Gear device of bending-grip type and method for its manufacture

Abstract

Gear device (1) of the bending engagement type, comprising: a wave generator (30A); an external gear (32) which is bent and deformed by the shaft generator (30A); an internal gear (41G, 42G) that engages with the external gear (32); and a shaft generator bearing (31) which is arranged between the outer gear (32) and the shaft generator (30A), wherein the shaft generator bearing (31) contains an outer ring (31a) which is separated from the outer gear (32), the outer gear (32) has a coating of the same component on an inner circumferential surface and a tooth surface and the coating has properties that allow the coating to be removed in an engagement section by the engagement of the outer gear (32) with the inner gear (41G, 42G) when the bending engagement type gear device (1) is operated.

Description

Technical area

[0001] The present invention relates to a gear device of the bending engagement type and a method for its manufacture. State of the art

[0002] In the prior art, a bending engagement type gear device is known, which is provided with an external gear that is bent and deformed (see, for example, PTL 1). The external gear is bent and deformed by a wave generator, which is internally fitted via a wave generator bearing and in which the wave generator rotates. Furthermore, the external gear meshes with a rigid internal gear. Citation listPatent literature

[0003] [PTL 1] Japanese Unexamined Patent Publication No. 2018-096510 Summary of the inventionTechnical problem

[0004] In the prior art, a tooth surface of the external gear that is bent and deformed and a tooth surface of the internal gear may have a low affinity level, resulting in a problem of increased backlash. Additionally, there is a problem that fretting wear is likely to occur between an inner peripheral surface of the external gear that is bent and deformed and an outer ring of the shaft generator bearing.

[0005] One object of the present invention is to provide a gear device of the bending engagement type which is able to suppress dead load and frictional wear on the inner circumferential surface of an external gear, and a method for its manufacture. Solution to problem

[0006] A bending engagement type gear device of the present invention includes a wave generator, an external gear that is bent and deformed by the wave generator, an internal gear that engages with the external gear, and a wave generator bearing disposed between the external gear and the wave generator.

[0007] The external gear has a coating on an inner peripheral surface and a tooth surface.

[0008] The coating has properties that enable the coating to be removed in an engagement portion by engagement of the external gear with the internal gear when the bending engagement type gear device is operated.

[0009] Another bending engagement type gear device of the present invention includes a wave generator, an external gear that is bent and deformed by the wave generator, an internal gear that engages with the external gear, and a wave generator bearing disposed between the external gear and the wave generator.

[0010] The external gear has a coating on an inner peripheral surface and on a part except an engaging portion of a tooth surface, and the engaging portion does not have the coating.

[0011] A method for manufacturing a bending-type gear device of the present invention is a method for manufacturing a bending-type gear device comprising a shaft generator, an outer gear which is bent and deformed by the shaft generator, an inner gear which engages with the outer gear, and a shaft generator bearing which is arranged between the outer gear and the shaft generator.

[0012] The method includes a coating step of coating at least an inner peripheral surface and a tooth surface of the external gear and an assembling step of assembling the flexural engagement type gear device by combining a plurality of components including the coated external gear.

[0013] In the coating step, coating is performed such that a coating in an engaging portion is removed by engaging the internal gear when the assembled bending engagement type gear device is operated. Advantageous effects of the invention

[0014] According to the present invention, it is possible to provide a flexural engagement type gear device capable of suppressing backlash and fretting on the inner peripheral surface of an external gear, and a method for manufacturing the same. Short description of characters Fig. 1 is a cross-sectional view illustrating a flexural engagement type gear device according to Embodiment 1 of the present invention. Fig. 2 is a perspective view illustrating an external gear of Embodiment 1. Fig. 3 is an enlarged perspective view showing a tooth surface of the external gear. Fig. Figure 4 is an explanatory diagram showing a backlash. Fig. 5 is a flowchart illustrating a method for manufacturing the flexural engagement type gear device of Embodiment 1. Fig. 6 is a flowchart illustrating a method for manufacturing a flexural engagement type gear device of Embodiment 2. Description of embodiments

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. (Embodiment 1)

[0016] Fig. 1 is a cross-sectional view illustrating a flexural engagement type gear device according to Embodiment 1 of the present invention. Fig. 2 is a perspective view illustrating an external gear of Embodiment 1. Fig. 3 is an enlarged perspective view showing a tooth surface of the external gear.

[0017] A flexure engagement type gear device 1 of Embodiment 1 is a speed reducer in which a state in which an external gear 32 and internal gears 41G and 42G are non-affine (non-affinity driven) is a product state after manufacture (state at the time of shipment). The flexure engagement type gear device 1 includes a shaft generator shaft 30, a shaft generator bearing 31, the external gear 32, the two internal gears 41G and 42G, a housing 43, a first cover 44, a second cover 45, bearings 46 and 47, a main bearing 48, and stop rings 51 and 52.

[0018] The wave generator shaft 30 is a hollow, tubular shaft that rotates about an axis of rotation O1 and comprises a wave generator 30A with a non-circular (e.g., elliptical) outer shape in a cross-section perpendicular to the axis of rotation O1 and wave sections 30B and 30C provided on both axial sides of the wave generator 30A. The elliptical shape need not be geometrically exact and contains a substantially elliptical form. Each of the wave sections 30B and 30C is a shaft with a circular outer shape in a cross-section perpendicular to the axis of rotation O1.

[0019] The two internal gears 41G and 42G mesh with the external gear 32 in a state where they are aligned in the axial direction. One internal gear 41G is configured by providing teeth on a portion of the inner periphery of a rigid first internal gear member 41. The other internal gear 42G is configured by providing teeth on a portion of the inner periphery of a rigid second internal gear member 42.

[0020] The external gear 32 is a curved cylindrical member, and the outer periphery of the external gear 32 is provided with teeth. The external gear 32 comprises a cylindrical metal member with an outer periphery provided with teeth and a coating provided at least on the inner peripheral surface and the tooth surface of the member. In the present embodiment, not only the inner peripheral surface and the tooth surface but also the entire external gear 32, including the axial end surface and the like, are coated. The coating has properties that enable the coating of an engagement portion H (see Fig. 3) in a relatively short time, for example, by an affinity process. The engagement portion H means the part of the tooth surface of the external gear 32 that comes into contact with the internal teeth of the internal gears 41G and 42G. The external gear 32, of which the coating of the engagement portion H in Fig. The removal of step 3 represents an operating state based on affinity. Although in Fig. 3 partially omitted, the engagement portion H is provided on both inclined surfaces (tooth surfaces) of each tooth of the external gear 32. Here, the engagement portion H is provided on both inclined surfaces of each tooth of the external gear 32 because the flexure engagement type gear device 1 is commonly used by rotating in both forward and reverse directions, and yet the engagement portion H may be provided only on one inclined surface in a case of an application in which the flexure engagement type gear device 1 rotates only in either the forward or reverse direction.

[0021] A manganese phosphate film or the like is applicable as the coating having properties that allow the coating of the engaging portion H to be removed as a result of a relatively short operation. Although a molybdenum film, a fluororesin film, a graphite film, a phosphate film, or the like is applicable as the coating having the properties described above, the present invention is not limited thereto. Molybdenum dioxide (MoS2) is an example of the specific component of the molybdenum film. Polytetrafluoroethylene (PTFE) is an example of the specific component of the fluororesin film. Graphite is an example of the specific component of the graphite film. Iron phosphate, zinc phosphate, or manganese phosphate is applicable as an example of the specific component of the phosphate film.Although it is preferred that the coating be a soft coating so that the tooth surface is not damaged even in a case where the peeled-off coating is trapped between the tooth surfaces, the present invention is not limited thereto.

[0022] The external gear 32 has a dimension such that the clearance between the external gear 32 and the internal gears 41G and 42G is negative when the engagement section H of the tooth surface has a coating. Furthermore, the external gear 32 has a dimension such that the clearance between the external gear 32 and the internal gears 41G and 42G is positive when the coating of the engagement section H of the tooth surface is removed. The negative clearance indicates a condition in which a preload is applied between the tooth surfaces of the internal gears 41G and 42G and the tooth surface of the external gear 32. The clearance between the external gear 32 and the internal gears 41G and 42G can become slightly positive as a result of the affinity process of the gear device of the bending engagement type and the removal of coating from the engagement section H of the tooth surface of the external gear 32.

[0023] The shaft generator bearing 31, for example, is a roller bearing and is arranged between the shaft generator 30A and the outer gear 32. The shaft generator bearing 31 has an outer ring 31a, and the outer ring 31a is fitted within the outer gear 32. The shaft generator 30A and the outer gear 32 are rotatable relative to each other via the shaft generator bearing 31.

[0024] The coating on the inner circumferential surface of the external gear 32 and the coating on the tooth surface are the same component. The coating on the inner circumferential surface of the external gear 32 and the coating on the tooth surface can be applied simultaneously. The coating on the inner circumferential surface is inserted between the coated metal element of the external gear 32 and the outer ring 31a of the shaft generator bearing 31, thus preventing direct contact between the metal element of the external gear 32 and the outer ring 31a and suppressing the occurrence of frictional wear on the part.

[0025] The stop rings 51 and 52 are arranged on both sides of the outer gear 32 and the shaft generator bearing 31 in the axial direction and regulate axial movements of the outer gear 32 and the shaft generator bearing 31.

[0026] The housing 43 covers the outer circumferential side of the internal gear 42G. An outer ring section 43o of the main bearing 48 is formed at the inner circumferential section of the housing 43, and the second internal gear element 42 is rotatably mounted via the main bearing 48. The housing 43 is connected to the first internal gear element 41 via a connecting element such as a screw.

[0027] The first cover 44 and the first internal gear member 41 are connected to each other, and the first cover 44 covers the meshing point between the external gear 32 and the internal gear 41G from a counter output side in the axial direction. An output side in the following description is connected to a counter member and is a side on which decelerated motion is output to the counter member, and the counter output side in the following description is opposite to the output side in the axial direction. The bearing 46 is arranged between the first cover 44 and the shaft portion 30B of the wave generator shaft 30, and the wave generator shaft 30 is rotatably supported by the first cover 44.

[0028] The second cover 45 and the second internal gear element 42 are connected to each other, and the second cover 45 covers the point where the external gear 32 and the internal gear 42G mesh from the output side in the axial direction. The second cover 45 and the second internal gear element 42 are connected to the mating element that transmits the decelerated motion. The bearing 47 is arranged between the second cover 45 and the shaft section 30C of the generator shaft 30, and the generator shaft 30 is rotatably mounted by the second cover 45. <verlangsamungsvorgang>

[0029] The motion of the shaft generator 30A is transmitted to the external gear 32 when a rotary motion is initiated by a motor (not shown) or the like, causing the shaft generator shaft 30 to rotate. In this case, the external gear 32 is machined to a shape along the outer circumferential surface of the shaft generator 30A and bent into an elliptical shape, having a major shaft portion and a minor shaft portion viewed from the axial direction. Furthermore, the external gear 32 engages with the internal teeth of the attached first internal gear element 41 on the major shaft portion. Accordingly, the external gear 32 does not rotate at the same speed as the shaft generator 30A, and the shaft generator 30A rotates relative to the external gear 32. Furthermore, during this relative rotation, the external gear 32 is bent and deformed such that the major shaft and minor shaft positions move in a circumferential direction.The period of this deformation is proportional to the rotation period of the wave generator shaft 30.

[0030] During the bending and deformation of the external gear 32, the position where the external gear 32 and the internal gear 41G mesh changes in the rotational direction due to the movement of the main axis position. Assuming that the number of teeth of the external gear 32 is 100 and the number of teeth of the internal gear 41G is 102, the meshing teeth of the external gear 32 and the internal gear 41G deviate each time the meshing position rotates, and the external gear 32 rotates as a result. With the number of teeth described above, the rotational motion of the wave generator shaft 30 is decelerated at a reduction ratio of 100:2 and transmitted to the external gear 32.

[0031] Meanwhile, the external gear 32 also meshes with the other internal gear 42G, and thus, as a result of the rotation of the wave generator shaft 30, the engagement position of the external gear 32 and the internal gear 42G also changes in the rotational direction. However, the number of teeth of the internal gear 42G and the number of teeth of the external gear 32 are equal to each other, and thus the external gear 32 and the internal gear 42G do not rotate relative to each other, and the rotational movement of the external gear 32 is transmitted to the internal gear 42G at a reduction ratio of 1:1. As a result, the rotational movement of the wave generator shaft 30 is decelerated at a reduction ratio of 100:2 and transmitted to the second internal gear element 42 and the second cover 45. Furthermore, this decelerated rotational movement is transmitted to the counter element.

[0032] In a post-shipment and pre-operation state, where the engagement section H of the external gear 32 has a coating, a preload is applied between the tooth surfaces of the internal gears 41G and 42G and the tooth surface of the external gear 32. This allows the affinity process to be carried out by applying a relatively large torque to the generator shaft 30. When the coating of the engagement section H of the external gear 32 is removed as a result of the affinity process, operation at normal torque is possible, the clearance between the external gear 32 and the internal gears 41G and 42G becomes positive, and the gear device 1 of the bending mesh type is realized with a small dead area.

[0033] The backlash of the gear device 1 of the bending engagement type of embodiment 1 is 0.15 arcmin to 3 arcmin and more preferably 0.15 arcmin to 1 arcmin in a state in which the coating of the engagement section H is removed. 1 [arcmin] is n / (180·60) [rad] in the SI system of units.

[0034] Fig. 4 is an explanatory diagram showing the backlash. The Fig. The stiffness hysteresis curve shown in Figure 4 is obtained by plotting a relationship after the input shaft (high-speed shaft) of the speed reducer is fixed and the load and displacement (twisting angle) of the output shaft (low-speed shaft) of the speed reducer are measured until the load is removed by slowly applying a load to a rated torque from the low-speed shaft side. The backlash is defined as the twisting angle at the point where the torque is ±3% of the rated torque. In the flexion meshing type gear device 1, the input shaft corresponds to the shaft generator shaft 30, and the output shaft corresponds to the second cover 45 and the second internal gear member 42. <Verfahren zur Herstellung von Zahnradvorrichtung des Biegeeingriffstyps>

[0035] Fig. 5 is a flowchart illustrating a method for manufacturing the flexural engagement type gear device of Embodiment 1.

[0036] The method for manufacturing the flexural engagement type gear device 1 of Embodiment 1 includes a coating step (step S1) of coating the metal member of the external gear 32 and an assembling step (step S2) of assembling the flexural engagement type gear device 1 by combining a plurality of components including the external gear 32.

[0037] The manufacturing process produces the bending-type gear device 1, which is capable of achieving a deceleration movement with a small amount of backlash by means of the subsequent short affinity process and suppressing frictional wear between the outer gear 32 and the outer ring 31a. It should be noted that the affinity process, which differs significantly from normal operation, is optional in cases where a customer performs the affinity process after the bending-type gear device 1 has been delivered. In cases where normal operation is initiated with the bending-type gear device 1 installed in a target machine, the operating time until the coating of the engagement section H is removed also serves as the affinity process. <Effekte von Ausführungsform>

[0038] As described above, in the bending-engagement type gear device 1 of the present embodiment, the outer gear 32 has a coating on its inner circumferential surface and tooth surface. Furthermore, this coating has properties that allow the coating of the engagement section H to be removed by the outer gear 32 and the meshing inner gears 41G and 42G when the bending-engagement type gear device 1 is operated. Accordingly, the coating improves the affinity between the outer gear 32 and the inner gears 41G and 42G. Affinity refers to the property that the shape of the tooth surface is improved by sliding, and the property that the condition of the film on the tooth surface approaches an ideal state.By improving the affinity, it is possible to make the tooth surface of the external gear 32 and the tooth surfaces of the internal gears 41G and 42G affine by operating the flexure engagement type gear device 1 for a relatively short time. Furthermore, fretting wear between the external gear 32 and the outer ring 31a of the wave generator bearing 31 can be suppressed by the coating on the inner peripheral surface of the external gear 32. By suppressing fretting wear, it is possible to suppress wear dust generated from this part, which adversely affects the tooth surface of the external gear 32 and the tooth surfaces of the internal gears 41G and 42G, and it is possible to suppress an increase in the backlash of the flexure engagement type gear device 1 due to the wear dust. The coating-based affinity enhancement is particularly effective in a case where grease is used as a lubricant.In a case where grease is used, it is unlikely that lubricant will penetrate into the engagement section H of the external gear 32 or into the inner circumferential surface of the external gear 32, and it is unlikely that a tribofilm will form on the tooth surface.

[0039] Furthermore, in the gear device 1 of the bending engagement type of the present embodiment, the tooth surface of the outer gear 32 has a dimension such that the clearance between the outer gear 32 and the internal gears 41G and 42G is negative when the engagement section H is coated. With this configuration, the clearance between the outer gear 32 and the internal gears 41G and 42G can be extremely reduced in a condition where the outer gear 32 and the internal gears 41G and 42G are affine.

[0040] Furthermore, the tooth surface of the outer gear 32 has a dimension such that the clearance between the outer gear 32 and the internal gears 41G and 42G is positive when the engagement section H is uncoated. With such a configuration, it is possible to reduce the torsional load generated between the outer gear 32 and the internal gears 41G and 42G, and to reduce the clearance between the outer gear 32 and the internal gears 41G and 42G in a state where the outer gear 32 and the internal gears 41G and 42G are affine.

[0041] Furthermore, in the bending-type gear device 1 of the present embodiment, the dead travel is 0.15 arcmin to 3 arcmin in a state where the engagement section H of the outer gear 32 has no coating. With the configuration of the present embodiment, it is possible to realize the bending-type gear device 1 with the extremely low dead travel. (Version 2)

[0042] The flexion engagement type gear device of Embodiment 2 differs from the flexion engagement type gear device of Embodiment 1 in that the engagement portion H of the external gear 32 has no coating in the product state after manufacture (state at a time of shipment), and the other components of Embodiment 2 are similar to those of Embodiment 1. The similar parts will not be described in detail.

[0043] The outer gear 32 of embodiment 2 has a coating on the inner circumferential surface and on a part other than the engagement section H (see Fig. 3) on the tooth surface. The external gear 32 of Embodiment 2 has no coating on the tooth surface at the engagement portion H. The component of the coating is the same as the coating of Embodiment 1.

[0044] The outer gear 32 has a dimension such that the clearance between the outer gear 32 and the inner gears 41G and 42G is positive in a state where the engagement section H of the tooth surface has no coating. Furthermore, in embodiment 2, the outer gear 32 also has a dimension such that the clearance between the outer gear 32 and the inner gears 41G and 42G is negative when the engagement section H of the outer gear 32 has a coating whose thickness is equal to the coating on the part of the tooth surface other than the engagement section H.

[0045] The bending-type gear device of embodiment 2 performs a deceleration process similar to the bending-type gear device of embodiment 1. The bending-type gear device of embodiment 2 is able to perform the main operation without performing the affinity process after product shipment, and thus the amount of backlash between the outer gear 32 and the internal gears 41G and 42G is small from the time of product shipment, and a small amount of dead load is achieved.

[0046] The backlash of the flexural engagement type gear device of Embodiment 2 is 0.15 arcmin to 3 arcmin, and more preferably 0.15 arcmin to 1 arcmin. <Verfahren zur Herstellung von Zahnradvorrichtung des Biegeeingriffstyps>

[0047] Fig. 6 is a flowchart illustrating a method of manufacturing the flexural engagement type gear device of Embodiment 2.

[0048] Similar to the manufacturing method of Embodiment 1, the manufacturing method of the flexural engagement type gear device of Embodiment 2 includes a coating step (step S11) of coating the inner peripheral surface and tooth surfaces of the external gear 32 and an assembly step (step S12) of assembling the flexural engagement type gear device 1. The tooth surface of the external gear 32, including the engagement portion H, is coated in the coating step.

[0049] Furthermore, the manufacturing method of Embodiment 2 includes a coating removal step (step S13) following the assembly step. In the coating removal step, the coating of the engagement portion H of the external gear 32 is removed by operating the assembled flexural engagement type gear device 1 for a predetermined time (for example, performing the affinity process).

[0050] The manufacturing process makes it possible to produce the bending-type gear device 1 with a low dead travel, which is able to suppress frictional wear between the outer gear 32 and the outer ring 31a.

[0051] As described above, in the bending-engagement type gear assembly of embodiment 2, the outer gear 32 has the coating on its inner circumferential surface and on the portion of the tooth surface excluding the engagement section H, and has no coating in the engagement section H. In this configuration, the coating portion is applied between the tooth surfaces at a point in time before or after contact between the tooth surface of the outer gear 32 and the tooth surfaces of the inner gears 41G and 42G in the engagement section H, thus reducing the clearance between the outer gear 32 and the inner gears 41G and 42G. Consequently, it is possible to implement a bending-engagement type gear assembly with low backlash. Furthermore, frictional wear between the outer gear 32 and the outer ring 31a of the shaft generator bearing 31 can be suppressed by the coating on the inner circumferential surface of the outer gear 32.By suppressing frictional wear, it is possible to suppress the abrasive powder generated by this part, which adversely affects the tooth surface of the outer gear 32 and the tooth surfaces of the inner gears 41G and 42G, and it is possible to suppress an increase in the backlash of the bending-type gear device 1 that is attributable to the abrasive powder. Additionally, effects similar to those of embodiment 1 can be obtained.

[0052] Furthermore, the manufacturing method for the bending engagement type gear device of Embodiment 2 has the effect that the main operation can be performed with a small backlash after product shipment by means of the coating removal step after the assembling step.

[0053] Two embodiments of the present invention have been described above. However, the present invention is not limited to the embodiments described above. For example, although the gear device of the bending engagement type has a so-called tubular configuration in the embodiments described above, the present invention is not limited thereto, and the gear device of the bending engagement type according to the present invention can, for example, be a so-called pot-type or cylinder-hat-type gear device of the bending engagement type. In addition, in the embodiments described above, the coating of the engagement section H is removed as a result of a process after the entire outer gear 32, including the tooth surface, has been coated. However, the present invention is not limited thereto.For example, the engagement portion H may not be coated by masking the area of ​​the engagement portion H when coating the external gear 32. Furthermore, the details described in the embodiments may be appropriately modified within the scope of the invention. Industrial applicability

[0054] The present invention can be used for a gear device of the bending engagement type and a method for its manufacture. List of reference symbols 1 Gear device of bending engagement type 30 shaft generator shaft 30A wave generator 31 shaft generator bearings 31a Outer ring 32 Outer gear 41 first internal gear element 42 second internal gear element 41G, 42G internal gear H Intervention section< / verlangsamungsvorgang>

Claims

[1] A gear device (1) of the bending engagement type, comprising: a wave generator (30A); an external gear (32) which is bent and deformed by the wave generator (30A); an internal gear (41G, 42G) meshing with the external gear (32); and a shaft generator bearing (31) arranged between the external gear (32) and the shaft generator (30A), wherein the shaft generator bearing (31) includes an outer ring (31a) which is separated from the external gear (32), the external gear (32) has a coating of the same component on an inner peripheral surface and a tooth surface and the coating has properties that enable the coating to be removed in an engagement portion by engagement of the external gear (32) with the internal gear (41G, 42G) when the bending engagement type gear device (1) is operated. [2] A gear device (1) of the bending engagement type, comprising: a wave generator (30A); an external gear (32) which is bent and deformed by the wave generator (30A); an internal gear (41G, 42G) meshing with the external gear (32); and a shaft generator bearing (31) arranged between the external gear (32) and the shaft generator (30A), wherein the external gear (32) has a coating on an inner peripheral surface and on a part other than an engaging portion of a tooth surface, and the engagement section does not have the coating. [3] The flexural engagement type gear device (1) according to claim 1 or 2, wherein the external gear (32) has a dimension in which a clearance between the external gear (32) and the internal gear (41G, 42G) is negative in a case where the engagement portion has the coating. [4] The flexural engagement type gear device (1) according to any one of claims 1 to 3, wherein the external gear (32) has a dimension in which a clearance between the external gear (32) and the internal gear (41G, 42G) is positive in a state where the coating of the engagement portion is not provided. [5] The flexure engagement type gear device (1) according to any one of claims 1 to 4, wherein a backlash of the flexure engagement type gear device (1) is 0.15 arcmin to 3 arcmin in a state where the coating is not provided in the engagement portion. [6] A method of manufacturing a gear device (1) of the bending engagement type including a wave generator (30A), an external gear (32) bent and deformed by the wave generator (30A), an internal gear (41G, 42G) meshing with the external gear (32), and a wave generator bearing (31) disposed between the external gear (32) and the wave generator (30A), wherein the wave generator bearing (31) includes an outer ring (31a) separated from the external gear (32), and the method comprises: a coating step of applying a coating of the same component to at least one inner peripheral surface and one tooth surface of the external gear (32); and an assembly step of assembling the gear device (1) of the bending engagement type by combining a plurality of components including the coated external gear (32), wherein in the coating step, the coating is performed such that a coating in an engaging portion is removed by engaging the internal gear (41G, 42G) when the assembled gear device (1) of the bending engagement type is operated. [7] A method of manufacturing a gear device (1) of the bending engagement type according to claim 6, further comprising: a coating removing step of removing the coating on a part of the external gear (32) that engages with the internal gear (41G, 42G) by operating the assembled bending engagement type gear device (1) for a predetermined time. [8] A flexural engagement type gear device (1) according to claim 1, wherein the coating is a manganese phosphate film.

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