GEAR DEVICE OF THE BENDING ENGINE TYPE

Abstract

Gear device (1) of the bending engagement type, comprising: a wave generator (10A); an external gear (12) that is bent and deformed by the shaft generator (10A); a shaft generator bearing (15) arranged between the shaft generator (10A) and the outer gear (12); and an internal gear (22g, 23g), wherein a rolling element (15A, 15B) of the shaft generator bearing (15) contains a roller, an end surface of the roller protrudes in an axial direction towards a driven element (56) from a engagement area (Ga1, Gb1) of the internal gear (22g, 23g) and the external gear (12) and towards an axial outside of the engagement area (Ga1, Gb1), and the outer gear (12) has a section that is not engaged with the inner gear (22g, 23g) at a position where the outer gear (12) and the inner gear (22g, 23g) are engaged in a circumferential direction of the outer gear (12), which is an axial position where the end face of the roller is arranged in the axial direction.

Description

BACKGROUND OF THE INVENTIONField of the invention

[0001] The present invention relates to a flexural engagement type gear device. Description of the state of the art

[0002] A prior art flexural engagement type gear device is provided with a wave generator, a wave generator bearing including a roller bearing, an external gear, and an internal gear.

[0003] When rotation is applied to the shaft generator, the external gear is deformed via the shaft generator bearing, and the meshing position of the external gear and the internal gear moves circularly in accordance with the rotation of the shaft generator. As a result, a relative deceleration rotation is generated between the internal gear and the external gear according to the difference in the number of teeth, and the deceleration rotation is extracted from the external gear or the internal gear and output to a driven element (see, for example, Japanese Unexamined Patent Publication No. 2009-299765). SUMMARY OF THE INVENTION

[0004] In the prior art bending engagement type gear device, a roller which is a rolling element of the wave generator bearing is arranged within the engagement area of ​​the internal gear and the external gear.

[0005] In the bending engagement type gear device, when a moment is applied from a driven element side, the meshing load of the internal gear and the external gear may be biased toward the driven element. In this case, contact pressure with the external gear increases near an end portion of the driven element side in an axial direction of the roller, and bending stress is generated in the external gear, thus creating a possibility of causing damage.

[0006] An object of the present invention is to effectively protect an external gear.

[0007] This object is achieved by a gear device according to claim 1.

[0008] According to one aspect of the present invention, there is provided a bending engagement type gear device comprising: a wave generator, an external gear bent and deformed by the wave generator, a wave generator bearing disposed between the wave generator and the external gear, and an internal gear, wherein a rolling element of the wave generator bearing includes a roller, and an end surface of the roller protrudes in an axial direction toward a driven member from an engagement portion of the internal gear and the external gear.

[0009] According to the present invention, it is possible to effectively protect the external gear. SHORT DESCRIPTION OF THE CHARACTERS Fig. 1 is a cross-sectional view illustrating a flexural engagement type gear device according to a first embodiment of the present invention. Fig. 2 is an enlarged cross-sectional view illustrating a positional relationship between an engagement portion of a first internal gear, a second internal gear, and an external gear and a rolling element of a wave generator bearing. Fig. 3 is an enlarged cross-sectional view illustrating a positional relationship between an engagement portion of a first internal gear, a second internal gear, and an external gear and a rolling element of a wave generator bearing in a comparative example. Fig. 4 is a cross-sectional view illustrating a flexural engagement type gear device according to a second embodiment of the present invention. Fig. 5 is an enlarged cross-sectional view illustrating the positional relationship between the meshing portion of the first internal gear, the second internal gear, and the external gear and the rolling element of the wave generator bearing. DETAILED DESCRIPTION OF THE INVENTION (First Embodiment)

[0010] Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a cross-sectional view illustrating a flexural engagement type gear device according to a first embodiment of the present invention.

[0011] Hereinafter, the direction along a rotation axis O1 of the drawing is defined as an axial direction, the direction perpendicular to the rotation axis O1 is defined as a radial direction, and the rotation direction centered on the rotation axis O1 is defined as a circumferential direction.

[0012] As in Fig. 1, a bending engagement type gear device 1 is a tubular bending engagement type gear device in which an external gear 12 is bent and deformed to transmit rotational motion about the rotation axis O1.

[0013] Specifically, the flexion-engagement type gear device 1 is provided with a wave generator shaft 10, the external gear 12 that is bent and deformed by the wave generator shaft 10, a first internal gear 22g and a second internal gear 23g that mesh with the external gear 12, and a wave generator bearing 15. Furthermore, the flexion-engagement type gear device 1 is provided with a first housing 22, an internal gear member 23, a second housing 24, a first cover 26, a second cover 27, drive bearings 31 and 32, and a main bearing 33.

[0014] The wave generator shaft 10 has a hollow shaft shape and includes a wave generator 10A having an elliptical outer shape of a cross section perpendicular to the rotation axis O1, and shaft sections 10B and 10C provided on both sides of the wave generator 10A in the axial direction and having a circular outer shape of a cross section perpendicular to the rotation axis O1. The elliptical shape is not limited to a geometrically exact ellipse and includes a substantially elliptical shape. The wave generator shaft 10 rotates around the rotation axis O1, and the center of the outer shape in the cross section perpendicular to the rotation axis O1 of the wave generator 10A coincides with the rotation axis O1. The wave generator shaft 10 is a drive shaft connected to a drive source (not shown), such as a motor, and to which a driving force is input.

[0015] The external gear 12 is a flexible cylindrical metal and has teeth on the outer circumference.

[0016] The first internal gear 22g and the second internal gear 23g are arranged so that the axial centers are aligned with the rotation axis O1, the first internal gear 22g is connected to an external member 55, and the second internal gear 23g is connected to a driven member 56.

[0017] The first internal gear 22g and the second internal gear 23g are provided side by side in the axial direction and mesh with the external gear 12. Specifically, one of the first internal gear 22g and the second internal gear 23g meshes with the tooth portion on one side of the center of the external gear 12 in the axial direction, and the other meshes with the tooth portion on the other side of the center of the external gear 12 in the axial direction. The first internal gear 22g is configured such that an internal tooth is provided at a corresponding portion of an inner peripheral portion of the first housing 22. The second internal gear 23g is configured such that an internal tooth is provided at a corresponding portion of an inner peripheral portion of the internal gear member 23.

[0018] The shaft generator bearing 15 is arranged between the shaft generator 10A and the external gear 12. The shaft generator bearing 15 includes a plurality of rolling elements (rollers) 15A and 15B and a retainer 15C for retaining the plurality of rolling elements 15A and 15B. The plurality of rolling elements 15A and 15B roll as rolling contact surfaces around the outer peripheral surface of the shaft generator 10A and the inner peripheral surface of the external gear 12.

[0019] The rolling element 15A is located inside the first internal gear 22g in the radial direction via the external gear 12, and the plurality of rolling elements 15A are provided side by side in the circumferential direction to perform rolling. Similarly, the rolling element 15B is located inside the second internal gear 23g in the radial direction via the external gear 12, and the plurality of rolling elements 15B are provided side by side in the circumferential direction to perform rolling.

[0020] The shaft generator bearing 15 may include an inner ring separate from the shaft generator 10A and an outer ring separate from the external gear 12.

[0021] On both sides of the external gear 12 and the holder 15C of the shaft generator bearing 15 in the axial direction, spacer rings 36 and 37 are provided as regulating members, which come into contact with the external gear 12 and the holder 15C and which regulate the movement of the external gear 12 and the holder 15C in the axial direction.

[0022] The first housing 22 and the second housing 24 are connected to each other with a screw 57, which is a connecting member, and cover the outer side of the first internal gear 22g, the second internal gear 23g, and the external gear 12 in the radial direction. Of these housings, the first housing 22 is provided with internal teeth in a part of the inner peripheral portion, as described above, and is formed integrally with the first internal gear 22g.

[0023] In addition, the first housing 22 and the second housing 24 are provided with screw connection holes 22h and 24h located at end portions on a counter load side (right side in Fig. 1) extending continuously in the axial direction. When the flexural engagement type gear device 1 is connected to the outer member 55 (for example, an arm member on a base end side of a robot) outside the device, the first housing 22 and the second housing 24 are connected by being jointly fastened to the outer member 55 with a screw 53, which is a connecting member, via the screw connecting holes 22h and 24h. These screw connecting holes 22h and 24h are provided at a plurality of locations in the circumferential direction. Furthermore, the first housing 22 and the second housing 24 include screw holes 22j and 24j separate from the screw connecting holes 22h and 24h, and are connected (temporarily fastened) to each other by the screw 57 (described above) inserted and screwed into the screw holes 22j and 24j.

[0024] At least a part of the internal gear member 23 is arranged radially inside the second housing 24 and radially outside the wave generator shaft 10. Furthermore, as described above, the internal gear member 23 is provided with internal teeth in a part of the inner peripheral portion and is formed integrally with the second internal gear 23g.

[0025] The first cover 26 and the first housing 22 have screw holes 26k and 22k on the counterload side and are connected to each other by a screw 51 inserted into the screw holes 26k and 22k and screwed therein.

[0026] The first cover 26 covers the outer peripheral portion on one end side of the wave generator shaft 10.

[0027] The second cover 27 is connected to the internal gear member 23 and covers the outer peripheral portion on the other end side of the wave generator shaft 10. The second cover 27 and the internal gear member 23 are provided with screw connection holes 27h and 23h located at end portions on a load side (left side in Fig. 1) extending continuously in the axial direction. When the flexural engagement type gear device 1 is connected to the driven member 56 (for example, an arm member on a tip end side of the robot) outside the device from the load side, the second cover 27 and the internal gear member 23 are connected to the driven member 56 via the screw connecting holes 27h and 23h by being fastened together with a screw 54, which is a connecting member. These screw connecting holes 27h and 23h are provided at a plurality of locations in the circumferential direction. Furthermore, the second cover 27 and the internal gear member 23 include screw holes 27j and 23j separate from the screw connecting holes 27h and 23h, and are connected (temporarily fastened) to each other by a screw 52 inserted and screwed into the screw holes 27j and 23j.

[0028] The drive bearing 31 is, for example, a ball bearing having an inner ring 31a, an outer ring 31b, and a rolling element 31c, and is arranged between the shaft portion 10B of the wave generator shaft 10 and the first cover 26. The first cover 26 rotatably supports the wave generator shaft 10 via the drive bearing 31. The drive bearing 31 is not limited to the ball bearing; various bearings can be used, such as a roller bearing. Furthermore, if the inner ring does not have a dedicated inner ring or outer ring, it may be formed integrally with the wave generator shaft 10, or the outer ring may be formed integrally with the first cover 26.

[0029] The drive bearing 32 is, for example, a ball bearing having an inner ring 32a, an outer ring 32b, and a rolling element 32c, and is arranged between the shaft portion 10C of the wave generator shaft 10 and the second cover 27. The second cover 27 rotatably supports the wave generator shaft 10 via the drive bearing 32. The drive bearing 32 is not limited to the ball bearing; various bearings can be used, such as a roller bearing. Furthermore, if the inner ring does not have a dedicated inner ring or outer ring, it may be formed integrally with the wave generator shaft 10, or the outer ring may be formed integrally with the second cover 27.

[0030] In addition, the drive bearings 31 and 32 are both bearings with a seal in which a lubricant is sealed, but these bearings do not need to have a seal.

[0031] The main bearing 33 is, for example, a ball bearing including an inner ring 33a, an outer ring 33b, and a rolling element 33c, and is disposed between the internal gear member 23 and the second housing 24. The second housing 24 rotatably supports the internal gear member 23 via the main bearing 33. The main bearing 33 is not limited to the ball bearing, and various bearings can be used. The main bearing 33 may be, for example, a crossed roller bearing or may include multiple bearings (angular contact ball bearings, tapered roller bearings, and the like) spaced apart in the axial direction between the internal gear member 23 and the second housing 24. Furthermore, in the main bearing 33, if it does not have a dedicated inner ring or outer ring, the inner ring may be formed integrally with the internal gear member 23, or the outer ring may be formed integrally with the second housing 24.In addition, the main bearing 33 is not particularly limited and may be a bearing with a seal in which a lubricant is sealed.

[0032] On the outer side of the drive bearings 31 and 32 and the main bearing 33 in the axial direction with respect to a lubricant seal space S in which mechanical parts of the flexural engagement type gear device 1 are accommodated, seal portions 41 to 43, which are shaft seal portions, are provided to ensure the sealing property of these bearings.

[0033] The sealing portion 41 of the drive bearing 31 extends from the first cover 26 in the radial direction inward to the vicinity of the outer peripheral surface of the wave generator shaft 10 (shaft portion 10B) and includes a wall surface covering the outside of the drive bearing 31 in the axial direction and forming a narrow gap with the outer periphery of the shaft portion 10B to hinder the movement of the lubricant.

[0034] The sealing portion 42 of the drive bearing 32 extends from the second cover 27 in the radial direction inward to the vicinity of the outer peripheral surface of the wave generator shaft 10 (shaft portion 10C) and includes a wall surface covering the outside of the drive bearing 32 in the axial direction and forming a narrow gap with the outer periphery of the shaft portion 10C to hinder the movement of the lubricant.

[0035] The sealing portion 43 of the main bearing 33 extends radially inward from the second housing 24 to near the outer peripheral surface of the second cover 27, and includes a wall surface that covers the outer side of the main bearing 33 in the axial direction, forming a narrow gap with the outer periphery of the second housing 27 to prevent the movement of lubricant. Furthermore, the inner side of the sealing portion 43 (the main bearing 33 side) includes a protrusion that protrudes radially outward from the second cover 27. A labyrinth structure is formed by the sealing portion 43 and the protrusion. [Arrangement of engagement area and rolling elements]

[0036] Fig. 2 is an enlarged cross-sectional view illustrating the positional relationship between the meshing portion of the first internal gear 22g, the second internal gear 23g, and the external gear 12 and the rolling element 15B of the wave generator bearing 15.

[0037] As described above, each of the rolling elements 15A and 15B of the wave generator bearing includes 15 rollers (including needles).

[0038] In the rolling element 15B corresponding to the second internal gear 23g connected to the driven element 56 (arrangement overlapping in the axial direction), the end surface in the axial direction on the side of the driven element 56 is in the entire width CL in the axial direction (left end surface of the rolling element 15B in Fig. 2, in other words, a portion closest to the driven member 56 in the axial direction) toward the driven member 56 side (in the axial direction) from an engagement area Gb1 of the second internal gear 23g and the external gear 12.

[0039] Fig. 3 is an enlarged cross-sectional view illustrating the positional relationship between the meshing portion of the first internal gear 22g, the second internal gear 23g, and the external gear 12 and the rolling element 15B of the wave generator bearing 15 in a comparative example not provided with a characteristic configuration of the present invention. In the drawing of the comparative example, for the sake of simplicity, the same reference numerals are assigned as those in the flexural meshing type gear device 1 embodying the invention (configuration of Fig. 2) attached.

[0040] In the bending engagement type gear device 1, when a moment load is applied from the driven member 56 side due to various factors such as an external force and the weight of members during a rotating operation, the engagement load between the second internal gear 23g connected to the driven member 56 and the external gear 12 may be biased toward the driven member 56 side.

[0041] In this case, the focus is on the comparative example of Fig. 3, the contact pressure with respect to the external gear 12 is applied to the end portion (near the corner portion) of the rolling element 15B on the driven member 56 side, and the bending stress is applied to the external gear 12, so that there is a possibility of damage.

[0042] On the other hand, in the configuration of Fig. 2, even in a case where the engagement load between the second internal gear 23g and the external gear 12 is biased toward the driven member 56, the end surface of the rolling element 15B in the axial direction on the driven member 56 side is separated from the engagement area Gb1 of the second internal gear 23g and the external gear 12. Therefore, it is possible to avoid the concentration of contact pressure at the end portion of the rolling element 15B on the driven member 56 side and suppress the occurrence of damage to the external gear 12.

[0043] The second internal gear 23g includes chamfered portions 23m and 23m formed at both end portions of the tooth tips of the internal teeth in the axial direction, and the above-described engagement area Gb1 indicates an area excluding the chamfered portions 23m and 23m of the tooth tips of the internal teeth of the second internal gear 23g.

[0044] The end surface of the rolling element 15B in the axial direction on the driven element 56 side protrudes further toward the driven element 56 side from the area Gb2 including the chamfered portions 23m and 23m on both sides of the second internal gear 23g. That is, the end surface of the rolling element 15B in the axial direction on the driven element 56 side protrudes further toward the driven element 56 side from a terminal end 23ms of the chamfered portion 23m on the driven element 56 side of the second internal gear 23g. Here, the terminal end 23ms of the chamfered portion 23m is a portion where the inner diameter of the chamfered portion 23m is maximized.

[0045] As a result, it is possible to more effectively avoid the concentration of contact pressure on the end portion of the rolling element 15B on the driven member 56 side when the meshing load of the second internal gear 23g and the external gear 12 is preloaded, and to suppress the occurrence of damage.

[0046] In the present embodiment, since the entire axial region of the second internal gear 23g lies within the axial region of the external gear 12, the meshing region Gb1 between the second internal gear 23g and the external gear 12 coincides with the axial region of the second internal gear 23g. However, the present invention is not limited to this, and in a case where the entire axial region of the external gear 12 lies within the axial region of the second internal gear 23g, the axial region of the external gear 12 is the meshing region Gb1. Moreover, in a case where the axial region of the second internal gear 23g and the axial region of the external gear 12 are shifted in the axial direction and mesh with each other, the region where both mesh with each other is the meshing region Gb1.

[0047] It is unlikely that the bias of the engagement load toward the driven member 56 side due to the moment load during the rotational operation occurs at the end portion of the second internal gear 23g opposite to the driven member 56 side. Therefore, as shown in Fig. 2, the end face of the rolling element 15B in the axial direction opposite to the side of the driven element 56 (right end face of the rolling element 15B in Fig. 2) within the ranges of the meshing area Gb1 of the second internal gear 23g and the external gear 12 and the area Gb2 including the chamfer portion of the second internal gear 23g.

[0048] In addition, the bias of the engagement load toward the driven member 56 side is unlikely to occur due to the moment load during the rotation between the first internal gear 22g and the external gear 12. Therefore, as shown in Fig. 2, the end face of the roller in the axial direction (left end face of the rolling element 15A in Fig. 2) located at the end portion on the driven member 56 side in the entire width CR of the rolling element 15A in the axial direction, within the ranges of the meshing area Ga1 of the first internal gear 22g and the external gear 12 and the area Ga2 including the chamfer portion of the first internal gear 22g. [Operational description]

[0049] In the bending engagement type gear device 1 having the above configuration, when the wave generator shaft 10 is rotationally driven by a drive source such as a motor, the motion of the wave generator 10A is transmitted to the external gear 12. In this case, the external gear 12 is set to a shape along the outer peripheral surface of the wave generator 10A and is bent into an elliptical shape, viewed from the axial direction, having a major axis portion and a minor axis portion. Moreover, the external gear 12 meshes with the fixed first internal gear 22g at the major axis portion. Therefore, the external gear 12 does not rotate at the same speed as the wave generator 10A, and the wave generator 10A rotates relatively within the external gear 12.During this relative rotation, the external gear 12 is bent and deformed such that a major axis position and a minor axis position move in the circumferential direction. The period of this deformation is proportional to the rotation period of the wave generator shaft 10.

[0050] When the external gear 12 is bent and deformed, the main axis position thereof moves, so that the position where the external gear 12 and the first internal gear 22g mesh changes in the rotation direction. For example, assuming that the number of teeth of the external gear 12 is 100 and the number of teeth of the first internal gear 22g is 102, every time the meshing position is rotated, the meshing teeth of the external gear 12 and the first internal gear 22g are shifted. For example, in a case where the outer member 55 is fixed, the first internal gear 22g is fixed, so that the external gear 12 rotates. With the above number of teeth, the rotation of the wave generator shaft 10 is decelerated at a reduction ratio of 100:2 and transmitted to the external gear 12.

[0051] On the other hand, since the external gear 12 meshes with the second internal gear 23g, the engagement position between the external gear 12 and the second internal gear 23g also changes in the rotational direction due to the rotation of the wave generator shaft 10. Here, assuming that the number of teeth of the external gear 12 and the number of teeth of the second internal gear 23g are the same, the external gear 12 and the second internal gear 23g do not rotate relative to each other, and the rotational movement of the external gear 12 is transmitted to the second internal gear 23g at a reduction ratio of 1:1. As a result, the rotational movement of the wave generator shaft 10 is decelerated at a reduction ratio of 100:2, is transmitted to the internal gear member 23 and the second cover 27, and is output to the driven member 56. [Technical Effects of the Present Embodiment]

[0052] In the flexural engagement type gear device 1, the end surface of the rolling element 15B in the axial direction of the wave generator bearing 15, which corresponds to the second internal gear 23g on the driven member 56 side, protrudes toward the driven member 56 side from the engagement portion Gb1 of the second internal gear 23g and the external gear 12.

[0053] Therefore, even in a case where the engagement load between the second internal gear 23g and the external gear 12 is biased toward the driven member 56, it is possible to avoid the concentration of contact pressure at the end portion of the rolling element 15B on the driven member 56 side and suppress the occurrence of damage to the external gear 12.

[0054] Further, in the flexural engagement type gear device 1, the end surface of the rolling element 15B protrudes in the axial direction on the driven member 56 side toward the driven member 56 side from the terminal end 23ms of the driven member 56 side chamfer portion 23m of the second internal gear 23g.

[0055] As a result, when the engagement load between the second internal gear 23g and the external gear 12 is biased toward the driven member 56, it is possible to more effectively avoid the concentration of contact pressure at the end portion of the rolling element 15B on the driven member 56 side and further suppress the occurrence of damage to the external gear 12.

[0056] Moreover, the other end surface of the rolling element 15B in the axial direction opposite to the driven member 56 is within the meshing range Gb1 of the second internal gear 23g and the external gear 12.

[0057] As described above, since the rolling element 15B has a structure in which the end surface on the driven element 56 side protrudes from the engagement region Gb1 toward the driven element 56 side, by setting the other end surface of the rolling element 15B in the axial direction within the engagement region Gb1, it is possible to suppress the size increase of the rolling element 15B in the axial direction, and by reducing the contact area of ​​the rolling element 15B during rolling, it is possible to reduce the loss during rolling. (Second embodiment)

[0058] A second embodiment of the present invention will be described in detail with reference to the drawings.

[0059] Since most of the configuration of a flexural engagement type gear device 1 of the second embodiment is the same as that of the flexural engagement type gear device 1 of the first embodiment, only differences therefrom will be mainly described.

[0060] Fig. Fig. 4 is a cross-sectional view illustrating a flexural engagement type gear device 1 according to a second embodiment, and Fig. 5 is an enlarged cross-sectional view illustrating the positional relationship between the engagement portion of the first internal gear 22g, the second internal gear 23g, and the external gear 12 and the rolling elements 15A and 15B of the wave generator bearing 15.

[0061] As in Fig. 4 and Fig.5, the flexural engagement type gear device 1 in the second embodiment differs from the above-described flexural engagement type gear device 1 of the first embodiment in that the entire area of ​​the rolling element 15A corresponding to the first internal gear 22g in the axial direction is within the engagement area Ga1 of the first internal gear 22g and the external gear 12, and is within the area Ga2 including the chamfer portions at both end portions of the first internal gear 22g.

[0062] The bias of the engagement load toward the driven member 56 side due to the moment load during rotation is unlikely to occur in the first internal gear 22g. Therefore, even if the entire area of ​​the rolling element 15A in the axial direction is within the engagement area Ga1 of the first internal gear 22g and the external gear 12, the concentration of contact pressure is unlikely to occur at the end portion of the rolling element 15A, as in the rolling element 15B on the second internal gear 23g side.

[0063] On the other hand, by setting the entire area of ​​the rolling element 15A within the engagement area Ga1, it is possible to suppress the size increase of the rolling element 15A in the axial direction, and by reducing the contact area of ​​the rolling element 15A during rolling, it is possible to reduce the loss during rolling. [More]

[0064] The embodiments of the present invention will be described below, and the present invention is not limited to each of the above embodiments.

[0065] For example, in each of the above embodiments, a so-called tubular flexure engagement type gear device is illustrated as the flexure engagement type gear device 1. However, the present invention is not limited thereto and is also applicable to, for example, a so-called pot-type or cylinder-hat-type flexure engagement type gear device.

[0066] These flexural engagement type gear devices are configured to include an internal gear, and in a case where the internal gear or the external gear is connected to the driven member, the end surface of the rolling element in the axial direction including the roller of the wave generator bearing is configured to protrude toward a driven member from the engagement portion of the internal gear and the external gear.

[0067] As a result, even in the case of a cup-type or cylinder-hat-type gear device of the flexural engagement type, in a case where the engagement load between the internal gear and the external gear is biased toward the driven member, it is possible to avoid the concentration of the contact pressure at the end portion of the rolling element on the driven member side and to suppress the occurrence of damage to the external gear.

[0068] Furthermore, the details shown in the embodiments described above can be appropriately changed without departing from the scope of the invention. Brief description of the reference symbols 1 Gear device of bending engagement type 10A wave generator 12 external gear 15 shaft generator bearings 15A, 15B rolling elements 22 first housing 22g first internal gear 23 Internal gear element 23g second internal gear 24 second housing 55 exterior element 56 driven element Ga1, Gb1 intervention area

Claims

[1] A gear device (1) of the bending engagement type, comprising: a wave generator (10A); an external gear (12) which is bent and deformed by the wave generator (10A); a shaft generator bearing (15) arranged between the shaft generator (10A) and the external gear (12); and an internal gear (22g, 23g), where a rolling element (15A, 15B) of the shaft generator bearing (15) contains a roller, an end surface of the roller protrudes in an axial direction toward a driven element (56) from an engagement portion (Ga1, Gb1) of the internal gear (22g, 23g) and the external gear (12) and toward an axial outer side of the engagement portion (Ga1, Gb1), and the external gear (12) has a portion that does not mesh with the internal gear (22g, 23g) at a position where the external gear (12) and the internal gear (22g, 23g) mesh in a circumferential direction of the external gear (12), which is an axial position where the end face of the roller is located in the axial direction. [2] A gear device (1) of the bending engagement type according to claim 1, wherein a chamfer portion (23m) is provided at an end portion of an internal tooth of the internal gear (22g, 23g) in the axial direction, and the end face of the roller protrudes in the axial direction toward the driven member (56) from a terminal end (23ms) of the chamfer portion (23m). [3] A gear device (1) of the bending engagement type according to claim 1 or 2, wherein the internal gear (22g, 23g) includes a first internal gear (22g) and a second internal gear (23g) connected to the driven element (56), and the end face of the roller protrudes in the axial direction toward the driven member (56) from the engagement portion (Gb1) of the second internal gear (23g) and the external gear (12). [4] The bending engagement type gear device (1) according to claim 3, wherein the roller corresponding to the first internal gear (22g) is located within the engagement range (Ga1) of the first internal gear (22g) and the external gear (12). [5] The bending engagement type gear device (1) according to any one of claims 1 to 4, wherein the other end surface of the roller in the axial direction is located within the engagement range (Ga1, Gb1) of the internal gear (22g, 23g) and the external gear (12).

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