Eccentric oscillating gear device

Abstract

The invention provides an eccentric swing type gear device capable of reducing collision sound of rolling bodies. The eccentric oscillating gear device is provided with: a crankshaft having an eccentric body; a swing gear swung by the eccentric body; and an eccentric bearing (20) disposed between the oscillating gear and the eccentric body, the eccentric bearing (20) being provided with a plurality of rolling bodies (50), some of the plurality of rolling bodies (50) adjacent in the circumferential direction being capable of contacting each other, and spacers being disposed between the other some of the rolling bodies (50) adjacent in the circumferential direction.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2023-206180 filed on December 6, 2023. The entire contents of the Japanese Patent Application are incorporated herein by reference. Technical Field

[0002] The invention relates to an eccentric swing type gear device. Background Art

[0003] Patent Document 1 discloses an eccentric oscillating gear device including: a crankshaft having an eccentric body; an oscillating gear oscillated by the eccentric body; and an eccentric bearing disposed between the oscillating gear and the eccentric body.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2019-056478

[0005] The inventors of the present invention have newly recognized that there are the following unique problems in eccentric oscillating gear devices. When the eccentric bearing is set as a full roller structure, the adjacent rolling elements of the eccentric bearing can contact each other. In this case, there is the following problem: when the gear device is running, the rolling elements collide with each other and produce a collision sound. Summary of the invention

[0006] Therefore, an object of the present invention is to provide an eccentric oscillating type gear device capable of reducing the collision sound of rolling elements.

[0007] An eccentric swinging gear device according to one embodiment of the present invention comprises: a crankshaft having an eccentric body; a swinging gear which is swung by the eccentric body; and an eccentric bearing which is arranged between the swinging gear and the eccentric body, wherein the eccentric bearing comprises a plurality of rolling elements, a portion of the rolling elements which are adjacent in the circumferential direction can contact each other, and a spacer is arranged between another portion of the rolling elements which are adjacent in the circumferential direction.

[0008] According to the present invention, there is provided an eccentric oscillating gear device capable of reducing the collision sound of a rolling element. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is an explanatory diagram schematically showing the operation of the eccentric bearing when the gear device is operating.

[0010] Figure 2 (A) is a first explanatory diagram for explaining the deceleration of the rolling element in the no-load range. Figure 2 The middle (B) is a second explanatory diagram for explaining the collision sound of the rolling element.

[0011] Figure 3 It is a side cross-sectional view showing the gear device according to the embodiment.

[0012] Figure 4 This is a cross-sectional view of the eccentric bearing and the surrounding structure according to the embodiment, as viewed from the axial direction.

[0013] Figure 5 Yes Figure 4 An enlarged view of the eccentric bearing.

[0014] Figure 6 It is magnified Figure 3 Part of the diagram.

[0015] In the figure: 10 - eccentric swing type gear device, 12 - eccentric body, 14 - crankshaft, 16 - swing gear, 20 - eccentric bearing, 50 - rolling element, 62 - spacer. DETAILED DESCRIPTION

[0016] The following is an explanation of the embodiment of the eccentric oscillating gear device of the present invention. The same or equivalent components are marked with the same symbols, and repeated descriptions are omitted. In each of the drawings, components are appropriately omitted, enlarged, or reduced for ease of description. The drawings are viewed in the direction of the symbols.

[0017] First, the background of the eccentric oscillating gear device (hereinafter referred to as the gear device) of the present invention is described. The inventors of the present invention have newly recognized that when the rolling elements of the eccentric bearing are set as a full roller structure, there is a problem that the rolling elements collide with each other during the operation of the gear device, and a "clicking" collision sound is generated. The inventors of the present invention have studied the cause of this problem, and as a result, newly recognized that the cause is the following unique behavior existing in the eccentric bearing of the full roller structure.

[0018] Figure 1 This is an explanatory diagram showing the operation of the eccentric bearing when the eccentric oscillating gear device is in operation. Here, the case where rotation is input from the driving source to the crankshaft described later is described as an example.

[0019] When the gear device is running, the eccentric bearing 20 has a load range R1 in which a load acts on the rolling element 50 and a no-load range R2 in which a load hardly or completely acts on the rolling element. The load range R1 and the no-load range R2 are ranges corresponding to the type, size, 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 during the process in which the axis C12 of the eccentric body 12 swings in the swing direction D3 around the rotation center line C14 of the crankshaft 14, but the size of the range is almost unchanged. The load range R1 generally includes an angle range R1a that is rotated 90° from a half straight line extending from the rotation center line C14 of the crankshaft 14 toward the maximum eccentric direction D1 (described later) toward the swing direction D3. In addition, the load range R1 generally has a starting point within an angle range of -90° in the opposite direction of the swing direction D3 from the angle range R1a, and an end point within an angle range of 90° in the swing direction D3 from the angle range R1a.

[0020] When the gear device is running, the rolling element 50 of the eccentric bearing 20 moves in a manner that alternately passes through the load range R1 and the no-load range R2. When the rolling element 50 passes through the load range R1, a load acts on the rolling element 50 between the inner rolling surface 52 and the outer rolling surface 54. If the eccentric body 12 is swung in this state, the rolling element 50 will roll in contact with both the inner rolling surface 52 and the outer rolling surface 54 without sliding, and thus move along the circumferential direction of the eccentric body (described later) accompanied by rotation. At this time, when the rotation of a constant angular velocity is input to the crankshaft 14, the rolling element 50 moves at an almost constant travel speed.

[0021] In contrast, when passing through the no-load range R2, the load between the inner rolling surface 52 and the outer rolling surface 54 hardly or completely acts on the rolling element 50. If the eccentric body 12 is swung in this state, the rolling element 50 will not slide in rolling contact with the inner rolling surface 52 and the outer rolling surface 54. At this time, each rolling element 50 in the no-load range R2 does not move along with rotation by rolling contact, but is pushed in the direction F1 by the subsequent rolling element 50 (hereinafter, also referred to as the subsequent rolling element 50-1) that is intended to enter the no-load range R2 from the load range R1, so that it moves without rotation. The rolling element 50 that enters the load range R1 from the no-load range R2 resumes rolling contact, thereby moving along the circumferential direction of the eccentric body.

[0022] refer to Figure 2 As described above, each rolling element 50 in the no-load range R2 is pushed by the subsequent rolling element 50-1 that wants to enter the no-load range R2 from the load range R1. Figure 2If the circumferential clearance 100 (described later) of the eccentric bearing 20 shown in (A) is large, the leading rolling element 50 (hereinafter, also referred to as the leading rolling element 50-2) that has just entered the no-load range R2 will be temporarily not pushed by the rolling element 50 in the load range R1. Therefore, each rolling element 50 in the no-load range R2 (including the leading rolling element 50-2) will be decelerated until it begins to be pushed by the rolling element 50 in the load range R1. In this way, if each rolling element 50 in the no-load range R2 is decelerated, a speed difference in the circumferential direction of the eccentric body will be generated relative to the rolling element 50 in the load range R1. In the state where this speed difference is generated, if Figure 2 When the following rolling element 50 - 1 in the load range R1 shown in (B) collides with the preceding rolling element 50 - 2 in the no-load range R2 , a collision sound is generated.

[0023] The problem of the collision sound of the rolling element 50 is a problem that is unique to the case where the eccentric bearing 20 having a load range R1 and a no-load range R2 is configured so that adjacent rolling elements 50 can contact each other like a full roller structure. The present inventors have recognized that reducing the circumferential gap 100 of the eccentric bearing 20 is effective in reducing the collision sound of the rolling elements that is a problem unique to the eccentric bearing. Furthermore, the present inventors have recognized that in order to reduce the circumferential gap 100 of the eccentric bearing 20 in this way, it is possible to allow adjacent portions of the plurality of rolling elements 50 to contact each other in the circumferential direction and to arrange a spacer 62 between the adjacent portions of the rolling elements 50 (see Figure 5 ) is effective. By configuring the spacer 62, the circumferential gap 100 of the eccentric bearing 20 can be reduced compared to the case where the spacer 62 is not configured. The smaller the circumferential gap 100 is, the shorter the time interval from when the rolling element 50 enters the no-load range R2 to when it starts to be pushed by the rolling element 50 in the load range R1 can be, and the deceleration degree of each rolling element 50 in the no-load range R2 can be reduced. Furthermore, the speed difference when the subsequent rolling element 50-1 in the load range R1 collides with the preceding rolling element 50-2 in the no-load range R2 can be reduced, thereby reducing the collision sound generated thereby. The following is a detailed description of the gear device 10 made under such a background.

[0024] refer to Figure 3 The eccentric swing type gear device 10 comprises: a crankshaft 14 having at least one eccentric body 12; a swing gear 16 which is swung by the eccentric body 12; an engaging gear 18 which meshes with the swing gear 16; an eccentric bearing 20 which is arranged between the eccentric body 12 and the swing gear 16; a wheel carrier 22 which is synchronized with the rotation component of the swing gear 16; and a housing 24 which is arranged radially outward with respect to the swing gear 16. One of the main features of the gear device 10 of this embodiment is the eccentric bearing 20, but the peripheral structure thereof will be described first.

[0025] In this embodiment, a center crank type eccentric oscillating type gear device is described as the gear device 10. In this type of gear device 10, the crankshaft 14 is arranged on the oscillation center C16a of the oscillation gear 16. Hereinafter, the direction along the oscillation center C16a of the oscillation gear 16 is referred to as the axial direction, and the radial direction and the circumferential direction of the circle centered on the oscillation center C16a are referred to as the radial direction and the circumferential direction, respectively.

[0026] The gear device 10 includes an input member 26 for inputting rotation from a driving source (not shown), a fixed member 28 fixed to an external fixed member (not shown), and an output member 30 for outputting rotation to an external driven member (not shown). Here, an example in which the crankshaft 14 constitutes the input member 26, the housing 24 constitutes the fixed member 28, and the wheel frame 22 constitutes the output member 30 is described. The driving source is, for example, a motor, but in addition, it may also be a gear motor, an engine, etc. The driven member is, for example, a part of various machines such as (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) vehicles.

[0027] 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 crankshaft bearings 34 disposed between the housing 24 or the wheel carrier 22 and the shaft body 32. The eccentric body 12 and the shaft body 32 are provided as the same component, but may also be provided separately.

[0028] The crankshaft 14 of the present embodiment has a total of two eccentric bodies 12, but the number is not particularly limited and can be any one of one and three or more. The eccentric body 12 is in a circular shape in which the axis C12 of the eccentric body 12 is eccentric relative to the rotation center line C14 of the crankshaft 14. In a cross section orthogonal to the axial direction passing through the eccentric body 12, the axis C12 of the eccentric body 12 becomes the geometric center of the shape formed by the outer peripheral surface of the eccentric body 12. The eccentric body 12 can rotate around the rotation center line C14 of the crankshaft 14 to cause the swing gear 16 to swing. The "swing" here means that the gear center C16b of the swing gear 16 rotates around the swing center C16a.

[0029] The eccentric bearings 20 are provided corresponding to the plurality of eccentric bodies 12, respectively, and support the swing gears 16 corresponding to the eccentric bodies 12 so as to be rotatable. Here, an example in which the swing gear 16 is an external gear and the meshing gear 18 is an internal gear is described. The swing gears 16 are provided corresponding to the plurality of eccentric bodies 12, respectively. The swing gear 16 includes an eccentric bearing hole 16a for arranging the eccentric bearing 20. The meshing gear 18 of the present embodiment is integrated with the housing 24. The meshing gear 18 includes a meshing gear body 18a and a tooth portion 18b provided on the periphery of the meshing gear body 18a and meshing with the swing gear 16. In the present embodiment, the tooth portion 18b is integrated with the meshing gear body 18a, but may also be composed of a pin rotatably supported on the meshing gear body 18a.

[0030] The wheel frame 22 of the present embodiment is arranged only on one side in the axial direction relative to the swing gear 16, but can also be arranged on the other side in the axial direction. The wheel frame 22 of the present embodiment is composed of a plurality of (here two) wheel frame components 22a. The pin body 36 protrudes axially from the wheel frame 22. The pin body 36 passes through the pin hole 16b provided in the swing gear 16. The pin body 36 of the present embodiment can receive the load from the swing gear 16 via the roller 38 into which the pin body 36 is inserted.

[0031] The wheel carrier 22 can be synchronized with the rotation component of the swing gear 16 by the pin body 36 that penetrates the swing gear 16. Here, "synchronized with the rotation component" means that the rotation component of the wheel carrier 22 is maintained at the same magnitude within a numerical range including zero relative to the rotation component of the swing gear 16. For example, when the wheel carrier 22 serves as the output member 30, the swing gear 16 rotates, and the rotation component is transmitted to the wheel carrier 22 via the pin body 36, and the wheel carrier 22 rotates with the same magnitude as the rotation component. At this time, the wheel carrier 22 rotates with the same magnitude as the rotation component of the swing gear 16, thereby being synchronized with the rotation component of the swing gear 16. In contrast, when the wheel carrier 22 serves as the fixed member 28, the rotation component of the wheel carrier 22 is maintained at zero, the rotation of the swing gear 16 is restrained by the wheel carrier 22 and the pin body 36, and the rotation component of the swing gear 16 is also maintained at zero. As a result, the rotation component of the carrier 22 and the rotation component of the swing gear 16 are synchronized.

[0032] The housing 24 of this embodiment is formed by combining a plurality of (here, three) housing members 24 a. A main bearing 40 is disposed between the housing 24 and the carrier 22 .

[0033] Next, the operation of the above gear device 10 will be described. The crankshaft 14 rotates by the rotation output from the driving source. If the crankshaft 14 rotates, the swing gear 16 is swung by the eccentric body 12. If the swing gear 16 swings, the meshing position between the swing gear 16 and the meshing gear 18 changes in the circumferential direction. Therefore, every time the crankshaft 14 rotates once, one of the swing gear 16 and the meshing gear 18 (here, the swing gear 16) only rotates by an amount equivalent to the difference in the number of teeth between the swing gear 16 and the meshing gear 18, and this self-rotation component is transmitted to the output member 30. At this time, the self-rotation component after the rotation of the crankshaft 14 is decelerated 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 self-rotation component is output from the output member 30 to the driven member.

[0034] refer to Figure 4 .exist Figure 4 The rotation phase of the crankshaft 14 is shown in Figure 3 Different states. On the half straight 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 called the maximum eccentric direction D1. And, the circumferential direction of the circle centered on the axis C12 of the eccentric body 12 is called the eccentric body circumferential direction.

[0035] The eccentric bearing 20 includes a plurality of rolling elements 50 , an inner rolling surface 52 provided radially inside the rolling elements 50 and on which the rolling elements 50 roll, and an outer rolling surface 54 provided radially outside the rolling elements 50 and on which the rolling elements 50 roll.

[0036] The rolling element 50 of the present 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 spherical body.

[0037] The inner ring of the eccentric bearing 20 of this embodiment is also used by the eccentric body 12, and the inner rolling surface 52 is provided on the outer peripheral surface thereof. 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.

[0038] The outer ring of the eccentric bearing 20 of this embodiment is also used by the swing gear 16, and the eccentric bearing hole 16a is provided with an outer rolling surface 54. Alternatively, the eccentric bearing 20 may include a dedicated outer ring, and the outer rolling surface 54 may be provided on the outer ring.

[0039] refer to Figure 5. The combination of rolling elements 50 adjacent to each other in the circumferential direction of the eccentric body is referred to as a rolling element group 60A, 60B. The rolling element group 60A, 60B is composed of two rolling elements 50 adjacent to each other in the circumferential direction of the eccentric body. A plurality of rolling elements 50 constitute a plurality of rolling element groups 60A, 60B, the number of which is the same as the number of rolling elements 50. One rolling element 50 is repeated between two rolling element groups 60A, 60B. That is, one rolling element 50 is combined with another rolling element 50 adjacent to one side of the eccentric body in the circumferential direction to form one rolling element group 60A, 60B, and is combined with another rolling element 50 adjacent to the other side of the eccentric body in the circumferential direction to form another rolling element group 60A, 60B.

[0040] The eccentric bearing 20 of this embodiment does not include a retainer for maintaining the intervals between adjacent rolling elements 50. The retainer generally includes an annular portion arranged in the axial direction relative to the plurality of rolling elements 50, and a plurality of interval maintaining portions protruding in the axial direction from the annular portion to maintain the intervals between adjacent rolling elements 50. The retainer generally includes the same number of interval maintaining portions as the number of the plurality of rolling elements 50, and the plurality of interval maintaining portions are respectively arranged between the rolling elements 50 of each rolling element group 60A, 60B.

[0041] A portion of the rolling elements 50 adjacent in the circumferential direction among the plurality of rolling elements 50 can contact each other. A spacer 62 is arranged between another portion of the rolling elements 50 adjacent in the circumferential direction among the plurality of rolling elements 50. From another point of view, the plurality of rolling element groups 60A and 60B include a first rolling element group 60A in which the rolling elements 50 adjacent in the circumferential direction can contact each other and a second rolling element group 60B in which a spacer 62 is arranged between the rolling elements 50 adjacent in the circumferential direction. From the viewpoint of improving the rolling element filling rate, the larger the ratio of the number of the first rolling element group 60A to the total number of the rolling element groups 60A and 60B, the more preferred. The rolling element filling rate here refers to the ratio of all the rolling elements 50 constituting the eccentric bearing 20 to the rolling element arrangement space 64 in which the rolling elements 50 are arranged in the eccentric bearing 20. From this point of view, the number of the first rolling element group 60A is preferably more than half of the total number of the rolling element groups 60A and 60B, more preferably (total number of groups - 2), and further preferably (total number of groups - 1). It can be said that the number of the second rolling element group 60B is preferably less than half of the total number, more preferably less than 2, and further preferably 1. Here, an example in which the number of the first rolling element group 60A is (total number - 1) and the number of the second rolling element group 60B is 1 is described.

[0042] The spacer 62 is used to reduce the circumferential clearance 100 of the eccentric bearing 20 compared to the case without the spacer 62. The "circumferential clearance" here refers to the clearance between the movable parts in the combination of at least one adjacent movable part among the plurality of movable parts arranged along the circumferential direction in the rolling element arrangement space 64, so as to allow the plurality of movable parts to loosen in the circumferential direction. The "movable parts" here include the spacer 62 in addition to the plurality of rolling elements 50.

[0043] The tangential dimension L62a of the spacer 62 is discussed. The tangential dimension L62a here refers to the dimension in the tangential direction of the eccentric body 12, specifically, the dimension in the tangential direction of the tangent line A1 of the 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 in the cross section orthogonal to the axial direction passing through the eccentric bearing 20. Depending on the shape of the spacer 62, if the spacer 62 is rotated around the outer shape center C62, the tangential dimension will change. Therefore, the tangential dimension L62a of the spacer 62 is based on the rotation position around the outer shape center C62 where the tangential dimension becomes the smallest.

[0044] The radial dimension L62b of the spacer 62 is discussed. The radial dimension L62b here refers to the dimension in the radial direction of the radius line A2 of the circle passing through the outer shape center C62 of the spacer 62 and centered on the axis C12 of the eccentric body 12 in the 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 rotation position around the outer shape center C62 where the tangential direction dimension L62a of the spacer 62 becomes the smallest. The spacer 62 of this embodiment is in the shape of a plate whose thickness direction is consistent with the tangential direction when it is in the rotation position where the tangential direction dimension L62a becomes the smallest. The tangential direction dimension L62a of the spacer 62 becomes the dimension in the thickness direction, and its radial dimension L62b becomes the dimension in the width direction of the plate formed by the spacer 62.

[0045] At this time, it is preferred that 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: when the rolling element 50 is a roller, it refers to the diameter of the rolling element 50 when viewed from the direction along the rotation center line of the roller, and when the rolling element 50 is a sphere, it refers to the diameter of the sphere. Therefore, compared with the case where the tangential dimension L62a of the spacer 62 is greater than the diameter L50a of the rolling element 50, it is advantageous in improving the rolling element filling rate. In addition, when the spacer 62 passes through the above-mentioned load range R1, since the spacer 62 cannot bear the load, the load is distributed and borne by 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 in the load range R1. As a result, the load borne by the plurality of rolling elements 50 existing in the load range R1 can be reduced, which is advantageous in ensuring the strength of the rolling element 50. The lower limit of the tangential direction dimension L62a of the spacer 62 is not particularly limited, and may be set to, for example, 0.1 mm in consideration of actual ease of manufacturing, and is more preferably set to 0.5 mm in consideration of further ease of manufacturing.

[0046] The radial dimension L62b of the spacer 62 is preferably larger than the tangential dimension L62a of the spacer 62. As a result, compared with a case where the radial dimension L62b of the spacer 62 is less than the tangential dimension L62a of the spacer 62, when viewed from the axial direction, it is difficult for the spacer 62 to rotate around the outer shape center C62 of the spacer 62. Furthermore, by suppressing the rotation of the spacer 62, the stability of the spacer 62 when it moves along the circumferential direction of the eccentric body is improved. From the viewpoint of suppressing the sliding of the spacer 62 relative to the rolling surfaces 52 and 54 of the eccentric bearing 20, the radial dimension L62b of the spacer 62 is preferably set to a size smaller than the diameter L50a of the rolling element 50.

[0047] The spacer 62 and the rolling element 50 can be in line contact. The contact range between the spacer 62 and the rolling element 50 is in the shape of a line extending in the axial direction. To achieve this, the rolling element 50 is composed of rollers such as cylindrical rollers, and the spacer 62 is composed of a plate or the like instead of a sphere. As a result, compared with the case where the spacer 62 and the rolling element 50 are in point contact, the contact surface pressure acting on the contact portion of the spacer 62 and the rolling element 50 when the spacer 62 and the rolling element 50 collide can be reduced, which is conducive to ensuring the strength of the spacer 62.

[0048] The spacer 62 is preferably made of a material having a Young's modulus (MPa) smaller than that of the rolling element 50. Thus, the spacer 62 can be made softer than the rolling element 50. Thus, when the subsequent rolling element 50-1 collides with the preceding rolling element 50-2, the spacer 62 can be used to reduce the impact load caused by the collision, which is conducive to ensuring the strength of the eccentric bearing 20. In order to achieve this, the rolling element 50 can be made of a metal material, and the spacer 62 can be made of a resin material. As a metal material, in addition to iron materials such as bearing steel, aluminum materials such as aluminum alloys can also be used. As a resin material, in addition to general engineering plastics headed by nylon resins such as PA46, plastic materials such as special engineering plastics can also be used. In addition to being made of metal (including alloys) as the main material, the metal material can also be made of a composite material of other materials such as fibers and the main material. In addition to being made of resin as the main material, the resin material can also be made of a composite material of other materials such as fibers and the main material.

[0049] The eccentric bearing 20 is in an environment where it is easily heated to a high temperature by the heat caused by the meshing of the swing gear 16 and the meshing gear 18. Therefore, the spacer 62 is preferably made of a material that can withstand a heat-resistant temperature even when heated to a high temperature. Regarding the heat-resistant temperature, for example, it is preferably made of a material with a heat-resistant temperature of 100°C or more. At this time, any of the above-mentioned metal-based materials and resin-based materials can also be used.

[0050] When the gear device 10 is in operation, the spacer 62 does not roll on the rolling surface of the eccentric bearing 20, but is pushed by other subsequent rolling elements 50 and moves along the circumferential direction of the eccentric body. Here, "when the gear device 10 is in operation" is when the crankshaft 14 rotates. It can also be said that the spacer 62 does not move along the circumferential direction of the eccentric body by repeatedly rotating in the same direction with the outer shape center C62 when the spacer 62 is viewed from the axial direction as the center. This is satisfied when the spacer 62 is located in any range of the load range R1 and the no-load range R2. Even if the spacer 62 contacts the rolling surfaces 52 and 54 of the eccentric bearing 20, it does not roll in contact but moves along the circumferential direction of the eccentric body while sliding in contact.

[0051] refer to Figure 6 .exist Figure 6 In FIG. 1 , the phase of each rolling element 50 of the eccentric bearing 20 around the axis C12 is shown. Figure 3 The gear device 10 has a pair of limiting portions 70 for limiting the axial movement of the plurality of rolling elements 50. The pair of limiting portions 70 are provided corresponding to the plurality of eccentric bearings 20. In the present embodiment, one limiting portion 70 of the pair of limiting portions 70 is provided separately from the crankshaft 14, and the other limiting portion 70 is provided integrally with the crankshaft 14 by the same component as the crankshaft 14.

[0052] The axial dimension L62c of the spacer 62 is preferably set smaller than the axial dimension L50b of the rolling element 50. This is advantageous in avoiding sliding with the pair of restricting portions 70 that restrict the axial movement of the rolling element 50.

[0053] Next, the effects of the gear device 10 described above will be described. The spacers 62 are arranged between some of the adjacent rolling elements 50 among the plurality of rolling elements 50. Therefore, as described above, the collision sound of the rolling elements 50 can be reduced.

[0054] Furthermore, a portion of the adjacent rolling elements 50 among the plurality of rolling elements 50 can contact each other in the circumferential direction, thus having the following advantages. In an eccentric bearing, a retainer is usually assembled in order to maintain the interval between adjacent rolling elements 50. The retainer has an interval retaining portion for maintaining the interval between adjacent rolling elements 50. When the radial dimension of the gear device 10 is miniaturized, the thickness dimension of the interval retaining portion of the retainer is miniaturized while the radial dimension of the retainer is reduced. However, the miniaturization of the thickness dimension of the interval retaining portion of the retainer is limited in manufacturing. Therefore, if the radial dimension of the gear device 10 is miniaturized to a certain extent, it is necessary to ensure a certain thickness dimension for the interval retaining portion of the retainer, and the rolling elements have to be reduced. In this way, if the rolling element filling rate is reduced due to the reduction in the rolling element, there is a problem that the strength of the eccentric bearing 20 is reduced. That is, the miniaturization of the radial dimension of the gear device 10 and the strength of the eccentric bearing 20 are in a relationship of one increasing while the other decreases.

[0055] In this regard, according to the present embodiment, a portion of adjacent rolling elements 50 can contact in the circumferential direction. Therefore, when miniaturizing the radial dimension of the gear device 10, the rolling element filling rate of the eccentric bearing 20 can be increased compared to the case of using a retainer, which is beneficial to improving the strength of the eccentric bearing 20. In particular, it is advantageous in that the miniaturization of the radial dimension of the gear device 10 and the strength of the eccentric bearing, which are in a trade-off relationship, can be taken into account. From the perspective of miniaturizing the radial dimension of the gear device 10, the inner diameter of the outer rolling surface 54 of the eccentric bearing 20 (the radial dimension of the circle centered on the axis C12 of the eccentric body 12) can be set to, for example, less than 50 mm.

[0056] In addition, in the eccentric oscillating gear device 10, a plurality of types of rolling elements 50 having different outer diameters are sometimes prepared, and when the gear device 10 is assembled, the diameter L50a of the rolling element 50 is adjusted to adjust the radial internal clearance of the eccentric bearing 20. The radial internal clearance is adjusted in this way because the radial internal clearance has a great influence on various performances such as the strength, lost motion, and efficiency of the gear device 10. However, even if such radial internal clearance is adjusted, it is difficult to adjust the circumferential clearance 100 of the eccentric bearing 20. In the gear device 10 of the present embodiment, the circumferential clearance 100 that is difficult to adjust can be adjusted by the spacer 62, which is particularly effective in this regard. In this way, when adjusting the circumferential clearance 100, the number of spacers 62 arranged between adjacent rolling elements 50 of the second rolling element group 60B is not particularly limited. Between these rolling elements 50, only one spacer 62 may be arranged as in the embodiment, or a plurality of spacers 62 may be arranged.

[0057] Assuming that the spacer 62 rolls, the spacer 62 rotates around the outer shape center C62 when viewed from the axial direction. Therefore, depending on the shape of the spacer 62, the actual tangential dimension of the spacer 62 will vary significantly depending on the rotation position around its outer shape center C62. Here, "according to the shape of the spacer 62" is, for example, a case where the tangential dimension L62a of the spacer 62 is different from the radial dimension L62b as described above. In this regard, the spacer 62 of the present embodiment does not roll on the rolling surface, but is pushed by other rolling elements 50 and moves along the circumferential direction of the eccentric body. Therefore, regardless of the shape of the spacer 62, the actual tangential dimension of the spacer 62 is difficult to vary significantly, and it is easy to suppress the change of the circumferential clearance of the eccentric bearing 20 adjusted by the spacer 62. Furthermore, regardless of the shape of the spacer 62, the collision sound reduction effect based on the spacer 62 can be stably obtained.

[0058] Next, modifications of the above-described constituent elements will be described.

[0059] The specific type of the gear device 10 is not particularly limited. The gear device 10 may be, for example, a distributed type in which a plurality of crankshafts 14 are arranged at positions offset in the radial direction with respect to the oscillation center C16 a of the oscillation gear 16 .

[0060] The output member 30 may also be the housing 24 to replace the wheel carrier 22. The swing gear 16 may also be an internal gear, and the meshing gear 18 may also be an external gear.

[0061] In the above, the gear device 10 is described as an example of a speed reducing device. Alternatively, the gear device 10 may be a speed increasing device. In this case, the carrier 22 and the housing 24 may be input members, and the crankshaft 14 may be an output member.

[0062] 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 also be less than the tangential dimension L62a of the spacer 62. The spacer 62 may be composed of a sphere that rolls on the rolling surfaces 52 and 54 of the eccentric bearing 20 when the gear device 10 is in operation. The material of the spacer 62 is not particularly limited, and may be made of a material having a Young's modulus greater than that of the rolling element 50. In addition to being made of a resin-based material, the spacer 62 may also be made of a metal-based material.

[0063] The above embodiments and variations are for illustration only. These abstract technical ideas should not be interpreted as limiting the contents of the embodiments and variations. The contents of the embodiments and variations can undergo various design changes such as changes, additions, and deletions of constituent elements. In the above embodiments, the content that can undergo such design changes is emphasized by the mark "this embodiment". However, it does not mean that design changes are not allowed for content without such marks. The hatching marked on the cross-section of the drawings is not used to limit the material of the object marked with the hatching. The constituent element composed of a single component in the embodiments may also be composed of multiple components. Similarly, the constituent element composed of multiple components in the embodiments may also be composed of a single component.

Claims

1. An eccentric oscillating gear device, comprising: A crankshaft having an eccentric body; A swing gear, which is swung by the eccentric body; and An eccentric bearing is disposed between the swing gear and the eccentric body. The eccentric oscillating gear device is characterized in that: The eccentric bearing has a plurality of rolling elements. A portion of the rolling elements adjacent to each other in the circumferential direction among the plurality of rolling elements can contact each other, and a spacer is arranged between another portion of the rolling elements adjacent to each other in the circumferential direction.

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

3. The eccentric oscillating gear device according to claim 2, characterized in that: When the dimension of the eccentric body in the radial direction is referred to as a radial dimension, the radial dimension of the spacer is larger than the tangential dimension of the spacer.

4. The eccentric oscillating gear device according to claim 1, characterized in that: When the gear device is in operation, the spacer does not roll on the rolling surface of the eccentric bearing, but is pushed by the rolling element to move along the circumferential direction of the eccentric element.

5. The eccentric oscillating gear device according to claim 1, characterized in that: The spacer is made of a material having a Young's modulus smaller than that of the rolling element.

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