Ball bearing

Abstract

A ball bearing 10 comprises an inner race 11, an outer race 12, a plurality of balls 13, and an annular wave-shaped cage 14 that holds the plurality of balls 13. The wave-shaped cage 14 has: two wave-shaped discs 31, 32 which are annular and which each have flat parts and accommodation parts alternatingly in the bearing circumferential direction; and a rivet 33 which is for joining two flat parts 42, 52 that overlap in the bearing axial direction. The flat parts 42, 52 have rivet holes 43, 53 through which the rivet 33 passes. When the diameter of a virtual circle Q that passes through the center position P in the bearing radial direction of the flat parts 42, 52 is represented as A and the diameter of a pitch circle Z of the rivet holes 43, 53 is represented as B, the expression A>B is satisfied.

Description

Ball bearing

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

[0002] Ball bearings are used in various rotating devices, for example, in the e-Axle of an automobile. In this case, the ball bearing rotates at high speed, and the cage needs to hold the balls appropriately. As a cage for a ball bearing, for example, as in Patent Document 1, a wave-shaped cage in which two wave-shaped annular parts (wave-shaped disks) are joined by rivets is known.

[0003] Japanese Patent Application Laid-Open No. 2015-44220

[0004] The wave-shaped disk is made of metal and formed by pressing. The wave-shaped cage has pockets for accommodating the balls, and it is relatively difficult to set the gap between the pockets and the balls. When a ball bearing having such a wave-shaped cage is used particularly at high speed, it is necessary to improve the dimensional accuracy (accuracy of the gap) of the wave-shaped cage.

[0005] The wave-shaped cage has two wave-shaped disks, and these wave-shaped disks are joined by rivets. Due to the influence of the rivets, such as press-fitting of the rivets into the rivet holes of the wave-shaped disks and caulking of the rivets, the wave-shaped disks may be greatly warped. When the wave-shaped disks are greatly warped, the dimensional accuracy of the wave-shaped cage decreases. Therefore, an object of the present invention is to provide a ball bearing having technical means capable of suppressing the warping of the wave-shaped cage.

[0006] The ball bearing of the present invention has an inner ring, an outer ring, a plurality of balls, and an annular wave-shaped cage for holding the plurality of balls. The wave-shaped cage has two annular wave-shaped disks having flat portions and accommodating portions alternately along the circumferential direction of the bearing, and a rivet for joining the two flat portions overlapping in the axial direction of the bearing. The flat portion has a rivet hole through which the rivet passes. When the diameter of a virtual circle passing through the center position in the radial direction of the bearing of the flat portion is A and the diameter of the pitch circle of the rivet holes is B, A > B.

[0007] Figure 1 is a cross-sectional view showing one embodiment of the ball bearing of the present invention. Figure 2 is a perspective view of a corrugated retainer. Figure 3 is a cross-sectional view of a part of the corrugated retainer. Figure 4 is an explanatory diagram showing a part of the two corrugated discs. Figure 5 is an explanatory diagram showing a part of the two corrugated discs.

[0008] <Outline of Embodiments of the Present Invention> The outline of embodiments of the present invention will be described below. (1) A ball bearing according to an embodiment of the present invention comprises an inner ring, an outer ring, a plurality of balls, and an annular corrugated retainer that holds the plurality of balls, wherein the corrugated retainer comprises two annular corrugated discs having flat portions and housing portions alternately along the bearing circumferential direction, and rivets for joining the two flat portions that overlap in the bearing axial direction, wherein the flat portions have rivet holes through which the rivets pass, and when the diameter of a virtual circle passing through the center position of the flat portion in the bearing radial direction is A, and the diameter of the pitch circle of the rivet hole is B, then A > B.

[0009] With respect to the annular corrugated disc, the inner circumference is more rigid than the outer circumference. Due to the relationship A > B, the flat portion of the corrugated disc has rivet holes that are biased towards the inner circumference. As a result, the warping of the corrugated disc caused by the rivets is suppressed, and consequently, the warping of the corrugated holder, which is formed by joining two corrugated discs, can be suppressed.

[0010] (2) In the ball bearing of (1) above, if the inner diameter of the corrugated disc is C, the thickness of the flat portion is D, and the diameter of the rivet hole is E, then B > (C + 1.4 × D + E). In the flat portion, the rivet hole is biased toward the inner circumference side of the corrugated disc, but with the above configuration, the dimension between the inner surface of the corrugated disc and the rivet hole is appropriately ensured. For example, the rivet hole is formed by punching. The reduction in the dimensional accuracy of the rivet hole is suppressed.

[0011] (3) In the ball bearing of (1) or (2) above, the rivet has a head, a body, and a crimped tip, and the body has a large diameter portion that fits tightly into the first rivet hole of the first corrugated disc, and a small diameter portion that passes through the second rivet hole of the second corrugated disc and is smaller in diameter than the large diameter portion. The rivet before crimping is held in the rivet hole of the first corrugated disc. The second corrugated disc is combined with the first corrugated disc to facilitate the assembly of the corrugated retainer.

[0012] (4) In the ball bearing described in (3) above, if the diameter of the rivet hole is E and the width dimension of the flat portion in the bearing radial direction is F, then E / F ≤ 0.45. As the rivet hole becomes smaller, it becomes easier to offset the position of the rivet hole toward the inner circumference side of the corrugated disc. The rivet size becomes smaller, making it possible to suppress the effect of the rivet on the warping of the corrugated disc.

[0013] (5) In the ball bearing of (3) or (4) above, if the diameter of the rivet hole is E and the outer diameter of the crimped tip is G, then G / E ≤ 1.45. The crimped tip is small, which makes it possible to suppress the effect of warping of the corrugated disc due to rivet crimping.

[0014] <Details of Embodiments of the Invention> Figure 1 is a cross-sectional view showing one embodiment of the ball bearing of the present invention. The ball bearing 10 shown in Figure 1 has an inner ring 11, an outer ring 12, a plurality of balls 13 provided between the inner ring 11 and the outer ring 12, and an annular corrugated retainer 14 that holds the plurality of balls 13. Figure 1 shows a cross-section including the center line CL of the ball bearing 10.

[0015] The directions of the rolling bearing 10 and the corrugated retainer 14 are defined as follows: The direction along the center line CL of the ball bearing 10, and the direction parallel to the center line CL, are defined as the axial direction of the rolling bearing 10 and are called the "bearing axial direction." The direction perpendicular to the center line CL is defined as the radial direction of the rolling bearing 10 and is called the "bearing radial direction." The direction along the circle centered on the center line CL is defined as the circumferential direction of the rolling bearing 10 and is called the "bearing circumferential direction."

[0016] In the state shown in Figure 1, the center line of the corrugated retainer 14 coincides with the center line CL of the rolling bearing 10. Therefore, each direction of the corrugated retainer 14 is defined by each direction of the rolling bearing 10. In other words, the axial, radial, and circumferential directions of the corrugated retainer 14 coincide with (are the same as) the bearing axial direction, bearing radial direction, and bearing circumferential direction, respectively. In the following, the configuration of the corrugated retainer 14 will be described using each direction of the rolling bearing 10.

[0017] The inner ring 11 is an annular member and has an inner ring raceway 21 on its outer circumference into which the balls 13 roll and make contact. The outer ring 12 is an annular member and has an outer ring raceway 22 on its inner circumference into which the balls 13 roll and make contact. Multiple balls 13 are provided between the inner ring raceway 21 and the outer ring raceway 22. The corrugated retainer 14 holds the multiple balls 13 at intervals in the circumferential direction. The corrugated retainer 14 is made of metal, particularly iron-based metal.

[0018] Figure 2 is a perspective view of the corrugated retainer 14. Figure 2 shows the state of the corrugated retainer 14 before assembly is complete (before joining with rivets 33). The corrugated retainer 14 has a plurality of pockets 15 and a plurality of connecting parts 16. Each pocket 15 has a shape that follows the outer surface of a single ball 13 and is a part that accommodates a single ball 13. The connecting parts 16 are parts that connect adjacent pockets 15, 15 in the bearing circumferential direction. The pockets 15 and connecting parts 16 are arranged alternately along the bearing circumferential direction.

[0019] The corrugated holder 14 has two corrugated discs 31 and 32 that sandwich a plurality of balls 13 from both axial sides, and a rivet 33. The corrugated disc 31 on the first axial side (left side in Figure 2) is the first corrugated disc 31, and the corrugated disc 32 on the second axial side (right side in Figure 2) is the second corrugated disc 32. Each of the corrugated discs 31 and 32 is an annular member having an uneven corrugated shape. Each of the corrugated discs 31 and 32 is a plastically deformed product formed by press-working a thin sheet metal member. The first corrugated disc 31 and the second corrugated disc 32 have the same shape. The first corrugated disc 31 and the second corrugated disc 32 are separate parts and are joined and integrated by the rivet 33.

[0020] The first corrugated disc 31 is annular and has a plurality of first housing portions 41 and a plurality of first flat portions 42. The first corrugated disc 31 has the first housing portions 41 and the first flat portions 42 alternately along the bearing circumferential direction. The first housing portion 41 is a thin, hemispherical portion that has a shape along the outer circumferential surface of the ball 13. The first housing portion 41 becomes part (half) of the pocket 15. A gap is provided between the first housing portion 41 and the ball 13.

[0021] The first flat portion 42 is a thin, flat plate portion that connects adjacent first housing portions 41, 41 in the bearing circumferential direction. The first flat portion 42 is part (half) of the connecting portion 16. The first flat portion 42 has a first rivet hole 43 through which the rivet 33 (body portion 36) passes (see Figure 3). Figure 3 is a cross-sectional view of a part of the corrugated retainer 14, showing the state after the assembly of the corrugated retainer 14 is completed (after joining with rivets 33).

[0022] In Figure 2, the second corrugated disc 32 is annular and has a plurality of second housing portions 51 and a plurality of second flat portions 52. The second corrugated disc 32 has the second housing portions 51 and the second flat portions 52 alternately along the bearing circumferential direction. The second housing portion 51 is a thin, plate-like hemispherical portion that has a shape along the outer circumferential surface of the ball 13. The second housing portion 51 becomes the other half of the pocket 15. A gap is provided between the second housing portion 51 and the ball 13.

[0023] The second flat portion 52 is a thin, flat plate portion that connects adjacent second housing portions 51, 51 in the bearing circumferential direction. The second flat portion 52 is the other half of the connecting portion 16. The second flat portion 52 has a second rivet hole 53 through which the rivet 33 (body portion 36) passes (see Figure 3).

[0024] The rivet 33 is a plastically deformable member that joins two flat portions 42 and 52 that overlap in the bearing axial direction. The rivet 33 has a head 35, a body 36, and a crimped tip 37 (see Figure 3). The diameter H of the head 35 is greater than the diameter E of the rivet holes 43 and 53. The body 36 passes through the rivet holes 43 and 53. The tip 37 is crimped, and the diameter G of the tip 37 is greater than the diameter E of the rivet holes 43 and 53. The rivet 33 integrates the first corrugated disc 31 and the second corrugated disc 32, forming a single corrugated retainer 14.

[0025] The body 36 of the rivet 33 is cylindrical and has a large diameter portion 361 on the head 35 side and a small diameter portion 362 on the tip 37 side. The large diameter portion 361 passes through the first rivet hole 43 and fits tightly into the first rivet hole 43. In other words, the outer diameter d1 of the large diameter portion 361 is slightly larger than the diameter E of the first rivet hole 43 (d1 > E).

[0026] The small-diameter portion 362 has a smaller diameter than the large-diameter portion 361. The small-diameter portion 362 passes through the second rivet hole 53, leaving a gap between it and the second rivet hole 53, and does not fit into the second rivet hole 53. In other words, the outer diameter d2 of the small-diameter portion 362 is slightly smaller than the diameter E of the second rivet hole 53 (d2 < E). Note that the diameter E of the first rivet hole 43 and the diameter E of the second rivet hole 53 are the same. The first corrugated disc 31 and the second corrugated disc 32 have the same shape, including the rivet holes 43 and 53.

[0027] The large-diameter portion 361 of the rivet 33 fits snugly into the first rivet hole 43. Therefore, when assembling the corrugated retainer 14, the rivet 33 is held by the first corrugated disc 31 before crimping. The second corrugated disc 32 is then combined with the first corrugated disc 31, and the tip 37 of the rivet 33 is crimped, thereby assembling the corrugated retainer 14, making the assembly process easy.

[0028] Figures 4 and 5 are explanatory diagrams showing parts of the two corrugated discs 31 and 32. Figures 4 and 5 are views along the bearing axis. The first corrugated disc 31 and the second corrugated disc 32 are overlapping in the bearing axis direction. Figure 4 shows the state in which the tip 37 of the rivet 33 is crimped and the corrugated retainer 14 is assembled. Figure 5 is an illustrative diagram showing the state in which the rivet 33 has been removed.

[0029] Multiple first rivet holes 43 are provided in the first corrugated disc 31 along a single pitch circle Z. Multiple second rivet holes 53 are provided in the second corrugated disc 32 along a single pitch circle Z. The diameter of the pitch circle Z of the first rivet holes 43 is the same as the diameter of the pitch circle Z of the second rivet holes 53. In Figures 4 and 5, the diameters of these pitch circles Z are indicated by "B".

[0030] A virtual circle Q is shown in Figures 4 and 5. The virtual circle Q is a circle centered on the centerline CL (bearing centerline) of the ball bearing 10, and passes through the center position P in the bearing radial direction of the flat sections 42 and 52. The center position P will be explained below. The intersection point of the virtual straight line K0 in the bearing radial direction that passes through the centerline CL of the ball bearing 10 and the outer circumferential surface of the flat sections 42 and 52 is "K1". The intersection point of the virtual straight line K0 and the inner circumferential surface of the flat sections 42 and 52 is "K2". The center position P is the midpoint between the intersection points K1 and K2 on the virtual straight line K0. In other words, the distance between the intersection point K1 and the center position P is "S1", and the distance between the intersection point K2 and the center position P is "S2", so S1 and S2 are the same value.

[0031] The diameter of the virtual circle Q passing through the central position P is "A". The relationship between the diameter A of the virtual circle Q and the diameter B of the pitch circle Z is given by the following equation (1), as shown in Figures 4 and 5.

[0032] A>B...Formula (1)

[0033] With respect to the annular first and second corrugated discs 31 and 32, the inner circumference is more rigid than the outer circumference. This is also true for general annular members. In the case of the corrugated retainer 14 of this embodiment, according to the relationship in formula (1), the flat portions 42 and 52 each have rivet holes 43 and 53 that are offset towards the inner circumference side from the center position P.

[0034] Therefore, when the body 36 of the rivet 33 is press-fitted into the first rivet hole 43, and when the tip 37 is crimped, the warping of the first and second corrugated discs 31 and 32 caused by the rivet 33 is suppressed. In other words, in the case of the corrugated retainer 14 of this embodiment, the position of the rivet 33 (pitch circle Z) coincides with the rigidity center position of the corrugated discs 31 and 32, or is closer to the rigidity center position than in the conventional design. The rigidity center position is located inward in the bearing radial direction from the bearing radial center position P, and is a position in which tilting or warping is less likely to occur in each of the corrugated discs 31 and 32 due to their geometric shape.

[0035] As described above, according to formula (1), the warping of the first and second corrugated discs 31 and 32 caused by the rivets 33 is suppressed. As a result, the warping of the corrugated retainer 14 having these first and second corrugated discs 31 and 32 is suppressed.

[0036] The diameter B of the pitch circle Z of the first and second rivet holes 43 and 53 will be explained further. In Figures 4 and 5, the inner circumferential surfaces 34 of the first and second corrugated discs 31 and 32 have a shape that follows a cylindrical surface centered on the center line CL. The inner diameter of the inner circumferential surface 34 is "C". In Figure 3, the thickness of the first and second flat portions 42 and 52 is "D". The diameter of the first and second rivet holes 43 and 53 is "E". In this embodiment, the diameter B of the pitch circle Z satisfies the following equation (2) in relation to the diameter B of the pitch circle Z, the inner diameter C, and the thickness D.

[0037] B>(C+1.4×D+E)...Formula (2)

[0038] Here, the first and second rivet holes 43 and 53 are obtained by punching using a press. Taking the first corrugated disc 31 as an example, in order to prevent the shape of the rivet hole 43 from being distorted during punching and thus reducing its dimensional accuracy, it is desirable that the dimension V between the inner circumferential surface 34 of the first corrugated disc 31 and the rivet hole 43 (see Figure 5) be greater than 70% of the thickness D of the flat portion 42 (V > 0.7 × D). The dimension V is "B / 2 - E / 2 - C / 2". Thus, equation (2) is obtained.

[0039] In this embodiment, in the flat portions 42 and 52, the rivet holes 43 and 53 are biased towards the inner circumference side of the corrugated discs 31 and 32. However, according to the configuration of formula (2), the dimension V between the inner surface 34 of the corrugated discs 31 and 32 and the rivet holes 43 and 53 is appropriately secured. This suppresses a decrease in dimensional accuracy when punching out the rivet holes 43 and 53. In order to more effectively suppress the decrease in dimensional accuracy when punching out the rivet holes 43 and 53, the following formula (3) may be used instead of formula (2).

[0040] B>(C+1.6×D+E) ...Formula (3)

[0041] Let us further explain the diameter E of the rivet holes 43 and 53. In Figure 5, the width dimension of the flat portions 42 and 52 in the bearing radial direction is "F". Note that F = S1 + S2. It is preferable that the diameter E of the rivet holes 43 and 53 and the width dimension F of the flat portions 42 and 52 satisfy the following equation (4). Furthermore, it is preferable that it satisfies equation (5).

[0042] E / F≦0.45...Equation (4) 0.35≦E / F...Equation (5)

[0043] According to equation (4), the rivet holes 43 and 53 become smaller with respect to the bearing radial width dimension F of the flat portions 42 and 52. This makes it easy to offset the position of the rivet holes 43 and 53 towards the inner circumference of the corrugated discs 31 and 32. As the rivet holes 43 and 53 become smaller, the size of the rivets 33 also becomes smaller, making it possible to suppress the effect of the rivets 33 on the warping of the corrugated discs 31 and 32.

[0044] Describe the dimensions of the caulked tip 37 of the rivet 33. In FIG. 3, the outer diameter of the caulked tip 37 is "G". It is preferable that the outer diameter G and the diameters E of the rivet holes 43 and 53 satisfy the following formula (6). Further, it is preferable to satisfy formula (7).

[0045] G / E ≤ 1.45 ··· Formula (6) 1.35 ≤ G / E ··· Formula (7)

[0046] According to formula (6), the caulked tip 37 is relatively small. Therefore, it is possible to suppress the influence of the warpage of the corrugated disks 31 and 32 caused by caulking the rivet 33.

[0047] As described above, according to the corrugated retainer 14 of the present embodiment, the warpage of the corrugated disks 31 and 32 due to the rivet 33 is suppressed, and it is possible to suppress a decrease in the dimensional accuracy of the corrugated retainer 14. As a result, the accuracy of the clearance formed between the ball 13 and the pocket 15 is improved. Therefore, particularly when the ball bearing 10 is used at high speed rotation, a suitable corrugated retainer 14 can be obtained.

[0048] 〔Others〕The above embodiments are illustrative in all respects and not restrictive. The scope of the rights of the present invention is shown not by the above embodiments but by the scope of the claims, and includes all modifications within the scope equivalent to the configurations described in the claims.

[0049] 10 Ball bearing 11 Inner ring 12 Outer ring 13 Ball 14 Corrugated retainer 31 First corrugated disk 32 Second corrugated disk 33 Rivet 35 Head 36 Body 37 Tip 41 First accommodating portion 42 First flat portion 43 First rivet hole 51 Second accommodating portion 52 Second flat portion 53 Second rivet hole 361 Large diameter portion 362 Small diameter portion A Diameter of virtual circle B Pitch circle diameter C Inner diameter of corrugated disk D Thickness of flat portion E Diameter of rivet hole F Width dimension of flat portion in bearing radial direction G Outer diameter of caulked tip P Center position Q Virtual circle Z Pitch circle

Claims

1. A ball bearing comprising an inner ring, an outer ring, a plurality of balls, and an annular corrugated retainer holding the plurality of balls, wherein the corrugated retainer comprises two annular corrugated discs having alternating flat portions and housing portions along the bearing circumferential direction, and rivets for joining the two flat portions that overlap in the bearing axial direction, wherein the flat portions have rivet holes through which the rivets pass, and when the diameter of a virtual circle passing through the bearing radial center of the flat portion is A, and the diameter of the pitch circle of the rivet hole is B, A > B.

2. The ball bearing according to claim 1, wherein, when the inner diameter of the corrugated disc is C, the thickness of the flat portion is D, and the diameter of the rivet hole is E, B > (C + 1.4 × D + E).

3. The ball bearing according to claim 1 or 2, wherein the rivet has a head, a body, and a crimped tip, and the body has a large-diameter portion that fits tightly into the first rivet hole of the first corrugated disc, and a small-diameter portion that passes through the second rivet hole of the second corrugated disc and has a smaller diameter than the large-diameter portion.

4. The ball bearing according to claim 3, wherein E is the diameter of the rivet hole and F is the width dimension of the flat portion in the bearing radial direction, and E / F ≤ 0.

45.

5. The ball bearing according to claim 3 or claim 4, wherein, when the diameter of the rivet hole is E and the outer diameter of the crimped tip is G, G / E ≤ 1.45.

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