Robotic mechanical arm structure, gear system, and robotic joint system

Abstract

The present invention provides a robotic mechanical arm structure and a gear system equipped with a robotic joint device that facilitates stable meshing between internal and external teeth. [Solution] The gear device comprises an internal gear, an annular external gear, a deflection generator, and a bearing member. The external gear has external teeth and is positioned inside the internal gear. The deflection generator has a non-circular cam that is rotationally driven around a rotation axis, and a bearing mounted on the outside of the cam. The deflection generator is positioned inside the external gear and causes deflection in the external gear. The gear device deforms the external gear as the cam rotates, engaging a portion of the external teeth with a portion of the internal teeth, and rotating the external gear relative to the internal gear according to the difference in the number of teeth between them. The bearing member has a first bearing member and a second bearing member that rotatably support the external gear relative to the gear body at two axial locations parallel to the rotation axis. This makes it easier to stabilize the meshing between the internal and external teeth.

Description

Technical Field

[0001] The present disclosure relates to the field of robotics, and more particularly to a robotic arm structure equipped with a robotic joint device and a gear device, wherein the robotic joint device includes the gear device.

Background Art

[0002] As a related technology, an internal meshing planetary gear device is known that includes an external gear and an internal gear and is configured to extract only the rotational component of the external gear (see, for example, Patent Document 1). The external gear is attached so as to be eccentrically rotatable with respect to the rotation center of the input shaft. The internal gear has a plurality of external pins that rotate while being internally meshed with the external teeth of the external gear, and a gear body (external pin holder) having a cylindrical inner surface that rotatably holds each external pin.

[0003] Here, the gear body has a plurality of inner circumferential grooves (pin grooves) that are recessed axially on the inner surface to hold the external pins. External teeth such as a trochoidal tooth profile or an arc tooth profile are provided on the outer circumference of the external gear. The external pin is a thin cylindrical pin member that is deflected by the force from the external gear during rotation, and is arranged such that its axial direction is parallel to the rotation center and functions as an internal tooth. In the gear body in the related technology, there are portions where the inner diameter (radius) is different within one inner circumferential groove, and partially, the inner diameter of the inner circumferential groove is larger than the outer diameter of the external pin, resulting in play due to the clearance between the outer peripheral surface of the external pin and the inner surface of the inner circumferential groove. Therefore, the external pin can rotate with low loss.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the above-mentioned related technologies, play occurs between the outer surface of the outer pin and the inner surface of the inner groove. As a result, when the inner tooth (outer pin) and outer tooth mesh together, a force acts on the outer pin in a direction that pulls it out of the inner groove, which may cause instability in the meshing between the inner and outer teeth.

[0006] The purpose of this disclosure is to provide a robotic mechanical arm structure and a gear device, which include a robotic joint device having a gear device that facilitates stable meshing between internal and external teeth. [Means for solving the problem]

[0007] A robotic mechanical arm structure according to one aspect of the present disclosure comprises a robotic joint device. The robotic joint device comprises a gear device, a first member, and a second member. The gear device comprises an internal gear, an annular external gear, a deflection generator, and a bearing member. The internal gear has 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 circumferential surface of the gear body and constitute the internal teeth. The external gear has external teeth and is positioned inside the internal gear. The deflection generator has a non-circular cam that is rotationally driven around a rotation axis, and a bearing mounted on the outside of the cam. The deflection generator is positioned inside the external gear and causes deflection in the external gear. The gear device deforms the external gear as the cam rotates, engaging a portion of the external teeth with a portion of the internal teeth, and causing the external gear to rotate relative to the internal gear according to the difference in the number of teeth between the external gear and the internal gear. The bearing member has a first bearing member and a second bearing member that rotatably support the external gear relative to the gear body at two locations in the axial direction parallel to the rotation axis. The first member is fixed to the gear body. The second member rotates relative to the first member in accordance with the relative rotation of the planetary gear relative to the internal gear.

[0008] A gear apparatus according to one aspect of the present disclosure comprises an internal gear, an annular external gear, a deflection generator, and a bearing member. The internal gear has 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. The external gear has external teeth and is positioned inside the internal gear. The deflection generator has a non-circular cam that is rotationally driven around a rotation axis, and a bearing mounted on the outside of the cam. The deflection generator is positioned inside the external gear and causes deflection in the external gear. The gear apparatus deforms the external gear as the cam rotates, engaging a portion of the external teeth with a portion of the internal teeth, and causing the external gear to rotate relative to the internal gear according to the difference in the number of teeth between the external gear and the internal gear. The bearing member has a first bearing member and a second bearing member that rotatably support the external gear relative to the gear body at two locations in the axial direction parallel to the rotation axis.

[0009] A robotic joint device according to one aspect of the present disclosure comprises a 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 a robot joint device and a gear device that include a gear device for robots in which the meshing between internal and external teeth is easily stabilized. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a perspective view showing the schematic configuration of an actuator including a gear mechanism related to basic configuration 1. [Figure 2] Figure 2 is a schematic exploded perspective view of the same gear mechanism as seen from the output side of the rotating shaft. [Figure 3] Figure 3 is a schematic cross-sectional view of the gear mechanism shown above. [Figure 4]Figure 4 is a cross-sectional view taken along line A1-A1 of FIG. 3, showing the same gear device as above. [Figure 5A] FIG. 5A is a perspective view showing the planetary gear of the same gear device alone. [Figure 5B] FIG. 5B is a front view showing the planetary gear of the same gear device alone. [Figure 6A] FIG. 6A is a perspective view showing the bearing member of the same gear device alone. [Figure 6B] FIG. 6B is a front view showing the bearing member of the same gear device alone. [Figure 7A] FIG. 7A is a perspective view showing the eccentric shaft of the same gear device alone. [Figure 7B] FIG. 7B is a front view showing the eccentric shaft of the same gear device alone. [Figure 8A] FIG. 8A is a perspective view showing the support of the same gear device alone. [Figure 8B] FIG. 8B is a front view showing the support of the same gear device alone. [Figure 9] FIG. 9 is an enlarged view of region Z1 of FIG. 3, showing the same gear device as above. [Figure 10] FIG. 10 is a cross-sectional view taken along line B1-B1 of FIG. 3, showing the same gear device as above. [Figure 11] FIG. 11 is a schematic cross-sectional view of the gear device according to Basic Configuration 2, showing a schematic enlarged view of the main part in an inset. [Figure 12] FIG. 12 is a cross-sectional view taken along line A1-A1 of FIG. 11, showing the same gear device as above. [Figure 13] FIG. 13 is a cross-sectional view taken along line A1-A1 of FIG. 11, showing the same gear device as above. [Figure 14A] FIG. 14A is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device. [Figure 14B] FIG. 14B is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device. [Figure 15A] FIG. 15A is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device. [Figure 15B] Figure 15B is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device as above. [Figure 16A] Figure 16A is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device as above. [Figure 16B] Figure 16B is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device as above. [Figure 17A] Figure 17A is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device as above. [Figure 17B] Figure 17B is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device as above. [Figure 18A] Figure 18A is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device as above. [Figure 18B] Figure 18B is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device as above. [Figure 19A] Figure 19A is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device as above. [Figure 19B] Figure 19B is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device as above. [Figure 20A] Figure 20A is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device as above. [Figure 20B] Figure 20B is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device as above. [Figure 21A] Figure 21A is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device as above. [Figure 21B] Figure 21B is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device as above. [Figure 22A] Figure 22A is a conceptual diagram for explaining the tooth profile design procedure of the external gear in the same gear device as above. [Figure 22B] Figure 22B is a conceptual diagram illustrating the procedure for designing the tooth profile of an external gear in the gear system described above. [Figure 23] Figure 23 is an enlarged view of the main parts of the external and internal teeth in the gear mechanism described above. [Figure 24] Figure 24 is a schematic cross-sectional view showing a robot joint device using the gear mechanism described above. [Figure 25] Figure 25 is a schematic cross-sectional view of a gear device according to Embodiment 1, with a schematic enlarged view of the main part shown in the callout. [Figure 26] Figure 26 is a cross-sectional view taken along line A1-A1 in Figure 25, showing the gear mechanism described above. [Figure 27] Figure 27 is a cross-sectional view taken along line A2-A2 in Figure 25, showing the same gear mechanism. [Figure 28] Figure 28 is a schematic cross-sectional view showing a robot joint device using the gear mechanism described above. [Figure 29] Figure 29 is a schematic cross-sectional view of a gear device according to Embodiment 2. [Modes for carrying out the invention]

[0012] (Basic configuration 1) (1) Overview The following describes the general outline of the gear unit 1 relating to this basic configuration with reference to Figures 1 to 3. The drawings referenced in this disclosure are all schematic, and the ratios of the size and thickness of each component shown in the figures do not necessarily reflect the actual dimensional ratios. For example, the tooth profile, dimensions, and number of teeth of the internal teeth 21 and external teeth 31 in Figures 1 to 3 are all shown schematically for illustrative purposes only and are not intended to limit the actual shape to those shown.

[0013] The gear device 1 according to this basic configuration is a gear device comprising an internal gear 2, an external gear 3, and a plurality of internal pins 4. In this gear device 1, the external gear 3 is arranged inside the annular internal gear 2, and an eccentric bearing 5 is further arranged inside the external gear 3. The eccentric bearing 5 has an eccentric inner ring 51 and an eccentric outer ring 52, and the external gear 3 is oscillated by the rotation (eccentric motion) of the eccentric inner ring 51 around a rotation axis Ax1 (see Figure 3) which is offset from the center C1 (see Figure 3) of the eccentric inner ring 51. The eccentric inner ring 51 rotates (eccentric motion) around the rotation axis Ax1 by, for example, the rotation of an eccentric shaft 7 inserted into the eccentric inner ring 51. The gear device 1 also further comprises a bearing member 6 having an outer ring 62 and an inner ring 61. The inner ring 61 is positioned inside the outer ring 62 and is supported so as to be rotatable relative to the outer ring 62.

[0014] 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 rotatable state and constitute the internal teeth 21. The external gear 3 has external teeth 31 that partially mesh with the internal teeth 21. That is, the external gear 3 is in contact 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 eccentric shaft 7 rotates, the external 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 occurs between the two gears (internal gear 2 and external gear 3) according to the difference in the number of teeth between the external gear 3 and the internal gear 2. If the internal gear 2 is fixed, then the external gear 3 will rotate (rotate on its own axis) in conjunction with the relative rotation of the two gears. As a result, the external 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.

[0015] This type of gear device 1 is used to extract the rotational component of the external gear 3 as the rotation of an output shaft integrated with the inner ring 61 of the bearing member 6, for example. As a result, the gear device 1 functions as a gear device with a relatively high reduction ratio, with the eccentric shaft 7 as the input side and the output shaft as the output side. In this basic configuration of the gear device 1, the external gear 3 and the inner ring 61 are connected by a plurality of internal pins 4 in order to transmit the rotational component of the external gear 3 to the inner ring 61 of the bearing member 6. The plurality of internal pins 4 are each inserted into a plurality of loose fitting holes 32 formed in the external gear 3, and each rotates relative to the internal gear 2 while revolving within the loose fitting holes 32. In other words, the loose fitting holes 32 have a larger diameter than the internal pins 4, and the internal pins 4 are movable so as to revolve within the loose fitting holes 32 while inserted into them. The oscillation component of the external gear 3, that is, the revolution component of the external gear 3, is absorbed by the loose fitting between the loose fitting hole 32 of the external gear 3 and the internal pin 4. In other words, the oscillation component of the external gear 3 is absorbed as multiple internal pins 4 move so as to revolve within multiple loose fitting holes 32. Therefore, the rotation (rotation component) of the external gear 3, excluding the oscillation component (revolution component), is transmitted to the inner ring 61 of the bearing member 6 by the multiple internal pins 4.

[0016] Incidentally, in this type of gear device 1, the rotation of the external gear 3 is transmitted to multiple internal pins 4 as the internal pins 4 revolve within the loose fitting holes 32 of the external gear 3. Therefore, as a first related technology, it is known that an internal roller is used that is mounted on the internal pins 4 and can rotate around the internal pins 4 as an axis. In other words, in the first related technology, the internal pins 4 are held in a press-fitted state against the inner ring 61 (or a carrier integrated with the inner ring 61), and as the internal pins 4 revolve within the loose fitting holes 32, the internal pins 4 slide against the inner circumferential surface 321 of the loose fitting holes 32. Therefore, as a first related technology, an internal roller is used to reduce losses due to frictional resistance between the inner circumferential surface 321 of the loose fitting holes 32 and the internal pins 4. However, if a configuration with an internal roller is used as in the first related technology, the loose fitting holes 32 must have a diameter that allows the internal pins 4 with the internal rollers to revolve, making it difficult to miniaturize the loose fitting holes 32. If the loose fitting hole 32 is difficult to miniaturize, it will hinder the miniaturization (especially the reduction in diameter) of the external gear 3, and consequently, the miniaturization of the entire gear unit 1. The gear unit 1 according to this basic configuration can be made more easily miniaturized by the following configuration.

[0017] In other words, the gear device 1 according to this basic configuration comprises a bearing member 6, an internal gear 2, an external gear 3, and a plurality of internal pins 4, as shown in Figures 1 to 3. The bearing member 6 has an outer ring 62 and an inner ring 61 positioned inside the outer ring 62. The inner ring 61 is supported so as to be rotatable relative to the outer ring 62. The internal gear 2 has internal teeth 21 and is fixed to the outer ring 62. The external gear 3 has external teeth 31 that partially mesh with the internal teeth 21. The plurality of internal pins 4 are inserted into a plurality of loose fitting holes 32 formed in the external gear 3, and rotate relative to the internal gear 2 while revolving within the loose fitting holes 32. Here, each of the plurality of internal pins 4 is held by the inner ring 61 in a state in which it can rotate on its own. Furthermore, at least a portion of each of the plurality of internal pins 4 is positioned in the same position as the bearing member 6 in the axial direction of the bearing member 6.

[0018] In this embodiment, each of the multiple inner pins 4 is held by the inner ring 61 in a state that allows it to rotate on its own, so that the inner pin 4 can rotate on its own when it revolves within the loose fitting hole 32. Therefore, even without using an inner roller that is attached to the inner pin 4 and can rotate around the inner pin 4 as an axis, the loss due to frictional resistance between the inner circumferential surface 321 of the loose fitting hole 32 and the inner pin 4 can be reduced. Thus, the gear device 1 according to this basic configuration does not require an inner roller and has the advantage of being easy to miniaturize. Moreover, since at least a portion of each of the multiple inner pins 4 is positioned at the same position as the bearing member 6 in the axial direction of the bearing member 6, the dimensions of the gear device 1 in the axial direction of the bearing member 6 can be kept small. In other words, compared to a configuration in which the bearing member 6 and the inner pins 4 are aligned (facing each other) in the axial direction of the bearing member 6, the gear device 1 according to this basic configuration can reduce the dimensions of the gear device 1 in the axial direction, which can contribute to further miniaturization (thinning) of the gear device 1.

[0019] Furthermore, if the dimensions of the external gear 3 are the same as those of the first related technology described above, it is possible to, for example, increase the number of internal pins 4 to make the transmission of rotation smoother, or to make the internal pins 4 thicker to improve strength, compared to the first related technology described above.

[0020] Furthermore, in this type of gear device 1, the internal pins 4 need to revolve within the loose fitting holes 32 of the external gear 3. As a second related technology, the multiple internal pins 4 may be held only by the inner ring 61 (or a carrier integrated with the inner ring 61). According to the second related technology, it is difficult to improve the accuracy of centering the multiple internal pins 4, and poor centering can lead to problems such as vibration and reduced transmission efficiency. In other words, the multiple internal pins 4 each revolve within the loose fitting holes 32 and rotate relative to the internal gear 2, thereby transmitting the rotation component of the external gear 3 to the inner ring 61 of the bearing member 6. At this time, if the accuracy of centering the multiple internal pins 4 is insufficient, and the rotation axes of the multiple internal pins 4 are misaligned or tilted relative to the rotation axis of the inner ring 61, it results in poor centering, which can lead to problems such as vibration and reduced transmission efficiency. The gear device 1 according to this basic configuration provides a gear device 1 that is less prone to problems caused by poor centering of the multiple internal pins 4 through the following configuration.

[0021] In other words, the gear device 1 according to this basic configuration comprises an internal gear 2, an external gear 3, a plurality of internal pins 4, and a support 8, as shown in Figures 1 to 3. 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 rotatable state and constitute the internal teeth 21. The external gear 3 has external teeth 31 that partially mesh with the internal teeth 21. The plurality of internal pins 4 are inserted into a plurality of loose fitting holes 32 formed in the external gear 3, and rotate relative to the gear body 22 while revolving within the loose fitting holes 32. The support 8 is annular and supports the plurality of internal pins 4. Here, the position of the support 8 is restricted by bringing its outer circumferential surface 81 into contact with the plurality of external pins 23.

[0022] In this embodiment, since the multiple inner pins 4 are supported by an annular support 8, the multiple inner pins 4 are bundled together by the support 8, and relative displacement and tilting of the multiple inner pins 4 are suppressed. Moreover, the outer circumferential surface 81 of the support 8 is in contact with the multiple outer pins 23, thereby regulating the position of the support 8. In short, the support 8 is centered by the multiple outer pins 23, and as a result, the multiple inner pins 4 supported by the support 8 are also centered by the multiple outer pins 23. Therefore, the gear device 1 according to this basic configuration has the advantage that it is easy to improve the accuracy of centering the multiple inner pins 4, and malfunctions caused by poor centering of the multiple inner pins 4 are less likely to occur.

[0023] 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 external gear 3. Specifically, the drive source 101 oscillates the external gear 3 by rotating the eccentric shaft 7 around the rotation axis Ax1.

[0024] (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.

[0025] In this disclosure, "loose fitting" means fitting with some play (gap), and the loose fitting hole 32 is the hole into which the inner pin 4 is loosely fitted. In other words, the inner pin 4 is inserted into the loose fitting hole 32 while ensuring a spatial margin (gap) between it and the inner circumferential surface 321 of the loose fitting hole 32. To put it another way, the diameter of at least the portion of the inner pin 4 that is inserted into the loose fitting hole 32 is smaller (thinner) than the diameter of the loose fitting hole 32. Therefore, the inner pin 4 is movable within the loose fitting hole 32 while inserted into it, that is, it is movable relative to the center of the loose fitting hole 32. Thus, the inner pin 4 can revolve within the loose fitting hole 32. However, it is not essential that a gap as a cavity is secured between the inner circumferential surface 321 of the loose fitting hole 32 and the inner pin 4; for example, this gap may be filled with a fluid such as liquid.

[0026] In this disclosure, "revolution" means that an object revolves around an axis of rotation other than the central axis passing through the center (center of gravity) of the object. 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 inner pin 4 revolves within the loose fitting hole 32 by revolving around an axis of rotation passing through the center of the loose fitting hole 32.

[0027] Furthermore, in this disclosure, one side of the rotating shaft Ax1 (the left side in Figure 3) may be referred to as the "input side," and the other side of the rotating shaft Ax1 (the right side in Figure 3) may be referred to as the "output side." In the example in Figure 3, rotation is applied to the rotating body (eccentric inner ring 51) from the "input side" of the rotating shaft Ax1, and the rotation of the multiple inner pins 4 (inner rings 61) 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 viewed from the gear device 1.

[0028] In this disclosure, "axis of rotation" refers to a hypothetical 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 eccentric inner ring 51 rotates around the axis of rotation Ax1.

[0029] 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 external gear 3 consist of a collection of multiple teeth arranged on the outer circumferential surface of the external gear 3.

[0030] (3) Composition The detailed configuration of the gear unit 1 related to this basic configuration will be explained below with reference to Figures 1 to 8B.

[0031] 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 output side of the rotating shaft Ax1. Figure 3 is a schematic cross-sectional view of the gear unit 1. Figure 4 is a cross-sectional view taken along line A1-A1 in Figure 3. However, in Figure 4, hatching is omitted for parts other than the eccentric shaft 7, even in cross-section. Furthermore, in Figure 4, the inner circumferential surface 221 of the gear body 22 is not shown. Figures 5A and 5B are perspective and front views showing the external gear 3 by itself. Figures 6A and 6B are perspective and front views showing the bearing member 6 by itself. Figures 7A and 7B are perspective and front views showing the eccentric shaft 7 by itself. Figures 8A and 8B are perspective and front views showing the support 8 by itself.

[0032] (3.1) Overall structure As shown in Figures 1 to 3, the gear unit 1 in this basic configuration comprises an internal gear 2, an external gear 3, a plurality of internal pins 4, an eccentric bearing 5, a bearing member 6, an eccentric shaft 7, and a support 8. In this basic configuration, the gear unit 1 further comprises a first bearing 91, a second bearing 92, and a case 10. In this basic configuration, the materials of the components of the gear unit 1, such as the internal gear 2, external gear 3, plurality of internal pins 4, eccentric bearing 5, bearing member 6, eccentric shaft 7, and support 8, are metals such as stainless steel, cast iron, carbon steel for machine structures, chromium-molybdenum steel, phosphor bronze, or aluminum bronze. The term "metal" here includes metals that have undergone surface treatment such as nitriding.

[0033] Furthermore, in this basic configuration, an internal planetary gear system using a trochoidal tooth profile is given as an example of a gear system 1. In other words, the gear system 1 in this basic configuration is equipped with an internal external gear 3 having a trochoidal curved tooth profile.

[0034] 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 external gear 3 rotates relative to the fixed member (case 10, etc.) as the internal gear 2 and the external gear 3 rotate relative to each other.

[0035] Furthermore, in this basic configuration, when the gear unit 1 is used as the actuator 100, a rotational force is applied to the eccentric shaft 7 as input, and a rotational force is extracted as output from the output shaft, which is integrated with the inner ring 61 of the bearing member 6. In other words, the gear unit 1 operates using the rotation of the eccentric shaft 7 as the input rotation and the rotation of the output shaft, which is integrated with the inner ring 61, as the output rotation. As a result, the gear unit 1 obtains an output rotation that is reduced at a relatively high reduction ratio relative to the input rotation.

[0036] The drive source 101 is a power source such as a motor. The power generated by the drive source 101 is transmitted to the eccentric shaft 7 in the gear unit 1. Specifically, the drive source 101 is connected to the eccentric shaft 7 via an input shaft, and the power generated by the drive source 101 is transmitted to the eccentric shaft 7 via the input shaft. This allows the drive source 101 to rotate the eccentric shaft 7.

[0037] Furthermore, in the gear unit 1 relating to this basic configuration, as shown in Figure 3, 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 eccentric shaft 7 to which the input rotation is applied, and the output rotation axis Ax1 is the rotation center of the inner ring 61 (and output shaft) that generates the output rotation. In other words, in the gear unit 1, an output rotation reduced at a relatively high reduction ratio relative to the input rotation is obtained on the same axis.

[0038] As shown in Figure 4, 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.

[0039] 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 (along with the outer ring 62) is fixed to the case 10. For this reason, the gear body 22 has multiple fixing holes 222 formed therein.

[0040] As shown in Figure 4, the external gear 3 is an annular component having external teeth 31. In this basic configuration, the external 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 external gear 3, along the circumferential direction of the external gear 3. All of the teeth constituting the external teeth 31 are of the same shape and are provided at equal pitches over the entire circumferential area of ​​the outer circumferential surface of the external gear 3. In other words, the pitch circle of the external teeth 31 is a perfect circle in plan view. The center C1 of the pitch circle of the external teeth 31 is located at a distance ΔL (see Figure 4) from the rotation axis Ax1. The external 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 external gear 3. The tooth traces of the external teeth 31 are all parallel to the rotation axis Ax1. Unlike the internal gear 2, in the external gear 3, the external teeth 31 are integrally formed with the body of the external gear 3 using a single metal component.

[0041] Here, an eccentric bearing 5 and an eccentric shaft 7 are combined with the external gear 3. In other words, the external gear 3 has a circular opening 33 formed therein. The opening 33 is a hole that penetrates the external gear 3 along the thickness direction. In a plan view, the center of the opening 33 coincides with the center of the external gear 3, and the inner circumferential surface of the opening 33 (the inner circumferential surface of the external gear 3) and the pitch circle of the external teeth 31 are concentric. The eccentric bearing 5 is housed in the opening 33 of the external gear 3. Furthermore, the eccentric shaft 7 is inserted into the eccentric bearing 5 (specifically, the eccentric inner ring 51), thereby combining the eccentric bearing 5 and the eccentric shaft 7 with the external gear 3. With the eccentric bearing 5 and the eccentric shaft 7 combined with the external gear 3, when the eccentric shaft 7 rotates, the external gear 3 oscillates around the rotation axis Ax1.

[0042] The external gear 3, configured in this way, is positioned inside the internal gear 2. In a plan view, the external gear 3 is formed to be slightly smaller than the internal gear 2, and when combined with the internal gear 2, the external gear 3 is able to swing inside the internal gear 2. Here, external teeth 31 are formed on the outer circumferential surface of the external gear 3, and internal teeth 21 are formed on the inner circumferential surface of the internal gear 2. Therefore, when the external gear 3 is positioned inside the internal gear 2, the external teeth 31 and the internal teeth 21 face each other.

[0043] Furthermore, the pitch circle of the external teeth 31 is slightly smaller than the pitch circle of the internal teeth 21. When the external gear 3 is tangent to the internal gear 2, the center C1 of the pitch circle of the external teeth 31 is located at a distance ΔL (see Figure 4) from the center of the pitch circle of the internal teeth 21 (rotation axis Ax1). Therefore, at least a portion of the external teeth 31 and the internal teeth 21 face each other with a gap in between, and their entire circumferential surfaces do not mesh with each other. However, since the external gear 3 oscillates (revolves) around the rotation axis Ax1 inside the internal gear 2, the external teeth 31 and the internal teeth 21 partially mesh. In other words, as the external gear 3 oscillates around the rotation axis Ax1, as shown in Figure 4, some of the teeth of the external teeth 31 mesh with some of the teeth of the internal teeth 21. As a result, the gear device 1 makes it possible to mesh a portion of the external teeth 31 with a portion of the internal teeth 21.

[0044] Here, the number of teeth of the internal teeth 21 in the internal gear 2 is N (where N is a positive integer) greater than the number of teeth of the external teeth 31 in the external gear 3. In this basic configuration, as an example, N is "1", and the number of teeth of the external gear 3 (external teeth 31) is "1" greater than the number of teeth of the internal gear 2 (internal teeth 21). This difference in the number of teeth between the external gear 3 and the internal gear 2 defines the reduction ratio of the output rotation to the input rotation in the gear device 1.

[0045] Furthermore, in this basic configuration, as an example, the thickness of the external gear 3 is smaller than the thickness of the gear body 22 of the internal gear 2. Moreover, the dimension of the external teeth 31 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 will be contained within the range of the tooth trace of the internal teeth 21.

[0046] In this basic configuration, as described above, the rotational component of the external gear 3 is extracted as the rotation (output rotation) of the output shaft, which is integrated with the inner ring 61 of the bearing member 6. Therefore, the external gear 3 is connected to the inner ring 61 by a plurality of inner pins 4. As shown in Figures 5A and 5B, the external gear 3 has a plurality of loose fitting holes 32 for inserting the plurality of inner pins 4. The same number of loose fitting holes 32 as the number of inner pins 4 are provided, and in this basic configuration, as an example, there are 18 loose fitting holes 32 and 18 inner pins 4. Each of the plurality of loose fitting holes 32 has a circular opening and is a hole that penetrates the external gear 3 along the thickness direction. The plurality (18 in this case) of loose fitting holes 32 are arranged at equal intervals in the circumferential direction on a virtual circle concentric with the opening 33.

[0047] The multiple internal pins 4 are components that connect the external gear 3 to the inner ring 61 of the bearing member 6. Each of the multiple internal pins 4 is formed in a cylindrical shape. The diameter and length of the multiple internal pins 4 are common to all of them. The diameter of the internal pins 4 is slightly smaller than the diameter of the loose fitting hole 32. As a result, the internal pins 4 are inserted into the loose fitting hole 32 with a spatial clearance (gap) between them and the inner circumferential surface 321 of the loose fitting hole 32 (see Figure 4).

[0048] 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 3).

[0049] As shown in Figures 6A and 6B, the outer ring 62 and the inner ring 61 are both 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 surface of the outer ring 62 and the outer surface of the inner ring 61.

[0050] The inner ring 61 has multiple retaining holes 611 into which multiple inner pins 4 are each inserted. The number of retaining holes 611 is the same as the number of inner pins 4, and in this basic configuration, as an example, there are 18 retaining holes 611. Each of the multiple retaining holes 611 has a circular opening, as shown in Figures 6A and 6B, and is a hole that penetrates the inner ring 61 along the thickness direction. The multiple (18 in this case) retaining holes 611 are arranged at equal intervals in the circumferential direction on a virtual circle concentric with the outer circumference of the inner ring 61. The diameter of the retaining holes 611 is greater than or equal to the diameter of the inner pins 4, but smaller than the diameter of the loose fitting holes 32.

[0051] Furthermore, the inner ring 61 is integrated with the output shaft, and the rotation of the inner ring 61 is extracted as the rotation of the output shaft. For this reason, the inner ring 61 has multiple output-side mounting holes 612 (see Figure 2) for attaching the output shaft. In this basic configuration, the multiple output-side mounting holes 612 are located inside the multiple retaining holes 611 and are arranged on a virtual circle concentric with the outer circumference of the inner ring 61.

[0052] The outer ring 62 is fixed to a fixing member such as the case 10 together with the gear body 22 of the internal gear 2. For this purpose, the outer ring 62 has multiple through holes 621 for fixing. Specifically, as shown in Figure 3, the outer ring 62 is fixed to the case 10 with fixing screws (bolts) 60 passing through the through holes 621 and fixing holes 222 in the gear body 22, with the gear body 22 sandwiched between the outer ring 62 and the case 10.

[0053] 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.

[0054] In this basic configuration, the bearing member 6 is, as an example, a cross-roller bearing. That is, the bearing member 6 has cylindrical rollers as rolling elements 63. The axes of the cylindrical rolling elements 63 are inclined at a 45-degree angle with respect to a plane perpendicular to the rotation axis Ax1, and perpendicular to the outer circumference of the inner ring 61. Furthermore, a pair of rolling elements 63 adjacent to each other in the circumferential direction of the inner ring 61 are arranged so that their axial directions are perpendicular to each other. A bearing member 6 made of such a cross-roller bearing is susceptible to radial loads, thrust loads (in the direction along the rotation axis Ax1), and bending forces (bending moment loads) relative to the rotation axis Ax1. Moreover, a single bearing member 6 can withstand these three types of loads, ensuring the necessary rigidity.

[0055] As shown in Figures 7A and 7B, the eccentric shaft 7 is a cylindrical component. The eccentric shaft 7 has an axial portion 71 and an eccentric portion 72. The axial portion 71 has a cylindrical shape, at least its outer surface being a perfect circle in plan view. The center (central axis) of the axial portion 71 coincides with the rotation axis Ax1. The eccentric portion 72 has a disc shape, at least its outer surface being a perfect circle in plan view. The center (central axis) of the eccentric portion 72 coincides with a center C1 offset from the rotation axis Ax1. Here, the distance ΔL (see Figure 7B) between the rotation axis Ax1 and the center C1 is the amount of eccentricity of the eccentric portion 72 relative to the axial portion 71. The eccentric portion 72 has a flange shape that protrudes from the outer surface of the axial portion 71 around its entire circumference at the center of the axial portion 71 in the longitudinal direction (axial direction). According to the above configuration, the eccentric shaft 7 undergoes eccentric motion as the axial portion 71 rotates (rotates) around the rotation axis Ax1, causing the eccentric portion 72 to move eccentrically.

[0056] In this basic configuration, the central part 71 and the eccentric part 72 are integrally formed from a single metal member, thereby realizing a seamless eccentric shaft 7. This eccentric shaft 7 is combined with the external gear 3 together with the eccentric bearing 5. Therefore, when the eccentric shaft 7 rotates with the external gear 3 combined with the eccentric bearing 5, the external gear 3 oscillates around the rotation axis Ax1.

[0057] Furthermore, the eccentric shaft 7 has a through hole 73 that penetrates the axial (longitudinal) portion 71. The through hole 73 opens circularly on both axial end faces of the axial portion 71. The center (central axis) of the through hole 73 coincides with the rotation axis Ax1. Cables such as power lines and signal lines can be passed through the through hole 73.

[0058] Furthermore, in this basic configuration, a rotational force is applied as input to the eccentric shaft 7 from the drive source 101. For this reason, the eccentric shaft 7 has multiple input-side mounting holes 74 (see Figures 7A and 7B) for attaching the input shaft connected to the drive source 101. In this basic configuration, the multiple input-side mounting holes 74 are arranged around the through hole 73 on one end face in the axial direction of the shaft core 71, and are positioned on a virtual circle concentric with the through hole 73.

[0059] The eccentric bearing 5 has an eccentric outer ring 52 and an eccentric inner ring 51, and is a component that absorbs the rotational component of the rotation of the eccentric shaft 7 and transmits only the rotation of the eccentric shaft 7, i.e., the oscillating component (revolutional component) of the eccentric shaft 7, to the external gear 3. In addition to the eccentric outer ring 52 and the eccentric inner ring 51, the eccentric bearing 5 has a plurality of rolling elements 53 (see Figure 3).

[0060] Both the eccentric outer ring 52 and the eccentric inner ring 51 are annular components. Both the eccentric outer ring 52 and the eccentric inner ring 51 have annular shapes that are perfect circles in plan view. The eccentric inner ring 51 is slightly smaller than the eccentric outer ring 52 and is positioned inside the eccentric outer ring 52. Here, since the inner diameter of the eccentric outer ring 52 is larger than the outer diameter of the eccentric inner ring 51, a gap is created between the inner circumferential surface of the eccentric outer ring 52 and the outer circumferential surface of the eccentric inner ring 51.

[0061] Multiple rolling elements 53 are arranged in the gap between the eccentric outer ring 52 and the eccentric inner ring 51. The multiple rolling elements 53 are arranged in a line along the circumference of the eccentric outer ring 52. All of the multiple rolling elements 53 are metal parts of the same shape and are provided at equal pitches over the entire circumference of the eccentric outer ring 52. In this basic configuration, as an example, the eccentric bearing 5 consists of a deep groove ball bearing using balls as rolling elements 53.

[0062] Here, the inner diameter of the eccentric inner ring 51 matches the outer diameter of the eccentric portion 72 of the eccentric shaft 7. The eccentric bearing 5 is assembled with the eccentric shaft 7 with the eccentric portion 72 of the eccentric shaft 7 inserted into the eccentric inner ring 51. Also, the outer diameter of the eccentric outer ring 52 matches the inner diameter (diameter) of the opening 33 of the external gear 3. The eccentric bearing 5 is assembled with the external gear 3 with the eccentric outer ring 52 fitted into the opening 33 of the external gear 3. In other words, the eccentric bearing 5, mounted on the eccentric portion 72 of the eccentric shaft 7, is housed in the opening 33 of the external gear 3.

[0063] Furthermore, in this basic configuration, as an example, the width dimension (in the direction parallel to the rotation axis Ax1) of the eccentric inner ring 51 of the eccentric bearing 5 is approximately the same as the thickness of the eccentric portion 72 of the eccentric shaft 7. The width dimension (in the direction parallel to the rotation axis Ax1) of the eccentric outer ring 52 is slightly smaller than the width dimension of the eccentric inner ring 51. Moreover, the width dimension of the eccentric outer ring 52 is larger than the thickness of the external gear 3. Therefore, in the direction parallel to the rotation axis Ax1, the external gear 3 will fit within the range of the eccentric bearing 5. On the other hand, the width dimension of the eccentric outer ring 52 is smaller than the tooth trace dimension (in the direction parallel to the rotation axis Ax1) of the internal teeth 21. Therefore, in the direction parallel to the rotation axis Ax1, the eccentric bearing 5 will fit within the range of the internal gear 2.

[0064] When the eccentric shaft 7 rotates while the eccentric bearing 5 and eccentric shaft 7 are assembled to the external gear 3, the eccentric bearing 5 causes the eccentric inner ring 51 to rotate (eccentrically) around a rotation axis Ax1 offset from the center C1 of the eccentric inner ring 51. At this time, the rotational component of the eccentric shaft 7 is absorbed by the eccentric bearing 5. Therefore, the external gear 3 receives only the rotation of the eccentric shaft 7, excluding its rotational component, i.e., the oscillation component (revolution component) of the eccentric shaft 7, through the eccentric bearing 5. Thus, when the eccentric shaft 7 rotates while the eccentric bearing 5 and eccentric shaft 7 are assembled to the external gear 3, the external gear 3 oscillates around the rotation axis Ax1.

[0065] As shown in Figures 8A and 8B, the support 8 is a ring-shaped component that supports a plurality of inner pins 4. The support 8 has a plurality of support holes 82 into which each of the plurality of inner pins 4 is inserted. The number of support holes 82 is the same as the number of inner pins 4, and in this basic configuration, as an example, there are 18 support holes 82. Each of the plurality of support holes 82 opens in a circular shape, as shown in Figures 8A and 8B, and is a hole that penetrates the support 8 along the thickness direction. The plurality (18 in this case) of support holes 82 are arranged at equal intervals in the circumferential direction on a virtual circle concentric with the outer circumferential surface 81 of the support 8. The diameter of the support holes 82 is greater than or equal to the diameter of the inner pins 4, and less than the diameter of the loose fitting holes 32. In this basic configuration, as an example, the diameter of the support holes 82 is equal to the diameter of the retaining holes 611 formed in the inner ring 61.

[0066] As shown in Figure 3, the support 8 is positioned facing the external gear 3 from one side (input side) of the rotation axis Ax1. Multiple internal pins 4 are inserted into multiple support holes 82, and the support 8 functions to bundle the multiple internal pins 4 together. Furthermore, the position of the support 8 is restricted by contacting the multiple external pins 23 with its outer circumferential surface 81. As a result, the support 8 is centered by the multiple external pins 23, and consequently, the multiple internal pins 4 supported by the support 8 are also centered by the multiple external pins 23. The support 8 will be described in detail in the section "(3.3) Support".

[0067] The first bearing 91 and the second bearing 92 are each mounted on the axial center 71 of the eccentric shaft 7. Specifically, as shown in Figure 3, the first bearing 91 and the second bearing 92 are mounted on both sides of the eccentric portion 72 on the axial center 71, sandwiching the eccentric portion 72 in a direction parallel to the rotation axis Ax1. The first bearing 91 is positioned on the input side of the rotation axis Ax1 when viewed from the eccentric portion 72. The second bearing 92 is positioned on the output side of the rotation axis Ax1 when viewed from the eccentric portion 72. The first bearing 91 rotatably holds the eccentric shaft 7 with respect to the case 10. The second bearing 92 rotatably holds the eccentric shaft 7 with respect to the inner ring 61 of the bearing member 6. As a result, the axial center 71 of the eccentric shaft 7 is rotatably held at two locations on both sides of the eccentric portion 72 in a direction parallel to the rotation axis Ax1.

[0068] The case 10 is cylindrical and has a flange portion 11 on the output side of the rotating shaft Ax1. The flange portion 11 has a plurality of mounting holes 111 for fixing the case 10 itself. In addition, a bearing hole 12 is formed on the end face of the case 10 on the output side of the rotating shaft Ax1. The bearing hole 12 has a circular opening. The first bearing 91 is attached to the case 10 by fitting it into the bearing hole 12.

[0069] Furthermore, on the output end face of the rotating shaft Ax1 in case 10, a plurality of screw holes 13 are formed around the bearing hole 12. The plurality of screw holes 13 are used to fix the gear body 22 of the internal gear 2 and the outer ring 62 of the bearing member 6 to case 10. Specifically, fixing screws 60 are tightened into the screw holes 13 through the through holes 621 of the outer ring 62 and the fixing holes 222 of the gear body 22, thereby fixing the gear body 22 and the outer ring 62 to case 10.

[0070] Furthermore, the gear unit 1 relating to this basic configuration is further equipped with a plurality of oil seals 14, 15, 16, etc., as shown in Figure 3. Oil seal 14 is attached to the input end of the rotating shaft Ax1 on the eccentric shaft 7 and seals the gap between the case 10 and the eccentric shaft 7 (axis center 71). Oil seal 15 is attached to the output end of the rotating shaft Ax1 on the eccentric shaft 7 and seals the gap between the inner ring 61 and the eccentric shaft 7 (axis center 71). Oil seal 16 is attached to the output end face of the rotating shaft Ax1 on the bearing member 6 and seals the gap between the inner ring 61 and the outer ring 62. The space sealed by these plurality of oil seals 14, 15, 16 constitutes a lubricant retention space 17 (see Figure 9). The lubricant retention space 17 includes the space between the inner ring 61 and the outer ring 62 of the bearing member 6. Furthermore, the lubricant-holding space 17 houses multiple external pins 23, external gears 3, eccentric bearings 5, support 8, first bearings 91 and second bearings 92, and the like.

[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 external 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] In the gear device 1 with the configuration described above, a rotational force is applied as input to the eccentric shaft 7, causing the eccentric shaft 7 to rotate around the rotation axis Ax1, and the external gear 3 oscillates (revolves) around the rotation axis Ax1. At this time, the external 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 external gear 3 and the internal gear 2 occurs between the two gears (internal gear 2 and external gear 3). Then, the rotation (rotational component) of the external gear 3, excluding the oscillating component (revolving component) of the external gear 3, is transmitted to the inner ring 61 of the bearing member 6 by a plurality of internal pins 4. As a result, a rotational output reduced at a relatively high reduction ratio according to the difference in the number of teeth of the two gears is obtained from the output shaft integrated with the inner ring 61.

[0073] By the way, 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 external 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 external gear 3 is "V2", the reduction ratio R1 is expressed by the following equation 1.

[0074] R1 = V2 / (V1 - V2) ... (Equation 1) In short, the smaller the difference in the number of teeth between the internal gear 2 and the external gear 3 (V1-V2), the larger the reduction ratio R1. For example, the number of teeth V1 of the internal gear 2 is "52", the number of teeth V2 of the external gear 3 is "51", and the difference in the number of teeth (V1-V2) is "1", so from equation 1 above, the reduction ratio R1 is "51". In this case, when viewed from the input side of the rotation axis Ax1, if the eccentric shaft 7 rotates clockwise one full turn (360 degrees) around the rotation axis Ax1, the inner ring 61 rotates counterclockwise around the rotation axis Ax1 by the amount of the tooth difference "1" (i.e., approximately 7.06 degrees).

[0075] According to the gear device 1 of this basic configuration, such a high reduction ratio R1 can be achieved with a single-stage gear combination (internal gear 2 and external gear 3).

[0076] Furthermore, the gear device 1 only needs to include at least an internal gear 2, an external gear 3, a plurality of internal pins 4, a bearing member 6, and a support 8, and may further include components such as spline bushings.

[0077] Incidentally, in gear devices 1 relating to this basic configuration, when the input rotation on the high-speed rotation side involves eccentric motion, if the weight balance of the high-speed rotating body is not maintained, it may lead to vibrations, etc. Therefore, weight balance is sometimes achieved using counterweights or the like. That is, since the rotating body consisting of at least one of the eccentric inner ring 51 and the member that rotates together with the eccentric inner ring 51 (eccentric shaft 7) undergoes high-speed eccentric motion, it is preferable to balance the weight of the rotating body with respect to the rotation axis Ax1. In this basic configuration, as shown in Figures 3 and 4, the weight balance of the rotating body with respect to the rotation axis Ax1 is achieved by providing a gap 75 in a part of the eccentric portion 72 of the eccentric shaft 7.

[0078] In short, in this basic configuration, instead of adding counterweights or the like, the weight is reduced by hollowing out a part of the rotating body (in this case, the eccentric shaft 7), thereby balancing the weight of the rotating body with respect to the rotating shaft Ax1. That is, the gear device 1 in this basic configuration is housed in an opening 33 formed in the external gear 3 and is equipped with an eccentric bearing 5 that causes the external gear 3 to oscillate. The eccentric bearing 5 has an eccentric outer ring 52 and an eccentric inner ring 51 positioned inside the eccentric outer ring 52. The rotating body, consisting of at least one of the eccentric inner ring 51 and a member that rotates with the eccentric inner ring 51, has a gap 75 in a part of the eccentric outer ring 52 on the center C1 side when viewed from the rotation shaft Ax1 of the eccentric inner ring 51. In this basic configuration, the eccentric shaft 7 is the "member that rotates with the eccentric inner ring 51" and corresponds to the "rotating body". Therefore, the gap 75 formed in the eccentric part 72 of the eccentric shaft 7 corresponds to the gap 75 of the rotating body. As shown in Figures 3 and 4, this gap 75 is located on the side of the center C1 when viewed from the rotation axis Ax1, and therefore acts to bring the weight balance of the eccentric shaft 7 closer to being uniform in the circumferential direction from the rotation axis Ax1.

[0079] More specifically, the gap 75 includes a recess formed on the inner surface of the through-hole 73 that penetrates the rotating body along the rotation axis Ax1 of the eccentric inner ring 51. In other words, in this basic configuration, since the rotating body is the eccentric shaft 7, the recess formed on the inner surface of the through-hole 73 that penetrates the eccentric shaft 7 along the rotation axis Ax1 functions as the gap 75. By utilizing the recess formed on the inner surface of the through-hole 73 as the gap 75 in this way, it becomes possible to balance the weight of the rotating body without changing its appearance.

[0080] (3.2) Rotation structure of the internal pin Next, the rotational structure of the internal pin 4 of the gear device 1 related to this basic configuration will be explained in more detail with reference to Figure 9. Figure 9 is an enlarged view of region Z1 in Figure 3.

[0081] First, as a premise, the multiple internal pins 4 are components that connect the external gear 3 and the inner ring 61 of the bearing member 6, as described above. Specifically, one end of the internal pin 4 in the longitudinal direction (the input side end of the rotating shaft Ax1 in this basic configuration) is inserted into the loose fitting hole 32 of the external gear 3, and the other end of the internal pin 4 in the longitudinal direction (the output side end of the rotating shaft Ax1 in this basic configuration) is inserted into the retaining hole 611 of the inner ring 61.

[0082] Here, the diameter of the inner pin 4 is slightly smaller than the diameter of the loose fitting hole 32, so a gap is maintained between the inner pin 4 and the inner circumferential surface 321 of the loose fitting hole 32, and the inner pin 4 is movable within the loose fitting hole 32, that is, it is movable relative to the center of the loose fitting hole 32. On the other hand, the diameter of the retaining hole 611 is greater than or equal to the diameter of the inner pin 4, but smaller than the diameter of the loose fitting hole 32. In this basic configuration, the diameter of the retaining hole 611 is approximately the same as the diameter of the inner pin 4, and slightly larger than the diameter of the inner pin 4. Therefore, the movement of the inner pin 4 within the retaining hole 611 is restricted, that is, relative movement with respect to the center of the retaining hole 611 is prohibited. Consequently, the inner pin 4 is held in a state in which it can revolve within the loose fitting hole 32 in the external gear 3, but is held in a state in which it cannot revolve within the retaining hole 611 relative to the inner ring 61. As a result, the oscillation component of the external gear 3, that is, the revolution component of the external gear 3, is absorbed by the loose fitting between the loose fitting hole 32 and the inner pin 4, and the rotation (rotation component) of the external gear 3, excluding the oscillation component (revolution component), is transmitted to the inner ring 61 by the multiple inner pins 4.

[0083] Incidentally, in this basic configuration, the diameter of the inner pin 4 is slightly larger than the retaining hole 611. As a result, when the inner pin 4 is inserted into the retaining hole 611, it is prohibited from revolving within the retaining hole 611, but it is able to rotate within the retaining hole 611. In other words, even when the inner pin 4 is inserted into the retaining hole 611, it is not press-fitted into the retaining hole 611, so it is able to rotate within the retaining hole 611. Thus, in the gear device 1 according to this basic configuration, each of the multiple inner pins 4 is held in the inner ring 61 in a state where it can rotate, so when the inner pin 4 revolves within the loose fitting hole 32, the inner pin 4 itself is able to rotate.

[0084] In short, in this basic configuration, the inner pin 4 is held in a state where it can both revolve and rotate within the loose fitting hole 32 relative to the external gear 3, and is held in a state where it can only rotate within the holding hole 611 relative to the inner ring 61. That is, each of the multiple inner pins 4 is able to rotate (revolve) around the rotation axis Ax1 while its own rotation is not constrained (it is able to rotate), and it is also able to revolve within the multiple loose fitting holes 32. Therefore, when the rotation (rotation component) of the external gear 3 is transmitted to the inner ring 61 by the multiple inner pins 4, the inner pins 4 can revolve and rotate within the loose fitting hole 32 while also being able to rotate within the holding hole 611. As a result, when the inner pin 4 revolves within the loose fitting hole 32, it is in a state where it can rotate, and therefore rolls against the inner circumferential surface 321 of the loose fitting hole 32. In other words, the inner pin 4 revolves within the loose fitting hole 32 by rolling on the inner circumferential surface 321 of the loose fitting hole 32, so that frictional resistance between the inner circumferential surface 321 of the loose fitting hole 32 and the inner pin 4 does not easily cause losses.

[0085] Thus, in the configuration relating to this basic configuration, since frictional resistance between the inner surface 321 of the loose fitting hole 32 and the inner pin 4 is unlikely to cause losses, it is possible to omit the inner roller. Therefore, in this basic configuration, each of the multiple inner pins 4 is configured to directly contact the inner surface 321 of the loose fitting hole 32. In other words, in this basic configuration, the inner pins 4 without the inner roller are inserted into the loose fitting hole 32, and the inner pins 4 directly contact the inner surface 321 of the loose fitting hole 32. As a result, the inner roller can be omitted and the diameter of the loose fitting hole 32 can be kept relatively small, which makes it possible to miniaturize the external gear 3 (especially reduce its diameter), and makes it easier to miniaturize the gear device 1 as a whole. If the dimensions of the external gear 3 are kept constant, compared to the first related technology described above, it is possible to increase the number of inner pins 4 to smooth the transmission of rotation, or to make the inner pins 4 thicker to improve their strength. Furthermore, the absence of internal rollers reduces the number of parts, leading to a lower cost for the gear unit 1.

[0086] Furthermore, in the gear device 1 according to this basic configuration, at least a portion of each of the multiple inner pins 4 is positioned at the same location as the bearing member 6 in the axial direction of the bearing member 6. In other words, as shown in Figure 9, in the direction parallel to the rotation axis Ax1, at least a portion of the inner pins 4 is positioned at the same location as the bearing member 6. To put it another way, at least a portion of the inner pins 4 is located between the end faces of the bearing member 6 in the direction parallel to the rotation axis Ax1. To put it another way, at least a portion of each of the multiple inner pins 4 is positioned inside the outer ring 62 of the bearing member 6. In this basic configuration, the output end of the inner pin 4 on the rotation axis Ax1 is in the same location as the bearing member 6 in the direction parallel to the rotation axis Ax1. In short, since the output end of the inner pin 4 on the rotation axis Ax1 is inserted into the retaining hole 611 formed in the inner ring 61 of the bearing member 6, at least that end is positioned at the same location as the bearing member 6 in the axial direction of the bearing member 6.

[0087] In this way, by positioning at least a portion of each of the multiple internal pins 4 at the same location as the bearing member 6 in the axial direction of the bearing member 6, the dimensions of the gear device 1 in the direction parallel to the rotation axis Ax1 can be kept small. In other words, compared to a configuration in which the bearing member 6 and the internal pins 4 are aligned (facing each other) in the axial direction of the bearing member 6, the gear device 1 according to this basic configuration can reduce the dimensions of the gear device 1 in the direction parallel to the rotation axis Ax1, and can contribute to further miniaturization (thinning) of the gear device 1.

[0088] Here, the opening on the output side of the rotating shaft Ax1 in the holding hole 611 is closed off by, for example, the output shaft integrated with the inner ring 61. As a result, the movement of the inner pin 4 toward the output side of the rotating shaft Ax1 (right side in Figure 9) is restricted by the output shaft integrated with the inner ring 61.

[0089] Furthermore, in this basic configuration, the following configuration is adopted to ensure that the inner pin 4 rotates smoothly relative to the inner ring 61. Specifically, a lubricant (lubricating oil) is interposed between the inner circumferential surface of the retaining hole 611 formed in the inner ring 61 and the inner pin 4, thereby ensuring the smooth rotation of the inner pin 4. In particular, in this basic configuration, there is a lubricant retaining space 17 into which lubricant is injected between the inner ring 61 and the outer ring 62, and the lubricant in the lubricant retaining space 17 is used to ensure the smooth rotation of the inner pin 4.

[0090] In this basic configuration, as shown in Figure 9, the inner ring 61 has multiple retaining holes 611 into which multiple inner pins 4 are inserted, and multiple connecting passages 64. The multiple connecting passages 64 connect the lubricant retaining space 17 between the inner ring 61 and the outer ring 62 to the multiple retaining holes 611. Specifically, the inner ring 61 has connecting passages 64 that extend radially from a part of the inner circumferential surface of the retaining hole 611 that corresponds to the rolling element 63. The connecting passage 64 is a hole that penetrates between the bottom surface of the recess (groove) that accommodates the rolling element 63 on the surface of the inner ring 61 facing the outer ring 62, and the inner circumferential surface of the retaining hole 611. In other words, the opening surface of the connecting passage 64 on the lubricant retaining space 17 side is positioned facing (opposing) the rolling element 63 of the bearing member 6. The lubricant retaining space 17 and the retaining hole 611 are spatially connected via such connecting passages 64.

[0091] According to the above configuration, the lubricant holding space 17 and the holding hole 611 are connected by the connecting passage 64, so that the lubricant in the lubricant holding space 17 is supplied to the holding hole 611 through the connecting passage 64. In other words, when the bearing member 6 operates and the rolling elements 63 rotate, the rolling elements 63 function as a pump, making it possible to send the lubricant in the lubricant holding space 17 to the holding hole 611 via the connecting passage 64. In particular, because the opening surface of the connecting passage 64 on the lubricant holding space 17 side is positioned facing (opposing) the rolling elements 63 of the bearing member 6, the rolling elements 63 act efficiently as a pump when they rotate. As a result, lubricant is interposed between the inner circumferential surface of the holding hole 611 and the inner pin 4, which facilitates the smooth rotation of the inner pin 4 relative to the inner ring 61.

[0092] (3.3) Support Next, the configuration of the support body 8 of the gear device 1 relating to this basic configuration will be explained in more detail with reference to Figure 10. Figure 10 is a cross-sectional view taken along line B1-B1 in Figure 3. However, in Figure 10, hatching is omitted for parts other than the support body 8, even in cross-section. Also, in Figure 10, only the internal gear 2 and the support body 8 are shown, and the illustration of other parts (internal pin 4, etc.) is omitted. Furthermore, in Figure 10, the illustration of the inner circumferential surface 221 of the gear body 22 is omitted.

[0093] First, as a premise, the support 8 is a component that supports multiple inner pins 4, as described above. In other words, the support 8 distributes the load on the multiple inner pins 4 when transmitting the rotation (rotational component) of the external gear 3 to the inner ring 61 by bundling the multiple inner pins 4 together. Specifically, it has multiple support holes 82 into which each of the multiple inner pins 4 is inserted. In this basic configuration, as an example, the diameter of the support holes 82 is equal to the diameter of the holding holes 611 formed in the inner ring 61. Therefore, the support 8 supports the multiple inner pins 4 in a state in which each of the multiple inner pins 4 is able to rotate. In other words, each of the multiple inner pins 4 is held in a state in which it can rotate with respect to either the inner ring 61 of the bearing member 6 or the support 8.

[0094] In this way, the support 8 positions the multiple inner pins 4 relative to the support 8 in both the circumferential and radial directions. That is, by being inserted into the support holes 82 of the support 8, the movement of the inner pins 4 in all directions within the plane perpendicular to the rotation axis Ax1 is restricted. Therefore, the inner pins 4 are positioned by the support 8 not only in the circumferential direction but also in the radial direction.

[0095] Here, the support 8 has an annular shape, with at least its outer circumferential surface 81 being a perfect circle in plan view. The support 8 is positioned by bringing its outer circumferential surface 81 into contact with a plurality of outer pins 23 of the internal gear 2. Since the plurality of outer pins 23 constitute the internal teeth 21 of the internal gear 2, in other words, the support 8 is positioned by bringing its outer circumferential surface 81 into contact with the internal teeth 21. Here, the diameter of the outer circumferential surface 81 of the support 8 is the same as the diameter of the virtual circle (tip circle) passing through the tip of the internal teeth 21 of the internal gear 2. Therefore, all of the plurality of outer pins 23 are in contact with the outer circumferential surface 81 of the support 8. Thus, when the support 8 is positioned by the plurality of outer pins 23, the center of the support 8 is positioned to coincide with the center (rotation axis Ax1) of the internal gear 2. This centers the support 8, and as a result, the plurality of internal pins 4 supported by the support 8 are also centered by the plurality of outer pins 23.

[0096] Furthermore, the multiple internal pins 4 rotate (revolve) around the rotation axis Ax1, transmitting the rotation (rotational component) of the external gear 3 to the inner ring 61. Therefore, the support body 8 that supports the multiple internal pins 4 rotates together with the multiple internal pins 4 and the inner ring 61 around the rotation axis Ax1. At this time, since the support body 8 is centered by the multiple external pins 23, the support body 8 rotates smoothly while its center is maintained on the rotation axis Ax1. Moreover, since the support body 8 rotates with its outer circumferential surface 81 in contact with the multiple external pins 23, each of the multiple external pins 23 rotates (rotates) in conjunction with the rotation of the support body 8. Thus, the support body 8, together with the internal gear 2, constitutes a needle bearing (needle roller bearing) and rotates smoothly.

[0097] In other words, the outer surface 81 of the support 8 rotates relative to the gear body 22 together with the multiple inner pins 4 while in contact with the multiple outer pins 23. Therefore, if we consider the gear body 22 of the internal gear 2 as the "outer ring" and the support 8 as the "inner ring," the multiple outer pins 23 interposed between them function as "rolling elements (rollers)." In this way, the support 8, together with the internal gear 2 (gear body 22 and multiple outer pins 23), constitutes a needle bearing, enabling smooth rotation.

[0098] Furthermore, since the support 8 sandwiches multiple outer pins 23 between itself and the gear body 22, the support 8 also functions as a "stopper" that suppresses the movement of the outer pins 23 away from the inner circumferential surface 221 of the gear body 22. In other words, the multiple outer pins 23 are sandwiched between the outer circumferential surface 81 of the support 8 and the inner circumferential surface 221 of the gear body 22, thereby suppressing the lifting of the gear body 22 away from the inner circumferential surface 221. In short, in this basic configuration, each of the multiple outer pins 23 is restricted from moving away from the gear body 22 by contacting the outer circumferential surface 81 of the support 8.

[0099] In this basic configuration, as shown in Figure 9, the support 8 is located on the opposite side of the bearing member 6 from the inner ring 61, with the external gear 3 in between. In other words, the support 8, the external gear 3, and the inner ring 61 are arranged in a direction parallel to the rotation axis Ax1. In this basic configuration, as an example, the support 8 is located on the input side of the rotation axis Ax1 when viewed from the external gear 3, and the inner ring 61 is located on the output side of the rotation axis Ax1 when viewed from the external gear 3. The support 8, together with the inner ring 61, supports both ends of the inner pin 4 in the longitudinal direction (parallel to the rotation axis Ax1), and the longitudinal center of the inner pin 4 is inserted into the loose fitting hole 32 of the external gear 3. In short, the gear device 1 according to this basic configuration has an outer ring 62 and an inner ring 61 arranged inside the outer ring 62, and is equipped with a bearing member 6 that supports the inner ring 61 so that it can rotate relative to the outer ring 62. The gear body 22 is fixed to the outer ring 62. Here, the external gear 3 is positioned between the support 8 and the inner ring 61 in the axial direction of the support 8.

[0100] In this configuration, the support 8 and inner ring 61 support both ends of the inner pin 4 in the longitudinal direction, making it difficult for the inner pin 4 to tilt. In particular, it becomes easier to withstand the bending force (bending moment load) applied to the rotation axis Ax1 by multiple inner pins 4. Furthermore, in this basic configuration, the support 8 is sandwiched between the external gear 3 and the case 10 in a direction parallel to the rotation axis Ax1. As a result, the movement of the support 8 toward the input side of the rotation axis Ax1 (left side in Figure 9) is restricted by the case 10. The movement of the inner pin 4, which protrudes from the support 8 through the support hole 82 of the support 8 toward the input side of the rotation axis Ax1 (left side in Figure 9), is also restricted by the case 10.

[0101] In this basic configuration, the support 8 and inner ring 61 also contact both ends of the multiple outer pins 23. That is, as shown in Figure 9, the support 8 contacts one end of the outer pin 23 in the longitudinal direction (parallel to the rotation axis Ax1) (the input end of the rotation axis Ax1). The inner ring 61 contacts the other end of the outer pin 23 in the longitudinal direction (parallel to the rotation axis Ax1) (the output end of the rotation axis Ax1). With this configuration, the support 8 and inner ring 61 are centered at both ends of the outer pin 23 in the longitudinal direction, so tilting of the inner pins 4 is less likely to occur. In particular, it becomes easier to receive bending forces (bending moment loads) on the rotation axis Ax1 applied to the multiple inner pins 4.

[0102] Furthermore, the multiple external pins 23 have a length greater than or equal to the thickness of the support 8. In other words, in the direction parallel to the rotation axis Ax1, the support 8 is contained within the range of the tooth traces of the internal teeth 21. As a result, the outer circumferential surface 81 of the support 8 contacts the multiple external pins 23 along its entire length in the direction of the tooth traces of the internal teeth 21 (the direction parallel to the rotation axis Ax1). Therefore, problems such as "uneven wear," where the outer circumferential surface 81 of the support 8 is partially worn, are less likely to occur.

[0103] Furthermore, in this basic configuration, the outer surface 81 of the support 8 has less surface roughness than an adjacent surface of the support 8. In other words, the surface roughness of the outer surface 81 is less than that of both end faces in the axial direction (thickness direction) of the support 8. In this disclosure, "surface roughness" refers to the degree of roughness of the surface of an object; the smaller the value, the less irregular the surface and the smoother it is. In this basic configuration, as an example, the surface roughness is assumed to be the arithmetic mean roughness (Ra). For example, by processing such as polishing, the surface roughness of the outer surface 81 is made smaller than that of other surfaces of the support 8. In this configuration, the rotation of the support 8 becomes smoother.

[0104] Furthermore, in this basic configuration, the hardness of the outer circumferential surface 81 of the support 8 is lower than that of the circumferential surfaces of the multiple outer pins 23, but higher than that of the inner circumferential surface 221 of the gear body 22. In this disclosure, "hardness" refers to the degree of hardness of an object. The hardness of a metal is expressed, for example, by the size of the indentation created when a steel ball is pressed with a certain pressure. Specifically, examples of metal hardness include Rockwell hardness (HRC), Brinell hardness (HB), Vickers hardness (HV), or Shore hardness (Hs). Means of increasing (hardening) the hardness of metal parts include, for example, alloying or heat treatment. In this basic configuration, as an example, the hardness of the outer circumferential surface 81 of the support 8 is increased by a treatment such as carburizing and quenching. In this configuration, wear particles are less likely to be generated even when the support 8 rotates, and smooth rotation of the support 8 can be easily maintained over a long period of time.

[0105] (4) Examples of application Next, we will explain examples of applications for the gear unit 1 and actuator 100 related to this basic configuration.

[0106] The gear unit 1 and actuator 100 related to this basic configuration are applicable to robots such as horizontal articulated robots, or so-called SCARA (Selective Compliance Assembly Robot Arm) type robots.

[0107] Furthermore, the application examples of the gear unit 1 and actuator 100 related to this basic configuration are not limited to horizontal articulated robots as described above, but may also include, for example, industrial robots other than horizontal articulated robots, or robots other than industrial robots. Examples of industrial robots other than horizontal articulated robots include vertical articulated robots or parallel link robots. Examples of robots other than industrial robots include household robots, nursing care robots, or medical robots.

[0108] (Basic configuration 2) <Overview> As shown in Figures 11 to 13, the gear device 1A relating to this basic configuration differs from the gear device 1 relating to basic configuration 1 mainly in the configuration for driving the external gear 3 and the external gear 3. Hereafter, components similar to those in basic configuration 1 will be given common reference numerals and their explanations will be omitted as appropriate. Figure 11 is a schematic cross-sectional view of the gear device 1A. In Figure 11, enlarged views of regions Z1 and Z2 are shown in callouts. Figures 12 and 13 are cross-sectional views taken along the line A1-A1 in Figure 11. However, hatching is omitted in Figures 12 and 13 even in cross-sections. Furthermore, the inner circumferential surface 221 of the gear body 22 is not shown in Figures 12 and 13.

[0109] The internal gear 2 has the same configuration as the basic configuration 1, and in this basic configuration as well, 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. On the other hand, in this basic configuration, the external gear 3 has external teeth 31 and is an annular member arranged inside the internal gear 2. Furthermore, a major difference between the gear device 1A in this basic configuration and the basic configuration 1 is that it is equipped with a deflection generator 40 arranged inside the external gear 3 and causes deflection in the external gear 3. The deflection generator 40 has a non-circular cam 41 that is rotationally driven around the rotation axis Ax1, and a bearing 42 mounted on the outside of the cam 41. The gear unit 1A deforms the external gear 3 as the cam 41 rotates, engaging a portion of the external teeth 31 with a portion of the internal teeth 21, and causing the external gear 3 to rotate relative to the internal gear 2 in accordance with the difference in the number of teeth between the external gear 3 and the internal gear 2.

[0110] In this disclosure, "non-circular shape" means a shape that is not a perfect circle, and includes, for example, elliptical and oblong shapes. In this basic configuration, as an example, the non-circular cam 41 of the deflection generator 40 is "oblong." In other words, in this basic configuration, the deflection generator 40 deflects the external gear 3 in an oblong shape. In this disclosure, "oblong shape" means a shape formed by connecting two semicircles with two straight lines, and refers to a so-called track shape (oval shape). More specifically, an "oblong shape" is a shape formed by connecting two semicircles of equal radius with two common external tangents.

[0111] In other words, in this basic configuration, the gear body 22 of the internal gear 2 is rigid, while the external gear 3 is flexible. In this disclosure, "rigidity" refers to the property of an object to resist deformation when an external force is applied to it. In other words, a rigid object is difficult to deform even when an external force is applied. Also, in this disclosure, "flexibility" refers to the property of an object to elastically deform (bend) when an external force is applied to it. In other words, a flexible object is easily elastically deformed when an external force is applied. Therefore, "rigidity" and "flexibility" have opposite meanings.

[0112] In particular, in this disclosure, the terms "rigidity" of the gear body 22 of the internal gear 2 and "flexibility" of the external gear 3 are used in a relative sense. That is, the "rigidity" of the gear body 22 means that the gear body 22 has high rigidity, at least relatively compared to the external gear 3, meaning that it is less likely to deform even when an external force is applied. Similarly, the "flexibility" of the external gear 3 means that the external gear 3 has high flexibility, at least relatively compared to the gear body 22, meaning that it is more easily elastically deformed when an external force is applied.

[0113] In the gear device 1A of this basic configuration, the deflection generator 40 deflects the external gear 3 into a non-circular shape (for example, an oval shape), thereby partially engaging the external teeth 31 of the external gear 3 with the internal teeth 21 (external pin 23) of the internal gear 2. In this state, when the cam 41 of the deflection generator 40 rotates, 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 external gear 3 and the internal gear 2 occurs between the two gears (internal gear 2 and external gear 3). In short, the external gear 3 does not rotate eccentrically (oscillate) around an eccentric axis offset from the rotation axis Ax1 as in the basic configuration 1. Instead, the long axis direction D1 (see Figure 12), which is deformed into a non-circular shape (for example, an oval shape) by the deflection generator 40, rotates around the rotation axis Ax1, causing the meshing position between the internal teeth 21 and the external teeth 31 to move in the circumferential direction of the internal gear 2. If the gear body 22 of the internal gear 2 is fixed, the external gear 3 will rotate in conjunction with the relative rotation of the two gears. As a result, the external gear 3 will produce a rotational output that is reduced at a relatively high reduction ratio according to the difference in the number of teeth of the two gears.

[0114] In the gear device 1A relating to this basic configuration, as shown in Figure 13, the internal teeth 21 and external teeth 31 mesh in a simultaneous meshing range Ra1 that occupies more than 180 degrees in the circumferential direction of the internal gear 2. The "simultaneous meshing range" as used in this disclosure means the range in which the internal teeth 21 and external teeth 31 mesh simultaneously at any given timing, and the entire simultaneous meshing range is the meshing position of the internal teeth 21 and external teeth 31. That is, in the gear device 1A, the external teeth 31 of the external gear 3 partially mesh with the internal teeth 21 (external pin 23) of the internal gear 2, and the internal teeth 21 and external teeth 31 mesh only in the simultaneous meshing range Ra1 in the circumferential direction of the internal gear 2, and do not mesh outside of the simultaneous meshing range Ra1. The simultaneous meshing range Ra1, which is the meshing position of the internal teeth 21 and external teeth 31, moves in the circumferential direction of the internal gear 2 as the cam 41 rotates. In this basic configuration, the simultaneous meshing range Ra1 occupies more than 180 degrees in the circumferential direction of the internal gear 2, that is, more than half. In other words, the non-meshing range Ra2, in which the internal teeth 21 and external teeth 31 do not mesh, is less than 180 degrees in the circumferential direction of the internal gear 2, that is, less than half.

[0115] In short, in the gear unit 1A according to this basic configuration, the external gear 3 is constrained from the internal gear 2 in the simultaneous meshing range Ra1 of more than half of the circumferential direction of the internal gear 2, thereby suppressing the movement (deformation) of the external gear 3 away from the deflection generator 40. Therefore, the meshing between the internal teeth 21 and the external teeth 31 can be stabilized over a wide range of more than half of the circumferential direction of the internal gear 2. As a result, the gear unit 1A is less prone to malfunctions such as ratcheting, where the meshing between the internal gear 2 and the external gear 3 momentarily shifts due to vibration during operation or excessive torque during operation. In other words, the gear unit 1A according to this basic configuration has the advantage of realizing a structure that is low vibration and has improved shock resistance.

[0116] Furthermore, in this basic configuration, as described above, the external gear 3 does not rotate eccentrically (oscillate) around an eccentric axis offset from the rotation axis Ax1, but rather its long axis D1, which is deformed into a non-circular shape by the deflection generator 40, rotates around the rotation axis Ax1. For this reason, in the gear device 1A relating to this basic configuration, the eccentric axis 7 for causing the external gear 3 to move eccentrically is omitted, and instead of the eccentric axis 7, the cam 41 of the deflection generator 40 is provided as an input means.

[0117] Furthermore, since the external gear 3 only rotates (spins) around the (output side) rotation axis Ax1 and does not generate an oscillating component (revolution component) of the external gear 3, the rotation (spinning component) of the external gear 3 can be directly extracted from the external gear 3 without using multiple internal pins 4. Therefore, in the gear device 1A according to this basic configuration, multiple internal pins 4 and the support body 8 that supports the multiple internal pins 4 are also omitted. Naturally, the multiple loose fitting holes 32 into which the multiple internal pins 4 are inserted in the external gear 3 are also omitted.

[0118] <Configuration Details> The detailed configuration of the gear unit 1A related to this basic configuration will be explained below with reference to Figures 11 to 13.

[0119] As described above, the gear unit 1A in this basic configuration includes an internal gear 2, an external gear 3, and a deflection generator 40. In this basic configuration, the materials of the internal gear 2, external gear 3, and deflection generator 40, which are components of the gear unit 1A, are metals such as stainless steel, cast iron, structural carbon steel, chromium-molybdenum steel, phosphor bronze, or aluminum bronze. The term "metal" here includes metals that have undergone surface treatment such as nitriding.

[0120] Furthermore, the gear unit 1A in this basic configuration uses a cylindrical external gear 3. The deflection generator 40 is combined with the external gear 3 so as to be housed inside the cylindrical external gear 3.

[0121] In this basic configuration, as an example, the gear unit 1A includes a first carrier 18 (see Figure 11) and a second carrier 19 (see Figure 11). The first carrier 18 is fixed to the gear body 22 of the internal gear 2, and the second carrier 19 is fixed to the external gear 3. Furthermore, the first carrier 18 is fixed to the inner ring 61 of the bearing member 6, and the second carrier 19 is fixed to the outer ring 62 of the bearing member 6. In this basic configuration, the first carrier 18 is integrated with the inner ring 61, and the second carrier 19 is integrated with the outer ring 62. As a result, the second carrier 19 (and the outer ring 62), which is a movable member, rotates relative to the first carrier 18 (and the inner ring 61), which is a fixed member, as the internal gear 2 and the external gear 3 rotate relative to each other. The first carrier 18 has a mounting hole 181 for attaching a mating member, and the second carrier 19 has a mounting hole 191 for attaching a mating member.

[0122] Furthermore, in this basic configuration, when the gear unit 1A is used as the actuator 100, a rotational force is applied as input to the deflection generator 40, and a rotational force is extracted as output from the second carrier 19 fixed to the external gear 3. In other words, the gear unit 1A operates using the rotation of the deflection generator 40 as the input rotation and the rotation of the external gear 3 (second carrier 19) as the output rotation. As a result, the gear unit 1A obtains an output rotation that is reduced at a relatively high reduction ratio relative to the input rotation.

[0123] Furthermore, in the gear unit 1A relating to this basic configuration, the input rotation axis Ax1 and the output rotation axis Ax1 are on the same straight line. In other words, the rotation axis Ax1 of the deflection generator 40, which is the input side, and the rotation axis Ax1 of the external gear 3, which is the output side, are coaxial. Here, the input rotation axis Ax1 is the rotation center of the deflection generator 40 to which the input rotation is applied, and the output rotation axis Ax1 is the rotation center of the external gear 3 that generates the output rotation. In other words, in the gear unit 1A, an output rotation reduced at a relatively high reduction ratio relative to the input rotation is obtained on the same axis.

[0124] The internal gear 2, like the basic configuration 1, has an annular (circular) gear body 22 and a plurality of external pins 23. As described above, the gear body 22 of the internal gear 2 is fixed to the first carrier 18 (and inner ring 61). For this reason, the gear body 22 has a plurality of fixing holes 222 (see Figure 12) for fixing.

[0125] The external gear 3 is a flexible, annular component having external teeth 31. In this basic configuration, the external gear 3 is a cylindrical component formed from a relatively thin-walled metallic elastic body (metal plate). In other words, the external gear 3 is flexible because of its relatively small thickness (thinness). The external gear 3 has a cylindrical body portion 34 and a flange portion 35. The body portion 34 has a cylindrical shape such that at least its inner circumferential surface 301 is a perfect circle in plan view when the external gear 3 is not undergoing elastic deformation. The central axis of the body portion 34 coincides with the rotation axis Ax1. The flange portion 35 is continuous with one open end of the body portion 34 and extends radially outward from the body portion 34, thus having an annular shape that is a perfect circle in plan view.

[0126] As described above, the external gear 3 is fixed to the second carrier 19 (and outer ring 62). Therefore, the flange portion 35 of the external gear 3 has multiple fixing holes 351 (see Figure 11) for fixing. The area around the fixing holes 351 in the flange portion 35 is thicker than other parts of the flange portion 35. Furthermore, in the main body portion 34, an opening surface 36 is formed on the end face opposite to the flange portion 35 in the direction of the rotation axis Ax1. In this basic configuration, the main body portion 34 and the flange portion 35 are integrally formed from a single metal member, thereby realizing a seamless external gear 3.

[0127] Here, the deflection generator 40 is fitted to the external gear 3 so as to be fitted inside the main body 34. As a result, the external gear 3 receives an external force from the deflection generator 40 in the radial direction (direction perpendicular to the rotation axis Ax1) from the inside to the outside, causing it to elastically deform in a non-circular shape. In this basic configuration, when the deflection generator 40 is combined with the external gear 3, the main body 34 of the external gear 3 elastically deforms into an oval shape. In other words, a state in which elastic deformation does not occur in the external gear 3 means that the deflection generator 40 is not combined with the external gear 3. Conversely, a state in which elastic deformation occurs in the external gear 3 means that the deflection generator 40 is combined with the external gear 3.

[0128] More specifically, the deflection generator 40 is fitted into the end of the main body 34 of the external gear 3 on the side of the opening surface 36 in the direction of the rotation axis Ax1. Therefore, when elastic deformation occurs in the external gear 3, the external gear 3 deforms more at the end on the side of the opening surface 36 in the direction of the rotation axis Ax1 compared to the end on the side of the flange portion 35, and takes on a shape closer to an oval. Due to this difference in the amount of deformation in the direction of the rotation axis Ax1, when elastic deformation occurs in the external gear 3, the inner circumferential surface of the main body 34 of the external gear 3 includes a tapered surface that is inclined with respect to the rotation axis Ax1.

[0129] Furthermore, external teeth 31 are formed along the circumferential direction of the main body portion 34 at least on the end of the outer circumferential surface of the main body portion 34 opposite to the flange portion 35 (the input side of the rotation axis Ax1). In other words, the external teeth 31 are provided at least on the end of the main body portion 34 of the external gear 3 on the side of the opening surface 36 in the direction of the rotation axis Ax1. 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 main body portion 34. That is, the pitch circle of the external teeth 31 is a perfect circle in plan view when no elastic deformation occurs in the external gear 3. The external teeth 31 are formed only within a certain width range from the edge of the main body portion 34 on the side of the opening surface 36. Specifically, of the main body portion 34, external teeth 31 are formed on the outer circumferential surface of at least the portion (the end on the side of the opening surface 36) into which the deflection generator 40 (and its bearing 42) is fitted in the direction of the rotation axis Ax1. The tooth structures of all external teeth 31 are parallel to the axis of rotation Ax1.

[0130] In short, in the gear device 1A relating to this basic configuration, the tooth traces of both the internal teeth 21 of the internal gear 2 and the external teeth 31 of the external gear 3 are parallel to the rotation axis Ax1. Therefore, in this basic configuration, the "tooth trace direction" is the direction parallel to the rotation axis Ax1. Furthermore, since the dimension in the tooth trace direction of the internal teeth 21 is the tooth width of the internal teeth 21, and similarly, the dimension in the tooth trace direction of the external teeth 31 is the tooth width of the external teeth 31, the tooth trace direction is synonymous with the tooth width direction.

[0131] The external gear 3, configured in this way, is positioned inside the internal gear 2. Here, the external gear 3 is combined with the internal gear 2 such that only the end of the main body 34 opposite to the flange portion 35 is inserted inside the internal gear 2. In other words, of the main body 34, the portion of the external gear 3 where the deflection generator 40 is fitted (the end on the opening surface 36 side) is inserted inside the internal gear 2 in the direction of the rotation axis Ax1. Here, external teeth 31 are formed on the outer surface of the external gear 3, and internal teeth 21 (multiple external pins 23) are formed on the inner surface of the internal gear 2. Therefore, when the external gear 3 is positioned inside the internal gear 2, the external teeth 31 and the internal teeth 21 face each other.

[0132] Here, the number of teeth of the internal teeth 21 in the internal gear 2 is 2N (where N is a positive integer) more than the number of teeth of the external teeth 31 in the external gear 3. In this basic configuration, as an example, if N is "1", the number of teeth (external teeth 31) of the external gear 3 (58) is "2" fewer than the number of teeth (internal teeth 21) of the internal gear 2 (60). This difference in the number of teeth between the external gear 3 and the internal gear 2 defines the reduction ratio of the output rotation to the input rotation in the gear device 1A.

[0133] In this basic configuration, as an example, the dimension (tooth width) of the external tooth 31 in the tooth trace direction is smaller than the dimension (tooth width) of the internal tooth 21 (external pin 23) in the tooth trace direction. Therefore, in the direction parallel to the axis of rotation Ax1, the external tooth 31 will be contained within the range of the tooth trace of the internal tooth 21. In other words, the internal tooth 21 protrudes from the external tooth 31 in at least one direction in the tooth trace direction. In this basic configuration, the internal tooth 21 protrudes from the external tooth 31 in both directions in the tooth trace direction.

[0134] Here, in a state where no elastic deformation occurs in the external gear 3 (a state where the deflection generator 40 is not attached to the external gear 3), the pitch circle of the circular external teeth 31 is set to be slightly smaller than the pitch circle of the circular internal teeth 21. In other words, when no elastic deformation occurs in the external gear 3, the external teeth 31 and the internal teeth 21 face each other with a gap in between, and do not mesh with each other.

[0135] On the other hand, when the external gear 3 undergoes elastic deformation (when the deflection generator 40 is attached to the external gear 3), the main body 34 bends into an oval shape (non-circular shape), causing the external teeth 31 of the external gear 3 to partially mesh with the internal teeth 21 of the internal gear 2. In other words, as shown in Figure 12, the elastic deformation of the main body 34 of the external gear 3 (at least the end on the side of the opening surface 36) causes the external teeth 31 located at both ends of the oval-shaped long axis D1 to mesh with the internal teeth 21. In contrast, the external teeth 31 located at both ends of the oval-shaped short axis D2 do not mesh with the internal teeth 21.

[0136] In other words, the major axis of the pitch circle of the oval-shaped external gear 31 coincides with the diameter of the pitch circle of the circular internal gear 21, and the minor axis of the pitch circle of the oval-shaped external gear 31 is smaller than the diameter of the pitch circle of the circular internal gear 21. In this way, when the external gear 3 undergoes elastic deformation, some of the teeth of the multiple teeth constituting the external gear 31 mesh with some of the teeth of the multiple teeth constituting the internal gear 21 (external pins 23). As a result, the gear device 1A makes it possible to mesh some of the external teeth 31 with some of the internal teeth 21.

[0137] The deflection generator 40 is a component that causes deflection in the external gear 3, thereby generating wave motion in the external teeth 31 of the external gear 3. In this basic configuration, the deflection generator 40 is a component whose outer circumference is non-circular, specifically oval, when viewed from above.

[0138] The deflection generator 40 includes a non-circular (in this case, oval) cam 41 and a bearing 42 mounted on the outer circumference of the cam 41. In other words, the cam 41 is fitted into the bearing 42 so that it fits inside the inner ring 422 of the bearing 42. As a result, the bearing 42 receives an external force from the cam 41 in the radial direction (direction perpendicular to the rotation axis Ax1) from the inside to the outside of the inner ring 422, causing it to elastically deform in a non-circular shape. In other words, a state in which no elastic deformation occurs in the bearing 42 means that the cam 41 is not assembled to the bearing 42. Conversely, a state in which elastic deformation occurs in the bearing 42 means that the cam 41 is assembled to the bearing 42.

[0139] The cam 41 is a non-circular (in this case, oval) component that is rotationally driven around the input rotation axis Ax1. The cam 41 has a cylindrical portion 411 (see Figure 11) and a non-circular portion 412 (see Figure 11), and at least the outer surface of the non-circular portion 412 is non-circular in plan view. The non-circular portion 412 has a predetermined thickness in the direction of the rotation axis Ax1. As a result, the non-circular portion 412 has a rigidity similar to that of the internal gear 2. However, the thickness of the non-circular portion 412 is smaller (thinner) than that of the internal gear 2. In this basic configuration, as described above, the rotation of the deflection generator 40 is used as the input rotation. Therefore, the drive source 101 of the actuator 100 is attached to the deflection generator 40. A cam hole 413 for attaching the drive source 101 is formed in the cylindrical portion 411 of the cam 41 of the deflection generator 40.

[0140] The bearing 42 has an outer ring 421, an inner ring 422, and a plurality of rolling elements 423. In this basic configuration, as an example, the bearing 42 is a deep groove ball bearing using spherical balls as the rolling elements 423.

[0141] Both the outer ring 421 and the inner ring 422 are annular components. Both the outer ring 421 and the inner ring 422 are annular components formed from relatively thin-walled metallic elastic material (metal plate). In other words, each of the outer ring 421 and the inner ring 422 is flexible due to its relatively small thickness (thinness). In this basic configuration, both the outer ring 421 and the inner ring 422 have annular shapes that are perfectly round in plan view when the bearing 42 is not elastically deformed (when the cam 41 is not assembled to the bearing 42). The inner ring 422 is slightly smaller than the outer ring 421 and is positioned inside the outer ring 421. Here, since the inner diameter of the outer ring 421 is larger than the outer diameter of the inner ring 422, a gap is created between the inner circumferential surface 425 of the outer ring 421 and the outer circumferential surface of the inner ring 422.

[0142] Multiple rolling elements 423 are arranged in the gap between the outer ring 421 and the inner ring 422. The multiple rolling elements 423 are arranged in a line along the circumference of the outer ring 421. All of the multiple rolling elements 423 are metal balls of the same shape and are provided at equal pitches over the entire circumference of the outer ring 421. The bearing 42 further has a cage 424, and the multiple rolling elements 423 are held between the outer ring 421 and the inner ring 422 by the cage 424.

[0143] With this configuration of the bearing 42, when the cam 41 is assembled to the bearing 42, the inner ring 422 of the bearing 42 is fixed to the cam 41, and the inner ring 422 elastically deforms into an oval shape that follows the outer circumference shape of the non-circular portion 412 of the cam 41. At this time, the outer ring 421 of the bearing 42 is pressed by the inner ring 422 via the multiple rolling elements 423 and elastically deforms into an oval shape. Therefore, both the outer ring 421 and the inner ring 422 of the bearing 42 elastically deform into an oval shape. In this state where elastic deformation occurs in the bearing 42 (with the cam 41 assembled to the bearing 42), the outer ring 421 and the inner ring 422 have similar oval shapes.

[0144] Even when the bearing 42 is elastically deformed, the gap between the outer ring 421 and the inner ring 422 is kept approximately constant around the entire circumference of the outer ring 421 because of the multiple rolling elements 423 interposed between them. In this state, the multiple rolling elements 423 between the outer ring 421 and the inner ring 422 roll, allowing the outer ring 421 to rotate relative to the inner ring 422. Therefore, when the cam 41 rotates around the rotation axis Ax1 while the bearing 42 is elastically deformed, the rotation of the cam 41 is not transmitted to the outer ring 421, but the elastic deformation of the inner ring 422 is transmitted to the outer ring 421 via the multiple rolling elements 423. In other words, in the deflection generator 40, when the cam 41 rotates around the rotation axis Ax1, the outer ring 421 elastically deforms so that the long axis direction D1 of the oval shape formed by the outer ring 421 rotates around the rotation axis Ax1. Therefore, the overall shape of the deflection generator 40, which is oval-shaped when viewed from one side of the rotation axis Ax1, changes as the cam 41 rotates, such that its major axis (major axis direction D1) rotates around the rotation axis Ax1.

[0145] The deflection generator 40, configured in this way, is positioned inside the external gear 3. Here, the external gear 3 is assembled with the deflection generator 40 such that only the end of the main body 34 opposite to the flange portion 35 (the side with the opening surface 36) is fitted into the deflection generator 40. At this time, the bearing 42 of the deflection generator 40 is positioned between the outer circumferential surface of the non-circular portion 412 of the cam 41 and the inner circumferential surface of the main body 34 of the external gear 3. Here, the outer diameter of the outer ring 421 when no elastic deformation occurs in the bearing 42 (when the cam 41 is not assembled to the bearing 42) is the same as the inner diameter of the external gear 3 (main body 34) when no elastic deformation occurs. Therefore, the outer circumferential surface of the outer ring 421 in the deflection generator 40 contacts the inner circumferential surface of the external gear 3 over the entire circumference of the bearing 42. Therefore, when elastic deformation occurs in the external gear 3 (when the deflection generator 40 is combined with the external gear 3), the main body 34 will bend into an oval shape (non-circular shape). In this state, the external gear 3 is fixed to the outer ring 421 of the bearing 42.

[0146] However, since the external gear 3 and the deflection generator 40 are only fitted together, the external gear 3 and the outer ring 421 of the bearing 42 are not completely fixed. Therefore, a small gap will be created between the external gear 3 and the outer ring 421 fitted inside the external gear 3. More precisely, since the outer surface of the outer ring 421 is slightly smaller in diameter than the inner surface of the external gear 3, the gap between the outer ring 421 and the external gear 3 will not be completely filled, and at least a partial gap will remain.

[0147] In this disclosure, "gap" refers to the space that can occur between the opposing surfaces of two objects, and a gap can occur between the two objects even if they are not separated. In other words, even if two objects are in contact, a small gap can still occur between them. Between the external gear 3 and the outer ring 421 fitted inside the external gear 3, a gap occurs between the outer circumferential surface of the outer ring 421 and the inner circumferential surface of the external gear 3, which are opposite each other. However, basically, the outer circumferential surface of the outer ring 421 and the inner circumferential surface of the external gear 3 are in contact, so a large gap does not occur between them. Therefore, the gap between the outer ring 421 and the external gear 3 is a small gap that may occur partially between the outer circumferential surface of the outer ring 421 and the inner circumferential surface of the external gear 3. As an example, a microscopic gap occurs between the outer circumferential surface of the outer ring 421 and the inner circumferential surface of the external gear 3, to the extent that lubricant can penetrate.

[0148] In the gear device 1A with the above configuration, as shown in Figure 12, the external gear 3 bends into an oval shape (non-circular shape), causing the external teeth 31 of the external gear 3 to partially mesh with the internal teeth 21 of the internal gear 2. In other words, as the external gear 3 (its main body 34) elastically deforms into an oval shape, the two external teeth 31 corresponding to both ends of the oval-shaped longitudinal axis D1 mesh with the internal teeth 21. When the cam 41 rotates around the rotation axis Ax1, the rotation of the cam 41 is not transmitted to the outer ring 421 and the external gear 3, but the elastic deformation of the inner ring 422 is transmitted to the outer ring 421 and the external gear 3 via the multiple rolling elements 423. Therefore, the outer circumference shape of the oval-shaped external gear 3, as viewed from one side of the rotation axis Ax1, changes with the rotation of the cam 41 so that its major axis (longitudinal axis D1) rotates around the rotation axis Ax1.

[0149] As a result, wave motion occurs in the external teeth 31 formed on the outer surface of the external gear 3. The wave motion of the external teeth 31 causes the meshing position between the internal teeth 21 and the external teeth 31 to move in the circumferential direction of the internal gear 2, and relative rotation occurs between the external gear 3 and the internal gear 2. In other words, since the external teeth 31 mesh with the internal teeth 21 at both ends of the long axis D1 of the oval shape formed by the external gear 3 (the main body portion 34), the meshing position between the internal teeth 21 and the external teeth 31 moves as this long axis of the oval shape rotates around the rotation axis Ax1. In this way, the gear device 1A according to this basic configuration deforms the external gear 3 in accordance with the rotation of the deflection generator 40 around the rotation axis Ax1, meshing a part of the external teeth 31 with a part of the internal teeth 21, and rotating the external gear 3 according to the difference in the number of teeth between it and the internal gear 2.

[0150] By the way, in gear unit 1A, as described above, the difference in the number of teeth between the external gear 3 and the internal gear 2 determines the reduction ratio of the output rotation to the input rotation in gear unit 1A. In other words, if the number of teeth of the internal gear 2 is "V1" and the number of teeth of the external gear 3 is "V2", the reduction ratio R1 is expressed by the following equation 1.

[0151] R1 = V2 / (V1 - V2) ... (Equation 1) In short, the smaller the difference in the number of teeth between the internal gear 2 and the external gear 3 (V1-V2), the larger the reduction ratio R1. For example, if the number of teeth V1 of the internal gear 2 is "60", the number of teeth V2 of the external gear 3 is "58", and the difference in the number of teeth (V1-V2) is "2", then from equation 1 above, the reduction ratio R1 is "29". In this case, when viewed from the input side of the rotation axis Ax1, if the cam 41 rotates clockwise one full turn (360 degrees) around the rotation axis Ax1, the external gear 3 rotates counterclockwise by the amount of the difference in the number of teeth "2" (i.e., 12.9 degrees) around the rotation axis Ax1.

[0152] According to the gear device 1A of this basic configuration, such a high reduction ratio R1 can be achieved with a single-stage gear combination (internal gear 2 and external gear 3).

[0153] Incidentally, as described above, the gear device 1A relating to this basic configuration is configured such that the simultaneous meshing range Ra1 in which the internal teeth 21 and external teeth 31 mesh occupies 180 degrees or more in the circumferential direction of the internal gear 2. In other words, as shown in Figure 13, the simultaneous meshing range Ra1 occupies 180 degrees or more in the circumferential direction of the internal gear 2, that is, more than half, while the non-meshing range Ra2 in which the internal teeth 21 and external teeth 31 do not mesh is limited to less than 180 degrees in the circumferential direction of the internal gear 2, that is, less than half.

[0154] More specifically, the simultaneous meshing range Ra1 occupies an area of ​​180 degrees or more and 300 degrees or less in the circumferential direction of the internal gear 2. In other words, the non-meshing range Ra2 occupies an area of ​​60 degrees or more and 180 degrees or less in the circumferential direction of the internal gear 2. The upper limit of the range occupied by the simultaneous meshing range Ra1 in the circumferential direction of the internal gear 2 is not limited to 300 degrees, but may be greater than 300 degrees, or may be 190 degrees, 200 degrees, 220 degrees, 240 degrees, 260 degrees, or 280 degrees, etc.

[0155] Furthermore, in this basic configuration, the simultaneous meshing range Ra1 is provided in two locations in the circumferential direction of the internal gear 2. In other words, as shown in Figure 13, the internal teeth 21 and external teeth 31 mesh in the simultaneous meshing range Ra1 provided in two locations in the circumferential direction of the internal gear 2. Therefore, the non-meshing range Ra2 is similarly provided in two locations in the circumferential direction of the internal gear 2.

[0156] Furthermore, in this basic configuration, the cam 41 has an oval shape formed by connecting two semicircles with two straight lines. Therefore, even in the external gear 3 which is elastically deformed by the cam 41, (at least the end on the opening surface 36 side) is elastically deformed into an oval shape. Consequently, the external teeth 31 located at both ends of the major axis direction D1 of the oval shape mesh with the internal teeth 21, and the external teeth 31 mesh with the internal teeth 21 in two simultaneous meshing ranges Ra1 in the circumferential direction of the internal gear 2.

[0157] Furthermore, since the simultaneous meshing range Ra1 occupies more than 180 degrees in the circumferential direction of the internal gear 2, not only the external teeth 31 located at both ends of the oval-shaped major axis direction D1, but also a portion of the external teeth 31 located on the oval-shaped minor axis direction D2 side will mesh with the internal teeth 21. In short, when the internal gear 2 is divided circumferentially into four equal regions centered on the oval-shaped major axis direction D1 and minor axis direction D2, at least a portion of the two regions located on both sides of the minor axis direction D2 will also mesh with the external teeth 31 and internal teeth 21 as part of the simultaneous meshing range Ra1.

[0158] Therefore, in the simultaneous meshing range Ra1 of more than half of the circumferential direction of the internal gear 2, the external gear 3 is constrained from the internal gear 2, and the movement (deformation) of the external gear 3 away from the deflection generator 40 is suppressed. In other words, even the external teeth 31 located on the oval-shaped short axis direction D2 side are constrained from the internal gear 2 to at least a portion thereof, and their movement away from the deflection generator 40 is restricted. As a result, the meshing between the internal teeth 21 and the external teeth 31 can be stabilized over a wide range of more than half of the circumferential direction of the internal gear 2, and the gear device 1A is less prone to malfunctions such as ratcheting, where the meshing between the internal gear 2 and the external gear 3 momentarily shifts due to vibration during operation or excessive torque during operation.

[0159] In this basic configuration, as an example, the simultaneous meshing range Ra1 of the internal gear 2 is on both sides of the oval-shaped major axis D1, within a range of 150 degrees centered on the major axis D1. Therefore, the simultaneous meshing range Ra1 over the entire circumferential direction of the internal gear 2 is 300 degrees. In contrast, the non-meshing range Ra2 of the internal gear 2 is on both sides of the oval-shaped minor axis D2, within a range of 30 degrees centered on the minor axis D2. Therefore, the non-meshing range Ra2 over the entire circumferential direction of the internal gear 2 is 60 degrees.

[0160] As described above, in order to make the simultaneous meshing range Ra1 of the circumferential range of the internal gear 2 more than 180 degrees, it is necessary to keep the deformation of the external gear 3 relatively small and to keep the difference between the pitch circle of the internal teeth 21 of the internal gear 2, which is perfectly round, and the pitch circle of the external teeth 31 of the external gear 3, which is oval-shaped, to a minimum. For this reason, the tooth profile of the external teeth 31 of the external gear 3 is not based on an approximate tooth profile, but rather on a tooth profile that can achieve meshing that satisfies the meshing conditions of gears that transmit rotation at a constant velocity ratio in kinematics. Specifically, the external teeth 31 have a trochoidal tooth profile. The difference in the number of teeth of the external teeth 31 compared to the internal teeth 21 is two teeth.

[0161] In other words, the gear unit 1A in this basic configuration is not a "wave drive gear unit" in which the external gear 3 meshes with the internal gear 2 by elastic deformation, but is based on an internal planetary gear unit that achieves a large number of teeth simultaneously meshing between the internal gear 2 and the external gear 3 without elastic deformation, thereby ensuring a large number of meshings that satisfy the kinematic meshing conditions of the gears. As a result, the gear unit 1A can distribute the load, and by keeping the amount of deformation of the external gear 3 small, stress concentration on the external gear 3 is less likely to occur. Consequently, damage to the external gear 3 during elastic deformation is less likely to occur, and the durability of the gear unit 1A is improved.

[0162] <External gear tooth profile design> The tooth profile design of the external gear 3 used in the gear unit 1A of this basic configuration will be explained with reference to Figures 14A to 23. Figures 14A to 23 are conceptual diagrams for explaining the procedure for designing the tooth profile of the external gear 3, and do not represent the configuration (including the number of teeth, etc.) of the gear unit 1A of this basic configuration.

[0163] First, as shown in Figure 14A, a node S1 corresponding to the internal gear 2 and a node S2 corresponding to the external gear 3 are set. The center of node S2 is eccentric by an eccentricity e1 relative to the center of node S1. The inner diameter d1 of node S1 is the diameter of the pitch circle of the internal gear 2 in meshing, and is expressed by the following equation 2 using a positive integer "n". d1=(n+1)×e1×2...(Formula 2)

[0164] On the other hand, the outer diameter d2 of node S2 is the diameter of the pitch circle of the external gear 3 in meshing, and is expressed by the following equation 3 using a positive integer "n". d2=n×e1×2...(Formula 3)

[0165] Furthermore, a virtual pin V0, corresponding to the external pin 23 that constitutes the internal tooth 21, is set at a distance L0 from the center of node S1 in the direction of displacement of node S2 (to the right in Figure 14A). The relative position of the virtual pin V0 with respect to node S1 is fixed, and as will be described later, when node S1 revolves (rotates), the virtual pin V0 also revolves (rotates) together with node S1. The diameter dp1 of the virtual pin V0 is the diameter of the external pin 23. This virtual pin V0 creates the tooth profile (of the external tooth 31) that will mesh with node S1 (internal tooth 21) on node S2.

[0166] Here, as an example, let's assume that the integer n is "49" and the eccentricity e1 is "0.7". In this case, the inner diameter d1 of node S1 is "70" and the outer diameter d2 of node S2 is "68.6". Furthermore, let's assume that the distance L0 from the center of node S1 to the center of virtual pin V0 is "42.3".

[0167] Specifically, as shown in Figure 14B, when node S1 revolves n times (49 times in this basic configuration) on node S2 without slipping, the virtual pin V0, which is in a fixed position relative to node S1, revolves n times around node S2. At this time, the trajectory of the center of the virtual pin V0 forms a trochoidal curve, and the envelope formed by the virtual pin V0 on this trochoidal curve becomes the tooth profile of the external tooth 31. As a result, n (49) tooth profiles are formed, and n tooth tips and n tooth roots are formed.

[0168] Furthermore, as shown in Figure 15A, we consider the case where the number of virtual pins V0 associated with node S1 is "n+1" (50 in this basic configuration), and these "n+1" virtual pins V0 are arranged at equal pitches in the circumferential direction of node S1. In this case, as node S1 revolves once without sliding on node S2, the trajectories of the centers of the multiple ("n+1") virtual pins V0 that are in fixed positions relative to node S1 form a trochoidal curve, and as shown in Figure 15B, the envelope formed by the virtual pins V0 on this trochoidal curve becomes the tooth profile of the external tooth 31. As a result, n (49) tooth profiles are formed in one revolve of node S1, similar to Figure 14B.

[0169] In Figure 15B, the meshing between the external teeth 31 and internal teeth 21 (multiple external pins 23) of the created external gear 3 satisfies the kinematic meshing conditions of the gear, as the common normal of all contact points passes through a fixed point (pitch point Pp1). The common normal is shown as a dashed line (double-dot line) in Figure 15B, and the extension direction of these common normals coincides with the direction of the load applied from the external gear 3 to the internal gear 2. When the first quadrant Q1, second quadrant Q2, third quadrant Q3, and fourth quadrant Q4 are set in the circumferential direction of node S1, it can be seen that the meshing generating the effective load is in the first quadrant Q1 and fourth quadrant Q4, given the direction of the load. On the other hand, in the second quadrant Q2 and third quadrant Q3, it can be seen that there is almost no meshing generating the effective load, given the direction of the load. Therefore, to eliminate the occlusion between the external teeth 31 and internal teeth 21 in the second quadrant Q2 and third quadrant Q3 where effective occlusion does not occur, another external tooth 31 with a phase shift of 180 degrees is placed in the second quadrant Q2 and third quadrant Q3.

[0170] In other words, as shown in Figures 16A and 16B, we assume two external gears 3 with eccentricity directions differing by 180 degrees in an internal planetary gear system similar to that shown in basic configuration 1. Figure 16A shows an external gear 3A that is eccentric by an amount e1 to the right of the center of the internal gear 2, and Figure 16B shows an external gear 3B that is eccentric by an amount e1 to the left of the center of the internal gear 2.

[0171] Then, using these two external gears 3A and 3B, which have a phase difference of 180 degrees, the external teeth 31 of the external gear 3 in the gear device 1A relating to this basic configuration are constructed. Specifically, as shown in Figure 17A, with the centers of the internal gear 2 aligned, the two external gears 3A and 3B with different phases are superimposed. Then, by extracting the two superimposed trochoid curves from Figure 17A, two curves S3 and S4 are obtained as shown in Figure 17B.

[0172] Next, Figure 18A shows the state in which the tooth profile of the external gear 3A (external teeth 31) is formed by extracting only the inner part of the two curves S3 and S4 that overlap in the radial direction in Figure 17B, and then superimposing it with the internal gear 2. Here, the external gear 3A is eccentric by an eccentricity e1 to the right of the center of the internal gear 2. Furthermore, Figure 18B shows the state in which the external gear 3A in Figure 16A is replaced with the external gear 3A in Figure 18A.

[0173] Similarly, Figure 19A shows the tooth profile of the external gear 3B (external teeth 31) formed by extracting only the inner part of the two curves S3 and S4 that overlap in the radial direction in Figure 17B, and then superimposing it with the internal gear 2. Here, the external gear 3B is eccentric by an eccentricity e1 to the left of the center of the internal gear 2. Furthermore, Figure 19B shows the external gear 3B in Figure 16B replaced with the external gear 3B in Figure 19A.

[0174] Furthermore, in order to enable the rotation (self-rotation component) of the external gear 3 to be directly extracted from the external gear 3 without using multiple internal pins 4, the following configuration is adopted.

[0175] Specifically, Figure 20A shows a configuration in which the internal pin 4 and other components located inside the external gear 3A are omitted from the state shown in Figure 18B, and the opening of the external gear 3A is enlarged to the vicinity of the tooth roots of the external teeth 31. Similarly, Figure 20B shows a configuration in which the internal pin 4 and other components located inside the external gear 3B are omitted from the state shown in Figure 19B, and the opening of the external gear 3B is enlarged to the vicinity of the tooth roots of the external teeth 31.

[0176] Figure 21A shows a configuration in which a deflection generator 40A is fitted inside the external gear 3A of Figure 20A. Here, the deflection generator 40A has a circular cam 41, and the center of the cam 41 is eccentrically offset to the right by an eccentricity e1 from the center of the internal gear 2. Similarly, Figure 21B shows a configuration in which a deflection generator 40B is fitted inside the external gear 3B of Figure 20B. Here, the deflection generator 40B has a circular cam 41, and the center of the cam 41 is eccentrically offset to the left by an eccentricity e1 from the center of the internal gear 2.

[0177] Then, as described above, the two sets of meshing gears 3A and 3B, which are 180 degrees out of phase, are combined. Specifically, as shown in Figure 22A, the external gears 3A and 3B shown in Figures 20A and 20B are extended in the opposite direction to the eccentricity (to the left for external gear 3A and to the right for external gear 3B) so that they mesh with the internal gear 2 at both ends in the longitudinal direction, thereby obtaining a non-circular (in this case, oval) external gear 3. Here, the external gears 3A and 3B undergo elastic deformation, causing their dimensions in the left-right direction (long axis direction) in the figure to increase, while their dimensions in the up-down direction (short axis direction) in the figure to decrease.

[0178] However, the external gears 3A and 3B do not simply undergo elastic deformation, but rather they elastically deform to match the shape of the cam 41, which is designed so that the external gear 3 and the internal gear 2 satisfy the kinematic meshing conditions. In other words, as shown in Figure 21A, an arc consisting of the right half of a perfectly circular cam 41 eccentric to the right from the center of the internal gear 2, and as shown in Figure 21B, an arc consisting of the left half of a perfectly circular cam 41 eccentric to the left from the center of the internal gear 2, are superimposed to design an oval cam 41. The cam 41 has an oval shape formed by connecting the two arcs with a pair of straight lines of length "2 × e1".

[0179] As a result, as shown in Figure 22B, a gear mechanism 1X is obtained in which the cam 41 in Figure 21A or Figure 21B is replaced with an oval-shaped cam 41 having a pair of eccentric centers that are eccentric on both sides in the long axis direction (left-right direction) relative to the center of the internal gear 2. The gear mechanism 1X obtained in this way has the functions of both the gear mechanism in Figure 21A and the gear mechanism in Figure 21B. The gear device 1A according to this basic configuration is realized by incorporating the gear mechanism 1X obtained in this way into the gear body 22 of the internal gear 2.

[0180] By the way, in the gear mechanism 1X shown in Figure 22B, it is necessary that the external gear 3 does not interfere with the internal gear 2 in the non-meshing range Ra2, which is at both ends in the short axis direction. That is, as shown in Figure 23, which is an enlargement of region Z1 in Figure 22B, the tooth profile of the external gear 3 (external teeth 31) is set so that the external teeth 31 of the external gear 3 do not come into contact with the internal teeth 21 (external pin 23) of the internal gear 2 at both ends in the short axis direction of the cam 41. In other words, as shown by the dashed lines (two-dot lines) in Figure 23, if the two curves S3 and S4, which are trochoid curves extracted from Figure 17A, remain as they are, the tooth height of the external teeth 31 will be relatively large, and the tooth tips of the external teeth 31 will interfere with the internal teeth 21.

[0181] Therefore, in this basic configuration, as shown in Figure 23, at the point where two curves S3 and S4 overlap in the radial direction, only the inner curves S3 and S4 are extracted to form the tooth profile of the external teeth 31. More precisely, the tooth tips of the external teeth 31 have a rounded shape further inward from the intersection of curves S3 and S4, so that the tooth height is lower than the intersection of curves S3 and S4. In other words, in this basic configuration, the external teeth 31 have a shape that lacks a tooth tip portion 311. As a result, the interference height between the external teeth 31 of the external gear 3 and the internal teeth 21 (external pin 23) of the internal gear 2 becomes sufficiently small compared to the eccentricity e1, and interference between the external gear 3 and the internal gear 2 becomes less likely in the non-meshing range Ra2 at both ends in the short axis direction.

[0182] The tooth profile design described above satisfies the meshing conditions for gears that transmit rotation at a constant velocity ratio in kinematics, rather than relying on meshing based on approximate tooth profiles. In other words, it satisfies the meshing condition that "the common normal at the contact point of the two nodes passes through a fixed point (pitch point Pp1)." To put it another way, by ensuring a large number of meshes that satisfy the kinematic meshing conditions, load distribution can be improved. This improves power transmission performance, and in addition, it improves rotational accuracy and backlash performance.

[0183] Furthermore, in the gear unit 1A relating to this basic configuration, the amount of deformation when the external gear 3 undergoes elastic deformation is kept relatively small, so there is no need to make the external gear 3 extremely thin, and it is easy to ensure sufficient strength as an external gear 3. In addition, because the external pin 23 is used for the internal teeth 21, sliding contact occurs at a contact area between the external pin 23 and the internal groove 223 where the relative radius of curvature is large and the surface pressure is small, which also contributes to improving the power transmission efficiency of the gear unit 1A (especially the starting efficiency and static efficiency).

[0184] In addition, this basic configuration ensures that the tooth profile portion has a large load component (effective load component) that causes the external gear 3 to rotate in the direction of the common normal (which is also the load direction) at the contact point between the internal teeth 21 and the external teeth 31, while eliminating the meshing portion with a small load component (the tooth tip portion 311 of the external teeth 31) to keep the tooth height low. As a result, the external teeth 31 are less likely to interfere with the internal teeth 21 in the short axis direction D2 of the external gear 3.

[0185] <Examples of application> As shown in Figure 24, the gear device 1A according to this basic configuration, together with the first member 201 and the second member 202, constitutes the robot joint device 200. In other words, the robot joint device 200 according to this basic configuration 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 external gear 3 with respect to the internal gear 2. Figure 24 is a schematic cross-sectional view of the robot joint device 200.

[0186] In this basic configuration, as an example, the first member 201 is fixed to the inner ring 61, and the second member 202 is fixed to the outer ring 62. As a result, the second member 202 rotates relative to the first member 201 in accordance with the relative rotation of the external gear 3 with respect to the internal gear 2. More specifically, the first member 201 is indirectly fixed to the inner ring 61 of the bearing member 6 by being fixed to the first carrier 18. The second member 202 is indirectly fixed to the outer ring 62 of the bearing member 6 by being fixed to the second carrier 19.

[0187] 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 cam 41 of the deflection generator 40 of the gear device 1A is driven by the first motor 203, which acts as a drive source 101 (see Figure 1), 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.

[0188] More specifically, a first pulley P1 is fixed to the output shaft of the first motor 203. A second pulley P2 is connected to the first pulley P1 via a timing belt T1. Here, the second pulley P2 is fixed to the cam 41 of the deflection generator 40 as a mating member. In other words, when the first motor 203 is driven, its rotation is transmitted to the cam 41, which acts as the input shaft, via the first pulley P1, the timing belt T1, and the second pulley P2.

[0189] The robot joint device 200 also includes a second motor 204. A third pulley P3 is fixed to the output shaft of the second motor 204. A fourth pulley P4 is connected to the third pulley P3 via a timing belt T2. Here, the fourth pulley P4 is fixed to a shaft 205. The shaft 205 passes through the gear device 1A in the direction of the rotation axis Ax1 through the inside (opening) of the cam 41. A fifth pulley P5 is fixed to the end of the shaft 205 opposite to the fourth pulley P4. Thus, when the second motor 204 is driven, its rotation is transmitted to the fifth pulley P5 via the third pulley P3, timing belt T2, fourth pulley P4 and shaft 205.

[0190] 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 relating to this basic configuration 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).

[0191] <Variation> Basic Configuration 2 is merely one of many configuration examples provided in this disclosure. Basic Configuration 2 can be modified in various ways depending on the design, etc., as long as the objectives of this disclosure are achieved. Furthermore, the drawings referenced in this disclosure are all schematic diagrams, and the ratios of the size and thickness of each component shown in the drawings do not necessarily reflect the actual dimensional ratios. The following lists some modifications of Basic Configuration 2. The modifications described below can be combined and applied as appropriate.

[0192] Furthermore, the bearing member 6 is not limited to a cross roller bearing, but may also be, for example, an angular contact ball bearing, a deep groove ball bearing, or a four-point contact ball bearing.

[0193] Furthermore, the number of external pins 23 (number of internal teeth 21) and the number of external teeth 31, as explained in Basic Configuration 2, are merely examples and can be changed as appropriate.

[0194] 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.

[0195] Furthermore, the gear unit 1A only needs to be able to extract the relative rotation between the inner ring 61 and the outer ring 62 of the bearing member 6 as an output, and is not limited to a configuration in which the rotational force of the outer ring 62 (second carrier 19) is extracted as an output. For example, the rotational force of the inner ring 61 (first carrier 18) that rotates relative to the outer ring 62 may be extracted as an output.

[0196] Furthermore, the lubricant is not limited to liquid substances such as lubricating oil, but may also be a gel-like substance such as grease.

[0197] (Embodiment 1) As shown in Figures 25 to 27, the gear assembly 1C according to this embodiment differs from the gear assembly 1A according to basic configuration 2 mainly in the configuration of the bearing member 6. Hereinafter, components similar to those in basic configuration 2 will be denoted by common reference numerals and their explanations will be omitted as appropriate. Figure 25 is a schematic cross-sectional view of the gear assembly 1C. In Figure 25, enlarged views of regions Z1 and Z2 are shown in callouts. Figure 26 is a cross-sectional view taken along line A1-A1 in Figure 25, and Figure 27 is a cross-sectional view taken along line A2-A2 in Figure 25. However, in Figures 25 to 27, hatching is omitted even in cross-sections, except for the bearing member 6, bearing 42, first bearing 91 and second bearing 92 in Figure 25, and the bearing member 6 in Figure 26.

[0198] The internal gear 2 has the same configuration as the basic configuration 2, and in this embodiment as well, 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. Furthermore, the external gear 3 also has the same configuration as the basic configuration 2, and in this embodiment as well, the external gear 3 has external teeth 31 and is an annular member arranged inside the internal gear 2. The gear body 22 of the internal gear 2 is rigid, while the external gear 3 is flexible.

[0199] Furthermore, the gear device 1C according to this embodiment, like the basic configuration 2, includes a deflection generator 40 positioned inside the external gear 3 to cause deflection in the external gear 3. The deflection generator 40 has a non-circular cam 41 that is rotationally driven around a rotation axis Ax1, and a bearing 42 mounted on the outside of the cam 41. As the cam 41 rotates, the gear device 1C deforms the external gear 3, engaging a portion of the external teeth 31 with a portion of the internal teeth 21, and causing the external gear 3 to rotate relative to the internal gear 2 in accordance with the difference in the number of teeth between the external gear 3 and the internal gear 2.

[0200] In the gear apparatus 1C according to this embodiment, the deflection generator 40 deflects the external gear 3 into a non-circular shape (for example, an oval shape), thereby partially engaging the external teeth 31 of the external gear 3 with the internal teeth 21 (external pin 23) of the internal gear 2. In this state, when the cam 41 of the deflection generator 40 rotates, 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 occurs between the two gears (internal gear 2 and external gear 3) according to the difference in the number of teeth between the external gear 3 and the internal gear 2. If the gear body 22 of the internal gear 2 is fixed, the external gear 3 will rotate in conjunction with the relative rotation of the two gears. As a result, a rotational output reduced at a relatively high reduction ratio according to the difference in the number of teeth of the two gears can be obtained from the external gear 3.

[0201] Furthermore, the tooth profile of the external teeth 31 in the external gear 3 is the same as that of the basic configuration 2, as shown in Figure 26. Instead of meshing using an approximate tooth profile, a tooth profile is adopted that can achieve meshing that satisfies the meshing conditions of gears that transmit rotation at a constant velocity ratio in kinematics. Specifically, the external teeth 31 have a trochoidal tooth profile. The difference in the number of teeth of the external teeth 31 compared to the internal teeth 21 is two. This satisfies the meshing condition that "the common normal at the contact point of the two nodes passes through a fixed point (pitch point Pp1)". In other words, by ensuring a large number of meshes that satisfy the kinematic meshing conditions, load distribution can be improved, power transmission performance can be improved, and in addition, rotational accuracy and backlash performance can be improved.

[0202] Furthermore, in this embodiment, at locations where two curves S3 and S4 overlap in the radial direction, only the inner curves S3 and S4 are extracted to form the tooth profile of the external teeth 31 (see Figure 23). As a result, the tooth tips of the external teeth 31 have a rounded shape further inward from the intersection of curves S3 and S4, so that the tooth height is lower than the intersection of curves S3 and S4. In other words, in this embodiment, the external teeth 31 have a shape that lacks a tooth tip portion 311 (see Figure 23). As a result, the interference height between the external teeth 31 of the external gear 3 and the internal teeth 21 (external pin 23) of the internal gear 2 becomes sufficiently small compared to the eccentricity e1, and interference between the external gear 3 and the internal gear 2 becomes less likely in the non-meshing range Ra2 at both ends in the short axis direction.

[0203] Furthermore, in the gear device 1C according to this embodiment, the internal teeth 21 and external teeth 31 mesh in a simultaneous meshing range Ra1 (see Figure 13) that occupies more than 180 degrees in the circumferential direction of the internal gear 2. In this embodiment, this simultaneous meshing range Ra1 occupies more than 180 degrees in the circumferential direction of the internal gear 2, that is, more than half, similar to the basic configuration 2. Therefore, the meshing between the internal teeth 21 and external teeth 31 can be stabilized over a wide area of ​​more than half of the circumferential direction of the internal gear 2. As a result, the gear device 1C is less prone to malfunctions such as ratcheting, where the meshing between the internal gear 2 and external gear 3 momentarily shifts due to vibration during operation or excessive torque applied during operation.

[0204] Furthermore, in this embodiment, since the cylindrical portion 411 of the input shaft cam 41 is hollow (cylindrical), it is possible to arrange other power transmission shafts, electrical wiring, hydraulic piping, etc., inside the cylindrical portion 411.

[0205] Incidentally, in the gear device 1C according to this embodiment, as shown in Figure 25, the bearing member 6 that rotatably supports the external gear 3 relative to the gear body 22 has a first bearing member 601 and a second bearing member 602. In other words, the gear device 1C is equipped with a pair of bearing members 6 consisting of a first bearing member 601 and a second bearing member 602. The first bearing member 601 and the second bearing member 602 rotatably support the external gear 3 relative to the gear body 22 at two locations in the axial direction parallel to the rotation axis Ax1. Each of the first bearing member 601 and the second bearing member 602 has an inner ring 61, an outer ring 62, and a plurality of rolling elements 63, similar to the bearing member 6 in the basic configuration 2.

[0206] Here, each of the first bearing member 601 and the second bearing member 602 directly or indirectly supports the external gear 3 relative to the gear body 22 so that it can rotate. In this embodiment, there is a first carrier 18 fixed (integrated) to the gear body 22 and a second carrier 19 fixed to the external gear 3. The inner ring 61 of each of the first bearing member 601 and the second bearing member 602 is fixed to the first carrier 18. The outer ring 62 of each of the first bearing member 601 and the second bearing member 602 is fixed to the second carrier 19. Therefore, each of the first bearing member 601 and the second bearing member 602 indirectly supports the external gear 3 relative to the gear body 22 via the first carrier 18 and the second carrier 19. As a result, the second carrier 19 (and outer ring 62), which is a movable member, rotates relative to the first carrier 18 (and inner ring 61), which is a fixed member, as the internal gear 2 and the external gear 3 rotate relative to each other.

[0207] Specifically, as shown in Figure 25, a first bearing member 601 is positioned on the input side of the rotation axis Ax1 (left side in Figure 25), and a second bearing member 602 is positioned on the output side of the rotation axis Ax1 (right side in Figure 25). These first bearing member 601 and second bearing member 602 are configured to withstand radial loads, thrust loads (in the direction along the rotation axis Ax1), and bending forces (bending moment loads) on the rotation axis Ax1.

[0208] The first bearing member 601 and the second bearing member 602 are positioned on both sides of the rotation axis Ax1 (axial direction) relative to the meshing portion between the internal teeth 21 and the external teeth 31, and are oriented opposite to each other in the direction parallel to the rotation axis Ax1. In other words, the bearing member 6 is a "combined angular contact ball bearing" which combines 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 outer rings 62 move closer to each other. Furthermore, in the gear device 1C, 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 outer rings 62 by tightening them in a direction that brings their respective outer rings 62 closer to each other.

[0209] In this disclosure, the positions of the first bearing member 601 and the second bearing member 602 in the direction parallel to the rotation axis Ax1 (axial direction) are defined by the positions of the outer ends of the first bearing member 601 and the second bearing member 602 in the axial direction. In other words, the meshing portion of the internal teeth 21 and the external teeth 31 is located between the outer ends of the first bearing member 601 and the second bearing member 602 in the axial direction, so that the first bearing member 601 and the second bearing member 602 are located on both sides in the axial direction with respect to the meshing portion of the internal teeth 21 and the external teeth 31.

[0210] In this embodiment, the cylindrical portion 411 of the cam 41 is rotatably supported relative to the second carrier 19 by a first bearing 91 and a second bearing 92. Specifically, as shown in Figure 25, the first bearing 91 and the second bearing 92 are mounted on both sides of the non-circular portion 412 of the cylindrical portion 411, sandwiching the non-circular portion 412 in a direction parallel to the rotation axis Ax1 (axial direction). The first bearing 91 is positioned on the input side of the rotation axis Ax1 when viewed from the non-circular portion 412. The second bearing 92 is positioned on the output side of the rotation axis Ax1 when viewed from the non-circular portion 412. As a result, the cam 41 of the deflection generator 40 is rotatably held at two locations on both sides of the non-circular portion 412 in a direction parallel to the rotation axis Ax1. In this embodiment, as an example, each of the first bearing 91 and the second bearing 92 consists of a deep groove ball bearing using spherical balls as rolling elements.

[0211] Furthermore, in this embodiment, the gear body 22 integrated with the first carrier 18 has through holes 224 for passing lubricant, as shown in Figure 27. The through holes 224 penetrate the gear body 22 (or the first carrier 18) radially (in a direction perpendicular to the rotation axis Ax1). Here, multiple through holes 224 are formed in the gear body 22 (for example, six). The multiple through holes 224 are arranged at equal intervals in the circumferential direction of the gear body 22.

[0212] Here, as shown in Figure 25, each through-hole 224 is positioned between the first bearing member 601 and the second bearing member 602 in the axial direction parallel to the rotation axis Ax1. This creates an "oil reservoir" in the space between the first bearing member 601 and the second bearing member 602 within the gap between the gear body 22 (or first carrier 18) and the second carrier 19, allowing the lubricant to be easily supplied to the meshing area between the internal teeth 21 and the external teeth 31 through the through-hole 224. In particular, when the bearing members 6 (first bearing member 601 and second bearing member 602) operate and the rolling elements 63 rotate, the rolling elements 63 function as a pump, enabling the lubricant between the first bearing member 601 and the second bearing member 602 to be sent to the meshing area via the through-hole 224. In particular, because the outer circumferential opening surface of the through hole 224 faces (opposes) the space between the first bearing member 601 and the second bearing member 602, the rolling element 63 acts efficiently as a pump when it rotates. As a result, the lubricant is less likely to run out at the meshing portion between the internal teeth 21 and the external teeth 31, and the operation of the gear device 1C can be made smoother.

[0213] As described above, in the gear apparatus 1C according to this embodiment, the bearing member 6 has a first bearing member 601 and a second bearing member 602 that rotatably support the external gear 3 with respect to the gear body 22 at two locations in the axial direction parallel to the rotation axis Ax1 (directly or indirectly).

[0214] In this way, by providing a structure in which the external gear 3 (or the second carrier 19 integrated with the external gear 3) is supported at two points in the axial direction by the first bearing member 601 and the second bearing member 602, the rotation of the external gear 3 can be stabilized even though the external gear 3 is flexible. As a result, there is the advantage that the meshing between the internal teeth 21 and the external teeth 31 is more stable.

[0215] Furthermore, by structuring the external gear 3 (or second carrier 19) to be supported at two points in the axial direction by the first bearing member 601 and the second bearing member 602, it is easier to improve the adjustment accuracy of the gap or preload of the first bearing member 601 and the second bearing member 602. In other words, when assembling the gear device 1C, it is possible to prepare an intermediate product in which the first bearing member 601 and the second bearing member 602 are assembled to the external gear 3 (or second carrier 19), and then combine the intermediate product with the internal gear 2, etc. As a result, the assembly of the first bearing member 601 and the second bearing member 602, which requires precise adjustment of the gap or preload, can be separated from the overall assembly of the gear device 1C, leading to an improvement in the adjustment accuracy of the gap or preload of the first bearing member 601 and the second bearing member 602.

[0216] Furthermore, in this embodiment, the first bearing member 601 and the second bearing member 602 are located on both sides of the meshing portion between the internal teeth 21 and the external teeth 31 in the axial direction (parallel to the rotation axis Ax1). In other words, in the axial direction (parallel to the rotation axis Ax1), the meshing portion between the internal teeth 21 and the external teeth 31 is located between the first bearing member 601 and the second bearing member 602 (both outer ends). This suppresses the tilt of the internal teeth 21 (external pin 23) or the external teeth 31 with respect to the rotation axis Ax1, and makes the meshing between the internal teeth 21 and the external teeth 31 more stable.

[0217] Furthermore, in this embodiment, the first bearing member 601 and the second bearing member 602 are located on both sides of the deflection generator 40 in the axial direction (parallel to the rotation axis Ax1). In other words, in the axial direction (parallel to the rotation axis Ax1), the deflection generator 40 is located between the first bearing member 601 and the second bearing member 602 (both outer ends). This suppresses the inclination of the internal teeth 21 (external pin 23) or external teeth 31 with respect to the rotation axis Ax1, and makes the meshing between the internal teeth 21 and external teeth 31 more stable.

[0218] In short, in the axial direction, there is no planetary gear like the external gear 3 of the basic configuration 1 between the first bearing member 601 and the second bearing member 602.

[0219] The gear device 1C according to this embodiment, together with the first member 201 and the second member 202, constitutes a robot joint device 200, as shown in Figure 28, for example. In other words, the robot joint device 200 according to this embodiment comprises the gear device 1C, 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 external gear 3 with respect to the internal gear 2. Figure 28 is a schematic cross-sectional view of the robot joint device 200.

[0220] In this embodiment, as an example, the first member 201 is fixed to the inner ring 61, and the second member 202 is fixed to the outer ring 62. As a result, the second member 202 rotates relative to the first member 201 in accordance with the relative rotation of the external gear 3 with respect to the internal gear 2. More specifically, the first member 201 is indirectly fixed to the inner ring 61 of the bearing member 6 by being fixed to the first carrier 18. The second member 202 is indirectly fixed to the outer ring 62 of the bearing member 6 by being fixed to the second carrier 19.

[0221] Furthermore, in the example shown in Figure 28, the inner ring 61 of the second bearing member 602 is seamlessly integrated with the output shaft (the first carrier 18 to which the first member 201 is fixed).

[0222] Embodiment 1 is merely one of many embodiments of this disclosure. Embodiment 1 can be modified in various ways depending on the design, etc., as long as the objectives of this disclosure are achieved. The configuration of Embodiment 1 can be used in appropriate combination with various configurations (including modified versions) described in Basic Configuration 1 or Basic Configuration 2. Furthermore, the drawings referenced in this disclosure are all schematic diagrams, and the ratios of the size and thickness of each component in the drawings do not necessarily reflect the actual dimensional ratios. Modifications of Embodiment 1 are listed below. The modifications described below can be applied in appropriate combinations.

[0223] As a variation of Embodiment 1, it is not essential that the first bearing member 601 and the second bearing member 602 are angular contact ball bearings. For example, at least one of the first bearing member 601 and the second bearing member 602 may be a deep groove ball bearing, a tapered roller bearing, a cylindrical roller bearing, or a cross roller bearing, etc.

[0224] Furthermore, it is not essential that the first bearing member 601 and the second bearing member 602 are located on both sides of the meshing portion between the internal teeth 21 and the external teeth 31 and / or the deflection generator 40 in the axial direction. For example, the first bearing member 601 and the second bearing member 602 may be located on one side of the meshing portion between the internal teeth 21 and the external teeth 31 in the axial direction, or on one side of the deflection generator 40.

[0225] (Embodiment 2) The gear device 1B according to this embodiment differs from the gear device 1C according to Embodiment 1 in that the shape of the cam 41 of the deflection generator 40 is elliptical, as shown in Figure 29. Hereinafter, components similar to those in Embodiment 1 will be denoted by common reference numerals and their descriptions will be omitted as appropriate. Figure 29 is a cross-sectional view showing the schematic configuration of the gear device 1B. In Figure 29, hatching is omitted even in the cross-section, and the inner circumferential surface 221 of the gear body 22 is not shown.

[0226] In other words, in this embodiment, the cam 41 has an elliptical shape. The term "elliptical shape" as used in this disclosure refers to any shape in which a perfect circle is compressed and the intersection of mutually orthogonal major axes (major axis direction D1) and minor axes (minor axis direction D2) is located at the center, and is not limited to a mathematical "ellipse" which is a curve consisting of a set of points whose sum of distances from two fixed points on a plane is constant. In other words, the cam 41 in this embodiment may be a curve consisting of a set of points whose sum of distances from two fixed points on a plane is constant, like a mathematical "ellipse," or it may be an elliptical shape other than a mathematical "ellipse."

[0227] In the gear assembly 1B according to this embodiment, as shown in Figure 29, the external teeth 31 located at both ends of the elliptical major axis direction D1 mesh with the internal teeth 21. In contrast, the external teeth 31 located at both ends of the elliptical minor axis direction D2 do not mesh with the internal teeth 21.

[0228] The configuration of Embodiment 2 can be adopted in appropriate combination with the various configurations (including modified versions) described in Embodiment 1.

[0229] (summary) As described above, the gear apparatus (1, 1A, 1B, 1C) according to the first embodiment comprises an internal gear (2), an annular external gear (3), a deflection generator (40), and a bearing member (6). 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 internal teeth (21). The external gear (3) has external teeth (31) and is arranged inside the internal gear (2). The deflection generator (40) has a non-circular cam (41) that is rotationally driven around a rotation axis (Ax1), and a bearing (42) mounted on the outside of the cam (41). The deflection generator (40) is arranged inside the external gear (3) and causes deflection in the external gear (3). The gear assembly (1, 1A, 1B, 1C) deforms the external gear (3) as the cam (41) rotates, engaging a portion of the external teeth (31) with a portion of the internal teeth (21), and causing the external gear (3) to rotate relative to the internal gear (2) in accordance with the difference in the number of teeth between the external gear (3) and the internal gear (2). The bearing member (6) has a first bearing member (601) and a second bearing member (602) that rotatably support the external gear (3) relative to the gear body (22) at two locations in the axial direction parallel to the rotation axis (Ax1).

[0230] In this embodiment, since the external gear (3) is supported at two points in the axial direction by the first bearing member (601) and the second bearing member (602), the rotation of the external gear (3) can be stabilized even though the external gear (3) is flexible. As a result, there is an advantage that the meshing between the internal teeth (21) and the external teeth (31) is more stable.

[0231] In the gear apparatus (1, 1A, 1B, 1C) according to the second embodiment, in the first embodiment, the internal teeth (21) and external teeth (31) mesh in a simultaneous meshing range (Ra1) that occupies 180 degrees or more in the circumferential direction of the internal gear (2).

[0232] In this configuration, the external gear (3) is constrained from the internal gear (2) in the simultaneous meshing range (Ra1) of more than half of the circumferential direction of the internal gear (2), and the movement (deformation) of the external gear (3) away from the deflection generator (40) is suppressed. Therefore, the meshing between the internal teeth (21) and the external teeth (31) can be stabilized over a wide range of more than half of the circumferential direction of the internal gear (2). In other words, there is an advantage in that the meshing between the internal teeth (21) and the external teeth (31) is easily stabilized. As a result, the gear devices (1,1A,1B,1C) are less prone to malfunctions such as ratcheting, where the meshing between the internal gear (2) and the external gear (3) momentarily shifts when vibration occurs during operation or when excessive torque is applied during operation. In other words, the gear devices (1,1A,1B,1C) enable the realization of a structure with low vibration and improved shock resistance.

[0233] In the gear apparatus according to the third embodiment (1, 1A, 1B, 1C), in the first or second embodiment, the first bearing member (601) and the second bearing member (602) are located on both sides of the meshing portion between the internal teeth (21) and the external teeth (31) in the axial direction.

[0234] According to this embodiment, the inclination of the internal teeth (21) or external teeth (31) with respect to the axis of rotation (Ax1) is suppressed, and the meshing between the internal teeth (21) and external teeth (31) becomes even more stable.

[0235] In the gear apparatus according to the fourth embodiment (1, 1A, 1B, 1C), in any of the first to third embodiments, the first bearing member (601) and the second bearing member (602) are located on both sides of the deflection generator (40) in the axial direction.

[0236] According to this embodiment, the inclination of the internal teeth (21) or external teeth (31) with respect to the axis of rotation (Ax1) is suppressed, and the meshing between the internal teeth (21) and external teeth (31) becomes even more stable.

[0237] In the gear apparatus (1, 1A, 1B, 1C) according to the fifth embodiment, in any of the first to fourth embodiments, the external teeth (31) have a trochoidal tooth profile, and the difference in the number of teeth of the external teeth (31) compared to the internal teeth (21) is two.

[0238] According to this embodiment, the tooth profile of the external teeth (31) of the external gear (3) can be set to satisfy the gear meshing conditions for transmitting rotation at a constant velocity ratio in kinematics, rather than meshing based on an approximate tooth profile. As a result, it is possible to secure a large number of meshes that satisfy the kinematic meshing conditions, making it possible to distribute the load, and furthermore, by keeping the amount of deformation of the external gear (3) small, stress concentration in the external gear (3) becomes less likely to occur.

[0239] In the gear apparatus (1, 1A, 1B, 1C) according to the sixth embodiment, the external teeth (31) have a shape lacking a tooth tip (311) as in the fifth embodiment.

[0240] According to this embodiment, interference between the internal teeth (21) and external teeth (31) is less likely to occur in the non-meshing range (Ra2) where the internal teeth (21) and external teeth (31) do not mesh.

[0241] The robot joint device (200) according to the seventh embodiment comprises a gear device (1, 1A, 1B, 1C) according to any of the first to sixth 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 external gear (3) with respect to the internal gear (2).

[0242] This embodiment has the advantage of making it easier to stabilize the occlusion between the inner teeth (21) and the outer teeth (31).

[0243] The configurations relating to the second to sixth aspects are not essential to the gear unit (1, 1A, 1B, 1C) and can be omitted as appropriate. [Explanation of Symbols]

[0244] 1,1A,1B,1C Gear system 2 Internal gear 3 External gears 6. Bearing Member 21 Inner teeth 22 Gear body 23 Outer pin 31 External teeth 40. Deflection Generator 41 Cam 42 bearings 221 Inner surface (of the gear body) 223 Inner circumferential groove 311 Tooth tip 601 First bearing member 602 Second bearing member Ax1 Rotation axis Ra1 Simultaneous Occlusion Range

Claims

1. A robotic mechanical arm structure equipped with a robotic joint device, The aforementioned robot joint device is 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, An annular external gear having external teeth and positioned inside the internal gear, A deflection generator having a non-circular cam that is rotationally driven around a rotation axis, and a bearing mounted on the outside of the cam, positioned inside the external gear, and causing deflection in the external gear, A bearing member is provided, As the cam rotates, the external gear is deformed, a portion of the external teeth engages with a portion of the internal teeth, and the external gear rotates relative to the internal gear according to the difference in the number of teeth between the external gear and the internal gear. The bearing member comprises a first bearing member and a second bearing member that rotatably support the external gear relative to the gear body at two locations in the axial direction parallel to the rotation axis, in a gear device, A first member fixed to the gear body, The gear comprises a second member that rotates relative to the first member in accordance with the relative rotation of the external gear with respect to the internal gear, Robotic mechanical arm structure.

2. 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, An annular external gear having external teeth and positioned inside the internal gear, A deflection generator having a non-circular cam that is rotationally driven around a rotation axis, and a bearing mounted on the outside of the cam, positioned inside the external gear, and causing deflection in the external gear, A bearing member is provided, As the cam rotates, the external gear is deformed, a portion of the external teeth engages with a portion of the internal teeth, and the external gear rotates relative to the internal gear according to the difference in the number of teeth between the external gear and the internal gear. The bearing member has a first bearing member and a second bearing member that rotatably support the external gear relative to the gear body at two locations in the axial direction parallel to the rotation axis. Gear mechanism.

3. In the simultaneous meshing range that occupies 180 degrees or more in the circumferential direction of the internal gear, the internal teeth and the external teeth mesh together. The gear apparatus according to claim 2.

4. The first bearing member and the second bearing member are located on both sides of the meshing portion between the internal teeth and the external teeth in the axial direction. The gear apparatus according to claim 2 or 3.

5. The first bearing member and the second bearing member are located on both sides of the deflection generator in the axial direction. The gear apparatus according to claim 2 or 3.

6. The aforementioned external teeth have a trochoidal tooth profile, The difference in the number of teeth between the internal teeth and the external teeth is two teeth. The gear apparatus according to claim 2 or 3.

7. The aforementioned external teeth have a shape lacking a tooth tip. The gear apparatus according to claim 6.

8. A gear device according to claim 2 or 3, A first member fixed to the gear body, The gear comprises a second member that rotates relative to the first member in accordance with the relative rotation of the external gear with respect to the internal gear, Joint device for robots.

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