Ball bearing

Abstract

To provide a ball bearing that has a resin-made snap cage incorporated such that a cage prong of the snap cage is effectively suppressed from deforming against centrifugal force during rotation.SOLUTION: A reinforcement part 9 of a cage prong 6 of a snap cage 4 is formed in a block shape having an outer peripheral surface 9a connecting with an annular base 5 radially outside a radial center position A of a pocket 7 and an inner peripheral surface 9b connecting with the annular base 5 radially inside the radial center position A of the pocket 7, and a part of the outer peripheral surface 9a is formed into an inclined surface 9a2 inclined to approach the inner peripheral surface 9b toward one axial side. Consequently, while the cage prong 6 of the snap cage 4 is reduced in thickness to be made light-weight, the cage prong 6 is reduced in total radial and circumferential strength decrease, so that the cage prong 6 is effectively suppressed from deforming when the snap cage 4 receives centrifugal force due to rotation.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a ball bearing incorporating a crown cage made of resin. [Background technology]

[0002] In the field of electric vehicle technology, there is a trend to increase the rotational speed of electric motors while also making them smaller and lighter to increase the output density of the motors as a means of reducing electricity costs and improving driving performance. However, when trying to increase the speed of electric motors, the rolling bearings that support the rotating shaft to which the rotation of the motor is input experience greater centrifugal force acting on the internal parts as the rotational speed increases, and the resulting increased deformation of the internal parts makes them more susceptible to various problems.

[0003] In particular, in ball bearings incorporating a resin crown cage (hereinafter simply referred to as the "cage"), the cantilevered horns of the cage are prone to deformation radially outward due to centrifugal force when used at high speeds. The deformed horns then come into strong contact with the inner circumferential surface of the outer ring or the balls, increasing rotational resistance and generating heat, which can lead to seizure or other problems that can cause the bearing to malfunction.

[0004] For this reason, ball bearings that incorporate the above-mentioned resin crown cage and are used under high-speed rotation often have the cage horns thinned to reduce weight, thereby preventing deformation of the horns due to centrifugal force (see, for example, Patent Document 1).

[0005] As shown in Fig. 13, the ball bearing disclosed in Patent Document 1 includes an outer ring 51, an inner ring 52 disposed radially inside the outer ring 51, a plurality of balls 53 disposed for free rolling between the outer ring 51 and the inner ring 52, and a resin crown-shaped cage 54 for holding the plurality of balls 53. As shown in Figs. 13 to 15, the cage 54 includes an annular base (annular body) 55 and a plurality of tines 56 extending axially from the annular base 55 at equal intervals in the circumferential direction, with pockets 57 for accommodating the balls 53 formed between adjacent tines 56 in the circumferential direction. The tines 56 are configured such that a plate-shaped reinforcing portion (stiffening rib) 59 is provided between a pair of cantilevered claws (claw bodies) 58 facing each other in the circumferential direction, so as to connect the claws 58 to each other.

[0006] Furthermore, by configuring the horns 56 of the cage 54 as described above and forming missing portions in the horns 56 (portions that are missing compared to the horns of a typical crown-shaped cage), the weight of the horns 56 can be reduced, reducing deformation of the horns 56 due to centrifugal force, and the reinforcing portions 59 can prevent a decrease in the strength of the horns 56. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-076187 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the ball bearing of Patent Document 1, the reinforcing portion 59 of the horns 56 of the retainer 54 is formed in the shape of a plate extending radially inward from the annular base 55 to one axial side (the direction in which the horns 56 protrude) radially inward of the radial center position C of the pocket 57, so that under high-speed rotation, it is not possible to sufficiently suppress radially outward deformation of the claw portions 58 due to centrifugal force, and there is a risk that problems caused by contact of the claw portions 58 with the outer ring 51 or the balls 53 cannot be prevented.

[0009] SUMMARY OF THE INVENTION An object of the present invention is to provide a ball bearing incorporating a resin crown cage, capable of effectively suppressing deformation of the horns of the cage due to centrifugal force during rotation. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides a bearing comprising an outer ring, an inner ring disposed radially inside the outer ring, a plurality of balls disposed so as to be able to roll between the outer ring and the inner ring, and a resin cage that holds the plurality of balls, the cage comprising an annular base and a plurality of tines that extend from the annular base to one side in the axial direction at equal intervals in the circumferential direction, and having pockets for accommodating the balls formed between adjacent tines in the circumferential direction, the tines of the cage being disposed between a pair of cantilever-shaped claws that face each other in the circumferential direction. In a ball bearing in which a reinforcing portion is provided to connect the claw portions of the retainer, the reinforcing portion of the horn is formed in a block shape having an outer peripheral surface that is continuous with the annular base portion radially outside the radial center position of the pocket, and an inner peripheral surface that is continuous with the annular base portion radially inside the radial center position of the pocket, and at least a portion of the outer peripheral surface of the reinforcing portion is inclined so as to approach the inner peripheral surface as it moves toward one axial side (Configuration 1).

[0011] In other words, in the ball bearing of configuration 1, the reinforcing portion of the horn of the cage is made block-shaped and extends inward and outward from the radial center position of the pocket, and at least a portion of the outer peripheral surface is inclined so that it approaches the inner peripheral surface as it moves toward one axial side. This makes the cage horn thinner and lighter than those of general specifications, while reducing the reduction in strength of the entire horn in the radial and circumferential directions less than that of Patent Document 1 mentioned above, so that deformation of the horn is effectively suppressed when the cage is subjected to centrifugal force due to rotation.

[0012] This invention can be particularly effectively applied when the claws of the cage are formed in a shape in which the outer diameter decreases toward the tip (Configuration 2). Horns with claws of this shape are less susceptible to centrifugal force and are less likely to deform than horns of general specifications (horns with claws formed to a constant outer diameter).

[0013] Furthermore, in the above configurations 1 and 2, if the reinforcing portion of the retainer is configured such that a U-shaped recess is formed in the circumferential center of the outer peripheral surface when viewed from one axial side (configuration 3), it is possible to further reduce the weight of the horn while preventing a decrease in the overall strength of the horn, and to further minimize deformation of the horn due to centrifugal force.

[0014] In any of the above configurations 1 to 3, the outer peripheral surface of the reinforcing portion of the retainer can be formed into a shape that includes at least one straight line or at least one R-shape in the axial cross section (configuration 4). [Effects of the Invention]

[0015] As described above, in the ball bearing of the present invention, the reinforcing portions of the cage horns are block-shaped and extend inward and outward from the radial center of the pocket, and at least a portion of the outer peripheral surface is inclined so that it approaches the inner peripheral surface as it moves toward one axial side. This makes it possible to reduce the weight of the cage horns while ensuring their strength, and effectively suppress deformation of the horns due to centrifugal force during rotation. Therefore, problems caused by contact between the claws of the cage horns and the outer ring or balls are less likely to occur, making it suitable for high-speed rotation applications. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a front cross-sectional view of a ball bearing according to an embodiment of the present invention; [Figure 2] An external perspective view of the cage in FIG. 1 [Figure 3] FIG. 2 is an enlarged front cross-sectional view showing a main part of the cage of FIG. 1. [Figure 4] 2 is a side view of the main part of the cage of FIG. 1 as seen from one axial side. [Figure 5] FIG. 5 is a side view of a main part showing a first modified example of the shape of the horns of the cage, corresponding to FIG. 4; [Figure 6] FIG. 4 is a front cross-sectional view of a main part showing a second modified example of the shape of the horns of the cage, corresponding to FIG. 3; [Figure 7] FIG. 4 is a front cross-sectional view of a main part showing a third modified example of the shape of the horns of the cage, corresponding to FIG. 3; [Figure 8] FIG. 4 is a front cross-sectional view of a main part showing a fourth modified example of the shape of the horns of the cage, corresponding to FIG. 3; [Figure 9] FIG. 5 is a front cross-sectional view of a main part showing a fifth modified example of the shape of the horns of the cage, corresponding to FIG. 3; [Figure 10] FIG. 5 is a front cross-sectional view of a main part showing a sixth modified example of the shape of the horns of the cage, corresponding to FIG. 3; [Figure 11] FIG. 7 is a front cross-sectional view of a main part showing a seventh modified example of the shape of the horns of the cage, corresponding to FIG. 3; [Figure 12] 12 is a graph showing the results of numerical analysis of the deformation of the cage of FIG. 1, the cage of FIG. 11, and a comparative example of the cage. [Figure 13] Front cross-sectional view of a conventional ball bearing [Figure 14] 14 is a plan view of the main part of the cage of FIG. 13 as seen from the radially outer side. [Figure 15] FIG. 14 is an enlarged front cross-sectional view showing a main part of the cage of FIG. 13. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment of the present invention will be described below with reference to Figures 1 to 12. As shown in Figure 1, this ball bearing is a ball bearing (deep groove ball bearing) that includes an outer ring 1 having a raceway surface 1a formed on its inner peripheral surface, an inner ring 2 that is arranged radially inward of the outer ring 1 and has a raceway surface 2a formed on its outer peripheral surface, a plurality of balls 3 that are arranged so as to roll freely between the raceway surface 1a of the outer ring 1 and the raceway surface 2a of the inner ring 2, and a resin crown cage 4 that holds the plurality of balls 3 at equal intervals so as to roll freely.

[0018] Here, the central axes (not shown) of the outer ring 1, inner ring 2, and cage 4 are arranged coaxially and correspond to the bearing central axis, which is the design center of rotation of the ball bearing. Hereinafter, the central axis of the cage 4 will be simply referred to as the "central axis."

[0019] The axial direction refers to the direction along the central axis, with one axial side being the left side in FIG. 1 and the other axial side being the right side in FIG. 1. The radial direction refers to the direction perpendicular to the central axis. The radially outward direction refers to the direction moving away from the central axis in the radial direction, and the radially inward direction refers to the direction moving closer to the central axis in the radial direction. The circumferential direction refers to the direction along the circumference going around the central axis.

[0020] As shown in Figures 1 to 3, the cage 4 consists of an annular base 5 extending in the circumferential direction and a plurality of horns 6 extending from the annular base 5 to one side in the axial direction at equal intervals in the circumferential direction, with pockets 7 for accommodating balls 3 formed between adjacent horns 6 in the circumferential direction. The outer and inner peripheral surfaces of the annular base 5 are each cylindrical. The pockets 7 are spaces that open radially outward, radially inward, and to one side in the axial direction, and the same number of pockets 7 are formed as the horns 6.

[0021] The inner surface of pocket 7 is spherical, and the openings on the radially outer side, radially inner side, and one axial side are sized to not allow balls 3 to pass through. Therefore, when assembling the ball bearing, balls 3 are stored in pocket 7 by pressing horns 6 of cage 4 from the other axial side against balls 3 arranged between raceway surface 1a of outer ring 1 and raceway surface 2a of inner ring 2, thereby elastically deforming horns 6 and allowing balls 3 to enter pocket 7 while widening the opening on one axial side of pocket 7 in the circumferential direction.

[0022] The horns 6 of the cage 4 have a pair of cantilevered claws 8 facing each other in the circumferential direction, and a reinforcing portion 9 is provided between the claws 8 to connect the claws 8. Each claw 8 has an outer circumferential surface 8a that is flush with the outer circumferential surface of the annular base 5. A cylindrical surface 8a1 and two concave curved surfaces 8a2 and 8a3 are connected in order from the other axial side, and the outer diameter decreases toward the tip. The inner circumferential surface 8b of the claw 8 is flush with the inner circumferential surface of the annular base 5.

[0023] As shown in FIG. 3 , the reinforcing portion 9 of each of the horns 6 is formed in a block shape having an outer peripheral surface 9a that is continuous with the annular base portion 5 radially outward from the radial center position A of the pocket 7, an inner peripheral surface 9b that is continuous with the annular base portion 5 radially inward from the radial center position A of the pocket 7, and a tip surface 9c that is continuous with the outer peripheral surface 9a and the inner peripheral surface 9b radially inward from the radial center position A of the pocket 7. The inner peripheral surface 9b is formed flush with the inner peripheral surface 8b of the claw portion 8 and the inner peripheral surface of the annular base portion 5. The radial center position A of the pocket 7 coincides with the midpoint between the outer peripheral surface and the inner peripheral surface of the annular base portion 5, and can be determined by measuring the curved surface of the pocket 7 excluding the grooves using a three-dimensional measuring machine.

[0024] The outer peripheral surface 9a of the reinforcing portion 9 comprises a cylindrical surface 9a1 and an inclined surface 9a2 that is inclined so as to approach the inner peripheral surface 9b as it approaches one axial side, and these are connected in order from the other axial side. The cylindrical surface 9a1 is formed to have a smaller diameter than the cylindrical surface 8a1 (the outer peripheral surface of the annular base portion 5) on the outer periphery of the claw portion 8. The inclined surface 9a2 is formed linearly in the axial cross section. Note that the cylindrical surface 9a1 on the other axial side can also be changed to an inclined surface that approaches the inner peripheral surface at an inclination different from that of the inclined surface 9a2 as it approaches one axial side.

[0025] The tip surface 9c of the reinforcing portion 9 is formed on a plane that extends radially on the other axial side from the axial center position B of the pocket 7. Forming the tip surface 9c at this position is to make the tip side of the claw portion 8 easily deformable in the circumferential direction and to improve the ease of incorporating the ball 3 into the pocket 7. Incidentally, the tip surface 9c can also be changed to an inclined surface that inclines so as to approach the tip of the claw portion 8 as it goes radially inward.

[0026] Also, in the circumferential center portion of the outer peripheral surface 9a of the reinforcing portion 9, a recess 9d is formed that is U-shaped when viewed from one axial side and reaches the end surface on one axial side of the annular base portion 5. As shown in FIG. 4, the recess 9d has a semi-circular bottom surface 9d1 centered on the radial center position A of the pocket 7 when viewed from one axial side, and a pair of side surfaces 9d2 that extend parallel to each other radially outward from both circumferential ends of the bottom surface 9d1. And its maximum width (the diameter of the semi-circle of the bottom surface 9d1) Wa is formed such that 0.5Wb ≦ Wa < Wb with respect to the minimum width Wb between the pair of claw portions 8.

[0027] This ball bearing has the above-described configuration, and the six reinforcing portions 9 of the cage 4 are formed in a block shape that expands inside and outside the radial center position A of the pocket 7. The inclined surface 9a2 that occupies almost all of the outer peripheral surface 9a of the reinforcing portion 9 inclines so as to approach the inner peripheral surface 9b as it goes toward one axial side. Also, since the recess 9d is formed in the circumferential center portion of the outer peripheral surface 9a, it is possible to achieve both weight reduction and strength assurance of the six of the cage 4, and effectively suppress the deformation of the six due to the centrifugal force during rotation. For this reason, troubles caused by the contact of the six claw portions 8 of the cage 4 with the outer ring 1 and the ball 3 are unlikely to occur, and it can be particularly effectively applied to applications that rotate at high speeds.

[0028] Also, in this ball bearing, since the six claw portions 8 and the reinforcing portions 9 of the cage 4 are both formed such that the radial dimension becomes smaller on one axial side, the tip side of the claw portion 8 is easily deformed when incorporating the ball 3 into the pocket 7 of the cage 4, and there is also the feature that the incorporation work is easy. <5 shows a first modified example of the shape of the horns of the cage 4. In this first modified example, the recesses 9d of the reinforcing portions 9 of the horns 6 are formed so that the center of the semicircle of the bottom surface 9d1, as viewed from one axial side, is located radially outward of the radial center position A of the pocket 7, and the side surface 9d2 is eliminated.

[0030] 6 to 8 show second to fourth modified examples of the shape of the horns of the cage 4, respectively. All of these modifications change the shape of the outer peripheral surface of the reinforcing portion 9 of the horn 6. In the second modified example shown in FIG. 6, the inclined surface 9a2 of the outer peripheral surface 9a of the reinforcing portion 9 is curved in an axial cross section. In the third modified example shown in FIG. 7, the inclined surface 9a2 of the reinforcing portion 9 is formed into a shape consisting of two straight lines with different inclination angles in an axial cross section. Meanwhile, in the fourth modified example shown in FIG. 8, the inclined surface 9a2 of the reinforcing portion 9 is formed into a shape consisting of a straight line and a curved shape that are connected in order from the other axial side in an axial cross section.

[0031] 9 to 11 show fifth to seventh modified examples of the shape of the horns of the cage 4. These modifications do not change the shape of the reinforcing portions 9 of the horns 6 of the example shown in FIGS. 1 to 4 , but change the shape of the outer peripheral surface of the claw portion 8. In the fifth modified example shown in FIG. 9 , the outer peripheral surface 8 a of the claw portion 8 is formed into a shape consisting of two straight lines with different inclination angles in axial cross section, with the inclination angle of the lines being larger on one axial side than on the other axial side. In the sixth modified example shown in FIG. 10 , the outer peripheral surface 8 a of the claw portion 8 is formed into a cylindrical surface formed on the same plane as the outer peripheral surface of the annular base portion 5, and an inclined surface formed of two straight lines with different inclination angles in axial cross section, which are connected in sequence from the other axial side. The inclination angle of the lines is set larger on the other axial side than on the one axial side, contrary to the fifth modified example shown in FIG. 9 . In the seventh modified example shown in FIG. 11 , the entire outer peripheral surface 8 a of the claw portion 8 is formed into a cylindrical surface that is the same as the outer peripheral surface of the annular base portion 5.

[0032] Each of these modified examples can achieve the same effect as the examples shown in Figures 1 to 4. Of these, the seventh modified example in Figure 11 has the claw portion 8 formed with a constant radial dimension, which is disadvantageous compared to the other examples in terms of ease of installation of the ball 3 and weight reduction of the tines 6, but the strength of the tines 6 is increased.

[0033] Next, a description will be given of a numerical analysis that confirmed the effect of reducing the amount of deformation of the horns 6 of the cage 4 in the ball bearing of this embodiment.

[0034] The numerical analysis was performed on the example (Example 1) shown in Figures 1 to 4, the seventh modified example (Example 2) shown in Figure 11, Comparative Example 1 in which the reinforcing portion of Example 1 was eliminated, and Comparative Example 2 in which the reinforcing portion of Example 2 was eliminated, and the amount of deformation when the surface temperature of the cage was set to 25°C was calculated under multiple rotational speed conditions.

[0035] Figure 12 shows the calculation results for the radial outward deformation rate (ratio of deformation amount to radial dimension) of the claws of the horns for each cage example analyzed. Here, the dmn value in the figure is calculated by multiplying the pitch circle diameter dm (mm) of the ball by the rotation speed n (min -1 ) From this figure, it can be seen that Examples 1 and 2 are able to suppress the deformation rate (amount of deformation) of the claws compared to Comparative Examples 1 and 2, respectively, and that the deformation rate can be reduced by approximately 10 to 20% particularly in the high-speed rotation range where the dmn value exceeds 2 million. This confirms that the present invention has a significant effect in reducing deformation of the horns due to centrifugal force, particularly under high-speed rotation.

[0036] Therefore, for example, if the ball bearing of the present invention is incorporated into the electric motor of an electric vehicle, the allowable rotational speed of the electric motor can be increased, which is expected to contribute to the miniaturization of the electric motor.

[0037] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0038] Furthermore, the present invention is not limited to deep groove ball bearings as in the above-described embodiments, but can also be applied to angular contact ball bearings incorporating a crown cage. [Explanation of symbols]

[0039] 1 outer ring 2. Inner circle 3 balls 4 Cage 5 Circular base Six 7 pockets 8 Claw 9 Reinforcement 9a Outer surface 9a2 Slope 9b Inner surface 9d Recess

Claims

1. The bearing comprises an outer ring (1), an inner ring (2) disposed radially inside the outer ring (1), a plurality of balls (3) disposed between the outer ring (1) and the inner ring (2) so as to be capable of rolling freely, and a resin cage (4) for holding the plurality of balls (3), The cage (4) comprises an annular base portion (5) and a plurality of tines (6) extending from the annular base portion (5) to one side in the axial direction at equal intervals in the circumferential direction, and has pockets (7) formed between adjacent tines (6) in the circumferential direction for accommodating the balls (3), In the ball bearing, the horns (6) of the cage (4) are provided with a reinforcing portion (9) between a pair of cantilever-shaped claw portions (8) facing each other in the circumferential direction so as to connect the claw portions (8), The retainer (4) is a ball bearing characterized in that the reinforcing portion (9) of the horn (6) is formed in a block shape having an outer peripheral surface (9a) that is continuous with the annular base portion (5) radially outer than the radial center position (A) of the pocket (7), and an inner peripheral surface (9b) that is continuous with the annular base portion (5) radially inner than the radial center position (A) of the pocket (7), and at least a portion of the outer peripheral surface (9a) of the reinforcing portion (9) is inclined so as to approach the inner peripheral surface (9b) as it proceeds toward one axial side.

2. 2. The ball bearing according to claim 1, wherein the claw portion (8) of the cage (4) is formed in a shape in which the outer diameter dimension becomes smaller toward the tip.

3. 3. The ball bearing according to claim 1, wherein the reinforcing portion (9) of the retainer (4) has a U-shaped recess (9d) formed in the circumferential center of the outer circumferential surface (9a) when viewed from one axial side.

4. 3. The ball bearing according to claim 1, wherein an outer peripheral surface (9a) of the reinforcing portion (9) of the retainer (4) is formed into a shape including at least one straight line or at least one R shape in an axial cross section.

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