JP2025127167A - deep groove ball bearing - Google Patents

Abstract

The present invention aims to improve the dischargeability of lubricating oil in an outer ring guide deep groove ball bearing, and reduce the agitation resistance of the lubricating oil caused by the cage and rolling elements.
[Solution] In an outer ring guide deep groove ball bearing, multiple balls 3 are arranged circumferentially between the raceway surface 5 of the outer ring 1 and the raceway surface 6 of the inner ring 2, the spacing between the balls 3 is maintained by a cage 4, and the cage 4 is guided by a guide surface 8 formed on the inner circumference of the shoulder portion 7 of the outer ring 1.A tapered surface 9 is formed that is inclined so that the inner circumference of the shoulder portion 7 of the outer ring 1 expands in diameter from the guide surface 8 toward the width face of the outer ring 1, and the inclination angle α of the tapered surface 9 is set to be 20° to 35° with respect to the guide surface 8, which is a cylindrical surface parallel to the axis.
[Selected Figure] Figure 1

Description

This invention relates to lubrication in deep groove ball bearings incorporating outer ring guide type cages.

In recent years, there has been an urgent need to popularize electric vehicles, which run on electricity, in light of global climate change countermeasures and energy conservation. Electric vehicles include BEVs (battery electric vehicles), HEVs (hybrid electric vehicles), PHEVs (plug-in hybrid electric vehicles), and FCEVs (fuel cell electric vehicles), and e-axles, which compactly integrate motors, inverters, transmissions, and other components, are being put into practical use as drive units for these vehicles.

In such e-axles, the bearings used on the motor's main shaft need to be able to handle high-speed rotation. However, if deep groove ball bearings are used as these bearings at high speeds, the cage that maintains the spacing between the rolling elements will deform due to centrifugal force, raising concerns that it may interfere with the rolling elements or outer ring, generating wear particles, generating abnormal heat, or shortening the bearing's lifespan. One effective solution to this problem is to use an outer ring guided cage, as described in Patent Document 1.

As shown in Figure 6, an outer ring guided deep groove ball bearing has multiple balls 53 arranged circumferentially between the raceway surface 55 of the outer ring 51 and the raceway surface 56 of the inner ring 52. The spacing between the balls 53 is maintained by a cage 54, which is guided by a guide surface 58, a cylindrical surface parallel to the axis formed on the inner circumference of the shoulder 57 of the outer ring 51.

By the way, there are two types of bearing lubrication: grease lubrication, which uses a semi-solid, cream-like grease, and oil lubrication, which uses liquid lubricating oil. Oil lubrication is the mainstream for e-axles, and many motor main shaft bearings are also designed to be lubricated with the transmission's lubricating oil. For example, in the case of a deep groove ball bearing such as the one shown in Figure 6, lubricating oil flows between the outer ring 51 and inner ring 52, reducing friction at each contact surface, and the lubricating oil is stirred between the balls 53 and cage 54 before being discharged.

Patent No. 5056394

However, in a conventional outer ring guide type deep groove ball bearing such as that shown in Figure 6, while deformation of the cage 54 due to centrifugal force can be suppressed, if the large amount of lubricating oil that flows between the outer ring 51 and inner ring 52 cannot be discharged effectively, there is a concern that the resistance to stirring the lubricating oil caused by the balls 53 and cage 54 will increase, resulting in increased torque that acts as resistance to rotation.

The objective of this invention is to improve the lubricating oil discharge performance in outer ring guide deep groove ball bearings and reduce the agitation resistance of the lubricating oil caused by the cage and rolling elements.

In order to solve the above problems, the present invention provides an outer ring guide deep groove ball bearing in which a plurality of balls are arranged in the circumferential direction between the raceway surface of an outer ring and the raceway surface of an inner ring, the spacing between the balls is maintained by a cage, and the cage is guided by a guide surface formed on the inner periphery of a shoulder portion of the outer ring,
a tapered surface is formed that is inclined so that the inner circumference of the shoulder portion of the outer ring expands in diameter from the guide surface toward the outer ring width surface,
The inclination angle of the tapered surface is set to be 20° to 35° with respect to the guide surface, which is a cylindrical surface parallel to the axis.

Furthermore, the tapered surface is formed so as to extend axially inward beyond the width surface of the retainer.

Furthermore, the axial length of the guide surface is set in the range of 0.5 mm to 1.0 mm.

Furthermore, a tapered surface is formed on a portion of the shoulder of the inner ring facing the inlet, the tapered surface being inclined so that the inner circumference has a smaller diameter toward the inner ring width surface,
The inclination angle of the tapered surface is set to be 20° to 35° with respect to the outer peripheral surface of the shoulder portion of the inner ring, which is a cylindrical surface parallel to the axis.

The cage is one of the following: a stamped steel cage, a resin cage, a rivet-fastened steel cage, or a machined high-strength brass cage.

Compared to conventional bearings, the outer ring guide deep groove ball bearing of this invention has a tapered surface formed on the portion of the outer ring shoulder facing the inlet. This makes it easier for lubricating oil that has flowed between the outer and inner rings to be expelled by the centrifugal force generated by the rotation of the balls (which act as rolling elements) and the cage, thereby reducing the agitation resistance of the lubricating oil caused by the balls and cage.

FIG. 1 is a cross-sectional view of a main portion of an outer ring guide deep groove ball bearing having a tapered surface on the shoulder of the outer ring according to an embodiment of the present invention. 1 is a cross-sectional view of the main part showing the flow of lubricating oil inside the bearing of the same FIG. 10 is a cross-sectional view of a main portion of the outer ring guide deep groove ball bearing having tapered surfaces on the shoulders of the outer ring and inner ring of the same. FIG. 10 is a cross-sectional view of a main part of the outer ring guide deep groove ball bearing equipped with the resin cage and having a tapered surface on the shoulder of the outer ring. A cross-sectional view of the main part of the outer ring guide deep groove ball bearing equipped with the above-mentioned steel plate rivet caulked cage and having a tapered surface on the shoulder of the outer ring. Cross-sectional view of a main part of a conventional outer ring guide deep groove ball bearing

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, the direction parallel to the axis of the rotating shaft of a deep groove ball bearing is referred to as the axial direction, and the direction around the axis of the rotating shaft is referred to as the circumferential direction.

As shown in Figure 1, this outer ring guide type deep groove ball bearing has multiple balls 3, which serve as rolling elements, arranged circumferentially between an outer ring 1 and an inner ring 2, with the spacing between the balls 3 maintained by a cage 4. These balls 3 roll along raceway surfaces 5 formed on the inner surface of the outer ring 1 and raceway surfaces 6 formed on the outer surface of the inner ring 2.

The cage 4 is guided by a guide surface 8 formed on the inner circumference of the shoulder 7 of the outer ring 1. The guide surface 8 is a cylindrical surface parallel to the axis of the rotating shaft of this deep groove ball bearing, and is ground. Note that the cage 4 being guided by the guide surface 8 refers to a state in which the guide surface 8 and the cage 4 are close to each other and can move only in the axial direction.

A tapered surface 9 is formed by turning on the portion of the shoulder 7 near both ends of the outer ring 1 facing the inlet, inclined from the guide surface 8 toward the width surface of the outer ring 1 so that the inner circumference of the shoulder 7 of the outer ring 1 expands in diameter. The inclination angle α of the tapered surface 9 is set to 20° to 35° with respect to the guide surface 8. Furthermore, a chamfered portion 10 is formed, continuing from the tapered surface 9.

The tapered surface 9 is a relatively large inclined surface, and is formed to extend axially inward beyond the width surface of the cage 4.

In the e-axle, this deep groove ball bearing is incorporated as a bearing for the motor's main shaft, with the width surface f of the shoulder 7 of the outer ring 1 contacting the housing. As shown in Figure 2, lubricating oil, which also serves as a lubricant for the transmission, flows between the outer ring 1 and inner ring 2, reducing friction in each part, and the lubricating oil is stirred by the balls 3 and cage 4 before being discharged.

Compared to conventional bearings, this type of outer ring guide deep groove ball bearing has a tapered surface 9 formed on the portion of the shoulder 7 of the outer ring 1 facing the inlet. This makes it easier for lubricating oil that has flowed between the outer ring 1 and inner ring 2 to be expelled by the centrifugal force caused by the rotation of the balls 3 and cage 4, thereby reducing the agitation resistance of the lubricating oil caused by the balls 3 and cage 4.

In addition, on the lubricating oil inflow side, the formation of a tapered surface 9 on the portion of the shoulder 7 of the outer ring 1 facing the inlet creates a wedge effect that draws in the lubricating oil, making it easier for an oil film to form between the guide surface 8 of the outer ring 1 and the cage 4. In particular, the amount of oil on the lubricating oil discharge side increases, making it easier for a thick oil film to form.

If the inclination angle α of the tapered surface 9 is too large, the flat surface of the width surface f will become smaller, increasing the surface pressure generated at the contact surface with the housing and potentially causing abnormal wear on the contact surface. Conversely, if it is too small, the ability to drain the lubricating oil will decrease.

Here, the relationship between the inclination angle α of the tapered surface 9 and the lubricant discharge characteristics and the surface pressure of the width surface f was examined, and the results are shown in Table 1. In Table 1, ◎ indicates a very favorable result, ○ indicates a result that is not as good as ◎ but is still favorable, and × indicates an unfavorable result.
Based on the above verification results, the range of the inclination angle α of the tapered surface 9 in the deep groove ball bearing of the present invention is set to 20° to 35° with respect to the guide surface 8.

Furthermore, on the outer ring 1 side where the guide surface 8 of the cage 4 is formed, the guide resistance generated by contact between the cage 4 and the outer ring 1 at the guide surface 8 can cause rotational resistance, such as increased torque and abnormal heat generation, so it is undesirable for the axial length L of the guide surface 8 to be too long.

Furthermore, since the guide surface 8 needs to be finished by costly grinding to mitigate its aggressiveness towards the cage 4, it is undesirable for the axial length L of the guide surface 8 to be too long.

Therefore, by increasing the axial length of the tapered surface 9 and shortening the axial length L of the guide surface 8, the area to be ground is reduced, extending the life of the grinding wheel and reducing the cycle time of the machining process.

On the other hand, if the axial length L of the guide surface 8 is too short, the surface pressure on the contact surface with the cage 4 increases, causing severe wear on the cage 4.

In light of these circumstances, the deep groove ball bearings used in the main shaft of e-axle motors typically have an outer diameter of 60 mm to 90 mm, an inner diameter of 30 mm to 40 mm, and a thickness of approximately 15 mm to 25 mm, so the axial length L of the guide surface 8 should be set in the range of 0.5 mm to 1.0 mm.

Here, the relationship between the axial length L of the guide surface 8 of the outer ring 1 and the guiding resistance caused by contact with the cage 4, wear of the cage 4, and the cost required for grinding was examined, and the results are shown in Table 2. In Table 2, ◎ indicates a very favorable result, ○ indicates a result that is not as good as the ◎ result but is still favorable, and × indicates an unfavorable result.
Based on the above verification results, the range of the axial length L of the guide surface 8 in the deep groove ball bearing of the present invention is set to 0.5 mm to 1.0 mm.

In the above embodiment, the tapered surface 9 is formed only on the outer ring 1 side where the guide surface 8 of the cage 4 is formed. However, as shown in Figure 3, the inner ring 2 side, which does not guide the cage 4, may also have a tapered surface 12 that slopes so that the inner circumference becomes smaller in diameter toward the width face sides at both ends, on the part of the shoulder portion 11 of the inner ring 2 facing the inlet, and a chamfered portion 13 that is continuous with the tapered surface 12.

The inclination angle β of the tapered surface 12 should be set to 20° to 35° with respect to the outer peripheral surface of the shoulder portion 11 of the inner ring 2, which is a cylindrical surface parallel to the axis of the rotation shaft of this deep groove ball bearing.

The cage 4 may be a stamped steel cage as described above, a plastic cage as shown in Figure 4, a rivet-fastened steel cage as shown in Figure 5, or a machined high-strength brass cage with the same cross-sectional shape as Figure 1. Plastic cages are used in bearings that must be able to handle high-speed rotation and suppress rotational noise, while rivet-fastened steel cages are used in small bearings that are subjected to relatively small forces, and machined high-strength brass cages are used in large bearings that are subjected to large forces.

1 Outer ring 2 Inner ring 3 Ball 4 Cage 5, 6 Raceway surface 7 Shoulder portion 8 Guide surface 9 Tapered surface 10 Chamfered portion 11 Shoulder portion 12 Tapered surface 13 Chamfered portion

Claims (5)

In an outer ring guide deep groove ball bearing, a plurality of balls are arranged circumferentially between the raceway surface of an outer ring and the raceway surface of an inner ring, the spacing between the balls is maintained by a cage, and the cage is guided by a guide surface formed on the inner periphery of a shoulder portion of the outer ring,
a tapered surface is formed that is inclined so that the inner circumference of the shoulder portion of the outer ring expands in diameter from the guide surface toward the outer ring width surface,
An outer ring guide deep groove ball bearing characterized in that the inclination angle of the tapered surface is set to be 20° to 35° with respect to the guide surface, which is a cylindrical surface parallel to the axis. An outer ring guide deep groove ball bearing as described in claim 1, characterized in that the tapered surface is formed so as to extend axially inward beyond the width surface of the cage. An outer ring guide deep groove ball bearing as described in claim 1, characterized in that the axial length of the guide surface is set in the range of 0.5 mm to 1.0 mm. a tapered surface is formed on a portion of the shoulder of the inner ring facing the inlet, the tapered surface being inclined so that the inner circumference has a smaller diameter toward the inner ring width face side;
An outer ring guide deep groove ball bearing as described in claim 1, characterized in that the inclination angle of the tapered surface is set to be 20° to 35° with respect to the outer peripheral surface of the shoulder portion of the inner ring, which is a cylindrical surface parallel to the axis. An outer ring guide deep groove ball bearing as described in claim 1, characterized in that the cage is one of a stamped steel cage, a resin cage, a rivet-fastened steel cage, and a machined high-strength brass cage.