Eccentric oscillating gear device

Abstract

To provide an eccentric oscillation type gear device which can achieve reduction of component cost of an external gear while achieving increase of rigidity of a bearing hole.SOLUTION: An eccentric oscillation type gear device includes: an external gear 16; an internal gear which engages with the external gear 16; an eccentric body which causes the external gear 16 to oscillate; and an eccentric bearing disposed between a bearing hole 30 provided at the external gear 16 and the eccentric body. An inner peripheral surface of the bearing hole 30 forms a rolling surface on which rolling elements of the eccentric bearing roll. Surface hardness of the inner peripheral surface of the bearing hole 30 is higher than surface hardness of a tooth surface 54 of the external gear 16 by 100 HV or more.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an eccentric oscillating gear device. [Background technology]

[0002] Patent Document 1 discloses an eccentric oscillating gear device that includes an external gear, an internal gear that meshes with the external gear, an eccentric body that oscillates the external gear, and an eccentric bearing that is arranged between a bearing hole provided in the external gear and the eccentric body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-194869 Summary of the Invention [Problem to be solved by the invention]

[0004] When the rolling elements of an eccentric bearing roll in the bearing hole of an external gear, high surface pressure is generated in the bearing hole due to the rolling of the rolling elements. To ensure strength against this surface pressure, the bearing hole must be hardened by heat treatment. In order to perform such heat treatment, heat treatment such as deep quenching has traditionally been performed on the entire external gear (see, for example, Patent Document 1).

[0005] However, when the entire external gear is subjected to heat treatment, the amount of thermal distortion is likely to increase, which increases the cost of post-processing required to remove the thermal distortion. This increases the component cost of the external gear, and therefore improvement in this regard is desired.

[0006] An object of the present disclosure is to provide an eccentric oscillating gear device that can reduce the component costs of the external gear while increasing the hardness of the bearing hole. [Means for solving the problem]

[0007] The eccentric oscillating gear device of the present disclosure is an eccentric oscillating gear device comprising an external gear, an internal gear that meshes with the external gear, an eccentric body that oscillates the external gear, and an eccentric bearing that is arranged between a bearing hole provided in the external gear and the eccentric body, wherein the inner surface of the bearing hole forms a rolling surface along which the rolling elements of the eccentric bearing roll, and the surface hardness of the inner surface of the bearing hole is 100 HV or more higher than the surface hardness of the tooth surface of the external gear. [Effects of the Invention]

[0008] According to the eccentric oscillating gear device of the present disclosure, it is possible to increase the hardness of the bearing hole while reducing the component costs of the external gear. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a side cross-sectional view of the gear device of the first embodiment. [Figure 2] 1 is a cross-sectional view perpendicular to the axial direction of a gear device according to a first embodiment. [Figure 3] FIG. 2 is a cross-sectional view of the external gear of the first embodiment. [Figure 4] FIG. 2 is an enlarged view of a meshing portion between an external gear and an internal gear according to the first embodiment. [Figure 5] FIG. 10 is a cross-sectional view perpendicular to the axial direction of a gear device according to a second embodiment. [Figure 6] FIG. 10 is a side cross-sectional view of an external gear according to a third embodiment. [Figure 7] FIG. 10 is a cross-sectional view perpendicular to the axial direction of a gear device according to a third embodiment. [Figure 8] FIG. 10 is a view showing a part of a cross section perpendicular to the axial direction of a gear device according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes the embodiments. Identical components are designated by the same reference numerals, and redundant explanations will be omitted. In each drawing, components are omitted, enlarged, or reduced as appropriate for the sake of convenience. The drawings should be viewed in accordance with the orientation of the reference numerals.

[0011] The background that led to the conception of the gear device of the embodiment will be explained. As mentioned above, high surface pressure is generated in the bearing hole of the external gear due to the rolling of the rolling elements, and therefore high hardness through heat treatment is required. When performing heat treatment to harden such a bearing hole, it has traditionally been thought that the tooth flank, which generates high surface pressure due to meshing with the internal gear, also needs to have the same level of surface hardness as the bearing hole. For this reason, in order to harden the bearing hole, heat treatment (surface hardening) such as deep quenching has been performed on the entire external gear, thereby ensuring the same level of high surface hardness for both the bearing hole and the tooth flank.

[0012] However, the higher the surface hardness achieved by heat treatment (surface hardening treatment), the greater the amount of thermal distortion, which tends to increase the cost of post-processing (e.g., grinding) required to remove the thermal distortion. In particular, the tooth flanks of external gears, which have complex shapes, require strict dimensional accuracy, which has become a factor in further increasing the cost of post-processing.

[0013] As a countermeasure, the present inventors came up with the idea that, in order to increase the hardness of the bearing hole, it would be effective to intentionally lower the surface hardness of the tooth flanks than that of the bearing hole, rather than, as a matter of course, making the surface hardness of the tooth flanks equal to that of the bearing hole. Through experimental and analytical studies, the present inventors discovered that it is effective to make the surface hardness of the tooth flanks 100 HV or more lower than that of the bearing hole, i.e., to make the surface hardness of the bearing hole 100 HV or more higher than that of the tooth flanks. This reduces the amount of thermal strain on the tooth flanks due to heat treatment (surface hardening treatment) compared to when the tooth flanks are made to have a surface hardness equal to that of the bearing hole, thereby effectively reducing the cost of post-processing. In particular, reducing the amount of thermal strain on the tooth flanks, which require strict dimensional accuracy, effectively reduces the cost of post-processing. Consequently, the component costs of the external gear can be reduced while increasing the hardness of the bearing hole. The inventors of the present application also came up with the idea that, depending on the application of the gear device and the design of the external gear and internal gear, the surface pressure on the tooth flank of the external gear may be relatively smaller than the surface pressure on the bearing hole. Based on this idea, the present disclosure was made by arriving at the idea that the tooth flank of the external gear does not necessarily need to be made as hard as the bearing hole.

[0014] The "amount of thermal strain" here refers to the amount of thermal strain that occurs when surface hardening is performed on the base material region 50 (described later) of the workpiece, which is the material for the surface hardening treatment. Also, "reducing the amount of thermal strain" also includes the case where the amount of thermal strain is reduced to zero without performing surface hardening on the referenced portion (here, the tooth surface) of the base material region 50 of the workpiece.

[0015] (First embodiment) A gear device of this embodiment will be described in detail. Reference is made to Figs. 1 and 2. The eccentric oscillating gear device 10 comprises a crankshaft 12, an eccentric body 14 provided on the crankshaft 12, an external gear 16 that oscillates due to the eccentric body 14, and an internal gear 18 that meshes with the external gear 16. The gear device 10 also comprises an eccentric bearing 20 arranged between a bearing hole 30 (described later) of the external gear 16 and the eccentric body 14, carriers 22A and 22B arranged axially on both sides of the external gear 16, an inner pin 24 protruding from the carrier 22A, and a casing 26 that houses the external gear 16. The eccentric oscillating gear device 10 of this embodiment is a center crank type in which the crankshaft 12 is arranged on a center C18 of the internal gear 18. In this specification, the direction along the center C16 of the external gear 16 is simply referred to as the axial direction, and the circumferential and radial directions about the center C16 are simply referred to as the circumferential and radial directions.

[0016] The crankshaft 12 of this embodiment constitutes an input member to which rotational power is input from a drive source (not shown). The drive source is, for example, a motor, a gear motor, an engine, or the like.

[0017] The crankshaft 12 includes a shaft body 28 extending in the axial direction and an eccentric body 14 that can rotate integrally with the shaft body 28. In this embodiment, the eccentric body 14 is provided as part of the same member as the shaft body 28, but may be provided separately from 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 rotates around the rotation center C12 to oscillate the external gear 16. The eccentric phases of the multiple eccentric bodies 14 are shifted by 360° / M, where M is the number of eccentric bodies 14 (two in this embodiment). The number of eccentric bodies 14 is not particularly limited and may be one or three or more.

[0018] The external gears 16 are individually provided corresponding to the multiple eccentric bodies 14, and are supported by the corresponding eccentric bodies 14 via eccentric bearings 20 so as to be relatively rotatable. The external gears 16 include a bearing hole 30 through which the crankshaft 12 is inserted, and an inner pin hole 32 through which the inner pin 24 is inserted. The bearing hole 30 of this embodiment passes axially through the center C16 of the external gear 16. The inner pin holes 32 of this embodiment are provided at positions radially offset from the center C16 of the external gear 16 and spaced apart in the circumferential direction.

[0019] The internal gear 18 of this embodiment includes an internal gear main body 34 that is integrated with the casing 26, and a plurality of internal teeth 36 that are provided on the inner circumferential portion of the internal gear main body 34. The plurality of internal teeth 36 are formed directly on the inner circumferential surface of the internal gear main body 34. It can also be said that the internal gear main body 34 and the internal teeth 36 are integrally formed from the same member.

[0020] The eccentric bearing 20 has a plurality of rolling elements 38 arranged at intervals in the circumferential direction between the bearing hole 30 of the external gear 16 and the eccentric body 14. The rolling elements 38 in this embodiment are rollers. The eccentric bearing 20 in this embodiment does not have a dedicated inner ring, and the eccentric body 14 also serves as the inner ring. Alternatively, the eccentric bearing 20 may have a dedicated inner ring separate from the eccentric body 14. The eccentric bearing 20 does not have a dedicated outer ring, and the bearing hole 30 of the external gear 16 also serves as the outer ring. The inner circumferential surface of the bearing hole 30 forms the rolling surface on which the rolling elements 38 roll.

[0021] The carriers 22A, 22B include a first carrier 22A disposed on one axial side (the left side of the paper in FIG. 1) and a second carrier 22B disposed on the other axial side (the right side of the paper in FIG. 1). The second carrier 22B in this embodiment is formed by combining a plurality of carrier members 22a, 22b.

[0022] The inner pin 24 is integrated with the first carrier 22A. In this embodiment, the inner pin 24 is integrally formed with the first carrier 22A using the same material, but may be formed separately from the first carrier 22A.

[0023] The inner pin 24 is in contact with the inner pin hole 32 of the external gear 16, and can be synchronized with the rotation component of the external gear 16 when the external gear 16 oscillates. Here, "synchronizing with the rotation component" means maintaining the rotation component of the external gear 16 and the revolution component of the inner pin 24 at the same magnitude, within a numerical range including zero. The inner pin 24 of this embodiment is in contact with the inner pin hole 32 of the external gear 16 via a roller 40 arranged on its outer periphery. Alternatively, the inner pin 24 may be in direct contact with the inner pin hole 32. The roller 40 is rotatably supported by the inner pin 24, and is in rolling contact with both the inner pin hole 32 and the inner pin 24.

[0024] The casing 26 of this embodiment is formed by combining a plurality of casing members 26a and 26b.

[0025] One of the casing 26 and the first carrier 22A serves as an output member that outputs output rotation to a driven member outside the gear device 10. In this embodiment, the first carrier 22A serves as the output member, but the casing 26 may also serve as the output member.

[0026] The operation of the gear device 10 described above 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. When 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 first carrier 22A) 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.

[0027] Refer to FIG. 3. The external gear 16 is made of a hardenable steel material, such as alloy steel for machine structures, i.e., a metal. The external gear 16 of this embodiment is made of, for example, bearing steel. The external gear 16 is provided with a base material region 50 and a surface-hardened layer 52. In FIG. 3, only the surface-hardened layer 52 is hatched, and the base material region 50 is not hatched. The base material region 50 is a region that has the hardness of the workpiece itself, which is the material for the surface treatment of the external gear 16. The base material region 50 is a region where the surface-hardened layer 52 is not provided, and has a lower hardness than the surface-hardened layer 52. The surface-hardened layer 52 is provided by performing a surface-hardening treatment on the workpiece, which is the material for the surface-hardening treatment of the external gear 16. The surface-hardened layer 52 has a unique structure distribution and hardness distribution that correspond to the surface-hardening treatment performed on it.

[0028] The surface-hardened layer 52 of this embodiment includes a first surface-hardened layer 52A that has been subjected to a first surface-hardening treatment. Specific examples of the first surface-hardening treatment are not particularly limited, and may include, for example, partial hardening and laser cladding. The first surface-hardened layer 52A of this embodiment is subjected to partial hardening treatment by heating using a laser as the first surface-hardening treatment. When partial hardening treatment is performed, a hardened structure having martensite or the like as a main phase is provided in at least the surface layer portion of the surface-hardened layer 52. In addition to partial hardening treatments such as induction hardening, partial hardening treatments may also be used as the first surface-hardening treatment, in which areas other than the heat-treated area are masked with a carburization-proofing treatment or the like and heated in a heating furnace.

[0029] The surface hardness of the external gear 16 is assumed to be Ha, the surface hardness of the inner peripheral surface of the bearing hole 30, Hb, the surface hardness of the tooth surface 54, and Hc, the surface hardness of the inner peripheral surface of the inner pin hole 32. The surface hardnesses Ha, Hb, and Hc (as well as Hd, which will be described later) here refer to Vickers surface hardness measured by a method conforming to JIS Z2244.

[0030] The surface hardness Ha of the bearing hole 30 is 100 HV or more higher than the surface hardness Hb of the tooth flank 54. In this embodiment, this is achieved by providing a first surface-hardened layer 52A on the inner circumferential surface of the bearing hole 30 and providing a base material region 50 on the tooth flank 54. In other words, the surface hardness of the first surface-hardened layer 52A is 100 HV or more higher than the surface hardness of the base material region 50.

[0031] The surface hardness Hc of the inner pin hole 32 is lower than the surface hardness Ha of the bearing hole 30 by 100 HV or more. In this embodiment, this condition is met between all of the inner pin holes 32 and the bearing hole 30, but it is sufficient that it is met between at least one of the inner pin holes 32 and the bearing hole 30. In this embodiment, this is achieved by providing a first surface-hardened layer 52A on the inner circumferential surface of the bearing hole 30 and providing a base material region 50 on the inner circumferential surface of the inner pin hole 32. The surface hardness Hc of the inner pin hole 32 is approximately the same as the surface hardness Hb of the tooth flank 54. In this embodiment, in a cross section perpendicular to the axial direction of the external gear 16, the base material region 50 is provided on the outer surface except for the inner circumferential surface of the bearing hole 30 (i.e., no surface hardening treatment is performed).

[0032] The specific ranges of the surface hardnesses Ha, Hb, and Hc are not particularly limited. For example, the surface hardness Ha is in the range of 450 HV or more. For example, the surface hardnesses Hb and Hc are in the range of 350 HV or less.

[0033] Referring to FIG. 4 , in a cross section perpendicular to the axial direction of the external gear 16, at the meshing portion between the external gear 16 and the internal gear 18, one of the tooth flank 54 of the external gear 16 and the tooth flank 18a of the internal gear 18 is a convex curved surface 70, and the other is a concave curved surface 72. The meshing between the external gear 16 and the internal gear 18 is a convex-concave contact, where the convex curved surface 70 and the concave curved surface 72 come into contact. In other words, the contact points between the external gear 16 and the internal gear 18 are a combination of the convex curved surface 70 and the concave curved surface 72. Here, an example is shown in which the tooth flank 54 of the external gear 16 is a convex curved surface 70, and the tooth flank 18a of the internal gear 18 is a concave curved surface 72. It is also possible that the tooth flank 54 of the external gear 16 is a concave curved surface 72, and the tooth flank 18a of the internal gear 18 is a convex curved surface 70. In this embodiment, at the meshing portion between the external gear 16 and the internal gear 18, the points of contact from the start of meshing to the end of meshing are a combination of a convex curved surface 70 and a concave curved surface 72. The types of tooth profiles of the external gear 16 and the internal gear 18 that achieve this are not particularly limited.

[0034] The effects of the above gear device 10 will now be described.

[0035] (A) The surface hardness Ha of the bearing hole 30 is set to be 100 HV or more higher than the surface hardness Hb of the tooth flank 54. Therefore, as described above, compared to when the surface hardness Hb of the tooth flank 54 is set to be approximately the same as the surface hardness Ha of the bearing hole 30, the amount of thermal strain on the tooth flank 54 due to heat treatment (surface hardening treatment) can be reduced, and the cost required for post-processing can be reduced. Consequently, the component cost of the external gear 16 can be reduced while increasing the hardness of the bearing hole 30.

[0036] (B) The meshing between the external gear 16 and the internal gear 18 is convex-concave contact. Therefore, compared to when the meshing between the external gear 16 and the internal gear 18 is convex-convex contact, which is contact between convex curved surfaces, it is possible to reduce the surface pressure generated on the tooth flanks of both the external gear 16 and the internal gear 18 due to their meshing. Convex-convex contact here is achieved, for example, when the internal teeth 36 of the internal gear 18 are formed by pins separate from the internal gear main body 34. By reducing the surface pressure generated on the tooth flanks 54 of the external gear 16 in this way, it is possible to extend the life of the tooth flanks 54 even when an external gear 16 having a low hardness tooth flank 54 is used for the bearing hole 30.

[0037] (C) The surface hardness Hc of the inner pin hole 32 is 100 HV or more lower than the surface hardness Ha of the bearing hole 30. Therefore, compared to when the surface hardness Hc of the inner pin hole 32 is set to be approximately the same as the surface hardness Ha of the bearing hole 30, the amount of thermal strain in the inner pin hole 32 due to heat treatment (surface hardening treatment) can be reduced, and the cost required for post-processing can be reduced.

[0038] (C) The outer diameter of the contact member that contacts this inner pin hole 32 is larger than the outer diameter of the rolling element 38 of the eccentric bearing 20. Here, the contact member refers to either the inner pin 24 or the roller 40. Therefore, the surface pressure generated in the inner pin hole 32 due to contact of the contact member is smaller than the surface pressure generated in the bearing hole 30 due to the rolling of the rolling element 38. Because of this low surface pressure condition, the life of the inner pin hole 32 can be extended even when using an external gear 16 having an inner pin hole 32 that is lower in hardness than the bearing hole 30.

[0039] (C) A straight line La (see FIG. 3 ) is assumed to pass through the point where the gap between the inner pin hole 32 and the bearing hole 30 is narrowest, and the direction along this straight line La is referred to as the depth direction. When the surface hardness Hc of the inner pin hole 32 is lower than that of the bearing hole 30, a more appropriate hardness difference can be achieved in the hardness distribution in the depth direction in the local region between the inner pin hole 32 and the bearing hole 30, compared to when the surface hardness Hc of the inner pin hole 32 is matched to the surface hardness Ha of the bearing hole 30. Consequently, toughness can be ensured in this local region, and the life of the external gear 16 can be extended, compared to when the surface hardness Hc of the inner pin hole 32 is matched to the surface hardness Ha of the bearing hole 30.

[0040] (Second embodiment) See Fig. 5. In the first embodiment, the meshing between the external gear 16 and the internal gear 18 is uneven contact, in order to use the external gear 16 under conditions that can reduce the surface pressure generated on the tooth flanks 54 of the external gear 16. In this embodiment, the following measures are taken to use the external gear 16 under similar conditions.

[0041] Assume an inner diameter R30 of the bearing hole 30 and a pitch diameter R16 of the external gear 16. The pitch diameter R16 is the diameter of a circle connecting the centers of the multiple external teeth of the external gear 16 in the tooth height direction. Consider a case in which the pitch diameter 16 of the external gear 16 is changed relative to the inner diameter R30 of the bearing hole 30 under the same conditions: the input torque input from the crankshaft 12 to the external gear 16 and the output torque output from the external gear 16 to an output member (here, the first carrier 22A). In this case, the smaller the inner diameter R30 of the bearing hole 30 is made relative to the pitch diameter R16 of the external gear 16, the more the surface pressure on the tooth surface 54 can be reduced relative to the surface pressure on the bearing hole 30 under the same conditions: the input torque and the output torque.

[0042] In the external gear 16 of this embodiment, the inner diameter R30 of the bearing hole 30 is set to ⅓ or less of the pitch circle diameter R16. This reduces the surface pressure generated on the tooth flanks 54 compared to when the inner diameter R30 is set to more than ⅓ of the pitch circle diameter R16 under the same conditions of input torque and output torque. This effectively extends the life of the tooth flanks 54, even when an external gear 16 having a low-hardness tooth flank 54 is used for the bearing hole 30. There is no particular lower limit to the inner diameter R30 of the bearing hole 30, but it is determined according to a size that can actually be manufactured. These findings are the result of experimental and analytical studies by the inventors of the present application.

[0043] In addition, in terms of design, when changing the size of the pitch circle diameter R16 of the external gear 16 relative to the bearing hole 30, if an application allows for a large external gear 16, the pitch circle diameter R16 of the external gear 16 can be increased while leaving the size of the bearing hole 30 unchanged. Also, if an application allows for a reduction in the bearing capacity of the eccentric bearing 20, the size of the pitch circle diameter R16 of the external gear 16 can be decreased while leaving the size of the bearing hole 30 unchanged.

[0044] In addition, the gear device 10 of this embodiment is provided with the components (not shown) described above in (A), (B), and (C), and provides the effects corresponding to those descriptions.

[0045] (Third embodiment) See Figures 6 and 7. Figure 7 shows not only the external gear 16 but also the members inside the external gear 16. Also, in Figure 7, with regard to the external gear 16, only the surface-hardened layer 52 is hatched.

[0046] The eccentric oscillating gear device 10 of this embodiment is a distribution type that includes multiple crankshafts 12 arranged at positions radially offset from the center of the internal gear 18, and a crankshaft gear 90 provided on at least one crankshaft 12. In the crankshaft 12 of this embodiment, the shaft body 28 and the eccentric body 14 are provided separately.

[0047] The crankshaft gear 90 constitutes an input member to which rotational power transmitted from the drive source is input. In this embodiment, a crankshaft gear 90 (not shown) is provided on each of the multiple crankshafts 12. A common gear (not shown) meshes with the crankshaft gear 90 of each of the multiple crankshafts 12, and the rotational power of the drive source is distributed to each of the multiple crankshafts 12 via that gear. This allows the multiple crankshaft gears 90 to rotate in the same direction at the same rotational speed.

[0048] The bearing holes 30 of the external gear 16 in this embodiment are provided at positions radially offset from the center C16 of the external gear 16. A plurality of bearing holes 30 in this embodiment are provided at intervals in the circumferential direction around the center C16 of the external gear 16. The external gear 16 also has a central through hole 92 provided at its own center C16, and an offset through hole 94 provided separately from the bearing holes 30 at a position radially offset from its own center C16. A pillar member 96 connecting adjacent carriers 22A, 22B is inserted into the offset through hole 94.

[0049] Regarding the external gear 16, in addition to the surface hardness Ha of the bearing hole 30 and the surface hardness Hb of the tooth flank 54 described above, a surface hardness Hd of the inner circumferential surface of the central through hole 92 is assumed. The relationship between the surface hardness Ha of the bearing hole 30 and the surface hardness Hb of the tooth flank 54 is the same as in the first embodiment.

[0050] As in the first embodiment, the surface hardness Ha of the bearing holes 30 is at least 100 HV higher than the surface hardness Hb of the tooth flanks 54. In this embodiment, this condition is met between all bearing holes 30 and tooth flanks 54, but it is sufficient that this condition is met between at least one bearing hole 30 and tooth flank 54.

[0051] The surface hardness Hd of the central through hole 92 is lower by 100 HV or more than the surface hardness Ha of the bearing hole 30. In this embodiment, this condition is met between all of the bearing holes 30 and the central through hole 92, but it is sufficient that it is met between at least one of the bearing holes 30 and the central through hole 92. In this embodiment, this is achieved by providing a first surface-hardened layer 52A on the inner circumferential surface of the bearing hole 30 and providing a base material region 50 in the central through hole 92. The surface hardness Hd of the central through hole 92 is approximately the same as the surface hardness Hb of the tooth flank 54. In this embodiment, in a cross section perpendicular to the axial direction of the external gear 16, the base material region 50 is provided on the outer surface except for the inner circumferential surface of the bearing hole 30.

[0052] The surface hardness Hd of the central through hole 92 is 100 HV or more lower than the surface hardness Ha of the bearing hole 30. Therefore, compared to when the surface hardness Hd of the central through hole 92 is set to be approximately the same as the surface hardness Ha of the bearing hole 30, the amount of thermal strain in the central through hole 92 due to heat treatment can be reduced, and the cost required for post-processing can be reduced.

[0053] A straight line Lb is assumed to pass through the point where the distance between the central through hole 92 and the bearing hole 30 is narrowest, and the direction along this straight line Lb is referred to as the depth direction. When the surface hardness of the central through hole 92 is lower than that of the bearing hole 30, a more appropriate hardness difference can be achieved in the hardness distribution in the depth direction in the local region between the central through hole 92 and the bearing hole 30, compared to when the surface hardness Hd of the central through hole 92 is matched to the surface hardness Ha of the bearing hole 30. Consequently, toughness can be ensured in this local region, and the life of the external gear 16 can be extended, compared to when the surface hardness Hd of the central through hole 92 is matched to the surface hardness Ha of the bearing hole 30. The same is true for the local region between the tooth surface 54 of the external gear 16 and the bearing hole 30.

[0054] In addition, the gear device 10 of this embodiment includes the components (not shown) described above in (A) and (B), and provides the effects corresponding to those descriptions.

[0055] (Fourth Embodiment) See FIG. 8. The external gear 16 of this embodiment differs from the external gear 16 of the first embodiment in the second surface-hardened layer 52B, which will be described below. FIG. 8 is a diagram showing the same area as the area Sa in FIG. 3 , enlarged, in the external gear 16 of the fourth embodiment. In the above-described embodiment, the surface-hardened layer 52 includes only the first surface-hardened layer 52A. Alternatively, the surface-hardened layer 52 may include a second surface-hardened layer 52B that has been subjected to a second surface-hardened treatment different from that of the first surface-hardened layer 52A. The second surface-hardened layer 52B has a lower surface hardness than the first surface-hardened layer 52A. The combination of the first and second surface-hardened treatments to achieve this is not particularly limited. As an example, the first surface-hardened treatment may be partial quenching using a laser for heating, and the second surface-hardened treatment may be thermal refining, carburizing, nitriding, or the like. The second surface hardening treatment described here is assumed to be performed before the first surface hardening treatment, but may be performed after the first surface hardening treatment with the first surface hardened layer 52A masked.

[0056] As described above, the surface hardness Ha of the bearing hole 30 is at least 100 HV higher than the surface hardness Hb of the tooth flank 54. To satisfy this condition, in this embodiment, a first surface-hardened layer 52A is provided on the inner circumferential surface of the bearing hole 30, and a second surface-hardened layer 52B is provided on the tooth flank 54. In other words, the surface hardness of the first surface-hardened layer 52A is at least 100 HV higher than the surface hardness of the second surface-hardened layer 52B.

[0057] As described above, the surface hardness Hc of the inner pin hole 32 is lower by 100 HV or more than the surface hardness Ha of the bearing hole 30. To satisfy this condition, in this embodiment, a first surface-hardened layer 52A is provided on the inner circumferential surface of the bearing hole 30, and a second surface-hardened layer 52B is provided on the inner circumferential surface of the inner pin hole 32. In this way, in a cross section perpendicular to the axial direction of the external gear 16, to create a hardness difference between the bearing hole 30 and other outer surfaces (tooth surfaces 54, inner pin holes 32, central through hole 92, etc.), it is sufficient that either the base material region 50 or the second surface-hardened layer 52B is provided on these outer surfaces.

[0058] The gear device 10 of this embodiment includes the components (not shown) described above in (A) and (B), and provides the effects corresponding to those descriptions.

[0059] Next, variations of the components described above will be described.

[0060] So far, an example has been described in which the gear device 10 functions as a reduction gear. In this gear device, the input member is a high-speed member that rotates at a high speed, and the output member is a low-speed member that rotates at a low speed, and the external gear 16 and the internal gear 18 are used to reduce the rotation input to the high-speed member and transmit it to the low-speed member. Alternatively, the gear device 10 may function as a speed-increasing device. In this gear device, the input member is a low-speed member (such as the first carrier 22A) and the output member is a high-speed member (such as the crankshaft 12), and the external gear 16 and the internal gear 18 are used to increase the rotation input to the low-speed member and transmit it to the high-speed member.

[0061] The number of the distribution type crankshaft gears 90 is not particularly limited as long as they are provided on at least one of the multiple crankshafts 12. When there is a single crankshaft gear 90, only one crankshaft 12 may be driven by the crankshaft gear 90, and the other crankshafts 12 may be driven by the oscillation of the external gear 16.

[0062] 2 and 5 illustrate an example in which an external gear 16 having a surface hardness difference of 100 HV or more between the bearing hole 30 and the tooth flank 54 is used under conditions that allow for reduced surface pressure on the tooth flank 54 of the external gear 16. It is not essential that an external gear 16 having such a surface hardness difference be used under conditions that allow for reduced surface pressure on the tooth flank 54 of the external gear 16. In other words, an external gear 16 having the aforementioned surface hardness difference may be used under conditions that do not allow for uneven contact between the external gear 16 and the internal gear 18 and that do not allow for an inner diameter R30 of the bearing hole 30 to be equal to or greater than one-third the pitch circle diameter R16. It can also be said that, in relation to the objective of reducing the component cost of the external gear 16, it is not essential to combine a configuration for extending the life of the tooth flank 54. For example, an external gear 16 having the aforementioned surface hardness difference may be used under conditions in which the gear train 10 is operated infrequently and a long life is not required of the gear train 10.

[0063] There are no particular limitations on the shape of the tooth flanks at the meshing portion between the external gear 16 and the internal gear 18. At this meshing portion, for example, both the tooth flanks of the external gear 16 and the internal gear 18 may be convexly curved surfaces.

[0064] The multiple internal teeth 36 of the internal gear 18 may be formed by pins that are separate from the internal gear body 34.

[0065] The inner diameter R30 of the bearing hole 30 may be more than 1 / 3 the pitch circle diameter R16 of the external gear 16.

[0066] Although the example in which the inner pin 24 is provided separately from the carriers 22A, 22B has been described, the inner pin 24 may be provided integrally with one of the carriers 22A, 22B using the same member. The surface hardness Hc of the inner pin hole 32 may be set independently of the surface hardness Ha of the bearing hole 30. For example, the surface hardness Hc of the inner pin hole 32 may be lower than the surface hardness Ha of the bearing hole 30 within a range of less than 100 HV, or may be equal to or higher than the surface hardness Ha of the bearing hole 30.

[0067] The surface hardness Hd of the central through hole 92 may be set independently of the surface hardness Ha of the bearing hole 30. For example, the surface hardness Hd of the central through hole 92 may be lower than the surface hardness Ha of the bearing hole 30 within a range of less than 100 HV, or may be equal to or higher than the surface hardness Ha of the bearing hole 30.

[0068] The above-described embodiments and variations are merely examples. The abstract technical concepts should not be interpreted as being limited to the contents of the embodiments and variations. Many design changes are possible in the contents of the embodiments and variations, such as changes, additions, and deletions of components. In the above-described embodiments, the contents that allow such design changes are emphasized by adding the notation "embodiment." However, design changes are also permitted even in contents without such notation. Hatching on cross sections in the drawings does not limit the material of the hatched objects. The structures / numerical values ​​referred to in the embodiments and variations naturally include those that can be considered identical when taking into account manufacturing errors, etc.

[0069] Any combination of the above components is also valid. For example, any description of another embodiment may be combined with the embodiment, or any description of an embodiment and another variation may be combined with the embodiment. [Explanation of symbols]

[0070] 10...eccentric oscillating gear device, 14...eccentric body, 16...external gear, 18...internal gear, 20...eccentric bearing, 24...inner pin, 30...bearing hole, 32...inner pin hole, 34...internal gear body, 36...internal tooth, 38...rolling element, 50...base material region, 52A...first surface hardened layer, 52B...second surface hardened layer, 54...tooth surface, 70...convex curved surface, 72...concave curved surface, 92...central through hole, 94...through hole.

Claims

1. an external gear; an internal gear that meshes with the external gear; an eccentric body that oscillates the external gear; an eccentric bearing disposed between a bearing hole provided in the external gear and the eccentric body, an inner peripheral surface of the bearing hole constitutes a rolling surface on which the rolling elements of the eccentric bearing roll; An eccentric oscillating gear device in which the surface hardness of the inner peripheral surface of the bearing hole is 100 HV or more higher than the surface hardness of the tooth surface of the external gear.

2. a first surface-hardened layer that has been subjected to surface hardening treatment is provided on an inner peripheral surface of the bearing hole; 2. The eccentric oscillating gear device according to claim 1, wherein a second surface-hardened layer or a base material region having a lower surface hardness than the first surface-hardened layer is provided on the tooth surface of the external gear by a surface hardening treatment different from that of the first surface-hardened layer.

3. 3. An eccentric oscillating gear device according to claim 1 or 2, wherein at the meshing portion between the external gear and the internal gear, one of the tooth surfaces of the external gear and the internal gear is a convex curved surface, and the other is a concave curved surface.

4. 4. The eccentric oscillating gear device according to claim 3, wherein the internal gear comprises an internal gear body and internal teeth formed directly on the inner peripheral surface of the internal gear body.

5. 5. The eccentric oscillating gear device according to claim 1, wherein the inner diameter of the bearing hole is equal to or less than 1 / 3 the pitch circle diameter of the external gear.

6. the external gear is provided at a position radially offset from its center and includes an inner pin hole through which an inner pin is inserted, 6. The eccentric oscillating gear device according to claim 1, wherein the surface hardness of the inner peripheral surface of the inner pin hole is lower by 100 HV or more than the surface hardness of the inner peripheral surface of the bearing hole.

7. the external gear includes the bearing hole provided at a position radially offset from its center, and a central through hole provided at its center, 6. The eccentric oscillating gear device according to claim 1, wherein the surface hardness of the inner peripheral surface of the central through hole is lower by 100 HV or more than the surface hardness of the inner peripheral surface of the bearing hole.

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