JP2013170611A - Strain wave gearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a strain wave gearing capable of ensuring required strength when external teeth of a flex spline having flexibility are formed of a resin material.SOLUTION: A strain wave gearing 1 includes: a first member 10 and a second member 20 having internal teeth 11, 21, respectively, with different numbers of teeth from each other; a flexible member 30 having external teeth 31 formed of a resin material; and a strain wave generating mechanism 40 which bends the flexible member 30 into elliptical, makes the internal teeth 11, 21 of the first member 10 and the second member 20 be partially engaged with the external teeth 31, respectively, and also rotates the engaged portions of the internal teeth 11, 21 with the external teeth 31 in a circumferential direction. At least one of the internal teeth 11 of the first member 10 and the internal tooth 21 of the second member 20 has a gradually changing region 114, 214 of a tooth shape such that the tooth thickness of the internal tooth 11, 21 gradually decreases from the axial center side toward the end face side of the tooth.

Description

  The present invention relates to a wave gear device.

  The wave gear device is a flexure-meshing gear device, and is used for various applications as a small and highly efficient reduction gear. The wave gear device includes a circular spline having internal teeth, a flexible flex spline having external teeth, and a wave generator that partially flexibly engages the internal and external teeth by bending the flex spline into an elliptical shape. (Wave generation mechanism). Then, the wave generator to which the rotational driving force is inputted rotates the meshing portion of the inner teeth and the outer teeth in the circumferential direction, and the rotational driving force is decelerated by the differential between the circular spline and the flex spline.

  As such a wave gear device, for example, Patent Documents 1 and 2 disclose wave gear devices having different output methods. In the wave gear device of Patent Document 1, a circular spline is fixed to a housing, and a rotational driving force is output from a flex spline connected to an output shaft. On the other hand, the wave gear device of Patent Document 2 includes a set of circular splines that mesh with the external teeth of the flex spline and have different numbers of internal teeth, one circular spline fixed to the housing, and the output shaft. A rotational driving force is output from the other connected circular spline.

JP 2009-214779 A JP 2005-188740 A

  By the way, with the diversification of applications in which the wave gear device is used, there is a demand for the wave gear device to be reduced in weight and manufacturing cost. Under such circumstances, for example, it is conceivable to form a flex spline or the like with a resin material. However, especially in the system that outputs the rotational driving force from the circular spline, a load in the opposite direction from the inner teeth is applied to the outer teeth of the flexspline. Therefore, if the material is simply replaced with resin, The strength of the external teeth may be insufficient.

  The present invention has been made in view of such problems, and a wave gear device capable of ensuring the required strength when the outer teeth of a flexible flex spline are formed of a resin material. The purpose is to provide.

  In order to solve the above-described problem, according to the first aspect of the present invention, the first member and the second member that are arranged coaxially and have internal teeth with different numbers of teeth, the first member, and the second member A flexible member that is disposed inside the member and has external teeth formed of a resin material; and the flexible member is bent into an elliptical shape so that each of the internal teeth and the external member of the first member and the second member And a wave generating mechanism that partially meshes teeth and rotates a meshing portion of each of the inner teeth and the outer teeth in a circumferential direction, and at least one of the inner members of the first member and the second member In the tooth, a gradual change region of the tooth profile is formed so that the tooth thickness of the internal tooth gradually decreases from the axial center to the end face.

According to the invention of claim 2, the gradual change region is formed in a convex curved surface shape.
According to the invention of claim 3, the gradual change region is formed when the wave generating mechanism rotates the meshing portions of the inner teeth and the outer teeth in the circumferential direction. A boundary portion between the axial end surface of the inner tooth and the gradual change region is formed so as not to contact the tooth surface of the outer tooth.
According to the invention which concerns on Claim 4, each said internal tooth of said 1st member and said 2nd member is comprised so that rigidity may become higher than the said external tooth of the said flexible member.

  According to the invention according to claim 1, in the wave gear device, the external teeth of the flexible member are formed of a resin material, and the internal teeth of the first member and the second member mesh with the external teeth. Yes. Therefore, in the operating state of the wave gear device, a load in the opposite direction from the inner teeth is applied to the outer teeth of the flexible member. At this time, the external teeth made of a resin having a lower rigidity than that of the metal are elastically deformed by a reverse load and the tooth surface is curved. If it does so, the load which an external tooth applies from an internal tooth will become large as it goes to the edge part side of the axial direction of an internal tooth. It has been found that such a state is one of the causes that the strength of the external teeth is insufficient when the external teeth are made of resin.

  Therefore, in the present invention, a gradual change region of the tooth profile is formed on at least one of the internal teeth meshing with the resin external teeth. As a result, even when the external teeth are elastically deformed by a reverse load in the operating state of the wave gear device, the gradually changing region of the internal teeth comes into contact with the curved tooth surface. Accordingly, a load corresponding to the gradually changing inner tooth thickness is applied to the curved tooth surface of the outer tooth, so that the load applied in the width direction (axial direction) of the outer tooth can be made uniform. Can do. As described above, in the resin-made external teeth that are elastically deformed according to the present invention, it is possible to prevent a large load from being applied locally from the internal teeth, and thus it is possible to ensure the necessary strength as a whole. Further, by using a resin material for the external teeth of the flexible member, the wave gear device can be reduced in weight and the manufacturing cost can be reduced.

  According to the invention which concerns on Claim 2, you may make it form the gradual change area | region of an internal tooth in a convex curve shape. As described above, in the operating state of the wave gear device, the external teeth to which a reverse load is applied from each internal tooth are elastically deformed and the tooth surface is curved. At this time, the tooth surfaces of the external teeth of the flexible member are curved in a concave curved surface shape. Therefore, in the present invention, the gradual change region of the internal tooth that contacts the curved tooth surface of the external tooth is formed in a convex curved surface shape along the concave curved surface shape. Thereby, the load applied over the width direction of an external tooth can be equalized more reliably.

  According to the third aspect of the present invention, the gradual change region is rotated when the wave generating mechanism rotates the meshing portions of the internal teeth and the external teeth in the circumferential direction, that is, in the operating state of the wave gear device. When the force is decelerated and transmitted, the boundary portion of the inner teeth may be formed so as not to contact the tooth surface of the outer teeth. The boundary part of the internal tooth is an edge part located at the boundary between the end face of the internal tooth and the gradually changing region. For example, when the end face of the internal tooth and the edge of the tooth surface contact the tooth surface of the external tooth against the elastically deforming external tooth, a large stress is locally generated on the tooth surface of the external tooth that contacts the edge part. Will do. Therefore, in the operating state of the wave gear device, the shape of the gradually changing region is set so that the boundary between the end surface of the internal tooth and the gradually changing region is not in contact with the tooth surface of the external tooth. Thereby, since the edge part of an internal tooth does not contact the tooth surface of the external tooth which deform | transforms elastically, it can prevent generating a big stress locally on the tooth surface of an external tooth.

  According to the invention which concerns on Claim 4, each internal tooth of a 1st member and a 2nd member may be made to be comprised so that rigidity may become higher than the external tooth of a flexible member. If each internal tooth of the first member and the second member is made of resin, each internal tooth is elastically deformed by receiving a reaction force from the external tooth when the rotational driving force is transmitted. However, in order to make each inner tooth more rigid than the outer teeth of the flexible member, for example, a hard resin material (a resin material having a relatively high rigidity by adding another kind of hard resin or reinforcing material) or structurally By adopting a shape that improves the rigidity, the external teeth of the flexible member are mainly elastically deformed. In other words, in the driving state of the wave gear device, the tooth surface of the external tooth is mainly curved, and a gradual change region is formed in the internal tooth so as to follow this curved shape, so that the tooth width direction of the external tooth is extended. Thus, the applied load can be made more uniform. Moreover, since each internal tooth is made of resin, a gradual change region can be easily formed by molding using a mold, so that the processing cost can be reduced.

It is sectional drawing of the wave gear apparatus in embodiment. It is AA sectional drawing in FIG. It is an enlarged view which shows the internal tooth of a circular spline. It is a figure which shows the meshing state of each tooth | gear, and the load applied to an external tooth. It is the enlarged schematic diagram which shows the state which looked at the external tooth which elastically deformed from radial direction. It is a schematic diagram which expands and further shows the B part in FIG. It is a schematic diagram which expands and further shows the C part in FIG.

<Embodiment>
An embodiment embodying a wave gear device of the present invention will be described with reference to FIGS. In this embodiment, the wave gear device 1 receives a rotational driving force from an input shaft 2 rotatably supported by a housing H, and after being decelerated by a predetermined speed ratio, outputs a flexure meshing gear. Device. The housing H is a fixing member having a cylindrical portion for accommodating the speed change mechanism inside. The input shaft 2 and the output shaft 3 are shaft members that can relatively rotate about the input / output axis Ax.

(Configuration of wave gear device 1)
As shown in FIG. 1, the wave gear device 1 includes a first circular spline 10, a second circular spline 20, a flex spline 30, a wave generation mechanism 40, and a center shaft 50. The first circular spline 10 (corresponding to the “first member” of the present invention) has an annular shape, and is integrally fixed to the cylindrical portion of the housing H by bolt fastening so that the center axis thereof is the input / output axis Ax. Has been. A plurality of internal teeth 11 are formed on the inner peripheral surface of the first circular spline 10 as shown in FIG. Details of the number of teeth of the first circular spline 10, the shape and material related to the internal teeth 11 will be described later.

  The second circular spline 20 (corresponding to the “second member” of the present invention) has an annular shape, and is a flange portion formed at the axial end of the output shaft 3 so that the center axis thereof is the input / output axis Ax. It is integrally formed with 3a. Thereby, the first circular spline 10 and the second circular spline 20 are arranged coaxially in the wave gear device 1. A plurality of internal teeth 21 having a different number of teeth from the internal teeth 11 of the first circular spline 10 are formed on the inner peripheral surface of the second circular spline 20. Details of the number of teeth of the second circular spline 20, the shape and materials related to the internal teeth 21 will be described later.

  The flex spline 30 (corresponding to the “flexible member” of the present invention) is an annular member that is disposed inside the first circular spline 10 and the second circular spline 20 and is flexible at least in the radial direction. Further, outer teeth 31 formed of a resin material are formed on the outer peripheral surface of the flex spline 30. As shown in FIG. 1, the external teeth 31 of the flex spline 30 are set to have a tooth width spanning the internal teeth 11 and the internal teeth 21. In this embodiment, the external teeth 31 are set to have the same number of teeth as the second circular spline 20. Yes. Details of the external teeth 31 will be described later.

  The wave generating mechanism 40 is a mechanism that bends the flex spline 30 in an elliptical shape from the inner peripheral side and rotates the shape of the flex spline 30 that forms an elliptical shape. As shown in FIGS. 1 and 2, the wave generating mechanism 40 includes a turning plate 41 and two rollers 42. The swivel plate 41 has a disk shape and is integrally formed at the axial end of the input shaft 2 so that the center axis thereof is the input / output axis Ax. Further, two support shafts 411 extending in the direction of the input / output axis Ax are formed on the end surface of the swivel plate 41 at positions symmetrical with respect to the rotation center. The two rollers 42 are respectively supported by the two support shafts 411 of the swivel plate 41 and are rotatable about the support shaft 411.

  Further, the outer peripheral surface of each roller 42 presses the inner peripheral surface of the flex spline 30 to bend the flex spline 30 into an elliptical shape. At this time, in the flex spline 30, the external teeth 31 in the elliptical long axis direction mesh with the internal teeth 11 of the first circular spline 10 and the internal teeth 21 of the second circular spline 20. That is, of the external teeth 31 of the flex spline 30, the external teeth 31 located in the elliptical minor axis direction are in a state of being detached from the internal teeth 11, 21. Thus, the wave generation mechanism 40 partially meshes the inner teeth 11 and 21 and the outer teeth 31.

  Furthermore, when the turning plate 41 of the wave generating mechanism 40 rotates as the input shaft 2 rotates, the portion where each roller 42 presses the flex spline 30 moves. Thereby, the wave generation mechanism 40 rotates the shape of the flex spline 30 that forms an ellipse, and rotates the meshing portions of the inner teeth 11 and 21 and the outer teeth 31 in the circumferential direction.

  The center shaft 50 is a solid shaft member, and one end in the axial direction is fitted and fixed to the cylindrical inner peripheral surface of the input shaft 2 so that the center axis thereof is the input / output axis Ax. The other axial end of the center shaft 50 is inserted into the inner peripheral side of the flange portion 3 a of the output shaft 3 and supported through a bearing 51. Accordingly, the input shaft 2 and the output shaft 3 are configured to be relatively rotatable via the center shaft 50 and to support each other, thereby stabilizing the operation.

(Detailed configuration of inner teeth 11, 21 and outer teeth 31)
Next, internal teeth 11 (hereinafter referred to as “input-side internal teeth 11”) of the input-side first circular spline 10 and internal teeth 21 (hereinafter referred to as “output-side internal teeth 21” of the output-side second circular spline 20). The detailed configuration of the external teeth 31 of the flex spline 30 will be described. The first circular spline 10 and the second circular spline 20 are set to have different numbers of teeth as described above. In the present embodiment, the number of teeth of the first circular spline 10 is set to “72”, and the number of teeth of the second circular spline 20 is set. The number of teeth is set to “70”. Further, the flex spline 30 is set to have the same number of teeth as the second circular spline 20 as described above, and the number of teeth is set to “70” in the present embodiment. Accordingly, the reduction ratio of the wave gear device 1 in the present embodiment is “35: 1”.

  Here, the input side internal teeth 11, the output side internal teeth 21, and the external teeth 31 are formed of a resin material. More specifically, the input side internal teeth 11 and the output side internal teeth 21 are formed of a general-purpose engineer plastic such as polyacetal or polyamide as a resin material having no initial deformation. Moreover, although the 1st circular spline 10 and the 2nd circular spline 20 are set to a mutually different number of teeth as mentioned above, they are formed so that a tip circle and a root circle may become equal. As described above, the specifications of the input-side internal teeth 11 and the output-side internal teeth 12 are different, but in the present embodiment, by taking these into consideration and selecting the resin material forming each, Both inner teeth 11 and 21 have equal rigidity.

  The external teeth 31 are made of a resin material that is a high-strength material such as PEEK (polyetheretherketone) or aromatic polyamide in addition to general-purpose engineer plastics in consideration of stress due to initial deflection. Yes. Therefore, the input side internal teeth 11 and the output side internal teeth 21 are formed of a resin material harder than the external teeth 31 of the flexible flex spline 30 and are configured to have higher rigidity than the external teeth 31. Has been.

  Further, the input-side internal teeth 11 and the output-side internal teeth 21 have a gradual change region of the tooth profile so that the tooth thickness gradually decreases from the center side in the input / output axis Ax direction (tooth width direction) toward the end faces 112 and 212. 114, 214 are formed. Here, the gradual change region 114 of the tooth profile of the input-side internal tooth 11 will be described with reference to FIGS. In this embodiment, since the gradual change region 214 of the output side internal teeth 21 is the same as the gradual change region of the input side internal teeth 11, in FIG. 3, each part (111 to 115) of the input side internal teeth 11 is provided. Each part (211 to 215) of the corresponding output side internal tooth 21 is indicated by a symbol in parentheses.

  The gradually changing region 114 of the input-side internal teeth 11 is a region indicated by the hatched portion in FIG. 3, and the tooth thickness S2 on the end face 112 side is shorter than the tooth thickness S1 on the center side in the tooth width direction. Is formed. The gradual change region 114 is connected so that the boundary between the input side internal teeth 11 and the tooth surface 111 is smooth, and is formed in a convex curved shape. By such a gradual change region 114, the tooth tip surface 113 of the input-side internal tooth 11 is tapered toward the end surface 112 side in the tooth width direction.

  Here, the state in which the wave gear device 1 rotates the meshing portion of the input side internal teeth 11 and the output side internal teeth 21 and the external teeth 31 in the circumferential direction, that is, the rotational driving force is input from the input shaft 2 to reduce the speed. In a working state, the cross section including the meshing part can be shown by a schematic diagram as shown in FIG. At this time, a load in the direction of arrow R1 in FIG. 5 is applied to the external teeth 31 from the input-side internal teeth 11 fixed to the housing H. Further, the external tooth 31 receives a reaction force in the direction of arrow R2 in FIG. 5 from the output side internal tooth 21 in order to transmit the rotational driving force to the output side internal tooth 21. Arrows R1 and R2 are parallel to the circumferential direction of the flex spline 30 and in opposite directions.

  Therefore, the external teeth 31 in the operating state of the wave gear device 1 are elastically deformed by a reverse load and the tooth surface 311 is curved into a concave curved surface as shown in FIG. The state of elastic deformation 31 is exaggerated). In the present embodiment, as described above, the input-side internal teeth 11 and the output-side internal teeth 21 are configured to have higher rigidity than the external teeth 31, so that the input-side internal teeth 11 and the output-side internal teeth 11 are output. The amount of deformation by which the outer teeth 31 are elastically deformed is larger than that of the side inner teeth 21. Then, the gradual change region 114 of the input side internal tooth 11 that contacts the tooth surface 311 of the curved external tooth 31 is formed in a convex curved surface shape so as to follow the concave curved surface shape of the tooth surface 311.

  Further, as shown in FIG. 6, the gradual change region 114 of the input side internal tooth 11 has a boundary 115 between the end surface 112 of the input side internal tooth 11 and the gradual change region 114 in the operating state of the wave gear device 1. It is formed so as not to contact the tooth surface 311 of the tooth 31. Therefore, for example, the gradual change region 114 is formed so that the curvature near the boundary 115 becomes smaller than other portions. Thereby, a gap S <b> 1 is formed between the boundary portion 115 and the tooth surface 311. The same applies to the gradual change region 114 of the output side internal teeth 21, and as shown in FIG. 7, the gradual change region 214 has a boundary portion 215 of the output side internal teeth 21 that is not on the tooth surface 311 of the external teeth 31. It is formed to be in contact. Thereby, a gap S <b> 2 is formed between the boundary portion 215 and the tooth surface 311.

(Operation and effect of the wave gear device 1)
In the wave gear device 1 having such a configuration, the external teeth 31 are engaged with each other across the input side internal teeth 11 and the output side internal teeth 21. Therefore, the external teeth 31 formed of the resin material are elastically deformed by a load applied in the opposite direction in the circumferential direction when the wave gear device 1 is in operation, and the tooth surface 311 is curved. Then, in such a state, in the conventional wave gear device, as indicated by the broken line in the graph of FIG. 4, the load to which the external teeth are applied is the end side in the axial direction of each internal tooth (external teeth). It becomes larger toward the center side in the axial direction. For this reason, when the external teeth 31 are made of resin, it is considered that the local increase in stress in this way is a cause of insufficient strength of the external teeth 31.

  Therefore, the wave gear device 1 of the present embodiment is configured such that the tooth profile gradually changing regions 114 and 214 are formed in the input-side inner teeth 11 and the output-side inner teeth 21 that mesh with the resin-made outer teeth 31. As a result, even when the external teeth 31 are elastically deformed by a reverse load in the operating state of the wave gear device 1, the gradually changing regions 114 and 214 come into contact with the curved tooth surface 311. Therefore, since the load corresponding to the tooth thickness of the input side internal tooth 11 and the output side internal tooth 21 which change gradually is applied to the curved tooth surface 311 of the external tooth 31, as shown by the solid line in the graph of FIG. The load peak value in the prior art can be reduced. Thereby, the load applied over the width direction of the external teeth 31 can be made uniform. Therefore, it is possible to ensure the necessary strength as a whole. Further, by using a resin material for the external teeth 31 of the flex spline 30, the wave gear device 1 can be reduced in weight and the manufacturing cost can be reduced.

  In addition, the gradual change regions 114 and 214 are formed in a convex curved surface shape. As described above, in the operating state of the wave gear device 1, the external teeth 31 to which a reverse load is applied from the input-side internal teeth 11 and the output-side internal teeth 21 are elastically deformed, and the tooth surface 311 is curved into a concave curved surface shape. Will do. Therefore, in this embodiment, the gradual change regions 114 and 214 that come into contact with the tooth surface 311 of the curved external tooth 31 are formed in a convex curved surface shape along the concave curved surface shape. Thereby, the load applied over the tooth width direction of the external tooth 31 can be made more uniform.

  Further, the gradual change regions 114 and 214 are formed such that the boundary portions 115 and 215 are not in contact with the tooth surface 311 of the external tooth 31 in the operating state of the wave gear device 1. The boundary part 115 is an edge part located at the boundary between the end face 112 of the input side internal tooth 11 and the gradual change region 114. For example, if the edge portion contacts the tooth surface 311 of the external tooth 31 with respect to the elastically deforming external tooth 31, a large stress may be locally generated on the tooth surface 311 of the external tooth 31. Therefore, by setting the shape of the gradual change regions 114 and 214 so that the boundary portions 115 and 215 are not in contact with the tooth surface 311 of the external tooth 31, the tooth surface 311 of the external tooth 31 is locally provided. Generation of large stress can be reliably prevented.

  In addition, the input side internal teeth 11 and the output side internal teeth 21 are configured to have higher rigidity than the external teeth 31 of the flex spline 30. When the input side internal teeth 11 and the output side internal teeth 21 are formed of a resin material, the input side internal teeth 11 and the output side internal teeth 21 are elastically deformed by receiving a reaction force from the external teeth 31 when transmitting the rotational driving force. However, since the inner teeth 11 and 21 are made of a resin material harder than the outer teeth 31, the rigidity becomes higher than that of the outer teeth 31, so that the outer teeth 31 are mainly elastically deformed and the tooth surfaces 311 of the outer teeth 31 are formed. I try to bend. Then, by forming the gradual change region 114 of the input side internal teeth 11 and the gradual change region 214 of the output side internal teeth 21 along this curved shape, the load applied across the tooth width direction of the external teeth 31 is applied. Uniformity can be ensured more reliably. Moreover, since the input side internal teeth 11 and the output side internal teeth 21 are made of resin, the gradual change regions 114 and 214 can be easily formed by molding using a mold, thereby reducing the processing cost. Can do.

<Modification of Embodiment>
In the present embodiment, the gradual change region is formed in the input side internal teeth 11 of the first circular spline 10 and the output side internal teeth 21 of the second circular spline 20. In contrast, the gradual change region may be formed only on one of the internal teeth. In addition, the input side internal teeth 11 and the output side internal teeth 21 are formed with gradually changing regions 114 and 214 on both sides in the circumferential direction of the tooth surfaces 111 and 211, respectively. This is intended to cope with the case where the rotational driving force input to the wave gear device 1 is reversed. Therefore, when the rotational driving force input to the wave gear device 1 is constant, the gradual change regions 114 and 214 may be formed only on the side in contact with the external teeth 31.

  In addition, the gradual change regions 114 and 214 are convex curved surfaces, but may be formed so that the tooth thickness gradually decreases from the axial center side toward the end face side. It is good also as a flat slope inclined with respect to 111,211.

  Furthermore, although the input side internal teeth 11 and the output side internal teeth 21 are formed of a resin material harder than the external teeth 31, this is to add the rigidity of the material of the resin material itself or a reinforcing material. The rigidity which changes with is included. In addition, in order to configure the input side internal teeth 11 and the output side internal teeth 12 to be higher in rigidity than the external teeth 31, in addition to changing the material as described above, the rigidity is structurally improved. It is good also as a shape to make.

1: wave gear device, 2: input shaft, 3: output shaft, 3a: flange portion 10: first circular spline (first member)
11: (input side) internal tooth, 111: tooth surface, 112: end surface, 113: tooth tip surface 114: gradual change region, 115: boundary portion 20: second circular spline (second member)
21: (output side) internal teeth, 211: tooth surface, 211: end surface, 213: tooth tip surface 214: gradually changing region, 215: boundary 30: flex spline (flexible member), 31: external tooth, 311: Tooth surface 40: Wave generation mechanism, 41: Swivel plate, 411: Support shaft, 42: Roller 50: Center shaft, 51: Bearing H: Housing, Ax: Input / output axis

Claims (4)

A first member and a second member arranged on the same axis and having internal teeth with different numbers of teeth;
A flexible member disposed inside the first member and the second member and having external teeth formed of a resin material;
The flexible member is bent into an oval shape so that the inner teeth and the outer teeth of the first member and the second member are partially meshed, and the meshing sites of the inner teeth and the outer teeth are surrounded. A wave generation mechanism that rotates in a direction,
At least one internal tooth of the first member and the second member is formed with a gradual change region of a tooth profile so that the tooth thickness of the internal tooth gradually decreases from the axial center side to the end face side. Wave gear unit. In claim 1,
The gradual change region is a wave gear device formed in a convex curved surface shape. In claim 1 or 2,
The gradual change region includes an axial end surface of the inner tooth in which the gradual change region is formed when the wave generating mechanism rotates the meshing portions of the inner teeth and the outer teeth in the circumferential direction. The wave gear device formed so that a boundary portion with the gradual change region is not in contact with a tooth surface of the external tooth. In any one of Claims 1-3,
The wave gear device configured such that each of the inner teeth of the first member and the second member has higher rigidity than the outer teeth of the flexible member.

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