Jade Axis

Abstract

To provide a ball bearing which employs a rivet-caulking cage, and is secured in a stable operation.SOLUTION: In a ball bearing having an inner ring 2, an outer ring 3 arranged at an external peripheral side of the inner ring 2 coaxially with the inner ring 2, balls 4 interposed between the inner ring 2 and the outer ring 3, and a cage 5 in which split pieces 5a, 5b which are split in an axial direction are integrated to each other by being caulked with rivets 6, and pockets 7 for holding the balls 4 in a peripheral direction with prescribed intervals are formed, a ball diameter D being a diameter of the ball 4 and an inner ring groove depth d being a depth of an inner ring raceway groove 8 formed at the inner ring 2 from an inner ring outside-diameter face 10 satisfy a relationship of ball diameter D / inner ring groove depth d>6, and a curvature radius of a cross section in a peripheral direction of the inner ring raceway groove 8 is within 1.015≤curvature radius≤1.08.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention particularly relates to a ball bearing that can be used in applications where a large centrifugal force acts due to the revolving of the bearing itself. [Background technology]

[0002] In recent years, changes in the automobile environment, such as weight reduction, have led to demands for smaller automotive parts such as ball bearings. When ball bearings are made smaller, the bearing cross-sectional height also becomes smaller, so bent-claw cages, which can easily accommodate smaller bearing cross-sectional heights, are often used, as shown in Patent Document 1 below, for example.

[0003] As shown in Figure 5, this ball bearing 20 has an inner ring 21, an outer ring 22 arranged coaxially with the inner ring 21 on the outer peripheral side of the inner ring 21, balls 23 interposed between the inner ring 21 and the outer ring 22, and a claw-bent cage 24 that holds the balls 23 at a predetermined circumferential interval. The claw-bent cage 24 is composed of a pair of segments 24a, 24b that are split axially. Each of the segments 24a, 24b has internally hemispherical pockets 25 formed at predetermined intervals in the circumferential direction to hold the balls 23.

[0004] 6 and 7, radially bent claws 26 are formed between the pockets 25 of one of the segments 24a, and these claws 26 are sandwiched between the pockets 25 of the other segment 24b shown in Figures 8 and 9 and crimped to integrate the two segments 24a, 24b. Particularly in small ball bearings 20, an inner ring guide type is often used in which the integrated cage 24 is guided by the outer diameter surface of the inner ring 21. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-165171 Summary of the Invention [Problem to be solved by the invention]

[0006] In particular, when a small-diameter or compact ball bearing 20 (for example, a bearing in which a diameter series index (= (outer diameter - 11) / bore diameter) is defined based on the inner diameter of inner ring 21 and the outer diameter of outer ring 22, and this diameter series index and the width of inner and outer rings 21, 22 satisfy the relationship: diameter series index x width ≦ 6 (both units are mm)) is used in an automobile part, this ball bearing 20 may be placed in an operating environment in which it revolves. In this case, as shown in Figure 10, an example of a three-dimensional calculation result of the external force acting on one of the segments 24a, the centrifugal force accompanying this revolution acts as an external force, via ball 23, to open the claws 26 of claw-bent cage 24 (particularly where the stippled pattern on the inside of claws 26 is darker), and the operational stability of ball bearing 20 may be impaired.

[0007] If a riveted cage is used in such a small-diameter, compact ball bearing 20, the radial gap between the outer diameter of the inner ring and the inner diameter of the outer ring is likely to become small. This requires the cage to be guided by the inner ring, but interference between the cage and the inner ring 21 can cause problems such as wear, heat generation, and guide torque. To use a rolling element guided cage, the cage band width must be reduced, but this reduces the strength of the cage. Furthermore, to prevent interference between the cage and the inner ring 21, the ball diameter must be increased within the limited bearing cross section. However, this reduces the wall thickness between the inner ring inner diameter and the raceway groove, potentially making it difficult to ensure the strength of the inner ring 21.

[0008] Therefore, an object of the present invention is to ensure stable operation of small-diameter and small-sized ball bearings that use riveted cages. [Means for solving the problem]

[0009] In order to solve this problem, in this invention, With inner circle, an outer ring arranged coaxially with the inner ring on the outer peripheral side of the inner ring; a ball interposed between the inner ring and the outer ring; a cage in which split pieces are axially separated and joined together by rivets, and in which pockets are formed to hold the balls at predetermined intervals in the circumferential direction; In a ball bearing having A ball bearing was constructed in which the ball diameter, which is the diameter of the balls, and the inner ring groove depth, which is the depth of the inner ring raceway groove formed in the inner ring from the outer diameter surface of the inner ring, satisfy the relationship: ball diameter / inner ring groove depth > 6, and the curvature of the inner ring raceway groove in the circumferential cross section is in the range of 1.015≦curvature≦1.08.

[0010] This ensures as large a radial gap as possible between the outer diameter surface of the inner ring and the inner diameter surface of the outer ring, allowing the cage to guide the rolling elements. This prevents wear, heat, and guide torque caused by interference between the cage and the inner ring, ensuring stable bearing operation. While reducing the outer diameter of the inner ring to ensure that the ball diameter and inner ring groove depth satisfy the above relationship reduces the allowable axial load, increasing the curvature of the inner ring raceway groove to the above range makes it easier for the inner ring raceway groove to hold the balls, ensuring a specified allowable axial load.

[0011] In the above configuration, it is preferable that the inner diameter dimension of the inner ring, the outer diameter dimension of the outer ring, and the width dimensions of the inner and outer rings satisfy the relationship ((outer diameter dimension - 11) / inner diameter dimension) × width dimension ≦ 6 (all in mm).

[0012] A ball bearing in which the relationship between ball diameter and inner ring groove depth and the range of curvature are specified as described above is particularly suitable for small-diameter and compact ball bearings whose inner diameter, outer dimensions, and width dimensions satisfy the above relationships, and can improve the stable operation of these ball bearings.

[0013] In each of the above configurations, it is preferable that the ball diameter is 3.5 mm or more.

[0014] In this way, it is possible to ensure as large a radial gap as possible between the outer diameter surface of the inner ring and the inner diameter surface of the outer ring, and the cage can reliably guide the rolling elements.

[0015] In each of the above configurations, the inner diameter of the rivet hole formed in the split piece for passing the rivet through is smaller than the shank diameter of the rivet, there is an interference between the rivet and the rivet hole, and a tapered surface is formed so that the inner diameter at the tip end of the rivet hole is larger than the shank diameter of the rivet, and it is preferable that the configuration be such that the interference volume, which is the overlap between the outer diameter surface of the rivet and the inner diameter surface of the rivet hole when no external force is acting on the rivet and the rivet hole, and the gap volume, which is the gap between the inner diameter at the tip end of the rivet hole and the outer diameter of the rivet, satisfy the relationship: gap volume < interference volume.

[0016] In this way, the pair of split pieces of the retainer can be securely joined together by fastening them with rivets, and even if a large centrifugal force acts on the bearing itself due to revolution, etc., it is possible to prevent a large external force from acting on the split parts of the retainer and causing the split pieces to separate.

[0017] In each of the above configurations, it is preferable that a soft nitride coating is formed on the surface of the cage.

[0018] This makes it possible to impart high hardness and appropriate toughness to the cage, thereby reducing wear and the like of the cage and ensuring stable operation.

[0019] In each of the above configurations, it is preferable that the cage is made of a cold-rolled steel plate.

[0020] In this way, sufficient tensile strength (for example, 240 MPa) can be imparted to the cage, thereby making it possible to suppress trouble during operation. [Effects of the Invention]

[0021] The ball bearing of this invention employs a riveted retainer, and by specifying the relationship between ball diameter and inner ring groove depth, and the range of curvature of the inner ring raceway groove as described above, the retainer acts as a rolling element guide, preventing wear, heat generation, and the generation of guide torque that would otherwise result from interference between the retainer and the inner ring, and ensuring a specified allowable axial load to ensure stable operation of the bearing. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view showing an embodiment of a ball bearing according to the present invention; [Figure 2] A front view showing the main part of the cage of the ball bearing shown in Figure 1 [Figure 3] A cross-sectional view showing a state in which a rivet is inserted into a rivet hole formed in a divided piece of the cage. [Figure 4] A diagram showing an example of the results of a three-dimensional calculation of the external forces acting on the cage shown in Figure 2. [Figure 5] Cross-sectional view of a ball bearing according to the prior art [Figure 6] FIG. 10 is a perspective view showing a main portion of one of the divided pieces of the bent claw retainer; [Figure 7] A front view of one of the split pieces shown in Figure 6 [Figure 8] FIG. 10 is a perspective view showing a main portion of the other divided piece of the bent claw retainer; [Figure 9] FIG. 9 is a front view of the other divided piece shown in FIG. 8 . [Figure 10] FIG. 7 is a diagram showing an example of a three-dimensional calculation result of the external force acting on one of the divided pieces shown in FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0023] An embodiment of a ball bearing 1 according to the present invention will be described with reference to Figures 1 to 4. This ball bearing 1 has an inner ring 2, an outer ring 3 arranged coaxially with the inner ring 2 on the outer peripheral side of the inner ring 2, balls 4 interposed between the inner ring 2 and the outer ring 3, and a cage 5 formed by axially separated segments 5a, 5b that are joined together by rivets 6 and in which pockets 7 are formed to hold the balls 4 at predetermined intervals in the circumferential direction.

[0024] In the following, the direction along the central axis of this ball bearing 1 will be referred to as the "axial direction," which corresponds to the left-right direction in Figure 1. The direction perpendicular to the central axis will be referred to as the "radial direction," which corresponds to the up-down direction in Figure 1. The circumferential direction around the central axis will be referred to as the "circumferential direction."

[0025] The inner ring 2 is an annular member with an inner ring raceway groove 8 formed on its outer circumference and a through hole 9 formed in its axial center for inserting a boss (not shown) such as a pulley. The groove depth d of the inner ring raceway groove 8 is defined by the radial distance from the inner ring outer diameter surface 10 to the groove bottom of the inner ring raceway groove 8. The outer ring 3 is an annular member with an outer ring raceway groove 11 formed on its inner circumference. The balls 4 roll circumferentially, guided by the inner ring raceway groove 8 and the outer ring raceway groove 11. The inner ring 2, outer ring 3, and balls 4 are all made of bearing steel.

[0026] As shown in FIG. 2, rivet holes 12 for passing rivets 6 are formed between the pockets 7 of the split pieces 5a, 5b that make up the cage 5. The inner diameter of these rivet holes 12 is slightly smaller than the shank diameter of the rivet 6, leaving an interference between the rivet 6 and the rivet hole 12. As shown in FIG. 3, a tapered surface 13 is formed at the tip end (the lower side in FIG. 3) of the rivet hole 12 so that the inner diameter gradually becomes larger than the shank diameter of the rivet 6. The material used for this cage 5 is cold-rolled steel plate (SPC) with a tensile strength of 240 MPa or more. The surface of the cage 5 is also formed with a soft nitride coating that has high hardness and moderate toughness.

[0027] In this cage 5, the interference volume, which is the overlap between the outer diameter surface of rivet 6 and the inner diameter surface of rivet hole 12 (the area surrounded by a two-dot chain line in Figure 3) when no external force is acting on rivet 6 and rivet hole 12, and the clearance volume, which is the gap between the inner diameter on the tip side of rivet hole 12 and the outer diameter of rivet 6, satisfy the relationship of "clearance volume < interference volume." For this reason, the pair of split pieces 5a, 5b of cage 4 can be reliably integrated by crimping with rivet 6, and even if a large centrifugal force acts due to the revolution of ball bearing 1 itself, etc., it is possible to prevent the split pieces 5a, 5b from separating from each other due to a large external force acting on the split parts of cage 5.

[0028] In the ball bearing 1 according to this embodiment, the relationship between the ball diameter D and the inner ring groove depth d, which is the radial distance between the inner ring outer diameter surface 10 and the groove bottom of the inner ring raceway 8, is "ball diameter D / inner ring groove depth d>6." This ensures as large a radial gap as possible between the inner ring outer diameter surface 10 and the outer ring inner diameter surface 14, making it easier for the cage 5 to guide the rolling elements. This prevents wear, heat generation, and the generation of guide torque due to interference between the cage 5 and the inner ring 2, ensuring stable operation of the ball bearing 1.

[0029] Furthermore, in the ball bearing 1 according to this embodiment, the curvature of the inner ring raceway groove 8 in its circumferential cross section is set within the range of "1.015 ≦ curvature ≦ 1.08." If the inner ring outer diameter is reduced to make the ball diameter D and inner ring groove depth d satisfy the above relationship, the allowable axial load will decrease, but by increasing the curvature to the above range, the inner ring raceway groove 8 can more easily hold the balls 4, ensuring a specified allowable axial load. Furthermore, by setting this curvature within the range of "1.05 ≦ curvature ≦ 1.07," the balls 4 can roll more smoothly within the inner ring raceway groove 8 while still ensuring a specified allowable axial load.

[0030] Furthermore, in the ball bearing 1 according to this embodiment, the ball diameter D is set to 3.5 mm or more. This ensures that the radial gap between the inner ring outer diameter surface 10 and the outer ring inner diameter surface 14 is as large as possible, ensuring that the cage 5 guides the rolling elements reliably. When the ball diameter D is enlarged in this way, it is common to increase the inner ring groove depth d to ensure a certain allowable axial load. However, in this embodiment, by keeping the curvature within the above range, the certain allowable axial load is ensured without increasing the inner ring groove depth d. This ensures a sufficient thickness between the inner ring inner diameter and the inner ring raceway groove 8, ensuring the strength of the inner ring 2.

[0031] The size of the ball bearing 1 according to this embodiment is not particularly limited, but the inner diameter dimension D of the inner ring 2 in and outer diameter dimension D of outer ring 3 outFrom the diameter series index (= (outer diameter dimension D out -11) / Inner diameter D in ), the diameter series index and the width dimension w of the inner and outer rings 2, 3 satisfy the relationship "diameter series index x width dimension w ≦ 6 (both units are mm)." In small-diameter and small-sized ball bearings 1, it is difficult to increase the radial gap between the inner ring outer diameter surface 10 and the outer ring bore surface 14, and it is often necessary to use an inner ring guide for the cage 5. However, by specifying the relationship between the ball diameter D and the inner ring groove depth d, and the range of curvature of the inner ring raceway groove 8 as above, it is possible to use a rolling element guide in which the cage 5 is stably guided by the balls 4.

[0032] FIG. 4 shows an example of the results of a three-dimensional calculation of the external force acting on the cage 5 when the ball bearing 1 according to this embodiment is placed in an operating environment where it rotates on its own axis and is subjected to a large centrifugal force. The calculation results show the magnitude of the external force using shades of dots, with the maximum stress occurring around the rivet holes 12. This maximum stress is significantly smaller than the maximum stress in the bent-claw cage 24 shown in FIG. 10 (approximately 60% of that in the bent-claw cage 24), and does not exceed the tensile strength of 240 MPa of the material (cold-rolled steel plate) from which the cage 5 is made. Therefore, even in such an operating environment, the split pieces 5a and 5b of the cage 5 will not separate due to external forces, ensuring stable operation of the ball bearing 1.

[0033] The embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive. Therefore, the scope of the present invention is defined by the claims, not by the above description, and is intended to include meanings equivalent to the claims and all modifications thereof. [Explanation of symbols]

[0034] 1 ball bearing 2. Inner circle 3 outer ring 4 balls 5 Cage 5a, 5b split piece 6 rivets 7 pockets 8 Inner ring raceway groove 10 Inner ring outer diameter surface 12 rivet holes 13 Tapered surface d Inner ring groove depth D Ball diameter D in (inner ring) inner diameter D out (Outer ring) outer diameter w (inner and outer ring) width dimension

Claims

1. Inner circle (2) and an outer ring (3) arranged coaxially with the inner ring (2) on the outer peripheral side of the inner ring (2); a ball (4) interposed between the inner ring (2) and the outer ring (3); a cage (5) in which axially separated divided pieces (5a, 5b) are crimped together with rivets (6) to form pockets (7) for holding the balls (4) at predetermined intervals in the circumferential direction; In a ball bearing having a ball diameter (D) that is the diameter of the ball (4) and an inner ring groove depth (d) that is the depth of an inner ring raceway groove (8) formed in the inner ring (2) from an inner ring outer diameter surface (10) satisfy the relationship of ball diameter D / inner ring groove depth d>6; The ball bearing is characterized in that the inner diameter of the rivet hole (12) formed in the split pieces (5a, 5b) for passing the rivet (6) is smaller than the shank diameter of the rivet (6), there is an interference between the rivet (6) and the rivet hole (12), and the inner diameter of the tip end of the rivet hole (12) is larger than the shank diameter of the rivet (6), and the interference volume, which is the overlap between the outer diameter surface of the rivet (6) and the inner diameter surface of the rivet hole (12) when it is assumed that no external force is acting on the rivet (6) or the rivet hole (12), and the gap volume, which is the gap between the inner diameter of the tip end of the rivet hole (12) and the outer diameter of the rivet (6), satisfy the relationship of clearance volume < interference volume.

2. The inner diameter of the inner ring (2) (D ｉｎ ) and the outer diameter dimension (D ｏｕｔ ) and the width dimension (w) of the inner and outer rings (2, 3) is ((outer diameter dimension D ｏｕｔ -11) / inner diameter D ｉｎ 2. The ball bearing according to claim 1, wherein the relationship of:

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18. 19 ...

3. 3. A ball bearing according to claim 1, wherein the ball diameter (D) is 3.5 mm or more.

4. 4. The ball bearing according to claim 1, wherein a soft nitride coating is formed on the surface of the cage.

5. 5. A ball bearing according to claim 1, wherein the retainer (5) is made of a cold-rolled steel plate.

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