Eccentric oscillating gear device

Abstract

Provided is an eccentric oscillation type gear device that can achieve high hardness of a bearing hole and can reduce the cost of components of an external gear. An eccentric oscillation type gear device includes an external gear (16), an internal gear that meshes with the external gear (16), an eccentric body that oscillates the external gear (16), and an eccentric bearing that is disposed between a bearing hole (30) provided in the external gear (16) and the eccentric body, wherein an inner peripheral surface of the bearing hole (30) constitutes a rolling surface for rolling elements of the eccentric bearing, and the surface hardness of the inner peripheral surface of the bearing hole (30) is higher than the surface hardness of a tooth surface (54) of the external gear (16) by 100 HV or more.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2022-000265 filed on January 4, 2022. The entire contents of this Japanese application are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to an eccentric oscillation type gear device. BACKGROUND

[0003] Patent Document 1 discloses an eccentric oscillation type 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 disposed between a bearing hole provided in the external gear and the eccentric body.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2013-194869

[0005] In a case where the rolling elements of the eccentric bearing roll in the bearing hole of the external gear, a high surface pressure is generated on the bearing hole due to the rolling of the rolling elements. In order to ensure the strength against this surface pressure, it is required to perform a heat treatment to harden the bearing hole. In order to implement such a heat treatment, in the past, a heat treatment such as a through-hardening has been implemented as a whole of the external gear (for example, refer to Patent Document 1).

[0006] However, when the heat treatment is implemented as a whole of the external gear, the amount of thermal strain tends to be large, which tends to cause an increase in the cost required for a subsequent process for removing the thermal strain. This becomes a cause of an increase in the component cost of the external gear, and thus improvement thereof is expected. SUMMARY

[0007] One of the objects of the present application is to provide an eccentric oscillation type gear device that can achieve hardening of a bearing hole and can achieve reduction in the component cost of an external gear.

[0008] The eccentric oscillation type gear device of the present application 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 disposed between a bearing hole provided in the external gear and the eccentric body, wherein an inner peripheral surface of the bearing hole constitutes a rolling surface for rolling of rolling elements of the eccentric bearing, and the surface hardness of the inner peripheral surface of the bearing hole is higher than the surface hardness of a tooth surface of the external gear by 100 HV or more.

[0009] According to the eccentric oscillation type gear device of the present application, it is possible to achieve hardening of a bearing hole and to achieve reduction in the component cost of an external gear. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a side sectional view of the gear device of the first embodiment.

[0011] Figure 2 Fig. 1 is a cross-sectional view of a gear device according to a first embodiment, taken in a direction orthogonal to an axial direction.

[0012] Figure 3 Fig. 2 is a cross-sectional view of an external gear according to the first embodiment.

[0013] Figure 4 Fig. 3 is an enlarged view of a meshing portion of the external gear and an internal gear according to the first embodiment.

[0014] Figure 5 Fig. 4 is a cross-sectional view of a gear device according to a second embodiment, taken in a direction orthogonal to an axial direction.

[0015] Figure 6 Fig. 5 is a side cross-sectional view of an external gear according to a third embodiment.

[0016] Figure 7 Fig. 6 is a cross-sectional view of a gear device according to the third embodiment, taken in a direction orthogonal to an axial direction.

[0017] Figure 8 Fig. 7 is a view showing a part of a cross section of a gear device according to a fourth embodiment, taken in a direction orthogonal to an axial direction.

[0018] Fig. 1 is a cross-sectional view of a gear device according to a first embodiment, taken in a direction orthogonal to an axial direction. DETAILED DESCRIPTION

[0019] Hereinafter, the embodiments will be described. The same reference numerals are assigned to the same components, and repeated description will be omitted. In each drawing, components are appropriately omitted, enlarged, and reduced for convenience of explanation. The drawings are observed in the direction of the reference numerals.

[0020] First, the background of the gear device according to the embodiments will be described. As described above, a high surface pressure is generated in the bearing hole of the external gear based on the rolling of the rolling bodies, and thus, it is required to increase the hardness of the same based on heat treatment. In the case where heat treatment is performed for the purpose of increasing the hardness of such a bearing hole, it has been conventionally considered that the tooth surface, in which a high surface pressure is generated based on the meshing with the internal gear, also needs to have the same degree of surface hardness as the bearing hole. Therefore, conventionally, in order to achieve the increase in the hardness of the bearing hole, heat treatment such as overall quenching is performed as a whole of the external gear, and thus, the same degree of high surface hardness is ensured in both the bearing hole and the tooth surface.

[0021] However, the higher the surface hardness to be achieved by the heat treatment (surface hardening treatment) is, the more the thermal strain amount is likely to increase, which tends to increase the cost required for a subsequent process (e.g., grinding process) for removing the thermal strain. In particular, since the tooth surface of the externally toothed gear of a complex shape requires strict dimensional accuracy, it tends to be a cause of further increase in the cost of the subsequent process.

[0022] As a countermeasure thereto, the present inventors have obtained the following idea: it is effective to intentionally set the surface hardness of the tooth surface to be lower than the surface hardness of the bearing hole, in relation to the surface hardness of the tooth surface which is set to be the same degree as the surface hardness of the bearing hole when high-hardening of the bearing hole is achieved. As a result of research by the present inventors through experiments and analysis, the following insight has been obtained: it is effective to set the surface hardness of the tooth surface to be lower than the surface hardness of the bearing hole by 100 HV or more (i.e., to set the surface hardness of the bearing hole to be higher than the surface hardness of the tooth surface by 100 HV or more). Thereby, compared to a case where the surface hardness of the tooth surface is set to be the same degree high as the surface hardness of the bearing hole, it is possible to reduce the thermal strain amount generated in the tooth surface by performing the heat treatment (surface hardening treatment), and thereby it is possible to effectively reduce the cost required for the subsequent process. In particular, by reducing the thermal strain amount in the tooth surface which requires strict dimensional accuracy, it is possible to effectively reduce the cost required for the subsequent process. Furthermore, it is possible to achieve high-hardening of the bearing hole, and it is possible to achieve reduction in the component cost of the externally toothed gear. Also, the present inventors have obtained the following idea: depending on the use of the gear device, the design of the externally toothed gear or the internally toothed gear, the surface pressure of the tooth surface of the externally toothed gear sometimes becomes relatively smaller than the surface pressure of the bearing hole. Based on this idea, it is not necessarily required to perform the same high-hardening of the tooth surface of the externally toothed gear as the bearing hole, and thereby the present invention has been obtained.

[0023] In addition, the "thermal strain amount" here refers to the thermal strain amount generated when the surface hardening treatment is performed on the base material region 50 (to be described later) of the workpiece which is the material of the surface hardening treatment. Also, the "reduction in the thermal strain amount" includes a case where the thermal strain amount is zero due to the fact that the surface hardening treatment is not performed on the mentioned portion (here, the tooth surface) in the base material region 50 of the workpiece.

[0024] (First Embodiment)

[0025] The details of the gear device of the embodiment will be described. Referring to Figure 1 and Figure 2The eccentric oscillation type gear device 10 includes a crankshaft 12, an eccentric body 14 provided on the crankshaft 12, an outer gear 16 oscillated by the eccentric body 14, and an inner gear 18 engaged with the outer gear 16. Further, the gear device 10 includes an eccentric bearing 20 disposed between a bearing hole 30 (to be described later) of the outer gear 16 and the eccentric body 14, a carrier 22A, 22B disposed on an axial side of the outer gear 16, an inner pin 24 protruding from the carrier 22A, and a housing 26 accommodating the outer gear 16. The eccentric oscillation type gear device 10 of the present embodiment is a center crank type gear device in which the crankshaft 12 is disposed on a center C18 of the inner gear 18. In the present specification, a direction along a center C16 of the outer gear 16 is simply referred to as an axial direction, and a circumferential direction and a radial direction with the center C16 as a center are simply referred to as a circumferential direction and a radial direction, respectively.

[0026] The crankshaft 12 of the present embodiment constitutes an input member that inputs a rotational force transmitted from a drive source (not shown). The drive source is, for example, a motor, a gear motor, or an engine.

[0027] The crankshaft 12 includes a shaft body 28 extending in the axial direction and the eccentric body 14 rotatable integrally with the shaft body 28. The eccentric body 14 of the present embodiment is provided as a part of the same member as the shaft body 28, but can be provided separately from the shaft body 28. A center C14 of the eccentric body 14 is eccentric with respect to a rotation center C12 of the crankshaft 12, and the eccentric body 14 rotates in such a manner that the center C14 thereof revolves around the rotation center C12, thereby oscillating the outer gear 16. Regarding eccentric phases of the plurality of eccentric bodies 14, when the number of the eccentric bodies 14 is M (two in the present embodiment), the eccentric phases are offset from each other by an amount corresponding to 360° / M. The number of the eccentric bodies 14 is not particularly limited, and can be any one of one and more than three.

[0028] The outer gear 16 is provided corresponding to the plurality of eccentric bodies 14, and is rotatably supported with respect to the corresponding eccentric body 14 via the eccentric bearing 20. The outer gear 16 includes a bearing hole 30 into which the crankshaft 12 is inserted, and an inner pin hole 32 into which the inner pin 24 is inserted.

[0029] The bearing hole 30 of the present embodiment penetrates the center C16 of the outer gear 16 in the axial direction. The inner pin hole 32 of the present embodiment is provided at intervals in the circumferential direction at positions of the outer gear 16 that are offset in the radial direction from the center C16.

[0030] The inner gear 18 of the present embodiment includes an inner gear main body 34 integrated with the housing 26, and a plurality of inner teeth 36 provided at an inner peripheral portion of the inner gear main body 34. The plurality of inner teeth 36 are directly formed on an inner peripheral surface of the inner gear main body 34. It can be said that the inner gear main body 34 and the inner teeth 36 are formed integrally as the same member.

[0031] The eccentric bearing 20 has a plurality of rolling elements 38 arranged circumferentially between the bearing bore 30 of the external gear 16 and the eccentric body 14 at intervals. In this embodiment, the rolling elements 38 are rollers. The eccentric bearing 20 of this embodiment does not have a dedicated inner ring; the eccentric body 14 serves as the inner ring. Alternatively, the eccentric bearing 20 may have a dedicated inner ring different from the eccentric body 14. The eccentric bearing 20 does not have a dedicated outer ring; the bearing bore 30 of the external gear 16 serves as the outer ring. The inner circumferential surface of the bearing bore 30 forms a rolling surface for the rolling elements 38 to roll.

[0032] Wheel carriers 22A and 22B include one side configured in the axial direction ( Figure 1 The first wheel frame 22A (on the left side of the paper) and the other side (on the axial direction) Figure 1 The second wheel frame 22B is shown on the right side of the paper. In this embodiment, the first wheel frame 22A is composed of multiple wheel frame components 22a and 22b.

[0033] The inner pin 24 is integrated with the first wheel frame 22A. In this embodiment, the inner pin 24 is integrally formed from the same component as the first wheel frame 22A, but it can also be separately formed from the first wheel frame 22A.

[0034] The inner pin 24 contacts the inner pin hole 32 of the outer gear 16, and can synchronize with the rotation component of the outer gear 16 when the outer gear 16 oscillates. "Synchronized with the rotation component" means that, within a numerical range including zero, the rotation component of the outer gear 16 and the revolution component of the inner pin 24 maintain the same magnitude. In this embodiment, the inner pin 24 contacts the inner pin hole 32 of the outer gear 16 via a roller 40 disposed on its outer periphery. Alternatively, the inner pin 24 can also directly contact the inner pin hole 32. The roller 40 is rotatably supported on the inner pin 24 and can roll in contact with both the inner pin hole 32 and the inner pin 24.

[0035] The outer casing 26 in this embodiment is composed of multiple outer casing components 26a and 26b.

[0036] One of the housing 26 and the first wheel carrier 22A becomes an output component that outputs rotational output to the outside of the gear mechanism 10. In this embodiment, the first wheel carrier 22A becomes the output component, but the housing 26 may also become the output component.

[0037] Next, the operation of the gear assembly 10 will be explained. When the drive source drives the input component (here, crankshaft 12) to rotate, the external gear 16 is oscillated by the eccentric body 14 of the crankshaft 12. As the external gear 16 oscillates, the meshing position of the external gear 16 and the internal gear 18 changes sequentially in the circumferential direction. As a result, with each rotation of the crankshaft 12, the rotation of either the external gear 16 or the internal gear 18 (here, external gear 16) is equal to the difference in the number of teeth between the two. This rotational component is transmitted to the output component (here, the first gear carrier 22A) via the inner pin 24, and then output as output rotation to the driven component. In this embodiment, the output rotation, after decelerating the rotation of the input component, is transmitted to the output component.

[0038] refer to Figure 3 The external gear 16 is made of a hardenable steel (i.e., metal) such as alloy steel for mechanical structures. In this embodiment, the external gear 16 is made of, for example, bearing steel. A base material region 50 and a surface-cured layer 52 are provided on the external gear 16. Figure 3 In the diagram, only the surface-cured layer 52 is shaded; the base material region 50 is not shaded. The base material region 50 is the region with the hardness of the workpiece itself, which becomes the surface-treated material for the external gear 16. The base material region 50 is the region without the surface-cured layer 52, and has a hardness lower than that of the surface-cured layer 52. The surface-cured layer 52 is formed by performing a surface-curing treatment on the workpiece, which becomes the surface-cured material for the external gear 16. The surface-cured layer 52 has a unique microstructure and hardness distribution corresponding to the surface-curing treatment performed on it.

[0039] The surface-cured layer 52 of this embodiment includes a first surface-cured layer 52A that has undergone a first surface-curing treatment. Specific examples of the first surface-curing treatment are not particularly limited; however, for example, local quenching treatment, laser cladding treatment, etc., can be used. In the first surface-cured layer 52A of this embodiment, a local quenching treatment using laser heating is performed as the first surface-curing treatment. When a local quenching treatment is performed, a quenched structure with martensite or similar phases is provided in at least the surface portion of the surface-cured layer 52. In addition, as the first surface-curing treatment, for example, a local quenching treatment such as high-frequency quenching can be used, or a local quenching treatment performed in a furnace while the area outside the heat treatment region is covered by anti-carburizing treatment, etc., can also be used.

[0040] Regarding the surface hardness of the external gear 16, let's assume the surface hardness of the inner circumferential surface of the bearing hole 30 is Ha, the surface hardness of the tooth surface 54 is Hb, and the surface hardness of the inner circumferential surface of the inner pin hole 32 is Hc. Here, surface hardness Ha, Hb, and Hc (including Hd as described later) refer to Vickers surface hardness measured in accordance with JIS Z2244.

[0041] The surface hardness Ha of the bearing hole 30 is higher than the surface hardness Hb of the tooth surface 54 by 100 HV or more. This is achieved in the present embodiment by providing the first surface-hardened layer 52A on the inner peripheral surface of the bearing hole 30 and providing the base material region 50 on the tooth surface 54. It can also be said that the surface hardness of the first surface-hardened layer 52A is higher than the surface hardness of the base material region 50 by 100 HV or more.

[0042] 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. With regard to this condition, in the present embodiment, this condition is satisfied between all of the inner pin holes 32 and the bearing hole 30, but it is sufficient that this condition is satisfied between at least one of the inner pin holes 32 and the bearing hole 30. This is achieved in the present embodiment by providing the first surface-hardened layer 52A on the inner peripheral surface of the bearing hole 30 and providing the base material region 50 on the inner peripheral surface of the inner pin hole 32. The surface hardness Hc of the inner pin hole 32 becomes the same degree as the surface hardness Hb of the tooth surface 54. In the present embodiment, on the cross section orthogonal to the axial direction of the outer gear 16, the base material region 50 (i.e., surface-hardening treatment is not performed) is provided on the outer surface other than the inner peripheral surface of the bearing hole 30.

[0043] In addition, the specific ranges of the surface hardnesses Ha, Hb, and Hc are not particularly limited. As an example, the surface hardness Ha is in the range of 450 HV or more, for example. Also, as an example, the surface hardnesses Hb and Hc are in the range of 350 HV or less, for example.

[0044] Reference Figure 4 In the cross section orthogonal to the axial direction of the outer gear 16, in the meshing portion of the outer gear 16 and the inner gear 18, one of the tooth surface 54 of the outer gear 16 and the tooth surface 18a of the inner gear 18 is provided as a convex curved surface 70, and the other is provided as a concave curved surface 72. This means that the meshing of the outer gear 16 and the inner gear 18 becomes the contact of the convex curved surface 70 and the concave curved surface 72 (i.e., convex-concave contact). In other words, it can also be said that the portion of the contact points at which the outer gear 16 and the inner gear 18 contact each other becomes the combination of the convex curved surface 70 and the concave curved surface 72. Here, an example is shown in which the tooth surface 54 of the outer gear 16 is provided as the convex curved surface 70 and the tooth surface 18a of the inner gear 18 is provided as the concave curved surface 72. However, it can also be that the tooth surface 54 of the outer gear 16 is provided as the concave curved surface 72 and the tooth surface 18a of the inner gear 18 is provided as the convex curved surface 70. In the present embodiment, in the meshing portion of the outer gear 16 and the inner gear 18, the portion of the contact points from the start of the meshing to the end of the meshing is the combination of the convex curved surface 70 and the concave curved surface 72. The type of the tooth shape of the outer gear 16 and the inner gear 18 that achieves this is not particularly limited.

[0045] Next, the effects of the above gear device 10 will be described.

[0046] (A) The surface hardness Ha of the bearing hole 30 is higher than the surface hardness Hb of the tooth surface 54 by 100 HV or more. Therefore, as described above, compared to a case where the surface hardness Hb of the tooth surface 54 is higher than the surface hardness Ha of the bearing hole 30 by the same degree, it is possible to reduce the amount of thermal strain generated in the tooth surface 54 by performing heat treatment (surface hardening treatment), and thus it is possible to reduce the cost required for subsequent processes. Furthermore, it is possible to achieve high hardness of the bearing hole 30, and it is possible to achieve reduction of the component cost of the external gear 16.

[0047] (B) The engagement of the external gear 16 and the internal gear 18 becomes convex-concave contact. Therefore, compared to a case where the engagement of the external gear 16 and the internal gear 18 becomes convex-convex contact (i.e., convex-convex contact) of convex curved surfaces, it is possible to reduce the surface pressure generated in the tooth surfaces of both the external gear 16 and the internal gear 18 due to the engagement of the external gear 16 and the internal gear 18. The convex-convex contact here is achieved, for example, in a case where the internal teeth 36 of the internal gear 18 are constituted by pins separate from the internal gear body 34. Thus, by reducing the surface pressure generated in the tooth surface 54 of the external gear 16, even in a case where the external gear 16 having a tooth surface 54 with lower hardness relative to the bearing hole 30 is used, it is possible to extend the life of the tooth surface 54.

[0048] (C) The surface hardness Hc of the internal pin hole 32 is lower than the surface hardness Ha of the bearing hole 30 by 100 HV or more. Therefore, compared to a case where the surface hardness Hc of the internal pin hole 32 is higher than the surface hardness Ha of the bearing hole 30 by the same degree, it is possible to reduce the amount of thermal strain generated in the internal pin hole 32 by performing heat treatment (surface hardening treatment), and thus it is possible to reduce the cost required for subsequent processes.

[0049] (D) The outer diameter of a contact member that contacts the internal pin hole 32 is larger than the outer diameter of the rolling body 38 of the eccentric bearing 20. The contact member here refers to either one of the internal pin 24 and the roller 40. Therefore, the surface pressure generated in the internal pin hole 32 due to contact of the contact member becomes smaller than the surface pressure generated in the bearing hole 30 due to rolling of the rolling body 38. Thus, under conditions where the surface pressure is small, even in a case where the external gear 16 having an internal pin hole 32 with lower hardness relative to the bearing hole 30 is used, it is possible to extend the life of the internal pin hole 32.

[0050] (E) Assuming that a straight line La (refer to FIG. 2) passing through the narrowest portion of the interval between the internal pin hole 32 and the bearing hole 30, the surface hardness Hc of the internal pin hole 32 is lower than the surface hardness Ha of the bearing hole 30 by 100 HV or more at a position on the straight line La that is 0.5 mm or more from the internal pin hole 32. Therefore, compared to a case where the surface hardness Hc of the internal pin hole 32 is higher than the surface hardness Ha of the bearing hole 30 by the same degree at the position on the straight line La that is 0.5 mm or more from the internal pin hole 32, it is possible to reduce the amount of thermal strain generated in the internal pin hole 32 by performing heat treatment (surface hardening treatment), and thus it is possible to reduce the cost required for subsequent processes. Figure 3), and the direction along the straight line La is referred to as a depth direction. In the case where the surface hardness Hc of the inner pin hole 32 is lowered with respect to the bearing hole 30, the hardness distribution in the depth direction in the local area between the inner pin hole 32 and the bearing hole 30 can have a moderate hardness difference compared to the case where the surface hardness Hc of the inner pin hole 32 is consistent with the surface hardness Ha of the bearing hole 30. Furthermore, the toughness can be ensured in the local area compared to the case where the surface hardness Hc of the inner pin hole 32 is consistent with the surface hardness Ha of the bearing hole 30, and thus the life of the outer gear 16 can be extended.

[0051] (2nd Embodiment)

[0052] Reference Figure 5 In the 1st embodiment, the case where the engagement of the outer gear 16 and the inner gear 18 is set to convex-concave contact in order to use the outer gear 16 under the condition that the surface pressure generated on the tooth surface 54 of the outer gear 16 can be reduced was explained. In the present embodiment, the following measures are taken in order to use the outer gear 16 under the same condition.

[0053] The inner diameter R30 in the diameter of the bearing hole 30 and the pitch circle diameter R16 of the outer gear 16 are focused on. The pitch circle diameter R16 refers to the diameter of a circle connecting the tooth height direction central positions of the respective teeth of the plurality of outer teeth of the outer gear 16. The case where the size of the pitch circle diameter R16 of the outer gear 16 is changed with respect to the inner diameter R30 of the bearing hole 30 under the condition that the input torque input from the crankshaft 12 to the outer gear 16 is the same as the output torque output from the outer gear 16 to the output member (here, the 1st carrier 22A) is considered. At this time, the more the inner diameter R30 of the bearing hole 30 is reduced with respect to the pitch circle diameter R16 of the outer gear 16, the more the surface pressure of the tooth surface 54 can be relatively reduced with respect to the surface pressure of the bearing hole 30 under the condition that the input torque and the output torque are the same.

[0054] In the outer gear 16 of the present embodiment, the inner diameter R30 of the bearing hole 30 is set to be 1 / 3 or less of the pitch circle diameter R16. Thereby, under the condition that the input torque and the output torque are the same, the surface pressure generated on the tooth surface 54 can be reduced compared to the case where the inner diameter R30 is set to be more than 1 / 3 of the pitch circle diameter R16, and thus even in the case where the outer gear 16 having a tooth surface 54 with a lower hardness with respect to the bearing hole 30 is used, the life of the tooth surface 54 can be effectively extended. The lower limit value of the inner diameter R30 of the bearing hole 30 is not particularly limited, but becomes a size determined in accordance with the dimensions that can be actually manufactured. These are insights obtained as a result of research by the present inventors through experiments and analysis.

[0055] In addition, in terms of design, in order to change the size of the pitch circle diameter R16 of the outer gear 16 with respect to the bearing hole 30, the size of the bearing hole 30 is maintained and the pitch circle diameter R16 of the outer gear 16 is increased in order to allow use of a large outer gear 16. Also, in order to allow a decrease in the bearing capacity of the eccentric bearing 20, the size of the outer gear 16 is maintained and the size of the bearing hole 30 is decreased.

[0056] In addition to the above, the gear device 10 of the present embodiment has the configuration elements (not shown) described in (A), (B), (C), (D), and (E) above, and thus achieves the effects corresponding to these descriptions.

[0057] (Third Embodiment)

[0058] Reference Figure 6 and Figure 7 In Figure 7 , the components on the inner side of the outer gear 16 are shown together with the outer gear 16. Also, in Figure 7 , only the surface solidification layer 52 of the outer gear 16 is hatched.

[0059] The eccentric oscillation type gear device 10 of the present embodiment is a distribution type gear device that has a plurality of crankshafts 12 disposed at positions radially offset from the center of the pinion gear 18, and a crankshaft gear 90 provided on at least one of the crankshafts 12. The crankshaft 12 of the present embodiment is configured such that the shaft body 28 and the eccentric body 14 are provided separately.

[0060] The crankshaft gear 90 constitutes an input member that inputs rotational power transmitted from a drive source. In the present embodiment, the crankshaft gear 90 (not shown) is provided on each of the plurality of crankshafts 12. A common gear (not shown) is engaged with the crankshaft gears 90 of the plurality of crankshafts 12, and rotational power of the drive source is distributed to the plurality of crankshafts 12 via the gear. Thus, the plurality of crankshaft gears 90 can rotate at the same rotational speed in the same direction.

[0061] The bearing hole 30 of the outer gear 16 of the present embodiment is provided at a position radially offset from the center C16 of the outer gear 16. The bearing hole 30 of the present embodiment is provided at a plurality of positions circumferentially spaced apart around the center C16 of the outer gear 16. In addition, the outer gear 16 has a central through hole 92 provided at the center C16 thereof, and an offset through hole 94 provided at a position radially offset from the center C16 thereof and different from the bearing hole 30. A columnar member 96 that links adjacent wheel carriers 22A and 22B is inserted into the offset through hole 94.

[0062] With respect to the outer gear 16, in addition to the surface hardness Ha of the bearing hole 30 and the surface hardness Hb of the tooth surface 54 described above, the surface hardness Hd of the inner peripheral surface of the central through-hole 92 is also taken into account. The relationship between the surface hardness Ha of the bearing hole 30 and the surface hardness Hb of the tooth surface 54 is the same as in the first embodiment.

[0063] As in the first embodiment, the surface hardness Ha of the bearing hole 30 is higher than the surface hardness Hb of the tooth surface 54 by 100 HV or more. With respect to this condition, in the present embodiment, this condition is satisfied between all of the bearing holes 30 and the tooth surface 54, but it is sufficient that this condition is satisfied between at least one of the bearing holes 30 and the tooth surface 54.

[0064] The surface hardness Hd of the central through-hole 92 is lower than the surface hardness Ha of the bearing hole 30 by 100 HV or more. With respect to this condition, in the present embodiment, this condition is satisfied between all of the bearing holes 30 and the central through-hole 92, but it is sufficient that this condition is satisfied between at least one of the bearing holes 30 and the central through-hole 92. This is achieved in the present embodiment by providing the first surface hardened layer 52A on the inner peripheral surface of the bearing hole 30 and the base material region 50 on the central through-hole 92. The surface hardness Hd of the central through-hole 92 becomes the same degree as the surface hardness Hb of the tooth surface 54. In the present embodiment, the base material region 50 is provided on the outer surface other than the inner peripheral surface of the bearing hole 30 in the cross section orthogonal to the axial direction of the outer gear 16.

[0065] The surface hardness Hd of the central through-hole 92 is lower than the surface hardness Ha of the bearing hole 30 by 100 HV or more. Therefore, compared to the case where the surface hardness Hd of the central through-hole 92 is made the same degree as the surface hardness Ha of the bearing hole 30, it is possible to reduce the amount of thermal strain generated in the central through-hole 92 by performing heat treatment, and thus it is possible to reduce the cost required for subsequent processes.

[0066] A straight line Lb passing through the narrowest portion between the central through-hole 92 and the bearing hole 30 is assumed, and the direction along this straight line Lb is referred to as the depth direction. In the case where the surface hardness of the central through-hole 92 is lowered with respect to the bearing hole 30, compared to the case where the surface hardness Hd of the central through-hole 92 is made the same as the surface hardness Ha of the bearing hole 30, it is possible to have a moderate hardness difference in the hardness distribution in the depth direction in the local region located between the central through-hole 92 and the bearing hole 30. Furthermore, compared to the case where the surface hardness Hd of the central through-hole 92 is made the same as the surface hardness Ha of the bearing hole 30, it is possible to secure toughness in this local region, and thus it is possible to extend the life of the outer gear 16. In addition, it can be said that this is also the same in the local region located between the tooth surface 54 of the outer gear 16 and the bearing hole 30.

[0067] In addition, the gear device 10 of the present embodiment has the configuration elements (not shown) described in (A) and (B) above, thereby obtaining the effects corresponding to these descriptions.

[0068] (4th Embodiment)

[0069] Reference Figure 8 The outer gear 16 of the present embodiment differs from the outer gear 16 of the 1st embodiment in that a 2nd surface hardened layer 52B, described below, is different. Figure 8 is a view showing the same portion as the portion of the outer gear 16 of the 4th embodiment in which the range Sa of the enlarged Figure 3 In the above-described embodiments, the example in which the surface hardened layer 52 includes only the 1st surface hardened layer 52A has been described. In addition to this, the surface hardened layer 52 can include a 2nd surface hardened layer 52B that is different from the 1st surface hardened layer 52A and on which a 2nd surface hardening treatment is performed. The 2nd surface hardened layer 52B has a lower surface hardness than the 1st surface hardened layer 52A. The combination of the 1st surface hardening treatment and the 2nd surface hardening treatment that achieves this is not particularly limited. As one example, as the 1st surface hardening treatment, for example, a local quenching treatment using heating by laser can be employed, and as the 2nd surface hardening treatment, for example, a quenching and tempering treatment, a carburizing treatment, a nitriding treatment, or the like can be employed. The 2nd surface hardening treatment assumed here is performed before the 1st surface hardening treatment, but can also be performed after the 1st surface hardening treatment in a state in which the 1st surface hardened layer 52A is covered.

[0070] As described above, the surface hardness Ha of the bearing hole 30 is higher than the surface hardness Hb of the tooth surface 54 by 100 HV or more. In order to satisfy this condition, in the present embodiment, the 1st surface hardened layer 52A is provided to the inner peripheral surface of the bearing hole 30, and the 2nd surface hardened layer 52B is provided to the tooth surface 54. It can also be said that the surface hardness of the 1st surface hardened layer 52A is higher than the surface hardness of the 2nd surface hardened layer 52B by 100 HV or more.

[0071] As described above, 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 order to satisfy this condition, in the present embodiment, the 1st surface hardened layer 52A is provided to the inner peripheral surface of the bearing hole 30, and the 2nd surface hardened layer 52B is provided to the inner peripheral surface of the inner pin hole 32. In this way, in a cross section orthogonal to the axial direction of the outer gear 16, in order to have a difference in hardness between the bearing hole 30 and the other outer surfaces (the tooth surface 54, the inner pin hole 32, the central through hole 92, and the like), either one of the base material region 50 and the 2nd surface hardened layer 52B can be provided to the outer surface.

[0072] The gear device 10 of the present embodiment has the configuration elements (not shown) described in (A) and (B) above, thereby obtaining the effects corresponding to these descriptions.

[0073] Next, a modification of each of the configuration elements described above will be described.

[0074] The above describes an example in which the gear device 10 functions as a reduction device. In this gear device, the input member is a high-speed member that rotates at high speed, the output member is a low-speed member that rotates at low speed, and the rotation input to the high-speed member is transmitted to the low-speed member after being reduced in speed using the external gear 16 and the internal gear 18. Other than this, the gear device 10 can also function as a step-up device. In this gear device, the input member is a low-speed member (the first carrier 22A or the like), the output member is a high-speed member (the crankshaft 12 or the like), and the rotation input to the low-speed member is transmitted to the high-speed member after being increased in speed using the external gear 16 and the internal gear 18.

[0075] The distribution-type crankshaft gear 90 can be provided on at least one of the plurality of crankshafts 12, and the number thereof is not particularly limited. In the case where the crankshaft gear 90 is one, only one of the crankshafts 12 is driven by the crankshaft gear 90, and the other crankshafts 12 can be driven by the oscillation of the external gear 16.

[0076] In Figure 2 and Figure 5 , an example in which the external gear 16 having a surface hardness difference of 100 HV or more between the bearing hole 30 and the tooth surface 54 is used under the condition that the surface pressure generated on the tooth surface 54 of the external gear 16 can be reduced is described. The external gear 16 having such a surface hardness difference does not necessarily have to be used under the condition that the surface pressure generated on the tooth surface 54 of the external gear 16 can be reduced. In other words, the external gear 16 having the above-described surface hardness difference can also be used under the condition that the engagement of the external gear 16 and the internal gear 18 is not set to convex-concave contact and the inner diameter R30 of the bearing hole 30 is not set to 1 / 3 or less of the pitch circle diameter R16. It can also be said that, in relation to the purpose of reducing the component cost of the external gear 16, the structure for prolonging the life of the tooth surface 54 does not necessarily have to be combined. For example, the external gear 16 having the above-described surface hardness difference can also be used under the condition that the frequency of operation of the gear device 10 is low and the gear device 10 is not required to have a long life.

[0077] The shape of the tooth surface in the engagement portion of the external gear 16 and the internal gear 18 is not particularly limited. In this engagement portion, for example, both the tooth surface of the external gear 16 and the tooth surface of the internal gear 18 can be convex curved surfaces.

[0078] The plurality of internal teeth 36 of the internal gear 18 can also be formed by pins separate from the internal gear body 34.

[0079] The inner diameter R30 of the bearing hole 30 can be greater than 1 / 3 of the pitch diameter R16 of the external gear 16.

[0080] In the above, the example in which the internal pin 24 is provided separate from the wheel carrier 22A, 22B has been described, but the internal pin 24 can also be provided as one body with the same member as one of the wheel carriers 22A, 22B. The surface hardness Hc of the internal pin hole 32 can be set independently of the surface hardness Ha of the bearing hole 30. For example, the surface hardness Hc of the internal pin hole 32 can be lower than the surface hardness Ha of the bearing hole 30 in a range of less than 100 HV, or can be set to be the same as or higher than the surface hardness Ha of the bearing hole 30.

[0081] The surface hardness Hd of the central through hole 92 can 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 can be lower than the surface hardness Ha of the bearing hole 30 in a range of less than 100 HV, or can be set to be the same as or higher than the surface hardness Ha of the bearing hole 30.

[0082] The above embodiments and modified examples are examples. The abstract technical ideas should not be limited by the contents of the embodiments and modified examples. The contents of the embodiments and modified examples can be subjected to a large number of design changes such as changes, additions, and deletions of components. In the above embodiments, statements in which "embodiment" is noted are emphasized with respect to contents that can be subjected to such design changes. However, this does not mean that design changes are not allowed in contents in which such statements are not noted. The hatching of the cross sections of the drawings is not used to limit the material of the object to which the hatching is noted. The structures and values mentioned in the embodiments and modified examples certainly include structures and values that can be considered to be the same in consideration of manufacturing errors and the like.

[0083] Any combination of the above components is effective. For example, any of the items described in the embodiments can be combined with any of the items described in other embodiments, and any of the items described in the modified examples can be combined with any of the items described in the embodiments and other modified examples.

Claims

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

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

3. The eccentric oscillating gear device according to claim 1 or 2, wherein one of the tooth surface of the external gear and the tooth surface of the internal gear is a convex curved surface, and the other is a concave curved surface, in an engaged portion of the external gear and the internal gear.

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

5. The eccentric oscillating gear device according to claim 1 or 2, wherein an inner diameter of the bearing hole is 1 / 3 or less of a pitch circle diameter of the external gear.

6. The eccentric oscillating gear device according to claim 1 or 2, wherein the external gear comprises an internal pin hole provided at a position radially offset from a center of the external gear and through which an internal pin is inserted, and a surface hardness of an inner peripheral surface of the internal pin hole is lower than a surface hardness of the inner peripheral surface of the bearing hole by 100 HV or more.

7. The eccentric oscillating gear device according to claim 1 or 2, wherein the external gear comprises the bearing hole provided at a position radially offset from the center of the external gear, and a central through hole provided at the center of the external gear, and a surface hardness of an inner peripheral surface of the central through hole is lower than a surface hardness of the inner peripheral surface of the bearing hole by 100 HV or more. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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