Eccentric oscillation type gear device

Abstract

To provide an eccentric oscillation type gear device that can prevent a limiting member from being sandwiched between a crank bearing and an eccentric part of a crankshaft.SOLUTION: An eccentric oscillation type gear device comprises: a crankshaft 14 comprising an eccentric part 12A; an eccentric bearing 50A arranged on the eccentric part 12A; a limiting member 52A for limiting axial movement of the eccentric bearing 50A, and provided so as to be relatively rotatable with respect to the crankshaft 14; a crank bearing 54A arranged on the side opposite to the eccentric part 12A in an axial direction across the limiting member 52A, and supporting the crankshaft 14; and a positioning part 56A provided separately from the limiting member 52A, and positioning the crank bearing 54A in the axial direction with respect to the crankshaft 14 by being in contact with the crank bearing 54A from the side of the eccentric part 12A.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Patent Document 1 discloses an eccentric oscillating gear device including a crankshaft having an eccentric portion, an eccentric bearing arranged on the eccentric portion, a limiting member for limiting axial movement of the eccentric bearing, and a crank bearing arranged on the axial opposite side of the limiting member from the eccentric portion and supporting the crankshaft. In this gear device, an axial gap is provided between the crank bearing and the limiting member, so that the limiting member is rotatable relative to the crankshaft. This reduces the difference in rotational speed between the limiting member and the eccentric bearing, as compared to when the limiting member rotates integrally with the crankshaft, thereby suppressing wear of the limiting member due to sliding with the eccentric bearing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-28528 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology disclosed in Patent Document 1, the crank bearing is allowed to move axially toward the eccentric portion relative to the crankshaft by an amount corresponding to the axial gap between the crank bearing and the restricting member. Therefore, when the crank bearing moves axially toward the eccentric portion, the restricting member may be pinched between the crank bearing and the eccentric portion. If the restricting member is pinched in this way, the restricting member cannot rotate relative to the crankshaft. This makes it impossible to obtain the effect of suppressing wear of the restricting member that is the object of the technology disclosed in Patent Document 1, and therefore an improvement in this respect is desired.

[0005] Therefore, one object of the present disclosure is to provide an eccentric oscillating gear device that can prevent a limiting member from being pinched between the eccentric portion of the crankshaft and the crank bearing. [Means for solving the problem]

[0006] The eccentric oscillating type gear device disclosed herein is an eccentric oscillating type gear device comprising: a crankshaft having an eccentric portion, an eccentric bearing arranged on the eccentric portion, a limiting member that limits axial movement of the eccentric bearing and is arranged to be rotatable relative to the crankshaft, a crank bearing that is arranged on the axial opposite side of the limiting member from the eccentric portion and supports the crankshaft, and a positioning portion that is arranged between the eccentric portion and the crank bearing separately from the limiting member and that positions the crank bearing in the axial direction relative to the crankshaft. Effect of the Invention

[0007] According to the present disclosure, it is possible to prevent the restricting member from being pinched between the eccentric portion of the crankshaft and the crank bearing. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a side cross-sectional view showing the gear device of the embodiment. [Diagram 2] FIG. 2 is an enlarged view of a part of FIG. [Diagram 3] FIG. 3 is an enlarged view of a part of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment for implementing the eccentric oscillating gear device (hereinafter, simply referred to as a gear device) of the present disclosure will be described. The same or equivalent elements are given the same reference numerals, and duplicated explanations will be omitted. In each drawing, for the sake of convenience of explanation, components are omitted, enlarged, or reduced as appropriate. The drawings should be viewed according to the orientation of the reference numerals.

[0010] Please refer to Fig. 1. The gear device 10 is incorporated into a driven machine as a part of the driven machine. The driven machine is various machines such as industrial machines (machine tools, construction machines, etc.), robots (industrial robots, service robots, etc.), and transport equipment (conveyors, vehicles, etc.).

[0011] The gear device 10 includes a crankshaft 14 having at least one eccentric portion 12A, 12B, a oscillating gear 16 oscillating by the eccentric portions 12A, 12B, a meshing gear 18 meshing with the oscillating gear 16, carriers 22A, 22B supporting the crankshaft 14 via crank bearings 54A, 54B, and a casing 24 disposed radially outside the oscillating gear 16. In this embodiment, a distribution type eccentric oscillating gear device 10 will be described. This type of gear device 10 includes multiple crankshafts 14 disposed at positions offset radially from the oscillating center C16A of the oscillating gear 16, and a crankshaft gear 26 provided on at least one crankshaft 14.

[0012] The gear device 10 comprises an input member to which rotation is input from an external drive source, and an output member that outputs rotation to an external driven member. Here, an example will be described in which the crankshaft gear 26 is the input member and the carrier 22A is the output member. The drive source is, for example, a motor, but it may also be a gear motor, an engine, etc. The driven member is, for example, a part of the driven machine.

[0013] The number of crankshafts 14 in this embodiment is three, only one of which is shown in the figure. The crankshafts 14 are arranged at intervals in the circumferential direction of the oscillating gear 16. The crankshafts 14 penetrate the carriers 22A, 22B together with the oscillating gear 16 in the axial direction of the oscillating gear 16.

[0014] The crankshaft 14 includes at least one (here, two) eccentric portion 12A, 12B, and shaft portions 28A, 28B provided on both axial sides of the eccentric portions 12A, 12B. The shaft portions 28A, 28B include a first shaft portion 28A provided on one axial side (left side of the paper in FIG. 1) of the eccentric portions 12A, 12B, and a second shaft portion 28B provided on the other axial side (right side of the paper in FIG. 1) of the eccentric portions 12A, 12B. Hereinafter, for convenience of explanation, the one axial side is referred to as the load side, and the other axial side is referred to as the anti-load side. The first shaft portion 28A continues to one end portion 14a on the load side of the crankshaft 14, and the second shaft portion 28B continues to the other end portion 14b on the anti-load side of the crankshaft 14. The shaft portions 28A, 28B have a circular shape centered on the rotation center line C14 of the crankshaft 14. The eccentric portions 12A, 12B in this embodiment are integrally provided by the same member as the shaft portions 28A, 28B, but may be provided separately from the shaft portions 28A, 28B.

[0015] The axis C12 of the eccentric parts 12A and 12B is eccentric with respect to the rotation center line C14 of the crankshaft 14. The eccentric parts 12A and 12B have a circular shape centered on the axis C12. The eccentric parts 12A and 12B can oscillate the oscillating gear 16 by rotating around the rotation center line C14 of the crankshaft 14. Here, "oscillation" refers to the rotation of the gear center C16B of the oscillating gear 16 around the oscillation center C16A. The eccentric phases of the multiple eccentric parts 12A and 12B are shifted by 360° / M when the number of the eccentric parts 12A and 12B is M (two in this embodiment). The number of the eccentric parts 12A and 12B is not particularly limited, and may be either one or three or more.

[0016] In this embodiment, the number of crankshaft gears 26 is three, and only one of them is illustrated. The number of crankshaft gears 26 may be one. The crankshaft gears 26 are provided individually on each of the crankshafts 14. The crankshaft gear 26 is provided on the shaft portion 28B of the crankshaft 14 by spline connection or the like so as to be integrally rotatable. A common transmission gear 30 meshes with the crankshaft gear 26 of each of the crankshafts 14, and the rotational power of the drive source is distributed to each of the crankshafts 14 via the transmission gear 30. The transmission gear 30 is provided, for example, on the outer periphery of the output shaft 32 of the drive source.

[0017] In this embodiment, the oscillating gear 16 is an external gear, and the meshing gear 18 is an internal gear. The oscillating gear 16 is provided individually corresponding to each of the multiple eccentric parts 12A, 12B, and is supported by the corresponding eccentric parts 12A, 12B via eccentric bearings 50A, 50B. The meshing gear 18 of this embodiment includes a meshing gear body 18a integrated with the casing 24, and multiple teeth 18b provided on the meshing gear body 18a and meshing with the oscillating gear 16. The multiple teeth 18b of this embodiment are integrally provided by the same member as the meshing gear body 18a. Alternatively, the multiple teeth 18b may be provided by multiple pins rotatably supported by the meshing gear body 18a.

[0018] The carriers 22A, 22B include a first carrier 22A arranged on the load side of the oscillating gear 16, and a second carrier 22B arranged on the anti-load side of the oscillating gear 16. The first carrier 22A and the second carrier 22B are connected by a pin body 36 that penetrates the oscillating gear 16. A main bearing 38 is arranged between the casing 24 and the carriers 22A, 22B. An angular contact ball bearing is exemplified as the main bearing 38, but the specific example is not particularly limited, and the main bearing 38 may be a cross roller bearing, a ball bearing, or the like.

[0019] An example of the operation of the gear device 10 described above will be described. When the transmission gear 30 rotates due to the output of the drive source, the rotation of the transmission gear 30 is transmitted to at least one crankshaft 14 via the crankshaft gear 26, causing the crankshaft 14 to rotate. At this time, the rotation of the transmission gear 30 is reduced in speed by the crankshaft gear 26 and then transmitted to the crankshaft 14. When the crankshaft 14 rotates, the oscillating gear 16 is oscillated by the eccentric parts 12A and 12B of the crankshaft 14. When the oscillating gear 16 oscillates, the meshing position between the oscillating gear 16 and the meshing gear 18 changes in the circumferential direction. Accordingly, for each rotation of the crankshaft 14, one of the oscillating gear 16 and the meshing gear 18 (here, the oscillating gear 16) rotates on its axis, and the rotation component is taken out by the output member (here, the carriers 22A and 22B). At this time, an output rotation, which is reduced in speed by a reduction ratio according to the difference in the number of teeth between the oscillating gear 16 and the meshing gear 18 relative to the input rotation input to the crankshaft 14, is taken out by an output member.

[0020] 2, the gear device 10 includes eccentric bearings 50A, 50B arranged on the eccentric portions 12A, 12B, limiting members 52A, 52B that limit axial movement of the eccentric bearings 50A, 50B, crank bearings 54A, 54B that are arranged on the axial opposite side of the eccentric portions 12A, 12B with the limiting members 52A, 52B between them and support the crankshaft 14, and positioning portions 56A, 56B that axially position the crank bearings 54A, 54B with respect to the crankshaft 14.

[0021] The eccentric bearings 50A, 50B include a first eccentric bearing 50A which is the most axially loaded side of the eccentric bearings 50A, 50B arranged on the crankshaft 14, and a second eccentric bearing 50B which is the most axially non-load side. When multiple eccentric bearings 50A, 50B are present as in this embodiment, the first eccentric bearing 50A and the second eccentric bearing 50B are provided separately. In contrast, when only a single eccentric bearing 50A, 50B is present, the first eccentric bearing 50A and the second eccentric bearing 50B are configured by a single eccentric bearing.

[0022] The eccentric portions 12A, 12B of the crankshaft 14 include a first eccentric portion 12A in which the first eccentric bearing 50A is disposed, and a second eccentric portion 12B in which the second eccentric bearing 50B is disposed. When multiple eccentric portions 12A, 12B are present as in this embodiment, the first eccentric portion 12A and the second eccentric portion 12B are provided separately. In contrast, when only a single eccentric portion 12A, 12B is present, the first eccentric portion 12A and the second eccentric portion 12B are formed by a single eccentric portion.

[0023] The limiting members 52A, 52B include a first limiting member 52A that limits the axial movement of the first eccentric bearing 50A toward the load side, and a second limiting member 52B that limits the axial movement of the second eccentric bearing 50B toward the anti-load side. The first limiting member 52A is disposed radially outward of the first shaft portion 28A of the crankshaft 14, and the second limiting member 52B is disposed radially outward of the second shaft portion 28B of the crankshaft 14.

[0024] The crank bearings 54A, 54B include a first crank bearing 54A arranged on the axially opposite side of the first eccentric portion 12A across the first limiting member 52A, and a second crank bearing 54B arranged on the axially opposite side of the second eccentric portion 12B across the second limiting member 52B.

[0025] The positioning portions 56A, 56B include a first positioning portion 56A that axially positions the first crank bearing 54A relative to the crankshaft 14, and a second positioning portion 56B that axially positions the second crank bearing 54B relative to the crankshaft 14.

[0026] A set of the first eccentric portion 12A and the first shaft portion 28A of the crankshaft 14, the first eccentric bearing 50A, the first limiting member 52A, the first crank bearing 54A, and the first positioning portion 56A is referred to as the first set. A set of the second eccentric portion 12B and the second shaft portion 28B of the crankshaft 14, the second eccentric bearing 50B, the second limiting member 52B, the second crank bearing 54B, and the second positioning portion 56B is referred to as the second set. The components of the first set and the second set have the same characteristics and effects, except that their axial positional relationships on the crankshaft 14 are reversed. Below, the characteristics and effects common to the first and second sets will be described mainly with reference to the drawing (FIG. 3) related to the first set. The characteristics and effects described below for the first set are also similarly applied to the second set. In addition, in describing the positional relationships related to these, the axial, radial, and circumferential directions of the crankshaft 14 will be mainly used.

[0027] Please refer to FIG. 3. The eccentric bearings 50A and 50B include a plurality of rolling elements 50a, a cage 50b that holds the plurality of rolling elements 50a, and an outer ring 50c and an inner ring 50d on which the plurality of rolling elements 50a roll. The rolling elements 50a in this embodiment are rollers, but are not limited thereto, and various rolling elements such as spheres may be used. In this embodiment, the outer ring 50c is provided integrally with the oscillating gear 16 by the same member as the oscillating gear 16, but may be provided separately from the oscillating gear 16. In this embodiment, the inner ring 50d is provided integrally with the eccentric parts 12A and 12B by the same member as the eccentric parts 12A and 12B of the crankshaft 14, but may be provided separately from the eccentric parts 12A and 12B.

[0028] The cage 50b includes an annular portion 50ba that is continuous around the rotation center line C14 of the crankshaft 14, pockets 50bb that radially penetrate the annular portion 50ba and accommodate the rolling elements 50a, and flange portions 50bc that protrude radially inward from the annular portion 50ba. In this embodiment, the flange portions 50bc protrude radially inward from both axial ends of the annular portion 50ba, respectively.

[0029] The crank bearings 54A, 54B are disposed in bearing holes 62 (see also FIG. 2) formed in the carriers 22A, 22B. The crank bearings 54A, 54B are disposed between the bearing holes 62 of the carriers 22A, 22B and the shaft portions 28A, 28B of the crankshaft 14, and support the crankshaft 14 for free rotation.

[0030] The crank bearings 54A and 54B include a plurality of rolling elements 54a, and an outer ring 54b and an inner ring 54c on which the rolling elements 54a roll. The rolling elements 54a in this embodiment are tapered rollers, but the specific examples are not particularly limited, and various rolling elements such as balls and rollers may be used. The outer ring 54b in this embodiment is provided separately from the carriers 22A and 22B, but may be provided integrally with the carriers 22A and 22B by the same member as the carriers 22A and 22B. The inner ring 54c in this embodiment is provided separately from the crankshaft 14, but may be provided integrally with the crankshaft 14 by the same member as the crankshaft 14. The inner ring 54c in this embodiment is fixed to the shaft portions 28A and 28B of the crankshaft 14 by interference fit.

[0031] A bearing restricting member 64 (see also FIG. 2) is attached to the carriers 22A, 22B to restrict axial movement of the crank bearings 54A, 54B in the axially opposite direction to the eccentric portions 12A, 12B of the crankshaft 14. The bearing restricting member 64 in this embodiment is formed of a retaining ring fitted into a groove provided in the bearing hole 62 of the carriers 22A, 22B, but a specific example thereof is not particularly limited.

[0032] The limiting members 52A, 52B are annular and surround the rotation centerline C14 of the crankshaft 14. To achieve this, the limiting members 52A, 52B may be continuous over the entire circumference around the rotation centerline C14 of the crankshaft 14, or may be partially cut out. The limiting members 52A, 52B are plate-shaped with the thickness direction being the axial direction of the crankshaft 14.

[0033] The first limiting member 52A is disposed between the first eccentric portion 12A and the first eccentric bearing 50A of the crankshaft 14 and the first crank bearing 54A. A radially inner portion of the first limiting member 52A is disposed at a position overlapping with the first eccentric portion 12A of the crankshaft 14 in the axial direction. A radially outer portion of the first limiting member 52A is disposed at a position overlapping with the first eccentric bearing 50A in the axial direction. A portion of the first limiting member 52A in this embodiment is disposed at a position overlapping with the cage 50b of the first eccentric bearing 50A in the axial direction, but may be disposed at a position overlapping with only the rolling element 50a of the first eccentric bearing 50A in the axial direction.

[0034] When the first eccentric bearing 50A tries to move axially toward the first crank bearing 54A in the axial direction, the first eccentric bearing 50A (here, the retainer 50b of the first eccentric bearing 50A) hits the first limiting member 52A. After this, the first limiting member 52A moves axially toward the first crank bearing 54A together with the first eccentric bearing 50A until it hits the first crank bearing 54A. In addition, the axial movement of the first crank bearing 54A in the axially opposite direction to the first eccentric portion 12A is restricted by the bearing restricting member 64. Therefore, the axial movement of the first limiting member 52A is restricted by the first crank bearing 54A, and the axial movement of the first eccentric bearing 50A is restricted by the first limiting member 52A. In this way, the first limiting member 52A hits the first eccentric bearing 50A, thereby restricting the axial movement of the first eccentric bearing 50A toward the first crank bearing 54A.

[0035] In this embodiment, the first limiting member 52A limits the axial movement of the multiple eccentric bearings 50A, 50B including the first eccentric bearing 50A toward the first crank bearing 54A side (one axial side). The second limiting member 52B limits the axial movement of the multiple eccentric bearings 50A, 50B including the second eccentric bearing 50B toward the second crank bearing 54B side (the other axial side). The first limiting member 52A and the second limiting member 52B limit the axial movement of the multiple eccentric bearings 50A, 50B toward both axial sides.

[0036] The first limiting member 52A is provided to be rotatable relative to the crankshaft 14. To achieve this, in this embodiment, an axial gap 66 that allows axial movement of the first limiting member 52A relative to the crankshaft 14 is provided between at least one of the first crank bearing 54A and the first eccentric portion 12A of the crankshaft 14 (here, the first crank bearing 54A) and the first limiting member 52A. By providing this axial gap 66, it is possible to prevent the first limiting member 52A from being pinched between the first crank bearing 54A and the first eccentric portion 12A. Furthermore, in providing the first limiting member 52A to be rotatable relative to the crankshaft 14, the first limiting member 52A is supported by the first shaft portion 28A of the crankshaft 14 to be rotatable relative to the crankshaft 14. In this embodiment, a first positioning portion 56A is arranged between the first limiting member 52A and the first shaft portion 28A of the crankshaft 14, and the first limiting member 52A is supported by the first shaft portion 28A of the crankshaft 14 via the first positioning portion 56A so as to be freely rotatable relative to the first shaft portion 28A of the crankshaft 14.

[0037] The first positioning portion 56A is provided separately from the first restricting member 52A. The first positioning portion 14 is disposed between the first eccentric portion 12A of the crankshaft 14 and the first crank bearing 54A. When the first crank bearing 54A moves axially toward the first eccentric portion 12A, the first positioning portion 56A abuts against the first crank bearing 54A from the first eccentric portion 12A side, thereby positioning the first crank bearing 54A in the axial direction with respect to the crankshaft 14. The first positioning portion 56A restricts the axial movement of the first crank bearing 54A toward the first eccentric portion 12A side, thereby positioning the first crank bearing 54A in the axial direction with respect to the crankshaft 14. The first crank bearing 54A is positioned in the axial direction by the first positioning portion 56A, whereby the above-mentioned axial gap 66 is provided.

[0038] The first positioning portion 56A of this embodiment includes a positioning member 68 separate from the crankshaft 14. Alternatively, the first positioning portion 56A may be integrally formed of the same member as the crankshaft 14. In this case, the first positioning portion 56A may include a step portion that protrudes radially outward on the outer periphery of the first shaft portion 28A of the crankshaft 14, on the first crank bearing 54A side of the first eccentric portion 12A of the crankshaft 14. Alternatively, the first positioning portion 56A may include both the positioning member 68 and the step portion. The positioning member 68 has a shape (annular, partially cut-out annular, etc.) that surrounds the crankshaft 14. The positioning member 68 may be fitted to the outer periphery of the first shaft portion 28A of the crankshaft 14 by either an interference fit or a clearance fit.

[0039] The first positioning portion 56A includes an inner portion 70 located radially inward of the first restricting member 52A. In this embodiment, the first positioning portion 56A is configured only by the inner portion 70. At least a portion of the inner portion 70 is disposed at a position radially overlapping with the first restricting member 52A.

[0040] The first limiting member 52A includes an axially facing portion 72 that faces an axial end face 54d of the first crank bearing 54A in the axial direction, and an outer portion 74 that extends radially outward from the axially facing portion 72. The axial end face 54d of the first crank bearing 54A here refers to the end face of the first crank bearing 54A that is axially closest to the first eccentric portion 12A. In this embodiment, the axial end face 54d of the first crank bearing 54A is formed by the inner ring 54c of the first crank bearing 54A, but may be formed by the rolling elements 54a of the first crank bearing 54A.

[0041] The axial dimension L70 of the inner portion 70 of the first positioning portion 56A is larger than the axial dimension L72 of the axial facing portion 72 of the first limiting member 52A. This makes it possible to provide the above-mentioned axial gap 66 between at least one of the first crank bearing 54A and the first eccentric portion 12A and the axial facing portion 72 of the first limiting member 52A. In particular, when the first positioning portion 56A is a positioning member 68 separate from the crankshaft 14, this is advantageous in that the above-mentioned axial gap 66 can be provided without fixing the positioning member 68 to the crankshaft 14.

[0042] The axial dimension L72 of the axial facing portion 72 of the first limiting member 52A is preferably 0.5 times or more the axial dimension L70 of the inner portion 70 of the first positioning portion 56A. The advantages of this will be explained. When the axial movement of the first eccentric bearing 50A is limited by the first limiting member 52A, an axial load acts on the first limiting member 52A, so that the first limiting member 52A may deform so as to be inclined relative to the radial direction of the crankshaft 14. When the first limiting member 52A tries to deform in this way, by satisfying the above-mentioned condition of the axial dimensions L70, L72 (L72≧0.5×L70), the first limiting member 52A is more likely to come into contact with the axial end surface 54d of the first crank bearing 54A and the first eccentric portion 12A than when the axial dimension L72 of the first limiting member 52A is less than 0.5 times the axial dimension L70 of the first positioning portion 56A. As a result, deformation that increases the inclination angle of the first limiting member 52A relative to the radial direction is easily suppressed. In addition, by satisfying the above-mentioned condition, the axial movement allowance of the first limiting member 52A is smaller than when the axial dimension L72 of the first limiting member 52A is less than 0.5 times the axial dimension L70 of the first positioning portion 56A. As a result, the axial movement allowance of the first eccentric bearing 50A can be reduced. Note that the axial dimension L72 of the axially opposing portions 72 of the limiting members 52A and 52B may be less than 0.5 times the axial dimension L70 of the inner portion 70 of the positioning member 68. In addition, the upper limit value of the axial dimension L72 is, for example, less than the axial dimension L70.

[0043] In the portion where the first limiting member 52A and the first positioning portion 56A overlap in the radial direction, the outer diameter R56A of the first positioning portion 56A is smaller than the inner diameter R52A of the first limiting member 52A. The outer diameter R56A here is slightly smaller than the inner diameter R52A, and the drawing shows a case where they are the same in appearance. This allows a radial gap (not shown) that allows relative rotation between the first positioning portion 56A and the first limiting member 52A to be provided. Furthermore, even if a part of the first positioning portion 56A is disposed radially inside the first limiting member 52A, the limiting members 52A and 52B can be maintained in a state in which they can rotate relatively to the crankshaft 14. It can also be said that the first limiting member 52A is rotatable relatively to the first positioning portion 56A in addition to the crankshaft 14.

[0044] The effects of the above gear device 10 will be described. When the gear device 10 is in use, the first crank bearing 54A may tend to move axially relatively toward the first eccentric portion 12A side due to the load acting on the first crank bearing 54A and the crankshaft 14. In addition, when the first crank bearing 54A is pressed toward the first eccentric portion 12A side to tightly fit the inner ring 54c of the first crank bearing 54A into the first shaft portion 28A of the crankshaft 14, the first crank bearing 54A may unintentionally move largely axially relative to the crankshaft 14 toward the first eccentric portion 12A side.

[0045] When the first crank bearing 54A moves axially toward the first eccentric portion 12A in this manner, the first crank bearing 54A comes into contact with the first positioning portion 56A, and the first crank bearing 54A is axially positioned relative to the crankshaft 14 by the first positioning portion 56A. This makes it possible to avoid pinching the first limiting member 52A between the first crank bearing 54A and the first eccentric portion 12A, and thus to avoid a situation in which the first limiting member 52A cannot rotate relative to the crankshaft 14. As a result, the first limiting member 52A can be maintained in a rotatable state relative to the crankshaft 14, and the effect of suppressing wear of the first limiting member 52A due to sliding with the first eccentric bearing 50A can be stably obtained. This wear suppression effect can be obtained by suppressing the difference in rotational speed between the first limiting member 52A and the first eccentric bearing 50A, compared to when the first limiting member 52A rotates integrally with the crankshaft 14.

[0046] At least a part of the first positioning portion 56A is disposed at a position radially overlapping with the first restricting member 52A on the radially inner side thereof. This makes it possible to narrow the distance between the first eccentric portion 12A and the first crank bearing 54A, compared to disposing the first positioning portion 56A at a position shifted axially toward the first crank bearing 54A from the first restricting member 52A, which is advantageous for reducing the axial dimension of the entire gear device 10.

[0047] (A) The first positioning portion 56A includes a positioning member 68 separate from the crankshaft 14. Thus, by preparing a plurality of types of positioning members 68 with different axial dimensions, the plurality of types of positioning members 68 can be used as shims for adjusting the internal clearance (preload) of the crank bearings 54A, 54B. For example, the larger the axial dimension of the positioning member 68, the smaller the internal clearance (the larger the preload) of the crank bearings 54A, 54B can be. By using a positioning member 68 with an axial dimension corresponding to the required internal clearance of the crank bearings 54A, 54B, the required internal clearance (preload) can be adjusted according to that axial dimension.

[0048] So far, the effects of the gear device 10 have been described in relation to the first set (first limiting member 52A, first positioning portion 56A, etc.) described above. Similar effects can also be obtained in relation to the second set (second limiting member 52B, second positioning portion 56B, etc.). In relation to the effect (A) described above, it is sufficient that either the first positioning portion 56A or the second positioning portion 56B includes a positioning member 68 that is separate from the crankshaft 14.

[0049] A variation of the above gear device will now be described.

[0050] The eccentric oscillating gear device has been described using a distribution type as an example of a specific type. This type is not particularly limited, and may be, for example, a center crank type in which the crankshaft 14 is disposed on the oscillation center C16A of the oscillating gear 16. In this case, the crankshaft 14 may serve as an input member.

[0051] The casing 24 may serve as an output member instead of the carriers 22A, 22B. An internal gear may serve as the oscillating gear 16 instead of the external gear, and an external gear may serve as the meshing gear 18 instead of the internal gear. The gear device 10 may function as a speed increasing device. In this case, the carriers 22A, 22B or the casing 24 may serve as an input member instead of the crankshaft gear 26 (crankshaft 14), and the crankshaft gear 26 (crankshaft 14) may serve as an output member instead of the carriers 22A, 22B or the casing 24.

[0052] Although the gear device 10 has been described as including the first and second limiting members 52A, 52B and the first and second positioning portions 56A, 56B, it may instead include only the first limiting member 52A and the first positioning portion 56A.

[0053] The positioning portions 56A, 56B may be formed of a retaining ring or the like that is axially fixed to the crankshaft 14. In this case, the first positioning portion 56A is provided at a position shifted axially toward the first crank bearing 54A from the first limiting member 52A, and therefore does not need to be disposed at a position that radially overlaps with the first limiting member 52A.

[0054] The first positioning portion 56A may have a portion that protrudes radially outward from the inner portion 70. The example in which the outer diameter R56A of the first positioning portion 56A is uniformly smaller than the inner diameter R52A of the first restricting member 52A in the entirety has been described. In addition, the outer diameter of the first positioning portion 56A may vary in part. For example, the outer diameter of the first positioning portion 56A may be smaller than the inner diameter R52A of the first restricting member 52A in a portion that radially overlaps with the first restricting member 52A, and may be larger than the inner diameter R52A of the first restricting member 52A in a portion that does not radially overlap with the first restricting member 52A. The portion of the first positioning portion 56A that does not radially overlap with the restricting members 52A and 52B here is assumed to be a portion that is closer to the first crank bearing 54A in the axial direction than the first restricting member 52A.

[0055] The first restricting member 52A has been described as having the same axial dimension at the axially opposing portion 72 and the outer portion 74. The specific shape of the first restricting member 52A is not particularly limited, and for example, the axial dimension at the outer portion 74 may be larger than that of the axially opposing portion 72.

[0056] The above-mentioned embodiment and modified forms are examples. The technical ideas abstracted from these should not be interpreted as being limited to the contents of the embodiment and modified forms. The contents of the embodiment and modified forms are capable of many design changes, such as changes, additions, and deletions of components. In the above-mentioned embodiment, the contents in which such design changes are possible are emphasized by adding the notation "embodiment". However, design changes are permitted even in contents without such notation. The hatching on the cross section of the drawing does not limit the material of the hatched object. The structures and numerical values ​​referred to in the embodiment and modified forms naturally include those that can be considered to be the same when considering manufacturing errors, etc. In the embodiment, a component constituted by a single member may be constituted by multiple members. Similarly, a component constituted by multiple members in the embodiment may be constituted by a single member. [Explanation of symbols]

[0057] 10... eccentric oscillating gear device, 12A, 12B... eccentric portion, 14... crankshaft, 50A, 50B... eccentric bearing, 52A, 52B... limiting member, 54A, 54B... crank bearing, 56A, 56B... positioning portion, 68... positioning member, 70... inner portion, 72... axially opposing portion.

Claims

1. A crankshaft having an eccentric portion; an eccentric bearing disposed in the eccentric portion; a limiting member that limits axial movement of the eccentric bearing and is provided rotatably relative to the crankshaft; a crank bearing that is disposed on an axially opposite side of the eccentric portion with the limiting member therebetween and supports the crankshaft; a positioning portion that is provided separately from the limiting member and abuts against the crank bearing from the eccentric portion side, thereby positioning the crank bearing axially relative to the crank shaft.

2. The positioning portion includes an inner portion that is radially inward of the restricting member, The eccentric oscillating gear device according to claim 1 , wherein at least a portion of the inner portion is disposed in a position radially overlapping with the restricting member.

3. the limiting member includes an axially opposing portion that faces an axial end surface of the crank bearing in the axial direction, 3. The eccentric oscillating gear device according to claim 2, wherein the axial dimension of the inner portion is greater than the axial dimension of the axially opposing portion.

4. 4. The eccentric oscillating gear device according to claim 3, wherein the axial dimension of the axially opposing portion is at least 0.5 times the axial dimension of the inner portion.

5. 3. The eccentric oscillating gear device according to claim 2, wherein an outer diameter of the positioning portion is smaller than an inner diameter of the limiting member at a portion where the limiting member and the inner portion overlap in a radial direction.

6. The eccentric oscillating gear device according to claim 1 , wherein the positioning portion includes a positioning member separate from the crankshaft.

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