Ball bearing

Abstract

Provided is a ball bearing that can prevent the vibration of a retainer while preventing the deformation of the retainer in a harmonic drive gear device. This ball bearing (1) comprises: a deformable inner ring (2); a deformable outer ring (3) that is installed outside the inner ring (2); a plurality of spherical rolling elements (4) that are provided between the inner ring (2) and the outer ring (3); and a retainer (5) in which a plurality of pockets (10) are circumferentially provided at intervals therebetween, the plurality of rolling elements (4) being respectively accommodated in the pockets (10). Each of the plurality of pockets (10) has a pocket surface (11) that spreads around a pocket axis (x1) that extends in a radial direction, and a flange section (20) that protrudes toward the pocket axis (x1) from the pocket surface (11). The pocket surfaces (11) are formed so as to accommodate the rolling elements (4) with an interval therebetween, and the flange section (20) is formed so as to be in contact with at least the rolling elements (4) located at the position of the minor radius (rb) of the inner ring (2), from inside in the radial direction.

Description

ball bearing

[0001] The present invention relates to a ball bearing.

[0002] Wave gearing devices that can achieve a high reduction ratio are known as reducers. Some wave gearing devices have a wave generator with an elliptical outer peripheral surface. The wave generator has an elliptical cam and a ball bearing mounted on the outer peripheral surface of the elliptical cam. The inner and outer rings of the ball bearing are deformable, and as the elliptical cam rotates, the outer peripheral surfaces of the inner and outer rings deform radially in accordance with the elliptical shape of the outer peripheral surface of the elliptical cam, causing wave motion.

[0003] Due to this wave motion, the rolling space between the inner and outer rings moves radially when viewed from a fixed position in the circumferential direction. In other words, the rolling space is located at its outermost position in the radial direction at the position of the major axis of the elliptical cam, and at its innermost position in the radial direction at the position of the minor axis of the elliptical cam. Meanwhile, the cage of a ball bearing is an annular, rigid member. Therefore, when the cage is supported (guided) by spherical rolling elements, the cage deforms. This deformation can cause damage to the cage. To prevent this damage, in ball bearings of conventional strain wave gear devices, the cage is not supported by the rolling elements, and the rolling elements are accommodated with a relatively large gap between them. Because the cage of such a ball bearing is movable relative to the rolling elements, vibration occurs (see, for example, Patent Document 1).

[0004] Specification of Special Publication No. 6-103060

[0005] Thus, in the ball bearings of conventional strain wave gear devices, there is a demand for a configuration that can prevent the cage from vibrating while also preventing deformation of the cage.

[0006] The present invention has been made in view of the above-mentioned problems, and its object is to provide a ball bearing in a wave gear device that can prevent deformation of the cage while also preventing vibration of the cage.

[0007] In order to achieve the above-mentioned object, the ball bearing of the present invention is a ball bearing comprising a deformable inner ring, a deformable outer ring placed on the outside of the inner ring, a plurality of spherical rolling elements provided between the inner ring and the outer ring, and a cage in which a plurality of pockets are provided at intervals in the circumferential direction and in which each of the plurality of rolling elements is accommodated, wherein each of the plurality of pockets has a pocket surface which is a surface extending around an axis extending in the radial direction, and a flange portion which is a portion which protrudes toward the axis from the pocket surface, and the pocket surface is adapted to accommodate the rolling elements via a gap, and the flange portion is adapted to contact the rolling elements located at least at the position of the minor axis of the inner ring from the radially inner side, or to contact the rolling elements located at least at the position of the major axis of the inner ring from the radially outer side.

[0008] According to the ball bearing of the present invention, in a strain wave gear device, it is possible to prevent deformation of the cage and vibration of the cage.

[0009] 12 is a partial cross-sectional view of a ball bearing according to a first embodiment of the present invention. FIG. 13 is a diagram showing an example of a wave gear device provided with the ball bearing shown in FIG. 1. FIG. 14 is a partial perspective view of a cage in the ball bearing shown in FIG. 1. FIG. 3 is an enlarged view of a pocket of the cage shown in FIG. 3. FIG. 4 is a cross-sectional view of the cage in a cross section taken along line A-A extending radially relative to the pocket axis of FIG. 4. FIG. 14 is an enlarged view of the vicinity of a rolling element located at the position of the minor axis of the inner ring of the ball bearing shown in FIG. 1. FIG. 15 is an enlarged view of the vicinity of a rolling element located at the position of the minor axis of the inner ring in the ball bearing shown in FIG. 1. FIG. 16 is an enlarged view of the vicinity of a rolling element located at the position of the major axis of the inner ring in the ball bearing shown in FIG. 1. FIG. 17 is a diagram showing a modification of a flange portion of the ball bearing according to the first embodiment of the present invention. FIG. 18 is a diagram showing another modification of the flange portion of the ball bearing according to the first embodiment of the present invention. FIG. 19 is a partial cross-sectional view of a ball bearing according to a second embodiment of the present invention. FIG. 11 is an enlarged view of a pocket of the cage in the ball bearing shown in FIG. 11. FIG. 19 is a cross-sectional view of the cage in a cross section taken along line D-D extending radially in the pocket direction of FIG. 19 is an enlarged view of the vicinity of a rolling element located on the major axis of the inner ring in the ball bearing shown in FIG. 11. FIG. 20 is an enlarged view of the vicinity of a rolling element located on the major axis of the inner ring in the ball bearing shown in FIG. 11. FIG. 21 is an enlarged view of the vicinity of a rolling element located on the minor axis of the inner ring in the ball bearing shown in FIG. 11. FIG. 22 is an enlarged view of the vicinity of a rolling element located on the minor axis of the inner ring in the ball bearing shown in FIG. 11. FIG. 23 is a view showing a modified example of a flange portion of a ball bearing according to a second embodiment of the present invention. FIG. 24 is a view showing another modified example of a flange portion of a ball bearing according to the second embodiment of the present invention. FIG. 25 is an enlarged view of the vicinity of rolling elements and pockets located on the minor axis of a ball bearing according to a third embodiment of the present invention in a wave gear device. FIG. 26 is a cross-sectional view of a cage and rolling elements in a cross section taken along line G-G extending radially with respect to the pocket axis shown in FIG. 19. FIG. 27 is an enlarged view of the vicinity of rolling elements and pockets located on the minor axis of a ball bearing according to a fourth embodiment of the present invention in a wave gear device. FIG. 28 is a cross-sectional view of a cage and rolling elements in a cross section taken along line H-H extending radially with respect to the pocket axis shown in FIG.

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] Fig. 1 is a partial cross-sectional view of a ball bearing 1 according to a first embodiment of the present invention. In Fig. 1, the ball bearing 1 is shown mounted on an elliptical cam 102 of a strain wave gearing device 100, which will be described later. The ball bearing 1 includes a deformable inner ring 2, a deformable outer ring 3 disposed on the outside of the inner ring 2, a plurality of spherical rolling elements 4 disposed between the inner ring 2 and the outer ring 3, and a cage 5 having a plurality of circumferentially spaced pockets 10 in which the plurality of rolling elements 4 are respectively housed. Each of the plurality of pockets 10 has a pocket surface 11, which is a surface extending around a pocket axis x1 extending radially, and a flange portion 20, which protrudes from the pocket surface 11 toward the pocket axis x1. The pocket surface 11 is adapted to receive the rolling elements 4 via a gap, and the flange portion 20 is adapted to contact at least the rolling elements 4 located at the minor radius rb of the inner ring 2 from the radially inner side, or to contact at least the rolling elements 4 located at the major radius ra of the inner ring 2 from the radially outer side. The ball bearing 1 will now be described in detail. FIG. 1 shows the ball bearing 1 as viewed from the front, with the inner ring 2 and outer ring 3 cut away to reveal the cage 5 and all of the rolling elements 4. In addition, not all of the rolling elements 4 are designated by reference numerals in the drawings, and similarly, not all of the pockets 10 are designated by reference numerals. Similarly, not all of the components in the drawings are designated by reference numerals, and reference numerals are omitted as appropriate.

[0012] The ball bearing according to the present invention is applicable to wave gearing, including wave gearing. FIG. 2 shows a wave gearing 100 as an example of a wave gearing provided with a ball bearing 1. The ball bearing 1 constitutes part of a wave generator 101 of the wave gearing 100. In the wave generator 101, an elliptical cam 102 is fitted to the inner ring 2 of the ball bearing 1. The wave generator 101 is fitted to a cup-shaped flexspline 103, and the flexspline 103 is fitted to a circular spline 104. In the wave gearing 100, the cam 102 rotates, causing the inner ring 2 of the ball bearing 1 to rotate together with the cam 102. As the elliptical inner ring 2 rotates, various portions on the outer periphery of the outer ring 3 deform radially via the rolling elements 4, and at least a portion of the outer ring 3 located on the major axis comes into contact with the flexspline 103, causing the outer periphery of the flexspline 103 to undergo wave motion. The teeth 103 a located in the longitudinal direction of the flexspline 103 performing this wave motion mesh with the teeth 104 a of the circular spline 104, and due to the difference in the number of teeth of the teeth 103 a of the flexspline 103 and the number of teeth of the teeth 104 a of the circular spline 104, the circular spline 104 rotates relative to the flexspline 103, and the flexspline 103 or the circular spline 104 rotates at a reduced speed relative to the rotation of the cam 102.

[0013] The inner ring 2 of the ball bearing 1 has a configuration similar to that of the inner rings of conventionally known ball bearings used in strain wave gearing. It is a cylindrical or approximately cylindrical, flexible or elastic member with its central or approximate central axis being the axis x. When an elliptical cam 102 is fitted onto the inner ring 2, the inner ring 2 deforms into an elliptical or approximately elliptical cylindrical shape with its central or approximate central axis being the axis x, as shown in FIG. 1 . In the inner ring 2 with the elliptical cam 102 fitted onto it, the outer peripheral surface 2a, which is the surface facing radially outward of the inner ring 2, is an elliptical or approximately elliptical cylindrical surface with its central or approximate central axis being the axis x. As shown in FIG. 1 , a cross section of the outer peripheral surface 2a perpendicular to the axis x describes an ellipse or approximately ellipse with a major axis xa, a minor axis xb, a major axis ra, and a minor axis rb. The axis x is the axis of the ball bearing 1.

[0014] The outer ring 3 has a similar configuration to the outer ring of a conventionally known ball bearing used in a strain wave gear device, and is a cylindrical, flexible or elastic member around the axis x, as shown in Fig. 1. As shown in Fig. 1, the outer ring 3 has a shape similar to that of the inner ring 2 in the ball bearing 1. However, the inner ring 2 and the outer ring 3 each have a raceway groove (not shown), and the inner ring 2 and the outer ring 3 are not similar in terms of the raceway grooves.

[0015] As shown in FIG. 1 , the cage 5 is a rigid member having an annular or approximately annular shape with the axis x as its central axis or approximately as its central axis. The cage 5 is made of, for example, resin. Note that the cage 5 is not limited to being made of resin and may be made of other materials. As described above, the cage 5 has a plurality of pockets 10, each of which accommodates a rolling element 4. Note that the ball bearing 1 has an odd number of rolling elements 4; in the illustrated example, the ball bearing 1 has 23 rolling elements 4. Each pocket 10 extends along a pocket axis x1 extending in a radial direction perpendicular to the axis x, and penetrates the cage 5 between its inner circumferential surface 5 a and outer circumferential surface 5 b. Note that the inner circumferential surface 5 a faces radially inward of the cage 5, and the outer circumferential surface 5 b faces radially outward of the cage 5. In addition, the diameter of the inner surface 5a of the retainer 5 is larger than the major axis of the outer surface 2a of the inner ring 2, and the diameter of the outer surface 5b of the retainer 5 is smaller than the minor axis of the inner surface 3a of the outer ring 3 in the ball bearing 1.

[0016] FIG. 3 is a partial perspective view of the cage 5, FIG. 4 is an enlarged view of a pocket 10 of the cage 4, and FIG. 5 is a cross-sectional view of the cage 5 taken along line A-A in FIG. 4 , which extends radially relative to the pocket axis x1. Note that FIG. 4 shows the pocket 10 as viewed from the outer peripheral surface 5b toward the inner peripheral surface 5a in the direction of the pocket axis x1. As shown in FIGS. 3 and 4 , the cage 5 has a plurality of claws 5c extending along the axis x. The claws 5c are spaced apart in the circumferential direction around the axis x, and each pocket 10 is formed between adjacent claws 5c in the circumferential direction. The ends (tips 5d) of adjacent claws 5c on one side in the direction of the axis x are not connected, forming a gap, and each pocket 10 is open on one side in the direction of the axis x. 4, between the tip ends 5d of the claws 5c adjacent to each other in the circumferential direction, an opening 5f that opens the pocket 10 is formed by a surface (opening surface 5e) of the tip end 5d facing in the circumferential direction. The opening surface 5e continues to the pocket surface 11 and the flange portion 20 on the other side in the direction of the axis x.

[0017] As shown in FIG. 3 , the pocket axis x1 of each pocket 10 extends, for example, parallel or approximately parallel to the radial direction, and the multiple pockets 10 are arranged, for example, at equal or approximately equal angular intervals around the axis x. The pocket surface 11 of each pocket 10 is configured to accommodate the rolling elements 4 with gaps in the radial direction (hereinafter also referred to as the pocket radial direction) perpendicular to the pocket axis x1, and the radius r1 of the pocket surface 11 (see FIG. 4 ) is larger than the radius of the rolling elements 4. The pocket surface 11 is, for example, a conical surface, a cylindrical surface, or a portion of an approximately cylindrical surface with the pocket axis x1 as its central axis or approximately central axis. The pocket surface 11 may also be a portion of a conical surface, a cylindrical surface, or an approximately cylindrical surface extending along a line close to the pocket axis x1 passing through the axis x or a point nearby the axis x. The pocket surface 11 is capable of accommodating the rolling elements 4 with gaps therebetween over the entire range in the direction of the pocket axis x1. For example, as shown in FIG. 5 , the diameter r1 of the pocket surface 11 is uniform over the entire range in the direction of the pocket axis x1 (r1a = r1b), or increases in diameter from the flange portion 20 side toward the outer peripheral surface 5b in the direction of the pocket axis x1 (r1b > r1a). Note that the diameter r1a is the diameter r1 of the pocket surface 11 at the end on the flange portion 20 side, and the diameter r1b is the diameter r1 of the pocket surface 11 at the end on the outer peripheral surface 5b side. Connection portions 10a, 10b, which are portions where the pocket surface 11 and the pair of open surfaces 5e are connected, respectively, prevent the rolling elements 4 accommodated in the pocket 10 from coming out of the pocket 10 in the direction of the axis x. For example, the distance between the connection portions 10a and 10b is smaller than the diameter of the rolling elements 4.

[0018] As shown in Figures 4 and 5, the flange portion 20 of each pocket 10 is a portion that protrudes radially inward beyond the pocket surface 11 and extends around the pocket axis x1, and in this embodiment, is configured to contact at least the rolling elements 4 located at the minor radius rb of the inner ring 2 from the inside in the radial direction. Note that, as shown in Figure 1, the rolling elements 4 located at the minor radius rb of the inner ring 2 are rolling elements 4 that are in contact with the outer peripheral surface 2a of the inner ring 2 at the minor radius rb in the ball bearing 1, and are rolling elements 4 whose centers are located on the minor axis xb of the inner ring 2. For example, the flange portion 20 is configured to prevent the pocket 10 from moving relative to the rolling elements 4 when it comes into radial contact with the rolling elements 4 located at the minor radius rb of the inner ring 2 from the inside, and thereby the cage 5 is supported by the rolling elements 4. In addition, the fact that the pocket 10 cannot move relative to the rolling element 4 means that the position of the rolling element 4 in the pocket 10 does not change, and the rotation of the rolling element 4 is not included in the relative movement of the pocket 10 to the rolling element 4.

[0019] For example, as shown in FIG. 5 , at a predetermined radial position (position p1) in the radial direction of the ball bearing 1 (direction of the pocket axis x1) within a range (range s1) on the pocket axis x1 of the flange portion 20, the diameter (radius r2) of the flange portion 20 in a cross section (cross section B) perpendicular to the pocket axis x1 is the same or substantially the same as the diameter (radius r3) of the rolling element 4 located at the minor radius rb of the inner ring 2 in a cross section (cross section C) perpendicular to the minor axis xb at a predetermined radial position p1 on the minor axis xb of the rolling element 4 (see FIG. 6 ). Note that FIG. 6 is an enlarged view showing the vicinity of the rolling element 4 located at the minor radius rb of the inner ring 2 of the ball bearing 1. The cage 5 is omitted from FIG. 6 . Furthermore, cross sections B and C are the same cross section of the ball bearing 1.

[0020] Specifically, as shown in FIG. 5 , the flange portion 20 is provided radially inward of the pocket surface 11 of the ball bearing 1 and adjacent to the pocket surface 11, and is provided only at the inner end of the pocket 10 in the direction of the pocket axis x1. Specifically, as shown in FIG. 5 , the flange portion 20 has an inclined surface 21 that extends around the pocket axis x1 and expands in diameter toward the side that contacts the rolling elements 4 in the direction of the pocket axis x1 (toward the radially outer side of the ball bearing 1). The flange portion 20 protrudes continuously along the pocket surface 11 around the pocket axis x1. Specifically, as shown in FIG. 4 , the flange portion 20 extends between the open surfaces 5 e of the pair of claw portions 5 c along a circular or approximately circular ring extending around the pocket axis x1, extending longer than a semicircle. As shown in FIG. 5 , the cross-sectional shape of the flange portion 20 perpendicular to the extension direction is uniform or approximately uniform.

[0021] As described above, as shown in FIG. 5 , the projected range of the inclined surface 21 onto the pocket axis x1 in the pocket radial direction is the range s1, and the diameter of the inclined surface 21 at the radial position p1 within the range s1 is the diameter r2 in cross section B. Also, in the ball bearing 1, as shown in FIG. 6 , the diameter r3 of the rolling element 4 located at the minor radius rb of the inner ring 2 in cross section C at the radial position p1 on the minor axis xb is the same or approximately the same as the diameter r2 of the inclined surface 21 of the flange portion 20. Therefore, as shown in FIG. 7 (described later), the diameter r2 of the inclined surface 21 of the flange portion 20 contacts the portion of the diameter r3 of the circumferential surface of the rolling element 4 located at the minor radius rb of the inner ring 2 from the radial inside of the ball bearing 1. Position p1 is, for example, located inside the center of the width of the pocket 10 in the direction of the pocket axis x1. As shown in FIGS. 5 and 6 , the diameter of the ball bearing 1 at the radial position p1 is rp1.

[0022] As shown in FIG. 5 , the inclined surface 21 of the flange portion 20 is a tapered surface that describes a straight or approximately straight line in a cross section including the pocket axis x1. The inclined surface 21 is not limited to this tapered surface, and may have any other shape as long as it contacts at least the rolling element 4 located at the minor radius rb of the inner ring 2 from the inside in the radial direction of the ball bearing 1 at the position of radius r2 at radial position p1, as described above. For example, the inclined surface 21 may be a surface that describes a convex arc or arc toward the pocket axis x1 in a cross section including the pocket axis x1, a concave arc or arc toward the opposite side to the pocket axis x1, or a surface that describes another curve. Furthermore, the inclined surface 21 may be a surface that describes a line that is a combination of a curve and a straight line in a cross section including the pocket axis x1.

[0023] 5, each pocket 10 may have a recess 12 on the inside in the direction of the pocket axis x1 of the flange portion 20. The recess 12 extends between the inner end (inner end 21a) of the inclined surface 21 of the flange portion 20 in the direction of the pocket axis x1 and the inner circumferential surface 5a of the cage 5, and is, for example, a part of a conical surface, a cylindrical surface, or a substantially cylindrical surface with the pocket axis x1 as its central axis or substantially central axis. The form of the recess 12 is not limited to this form. Like the pocket surface 11, the recess 12 may be, for example, a part of a conical surface, a cylindrical surface, or a substantially cylindrical surface extending along a line close to the pocket axis x1 that passes through the axis x or a point nearby the axis x.

[0024] Next, we will explain the operation of the ball bearing 1 having the above-mentioned configuration. Figure 7 is an enlarged view of the vicinity of the rolling element 4 located at the position of the minor radius rb of the inner ring 2 in the ball bearing 1, and Figure 8 is an enlarged view of the vicinity of the rolling element 4 located at the position of the major radius ra of the inner ring 2 in the ball bearing 1.

[0025] In the strain wave gear device 100, when the cam 102 rotates, the inner ring 2 rotates about the axis x together with the cam 102, and this rotation of the inner ring 2 causes the cage 5 to rotate about the axis x together with the multiple rolling elements 4. The outer peripheral surface 2a of the inner ring 2 is elliptical, and each rolling element 4 traces an elliptical orbit centered on the axis x. Each rolling element 4 is closest to the axis x in the radial direction at the position of the minor radius rb of the inner ring 2. The radial position of each rolling element 4 moves further away from the axis x as it approaches the position of the major radius ra, and each rolling element 4 is farthest from the axis x in the radial direction at the position of the major radius ra of the inner ring 2. The radial position of each rolling element 4 approaches the axis x as it approaches the position of the minor radius rb. The rolling elements 4 repeat this radial movement while moving around the outer peripheral surface 2a of the inner ring 2.

[0026] On the other hand, the cage 5 is an annular, rigid member, and each pocket 10 of the cage 5 describes a circular orbit centered on the axis x. In other words, the radial position of each pocket 10 of the cage 5 from the axis x remains constant or almost constant as the cage 5 rotates. Therefore, each rolling element 4 circulating on the outer peripheral surface 2a of the inner ring 2 moves relative to the pocket 10 in the direction of the pocket axis x1 within the pocket 10 in which it is housed. At the position of the minor radius rb of the inner ring 2, each rolling element 4 moves inwardly relative to the pocket 10 in the direction of the pocket axis x1, and at the position of the major radius ra of the inner ring 2, each rolling element 4 moves outwardly relative to the pocket 10 in the direction of the pocket axis x1.

[0027] 7 , the rolling element 4, which is located at the minor radius rb of the inner ring 2 and has moved inward most inward relative to the pocket 10 in the direction of the pocket axis x1, comes into contact with the inclined surface 21 of the flange portion 20 of the pocket 10. Specifically, a portion of the inclined surface 21 with a radius r2 on the cross section B(C) at a position p1 radially spaced by a radius rp1 from the axis x comes into contact with a portion of the rolling element 4 with a radius r3 on the cross section C(B) at a position p1 radially spaced by a radius rp1 from the axis x. Due to this contact between the flange portion 20 and the rolling elements 4, the cage 5 is supported by the rolling elements 4 and is unable to move relative to the rolling elements 4 in the radial direction of the pocket or radially outward of the ball bearing 1.

[0028] As shown in Figure 7, when a rolling element 4 is located at the position of the minor radius rb of one inner ring 2 on the raceway of the rolling element 4 (right side in Figure 1), no rolling element 4 is located at the position of the minor radius rb of the other inner ring 2 on the raceway of the rolling element 4 (left side in Figure 1). However, two rolling elements 4 are located near the position of the minor radius rb of the other inner ring 2 on the raceway of the rolling element 4 (left side in Figure 1), and these two rolling elements 4, or one of these two rolling elements 4, act as described above in approximately the same way as a rolling element 4 located at the position of the minor radius rb of the inner ring 2. As described above, the cage 5 is not restricted in its movement in the direction of the minor axis xb toward the other side (left side in FIG. 1) by the rolling element 4 that it contacts at a position on one side (right side in FIG. 1) of the minor axis xb, but is substantially restricted in its relative movement toward the other side (left side in FIG. 1) in the direction of the minor axis xb by at least one of the two rolling elements 4 located near the position of the minor axis xb on the other side (left side in FIG. 1). Therefore, movement of the cage 5 in the ball bearing 1 is restricted by contact between one rolling element 4 located at the position of the minor radius rb of the inner ring 2 and one or two rolling elements 4 located near the position of the minor radius rb of the inner ring 2, and the flange portions 20 of one pocket 10 located on the minor axis xb of the inner ring 2 and one or two pockets 10 located near the minor axis xb of the inner ring 2. In this way, the movement of the retainer 5 in the ball bearing 1 is restricted by contact between two or three rolling elements 4 that move sequentially to the position of the minor radius rb of the inner ring 2 and its vicinity, and two or three flange portions 20 that move sequentially to the minor axis xb of the inner ring 2 and its vicinity.

[0029] On the other hand, when the rolling element 4, which is located at the minor radius rb of the inner ring 2, moves from the minor radius rb position toward the major radius ra position as the inner ring 2 rotates, contact between the moved rolling element 4 and the flange portion 20 of the pocket 10 in which the rolling element 4 is accommodated is released, and support of the retainer 5 by the rolling element 4 is released.

[0030] As described above, each rolling element 4 moves outward most relative to the pocket 10 in which it is accommodated in the direction of the pocket axis x1 at the position of the major diameter ra of the inner ring 2. In other words, as shown in Figure 8, the rolling element 4 located at the position of the major diameter ra of the inner ring 2 moves to a position farthest from the inclined surface 21 of the flange portion 20 of the pocket 10.

[0031] In this way, in the ball bearing 1, the cage 5 is supported only by the rolling elements 4 located in the vicinity of the minor radius rb of the inner ring 2. Therefore, when the ball bearing 1 is rotated and in use, the generation of forces that deform the cage 5 can be suppressed. Also, in the ball bearing 1, as shown in FIG. 7 , the flange portion 20 and the rolling elements 4 come into contact at the portion of radius r2 of the inclined surface 21 and the portion of radius r3 of the rolling elements 4 in cross section B (C) at position p1 of the same radius rp1. Therefore, no force that deforms the cage 5 is generated by contact between the flange portion 20 and the rolling elements 4. Therefore, in the ball bearing 1, the cage 5 is not deformed when in use.

[0032] If, due to manufacturing errors, assembly errors, etc., the position of the flange portion 20 in contact with the rolling element 4 located at the minor radius rb of the inner ring 2 is located at the radius of the inclined surface 21 in a cross section at a position radially outward from the position p1 of the radius rp1, a force is generated in the cage 5 at the position of the minor axis xb that deforms the cage 5 toward the axis x. When this force deforms the cage 5, the cage 5 bends at the position of the major axis xa, increasing its curvature and narrowing the circumferential spacing of the pockets 10 on the major axis xa. In particular, the circumferential width at the position of the inclined surface 21 of the flange portion 20 located radially inward is narrowed. Meanwhile, as described above, the rolling element 4 located at the major radius ra of the inner ring 2 moves outward most relative to the pocket 10 in which it is accommodated in the pocket axis x1, moving to a position farthest from the inclined surface 21 of the flange portion 20 of the pocket 10. Therefore, as described above, even if the retainer 5 is deformed due to contact between the rolling element 4 on the minor axis xb and the flange portion 20, the pocket 10 on the major axis xa can be avoided or suppressed from being pressed against the rolling element 5, further deformation of the retainer 5 can be avoided or suppressed, and damage to the retainer 5 can be avoided or suppressed.

[0033] Furthermore, when the ball bearing 1 is in use, the cage 5 does not come into contact with the inner ring 2 or the outer ring 3, preventing an increase in the torque resistance of the ball bearing 1. In this respect, deformation of the cage 5 in use is avoided or suppressed, and damage to the cage 5 is avoided or suppressed.

[0034] As described above, the flange portion 20 of the pocket 10 of the ball bearing 1 can restrict movement of the cage 5 in the ball bearing 1, and can prevent or reduce vibration of the cage 5 in the ball bearing 1. In addition, the pocket 10 of the ball bearing 1 can suppress deformation of the cage 5.

[0035] As described above, when a rolling element 4 is located at the position of the minor radius rb of one inner ring 2 on its raceway, two rolling elements 4 located near the position of the minor radius rb of the other inner ring 2 on its raceway act in approximately the same manner as the rolling element 4 located at the position of the minor radius rb of the inner ring 2, but at least one of the two rolling elements 4 located near the position of the minor radius rb of the other inner ring 2 on its raceway may act in the same manner as the rolling element 4 located at the position of the minor radius rb of the inner ring 2. Specifically, the rolling element 4 located at the position of the minor radius rb of one inner ring 2 on its raceway and at least one of the two rolling elements 4 located near the position of the minor radius rb of the other inner ring 2 on its raceway may come into contact with the flange portion 20 of the pocket 10.

[0036] In this way, with the ball bearing 1 according to the first embodiment of the present invention, in the strain wave gear device 100, it is possible to prevent deformation of the cage 5 while also preventing vibration of the cage 5.

[0037] Next, a modified example of the flange portion 20 of the ball bearing 1 according to the first embodiment of the present invention will be described. Fig. 9 is a diagram showing a modified example of the flange portion 20 of the ball bearing 1, and is an enlarged view of the vicinity of the rolling element 4 located at the minor radius rb of the inner ring 2 of the ball bearing 1. As shown in Fig. 9, the flange portion 20 of the ball bearing 1 may have a stepped surface 22 instead of the inclined surface 21 described above. The stepped surface 22 has an annular surface 22a that is an annular surface around the pocket axis x1 and extends from the inner end of the pocket surface 11 in the direction of the pocket axis x1 to the pocket radially inward, and a cylindrical surface 22b that extends along the pocket axis x1 from the inner end of the annular surface 22a in the direction of the pocket radially inward in the direction of the pocket axis x1 to the inner circumferential surface 5a.

[0038] The annular surface 22a is a surface extending along a plane perpendicular to the pocket axis x1. For example, as shown in FIG. 9, the annular surface 22a is a surface parallel or approximately parallel to the plane perpendicular to the pocket axis x1, and is a part of a torus or approximately torus surface having the pocket axis x1 as its central axis or approximately central axis. The cylindrical surface 22b is a part of a cylindrical surface extending along the pocket axis x1. For example, the cylindrical surface 22b is a part of a conical surface, cylindrical surface, or approximately cylindrical surface having the pocket axis x1 as its central axis or approximately central axis. The cylindrical surface 22b may be a part of a conical surface, cylindrical surface, or approximately cylindrical surface extending along a line close to the pocket axis x1 that passes through the axis x or a point nearby the axis x. The annular surface 22a and the cylindrical surface 22b extend continuously between the connecting portion 10a and the connecting portion 10b (see FIG. 4).

[0039] The connection portion 22c, where the annular surface 22a and the cylindrical surface 22b connect, is located on cross section B at position p1 of radius rp1 described above, and extends on a ring centered on the pocket axis x1. The radius of the connection portion 22c in the pocket radial direction is radius r2. Therefore, like the inclined surface 21 of the flange portion 20 described above, the stepped surface 22 of the flange portion 20 comes into contact with at least the rolling elements 4 located at the minor radius rb of the inner ring 2 at the connection portion 22c, thereby supporting the cage 5. Therefore, the stepped surface 22 of the flange portion 20 according to this modification also acts in the same manner as the inclined surface 21 of the flange portion 20 described above.

[0040] Next, another modification of the flange portion 20 of the ball bearing 1 according to the first embodiment of the present invention will be described. FIG. 10 is a diagram showing another modification of the flange portion 20 of the ball bearing 1, showing the pocket 10 as viewed from the outer peripheral surface 5b toward the inner peripheral surface 5a in the direction of the pocket axis x1. As shown in FIG. 10, the flange portion 20 may protrude intermittently along the pocket surface 11 around the pocket axis x1. Specifically, for example, as shown in FIG. 10, the flange portion 20 may be formed by multiple flange pieces 20a spaced apart around the pocket axis x1. The cross-sectional shape of each flange piece 20a, taken along the pocket axis x1, is the same as the cross-sectional shape of the flange portion 20 (see FIGS. 5 and 9) taken along the pocket axis x1. Furthermore, the inclined surface 21 or stepped surface 22 of each flange piece 20a overlaps the inclined surface 21 or stepped surface 22 at a corresponding position on the flange portion 20 (see FIG. 4). The number of flange pieces 20a is not limited to the number shown.

[0041] Next, a ball bearing 6 according to a second embodiment of the present invention will be described. The ball bearing 6 according to the second embodiment of the present invention has a cage 7 that is different from the cage 5 of the ball bearing 1 according to the first embodiment of the present invention described above. The cage 7 of the ball bearing 6 differs from the cage 5 described above in that it has pockets 13 that are different from the pockets 10 of the ball bearing 1. Hereinafter, for the ball bearing 6, components that are the same as those of the ball bearing 1 described above or have similar functions will be assigned the same reference numerals as those in the ball bearing 1 and will not be described again, and only components that are different from the ball bearing 1 will be described.

[0042] FIG. 11 is a partial cross-sectional view of a ball bearing 6 according to a second embodiment of the present invention. FIG. 11 shows the ball bearing 6 as viewed from the front, with the inner ring 2, outer ring 3, and cage 7 cut away. FIG. 12 is an enlarged view of a pocket 13 in the cage 7, and FIG. 13 is a cross-sectional view taken along line D-D in FIG. 12 , which extends radially in the pocket direction. In FIG. 11 , the ball bearing 6 is shown mounted on the elliptical cam 102 of the strain wave gear device 100, as in FIG. 1 . FIG. 12 also shows the pocket 13 as viewed from the inner circumferential surface 5a toward the outer circumferential surface 5b in the direction of the pocket axis x1.

[0043] 11 to 13, each pocket 13 of the cage 7 of the ball bearing 6 has a flange portion 23 for supporting the cage 7, like the flange portion 20 of the pocket 10 described above. Unlike the flange portion 20 described above, the flange portion 23 is configured to contact from the outside in the radial direction at least the rolling elements 4 located at the position of the major radius ra of the inner ring 2. Note that, as shown in FIG. 11, the rolling elements 4 located at the position of the major radius ra of the inner ring 2 are rolling elements 4 in the ball bearing 6 that are in contact with the outer peripheral surface 2a of the inner ring 2 at the position of the major radius ra, and whose centers are located on the major axis xa of the inner ring 2.

[0044] 11 , the plurality of pockets 13 in the cage 7 of the ball bearing 6 are formed between adjacent claw portions 5c in the circumferential direction, similar to the plurality of pockets 10 in the cage 5 described above. Each pocket 13 extends along a pocket axis x1 and penetrates the cage 7 between the inner circumferential surface 5a and the outer circumferential surface 5b of the cage 7. The pocket axis x1 of each pocket 13 extends, for example, parallel or approximately parallel to the radial direction, and the plurality of pockets 13 are provided, for example, at equal or approximately equal angular intervals around the axis x.

[0045] As shown in FIGS. 11 to 13 , each pocket 13 has a pocket surface 14 similar to the pocket surface 11 of the pocket 10 described above. The diameter r1 (see FIG. 12 ) of the pocket surface 14 is larger than the radius of the rolling elements 4. The pocket surface 14 is, for example, a conical surface, a cylindrical surface, or a portion of a substantially cylindrical surface with the pocket axis x1 as its central axis or approximately its central axis. The pocket surface 14 may also be a portion of a conical surface, a cylindrical surface, or a substantially cylindrical surface extending along a line close to the pocket axis x1 passing through the axis x or a point nearby the axis x. The pocket surface 14 is capable of accommodating the rolling elements 4 with a gap therebetween over the entire range in the direction of the pocket axis x1. For example, as shown in FIG. 13 , the diameter r1 of the pocket surface 14 is uniform over the entire range in the direction of the pocket axis x1 (r1a = r1c), or increases in diameter from the flange portion 23 side toward the inner circumferential surface 5a side in the direction of the pocket axis x1 (r1c > r1a). Note that diameter r1a is diameter r1 of the pocket surface 14 at the end on the flange portion 23 side, and diameter r1c is diameter r1 of the pocket surface 14 at the end on the inner circumferential surface 5a side. As shown in Figure 13, the flange portion 23 of each pocket 13 is a portion that protrudes inward in the pocket radial direction from the pocket surface 14 and extends around the pocket axis x1. For example, when the flange portion 23 comes into contact with the rolling elements 4 located at the position of the major diameter ra of the inner ring 2 from the outside in the radial direction, the flange portion 23 is shaped to prevent the pocket 13 from moving relative to the rolling elements 4, and thereby the cage 7 is supported by the rolling elements 4.

[0046] For example, as shown in FIG. 13 , at a predetermined radial position (position p2) in the radial direction of the ball bearing 6 (direction of the pocket axis x1) within a range (range s2) on the pocket axis x1 of the flange portion 23, the diameter (radius r4) of the flange portion 23 in a cross section (cross section E) perpendicular to the pocket axis x1 is the same or substantially the same as the diameter (radius r5) of the rolling element 4 located at the major axis ra of the inner ring 2 in a cross section (cross section F) perpendicular to the major axis xa at a predetermined radial position p2 on the major axis xa of the rolling element 4 (see FIG. 14 ). Note that FIG. 14 is an enlarged view showing the vicinity of the rolling element 4 located at the major axis ra of the inner ring 2 of the ball bearing 6. The cage 7 is omitted from FIG. 14 . Furthermore, cross sections E and F are the same cross section of the ball bearing 6.

[0047] Specifically, as shown in FIG. 13 , the flange portion 23 is provided adjacent to the pocket surface 14 and radially outward of the ball bearing 6, and is provided only at the outer end of the pocket 13 in the direction of the pocket axis x1. As shown in FIG. 13 , the flange portion 23 has an inclined surface 24 extending around the pocket axis x1 and expanding in diameter toward the side in the direction of contact with the rolling elements 4 (toward the radially inner side of the ball bearing 6). The flange portion 23 protrudes continuously along the pocket surface 14 around the pocket axis x1. As shown in FIGS. 12 and 13 , the flange portion 23 extends between the open surfaces 5 e of the pair of claw portions 5 c along a circular or substantially circular ring extending around the pocket axis x1, extending longer than a semicircle. As shown in FIG. 13 , the cross-sectional shape of the flange portion 23 perpendicular to the extension direction is uniform or substantially uniform.

[0048] As described above, as shown in FIG. 13 , the projected range of the inclined surface 24 onto the pocket axis x1 in the pocket radial direction is the range s2, and the diameter at the cross section E at the radial position p2 within the range s2 is the diameter r4. In addition, in the ball bearing 6, as shown in FIG. 14 , the diameter r5 at the cross section F at the radial position p2 on the major axis xa of the rolling element 4 located at the position of the major diameter ra of the inner ring 2 is the same or approximately the same as the diameter r4 at the inclined surface 24 of the flange portion 23. Therefore, as shown in FIG. 15 (described later), the diameter r4 of the inclined surface 24 of the flange portion 23 contacts the portion of the diameter r5 of the circumferential surface of the rolling element 4 located at the position of the major diameter ra of the inner ring 2 from the radial outside of the ball bearing 6. Position p2 is, for example, located outside the center of the width of the pocket 13 in the direction of the pocket axis x1. As shown in FIGS. 13 and 14 , the diameter at the radial position p3 of the ball bearing 6 is rp2.

[0049] As shown in FIG. 13 , the inclined surface 24 of the flange portion 23 is a tapered surface that describes a straight or approximately straight line in a cross section including the pocket axis x1. The inclined surface 24 is not limited to this tapered surface, and may have any other shape as long as it contacts at least the rolling element 4 located at the major radius ra of the inner ring 2 from the outside in the radial direction of the ball bearing 6 at the position of radius r4 at radial position p2, as described above. For example, the inclined surface 24 may be a surface that describes a convex arc or arc toward the pocket axis x1 in a cross section including the pocket axis x1, a concave arc or arc toward the opposite side from the pocket axis x1, or a surface that describes another curve. Furthermore, the inclined surface 24 may be a surface that describes a line that is a combination of a curve and a straight line in a cross section including the pocket axis x1.

[0050] 13 , each pocket 13 may have a recess 15 on the outside in the direction of the pocket axis x1 of the flange portion 23. The recess 15 extends between the outer end (outer end 24 a) of the inclined surface 24 of the flange portion 23 in the direction of the pocket axis x1 and the outer peripheral surface 5 b of the cage 7, and is, for example, a part of a conical surface, a cylindrical surface, or a substantially cylindrical surface with the pocket axis x1 as its central axis or substantially central axis. The shape of the recess 15 is not limited to this. Like the pocket surface 14, the recess 15 may be, for example, a part of a conical surface, a circle, or a substantially cylindrical surface extending along a line close to the pocket axis x1 that passes through the axis x or a point nearby it.

[0051] Next, the operation of the ball bearing 6 having the above-described configuration will be described. Fig. 15 is an enlarged view of the vicinity of the rolling element 4 located at the position of the major radius ra of the inner ring 2 in the ball bearing 6, and Fig. 16 is an enlarged view of the vicinity of the rolling element 4 located at the position of the minor radius rb of the inner ring 2 in the ball bearing 6.

[0052] Similar to the rotation of the ball bearing 1 described above, in the strain wave gear device 100, when the inner ring 2 rotates about the axis x with the rotation of the cam 102 and the cage 7 rotates about the axis x together with the multiple rolling elements 4, each rolling element 4 circling on the outer peripheral surface 2a of the inner ring 2 moves in the direction of the pocket axis x1 relative to the pocket 13 in which it is accommodated. At the position of the minor radius rb of the inner ring 2, each rolling element 4 moves inward most relative to the pocket 13 in the direction of the pocket axis x1, and at the position of the major radius ra of the inner ring 2, each rolling element 4 moves inward most relative to the pocket 13 in the direction of the pocket axis x1.

[0053] 15 , the rolling element 4, which is located at the position of the major radius ra of the inner ring 2 and has moved outward most relative to the pocket 13 in the direction of the pocket axis x1, comes into contact with the inclined surface 24 of the flange portion 23 of the pocket 13. Specifically, a portion of the inclined surface 24 with a radius r4 on the cross section E(F) at a position p2 radially spaced by a radius rp2 from the axis x comes into contact with a portion of the rolling element 4 with a radius r5 on the cross section F(E) at a position p2 radially spaced by a radius rp2 from the axis x. Due to this contact between the flange portion 23 and the rolling elements 4, the cage 7 is supported by the rolling elements 4 and is unable to move relative to the rolling elements 4 in the radial direction of the pocket and radially inward of the ball bearing 6.

[0054] As shown in Figure 15, when a rolling element 4 is located at the position of the major radius ra of one inner ring 2 on the raceway of the rolling element 4 (upper side in Figure 11), no rolling element 4 is located at the position of the major radius ra of the other inner ring 2 on the raceway of the rolling element 4 (lower side in Figure 11). However, two rolling elements 4 are located near the position of the major radius ra of the other inner ring 2 on the raceway of the rolling element 4 (lower side in Figure 11), and these two rolling elements 4, or one of these two rolling elements 4, act as described above in approximately the same way as a rolling element 4 located at the position of the major radius ra of the inner ring 2. As described above, the cage 7 is not restricted in its relative movement to one side (upper side in FIG. 11 ) in the direction of the major axis xa by the rolling element 4 that it contacts at one position on the major axis xa (upper side in FIG. 11 ), but is substantially restricted in its relative movement to one side (upper side in FIG. 11 ) in the direction of the major axis xa by at least one of the two rolling elements 4 located near the other position of the major axis xa (lower side in FIG. 11 ). Therefore, movement of the cage 7 in the ball bearing 6 is restricted by contact between one rolling element 4 located at the position of the major axis ra of the inner ring 2 and one or two rolling elements 4 located near the position of the major axis ra of the inner ring 2, and one pocket 13 located on the major axis xa of the inner ring 2 and the flange portions 23 of one or two rolling elements 4 located near the major axis xa of the inner ring 2. In this way, the movement of the retainer 7 in the ball bearing 6 is restricted by contact between two or three rolling elements 4 that move sequentially to the position of the major axis ra of the inner ring 2 and its vicinity, and two or three flange portions 23 that move sequentially to the major axis xa of the inner ring 2 and its vicinity.

[0055] On the other hand, when the rolling element 4 located at the position of the long radius ra of the inner ring 2 moves from the position of the long radius ra toward the position of the short radius rb as the inner ring 2 rotates, contact between the moved rolling element 4 and the flange portion 23 of the pocket 13 in which the rolling element 4 is accommodated is released, and support of the retainer 7 by the rolling element 4 is released.

[0056] As described above, each rolling element 4 moves inward most in the direction of the pocket axis x1 with respect to the pocket 13 in which it is accommodated at the position of the minor radius rb of the inner ring 2. In other words, as shown in Figure 16, the rolling element 4 located at the position of the minor radius rb of the inner ring 2 moves to a position farthest from the inclined surface 24 of the flange portion 23 of the pocket 13.

[0057] In this way, in the ball bearing 6, the cage 7 is supported only by the rolling elements 4 located in the vicinity of the major radius ra of the inner ring 2. Therefore, the generation of forces that deform the cage 7 can be suppressed when the ball bearing 6 is in use. Also, in the ball bearing 6, as shown in FIG. 14 , the flange portion 23 and the rolling elements 4 come into contact at a portion of radius r4 of the inclined surface 24 and a portion of radius r5 of the rolling elements 4 in cross section E (F) at position p2 of the same radius rp2. Therefore, no force that deforms the cage 7 is generated by contact between the flange portion 23 and the rolling elements 4. Therefore, in the ball bearing 6, the cage 7 is not deformed when in use.

[0058] If, due to manufacturing errors, assembly errors, etc., the position of the flange portion 23 in contact with the rolling elements 4 located at the major radius ra of the inner ring 2 is located at the radius of the inclined surface 24 in a cross section at a position radially inward from the position p2 of the radius rp2, a force is generated in the cage 7 at the position of the major axis xa that deforms the cage 7 toward the axis x. When this force deforms the cage 7, the cage 7 bends at the position of the minor axis xb, increasing its curvature and narrowing the circumferential spacing of the pockets 13 on the minor axis xb. In particular, the circumferential width of the pocket surface 14 located radially inward is narrowed. Meanwhile, as described above, the rolling elements 4 located at the minor radius rb of the inner ring 2 move inwardmost relative to the pockets 13 in which they are accommodated in the direction of the pocket axis x1. Therefore, even if the cage 7 is deformed due to contact between the rolling elements 4 on the major axis xa and the flange portion 23 as described above, the diameter of the cylindrical portion 14 of the pocket 13 may be adjusted to avoid or suppress the pocket 13 on the minor axis xb from being pressed against the rolling elements 7. This adjustment makes it possible to avoid or suppress further deformation of the cage 7 and to avoid or suppress damage to the cage 7.

[0059] Furthermore, when the ball bearing 6 is in use, the cage 7 does not come into contact with the inner ring 2 or the outer ring 3, preventing an increase in the torque resistance of the ball bearing 6. In this respect, deformation of the cage 7 in use is avoided or suppressed, and damage to the cage 7 is avoided or suppressed.

[0060] As described above, the flange portion 23 of the pocket 13 of the ball bearing 6 can restrict movement of the cage 7 in the ball bearing 6, and can prevent or reduce vibration of the cage 7 in the ball bearing 6. In addition, the pocket 13 of the ball bearing 6 can suppress deformation of the cage 7.

[0061] As described above, when a rolling element 4 is located at the position of the major radius ra of one inner ring 2 on its raceway, two rolling elements 4 located near the position of the major radius ra of the other inner ring 2 on its raceway act in approximately the same way as the rolling element 4 located at the position of the major radius ra of the inner ring 2, but at least one of the two rolling elements 4 located near the position of the major radius ra of the other inner ring 2 on its raceway may act in the same way as the rolling element 4 located at the position of the major radius ra of the inner ring 2. Specifically, the rolling element 4 located at the position of the major radius ra of one inner ring 2 on its raceway and at least one of the two rolling elements 4 located near the position of the major radius ra of the other inner ring 2 on its raceway may come into contact with the flange portion 23 of the pocket 13.

[0062] In this way, the ball bearing 6 according to the second embodiment of the present invention can prevent deformation of the cage 7 in the strain wave gear device 100 while also preventing vibration of the cage 7.

[0063] Next, a modified example of the flange portion 23 of the ball bearing 6 according to the second embodiment of the present invention will be described. Fig. 17 is a diagram showing a modified example of the flange portion 23 of the ball bearing 6, and is an enlarged view of the vicinity of the rolling elements 4 located at the position of the major axis ra of the inner ring 2 of the ball bearing 6. As shown in Fig. 17, the flange portion 23 of the ball bearing 6 may have a stepped surface 25 instead of the inclined surface 24 described above. The stepped surface 25 has an annular surface 25a that is an annular surface around the pocket axis x1, extending from the outer end of the pocket surface 14 in the direction of the pocket axis x1 to the pocket radially inward, and a cylindrical surface 25b that extends along the pocket axis x1, extending from the inner end of the annular surface 25a in the pocket radial direction outward in the direction of the pocket axis x1 to the outer peripheral surface 5b.

[0064] The annular surface 25a is a surface extending along a plane perpendicular to the pocket axis x1. For example, as shown in FIG. 17 , the annular surface 25a is a surface parallel or approximately parallel to the plane perpendicular to the pocket axis x1, and is a part of a circular torus or approximately circular torus surface having the pocket axis x1 as its central axis or approximately central axis. The cylindrical surface 25b is a part of a cylindrical surface extending along the pocket axis x1. For example, the cylindrical surface 25b may be a part of a conical surface, cylindrical surface, or approximately cylindrical surface having the pocket axis x1 as its central axis or approximately central axis. For example, the cylindrical surface 25b may be a part of a conical surface, cylindrical surface, or approximately cylindrical surface extending along a line close to the pocket axis x1 that passes through the axis x or a point nearby the axis x. The annular surface 25a and the cylindrical surface 25b extend continuously between the connecting portion 10a and the connecting portion 10b (see FIG. 12 ).

[0065] The connection portion 25c, where the annular surface 25a and the cylindrical surface 25b connect, is located on the cross section E at the position p2 of the radius rp2 described above, and extends on a ring centered on the pocket axis x1. The radius of the connection portion 25c in the pocket radial direction is radius r4. Therefore, like the inclined surface 24 of the flange portion 23 described above, the stepped surface 25 of the flange portion 23 comes into contact with at least the rolling elements 4 located at the position of the major radius ra of the inner ring 2 at the connection portion 25c, thereby supporting the cage 7. Therefore, the stepped surface 25 of the flange portion 23 according to this modification also acts in the same manner as the inclined surface 24 of the flange portion 23 described above.

[0066] Next, another modification of the flange portion 23 of the ball bearing 6 according to the second embodiment of the present invention will be described. FIG. 18 is a diagram showing another modification of the flange portion 23 of the ball bearing 6, showing the pocket 13 as viewed from the inner circumferential surface 5a toward the outer circumferential surface 5b in the direction of the pocket axis x1. As shown in FIG. 18, the flange portion 23 may protrude intermittently along the pocket surface 14 around the pocket axis x1. Specifically, for example, as shown in FIG. 18, the flange portion 23 may be formed by providing multiple flange pieces 23a spaced apart around the pocket axis x1. The cross-sectional shape of each flange piece 23a, taken along the pocket axis x1, is the same as the cross-sectional shape of the flange portion 23 taken along the pocket axis x1 (see FIGS. 13 and 17). Furthermore, the inclined surface 24 or stepped surface 25 of each flange piece 23a overlaps the inclined surface 24 or stepped surface 25 at a corresponding position on the flange portion 23 (see FIG. 12). The number of flange pieces 23a is not limited to the number shown in the figure.

[0067] Next, a ball bearing 1A according to a third embodiment of the present invention will be described. The ball bearing 1A according to the third embodiment of the present invention has a cage 5A that is different from the cage 5 of the ball bearing 1 according to the first embodiment of the present invention described above. The cage 5A of the ball bearing 1A differs from the cage 5 described above in that it has pockets 16 that are different from the pockets 10 of the ball bearing 1. Hereinafter, for the ball bearing 1A, components that are the same as those of the ball bearing 1 described above or have similar functions will be assigned the same reference numerals as those in the ball bearing 1 and will not be described again, and only components that are different from the ball bearing 1 will be described.

[0068] Like the flange portion 20 of the pocket 10 described above, the pocket 16 of the cage 5A has a flange portion 26 that comes into contact from the radially inner side with at least the rolling elements 4 located at the position of the minor radius rb of the inner ring 2. Upon contact with at least the rolling elements 4 located at the position of the minor radius rb of the inner ring 2, the flange portion 26 is configured to prevent the rolling elements 4 from moving relative to the pocket 16, thereby supporting the cage 5A on the rolling elements 4. More specifically, upon contact with at least the rolling elements 4 located at the position of the minor radius rb of the inner ring 2, the flange portion 26, together with the pocket surface 11 of the pocket 16, is configured to prevent the pocket 16 from moving relative to the rolling elements 4, thereby supporting the cage 5A on the rolling elements 4.

[0069] Fig. 19 is an enlarged view of the rolling elements 4 and pockets 16 located at the minor radius rb of the ball bearing 1A in the strain wave gear device 100, and their vicinity, and Fig. 20 is a cross-sectional view taken along line G-G extending radially relative to the pocket axis x1 in Fig. 19. Note that Fig. 19 shows the rolling elements 4 and pockets 16 as viewed from the outer peripheral surface 5b side toward the inner peripheral surface 5a side in the direction of the pocket axis x1.

[0070] 19 and 20 , similar to the flange portion 20 in the first embodiment of the present invention, the flange portion 26 protrudes radially inward from the pocket surface 11, is adjacent to the cylindrical portion 11 on the inside in the direction of the pocket axis x1, and is provided only at the inner end of the pocket 16 in the direction of the pocket axis x1. Similarly to the flange portion 20 described above, the flange portion 26 extends continuously around the pocket axis x1 along the pocket surface 11. However, as shown in FIG. 19 , the flange portion 26 does not extend to the connection portions 10a and 10b. Similarly to the flange portion 20, the flange portion 26 has an inclined surface 27. Similar to the inclined surface 21, the inclined surface 27 is shaped to contact at least the rolling elements 4 located at the minor radius rb of the inner ring 2 from the radially inner side. However, unlike the inclined surface 21, the inclined surface 27 is shaped to contact the rolling elements 4 from the radially inner side when they come into contact with the pocket surface 11. The inclined surface 27 may be configured to contact the entire surface or a portion of the rolling elements 4 located at least at the position of the minor radius rb of the inner ring 2. The pocket surface 11 also contacts at least a portion of the rolling elements 4 located at the position of the minor radius rb of the inner ring 2.

[0071] In the ball bearing 1A of the wave gear device 100, the rolling element 4 located at the position of the minor radius rb of one of the inner rings 2 on the track of the rolling element 4 comes into contact with the inclined surface 27 of the flange portion 26 and the pocket surface 11 in the pocket 16 in which the rolling element 4 is accommodated. Furthermore, at least one of the two rolling elements 4 located near the position of the minor radius rb of the other inner ring 2 on the track of the rolling element 4 comes into contact with the inclined surface 27 of the flange portion 26 and the pocket surface 11 in approximately the same manner as the rolling element 4 located at the position of the minor radius rb of one of the inner rings 2. For this reason, as in the case of the ball bearing 1 described above, the rolling element 4 located near the position of the minor radius rb is substantially immovable relative to the pocket 16, and the cage 5A is supported by the rolling elements 4 and is immovable relative to the rolling elements 4 in the pocket radial direction and radially outward of the ball bearing 1A. As a result, movement of the cage 5A in the ball bearing 1A is constrained by contact between at least one of the one rolling element 4 located at the position of the minor radius rb of the inner ring 2 and the two rolling elements 4 located near the position of the minor radius rb of the inner ring 2, and the flange portions 26 and pocket surfaces 11 of one pocket 16 located on the minor axis xb of the inner ring 2 and one or two pockets 10 located near the minor axis xb of the inner ring 2. In this way, movement of the cage 5A in the ball bearing 1A is constrained by contact between the two or three rolling elements 4 that sequentially move to the position of the minor radius rb of the inner ring 2 and near the minor axis xb of the inner ring 2, and the flange portions 26 and pocket surfaces 11 of two or three pockets 16 that sequentially move to the position of the minor radius rb of the inner ring 2 and near the minor axis xb of the inner ring 2, respectively.

[0072] On the other hand, when the rolling element 4, which is located at the minor radius rb of the inner ring 2, moves from the minor radius rb position toward the major radius ra position as the inner ring 2 rotates, contact between the moved rolling element 4 and the flange portion 26 and pocket surface 11 of the pocket 16 in which the rolling element is accommodated is released, and support of the retainer 5A by the rolling element 4 is released.

[0073] As described above, the flange portion 26 and pocket surface 11 of the ball bearing 1A function in the same manner as the flange portion 20 of the ball bearing 1, and the ball bearing 1A exhibits the same effects as the ball bearing 1. Specifically, the flange portion 26 and pocket surface 11 of the pocket 16 can restrict movement of the cage 5A in the ball bearing 1A, thereby preventing or reducing vibration of the cage 5A in the ball bearing 1A. Furthermore, the pocket 16 of the ball bearing 1A can suppress deformation of the cage 5A.

[0074] As described above, when a rolling element 4 is located at the position of the minor radius rb of one inner ring 2 on its raceway, two rolling elements 4 located near the position of the minor radius rb of the other inner ring 2 on its raceway act in approximately the same manner as the rolling element 4 located at the position of the minor radius rb of the inner ring 2, but at least one of the two rolling elements 4 located near the position of the minor radius rb of the other inner ring 2 on its raceway may act in the same manner as the rolling element 4 located at the position of the minor radius rb of the inner ring 2. Specifically, the rolling element 4 located at the position of the minor radius rb of one inner ring 2 on its raceway and at least one of the two rolling elements 4 located near the position of the minor radius rb of the other inner ring 2 on its raceway may come into contact with the flange portion 26 of the pocket 16 and the pocket surface 11.

[0075] In this way, with the ball bearing 1A according to the third embodiment of the present invention, in the strain wave gear device 100, it is possible to prevent deformation of the retainer 5A while also preventing vibration of the retainer 5A.

[0076] The flange portion 26 can be modified in the same manner as the flange portion 20 of the ball bearing 1 according to the first embodiment of the present invention. That is, the flange portion 26 may have a stepped surface similar to the stepped surface 22, rather than an inclined surface 27, as shown in Fig. 9. Furthermore, the flange portion 26 may protrude discontinuously along the pocket surface 11 around the pocket axis x1, as shown in Fig. 10.

[0077] Next, a ball bearing 6A according to a fourth embodiment of the present invention will be described. The ball bearing 6A according to the fourth embodiment of the present invention has a cage 7A that is different from the cage 7 of the ball bearing 6 according to the second embodiment of the present invention described above. The cage 7A of the ball bearing 6A differs from the cage 7 described above in that it has pockets 17 that are different from the pockets 13 of the ball bearing 6. Hereinafter, for the ball bearing 6A, components that are the same as those of the ball bearing 6 described above or have similar functions will be assigned the same reference numerals as those of the ball bearing 6 and will not be described again, and only components that are different from the ball bearing 6 will be described.

[0078] Like the flange portion 23 of the pocket 13 described above, the pocket 17 of the cage 7A has a flange portion 28 that comes into contact from the radially outer side with at least the rolling elements 4 located at the position of the major radius ra of the inner ring 2. Upon contact with at least the rolling elements 4 located at the position of the major radius ra of the inner ring 2, the flange portion 28 is configured to prevent the rolling elements 4 from moving relative to the pocket 17, thereby supporting the cage 7A on the rolling elements 4. More specifically, upon contact with at least the rolling elements 4 located at the position of the major radius ra of the inner ring 2, the flange portion 28, together with the pocket surface 14 of the pocket 17, prevents the pocket 17 from moving relative to the rolling elements 4, thereby supporting the cage 7A on the rolling elements 4.

[0079] Fig. 21 is an enlarged view of the rolling elements 4 and pockets 17 located at the position of the major axis ra of the ball bearing 6A in the strain wave gear device 100, and Fig. 22 is a cross-sectional view taken along line H-H extending radially relative to the pocket axis x1 in Fig. 21. Note that Fig. 21 shows the rolling elements 4 and pockets 17 as viewed from the inner circumferential surface 5a toward the outer circumferential surface 5b in the direction of the pocket axis x1.

[0080] 21 and 22 , similar to the flange portion 23 in the second embodiment of the present invention, the flange portion 28 protrudes radially inward from the pocket surface 14, is adjacent to the outer side of the cylindrical portion 14 in the direction of the pocket axis x1, and is provided only at the outer end of the pocket 17 in the direction of the pocket axis x. Similarly to the flange portion 23 described above, the flange portion 28 extends continuously around the pocket axis x1 along the pocket surface 14. However, as shown in FIG. 21 , the flange portion 28 does not extend to the connection portions 10a and 10b. Similarly to the flange portion 23, the flange portion 27 has an inclined surface 29. Similar to the inclined surface 24, the inclined surface 29 is shaped to contact, from the radial outside, at least the rolling elements 4 located at the position of the major radius ra of the inner ring 2. However, unlike the inclined surface 24, the inclined surface 29 is shaped to contact the rolling elements 4 with the pocket surface 14 when they come into contact with each other. The inclined surface 29 may be configured to contact the entire surface or a portion of the rolling elements 4 located at least at the position of the major radius ra of the inner ring 2. The pocket surface 14 also contacts at least a portion of the rolling elements 4 located at the position of the major radius ra of the inner ring 2.

[0081] In the ball bearing 6A of the strain wave gear device 100, the rolling element 4 located at the position of the major radius ra of one of the inner rings 2 on the track of the rolling element 4 comes into contact with the inclined surface 29 of the flange portion 28 and the pocket surface 14 in the pocket 17 in which the rolling element 4 is housed. At least one of the two rolling elements 4 located near the position of the major radius ra of the other inner ring 2 on the track of the rolling element 4 comes into contact with the inclined surface 29 of the flange portion 28 and the pocket surface 14 in approximately the same manner as the rolling element 4 located at the position of the major radius ra of one of the inner rings 2. For this reason, as in the case of the ball bearing 6 described above, the rolling element 4 located near the position of the major radius ra is substantially immovable relative to the pocket 17, and the cage 7A is supported by the rolling elements 4 and is immovable relative to the rolling elements 4 in the pocket radial direction and radially inward of the ball bearing 6A. As a result, movement of the cage 7A in the ball bearing 6A is constrained by contact between at least one of one rolling element 4 located at the position of the major radius ra of the inner ring 2 and two rolling elements 4 located near the position of the major radius ra of the inner ring 2, and the flange portions 28 and pocket surfaces 14 of one pocket 17 located on the major axis xa of the inner ring 2 and one or two pockets 17 located near the major axis xa of the inner ring 2. In this way, movement of the cage 7A in the ball bearing 6A is constrained by contact between two or three rolling elements 4 that sequentially move to the position of the major radius ra of the inner ring 2 and near the major radius ra of the inner ring 2, and the flange portions 28 and pocket surfaces 14 of two or three pockets 17 that sequentially move on the major axis xa of the inner ring 2 and near the major axis xa of the inner ring 2, respectively.

[0082] On the other hand, when the rolling element 4 located at the position of the long radius ra of the inner ring 2 moves from the position of the long radius ra toward the position of the short radius rb as the inner ring 2 rotates, contact between the moved rolling element 4 and the flange portion 28 and pocket surface 14 of the pocket 17 in which the rolling element 4 is accommodated is released, and support of the retainer 7A by the rolling element 4 is released.

[0083] As described above, the flange portion 28 and pocket surface 14 of the ball bearing 6A function in the same manner as the flange portion 26 of the ball bearing 6, and the ball bearing 6A exhibits the same effects as the ball bearing 6. Specifically, the flange portion 28 and pocket surface 14 of the pocket 17 can restrict movement of the cage 7A in the ball bearing 6A, thereby preventing or reducing vibration of the cage 7A in the ball bearing 6A. Furthermore, the pocket 17 of the ball bearing 6A can suppress deformation of the cage 7A.

[0084] As described above, when a rolling element 4 is located at the position of the major radius ra of one inner ring 2 on its track, two rolling elements 4 located near the position of the major radius ra of the other inner ring 2 on its track act in approximately the same way as the rolling element 4 located at the position of the major radius ra of the inner ring 2, but at least one of the two rolling elements 4 located near the position of the major radius ra of the other inner ring 2 on its track may act in the same way as the rolling element 4 located at the position of the major radius ra of the inner ring 2. Specifically, the rolling element 4 located at the position of the major radius ra of one inner ring 2 on its track and at least one of the two rolling elements 4 located near the position of the major radius ra of the other inner ring 2 on its track may come into contact with the flange portion 28 of the pocket 17 and the pocket surface 14.

[0085] In this way, with the ball bearing 6A according to the fourth embodiment of the present invention, in the strain wave gear device 100, it is possible to prevent deformation of the retainer 7A while also preventing vibration of the retainer 7A.

[0086] The flange portion 27 can be modified in the same manner as the flange portion 23 of the ball bearing 6 according to the second embodiment of the present invention. That is, the flange portion 28 may have a stepped surface similar to the stepped surface 25, rather than an inclined surface 29, as shown in Fig. 17. Furthermore, the flange portion 28 may protrude discontinuously along the pocket surface 14 around the pocket axis x1, as shown in Fig. 18.

[0087] Although the embodiments of the present invention have been described above, the present invention is not limited to the ball bearings 1, 1A, 6, and 6A according to the above-described embodiments of the present invention, and includes all aspects within the concept and scope of the claims of the present invention. Furthermore, the various components may be appropriately and selectively combined to achieve at least some of the above-described problems and advantages. For example, the shape, material, arrangement, size, etc. of the various components in the above-described embodiments may be appropriately modified depending on the specific use of the present invention.

[0088] 1, 1A, 6, 6A... ball bearing, 2... inner ring, 2a... outer peripheral surface, 3... outer ring, 3a... inner peripheral surface, 4... rolling element, 5, 5A, 7, 7A... cage, 5a... inner peripheral surface, 5b... outer peripheral surface, 5c... claw portion, 5d... tip portion, 5e... open surface, 5f... open portion, 10, 13, 16, 17... pocket, 10a, 10b... connection portion, 11, 14... pocket surface, 12, 15... relief portion, 20, 23, 26, 28... flange portion, 21, 24, 27, 29... inclined surface, 21a... inner end, 22, 25... step surface, 22a, 25a... annular surface, 22b, 25b ...Cylindrical surface, 22c, 25c...Connection portion, 20a, 23a...Flange piece, 24a...Outer end, 100...Harmonic gear device, 101...Wave generator, 102...Cam, 103...Flexspline, 103a...Tooth, 104...Circular spline, 104a...Tooth, A, B, C, E, F...Cross section, p1, p2...Position, r1, r1a, r1b, r1c, r2, r3, r4, r5, rp1, rp2...Radius, ra...Major axis, rb...Minor axis, s1, s2...Range, x...Axis, x1...Pocket axis, xa...Major axis, xb...Minor axis

Claims

1. A ball bearing comprising a deformable inner ring, a deformable outer ring disposed outside the inner ring, a plurality of spherical rolling elements provided between the inner ring and the outer ring, and a cage provided with a plurality of pockets circumferentially spaced apart for respectively accommodating the plurality of rolling elements, Each of the plurality of pockets has a pocket surface which is a surface extending around an axis extending in the radial direction, and a flange portion which is a portion protruding toward the axis side from the pocket surface, The pocket surface is adapted to accommodate the rolling element via a gap, The flange portion is adapted to contact, from the radially inner side, at least the rolling element located at the minor diameter position of the inner ring, or is adapted to contact, from the radially outer side, at least the rolling element located at the major diameter position of the inner ring, The flange portion has a relief portion on the side opposite to the pocket surface in the axial direction with respect to the portion contacting the rolling element, Ball bearing.

2. The flange portion protrudes continuously along the pocket surface around the axis, The ball bearing according to claim 1.

3. The flange portion is adapted to make the pocket immovable relative to the rolling element during the contact, The ball bearing according to claim 1.

4. The flange portion is adapted to make the pocket immovable relative to the rolling element together with the pocket surface during the contact, The ball bearing according to claim 1.

5. In the ball bearing having the flange portion adapted to contact, from the radially inner side, at least the rolling element located at the minor diameter position of the inner ring, The diameter of the flange portion in a cross-section orthogonal to the axis at a predetermined position in the radial direction within the range on the axis of the flange portion is the same as the diameter of the rolling element in a cross-section orthogonal to the minor axis at a predetermined position in the radial direction on the minor axis of the rolling element located at the position of the minor diameter of the inner ring. The ball bearing according to claim 3.

6. In the ball bearing having the flange portion that comes into contact with at least the rolling element located at the major diameter position of the inner ring from the outside in the radial direction, The diameter of the flange portion in a cross-section orthogonal to the axis at a predetermined position in the radial direction within the range on the axis of the flange portion is the same as the diameter of the rolling element in a cross-section orthogonal to the major axis at a predetermined position in the radial direction on the major axis of the rolling element located at the major diameter position of the inner ring. The ball bearing according to claim 3.

7. In each of the pockets, the flange portion is provided adjacent to the pocket surface on the inner side in the radial direction. The ball bearing according to any one of claims 1 to 4.

8. In each of the pockets, the flange portion is provided adjacent to the pocket surface on the outer side in the radial direction. The ball bearing according to any one of claims 1 to 4.

9. The flange portion has a surface extending around the axis that expands in diameter toward the side in the direction of contacting the rolling element in the axial direction. The ball bearing according to any one of claims 1 to 6.