Eccentric oscillation type gear device

Abstract

To provide an eccentric oscillation type gear device that can reduce collision sound of rolling bodies.SOLUTION: An eccentric oscillation type gear device comprises a crankshaft comprising an eccentric body, an oscillation gear to be oscillated by the eccentric body, and an eccentric bearing 20 arranged between the oscillation gear and the eccentric body. The eccentric bearing 20 comprises a plurality of rolling bodies 50. Rolling bodies 50 adjacent to each other in a circumferential direction in a portion out of the plurality of rolling bodies 50 can come into contact with each other, and a spacer is arranged between rolling bodies 50 adjacent to each other in the circumferential direction in another portion out of them.SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses an eccentric swing type gear device including a crankshaft having an eccentric body, a swing gear swung by the eccentric body, and an eccentric bearing disposed between the swing gear and the eccentric body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventor of the present application newly recognized that there is the following specific problem in an eccentric swing type gear device. When the eccentric bearing has a full spherical structure or the like, adjacent rolling elements of the eccentric bearing can contact each other. At this time, there is a problem that a collision sound is generated due to the collision between the rolling elements during the operation of the gear device.

[0005] Therefore, one of the objects of the present disclosure is to provide an eccentric swing type gear device capable of reducing the collision sound of rolling elements.

Means for Solving the Problems

[0006] An eccentric swing type reduction gear according to an aspect of the present disclosure is an eccentric swing type gear device including a crankshaft having an eccentric body, a swing gear swung by the eccentric body, and an eccentric bearing disposed between the swing gear and the eccentric body, wherein the eccentric bearing includes a plurality of rolling elements, adjacent rolling elements in the circumferential direction of a part of the plurality of rolling elements can contact each other, and a spacer is disposed between adjacent rolling elements in the circumferential direction of another part of them.

Advantages of the Invention

[0007] According to the present disclosure, an eccentric swing type gear device capable of reducing the collision noise of rolling elements can be provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments for implementing the eccentric swing type gear device of the present disclosure will be described. The same or equivalent components are denoted by the same reference numerals, and redundant descriptions are omitted. In each drawing, for convenience of explanation, components are appropriately omitted, enlarged, or reduced. The drawings are to be viewed in accordance with the direction of the reference numerals.

[0010] First, the background leading to the conception of the eccentric swing type gear device (hereinafter, also simply referred to as the gear device) of the present disclosure will be described. The inventor of the present application newly recognized that when each rolling element of the eccentric bearing has a total rolling structure, there is a problem that a collision noise is generated due to the collision of the rolling elements with each other, such as "clickety-clack", during the operation of the gear device. When the inventor of the present application examined this cause, it was newly recognized that in the eccentric bearing with a total rolling structure, the following specific behavior is the cause.

[0011] Figure 1 is an explanatory diagram showing the behavior of the eccentric bearing during the operation of the eccentric swing type gear device. Here, the case where rotation is input from a drive source to the crankshaft described later will be described as an example.

[0012] During the operation of the gear device, a load range R1 where a load acts on the rolling elements 50 and a no-load range R2 where almost no or no load acts on the rolling elements occur in the eccentric bearing 20. The load range R1 and the no-load range R2 are in a range corresponding to the type, dimensions, reduction ratio, etc. of the gear device 10. The load range R1 and the no-load range R2 swing together with the eccentric body 12 in the process of the axis C12 of the eccentric body 12 swinging around the rotation center line C14 of the crankshaft 14 in the swing direction D3, but the size of the range hardly varies. The load range R1 usually includes an angular range R1a of 90° in the swing direction D3 from a half-line extending from the rotation center line C14 of the crankshaft 14 in the maximum eccentricity direction D1 (described later). Further, the load range R1 usually has a starting point within an angular range of -90° in the direction opposite to the swing direction D3 from the angular range R1a, and an end point within an angular range of 90° in the swing direction D3 from the angular range R1a.

[0013] During the operation of the gear device, the rolling elements 50 of the eccentric bearing 20 proceed so as to alternately pass through the load range R1 and the no-load range R2. When passing through the load range R1, a load acts between the inner rolling surface 52 and the outer rolling surface 54 on the rolling elements 50. When the eccentric body 12 swings under this state, the rolling elements 50 roll and contact both the inner rolling surface 52 and the outer rolling surface 54 without slipping, and proceed in the circumferential direction of the eccentric body (described later) with rotation. At this time, when a rotation with a constant angular velocity is input to the crankshaft 14, the rolling elements 50 proceed at a substantially constant traveling speed.

[0014] On the other hand, when passing through the no-load range R2, almost no or no load acts on the rolling elements 50 between the inner rolling surface 52 and the outer rolling surface 54. When the eccentric body 12 swings under this condition, the rolling elements 50 slide without rolling contact with respect to the inner rolling surface 52 and the outer rolling surface 54. At this time, each rolling element 50 within the no-load range R2 does not rotate and progress due to rolling contact, but progresses without rotation by being pushed in the direction F1 by the subsequent rolling element 50 (hereinafter also referred to as the subsequent rolling element 50-1) that attempts to shift from the load range R1 to the no-load range R2. The rolling element 50 that has shifted from the no-load range R2 to the load range R1 begins to roll contact again and thus progresses in the circumferential direction of the eccentric body.

[0015] Refer to FIGS. 2(A) and 2(B). As described above, each rolling element 50 within the no-load range R2 progresses by being pushed by the subsequent rolling element 50-1 that attempts to shift from the load range R1 to the no-load range R2. Therefore, if, as shown in FIG. 2(A), the circumferential clearance 100 (described later) of the eccentric bearing 20 is large, the leading rolling element 50 (hereinafter also referred to as the leading rolling element 50-2) immediately after shifting to the no-load range R2 will be in a state where it is not temporarily pushed by the rolling elements 50 within the load range R1. For this reason, each rolling element 50 (including the leading rolling element 50-2) within the no-load range R2 is decelerated until it begins to be pushed by the rolling elements 50 within the load range R1. When each rolling element 50 within the no-load range R2 is decelerated in this way, a speed difference in the circumferential direction of the eccentric body occurs with respect to the rolling elements 50 within the load range R1. In a state where this speed difference has occurred, as shown in FIG. 2(B), when the subsequent rolling element 50-1 within the load range R1 collides with the leading rolling element 50-2 within the no-load range R2, a collision sound is generated due to this.

[0016] The problem of the collision sound of the rolling elements 50 is a problem peculiar to the case where adjacent rolling elements 50 are made contactable with each other like a total rolling structure with respect to the eccentric bearing 20 having the load range R1 and the no-load range R2. The inventor of the present application has obtained the recognition that it is effective to reduce the circumferential clearance 100 of the eccentric bearing 20 in order to reduce the collision sound of the rolling elements, which is a problem peculiar to the eccentric bearing. Further, the inventor of the present application has obtained the recognition that in order to reduce the circumferential clearance 100 of the eccentric bearing 20 in this way, some adjacent rolling elements 50 among the plurality of rolling elements 50 can be made contactable in the circumferential direction, while a spacer 62 (see FIG. 5) is arranged between some other adjacent rolling elements 50. By arranging this spacer 62, the circumferential clearance 100 of the eccentric bearing 20 can be reduced as compared with the case where the spacer 62 is not arranged. The smaller the circumferential clearance 100 is, the shorter the time interval from when the rolling element 50 moves into the no-load range R2 until it starts to be pushed by the rolling element 50 within the load range R1 can be made, and the deceleration of each rolling element 50 within the no-load range R2 can be reduced. As a result, the speed difference when the subsequent rolling element 50-1 within the load range R1 collides with the preceding rolling element 50-2 within the no-load range R2 can be reduced, and the collision sound caused thereby can be reduced. Hereinafter, the details of the gear device 10 made under such a background will be described.

[0017] Refer to FIG. 3. The eccentric swing type gear device 10 includes a crankshaft 14 having at least one eccentric body 12, a swing gear 16 swung by the eccentric body 12, a meshing gear 18 meshing with the swing gear 16, an eccentric bearing 20 disposed between the eccentric body 12 and the swing gear 16, a carrier 22 synchronized with the rotation component of the swing gear 16, and a casing 24 disposed radially outside the swing gear 16. The gear device 10 of the present embodiment has one of the main features in the eccentric bearing 20, but will be described from the peripheral structure first.

[0018] In this embodiment, as the gear device 10, an eccentric swing type gear device of the center crank type will be described. In this type of gear device 10, the crankshaft 14 is arranged on the swing center C16a of the swing gear 16. Hereinafter, the direction along the swing center C16a of the swing gear 16 will be simply referred to as the axial direction, and the radial direction and the circumferential direction of the circle centered on the swing center C16a will also be simply referred to as the radial direction and the circumferential direction, respectively.

[0019] The gear device 10 includes an input member 26 to which rotation is input from a drive source (not shown), a fixing member 28 fixed to an external fixed member (not shown), and an output member 30 that outputs rotation to an external driven member (not shown). Here, an example will be described in which the crankshaft 14 constitutes the input member 26, the casing 24 constitutes the fixing member 28, and the carrier 22 constitutes the output member 30. The drive source is, for example, a motor, but in addition to this, a gear motor, an engine, etc. may also be used. The driven member is, for example, (1) industrial machines such as machine tools and construction machines, (2) robots such as industrial robots and service robots, (3) conveying machines such as conveyors and film conveying devices, and (4) a part of various machines such as vehicles.

[0020] The crankshaft 14 includes, in addition to the eccentric body 12, shaft bodies 32 provided on both axial sides of the eccentric body 12. The crankshaft 14 is supported by a crank bearing 34 disposed between the casing 24 or the carrier 22 and the shaft body 32. The eccentric body 12 and the shaft body 32 are provided by the same member, but they may also be provided separately.

[0021] The crankshaft 14 of this embodiment includes a total of two eccentric bodies 12, but the number thereof is not particularly limited, and it may be either a single one or three or more. The eccentric body 12 has a circular shape in which the axis C12 of the eccentric body 12 is eccentric with respect to the rotation center line C14 of the crankshaft 14. The axis C12 of the eccentric body 12 is the geometric center of the shape formed by the outer peripheral surface of the eccentric body 12 in a cross section perpendicular to the axial direction passing through the eccentric body 12. The eccentric body 12 can swing the swing gear 16 by rotating around the rotation center line C14 of the crankshaft 14. Here, "swing" means that the gear center C16b of the swing gear 16 rotates around the swing center C16a.

[0022] The eccentric bearing 20 is provided individually corresponding to each of the plurality of eccentric bodies 12, and rotatably supports the oscillating gear 16 corresponding to the eccentric body 12. Here, an example in which the oscillating gear 16 is an external gear and the meshing gear 18 is an internal gear will be described. The oscillating gear 16 is provided individually corresponding to each of the plurality of eccentric bodies 12. The oscillating gear 16 includes an eccentric bearing hole 16a in which the eccentric bearing 20 is disposed. The meshing gear 18 of the present embodiment is integrated with the casing 24. The meshing gear 18 includes a meshing gear main body 18a and a tooth portion 18b provided on the peripheral portion of the meshing gear main body 18a and meshing with the oscillating gear 16. Although the tooth portion 18b of the present embodiment is integrated with the meshing gear main body 18a, it may be constituted by a pin rotatably supported by the meshing gear main body 18a.

[0023] The carrier 22 of the present embodiment is disposed only on one axial side with respect to the oscillating gear 16, but may also be disposed on the other axial side. The carrier 22 of the present embodiment is configured by combining a plurality (here, two) of carrier members 22a. A pin body 36 protrudes axially from the carrier 22. The pin body 36 penetrates a pin hole 16b provided in the oscillating gear 16. The pin body 36 of the present embodiment can receive a load from the oscillating gear 16 via a roller 38 through which the pin body 36 is inserted.

[0024] The carrier 22 can be synchronized with the rotation component of the swing gear 16 by a pin body 36 that penetrates the swing gear 16. "Synchronizing with the rotation component" here means maintaining the rotation component of the carrier 22 at the same magnitude as the rotation component of the swing gear 16 within a numerical range including zero. For example, when the carrier 22 becomes the output member 30, the swing gear 16 rotates, and its rotation component is transmitted to the carrier 22 via the pin body 36, and the carrier 22 rotates with a rotation component of the same magnitude as that rotation component. At this time, the carrier 22 rotates with a rotation component of the same magnitude as the rotation component of the swing gear 16, thereby synchronizing with the rotation component of the swing gear 16. On the other hand, when the carrier 22 becomes the fixed member 28, the rotation component of the carrier 22 is maintained at zero, and the rotation of the swing gear 16 is restricted by the carrier 22 and the pin body 36, so that the rotation component of the swing gear 16 is also maintained at zero. As a result, the rotation component of the carrier 22 synchronizes with the rotation component of the swing gear 16.

[0025] The casing 24 of this embodiment is configured by combining a plurality (here, three) of casing members 24a. A main bearing 40 is disposed between the carrier 22 and the casing 24.

[0026] The operation of the above-described gear device 10 will be described. The crankshaft 14 rotates due to the rotation output from the drive source. When the crankshaft 14 rotates, the swing gear 16 swings by the eccentric body 12. When the swing gear 16 swings, the meshing position of the swing gear 16 and the meshing gear 18 changes in the circumferential direction. Along with this, every time the crankshaft 14 makes one rotation, one of the swing gear 16 and the meshing gear 18 (here, the swing gear 16) rotates by the difference in the number of teeth between the swing gear 16 and the meshing gear 18, and its rotation component is transmitted to the output member 30. At this time, a rotation component decelerated from the rotation of the crankshaft 14 at a reduction ratio corresponding to the difference in the number of teeth between the swing gear 16 and the meshing gear 18 is transmitted to the output member 30. This rotation component is output from the output member 30 to the driven member.

[0027] Refer to FIG. 4. FIG. 4 shows a state where the rotational phase of the crankshaft 14 is different from that in FIG. 3. On the half-line extending from the rotation center line C14 of the crankshaft 14 and passing through the axis C12 of the eccentric body 12, the direction from the rotation center line C14 toward the axis C12 is defined as the maximum eccentricity direction D1. Also, the circumferential direction of the circle centered on the axis C12 of the eccentric body 12 is defined as the eccentric body circumferential direction.

[0028] The eccentric bearing 20 includes a plurality of rolling elements 50, an inner rolling surface 52 provided on the radially inner side of the rolling elements 50 for the rolling elements 50 to roll on, and an outer rolling surface 54 provided on the radially outer side of the rolling elements 50 for the rolling elements 50 to roll on.

[0029] The rolling element 50 of this embodiment is a roller whose rotation center line is parallel to the rotation center line C14 of the crankshaft 14. In addition, the rolling element 50 may be various rolling elements such as a sphere.

[0030] The inner ring of the eccentric bearing 20 of this embodiment is also served as the eccentric body 12, and the inner rolling surface 52 is provided on its outer peripheral surface. In addition, the eccentric bearing 20 may include a dedicated inner ring, and the inner rolling surface 52 may be provided on the inner ring.

[0031] The outer ring of the eccentric bearing 20 of this embodiment is also served as the oscillating gear 16, and the outer rolling surface 54 is provided in the eccentric bearing hole 16a. In addition, the eccentric bearing 20 may include a dedicated outer ring, and the outer rolling surface 54 may be provided on the outer ring.

[0032] Refer to FIG. 5. Combinations of rolling elements 50 adjacent to each other in the eccentric body circumferential direction are referred to as rolling element sets 60A and 60B. The rolling element sets 60A and 60B are composed of two rolling elements 50 adjacent to each other in the eccentric body circumferential direction. The plurality of rolling elements 50 constitute a plurality of sets of rolling element sets 60A and 60B that are the same in number as the number of rolling elements 50. One rolling element 50 overlaps between the two rolling element sets 60A and 60B. That is, one rolling element 50 forms one rolling element set 60A or 60B in combination with another rolling element 50 adjacent to it on one side in the eccentric body circumferential direction, and forms another rolling element set 60A or 60B in combination with another rolling element 50 adjacent to it on the other side in the eccentric body circumferential direction.

[0033] The eccentric bearing 20 of this embodiment does not include a retainer for holding the intervals between adjacent rolling elements 50. A retainer generally includes an annular portion arranged axially with respect to a plurality of rolling elements 50, and a plurality of interval holding portions that project axially from the annular portion and hold the intervals between adjacent rolling elements 50. A retainer generally includes the same number of interval holding portions as the number of a plurality of rolling elements 50, and each of the plurality of interval holding portions is arranged between the rolling elements 50 of each of the plurality of rolling element sets 60A and 60B.

[0034] Among the plurality of rolling elements 50, the rolling elements 50 adjacent to each other in the circumferential direction can be in contact with each other. A spacer 62 is arranged between the rolling elements 50 adjacent to each other in the circumferential direction of another part of the plurality of rolling elements 50. From another perspective, the plurality of rolling element sets 60A and 60B include a first rolling element set 60A in which the rolling elements 50 adjacent to each other in the circumferential direction can be in contact with each other, and a second rolling element set 60B in which a spacer 62 is arranged between the rolling elements 50 adjacent to each other in the circumferential direction. From the perspective of increasing the rolling element filling rate, it is more desirable that the ratio of the number of the first rolling element sets 60A to the total number of the rolling element sets 60A and 60B is larger. The rolling element filling rate here refers to the ratio of the rolling element arrangement space 64 where the rolling elements 50 are arranged in the eccentric bearing 20 occupied by all the rolling elements 50 constituting the eccentric bearing 20. From such a perspective, the number of the first rolling element sets 60A is preferably, for example, more than half of the total number of the rolling element sets 60A and 60B, (total number - 2) or more, (total number - 1) in this order. It can also be said that the number of the second rolling element sets 60B is preferably, for example, less than half of the total number, 2 or less, 1 in this order. Here, an example where the number of the first rolling element sets 60A is (total number - 1) and the number of the second rolling element sets 60B is 1 will be described.

[0035] The spacer 62 is used to reduce the circumferential clearance 100 of the eccentric bearing 20 compared to the case where there is no spacer 62. The "circumferential clearance" here refers to the clearance that exists between movable members in a combination of at least one pair of adjacent movable members among the plurality of movable members arranged in the circumferential direction in the aforementioned rolling element arrangement space 64 and allows play in the circumferential direction of the plurality of movable members. The "movable members" here include the spacer 62 in addition to the plurality of rolling elements 50.

[0036] Consider the tangential dimension L62a of the spacer 62. The tangential dimension L62a here refers to the dimension of the eccentric body 12 in the tangential direction. Specifically, in a cross-section perpendicular to the axial direction passing through the eccentric bearing 20, it refers to the dimension in the tangential direction along the tangent line A1 of a circle centered on the axis C12 of the eccentric body 12 and passing through the outer shape center C62 which is the geometric center of the outer shape of the spacer 62. Depending on the shape of the spacer 62, the tangential dimension may vary due to the rotation of the spacer 62 around the outer shape center C62. Therefore, the tangential dimension L62a of the spacer 62 is based on the rotational position around the outer shape center C50 where the tangential dimension is the smallest.

[0037] Consider the radial dimension L62b of the spacer 62. The radial dimension L62b here refers to the dimension in the radial direction along the radius line A2 of a circle centered on the axis C12 of the eccentric body 12 and passing through the outer shape center C62 of the spacer 62 in a cross-section perpendicular to the axial direction passing through the eccentric bearing 20. The radial dimension L62b of the spacer 62 is also based on the rotational position around the outer shape center C50 where the tangential dimension L62a of the spacer 62 is the smallest. The spacer 62 of this embodiment is formed in a plate shape such that the thickness direction is aligned in the tangential direction when in the rotational position where the tangential dimension L62a is the smallest. The tangential dimension L62a of the spacer 62 is the dimension in this thickness direction, and the radial dimension L62b is the dimension in the width direction of the plate formed by the spacer 62.

[0038] At this time, preferably, the tangential dimension L62a of the spacer 62 is smaller than the diameter L50a of the rolling element 50. The diameter L50a of the rolling element 50 here refers to the diameter of the rolling element 50 as viewed from the direction along the rotation center line of the roller when the rolling element 50 is a roller, and the diameter of the sphere when the rolling element 50 is a sphere. Thereby, compared with the case where the tangential dimension L62a of the spacer 62 is equal to or larger than the diameter L50a of the rolling element 50, it is advantageous for increasing the rolling element filling rate. Further, when the spacer 62 passes through the aforementioned load range R1, since the spacer 62 cannot receive a load, the load is received dispersively by the other rolling elements 50 passing through the load range R1. At this time, the smaller the tangential dimension L62a of the spacer 62 is, the easier it is to increase the number of rolling elements 50 existing within the load range R1. As a result, the load received by the plurality of rolling elements 50 existing within the load range R1 can be reduced, which is advantageous for ensuring the strength of the rolling elements 50. The lower limit value of the tangential dimension L62a of the spacer 62 is not particularly limited, but for example, it may be 0.1 mm in consideration of practical manufacturability, and more preferably 0.5 mm in consideration of further manufacturability.

[0039] The radial dimension L62b of the spacer 62 is preferably larger than the tangential dimension L62a of the spacer 62. Thereby, compared with the case where the radial dimension L62b of the spacer 62 is equal to or smaller than the tangential dimension L62a of the spacer 62, it becomes difficult for the spacer 62 to rotate around the outer shape center C62 of the spacer 62 when viewed from the axial direction. As a result, by suppressing the rotation of the spacer 62, the stability is improved in advancing the spacer 62 in the circumferential direction of the eccentric body. The radial dimension L62b of the spacer 62 is preferably set to be less than the diameter L50a of the rolling element 50 from the viewpoint of suppressing sliding with respect to the respective rolling surfaces 52 and 54 of the eccentric bearing 20.

[0040] The spacer 62 can be in line contact with the rolling element 50. The contact range between the spacer 62 and the rolling element 50 will form a linear shape extending in the axial direction. To achieve this, the rolling element 50 is constituted by, for example, a roller such as a cylindrical roller, and the spacer 62 is constituted by, for example, a plate material rather than a sphere. Thereby, compared with the case where the spacer 62 and the rolling element 50 are in point contact, the contact surface pressure acting at the contact portion between the two can be reduced when the spacer 62 and the rolling element 50 collide, which is advantageous for ensuring the strength of the spacer 62.

[0041] The spacer 62 is preferably made of a material having a smaller Young's modulus (MPa) than the rolling element 50. Thereby, the spacer 62 can be made softer than the rolling element 50. Thereby, when the subsequent rolling element 50-1 collides with the preceding rolling element 50-2 as described above, the impact load due to the collision can be cushioned by the spacer 62, which is advantageous for ensuring the strength of the eccentric bearing 20. To achieve this, the rolling element 50 may be made of a metal-based material, and the spacer 62 may be made of a resin-based material. As the metal-based material, in addition to iron-based materials such as bearing steel, aluminum-based materials such as aluminum alloys may be adopted. As the resin-based material, in addition to general-purpose engineering plastics such as nylon-based resins such as PA46, plastic-based materials such as special engineering plastics may be adopted. The metal-based material may be constituted by a composite material of other materials such as fibers and the main material, in addition to the main metal (including alloys). The resin-based material may be constituted by a composite material of other materials such as fibers and the main material, in addition to the main resin.

[0042] The eccentric bearing 20 is in an environment where it is likely to be heated to a high temperature due to the influence of heat or the like caused by the meshing of the oscillating gear 16 and the meshing gear 18. Therefore, the spacer 62 is preferably made of a material having a heat resistance temperature such that it can withstand even when heated to a high temperature. This heat resistance temperature is preferably, for example, a material having a heat resistance temperature of 100°C or higher. Also in this case, any of the above-described metal-based materials and resin-based materials may be adopted.

[0043] During the operation of the gear device 10, the spacer 62 advances in the circumferential direction of the eccentric body by being pushed by other subsequent rolling elements 50 without rolling on the rolling surfaces of the eccentric bearings 20. Here, "during the operation of the gear device 10" also means when the crankshaft 14 rotates. It can also be said that the spacer 62 advances in the circumferential direction of the eccentric body without repeatedly rotating in the same direction around the outer shape center C60 when the spacer 62 is viewed axially. This is satisfied whether the spacer 62 is in the load range R1 or the no-load range R2. Even if the spacer 62 comes into contact with the rolling surfaces 52 and 54 of the eccentric bearing 20, it advances in the circumferential direction of the eccentric body while making sliding contact without rolling contact.

[0044] Refer to FIG. 6. FIG. 6 shows a state different from that in FIG. 3 in terms of the phase around the axis center C12 of each rolling element 50 of the eccentric bearing 20. The gear device 10 includes a pair of restricting portions 70 that restrict the axial movement of the plurality of rolling elements 50. The pair of restricting portions 70 are provided corresponding to each of the plurality of eccentric bearings 20. One of the pair of restricting portions 70 in this embodiment is provided separately from the crankshaft 14, and the other of them is integrally provided by the same member as the crankshaft 14.

[0045] The axial dimension L62c of the spacer 62 is preferably made smaller than the axial dimension L50b of the rolling element 50. This is advantageous for avoiding sliding against the pair of restricting portions 70 that restrict the axial movement of the rolling element 50.

[0046] The effects of the gear device 10 described above will be explained. The spacer 62 is disposed between some adjacent rolling elements 50 among the plurality of rolling elements 50. Therefore, as described above, the collision noise of the rolling elements 50 can be reduced.

[0047] Also, since some adjacent rolling elements 50 among the plurality of rolling elements 50 can be in contact in the circumferential direction, there are the following advantages. In an eccentric bearing, a retainer is usually incorporated to maintain the interval between adjacent rolling elements 50. The retainer includes an interval maintaining portion that maintains the interval between adjacent rolling elements 50. When reducing the radial dimension of the gear device 10, the thickness dimension of the interval maintaining portion of the retainer is reduced along with the radial dimension of the retainer. However, there is a manufacturing upper limit to reducing the thickness dimension of this interval maintaining portion of the retainer. For this reason, when the reduction of the radial dimension of the gear device 10 proceeds to a certain extent, it becomes necessary to secure a certain thickness dimension for the interval maintaining portion of the retainer, and the number of rolling elements has to be reduced. If the rolling element filling rate is lowered by reducing the number of rolling elements in this way, there is a problem of causing a decrease in the strength of the eccentric bearing 20. That is, there is a trade-off relationship between the reduction of the radial dimension of the gear device 10 and the strength of the eccentric bearing 20.

[0048] In this regard, according to the present embodiment, some adjacent rolling elements 50 can be in contact in the circumferential direction. Therefore, when reducing the radial dimension of the gear device 10, the rolling element filling rate of the eccentric bearing 20 can be increased compared with the case of using a retainer, which is advantageous for improving the strength of the eccentric bearing 20. In particular, it is advantageous in that it can achieve both the reduction of the radial dimension of the gear device 10, which is in a trade-off relationship, and the strength of the eccentric bearing. From the perspective of such reduction of the radial dimension of the gear device 10, the inner diameter of the outer rolling surface 54 of the eccentric bearing 20 (the dimension in the radial direction of the circle centered on the axis C12 of the eccentric body 12) may be, for example, 50 mm or less.

[0049] Note that in the eccentric swing type gear device 10, a plurality of types of rolling elements 50 with different outer diameters are prepared, and the internal clearance in the radial direction of the eccentric bearing 20 may be adjusted by adjusting the diameter L50a of the rolling element 50 during the assembly of the gear device 10. Adjusting the internal clearance in the radial direction in this way is because the internal clearance in the radial direction greatly affects various performances such as the strength, lost motion, and efficiency of the gear device 10. However, even if such an internal clearance in the radial direction is adjusted, it is difficult to adjust the circumferential clearance 100 of the eccentric bearing 20. The gear device 10 of this embodiment is particularly effective in that the circumferential clearance 100, which is difficult to adjust in this way, can be adjusted by the spacer 62. In adjusting the circumferential clearance 100 in this way, the number of spacers 62 arranged between adjacent rolling elements 50 of the second rolling element set 60B is not particularly limited. Only a single spacer 62 may be arranged between these rolling elements 50 as in the embodiment, or a plurality of spacers 62 may be arranged.

[0050] If the spacer 62 rolls, the spacer 62 rotates around the outer shape center C62 as viewed from the axial direction. Therefore, depending on the shape of the spacer 62, the actual tangential dimension of the spacer 62 changes greatly depending on the rotational position around the outer shape center C62. Here, "depending on the shape of the spacer 62" means, for example, the case where the tangential dimension L62a and the radial dimension L62b of the spacer 62 are different as described above. In this regard, the spacer 62 of this embodiment advances in the circumferential direction of the eccentric body by being pushed by other rolling elements 50 without rolling on the rolling surface. Therefore, regardless of the shape of the spacer 62, it is difficult for the actual tangential dimension of the spacer 62 to change greatly, and it becomes easier to suppress the variation of the circumferential clearance of the eccentric bearing 20 adjusted by the spacer 62. As a result, regardless of the shape of the spacer 62, the effect of reducing the collision sound by the spacer 62 can be stably obtained.

[0051] Next, modified forms of each component described so far will be described.

[0052] The specific type of the gear device 10 is not particularly limited. The gear device 10 may be, for example, a distribution type in which a plurality of crankshafts 14 are arranged at positions radially offset with respect to the swing center C16a of the swing gear 16.

[0053] The output member 30 may be the casing 24 instead of the carrier 22. The swing gear 16 may be an internal gear and the meshing gear 18 may be an external gear.

[0054] An example in which the gear device 10 is a speed reduction device has been described. In addition to this, the gear device 10 may be a speed increase device. In this case, the carrier 22 and the casing 24 may be input members, and the crankshaft 14 may be an output member.

[0055] The tangential dimension L62a of the spacer 62 may be the same as the diameter L50a of the rolling element 50, or may be larger than the diameter L50a. The radial dimension L62b of the spacer 62 may be equal to or less than the tangential dimension L62a of the spacer 62. The spacer 62 may be constituted by spheres that roll on the rolling surfaces 52 and 54 of the eccentric bearing 20 during the operation of the gear device 10. The material of the spacer 62 is not particularly limited, and it may be constituted by a material having a Young's modulus larger than that of the rolling element 50. The spacer 62 may be constituted by a metal-based material in addition to a resin-based material.

[0056] The above embodiments and modified forms are examples. The technical ideas abstracted from these should not be construed as being limited to the contents of the embodiments and modified forms. Many design changes such as changes, additions, and deletions of components are possible for the contents of the embodiments and modified forms. In the foregoing embodiments, regarding the contents for which such design changes are possible, the notation "this embodiment" is attached and emphasized. However, design changes are also allowed for the contents without such notation. The hatching attached to the cross-section of the drawing does not limit the material of the object to which the hatching is attached. A component constituted by a single member in the embodiment may be constituted by a plurality of members. Similarly, a component constituted by a plurality of members in the embodiment may be constituted by a single member.

Explanation of Reference Numerals

[0057] 10…Eccentric swing type gear device, 12…Eccentric body, 14…Crankshaft, 16…Swing gear, 20…Eccentric bearing, 50…Rolling element, 62…Spacer.

Claims

1. A crankshaft having an eccentric body, A rocking gear rocked by the eccentric body, An eccentric rocking type gear device comprising an eccentric bearing disposed between the rocking gear and the eccentric body, wherein the eccentric bearing includes a plurality of rolling elements, some of the plurality of rolling elements adjacent to each other in the circumferential direction are in contact with each other, and a spacer is disposed between some of the other rolling elements adjacent to each other in the circumferential direction.

2. When the dimension of the eccentric body in the tangential direction is referred to as the tangential dimension, the tangential dimension of the spacer is smaller than the diameter of the rolling element. The eccentric rocking type gear device according to claim 1.

3. When the dimension of the eccentric body in the radial direction is referred to as the radial dimension, the radial dimension of the spacer is larger than the tangential dimension of the spacer. The eccentric rocking type gear device according to claim 2.

4. The spacer progresses in the circumferential direction of the eccentric body by being pushed by the rolling element without rolling on the rolling surface of the eccentric bearing during operation of the gear device. The eccentric rocking type gear device according to claim 1.

5. The spacer is made of a material having a smaller Young's modulus than that of the rolling element. The eccentric rocking type gear device according to claim 1.

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