Apparatus and manufacturing method

Abstract

To provide a technique capable of suppressing a first member from having a shorter lifetime even in a case in which a low-hardness region appears on a first confronting surface of the first member in addition to a high-hardness region.SOLUTION: There is provided a device that comprises a first member 50 and a second member 52 moving relatively to contact the first member 50. The first member 50 comprises a first confronting surface 54, and the second member 52 comprises a second confronting surface 56 confronting and contacting the first confronting surface 54 in relative movement; the first confronting surface 54 comprises a high-hardness region 60 contacting the second confronting surface 56 and a low-hardness region 62 having lower surface hardness than the high-hardness region 60; and one of the first confronting surface 54 and second confronting surface 56 is provided with a relief part 70 which separates the second confronting surface 56 and low-hardness region 62 when they contact each other.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a device comprising a plurality of contacting first and second members. [Background technology]

[0002] Patent Document 1 discloses a device including a first member (oscillating gear) and a second member (rolling element) that moves relative to and comes into contact with the first member. The first member and the second member each have a first opposing surface and a second opposing surface that face and come into contact with each other when the first member and the second member move relative to each other.

[0003] In order to improve the fatigue strength of the first opposing surface of the first member, it is sometimes required to increase the hardness of the first opposing surface. To achieve this, the technology disclosed in Patent Document 1 employs heat treatment (laser hardening) to increase the hardness of the first opposing surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-167589 Summary of the Invention [Problem to be solved by the invention]

[0005] In increasing the hardness of the first opposing surface, in addition to the high-hardness region, a low-hardness region with a surface hardness lower than that of the high-hardness region may appear on the first opposing surface. In this case, if high contact pressure acts on the low-hardness region of the first member due to contact with the second member, this may lead to a reduction in the lifespan of the first member due to contact fatigue. The technology disclosed in Patent Document 1 does not address this issue, and improvements in this area are desired.

[0006] One object of the present disclosure is to provide a technology that can suppress a decrease in the lifespan of a first member even when a low hardness region appears in addition to a high hardness region on the first opposing surface of the first member. [Means for solving the problem]

[0007] The device disclosed herein is a device comprising a first member and a second member that comes into contact with the first member while moving relative to the first member, wherein the first member has a first opposing surface, and the second member has a second opposing surface that faces and comes into contact with the first opposing surface during the relative movement, the first opposing surface having a high hardness region that comes into contact with the second opposing surface and a low hardness region that has a surface hardness lower than that of the high hardness region, and at least one of the first opposing surface and the second opposing surface is provided with a relief portion that separates the second opposing surface and the low hardness region when they come into contact with each other.

[0008] The manufacturing method disclosed herein is a manufacturing method for obtaining a first member and a second member that come into contact with each other while moving relative to each other, wherein the first member has a first opposing surface, and the second member has a second opposing surface that faces and comes into contact with the first opposing surface during the relative movement, the manufacturing method comprising: a heat treatment process for heat treating the first member to provide the first opposing surface with a high hardness region that comes into contact with the second opposing surface and a low hardness region that has a surface hardness lower than that of the high hardness region; and a relief portion forming process for forming a relief portion in at least one of the first opposing surface and the second opposing surface that separates the second opposing surface and the low hardness region when they come into contact with each other. [Effects of the Invention]

[0009] According to the present disclosure, even when a low hardness region appears in addition to a high hardness region on the first opposing surface of the first member, it is possible to suppress a decrease in the lifespan of the first member. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a side cross-sectional view of the device of the first embodiment. [Figure 2] FIG. 1 is a cross-sectional view of a first member and a second member according to a first embodiment, as viewed from the front; [Figure 3] FIG. 2 is a perspective view of a first member of the first embodiment. [Figure 4] FIG. 2 is a plan view of a first member of the first embodiment. [Figure 5] FIG. 5 is a diagram showing a part of the cross section AA of FIG. [Figure 6] FIG. 2 is an explanatory diagram of a heat treatment process according to the first embodiment. [Figure 7] FIG. 2 is an explanatory diagram of a heating path in the first embodiment. [Figure 8] FIG. 10 is a perspective view of a first member of the second embodiment. [Figure 9] FIG. 10 is a side cross-sectional view of a first member and a second member of a second embodiment. [Figure 10] FIG. 10 is an enlarged view of a portion of FIG. [Figure 11] FIG. 10 is an explanatory diagram of a first heating step of the second embodiment. [Figure 12] FIG. 10 is an explanatory diagram of a second heating step in the second embodiment. [Figure 13] FIG. 10 is a perspective view of a first member of the third embodiment. [Figure 14] 10 is a diagram showing a cross section of a contact point between a first member and a second member in a third embodiment. FIG. [Figure 15] FIG. 13 is a diagram showing a cross section of a contact portion between a first member and a second member in a fourth embodiment; [Figure 16] FIG. 10 is a diagram showing a first member and a second member of the fifth embodiment. [Figure 17] FIG. 13 is a diagram showing a first member and a second member of the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following describes the embodiments. The same components are designated by the same reference numerals, and redundant explanations will be omitted. In each drawing, for the sake of convenience, components are omitted, enlarged, or reduced as appropriate. The drawings should be viewed in accordance with the orientation of the reference numerals.

[0012] (First embodiment) Refer to FIG. 1. An apparatus 10 in which a first member 50 and a second member 52 of this embodiment are used will be described. The apparatus 10 of this embodiment is a gear device, more specifically, an eccentric oscillating gear device. The apparatus 10 includes a crankshaft 12, an eccentric body 14 provided on the crankshaft 12, an external gear 16 oscillated by the eccentric body 14, and an internal gear 18 meshing with the external gear 16. In addition, the apparatus 10 includes an eccentric bearing 20 disposed between a first through hole 30 (described later) of the external gear 16 and the eccentric body 14, a carrier 22 disposed axially to the external gear 16, an inner pin 24 protruding from the carrier 22, and a casing 26 that houses the external gear 16. The eccentric oscillating gear device of this embodiment is a center crank type in which the crankshaft 12 is disposed on the center C18 of the internal gear 18.

[0013] Rotational power transmitted from a drive source (not shown) is input to the crankshaft 12. The drive source is, for example, a motor, a gear motor, an engine, or the like.

[0014] In addition to the multiple eccentric bodies 14, the crankshaft 12 also includes a shaft body 28 that can rotate integrally with the eccentric bodies 14. In this embodiment, the eccentric body 14 is provided separately from the shaft body 28 and can rotate integrally with the shaft body 28 using a key or the like. Alternatively, the eccentric body 14 may be provided as part of the same member as the shaft body 28. The center C14 of the eccentric body 14 is eccentric with respect to the rotation center C12 of the crankshaft 12, and rotation around the rotation center C12 can oscillate the external gear 16. The eccentric phases of the multiple eccentric bodies 14 are shifted by 360° / M, assuming that the number of eccentric bodies 14 is M (two in this embodiment). The number of eccentric bodies 14 is not particularly limited and may be one or three or more. Although an example in which the multiple eccentric bodies 14 are separate bodies is shown here, the multiple eccentric bodies 14 may be provided as part of the same member.

[0015] The external gears 16 are individually provided corresponding to the multiple eccentric bodies 14, and are supported for relative rotation by the corresponding eccentric bodies 14 via eccentric bearings 20. The external gears 16 include a first through hole 30 that passes through the center C16 of the external gear 16, and multiple second through holes 32 that pass through positions offset from the center C16 and are provided at intervals around the center C16 of the external gear 16.

[0016] The internal gear 18 is integrated with the casing 26. The internal gear 18 of this embodiment includes an internal gear main body 18a that is integrated with the casing 26, outer pins 18b that are rotatably supported by the internal gear main body 18a, and outer rollers 18c that are rotatably supported by the outer pins 18b and form the internal teeth. The internal teeth of the internal gear 18 may be formed directly on the internal gear main body 18a, or may be formed by the outer pins 18b.

[0017] The eccentric bearing 20 includes a plurality of rolling elements 20a and a retainer 20b that maintains the relative positions of the plurality of rolling elements 20a. The rolling elements 20a in this embodiment are rollers. The eccentric bearing 20 in this embodiment does not include a dedicated inner ring, and the eccentric body 14 also serves as the inner ring. The rolling elements 20a roll directly on the outer peripheral surface of the eccentric body 14, with the outer peripheral surface serving as the rolling surface. The eccentric bearing 20 also includes a dedicated outer ring, and the first through hole 30 of the external gear 16 also serves as the outer ring. The rolling elements 20a roll directly on the inner peripheral surface of the first through hole 30, with the inner peripheral surface serving as the rolling surface. Alternatively, the eccentric bearing 20 may include dedicated outer and inner rings.

[0018] The inner pin 24 passes through the second through hole 32 of the external gear 16. The inner pin 24 receives a load from the external gear 16 when the external gear 16 oscillates, and can be synchronized with the rotation component of the external gear 16. Here, "synchronized with the rotation component" means that the rotation component of the external gear 16 and the orbital component of the inner pin 24 are maintained at the same magnitude within a numerical range including zero. In this embodiment, the inner pin 24 receives a load from the external gear 16 via a roller 34 that the inner pin 24 rotatably supports. Alternatively, the inner pin 24 may receive a load directly from the external gear 16.

[0019] One of the carrier 22 and the casing 26 serves as an output member that outputs output rotation to a driven member outside the gear device 10. In this embodiment, the carrier 22 serves as the output member, but the casing 26 may also serve as the output member.

[0020] The operation of the above device 10 (gear device) will now be described. When the input member (here, the crankshaft 12) is rotated by a drive source, the eccentric body 14 of the crankshaft 12 causes the external gear 16 to oscillate. As the external gear 16 oscillates, the meshing position between the external gear 16 and the internal gear 18 sequentially changes circumferentially. As a result, with each rotation of the crankshaft 12, either the external gear 16 or the internal gear 18 (here, the external gear 16) rotates by an amount corresponding to the difference in the number of teeth between the two. This rotation component is transmitted to the output member (here, the carrier 22 via the inner pin 24) and then output to the driven member as output rotation. In this embodiment, output rotation that is decelerated relative to the rotation of the input member is transmitted to the output member.

[0021] Please refer to Figures 2 to 5. Figure 2 is also a cross-sectional view taken along line BB in Figure 4. The device 10 includes a first member 50 and a second member 52 that moves relative to the first member 50 and comes into contact with the first member 50 when the device 10 is in operation. In this embodiment, the first member 50 is the eccentric body 14, and the second member 52 is the rolling element 20a of the eccentric bearing 20. The device 10 includes a plurality of second members 52 (rolling elements 20a).

[0022] The first member 50 has a first opposing surface 54. The second member 52 has a second opposing surface 56 that faces and comes into contact with the first opposing surface 54 during relative movement between the first member 50 and the second member 52. The first opposing surface 54 is, for example, either the outer peripheral surface or the inner peripheral surface of the first member 50. In this embodiment, the first opposing surface 54 is the outer peripheral surface of the eccentric body 14, and the second opposing surface 56 is the outer peripheral surface of the rolling element 20a. In this embodiment, the first opposing surface 54 and the second opposing surface 56 are in line contact. Hereinafter, the direction along the center C54 of the first opposing surface 54 will be referred to as the axial direction X, and the radial and circumferential directions of a circle concentric with the center C54 will be simply referred to as the radial and circumferential directions. The center C54 of the first opposing surface 54 is the center of the outer peripheral surface when the outer peripheral surface of the first member 50 becomes the first opposing surface 54, and is the center of the inner peripheral surface when the inner peripheral surface of the first member 50 becomes the first opposing surface 54.

[0023] In this embodiment, during operation of the device 10, the second member 52 rotates (revolves while rotating) relative to the first member 50 around the center C54 of the first opposing surface 54. The second opposing surface 56 comes into contact with the first opposing surface 54 by at least one of sliding contact and rolling contact during relative motion between the first member 50 and the second member 52. For example, when the second member 52 is the rolling element 20a as in this embodiment, the second opposing surface 56 comes into contact with the first opposing surface 54 mainly by rolling contact. Furthermore, when the first member 50 and the second member 52 are two gears as in a third embodiment described below, the second opposing surface 56 comes into contact with the first opposing surface 54 mainly by sliding contact. In other words, in this case, the first opposing surface 54 and the second opposing surface 56 slide against each other.

[0024] In this embodiment, the contact point 72 between the first opposing surface 54 and the second opposing surface 56 moves on the first opposing surface 54 in a movement direction Da during relative movement between the first member 50 and the second member 52. In this embodiment, the movement direction Da is a circumferential direction around the center C54 of the first opposing surface 54. Hereinafter, a cross section that is perpendicular to the movement direction Da of the contact point 72 between the first opposing surface 54 and the second opposing surface 56 and passes through the contact point 72 between them will also be referred to simply as a "cross section passing through the contact point between the first opposing surface 54 and the second opposing surface 56." Figure 5 is also a diagram showing a cross section that satisfies this condition. In this cross section, the direction along the straight line connecting both ends 72a of the contact point 72 between the first opposing surface 54 and the second opposing surface 56 is referred to as a width direction Db, and the direction perpendicular to the width direction Db is referred to as a contact direction Dc. Furthermore, when the contact point 72 of the first opposing surface 54 and the second opposing surface 56, which are in line contact with each other, is viewed from the facing direction Dc, the straight line along the contact point 72 is called the contact line 58 (see FIG. 4). When the contact point 72 of the first opposing surface 54 and the second opposing surface 56 is projected onto an imaginary plane perpendicular to the facing direction Dc, the contact line 58 can also be said to be the straight line passing through the line contact point 72.

[0025] The first opposing surface 54 includes a high hardness region 60 and a low hardness region 62 having a surface hardness lower than that of the high hardness region 60. For ease of explanation, in the following Figure 3 and the like, the high hardness region 60 and the low hardness region 62 are also hatched on the outer surface of the first member 50. For ease of explanation, in cross-sectional views such as Figure 2, the boundaries between the high hardness region 60, the low hardness region 62, and the base material region 66 are marked with lines. Here, surface hardness refers to Vickers hardness measured by a method conforming to JIS Z2244. The difference in surface hardness between the high hardness region 60 and the low hardness region 62 is, for example, 50 HV or more in Vickers hardness.

[0026] The high hardness region 60 is provided in a location that comes into contact with the second opposing surface 56 during relative movement between the first member 50 and the second member 52. The first opposing surface 54 is required to have fatigue strength to resist fatigue caused by contact with the second opposing surface 56. By providing the high hardness region 60 in a location that requires such fatigue strength, the life of the first member 50 can be extended.

[0027] The high-hardness region 60 and the low-hardness region 62 are formed by surface-hardened regions formed by heat treatment of a workpiece (intermediate product) for obtaining the first member 50. In this embodiment, partial hardening using a light beam 82 (laser beam), which will be described later, is used as this heat treatment. The surface-hardened region has a higher surface hardness than the base material region 66, which corresponds to the hardness of the workpiece itself, which is the material for the heat treatment. The surface-hardened region has a unique texture distribution and hardness distribution corresponding to the heat treatment from its surface toward the depth direction (the normal direction of the surface from the surface toward the interior). The base material region 66 is formed on the outer surface of the first member 50 in a location where no surface-hardened region is formed. The first member 50 is made of a metal that can be hardened by such heat treatment, and in this embodiment, steel is used as the material. The type of steel is not particularly limited, but bearing steel, for example, is used.

[0028] The high hardness region 60 is a hardened region formed by partial hardening through the heat treatment described above. The microstructure of such a high hardness region 60 has a hardened structure such as α-martensite as a main phase. The low hardness region 62 of this embodiment is a tempered region tempered in the heat treatment described above, and is a region known as a soft zone. The microstructure of such a low hardness region 62 has a tempered structure such as trussite or sorbite as a main phase.

[0029] The low hardness region 62 is strip-shaped on the first opposing surface 54 and is inclined with respect to the contact line 58 between the first opposing surface 54 and the second opposing surface 56. When the contact point 72 between the first opposing surface 54 and the second opposing surface 56 is viewed from the opposing direction Dc (viewpoint in FIG. 4 ), the low hardness region 62 can also be said to be inclined with respect to the contact line 58. When the first opposing surface 54 is developed into a plane, the low hardness region 62 is inclined with respect to the contact line 58. The low hardness region 62 of this embodiment extends in the axial direction X of the first opposing surface 54 and is inclined with respect to the axial direction X when viewed from the radial direction. The high hardness region 60 is provided in a location on the first opposing surface 54 other than the low hardness region 62.

[0030] At least one of the first opposing surface 54 and the second opposing surface 56 is provided with a relief portion 70 that separates the low hardness region 62 of the first opposing surface 54 from the second opposing surface 56 when they come into contact with each other. The relief portion 70 is provided as a recess in the opposing surface on which the relief portion 70 is provided (here, the first opposing surface 54) that is recessed into a contact point 72 between the opposing surfaces 54, 56. In a cross section passing through the contact point 72 between the first opposing surface 54 and the second opposing surface 56, a portion that faces the low hardness region 62 of the first opposing surface 54 in the facing direction Dc is referred to as a facing region 74. If the first opposing surface 54 and the second opposing surface 56 did not have the relief portion 70, the facing region 74 would be in contact with the low hardness region 62 of the first opposing surface 54 on this cross section. "Separating the low hardness region 62 of the first opposing surface 54 from the second opposing surface 56" means that the first opposing surface 54 and the second opposing surface 56 are spaced apart compared to when there are no relief portions 70 in the first opposing surface 54 and the second opposing surface 56 and the low hardness region 62 of the first opposing surface 54 and the opposing region 74 of the second opposing surface 56 are in contact with each other. The relief portions 70 are provided so that when the first opposing surface 54 and the second opposing surface 56 come into contact with each other, the surface pressure acting on the low hardness region 62 is smaller than the surface pressure acting on the high hardness region 60 at the contact point 72 between them.

[0031] The relief portion 70 in this embodiment is provided in the low hardness region 62 of the first opposing surface 54. When providing the relief portion 70 in the low hardness region 62, it is sufficient that it is provided in at least a portion of the low hardness region 62. In this embodiment, the relief portion 70 is provided in the entire low hardness region 62. In this embodiment, like the low hardness region 62, the relief portion 70 is also inclined with respect to the contact line 58 between the first opposing surface 54 and the second opposing surface 56. Like the low hardness region 62, the relief portion 70 in this embodiment is provided as a groove portion extending in a strip shape.

[0032] The first opposing surface 54 and the second opposing surface 56 can be in contact with each other simultaneously on both sides of the recessed portion 70. In this embodiment, the first opposing surface 54 and the second opposing surface 56 can be in contact with each other simultaneously on both sides of the axial direction X of the first opposing surface 54, with the recessed portion 70 sandwiched therebetween. This condition is met (almost always in this embodiment) during the relative movement of the first member 50 and the second member 52 when the recessed portion 70 is present on a cut plane passing through the contact point 72 between the first opposing surface 54 and the second opposing surface 56. Note that in this embodiment, when the first opposing surface 54 and the second opposing surface 56 come into contact with each other during the relative movement of the first member 50 and the second member 52, the high hardness region 60 of the first opposing surface 54 and the second opposing surface 56 are always in contact with each other.

[0033] The effects of the above-described device 10 will now be described.

[0034] (A) At least one of the first opposing surface 54 and the second opposing surface 56 is provided with a recess 70 that separates the second opposing surface 56 and the low-hardness region 62 when they come into contact with each other. Therefore, when the first opposing surface 54 and the second opposing surface 56 come into contact with each other, the recess 70 prevents the low-hardness region 62 from coming into contact with the second opposing surface 56. Even if the low-hardness region 62 and the second opposing surface 56 come into contact due to elastic deformation of the high-hardness region 60 of the first member 50, the contact pressure in the low-hardness region 62 can be reduced compared to when the recess 70 is not provided. Therefore, contact fatigue that may occur in the low-hardness region 62 when the first opposing surface 54 and the second opposing surface 56 come into contact with each other can be suppressed. Consequently, even when the low-hardness region 62 appears in the first opposing surface 54, a decrease in the lifespan of the first member 50 can be suppressed.

[0035] (B) The first opposing surface 54 and the second opposing surface 56 can be in contact simultaneously on both sides of the recess 70. Therefore, compared to when the first opposing surface 54 and the second opposing surface 56 are in contact with the recess 70 on only one side, the contact state between the first opposing surface 54 and the second opposing surface 56 can be stabilized by increasing the contact area between them.

[0036] The low hardness region 62 and the relief portion 70 of the first opposing surface 54 are inclined with respect to the contact line 58 between the first opposing surface 54 and the second opposing surface 56. Therefore, when the relief portion 70 passes through a position overlapping the contact line 58 in the opposing direction Dc, it is possible to easily position the high hardness region 60 on the contact line 58. As a result, when the relief portion 70 passes through a position overlapping the contact line 58 in the opposing direction Dc, it is possible to stably bring the high hardness region 60 into contact with the second opposing surface 56, making it easier to avoid a situation in which only the low hardness region 62 comes into contact with the second opposing surface 56.

[0037] A description will now be given of a manufacturing method for obtaining the above-described first member 50 and second member 52. The manufacturing method described here is performed on intermediate products (workpieces) for obtaining the first member 50 and second member 52, which will become the final products.

[0038] The manufacturing method mainly includes a heat treatment step of heat treating the first member 50 to provide a high hardness region 60 and a low hardness region 62 in the first opposing surface 54, and a relief portion forming step of forming a relief portion 70 in at least one of the first opposing surface 54 and the second opposing surface 56 (in this embodiment, the first opposing surface 54). Note that the workpiece that serves as the intermediate product may be obtained by performing a rough machining step of forming the outer shape of the workpiece by machining such as cutting prior to the heat treatment step. Furthermore, the first member 50 that has undergone the heat treatment step may be subjected to a finish machining step of grinding by machining such as cutting in order to remove thermal distortion.

[0039] See FIG. 6. The heat treatment step is performed by heating the first opposing surface 54 of the first member 50 to a temperature equal to or higher than the quenching temperature using a heating device 80. The quenching temperature here is a temperature at which quenching can be achieved by heating to that temperature and then cooling, and is a temperature determined depending on the material of the first member 50. For example, the quenching temperature may be the A3 point for hypo-eutectoid steel or the Ac1 point for hyper-eutectoid steel. The upper limit of the heating temperature in the heat treatment step is not particularly limited, but in reality, the upper limit is the melting point of the material of the first member 50.

[0040] The heating device 80 of this embodiment is an irradiation head that irradiates a light beam 82. The light beam 82 of this embodiment is a laser beam, but the specific example is not particularly limited, and an electron beam or the like may also be used.

[0041] Please refer to Figures 6 and 7. Figure 7 is a development view of the first opposing surface 54, in which a portion of the circumferential direction of the first opposing surface 54 is cut along the axial direction X and developed into a plane. In Figure 7, the heating path 84 of the light beam 82 is indicated by an arrow marking the path of the optical axis of the light beam 82. In the example of Figure 7, the start point S and end point G of the heating path 84 of the light beam 82 are at the same position.

[0042] In the heat treatment process, the heating device 80 heats the first opposing surface 54 to a temperature equal to or higher than the hardening temperature by moving the heating portion along a heating path 84. In this manner, the heating portion can be moved by moving at least one of the heating device 80 and the first member 50. In this embodiment, the heating device 80 is fixed in position and the first member 50 is rotated, thereby moving the heating portion along the next heating path 84 and heating the entire circumferential range of the first opposing surface 54 to a temperature equal to or higher than the hardening temperature. This heating path 84 is annular, with a starting point 84a, which is the heating start position, and an ending point 84b, which is the heating end position, overlapping partially in the circumferential direction of the first opposing surface 54. The region where the starting point 84a and ending point 84b of this heating path 84 overlap in the circumferential direction is referred to as a circumferential overlap region 86. In the heat treatment process of the present embodiment, the first opposing surface 54 of the first member 50 is heated by directly irradiating the first opposing surface 54 with a light beam 82. At this time, the irradiated portion of the light beam is caused to move along the same irradiation path as the heating path 84 described above, so that the heated portion moves along the heating path 84 on the first opposing surface 54.

[0043] As a result, areas of the first opposing surface 54 other than the circumferential overlap region 86 are heated to a temperature equal to or higher than the hardening temperature, and then cooled by self-cooling or the like, thereby being hardened. As a result, a high-hardness region 60, which is a hardened region, is provided in areas of the first opposing surface 54 other than the circumferential overlap region 86. In contrast, in the circumferential overlap region 86 of the first opposing surface 54, the hardened region is tempered by being reheated to a temperature equal to or higher than the hardening temperature. As a result, a low-hardness region 62, which is a tempered region, is provided in the circumferential overlap region 86 of the first opposing surface 54.

[0044] In the heat treatment step, the heating device 80 irradiates the light beam 82 so as to form a band-shaped beam spot on the first opposing surface 54. Assuming that there is a contact line 58 due to the line contact between the second opposing surface 56 and the first opposing surface 54, this beam spot is formed so as to be inclined with respect to the contact line 58 when viewed from the opposing direction Dc. As a result, as described above, a band-shaped low-hardness region 62 inclined with respect to the contact line 58 is provided.

[0045] The relief portion forming step is performed by grinding the portion where the relief portion 70 is to be formed on the opposing surface where the relief portion 70 is to be formed (here, the first opposing surface 54) with a grinding tool such as a grindstone. The order of the heat treatment step and the relief portion forming step does not matter. The relief portion forming step may be performed before or after the heat treatment step.

[0046] By using the above manufacturing method, it is possible to provide the high hardness region 60 and the low hardness region 62 in the first opposing surface 54, and then form the relief portion 70 in one of the first opposing surface 54 and the second opposing surface 56.

[0047] Second Embodiment: See FIGS. 8 to 10. For ease of explanation, the second through hole 32 of the external gear 16 is omitted from FIG. 8 and other figures. In this embodiment, the first member 50 is the external gear 16, and the second member 52 is the rolling element 20a of the eccentric bearing 20. As described above, the rolling element 20a of the second member 52 is disposed in the first through hole 30 of the first member 50 and rolls on the inner circumferential surface of the first through hole 30. In this embodiment, the first opposing surface 54 is the inner circumferential surface of the first through hole 30 of the first member 50 (external gear 16), and the second opposing surface 56 is the outer circumferential surface of the second member 52 (rolling element 20a). In this embodiment, the movement direction Da of the contact point between the first opposing surface 54 and the second opposing surface 56 is the circumferential direction around the center C54 of the first opposing surface 54, as in the first embodiment. FIG. 10 is also a diagram showing a cross section passing through the contact point between the first opposing surface 54 and the second opposing surface 56 described above.

[0048] The first member 50 (externally toothed gear 16) is a plate-like member having a plate shape as a whole. The axial direction X of the first opposing surface 54 of the first member 50 is parallel to the thickness direction of the first member 50. The first member 50 has a first side surface 50a on one axial side (one side in the thickness direction) and a second side surface 50b on the other axial side (other side in the thickness direction). Each of the side surfaces 50a, 50b is adjacent to the first opposing surface 54.

[0049] In this embodiment, the low hardness region 62 of the first opposing surface 54 includes a first low hardness region 62A and a second low hardness region 62B. The first low hardness region 62A is annularly provided on the first opposing surface 54 and is continuous around the center C54 of the first opposing surface 54. The second low hardness region 62B has a strip shape extending in the axial direction X and is provided on both sides of the annular first low hardness region 62A in the axial direction X. The high hardness regions 60 are provided on both sides of the annular first low hardness region 62A in the axial direction X on the first opposing surface 54. The high hardness regions 60 of this embodiment are provided in locations other than the strip-shaped second low hardness regions 62B on both sides of the annular first low hardness region 62A in the axial direction X.

[0050] In the present embodiment, the relief portion 70 is provided in the first low hardness region 62A of the first opposing surface 54. Like the annular first low hardness region 62A, the relief portion 70 is provided in an annular shape in the first opposing surface 54 and is continuous around the center C54 of the first opposing surface 54.

[0051] In this embodiment, similarly to the first embodiment, the first opposing surface 54 and the second opposing surface 56 can be in contact with each other simultaneously on both sides in the axial direction X of the annular first relief portion 70. In this embodiment, this condition is always satisfied during the process of relative movement between the first member 50 and the second member 52.

[0052] The effects of the device 10 of this embodiment will be described.

[0053] In this embodiment, too, a recess 70 is provided in the first low-hardness region 62A of the first opposing surface 54. Therefore, when the first opposing surface 54 and the second opposing surface 56 come into contact with each other, the recess 70 can prevent the low-hardness region 62 of the first opposing surface 54 from coming into contact with the second opposing surface 56, thereby achieving the same effect as (A) described above. Note that, in relation to the effect of (A), it is sufficient to provide the recess 70 in a portion of the low-hardness region 62 of the first opposing surface 54 and separate that portion of the low-hardness region 62 from the second opposing surface 56. Therefore, when the first opposing surface 54 has a second low-hardness region 62B in addition to the first low-hardness region 62A, as in the embodiment, it is not necessary to provide the recess 70 for separating the second low-hardness region 62B from the second opposing surface 56. In addition to this, it goes without saying that other relief portions 70 for separating the second low hardness region 62B and the second opposing surface 56 may be provided.

[0054] (C) The low hardness region 62 of the first opposing surface 54 is annularly provided in the first opposing surface 54, and the relief portion 70 is annularly provided in the annular low hardness region 62. Therefore, even when the annular low hardness region 62 is present, the annular relief portion 70 can prevent contact between the low hardness region 62 and the second opposing surface 56 when the first opposing surface 54 and the second opposing surface 56 come into contact. Note that, to obtain a similar effect, instead of the low hardness region 62 of the first opposing surface 54, the relief portion 70 may be annularly provided in the opposing region 74 that faces the low hardness region 62.

[0055] In addition, the device 10 of this embodiment also includes the components explained in (B) above, and can obtain the effects corresponding to those explained therein.

[0056] A manufacturing method for obtaining the above-described first member 50 and second member 52 will now be described. Reference is made to FIGS. 11 and 12. The manufacturing method of this embodiment differs from the first embodiment in the heat treatment process. Specifically, the heat treatment process of this embodiment includes a first heating step (see FIG. 11) and a second heating step (see FIG. 12). In the first heating step, a first heating range Ra on one side of the first opposing surface 54 in the axial direction X is heated to a temperature equal to or higher than the quenching temperature. In the second heating step, a second heating range Rb on the other side of the first opposing surface 54 in the axial direction X is heated to a temperature equal to or higher than the quenching temperature.

[0057] In this embodiment, both the first heated area Ra and the second heated area Rb cover the entire circumferential area of ​​the first opposing surface 54. The first heated area Ra is, for example, a continuous area from one side edge 54a of the first opposing surface 54 toward the other side edge 54b. The second heated area Rb is, for example, a continuous area from the other side edge 54b of the first opposing surface 54 toward the one side edge 54a. This second heated area Rb overlaps with the first heated area Ra at an axially intermediate portion of the first opposing surface 54. The area where the first heated area Ra and the second heated area Rb overlap in the axial direction X is referred to as an axial overlap area 90.

[0058] In the heat treatment process of this embodiment, the first opposing surface 54 is heated to a temperature equal to or higher than the quenching temperature by progressing the heating portion along a heating path corresponding to each heating step. Although not shown, this heating path is annular in shape, with the start point and end point of each heating range Ra, Rb of the first opposing surface 54 partially overlapping in the circumferential direction, as in the first embodiment.

[0059] In the heat treatment process of this embodiment, the light beam 82 is not irradiated directly onto the first opposing surface 54 of the first member 50, but rather onto both side surfaces 50a, 50b of the first member 50. More specifically, in the first heating step, the light beam 82 is irradiated onto the first side surface 50a of the first member 50, thereby heating the first heating range Ra of the first opposing surface 54 to a temperature equal to or higher than the hardening temperature. At this time, for example, the heating device 80 is fixed at one axial side of the first member 50, and the first side surface 50a of the first member 50 is irradiated with the light beam 82 while rotating the first member 50. Furthermore, in the second heating step, the light beam 82 is irradiated onto the second side surface 50b of the first member 50, thereby heating the second heating range Rb of the first opposing surface 54 to a temperature equal to or higher than the hardening temperature. At this time, for example, the heating device 80 is fixed in position on the other axial side of the first member 50, and the light beam 82 is irradiated onto the second side surface 50b of the first member 50 while the first member 50 is being rotated.

[0060] When irradiating the first side surface 50a with the light beam 82, the light beam 82 is irradiated onto a first heating irradiation region 92A capable of heating a first heating region Ra of the first opposing surface 54. When irradiating the second side surface 50b with the light beam 82, the light beam 82 is irradiated onto a second heating irradiation region 92B capable of heating a second heating region Rb of the first opposing surface 54. The heating irradiation regions 92A and 92B are regions of the side surfaces 50a and 50b that include the peripheral edge portions of the side surfaces 50a and 50b around the edges formed by the opposing surface 54 and the side surfaces 50a and 50b. When irradiating the side surface 50a of the first member 50 with the light beam 82, it is necessary to adjust the axial lengths of the heating regions Ra and Rb so that the heating regions Ra and Rb overlap in the axial direction X. In this way, the axial lengths of the heating regions Ra and Rb may be adjusted by adjusting the energy density of the light beam 82, the hardenability of the material of the first member 50, or the like.

[0061] In the heat treatment step, unlike the first embodiment, the irradiation area of ​​the light beam 82 is caused to move along an irradiation path on the side surfaces 50a, 50b that is different from the heating path on the first opposing surface 54. As a result, the heating area is caused to move along the heating path on the first opposing surface 54, and the entire circumferential range of the heating ranges Ra, Rb of the first opposing surface 54 is heated to the hardening temperature or higher. Similar to the heating path, this irradiation path forms an annular shape in which the starting point and ending point of the heating irradiation regions 92A, 92B on the side surfaces 50a, 50b of the first member 50 overlap partially in the circumferential direction.

[0062] As a result, the first heating range Ra of the first opposing surface 54 is heated to a temperature above the hardening temperature by performing the first heating step, and then cooled by self-cooling or the like, thereby being hardened. Similarly, the second heating range Rb of the first opposing surface 54 is heated to a temperature above the hardening temperature by performing the second heating step, and then cooled by self-cooling or the like, thereby being hardened. Here, the first heating range Ra and the second heating range Rb overlap. Therefore, in the axial overlap region 90 where the first heating range Ra and the second heating range Rb overlap, the first heating range Ra is hardened by heating in the previous heating step, and then tempered by reheating to a temperature above the hardening temperature in the subsequent heating step. As a result, an annular low-hardness region 62, which is a tempered region, is provided in the axial overlap region 90 of the first opposing surface 54.

[0063] In this embodiment, the heating paths 84 corresponding to the first heating range Ra and the second heating range Rb overlap in the circumferential direction, and therefore a band-shaped second low hardness region 62B, which is a tempering region, is also provided in a circumferential overlap region (not shown) at the overlapping point. In contrast, a high hardness region 60, which is a quenching region, is provided in a portion of the first opposing surface 54 other than the axial overlap region 90 and the circumferential overlap region 86.

[0064] In the relief portion forming step of this embodiment as well, the location where the relief portion 70 is to be formed is ground with a grinding tool on the opposing surface where the relief portion 70 is to be formed (here, the first opposing surface 54). In this embodiment, the annular relief portion 70 can be easily formed by grinding the opposing surface where the relief portion 70 is to be formed with a grinding tool while rotating the member where the relief portion 70 is to be formed (here, the first member 50) around the center of the opposing surface (here, the first opposing surface 54).

[0065] The order of the first heating step and the second heating step does not matter, and either may be performed first. The first heating step and the second heating step may also be performed simultaneously. In this case, it is preferable to stagger the timing of heating the axial overlap region 90 in each heating step so that the axial overlap region 90 is heated in the later heating step after hardening of the axial overlap region 90 of the first opposing surface 54 in the earlier heating step is completed.

[0066] (Third embodiment) See FIGS. 13 and 14. In this embodiment, the first member 50 is an external gear 16, and the second member 52 is an internal gear 18 that meshes with the external gear 16. The first opposing surface 54 is provided on the outer circumferential surface of the external gear 16 and serves as a tooth surface that meshes with the internal gear 18. The second opposing surface 56 is provided on the inner circumferential surface of the internal gear 18 and serves as a tooth surface that meshes with the external gear 16. In this embodiment, the movement direction (not shown) of the contact point between the first opposing surface 54 and the second opposing surface 56 is the circumferential direction around the center C54 of the first opposing surface 54, as in the first embodiment. In this embodiment, as in the second embodiment, an annular first low-hardness region 62A is provided in the first opposing surface 54. In this embodiment, as in the second embodiment, an annular relief portion 70 is provided in the annular first low-hardness region 62A.

[0067] The device 10 of this embodiment also includes the components described above in (A), (B), and (C), and provides the effects corresponding to those descriptions.

[0068] In this way, when providing the annular first low-hardness region 62A in the first opposing surface 54, the first opposing surface 54 of the first member 50 may be either the outer peripheral surface (third embodiment) or the inner peripheral surface (second embodiment) of the first member 50. Furthermore, even when the outer peripheral surface of the first member 50 is used as the first opposing surface 54 as in this embodiment, the annular low-hardness region 62 may be provided in the first opposing surface 54 using the heat treatment process described in the second embodiment.

[0069] (Fourth embodiment) Refer to Figure 15. In this embodiment, as in the second embodiment, the first member 50 is the external gear 16, and the second member 52 is the rolling element 20a of the eccentric bearing 20. In this embodiment, as in the second embodiment, the first opposing surface 54 is the inner circumferential surface of the first through hole 30 of the first member 50 (external gear 16), and the second opposing surface 56 is the outer circumferential surface of the second member 52 (rolling element 20a). In this embodiment, as in the second embodiment, an annular first low-hardness region 62A is provided in the first opposing surface 54 of the first member 50.

[0070] In this embodiment, an annular first relief portion 70 is provided in the facing region 74 of the second facing surface 56 to separate the annular first low-hardness region 62A from the second facing surface 56. When providing the relief portion 70 in the facing region 74 of the second facing surface 56, it is sufficient that the relief portion 70 is provided in at least a part of the facing region 74. In this embodiment, the relief portion 70 is provided in the entire facing region 74.

[0071] The device 10 of this embodiment also includes the components described in (A) and (B) above (some not shown), and provides the effects corresponding to those descriptions. Furthermore, as in the description of (C), even when the annular low-hardness region 62 is present, the annular relief portion 70 can prevent contact between the low-hardness region 62 and the second opposing surface 56.

[0072] Here, an example has been described in which a recess 70 is provided in the facing region 74 of the second member 52, but a recess 70 may also be provided in both the low hardness region 62 of the first member 50 and the facing region 74 of the second member 52.

[0073] Next, other improvements to the content described in the first embodiment will be described. Refer to Figure 2. The direction from the center C14 of the eccentric body 14 directly opposite the rotation center C12 of the crankshaft 12 is called the maximum eccentric direction Dd1, and the direction directly opposite the maximum eccentric direction Dd1 is called the anti-maximum eccentric direction Dd2. The center C14 of the eccentric body 14 refers to the geometric center of the shape formed by the outer circumferential surface of the eccentric body 14. A line extending from the center C14 of the eccentric body 14 in the maximum eccentric direction Dd1 is called a first reference line La1, and a line extending from the center C14 in the anti-maximum eccentric direction Dd2 is called a second reference line La2.

[0074] On the first opposing surface 54 (outer peripheral surface) of the first member 50 (eccentric body 14), a circumferential range of ±90 degrees from the first reference line La1 is referred to as the high-load range Rc1, and a circumferential range of ±90 degrees from the second reference line La2 is referred to as the low-load range Rc2. When the first opposing surface 54 is the outer peripheral surface of the eccentric body 14, the maximum load is applied to the first opposing surface 54 in the high-load range Rc1 due to contact with the second member 52 (rolling element 20a), and almost no load is applied in the low-load range Rc2. The low-load range Rc2 can be considered to be a range of the first opposing surface 54 (outer peripheral surface of the eccentric body 14) where the load is lower than other portions. The low-load range Rc2 can also be considered to be a range where the load on the first opposing surface 54 is lower within the entire circumferential range of the first opposing surface 54. The load here is assumed to be a load that would act on the first opposing surface 54 if the first opposing surface 54 and the second opposing surface 56 did not have the relief portion 70 .

[0075] The low hardness region 62 and the relief portion 70 of the first opposing surface 54 are preferably provided within the low load range Rc2. This means that the entire low hardness region 62 and the relief portion 70 are provided so as to fall within the low load range Rc2. The high hardness region 60 is provided throughout the entire high load range Rc1 and in a location other than the first low hardness region 62A in the low load range Rc2. The low hardness region 62 and the relief portion 70 are more preferably provided within a circumferential range of ±30 degrees with respect to the second reference line La2.

[0076] (D) In ​​a cross section passing through the contact point between the first opposing surface 54 and the second opposing surface 56, if there is a relief portion 70 at the opposing point of each opposing surface 54, 56, a large load is more likely to act on the high hardness region 60 than if there were no relief portion 70. In this regard, by providing the relief portion 70 in the low load range Rc2, it is possible to avoid the situation in which a large load is applied to the high hardness region 60 as described above, and to prevent a reduction in lifespan due to such a situation.

[0077] As described above, there are no particular limitations on the specific example of providing the relief portion 70 in the low load range Rc2 where the load is lower than other portions of the first opposing surface 54. Other examples will be described in the following fifth and sixth embodiments.

[0078] Fifth Embodiment: Refer to FIG. 16 . In this embodiment, an example will be described in which the first member 50 is an external gear 16, and the second member 52 is an inserting member 100 that is inserted into the second through hole 32 of the first member 50 and comes into contact with the second through hole 32. The inserting member 100 is either an inner pin 24 or a roller 34, and in this embodiment, it is a roller 34. Alternatively, the inserting member 100 may be the inner pin 24. In this embodiment, the first opposing surface 54 of the first member 50 is the inner circumferential surface of the second through hole 32, and the second opposing surface 56 of the second member 52 is the outer circumferential surface of the inserting member 100. In this embodiment, as in the first embodiment, a band-shaped low-hardness region 62 and a relief portion 70 are provided in the first opposing surface 54.

[0079] Within the range around the center C54 of the first opposing surface 54 (second through hole 32), the radially outer range is referred to as the high-load range Rc1, and the radially inner range is referred to as the low-load range Rc2. A line passing through the center C54 and perpendicular to the line passing through the center C16 of the external gear 16 (first member 50) and the center C54 of the first opposing surface 54 (second through hole 32) is referred to as the reference line Lb. The high-load range Rc1 is a range located radially outward from the reference line Lb, and the low-load range Rc2 is a range located radially inward from the reference line Lb. When the first opposing surface 54 is the inner peripheral surface of the second through hole 32 offset from the center C16 of the external gear 16, the maximum load is applied to the high-load range Rc1 of the first opposing surface 54, and almost no load is applied to the low-load range Rc2. The low-load range Rc2 can be considered a range of the first opposing surface 54 where the load is lower than other portions. The low-load range Rc2 can also be understood as a range in which the load on the first opposing surface 54 is low within the entire circumferential range of the first opposing surface 54. As described above, the load here is assumed to be the load that would act on the first opposing surface 54 if the first opposing surface 54 and the second opposing surface 56 did not have the relief portion 70.

[0080] In this case, similarly to the above, the low hardness region 62 and the relief portion 70 of the first opposing surface 54 may be provided within the low load range Rc2, thereby achieving the same effect as (D) above.

[0081] (Sixth embodiment) Refer to Figure 17. The device 10 of this embodiment is a flexible mesh gear device, and Figure 17 is a cross-sectional view showing a schematic representation of a portion thereof. The flexible mesh gear device comprises a vibrator 110, a flexible gear 112 that is flexibly deformed by the vibrator 110, and a vibrator bearing 114 that is arranged between the vibrator 110 and the flexible gear 112. The teeth of the flexible gear 112 are not shown here.

[0082] The vibrator 110 has a gear-opposing surface 110a that opposes the flexible gear 112. In this embodiment, the flexible gear 112 is an external gear, and the gear-opposing surface 110a is the outer peripheral surface of the vibrator 110. In contrast, if the flexible gear 112 is an internal gear, the gear-opposing surface 110a is the inner peripheral surface of the vibrator 110. The gear-opposing surface 110a is elliptical in a cross section perpendicular to the rotation center line (not shown) of the vibrator 110. Here, the "ellipse" is not limited to a geometrically strict ellipse, but also includes an approximate ellipse. The vibrator 110 can flexibly deform the flexible gear 112 by rotating the elliptical gear-opposing surface 110a around the rotation center C110 of the vibrator 110.

[0083] The flexure gear 112 is a flexible cylindrical member and is supported by the vibrator 110 via a vibrator bearing 114 so as to be rotatable relative to the vibrator 110.

[0084] The vibrator bearing 114 includes a plurality of rolling elements 114a and a retainer 114b that maintains the relative positions of the plurality of rolling elements 114a. The rolling elements 114a roll directly on the gear-opposing surface 110a of the flexure gear 112, with the gear-opposing surface 110a serving as the rolling surface.

[0085] Here, in this embodiment, an example will be described in which the first member 50 is the vibrator 110 and the second member 52 is the rolling element 114a of the vibrator bearing 114. The first opposing surface 54 of the first member 50 becomes the gear-opposing surface 110a (outer peripheral surface) of the vibrator 110, and the second opposing surface 56 of the second member 52 becomes the outer peripheral surface of the rolling element 114a. In this embodiment, as in the first embodiment, a band-shaped low hardness region 62 and a relief portion 70 are provided on the first opposing surface 54.

[0086] A straight line extending from the rotation center C110 of the vibrator 110 along the major axis direction De1 of the vibrator 110 is defined as a first reference line Lc1, and a straight line extending from the rotation center C110 along the minor axis direction De2 is defined as a second reference line Lc2. The major axis direction De1 refers to the direction along the major axis of the ellipse that forms the cross-sectional shape of the vibrator 110. The minor axis direction De2 refers to the direction along the minor axis of the ellipse that forms the cross-sectional shape of the vibrator 110. The cross-sectional shape of the vibrator 110 here refers to the shape of a cross section that is perpendicular to the rotation center C110.

[0087] On the first opposing surface 54 (gear-opposing surface 110a) of the vibrator 110, the range of ±45 degrees from the first reference line Lc1 is referred to as the high-load range Rc1, and the range of ±45 degrees from the second reference line Lc2 is referred to as the low-load range Rc2. When the first opposing surface 54 is the elliptical gear-opposing surface 110a of the vibrator 110, the highest load is applied to the first opposing surface 54 in the high-load range Rc1 due to contact with the second member 52 (rolling element 114a), and almost no load is applied to the low-load range Rc2. The low-load range Rc2 can be considered to be a range of the first opposing surface 54 where the load is lower than other parts. The low-load range Rc2 can also be considered to be a range where the load on the first opposing surface 54 is lower within the entire circumferential range of the first opposing surface 54. The load here is assumed to be the load that would act on the first opposing surface 54 if the first opposing surface 54 and the second opposing surface 56 did not have the relief portion 70, as described above.

[0088] In this case, similarly to the above, the low hardness region 62 and the relief portion 70 may be provided within the low load range Rc2, thereby achieving the same effect as in (D) above.

[0089] Next, variations of the components described above will be described.

[0090] The specific example of the device 10 is not particularly limited. As an example of the device 10, a gear device, that is, a power transmission device (mechanical device) has been described. When the device 10 is a power transmission device, the specific example of the power transmission element is not particularly limited. The power transmission element may be, for example, a gear, a belt, a pulley, a traction gear, or the like.

[0091] When the device 10 is a gear device, the specific example of the type of gear device is not particularly limited. The type of gear device may be, for example, the eccentric oscillating gear device described above, as well as a simple planetary gear device, a right-angle gear device, a parallel-axis gear device, a flexible mesh gear device, etc. In the embodiment, the eccentric oscillating gear device has been described as an example of a center crank type in which the crankshaft 12 is disposed on the axis of the internal gear 18. The type of eccentric oscillating gear device is not particularly limited, and may be, for example, a distributed type in which multiple crankshafts 12 are disposed at positions offset from the axis of the internal gear 18. In the distributed type, the crankshafts 12 may pass through the second through hole 32 of the external gear 16, and the inner peripheral surface of this second through hole 32 may serve as the first opposing surface 54. The type of flexible mesh gear device is not particularly limited, and may be, for example, a cup type, a top hat type, a cylindrical type, etc.

[0092] The combination of the first member 50 and the second member 52 is not particularly limited as long as they come into contact with each other when the first member 50 and the second member 52 move relative to each other due to operation of the device 10. This contact may be either sliding contact or rolling contact. When the device 10 is a gear device, the first member 50 may be, for example, a casing, a carrier, or a bearing component (e.g., an outer ring, an inner ring, etc.), and the second member 52 may be a rolling element that rolls on the first member 50, etc.

[0093] When the device 10 is a gear device, the first member 50 and the second member 52 may be two gears that mesh with each other. As an example, in the third embodiment, the first opposing surface 54 of the first member 50 is the inner circumferential surface of the external gear 16, and the second opposing surface 56 of the second member 52 is the inner circumferential surface of the internal gear 18. Alternatively, the first opposing surface 54 of the first member 50 may be the inner circumferential surface of the internal gear 18, and the second opposing surface 56 of the second member 52 may be the outer circumferential surface of the external gear 16. Alternatively, the first member 50 and the second member 52 may be two external gears that mesh with each other. Alternatively, when the device 10 is a flexible mesh type gear device, one of the external gear 16 and the internal gear 18 may be a flexible gear that meshes with a meshing gear due to flexible deformation, and the other may be a meshing gear. Furthermore, the types of the two gears that make up the first member 50 and the second member 52 are not particularly limited, and any of spur gears, bevel gears, racks, etc. may be used.

[0094] In the examples described above, the case has been described in which one of the first member 50 and the second member 52 moves relative to each other so as to rotate, and the direction of movement Da of their contact point on the first opposing surface 54 is the circumferential direction around the center of the first opposing surface 54. The manner of relative movement of the first member 50 and the second member 52 is not particularly limited. For example, one of the first member 50 and the second member 52 may move relative to each other so as to move linearly, and the direction of movement Da of their contact point may be a linear direction.

[0095] Although the example in which the low-hardness region 62 is constituted by a tempered region has been described, the specific example is not particularly limited. The low-hardness region 62 may be constituted by, for example, a base material region 66 or the like.

[0096] The first opposing surface 54 and the second opposing surface 56 may be able to come into contact with each other only on one side of the recess 70 .

[0097] The first opposing surface 54 and the second opposing surface 56 may be in surface contact rather than line contact. When the first opposing surface 54 and the second opposing surface 56 are in line contact, the low hardness region 62 and the relief portion 70 do not necessarily have to be inclined with respect to the line of contact 58 thereof, and may be, for example, parallel to the line of contact 58.

[0098] When providing the annular first low hardness region 62A in the first opposing surface 54, the high hardness region 60 may be provided on only one axial side of the first low hardness region 62A in the first opposing surface 54.

[0099] The specific heat treatment method used in the heat treatment process is not particularly limited, and various heat treatment methods can be applied. For example, the heat treatment method may be heat treatment using a light beam or high-frequency heating. The heating device 80 is not limited to an irradiation head that irradiates the light beam 82, but may also be a high-frequency heating coil that performs high-frequency heating. When the first and second heating steps in the heat treatment process are performed using a high-frequency heating coil, the circumferential overlap region 86 does not need to be formed in each heating step. Therefore, the band-shaped second low-hardness region 62B that was formed in the circumferential overlap region 86 on the first opposing surface 54 of the first member 50 does not need to be formed. Furthermore, in the first and second heating steps, the light beam 82 may be directly irradiated onto the first opposing surface 54 of the first member 50 to heat the heating ranges Ra and Rb of the first opposing surface 54 to a temperature equal to or higher than the hardening temperature.

[0100] The above-described embodiments and variations are merely examples. The abstract technical concepts should not be interpreted as being limited to the content of the embodiments and variations. Many design changes are possible in the content of the embodiments and variations, such as changing, adding, or deleting components. In the above-described embodiments, the term "embodiment" is used to emphasize that such design changes are possible. However, design changes are also permitted even in content not so marked. Hatching on cross sections in the drawings does not limit the material of the hatched object. The structures referred to in the embodiments and variations naturally include those that can be considered identical when manufacturing errors, etc. are taken into account.

[0101] Any combination of the above components is also valid. For example, any description of another embodiment may be combined with an embodiment, or any description of an embodiment and another variation may be combined with an embodiment.

[0102] In the embodiments, a component that is made up of a single member may be made up of multiple members. Similarly, in the embodiments, a component that is made up of multiple members may be made up of a single member. [Explanation of symbols]

[0103] 10...device, 14...eccentric body, 16...external gear, 18...internal gear, 50...first member, 52...second member, 54...first opposing surface, 56...second opposing surface, 58...contact line, 60...high hardness region, 62...low hardness region, 70...relief portion, 74...opposing region, 84...heating path, 84a...starting point portion, 84b...end point portion.

Claims

1. A device comprising a first member and a second member in contact with the first member with relative movement, the first member has a first opposing surface; the second member has a second opposing surface that faces and comes into contact with the first opposing surface during the relative movement, The first opposing surface includes a high hardness region in contact with the second opposing surface and a low hardness region having a surface hardness lower than that of the high hardness region, At least one of the first opposing surface and the second opposing surface is provided with a relief portion that separates the second opposing surface and the low hardness region when they contact each other, The low hardness region is provided in an annular shape on the first opposing surface, The recess is annularly provided in at least one of the low hardness region and an opposing region that faces the low hardness region on the second opposing surface.

2. The high hardness region is provided by heat treatment, The device according to claim 1 , wherein the low hardness region is a tempered region that has been tempered in the heat treatment.

3. The device according to claim 1 or 2, wherein the first and second opposing surfaces are capable of simultaneously contacting each other on both sides of the recess.

4. the first member is an external gear, the second member is disposed in a through hole that penetrates the external gear, The device according to claim 1 , wherein the first opposing surface is an inner peripheral surface of the through hole.

5. the first member is an external gear, the second member is an internal gear that meshes with the external gear, The device according to claim 1 , wherein the first opposing surface is a tooth surface provided on an outer circumferential surface of the external gear.

6. The device according to claim 1 , wherein the high hardness regions are provided on both axial sides of the annular low hardness region on the first opposing surface.

7. A manufacturing method for obtaining a first member and a second member that are in contact with each other while moving relative to each other, comprising: the first member has a first opposing surface; the second member has a second opposing surface that faces and comes into contact with the first opposing surface during the relative movement, a heat treatment process for heat-treating the first member to provide the first opposing surface with a high hardness region in contact with the second opposing surface and a low hardness region having a surface hardness lower than that of the high hardness region; a relief portion forming step of forming a relief portion in at least one of the first opposing surface and the second opposing surface that separates the second opposing surface and the low hardness region when the first opposing surface and the second opposing surface come into contact with each other, The low hardness region is provided in an annular shape on the first opposing surface, The recess is formed in an annular shape in at least one of the low hardness region and an opposing region that faces the low hardness region on the second opposing surface.

8. In the heat treatment step, the first opposing surface is heated to a temperature equal to or higher than a hardening temperature by moving a heating point along a heating path, The manufacturing method according to claim 7 , wherein the heating path is a loop whose starting point and ending point overlap each other.

9. the first opposing surface is an outer circumferential surface or an inner circumferential surface of the first member, 8. The manufacturing method according to claim 7, wherein the heat treatment process includes a first heating step of heating a first heating area on one axial side of the first member on the first opposing surface to a hardening temperature or higher, and a second heating step of heating a second heating area on the other axial side of the first opposing surface that overlaps with the first heating area to a hardening temperature or higher.

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