Gear device

Abstract

The present invention addresses the problem of providing a gear device capable of reducing the size of the gear device and more favorably suppressing the loss of a preload applied to a main bearing. A gear device is provided with a housing, an internal gear, and a main bearing, and the housing is provided with: a protruding part (42) which protrudes further inward in the radial direction than an outer ring arrangement surface (40) of the housing and in which an internal tooth groove (44) is formed; and a receiving surface (54) provided on the protruding portion and receiving an outer ring (48) of the main bearing, the outer ring being provided with: an inner side surface (60) provided on the receiving surface side in the axial direction of the outer ring; and an inner inclined portion (64) provided between an outer peripheral contact surface (62) of the outer ring and the inner side surface, the maximum inner diameter (R48a) of a rolling surface (48a) of the outer ring being smaller than the inner diameter (R44a) of a groove bottom (44a) of the inner tooth groove, and the radial length (L64) of the inner inclined portion being smaller than the radial length (L42) of the protruding portion from the outer ring arrangement surface to the groove bottom.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2023-218075 filed on December 25, 2023. The entire content of the Japanese application is incorporated herein by reference. Technical Field

[0002] The present invention relates to a gear device. Background Art

[0003] Patent Document 1 discloses a gear device including a housing, an internal gear provided in the housing, and a main bearing disposed in the housing. The internal gear includes internal tooth grooves formed in the housing and internal tooth pins fitted into the internal tooth grooves. The housing includes: an outer ring mounting surface for mounting the outer ring of the main bearing; a protruding portion that protrudes more radially inward than the outer ring mounting surface and is formed with the internal tooth grooves; and a bearing surface provided on the protruding portion for bearing the outer ring of the main bearing.

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2021-4660

[0005] The inventors of the present application studied the gear device of Patent Document 1. As a result, the following new findings were obtained: When miniaturizing the gear device, under more severe usage conditions or when excessive loads are applied, wear is likely to occur on the bearing surface of the housing, and the preload applied to the main bearing may sometimes disappear. Summary of the Invention

[0006] Therefore, one object of the present invention is to provide a gear device that can miniaturize the gear device while more effectively suppressing the disappearance of the preload applied to the main bearing.

[0007] The gear device of the present invention includes: a housing; an internal gear having internal tooth grooves formed in the housing and internal tooth pins fitted into the internal tooth grooves; and a main bearing having an outer ring disposed on the outer ring mounting surface of the housing and rolling elements rolling on the rolling surface of the outer ring. The housing includes: a protruding portion that protrudes more radially inward than the outer ring mounting surface and is formed with the internal tooth grooves; and a bearing surface provided on the protruding portion for bearing the outer ring. The outer ring includes: an inner side surface provided on the bearing surface side in the axial direction of the outer ring; and an inner inclined portion provided between the outer peripheral contact surface of the outer ring in contact with the outer ring mounting surface and the inner side surface. The maximum inner diameter of the rolling surface is smaller than the inner diameter of the bottom of the internal tooth groove, and the radial length of the inner inclined portion is smaller than the radial length of the protruding portion from the outer ring mounting surface to the bottom of the groove.

[0008] According to the present invention, it is possible to provide a gear device that can miniaturize the gear device while more effectively suppressing the disappearance of the preload applied to the main bearing. Description of the Drawings

[0009] Figure 1 is a side cross-sectional view showing the gear device of the first embodiment.

[0010] Figure 2 is Figure 1 an enlarged view of

[0011] Figure 3 is a schematic view when a part of the protruding portion of the housing is observed axially.

[0012] Figure 4 is a view when observing the gear device of the reference embodiment from the same line of sight direction as Figure 2 the same.

[0013] Figure 5 is a view when observing the gear device of the second embodiment from the same line of sight direction as Figure 2 the same.

[0014] Figure 6 is an explanatory view regarding the tipping of the clamping member.

[0015] In the drawings: 10 - gear device, 12 - housing, 14 - internal gear, 16 - main bearing, 34 - pin, 40 - outer ring mounting surface, 42 - protruding portion, 44 - internal tooth groove, 44a - bottom of the groove, 46 - internal tooth pin, 48 - outer ring, 52 - rolling element, 54 - bearing surface, 56 - portion between grooves, 58 - inclined portion between grooves, 60 - inner side surface, 62 - outer peripheral contact surface, 64 - inner inclined portion, 68 - outer inclined portion, 90 - clamping member. Detailed Embodiment

[0016] Hereinafter, embodiments of the gear device of the present invention will be described. The same or equivalent elements are denoted by the same reference numerals, and repeated descriptions are omitted. In each drawing, for the sake of convenience of explanation, constituent elements are appropriately omitted, enlarged, or reduced. The drawings are observed according to the direction of the reference numerals.

[0017] (First Embodiment)

[0018] Refer to Figure 1 . The gear device 10 includes: a housing 12; an internal gear 14 provided in the housing 12; a main bearing 16 disposed radially inside the housing 12; a carrier 18 as an inner member disposed radially inside the main bearing 16; and an external gear 20 meshing with the internal gear 14. In this specification, the rotation center when the outer ring 48 and the inner ring 50 of the main bearing 16 rotate relative to each other is referred to as the rotation center line C16 of the main bearing 16. Further, the direction along the rotation center line C16 of the main bearing 16 is simply referred to as the axial direction, and the radial direction and the circumferential direction of a circle concentric with the rotation center line C16 are simply referred to as the radial direction and the circumferential direction, respectively.

[0019] The housing 12 has a hollow structure that is integrally annular, and various components such as the main bearing 16, the wheel carrier 18, and the external gear 20 are accommodated inside thereof. The housing 12, the internal gear 14, and the main bearing 16 will be described later.

[0020] The gear device 10 includes: an input member 22 that transmits the rotation input from the drive source to a gear mechanism constituted by the internal gear 14 and the external gear 20; an output member 24 that outputs the rotation transmitted from the gear mechanism to the driven member; and a fixing member 26 that is fixed to an external member. In the present embodiment, the input member 22 is a crankshaft 30 having an eccentric body 28 that swings the external gear 20, the output member 24 is the wheel carrier 18, and the fixing member 26 is the housing 12. The rotation is input to the input member 22 directly from the drive source or via a power transmission path. Specific examples of the drive source are not particularly limited, and for example, they are a motor, a gear motor, an engine, etc. Specific examples of the driven member are not particularly limited, and for example, they are part of (1) industrial machines such as machine tools and construction machines, (2) robots such as industrial robots and service robots, (3) conveying equipment such as conveyors, and (4) various machines such as vehicles.

[0021] In the present embodiment, the gear mechanism constituted by the internal gear 14 and the external gear 20 constitutes an eccentric swing type gear mechanism which is a kind of planetary gear mechanism. And, the gear mechanism of the present embodiment is a distributed eccentric swing type gear mechanism in which a plurality of crankshafts 30 are arranged at positions radially offset from the rotation center line C16 of the main bearing 16. At this time, crankshaft gears (not shown) are provided on the plurality of crankshafts 30, and the rotation of pinions (not shown) meshing with the respective crankshaft gears of the plurality of crankshafts is input to the plurality of crankshafts 30.

[0022] The crankshaft 30 has at least one (here, two) eccentric bodies 28. The eccentric body 28 has a circular shape that is eccentric with respect to the rotation center line C30 of the crankshaft 30. The external gears 20 are provided corresponding to the plurality of eccentric bodies 28 of the crankshaft 30, and are supported by the corresponding eccentric bodies 28 via eccentric bearings 32. The wheel carriers 18 of the present embodiment are separately arranged on both axial sides of the external gear 20. The pin 34 projects from one wheel carrier 18 and penetrates the through hole 20a of the external gear 20. The pin 34 directly or indirectly abuts against the through hole 20a of the external gear 20, so that the rotation component of the external gear 20 can be synchronized with the wheel carrier 18. The pins 34 of the present embodiment connect the respective wheel carriers 18.

[0023] Next, the operation of the above-described gear device 10 will be described. When the input member 22 rotates, the gear mechanism composed of the internal gear 14 and the external gear 20 starts to operate. When the gear mechanism operates, the output member 24 outputs rotation from the gear mechanism, and this rotation is output from the output member 24 to the driven member. In the present embodiment, the rotation obtained by decelerating the rotation of the input member 22 is output from the output member 24. In the present embodiment, when the crankshaft 30 of the input member 22 rotates, its eccentric body 28 causes the external gear 20 to swing. When the external gear 20 swings, the meshing position between the external gear 20 and the internal gear 14 changes circumferentially. Thus, every time the crankshaft 30 rotates one revolution, one of the external gear 20 and the internal gear 14 (here, the external gear 20) rotates on its own axis, and the output member 24 outputs the component of its rotation on its own axis.

[0024] Reference Figure 2 . The housing 12 includes an outer ring arrangement surface 40 for arranging the outer ring 48 of the main bearing 16 and a protruding portion 42 that protrudes more radially inward than the outer ring arrangement surface 40.

[0025] The internal gear 14 includes: a plurality of internal tooth grooves 44 formed in the inner circumferential portion of the protruding portion 42 of the housing 12; and a plurality of internal tooth pins 46 respectively fitted into the plurality of internal tooth grooves 44 (also refer to Figure 3 ). When viewed axially, the plurality of internal tooth grooves 44 are each recessed radially outward and are arc-shaped. The internal tooth pins 46 are rotatably supported by the internal tooth grooves 44. The internal tooth pins 46 constitute the internal tooth portion of the internal gear 14 that meshes with the external gear 20.

[0026] In the present embodiment, the main bearings 16 are respectively arranged on both sides in the axial direction with respect to the protruding portion 42 of the housing 12. Hereinafter, the relationship between the main bearing 16 arranged on one side in the axial direction with respect to the protruding portion 42 and the surrounding structure will be mainly described. The matters described regarding their relationship can also be satisfied between the main bearing 16 arranged on the other side in the axial direction with respect to the protruding portion 42 and the surrounding structure. And, when focusing on one main bearing 16 and the protruding portion 42 of the housing 12, the side ([[]] Figure 2 the right side of the paper surface) facing the main bearing 16 along the axial direction from the protruding portion 42 is referred to as the axially outer side, and the side opposite thereto in the axial direction ([[]] Figure 2 the left side of the paper surface) is referred to as the axially inner side.

[0027] The main bearing 16 is disposed between the housing 12 and the wheel carrier 18. The main bearing 16 includes an outer ring 48 disposed on the outer ring mounting surface 40 of the housing 12, an inner ring 50 integrated with the wheel carrier 18, and rolling elements 52 that roll on the outer rolling surface 48a of the outer ring 48 and the inner rolling surface 50a of the inner ring 50. The main bearing 16 of the present embodiment includes a dedicated inner ring 50 that is separate from the wheel carrier 18, but the inner ring 50 may also be integrated with the wheel carrier 18 by being formed integrally with the wheel carrier 18 from the same component as the wheel carrier 18. The inner ring 50 of the present embodiment is integrated with the wheel carrier 18 by interference fit or the like. The rolling elements 52 of the present embodiment are spherical, but the specific examples thereof are not particularly limited, and various rolling elements such as rollers may also be used.

[0028] The main bearing 16 is a type of bearing that imparts a preload in the axial direction. The main bearing 16 can also be said to be a type of bearing that adjusts the preload. The preload is adjusted, for example, by changing the axial dimension of the clamping member 90 described later or by changing the axial dimensions of the outer ring 48 and the inner ring 50. In the present embodiment, as this type of bearing, an angular contact ball bearing is exemplified. As this type of bearing, in addition to this, tapered roller bearings, angular contact roller bearings, etc. may also be used. The preload is mainly imparted to ensure bearing characteristics such as the torque rigidity of the main bearing 16. The preload acts in the direction along the action line L1 of the load acting on the rolling elements 52. When the rolling elements 52 are spherical, this action line L1 becomes a straight line connecting the contact point between the rolling element 52 and the outer ring 48 and the contact point between the rolling element 52 and the inner ring 50. The action line L1 of the present embodiment is inclined with respect to the axial direction so as to extend radially inward as it extends axially outward from the protrusion 42 of the housing 12.

[0029] The housing 12 includes a bearing surface 54 provided on the axially outer surface of the protrusion 42 and bearing the outer ring 48 in the axial direction. The bearing surface 54 can bear the inward load transmitted from the inner outer surface 60 (described later) of the outer ring 48. When the bearing surface 54 bears the outer ring 48 in the axial direction, it may be in contact with the outer ring 48 to directly bear the outer ring 48, or may be borne by the clamping member 90 (refer to Figure 5 ) disposed between it and the outer ring 48. In the present embodiment, the inner outer surface 60 of the outer ring is in contact with the bearing surface 54, and there is no clamping member 90 (described later) between them. At this time, the inward load is directly transmitted from the inner outer surface 60 to the bearing surface 54 via the contact portion between the inner outer surface 60 and the bearing surface 54. In contrast, in the case where there is a clamping member 90, the load is transmitted from the inner surface of the outer ring 60 to the bearing surface 54 via the contact portion between the inner outer surface 60 and the clamping member 90 and the contact portion between the clamping member 90 and the bearing surface 54.

[0030] The protrusion 42 of the housing 12 has an inter-groove portion 56 provided between circumferentially adjacent inner tooth grooves 44 and an inter-groove inclined portion 58 provided on the inner peripheral edge portion of the inter-groove portion 56 (see Figure 3 ). The inter-groove inclined portion 58 is inclined with respect to the axial direction, and its inner diameter increases as it goes toward the outer side in the axial direction. The inter-groove inclined portion 58 is formed by a chamfered portion obtained by chamfering the corner formed by the end face of the inter-groove portion 56 (the end face of the protrusion 42) and the bearing surface 54. The inter-groove inclined portion 58 is planar, but its specific shape is not particularly limited and may also be curved or the like. The purpose of providing the inter-groove inclined portion 58 is to prevent indentations from being generated due to contact with other components when assembling the gear device 10 or the like.

[0031] The bearing surface 54 has: an outer portion 54a which is located radially outside of the bottom circle Ca circumscribing the bottom portion 44a of the inner tooth groove 44; and an inner portion 54b which is located radially inside of the bottom circle Ca. The bottom circle Ca is a circle concentric with the rotation center line C16 of the main bearing 16. The outer portion 54a is in the form of a circumferentially continuous ring. A plurality of inner portions 54b are provided so as to protrude radially inward with respect to the outer portion 54a. The inner portions 54b are provided in the inter-groove portion 56 of the protrusion 42 described above, radially outside of the inter-groove inclined portion 58.

[0032] The outer ring 48 has: an outer ring inner surface 60 which is provided on the bearing surface 54 side of the housing 12 of the outer ring 48 in the axial direction; an outer peripheral contact surface 62 which contacts the outer ring arrangement surface 40 of the housing 12; and a first inner inclined portion 64 which is provided between the outer ring inner surface 60 and the outer peripheral contact surface 62. In addition, the outer ring 48 further has: an outer ring outer surface 66 which is provided on the side of the outer ring 48 opposite to the outer ring inner surface 60 in the axial direction; and an outer inclined portion 68 which is provided between the outer ring outer surface 66 and the outer peripheral contact surface 62. In addition, the outer ring 48 further has: an inner inner peripheral surface 70 which is provided axially inside with respect to the outer rolling surface 48a; and a second inner inclined portion 72 which is provided between the inner inner peripheral surface 70 and the outer ring inner surface 60.

[0033] The outer ring inner surface 60 is provided on the axial inner side of the outer ring 48. When viewed from the axial direction, the outer ring inner surface 60 is provided at a position overlapping the bearing surface 54 of the housing 12. The outer ring inner surface 60 is composed of a flat surface orthogonal to the axial direction. The first inner inclined portion 64 is provided at the first inner corner portion 74 of the outer ring 48 located between the outer ring inner surface 60 and the outer peripheral contact surface 62. The first inner inclined portion 64 is inclined with respect to the axial direction, and its outer diameter decreases as it goes toward the axial inner side. The first inner inclined portion 64 is formed by a chamfered portion obtained by chamfering the first inner corner portion 74. The first inner inclined portion 64 is curved, but its specific shape is not particularly limited and may also be planar or the like.

[0034] The outer circumferential outer side surface 66 is provided on the axially outer side of the outer ring 48. The outer circumferential outer side surface 66 is composed of a flat surface orthogonal to the axis. The outer inclined portion 68 is provided at the outer corner portion 76 of the outer ring 48 located between the outer circumferential outer side surface 66 and the outer peripheral contact surface 62. The outer inclined portion 68 is inclined with respect to the axis, and its outer diameter becomes smaller as it faces the axially outer side. The outer inclined portion 68 is composed of a chamfered portion that chamfers the outer corner portion 76. The outer inclined portion 68 has a curved surface shape, but its specific shape is not particularly limited and may also be a planar shape or the like.

[0035] In the present embodiment, the inner circumferential inner side surface 70 is provided on the end surface of the convex portion 78 that protrudes more radially inward than the outer circumferential rolling surface 48a of the outer ring 48. The second inner inclined portion 72 is provided at the second inner corner portion 80 of the outer ring 48 located between the inner circumferential inner side surface 60 and the inner circumferential inner side surface 70. The second inner inclined portion 72 is inclined with respect to the axis, and its inner diameter becomes larger as it faces the axially inner side. The second inner inclined portion 72 is composed of a chamfered portion that chamfers the second inner corner portion 80. The second inner inclined portion 72 has a curved surface shape, but its specific shape is not particularly limited and may also be a planar shape or the like.

[0036] Here, the background of the gear device 10 of the present embodiment will be described. Refer to Figure 4 . Figure 4 The gear device 10 showing the reference embodiment is shown. In Figure 4 the same reference numerals are given to the same components as Figure 2 .

[0037] When miniaturizing the gear device 10, it is required to miniaturize the outer diameter of the main bearing 16. At this time, sometimes the outer diameter of the main bearing 16 is required to be miniaturized based on the reduction of the dimensional difference between the outer ring mounting surface 40 of the housing 12 and the bottom of the internal tooth groove 44 (hereinafter referred to as the internal tooth groove bottom 44a). That is, the outer ring mounting surface 40 is brought closer to the radially inner side with respect to the internal tooth groove bottom 44a, thereby reducing the dimensional difference between the outer ring mounting surface 40 and the internal tooth groove bottom 44a.

[0038] If the outer diameter of the main bearing 16 is miniaturized based on the reduction of the dimensional difference between the internal tooth groove bottom 44a and the outer ring mounting surface 40, then as Figure 4As shown, the maximum inner diameter R48a of the outer rolling surface 48a becomes smaller than the inner diameter R44a of the bottom 44a of the inner tooth groove. And thus, if the dimensional difference between the bottom 44a of the inner tooth groove and the outer ring mounting surface 40 decreases, the radial length L42 of the protrusion 42 from the outer ring mounting surface 40 to the bottom 44a of the inner tooth groove becomes smaller than the radial length L64 of the first inner inclined portion 64 of the outer ring 48. Thus, if the radial length L42 of the protrusion 42 becomes smaller, the area of the portion where the inner side surface 60 of the outer ring overlaps with the bearing surface 54 when viewed axially (i.e., the overlapping area) will be significantly reduced. In particular, only the inner portion 54b of the bearing surface 54 exists radially inside the bottom 44a of the inner tooth groove. Therefore, when viewed axially, the outer portion 54a of the annular continuous bearing surface 54 and the inner side surface 60 of the outer ring cannot overlap, resulting in a significant reduction in the above-mentioned overlapping area. If this overlapping area decreases, when an inward load in the axial direction is transmitted from the outer ring 48 to the bearing surface 54, the surface pressure of the inward load acting on the bearing surface 54 in the portion overlapping with the inner side surface 60 of the outer ring in the axial direction becomes very high. Therefore, when the outer diameter of the main bearing 16 is miniaturized, when an excessive inward load acts on the outer ring 48 due to an excessive torque or the like, in the portion overlapping with the inner side surface 60 of the outer ring in the axial direction, the bearing surface 54 is likely to undergo plastic deformation-based deformation.

[0039] Moreover, when the gear device 10 is in operation, due to the strain of the outer ring 48 in the circumferential direction, a strain creep, which is a kind of creep, is generated in the outer ring 48. This strain creep occurs regardless of the magnitude of the preload applied to the main bearing 16. If strain creep occurs, a phenomenon of relative circumferential sliding of the outer ring 48 with respect to the housing 12 will occur. When a preload is applied to the main bearing 16, under the influence of this preload, an inward load acts on the bearing surface 54 in the portion overlapping with the inner side surface 60 of the outer ring in the axial direction. As described above, when the outer diameter of the main bearing 16 is miniaturized, the overlapping area between the inner side surface 60 of the outer ring and the bearing surface 54 is significantly reduced. Therefore, due to this preload, the surface pressure of the inward load acting on the bearing surface 54 in the portion overlapping with the inner side surface 60 of the outer ring in the axial direction becomes very high. In this state, if strain creep occurs in the outer ring 48, the outer ring 48 or the clamping member 90 will relatively slide with respect to the bearing surface 54, and thus wear of the bearing surface 54 is likely to occur in the portion overlapping with the inner side surface 60 of the outer ring in the axial direction.

[0040] As a result, if the outer diameter of the main bearing 16 is miniaturized, wear or deformation is likely to occur in the bearing surface 54 of the housing 12, and thus the axial component of the preload applied to the main bearing 16 may disappear. In this way, if the preload applied to the main bearing disappears, further problems such as a reduction in the torque rigidity around the main bearing 16 or early damage to the main bearing 16 may occur, and thus it is desired to improve this problem. In particular, generally, the outer ring 48 is fixed to the housing 12 by an interference fit. Therefore, in the common technical knowledge in the technical field of the gear device 10 to date, the phenomenon of wear occurring in the bearing surface 54 due to relative sliding with respect to the housing 12 has not been considered.

[0041] Based on re-recognizing the background as described above, the present inventor has obtained the following new concept as a countermeasure. Refer to Figure 2 . Generally, the first inner inclined portion 64 of the outer ring 48 is provided in consideration of the assemblability, and it is considered that a certain radial length needs to be ensured to ensure the assemblability. The present inventor has obtained the following new concept: regarding the radial length of the first inner inclined portion 64 that is considered to be natural in relation to the assemblability, it is effective to set it to be smaller than the radial length L42 of the protruding portion 42 from the outer ring arrangement surface 40 to the bottom 44a of the inner tooth groove. Thus, compared with the case where this condition is not satisfied, the radial length of the inner side surface 60 of the outer ring can be expanded. Therefore, compared with the case where this condition is not satisfied, the overlapping area of the bearing surface 54 of the housing 12 and the inner side surface 60 of the outer ring when viewed axially can be increased, so that the surface pressure of the inward load transmitted from the outer ring 48 on the bearing surface 54 can be reduced. Therefore, even when the outer diameter of the main bearing 16 is miniaturized, not only can the deformation of the bearing surface 54 in the portion overlapping with the inner side surface 60 of the outer ring in the axial direction be suppressed, but also the wear of the bearing surface 54 caused by the creep of the outer ring 48 can be suppressed. Furthermore, while the gear device 10 can be miniaturized by miniaturizing the outer diameter of the main bearing 16, it is more beneficial to suppress the disappearance of the preload applied to the main bearing 16.

[0042] In addition, in the case where there is no clamping member 90, the contact portion between the inner side surface 60 of the rotating outer ring 48 and the bearing surface 54 slides, and thus wear of the bearing surface 54 caused by the creep of the outer ring 48 occurs on the bearing surface 54. In contrast, in the case where there is a clamping member 90, the clamping member 90 rotates together with the outer ring 48, and the contact portion between the clamping member 90 and the bearing surface 54 slides, and thus wear occurs in the bearing surface 54. In short, wear may occur in the bearing surface 54 in the portion overlapping with the inner side surface 60 of the outer ring in the axial direction. Hereinafter, the main features of the gear device 10 of the present embodiment will be described.

[0043] The maximum inner diameter R48a of the outer rolling surface 48a on the outer side of the outer ring 48 is smaller than the inner diameter R44a of the bottom of the inner tooth groove 44a (see also Figure 1 ). This is to stipulate that, compared with the case where this condition is not satisfied, the outer diameter of the main bearing 16 is miniaturized by reducing the dimensional difference between the bottom of the inner tooth groove 44a and the outer ring mounting surface 40. The maximum inner diameter R48a of the outer rolling surface 48a here refers to the inner diameter of the part where the inner diameter becomes the largest among the parts where the rolling elements 52 contact the outer rolling surface 48a on the cross-sectional plane cut axially.

[0044] The radial length L64 of the first inner inclined portion 64 of the outer ring 48 is smaller than the radial length L42 of the protruding portion 42 from the outer ring mounting surface 40 to the bottom of the inner tooth groove 44a. The radial length in this specification refers to the length in the radial direction of the corresponding part. The radial length L42 from the outer ring mounting surface 40 to the bottom of the inner tooth groove 44a here refers to the radial length of the part where the radial length from the outer ring mounting surface 40 to the inner tooth groove 44 becomes the smallest when viewed axially (see also Figure 3 ). When viewed axially, the first inner inclined portion 64 is provided at a position overlapping with the radial range from the outer ring mounting surface 40 to the bottom of the inner tooth groove 44a.

[0045] Thus, as described above, compared with the case where this condition is not satisfied, it is possible to increase the overlapping area of the bearing surface 54 of the housing 12 and the inner side surface 60 of the outer ring when viewed axially, and thus it is possible to reduce the surface pressure of the inward load transmitted from the outer ring 48 on the bearing surface 54. Therefore, even when the outer diameter of the main bearing 16 is miniaturized, in addition to being able to suppress the deformation of the bearing surface 54 of the part overlapping with the inner side surface 60 of the outer ring in the axial direction, it is also possible to suppress the generation of wear of the bearing surface 54 of the part overlapping in this axial direction due to the creep of the outer ring 48. Furthermore, while the gear device 10 can be miniaturized by miniaturizing the outer diameter of the main bearing 16, it is more conducive to suppressing the disappearance of the preload applied to the main bearing 16. In relation to this effect, for example, the radial length L64 of the outer ring 48 can be set to 0.5 times or less of the radial length L42 of the protruding portion 42 of the housing 12. In addition, the "case of miniaturizing the outer diameter of the main bearing" in this specification means the case where the outer diameter of the main bearing 16 is miniaturized by reducing the dimensional difference between the bottom of the inner tooth groove 44a and the outer ring mounting surface 40 until the maximum inner diameter R48a of the outer rolling surface 48a becomes smaller than the inner diameter R44a of the bottom of the inner tooth groove 44a as described above.

[0046] In the gear device 10 of the present embodiment, the radial length L64 of the first inner inclined portion 64 of the outer ring 48 is smaller than the radial length L68 of the outer inclined portion 68 of the outer ring 48. In addition to this, the radial length L64 of the first inner inclined portion 64 is smaller than the radial length L72 of the second inner inclined portion 72 of the outer ring 48. Among the radial lengths of the plurality of inclined portions 64, 68, 72 of the outer ring 48, the radial length L64 of the first inner inclined portion 64 is the smallest.

[0047] Thus, by making the radial length L64 of the first inner inclined portion 64 smaller than the radial length L68 of the outer inclined portion 68, it is easier to expand the radial length of the inner side surface 60 of the outer ring compared to the case where this condition is not satisfied. Therefore, compared to the case where this condition is not satisfied, it is easier to increase the overlapping area of the portion where the bearing surface 54 overlaps with the inner side surface 60 of the outer ring when viewed from the axial direction, and thus it is possible to easily reduce the surface pressure of the inward load transmitted from the outer ring 48 on the bearing surface 54. And compared to the case where the radial length L68 of the outer inclined portion 68 is the same as the radial length L64 of the first inner inclined portion 64, the outer inclined portion 68 is less likely to become a sharp shape. Furthermore, it is beneficial to alleviate the collision of other components against the outer inclined portion 68.

[0048] The radial length L58 of the groove-intermediate inclined portion 58 of the housing 12 (refer to Figure 3 ) is smaller than the radial length L64 of the first inner inclined portion 64 of the outer ring 48. The radial length L58 of the groove-intermediate inclined portion 58 is smaller than the radial length L42 from the outer-ring arrangement surface 40 of the protruding portion 42 to the bottom 44a of the inner tooth groove. The radial length L58 of the groove-intermediate inclined portion 58 is smaller than the radial lengths L72, L68 of the second inner inclined portion 72 and the outer inclined portion 68 of the outer ring 48.

[0049] Thus, by making the radial length L58 of the groove-intermediate inclined portion 58 smaller than the radial length L64 of the first inner inclined portion 64, it is possible to expand the radial length of the inner portion 54b of the bearing surface 54 radially inward compared to the case where this condition is not satisfied. Therefore, compared to the case where this condition is not satisfied, it is possible to further increase the overlapping area of the portion where the bearing surface 54 overlaps with the inner side surface 60 of the outer ring when viewed from the axial direction, and thus it is possible to further reduce the surface pressure of the inward load transmitted from the outer ring 48 on the bearing surface 54.

[0050] The inner side surface 60 of the outer ring 48 of the present embodiment is in contact with the bearing surface 54 of the housing 12. Thereby, compared to the case where a clamping member is disposed between the inner side surface 60 of the outer ring and the bearing surface 54, the number of components can be reduced.

[0051] In addition, in the case where the chamfered portions form the groove inclined portion 58 of the housing 12 and the inclined portions 64, 68, and 72 of the outer ring 48, the lower limit values of their radial lengths L58, L64, L68, and L72 can be set to 0.1 mm, for example, considering the range achievable in manufacturing. Sometimes, the respective inclined portions 58, 64, 68, and 72 are formed by flash removal machining, but in this case, their radial lengths are usually very small, less than 0.1 mm. It can be understood that the lower limit values of the radial lengths of the above-mentioned respective inclined portions 58, 64, 68, and 72 exclude the inclined portions 58, 64, 68, and 72 formed by such flash removal machining.

[0052] (Second Embodiment) Reference Figure 5 . In the following embodiments, the components not described below among the components described in the first embodiment can be applied with the same content as in the first embodiment.

[0053] The gear device 10 of the present embodiment includes a clamping member 90 that is clamped between the inner circumferential outer surface 60 of the outer ring 48 and the receiving surface 54 of the housing 12. The clamping member 90 of the present embodiment is configured as an annular plate body as a whole. The clamping member 90 of the present embodiment is composed of a wall thickness member 92 and at least one thin wall member 94 that is thinner than the wall thickness member 92 in the axial direction. The clamping member 90 of the present embodiment is used as a spacer for applying a preload to the main bearing 16. The wall thickness member 92 is used to prevent the thin wall member 94 from contacting the receiving surface 54 to protect the thin wall member 94. The thin wall member 94 is used to adjust the overall axial length of the clamping member 90 by adjusting the number thereof. The wall thickness member 92 and the thin wall member 94 are each composed of an annular plate material. The clamping member 90 contacts the inner circumferential outer surface 60 of the outer ring 48 and the receiving surface 54 of the housing 12. To achieve this, the wall thickness member 92 is arranged on the receiving surface 54 side in the axial direction, and the thin wall member 94 is arranged on the outer ring 48 side in the axial direction.

[0054] Reference Figure 6 . Similar to the above Figure 4 the following shows the case where the outer diameter of the main bearing 16 is miniaturized and the radial length L64 of the first inner inclined portion 64 of the outer ring 48 becomes larger than the radial length L42 of the protruding portion 42 from the outer ring arrangement surface 40 of the receiving surface 54 to the bottom 44a of the inner tooth groove. And different from the example of Figure 6 in Figure 4 in Figure 6In this case, it is premised that a clamping member 90 is clamped between the bearing surface 54 of the housing 12 and the outer ring 48. At this time, the contact position with respect to the inner circumferential outer surface 60 of the clamping member 90 is shifted radially inward beyond the bottom 44a of the inner tooth groove. Therefore, as described above, the overlapping area of the overlapping portion of the inner circumferential outer surface 60 and the bearing surface 54 in the axial direction is significantly reduced. At the same time, the bearing surface 54 cannot stably bear the inward load applied from the outer ring 48, and as Figure 6 shown, the inner circumferential side portion of the clamping member 90 is tilted inward in the axial direction. If such an inward tilt of the clamping member 90 occurs, the inner peripheral edge of the protruding portion 42 of the housing 12 and the clamping member 90 will be in edge contact, and thus the above-mentioned effects of wear and deformation will become greater.

[0055] Reference Figure 5 . Here, as described above, in the present embodiment, the radial length L64 of the first inner inclined portion 64 of the outer ring 48 is smaller than the radial length L42 of the protruding portion 42 from the outer ring mounting surface 40 to the bottom 44a of the inner tooth groove. Therefore, the contact position between the inner circumferential outer surface 60 of the outer ring and the clamping member 90 can be expanded as much as possible radially inward beyond the bottom 44a of the inner tooth groove, and the overlapping area of the overlapping portion of the inner circumferential outer surface 60 and the bearing surface 54 in the axial direction can also be expanded as much as possible. As a result, the inward load applied from the outer ring 48 can be stably borne by using a relatively wide radial range including the outer side portion 54a of the bearing surface 54, thereby suppressing the inward tilt of the clamping member 90. Furthermore, the effects of wear and deformation of the protruding portion 42 caused by edge contact due to the inward tilt of the clamping member 90 can be effectively suppressed.

[0056] Next, a modification example of each of the above-described constituent elements will be described.

[0057] When the gear mechanism composed of the internal gear 14 and the external gear 20 adopts a planetary gear mechanism, any one of a simple planetary gear mechanism, an eccentric swing type gear mechanism, and a flexure engagement type gear mechanism can be adopted. The specific example of the eccentric swing type gear mechanism is not particularly limited. As a specific example, a distributive eccentric swing type gear mechanism is described as an example. In addition to this, a central crank type eccentric swing type gear mechanism in which the crankshaft 30 is arranged on the rotation center line C16 of the main bearing 16 can also be adopted. The specific example of the flexure engagement type gear mechanism is not particularly limited, and it can be any type such as a cylindrical type, a top hat type, or a cup type.

[0058] The output member 24 may be provided as the housing 12 instead of the wheel carrier 18, and the fixing member 26 may be provided as the wheel carrier 18 instead of the housing 12. Above, an example in which the gear device 10 functions as a speed reduction device has been described. In addition to this, the gear device 10 may also function as a speed increasing device. At this time, for example, the input member 22 may be provided as the housing 12 or the wheel carrier 18, and the output member 24 may be provided as the crankshaft 30 or the like.

[0059] Some parts of the protruding portion 42 and the outer ring arrangement surface 40 of the housing 12 may be integrally provided by the same member or may be separately provided.

[0060] The radial length L64 of the first inner inclined portion 64 of the outer ring 48 may also be greater than the radial length L68 of the outer inclined portion 68. This is a case where, for example, both the radial length L64 of the first inner inclined portion 64 and the radial length L68 of the outer inclined portion 68 are smaller than the radial length L42 of the protruding portion 42. The radial length L58 of the inclined portion between the grooves may be equal to or greater than the radial length L64 of the first inner inclined portion 64.

[0061] The above embodiments and modification examples are for illustration. These abstracted technical ideas should not be construed in a limited manner by the content of the embodiments and modification examples. Regarding the content of the embodiments and modification examples, various design changes such as changes, additions, and deletions of constituent elements can be made. In the above embodiments, for the content that allows such design changes, a mark of "embodiment" is marked and emphasized. However, it does not mean that design changes are not allowed for the content without such a mark. The hatching marked on the cross-section of the drawings is not used to limit the material of the object marked with hatching.

[0062] Of course, the structures and numerical values mentioned in the embodiments and modification examples also include structures and numerical values that can be regarded as the same when considering manufacturing errors, dimensional errors, and other errors. A constituent element that is composed of a single member in the embodiment may also be composed of a plurality of members. Similarly, a constituent element that is composed of a plurality of members in the embodiment may also be composed of a single member.

Claims

1. A gear device comprising: shell; an internal gear having an internal tooth groove formed on the housing and an internal tooth pin embedded in the internal tooth groove; and The main bearing comprises an outer ring arranged on the outer ring arrangement surface of the housing and a rolling element rolling on the rolling surface of the outer ring. The gear device is characterized in that The housing includes: a protrusion that protrudes radially inward from the outer ring arrangement surface and is formed with the inner tooth groove; and a receiving surface that is provided on the protrusion and receives the outer ring. The outer ring comprises: an inner side surface provided on the receiving surface side in the axial direction of the outer ring; and an inner side inclined portion provided between the outer peripheral contact surface of the outer ring in contact with the outer ring configuration surface and the inner side surface, The maximum inner diameter of the rolling surface is smaller than the inner diameter of the groove bottom of the inner tooth groove, The radial length of the inner inclined portion is smaller than the radial length of the protruding portion from the outer ring arrangement surface to the groove bottom.

2. The gear device according to claim 1, characterized in that: The outer ring includes: an outer side surface provided on the side opposite to the inner side surface in the axial direction of the outer ring; and an outer inclined portion provided between the outer side surface and the outer peripheral contact surface. The radial length of the inner inclined portion is smaller than the radial length of the outer inclined portion.

3. The gear device according to claim 1, characterized in that: The protrusion includes: an inter-groove portion provided between the inner tooth grooves adjacent to each other in the circumferential direction; and an inter-groove inclined portion provided at the inner peripheral edge of the inter-groove portion. The radial length of the inter-groove inclined portion is smaller than the radial length of the inner inclined portion.

4. The gear device according to claim 1, characterized in that: An intervening member is provided, the intervening member being interposed between the inner side surface and the receiving surface of the outer ring and being in contact with the inner side surface and the receiving surface.

5. The gear device according to claim 1, characterized in that: The inner side surface of the outer ring is in contact with the receiving surface.

Images