Internally meshing planetary gear system and robotic joint system

Abstract

To provide an internal meshing planetary gear device capable of regulating axial movement of a crankshaft even with a relatively simple configuration, and an articulation device for a robot.SOLUTION: An internal meshing planetary gear device 1B comprises an internal gear 2, a planetary gear 3, an input side carrier 18, an output side carrier 19, a first regulation structure 91, and a second regulation structure 92. The first regulation structure 91 includes an input side cover 13 attached to the input side carrier 18 on a side opposite to the planetary gear 3 in an axial direction. The first regulation structure 91 regulates movement of a crankshaft 7A in one axial direction by bringing a step part 70 into contact with the input side cover 13 directly or indirectly. The second regulation structure 92 regulates movement of the crankshaft 7A in the other axial direction by bringing the step part 70 into contact with the output side carrier 19 directly or indirectly.SELECTED DRAWING: Figure 17

Description

Technical Field

[0001] The present disclosure generally relates to an internal meshing planetary gear device and a joint device for a robot, and more particularly, to an internal meshing planetary gear device and a joint device for a robot in which a planetary gear having external teeth is disposed inside an internal gear having internal teeth.

Background Art

[0002] As a related art, an eccentric swing type internal meshing planetary gear device called a distribution type is known (see, for example, Patent Document 1). In the internal meshing planetary gear device according to the related art, a plurality (for example, three) of crank shafts disposed at positions offset from the axial center of the internal gear are provided, and each crank shaft is synchronously driven by a crank shaft gear, whereby the planetary gear (external gear) is internally meshed with the internal gear while swinging.

[0003] The planetary gear includes a first planetary gear and a second planetary gear. A pair of carriers are disposed on both axial sides of the first planetary gear and the second planetary gear. Each crank shaft is supported by a pair of carriers via a pair of tapered roller bearings. When the input gear rotates, the three crank shaft gears meshing with the input gear at the same time rotate in the same direction at the same rotational speed. Since a crank shaft is spline-connected to each crank shaft gear, the three crank shafts rotate in the same direction at the same rotational speed in a state decelerated by the gear ratio between the input gear and the crank shaft gear. As a result, the three first eccentric portions formed at the same axial position of the three crank shafts rotate synchronously to swing the first planetary gear, and the three second eccentric portions respectively formed at the same axial position of the three crank shafts rotate synchronously to swing the second planetary gear.

[0004] The first and second planetary gears are internally meshed with an internal gear. The internal gear has a gear body and external pins (pin members) that are rotatably mounted within the gear body and constitute the internal teeth of the internal gear. Here, the number of teeth (number of external pins) of the internal gear is slightly greater than the number of teeth of each planetary gear. Therefore, with each oscillation of each planetary gear, the first and second planetary gears rotate (shift in phase in the circumferential direction by the difference in the number of teeth) relative to the internal gear, and this rotation is transmitted to the pair of carriers as revolution around the axis (axis of rotation) of the internal gear of each crankshaft. This allows the pair of carriers to rotate relative to the gear body (and the casing integrated with it) around the axis of rotation. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2016-75354 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In the configuration of the related technologies described above, each crankshaft is supported by a pair of carriers via a pair of tapered roller bearings, which restricts axial movement. This results in a complex configuration and makes it difficult to miniaturize the entire device.

[0007] The purpose of this disclosure is to provide an internally joined planetary gear system and a robotic joint system that can restrict the axial movement of a crankshaft, despite having a relatively simple configuration. [Means for solving the problem]

[0008] An internally meshing planetary gear system according to one aspect of the present disclosure comprises an internal gear, planetary gears, a crankshaft, an input carrier and an output carrier, wherein the planetary gears are rotated relative to the internal gear by oscillating the planetary gears. The internal gear has an annular gear body and a plurality of external pins that are rotatably held in a plurality of internal grooves formed on the inner surface of the gear body and constitute the internal teeth. The planetary gears have external teeth that partially mesh with the internal teeth. The crankshaft has stepped portions at least two locations in the axial direction along its axis and oscillates the planetary gears by rotating about the axis. The input carrier and the output carrier are arranged on both sides of the planetary gears in the axial direction and rotatably support the crankshaft. The internally meshing planetary gear system further comprises a first restricting structure and a second restricting structure. The first restricting structure includes an input cover mounted on the input carrier on the side opposite to the planetary gears in the axial direction. The first restricting structure restricts the movement of the crankshaft in one axial direction by directly or indirectly contacting the stepped portion with the input-side cover. The second restricting structure restricts the movement of the crankshaft in the other axial direction by directly or indirectly contacting the stepped portion with the output-side carrier.

[0009] A robotic joint device according to one aspect of the present disclosure comprises: an internal meshing planetary gear device; a first member fixed to the gear body; and a second member that rotates relative to the first member in accordance with the relative rotation of the planetary gear with respect to the internal gear. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide an internally joined planetary gear system and a robotic joint system that can restrict the axial movement of a crankshaft, despite having a relatively simple configuration. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a perspective view showing the schematic configuration of an actuator, including an internally meshing planetary gear system, which is part of the basic configuration. [Figure 2] Figure 2 is a schematic exploded perspective view of the same internally meshed planetary gear system as seen from the input side of the rotating shaft. [Figure 3] Figure 3 is a schematic exploded perspective view of the same internally meshing planetary gear mechanism as seen from the output side of the rotating shaft. [Figure 4] Figure 4 is a schematic cross-sectional view of the internally meshing planetary gear set shown above. [Figure 5] Figure 5 is a cross-sectional view taken along line A1-A1 in Figure 4, showing the same internally meshed planetary gear mechanism. [Figure 6] Figure 6 is a cross-sectional view taken along line B1-B1 in Figure 4, showing the same internally meshing planetary gear system. [Figure 7] Figure 7 is a schematic cross-sectional view of an internally meshing planetary gear system according to Reference Example 1. [Figure 8] Figure 8 is a schematic diagram of the same internally meshed planetary gear system as seen from the output side of the rotating shaft. [Figure 9] Figure 9 is a schematic perspective view showing the configuration around the crankshaft of the internally meshing planetary gear system described above. [Figure 10] Figure 10 is a schematic exploded perspective view showing the configuration around the crankshaft of the internally meshing planetary gear system described above. [Figure 11] Figure 11 is a schematic perspective view showing the crankshaft of the internally meshed planetary gear system described above. [Figure 12] Figure 12 shows the main parts of the internally meshing planetary gear mechanism described above, and is a schematic enlarged view of region Z1 in Figure 7. [Figure 13] Figure 13 shows the main components of the internally meshing planetary gear system described above, and is a schematic enlarged view of region Z2 in Figure 7. [Figure 14] Figure 14 shows the main parts of the internally meshing planetary gear system described above, and is a schematic enlarged view of region Z1 in Figure 13. [Figure 15] Figure 15 is a schematic diagram showing a robot joint device using the internal meshing planetary gear system described above. [Figure 16] Figure 16 is a schematic cross-sectional view of an internally meshing planetary gear system according to Embodiment 1. [Figure 17]FIG. 17 shows a main part of the above-mentioned internal meshing planetary gear device and is a schematic enlarged view of region Z1 in FIG. 16.

Embodiment for Carrying out the Invention

[0012] (Basic Configuration) (1) Overview Hereinafter, the overview of the internal meshing planetary gear device 1 according to this basic configuration will be described with reference to FIGS. 1 to 4. All the drawings referred to in this disclosure are schematic drawings, and the ratios of the sizes and thicknesses of each component in the drawings do not necessarily reflect the actual dimensional ratios. For example, in FIGS. 1 to 4, the tooth profiles, dimensions, number of teeth, etc. of the internal teeth 21 and the external teeth 31 are merely schematically shown for the purpose of explanation and are not intended to be limited to the illustrated shapes.

[0013] The internal meshing planetary gear device 1 according to this basic configuration (hereinafter, also simply referred to as "gear device 1") is a gear device including an internal gear 2 and a planetary gear 3. In this gear device 1, the planetary gear 3 is arranged inside the annular internal gear 2, and by swinging the planetary gear 3, the planetary gear 3 is rotated relative to the internal gear 2. Further, the internal meshing planetary gear device 1 further includes a bearing member 6 having an outer ring 62 and an inner ring 61. The inner ring 61 is arranged inside the outer ring 62 and is supported so as to be rotatable relative to the outer ring 62. In particular, the gear device 1 according to this basic configuration is an eccentric swing type internal meshing planetary gear device called a distribution type.

[0014] As shown in Figures 1 to 4, the gear unit 1 in this basic configuration includes multiple (three in the basic configuration) crankshafts (eccentric shafts) 7A, 7B, and 7C positioned at an offset location from the axis (rotation axis Ax1) of the internal gear 2. Furthermore, the gear unit 1 includes an input shaft 500 centered on the rotation axis Ax1, which is positioned on the axis (rotation axis Ax1) of the internal gear 2, and an input gear 501 formed integrally with the input shaft 500. Crankshaft gears 502A, 502B, and 502C are spline-connected to the multiple crankshafts 7A, 7B, and 7C, respectively. These multiple (three in the basic configuration) crankshaft gears 502A, 502B, and 502C are arranged to mesh with the input gear 501. Therefore, when the input shaft 500 is driven, the gear unit 1 oscillates the planetary gear 3 by synchronously driving the crankshafts 7A, 7B, and 7C with the input gear 501.

[0015] The internal gear 2 has internal teeth 21 and is fixed to the outer ring 62. In particular, in this basic configuration, the internal gear 2 has an annular gear body 22 and a plurality of external pins 23. The plurality of external pins 23 are held on the inner circumferential surface 221 of the gear body 22 in a state where they can rotate, and constitute the internal teeth 21. The planetary gear 3 has external teeth 31 that partially mesh with the internal teeth 21. That is, the planetary gear 3 is inscribed with the internal gear 2 inside the internal gear 2, and a portion of the external teeth 31 meshes with a portion of the internal teeth 21. In this state, when the plurality of crankshafts 7A, 7B, and 7C are driven, the planetary gear 3 oscillates, the meshing position between the internal teeth 21 and the external teeth 31 moves in the circumferential direction of the internal gear 2, and relative rotation corresponding to the difference in the number of teeth between the planetary gear 3 and the internal gear 2 occurs between the two gears (internal gear 2 and planetary gear 3). If the internal gear 2 is fixed, then the planetary gear 3 will rotate (rotate on its own axis) in conjunction with the relative rotation of the two gears. As a result, the planetary gear 3 will produce a rotational output that is reduced at a relatively high reduction ratio, corresponding to the difference in the number of teeth of the two gears.

[0016] This type of gear device 1 is used to extract the rotational component of the planetary gear 3 as the rotation of a pair of carriers 18 and 19 integrated with the inner ring 61 of the bearing member 6. As a result, the gear device 1 functions as a gear device with a relatively high reduction ratio, with the input shaft 500 as the input side and the pair of carriers 18 and 19 as the output side. In this basic configuration of the gear device 1, the pair of carriers 18 and 19 support multiple crankshafts 7A, 7B, and 7C in order to transmit the rotational component of the planetary gear 3 to the pair of carriers 18 and 19. The pair of carriers 18 and 19 are arranged on both sides in the axial direction of the planetary gear 3 (along the rotation axis Ax1) and rotatably support each crankshaft 7A, 7B, and 7C.

[0017] Here, the multiple crankshafts 7A, 7B, and 7C are inserted into multiple openings 33 formed in the planetary gear 3, and rotate relative to the internal gear 2 as the planetary gear 3 rotates. Each crankshaft 7A, 7B, and 7C has an axial portion 71 and an eccentric portion 72 that is eccentric with respect to the axial portion 71. A pair of carriers 18 and 19 rotatably support the axial portion 71 of each crankshaft 7A, 7B, and 7C, and the eccentric portions 72 of each crankshaft 7A, 7B, and 7C are inserted into the openings 33 of the planetary gear 3. Therefore, the oscillation component of the planetary gear 3, that is, the orbital component of the planetary gear 3, is absorbed by the orbital component of the eccentric portion 72 relative to the axial portion 71. In other words, the eccentric portion 72 of the axial center 71 of each crankshaft 7A, 7B, and 7C rotates so as to revolve around the axial center 71, thereby absorbing the oscillation component of the planetary gear 3. Therefore, the rotation (rotation component) of the planetary gear 3, excluding the oscillation component (revolution component), is transmitted to the pair of carriers 18 and 19 by the multiple crankshafts 7A, 7B, and 7C.

[0018] Furthermore, the gear device 1 in this basic configuration, together with the drive source 101, constitutes an actuator 100, as shown in Figure 1. In other words, the actuator 100 in this basic configuration comprises the gear device 1 and the drive source 101. The drive source 101 generates a driving force to oscillate the planetary gear 3. Specifically, the drive source 101 oscillates the planetary gear 3 by rotating the input shaft 500 around the rotation axis Ax1.

[0019] (2) Definition As used in this disclosure, "ring-shaped" means a ring-like shape that forms an enclosed space (region) at least in a plan view, and is not limited to a circular shape (ring-shaped) that is a perfect circle in a plan view, but may also be an elliptical shape, a polygonal shape, etc. Furthermore, even a shape with a bottom, such as a cup shape, is included in "ring-shaped" if its peripheral wall is ring-shaped.

[0020] In this disclosure, "revolution" means that an object revolves around an axis of rotation other than the central axis passing through the object's center (center of gravity). When an object revolves, its center moves along the orbital path centered on the axis of rotation. Therefore, for example, if an object rotates around an eccentric axis parallel to the central axis passing through its center (center of gravity), the object is revolving around the eccentric axis as its axis of rotation. As an example, the planetary gear 3 revolves inside the internal gear 2 by oscillating, so as to revolve around the axis of rotation Ax1.

[0021] Furthermore, in this disclosure, one side of the rotating shaft Ax1 (the left side in Figure 4) may be referred to as the "output side," and the other side of the rotating shaft Ax1 (the right side in Figure 4) may be referred to as the "input side." In the example in Figure 4, rotation is applied to the input shaft 500 from the "input side" of the rotating shaft Ax1, and the rotation of the pair of carriers 18 and 19 is extracted from the "output side" of the rotating shaft Ax1. However, "input side" and "output side" are merely labels used for explanatory purposes and are not intended to limit the positional relationship between the input and output as seen from the gear device 1.

[0022] In this disclosure, "axis of rotation" refers to a virtual axis (straight line) that is the center of the rotational motion of the rotating body. In other words, the axis of rotation Ax1 is a virtual axis that does not have a physical form. The input shaft 500 performs rotational motion around the axis of rotation Ax1.

[0023] In this disclosure, "internal teeth" and "external teeth" refer not to individual "teeth," but to a collection (group) of multiple "teeth." In other words, the internal teeth 21 of the internal gear 2 consist of a collection of multiple teeth arranged on the inner circumferential surface 221 of the internal gear 2 (gear body 22). Similarly, the external teeth 31 of the planetary gear 3 consist of a collection of multiple teeth arranged on the outer circumferential surface of the planetary gear 3.

[0024] (3) Composition The detailed configuration of the internally meshing planetary gear unit 1 related to this basic configuration will be explained below with reference to Figures 1 to 6.

[0025] Figure 1 is a perspective view showing the schematic configuration of the actuator 100 including the gear unit 1. In Figure 1, the drive source 101 is schematically shown. Figure 2 is a schematic exploded perspective view of the gear unit 1 as seen from the input side of the rotating shaft Ax1. Figure 3 is a schematic exploded perspective view of the gear unit 1 as seen from the output side of the rotating shaft Ax1. Figure 4 is a schematic cross-sectional view of the gear unit 1. Figure 5 is a cross-sectional view taken along line A1-A1 in Figure 4. Figure 6 is a cross-sectional view taken along line B1-B1 in Figure 4. However, in Figures 5 and 6, hatching is omitted for parts other than the crankshafts 7A, 7B, and 7C, even in cross-sections.

[0026] (3.1) Overall structure As shown in Figures 1 to 4, the gear unit 1 in this basic configuration comprises an internal gear 2, a planetary gear 3, a bearing member 6, a plurality of crankshafts 7A, 7B, 7C, a pair of carriers 18, 19, and an input shaft 500. Furthermore, in this basic configuration, the gear unit 1 further comprises an input gear 501, a plurality of crankshaft gears 502A, 502B, 502C, a pair of rolling bearings 41, 42, an eccentric bearing 5, and a case 10. In this basic configuration, the materials of the components of the gear unit 1, such as the internal gear 2, planetary gear 3, the plurality of crankshafts 7A, 7B, 7C, and the pair of carriers 18, 19, are metals such as stainless steel, cast iron, carbon steel for machine structures, chromium-molybdenum steel, phosphor bronze, or aluminum bronze, or light metals such as aluminum or titanium. The term "metal" (including light metals) here includes metals that have undergone surface treatment such as nitriding.

[0027] Furthermore, in this basic configuration, an internal planetary gear system using a trochoidal tooth profile is given as an example of the gear system 1. In other words, the gear system 1 in this basic configuration is equipped with an internal planetary gear 3 having a trochoidal curved tooth profile.

[0028] Furthermore, in this basic configuration, as an example, the gear device 1 is used with the gear body 22 of the internal gear 2 fixed to a fixed member such as the case 10, together with the outer ring 62 of the bearing member 6. As a result, the planetary gear 3 rotates relative to the fixed member (case 10, etc.) as the internal gear 2 and the planetary gear 3 rotate relative to each other.

[0029] Furthermore, in this basic configuration, when the gear unit 1 is used as the actuator 100, a rotational force is applied to the input shaft 500 as input, and a rotational force is extracted as output from the pair of carriers 18 and 19 integrated with the inner ring 61 of the bearing member 6. In other words, the gear unit 1 operates with the rotation of the input shaft 500 as the input rotation and the rotation of the pair of carriers 18 and 19 integrated with the inner ring 61 as the output rotation. As a result, the gear unit 1 obtains an output rotation that is reduced with a relatively high reduction ratio relative to the input rotation.

[0030] The drive source 101 is a power source such as a motor. The power generated by the drive source 101 is transmitted to the input shaft 500 in the gear unit 1. Specifically, the drive source 101 is connected to the input shaft 500, and the power generated by the drive source 101 is transmitted to the input shaft 500. This allows the drive source 101 to rotate the input shaft 500.

[0031] Furthermore, in the gear device 1 relating to this basic configuration, as shown in Figure 4, the input rotation axis Ax1 and the output rotation axis Ax1 are on the same straight line. In other words, the input rotation axis Ax1 and the output rotation axis Ax1 are coaxial. Here, the input rotation axis Ax1 is the rotation center of the input shaft 500 to which the input rotation is applied, and the output rotation axis Ax1 is the rotation center of the inner ring 61 (and a pair of carriers 18, 19) that generates the output rotation. In other words, in the gear device 1, an output rotation reduced at a relatively high reduction ratio relative to the input rotation is obtained on the same axis.

[0032] As shown in Figures 5 and 6, the internal gear 2 is an annular component having internal teeth 21. In this basic configuration, the internal gear 2 has an annular shape, with at least its inner circumferential surface being a perfect circle in plan view. The internal teeth 21 are formed on the inner circumferential surface of the annular internal gear 2, along the circumferential direction of the internal gear 2. All of the teeth constituting the internal teeth 21 are of the same shape and are provided at equal pitches across the entire circumferential area of ​​the inner circumferential surface of the internal gear 2. In other words, the pitch circle of the internal teeth 21 is a perfect circle in plan view. The center of the pitch circle of the internal teeth 21 lies on the rotation axis Ax1. The internal gear 2 also has a predetermined thickness in the direction of the rotation axis Ax1. The tooth traces of the internal teeth 21 are all parallel to the rotation axis Ax1. The dimension of the internal teeth 21 in the direction of the tooth traces is slightly smaller than the thickness direction of the internal gear 2.

[0033] Here, the internal gear 2, as described above, has an annular (circular) gear body 22 and a plurality of external pins 23. The plurality of external pins 23 are held on the inner circumferential surface 221 of the gear body 22 in a state in which they can rotate, and constitute the internal teeth 21. In other words, the plurality of external pins 23 each function as a plurality of teeth that constitute the internal teeth 21. Specifically, as shown in Figure 2, a plurality of internal grooves 223 are formed on the inner circumferential surface 221 of the gear body 22 over the entire circumference. The plurality of internal grooves 223 are all the same shape and are provided at equal pitches. The plurality of internal grooves 223 are all parallel to the rotation axis Ax1 and are formed over the entire length of the gear body 22 in the thickness direction. The plurality of external pins 23 are assembled to the gear body 22 so as to fit into the plurality of internal grooves 223. Each of the plurality of external pins 23 is held in a state in which it can rotate within the internal groove 223. Furthermore, the gear body 22 is fixed to the case 10 (together with the outer ring 62). In addition, the gear body 22 has multiple fixing holes 222 (see Figure 5) for fixing.

[0034] As shown in Figures 5 and 6, the planetary gear 3 is an annular component having external teeth 31. In this basic configuration, the planetary gear 3 has an annular shape, with at least its outer circumferential surface being a perfect circle in plan view. The external teeth 31 are formed on the outer circumferential surface of the annular planetary gear 3, along the circumferential direction of the planetary gear 3. All of the teeth constituting the external teeth 31 are the same shape and are provided at equal pitches over the entire circumferential area of ​​the outer circumferential surface of the planetary gear 3. In other words, the pitch circle of the external teeth 31 is a perfect circle in plan view. The planetary gear 3 also has a predetermined thickness in the direction of the rotation axis Ax1. All of the external teeth 31 are formed along the entire length in the thickness direction of the planetary gear 3. The tooth traces of the external teeth 31 are all parallel to the rotation axis Ax1. In the planetary gear 3, unlike the internal gear 2, the external teeth 31 are integrally formed with the body of the planetary gear 3 from a single metal component.

[0035] Furthermore, the gear unit 1 in this basic configuration includes multiple planetary gears 3. Specifically, the gear unit 1 includes two planetary gears 3: a first planetary gear 301 and a second planetary gear 302. The two planetary gears 3 are arranged opposite each other in a direction parallel to the rotation axis Ax1. In other words, the planetary gear 3 includes a first planetary gear 301 and a second planetary gear 302 that are aligned in a direction parallel to the rotation axis Ax1 (axial direction). The shapes of the first planetary gear 301 and the second planetary gear 302 are the same.

[0036] These two planetary gears 3 (the first planetary gear 301 and the second planetary gear 302) are positioned with a 180-degree phase difference around the rotation axis Ax1. In the example in Figure 4, of the first planetary gear 301 and the second planetary gear 302, the center C1 (center of the pitch circle of the external teeth 31) of the first planetary gear 301, which is located on the input side of the rotation axis Ax1 (right side in Figure 4), is shifted (biased) upward relative to the rotation axis Ax1 in the figure. On the other hand, the center C2 (center of the pitch circle of the external teeth 31) of the second planetary gear 302, which is located on the output side of the rotation axis Ax1 (left side in Figure 4), is shifted (biased) downward relative to the rotation axis Ax1 in the figure. Here, the distance ΔL1 between the rotation axis Ax1 and the center C1 is the eccentricity of the first planetary gear 301 with respect to the rotation axis Ax1, and the distance ΔL2 between the rotation axis Ax1 and the center C2 is the eccentricity of the second planetary gear 302 with respect to the rotation axis Ax1. In this way, by arranging the multiple planetary gears 3 evenly in the circumferential direction around the rotation axis Ax1, it is possible to balance the weight and load among the multiple planetary gears 3.

[0037] The first planetary gear 301 and the second planetary gear 302 have centers C1 and C2 positioned 180 degrees rotationally symmetric with respect to the axis of rotation Ax1. In this basic configuration, the eccentricity ΔL1 and eccentricity ΔL2 are in opposite directions when viewed from the axis of rotation Ax1, but their absolute values ​​are the same.

[0038] More specifically, each crankshaft 7A, 7B, and 7C has two eccentric portions 72 with respect to one central axis 71. The eccentricity ΔL0 (see Figures 5 and 6) of the centers C0 of these two eccentric portions 72 from the center of the central axis 71 (axis Ax2) is the same as the eccentricity ΔL1 and ΔL2 of the first planetary gear 301 and the second planetary gear 302 with respect to the rotation axis Ax1, respectively. The shapes of the multiple crankshafts 7A, 7B, and 7C are common. Similarly, the shapes of the multiple crankshaft gears 502A, 502B, and 502C are also common.

[0039] Furthermore, a pair of carriers 18 and 19 are positioned on both sides of the first planetary gear 301 and the second planetary gear 302 in the direction parallel to the rotation axis Ax1 (axial direction). To distinguish between the pair of carriers 18 and 19, the carrier 18 located on the input side of the rotation axis Ax1 (right side in Figure 4) is called the "input side carrier 18," and the carrier 19 located on the output side of the rotation axis Ax1 (left side in Figure 4) is called the "output side carrier 19." Each crankshaft 7A, 7B, and 7C is held at both ends by the pair of carriers 18 and 19 via rolling bearings 41 and 42. In other words, each crankshaft 7A, 7B, and 7C is held by the input side carrier 18 and the output side carrier 19 in a state that allows it to rotate on both sides of the planetary gear 3 in the direction parallel to the rotation axis Ax1 (axial direction).

[0040] Eccentric bearings 5 ​​are mounted on the eccentric portions 72 of each crankshaft 7A, 7B, and 7C. Each of the first planetary gear 301 and the second planetary gear 302 has three openings 33 corresponding to the three crankshafts 7A, 7B, and 7C. Eccentric bearings 5 ​​are housed in each of the openings 33. In other words, eccentric bearings 5 ​​are attached to the first planetary gear 301 and the second planetary gear 302, and each crankshaft 7A, 7B, and 7C is inserted into the eccentric bearings 5, thereby assembling the eccentric bearings 5 ​​and each crankshaft 7A, 7B, and 7C into the planetary gear 3. When each crankshaft 7A, 7B, and 7C rotates in the state as the eccentric bearings 5 ​​and crankshafts 7A, 7B, and 7C are assembled into the planetary gear 3, the planetary gear 3 oscillates around the rotation axis Ax1.

[0041] According to the configuration described above, when a rotational force is applied as input to the input shaft 500, the input shaft 500 rotates around the rotation axis Ax1, and this rotational force is distributed from the input gear 501 to the multiple crankshafts 7A, 7B, and 7C. In other words, when the input gear 501 rotates, the three crankshaft gears 502A, 502B, and 502C that mesh with the input gear 501 simultaneously rotate in the same direction at the same rotational speed. Since the crankshafts 7A, 7B, and 7C are spline-connected to each of the crankshaft gears 502A, 502B, and 502C, the three crankshafts 7A, 7B, and 7C rotate in the same direction at the same rotational speed while being reduced by the tooth ratio between the input gear 501 and the crankshaft gears 502A, 502B, and 502C. As a result, the three eccentric portions 72 formed at the same position on the input side of the rotation axis Ax1 on the three crankshafts 7A, 7B, and 7C rotate synchronously, causing the first planetary gear 301 to oscillate. Furthermore, the three eccentric portions 72 formed at the same position on the output side of the rotation axis Ax1 on the three crankshafts 7A, 7B, and 7C rotate synchronously, causing the second planetary gear 302 to oscillate.

[0042] Figures 5 and 6 show the state of the first planetary gear 301 and the second planetary gear 302 at a certain point in time. Figure 5 is a cross-sectional view taken along line A1-A1 in Figure 4, showing the first planetary gear 301. Figure 6 is a cross-sectional view taken along line B1-B1 in Figure 4, showing the second planetary gear 302. As shown in Figures 5 and 6, the centers C1 and C2 of the first planetary gear 301 and the second planetary gear 302 are positioned approximately 180 degrees rotationally symmetric with respect to the rotation axis Ax1. In this basic configuration, the eccentricity ΔL1 and eccentricity ΔL2 are in opposite directions when viewed from the rotation axis Ax1, but their absolute values ​​are approximately the same (both are eccentricity ΔL0). According to the above configuration, as the axial core 71 rotates (rotates) around the axis Ax2, the first planetary gear 301 and the second planetary gear 302 rotate (eccentrically) around the rotation axis Ax1 with a phase difference of approximately 180 degrees around the rotation axis Ax1. Furthermore, by arranging the multiple planetary gears 3 almost evenly in the circumferential direction around the rotation axis Ax1, it is possible to balance the weight and load among the multiple planetary gears 3.

[0043] The planetary gear 3 (first planetary gear 301 and second planetary gear 302) configured in this way is positioned inside the internal gear 2. In plan view, the planetary gear 3 is formed to be slightly smaller than the internal gear 2, and when combined with the internal gear 2, the planetary gear 3 is able to oscillate inside the internal gear 2. Here, external teeth 31 are formed on the outer circumferential surface of the planetary gear 3, and internal teeth 21 are formed on the inner circumferential surface of the internal gear 2. Therefore, when the planetary gear 3 is positioned inside the internal gear 2, the external teeth 31 and the internal teeth 21 face each other.

[0044] Furthermore, the pitch circle of the external teeth 31 is slightly smaller than the pitch circle of the internal teeth 21. When the first planetary gear 301 is inscribed in the internal gear 2, the center C1 of the pitch circle of the external teeth 31 in the first planetary gear 301 is located at a distance ΔL1 from the center of the pitch circle of the internal teeth 21 (rotation axis Ax1). Similarly, when the second planetary gear 302 is inscribed in the internal gear 2, the center C2 of the pitch circle of the external teeth 31 in the second planetary gear 302 is located at a distance ΔL2 from the center of the pitch circle of the internal teeth 21 (rotation axis Ax1).

[0045] Therefore, in both the first planetary gear 301 and the second planetary gear 302, at least a portion of the external teeth 31 and internal teeth 21 will face each other with a gap in between, and if the difference in the number of teeth between the external teeth 31 and internal teeth 21 is "2" or more, the entire circumferential direction will not mesh with each other. However, since the planetary gear 3 oscillates (revolves) around the rotation axis Ax1 inside the internal gear 2, the external teeth 31 and internal teeth 21 will partially mesh. In other words, as the planetary gear 3 (first planetary gear 301 and second planetary gear 302) oscillates around the rotation axis Ax1, as shown in Figures 5 and 6, some of the teeth of the multiple teeth constituting the external teeth 31 will mesh with some of the teeth of the multiple teeth constituting the internal teeth 21. As a result, in the gear device 1, it is possible to mesh a portion of the external teeth 31 with a portion of the internal teeth 21.

[0046] Here, the number of teeth on the internal gear 21 is N (where N is a positive integer) greater than the number of teeth on the external gear 31 of the planetary gear 3. In this basic configuration, as an example, N is "2", and the number of teeth on the planetary gear 3 (external gear 31) is "2" less than the number of teeth on the internal gear 2 (internal gear 21). This difference in the number of teeth between the planetary gear 3 and the internal gear 2 defines the reduction ratio of the output rotation to the input rotation in the gear device 1.

[0047] Furthermore, in this basic configuration, as an example, the combined thickness of the first planetary gear 301 and the second planetary gear 302 is smaller than the thickness of the gear body 22 in the internal gear 2. Moreover, the dimension of the external teeth 31 of the combined first planetary gear 301 and the second planetary gear 302 in the tooth trace direction (direction parallel to the rotation axis Ax1) is smaller than the dimension of the internal teeth 21 in the tooth trace direction (direction parallel to the rotation axis Ax1). In other words, in the direction parallel to the rotation axis Ax1, the external teeth 31 of the first planetary gear 301 and the second planetary gear 302 are contained within the range of the tooth trace of the internal teeth 21.

[0048] Here, the first planetary gear 301 and the second planetary gear 302 are internally meshed with the internal gear 2. Therefore, with each oscillation of the first planetary gear 301 and the second planetary gear 302, a circumferential phase shift occurs between them and the internal gear 2 (between the internal teeth 21 and the external teeth 31) equal to the difference in the number of teeth, causing them to rotate. This rotation is transmitted to the pair of carriers 18 and 19 as revolutions around the axis (rotation axis Ax1) of the internal gear 2 of each crankshaft 7A, 7B, and 7C. This allows the pair of carriers 18 and 19 to rotate relative to the gear body (and the integrated case 10) around the rotation axis Ax1.

[0049] In short, the gear device 1 in this basic configuration uses multiple crankshafts 7A, 7B, and 7C, positioned offset from the rotation axis Ax1, to oscillate a planetary gear 3, and obtains rotational output by utilizing the oscillation of the planetary gear 3. That is, in the gear device 1, as the planetary gear 3 oscillates and the meshing position between the internal teeth 21 and the external teeth 31 moves in the circumferential direction of the internal gear 2, relative rotation occurs between the two gears (internal gear 2 and planetary gear 3) according to the difference in the number of teeth between the planetary gear 3 and the internal gear 2. If the internal gear 2 is fixed, the planetary gear 3 will rotate (rotate on its own axis) in conjunction with the relative rotation of the two gears. As a result, rotational output reduced at a relatively high reduction ratio according to the difference in the number of teeth between the two gears can be obtained from the planetary gear 3.

[0050] The bearing member 6 has an outer ring 62 and an inner ring 61, and is a component for extracting the output of the gear device 1 as the rotation of the inner ring 61 relative to the outer ring 62. In addition to the outer ring 62 and inner ring 61, the bearing member 6 has a plurality of rolling elements 63 (see Figure 4). Both the outer ring 62 and the inner ring 61 are annular components. Both the outer ring 62 and the inner ring 61 have annular shapes that are perfect circles in plan view. The inner ring 61 is slightly smaller than the outer ring 62 and is positioned inside the outer ring 62. Here, since the inner diameter of the outer ring 62 is larger than the outer diameter of the inner ring 61, a gap is created between the inner circumferential surface of the outer ring 62 and the outer circumferential surface of the inner ring 61.

[0051] Multiple rolling elements 63 are arranged in the gap between the outer ring 62 and the inner ring 61. Multiple rolling elements 63 are arranged in a line along the circumference of the outer ring 62. All of the multiple rolling elements 63 are metal parts of the same shape and are provided at equal pitches over the entire circumference of the outer ring 62.

[0052] More specifically, the gear apparatus 1 in this basic configuration includes a bearing member 6 comprising a first bearing member 601 and a second bearing member 602. The first bearing member 601 and the second bearing member 602 are each made of angular contact ball bearings. Specifically, as shown in Figure 4, the first bearing member 601 is positioned on the input side of the rotation axis Ax1 as viewed from the planetary gear 3 (right side in Figure 4), and the second bearing member 602 is positioned on the output side of the rotation axis Ax1 as viewed from the planetary gear 3 (left side in Figure 4). The bearing member 6 is configured such that the first bearing member 601 and the second bearing member 602 can withstand radial loads, thrust loads (in the direction along the rotation axis Ax1), and bending forces (bending moment loads) on the rotation axis Ax1.

[0053] Here, the first bearing member 601 and the second bearing member 602 are positioned on both sides of the planetary gear 3 in a direction parallel to the rotation axis Ax1 (axial direction), and are facing opposite directions in a direction parallel to the rotation axis Ax1. In other words, the bearing member 6 is a "combined angular contact ball bearing" which is a combination of multiple (in this case, two) angular contact ball bearings. As an example, the first bearing member 601 and the second bearing member 602 are a "back-to-back combination type" which receives a thrust load (direction along the rotation axis Ax1) in which their respective inner rings 61 move closer to each other. Furthermore, in the gear device 1, the first bearing member 601 and the second bearing member 602 are combined in such a state that an appropriate preload is applied to the inner rings 61 by tightening them in a direction that brings their respective inner rings 61 closer to each other.

[0054] Furthermore, in the gear device 1 according to this basic configuration, the input carrier 18 and the output carrier 19 are arranged on both sides of the planetary gear 3 in a direction parallel to the rotation axis Ax1, and are coupled to each other through the carrier holes 34 of the planetary gear 3 (see Figure 4). Specifically, as shown in Figure 4, the input carrier 18 is positioned on the input side of the rotation axis Ax1 (right side in Figure 4) as viewed from the planetary gear 3, and the output carrier 19 is positioned on the output side of the rotation axis Ax1 (left side in Figure 4) as viewed from the planetary gear 3. The inner rings 61 of the bearing members 6 (each of the first bearing member 601 and the second bearing member 602) are fixed to the input carrier 18 and the output carrier 19. In this basic configuration, as an example, the inner ring of the first bearing member 601 is seamlessly integrated with the input carrier 18. Similarly, the inner ring of the second bearing member 602 is seamlessly integrated with the output carrier 19.

[0055] The output carrier 19 has a plurality of carrier pins 191 (see Figure 2) (three as an example) that protrude from one surface of the output carrier 19 toward the input side of the rotation axis Ax1. These plurality of carrier pins 191 each pass through a plurality of carrier holes 34 (three as an example) formed in the planetary gear 3, and their tips are fixed to the input carrier 18 by carrier bolts 192 (see Figure 7). Here, a gap is ensured between the carrier pins 191 and the inner circumferential surface of the carrier holes 34, and the carrier pins 191 are movable within the carrier holes 34, that is, they are movable relative to the center of the carrier holes 34. As a result, the carrier pins 191 do not come into contact with the inner circumferential surface of the carrier holes 34 when the planetary gear 3 oscillates.

[0056] With the above configuration, the gear unit 1 is used to extract the rotation equivalent to the rotation component of the planetary gear 3 as the rotation of the input carrier 18 and output carrier 19, which are integrated with the inner ring 61 of the bearing member 6. In other words, in this basic configuration, the relative rotation between the planetary gear 3 and the internal gear 2 is extracted from the input carrier 18 and output carrier 19. In this basic configuration, as an example, the gear unit 1 is used with the outer ring 62 (see Figure 4) of the bearing member 6 fixed to the case 10, which is a fixed member. That is, the planetary gear 3 is connected to the input carrier 18 and output carrier 19, which are rotating members, by multiple crankshafts 7A, 7B, and 7C, and the gear body 22 is fixed to the fixed member, so the relative rotation between the planetary gear 3 and the internal gear 2 is extracted from the rotating members (input carrier 18 and output carrier 19). In other words, in this basic configuration, when the planetary gear 3 rotates relative to the gear body 22, the rotational forces of the input carrier 18 and the output carrier 19 are extracted as outputs.

[0057] Furthermore, in this basic configuration, the case 10 is seamlessly integrated with the gear body 22 of the internal gear 2. In other words, in a direction parallel to the rotation axis Ax1, the fixed member, the gear body 22, and the case 10 are provided seamlessly and continuously.

[0058] More specifically, the case 10 is cylindrical and constitutes the outer casing of the gear unit 1. In this basic configuration, the central axis of the cylindrical case 10 is configured to coincide with the rotation axis Ax1. That is, at least the outer surface of the case 10 is a perfect circle centered on the rotation axis Ax1 when viewed from a plan view (viewed from one side in the axial direction). The case 10 is formed in a cylindrical shape with both axial end faces open. Here, the gear body 22 of the internal gear 2 is seamlessly integrated into the case 10, and the case 10 and the gear body 22 are treated as a single part. Therefore, the inner surface of the case 10 includes the inner surface 221 of the gear body 22. Furthermore, the outer ring 62 of the bearing member 6 is fixed to the case 10. That is, the outer ring 62 of the first bearing member 601 is fitted and fixed to the input side of the rotation axis Ax1 (right side in Figure 4) when viewed from the gear body 22 on the inner surface of the case 10. On the other hand, the outer ring 62 of the second bearing member 602 is fitted and fixed to the output side (left side in Figure 4) of the rotating shaft Ax1 as seen from the gear body 22 on the inner circumferential surface of the case 10.

[0059] Furthermore, the input side (right side in Figure 4) end face of the rotating shaft Ax1 in case 10 is closed by the input side carrier 18, and the output side (left side in Figure 4) end face of the rotating shaft Ax1 in case 10 is closed by the output side carrier 19. As a result, as shown in Figure 4, components such as the planetary gear 3 (first planetary gear 301 and second planetary gear 302), multiple external pins 23, and eccentric bearing 5 are housed in the space enclosed by case 10, the input side carrier 18, and the output side carrier 19.

[0060] Each of the multiple (three in the basic configuration) crankshafts 7A, 7B, and 7C has an axial core 71 and two eccentric parts 72. The axial core 71 has a cylindrical shape, with at least its outer surface being a perfect circle in plan view. The axis Ax2, which is the center of the axial core 71, is parallel to the rotation axis Ax1. The axis Ax2 of the multiple crankshafts 7A, 7B, and 7C are arranged at equal intervals in the circumferential direction on a virtual circle centered on the rotation axis Ax1. Each eccentric part 72 has a disc shape, with at least its outer surface being a perfect circle in plan view. The center (central axis) C0 of each eccentric part 72 is parallel to the rotation axis Ax1 and is positioned radially offset from the rotation axis Ax1. Here, the distance ΔL0 between the axis Ax2 and the center C0 (see Figures 5 and 6) is the amount of eccentricity of the eccentric part 72 relative to the axial core 71. The eccentric portion 72 has a flange shape that protrudes from the outer circumferential surface of the shaft portion 71 around its entire circumference at the center of the shaft portion 71 in the longitudinal direction (axial direction). With the above configuration, each crankshaft 7A, 7B, and 7C will undergo eccentric motion as the shaft portion 71 rotates around the shaft Ax2.

[0061] In this basic configuration, the central shaft 71 and the two eccentric shafts 72 are integrally formed from a single metal component, thereby realizing seamless crankshafts 7A, 7B, and 7C. These crankshafts 7A, 7B, and 7C are combined with the planetary gear 3 along with the eccentric bearing 5. Therefore, when the crankshafts 7A, 7B, and 7C rotate with the planetary gear 3 assembled to the eccentric bearing 5, the planetary gear 3 oscillates around the rotation axis Ax1.

[0062] The eccentric bearing 5 has multiple rolling elements 51 (see Figure 4) and is a component that absorbs the rotational component of the rotation of the crankshafts 7A, 7B, and 7C, and transmits only the rotational component (orbital component) of the crankshafts 7A, 7B, and 7C to the planetary gear 3. The multiple rolling elements 51 are arranged between the outer circumferential surface of the eccentric portion 72 of each crankshaft 7A, 7B, and 7C and the inner circumferential surface of each opening 33 of the planetary gear 3. In other words, the eccentric portion 72 of each crankshaft 7A, 7B, and 7C functions as the inner ring of the eccentric bearing 5, and the inner circumferential surface of each opening 33 of the planetary gear 3 functions as the outer ring of the eccentric bearing 5.

[0063] When the eccentric bearing 5 and multiple crankshafts 7A, 7B, 7C are combined with the planetary gear 3, and each crankshaft 7A, 7B, 7C rotates, the eccentric bearing 5 rotates (eccentrically) around the axis Ax2. At this time, the rotational component of the crankshafts 7A, 7B, 7C is absorbed by the eccentric bearing 5. Therefore, the planetary gear 3 receives only the rotational component (orbital component) of the crankshafts 7A, 7B, 7C, excluding their rotational component, through the eccentric bearing 5. Thus, when the crankshafts 7A, 7B, 7C rotate with the eccentric bearing 5 combined with the planetary gear 3, the planetary gear 3 oscillates around the axis of rotation Ax1.

[0064] In the gear device 1 with the configuration described above, a rotational force is applied as input to the input shaft 500, causing the input shaft 500 to rotate around the rotation axis Ax1, and the planetary gear 3 oscillates (revolves) around the rotation axis Ax1. At this time, the planetary gear 3 oscillates inside the internal gear 2, with a portion of the external teeth 31 meshing with a portion of the internal teeth 21, so the meshing position between the internal teeth 21 and the external teeth 31 moves in the circumferential direction of the internal gear 2. As a result, relative rotation corresponding to the difference in the number of teeth between the planetary gear 3 and the internal gear 2 occurs between the two gears (internal gear 2 and planetary gear 3). Then, the rotation (rotation component) of the planetary gear 3, excluding the oscillating component (revolution component), is transmitted to the pair of carriers 18 and 19 by multiple crankshafts 7A, 7B, and 7C. As a result, the pair of carriers 18 and 19 will produce rotational output that is reduced at a relatively high reduction ratio, depending on the difference in the number of teeth of the two gears.

[0065] Incidentally, in the gear unit 1 relating to this basic configuration, as described above, the difference in the number of teeth between the internal gear 2 and the planetary gear 3 determines the reduction ratio of the output rotation to the input rotation in the gear unit 1. In other words, if the number of teeth of the internal gear 2 is "V1" and the number of teeth of the planetary gear 3 is "V2", the reduction ratio R1 is expressed by the following equation 1.

[0066] R1 = V2 / (V1 - V2) (Equation 1) In short, the smaller the difference in the number of teeth between the internal gear 2 and the planetary gear 3 (V1-V2), the larger the reduction ratio R1. For example, the number of teeth V1 of the internal gear 2 is "72", the number of teeth V2 of the planetary gear 3 is "70", and the difference in the number of teeth (V1-V2) is "2", so from equation 1 above, the reduction ratio R1 is "35". In this case, when viewed from the input side of the rotation axis Ax1, each crankshaft 7A, 7B, 7C rotates clockwise one full turn (360 degrees) around the axis Ax2 of the shaft center 71 (see Figures 5 and 6), the pair of carriers 18, 19 rotate counterclockwise around the rotation axis Ax1 by the amount of the difference in the number of teeth "2" (i.e., about 10.3 degrees).

[0067] According to the gear unit 1 of this basic configuration, such a high reduction ratio R1 can be achieved with the combination of the internal gear 2 and the planetary gear 3. Furthermore, between the input gear 501 and the multiple crankshaft gears 502A, 502B, and 502C, an appropriate reduction ratio can be achieved depending on the number of teeth of the input gear 501 and the crankshaft gears 502A, 502B, and 502C. As a result, a high reduction ratio can be achieved for the gear unit 1 as a whole.

[0068] Furthermore, the gear unit 1 only needs to include at least an internal gear 2, planetary gears 3, crankshafts 7A, 7B, 7C, and a pair of carriers 18, 19, and may further include a spacer 11, for example, as shown in Figure 4. The spacer 11 is positioned between the pair of planetary gears 3 (first planetary gear 301 and second planetary gear 302) in a direction parallel to the rotation axis Ax1 (axial direction).

[0069] (Reference example 1) The internally meshing planetary gear mechanism 1A (hereinafter also simply referred to as "gear mechanism 1A") in this reference example differs from the gear mechanism 1 in the basic configuration mainly in the configuration around the crankshafts 7A, 7B, and 7C, as shown in Figures 7 to 14. Hereafter, components similar to those in the basic configuration will be denoted by common reference numerals and their explanations will be omitted as appropriate. Figure 7 is a schematic cross-sectional view of gear mechanism 1A. Figure 8 is a schematic view of gear mechanism 1A as seen from the output side of the rotating shaft Ax1. Figure 9 is a schematic perspective view of the peripheral members of one crankshaft 7A. Figure 10 is a schematic exploded perspective view of the peripheral members of one crankshaft 7A. Figure 11 is a schematic perspective view of one crankshaft 7A. Figure 12 is an enlarged view of region Z1 in Figure 7. Figure 13 is an enlarged view of region Z2 in Figure 7. Figure 14 is an enlarged view of region Z1 in Figure 13.

[0070] As shown in Figure 7, the gear assembly 1A in this reference example further includes a plurality of oil seals 121, 122, etc. Oil seal 121 seals the gap between the case 10 and the outer circumferential surface of the output carrier 19. Oil seal 122 seals the central hole 193 formed in the center of the output carrier 19. The space sealed by these plurality of oil seals 121, 122, etc. constitutes a lubricant retention space 17. The lubricant retention space 17 includes the space between the inner ring 61 and the outer ring 62 of the bearing member 6. Furthermore, a plurality of outer pins 23, planetary gears 3, a pair of rolling bearings 41, 42 and an eccentric bearing 5 are housed within the lubricant retention space 17.

[0071] Lubricant is injected into the lubricant-holding space 17. The lubricant is a liquid and is fluid within the lubricant-holding space 17. Therefore, when the gear device 1 is in use, for example, the lubricant enters the meshing area between the internal teeth 21, which consist of a plurality of external pins 23, and the external teeth 31 of the planetary gear 3. In this disclosure, "liquid" includes liquid or gel-like substances. Here, "gel-like" means a state having properties intermediate between a liquid and a solid, and includes the colloid state consisting of two phases, a liquid phase and a solid phase. For example, states called gels or sols, such as emulsions where the dispersion medium is in the liquid phase and the dispersed phase is in the liquid phase, and suspensions where the dispersed phase is in the solid phase, are included in "gel-like". Also, states where the dispersion medium is in the solid phase and the dispersed phase is in the liquid phase are also included in "gel-like". In this basic configuration, as an example, the lubricant is a liquid lubricating oil.

[0072] The gear unit 1A in this reference example further includes a pair of covers 13 and 14 attached to both axial sides of a pair of carriers 18 and 19. To distinguish between the pair of covers 13 and 14, the cover 13 located on the input side (right side in Figure 7) of the rotation axis Ax1 is called the "input side cover 13," and the cover 14 located on the output side (left side in Figure 7) of the rotation axis Ax1 is called the "output side cover 14." In this reference example, the material of the pair of covers 13 and 14 is a metal such as stainless steel, cast iron, structural carbon steel, or chromium-molybdenum steel, or a metal that has been heat-treated therefrom.

[0073] The input-side cover 13 is formed in a disc shape centered on the rotation axis Ax1. Here, at least the outer surface of the input-side cover 13 is a perfect circle centered on the rotation axis Ax1 when viewed from above (from one side in the axial direction). The outer diameter of the input-side cover 13 is slightly smaller than the outer diameter of the input-side carrier 18. The input-side cover 13 is attached to the outside of the input-side carrier 18, that is, from the opposite side of the planetary gear 3 when viewed from the input-side carrier 18 (the right side in Figure 7).

[0074] The output side cover 14 is formed in a disc shape centered on the rotation axis Ax1. Here, at least the outer surface of the output side cover 14 is a perfect circle centered on the rotation axis Ax1 when viewed from above (from one side in the axial direction). The outer diameter of the output side cover 14 is slightly smaller than the outer diameter of the output side carrier 19. The output side cover 14 is attached to the outside of the output side carrier 19, that is, from the side opposite to the planetary gear 3 when viewed from the output side carrier 19 (the left side in Figure 7).

[0075] Here, the pair of covers 13 and 14 are detachably attached to the pair of carriers 18 and 19. That is, the input-side cover 13 is detachably attached to the input-side carrier 18, and the output-side cover 14 is detachably attached to the output-side carrier 19. In this reference example, each cover 13 and 14 is attached to each carrier 18 and 19 by a plurality of fixing bolts 142 (see Figure 8). Therefore, each cover 13 and 14 can be removed from each carrier 18 and 19 by removing the plurality of fixing bolts 142.

[0076] Here, in the output-side cover 14 of the pair of covers 13 and 14, as shown in Figure 8, multiple through-holes 141 are provided to match the multiple mounting holes 194 (see Figure 7) provided in the output-side carrier 19. That is, the output-side carrier 19 is provided with multiple mounting holes 194 (female threads) for fixing the mating member. Therefore, in the output-side cover 14 which is attached to the outside of the output-side carrier 19, multiple through-holes 141 are formed at positions corresponding to these multiple mounting holes 194. In particular, when high torque is transmitted from the output-side carrier 19 to the mating member, the number of mounting holes 194 and through-holes 141 increases. Furthermore, the arrangement and number of mounting holes 194 and through-holes 141 must be matched to the mating member.

[0077] On the other hand, the shaft holes 131 (see Figure 7) through which each crankshaft 7A, 7B, and 7C passes are provided only in the input-side cover 13 of the pair of covers 13 and 14. In other words, the input-side cover 13 is provided with multiple shaft holes 131 corresponding to the multiple crankshafts 7A, 7B, and 7C. The shaft core portion 71 of each crankshaft 7A, 7B, and 7C is inserted into each shaft hole 131. Here, the inner diameter of each shaft hole 131 is set to be slightly larger than the outer diameter of the shaft core portion 71 so that the shaft core portion 71 does not come into contact with the inner circumferential surface of the shaft hole 131.

[0078] By the way, to explain in more detail the configuration around each crankshaft 7A, 7B, and 7C, the gear unit 1A in this reference example employs the configuration shown in Figures 9 to 11. Here, we will explain using crankshaft 7A as an example, but the same configuration is adopted for crankshafts 7B and 7C.

[0079] In other words, the crankshaft 7A has a flange portion 73 between two eccentric portions 72 in the axial direction along the axis Ax2. The flange portion 73 is disc-shaped with the axis Ax2 as the center, and at least its outer surface is a perfect circle in plan view. The outer diameter of the flange portion 73 is set to be slightly larger than the outer diameter of the eccentric portions 72, and the flange portion 73 has a flange shape that protrudes from the outer surface of the eccentric portions 72 all the way around. In this reference example, the axis portion 71, the two eccentric portions 72 and the flange portion 73 are seamlessly integrated.

[0080] Here, since the crankshaft 7A has two eccentric portions 72 with respect to one central portion 71, it will have stepped portions 70 at least two locations in the axial direction. In other words, the diameter of the crankshaft 7A is not uniform along its entire length, and the diameter changes at least between the central portion 71 and each eccentric portion 72, resulting in two stepped portions 70 in this section. To put it another way, the end faces of each eccentric portion 72 that face outward in the axial direction (i.e., opposite to the flange portion 73) each become stepped portions 70.

[0081] In this example, the axial center portion 71 of the crankshaft 7A has a smaller diameter at both ends in the axial direction compared to the axial center portion. Therefore, stepped portions 70 are generated at each point where the diameter of the axial center portion 71 changes. As a result, the crankshaft 7A has stepped portions 70 at four locations in the axial direction. To distinguish between these stepped portions 70, they are designated as the first stepped portion 701, the second stepped portion 702, the third stepped portion 703, and the fourth stepped portion 704, respectively, starting from the input side (right side in Figure 7) of the rotating shaft Ax1. In other words, the first stepped portion 701 and the second stepped portion 702 are end faces facing the input side of the rotating shaft Ax1, while the third stepped portion 703 and the fourth stepped portion 704 are end faces facing the output side of the rotating shaft Ax1. The end of the axial core 71 that is further on the input side of the rotating shaft Ax1 than the first stepped portion 701 constitutes a mounting portion 74 for attaching the crankshaft gear 502A.

[0082] A pair of rolling bearings 41, 42, a pair of eccentric bearings 5, washers 81-85, and a retaining ring 86 are combined with the crankshaft 7A. Specifically, eccentric bearings 5 ​​are mounted on each of the two eccentric portions 72 of the crankshaft 7A. In addition, a pair of rolling bearings 41, 42 are mounted on the axial portion 71 of the crankshaft 7A at positions on both sides of the two eccentric portions 72 in the axial direction. Furthermore, a groove 75 for fitting the retaining ring 86 is formed at the output side (left side in Figure 7) of the rotating shaft Ax1, further than the fourth stepped portion 704, on the axial portion 71 of the crankshaft 7A. Therefore, the retaining ring 86 is attached to the output side end of the rotating shaft Ax1 on the axial portion 71.

[0083] Here, on the input side of the rotating shaft Ax1 as viewed from the flange portion 73 (right side in Figure 7), a washer 81, an eccentric bearing 5, a washer 82, and a rolling bearing 41 are mounted in this order from the flange portion 73 side. On the other hand, on the output side of the rotating shaft Ax1 as viewed from the flange portion 73 (left side in Figure 7), a washer 83, an eccentric bearing 5, a washer 84, a rolling bearing 42, a washer 85, and a retaining ring 86 are mounted in this order from the flange portion 73 side. Therefore, on the input side of the rotating shaft Ax1 as viewed from the flange portion 73, a washer 81 is interposed between the flange portion 73 and the eccentric bearing 5, and a washer 82 is interposed between the eccentric bearing 5 and the rolling bearing 41. On the output side of the rotating shaft Ax1 as viewed from the flange portion 73, a washer 83 is interposed between the flange portion 73 and the eccentric bearing 5, and a washer 84 is interposed between the eccentric bearing 5 and the rolling bearing 42. Furthermore, the rolling bearing 42 contacts the retaining ring 86 via a washer 85, thereby restricting its movement toward the output side of the rotating shaft Ax1.

[0084] More specifically, eccentric portions 72 are inserted into washers 81 and 83, respectively, and axial portions 71 are inserted into washers 82 and 84, respectively. Here, washer 82 is interposed between the second stepped portion 702 of the crankshaft 7A and the rolling bearing 41. On the other hand, washer 84 is interposed between the third stepped portion 703 of the crankshaft 7A and the rolling bearing 42. Furthermore, washer 85 is interposed between the fourth stepped portion 704 of the crankshaft 7A and the retaining ring 86. These washers 81 to 85 are, for example, made of metal and function as raceway rings (raceway discs) that reduce friction between the two members.

[0085] Incidentally, the gear apparatus 1A according to this reference example is equipped with a restricting structure 9 that restricts the axial movement of each crankshaft 7A, 7B, and 7C, as shown in Figure 12. In other words, in the gear apparatus 1A according to this reference example, the restricting structure 9 restricts the axial movement of the crankshafts 7A, 7B, and 7C. In this disclosure, "axial direction" means the direction along the axis Ax2 of the crankshafts 7A, 7B, and 7C, and in particular the direction parallel to the axis Ax2 of the crankshafts 7A, 7B, and 7C (thrust direction). Furthermore, in this disclosure, "restricting movement" means imposing some kind of restriction on movement, and includes not only completely prohibiting movement, but also limiting the range of movement or making movement difficult. In other words, in this reference example, the presence of the restricting structure 9 restricts the movement of the crankshafts 7A, 7B, and 7C in the axial direction along the axis Ax2 of the crankshafts 7A, 7B, and 7C.

[0086] In this reference example, the restricting structure 9 prohibits the movement of the crankshafts 7A, 7B, and 7C in both the axial direction (the input side of the rotation axis Ax1) and the other direction (the output side of the rotation axis Ax1). That is, in the example in Figure 8, the restricting structure 9 prohibits both the movement of the crankshafts 7A, 7B, and 7C to the right and to the left in the figure relative to the pair of carriers 18 and 19. As a result, the positions of the crankshafts 7A, 7B, and 7C in the axial direction are fixed (relative to the pair of carriers 18 and 19).

[0087] Specifically, in this reference example, the restricting structure 9 includes a pair of covers 13 and 14 attached to both axial sides of a pair of carriers 18 and 19. In short, the gear unit 1A restricts the axial movement of each crankshaft 7A, 7B, and 7C using the input-side cover 13 and output-side cover 14 described above. In particular, the gear unit 1A according to this reference example includes a first restricting structure 91 that restricts the movement of the crankshafts 7A, 7B, and 7C in one axial direction (to the right in Figure 8), and a second restricting structure 92 that restricts the movement of the crankshafts 7A, 7B, and 7C in the other axial direction (to the left in Figure 8).

[0088] Here, the input-side cover 13 is included in the first restricting structure 91 and receives a force F1 acting from the crankshafts 7A, 7B, 7C in one axial direction (to the right in Figure 8), thereby restricting the movement of the crankshafts 7A, 7B, 7C in one axial direction. On the other hand, the output-side cover 14 is included in the second restricting structure 92 and receives a force F2 acting from the crankshafts 7A, 7B, 7C in the other axial direction (to the left in Figure 8), thereby restricting the movement of the crankshafts 7A, 7B, 7C in the other axial direction.

[0089] More specifically, the first restricting structure 91 includes an input-side cover 13 and first stepped portions 701 of the crankshafts 7A, 7B, and 7C. With this first restricting structure 91, the first stepped portions 701 of the crankshafts 7A, 7B, and 7C, which face the input side (right side in Figure 8) of the rotation axis Ax1, come into contact with the shaft hole 131 on the output side (left side in Figure 8) of the rotation axis Ax1 of the input-side cover 13, thereby restricting the movement of the crankshafts 7A, 7B, and 7C in one axial direction (to the right in Figure 8). In other words, the movement of the crankshafts 7A, 7B, and 7C in one axial direction is prohibited by the contact of the first stepped portions 701 of the crankshafts 7A, 7B, and 7C with the input-side cover 13 attached to the input-side carrier 18.

[0090] The second restrictive structure 92 includes an output-side cover 14 and the output-side end faces 76 of the rotation axis Ax1 of the crankshafts 7A, 7B, and 7C. With this second restrictive structure 92, the end faces 76 of the crankshafts 7A, 7B, and 7C facing the output side (left side in Figure 8) of the rotation axis Ax1 of the crankshafts 7A, 7B, and 7C come into contact with the input-side (right side in Figure 8) side of the rotation axis Ax1 of the output-side cover 14, thereby restricting the movement of the crankshafts 7A, 7B, and 7C in the other axial direction (left side in Figure 8). In other words, the end faces 76 of the crankshafts 7A, 7B, and 7C come into contact with the output-side cover 14 attached to the output-side carrier 19, thereby prohibiting the movement of the crankshafts 7A, 7B, and 7C in the other axial direction.

[0091] In this configuration, the restricting structure 9 contacts the pair of covers 13 and 14 with parts of the crankshafts 7A, 7B, and 7C other than the end faces of the eccentric portion 72 (the second stepped portion 702 and the third stepped portion 703). In other words, the restricting structure 9 is located axially outward from the stepped portions 702 and 703, which are made up of the end faces of the eccentric portion 72, and restricts the axial movement of the crankshafts 7A, 7B, and 7C by contacting the end faces (the first stepped portion 701 or end face 76) that face outward in the axial direction. Therefore, friction does not occur at the stepped portions 702 and 703, which are made up of the end faces of the eccentric portion 72, due to contact with the pair of covers 13 and 14, etc., and wear of the stepped portions 702 and 703 can be reduced.

[0092] Incidentally, the gear device 1A according to this reference example comprises an internal gear 2, a planetary gear 3, crankshafts 7A, 7B, 7C, and a pair of carriers 18, 19. By oscillating the planetary gear 3, the planetary gear 3 is rotated relative to the internal gear 2. The internal gear 2 has an annular gear body 22 and a plurality of external pins 23 that are held in a rotatable state in a plurality of internal grooves 223 formed on the inner circumferential surface 221 of the gear body 22 and constitute the internal teeth 21. The planetary gear 3 has external teeth 31 that partially mesh with the internal teeth 21. The crankshafts 7A, 7B, 7C have stepped portions 70 at least two locations in the axial direction along the axis Ax2, and by rotating around the axis Ax2, they oscillate the planetary gear 3. The pair of carriers 18, 19 are arranged on both sides in the axial direction of the planetary gear 3 and rotatably support the crankshafts 7A, 7B, 7C. Here, as shown in Figure 13, a lubrication passage S1 for passing lubricant is formed between the stepped portion 70 and the pair of carriers 18 and 19.

[0093] In other words, in this reference example, a lubrication passage S1 is secured between the stepped portion 70 and the pair of carriers 18 and 19. By securing such a lubrication passage S1, the gear device 1A can circulate the lubricant through the lubrication passage S1, thereby improving the lubrication state of the pair of rolling bearings 41 and 42 and the pair of eccentric bearings 5. In Figure 13, the flow (circulation) of the lubricant through the lubrication passage S1 is conceptually represented by dashed arrows.

[0094] In this example, the lubrication passage S1 is formed within the lubricant holding space 17 into which the lubricant is injected. With the formation of such a lubrication passage S1, "lubricant depletion," where the lubricant is insufficient or depleted, is less likely to occur around the crankshafts 7A, 7B, and 7C, and a constant amount of lubricant or more is always supplied. Moreover, compared to a configuration in which the lubricant remains stationary in a fixed position, the circulation of the lubricant through the lubrication passage S1 allows for the lubricant to be replaced as needed around the crankshafts 7A, 7B, and 7C, thereby suppressing the deterioration of the lubricant.

[0095] Therefore, the lubrication of the pair of rolling bearings 41, 42 and the pair of eccentric bearings 5 ​​is improved, making lubrication failures less likely. As a result, even when the gear unit 1A is used over a long period of time, frictional losses can be reduced, making it easier to extend the lifespan of the gear unit 1A. In short, the gear unit 1A according to this reference example is less prone to a decrease in reliability, especially during long-term use, which in turn leads to improved transmission efficiency, longer lifespan, and higher performance of the gear unit 1A.

[0096] In this example, the lubrication passage S1 includes a radial passage S11 through which the lubricant passes in a radial direction perpendicular to the axial direction. That is, as shown in Figure 14, which is a schematic enlargement of region Z1 in Figure 13, the lubrication passage S1 formed between the stepped portion 70 and the pair of carriers 18 and 19 includes a radial passage S11 through which the lubricant passes in at least the radial direction. As a result, when the crankshafts 7A, 7B, and 7C rotate, the lubricant is driven radially by centrifugal force, allowing the lubricant to be efficiently circulated through the lubrication passage S1.

[0097] Furthermore, in this reference example, there is a gap in the axial direction between the stepped portions 702 and 703 and at least one of the pair of carriers 18 and 19, and the lubrication passage S1 includes this gap. In this reference example, as described above, the stepped portions 702 and 703, which consist of at least the end faces of the eccentric portion 72, are not used as the restricting structure 9, so a gap is provided between the stepped portions 702 and 703 and the pair of carriers 18 and 19, and this gap can be made part of the lubrication passage S1. In this reference example, as an example, the gaps that occur between the stepped portions 702 and 703 and both of the pair of carriers 18 and 19 constitute part of the lubrication passage S1.

[0098] Furthermore, this reference example further includes plate-shaped parts (washers 82, 84) positioned between the stepped portion 70 and a pair of carriers 18, 19. The lubrication passage S1 includes grooves 80 (see Figure 10) formed on the surfaces of the plate-shaped parts (washers 82, 84) facing the carriers 18, 19. That is, as shown in Figure 10, grooves 80 extending in the radial direction are formed on the surfaces of washers 81 to 84 that face outward in the axial direction (towards the carriers 18, 19). Here, it is preferable that multiple grooves 80 are formed for each washer 81 to 84, and in this reference example, four grooves 80 are formed for each washer 81 to 84. The four grooves 80 are arranged at equal intervals in the circumferential direction of each washer 81 to 84. With such grooves 80 provided, the lubricant flows through the grooves 80, and the grooves 80 are included in the lubrication passage S1. As a result, the cross-sectional area of ​​the lubrication passage S1 can be increased compared to the case without the groove 80, allowing the lubricant to circulate more easily.

[0099] Furthermore, in cases where multiple crankshafts 7A, 7B, and 7C are provided, as in this reference example, it is preferable to provide a connecting passage S2 that connects the multiple lubrication passages S1 formed around each of these crankshafts 7A, 7B, and 7C. This allows the lubricant to circulate among the multiple crankshafts 7A, 7B, and 7C, and to circulate the lubricant throughout the entire gear unit 1A, thus further improvement in the lubrication state can be expected.

[0100] Specifically, as shown in Figure 7, grooves 133 and 143 are formed on the axially inward-facing surfaces (the surfaces facing the planetary gear 3) of each of the pair of covers 13 and 14. In a plan view, the grooves 133 and 143 are annular grooves centered on the rotation axis Ax1, formed to pass through the rolling bearings 41 and 42 that support each of the multiple crankshafts 7A, 7B, and 7C (see Figure 8). Therefore, the lubrication passage S1, which includes multiple (in this case, three) rolling bearings 41, is connected by a connecting passage S2 consisting of the groove 133 of the input-side cover 13. Similarly, the lubrication passage S1, which includes multiple (in this case, three) rolling bearings 42, is connected by a connecting passage S2 consisting of the groove 143 of the output-side cover 14.

[0101] Furthermore, the gear apparatus 1A in this reference example includes an input gear 501 that rotates around a rotation axis Ax1, and a plurality of crankshaft gears 502A, 502B, and 502C. The plurality of crankshaft gears 502A, 502B, and 502C are arranged around the input gear 501 so as to mesh with the input gear 501, and rotate synchronously with each other when the input gear 501 rotates. Multiple crankshafts 7A, 7B, and 7C are provided so as to correspond one-to-one with the plurality of crankshaft gears 502A, 502B, and 502C. The plurality of crankshafts 7A, 7B, and 7C rotate together with the plurality of crankshaft gears 502A, 502B, and 502C, causing the planetary gear 3 to oscillate around the rotation axis Ax1.

[0102] Thus, in a distribution-type gear system 1A having multiple crankshafts 7A, 7B, and 7C, the axial movement of the multiple crankshafts 7A, 7B, and 7C can be restricted. Furthermore, by circulating lubricant around the multiple crankshafts 7A, 7B, and 7C, the lubrication state can be improved.

[0103] As shown in Figure 15, the gear device 1A in this reference example, together with the first member 201 and the second member 202, constitutes a robot joint device 200. In other words, the robot joint device 200 in this reference example comprises the gear device 1A, the first member 201, and the second member 202. The first member 201 is fixed to the gear body 22. The second member 202 rotates relative to the first member 201 in accordance with the relative rotation of the planetary gear 3 with respect to the internal gear 2. Figure 15 is a schematic cross-sectional view of the robot joint device 200. Also, Figure 15 schematically shows the first member 201, the second member 202, and the drive source 101.

[0104] The robot joint device 200 configured in this way functions as a joint device by the relative rotation of the first member 201 and the second member 202 around the rotation axis Ax1. Here, the input shaft 500 of the gear device 1A is driven by the drive source 101, causing the first member 201 and the second member 202 to rotate relative to each other. At this time, the rotation (input rotation) generated by the drive source 101 is reduced by the gear device 1A at a relatively high reduction ratio, driving the first member 201 or the second member 202 with relatively high torque. In other words, the first member 201 and the second member 202, which are connected by the gear device 1A, are able to perform bending and extending movements around the rotation axis Ax1.

[0105] The robot joint device 200 is used in robots such as horizontal articulated robots (SCARA type robots). Furthermore, the robot joint device 200 is not limited to horizontal articulated robots, but may also be used in industrial robots other than horizontal articulated robots, or in robots other than industrial robots. In addition, the gear device 1A in this reference example is not limited to the robot joint device 200, but may also be used as a wheel device such as an in-wheel motor in vehicles such as automated guided vehicles (AGVs).

[0106] <Variation> Reference Example 1 is merely one of many reference examples provided in this disclosure. Reference Example 1 can be modified in various ways depending on the design, etc., as long as the objectives of this disclosure are achieved. Furthermore, all drawings referenced in this disclosure are schematic diagrams, and the ratios of the size and thickness of each component in the drawings do not necessarily reflect the actual dimensional ratios. The following lists some modifications of Reference Example 1. The modifications described below can be combined and applied as appropriate.

[0107] The number of crankshafts 7A, 7B, and 7C is not limited to "3"; it may be 2 or 4 or more. Furthermore, if there is only one crankshaft, an eccentric oscillating internal meshing planetary gear system can be realized where the rotation axis Ax1 and the axis Ax2 of the crankshaft coincide, rather than a distribution type. In this case, the planetary gear 3 oscillates when the crankshaft is driven, and the pair of carriers 18 and 19 can be rotated relative to the gear body 22 around the rotation axis Ax1.

[0108] Furthermore, while Reference Example 1 illustrates two types of gear systems 1A with planetary gears 3, a gear system 1A may have three or more planetary gears 3. For example, if a gear system 1A has three planetary gears 3, it is preferable that these three planetary gears 3 are arranged with a phase difference of 120 degrees around the rotation axis Ax1. Alternatively, a gear system 1A may have only one planetary gear 3. Or, if a gear system 1A has three planetary gears 3, two of these three planetary gears 3 may be in phase, and the remaining planetary gear 3 may be arranged with a phase difference of 180 degrees around the rotation axis Ax1.

[0109] Furthermore, the bearing member 6 may be a cross roller bearing, a deep groove ball bearing, a four-point contact ball bearing, or the like.

[0110] Furthermore, the number of teeth of the input gear 501, the number of teeth of the crankshaft gears 502A, 502B, and 502C, the number of external pins 23 (number of teeth of internal teeth 21), and the number of teeth of external teeth 31, as explained in Reference Example 1, are merely examples and can be changed as appropriate.

[0111] Furthermore, the eccentric bearing 5 is not limited to a roller bearing; for example, it may be a deep groove ball bearing or an angular contact ball bearing.

[0112] Furthermore, the material of each component of the gear unit 1A is not limited to metal; for example, it may be a resin such as engineering plastic.

[0113] Furthermore, the gear unit 1A only needs to be able to output the relative rotation between the inner ring 61 and the outer ring 62 of the bearing member 6, and is not limited to a configuration in which the rotational force of the inner ring 61 (input carrier 18 and output carrier 19) is output. For example, the rotational force of the outer ring 62 (case 10) that rotates relative to the inner ring 61 may be output.

[0114] Furthermore, in Reference Example 1, the output end face 76 of the rotation axis Ax1 of the crankshafts 7A, 7B, and 7C is in direct contact with the output side cover 14. However, the configuration is not limited to this, and a plate-shaped component, such as a shim, may be placed between the end face 76 and the output side cover 14. In this case, when attaching the output side cover 14, the gap between the end face 76 and the output side cover 14 can be adjusted in the axial direction by adjusting the thickness (and / or number) of the plate-shaped component, thereby adjusting the axial "play" of the crankshafts 7A, 7B, and 7C. Moreover, the plate-shaped component functions as a raceway (raceway disc) that reduces friction between the end face 76 and the output side cover 14.

[0115] Furthermore, the lubricant is not limited to liquid substances such as lubricating oil, but may also be a gel-like substance such as grease.

[0116] (Embodiment 1) The internally meshing planetary gear mechanism 1B according to this embodiment (hereinafter also simply referred to as "gear mechanism 1B") differs from the gear mechanism 1A according to Reference Example 1 in that the output side cover 14 (see Figure 7) is omitted, as shown in Figures 16 and 17. Hereafter, components similar to those in Reference Example 1 will be denoted by common reference numerals and their descriptions will be omitted as appropriate. Figure 16 is a schematic cross-sectional view of the gear mechanism 1B. Figure 17 is an enlarged schematic view of region Z1 in Figure 16, with a partially enlarged view shown in the callout.

[0117] In the gear unit 1B according to this embodiment, instead of the output side cover 14, the output side carrier 19, washer 84, and third stepped portion 703 restrict the axial movement of each crankshaft 7A, 7B, and 7C to the other side. Furthermore, the axial movement of each crankshaft 7A, 7B, and 7C to one side is restricted by the input side cover 13 and stepped portion (first stepped portion 701), similar to Reference Example 1.

[0118] In other words, the gear unit 1B comprises an internal gear 2, a planetary gear 3, crankshafts 7A, 7B, 7C, an input carrier 18, and an output carrier 19, and rotates the planetary gear 3 relative to the internal gear 2 by oscillating the planetary gear 3. The internal gear 2 has an annular gear body 22 and a plurality of external pins 23 that are held in a rotatable state in a plurality of internal grooves 223 formed on the inner circumferential surface 221 of the gear body 22 and constitute the internal teeth 21. The planetary gear 3 has external teeth 31 that partially mesh with the internal teeth 21. The crankshafts 7A, 7B, 7C have stepped portions 70 at least two locations in the axial direction along the axis Ax2, and oscillate the planetary gear 3 by rotating around the axis Ax2. The input carrier 18 and the output carrier 19 are arranged on both sides in the axial direction of the planetary gear 3 and rotatably support the crankshafts 7A, 7B, 7C. Here, the gear unit 1B further comprises a first restricting structure 91 and a second restricting structure 92, as shown in Figure 17. The first restricting structure 91 includes an input-side cover 13 attached to the input-side carrier 18 on the opposite side of the planetary gear 3 in the axial direction, and restricts the movement of the crankshafts 7A, 7B, and 7C in one axial direction (to the right in Figure 17) by directly or indirectly contacting the stepped portion 70 (first stepped portion 701) with the input-side cover 13. The second restricting structure 92 restricts the movement of the crankshafts 7A, 7B, and 7C in the other axial direction (to the left in Figure 17) by directly or indirectly contacting the stepped portion 70 (third stepped portion 703) with the output-side carrier 19.

[0119] Thus, in this embodiment, the crankshafts 7A, 7B, and 7C have stepped portions 70, and the first restricting structure 91 includes an input-side cover 13 and restricts the movement of the crankshafts 7A, 7B, and 7C in one axial direction by directly or indirectly contacting the stepped portion 70 with the input-side cover 13. The second restricting structure 92 restricts the movement of the crankshafts 7A, 7B, and 7C in the other axial direction by directly or indirectly contacting the stepped portion 70 with the output-side carrier 19. In other words, in the gear device 1B, the axial movement (to the other side) of the crankshafts 7A, 7B, and 7C can be restricted by using the output-side carrier 19 instead of the output-side cover 14. As a result, the gear device 1B can restrict the axial movement of the crankshafts 7A, 7B, and 7C with a relatively simple configuration, without using tapered roller bearings or an output cover 14 attached to the output-side carrier 19. Therefore, according to the configuration of this embodiment, rattle and transmission losses caused by the axial movement of the crankshafts 7A, 7B, and 7C can be reduced.

[0120] Furthermore, the gear device 1B according to this embodiment has the following advantages compared to the gear device 1A according to Reference Example 1. Specifically, the depth of the multiple mounting holes 194 provided in the output carrier 19 can be increased by the thickness of the output cover 14, making it easier to improve the mounting strength of the mating member to the output carrier 19. Moreover, since the output cover 14, which has multiple through holes 141 corresponding to the multiple mounting holes 194, is omitted, there is no need to adjust the arrangement and number of through holes 141 to match the mating member. Also, since fixing bolts 142 (see Figure 8) for attaching the output cover 14 to the output carrier 19 are not required, it is possible to provide the mounting holes 194 without interfering with the fixing bolts 142.

[0121] Specifically, in this embodiment, the third stepped portion 703, which is the end face of the eccentric portion 72 of each crankshaft 7A, 7B, 7C, indirectly contacts the output-side carrier 19 via a washer 84. In other words, a washer 84 is sandwiched between the input-side (right side in Figure 17) surface of the rotation axis Ax1 on the output-side carrier 19 and the end face of the eccentric portion 72 (the third stepped portion 703).

[0122] Figure 17 is a schematic diagram showing an enlarged view of region Z1 in Figure 16. As shown in Figure 17, the first restricting structure 91 includes an input-side cover 13 and first stepped portions 701 of the crankshafts 7A, 7B, and 7C, similar to Reference Example 1. With such a first restricting structure 91, the first stepped portions 701 of the crankshafts 7A, 7B, and 7C, facing the input side of the rotation axis Ax1, come into contact with the shaft hole 131 on the output side of the rotation axis Ax1 of the input-side cover 13, thereby restricting the movement of the crankshafts 7A, 7B, and 7C in one axial direction. In other words, the movement of the crankshafts 7A, 7B, and 7C in one axial direction is prohibited by the contact of the first stepped portions 701 of the crankshafts 7A, 7B, and 7C with the input-side cover 13 attached to the input-side carrier 18. In other words, the input-side cover 13 attached to the input-side carrier 18 receives a force F1 acting from the crankshafts 7A, 7B, and 7C in one axial direction (to the right in Figure 17), thereby preventing the movement of the crankshafts 7A, 7B, and 7C in one axial direction.

[0123] In short, in the first restricting structure 91, the parts of the crankshafts 7A, 7B, and 7C that come into contact with the input-side cover 13 are parts other than the end face of the eccentric portion 72 (second stepped portion 702). That is, the first restricting structure 91 is located axially outward (to the right in Figure 17) from the end face of the eccentric portion 72 (second stepped portion 702) of the crankshafts 7A, 7B, and 7C, and restricts the movement of the crankshafts 7A, 7B, and 7C in one axial direction by directly or indirectly bringing the stepped portion (first stepped portion 701), which faces axially outward, into contact with the input-side cover 13. Therefore, friction does not occur at the second stepped portion 702, which is the end face of the eccentric portion 72, by contact with the input-side cover 13, and wear of the stepped portion 702 can be reduced. In this embodiment, the first stepped portion 701 is in direct contact with the input-side cover 13, but the configuration is not limited to this, and the first stepped portion 701 may indirectly contact the input-side cover 13 via a washer or the like.

[0124] The second restricting structure 92 includes an output-side carrier 19, a washer 84, and a third stepped portion 703. With this second restricting structure 92, the third stepped portion 703, which faces the output side of the rotation axis Ax1 of the crankshafts 7A, 7B, and 7C, comes into contact (indirectly via the washer 84) with the surface of the output-side carrier 19 that faces the input side (right side in Figure 17) of the rotation axis Ax1, thereby restricting the movement of the crankshafts 7A, 7B, and 7C in the other axial direction (left side in Figure 17). In other words, the output-side carrier 19 receives a force F2 acting from the third stepped portion 703 in the other axial direction (left side in Figure 17) via the washer 84, thereby preventing the movement of the crankshafts 7A, 7B, and 7C in the other axial direction.

[0125] In other words, in this embodiment, the second restricting structure 92 restricts the axial movement of the crankshafts 7A, 7B, and 7C to the other by indirectly bringing the stepped portion 70 (third stepped portion 703) into contact with the output-side carrier 19 via a plate-shaped component (washer 84). Therefore, the plate-shaped component (washer 84) functions as a raceway wheel (raceway plate) that reduces friction between the output-side carrier 19 and the stepped portion 70.

[0126] Furthermore, in this embodiment, the input-side cover 13 in the first restricting structure 91 is detachably attached to the input-side carrier 18. That is, the input-side cover 13 is a separate component from the input-side carrier 18 and is attached to the input-side carrier 18 during the assembly of the gear unit 1B. Therefore, during the assembly of the gear unit 1B, after inserting the crankshafts 7A, 7B, and 7C from the input-side carrier 18 side, the axial movement of the crankshafts 7A, 7B, and 7C in one direction can only be restricted by attaching the input-side cover 13 to the input-side carrier 18. Thus, by adjusting the attachment position of the input-side cover 13 to the input-side carrier 18, the axial "play" of the crankshafts 7A, 7B, and 7C can be adjusted.

[0127] Here, as shown in the callout in Figure 17, it is preferable that a shim member 132 is interposed between the input carrier 18 and the input cover 13. The shim member 132 is, for example, a thin metal plate. That is, in the axial direction, the input cover 13 contacts the input carrier 18 via the shim member 132. As a result, when installing the input cover 13, the gap between the first stepped portion 701 and the input cover 13 can be adjusted in the axial direction by adjusting the thickness (and / or number) of the shim member 132, and the "play" in the axial direction of the crankshafts 7A, 7B, and 7C can be adjusted.

[0128] Furthermore, in this embodiment, in the first restricting structure 91, the stepped portions 70 (first stepped portion 701) of the crankshafts 7A, 7B, and 7C directly or indirectly contact the input-side cover 13 attached to the input-side carrier 18, thereby restricting the axial movement of the crankshafts 7A, 7B, and 7C in one direction. In other words, the axial movement of the crankshafts 7A, 7B, and 7C is restricted by the input-side cover 13, not by the input-side carrier 18. The input-side cover 13 is detachably attached to the input-side carrier 18 and is therefore separate from the input-side carrier 18. As a result, while restricting the axial movement of the crankshafts 7A, 7B, and 7C in one direction, it is possible to secure a gap between the second stepped portion 702 and the input-side carrier 18 that becomes part of the lubrication passage S1 through which lubricant passes.

[0129] Therefore, in this embodiment, similar to Reference Example 1, a lubrication passage S1 for passing lubricant is formed between the stepped portion 70 (second stepped portion 702) and the input-side carrier 18. Consequently, the lubrication state of the pair of rolling bearings 41 and the pair of eccentric bearings 5 ​​is improved, making it less likely for lubrication failures to occur. As a result, even when the gear unit 1B is used for a long period of time, losses due to friction can be reduced, making it easier to extend the lifespan of the gear unit 1B. In short, the gear unit 1B according to this embodiment is less likely to experience a decrease in reliability, especially during long-term use, which in turn leads to improved transmission efficiency, longer lifespan, and higher performance of the gear unit 1B. On the other hand, in this embodiment, there is no gap between the output-side carrier 19 constituting the second restricting structure 92 and the third stepped portion 703, and when a general washer 84 is used, no lubrication passage is formed between the output-side carrier 19 and the third stepped portion 703. However, when a washer 84 with a groove 80 is used, the lubricant can flow through the groove 80, and a lubrication passage can also be formed between the output-side carrier 19 and the third stepped portion 703 that constitute the second restricting structure 92.

[0130] Furthermore, the gear device 1B according to this embodiment, similar to Reference Example 1, includes an input gear 501 that rotates around the rotation axis Ax1, and a plurality of crankshaft gears 502A, 502B, and 502C. The plurality of crankshaft gears 502A, 502B, and 502C are arranged around the input gear 501 so as to mesh with the input gear 501, and rotate synchronously with each other when the input gear 501 rotates. Multiple crankshafts 7A, 7B, and 7C are provided so as to correspond one-to-one with the plurality of crankshaft gears 502A, 502B, and 502C. The plurality of crankshafts 7A, 7B, and 7C rotate together with the plurality of crankshaft gears 502A, 502B, and 502C, causing the planetary gear 3 to oscillate around the rotation axis Ax1.

[0131] Thus, in a distribution-type gear system 1B having multiple crankshafts 7A, 7B, and 7C, the axial movement of the multiple crankshafts 7A, 7B, and 7C can be restricted. Furthermore, by circulating lubricant around the multiple crankshafts 7A, 7B, and 7C, the lubrication state can be improved.

[0132] The configuration of Embodiment 1 can be adopted in appropriate combination with the various configurations (including modified examples) described in Reference Example 1.

[0133] (summary) As described above, the internal meshing planetary gear device (1, 1A, 1B) according to the first embodiment comprises an internal gear (2), a planetary gear (3), a crankshaft (7A, 7B, 7C), an input carrier (18), and an output carrier (19), and rotates the planetary gear (3) relative to the internal gear (2) by oscillating the planetary gear (3). The internal gear (2) has an annular gear body (22) and a plurality of external pins (23) that are held in a rotatable state in a plurality of internal grooves (223) formed on the inner circumferential surface (221) of the gear body (22) and constitute the internal teeth (21). The planetary gear (3) has external teeth (31) that partially mesh with the internal teeth (21). The crankshafts (7A, 7B, 7C) have stepped portions (70) at least two locations in the axial direction along the axis (Ax2), and by rotating around the axis (Ax2), they cause the planetary gear (3) to oscillate. The input carrier (18) and output carrier (19) are positioned on both sides of the planetary gear (3) in the axial direction and rotatably support the crankshafts (7A, 7B, 7C). The internally meshing planetary gear unit (1, 1A, 1B) further comprises a first restricting structure (91) and a second restricting structure (92). The first restricting structure (91) includes an input cover (13) mounted on the input carrier (18) on the side opposite to the planetary gear (3) in the axial direction. The first restricting structure (91) restricts the movement of the crankshafts (7A, 7B, 7C) in one axial direction by directly or indirectly bringing the stepped portion (70) into contact with the input-side cover (13). The second restricting structure (92) restricts the movement of the crankshafts (7A, 7B, 7C) in the other axial direction by directly or indirectly bringing the stepped portion (70) into contact with the output-side carrier (19).

[0134] According to this embodiment, the axial movement of the crankshafts (7A, 7B, 7C) in one direction is restricted by directly or indirectly bringing the stepped portion (70) into contact with the input-side cover (13) attached to the input-side carrier (18). On the other hand, the axial movement of the crankshafts (7A, 7B, 7C) in the other direction is restricted by directly or indirectly bringing the stepped portion (70) into contact with the output-side carrier (19). As a result, the internally meshing planetary gear system (1, 1A, 1B) can restrict the axial movement of the crankshafts (7A, 7B, 7C) with a relatively simple configuration without using tapered roller bearings or the like. Therefore, rattle and transmission losses caused by the axial movement of the crankshafts (7A, 7B, 7C) can be reduced.

[0135] In the internally meshing planetary gear device (1,1A,1B) according to the second embodiment, a lubrication passage (S1) for passing lubricant is formed between the stepped portion (70) and the input-side carrier (18) as in the first embodiment.

[0136] According to this embodiment, the lubricant can be circulated by utilizing the gap between the stepped portion (70) and the input-side carrier (18) in the axial direction.

[0137] In the third embodiment of the internally meshing planetary gear system (1, 1A, 1B), in the first or second embodiment, the second restricting structure (92) restricts the axial movement of the crankshaft to the other by indirectly contacting the stepped portion with the output side carrier (19) via a plate-shaped component (washer 84), and the input side cover (13) is detachably attached to the input side carrier (18).

[0138] In this embodiment, the plate-shaped component (washer 84) functions as a raceway (raceway board) that reduces friction between the output-side carrier (19) and the stepped portion (70).

[0139] In the internally meshing planetary gear device (1,1A,1B) according to the fourth embodiment, a shim member (132) is interposed between the input carrier (18) and the input cover (13) in any of the first to third embodiments.

[0140] According to this embodiment, the gap between the stepped portion (70) and the input side cover (13) in the axial direction can be adjusted by adjusting the thickness (and / or number) of the shim members (132), thereby adjusting the "play" in the axial direction of the crankshafts (7A, 7B, 7C).

[0141] In the fifth embodiment of the internally meshing planetary gear system (1,1A,1B), in any of the first to fourth embodiments, the input side cover (13) is detachably attached to the input side carrier (18).

[0142] According to this embodiment, when assembling the internally meshing planetary gear unit (1, 1A, 1B), the axial movement of the crankshafts (7A, 7B, 7C) can be restricted only after inserting the crankshafts (7A, 7B, 7C) from the input carrier (18) side and then attaching the input cover (13) to the input carrier (18).

[0143] In the internally meshing planetary gear device (1,1A,1B) according to the sixth embodiment, in any of the first to fifth embodiments, the crankshaft (7A,7B,7C) has an eccentric portion (72) that is eccentric with respect to the axis (Ax2). The first restricting structure (91) is located axially outward from the end faces (stepped portions 702,703) of the eccentric portion (72) of the crankshaft (7A,7B,7C), and restricts the movement of the crankshaft (7A,7B,7C) in one axial direction by directly or indirectly contacting the stepped portion (701) facing outward in the axial direction with the input side cover (13).

[0144] According to this embodiment, the axial movement of the crankshafts (7A, 7B, 7C) is restricted at the stepped portion (701), which is not the end face (stepped portion 702, 703) of the eccentric portion (72), thereby reducing wear on the eccentric portion (72).

[0145] The internally meshing planetary gear device (1, 1A, 1B) according to the seventh embodiment further comprises, in any of the first to sixth embodiments, an input gear (501) that rotates about a rotation axis (Ax1), and a plurality of crankshaft gears (502A, 502B, 502C) arranged around the input gear (501) so as to mesh with the input gear (501) and rotate synchronously with each other when the input gear (501) rotates. Multiple crankshafts (7A, 7B, 7C) are provided so as to correspond one-to-one with the plurality of crankshaft gears (502A, 502B, 502C). The plurality of crankshafts (7A, 7B, 7C) rotate together with the plurality of crankshaft gears (502A, 502B, 502C) and cause the planetary gear (3) to oscillate about the rotation axis (Ax1).

[0146] According to this embodiment, in a distribution-type internal meshing planetary gear system (1,1A,1B), the axial movement of the crankshafts (7A,7B,7C) can be restricted with a relatively simple configuration.

[0147] The robot joint device (200) according to the eighth embodiment comprises an internal meshing planetary gear device (1, 1A, 1B) according to any of the first to seventh embodiments, a first member (201) fixed to the gear body (22), and a second member (202) that rotates relative to the first member (201) in accordance with the relative rotation of the planetary gear (3) with respect to the internal gear (2).

[0148] According to this embodiment, the axial movement of the crank shafts (7A, 7B, 7C) can be restricted with a relatively simple configuration.

[0149] The configurations relating to the second to seventh aspects are not essential to the internally meshing planetary gear system (1, 1A, 1B) and can be omitted as appropriate. [Explanation of Symbols]

[0150] 1,1A,1B Internally meshing planetary gear system 2 Internal gear 3 Planetary gears 7A, 7B, 7C crank axle 13 Input side cover 18 Input Carrier 19 Output carrier 21 Inner teeth 22 Gear body 23 Outer pin 31 External teeth 70, 701, 702, 703, 704 Stepped section 84 Washer (plate-shaped part) 91. Regulatory Structure 92. Regulatory Structure 2 132 Shim member 200 Robot Joint Devices 201 First Member 202 Second Member 221 Inner surface (of the gear body) 223 Inner circumferential groove 501 Input Gear 502A, 502B, 502C Crankshaft Gear Ax1 Rotation axis Ax2 axis center S1 Lubrication path

Claims

1. An internal gear having an annular gear body and a plurality of external pins that are held in a rotatable state in a plurality of internal grooves formed on the inner surface of the gear body and constitute internal teeth, A planetary gear having external teeth that partially mesh with the internal teeth, A crankshaft having stepped portions at least two locations in the axial direction along the axis, which rotates around the axis to oscillate the planetary gear, The planetary gear comprises an input carrier and an output carrier, which are arranged on both sides of the axial direction of the planetary gear and each rotatably support the crankshaft via bearings, By oscillating the planetary gear, the planetary gear is rotated relative to the internal gear, The input carrier includes an input cover mounted on the side of the input carrier opposite to the planetary gear in the axial direction, and the first restricting structure restricts the movement of the crankshaft in one direction in the axial direction by directly or indirectly contacting the stepped portion with the input cover, The system further comprises a second restricting structure that restricts the movement of the crankshaft in the other axial direction by directly or indirectly contacting the stepped portion with the output carrier, The second restricting structure restricts the movement of the crankshaft toward the other in the axial direction by inserting a plate-shaped component between the output-side carrier and the stepped portion in the axial direction, thereby indirectly bringing the stepped portion into contact with the output-side carrier via the plate-shaped component. The outer diameter of the stepped portion is smaller than the inner diameter of the outer ring of the bearing. Internally meshing planetary gear system.

2. A lubrication passage for passing lubricant is formed between the stepped portion and the input-side carrier. The internal meshing planetary gear device according to claim 1.

3. A shim member is interposed between the input carrier and the input cover. The internal meshing planetary gear device according to claim 1 or 2.

4. The input-side cover is detachably attached to the input-side carrier. The internal meshing planetary gear device according to claim 1 or 2.

5. The crankshaft has an eccentric portion that is eccentric with respect to the axis, The first restricting structure restricts the movement of the crankshaft in one direction in the axial direction by directly or indirectly contacting the stepped portion of the crankshaft, which is located on the axial side of the crankshaft and faces outward in the axial direction, with the input side cover. The internal meshing planetary gear device according to claim 1 or 2.

6. An input gear that rotates around a rotation axis, The system further comprises a plurality of crankshaft gears arranged around the input gear so as to mesh with the input gear, and which rotate synchronously with each other when the input gear rotates. The aforementioned crankshafts are provided in multiple quantities so as to correspond one-to-one with the plurality of crankshaft gears. The plurality of crankshafts rotate together with the plurality of crankshaft gears, causing the planetary gears to oscillate around the axis of rotation. The internal meshing planetary gear device according to claim 1 or 2.

7. An internal meshing planetary gear device according to claim 1 or 2, A first member fixed to the gear body, The system comprises a second member that rotates relative to the first member in accordance with the relative rotation of the planetary gear with respect to the internal gear, Joint device for robots.

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