Harmonic gear device and robot

Abstract

To provide a structure capable of fixing an output member to a flexible external tooth gear or a rigid internal tooth gear without restricting an assembling procedure of a speed reduction mechanism.SOLUTION: A wave gear device includes an input member, a speed reduction mechanism, and an output member. The speed reduction mechanism has a wave generator, a flexible external tooth gear, and a rigid internal tooth gear. Either one of the rigid internal tooth gear and the flexible external tooth gear is located on one side in the axial direction of the output member. Furthermore, the output member is fixed to the flexible external tooth gear or the rigid internal tooth gear by bolts which are inserted from the other side in the axial direction. With this, it is possible to fix the output member to the flexible external tooth gear or the rigid internal tooth gear without restricting the assembly process of the speed reduction mechanism.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a strain wave gear device and a robot. [Background technology]

[0002] Conventionally, reducers that reduce the speed of rotation of an electric motor and output the reduced speed have been known. A conventional reducer is described, for example, in Japanese Patent Application Laid-Open No. 2009-257409. The reducer disclosed in Japanese Patent Application Laid-Open No. 2009-257409 is a so-called wave gear device that includes a circular spline (30), a flexspline (40), and a wave generator (50).

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-257409 Summary of the Invention [Problem to be solved by the invention]

[0004] Wave gear devices have the advantages of being able to achieve a high reduction ratio, having little backlash, and being relatively easy to miniaturize. However, in the structure disclosed in JP 2009-257409 A, the flexspline (40) is fixed to the inner ring (73) of the cross roller bearing (70) with a screw (115). The screw (115) is inserted from the inside of the cup-shaped flexspline (40). This poses a problem in that, after assembling the reduction mechanism including the flexspline (40) and the wave generator (50), it is not possible to fix the inner ring (73), which is an output member, to the flexspline (40), which is a flexible external gear.

[0005] An object of the present invention is to provide a structure in a strain wave gear device that can fix an output member to a flexible external gear or a rigid internal gear without restricting the assembly procedure of the reduction mechanism. [Means for solving the problem]

[0006] A first invention of the present application comprises an input member that rotates around a central axis at a first rotation speed, a speed reduction mechanism that converts the rotational motion of the input member into rotational motion at a second rotation speed lower than the first rotation speed, and an output member that rotates around the central axis at the second rotation speed, wherein the speed reduction mechanism comprises: a non-circular wave generator that rotates together with the input member around the central axis at the first rotation speed; a flexible external gear that has a flexible cylindrical portion located radially outside the wave generator and has a plurality of external teeth on an outer peripheral surface of the cylindrical portion; and a rigid internal gear that is located radially outside the cylindrical portion and has a plurality of internal teeth on an annular inner peripheral surface centered on the central axis, wherein the number of internal teeth of the rigid internal gear and the number of external teeth of the flexible external gear are Differently, some of the external teeth of the plurality of external teeth are pressed by the wave generator to mesh with the internal teeth, and as the wave generator rotates, the meshing position between the internal teeth and the external teeth moves circumferentially at the first rotation speed, and due to the difference in the number of teeth between the internal teeth and the external teeth, one of the rigid internal gear and the flexible external gear rotates at the second rotation speed relative to the other of the rigid internal gear and the flexible external gear, in this wave gear device, one of the rigid internal gear and the flexible external gear is located on one axial side of the output member, and the output member is fixed to one of the flexible external gear and the rigid internal gear by a bolt inserted from the other axial side.

[0007] A second invention of the present application is a wave gear device comprising: a wave generator rotatable around a central axis; a flexible external gear arranged radially outside the wave generator and having a plurality of external teeth protruding radially outward; a rigid internal gear arranged radially outside the flexible external gear and having internal teeth protruding radially inward and meshing with some of the external teeth; and an output member, wherein at least one of the flexible external gear and the rigid internal gear is arranged on one axial side of the output member, and the output member is fixed to one of the flexible external gear and the rigid internal gear by a fixing member that can be inserted from the other axial side. [Effects of the Invention]

[0008] According to the first aspect of the present invention, either the rigid internal gear or the flexible external gear is located on one axial side of the output member. The output member is then fixed to the flexible external gear or the rigid internal gear with a bolt inserted from the other axial side. This allows the output member to be fixed to the flexible external gear or the rigid internal gear without restricting the assembly procedure of the reduction mechanism.

[0009] According to the second aspect of the present invention, either the rigid internal gear or the flexible external gear is located on one axial side of the output member. The output member is fixed to the flexible external gear or the rigid internal gear by a fixing member inserted from the other axial side. This allows the output member to be fixed to the flexible external gear or the rigid internal gear without restricting the assembly procedure of the reduction mechanism. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a vertical cross-sectional view of a strain wave gear device according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the strain wave gear device according to the first embodiment. [Figure 3] FIG. 3 is a vertical cross-sectional view of a strain wave gear device according to the second embodiment. [Figure 4] FIG. 4 is a vertical cross-sectional view of a strain wave gear device according to a third embodiment. [Figure 5] FIG. 5 is a vertical cross-sectional view of a strain wave gear device according to a fourth embodiment. [Figure 6] FIG. 6 is a vertical cross-sectional view of a strain wave gear device according to a fifth embodiment. [Figure 7] FIG. 7 is a vertical cross-sectional view of a strain wave gear device according to a sixth embodiment. [Figure 8] FIG. 8 is a vertical cross-sectional view of a strain wave gear device according to a seventh embodiment. [Figure 9] FIG. 9 is a vertical cross-sectional view of a strain wave gear device according to an eighth embodiment. [Figure 10]FIG. 10 is a diagram showing the state during the manufacturing of the strain wave gear device according to the eighth embodiment. [Figure 11] FIG. 11 is a vertical cross-sectional view of a strain wave gear device according to a ninth embodiment. [Figure 12] FIG. 12 is a vertical cross-sectional view of a strain wave gear device according to a tenth embodiment. [Figure 13] FIG. 13 is a schematic diagram of the robot. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In this application, the direction parallel to the central axis of the strain wave gear device will be referred to as the "axial direction," the direction perpendicular to the central axis will be referred to as the "radial direction," and the direction along the arc centered on the central axis will be referred to as the "circumferential direction." However, the above-mentioned "parallel direction" also includes a direction that is approximately parallel. Furthermore, the above-mentioned "orthogonal direction" also includes a direction that is approximately orthogonal.

[0012] In addition, in this application, the term "number of rotations" refers to the number of rotations per unit time, that is, the speed of rotation.

[0013] 1. First Embodiment <1-1. Structure of strain wave gear device> Fig. 1 is a longitudinal sectional view of a wave gear device 1 according to a first embodiment of the present invention. Fig. 2 is a transverse sectional view of the wave gear device 1 as seen from position AA in Fig. 1. In Fig. 2, hatching indicating cross sections and illustration of the teeth of each gear are omitted to avoid complicating the drawing.

[0014] This strain wave gearing 1 is a device (strain wave gear reducer) that reduces rotational motion of a first rotational speed input to an input member 10 to rotational motion of a second rotational speed lower than the first rotational speed and outputs the reduced rotational speed. The strain wave gearing 1 is used, for example, by being incorporated into a joint of a robot together with an electric motor. However, the strain wave gearing 1 may also be used in other devices such as an assist suit or an unmanned transport vehicle.

[0015] 1 and 2, the strain wave gear device 1 of this embodiment includes an input member 10, a reduction mechanism 20, and an output member 40. In Fig. 1, the input member 10 is indicated by a two-dot chain line.

[0016] The input member 10 is a member that rotates around the central axis 9 at a first rotation speed before deceleration. In this embodiment, the input member 10 is a columnar input shaft extending in the axial direction. The input member 10 is connected to the output shaft of the electric motor via a power transmission mechanism such as a gear, a belt, or a coupling. When the electric motor is driven, the driving force supplied from the electric motor causes the input member 10 to rotate around the central axis 9 at a first rotation speed.

[0017] The speed reduction mechanism 20 is a mechanism that converts the rotational motion of the input member 10 into rotational motion of a second rotational speed lower than the first rotational speed, and transmits the rotational motion to the output member 40. As shown in FIGS. 1 and 2 , the speed reduction mechanism 20 has a rigid internal gear 21, a flexible external gear 22, and a wave generator 23.

[0018] The rigid internal gear 21 is an annular gear having multiple internal teeth 211 on its inner circumferential surface. The rigid internal gear 21 is fixed, for example, to the casing of an electric motor directly or via another member. The rigid internal gear 21 is arranged coaxially with the central axis 9. The rigid internal gear 21 is also located radially outside a cylindrical portion 221 (described later) of the flexible external gear 22. The rigid internal gear 21 has a much higher rigidity than the cylindrical portion 221 of the flexible external gear 22. Therefore, the rigid internal gear 21 can be considered to be a substantially rigid body. The rigid internal gear 21 has an annular inner circumferential surface centered on the central axis 9. The multiple internal teeth 211 are arranged on the inner circumferential surface at a constant pitch in the circumferential direction. Each internal tooth 211 protrudes radially inward.

[0019] The flexible external gear 22 is a flexible, deformable annular gear. The flexible external gear 22 is supported rotatably around the central axis 9. The flexible external gear 22 has a cylindrical portion 221 and a disk portion 222. The cylindrical portion 221 extends cylindrically in the axial direction around the central axis 9. One axial end of the cylindrical portion 221 is located radially outside the wave generator 23 and radially inside the rigid internal gear 21. The cylindrical portion 221 is flexible and therefore capable of radial deformation. In particular, the one axial end of the cylindrical portion 221 is a free end and therefore capable of greater radial displacement than other portions.

[0020] The flexible external gear 22 has a plurality of external teeth 223. The plurality of external teeth 223 are provided on the outer peripheral surface near one axial end of the cylindrical portion 221. The plurality of external teeth 223 are arranged at a constant pitch in the circumferential direction. Each external tooth 223 protrudes radially outward. The number of internal teeth 211 that the rigid internal gear 21 has is slightly different from the number of external teeth 223 that the flexible external gear 22 has.

[0021] The disk portion 222 has a thin portion 224 and a thick portion 225. The thin portion 224 extends radially inward from the other axial end of the cylindrical portion 221 in a flat plate shape, and also extends in an annular shape in a direction perpendicular to the central axis 9. The thick portion 225 is an annular portion located radially inward of the thin portion 224. The axial dimension of the thick portion 225 is larger than the axial dimension of the thin portion 224. The thick portion 225 is located on one axial side of the output base portion 41, which will be described later.

[0022] The flexible external gear 22 also has a central hole 226 and a plurality of bolt fastening holes 227. The central hole 226 is located radially inward of the thick portion 225. The central hole 226 passes through the center (radial center) of the disk portion 222 in the axial direction. The plurality of bolt fastening holes 227 are located radially outward of the central hole 226. The plurality of bolt fastening holes 227 are provided at equal intervals in the circumferential direction around the central axis 9. Each bolt fastening hole 227 passes through the thick portion 225 in the axial direction. An internal thread is formed in the bolt fastening hole 227.

[0023] The wave generator 23 is a mechanism that generates periodic flexible deformation in the cylindrical portion 221 of the flexible external gear 22. The wave generator 23 has a cam 231 and a flexible bearing 232. The cam 231 is fixed to the input member 10. Therefore, the cam 231 rotates together with the input member 10 around the central axis 9 at a first rotation speed. Note that the input member 10 and the cam 231 may be formed from a single member. The outer peripheral surface of the cam 231 is elliptical when viewed in the axial direction. The flexible bearing 232 is interposed between the outer peripheral surface of the cam 231 and the inner peripheral surface of the cylindrical portion 221 of the flexible external gear 22. Therefore, the cam 231 and the cylindrical portion 221 can rotate at different rotation speeds.

[0024] The inner ring of the flexible bearing 232 contacts the outer peripheral surface of the cam 231. The outer ring of the flexible bearing 232 contacts the inner peripheral surface of the cylindrical portion 221 of the flexible external gear 22. As a result, the cylindrical portion 221 of the flexible external gear 22 is deformed into an elliptical shape that follows the outer peripheral surface of the cam 231. Then, at two locations corresponding to both ends of the major axis of the ellipse, the cylindrical portion 221 is pressed radially outward, causing some of the external teeth 223 of the flexible external gear 22 to mesh with the internal teeth 211 of the rigid internal gear 21. At other circumferential positions, the external teeth 223 and the internal teeth 211 do not mesh with each other.

[0025] When a driving force is input from the electric motor to the input member 10, the cam 231 rotates together with the input member 10 around the central axis 9 at a first rotation speed. As a result, the major axis of the ellipse described above of the flexible external gear 22 also rotates at the first rotation speed. As a result, the meshing position between the external teeth 223 and the internal teeth 211 also changes circumferentially at the first rotation speed. Also, as described above, the number of internal teeth 211 of the rigid internal gear 21 is slightly different from the number of external teeth 223 of the flexible external gear 22. Due to this difference in the number of teeth, the meshing position between the external teeth 223 and the internal teeth 211 changes slightly circumferentially with each rotation of the cam 231. As a result, the flexible external gear 22 rotates relative to the rigid internal gear 21 around the central axis 9 at a second rotation speed that is lower than the first rotation speed.

[0026] The output member 40 rotates at a second rotation speed around the central axis 9. In addition, the flexible external gear 22 is fixed to the output member 40. Therefore, the output member 40 rotates together with the flexible external gear 22 around the central axis 9 at the second rotation speed after reduction. The output member 40 of this embodiment has a substantially flat plate-shaped output base portion 41 and a convex portion 43. At least a portion of the output base portion 41 is located on the other axial side of the reduction mechanism 20. The output base portion 41 extends in a direction perpendicular to the central axis 9.

[0027] The output base portion 41 has a plurality of bolt insertion holes 411. The plurality of bolt insertion holes 411 are provided at positions that axially overlap with the bolt fastening holes 227 of the flexible external gear 22. In other words, the plurality of bolt insertion holes 411 are provided at equal intervals in the circumferential direction around the central axis 9. Each bolt insertion hole 411 passes through the output base portion 41 in the axial direction.

[0028] The protrusion 43 protrudes from the center (radial center) of the output base portion 41 toward one axial side. The input member 10 and the protrusion 43 are arranged coaxially along the central axis 9. The protrusion 43 is inserted into the central hole 226 of the flexible external gear 22.

[0029] At least a portion of the convex portion 43 contacts the flexible external gear 22 in the radial direction. More specifically, the convex portion 43 has a support surface 431 and a conical portion 432. The support surface 431 is a cylindrical surface extending in the axial direction. The support surface 431 contacts the inner circumferential surface of the central hole 226 of the flexible external gear 22. This allows the flexible external gear 22 and the output member 40 to be precisely positioned coaxially with respect to the central axis 9. The conical portion 432 is located on one axial side of the support surface 431. The diameter of the conical portion 432 gradually decreases as it approaches one axial side.

[0030] <1-2. Manufacturing method for strain wave gear device> When manufacturing the strain wave gear device 1, first the reduction mechanism 20 is assembled. That is, the flexible external gear 22 is arranged radially outside the wave generator 23, and the rigid internal gear 21 is arranged radially outside the flexible external gear 22.

[0031] Next, the output member 40 is assembled to the flexible external gear 22. Specifically, the output member 40 is moved from the other axial side of the flexible external gear 22 toward one axial side along the central axis 9. Then, the convex portion 43 of the output member 40 is inserted into the central hole 226 of the flexible external gear 22. At this time, the output member 40 is positioned circumferentially with respect to the flexible external gear 22 so that the bolt fastening holes 227 of the flexible external gear 22 and the bolt insertion holes 411 of the output member 40 overlap in the axial direction.

[0032] In the structure of this embodiment, one axial end of the protrusion 43 forms a cone portion 432. Therefore, the protrusion 43 can be easily inserted into the central hole 226. Furthermore, even if the orientation of the flexible external gear 22 is slightly tilted relative to the rigid internal gear 21 when the reduction gear mechanism 20 is assembled, by inserting the protrusion 43 into the central hole 226, the inner circumferential surface of the central hole 226 is guided by the outer circumferential surface of the cone portion 432, thereby correcting the orientation of the flexible external gear 22. This allows the rigid internal gear 21 and the flexible external gear 22 to be positioned coaxially with respect to the central axis 9 with high precision. Furthermore, the flexible external gear 22 and the output member 40 can be positioned coaxially with respect to the central axis 9 with high precision.

[0033] Thereafter, a first bolt 61, which is a fixing member, is inserted into the bolt insertion hole 411 of the output member 40 and the bolt fastening hole 227 of the flexible external gear 22 from the other axial side of the output member 40. Then, the first bolt 61 is fastened to the female thread provided in the bolt fastening hole 227. This fixes the output member 40 to the thick portion 225 of the flexible external gear 22.

[0034] In the structure of this embodiment, the support surface 431 of the protrusion 43 of the output member 40 comes into contact with the inner circumferential surface of the central hole 226 of the flexible external gear 22. Therefore, even if a force acts on the output member 40 in a direction that tilts it relative to the axial direction when the first bolt 61 is fastened, tilting of the output member 40 with respect to the flexible external gear 22 can be suppressed.

[0035] As described above, in the structure of this embodiment, the output member 40 is inserted into the flexible external gear 22 from the other axial side where the wave generator 23 is not present. The output member 40 is then fixed to the flexible external gear 22 by the first bolt 61 inserted from the other axial side. Therefore, the output member 40 can be fixed to the flexible external gear 22 without restricting the assembly procedure of the reduction mechanism 20.

[0036] In the above procedure, the output member 40 is fixed to the flexible external gear 22 after the reduction mechanism 20 is completely assembled. However, it is not essential to completely assemble the reduction mechanism 20 before fixing the output member 40. For example, it is also possible to assemble only the rigid internal gear 21 and the flexible external gear 22 of the reduction mechanism 20, then fix the output member 40 to the flexible external gear 22, and finally attach the wave generator 23.

[0037] In addition, in FIG. 1 relating to this embodiment, the rigid internal gear 21 is described as a fixed element and the flexible external gear 22 as a rotating element, but the flexible external gear 22 may be a fixed element and the rigid internal gear 21 as a rotating element.

[0038] 2. Second Embodiment Next, a second embodiment of the present invention will be described. Fig. 3 is a vertical cross-sectional view of a wave gear device 1 according to the second embodiment. The following description will focus on differences from the previously described embodiment. Note that duplicated descriptions of parts equivalent to those of the previously described embodiment will be omitted.

[0039] The output member 40 in Figure 3 has a cylindrical output wall 42. The output wall 42 extends from the outer periphery of the output base 41 toward one side in the axial direction. The output wall 42 is located radially outward of the protrusion 43. The reduction mechanism 20 is located radially inward of the output wall 42. In this way, the reduction mechanism 20 can be housed inside the cup-shaped output member 40. This makes it possible to configure a strain wave gearing 1 in which the reduction mechanism 20 is not exposed to the outside. Furthermore, components to be driven can be fixed to the outer periphery of the output wall 42. This allows the strain wave gearing 1 and the components to be driven to be reduced in the axial direction as a whole.

[0040] 3. Third Embodiment Next, a third embodiment of the present invention will be described. Fig. 4 is a vertical cross-sectional view of a wave gear device 1 according to the third embodiment. The following description will focus on differences from the previously described embodiments. Note that duplicated descriptions of parts equivalent to those of the previously described embodiments will be omitted.

[0041] The output member 40 in Figure 4 has an output shaft 45. The output shaft 45 extends from the output base portion 41 along the central axis 9 toward the other axial side. In this way, the part to be driven can be fixed to the output shaft 45 on the other axial side of the reduction mechanism 20. This allows the strain wave gear device 1 and the part to be driven to be made smaller in the radial direction as a whole. Examples of the part to be driven include gears, belts, and couplings.

[0042] 4. Fourth Embodiment Next, a fourth embodiment of the present invention will be described. Fig. 5 is a vertical cross-sectional view of a wave gear device 1 according to the fourth embodiment. The following description will focus on differences from the previously described embodiments. Note that duplicated descriptions of parts equivalent to those of the previously described embodiments will be omitted.

[0043] In the strain wave gearing 1 of Figure 5, the input member 10 serves as a shaft coupling. The output shaft of the electric motor can be directly connected to the shaft coupling that serves as the input member 10. In this way, the electric motor and strain wave gearing 1 can be made smaller in the axial direction as a whole compared to when other components are interposed between the output shaft of the electric motor and the input member 10 of the strain wave gearing 1.

[0044] The strain wave gear device 1 in FIG. 5 also has a housing 30. The housing 30 is a generally cup-shaped member that houses the reduction mechanism 20 inside. The housing 30 is fixed to, for example, the casing of an electric motor. The housing 30 has a generally flat housing base 31 and a cylindrical housing wall 32. At least a portion of the housing base 31 is located on one axial side of the reduction mechanism 20. The housing base 31 extends in a direction perpendicular to the central axis 9. The rigid internal gear 21 is fixed to the housing base 31 with a second bolt 62. The housing wall 32 extends from the outer periphery of the housing base 31 toward the other axial side. The reduction mechanism 20 is located radially inward of the housing wall 32. This allows for the construction of a strain wave gear device 1 in which the reduction mechanism 20 is not exposed to the outside.

[0045] The housing 30 does not necessarily house the entire speed reduction mechanism 20. For example, a part of the speed reduction mechanism 20 may be disposed inside the housing 30, and another part of the speed reduction mechanism 20 may be disposed outside the housing 30.

[0046] An input side bearing 51 is interposed in the radial gap between the housing base portion 31 and the input member 10. The input side bearing 51 may be, for example, a ball bearing. The inner ring of the input side bearing 51 is fixed to the outer peripheral surface of the input member 10. The outer ring of the input side bearing 51 is fixed to the inner peripheral surface of the housing base portion 31. This allows the input member 10 to be rotatably supported with respect to the housing 30. Note that the input side bearing 51 may be a bearing other than a ball bearing.

[0047] The output member 40 in FIG. 5 has an output wall portion 42, as in the second embodiment. The output wall portion 42 extends from the outer periphery of the output base portion 41 toward one axial side. The output wall portion 42 is inserted into the radially inner side of the housing wall portion 32. In other words, the output wall portion 42 is located radially inside the housing wall portion 32. By arranging the housing wall portion 32 and the output wall portion 42 so that they overlap in the radial direction in this way, the housing 30 and the output member 40 can be made smaller in the axial direction as a whole. Therefore, the wave gear device 1 can be made thinner in the axial direction.

[0048] A first outer bearing 521 and a second outer bearing 522 are interposed in a radial gap between the inner circumferential surface of the housing wall 32 and the outer circumferential surface of the output wall 42. This allows the housing wall 32 and the output wall 42 to rotate relative to each other. The second outer bearing 522 is located on the other axial side of the first outer bearing 521. The first outer bearing 521 and the second outer bearing 522 are, for example, ball bearings. The outer rings of the first outer bearing 521 and the second outer bearing 522 are fixed to the inner circumferential surface of the housing wall 32. The inner rings of the first outer bearing 521 and the second outer bearing 522 are fixed to the outer circumferential surface of the output wall 42. The housing wall 32 rotatably supports the output wall 42 via the first outer bearing 521 and the second outer bearing 522. This allows the output member 40 to be rotatably supported relative to the housing 30. The first outer bearing 521 and the second outer bearing 522 may be bearings other than ball bearings.

[0049] During manufacture of the strain wave gear device 1, the outer ring of the first outer bearing 521 and the outer ring of the second outer bearing 522 slide in the axial direction along the inner circumferential surface of the housing wall portion 32. This allows the protrusion 43 to move to one side in the axial direction while maintaining coaxiality with the central axis 9.

[0050] In a structure in which the housing 30 and the output member 40 cover both axial sides and the radial outside of the reduction mechanism 20, as in this embodiment, in the manufacturing process of the wave gear device 1, after the housing 30 and the output member 40 have been arranged, it is not possible to perform bolt tightening work in the internal space of the housing 30 and the output member 40. Therefore, the flexible external gear 22 and the output member 40 cannot be fixed with a bolt inserted from one axial side. However, in this wave gear device 1, the flexible external gear 22 and the output member 40 can be fixed with a first bolt 61 inserted from the other axial side. Therefore, in the manufacturing process of the wave gear device 1, after the housing 30 and the output member 40 have been arranged, the flexible external gear 22 and the output member 40 can be fixed.

[0051] 5. Fifth Embodiment Next, a fifth embodiment of the present invention will be described. Fig. 6 is a vertical cross-sectional view of a wave gear device 1 according to the fifth embodiment. The following description will focus on differences from the previously described embodiments. Note that duplicated descriptions of parts equivalent to those of the previously described embodiments will be omitted.

[0052] The strain wave gearing 1 of Fig. 6 is used, for example, by being incorporated into the wheels of an automatic guided vehicle. In the example of Fig. 6, an electric motor 70 is directly connected to one axial side of the strain wave gearing 1. The output shaft of the electric motor 70 serves as the input member 10 of the strain wave gearing 1. This reduces the number of parts compared to when the output shaft of the electric motor 70 and the input member 10 of the strain wave gearing 1 are separate parts. Furthermore, the electric motor 70 and strain wave gearing 1 can be made smaller in size in the axial direction as a whole.

[0053] The wave gear device 1 in Fig. 6 has a housing 30 similar to that of the fourth embodiment. The housing 30 has a substantially flat housing base portion 31 and a cylindrical housing wall portion 32. The output member 40 in Fig. 6 has an output wall portion 42 similar to that of the second and fourth embodiments.

[0054] However, in the example of FIG. 6 , the housing wall 32 is inserted radially inside the output wall 42. In other words, the housing wall 32 is located radially inside the output wall 42. The first outer bearing 521 and the second outer bearing 522 are interposed between the outer peripheral surface of the housing wall 32 and the inner peripheral surface of the output wall 42. Even with this arrangement, by arranging the housing wall 32 and the output wall 42 so that they overlap in the radial direction, the housing 30 and the output member 40 can be made smaller in size in the axial direction as a whole. Therefore, the wave gear device 1 can be made thinner in the axial direction.

[0055] During manufacture of the strain wave gear device 1, the inner circumferential surface of the output wall portion 42 slides in the axial direction along the outer ring of the first outer bearing 521 and the outer ring of the second outer bearing 522. This allows the protrusion 43 to move to one side in the axial direction while maintaining its coaxiality with the central axis 9.

[0056] The strain wave gearing 1 in FIG. 6 further includes an annular tire 80. The tire 80 is fixed to the outer peripheral surface of the output wall portion 42. The tire 80 is made of, for example, rubber. In this way, the reduction mechanism 20 is disposed radially inside the tire 80. This allows the mechanism for rotating the tire 80 to be made thinner in the axial direction. The strain wave gearing 1 may further include a wheel between the output wall portion 42 and the tire 80.

[0057] 6. Sixth Embodiment Next, a sixth embodiment of the present invention will be described. Fig. 7 is a vertical cross-sectional view of a wave gear device 1 according to the sixth embodiment. The following description will focus on differences from the previously described embodiments. Note that duplicated descriptions of parts equivalent to those of the previously described embodiments will be omitted.

[0058] The input member 10 in FIG. 7 is a cylindrical hollow shaft extending in the axial direction. The wave gear device 1 in FIG. 7 also has a non-rotating shaft 72. The non-rotating shaft 72 extends axially, passing through the input member 10. One axial end of the non-rotating shaft 72 is located on one axial side of the housing 30. The other axial end of the non-rotating shaft 72 is located on the other axial side of the output member 40. The non-rotating shaft 72 is fixed to, for example, the casing or an external frame of the electric motor 70. Therefore, the non-rotating shaft 72 does not rotate around the central axis 9.

[0059] An output-side bearing 53 is disposed in the radial gap between the non-rotating shaft 72 and the output member 40. The output-side bearing 53 may be, for example, a ball bearing. An inner ring of the output-side bearing 53 is fixed to the outer circumferential surface of the non-rotating shaft 72. An outer ring of the output-side bearing 53 is fixed to the inner circumferential portion of the output member 40. This allows the output member 40 to be rotatably supported relative to the non-rotating shaft 72. The output-side bearing 53 may be a bearing other than a ball bearing.

[0060] An outer bearing 523 is interposed in the radial gap between the outer peripheral surface of the housing base portion 31 and the inner peripheral surface of the output wall portion 42. The output member 40 is rotatably supported by the outer bearing 523 and the output-side bearing 53.

[0061] 7. Seventh Embodiment Next, a seventh embodiment of the present invention will be described. Fig. 8 is a vertical cross-sectional view of a wave gear device 1 according to the seventh embodiment. The following description will focus on differences from the previously described embodiments. Note that duplicated descriptions of parts equivalent to those of the previously described embodiments will be omitted.

[0062] 8 has a columnar or cylindrical output shaft 45. The output shaft 45 extends from the output base portion 41 toward the other axial side along the central axis 9. In this way, a part to be driven can be fixed to the output shaft 45 on the other axial side of the reduction mechanism 20.

[0063] 8, the housing 30 has a first cover portion 33 and a second cover portion 34. The first cover portion 33 and the second cover portion 34 are located on the other axial side of the reduction gear mechanism 20. The first cover portion 33 extends from the other axial end of the housing wall portion 32, radially inward and toward the other axial side, with its diameter tapering in a stepped manner. However, the first cover portion 33 may also be annular and extending radially inward from the other axial end of the housing wall portion 32. The second cover portion 34 extends cylindrically from the inner periphery of the first cover portion 33 toward the other axial side. The output shaft 45 is located radially inside the second cover portion 34.

[0064] A pair of output-side bearings 53 are interposed in the radial gap between the output shaft 45 and the second cover part 34. The output-side bearings 53 are, for example, ball bearings. Inner rings of the pair of output-side bearings 53 are fixed to the outer circumferential surface of the output shaft 45. Outer rings of the pair of output-side bearings 53 are fixed to the inner circumferential surface of the second cover part 34. This allows the output member 40 to be rotatably supported with respect to the housing 30. The output-side bearings 53 may be bearings other than ball bearings.

[0065] 8. Eighth Embodiment Next, an eighth embodiment of the present invention will be described. Fig. 9 is a vertical cross-sectional view of a wave gear device 1 according to the eighth embodiment. The following description will focus on differences from the previously described embodiments. Note that duplicated descriptions of parts equivalent to those of the previously described embodiments will be omitted.

[0066] In the example of FIG. 9, the reduction gear mechanism 20 has a collar 24. The collar 24 is an annular member centered on the central axis 9. The collar 24 is located on one axial side of the disk portion 222 of the flexible external gear 22. More specifically, the collar 24 is located on one axial side of the thick portion 225. The collar 24 has a plurality of bolt fastening holes 241. The bolt fastening holes 241 extend from the surface on the other axial side of the collar 24 toward one axial side. An internal thread is formed in the bolt fastening holes 241.

[0067] In this embodiment, the thick portion 225 of the flexible external gear 22 has a plurality of bolt insertion holes 228. The bolt insertion holes 228 pass through the thick portion 225 in the axial direction.

[0068] Fig. 10 is a diagram showing the manufacturing process of the strain wave gear device 1 according to the eighth embodiment. As shown in Fig. 10, when manufacturing the strain wave gear device 1, first, the input member 10 and the reduction mechanism 20 are assembled to the housing 30. This prepares a first unit U1 including the input member 10, rigid internal gear 21, flexible external gear 22, wave generator 23, collar 24, housing 30, and input-side bearing 51.

[0069] The cam 231 of the wave generator 23 has a first stopper surface 233. The first stopper surface 233 faces a surface of the collar 24 on one axial side in the axial direction. The housing base portion 31 also has a second stopper surface 311. The second stopper surface 311 faces an end of the cylindrical portion 221 of the flexible external gear 22 on one axial side in the axial direction. When the first unit U1 is prepared, the end face of the collar 24 on one axial side comes into contact with the first stopper surface 233 of the cam 231, or the end of the cylindrical portion 221 on one axial side comes into contact with the second stopper surface 311 of the housing 30.

[0070] Furthermore, the cam 231 of this embodiment has a guide protrusion 234. The guide protrusion 234 protrudes from the periphery of the first stopper surface 233 toward the other axial side. The guide protrusion 234 is annular and centered on the central axis 9. However, the guide protrusion 234 may be a plurality of protrusions arranged at intervals in the circumferential direction. The collar 24 is inserted radially inside the guide protrusion 234 in a loose fit state. This positions the collar 24 radially relative to the cam 231.

[0071] Next, the first outer bearing 521 and the second outer bearing 522 are assembled to the output member 40. In this way, a second unit U2 including the output member 40, the first outer bearing 521, and the second outer bearing 522 is prepared.

[0072] Next, as shown by the white arrow in Figure 10, the second unit U2 is moved from the other axial side of the first unit U1 toward one axial side. Then, the second unit U2 is inserted inside the housing wall portion 32. This assembles the second unit U2 to the first unit U1. After that, a retaining ring 36 is attached to a groove 35 formed on the inner circumferential surface of the housing wall portion 32. This prevents the second unit U2 from coming off the first unit U1.

[0073] At this time, the collar 24, the flexible external gear 22, and the output member 40 are positioned circumferentially so that the bolt fastening hole 241 of the collar 24, the bolt insertion hole 228 of the flexible external gear 22, and the bolt insertion hole 411 of the output member 40 overlap in the axial direction.

[0074] When assembling the second unit U2 to the first unit U1, the second unit U2 can be gradually positioned relative to the first unit U1 so that the center of the protrusion 43 coincides with the central axis 9. The protrusion 43 of the output member 40 is inserted radially inside the flexible external gear 22 and the collar 24. This positions the flexible external gear 22 and the collar 24 relative to the output member 40. In the structure of this embodiment, one axial end of the protrusion 43 forms a conical portion 432. Therefore, the protrusion 43 can be easily inserted into the central hole 226 of the flexible external gear 22.

[0075] Furthermore, even if the attitude of the flexible external gear 22 is slightly tilted relative to the rigid internal gear 21 when assembling the first unit U1, by inserting the convex portion 43 into the central hole 226, the inner circumferential surface of the central hole 226 is guided by the outer circumferential surface of the conical portion 432, and the attitude of the flexible external gear 22 can be corrected. Furthermore, even if a force acts on the output member 40 in a direction tilting it with respect to the axial direction when fastening the first bolt 61, tilting of the flexible external gear 22 relative to the output member 40 can be suppressed. Furthermore, by bringing the outer circumferential surface of the conical portion 432 into contact with the inner circumferential surface of the central hole 226, the flexible external gear 22 can be positioned radially relative to the output member 40. This allows the flexible external gear 22 and the output member 40 to be positioned coaxially with respect to the central axis 9 with high precision.

[0076] Thereafter, a first bolt 61, which is a fixing member, is inserted from the other axial side of the output member 40 into the bolt insertion hole 411 of the output member 40, the bolt insertion hole 228 of the flexible external gear 22, and the bolt fastening hole 241 of the collar 24. Then, the first bolt 61 is fastened to the female thread provided in the bolt fastening hole 241. This fixes the collar 24, the flexible external gear 22, and the output member 40. The thick portion 225 of the flexible external gear 22 is fixed while being sandwiched between the output base portion 41 and the collar 24.

[0077] By tightening the first bolt 61, the surface on the other axial side of the thick-walled portion 225 of the flexible external gear 22 comes into close contact with the surface on one axial side of the output base portion 41. Furthermore, by tightening the first bolt 61, the surface on the other axial side of the collar 24 comes into close contact with the surface on one axial side of the thick-walled portion 225 of the flexible external gear 22. This allows the flexible external gear 22 to be positioned in the axial direction with high precision. Furthermore, an appropriate axial gap L1 is formed between the surface on one axial side of the collar 24 and the first stopper surface 233 of the cam 231. Furthermore, an appropriate axial gap L2 is formed between the end on one axial side of the cylindrical portion 221 of the flexible external gear 22 and the second stopper surface 311.

[0078] As described above, in the structure of this embodiment, the output member 40 is inserted into the flexible external gear 22 from the other axial side where the housing 30 is not present. The output member 40 is then fixed to the flexible external gear 22 by the first bolt 61 inserted from the other axial side. Therefore, the output member 40 can be fixed to the flexible external gear 22 after the second unit U2 is assembled to the first unit U1.

[0079] 9. Ninth Embodiment Next, a ninth embodiment of the present invention will be described. Fig. 11 is a vertical cross-sectional view of a wave gear device 1 according to the ninth embodiment. The following description will focus on differences from the previously described embodiments. Note that duplicated descriptions of parts equivalent to those of the previously described embodiments will be omitted.

[0080] The flexible external gear 22 in FIG. 11 has a cylindrical portion 221 and a disk portion 222. The cylindrical portion 221 extends cylindrically in the axial direction around the central axis 9. The other axial end of the cylindrical portion 221 is located radially outside the wave generator 23 and radially inside the rigid internal gear 21. The cylindrical portion 221 is flexible and therefore capable of radial deformation. In particular, the other axial end of the cylindrical portion 221 is a free end and therefore capable of greater radial displacement than other portions. A plurality of external teeth 223 are provided on the outer peripheral surface of the cylindrical portion 221 near the other axial end.

[0081] The disk portion 222 has a thin portion 224 and a thick portion 225. The thin portion 224 extends radially outward from one axial end of the cylindrical portion 221 in a flat plate shape, and also extends in an annular shape in a direction perpendicular to the central axis 9. The thick portion 225 is an annular portion located radially outward from the thin portion 224. The axial dimension of the thick portion 225 is larger than the axial dimension of the thin portion 224. The thick portion 225 is fixed to the housing 30 by a third bolt 63.

[0082] The rigid internal gear 21 in Fig. 11 is located on one axial side of the output base portion 41. The rigid internal gear 21 and the output member 40 are fixed together by the first bolt 61. In this way, in this embodiment, the flexible external gear 22 is fixed to the housing 30, and the rigid internal gear 21 is fixed to the output member 40. For this reason, when the strain wave gear device 1 is driven, the flexible external gear 22 does not rotate, and the rigid internal gear 21 rotates around the central axis 9 relative to the flexible external gear 22 at a second rotation speed that is lower than the first rotation speed.

[0083] 11, the output member 40 is inserted into the rigid internal gear 21 from the other axial side. The output member 40 is then fixed to the rigid internal gear 21 by a first bolt 61 inserted from the other axial side. Therefore, the output member 40 can be fixed to the rigid internal gear 21 without restricting the assembly procedure of the reduction gear mechanism 20.

[0084] In FIG. 11, before the output member 40 is inserted, the gap L1=0, but after it is fixed by the first bolt 61, the gap L1 shown in FIG. 11 is formed.

[0085] 11 has a protrusion 43. The protrusion 43 protrudes from the output base 41 toward one axial side. The outer peripheral surface of the protrusion 43 contacts the inner peripheral surface of the rigid internal gear 21 in the radial direction. This allows the rigid internal gear 21 and the output member 40 to be positioned coaxially with respect to the central axis 9 with high precision.

[0086] 10. Tenth Embodiment Next, a tenth embodiment of the present invention will be described. Fig. 12 is a vertical cross-sectional view of a wave gear device 1 according to the tenth embodiment. The following description will focus on differences from the previously described embodiments. Note that duplicated descriptions of parts equivalent to those of the previously described embodiments will be omitted.

[0087] The strain wave gear device 1 in FIG. 12 has one outer bearing 52. The outer bearing 52 is located in the radial gap between the inner circumferential surface of the housing wall 32 and the outer circumferential surface of the output wall 42. The outer bearing 52 in FIG. 12 is a cross roller bearing. A cross roller bearing has multiple rollers between an outer ring and an inner ring. The multiple rollers are arranged with their orientations alternating between a V-shaped groove on the inner circumferential surface of the outer ring and a V-shaped groove on the outer circumferential surface of the inner ring. Such a cross roller bearing can obtain the required rigidity without being used in pairs like ball bearings. Therefore, the output member 40 can be stably supported relative to the housing 30 while reducing the number of outer bearings 52.

[0088] The strain wave gear device 1 in FIG. 12 also has an output-side bearing 53. The output-side bearing 53 is located in the radial gap between the input member 10 and the output member 40. The output-side bearing 53 is, for example, a ball bearing. The inner ring of the output-side bearing 53 is fixed to the outer peripheral surface of the input member 10. The outer ring of the output-side bearing 53 is fixed to the inner peripheral surface of the output member 40. This allows the input member 10 to be rotatably supported relative to the output member 40. The output-side bearing 53 may be a bearing other than a ball bearing.

[0089] <11. Variations> Although the first to tenth embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments.

[0090] In the above embodiment, the outer peripheral surface of cam 231 is elliptical. However, the outer peripheral surface of cam 231 may have a non-circular shape other than elliptical. Also, flexible bearing 232 may be omitted, and wave generator 23 may be formed only by cam 231.

[0091] Furthermore, the detailed shape of the strain wave gear device may differ from the shapes shown in the drawings of this application. Furthermore, the elements appearing in the above embodiments or modified examples may be selected as appropriate within the scope of not causing any contradictions.

[0092] <12.Robot> FIG. 13 is a schematic diagram of a robot 100 equipped with a strain wave gearing device 1. The robot 100 is a so-called industrial robot that performs tasks such as transporting, processing, and assembling parts on, for example, an industrial product production line. As shown in FIG. 13, the robot 100 has a base frame 101, an arm 102, a strain wave gearing device 1, and an electric motor 70. The strain wave gearing device 1 and the electric motor 70 are incorporated into a joint between the base frame 101 and the arm 102. This makes it possible to realize a robot 100 equipped with a strain wave gearing device 20 having a structure in which the output member 40 can be fixed to the flexible external gear 22 or the rigid internal gear 21 without restricting the assembly procedure of the reduction mechanism 20.

[0093] The base frame 101 is fixed to either the housing 30 of the strain wave gearing 1 or the casing of the electric motor 70. The output shaft of the electric motor 70 is fixed to the input member 10 of the strain wave gearing 1. The arm 102 is fixed to the output member 40 of the strain wave gearing 1. When the electric motor 70 is driven, the input member 10 rotates together with the output shaft of the electric motor 70 at a first rotation speed. Then, the arm 102 rotates together with the output member 40 at a second rotation speed. [Industrial Applicability]

[0094] The present invention can be used in a strain wave gear device and a robot. [Explanation of symbols]

[0095] 1 Strain wave gearing 9 Center axis 10 Input member 20 Reduction mechanism 21 Rigid internal gear 22 Flexible external gear 23 Wave Generator 24 colors 30 Case 31 Housing base 32 Housing wall 40 Output member 41 Output base 42 Output wall 43 Convex part 51 Input side bearing 52 Outer bearing 53 Output side bearing 61 First Bolt 62 Second bolt 63 Third Bolt 70 Electric motor 80 tires 100 robots 221 Cylindrical part 222 Disk section 224 Thin-walled section 225 Thick wall part 227 Bolt fastening hole 228 Bolt insertion hole 231 Cam 232 Flexible Bearing 233 First stopper surface 234 Guide protrusion 241 Bolt fastening hole 311 Second stopper surface 411 Bolt insertion hole 431 Support surface 432 Cone 521 1st outer bearing 522 2nd outer bearing U1 1st Unit U2 2nd Unit

Claims

1. an input member that rotates about a central axis at a first rotational speed; a speed reduction mechanism that converts the rotational motion of the input member into rotational motion at a second rotational speed that is lower than the first rotational speed; an output member that rotates about the central axis at the second rotation speed; Equipped with The reduction mechanism is a non-circular wave generator that rotates together with the input member about the central axis at the first rotation speed; a flexible external gear having a flexible cylindrical portion located radially outward of the wave generator, the flexible external gear having a plurality of external teeth on an outer circumferential surface of the cylindrical portion; a rigid internal gear located radially outside the cylindrical portion, the rigid internal gear having a plurality of internal teeth on an annular inner peripheral surface centered on the central axis; and the number of the internal teeth of the rigid internal gear is different from the number of the external teeth of the flexible external gear, some of the external teeth of the plurality of external teeth are pushed by the wave generator to mesh with the internal teeth; As the wave generator rotates, the meshing position between the internal teeth and the external teeth moves in the circumferential direction at the first rotation speed, a strain wave gearing device in which the flexible external gear rotates at the second rotation speed relative to the rigid internal gear due to a difference in the number of teeth between the internal teeth and the external teeth, the flexible external gear is located on one axial side of the output member, the output member is fixed to the flexible external gear by a bolt inserted from the other axial side, The flexible external gear is a disk portion extending radially inward from the other axial side of the cylindrical portion; and the disk portion is located on one axial side of the output member, The bolt is inserted into the disk portion from the other axial side, The reduction mechanism is a circular collar located on one axial side of the disk portion; and The bolt is fastened to a female screw provided in the collar, The disk portion is sandwiched and fixed between the output member and the collar, The wave generator comprises: a first contactable surface facing a surface on one axial side of the collar; a guide protrusion protruding from a periphery of the first contact surface toward the other axial side; and The collar is disposed radially inward of the guide projection.

2. 2. The strain wave gear device according to claim 1, A housing that houses the reduction mechanism Furthermore, The rigid internal gear is fixed to the housing.

3. 3. The strain wave gear device according to claim 2, The housing includes: a second contactable surface that faces the end of the cylindrical portion on one axial side in the axial direction; A strain wave gear device having the above structure.

4. 2. The strain wave gear device according to claim 1, The disk portion is a thin-walled portion that extends radially inward from the other axial side of the cylindrical portion; a thick portion located radially inside the thin portion and having an axial dimension larger than that of the thin portion; and The bolt passes through the output member and the thick portion and is fastened to the female thread provided in the collar.

5. 5. The strain wave gear device according to claim 1 or 4, The output member is an output base portion located on the other axial side of the reduction mechanism; a protrusion extending from a center of the output base portion toward one axial side; and The flexible external gear is A central hole axially passing through the center of the disk portion. and The convex portion is inserted into the central hole.

6. an input member that rotates about a central axis at a first rotational speed; a speed reduction mechanism that converts the rotational motion of the input member into rotational motion at a second rotational speed that is lower than the first rotational speed; an output member that rotates about the central axis at the second rotation speed; Equipped with The reduction mechanism is a non-circular wave generator that rotates together with the input member about the central axis at the first rotation speed; a flexible external gear having a flexible cylindrical portion located radially outward of the wave generator, the flexible external gear having a plurality of external teeth on an outer circumferential surface of the cylindrical portion; a rigid internal gear located radially outside the cylindrical portion, the rigid internal gear having a plurality of internal teeth on an annular inner peripheral surface centered on the central axis; and the number of the internal teeth of the rigid internal gear is different from the number of the external teeth of the flexible external gear, some of the external teeth of the plurality of external teeth are pushed by the wave generator to mesh with the internal teeth; As the wave generator rotates, the meshing position between the internal teeth and the external teeth moves in the circumferential direction at the first rotation speed, a strain wave gearing device in which the flexible external gear rotates at the second rotation speed relative to the rigid internal gear due to a difference in the number of teeth between the internal teeth and the external teeth, the flexible external gear is located on one axial side of the output member, the output member is fixed to the flexible external gear by a bolt inserted from the other axial side, The output member is an output base portion located on the other axial side of the reduction mechanism; a protrusion extending from a center of the output base portion toward one axial side; and The flexible external gear is a disk portion extending radially inward from the other axial side of the cylindrical portion; a central hole axially passing through the center of the disk portion; and The protrusion is inserted into the central hole, The convex portion is a cylindrical support surface in contact with an inner circumferential surface of the central hole; a conical portion located on one axial side of the support surface and having a diameter that decreases toward the one axial side; A strain wave gear device having the above structure.

7. 7. The strain wave gear device according to claim 5 or 6, The output member is a cylindrical output wall portion extending from the outer periphery of the output base portion toward one axial side; and The reduction mechanism is located radially inside the output wall portion.

8. 8. The strain wave gear device according to claim 7, A housing that houses the reduction mechanism Furthermore, The housing includes: a housing base portion located on one axial side of the reduction mechanism; a cylindrical housing wall portion extending from an outer periphery of the housing base portion toward the other axial side; and The reduction mechanism is a strain wave gear device located radially inside the housing wall portion.

9. 9. The strain wave gear device according to claim 8, an input-side bearing interposed between an inner peripheral surface of the housing base portion and the input member; an outer bearing interposed between the housing wall portion and the output wall portion; The strain wave gear device further comprises:

10. an input member that rotates about a central axis at a first rotational speed; a speed reduction mechanism that converts the rotational motion of the input member into rotational motion at a second rotational speed that is lower than the first rotational speed; a housing that accommodates the reduction mechanism; an output member that rotates about the central axis at the second rotation speed; Equipped with The reduction mechanism is a non-circular wave generator that rotates together with the input member about the central axis at the first rotation speed; a flexible external gear having a flexible cylindrical portion located radially outward of the wave generator, the flexible external gear having a plurality of external teeth on an outer circumferential surface of the cylindrical portion; a rigid internal gear located radially outside the cylindrical portion, the rigid internal gear having a plurality of internal teeth on an annular inner peripheral surface centered on the central axis; and the number of the internal teeth of the rigid internal gear is different from the number of the external teeth of the flexible external gear, some of the external teeth of the plurality of external teeth are pushed by the wave generator to mesh with the internal teeth; As the wave generator rotates, the meshing position between the internal teeth and the external teeth moves in the circumferential direction at the first rotation speed, a strain wave gearing device in which one of the rigid internal gear and the flexible external gear rotates at the second rotation speed relative to the other of the rigid internal gear and the flexible external gear due to a difference in the number of teeth between the internal teeth and the external teeth, one of the rigid internal gear and the flexible external gear is located on one axial side of the output member, the output member is fixed to one of the flexible external gear and the rigid internal gear by a bolt inserted from the other axial side, The output member is an output base portion located on the other axial side of the reduction mechanism; a cylindrical output wall portion extending from an outer periphery of the output base portion toward one axial side; and the reduction mechanism is located radially inside the output wall portion, The housing includes: a housing base portion located on one axial side of the reduction mechanism; a cylindrical housing wall portion extending from an outer periphery of the housing base portion toward the other axial side; and an outer bearing interposed between the housing wall and the output wall; and the output wall portion is inserted radially inward of the housing wall portion, The outer bearing is disposed between an inner peripheral surface of the housing wall portion and an outer peripheral surface of the output wall portion.

11. 10. The strain wave gear device according to claim 9, the housing wall portion is inserted radially inside the output wall portion, The outer bearing is disposed between an outer peripheral surface of the housing wall portion and an inner peripheral surface of the output wall portion.

12. 12. The strain wave gear device according to claim 11, a tire fixed to the outer peripheral surface of the output wall portion; The strain wave gear device further comprises:

13. 7. The strain wave gear device according to claim 5 or 6, A housing that houses the reduction mechanism Furthermore, The output member is an output shaft extending toward the other axial side of the output base portion; and The housing includes: a first cover portion located on the other axial side of the reduction mechanism; a cylindrical second cover portion extending from an inner circumferential portion of the first cover portion toward the other axial side; and The output shaft is located radially inside the second cover portion.

14. 11. The strain wave gear device according to claim 10, the flexible external gear is fixed to the housing, The rigid internal gear is fixed to the output member by the bolt.

15. 15. The strain wave gear device according to claim 14, The flexible external gear is a disk portion extending radially outward from one axial side of the cylindrical portion; and the disk unit is fixed to the housing, The bolt is inserted into the rigid internal gear from the other axial side.

16. A wave gear device according to any one of claims 1 to 15, The input member is an output shaft of an electric motor.

17. A wave gear device according to any one of claims 1 to 15, The strain wave gear device, wherein the input member is a shaft coupling that can be connected to an output shaft of an electric motor.

18. A wave gear device according to any one of claims 1 to 15, The input member is an input shaft.

19. A robot comprising the strain wave gear device according to any one of claims 1 to 18.

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