroidal graphite cast iron, the graphite is dispersed in the matrix in a spherical form, whereby the graphite is less likely to serve as a starting point of cracks, and therefore, for example, the strength of the matrix can be exhibited to the maximum extent as compared with flake graphite cast iron. As a result, the spheroidal graphite cast iron has excellent strength and toughness. The spheroidal graphite cast iron has sufficient strength and toughness by heat treatment described later. Therefore, the rigid gear 2 can have a longer life.

Further, since graphite contained in the spheroidal graphite cast iron functions as a lubricant, the internal teeth 23 of the rigid gear 2 are less likely to be stuck. Therefore, further reduction in wear of the rigid gear 2 can be achieved.

In addition, spheroidal graphite cast iron can convert transmitted vibration into thermal energy at the boundary between graphite and a matrix to be extinguished. Therefore, vibration and noise generated in the rigid gear 2 can be reduced.

Further, spheroidal graphite cast iron has high thermal conductivity and excellent heat dissipation properties. Therefore, the heat radiation performance of the rigid gear 2 is also improved, and the rigid gear 2 can be prevented from being significantly heated, so that the life of the gear device 10 can be prolonged.

The life of the gear device 10 is, for example, the time from when the gear device 10 starts to be used until any part of the gear device 10 is damaged. Such damage may be, for example, breakage of the rigid gear 2 or the flexible gear 3.

examples of the spheroidal graphite cast iron include those described in JIS G5502: 2001, and a material of the kind specified in 2001. Specifically, the numbers stipulated in JIS standards include FCD350-22, FCD350-22L, FCD400-18, FCD400-18L, FCD400-15, FCD400-10, FCD450-10, FCD500-7, FCD600-3, FCD700-2, and FCD 800-2.

Further, examples of the alloy composition of the spheroidal graphite cast iron include an alloy containing Fe (iron) as a main component and having a composition in terms of C (carbon): 2.0 to 6.0 mass% of Si (silicon): 0.5 to 3.5 mass% inclusive, Mn (manganese): 0.4 to 1.0 mass% inclusive of each component. Further, the spheroidal graphite cast iron may contain Cu (copper), Ni (nickel), Cr (chromium), Sn (tin), Mg (magnesium), and the like.

The material constituting the rigid gear 2 is spheroidal graphite cast iron subjected to quenching and tempering treatment or spheroidal graphite cast iron subjected to austempering treatment.

By subjecting spheroidal graphite cast iron to quenching and tempering, the matrix structure can be changed from a martensite structure to a fine cementite (Fe)₃C) The mixed structure with ferrite (α solid solution) is particularly preferably a structure that can be changed to a sorbite structure. Therefore, the material constituting the rigid gear 2 preferably contains a sorbite structure in a matrix in which graphite is dispersed, that is, includes spheroidal graphite cast iron containing the sorbite structure. This makes it possible to provide spheroidal graphite cast iron with good toughness and elongation while maintaining mechanical strength, and to realize a rigid gear 2 having particularly good durability.

The sorbite structure is a mixed structure of fine cementite and ferrite, and is a structure in which the fine cementite is granular. In this case, the granular cementite is considered to be a structure at least a part of which has a size that is visible under an optical microscope at a magnification of 400 times. By including the cementite structure having such an appropriate particle diameter and being in a granular (spherical) shape, the sorbite structure contributes to realizing the rigid gear 2 having particularly good toughness and elongation. In addition, a tissue other than the sorbite tissue may be mixed in the matrix.

The tensile strength of such spheroidal graphite cast iron having a sorbite structure is not particularly limited, but is preferably 600MPa or more, more preferably 650MPa or more and 1200MPa or less. This makes it possible to realize the gear device 10 having a particularly long life.

In the measurement of the tensile strength, for example, a JIS14A test piece is used, and the value obtained by dividing the maximum load (breaking load) that the test piece can withstand by the cross-sectional area of the parallel portion of the test piece is defined as the tensile strength.

The elongation of such spheroidal graphite cast iron having a sorbite structure is not particularly limited, but is preferably 10% or more, and more preferably 12% or more and 25% or less. This makes it possible to realize the gear device 10 having a particularly long life.

In the measurement of the elongation, for example, a JIS14B test piece is used, and the maximum elongation (elongation at break) until the test piece breaks is defined as the above-mentioned elongation.

Further, by subjecting the spheroidal graphite cast iron to the austempering treatment instead of the quenching and tempering treatments described above, the matrix structure can be changed to a bainite structure. Therefore, the material constituting the rigid gear 2 preferably includes a spheroidal graphite cast iron having a bainite structure in a matrix in which graphite is dispersed, that is, a bainite structure. This can provide spherical graphite cast iron with good toughness while maintaining mechanical strength, and can realize a rigid gear 2 having particularly good durability.

The bainite structure is a structure generated by heating steel at an austenitizing temperature (for example, about 820 ℃ to 900 ℃) and then subjecting the steel to an austempering treatment (constant temperature transformation treatment), and generally includes an acicular structure. Such a bainitic structure contributes to the realization of a rigid gear 2 having particularly good mechanical strength. In addition, a structure other than the bainite structure may be mixed in the matrix.

The tensile strength of the spheroidal graphite cast iron having a bainite structure is not particularly limited, but is preferably 700MPa or more, and more preferably 800MPa or more and 1250MPa or less. This makes it possible to realize the gear device 10 having a particularly long life. The tensile strength is measured in the same manner as described above.

The elongation of such a spheroidal graphite cast iron having a bainite structure is not particularly limited, but is preferably 1% or more, and more preferably 2% or more and 10% or less. This makes it possible to realize the gear device 10 having a particularly long life. The method of measuring the elongation is the same as the above method.

In particular, from the viewpoint of fatigue strength, spheroidal graphite cast iron having a sorbite structure is more preferable than spheroidal graphite cast iron having a bainite structure. This makes it possible to realize the gear device 10 having a particularly long life.

As described above, by using spheroidal graphite cast iron subjected to quenching and tempering treatment or spheroidal graphite cast iron subjected to austempering treatment, the gear device 10 having a particularly long life can be realized.

The material constituting the rigid gear 2 may include any material other than the spheroidal graphite cast iron subjected to the quenching and tempering treatment or the spheroidal graphite cast iron subjected to the austempering treatment. That is, the rigid gear 2 may be made of a composite material in which spheroidal graphite cast iron having been subjected to quenching and tempering or spheroidal graphite cast iron having been subjected to austempering is combined with other materials. However, the main material may be spheroidal graphite cast iron subjected to quenching and tempering or spheroidal graphite cast iron subjected to austempering, as long as the spheroidal graphite cast iron or the austempered spheroidal graphite cast iron has a structure in which the ratio (% by mass) of the whole spheroidal graphite cast iron or the austempered spheroidal graphite cast iron to the other materials is larger than the other materials.

Further, the vickers hardness of the surface of the rigid gear 2 (internal gear) is preferably equal to or less than the vickers hardness of the surface of the flexible gear 3 (external gear). As a result, the surfaces of the internal teeth 23 of the rigid gear 2 are appropriately worn, and graphite derived from the spheroidal graphite cast iron included in the rigid gear 2 is exposed, whereby the lubricity of the surfaces of the internal teeth 23 is improved. As a result, wear due to sticking of the surface of the external teeth 33 of the flexible gear 3 to the surface of the internal teeth 23 of the rigid gear 2 is less likely to occur, and the life of the gear device 10 can be prolonged.

Further, the vickers hardness is a value in accordance with JIS Z2244: the vickers hardness test defined in 2009. Here, the test force of the indenter was set to 9.8N (1kgf), and the retention time of the test force was set to 15 seconds. Then, the average of the measurement results at 10 points was set as the vickers hardness.

the vickers hardness of the surface of the flexible gear 3 (external gear) is preferably in the range of 400 to 520, and more preferably in the range of 450 to 520. This can balance the mechanical strength and toughness of the flexible gear 3, and can suitably extend the life of the flexible gear 3. On the other hand, if the vickers hardness is too low, the strength of the flexible gear 3 is insufficient, and the flexible gear 3 may not withstand the load stress and may be easily broken. On the other hand, if the vickers hardness is too high, the toughness of the flexible gear 3 tends to be lowered, and the flexible gear is easily broken by impact or the like, and the wear of the rigid gear 2 excessively progresses, and there is a possibility that the durability of the gear device 10 is lowered.

The vickers hardness of the surface of the rigid gear 2 (internal gear) is preferably in the range of 300 to 450, and more preferably 320 to 400. This can balance the mechanical strength and toughness of the rigid gear 2, and can suitably extend the life of the rigid gear 2. On the other hand, if the vickers hardness is too low, the abrasion of the rigid gear 2 excessively progresses, and the transmission efficiency of the gear device 10 may be reduced. In addition, the rigid gear 2 may not be able to withstand the load stress and may be easily damaged. On the other hand, if the vickers hardness is too high, the impact at the time of meshing the rigid gear 2 with the flexible gear 3 becomes large, and there is a possibility that the flexible gear 3 is damaged or the durability of the gear device 10 is lowered.

In addition, it is preferable to apply compressive residual stress to at least the surface of the outer teeth 33 of the flexible gear 3. This can realize the flexible gear 3 that can withstand high load stress while improving the fatigue strength of the external teeth 33, and as a result, can improve the durability of the gear device 10.

here, in order to obtain the above-described effects, the residual stress (compressive residual stress) of the flexible gear 3 is preferably in the range of-950 MPa to-450 MPa, more preferably in the range of-950 MPa to-550 MPa, and still more preferably in the range of-950 MPa to-750 MPa. On the other hand, if the absolute value of the residual stress is too small, the above-described effect tends to decrease. On the other hand, if the absolute value of the residual stress is too large, the external teeth 33 tend to be deformed too much due to the residual stress, and proper operation of the gear device 10 tends to be difficult.

In addition, such compressive residual stress can be provided by shot blasting the surface of the flexible gear 3. When the surface of the flexible gear 3 is subjected to the shot blasting in this manner, fine irregularities are formed on the surface of the flexible gear 3 as shown in fig. 4. This makes it possible to easily retain the lubricant G on the surface of the flexible gear 3. As a result, the durability of the gear device 10 can be improved.

Here, the surface roughness Ra1 of the external teeth 33 of the flexible gear 3 (external gear) is preferably in the range of 0.2 μm or more and 1.6 μm or less, and more preferably in the range of 0.2 μm or more and 0.8 μm or less. This makes it possible to reduce wear of the rigid gear 2 and to appropriately extend the life of the flexible gear 3 and the rigid gear 2 by facilitating retention of grease (lubricant G) on the external teeth 33 of the flexible gear 3. On the other hand, if the surface roughness is too small, the effect of easily retaining grease (lubricant G) on the external teeth 33 of the flexible gear 3 tends to be small. On the other hand, if the surface roughness is too large, contact resistance of the tooth surfaces of the external teeth 33 becomes large, efficiency of the gear device 10 is lowered, the rigid gear 2 tends to be easily worn, and durability of the gear device 10 tends to be lowered. Note that the surface roughness Ra1 is an arithmetic average roughness Ra of the external teeth 33, and is a roughness value in accordance with JIS B0601: 2013 by the method specified in the specification.

Further, the surface roughness Ra1 of the external teeth 33 of the flexible gear 3 (external gear) is preferably larger than the surface roughness Ra2 of the internal teeth 23 of the rigid gear 2 (internal gear). This makes it possible to reduce the contact resistance between the flexible gear 3 and the rigid gear 2 while facilitating the retention of grease (lubricant G) on the external teeth 33 of the flexible gear 3, and to suitably extend the life of the flexible gear 3 and the rigid gear 2.

On the other hand, the surface roughness Ra2 of the internal teeth 23 of the rigid gear 2 (internal gear) is preferably in the range of 0.1 μm or more and 0.8 μm or less, and more preferably in the range of 0.1 μm or more and 0.4 μm or less. This reduces the manufacturing cost of the rigid gear 2, and reduces the contact resistance between the flexible gear 3 and the rigid gear 2. On the other hand, if such surface roughness is too small, the effect of improving efficiency is small in terms of increasing the cost for machining the tooth form surface of the internal teeth 23. On the other hand, if the surface roughness is too large, contact resistance of the tooth surfaces of the internal teeth 23 becomes large, and the efficiency of the gear device 10 tends to be lowered. Note that the surface roughness Ra2 is an arithmetic average roughness Ra of the internal teeth 23, and is a roughness value in accordance with JIS B0601: 2013 by the method specified in the specification.

It is preferable that the average crystal grain size of the constituent material of the flexible gear 3 (external gear) is smaller than the average crystal grain size of the constituent material of the rigid gear 2 (internal gear). By the size relationship between the average crystal grain sizes of the constituent materials of the internal teeth 23 and the external teeth 33, the crystal grain size of the external teeth 33 can be reduced, and the lubricant G can be easily retained in the external teeth 33. Therefore, lubricant G can be left on outer teeth 33 against the centrifugal force due to the rotation of outer teeth 33. Here, lubricant G is preferentially held at the grain boundaries present on the surface of external teeth 33. This is considered because the grain boundaries function as fine recesses or grooves for receiving the lubricant G. Therefore, by reducing the crystal grain size of the external teeth 33, the density of the grain boundaries present on the surface of the external teeth 33 becomes high, and along with this, the lubricant G is easily retained on the surface of the external teeth 33.

When the crystal grain size of the external teeth 33 is reduced, the mechanical strength of the external teeth 33 can be improved, and the toughness of the external teeth 33 can be improved. As described above, the external teeth 33 repeatedly deform with the movement of the meshing position between the rigid gear 2 and the flexible gear 3, and therefore, higher mechanical strength and toughness than the internal teeth 23 are required. Therefore, it is extremely advantageous to improve the mechanical strength and toughness of the external teeth 33. Note that, in general, the mechanical strength of a metal increases in inverse proportion to the 1/2 power of the crystal grain size.

On the other hand, the crystal grain size of the internal teeth 23 can be increased by the above-described relationship in size of the average crystal grain size of the constituent materials of the internal teeth 23 and the external teeth 33, and the lubricant G can easily flow along the internal teeth 23. Therefore, the presence of unevenness or solidification of the lubricant G on the inner teeth 23 can be reduced. Here, since the internal teeth 23 do not rotate, the centrifugal force as in the above-described external teeth 33 does not act on the internal teeth 23, and thus the lubricant G tends to be easily retained. Therefore, by making the lubricant G on the internal teeth 23 flow easily, the sticking of the lubricant G or the shortage of the oil amount at a desired portion is prevented. This makes it possible to sufficiently exhibit the performance of lubricant G.

As described above, in the gear device 10, the above-described effect of retaining the lubricant G on the outer teeth 33 and the effect of reducing the uneven presence or solidification of the lubricant G on the inner teeth 23 can be simultaneously exhibited. These two effects act synergistically to effectively prolong the lubricating life of lubricant G. In particular, in a wave gear device such as the gear device 10, generally, the internal gear and the external gear mesh with each other with a very small backlash, and therefore, the requirement for the lubrication life of the lubricant is extremely high. Therefore, when the present invention is applied to such a gear device, the effect is remarkable.

Here, the "average crystal particle size" is a value determined in accordance with JIS G0551: 2013 "steel-grain size microscopic test method". When the average crystal grain size was measured, the surface of the test piece (internal teeth or external teeth) was etched with an etching solution to form grain boundaries, and the formed grain boundaries were observed with a microscope, and as the etching solution, 5% nital (5% nitric acid-ethanol) or an etching solution based on a picric acid aqueous solution (2% picric acid-0.2% sodium chloride-0.1% sulfuric acid-distilled water) was used. The above-described relationship in the size of the average crystal grain size may be satisfied at least by the internal teeth 23 and the external teeth 33, and may not be satisfied by other portions of the rigid gear 2 and the flexible gear 3, but the effect is remarkable when the other portions are satisfied. The crystal grain sizes of the internal teeth 23 and the external teeth 33 can be adjusted, for example, according to the material (metal composition) constituting them, the heat treatment at the time of production, and the like.

when the average crystal grain size of the constituent material of the external teeth 33 is represented by A and the average crystal grain size of the constituent material of the internal teeth 23 is represented by B, A and B may satisfy the relationship of A < B as described above, but in order to exhibit the above-described two effects appropriately, it is preferably 1.2. ltoreq. B/A. ltoreq.100, and more preferably 2. ltoreq. B/A. ltoreq.50. On the other hand, if the B/a ratio is too small, the balance of the above-described two effects tends to be poor, while if the B/a ratio is too large, the strength difference between the internal teeth 23 and the external teeth 33 tends to be too large, and the wear of one of the internal teeth 23 and the external teeth 33 tends to be rapid.

The average crystal grain size of the constituent material of the internal teeth 23 is preferably in the range of 20 μm to 150 μm, more preferably 30 μm to 100 μm, and still more preferably 30 μm to 50 μm. This enables the lubricant G to flow more efficiently along the internal teeth 23. In addition, when the internal teeth 23 are made of metal, the internal teeth 23 can be made excellent in mechanical strength. On the other hand, if such an average crystal grain size is too small, the fluidity of the lubricant G on the internal teeth 23 tends to decrease. On the other hand, if the average crystal grain size is too large, the strength of the internal teeth 23 may be insufficient depending on the constituent material of the internal teeth 23. Note that, if the range of the average crystal grain size is satisfied in the entire rigid gear 2, the above effect is significant.

On the other hand, the average crystal grain size of the constituent material of the external teeth 33 is preferably in the range of 0.5 μm or more and 30 μm or less, more preferably in the range of 5 μm or more and 20 μm or less, and still more preferably in the range of 5 μm or more and 15 μm or less. This enables lubricant G to be more effectively retained in external teeth 33. In addition, when the external teeth 33 are made of metal, the external teeth 33 can be made excellent in mechanical strength. On the other hand, if the average crystal grain size is too small, the workability at the time of manufacturing the external teeth 33 is deteriorated, and the depth of the recessed portions due to the grain boundaries present on the surface of the external teeth 33 is also reduced, so that the lubricant G is not easily retained in the external teeth 33. On the other hand, if the average crystal grain size is too large, the effect of holding the lubricant G in the external teeth 33 tends to be reduced, and it is difficult to secure the mechanical strength and toughness necessary for the external teeth 33. Note that, if the above range of the average crystal grain size is satisfied in the entire flexible gear 3, the above effect is remarkable.

In addition, a material other than the above-described materials may be added to the constituent material of the flexible gear 3 and the constituent material of the rigid gear 2 in a range of 0.01 mass% to 2 mass%. In particular, the constituent material of the flexible gear 3 (external gear) preferably contains the group iv element or the group v element in a range of 0.01 mass% to 0.5 mass%. Thus, even if heat treatment is performed during the production of the flexible gear 3, the growth of crystal grains of the ferrous material constituting the flexible gear 3 is suppressed, and the crystal grain size can be reduced. Therefore, the mechanical strength of the flexible gear 3 can be improved. Further, according to the gear device 10 including the flexible gear 3, durability of the gear device 10 can be improved by improving mechanical strength of the flexible gear 3.

Here, as described above, the group iv element or the group V element may be used as the additive element, but one of titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), and tantalum (Ta) is preferably used alone or in combination of two or more, more preferably at least one of zirconium (Zr) and niobium (Nb), and further preferably both of zirconium (Zr) and niobium (Nb). This makes it possible to more effectively exhibit an effect of suppressing the growth of crystal grains of the iron-based material constituting the flexible gear 3 (hereinafter, also referred to as "crystal grain growth suppression effect"). Note that the material constituting the flexible gear 3 may contain elements other than the group iv element and the group v element, and may contain yttrium (Y) from the viewpoint of effectively suppressing the growth of crystal grains of the iron-based material constituting the flexible gear 3, for example.

The content (addition amount) of the additive element in the constituent material of the flexible gear 3 is preferably in the range of 0.05 mass% to 0.3 mass%, and more preferably in the range of 0.1 mass% to 0.2 mass%. This can more effectively exhibit the effect of suppressing grain growth. On the other hand, if the content is too small, the effect of suppressing the grain growth may be significantly reduced. On the other hand, if the content is too large, not only the crystal grain growth suppression effect cannot be obtained, but also the toughness of the flexible gear 3 may be lowered, and the mechanical strength of the flexible gear 3 may be rather lowered or the workability in manufacturing the flexible gear 3 may be extremely poor.

(case)

The housing 5 shown in fig. 2 has: a substantially plate-shaped cover 11 that supports a shaft 61 (e.g., an input shaft) via a bearing 13; and a cup-shaped body 12 that supports a shaft 62 (e.g., an output shaft) via a bearing 14. Here, the cover 11 and the body 12 are coupled (fixed) to form a space, and the gear device body 1 is housed in the space. The rigid gear 2 of the gear device body 1 is fixed to at least one of the cover 11 and the body 12 by, for example, screwing.

The inner wall surface 111 of the lid 11 is formed in a shape expanding in a direction perpendicular to the axis a so as to cover the opening 36 of the flexible gear 3. In addition, the inner wall surface 121 of the main body 12 is formed in a shape along the outer peripheral surface and the bottom surface of the flexible gear 3. The housing 5 is fixed to the base 110 of the robot 100. Here, the lid body 11 may be separate from the base 110 and fixed to the base 110 by, for example, screwing or the like, or may be integral with the base 110. The material of the case 5 (the lid 11 and the body 12) is not particularly limited, but examples thereof include a metal material and a ceramic material.

(Lubricant)

The lubricant G is, for example, grease (semi-solid lubricant) and is disposed at least one of between the rigid gear 2 and the flexible gear 3 (meshing portion) as the portion to be lubricated and between the flexible gear 3 and the wave generator 4 (contact portion/sliding portion) (hereinafter also simply referred to as "portion to be lubricated"). This reduces friction in the part to be lubricated.

In this way, the gear device 10 includes the lubricant G disposed between the rigid gear 2 (internal gear) and the flexible gear 3 (external gear). Preferably, the lubricant G contains a base oil, a thickener, and an organic molybdenum compound, and the oil separation degree of the lubricant G is in the range of 4 mass% or more and 13.8 mass% or less. Since the lubricant G contains the organic molybdenum compound, friction at the meshing portion of the rigid gear 2 and the flexible gear 3 can be effectively reduced. Further, since the oil separation degree of the lubricant G is in the range of 4 mass% or more and 13.8 mass% or less, even if the lubricant G contains the organic molybdenum compound, the base oil is not easily inhibited from exuding from the thickener, and the base oil can be stably supplied to the contact portion between the flexible gear 3 and the wave generator 4. As a result, the life of the flexible gear 3 and the rigid gear 2 can be appropriately extended.

Examples of the base oil include mineral oils (refined mineral oils) such as paraffins and naphthenes, and synthetic oils such as polyolefins, esters, and silicones, and one of them may be used alone or two or more of them may be used in combination. Examples of the thickener include soaps such as calcium soap, calcium complex soap, sodium soap, aluminum soap, lithium soap, and lithium complex soap, and non-soaps such as polyurea, sodium terephthalate, Polytetrafluoroethylene (PTFE), organobentonite, and silica gel, and one of them may be used alone or two or more of them may be used in combination. In the lubricant G (grease) containing the base oil and the thickener as components, the three-dimensional structure formed by the thickener is complexly complexed to hold the base oil, and the held base oil is slightly oozed to exert a lubricating effect.

Here, it is preferable that the content of the base oil in the lubricant G is 75% by mass or more and 85% by mass or less, and the content of the thickener in the lubricant G is 10% by mass or more and 20% by mass or less. This improves the lubricating performance of lubricant G.

In addition, the organomolybdenum compound functions as a solid lubricant or an extreme pressure agent. This can effectively reduce friction in the portion to be lubricated, and can effectively prevent sticking and scratching even when the portion to be lubricated is in an extreme pressure lubrication state. In particular, the organic molybdenum compound exhibits extreme pressure properties and wear resistance equivalent to those of molybdenum disulfide, and has superior oxidation stability as compared to molybdenum disulfide. Therefore, the life of lubricant G can be prolonged.

Here, the organic molybdenum compound is added to the lubricant G in a particle state, and when used in the gear device 10, the organic molybdenum compound has an effect of reducing the friction coefficient by forming a film on the lubrication target portion by a decomposition reaction. Therefore, the organic molybdenum compound is suitable for lubrication of the engaging portion between the rigid gear 2 and the flexible gear 3 that engage with a very small backlash, and the very small backlash between the flexible gear 3 and the wave generator 4. In contrast, in the case of molybdenum disulfide, in order to reduce friction of the lubrication target portion, even if the molybdenum disulfide adheres to the lubrication target portion, the particle state must be maintained, and it cannot be said that the molybdenum disulfide is suitable for lubrication at the meshing portion between the rigid gear 2 and the flexible gear 3 and the contact portion between the flexible gear 3 and the wave generator 4.

The content of the organic molybdenum compound in the lubricant G is preferably 1 mass% or more and 5 mass% or less, for example. This makes it easy to develop the performance of the organomolybdenum compound as an extreme pressure agent, and the properties of the lubricant G are remarkably improved. It is noted that other extreme-pressure agents such as zinc dialkyldithiophosphate may be used in combination as the extreme-pressure agent or the solid lubricant in addition to the organomolybdenum compound.

The average particle size of the organic molybdenum compound is generally about 10 μm, and is relatively large. Therefore, when only the organic molybdenum compound is added to the lubricant G, the base oil of the lubricant G is inhibited from bleeding out from the thickener and is reduced due to the influence of the particles of the organic molybdenum compound, and lubrication of the lubrication target portion may be insufficient. For example, the contact portion between the flexible gear 3 and the wave generator 4 is not easily supplied with the entire grease because of a small clearance, and it is important to be supplied with the base oil that seeps out from the thickener, and therefore lubrication deficiency is easily caused.

Accordingly, the oil separation degree of lubricant G is preferably in the range of 4 mass% to 13.8 mass%, more preferably 6 mass% to 11 mass%, and still more preferably 6 mass% to 10 mass%. This makes it difficult to prevent the base oil of the lubricant G from seeping out of the thickener, and the base oil can be stably supplied to the portion to be lubricated (particularly, the contact portion between the flexible gear 3 and the wave generator 4). Thus, the lubricant G can stably supply the base oil to the lubrication target portion by the base oil bleeding from the thickener while exhibiting the excellent friction reduction effect by the organic molybdenum compound, and as a result, the life of the gear device 10 can be prolonged. Further, "oil separation degree" is an index indicating the ability to bleed out a base oil from a thickener, and is a value in accordance with JIS K2220: 2013 by the measurement method specified in the description.

Here, from the viewpoint of the effect of improving the oil separation degree of the lubricant G as described above, the average particle diameter of the organomolybdenum compound (solid lubricant or extreme-pressure agent) added to the lubricant G is preferably in the range of 1 μm or more and 10 μm or less.

In addition, the oil separation shows a tendency to be larger as the consistency is larger (i.e., softer), with a certain degree of correlation with respect to consistency. Thus, for example, the consistency is adjusted according to the mixing ratio of the base oil and the thickener, whereby the lubricant G having a desired oil separation degree can be obtained.

the consistency of lubricant G is preferably 280 to 400 inclusive, more preferably 300 to 380 inclusive, and still more preferably 325 to 365 inclusive. This makes it possible to easily leave the lubricant G in the lubrication target portion. Further, there is an advantage that the oil separation degree of lubricant G can be easily made within the above range. On the other hand, if the consistency of the lubricant G is too low, it is difficult to select the base oil and the thickener in the range of the oil separation degree, and the fluidity of the lubricant G is insufficient, so that it is difficult to sufficiently supply the lubricant G to the meshing portion between the rigid gear 2 and the flexible gear 3. On the other hand, if the consistency of the lubricant G is too high, the fluidity of the lubricant G becomes too high, and the lubricant G tends to leak to the outside of the gear device 10 (for example, an unintended position in the housing 5 or the outside of the housing 5), so that the supply of the lubricant G to the meshing portion of the rigid gear 2 and the flexible gear 3 becomes unstable, and conversely, poor lubrication at the meshing portion may tend to occur. The "consistency" is an index indicating the hardness of the grease, and is measured in accordance with JIS K2220: 2013 by the measurement method specified in the description.

Further, the dropping point of lubricant G is preferably in the range of 248 ℃ to 270 ℃. This makes it possible to optimize the consistency of lubricant G and to improve the heat resistance of lubricant G. The "dropping point" refers to a temperature at which the grease structure is broken and changes from a semisolid to a liquid state, and is a temperature in accordance with JIS K2220: 2013 by the measurement method specified in the description.

Among the above thickeners, lithium complex soap is preferably used as the thickener used for lubricant G. This can increase the dropping point of lubricant G, and can improve the heat resistance of lubricant G. In the case where the lithium complex soap is used as the thickener, the lithium complex soap may be used alone as the thickener, or another thickener may be used in combination with the lithium complex soap. When other thickener is used in combination with the lithium complex soap, the content of the lithium complex soap in the whole thickener is preferably 70 mass% or more.

The lubricant G may contain, in addition to the base oil, the thickener, and the extreme pressure agent (organic molybdenum compound), additives such as an antioxidant and a rust preventive, and further, a solid lubricant such as graphite, molybdenum disulfide, Polytetrafluoroethylene (PTFE), and the like.

As described above, the gear device 10 includes: a rigid gear 2 as an internal gear; a flexible gear 3 as an external gear having flexibility and partially meshing with the rigid gear 2; and a wave generator 4 that contacts the inner peripheral surface of the flexible gear 3 and moves the meshing position of the rigid gear 2 and the flexible gear 3 in the circumferential direction. The flexible gear 3 is mainly made of nickel-chromium-molybdenum steel, and the rigid gear 2 is mainly made of spheroidal graphite cast iron subjected to quenching and tempering treatment or spheroidal graphite cast iron subjected to austenite tempering treatment.

According to the gear device 10, since the material constituting the flexible gear 3 includes nickel-chromium-molybdenum steel, the mechanical properties (particularly, fatigue strength) of the flexible gear 3 can be improved, and the life of the flexible gear 3 can be extended. On the other hand, since the material constituting the rigid gear 2 includes spheroidal graphite cast iron subjected to quenching and tempering treatment or spheroidal graphite cast iron subjected to austempering treatment, durability can be imparted to the rigid gear 2, and the life of the rigid gear 2 can be extended. By extending the life of both the flexible gear 3 and the rigid gear 2 in this way, the life of the gear device 10 can be extended. Further, the allowable range of torque that can be input can be expanded, and therefore, the gear device 10 can be made to have a higher torque.

As described above, the robot 100 includes: a base 110 as a first member; a first arm 120 as a second member that rotates with respect to the base 110; a gear device 10 that transmits a driving force for rotating the first arm 120 relative to the base 110; and a motor 170 as a driving source that outputs a driving force to the gear device 10. Further, one of the rigid gear 2, the flexible gear 3, and the wave generator 4 is connected to the base 110 (first member), and the other is connected to the first arm 120 (second member).

This makes it possible to extend the life of the robot 100, because the gear device 10 has an extended life. Further, since the frequency of replacement or repair of the gear device 10 can be reduced, the substantial operation time of the robot 100 can be ensured to be longer, and the work efficiency of the robot 100 can be improved.

< second embodiment >

next, a second embodiment of the present invention will be described.

fig. 5 is a longitudinal sectional view showing a gear device according to a second embodiment of the present invention.

This embodiment is the same as the first embodiment described above, except that the configuration of the external gear is different from the configuration of the housing. In the following description, the present embodiment will be mainly described with respect to differences from the above-described embodiments, and the description of the same items will be omitted. In fig. 5, the same components as those of the above embodiment are denoted by the same reference numerals.

The gear device 10B shown in fig. 5 includes a gear device main body 1B and a case 5B that houses the gear device main body 1B. Further, the case 5B may be omitted.

The gear device 10B includes a flexible gear 3B as a hat-shaped (hat-shaped with a visor) external gear disposed inside the rigid gear 2. The flexible gear 3B has a flange portion 32B (connecting portion) connected to one end portion of the cylindrical body portion 31 and protruding to the opposite side of the axis a. An output shaft, not shown, is attached to the flange portion 32B.

The housing 5B has: a substantially plate-shaped cover 11B that supports a shaft 61 (e.g., an input shaft) via a bearing 13; and a cross roller bearing 18 attached to the flange portion 32B of the flexible gear 3B.

Here, the cover 11B is fixed to one (right side in fig. 5) side surface of the rigid gear 2 by, for example, screwing or the like. The cross roller bearing 18 includes an inner ring 15, an outer ring 16, and a plurality of rollers 17 disposed therebetween. The inner ring 15 is provided along the outer periphery of the main body portion 31 of the flexible gear 3, and is fixed to the other (left side in fig. 5) side surface of the rigid gear 2 by, for example, screwing. On the other hand, the outer ring 16 is fixed to the surface of the flange portion 32B of the flexible gear 3B on the side of the body portion 31 by, for example, screwing.

The inner wall surface 111B of the lid 11B is formed so as to extend in a direction perpendicular to the axis a so as to cover the opening 36 of the flexible gear 3B. The inner wall surface 151 of the inner race 15 of the cross roller bearing 18 is shaped to follow the outer peripheral surface of the main body portion 31 of the flexible gear 3B.

The gear device 10B as described above includes the lubricant G disposed in at least one of (the portion to be lubricated) between the rigid gear 2 and the flexible gear 3B and between the flexible gear 3B and the wave generator 4. Here, one member (the rigid gear 2 in the present embodiment, but the flexible gear 3B or the wave generator 4) of the rigid gear 2, the flexible gear 3B, and the wave generator 4 is connected to the base 110 (the first member), and the other member (the flexible gear 3B in the present embodiment, but the rigid gear 2 or the wave generator 4 may be connected to the first arm 120 (the second member).

The second embodiment described above can also exhibit the same effects as those of the first embodiment.

3. Method for manufacturing gear device

an embodiment of a method for manufacturing a gear device according to the present invention will be described below.

Fig. 6 is a process diagram showing an embodiment of a method for manufacturing a gear device according to the present invention.

The method for manufacturing a gear device according to the present embodiment includes: a member preparation step of preparing an internal gear member made mainly of spheroidal graphite cast iron; and a heat treatment step of subjecting the member for internal gear to quenching and tempering treatment or austempering treatment to obtain an internal gear. The respective steps are explained below.

[1] Component preparation step S1

First, an internal gear member made of a material containing spheroidal graphite cast iron was prepared. The member for internal gear may be a member produced by any method. The internal gear member is formed in the shape of the above-described rigid gear 2.

It is preferable that the spheroidal graphite cast iron included in the member for internal gears is mainly composed of graphite in a granular form and a matrix, wherein the matrix includes a pearlite structure. The pearlite structure is a lamellar cementite structure containing iron carbide as a main component. The term "lamellar" means a state in which the aspect ratio defined by the major axis/minor axis of the crystal structure is 5 or more. Since the matrix contains such a pearlite structure, when the spheroidal graphite cast iron is subjected to quenching and tempering treatment or austempering treatment, which will be described later, iron carbide can be efficiently dispersed in the matrix. As a result, the mechanical properties of the spheroidal graphite cast iron after heat treatment can be stabilized, and the durability of the rigid gear 2 can be further improved.

In particular, when the spheroidal graphite cast iron including the pearlite structure in the matrix is subjected to quenching and tempering treatment, the change from the pearlite structure to the sorbite structure can be easily generated. That is, the change from the lamellar cementite structure to the granular structure can be easily caused. As a result, the rigid gear 2 having a homogeneous sorbite structure and particularly excellent toughness and elongation can be realized.

the pearlite structure may be present alone or as a mixed structure with the ferrite structure or other structures.

[2] Heat treatment Process S2

Next, the member for an internal gear is subjected to quenching and tempering treatment or austempering treatment. Thereby, the rigid gear 2 (internal gear) is obtained.

(quenching and tempering treatment)

In the quenching and tempering treatment, the spherical graphite cast iron is sequentially subjected to the quenching treatment and the tempering treatment.

The quenching treatment includes, for example, a treatment of maintaining the temperature sufficiently at or above the austenitizing temperature and then quenching the steel in water or oil to cause martensitic transformation.

The heating temperature (quenching temperature) of the quenching treatment is slightly different depending on the alloy composition of the spheroidal graphite cast iron, but is preferably 800 ℃ or higher and 900 ℃ or lower, and more preferably 850 ℃ or higher and 900 ℃ or lower.

the holding time of the quenching temperature is appropriately set in accordance with the quenching temperature, the heat capacity of the object to be heated, and the like, and is preferably 10 minutes to 5 hours, and more preferably 30 minutes to 3 hours, as an example.

The temperature increase rate in the quenching treatment is appropriately set in accordance with the quenching temperature, the heat capacity of the object to be heated, and the like, and is preferably 30 ℃/hour or more and 200 ℃/hour or less, and more preferably 50 ℃/hour or more and 150 ℃/hour or less, as an example.

If the heating conditions are not as described above, there is a possibility that the sorbite structure or the structure based on the sorbite structure cannot be sufficiently generated.

On the other hand, as the tempering treatment, for example, a treatment of heating the martensite structure formed by the quenching treatment at a temperature which can be changed to a sorbite structure and then slowly cooling the heated martensite structure is exemplified.

The heating temperature (tempering temperature) for the tempering treatment is slightly different depending on the alloy composition of the spheroidal graphite cast iron, but is preferably 200 ℃ or more and 700 ℃ or less, and more preferably 250 ℃ or more and 650 ℃ or less.

The holding time of the tempering temperature is appropriately set depending on the tempering temperature, the heat capacity of the object to be heated, and the like, and is preferably 10 minutes to 3 hours, and more preferably 30 minutes to 2 hours, as an example.

the cooling rate during tempering is appropriately set according to the tempering temperature, the heat capacity of the object to be heated, and the like, and is preferably 10 ℃/hr or more and 100 ℃/hr or less, and more preferably 20 ℃/hr or more and 80 ℃/hr or less, as an example.

if the heating conditions are not as described above, there is a possibility that the sorbite structure or the structure based on the sorbite structure cannot be sufficiently generated.

(Austenitic tempering treatment)

Here, the austempering treatment includes, for example, a treatment (constant temperature transformation treatment) in which the spheroidal graphite cast iron is sufficiently held at a temperature equal to or higher than the austenitizing temperature, and then is rapidly cooled and held in a molten salt bath (salt bath).

The heating temperature for the austempering treatment is slightly different depending on the alloy composition of the spheroidal graphite cast iron, but is preferably 800 ℃ or higher and 900 ℃ or lower, and more preferably 850 ℃ or higher and 900 ℃ or lower.

The holding time of the heating temperature is appropriately set in accordance with the heating temperature, the heat capacity of the object to be heated, and the like, and is preferably 10 minutes or more and 3 hours or less, and more preferably 30 minutes or more and 1 hour or less, as an example.

The temperature increase rate in the austempering treatment is appropriately set in accordance with the heating temperature, the heat capacity of the object to be heated, and the like, and is preferably 30 ℃/hr or more and 200 ℃/hr or less, and more preferably 50 ℃/hr or more and 150 ℃/hr or less, as an example.

If the heating conditions are deviated from the above-described heating conditions, the bainite structure or the structure based on the bainite structure may not be sufficiently formed.

On the other hand, in the quenching and holding by the molten salt bath (salt bath), the temperature of the molten salt bath is preferably set to, for example, 200 ℃ or more and 450 ℃ or less, more preferably 230 ℃ or more and 400 ℃ or less.

The holding time in the molten salt bath is not particularly limited, but is preferably 10 minutes or more and 2 hours or less, and more preferably 30 minutes or more and 1 hour or less, as an example.

Examples of the molten salt used in the molten salt bath include nitrate-based molten salts and chloride-based molten salts.

If the heating conditions are deviated from the above-described heating conditions, the bainite structure or the structure based on the bainite structure may not be sufficiently formed.

[3] Assembling step S3

The method of manufacturing a gear device according to the present embodiment may further include a step of assembling the manufactured rigid gear 2 and other components. Further, lubricant G or the like is applied as necessary. Thereby, the gear device 10 can be obtained.

As described above, the method for manufacturing a gear device according to the present embodiment is a method for manufacturing a gear device such as the gear device 10 described above, and includes: a member preparation step of preparing an internal gear member made mainly of spheroidal graphite cast iron; and a heat treatment step of subjecting the member for internal gear to quenching and tempering treatment or austempering treatment to obtain a rigid gear 2 as an internal gear.

According to such a manufacturing method, the rigid gear 2 can be provided with excellent toughness and elongation, and the rigid gear 2 having high durability can be efficiently manufactured. As a result, the gear device 10 having a long life can be efficiently manufactured.

The robot, the gear device, and the method for manufacturing the gear device according to the present invention have been described above based on the illustrated embodiments, but the present invention is not limited thereto, and the configuration of each part may be replaced with any configuration having the same function. In addition, other arbitrary components may be added to the present invention.

In the above-described embodiment, the description has been given of the gear device in which the base provided in the robot is the "first member", the first arm is the "second member", and the driving force is transmitted from the first member to the second member, but the present invention is not limited to this, and the present invention can also be applied to a gear device in which the nth (n is an integer equal to or greater than 1) arm is the "first member", and the (n +1) th arm is the "second member", and the driving force is transmitted from one of the nth arm and the (n +1) th arm to the other. Further, the present invention can also be applied to a gear device that transmits a driving force from the second member to the first member.

In the above-described embodiment, the horizontal articulated robot has been described, but the robot of the present invention is not limited to this, and for example, the number of joints of the robot is arbitrary, and the present invention can also be applied to a vertical articulated robot.

In the above-described embodiments, the case where the gear device is incorporated into the robot has been described as an example, but the gear device of the present invention can be incorporated into various apparatuses having a configuration in which a driving force is transmitted from one side to the other side of the first member and the second member that rotate relative to each other.