JP7719618B2 - ball bearing - Google Patents

Description

This invention relates to a ball bearing that can be used in applications where large centrifugal forces are applied due to the bearing itself revolving.

In recent years, changes in the automotive environment, such as the need for 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. Therefore, as shown in Patent Document 1 below, for example, bent claw cages, which can more easily accommodate smaller bearing cross-sectional heights, are often used.

As shown in Figure 5, this ball bearing 20 has an inner ring 21, an outer ring 22 arranged coaxially around the inner ring 21, balls 23 interposed between the inner ring 21 and the outer ring 22, and a claw-shaped cage 24 that holds the balls 23 at a predetermined circumferential distance. The claw-shaped cage 24 is composed of a pair of segments 24a, 24b split axially. Each segment 24a, 24b has hemispherical inner pockets 25 formed at predetermined circumferential distances to hold the balls 23.

As shown in Figures 6 and 7, radially bent claws 26 are formed between each pocket 25 of one of the segments 24a. These claws 26 are sandwiched between each pocket 25 of the other segment 24b (shown in Figures 8 and 9) and crimped to integrate the two segments 24a and 24b. Small ball bearings 20 in particular often use an inner ring guide type in which the integrated cage 24 is guided by the outer diameter surface of the inner ring 21.

Japanese Patent Application Laid-Open No. 2001-165171

In particular, when a small-diameter/compact ball bearing 20 (for example, a bearing in which a diameter series index (= (outer diameter - 11) / inner diameter) is defined based on the inner diameter of the inner ring 21 and the outer diameter of the outer ring 22, and this diameter series index and the width of the inner and outer rings 21, 22 satisfy the relationship: diameter series index x width ≦ 6 (both units are mm)) is used in an automotive component, the 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 associated with this revolution acts as an external force, via the balls 23, to open the claws 26 of the claw-bent cage 24 (particularly where the stippled pattern on the inside of the claws 26 is darker), potentially compromising the operational stability of the ball bearing 20.

When a riveted cage is used in such small-diameter, compact ball bearings 20, the radial gap between the outer diameter of the inner ring and the inner diameter of the outer ring tends 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 the generation of guide torque. To use a cage with rolling element guide, the cage band width must be reduced, but this creates the problem of reducing 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, but this reduces the thickness between the inner ring inner diameter and the raceway groove, which could make it difficult to ensure the strength of the inner ring 21.

The objective of this invention is to ensure stable operation of small-diameter, compact ball bearings that use riveted cages.

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 integrated 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 a circumferential cross section is in the range of 1.015≦curvature≦1.08.

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 generation, and guide torque generation caused by interference between the cage and inner ring, ensuring stable bearing operation. If the outer diameter of the inner ring is reduced to ensure the ball diameter and inner ring groove depth satisfy the above relationship, the allowable axial load will decrease, but by increasing the curvature of the inner ring raceway groove to the above range, the balls are more easily held by the inner ring raceway groove, ensuring the specified allowable axial load.

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

Ball bearings with the relationship between ball diameter and inner ring groove depth, and the range of curvature specified as above, are 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.

In each of the above configurations, it is preferable that the ball diameter be 3.5 mm or greater.

This ensures that the radial gap between the outer diameter surface of the inner ring and the inner diameter surface of the outer ring is as large as possible, ensuring that the cage guides the rolling elements reliably.

In each of the above configurations, the inner diameter of the rivet hole formed in the split piece for passing the rivet 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 of the rivet hole is larger than the shank diameter of the rivet. It is preferable 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 of the rivet hole and the outer diameter of the rivet, satisfy the relationship: gap volume < interference volume.

In this way, the pair of cage segments can be securely fastened together with rivets, preventing the segments from separating due to large external forces acting on the cage segments even when large centrifugal forces are applied due to the bearing itself revolving.

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

This gives the cage high hardness and moderate toughness, reducing wear on the cage and ensuring stable operation.

In each of the above configurations, it is preferable to use cold-rolled steel plate as the material for the cage.

This allows the cage to have sufficient tensile strength (e.g., 240 MPa), thereby reducing problems during operation.

The ball bearing of this invention uses a riveted cage, 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 cage acts as a rolling element guide, preventing wear, heat generation, and the generation of guide torque that would otherwise result from interference between the cage and the inner ring, while also ensuring a specified allowable axial load and ensuring stable operation of the bearing.

1 is a cross-sectional view showing an embodiment of a ball bearing according to the present invention; FIG. 2 is a front view showing a main part of the cage of the ball bearing shown in FIG. 1; 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. FIG. 3 is a diagram showing an example of a three-dimensional calculation result of an external force acting on the cage shown in FIG. 2 . Cross-sectional view of a ball bearing according to the prior art FIG. 10 is a perspective view showing a main portion of one of the divided pieces of the bent claw retainer; FIG. 7 is a front view of one of the divided pieces shown in FIG. FIG. 10 is a perspective view showing a main portion of the other divided piece of the bent claw retainer; FIG. 9 is a front view of the other divided piece shown in FIG. FIG. 7 is a diagram showing an example of a three-dimensional calculation result of an external force acting on one of the divided pieces shown in FIG. 6 .

One 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 comprises an inner ring 2, an outer ring 3 arranged coaxially around the inner ring 2 on the outer periphery of the inner ring 2, balls 4 interposed between the inner ring 2 and the outer ring 3, and a cage 5 formed of axially separated segments 5a, 5b that are crimped together with rivets 6 and have pockets 7 formed therein that hold the balls 4 at predetermined intervals around the circumference.

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. Furthermore, 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. Furthermore, the circumferential direction around the central axis will be referred to as the "circumferential direction."

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 outer ring raceway groove 11. The inner ring 2, outer ring 3, and balls 4 are all made of bearing steel.

As shown in Figure 2, rivet holes 12 for passing rivets 6 are formed between the pockets 7 of the split pieces 5a and 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 Figure 3, a tapered surface 13 is formed at the tip end (lower side in Figure 3) of the rivet hole 12 so that its inner diameter gradually becomes larger than the shank diameter of the rivet 6. The cage 5 is made of cold-rolled steel plate (SPC) with a tensile strength of 240 MPa or more. The surface of the cage 5 is coated with a soft nitride coating that provides high hardness and moderate toughness.

In this cage 5, 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 (area surrounded by a two-dot chain line in Figure 3) when no external force is acting on the rivet 6 and rivet hole 12, and the gap volume, which is the gap between the inner diameter of the tip of the rivet hole 12 and the outer diameter of the rivet 6, satisfy the relationship "gap volume < interference volume." Therefore, the pair of segments 5a, 5b of the cage 4 can be reliably integrated by crimping them with the rivet 6, and even if a large centrifugal force is applied due to the revolution of the ball bearing 1 itself, a large external force acting on the segments of the cage 5 can be prevented, preventing the segments 5a, 5b from separating from each other.

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.

In addition, in the ball bearing 1 according to this embodiment, the curvature of the inner ring raceway groove 8 in circumferential cross section is set within the range of "1.015 ≦ curvature ≦ 1.08." Reducing the inner ring outer diameter to ensure that the ball diameter D and inner ring groove depth d satisfy the above relationship reduces the allowable axial load, but by increasing the curvature to the above range, the inner ring raceway groove 8 can more easily hold the balls 4, ensuring the 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 the specified allowable axial load.

In addition, in the ball bearing 1 according to this embodiment, the ball diameter D is 3.5 mm or more. 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, ensuring that the cage 5 guides the rolling elements reliably. When the ball diameter D is increased 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.

Although the size of the ball bearing 1 according to this embodiment is not particularly limited, it is primarily intended for small-diameter and compact sizes in which, when a diameter series index (= (outer diameter _Dout - 11) / inner diameter _Din ) is defined _from the inner diameter dimension Din of the _inner ring 2 and the outer diameter dimension Dout of the outer ring 3, this 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)." With small-diameter and compact ball bearings 1, it is difficult to increase the radial gap between the inner ring outer diameter surface 10 and the outer ring inner diameter 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 described above, the cage 5 can be used as a rolling element guide in which the balls 4 stably guide the balls.

Figure 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 indicate 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 Figure 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.

The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. Therefore, the scope of the present invention is indicated by the claims, not by the above description, and is intended to include meanings equivalent to the claims and all modifications thereof.

REFERENCE SIGNS LIST 1 ball bearing 2 inner ring 3 outer ring 4 ball 5 cage 5a, 5b divided piece 6 rivet 7 pocket 8 inner ring raceway groove 10 inner ring outer diameter surface 12 rivet hole 13 tapered surface d inner ring groove depth D ball diameter D _in (inner ring) inner diameter dimension D _out (outer ring) outer diameter dimension w (inner and outer rings) width dimension

Claims (5)

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 ball bearing according to claim 1, wherein the inner diameter dimension (D _in ) of the inner ring (2), the outer diameter dimension (D _out ) of the outer ring (3), and the width dimension (w) of the inner and outer rings (2, 3) satisfy the relationship ((outer diameter dimension D _out - 11) / inner diameter dimension D _in ) × width dimension w≦6 (all in mm). A ball bearing according to claim 1 or 2, wherein the ball diameter (D) is 3.5 mm or more. A ball bearing according to any one of claims 1 to 3, wherein a soft nitride coating is formed on the surface of the cage (5). A ball bearing according to any one of claims 1 to 4, wherein the retainer (5) is made of cold-rolled steel plate.