Bearing

Abstract

To provide a bearing excellent in assembling performance in being assembled to a mating side.SOLUTION: A bearing B1 includes a plurality of rolling elements 6 and a retainer 7 for retaining the rolling elements 6. The retainer 7 includes a first retainer 7A and a second retainer 7B. The first retainer 7A is formed into a cylindrical shape provided with a plurality of first opening portions A1 and having flexibility, retains the rolling elements 6 from an outer peripheral side of the first retainer 7A by a first bridge portion 72a formed between the first opening portions A1 at least at a major axis side of the cam member 5 in a state of being mounted on the cam member 5 with the rolling elements 6, and exposes the rolling elements 6 rotatably to the outer peripheral side of the first retainer 7A by the opening portions A1. The second retainer 7B is formed into a cylindrical shape provided with a plurality of second opening portions A2 and having flexibility, retains the rolling elements 16 from an inner peripheral side of the second retainer 7B by a second bridge portion 72b formed between the second opening portions A2, and rotatably exposes the rolling elements 6 to the inner peripheral side of the second retainer 7B by the second opening portions A2.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a bearing.

Background Art

[0002] Taking a harmonic gear device as an example, in the harmonic gear device, the assemblability when assembling a bearing between an elliptical cam member and an external gear is a problem. For example, when a roller is adopted as the rolling element, there is a problem that the assemblability to the elliptical cam deteriorates. In this regard, an example has been proposed in which a hole for inserting a roller is formed in the elliptical cam and the roller is inserted therefrom to improve the assemblability (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the case of the bearing having the configuration described in Patent Document 1 above, it is necessary to perform additional processing on the elliptical cam on the mating side to which the bearing is assembled. For this reason, the conventional bearing has a problem that productivity deteriorates, and there is still room for improvement.

[0005] An object of the present invention is to propose a bearing having a good assemblability when assembled to the mating side by devising the configuration of the bearing and the like with respect to the problems of the prior art as described above.

Means for Solving the Problems

[0006] The bearing according to the present invention includes a plurality of rolling elements arranged at intervals in the circumferential direction around an axis, and a rolling element retainer that holds the plurality of rolling elements. The rolling element retainer includes a first rolling element retainer and a second rolling element retainer. The first rolling element retainer is formed in a flexible cylindrical shape with a plurality of first openings formed at intervals in the circumferential direction. In a state where it is attached to a cam member together with the rolling elements, at least on the long axis side of the cam member, the rolling elements are held from the outer peripheral side of the first rolling element retainer by a first bridging portion formed between the plurality of first openings, and the rolling elements are rotatably exposed to the outer peripheral side of the first rolling element retainer by the first openings. And The second rolling element retainer is formed in a flexible cylindrical shape with a plurality of second openings formed at intervals in the circumferential direction. The rolling elements are held from the inner peripheral side of the second rolling element retainer by a second bridging portion formed between the plurality of second openings, and the rolling elements are rotatably exposed to the inner peripheral side of the second rolling element retainer by the second openings.

[0007] In the bearing according to the present invention, in the first rolling element retainer, the distance hx1 connecting the contact points of the rolling element and the first rolling element retainer satisfies the following formula (1), and the inner diameter D1 of the first rolling element retainer when it is a perfect circle satisfies the following formula (2). TIFF0007701297000001.tif15161 (d: diameter of the rolling element, t1: thickness of the first rolling element retainer, x1: distance from the outer peripheral surface of the first rolling element retainer to the contact point between the rolling element and the first bridging portion) a + b + d < D1 < 2·(a + d) …(2) (a: long axis radius of the cam member, b: short axis radius of the cam member, d: diameter of the rolling element)

[0008] In the bearing according to the present invention, the first bridging portion may have a holding surface that rotatably holds the rolling element, and the holding surface may be formed by an inclined surface or a curved surface.

[0009] In the bearing according to the present invention, the second spanning portion has a holding surface that rotatably holds the rolling elements, and the holding surface can be formed by an inclined surface or a curved surface.

[0010] In the bearing according to the present invention, the first rolling element retainer can be formed of resin or light metal.

[0011] In the bearing according to the present invention, the second rolling element retainer can be formed of resin or light metal.

[0012] The bearing according to the present invention can be formed by the rolling elements and the rolling element retainer.

[0013] The bearing according to the present invention can be formed by the rolling element retainer and a flexible outer ring.

[0014] The bearing according to the present invention can be formed by at least the rolling elements, the rolling element retainer, and a flexible inner ring.

[0015] In the bearing according to the present invention, the rolling elements can be rollers.

[0016] In the bearing according to the present invention, the rolling elements can be balls.

Advantages of the Invention

[0017] According to the present invention, it is possible to provide a bearing with good assemblability when assembling to the other side.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5

Figure 6A

Figure 6B

Figure 7A

Figure 7B

Figure 8A

Figure 8B

Figure 9A

Figure 9B

Figure 10

Figure 11

Figure 12

DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, with reference to the drawings, the bearing according to the embodiment of the present invention will be described.

[0020] In FIG. 1, reference numeral 1 denotes a wave gear device including a bearing B1 according to an embodiment of the present invention. The wave gear device 1 includes an internal gear 2, an external gear 3 which is flexible and disposed on the inner peripheral side of the internal gear 2, and a wave generator 4 disposed on the inner peripheral side of the external gear 3.

[0021] In the present disclosure, the internal gear 2 is an annular gear. The internal gear 2 has a plurality of internal teeth 2a and an annular main body 2b. The plurality of internal teeth 2a project radially inward from the inner circumference of the annular main body 2b. In the present disclosure, the internal gear 2 is fixed, for example, to a housing (not shown) of the harmonic gear device 1. The internal gear 2 is fixed to the housing with the axis О1 as the central axis. In the present disclosure, the axis О1 is the central axis of the harmonic gear device 1. That is, in the present disclosure, the internal gear 2 is a fixed gear with the axis О1 as the central axis. Further, in the present disclosure, the internal gear 2 is a rigid gear having high rigidity and being difficult to deform. The internal gear 2 is formed of, for example, an iron-based material such as cast iron, alloy steel, or carbon steel, a light metal alloy or a light metal single body such as a magnesium alloy, an aluminum alloy, or a titanium alloy, or a resin material such as an engineering plastic such as PEEK (polyetheretherketone), PPS (polyphenylene sulfide), or POM (polyoxymethylene).

[0022] In the present disclosure, the external gear 3 is also an annular gear. The external gear 3 has a plurality of external teeth 3a and an annular main body 3b. The plurality of external teeth 3a project radially outward from the outer circumference of the annular main body 3b. In the present disclosure, the external gear 3 is a rotating gear that can rotate about the axis О1. Further, in the present disclosure, the external gear 3 is a flexible gear having flexibility that is easy to deform. The external gear 3 can be mechanically deformed and restored, for example, by forming the annular main body 3b to be thin. When the annular main body 3b is formed to be thin, materials such as metal or resin can be used to form the external gear 3. Also, the external gear 3 can be deformed and restored in terms of material, for example, by using a flexible material (for example, a thin material made of alloy steel, carbon steel, or a light metal, or a resin material such as a flexible engineering plastic).

[0023] The wave generator 4 includes a bearing B1 and a non-circular cam member 5 to which the bearing B1 is attached on the outer peripheral side and which can rotate about the axis О1.

[0024] In the present disclosure, the wave generator 4 further includes a drive shaft 8. The drive shaft 8 is connected to a power source such as a motor (not shown). In the present disclosure, the drive shaft 8 is connected to the cam member 5. The central axis (rotation axis) of the drive shaft 8 is coaxial with the axis O1. That is, in the present disclosure, the wave generator 4 is arranged on the same axis as the central axis of the harmonic gear device 1. Thereby, the cam member 5 can rotate about the axis O1.

[0025] Further, the cam member 5 has a non-circular shape when viewed in the direction of the axis O1 (when viewed from the extending direction of the axis O1). The cam member 5 is a member having high rigidity, similar to the internal gear 2. The outer peripheral surface F5 of the cam member 5 functions as a cam surface. The cam member 5 has a non-circular shape. In the present disclosure, the cam member 5 is of a two-lobe type. The two-lobe type has an elliptical shape when viewed in the direction of the axis O1 as shown in the figure.

[0026] FIG. 2 shows the wave generator 4 employed in the harmonic gear device 1 alone. FIG. 3 schematically shows the bearing B1 in the axial direction according to an embodiment of the present invention.

[0027] As shown in FIG. 3, the bearing B1 includes a plurality of rolling elements (6) arranged at intervals in the circumferential direction around the axis O1, and a rolling element retainer (7) that holds the plurality of rolling elements.

[0028] In the present disclosure, the rolling element is a roller 6. That is, the rolling element retainer is a roller retainer 7.

[0029] In the present disclosure, the roller retainer 7 includes a first roller retainer 7A. Referring to FIG. 2, the first roller retainer 7A is formed in a flexible cylindrical shape with a plurality of openings A1 (hereinafter also referred to as "first openings A1") formed at intervals in the circumferential direction around the axis O1. Further, as shown in FIG. 2, when the first roller retainer 7A is attached to the cam member 5 together with the roller 6, at least on the long axis side of the cam member 5, the roller 6 is held from the outer peripheral side of the first roller retainer 7A (hereinafter also referred to as "the outer peripheral side of the first roller retainer") by a spanning portion 72a (hereinafter also referred to as "the first spanning portion 72a") formed between the plurality of first openings A1, and the roller 6 is rotatably exposed to the outer peripheral side of the first roller retainer by the first opening A1.

[0030] Here, the "outer peripheral side of the first roller retainer" means, for example, the side farther from the axis O1 when viewed in the direction of the axis O1. Alternatively, as shown in FIG. 1, the "outer peripheral side of the first roller retainer" means the side of a gear such as the external gear 3 (hereinafter also referred to as "gear side") when the wave generator 4 is disposed inside the harmonic gear device 1 when viewed in the direction of the axis O1.

[0031] Further, in the present disclosure, the roller retainer 7 includes a second roller retainer 7B. Referring to FIG. 2, the second roller retainer 7B is formed in a flexible cylindrical shape with a plurality of openings A2 (hereinafter also referred to as "second openings A2") formed at intervals in the circumferential direction around the axis O1. Further, the second roller retainer 7B holds the roller 6 from the inner peripheral side of the second roller retainer 7B (hereinafter also referred to as "the inner peripheral side of the second roller retainer") by a spanning portion 72b (hereinafter also referred to as "the second spanning portion 72b") formed between the plurality of second openings A2, and the roller 6 is rotatably exposed to the inner peripheral side of the second roller retainer by the second opening A2.

[0032] Here, the "inner circumferential side of the second roller retainer" refers to, for example, the side closer to the axis O1 when viewed in the direction of the axis O1. Alternatively, the "inner circumferential side of the second roller retainer" refers to the side of the cam member 5 (hereinafter also referred to as the "cam member side") in a state where the bearing B1 is disposed on the outer circumferential side of the cam member 5 when viewed in the direction of the axis O1.

[0033] In the present disclosure, the bearing B1 is a roller bearing that rotatably supports the cam member 5 and the external gear 3 with respect to each other.

[0034] As shown in FIG. 3, in the present disclosure, the bearing B1 includes a plurality of rollers 6 arranged at intervals in the circumferential direction around the axis O1, a first roller retainer 7A having flexibility, and a second roller retainer 7B also having flexibility. The plurality of rollers 6 are each rotatably held by the first roller retainer 7A and the second roller retainer 7B. That is, in the present disclosure, the bearing B1 is a roller bearing in which the first roller retainer 7A and the second roller retainer 7B integrally rotate the plurality of rollers 6 rotatably.

[0035] As shown in FIG. 3, the bearing B1 has a perfect circular shape in its initial state before being attached to the cam member 5. In FIG. 3, the axis O1 is shown as the central axis. Referring to FIG. 3, in the present disclosure, the first roller retainer 7A and the second roller retainer 7B are arranged concentrically about the axis O1 in a state where the plurality of rollers 6 are assembled around the axis O1. The second roller retainer 7B is disposed on the inner circumferential side of the first roller retainer 7A at a radial interval with respect to the first roller retainer 7A. That is, in the present disclosure, the first roller retainer 7A corresponds to a perfect circular outer cylinder having the axis O1 as the central axis when viewed in the direction of the axis O1, and the second roller retainer 7B corresponds to a perfect circular inner cylinder having the axis O1 as the central axis.

[0036] In the bearing B1, the first roller retainer 7A and the second roller retainer 7B have flexibility. Therefore, as shown in FIG. 2, the bearing B1 can be easily attached to the non-circular cam member 5. Further, in the present disclosure, the cam member side portion of the roller 6 is exposed to the cam member side through the second opening A2 of the second roller retainer 7B. Therefore, in the present disclosure, the bearing B1 can be easily attached to the cam member 5 such that the roller 6 directly contacts the outer peripheral surface (cam surface) F5 of the cam member 5.

[0037] The external gear 3 also has flexibility. Therefore, as shown in FIG. 1, the external gear 3 can be easily attached to the wave generator 4. Further, in the present disclosure, the gear side portion of the roller 6 is exposed to the gear side through the first opening A1 of the first roller retainer 7A. Therefore, in the present disclosure, the external gear 3 can be attached to the wave generator 4 such that the roller 6 directly contacts the inner peripheral surface F3 of the external gear 3. Further, in the present disclosure, the bearing B1 can also be attached to the external gear 3 such that the roller 6 directly contacts the inner peripheral surface F3 of the external gear 3.

[0038] That is, in the present disclosure, the bearing B1 is formed by the roller 6 and the roller retainer 7 as described above. More specifically, as shown in FIG. 3, the bearing B1 is formed by the roller 6, the first roller retainer 7A, and the second roller retainer 7B.

[0039] As shown in FIG. 1, the wave generator 4 can be assembled to the inner peripheral surface F3 of the external gear 3 to bend the external gear 3 non-circularly so that the external teeth 3a of the external gear 3 mesh with the internal teeth 2a of the internal gear 2. In the present disclosure, the external gear 3 and the internal gear 4 mesh at two positions on the major axis portion of the cam member 5. In FIG. 1, the symbol P indicates the meshing portion P between the external teeth 3a of the external gear 3 and the internal teeth 2a of the internal gear 2. As shown in FIG. 1, in the present disclosure, the meshing portion P is located on the two major axis sides of the cam member 5.

[0040] In the wave generator 4, the cam member 5 rotates about the axis О1 as the drive shaft 8 rotates. As a result, the cam member 5 can be relatively rotated with respect to the external gear 3 via the roller 6 of the bearing B1. On the other hand, the internal gear 2 is fixed, and there is a difference in the number of teeth (for example, a difference of 2 teeth) between the number of teeth Z F of the external teeth 3a of the external gear 3 and the number of teeth Z R of the internal teeth 2a of the internal gear 2. Therefore, when the cam member 5 is rotated, relative rotation caused by the difference in the number of teeth occurs between the internal gear 2 and the external gear 3. As a result, the meshing portion P of the external gear 3 moves in the circumferential direction of the internal gear 2 in the direction opposite to the rotation direction of the cam member 5. In the present disclosure, each time the cam member 5 rotates 180 degrees around the axis O1, the meshing portion P moves in the direction opposite to the rotation direction of the wave generator 4 with respect to the internal gear 2. That is, in the present disclosure, the input rotation from the drive shaft 8 is reversely output as a decelerated rotation from the external gear 3.

[0041] On the other hand, FIG. 4A schematically shows the relationship between the roller 6 and the roller cage 7 when the roller 6 of the bearing B1 is at the short axis portion of the cam member 5, with the cam member 5 and the cam member 5 and the roller cage 7 being developed in a plane. FIG. 4A is shown in a cross section orthogonal to the central axis (axis О1) of the bearing B1 (hereinafter, also referred to as an "axial orthogonal cross section").

[0042] The first roller retainer 7A prevents the roller 6 from falling off toward the gear side by means of a first spanning portion 72a formed between the first openings A1. On the other hand, basically, the cam member 5 does not generate a pressing force from the cam member 5 on the roller 6 at locations other than the long axis portion of the cam member 5 (for example, the short axis portion of the cam member 5). For this reason, as shown in Fig. 4A, the roller 6 covered by the first roller retainer 7A from the gear side is in a free state without contacting the first roller retainer 7A at, for example, the short axis portion of the cam member 5, which is other than the long axis portion of the cam member 5. For this reason, according to the first roller retainer 7A, frictional losses associated with contact between the first roller retainer 7A and the cam member 5, which may occur when the roller 6 passes through a location other than the long axis portion of the cam member 5, are reduced. Further, the first roller retainer 7A is configured to position the gear side portion of the roller 6 within the first opening A1 by adjusting the inner diameter D1 of the first roller retainer 7A when it is a perfect circle, as shown in Fig. 4A. For this reason, according to the first roller retainer 7A, the intervals between adjacent rollers 6 are maintained at appropriate intervals along the circumferential direction of the first roller retainer 7A.

[0043] On the other hand, Fig. 4B schematically shows the relationship between the roller 6 and the roller retainer 7 when the roller 6 of the bearing B1 is at the long axis portion of the cam member 5, with the cam member 5 and the cam member 5 and the roller retainer 7 being developed in a planar state. Fig. 4B is also shown in the axial cross section, similar to Fig. 4A.

[0044] As shown in FIG. 4B, in the bearing B1, the roller 6 is pressed from the gear side by being sandwiched between the long shaft portion of the cam member 5, the cam member 5, and the first roller retainer 7A (first spanning portion 72a). For this reason, the roller 6 aligns with the position of the first opening A1 so as to follow the shape of the first opening A1 of the first roller retainer 7A. That is, in the present disclosure, in a state where the first roller retainer 7A is attached to the cam member 5 together with the roller 6, at least on the long shaft side (long shaft portion) of the cam member 5, the first spanning portion 72a formed between the plurality of first openings A1 holds the roller 6 from the gear side, and the first opening A1 exposes the roller 6 rotatably to the gear side. As a result, the roller 6 can perform relative rolling with respect to the outer peripheral surface F5 of the cam member 5 and the inner peripheral surface F3 of the external gear 3 without causing skew at the long shaft portion of the cam member 5. Therefore, according to the first roller retainer 7A, skew of the roller 6 that may occur at the long shaft portion of the cam member 5 is prevented. As a result, according to the first roller retainer 7A, frictional loss due to skew of the roller 6 is also reduced.

[0045] As described above, according to the bearing B1, it becomes possible to integrally handle the roller 6 (rolling element) and the roller retainer (retainer). Therefore, the bearing B1 is a bearing with good assemblability when assembled to the mating cam member 5. Furthermore, according to the bearing B1, frictional loss can be reduced while preventing skew. Therefore, by using the bearing B1, frictional loss can be reduced while preventing skew, and furthermore, the assemblability to the cam member can be improved. In this way, by using the bearing B1, the wave generator 4 that can reduce frictional loss while preventing skew can be manufactured easily and inexpensively, and thus, the harmonic gear device 1 can be manufactured easily and inexpensively.

[0046] Specifically, in the state where the first roller retainer 7A is attached to the non-circular cam member 5, on the long axis side of the cam member 5, the roller 6 is pressed from the gear side, while on the short axis side of the cam member 5, the roller 6 is not pressed from the gear side. That is, in the state where the first roller retainer 1A is attached to the cam member 5 together with the roller 6, at least on the long axis side of the cam member 5, the first spanning portion 72a holds the roller 6 from the gear side, and the first opening A1 exposes the roller 6 rotatably to the gear side. Therefore, according to the wave generator 4 of the present disclosure, at locations other than the long axis portion of the cam member 5 (for example, the short axis portion of the cam member 5), the roller 6 is covered by the first roller retainer 7A but is not pressed against the first roller retainer 7A and the cam member 5. Therefore, according to the wave generator 4 of the present disclosure, the frictional loss that may occur when the roller 6 passes through a location other than the long axis portion of the cam member 5 is reduced. Further, according to the wave generator 4 of the present disclosure, at the long axis portion of the cam member 5, the roller 6 is restricted so as not to cause skew due to contact with the first spanning portion 72a and is rotatably exposed to the gear side from the first opening A1. Therefore, according to the wave generator 4 of the present disclosure, the skew of the roller 6 that may occur when the roller 6 passes through the long axis portion of the cam member 5 is prevented, and thereby the frictional loss caused by the skew is also reduced. Therefore, according to the wave generator 4 of the present disclosure, the frictional loss can be reduced while preventing skew. Further, according to the wave gear device 1 of the present disclosure employing the wave generator 4, the frictional loss can be reduced while preventing skew.

[0047] Also, when the first roller retainer 7A is formed in a flexible cylindrical shape with a plurality of first openings A1 formed at intervals in the circumferential direction and arranged to cover the roller 6 from the gear side, like the bearing B1 of the present disclosure, the outer ring of the bearing is not an essential component but an optional component.

[0048] That is, in the present disclosure, the bearing B1 can omit the outer ring by covering the roller 6 from the gear side with the first roller retainer 7A. Therefore, according to the bearing B1 of the present disclosure, the number of necessary parts can be reduced, and as a result, the manufacturing cost can be reduced.

[0049] Therefore, according to the bearing B1, the wave generator 4 that can reduce frictional loss while preventing skew can be manufactured easily and inexpensively, and thus, the harmonic gear device 1 can be manufactured easily and inexpensively.

[0050] Incidentally, in the present disclosure, as will be described in detail later, the first spanning portion 72a of the first roller retainer 7A has a holding surface 73a (hereinafter also referred to as the "first holding surface 73a") that rotatably holds the roller 6. The first holding surface 73a can be formed by an inclined surface or a curved surface. In this case, the roller 6 can be aligned with the first opening A1 so that the roller 6 rolls more smoothly. Furthermore, in this case, stress concentration at the time of contact between the first roller retainer 7A and the roller 6 can be alleviated.

[0051] Referring to FIG. 4A, in the present disclosure, the first opening A1 forms an outer peripheral side opening on the outer peripheral surface (gear side surface) F72a(out) of the first roller retainer 7A. The contour of the outer peripheral side opening extending in the width direction of the first roller retainer 7A is formed by the outer peripheral side edge 74а of the first spanning portion 72a.

[0052] Also, in the present disclosure, the first opening A1 forms an inner peripheral side opening on the inner peripheral surface (cam member side surface) F72a(in) of the first roller retainer 7A. The contour of the inner peripheral side opening extending in the width direction of the first roller retainer 7A is formed by the inner peripheral side edge 75а of the first spanning portion 72a.

[0053] Here, in the present disclosure, the circumferential length h1 of the first opening A1 is the extending length of the first opening A1 that extends along the circumferential direction of the first roller retainer 7A when the cylindrical first roller retainer 7A is developed in a plane.

[0054] As shown in FIG. 4A, in the present disclosure, when viewed in an axial cross-section (in the axial direction view), the circumferential length h11 between the outer peripheral side edges 74a of the two first spanning portions 72a among the circumferential length h1 of the first opening A1 is shorter than the circumferential length h12 between the inner peripheral side edges 75a of the two first spanning portions 72a, and the first holding surface 73a is linearly inclined from the outer peripheral side edge 74a toward the inner peripheral side edge 75a. That is, the first holding surface 73a is an inclined surface. For this reason, in the present disclosure, the circumferential length h1 of the first opening A1 increases at a constant rate from the outer peripheral surface F72a(out) to the inner peripheral surface F72a(in) of the first roller retainer 7A. As a result, as shown in FIG. 4B, the roller 6 contacts the first holding surface 73a at the contact point Px when viewed in an axial cross-section. That is, as shown in FIG. 4B, the roller 6 can rotate while making line contact in the width direction of the first roller retainer 7A (the extending direction of the first spanning portion 72a) on the contact point Px1 of the first holding surface 73a when viewed in an axial cross-section. Therefore, according to the first holding surface 73a according to the present disclosure, the roller 6 can be aligned with the first opening A1 so that the roller 6 rotates more smoothly with respect to the first spanning portion 72a. Furthermore, in this case, since the first roller retainer 7A and the roller 6 make line contact in the width direction of the first roller retainer 7A at the position of the contact point Px1, stress concentration at the time of contact between the first roller retainer 7A and the roller 6 can be alleviated. However, the first holding surface 73a can be a curved surface instead of the above-described inclined surface. As a specific example of the curved surface, it can be a curved surface that is convex inward toward the outer peripheral side (gear side) of the first roller retainer 7A. The curved surface can be, for example, a curved surface having the radius of the roller 6 as the radius of curvature. Also, the curved surface can be a curved surface that is convex outward toward the inner peripheral side (cam member side) of the first roller retainer 7A.

[0055] FIG. 5 schematically shows a cylindrical first roller retainer 7A together with a roller 6 in a state of being developed in a plane, as seen from the outer peripheral side (gear side) of the first roller retainer 7A.

[0056] Referring to FIG. 5, in the present disclosure, the roller 6 is a columnar member having a diameter d with an axis O6 (also referred to as the "roller axis O6") as the central axis. In the present disclosure, the roller 6 can be rotated about the axis O6.

[0057] On the other hand, in the present disclosure, the first roller retainer 7A includes two annular portions 71a (hereinafter also referred to as "first annular portions 71a") disposed adjacent to the axial ends 6e of the roller 6, and a plurality of first bridging portions 72a that connect the two first annular portions 71a and are arranged at intervals in the circumferential direction. That is, in the present disclosure, the first opening A1 is a rectangular opening defined by the two first annular portions 71a and the two first bridging portions 72a.

[0058] Referring to FIG. 5, in the present disclosure, the first roller retainer 7A is fitted over the roller 6 such that the outer peripheral side edge 74a of the first bridging portion 72a is parallel to the axis O6 of the roller 6. Also, the circumferential length h1 of the first opening A1 (in this example, the circumferential length h11 between the outer peripheral side edges 74a of the two first bridging portions 72a) is shorter than the diameter d of the roller 6. Further, in the present disclosure, as shown in FIG. 5, the first bridging portion 72a is formed with a first holding surface 73a that inclines away from the outer peripheral side edge 74a as it goes toward the inner peripheral side (the back side of the paper surface of FIG. 5) of the first roller retainer 7A with the outer peripheral side edge 74a as the base point. As a result, the gear side portion of the roller 6 (the front side portion of the paper surface of FIG. 5) can be exposed from the first opening A1, and at the contact point Px1 with the roller 6 on the first holding surface 73a (when viewed in plan view in FIG. 5, the contact point Px1 becomes a contact line Px1 extending in the width direction of the first roller retainer 7A), the roller 6 is rotatably held. In the present disclosure, the two first annular portions 71a are arranged so as to form a gap with the axial ends 6e of the roller 6, as shown in FIG. 5. Thereby, the frictional loss is further reduced.

[0059] Next, FIG. 6A schematically and exemplarily shows a state in which the roller 6 is properly rolling on the outer peripheral surface F5 of the elliptical cam member 5 in a state where the outer peripheral surface F5 of the elliptical cam member 5 is developed in a plane. In FIG. 6A, the first opening A1 of the first roller retainer 7A is shown for reference in order to understand the relationship with the roller 6. Further, FIG. 6B schematically and exemplarily shows a state in which the roller 6 is skewed on the outer peripheral surface F5 of the cam member 5 in a state where the outer peripheral surface F5 of the cam member 5 is developed in a plane.

[0060] Referring to FIG. 6A, it can be seen that the roller 6 can roll on the outer peripheral surface F5 of the cam member 5 without skewing with respect to the moving direction of the roller 6 by the first roller retainer 7A. On the other hand, as shown in FIG. 6B, according to the harmonic gear device without a roller retainer, the roller 6 will slide on the outer peripheral surface F5 of the cam member 5 while being skewed with respect to the moving direction of the roller 6. This sliding causes frictional loss associated with the skewing of the roller 6.

[0061] By the way, in the present disclosure, as described above, the cam member 5 is non-circular in the direction of the axis О1. In this case, in the first roller retainer 7A, the circumferential length hx1 (hereinafter, also referred to as "contact point length hx1") between the two contact points Px1 of the roller 6 and the two first spanning portions 72a in the first opening A1 can satisfy the following formula (1).

[0062]

Equation

[0063] In addition, when the cam member 5 has a non-circular shape, the inner diameter D1 of the first roller retainer 7A at the time of true circle of the first roller retainer 7A (hereinafter, also referred to as "true circle inner diameter D1 of the first roller retainer 7A") can satisfy the following formula (2).

[0064] [Number] (a: major axis radius of cam member 5, b: minor axis radius of cam member 5, d: diameter of roller 6)

[0065] When setting the major axis radius a and minor axis radius b of the cam member 5, the diameter d of the roller 6, the thickness t1 of the first roller retainer 7A, the contact point distance x1, the contact point length hx1 at the first opening A1, and the true circle inner diameter D1 of the first roller retainer 7A so as to satisfy the above formulas (1) and (2) simultaneously, as will be described in detail later, rollers 6, cam members 5, and first roller retainers 7A with appropriate dimensions according to applications, specifications, etc. can be easily derived. In this case, the wave generator 4 that can reduce frictional loss while preventing skew can be manufactured more easily and inexpensively, and thus, the wave gear device 1 can be manufactured more easily and inexpensively.

[0066] Specifically, the above formula (1) is a relational expression focusing on the contact point length hx1 at the first opening A1 of the first roller retainer 7A.

[0067] FIG. 7A is a diagram for schematically explaining the dimensional relationship between the first roller retainer 7A and the roller 6 so as not to drop the roller 6 from the first opening A1 of the first roller retainer 7A. FIG. 7A is shown in an axial cross section similar to FIG. 4A.

[0068] Here, the contact point length hx1 in the first opening A1 refers to the circumferential length between the contact points Px1 of one roller 6 and the two first spanning portions 72a that hold the one roller 6 among the circumferential length h1 of the first opening A1. The contact point length hx1 in the first opening A1 needs to be smaller than the diameter d of the roller 6 in order not to let the roller 6 fall off to the gear side. For this reason, from the geometric relationship as shown in FIG. 7A, it is necessary to set the contact point length hx1 in the first opening A1 and the diameter d of the roller 6 so as to satisfy the following relational expression (1A).

[0069]

Number

[0070] If the contact point length hx1 in the first opening A1 and the diameter d of the roller 6 are set so as to satisfy the above relational expression (1A), the roller 6 can be prevented from falling off from the first opening A1.

[0071] Next, FIG. 7B is a diagram for schematically explaining the dimensional relationship between the first roller retainer 7A and the roller 6 for exposing the roller 6 from the first opening A1 of the first roller retainer 7a. FIG. 7B is also shown in an axial cross-section, similar to FIG. 4B.

[0072] In the present disclosure, in addition to preventing the roller 6 from falling off from the first opening A1, the contact point length hx1 in the first opening A1 needs to expose the roller 6 from the first opening A1. For this reason, from the geometric relationship as shown in FIG. 7B, the contact point distance x1 and the contact point length hx1 in the first opening A1, the diameter d of the roller 6, and the thickness of the first roller retainer 7A (the thickness of the first spanning portion 72a) t1 need to be set so as to satisfy the following relational expression (1B). Here, the contact point distance x1 in the first opening A1 refers to the distance in the thickness direction of the first spanning portion 72a (first roller retainer 7A) from the outer peripheral surface F72a(out) of the first roller retainer 7A to the contact point Px1 when the cylindrical first roller retainer 7A is developed planarly.

[0073]

Number

[0074] If the contact point distance x1 and the contact point length hx1 at the first opening A1, the diameter d of the roller 6, and the thickness t1 of the first roller retainer 7A are set so as to satisfy the above relational expression (1B), the roller 6 can be exposed from the first opening A1. For example, the contact point length hx1 at the first opening A1 needs to be made long so that the gear side portion of the roller 6 protrudes from the position of the outer peripheral side surface (the outer peripheral side surface of the first spanning portion 72a) F72a(out) of the first roller retainer 7A. This condition is satisfied by setting the diameter d of the roller 6, the thickness t1 of the first roller retainer 7A, the contact point distance x1 and the contact point length hx1 at the first opening A1 so as to satisfy the relational expression (1B).

[0075] As is clear from the above relational expressions (1A) and (1B), the above-mentioned formula (1) focuses on the contact point length hx1 at the first opening A1. By using the above-mentioned formula (1), it is possible to easily derive the diameter d of the roller 6, the thickness (the thickness of the first spanning portion 72a) t1 of the first roller retainer 7A, the contact point distance x1 and the contact point length hx1 at the first opening A1, which can expose the roller 6 from the first opening A1 without dropping the roller 6 from the first opening A1. In this case, the wave generator 4 that can expose the roller 6 from the first opening A1 without dropping the roller 6 from the first opening A1 can be manufactured more easily and inexpensively. As a result, the harmonic gear device 1 that can expose the roller 6 from the first opening A1 without dropping the roller 6 from the first opening A1 can be manufactured more easily and inexpensively.

[0076] Further, the above-mentioned formula (2) is a relational expression focusing on the inner diameter D1 of the first roller retainer 7A when the first roller retainer 7A is in a true circular state.

[0077] FIG. 8A is a diagram for schematically explaining the dimensional relationship between the inner diameter D1 (see FIG. 3) of the first roller retainer 7A in a perfect circle state, the cam member 5, and the roller 6.

[0078] The inner diameter D1 of the first roller retainer 7A in a perfect circle state needs to apply a force that presses the roller 6 from the first roller retainer 7A toward the roller 6 at least on the major axis side of the cam member 5 when the roller 6 is attached to the cam member 5. For this reason, the inner diameter D1 of the first roller retainer 7A in a perfect circle state needs to be smaller than the dimensions when the roller 6 is arranged at each of the two major axis portions of the cam member 5. Referring to FIG. 8A, the dimension in the major axis direction of the wave generator 4 when the roller 6 is arranged at each of the two major axis portions of the cam member 5 is the value ((a + d) × 2) when twice the sum of the major axis radius a of the cam member 5 and the diameter d of the roller 6. Therefore, the inner diameter D1 of the first roller retainer 7A in a perfect circle state, the major axis radius a of the cam member 5, and the diameter d of the roller 6 need to be set to satisfy the following relational expression (2A).

[0079]

Equation

[0080] If the inner diameter D1 of the first roller retainer 7A in a perfect circle state, the major axis radius a of the cam member 5, and the diameter d of the roller 6 are set to satisfy the above relational expression (2A), as shown in FIG. 8A, when the first roller retainer 7A is attached to the cam member 5 together with the roller 6, at least on the major axis side of the cam member 5, a force that presses the roller 6 from the first roller retainer 7A can be applied.

[0081] FIG. 8B is a diagram for schematically explaining the dimensional relationship between the inner diameter D1 of the first roller retainer 7A, the cam member 5, and the roller 6.

[0082] The inner diameter D1 of the first roller retainer 7A at true circle is required to be increased such that the position of the inner peripheral surface F72a(in) of the first roller retainer 7A deformed on the major axis side of the cam member 5 is on the gear side (outer peripheral side of the wave generator 4) of the roller axis О6 on the major axis side of the cam member 5. When the first roller retainer 7A is deformed on the major axis side of the cam member 5, if the position of the inner peripheral surface F72a(in) of the first roller retainer 7A is on the cam member side of the center axis О6 of the roller 6 on the cam member 5, it becomes difficult to press the roller 6 into the first opening A1 by the first spanning portion 72a. For this reason, referring to Fig. 8B, from the Gauss-Kummer formula, the major axis radius a and minor axis radius b of the cam member 5 and the diameter d of the roller 6 need to be set to satisfy the following relational expression (2B).

[0083]

Number

[0084] If the major axis radius a and minor axis radius b of the cam member 5, the inner diameter D1 of the first roller retainer 7A at true circle, and the diameter d of the roller 6 are set to satisfy the above relational expression (2B), when the first roller retainer 7A is deformed on the major axis side of the cam member 5, the position of the first roller retainer 7A is on the gear side of the center axis О6 of the roller 6 on the cam member 5. As a result, when the first roller retainer 7A is deformed on the major axis side of the cam member 5, the first roller retainer 7A can press the roller 6 into the first opening A1 by the first spanning portion 72a.

[0085] As is also clear from the above relational expressions (2A) and (2B), the above-mentioned expression (2) focuses on the true circle diameter D1 of the first roller retainer 7A. By using the above-mentioned expression (2), in the state where the first roller retainer 7A is attached to the cam member 5 together with the roller 6, at least on the long axis side of the cam member 5, the gear side portion of the roller 6 is exposed from the first opening A1 of the first roller retainer 7A, and at the same time, the long axis radius a and the short axis radius b of the cam member 5, the diameter d of the roller 6, and the true circle inner diameter D1 of the first roller retainer 7A, which can press the roller 6 against the cam member side by the first spanning portion 72a of the first roller retainer 7A, can be easily derived. In this case, in the state where the first roller retainer 7A is attached to the cam member 5 together with the roller 6, at least on the long axis side of the cam member 5, the gear side portion of the roller 6 is exposed from the first opening A1 of the first roller retainer 7A, and at the same time, the wave generator 4 that can press the roller 6 against the cam member side by the first spanning portion 72a of the first roller retainer 7A can be manufactured more easily and inexpensively. As a result, the harmonic gear device 1 that can expose the gear side portion of the roller 6 from the first opening A1 of the first roller retainer 7A and at the same time press the roller 6 against the cam member side by the first spanning portion 72a of the first roller retainer 7A can be manufactured more easily and inexpensively.

[0086] Therefore, by using the above-mentioned expressions (1) and (2), the roller 6, the cam member 5, and the first roller retainer 7A with appropriate dimensions according to the use, specifications, etc. can be easily derived. In this case, the wave generator 4 that can reduce the frictional loss while preventing skew can be manufactured more easily and inexpensively. As a result, the harmonic gear device 1 can be manufactured more easily and inexpensively.

[0087] Incidentally, referring to FIG. 4A, in the present disclosure, the roller retainer 7 includes a second roller retainer 7B. As shown in FIG. 4A, the second roller retainer 7B prevents the roller 6 from falling off toward the cam member side by the second spanning portion 72b. On the other hand, as described above, the cam member 5 basically does not generate a pressing force from the cam member 5 on the roller 6 at a location other than the long axis portion of the cam member 5 (for example, the short axis portion of the cam member 5). Therefore, as shown in FIG. 4A, even when the second roller retainer 7B is included, the roller 6 is in a free state without contacting the first roller retainer 7A at, for example, the short axis portion of the cam member 5. For this reason, even when the second roller retainer 7B is included, frictional loss associated with contact between the roller retainer 7 and the cam member 5, which may occur when the roller 6 passes through a location other than the long axis portion of the cam member 5, is reduced. Further, as shown in FIG. 4A, the second roller retainer 7B is configured such that the cam member side portion of the roller 6 is positioned within the second opening A2 by the second opening A2. Therefore, according to the second roller retainer 7B, the interval between adjacent rollers 6 is maintained at an appropriate interval along the circumferential direction of the second roller retainer 7B.

[0088] On the other hand, as shown in FIG. 4B, the second roller retainer 7B basically does not generate a pressing force on the roller 6 even at the long-axis portion of the cam member 5. Therefore, even when the second roller retainer 7B is included, the roller 6 is only pressed from the gear side by being sandwiched between the cam member 5 and the first roller retainer 7A (first spanning portion 72a) at the long-axis portion of the cam member 5. For this reason, in the present disclosure, in a state where the second roller retainer 7B is attached to the cam member 5 together with the roller 6 and the first roller retainer 7A, at least on the short-axis side (short-axis portion) of the cam member 5, while allowing the roller 6 to move freely between the first roller retainer 7A and the second roller retainer 7B, the second spanning portion 72b formed between the plurality of second openings A2 holds the roller 6 so as not to drop from the cam member side, and at least on the long-axis side (long-axis portion) of the cam member 5, while avoiding contact with the second spanning portion 72b as much as possible, the roller 6 is rotatably exposed to the cam member side through the second opening A2. In addition, at least on the long-axis side (long-axis portion) of the cam member 5, in the second opening A2 of the second roller retainer 7B, as shown in FIGS. 4A and 4B, the roller 6 is aligned with the position of the second opening A2 so as to follow the shape of the second opening A2 of the second roller retainer 7B. As a result, even when the second roller retainer 7B is included, the roller 6 can perform relative rolling with respect to the outer peripheral surface F5 of the cam member 5 and the inner peripheral surface F3 of the external gear 3 without causing skew at the long-axis portion of the cam member 5. Therefore, according to the second roller retainer 7B, similar to the first roller retainer 7A, skew of the roller 6 that may occur at the long-axis portion of the cam member 5 is prevented. As a result, according to the second roller retainer 7B, frictional loss due to skew of the roller 6 is also reduced. Therefore, when the second roller retainer 7B is added as in the wave generator 4 of the present disclosure, skew can be further prevented while reducing frictional loss, and thus, the harmonic gear device 1 of the present disclosure employing the wave generator 4 can also further prevent skew while reducing frictional loss.

[0089] Also, like the bearing B1 of the present disclosure, when the second roller retainer 7B is formed into a flexible cylindrical shape with a plurality of second openings A2 formed at intervals in the circumferential direction and arranged to cover the roller 6 from the inner circumferential side of the wave generator 4, the inner ring of the bearing becomes an optional component rather than an essential one.

[0090] That is, in the bearing B1 of the present disclosure, the inner ring can be omitted by covering the roller 6 from the inner circumferential side of the wave generator 4 with the second roller retainer 7B. Therefore, according to the bearing B1 of the present disclosure, the number of necessary parts can be reduced, and as a result, the manufacturing cost can be reduced.

[0091] Therefore, when adding the second roller retainer 7B like the bearing B1 of the present disclosure, a wave generator 4 that can more effectively prevent skew while reducing frictional loss can be manufactured easily and inexpensively. As a result, a wave gear device 1 that can more effectively prevent skew while reducing frictional loss can be manufactured easily and inexpensively.

[0092] Also, when adding the second roller retainer 7B like the bearing B1 of the present disclosure, the second roller retainer 7B holds the roller 6 from the side of the cam member 5. In this case, as in the present disclosure, the roller 6 (rolling element) and the roller retainer (retainer) can be integrally handled as the bearing B1. In this case, as in the present disclosure, the bearing B1 can be circulated, transported, or used as a part during assembly work as a single bearing.

[0093] Also, in the present disclosure, the second spanning portion 72b of the second roller retainer 7B also has a holding surface 73b (hereinafter, also referred to as "second holding surface 73b") that rotatably holds the roller 6. The second holding surface 73b can also be formed by an inclined surface or a curved surface similar to the first holding surface 73a. In this case, similar to the first holding surface 73a, the roller 6 can be aligned with the second opening A2 so that the roller 6 rolls more smoothly. Furthermore, in this case, stress concentration during contact between the second roller retainer 7B and the roller 6 can be alleviated.

[0094] Referring to FIG. 4B, in the present disclosure, the second opening A2 forms an inner peripheral side opening on the inner peripheral surface (cam member side surface) F72b(in) of the second roller retainer 7B. The contour of the inner peripheral side opening extending in the width direction of the second roller retainer 7B is formed by the inner peripheral side edge 75b of the second bridging portion 72b.

[0095] Also, in the present disclosure, the second opening A2 forms an outer peripheral side opening on the outer peripheral surface (gear side surface) F72b(out) of the second roller retainer 7B. The contour of the outer peripheral side opening extending in the width direction of the second roller retainer 7B is formed by the outer peripheral side edge 74b of the second bridging portion 72b.

[0096] Here, in the present disclosure, the circumferential length h2 of the second opening A2 is the extension length of the second opening A2 extending along the circumferential direction of the second roller retainer 7B when the cylindrical second roller retainer 7B is developed flatly.

[0097] As shown in FIG. 4B, in the present disclosure, when viewed in the axial cross-section (in the axial direction view), the second holding surface 73b has a circumferential length h22 between the inner peripheral side edges 75b of the two second spanning portions 72b, which is shorter than the circumferential length h21 between the outer peripheral side edges 74b of the two second spanning portions 72b, among the circumferential length h2 of the second opening A2. The inner peripheral side edge 75b is linearly inclined toward the outer peripheral side edge 74b. That is, the second holding surface 73b is also an inclined surface. For this reason, in the present disclosure, the circumferential length h2 of the second opening A2 increases at a constant rate as it goes from the inner peripheral surface F72b(in) to the outer peripheral surface F72b(out) of the second roller retainer 7B. As a result, as shown in FIG. 7A described later, when viewed in the axial cross-section, the roller 6 can contact the second holding surface 73b at the contact point Px2. That is, as shown in FIG. 7A, when viewed in the axial cross-section, the roller 6 can rotate while making line contact in the width direction of the second roller retainer 7B (the extending direction of the second spanning portion 72b) on the contact point Px2 of the second holding surface 73b. Therefore, according to the second holding surface 73b according to the present disclosure, similar to the first holding surface 73a of the first roller retainer 7A, the roller 6 can be aligned with the second opening A2 so that the roller 6 rotates more smoothly with respect to the second spanning portion 72b. Furthermore, in this case, since the second roller retainer 7B and the roller 6 are in line contact in the width direction of the second roller retainer 7B at the position of the contact point Px2, similar to the first holding surface 73a, stress concentration at the time of contact between the second roller retainer 7B and the roller 6 can be alleviated. However, similar to the first holding surface 73a, the second holding surface 73a can be a curved surface instead of the above-mentioned inclined surface. As a specific example of the curved surface, it can be a curved surface that is convex inward toward the inner peripheral side (cam member side) of the second roller retainer 7B. The curved surface can be, for example, a curved surface having the radius of the roller 6 as the radius of curvature. Also, the curved surface can be a curved surface that is convex outward toward the outer peripheral side (gear side) of the second roller retainer 7B.

[0098] Also, as shown in FIG. 5, when FIG. 5 is assumed to be viewed from the inner peripheral surface side (cam member side) of the second roller retainer 7B, referring to FIG. 5, in the present disclosure, the second roller retainer 7B also, similar to the first roller retainer 7A, has two annular portions 71b (hereinafter also referred to as "second annular portions 71b") disposed adjacent to the axial ends 6e of the plurality of rollers 6, and a plurality of second bridging portions 72b that connect the two second annular portions 71b and are spaced apart in the circumferential direction. That is, in the present disclosure, the second opening A2 is also, similar to the first roller retainer 7A, a quadrangular opening defined by the two second annular portions 71b and the two second bridging portions 72b.

[0099] Referring to FIG. 5, in the present disclosure, the second roller retainer 7B is also covered over the roller 6 such that the inner peripheral side edge 75b of the second bridging portion 72b is parallel to the axis О3 of the roller 6. Also, the circumferential length h2 of the second opening A2 (in this example, the circumferential length h22 between the inner peripheral side edges 75b of the two second bridging portions 72b) is shorter than the diameter d of the roller 6. Further, in the present disclosure, as shown in FIG. 5, the second bridging portion 72b is formed with a second holding surface 73b that inclines away from the inner peripheral side edge 75b as it goes toward the outer peripheral side (the back side of the paper surface of FIG. 5) of the second roller retainer 7B with the inner peripheral side edge 75b as a base point. As a result, the cam member side (the front side of the paper surface of FIG. 5) portion of the roller 6 is exposed from the second opening A2 and is rotatably held at the contact point Px2 with the roller 6 on the second holding surface 73b (when viewed in plan view of FIG. 5, the contact point Px2 becomes a contact line Px2 extending in the width direction of the second roller retainer B). Note that in the present disclosure, the two second annular portions 71b are also arranged so as to form a gap with the axial ends 6e of the roller 6 as shown in FIG. 5. In this case, the frictional loss is further reduced.

[0100] Also, as shown in FIG. 6A, the roller 6 can roll on the outer peripheral surface F5 of the cam member 5 without skewing with respect to the moving direction of the roller 6 by the second roller retainer 7B as well.

[0101] Incidentally, in the second roller retainer 7B, the circumferential length hx2 between the two contact points Px2 of the roller 6 and the two second spanning portions 72b in the second opening A2 (hereinafter also referred to as "contact point length hx2") can satisfy the following formula (3).

[0102]

Number

[0103] In addition, when the cam member 5 has a non-circular shape, the inner diameter D2 of the second roller retainer 7B at the time of true circle of the second roller retainer 7B (hereinafter also referred to as "true circle inner diameter D2 of the second roller retainer 7B") can satisfy the following formula (4).

[0104]

Number

[0105] When setting the major axis radius a and minor axis radius b of the cam member 5, the diameter d of the roller 6, the thickness t2 of the second roller retainer 7B, the contact point distance x2, the contact point length hx2, and the true circle inner diameter D2 in the second opening A2 so as to satisfy the above formulas (3) and (4) simultaneously, as will be described in detail later, it is possible to easily derive the roller 6, the cam member 5, and the second roller retainer 7B having appropriate dimensions according to the application, specifications, etc. In this case, it is possible to manufacture the wave generator 4 that can more easily and inexpensively reduce friction loss and prevent skew, and thus, it is possible to manufacture the harmonic gear device 1 that can more easily and inexpensively reduce friction loss and prevent skew.

[0106] Specifically, the above formula (3) is a relational expression focusing on the contact point length hx2 at the second opening A2 of the second roller retainer 7B, similar to the first roller retainer 7A.

[0107] Here, the contact point length hx2 at the second opening A2 refers to the circumferential length between the contact points Px2 of one roller 6 and the two second spanning portions 72b that hold the one roller 6 among the circumferential length h2 of the second opening A2. Referring to FIG. 7A, similar to the first roller retainer 7A, the contact point length hx2 at the second opening A2 needs to be smaller than the diameter d of the roller 6 in order not to let the roller 6 fall off toward the cam member side. For this reason, similar to the first roller retainer 7A, from the geometric relationship as shown in FIG. 7A, the contact point length hx2 at the second opening A2 and the diameter d of the roller 6 need to be set to satisfy the following relational expression (3A).

[0108]

Equation

[0109] If the contact point length hx2 at the second opening A2 and the diameter d of the roller 6 are set so as to satisfy the above relational expression (3A), the roller 6 can be prevented from falling off from the second opening A2.

[0110] Next, referring to FIG. 7B, in the present disclosure, the contact point length hx2 at the second opening A2, similar to the contact point length hx1 at the first opening A1, in addition to preventing the roller 6 from falling off from the second opening A2, it is necessary to expose the roller 6 from the second opening A2. For this reason, similar to the first roller retainer 7A, from the geometric relationship shown in FIG. 7B, the contact point distance x2 and the contact point length hx2 at the second opening A2, the diameter d of the roller 6, and the thickness t2 of the second roller retainer 7B (the second spanning portion 72b) need to be set so as to satisfy the following relational expression (3B). Here, the contact point distance x2 at the second opening A2 refers to the distance in the thickness direction of the second spanning portion 72b (the second roller retainer 7B) from the inner peripheral surface F72b(in) of the second roller retainer 7B to the contact point Px2 when the cylindrical second roller retainer 7B is developed planarly.

[0111]

Number

[0112] If the contact point distance x2 and the contact point length hx2 at the second opening A2, the diameter d of the roller 6, and the thickness t2 of the second roller retainer 7B are set so as to satisfy the above relational expression (3B), similar to the first roller retainer 7A, the roller 6 can be exposed from the second opening A2. For example, the contact point length hx2 at the second opening A2 needs to be made long so that the cam member side portion of the roller 6 protrudes from the position of the inner peripheral surface (the inner peripheral side surface of the second spanning portion 72b) F72b(in) of the second roller retainer 7B. This condition is satisfied by setting the diameter d of the roller 6, the thickness t2 of the second roller retainer 7B, and the contact point distance x2 and the contact point length hx2 at the second opening A2 so as to satisfy the relational expression (3B).

[0113] As is clear from the above relational expressions (3A) and (3B), the above-described expression (3) focuses on the contact point length hx2 at the second opening A2. By using the above-described expression (3), it is possible to easily derive the diameter d of the roller 6, the thickness t2 of the second roller retainer 7B (the thickness of the second spanning portion 72b), the contact point distance x2, and the contact point length hx2 at the second opening A2, such that the roller 6 can be exposed from the second opening A2 without falling off from the second opening A2. In this case, the wave generator 4 that can expose the roller 6 from the second opening A2 without falling off from the second opening A2 can be manufactured more easily and inexpensively. As a result, the harmonic gear device 1 that can expose the roller 6 from the second opening A2 without falling off from the second opening A2 can be manufactured more easily and inexpensively.

[0114] Further, the above-described expression (4) is a relational expression focusing on the inner diameter D2 of the second roller retainer 7B when the second roller retainer 7B is in a perfect circular state.

[0115] FIG. 9A is a diagram for schematically explaining the dimensional relationship between the inner diameter D2 of the second roller retainer 7B in a perfect circular state, the cam member 5, and the roller 6.

[0116] The inner diameter D2 of the second roller retainer 7B in a perfect circular state needs to be made smaller such that the position of the inner peripheral surface F72b(in) of the second roller retainer 7B deformed on the long axis side of the cam member 5 is on the cam member side rather than the position of the roller axis О6 on the long axis side of the cam member 5. This is because when the second roller retainer 7B is deformed on the long axis side of the cam member 5, if the position of the inner peripheral surface F72a(in) of the second roller retainer 7B is on the gear side rather than the position of the central axis О6 of the roller 6 on the cam member 5, there is a possibility of interference with the first roller retainer 7A on the gear side of the roller 6. For this reason, referring to FIG. 9A, from Gauss-Kummer's formula, the major axis radius a and minor axis radius b of the cam member 5 and the diameter d of the roller 6 need to be set to satisfy the following relational expression (4A).

[0117]

Equation

[0118] If the inner diameter D2 of the second roller cage 7B at true circle, the major axis radius a of the cam member 5, and the diameter d of the roller 6 are set so as to satisfy the above relational expression (4A), the second roller cage 7B will not accidentally interfere with the roller 6, and further, it will not interfere with the first roller cage 7A either.

[0119] FIG. 9B is another view for schematically explaining the dimensional relationship between the inner diameter D2 of the second roller cage 7B at true circle, the cam member 5, and the roller 6.

[0120] The inner diameter D2 of the second roller cage 7B at true circle needs to be increased so that the circumference of the inner peripheral surface F72b(in) of the second roller cage 7B is longer than the circumference of the outer peripheral surface F5 of the cam member 5. Here, the "circumference" means the "length in the circumferential direction around the axis О1". If the inner diameter D2 of the second roller cage 7B at true circle is made smaller so that the circumference of the inner peripheral surface F72b(in) of the second roller cage 7B is shorter than the circumference of the outer peripheral surface F5 of the cam member 5, or if the circumference is smaller than that of the cam member 5, the second roller cage 7B and the cam member 5 may come into contact. For this reason, referring to FIG. 9B, from Gauss-Kummer's formula, the major axis radius a and the minor axis radius b of the cam member 5 need to be set so as to satisfy the following relational expression (4B).

[0121]

Equation

[0122] If the major axis radius a and the minor axis radius b of the cam member 5 are set so as to satisfy the above relational expression (4B), contact between the second roller cage 7B and the cam member 5 can be avoided. That is, if the major axis radius a and the minor axis radius b of the cam member 5 are set so as to satisfy the above relational expression (4B), the second roller cage 7B and the cam member 5 will also not interfere with each other.

[0123] As is also clear from the above relational expressions (4A) and (4B), the above-mentioned expression (4) focuses on the true circle diameter D2 of the second roller retainer 7B. By using the above-mentioned expression (4), while exposing the gear side portion of the roller 6 from the second opening A2 of the second roller retainer 7B, it is possible to easily derive the major axis radius a and minor axis radius b of the cam member 5, the diameter d of the roller 6, and the inner diameter D2 at the true circle of the second roller retainer 7B such that there is no accidental interference with the roller 6 and no interference with the first roller retainer 7A and the cam member 5 either.

[0124] Therefore, by using the above-mentioned expressions (3) and (4), it is possible to easily derive the roller 6, the cam member 5, and the second roller retainer 7B with appropriate dimensions according to the application, specifications, etc.

[0125] In the present disclosure, the first roller retainer 7A can be formed of resin or light metal. In this case, by using existing materials, the first roller retainer 7A can be easily manufactured. That is, in this case, by using existing materials, the wave generator 4, and as a result, the harmonic gear device 1 can be easily manufactured. Further, in the present disclosure, the second roller retainer 7B can also be formed of resin or light metal. Also in this case, by using existing materials, the wave generator 4, and as a result, the harmonic gear device 1 can be easily manufactured.

[0126] The roller retainer 7 can be formed of a resin material such as an engineering plastic such as an aluminum alloy, a titanium alloy, a light metal alloy having flexibility such as those alone, PEEK (polyetheretherketone), PPS (polyphenylene sulfide), POM (polyoxymethylene).

[0127] Incidentally, in the present disclosure, the bearing B1 is formed by the roller 6 and the roller retainer 7. In this case, the two members of the inner ring and the outer ring are omitted from the bearing B1. Therefore, in this case, the size of the wave generator 4 can be reduced, and as a result, the size of the harmonic gear device 1 can be reduced.

[0128] However, the bearing can be formed by the roller 6, the roller retainer 7, and the flexible outer ring 11. In this case, when such a bearing is attached to the cam member 5, the gear-side portion of the roller 6 rolls on the raceway surface of the outer ring 11. Therefore, in this case, the roller 6 can be smoothly rolled on the outer peripheral side of the wave generator 4.

[0129] Further, the bearing can be formed by at least the roller 6, the first roller retainer 7A, the second roller retainer 7B, and the flexible inner ring 12. That is, such a bearing may be formed by, for example, a roller (rolling element), a roller retainer (rolling element retainer), and an inner ring, or may be formed by a roller, a roller retainer, an inner ring, and an outer ring as described later. When the bearing has an inner ring, when such a bearing is attached to the cam member 5, the cam member-side portion of the roller 6 rolls on the raceway surface of the inner ring 12. Therefore, in this case, the roller 6 can be smoothly rolled on the cam member side.

[0130] Here, FIG. 10 schematically shows another example of the bearing according to another embodiment of the present invention.

[0131] FIG. 10 shows a bearing B2 according to another embodiment of the present invention. The bearing B2 includes a roller 6, a roller retainer 7, a flexible outer ring 11, and a flexible inner ring 12 as well.

[0132] FIG. 11 schematically shows a bearing B3 according to another embodiment of the present invention that can be adopted in the wave gear device 1 and its wave generator 4. FIG. 12 is a diagram schematically showing the bearing B3 in a state where it is developed in a plane. However, in the following description, the same reference numerals are used for parts that are substantially the same as the configurations of the bearings B1 and B2.

[0133] As shown in FIG. 11, the bearing B3 also includes a plurality of rolling elements (16) arranged at intervals in the circumferential direction around the axis О1, similar to the bearing B1, and a rolling element retainer (17) that holds the plurality of rolling elements.

[0134] In the present disclosure, the rolling element is a ball 16. In the present disclosure, the ball 16 is a sphere with a diameter d. That is, the rolling element retainer is a ball retainer 17.

[0135] In the present disclosure, the ball retainer 17 includes a first ball retainer 17A. Referring to FIG. 11, the first ball retainer 17A is formed in a flexible cylindrical shape with a plurality of openings A3 (hereinafter also referred to as "first openings A3") formed at intervals in the circumferential direction around the axis О1, similar to the first ball retainer 7A. Also, the first ball retainer 17A, in a state of being attached to the cam member 5 together with the ball 16, at least on the long axis side of the cam member 5, holds the ball 16 from the outer peripheral side of the first ball retainer (hereinafter also referred to as "the outer peripheral side of the first ball retainer") by a spanning portion 72a (hereinafter also referred to as "the first spanning portion 72a") formed between the plurality of first openings A3, and exposes the ball 16 rotatably to the outer peripheral side of the first ball retainer through the first opening A3. However, referring to FIG. 11, the first opening A3 is a circular opening defined by two first annular portions 71a and two first spanning portions 72a, different from the first roller retainer 7A, in a plan view.

[0136] Referring to FIG. 12, in the present disclosure, similar to the first roller retainer 7A, the first ball retainer 17A forms an outer peripheral side opening on the outer peripheral surface F72a(out) (the front side of the paper surface in FIG. 12) thereof. The contour of the outer peripheral side opening is formed by a circular outer peripheral side edge 74a.

[0137] Also, in the present disclosure, similar to the first roller retainer 7A, the first ball retainer 17A forms an inner peripheral side opening on the inner peripheral surface F72a(in) (not shown in the figure because it is on the back side of the paper surface in FIG. 12) thereof. The contour of the inner peripheral side opening is formed by a circular inner peripheral side edge 75a.

[0138] In the present disclosure, the first ball retainer 17A also has a first retaining surface 73a for rotatably retaining the balls 16, similar to the first roller retainer 7A. However, in the present disclosure, the first retaining surface 73a is circular in plan view.

[0139] Also, in the present disclosure, the ball retainer 17 also includes a second ball retainer 17B. Referring to FIG. 11, the second ball retainer 17B is formed in a flexible cylindrical shape with a plurality of openings A4 (hereinafter also referred to as "second openings A4") formed at intervals in the circumferential direction, similar to the second roller retainer 7B. Further, the second ball retainer 17B retains the balls 16 from the inner peripheral side of the second ball retainer 17B (hereinafter also referred to as "the inner peripheral side of the first ball retainer") by a bridging portion 72b (hereinafter also referred to as "the second bridging portion 72b") formed between the plurality of second openings A4, and exposes the balls 16 rotatably to the inner peripheral side of the second ball retainer through the second openings A4. However, referring to FIG. 11, in the present disclosure, the second opening A4 is also a circular opening defined by two second annular portions 71b and two second bridging portions 72b.

[0140] Referring to FIG. 12, in the present disclosure, similar to the second roller retainer 7B, the second ball retainer 17B forms an inner peripheral side opening on the inner peripheral surface F72b(in) (the front side of the paper surface in FIG. 12) thereof. The contour of the inner peripheral side opening is formed by a circular inner peripheral side edge 75b.

[0141] In the present disclosure, similar to the second roller retainer 7B, the second opening A4 forms an outer peripheral side opening on the outer peripheral surface F72b(out) of the second ball retainer 17B (not shown as it is on the back side of the paper in FIG. 12). The contour of the outer peripheral side opening is formed by a circular outer peripheral side edge 74b.

[0142] In the present disclosure, the second ball retainer 17B also has a second retaining surface 73b for rotatably retaining the balls 16, similar to the second roller retainer 7B. However, in the present disclosure, the second retaining surface 73b is also circular in a plan view.

[0143] In the bearing B3 as well, the first ball retainer 17A can be set by the above-described formulas (1) and (2). Also, in the bearing B3, the second ball retainer 17B can be set by the above-described formulas (3) and (4).

[0144] As described above, according to the present invention, it is possible to provide a bearing capable of integrally handling rolling elements and a retainer. Therefore, it is possible to provide a bearing with good assemblability when assembling to the mating side. In addition, according to the present invention, it is possible to provide a bearing that can reduce frictional loss while preventing skew and also improve the assemblability to the cam member.

[0145] What has been described above merely shows exemplary embodiments according to the present invention, and various modifications are possible according to the claims. In the present embodiment, the harmonic gear device 1 and the wave generator 4 have been described as two-lobe type, but the harmonic gear device 1 and the wave generator 4 are not limited to the two-lobe type. For example, the cam member 5 can be a multi-lobe type. Specific examples of the cam member 5 include, for example, a three-lobe type having a triangular shape and a four-lobe type having a quadrangular shape. Also, in the above description, the power transmission path of the harmonic gear device 1 has the wave generator 4 as an input and the external gear 3 as an output, but it is not limited thereto. For example, the power transmission path of the harmonic gear device 1 may have the external gear 3 as an input and the wave generator 4 as an output.

Explanation of Symbols

[0146] 1: Wave gear device, 2: Internal gear, 3: External gear, 4: Wave generator, 5: Cam member, 6: Roller (rolling element), 7: Roller retainer (rolling element retainer), 7A: First roller retainer (first rolling element retainer), 71a: First annular portion, 72a: First spanning portion, 73a; First holding surface, 73b; Second holding surface, 74a: Outer peripheral side edge of the first spanning portion, 75a: Inner peripheral side edge of the first spanning portion, 7B: Second roller retainer (first rolling element retainer), 71b: Second annular portion, 72b: Second spanning portion, 73b; Second holding surface, 74b: Outer peripheral side edge of the second spanning portion, 75b: Inner peripheral side edge of the second spanning portion, 8: Drive shaft, 11: Outer ring, 12: Inner ring, 16: Ball (rolling element), 17: Ball retainer (rolling element retainer), 17A: First ball retainer (first rolling element retainer), 17B: Second ball retainer (second rolling element retainer) A1: First opening, A2: Second opening, A3: First opening, A4: Second opening, B1: Bearing (roller bearing), B2: Bearing (roller bearing), B3: Bearing (ball bearing), d: Diameter of the roller, D1: Inner diameter at the time of true circle of the first roller retainer, D2: Inner diameter at the time of true circle of the second roller retainer, F72a(out): Outer peripheral surface of the first roller retainer, F72a(in): Inner peripheral surface of the first roller retainer, F72b(out): Outer peripheral surface of the second roller retainer, F72b(in): Inner peripheral surface of the second roller retainer, h1: Circumferential length of the first opening, h2: Circumferential length of the second opening, hx1: Contact point length in the first opening (circumferential length between the two contact points of the roller and the two first spanning portions in the first opening), hx2: Contact point length in the second opening (circumferential length between the two contact points of the roller and the two second spanning portions in the second opening), О1: Axis (central axis of the wave gear device 1), О6; Axis (axis of the roller), Px1: Contact point between the roller and the first holding surface, Px2: Contact point between the roller and the second holding surface, t1: Thickness of the first roller retainer, t2: Thickness of the second roller retainer, x1: Contact point distance in the first opening (distance from the outer peripheral surface of the first roller retainer to the contact point between the roller and the first spanning portion), x2: Contact point distance in the second opening (distance from the inner peripheral surface of the second roller retainer to the contact point between the roller and the second spanning portion)

Claims

1. A wave generator comprising a bearing and a non-circular cam member rotatable about an axis and attached to the outer peripheral side of the bearing, wherein the bearing includes a plurality of rolling elements arranged at intervals in the circumferential direction around the axis and a rolling element retainer for retaining the plurality of rolling elements, the rolling element retainer includes a first rolling element retainer and a second rolling element retainer formed of resin or light metal, the first rolling element retainer is formed in a flexible cylindrical shape with a plurality of first openings formed at intervals in the circumferential direction, and in a state where it is attached to the cam member together with the rolling elements, at least on the long axis side of the cam member, the rolling elements are held from the outer peripheral side of the first rolling element retainer by a first bridging portion formed between the plurality of first openings, and the rolling elements are rotatably exposed to the outer peripheral side of the first rolling element retainer by the first openings, and further, the rolling elements are positioned such that the rolling elements are along the outer peripheral surface of the cam member, the second rolling element retainer is formed in a flexible cylindrical shape with a plurality of second openings formed at intervals in the circumferential direction, and the rolling elements are held from the inner peripheral side of the second rolling element retainer by a second bridging portion formed between the plurality of second openings, and the rolling elements are rotatably exposed to the inner peripheral side of the second rolling element retainer by the second openings, in the first rolling element retainer, the distance hx1 connecting the contact points of the rolling elements and the first rolling element retainer satisfies the following formula (1), and the inner diameter D1 of the first rolling element retainer at the time of true circle of the first rolling element retainer satisfies the following formula (2), (d: diameter of the rolling element, t1: thickness of the first rolling element retainer, x1: distance from the outer peripheral surface of the first rolling element retainer to the contact point between the rolling element and the first bridging portion) a + b + d < D1 < 2·(a + d) …(2) (a: major axis radius of the cam member, b: minor axis radius of the cam member, d: diameter of the rolling element) In a state where the rolling element retainer is attached to the cam member, the rolling elements are only pressed against the first rolling element retainer at the major axis portion of the cam member, and fall out of neither the first rolling element retainer nor the second rolling element retainer at portions other than the major axis portion of the cam member, and are allowed to move freely between the first rolling element retainer and the second rolling element retainer, a wave generator.

2. The first spanning portion has a holding surface for rotatably holding the rolling elements, and the holding surface is formed by an inclined surface or a curved surface, the wave generator according to claim 1.

3. The second spanning portion has a holding surface for rotatably holding the rolling elements, and the holding surface is formed by an inclined surface or a curved surface, the wave generator according to claim 1 or 2.

4. The wave generator according to any one of claims 1 to 3, formed by the rolling elements and the rolling element retainer.

5. The wave generator according to any one of claims 1 to 3, formed by the rolling elements, the rolling element retainer, and a flexible outer ring.

6. At least formed by the rolling elements, the rolling element retainer, and a flexible inner ring, the wave generator according to any one of claims 1 to 3, 5.

7. The rolling elements are rollers, the wave generator according to any one of claims 1 to 6.

8. The rolling elements are balls, the wave generator according to any one of claims 1 to 6.

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