Deep groove ball bearing

Abstract

To improve discharge performance of lubricant in an outer ring guide deep groove ball bearing and reduce agitation resistance of the lubricant caused by a holder and a rolling element.SOLUTION: In an outer ring guide deep groove ball bearing, a plurality of balls 3 is arranged circumferentially between a raceway surface 5 of an outer ring 1 and a raceway surface 6 of an inner ring 2, the interval between the balls 3 is maintained by a holder 4, and the cage 4 is guided by a guide surface 8 formed on an inner periphery of a shoulder part 7 of the outer ring 1. A tapered surface 9 is formed to be inclined so that the inner periphery of the shoulder part 7 of the outer ring 1 expands in diameter from the guide surface 8 toward a width surface of the outer ring 1, and an 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 an axial line.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to lubrication in a deep groove ball bearing incorporating an outer ring guide type cage. [Background technology]

[0002] In recent years, the widespread use of electric vehicles, which run on electricity, has become an urgent priority from the perspective 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 to practical use as drive units for these vehicles.

[0003] In such e-axles, the bearings used in the motor's main shaft must 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 may deform due to centrifugal force, causing interference with the rolling elements and outer ring, resulting in the generation of wear particles, abnormal heat generation, and a shortened lifespan. Patent Document 1, as described above, suggests that an effective solution to this problem is to use an outer ring guided cage.

[0004] As shown in Figure 6, an outer ring guide type deep groove ball bearing has multiple balls 53 arranged circumferentially between a raceway surface 55 of an outer ring 51 and a raceway surface 56 of an inner ring 52, with the spacing between the balls 53 maintained by a cage 54, and the cage 54 is guided by a guide surface 58, which is a cylindrical surface parallel to the axis formed on the inner circumference of a shoulder portion 57 of the outer ring 51.

[0005] Incidentally, there are two types of bearing lubrication: grease lubrication, which uses a semi-solid, cream-like grease, and oil lubrication, which uses a liquid lubricant. Oil lubrication is the mainstream for e-axles, and many motor main shaft bearings are also designed to be lubricated with the lubricant from the transmission. For example, in the case of a deep groove ball bearing as shown in Figure 6, lubricant flows between outer ring 51 and inner ring 52, reducing friction at each contact surface, and the lubricant is stirred between balls 53 and cage 54 before being discharged. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5056394 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in a conventional outer ring guide type deep groove ball bearing as shown in Figure 6, although deformation of the retainer 54 due to centrifugal force can be suppressed, if the large amount of lubricating oil that flows between the outer ring 51 and the inner ring 52 cannot be discharged sufficiently, there is a concern that the resistance to stirring the lubricating oil caused by the balls 53 and retainer 54 will increase, and the torque that acts as resistance to rotation will increase.

[0008] Therefore, an object of the present invention is to improve the dischargeability of lubricating oil in an outer ring guide deep groove ball bearing and to reduce the agitation resistance of the lubricating oil caused by the cage and rolling elements. [Means for solving the problem]

[0009] 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.

[0010] The tapered surface is formed so as to extend axially inward beyond the width surface of the cage.

[0011] The axial length of the guide surface is set in the range of 0.5 mm to 1.0 mm.

[0012] 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.

[0013] The cage is one of a stamped steel cage, a resin cage, a rivet-fastened steel cage, and a machined high-strength brass cage. [Effects of the Invention]

[0014] In the outer ring guide deep groove ball bearing of this invention, compared to conventional bearings, a tapered surface is formed on the portion of the outer ring shoulder facing the inlet, making it easier for lubricating oil that has flowed between the outer ring and inner ring to be discharged by the centrifugal force associated with the rotation of the balls and cage, which are the rolling elements, and reducing the agitation resistance of the lubricating oil caused by the balls and cage. [Brief explanation of the drawings]

[0015] [Figure 1] 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. [Figure 2] 1 is a cross-sectional view of the main part showing the flow of lubricating oil inside the bearing of the same [Figure 3] 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. [Figure 4]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. [Figure 5] 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. [Figure 6] Cross-sectional view of a main part of a conventional outer ring guide deep groove ball bearing DETAILED DESCRIPTION OF THE INVENTION

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Here, a direction parallel to the axis of a rotating shaft of a deep groove ball bearing is referred to as an axial direction, and a direction around the axis of the rotating shaft is referred to as a circumferential direction.

[0017] As shown in Figure 1, this outer ring guide type deep groove ball bearing has multiple balls 3, which are 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.

[0018] 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. 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 is 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.

[0019] At the portions of shoulder portions 7 near both ends of the outer ring 1 facing the inlet, tapered surfaces 9 are formed by turning, inclined from guide surfaces 8 toward the width faces of the outer ring 1 so that the inner circumference of shoulder portions 7 of the outer ring 1 expands in diameter. The inclination angle α of tapered surfaces 9 is set to be 20° to 35° with respect to guide surfaces 8. Furthermore, chamfered portions 10 are formed, continuing from tapered surfaces 9.

[0020] The tapered surface 9 is a relatively large inclined surface, and is formed so as to extend axially inward beyond the width surface of the cage 4 .

[0021] 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 lubricating oil for the transmission, flows between the outer ring 1 and inner ring 2, reducing friction in each part, and is stirred by the balls 3 and cage 4 before being discharged.

[0022] In this type of outer ring guide deep groove ball bearing, compared to conventional bearings, a tapered surface 9 is formed on the portion of the shoulder 7 of the outer ring 1 facing the inlet, making it easier for lubricating oil that has flowed between the outer ring 1 and the inner ring 2 to be discharged 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.

[0023] Furthermore, on the lubricating oil inflow side, the formation of a tapered surface 9 on the portion of shoulder 7 of outer ring 1 facing the inlet creates a wedge effect that draws in the lubricating oil, making it easier to form an oil film between guide surface 8 of outer ring 1 and cage 4. In particular, the amount of oil on the lubricating oil discharge side increases, making it easier to form a thick oil film.

[0024] If the inclination angle α of the tapered surface 9 is too large, the flat surface of the width surface f will become small, and the surface pressure generated at the contact surface with the housing will increase, which may cause abnormal wear on the contact surface. Conversely, if the inclination angle α is too small, the dischargeability of the lubricating oil will decrease.

[0025] 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. [Table 1] 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 based on the above verification results.

[0026] Furthermore, on the outer ring 1 side where the guide surface 8 of the retainer 4 is formed, the guide resistance generated by contact between the retainer 4 and the outer ring 1 at the guide surface 8 can also cause increased torque and abnormal heat generation, which in turn causes resistance to rotation, so it is not desirable for the axial length L of the guide surface 8 to be too long.

[0027] Furthermore, from the viewpoint that the guide surface 8 needs to be finished by costly grinding in order to reduce its aggressiveness towards the retainer 4, it is not preferable for the axial length L of the guide surface 8 to be too long.

[0028] 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, thereby extending the life of the grinding wheel and reducing the cycle time of the processing process.

[0029] 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 the problem of severe wear of the cage 4.

[0030] In view of these circumstances, in the case of deep groove ball bearings used in the main shaft of e-axle motors, those with an outer diameter of approximately 60 mm to 90 mm, an inner diameter of approximately 30 mm to 40 mm, and a thickness of approximately 15 mm to 25 mm are used, so the axial length L of the guide surface 8 should be set in the range of 0.5 mm to 1.0 mm.

[0031] Here, we investigated the relationship between the axial length L of the guideway surface 8 of the outer ring 1 and the guiding resistance caused by contact with the cage 4, the wear of the cage 4, and the cost required for grinding, 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 ◎ but is still favorable, and × indicates an unfavorable result. [Table 2] 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.

[0032] 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 FIG. 3 , the inner ring 2 side, which does not guide the cage 4, may also be formed with a tapered surface 12 that slopes so that the inner circumference has a smaller diameter toward the width face sides at both ends, on the portion facing the inlet of the shoulder portion 11 of the inner ring 2, and a chamfered portion 13 that is continuous with the tapered surface 12.

[0033] The inclination angle β of the tapered surface 12 is preferably 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.

[0034] Furthermore, as for cage 4, in addition to the stamped steel cage described above, any of the following may be selected: a resin cage as shown in Fig. 4, a rivet-fitted steel cage as shown in Fig. 5, or a machined high-strength brass cage with the same cross-sectional shape as Fig. 1. Resin cages are used for bearings that must be able to handle high-speed rotation and suppress rotational noise, while rivet-fitted steel cages are used for small bearings that are subjected to relatively small forces, and machined high-strength brass cages are used for large bearings that are subjected to large forces. [Explanation of symbols]

[0035] 1 outer ring 2. Inner circle 3 balls 4 Cage 5,6 Raceway surface 7 Shoulder 8 Guide surface 9 Tapered surface 10 Chamfer 11 Shoulder 12 Tapered surface 13 Chamfer

Claims

1. In an outer ring guide deep groove ball bearing, 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, 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.

2. 2. An outer ring guide deep groove ball bearing according to claim 1, wherein the tapered surface is formed so as to extend axially inward beyond the width surface of the cage.

3. 2. An outer ring guide deep groove ball bearing according to claim 1, wherein the axial length of said guide surface is set in the range of 0.5 mm to 1.0 mm.

4. 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.

5. 2. An outer ring guide deep groove ball bearing according to claim 1, wherein the cage is one of a stamped steel cage, a resin cage, a rivet-fastened steel cage, and a machined high-strength brass cage.

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