Eccentric oscillating gear system

Abstract

The present invention provides an eccentric oscillating gear mechanism that is advantageous in suppressing roller tilting during roller placement. [Solution] An eccentric oscillating gear device comprising a crankshaft 14 having an eccentric portion 12, an oscillating gear that can oscillate by the eccentric portion 12, and an eccentric bearing 20 disposed between the eccentric portion 12 and the oscillating gear 16, wherein the eccentric bearing 20 comprises a group of rollers 52 consisting of a plurality of rollers 50 and does not have a cage that holds the relative positions of the plurality of rollers 50, the crankshaft 14 comprises a receiving portion 60 that can restrict the axial movement of the corresponding group of rollers 52, the receiving portion 60 corresponds to the eccentric portion 12 which is positioned to overlap the receiving portion 60, the corresponding group of rollers 52 and the crankshaft 14 in the radial direction, and the outer diameter dimension L60 from the central axis L12 of the eccentric portion 12 corresponding to the receiving portion 60 to the outer peripheral end of the receiving portion 60 is greater than the circumscribed circle radius R52 of the roller group 52 corresponding to the receiving portion 60 in the maximum eccentricity direction Da of the eccentric portion 12.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses an eccentric oscillating gear device including a crankshaft having an eccentric portion, an oscillating gear that can oscillate due to the eccentric portion, and an eccentric bearing disposed between the eccentric portion and the oscillating gear. This crankshaft includes a receiving portion capable of restricting axial movement of the eccentric bearing. In the gear device of Patent Document 1, the outer diameter dimension (described later) from the central axis of the eccentric portion to the outer peripheral end of the receiving portion is smaller than the circumscribed circle radius of a plurality of rolling elements used for the eccentric bearing in the maximum eccentricity direction of the eccentric portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In some cases, a bearing having a plurality of rollers and not provided with a cage for holding the relative positions of the plurality of rollers is used as the eccentric bearing. In this case, when assembling the gear device, it is necessary to individually arrange a plurality of rollers between the eccentric portion of the crankshaft and the oscillating gear.

[0005] The inventor of the present application has recognized that, based on the structure of Patent Document 1, there is a problem that the rollers are likely to fall during the arrangement operation of the rollers. If the rollers fall during the arrangement operation of the rollers, it is necessary to extract the fallen rollers and then rearrange the rollers again, resulting in an increase in the working hours of the operation.

[0006] Therefore, one of the objects of the present disclosure is to provide an eccentric oscillating gear device that is advantageous for suppressing the fall of rollers during the roller arrangement operation. [Means for solving the problem]

[0007] The eccentric oscillating gear device of the present disclosure comprises a crankshaft having an eccentric portion, an oscillating gear that can oscillate by the eccentric portion, and an eccentric bearing disposed between the eccentric portion and the oscillating gear, wherein the eccentric bearing comprises a group of rollers and does not have a cage that maintains the relative positions of the multiple rollers, the crankshaft comprises a receiving portion capable of restricting the axial movement of the corresponding group of rollers, the receiving portion corresponds to the eccentric portion disposed in a position that overlaps the receiving portion, the corresponding group of rollers, and the crankshaft, and the outer diameter dimension from the central axis of the eccentric portion corresponding to the receiving portion to the outer peripheral end of the receiving portion is greater than the circumscribed circle radius of the group of rollers corresponding to the receiving portion in the direction of maximum eccentricity of the eccentric portion. [Effects of the Invention]

[0008] The eccentric oscillating gear device of this disclosure is advantageous in suppressing roller tilting during roller placement work. [Brief explanation of the drawing]

[0009] [Figure 1] This is a side cross-sectional view showing a gear device according to an embodiment. [Figure 2] This is an enlarged view of the gear mechanism shown in Figure 1. [Figure 3] Figure 3(A) is a cross-sectional view showing a portion of the AA section of Figure 2 and the first receiving portion, and Figure 3(B) is a cross-sectional view showing a portion of the BB section of Figure 2 and the second receiving portion. [Figure 4] This is an explanatory diagram showing the arrangement of gears using the gear device of the embodiment. [Figure 5] Figure 5(A) is a side cross-sectional view showing the main parts of a gear mechanism of a reference form, and Figure 5(B) is a cross-sectional view showing a part of the CC cross-section of Figure 5(A) and the first receiving portion. [Figure 6]Figure 6(A) is an explanatory diagram showing the tilt of the rollers when using a gear system of the reference form, and Figure 6(B) is an explanatory diagram showing the tilt of the rollers when viewed from the eccentric part and bearing hole as seen from arrow V in Figure 6(A). [Modes for carrying out the invention]

[0010] Embodiments for implementing the eccentric oscillating gear apparatus of this disclosure are described below. The same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted. For the sake of clarity, components are omitted, enlarged, or reduced as appropriate in each drawing. The drawings should be viewed in accordance with the orientation of the reference numerals.

[0011] Refer to Figure 1. The eccentric oscillating gear unit 10 (hereinafter also simply referred to as the gear unit) is incorporated into the master machine. The gear unit 10 can drive the driven element (not shown) of the master machine by outputting rotation. The master machine is, for example, (1) industrial machinery such as machine tools and construction machinery, (2) robots such as industrial robots and service robots, (3) transportation equipment such as conveyors, and (4) various machines such as vehicles.

[0012] The gear unit 10 comprises a crankshaft 14 having an eccentric portion 12, an oscillating gear 16 that can swing due to the eccentric portion 12, a meshing gear 18 that meshes with the oscillating gear 16, and an eccentric bearing 20 positioned between the eccentric portion 12 and the oscillating gear 16. The gear unit 10 also comprises a carrier 22 provided as a first lateral member on one axial side (left side of the paper in Figure 1) relative to the oscillating gear 16, a cover 24 provided as a second lateral member on the other axial side (right side of the paper in Figure 1) relative to the oscillating gear 16, and a casing 26 that houses at least the oscillating gear 16. In this specification, the direction along the rotational centerline of the crankshaft 14 (hereinafter referred to as the crankshaft axis L14) is simply referred to as the axial direction.

[0013] The eccentric oscillating gear device 10 can rotate the output member 30 by causing the oscillating gear 16 to oscillate with the rotation of the input member 28, thereby causing one of the oscillating gear 16 and the meshing gear 18 to rotate on its own axis, and the component of this rotation causes the output member 30 to rotate. In this embodiment, an example is described in which the crankshaft 14 is the input member 28 and the carrier 22 is the output member 30. The input member 28 receives rotation output from an external drive source. The drive source is, for example, a motor, gear motor, engine, etc. The output member 30 outputs rotation to the driven element of an external master machine.

[0014] The crankshaft 14 comprises at least one eccentric portion 12 and shaft portions 32 provided on both axial sides of the eccentric portion 12. A first crankshaft bearing 34A is positioned between the shaft portion 32 on one axial side of the eccentric portion 12 and the carrier 22. A second crankshaft bearing 34B is positioned between the shaft portion 32 on the other axial side of the eccentric portion 12 and the cover 24. Details of the crankshaft 14 will be described later.

[0015] One of the oscillating gear 16 and the meshing gear 18 is an external gear, and the other is an internal gear. In this embodiment, the oscillating gear 16 is an external gear. The oscillating gear 16 is supported so as to be rotatable relative to the corresponding eccentric portion 12 via an eccentric bearing 20. The oscillating gear 16 has a bearing hole 16a in which the eccentric bearing 20 is located on the inside. The meshing gear 18 in this embodiment is provided on the inner circumference of the casing 26.

[0016] A pin 36 protrudes axially from the carrier 22, and the pin 36 passes through the oscillating gear 16. The pin 36 can synchronize the rotational components of the carrier 22 and the oscillating gear 16. In this embodiment, the pin 36 contacts the pin hole 16b of the oscillating gear 16 via a roller 38 that is rotatably supported by the pin 36, but it may also contact directly.

[0017] The casing 26 houses, in addition to the oscillating gear 16, the crankshaft 14, the carrier 22, etc. The casing 26 of the present embodiment is composed of a plurality of casing members 40 connected by bolts or the like, but it may be composed of a single member. One casing member 40 of the present embodiment also serves as the cover 24. A main bearing 42 is disposed between the carrier 22 and the casing 26.

[0018] Refer to FIG. 2. In this figure, for the sake of convenience of explanation, hatching is omitted. The eccentric portion 12 of the crankshaft 14 of the present embodiment is integrally provided by the same member as the central portion on the crankshaft line L14 side with respect to the eccentric portion 12, but it may be provided separately from the central portion. The eccentric portion 12 has a circular shape in which its central axis L12 is eccentric with respect to the crankshaft line L14. The eccentric portion 12 can swing the oscillating gear 16 by rotating around the crankshaft line L14. Here, "swing" means that the entire oscillating gear 16 moves so that the central axis L16 of the oscillating gear 16 revolves around the swing center Ca. The direction from the crankshaft line L14 toward the central axis L12 of the eccentric portion 12 is referred to as the maximum eccentric direction Da of the eccentric portion 12. Also, the direction opposite to the maximum eccentric direction Da from the central axis L12 of the eccentric portion 12 is referred to as the anti-maximum eccentric direction Db of the eccentric portion 12.

[0019] The number of the eccentric portions 12 of the present embodiment is two, but it is not limited thereto, and it may be either a single number or three or more. When the number of the eccentric portions 12 is M, the eccentric phases of the eccentric portions 12 are shifted by 360° / M. Here, the eccentric phase refers to the phase of the maximum eccentric direction Da of the eccentric portion 12 determined based on the angle around the crankshaft line L14.

[0020] The crankshaft 14 may include a flange portion 14c that protrudes radially outward of the crankshaft 14 on the outer peripheral portion of the crankshaft 14. The flange portion 14c of the present embodiment is integrally provided by the same member as the central portion on the crankshaft line L14 side with respect to the flange portion 14c, but it may be provided separately from the central portion. The flange portion 14c is provided between adjacent eccentric portions 12 in the arrangement order of the plurality of eccentric portions 12.

[0021] The eccentric bearing 20 includes a roller group 52 composed of a plurality of rollers 50. A roller accommodation space 54 for accommodating the roller group 52 is provided between the bearing hole 16a of the oscillating gear 16 and the eccentric portion 12. The eccentric bearing 20 is a bearing that does not include a cage for holding the relative positions of the plurality of rollers 50. As will be described later, this bearing refers to a bearing that requires an operation of individually arranging the plurality of rollers 50 in the roller accommodation space 54 during the assembly of the gear device 10. In this embodiment, as this bearing, a total roller bearing that accommodates the maximum number of rollers 50 that can be filled in the roller accommodation space 54 is used. As this bearing, in addition to this, a bearing that accommodates a number of rollers 50 less than the maximum number of rollers 50 that can be filled in the roller accommodation space 54 may also be used. Also, as this bearing, a bearing in which spacers are arranged between some adjacent rollers 50 in the arrangement order of the plurality of rollers 50 may be used.

[0022] By using a bearing without a cage as the eccentric bearing 20 in this way, the arrangement space of the cage can be utilized as the arrangement space of the rollers, which is advantageous in ensuring the filling rate of the rollers. In particular, when miniaturizing the gear device 10, there is also a manufacturing upper limit in miniaturizing the dimensions of the cage in the circumferential direction of the crankshaft 14, and there is a problem that the filling rate of the rollers decreases due to the influence of the cage. By omitting the cage that causes such a decrease in the filling rate of the rollers, there is an advantage that the filling rate of the rollers can be ensured while miniaturizing the gear device 10.

[0023] The rotation axis of the roller 50 in this embodiment extends along the axial direction. The eccentric bearing 20 of this embodiment does not include a dedicated inner ring, and the outer peripheral surface of the eccentric portion 12 also serves as the inner ring. Also, the eccentric bearing 20 of this embodiment does not include a dedicated outer ring, and the inner peripheral surface of the bearing hole 16a also serves as the outer ring. In addition to this, the eccentric bearing 20 may include either a dedicated inner ring fixed to the outer peripheral surface of the eccentric portion 12 or a dedicated outer ring fixed to the bearing hole 16a.

[0024] Refer to Figures 2, 3(A), and 3(B). The crankshaft 14 is provided with a receiving portion 60 that can restrict the axial movement of the corresponding roller group 52 by receiving the end faces of each roller 50 of the corresponding roller group 52. The receiving portion 60 as a whole is flat and perpendicular to the axial direction. The receiving portion 60 includes a first receiving portion 60A and a second receiving portion 60B that faces the opposite axial direction from the first receiving portion 60A. In this embodiment, the first receiving portion 60A is provided on one side surface of the flange portion 14c, and the second receiving portion 60B is provided on the side surface of the flange portion 14c that is axially opposite to the first receiving portion 60B.

[0025] The roller group 52 includes a first roller group 52A corresponding to the first receiving portion 60A and a second roller group 52B corresponding to the second receiving portion 60B. The first receiving portion 60A can restrict the axial movement of the corresponding first roller group 52A, and the second receiving portion 60B can restrict the axial movement of the corresponding second roller group 52B. The eccentric portion 12 includes a first eccentric portion 12A corresponding to the first receiving portion 60A and a second eccentric portion 12B corresponding to the second receiving portion 60B. The first eccentric portion 12A and the second eccentric portion 12B differ in their eccentric phases. The oscillating gear 16 includes a first oscillating gear 16A corresponding to the first receiving portion 60A and a second oscillating gear 16B corresponding to the second receiving portion 60B. The first eccentric portion 12A and the first oscillating gear 16A are positioned to overlap radially with the first roller group 52A corresponding to the first bearing portion 60A on the crankshaft 14. The second eccentric portion 12B and the second oscillating gear 16B are positioned to overlap radially with the second roller group 52B corresponding to the second bearing portion 60B on the crankshaft 14.

[0026] A first pressing member 62A is positioned on the axial side of the first roller group 52A opposite to the first receiving portion 60A. The first pressing member 62A restricts the axial movement of the first roller group 52A in the direction opposite to the first receiving portion 60A. A second pressing member 62B is positioned on the axial side of the second roller group 52B opposite to the second receiving portion 60B. The second pressing member 62B restricts the axial movement of the second roller group 52B in the direction opposite to the second receiving portion 60B.

[0027] The receiving portion 60 includes an eccentric side region 64, which is a half-circumferential region on the Da side of the maximum eccentricity direction of the eccentric portion 12 with respect to the central axis L12 of the corresponding eccentric portion 12, and an anti-eccentric side region 66, which is a half-circumferential region on the Db side of the eccentric portion 12 opposite to the maximum eccentricity direction with respect to the central axis L12.

[0028] In this embodiment, the radial radius R60 of the crankshaft 14 from the crank axis L14 to the outer circumference of the receiving portion 60 is the same size throughout the entire circumference around the crank axis L14. Here, "outer circumference of the receiving portion 60" refers to the outer circumference of the portion that can make surface contact with the roller 50 when the receiving portion 60 receives the end face of the roller 50 during the roller placement process.

[0029] The radial direction perpendicular to the central axis L12 of the eccentric portion 12 is simply called the radial direction of the eccentric portion 12. Also, the radial dimension of the eccentric portion 12 from the central axis L12 of the eccentric portion 12 corresponding to the receiving portion 60 to the outer peripheral end of the receiving portion 60 is called the outer diameter dimension L60 of the receiving portion 60 with respect to the eccentric portion 12. In this embodiment, the outer diameter dimension L60 of the receiving portion 60 with respect to the eccentric portion 12 is smallest in the direction of maximum eccentricity Da of the eccentric portion 12 and largest in the opposite direction of maximum eccentricity Db. Figures 2 and 3 show this smallest outer diameter dimension L60. This outer diameter dimension L60 of the receiving portion 60 gradually decreases in the circumferential direction around the central axis L12 of the eccentric portion 12 from the opposite direction of maximum eccentricity Db to the maximum eccentricity Da.

[0030] The radius of the circumscribed circle 56 that circumscribes the roller group 52 corresponding to the receiving portion 60 is called the circumscribed circle radius R52 of the roller group 52. The circumscribed circle radius R52 is the same size over the entire circumference around the central axis L12 of the eccentric portion 12 corresponding to the receiving portion 60. The circumscribed circle radius R52 is also the inner radius of the circular rolling surface on which the roller group 52 rolls, provided on the bearing hole 16a side relative to the roller group 52. In this embodiment, this rolling surface is provided in the bearing hole 16a, but it may also be provided on the outer ring of the eccentric bearing 20 fixed to the bearing hole 16a.

[0031] Here, the outer diameter dimension L60 of the receiving portion 60, relative to the eccentric portion 12, is larger than the circumscribed circle radius R52 of the roller group 52 corresponding to the receiving portion 60 in the direction of maximum eccentricity Da of the eccentric portion 12. Furthermore, the outer diameter dimension L60 of the receiving portion 60 is larger than the circumscribed circle radius R52 of the roller group 52 corresponding to the receiving portion 60 in both the eccentric side region 64 and the anti-eccentric side region 66. This will be described in detail below.

[0032] Refer to Figure 3(A). The outer diameter L60 of the first support portion 60A, with respect to the first eccentric portion 12A, is larger than the circumscribed circle radius R52 of the first roller group 52A corresponding to the first support portion 60A in the direction of maximum eccentricity Da of the first eccentric portion 12A. This outer diameter L60 of the first support portion 60A is larger than the circumscribed circle radius R52 of the first roller group 52A in its eccentric side region 64. To satisfy this condition, this outer diameter L60 is larger than its circumscribed circle radius R52 in at least a large portion of its eccentric side region 64. Furthermore, the outer diameter L60 of the first support portion 60A is larger than the circumscribed circle radius R52 of the first roller group 52A in its anti-eccentric side region 66. To satisfy this condition, this outer diameter L60 is larger than its circumscribed circle radius R52 in at least a large portion of its anti-eccentric side region 66. In this specification, "most" means 90% or more of the circumferential range of the eccentric portion 12 around its central axis L12. In this embodiment, the outer diameter dimension L60 of the first receiving portion 60A is larger than its circumscribed circle radius R52 throughout the entire eccentric side region 64 and the anti-eccentric side region 66.

[0033] Refer to Figure 3(B). The outer diameter dimension L60 of the second support portion 60B, with respect to the second eccentric portion 12B, is larger than the circumscribed circle radius R52 of the second roller group 52B corresponding to the second eccentric portion 12B in the direction of maximum eccentricity Da of the second eccentric portion 12B. This outer diameter dimension L60 of the second support portion 60B is larger than the circumscribed circle radius R52 of the second roller group 52B in its eccentric side region 64. To satisfy this condition, this outer diameter dimension L60 is larger than its circumscribed circle radius R52 in at least a large portion of the eccentric side region 64. Furthermore, the outer diameter dimension L60 of the second support portion 60B is larger than the circumscribed circle radius R52 of the second roller group 52B in its anti-eccentric side region 66. To satisfy this condition, this outer diameter dimension L60 is larger than its circumscribed circle radius R52 in at least a large portion of the anti-eccentric side region 66. In this embodiment, the outer diameter dimension L60 of the second receiving portion 60B is larger than the circumscribed circle radius R52 throughout the entire eccentric region 64 and the anti-eccentric region 66.

[0034] The member that overlaps the receiving portion 60 in the radial direction of the crankshaft 14 and is closest to the receiving portion 60 is called the nearest member. In this embodiment, the nearest member is a roller 38 (see Figure 2), but it is not limited to this and may be a pin 36 or the like. The outer diameter radius R60 of each receiving portion 60 is smaller than the radial dimension of the crankshaft 14 from the crank axis L14 of the crankshaft 14 on which the receiving portion 60 is provided to the nearest member, so as to avoid contact with the nearest member.

[0035] An example of the assembly procedure for the gear unit 10 described above is explained below. First, the crankshaft 14 is inserted into the bearing holes 16a of each oscillating gear 16. After this, the rollers 50 are placed in the roller housing space 54 between the crankshaft 14 and each oscillating gear 16 to obtain the gear assembly (described later). After this, the carrier 22 is attached to the gear assembly via the first crankshaft bearing 34A. After this, the casing 26 and the carrier 22 are attached to the gear assembly via the second crankshaft bearing 34B. This completes the assembly of the gear unit 10.

[0036] When assembling the gear unit 10, if an eccentric bearing 20 without a cage is used, the process involves arranging each roller 50 of the roller group 52 in the roller housing space 54 between the eccentric portion 12 of the crankshaft 14 and the oscillating gear 16. In this roller 50 arrangement process, each roller 50 of the roller group 52 is individually placed in its corresponding roller housing space 54. The roller 50 arrangement process includes a first step of arranging each roller 50 of the first roller group 52A in the roller housing space 54, and a second step of arranging each roller 50 of the second roller group 52B in the roller housing space 54.

[0037] Refer to Figure 4. In the first step, with the roller housing space 54 for housing the first roller group 52A positioned above the first receiving portion 60A, each roller 50 of the first roller group 52A is inserted into the roller housing space 54 from above, and the rollers 50 are placed on the first receiving portion 60A in a roller loading operation. By performing the roller loading operation for each roller 50 of the first roller group 52A, the first roller group 52A is positioned in the roller housing space 54. After this, in order to prevent the first roller group 52A from falling out of the roller housing space 54, a first retaining member 62A is positioned to restrict the axial movement of the first roller group 52A.

[0038] After this, although not shown in the diagram, the crankshaft 14 and each oscillating gear 16 are inverted and the second step is performed. In the second step, with the roller housing space 54 for housing the second roller group 52B positioned on the upper side of the second receiving portion 60B, each roller 50 of the second roller group 52B is inserted into the roller housing space 54 from above, and the rollers 50 are placed on the second receiving portion 60B in a roller-placing operation. By performing the roller-placing operation for each roller 50 of the second roller group 52B, the second roller group 52B is positioned in the roller housing space 54. After this, in order to prevent the second roller group 52B from falling out of the roller housing space 54, a second retaining member 62B is placed to restrict the axial movement of the second roller group 52B. This gives rise to the gear assembly.

[0039] Next, the background to the invention of the gear apparatus 10 will be explained, along with the effects of the gear apparatus 10 of this embodiment. Figure 5(A) is a side cross-sectional view showing the main part of the gear apparatus of the reference embodiment. Figure 5(B) is a cross-sectional view showing a part of the CC cross-section of Figure 5(A) and the first receiving portion 60A. The gear apparatus of the reference embodiment differs from the embodiment only in the outer diameter dimension L60 of each receiving portion 60 of the crankshaft 14.

[0040] In the gear apparatus of the reference embodiment, as shown in Patent Document 1, the outer diameter dimension L60 of the receiving portion 60 with respect to the eccentric portion 12 is smaller than the circumscribed circle radius R52 of the roller group 52 in the maximum eccentricity direction Da of the eccentric portion 12. Furthermore, in the gear apparatus of the reference embodiment, the outer diameter dimension L60 of the receiving portion 60 is smaller than the circumscribed circle radius R52 throughout the entire eccentric side region 64, and also smaller than the circumscribed circle radius R52 in a part of the anti-eccentric side region 66. In this case, as shown in Figure 6(A), in the aforementioned roller placement work, it becomes difficult to place the rollers 50 over a wide area in the eccentric side region 64 of the receiving portion 60 on the side of the maximum eccentricity direction Da of the eccentric portion 12, and the posture of the rollers 50 tends to become unstable. As a result, the rollers 50 tend to tilt, which makes them more prone to tipping over.

[0041] Here, the inclination of the roller 50 refers to the inclination of the roller 50 such that, for example, as it moves away from the receiving portion 60 in the axial direction, the rotation axis L50 of the roller 50 moves away from the crank axis L14. See Figure 6(B). As shown by the dashed line, the roller 50 is correctly positioned with its rotation axis L50 aligned along the axial direction. Here, the tilt of the roller 50 refers to the state in which its rotation axis L50 is positioned approximately parallel to a plane perpendicular to the axial direction, as shown by the solid line. During the placement of the roller 50, we assume a case where the roller housing space 54 expands in the part of the eccentric portion 12 on the side of the maximum eccentricity direction Da due to an unintended misalignment La between the central axis L12 of the eccentric portion 12 and the central axis L16a of the bearing hole 16a of the oscillating gear 16. In this case, a wide space is created in the roller housing space 54 that allows the roller 50 to tilt, and it becomes difficult to place the roller 50 over a wide area in the eccentric region 64 of the receiving part 60, making it easier for the roller 50 to tip over.

[0042] In particular, the smaller the gear unit 10 becomes, the more likely it is that the rollers 50 will tilt due to the misalignment between the eccentric portion 12 and the bearing hole 16a. This is because, as the gear unit 10 becomes smaller, accompanied by the miniaturization of the roller group 52, when the same absolute amount of misalignment occurs between the eccentric portion 12 and the bearing hole 16a, the space that allows for the tilt of the rollers 50 caused by that misalignment tends to become relatively larger relative to the rollers 50. For example, depending on the size of the roller group 52, even a 0.1 mm misalignment between the central axis L12 of the eccentric portion 12 and the central axis L16a of the bearing hole 16a can easily cause the rollers 50 to tilt. Furthermore, this problem of roller tilting is more likely to occur when the number of rollers 50 arranged in the roller housing space 54 is small and the tilt of the rollers 50 cannot be regulated by the other rollers 50.

[0043] As a countermeasure, in this embodiment, the outer diameter dimension L60 of the receiving portion 60 relative to the eccentric portion 12 is larger than the circumscribed circle radius R52 of the roller group 52 in the maximum eccentricity direction Da of the eccentric portion 12. As a result, as shown in Figure 4, compared to the case where this condition is not met, it becomes easier to place the rollers 50 over a wide area of ​​the eccentric side region 64 of the receiving portion 60 during the roller placement work described above, and it becomes easier to stabilize the posture of the rollers 50. In turn, this is advantageous in suppressing the tilting of the rollers 50 during the placement work. For example, in Figure 4, although the central axis L12 of the eccentric portion 12 and the central axis L16a of the bearing hole 16a are misaligned by the same amount of misalignment La as in Figure 6, the posture of the rollers 50 is stable because the rollers 50 are placed over a wide area of ​​the eccentric side region 64 of the receiving portion 60.

[0044] In this embodiment, the outer diameter dimension L60 of the receiving portion 60, relative to the eccentric portion 12, is larger than the circumscribed circle radius R52 of the roller group 52 in the eccentric side region 64. This makes it easier to place the rollers 50 on the receiving portion 60 over a wider area of ​​the eccentric side region 64 of the receiving portion 60 during the placement of the rollers 50, compared to the case where this condition is not met. Consequently, it is possible to further improve the suppression of the rollers 50 tipping over during the placement of the rollers 50.

[0045] In this embodiment, the outer diameter dimension L60 of the receiving portion 60, relative to the eccentric portion 12, is larger than the circumscribed circle radius R52 of the roller group 52 in the anti-eccentric region 66. This makes it easier to place the rollers 50 on the receiving portion 60 over a wider range in both the eccentric region 64 and the anti-eccentric region 66 during the roller placement process, compared to the case where this condition is not met. Consequently, it is possible to further improve the suppression of the rollers 50 tipping over during the placement process.

[0046] In this embodiment, the outer diameter L60 of the first support portion 60A is larger than the circumscribed circle radius R52 of the first roller group 52A in the maximum eccentricity direction Da of the first eccentric portion 12A. Similarly, the outer diameter L60 of the second support portion 60B is larger than the circumscribed circle radius R52 of the second roller group 52B in the maximum eccentricity direction Da of the second eccentric portion 12B. As a result, compared to the case where the condition regarding the outer diameter L60 of the first support portion 60A is not met, it becomes easier to place the rollers 50 belonging to the first roller group 52A on the first support portion 60A over a wide area of ​​the eccentric side region 64 of the first support portion 60A during the placement work of the rollers 50, which is advantageous in suppressing the tilting of the rollers 50. Furthermore, compared to the case where the conditions regarding the outer diameter dimension L60 of the second support portion 60B are not met, when arranging the rollers 50 belonging to the second roller group 52B, it becomes easier to place the rollers 50 on the second support portion 60B over a wide area of ​​the eccentric side region 64 of the second support portion 60B, which is advantageous in suppressing the tilting of the rollers 50. In other words, when arranging the rollers 50 belonging to either the first or second roller group 52A or 52B, it is advantageous in suppressing the tilting of the rollers 50.

[0047] The above-mentioned effect of favorably suppressing the tilting of the rollers 50 is effective in that it can be obtained when the gear unit 10 is miniaturized along with the miniaturization of the roller group 52. In relation to this effect, the circumscribed circle radius R52 of the roller group 52 may be, for example, 10 mm or less.

[0048] Next, other features of the gear mechanism 10 of this embodiment will be described. Refer to Figure 1. The gear mechanism 10 includes a spacer 70 that positions the oscillating gear 16 axially between the carrier 22 and the cover 24. The spacer 70 of this embodiment includes a first spacer 70A positioned between the first oscillating gear 16A and the second oscillating gear 16B, and a second spacer 70B positioned between the second oscillating gear 16B and the cover 24. The first oscillating gear 16A is positioned axially by contacting the carrier 22 and the first spacer 70A, respectively. The second oscillating gear 16B is positioned axially by contacting the first spacer 70A and the second spacer 70B, respectively.

[0049] Refer to Figure 2. The oscillating gear 16 is positioned axially opposite to the receiving portion 60, with a gap 72 between it and the receiving portion 60. Specifically, the first oscillating gear 16A is positioned axially opposite to the first receiving portion 60A, with a gap 72 between it and the first receiving portion 60A. The second oscillating gear 16B is positioned axially opposite to the second receiving portion 60B, with a gap 72 between it and the second receiving portion 60B. These gaps 72 may be provided between the receiving portion 60 and the oscillating gear 16 over the entire circumference of the crank axis L14 of the crankshaft 14. By positioning the oscillating gear 16 axially with the aforementioned spacer 70, the state of having a gap 72 between the receiving portion 60 and the oscillating gear 16 is maintained.

[0050] In the gear device 10 of this embodiment, as described above, the outer diameter dimension L60 of the receiving portion 60 with respect to the eccentric portion 12 is increased, and the oscillating gear 16 is provided in a position opposite the receiving portion 60 in the axial direction over a wide range in the circumferential direction around the crankshaft 14. Therefore, if the oscillating gear 16 and the receiving portion 60 are in contact, increasing the outer diameter dimension L60 of the receiving portion 60 in this way may lead to problems such as power loss due to the increased frictional resistance between the oscillating gear 16 and the receiving portion 60.

[0051] In this respect, the oscillating gear 16 in this embodiment is provided with an axial gap 72 between it and the receiving portion 60 which is facing it in the axial direction. Therefore, even when the outer diameter dimension L60 of the receiving portion 60 is increased, an increase in frictional resistance due to contact between the receiving portion 60 and the oscillating gear 16 can be avoided. In particular, in this embodiment, the first and second oscillating gears 16A and 16B are each provided with an axial gap 72 between them and different receiving portions 60A and 60B which are facing each other in the axial direction. Therefore, even when the outer diameter dimension L60 of each receiving portion 60A and 60B is increased, an increase in frictional resistance due to contact between each receiving portion 60A and 60B and both the first and second oscillating gears 16A and 16B can be avoided.

[0052] Next, we will describe the transformation forms of each component described so far.

[0053] As a specific type of eccentric oscillating gear device 10, a center-crank type was described in which the crankshaft 14 is positioned on the oscillation center Ca of the oscillating gear 16. This type is not particularly limited, and for example, a distribution type in which multiple crankshafts 14 are positioned radially offset from the oscillation center Ca of the oscillating gear 16 may also be used.

[0054] The casing 26 may replace the carrier 22 as the output member 30. In the embodiment, the eccentric oscillating gear device 10 described is an external gear oscillating type in which the external gear is the oscillating gear 16. Alternatively, the eccentric oscillating gear device 10 may be an internal gear oscillating type in which the internal gear is the oscillating gear 16. In the embodiment, an example in which the gear device 10 functions as a reduction gear was described, but it may also function as a speed increaser. In this case, the carrier 22 or casing 26 may replace the crankshaft 14 as the input member 28, and the crankshaft 14 may replace the carrier 22 or casing 26 as the output member 30.

[0055] The outer diameter L60 of the receiving portion 60 may be larger than the circumscribed circle radius R52 of the roller group 52 only in the maximum eccentricity direction Da of the eccentric portion 12, while being less than or equal to the circumscribed circle radius R52 at other locations. Alternatively, the outer diameter L60 of the receiving portion 60 may be larger than the circumscribed circle radius R52 of the roller group 52 only in the maximum eccentricity direction Da of the eccentric portion 12 and in the anti-eccentricity side region 66, while being less than or equal to the circumscribed circle radius R52 at other locations. The outer diameter L60 of the first receiving portion 60A may be larger than the circumscribed circle radius R52 of the first roller group 52A in the maximum eccentricity direction Da of the first eccentric portion 12A, while the outer diameter L60 of the second receiving portion 60B may be smaller than the circumscribed circle radius R52 of the second roller group 52B in the maximum eccentricity direction Da of the second eccentric portion 12B.

[0056] The oscillating gear 16 may be in contact with the receiving portion 60. To achieve this, a gap 72 may be provided only between the first oscillating gear 16A and the first receiving portion 60A, while the second oscillating gear 16B and the second receiving portion 60B are in contact. Alternatively, the first oscillating gear 16A may be in contact with the first receiving portion 60A, and the second oscillating gear 16B may be in contact with the second receiving portion 60B.

[0057] The contents of each component described in the embodiments above are illustrative. The abstract technical ideas derived from these should not be interpreted restrictively to the contents of this specification. Many design changes, such as modifications, additions, and deletions, are possible for each component described in the embodiments. Such modifications are emphasized with the notation "this form" or "embodiment." However, design changes are also permitted for contents without such notation. Any combination of the above components is also valid. The hatching applied to the cross-sections in the drawings does not limit the material to which the hatching is applied. The structures and numerical values ​​mentioned in the embodiments and variations naturally include those that can be considered identical when considering manufacturing tolerances, etc. Components composed of a single member in the description herein may be composed of multiple members. Similarly, components composed of multiple members may be composed of a single member. [Explanation of Symbols]

[0058] 10...Eccentric oscillating gear mechanism, 12...Eccentric part, 12A...First eccentric part, 12B...Second eccentric part, 14...Crankshaft, 16...Oscillating gear, 16A...First oscillating gear, 16B...Second oscillating gear, 20...Eccentric bearing, 50...Roller, 52...Roller group, 52A...First roller group, 52B...Second group, 60...Support part, 60A...First support part, 60B...Second support part, 64...Eccentric side region, 66...Anti-eccentric side region, 72...Gap.

Claims

1. A crankshaft having an eccentric portion, The oscillating gear, which is oscillating due to the eccentric portion, The system includes an eccentric bearing positioned between the eccentric portion and the oscillating gear, The eccentric bearing comprises a group of rollers and does not include a cage that maintains the relative positions of the multiple rollers. The crankshaft is provided with a receiving portion capable of restricting the axial movement of the corresponding roller group, The receiving portion corresponds to the roller group corresponding to the receiving portion and the eccentric portion which is positioned to overlap in the radial direction of the crankshaft, An eccentric oscillating gear device in which the outer diameter dimension from the central axis of the eccentric portion corresponding to the receiving portion to the outer peripheral end of the receiving portion is greater than the circumscribed circle radius of the roller group corresponding to the receiving portion in the direction of maximum eccentricity of the eccentric portion.

2. The receiving portion includes an eccentric side region which is a half-circumferential region on the side of the eccentric portion that is on the side of the maximum eccentricity direction of the eccentric portion with respect to the central axis of the corresponding eccentric portion. The eccentric oscillating gear device according to claim 1, wherein the outer diameter dimension of the receiving portion is greater than the circumscribed radius of the roller group corresponding to the receiving portion in the eccentric region.

3. The receiving portion includes an anti-eccentric side region which is a semicircular region on the side of the eccentric portion opposite to the maximum eccentricity direction with respect to the central axis of the corresponding eccentric portion. The eccentric oscillating gear device according to claim 2, wherein the outer diameter dimension of the receiving portion is greater than the circumscribed radius of the roller group corresponding to the receiving portion in the anti-eccentric region.

4. The receiving portion includes a first receiving portion and a second receiving portion facing axially opposite to the first receiving portion. The roller group includes a first roller group whose axial movement is restricted by the first receiving portion, and a second roller group whose axial movement is restricted by the second receiving portion. The eccentric portion includes a first eccentric portion corresponding to the first receiving portion and a second eccentric portion corresponding to the second receiving portion. The outer diameter dimension from the central axis of the first eccentric portion to the outer peripheral end of the first receiving portion is greater than the circumscribed circle radius of the first roller group in the direction of maximum eccentricity of the first eccentric portion. The eccentric oscillating gear device according to claim 1, wherein the outer diameter dimension from the central axis of the second eccentric portion to the outer peripheral end of the second receiving portion is greater than the circumscribed radius of the second roller group in the direction of maximum eccentricity of the second eccentric portion.

5. The eccentric oscillating gear device according to claim 1, wherein the oscillating gear is provided facing the receiving portion in the axial direction and with a gap between it and the receiving portion.

6. The receiving portion includes a first receiving portion and a second receiving portion facing axially opposite to the first receiving portion. The oscillating gear includes a first oscillating gear that faces the first receiving portion in the axial direction, and a second oscillating gear that faces the second receiving portion in the axial direction. The first oscillating gear is provided with a gap between it and the first receiving portion. The eccentric oscillating gear device according to claim 5, wherein the second oscillating gear is provided with a gap between it and the second receiving portion.

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