Wheel bearing device

Abstract

The present invention provides a wheel bearing device that can reduce the rotational torque of the bearing device and improve the fuel efficiency and electricity consumption of a vehicle. [Solution] The cage 8 of the wheel bearing device 1 comprises an annular portion 81 that can rotate around a rotation axis, a plurality of columnar portions 82 that extend axially from the annular portion 81, and a pocket 83 that holds a ball 7 and has a pocket surface 831 formed by adjacent columnar portions 82 and the annular portion 81. The size of the gap d in the diametrical direction of the ball 7 formed between the pocket surface 831 and the ball 7 held by the pocket 83 is constant in the radial direction of the cross section along the straight line L1 connecting the center P1 of the ball 7 and the contact point 41a, or the ends in the radial direction are smaller than the central part. The columnar portions 82 are formed in a region of the pocket surface 831 that includes the point through which a pitch circle C1 passes, passing through the center of curvature Pa of the pocket surface 831 with the rotation axis of the annular portion 81 as the center, and have a notch 821 that is recessed from the pocket surface 831.

Description

Technical Field

[0001] The present invention relates to a wheel bearing device.

Background Art

[0002] Conventionally, a wheel bearing device that rotatably supports a wheel in a suspension device such as an automobile is known. In the wheel bearing device, an inner member including a hub ring is rotatably supported by an outer member via a plurality of balls.

[0003] The outer member has an outer raceway surface on its inner circumference, the inner member has an inner raceway surface facing the outer raceway surface, and the balls are interposed between the outer raceway surface and the inner raceway surface so as to be freely rollable. There is grease between the balls and the outer raceway surface and the inner raceway surface.

[0004] Further, the balls are held in a state of being equally distributed in the circumferential direction by a cage. The cage includes, for example, an annular portion formed in an annular shape, a plurality of column portions extending in the axial direction from the annular portion, and a pocket having a pocket curved surface formed along the outer peripheral surface of the rolling elements by the adjacent column portions and the annular portion. The balls are held by the pockets of the cage, and there is grease between the pocket curved surface of the pocket and the balls.

[0005] When the bearing device rotates, resistance is generated by shearing of the grease between the balls and the pocket curved surface. Further, when the bearing device rotates, the grease between the balls and the outer raceway surface and the inner raceway surface adheres to the balls and enters between the balls and the pocket curved surface as the balls rotate, so that the resistance caused by the shearing of the grease continues to occur.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

[0007] In wheel bearing systems, the shear resistance generated in the grease between the balls and the curved pocket surface increases rotational torque, which is a factor that reduces the fuel efficiency or electric power consumption of the vehicle on which the bearing system is installed.

[0008] This invention has been made in view of the above circumstances, and provides a wheel bearing device that can improve the fuel efficiency and electricity consumption of a vehicle by suppressing the increase in rotational torque of the bearing device. [Means for solving the problem]

[0009] In other words, the wheel bearing device comprises an outer member having an outer raceway surface formed on its inner circumference, an inner member having an inner raceway surface facing the outer raceway surface, a plurality of rolling elements interposed between the two raceway surfaces of the outer member and the inner member so as to be rotatable, and a retainer that holds the rolling elements, the retainer being formed in an annular shape and having an annular portion that is rotatable about a rotation axis, a plurality of columnar portions extending axially from the annular portion and arranged at regular intervals in the circumferential direction, and having a pocket curved surface formed by adjacent columnar portions and the annular portion, which is formed to conform to the outer circumferential surface of the rolling elements The device comprises a pocket for holding a rolling element, wherein the size of the gap in the diametrical direction of the rolling element formed between the curved surface of the pocket and the rolling element held by the pocket is constant in the radial direction of the cross section along the straight line connecting the center of the rolling element and the contact point of the rolling element with the inner raceway surface, or the radial end is smaller than the radial center, and the column portion is formed in a region of the curved surface of the pocket that includes the point through which a pitch circle passes, centering the rotation axis of the annular portion and passing through the center of curvature of the curved surface of the pocket, and has a notch that is recessed from the curved surface of the pocket. [Effects of the Invention]

[0010] According to the present invention, it is possible to suppress the increase in rotational torque of a wheel bearing device and improve the fuel efficiency or electric power consumption of a vehicle equipped with a wheel bearing device. [Brief explanation of the drawing]

[0011] [Figure 1] This is a side cross-sectional view showing a wheel bearing device. [Figure 2] This is a perspective view showing the retainer. [Figure 3] This is a partial cross-sectional view of the retainer for the inner ball row, as seen from the circumferential direction. [Figure 4] This is a perspective view showing the retainer and balls of the inner ball row, in a cross-section cut along a line connecting the center of the ball and the contact point. [Figure 5] This is a view of the retainer and balls of the inner ball row, as seen from a direction perpendicular to the cutting plane, in a cross-section obtained by cutting along a line connecting the center of the ball and the contact point. [Figure 6] This is a cross-sectional view showing a retainer and balls for an inner ball row, where, in a cross-section taken along a straight line connecting the center of the ball and the contact point, the size of the gap between the pocket surface and the ball is formed such that the radial end is smaller than the radial center. [Figure 7] This is a partial cross-sectional view of the outer ball row retainer, as seen from the circumferential direction. [Figure 8] This is a view of the retainer and balls of the outer ball row, specifically a cross-section of the retainer and balls cut along a straight line connecting the center of the ball and the contact point, as seen from a direction perpendicular to the cutting surface. [Figure 9] This is a modified example of a retainer for an inner ball row, and is a partial cross-sectional view of the retainer as seen from the circumferential direction. [Figure 10] This is a perspective view showing the retainer and balls of an inner ball row according to a modified example, in a cross-section obtained by cutting along a plane that connects the center of the ball to the contact point. [Figure 11] A drawing, seen from a direction orthogonal to the plane of section, of a cage and balls of an inner-side ball row according to a modified example, the cage and balls being in a plane of section obtained by cutting along a plane along a straight line connecting the center of a ball and a contact point. [Figure 12] A cross-sectional view showing a cage and balls formed such that the size of the gap between the pocket curved surface and the balls is larger at the radial end than at the radial center. [Embodiments for Carrying Out the Invention]

[0012] Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

[0013] [Wheel Bearing Device] A wheel bearing device 1 shown in FIG. 1 is an embodiment of a wheel bearing device according to the present invention and rotatably supports a wheel in a suspension device of a vehicle such as an automobile.

[0014] In the following description, the axial direction represents the direction along the rotation axis X of the wheel bearing device 1, the radial direction represents the direction orthogonal to the rotation axis X of the wheel bearing device 1, and the circumferential direction represents the direction along an arc centered on the rotation axis X of the wheel bearing device 1. Also, the outer side represents one side in the axial direction and the wheel side of the wheel bearing device 1 when attached to the vehicle body, and the inner side represents the other side in the axial direction and the vehicle body side of the wheel bearing device 1 when attached to the vehicle body.

[0015] The wheel bearing device 1 has a configuration called the third generation and includes an outer ring 2 as an outer member, a hub ring 3 and an inner ring 4 as inner members, two rows of inner-side ball rows 5 and outer-side ball rows 6 as rolling element rows, an outer-side seal member 9, and an inner-side seal member 10.

[0016] An inner opening 21 into which an inner seal member 10 can be fitted is formed at the inner end of the outer ring 2. An outer opening 22 into which an outer seal member 9 can be fitted is formed at the outer end of the outer ring 2.

[0017] When the inner seal member 10 is fitted into the inner opening 21, the inner opening end of the annular space S formed by the outer ring 2 as an outer member, the hub ring 3 and the inner ring 4 as inner members is closed. When the outer seal member 9 is fitted into the outer opening 22, the outer opening end of the annular space S is closed.

[0018] The inner seal member 10 and the outer seal member 9 are sealing devices that close the opening ends of the annular space S. Thus, by closing the inner and outer opening ends of the annular space S with the inner seal member 10 and the outer seal member 9, it is possible to prevent foreign matters such as muddy water from entering the inside of the wheel bearing device 1.

[0019] On the inner peripheral surface 28 of the outer ring 2, an inner outer raceway surface 23 and an outer outer raceway surface 24 are formed. On the outer peripheral surface 27 of the outer ring 2, a vehicle body mounting flange 25 for attaching the outer ring 2 to a vehicle body side member is integrally formed. The vehicle body mounting flange 25 is provided with bolt holes 26 into which fastening members (here, bolts) for fastening the vehicle body side member and the outer ring 2 are inserted.

[0020] At the inner end of the outer peripheral surface of the hub ring 3, a small diameter step portion 31 having a smaller diameter than the outer end is formed. At the outer end of the hub ring 3, a wheel mounting flange 32 for attaching a wheel is integrally formed.

[0021] The wheel mounting flange 32 is formed with a plurality of bolt holes 35. Hub bolts 36 for fastening the hub ring 3 and a wheel or brake parts can be press-fitted into the bolt holes 35.

[0022] In the hub wheel 3, a sliding contact surface 34 is formed on the base side of the wheel mounting flange 32, into which the outer sealing member 9 slides. On the outer circumferential surface of the hub wheel 3, an inner raceway surface 33 is provided so as to face the outer raceway surface 24 of the outer ring 2. In other words, the inner raceway surface 33 is formed on the outer side of the inner member by the hub wheel 3.

[0023] An axle hole 37 is formed in the inner diameter portion of the hub wheel 3, extending along the axial direction. The axle hole 37 penetrates the hub wheel 3 along the axial direction, and the shaft portion of a constant velocity universal joint can be connected to the axle hole 37.

[0024] An inner ring 4 is provided on the small-diameter stepped portion 31 of the hub ring 3. The inner ring 4 is fixed to the small-diameter stepped portion 31 of the hub ring 3 by press-fitting. An inner raceway surface 41 is provided on the outer circumferential surface of the inner ring 4 so as to face the outer raceway surface 23 on the inner side of the outer ring 2. In other words, the inner raceway surface 41 is formed on the inner side of the inner member by the inner ring 4.

[0025] The inner ball row 5 and the outer ball row 6, which are rolling elements, are composed of multiple balls 7, which are rolling elements, held by a retainer 8.

[0026] The inner ball row 5 is rotatably sandwiched between the inner raceway surface 41 of the inner ring 4 and the inner outer raceway surface 23 of the outer ring 2. The outer ball row 6 is rotatably sandwiched between the inner raceway surface 33 of the hub ring 3 and the outer outer raceway surface 24 of the outer ring 2. In other words, the inner ball row 5 and the outer ball row 6 are rotatably housed between the raceway surfaces of the outer and inner members.

[0027] The balls 7 in the inner ball row 5 are formed in a spherical shape and are in contact with the inner raceway surface 41 at the contact point 41a. The contact angle of the balls 7 in the inner ball row 5 with respect to the inner raceway surface 41 is θ1 (see Figure 3). The contact angle θ1 is the angle of inclination of the straight line L1 connecting the center P1 of the ball 7 in the inner ball row 5 and the contact point 41a with respect to the radial direction.

[0028] The balls 7 in the outer ball row 6 are formed in a spherical shape and are in contact with the inner raceway surface 33 at the contact point 33a. The contact angle of the balls 7 in the outer ball row 6 with respect to the inner raceway surface 33 is θ2 (see Figure 7). The contact angle θ2 is the angle of inclination of the straight line L2 connecting the center P2 of the ball 7 in the outer ball row 6 and the contact point 33a with respect to the radial direction.

[0029] Grease is applied between the balls 7 in the inner ball row 5 and the inner raceway surface 41 and the outer raceway surface 23, and between the balls 7 in the outer ball row 6 and the inner raceway surface 33 and the outer raceway surface 24.

[0030] In the wheel bearing device 1, a double-row angular contact ball bearing is constructed from an outer ring 2, a hub ring 3 and an inner ring 4, an inner ball row 5, and an outer ball row 6.

[0031] [Ball pitch circle] The pitch circle C1 (see Figure 5) of the balls 7 that make up the inner ball row 5 is a circle that centers on the axis of rotation X and passes through the center P1 of the balls 7 in the inner ball row 5. The pitch circle C2 (see Figure 8) of the balls 7 that make up the outer ball row 6 is a circle that centers on the axis of rotation X and passes through the center P2 of the balls 7 in the outer ball row 6.

[0032] The pitch circle diameter of the balls 7 constituting the inner ball row 5 and the pitch circle diameter of the balls 7 constituting the outer ball row 6 are formed to be the same size, and the pitch circle diameter of the balls 7 constituting the inner ball row 5 and the outer ball row 6 is a. The radius of the balls 7 held in the retainer 8 is r (see Figures 5 and 8).

[0033] The pitch circle diameters of the balls 7 constituting the inner ball row 5 and the pitch circle diameters of the balls 7 constituting the outer ball row 6 can be formed to be different sizes. For example, the pitch circle diameters of the balls 7 constituting the inner ball row 5 can be made larger than those of the balls 7 constituting the outer ball row 6. Similarly, the pitch circle diameters of the balls 7 constituting the outer ball row 6 can also be made larger than those of the balls 7 constituting the inner ball row 5.

[0034] [Cage] The details of the retainer 8 are described below.

[0035] The retainer 8 is rotatable about its axis of rotation. The axial direction of the retainer 8 is along the axis of rotation X. The radial direction of the retainer 8 is perpendicular to the axial direction of the retainer 8. The circumferential direction of the retainer 8 is along the arc centered on the axis of rotation of the retainer 8. The axis of rotation of the retainer 8 can be made to coincide with the axis of rotation X.

[0036] (Inner ball row holder) As shown in Figures 2 to 5, the retainer 8 in the inner ball row 5 comprises an annular portion 81 formed in an annular shape, a plurality of columnar portions 82 extending inward from the annular portion 81 in the axial direction and arranged at regular intervals along the circumferential direction, and a pocket 83 formed by adjacent columnar portions 82 and the annular portion 81, which holds the ball 7 by having a pocket surface 831 formed along the outer circumferential surface of the ball 7. The annular portion 81 formed in an annular shape is configured to be rotatable about a rotation axis. The rotation axis of the annular portion 81 extends in a direction along the rotation axis X. The direction in which the rotation axis of the annular portion 81 extends coincides with the axial direction of the retainer 8. The rotation axis of the annular portion 81 and the rotation axis of the retainer 8 coincide. Grease is applied between the pocket surface 831 of the retainer 8 and the ball 7.

[0037] The pocket surface 831 is formed in a spherical shape with the center P1 of the ball 7 constituting the inner ball row 5 as the center. In other words, the center of curvature Pa of the pocket surface 831 coincides with the center P1 of the ball 7 constituting the inner ball row 5. Therefore, the pitch circle passing through the center of curvature Pa of the pocket surface 831 with the rotation axis of the annular portion 81 as the center is the same as the pitch circle C1 of the ball 7 constituting the inner ball row 5. The pocket surface 831 is formed in a spherical shape throughout its entire surface.

[0038] The column portion 82 has a notch portion 821 that is recessed in the circumferential direction from the pocket curved surface 831. The notch portion 821 is cut out from the inner end of the column portion 82 toward the outer side and penetrates the column portion 82 in the circumferential direction.

[0039] By forming a notch 821 in the column portion 82, the inner portion of the column portion 82 is divided into an outer diameter side column portion 82A located on the outer diameter side and an inner diameter side column portion 82B located on the inner diameter side of the outer diameter side column portion 82A.

[0040] The notch 821 is formed in a region of the pocket surface 831 that includes a point through which the pitch circle C1 passes, centering on the rotation axis of the annular portion 81 and passing through the center P1 of the ball 7. In other words, the notch 821 is formed in a region of the pocket surface 831 that includes a point through which the pitch circle passes, centering on the rotation axis of the annular portion 81 and passing through the center of curvature Pa of the pocket surface 831.

[0041] The portion of the column 82 where the notch 821 is formed does not come into contact with the ball 7. Therefore, the formation of the notch 821 in the column 82 reduces the contact area between the pocket surface 831 and the ball 7 compared to when the notch 821 is not formed in the column 82.

[0042] In this embodiment, the notch 821 penetrates the column portion 82 in the circumferential direction. However, if the notch is configured to be recessed in the circumferential direction from the pocket curved surface 831, it is also possible to form it in a shape that does not penetrate the column portion 82 in the circumferential direction.

[0043] As shown in Figure 2, a claw portion 824 for holding the ball 7 is formed at the tip of the outer diameter column portion 82A. The surface of the claw portion 824 facing the ball 7 is a pocket curved surface 831. Similarly, a claw portion 825 for holding the ball 7 is formed at the tip of the inner diameter column portion 82B. The surface of the claw portion 825 facing the ball 7 is a pocket curved surface 831.

[0044] The column portion 82 has an outer diameter end face 822 located at the outer diameter end and an inner diameter end face 823 located at the inner diameter end. The outer diameter end face 822 and the inner diameter end face 823 are inclined surfaces that are tilted with respect to the axial direction.

[0045] The outer diameter end face 822 is inclined toward the inner diameter side as it approaches the annular portion 81 in the axial direction. The outer diameter end face 822 is an inclined surface that slopes axially from the end of the retainer 8 on the column portion 82 side toward the annular portion 81 side. The inclination angle α of the outer diameter end face 822 with respect to the axial direction is set to 10° to 50°.

[0046] The inner diameter end face 823 is inclined toward the outer diameter side as it approaches the annular portion 81 in the axial direction. The inner diameter end face 823 is an inclined surface that is inclined with respect to the axial direction from the end of the retainer 8 on the column portion 82 side to the end on the annular portion 81 side. The inclined surface of the inner diameter end face 823 is composed of a single inclined surface with a constant inclination angle from the axial end of the column portion 82 to the axial end of the annular portion 81. The inclination angle β of the inner diameter end face 823 with respect to the axial direction is set to 10° to 50°.

[0047] The center of curvature Pa of the pocket surface 831 coincides with the center P1 of the balls 7 that make up the inner ball row 5, and the radius of curvature ra of the pocket surface 831 is formed to be slightly larger than the radius r of the balls 7 that make up the inner ball row 5.

[0048] Therefore, a gap d is formed between the pocket surface 831 and the ball 7. The gap d is the gap in the diametrical direction of the ball 7 that is formed between the pocket surface 831 and the ball 7. As shown in Figure 5, in a cross-section along the straight line L1 connecting the center P1 of the ball 7 and the contact point 41a of the ball 7 with the inner raceway surface 41, the size of the gap d is constant in the radial direction.

[0049] Specifically, as shown in Figure 5, the gap d1 between the pocket curved surface 831 located at the outer diameter end of the column portion 82 and the ball 7, the gap d2 between the pocket curved surface 831 located at the inner diameter end of the column portion 82 and the ball 7, and the gap d3 between the pocket curved surface 831 located at the radial center of the column portion 82 and the ball 7 are formed to be the same value.

[0050] Thus, the gap d remains constant regardless of the radial position of the cross-section along the straight line L1 connecting the center P1 of the ball 7 and the contact point 41a of the ball 7 with the inner raceway surface 41.

[0051] Furthermore, since the pocket surface 831 is formed in a spherical shape throughout its entire area, and in addition, the center P1 of the ball 7 and the center of curvature Pa coincide, the size of the gap d is constant in the radial direction in a cross-section passing through the center P1 of the ball 7. Therefore, in a cross-section passing through the center P1 of the ball 7 and the outer diameter side column 82A or the inner diameter side column 82B, the gap d between the claw portions 824 and 825 at the tips of the outer diameter side column 82A and the inner diameter side column 82B and the ball is also constant.

[0052] In the retainer 8, the gap d between the pocket surface 831 and the ball 7 is set to be 0.1 mm to 0.5 mm. In other words, the radius of curvature ra of the pocket surface 831 is formed to a size such that the gap d is 0.1 mm to 0.5 mm.

[0053] Here, for example, as in the cage 18 shown in Figure 12, if the gap D between the pocket curved surface 1831 of the column 182 and the ball 7 is formed such that the gap D at the outer diameter end and inner diameter end of the column 82 is larger than the gap D at the radial center of the column 82, then the grease between the ball 7 and the outer raceway surface 23 and the inner raceway surface 41 adheres to the ball 7 and easily penetrates between the ball 7 and the pocket curved surface 1831 as the ball 7 rotates. This increases the resistance caused by the shearing of the grease, which is a factor that increases the rotational torque of the bearing device.

[0054] However, in the retainer 8, the size of the gap d between the pocket curved surface 831 and the ball 7 is formed to be constant in the radial direction, and the gap d1 at the outer diameter end and the gap d2 at the inner diameter end are not larger than the gap d3 at the radial center.

[0055] Therefore, when the grease between the ball 7 and the outer raceway surface 23 and the inner raceway surface 41 adheres to the ball 7 and attempts to enter the gap between the ball 7 and the pocket curved surface 831, it is scraped off by the outer diameter end face 822 or the inner diameter end face 823 of the column portion 82, reducing the amount of grease that enters the gap d.

[0056] This makes it possible to suppress the increase in rotational torque of the wheel bearing device 1 due to the shear resistance of grease that has entered between the ball 7 and the pocket surface 831. Consequently, it is possible to improve the fuel efficiency or electric power consumption of the vehicle on which the wheel bearing device 1 is installed.

[0057] In particular, in the retainer 8, the gap d between the pocket curved surface 831 and the ball 7 is set to 0.1 mm to 0.5 mm, which effectively reduces the amount of grease that enters the gap d.

[0058] Furthermore, since the column portion 82 has a notch portion 821 that is recessed in the circumferential direction from the pocket curved surface 831, the contact area between the pocket curved surface 831 and the ball 7 is reduced, thereby reducing the area over which shear resistance occurs in the grease present between the pocket curved surface 831 and the ball 7. This suppresses the increase in rotational torque of the wheel bearing device 1, thereby improving the fuel efficiency or electric power consumption of the vehicle on which the wheel bearing device 1 is installed.

[0059] Furthermore, since the outer diameter end face 822 and the inner diameter end face 823 of the column portion 82 are inclined surfaces that are tilted with respect to the axial direction, the grease scraped out by the outer diameter end face 822 and the inner diameter end face 823 moves toward the outer diameter side along the outer diameter end face 822 and the inner diameter end face 823 due to the centrifugal force accompanying the rotation of the retainer 8. This makes it possible to reduce the amount of grease that enters the gap d between the pocket curved surface 831 and the ball 7.

[0060] Specifically, the outer diameter end face 822 is inclined towards the outer diameter as it moves from the outer side to the inner side, so the grease moves along the outer diameter end face 822 towards the inner and outer diameter sides. The inner side in the axial direction is the side away from the outer raceway surface 23, and the grease that has moved along the outer diameter end face 822 is discharged to the inner and outer diameter side of the outer raceway surface 23, preventing it from flowing back into the outer raceway surface 23.

[0061] This reduces the amount of grease between the outer raceway surface 23 and the ball 7 that penetrates into the gap d between the pocket curved surface 831 and the ball 7, thereby suppressing an increase in the rotational torque of the wheel bearing device 1.

[0062] In particular, since the inclination angle α of the outer diameter end face 822 with respect to the axial direction is set to 10° to 50°, it is possible to effectively discharge grease to the inner and outer diameter sides of the outer raceway surface 23.

[0063] Furthermore, since the inner diameter end face 823 is inclined toward the outer diameter as it moves from the inner side to the outer side, the grease moves toward the outer and outer diameter side along the inner diameter end face 823. The outer side in the axial direction is the side away from the inner raceway surface 41, and the grease that has moved toward the inner diameter end face 823 is discharged toward the outer and outer diameter side of the inner raceway surface 41, preventing it from flowing back into the inner raceway surface 41.

[0064] This reduces the amount of grease between the inner raceway surface 41 and the ball 7 that penetrates into the gap d between the pocket curved surface 831 and the ball 7, thereby suppressing an increase in the rotational torque of the wheel bearing device 1.

[0065] In particular, since the inclination angle β of the inner raceway surface 41 with respect to the axial direction is set to 10° to 50°, it is possible to effectively discharge grease to the outer side and outer diameter side of the inner raceway surface 41.

[0066] In this embodiment, the outer diameter end face 822 of the column portion 82 is inclined toward the outer diameter as it moves from the outer side to the inner side, and the inner diameter end face 823 is inclined toward the outer diameter as it moves from the inner side to the outer side. However, it is also possible to configure it so that the outer diameter end face 822 is inclined toward the outer diameter as it moves from the inner side to the outer side, and the inner diameter end face 823 is inclined toward the outer diameter as it moves from the outer side to the inner side.

[0067] In this case as well, the grease scraped out by the outer diameter end face 822 and the inner diameter end face 823 can be moved axially and outward along the outer diameter end face 822 and the inner diameter end face 823, thereby reducing the amount of grease that enters the gap d between the pocket curved surface 831 and the ball 7.

[0068] However, if the outer diameter end face 822 is inclined toward the outer diameter side as it moves from the outer side to the inner side, and the inner diameter end face 823 is inclined toward the outer diameter side as it moves from the inner side to the outer side, it is possible to secure a larger radial length at the inner end of the outer diameter column portion 82A and the inner diameter column portion 82B, and the strength of the retainer 8 when a notch portion 821 is formed in the column portion 82 can be further increased.

[0069] As shown in Figure 6, the gap d between the pocket surface 831 and the ball 7 in the retainer 8 can also be formed such that the gap d1 at the outer diameter end of the column 82 and the gap d2 at the inner diameter end of the column 82 are smaller than the gap d3 at the radial center of the column 82. In other words, the gap d can be formed such that, in a cross-section along the straight line L1 connecting the center P1 of the ball 7 and the contact point 41a of the ball 7 with the inner raceway surface 41, the ends in the radial direction are smaller than the central part in the radial direction.

[0070] Making the gap d1 at the outer diameter end and the gap d2 at the inner diameter end smaller than the gap d3 at the radial center can be achieved, for example, by making the radius of curvature ra of the pocket surface 831 smaller than the radius r of the balls 7 that make up the inner ball row 5, and by positioning the pocket surface 831 such that the center of curvature Pa of the pocket surface 831 is closer to the pocket surface 831 than the center P1 of the ball 7. In this case, the center of curvature Pa of the pocket surface 831 can be positioned on the pitch circle C1 of the ball 7.

[0071] In this way, by making the gap d1 at the outer diameter end and the gap d2 at the inner diameter end smaller than the gap d3 at the radial center, the amount of grease entering the gap d between the pocket curved surface 831 and the ball 7 can be further reduced, thereby effectively suppressing the increase in rotational torque of the wheel bearing device 1. Furthermore, even when gaps d1 and d2 are made smaller than gap d3, it is preferable to set the gap d to be between 0.1 mm and 0.5 mm.

[0072] (Retainer for the outer ball row) As shown in Figures 7 and 8, the retainer 8 in the outer ball row 6 comprises an annular portion 81 formed in an annular shape, a plurality of columnar portions 82 extending axially outward from the annular portion 81 and arranged at regular intervals along the circumferential direction, and a pocket 83 formed by adjacent columnar portions 82 and the annular portion 81, which holds the ball 7 by having a pocket surface 831 formed along the outer circumferential surface of the ball 7. The annular portion 81 is configured to be rotatable about a rotation axis. The rotation axis of the annular portion 81 extends in a direction along the rotation axis X. The direction in which the rotation axis of the annular portion 81 extends coincides with the axial direction of the retainer 8. The rotation axis of the annular portion 81 and the rotation axis of the retainer 8 coincide. Grease is applied between the pocket surface 831 of the retainer 8 and the ball 7.

[0073] The pocket surface 831 is formed in a spherical shape centered on the center P2 of the balls 7 that make up the outer ball row 6. In other words, the center of curvature Pa of the pocket surface 831 coincides with the center P2 of the balls 7 that make up the outer ball row 6. Therefore, the pitch circle passing through the center of curvature Pa of the pocket surface 831 with the rotation axis of the annular portion 81 as the center is the same as the pitch circle C2 of the balls 7 that make up the outer ball row 6. The pocket surface 831 is formed in a spherical shape throughout its entire surface.

[0074] The column portion 82 has a notch portion 821 that is recessed in the circumferential direction from the pocket curved surface 831. The notch portion 821 is cut out from the outer end of the column portion 82 toward the inner side and penetrates the notch portion 821 in the circumferential direction.

[0075] The notch 821 is formed in a region of the pocket surface 831 that includes a point through which the pitch circle C2 passes, with the rotation axis of the annular portion 81 as the center P2 of the ball 7. In other words, the notch 821 is formed in a region of the pocket surface 831 that includes a point through which the pitch circle passes, with the rotation axis of the annular portion 81 as the center of curvature Pa of the pocket surface 831.

[0076] The center of curvature Pa of the pocket surface 831 coincides with the center P2 of the balls 7 that make up the outer ball row 6, and the radius of curvature ra of the pocket surface 831 is formed to be slightly larger than the radius r of the balls 7 that make up the outer ball row 6.

[0077] Therefore, a gap d is formed between the pocket surface 831 and the ball 7. The gap d is the gap in the diametrical direction of the ball 7 that is formed between the pocket surface 831 and the ball 7. As shown in Figure 8, in a cross-section along the straight line L2 connecting the center P2 of the ball 7 and the contact point 33a of the ball 7 with the inner raceway surface 33, the size of the gap d is constant in the radial direction.

[0078] Furthermore, the pocket surface 831 is formed in a spherical shape throughout its entire length, and in addition, the center P2 of the ball 7 and the center of curvature Pa coincide. Therefore, in a cross-section passing through the center P2 of the ball 7, the size of the gap d is constant in the radial direction. Consequently, in a cross-section passing through the center P1 of the ball 7 and the outer diameter side column 82A or the inner diameter side column 82B, the gap d between the claw portions 824 and 825 at the tips of the outer diameter side column 82A and the inner diameter side column 82B and the ball is also constant.

[0079] The outer diameter end face 822 of the column portion 82 is inclined toward the outer diameter as it moves from the inner side to the outer side. Grease scraped off by the outer diameter end face 822 moves toward the outer and outer diameter side along the outer diameter end face 822. The outer side in the axial direction is the side away from the outer raceway surface 24, and the grease that has moved toward the outer diameter end face 822 is discharged toward the inner and outer diameter side of the outer raceway surface 24, preventing it from flowing back into the outer raceway surface 24.

[0080] The inner diameter end face 823 of the column portion 82 is inclined toward the outer diameter as it moves from the outer side to the inner side. Grease scraped off by the inner diameter end face 823 moves toward the inner and outer diameter sides along the inner diameter end face 823. The inner side in the axial direction is the side away from the inner raceway surface 33, and the grease that has moved toward the inner diameter end face 823 is discharged toward the inner and outer diameter side of the inner raceway surface 33, preventing it from flowing back into the inner raceway surface 33.

[0081] The retainer 8 in the outer ball row 6 has the same configuration as the retainer 8 in the inner ball row 5, except that it is positioned symmetrically to the retainer 8 in the inner ball row 5, with a plane perpendicular to the axial direction in between. Therefore, a description of the other configurations of the retainer 8 in the outer ball row 6 is omitted.

[0082] [Examples of retainers] (Modified example of the retainer for the inner ball row) The retainer 8 in the inner ball row 5 can also be configured as retainer 8A shown in Figures 9 to 11.

[0083] The retainer 8A differs from retainer 8, in that the outer diameter end face 822 and the inner diameter end face 823 of the column portion 82 are formed on surfaces parallel to the axial direction, while the outer diameter end face 822 and the inner diameter end face 823 are inclined surfaces inclined with respect to the axial direction. The other configurations of retainer 8A are the same as those of retainer 8.

[0084] In the retainer 8A, the column portion 82 has a notch portion 821 that is recessed in the circumferential direction from the pocket surface 831. The notch portion 821 is formed in a region of the pocket surface 831 that includes a point through which a pitch circle passes, centered on the rotation axis X and passing through the center of curvature Pa of the pocket surface 831.

[0085] Therefore, the contact area between the pocket surface 831 and the ball 7 is reduced, and the area over which shear resistance occurs in the grease between the pocket surface 831 and the ball 7 can be reduced. This suppresses the increase in rotational torque of the wheel bearing device 1, thereby improving the fuel efficiency or electric power consumption of the vehicle on which the wheel bearing device 1 is installed.

[0086] Furthermore, in the cage 8A, the size of the gap d between the pocket surface 831 and the ball 7 is constant in the radial direction in a cross-section along the straight line L1 connecting the center P1 of the ball 7 and the contact point 41a of the ball 7 with the inner raceway surface 41. This reduces the amount of grease that enters the gap d between the ball 7 and the pocket surface 831, and makes it possible to suppress the increase in rotational torque of the wheel bearing device 1 due to the shear resistance of the grease that has entered between the ball 7 and the pocket surface 831. Consequently, the fuel efficiency or electric power consumption of the vehicle on which the wheel bearing device 1 is installed can be improved.

[0087] Furthermore, in the retainer 8A, the radius of curvature ra of the pocket surface 831 is formed to a size such that the gap d is 0.1 mm to 0.5 mm. This makes it possible to effectively reduce the amount of grease that enters the gap d.

[0088] (Modified example of the outer ball row retainer) The retainer 8 in the outer ball row 6 can also be configured in the same way as the retainer 8A for the retainer 8 in the inner ball row 5, with the outer diameter end face 822 and inner diameter end face 823 of the column portion 82 formed on surfaces parallel to the axial direction.

[0089] In this embodiment, a third-generation wheel bearing device 1 has been described in which the inner raceway surface 33 of the outer ball row 6 is directly formed on the outer circumference of the hub ring 3. However, the wheel bearing device is not limited to this, and may also be a second-generation structure in which a pair of inner rings are press-fitted and fixed to the hub ring, or a first-generation structure consisting of an outer ring which is an outer member and a pair of inner rings which are inner members, without a hub ring.

[0090] Although embodiments of the present invention have been described above, the present invention is not limited in any way to these embodiments, but is merely illustrative. It can be implemented in various other forms without departing from the spirit of the invention, and the scope of the present invention is indicated by the claims, and further includes all modifications within the meaning and scope of equivalents as described in the claims. [Explanation of Symbols]

[0091] 1. Wheel bearing device 2 Outer ring 3 Hub wheels 4. Inner Ring 5. Inner ball row 6 Outer ball row 7 Ball 8, 8A, 18 retainer 23 (Inner side) outer raceway surface 24 (Outer side) outer track surface 33 (Outer side) Inner raceway surface 41 (Inner side) Inner track surface 81 Annular section 82 Column section 83 pockets 821 Notch 822 Outer diameter end face 823 Inner diameter side end face 831 Pocket Curved Surface C1, C2 Pitch Circles d (the gap between the curved surface of the pocket and the ball) Center of curvature of the pocket surface (Pa) ra (radius of curvature of a pocket surface) X Rotation axis α (angle of inclination of the outer diameter end face) β (angle of the inner diameter end face)

Claims

1. An outer member having an outer raceway surface formed on its inner circumference, An inner member having an inner raceway surface facing the outer raceway surface, A plurality of rolling elements are interposed between the raceway surfaces of the outer member and the inner member so as to be able to roll, The system includes a retainer for holding the rolling elements, The aforementioned retainer is, A ring-shaped annular portion that is rotatable around a rotation axis, Multiple columnar portions extending axially from the annular portion and arranged at regular intervals in the circumferential direction, A pocket formed by adjacent columnar portions and annular portions, having a curved pocket surface formed along the outer circumferential surface of the rolling element, and holding the rolling element, Equipped with, The size of the gap in the radial direction of the rolling element formed between the curved surface of the pocket and the rolling element held by the pocket is constant in the radial direction of the cross section along the line connecting the center of the rolling element and the contact point of the rolling element with the inner raceway surface, or the radial end is smaller than the radial center. The aforementioned column section is A wheel bearing device having a notch formed in the pocket surface, which includes a point through which a pitch circle passes, centering on the rotation axis of the annular portion and passing through the center of curvature of the pocket surface, and recessed from the pocket surface.

2. The wheel bearing device according to claim 1, wherein the outer diameter end face and the inner diameter end face of the column portion are inclined surfaces that are inclined with respect to the axial direction from the end of the retainer on the column portion side to the annular portion side.

3. The outer diameter end face of the column portion is inclined toward the inner diameter side as it approaches the annular portion in the axial direction. The wheel bearing device according to claim 2, wherein the inner diameter end face of the column portion is inclined toward the outer diameter side as it approaches the annular portion in the axial direction.

4. The inclination angle α of the outer diameter end face with respect to the axial direction is 10° to 50°. The wheel bearing device according to claim 2 or claim 3, wherein the inclination angle β of the inner diameter side end face with respect to the axial direction is 10° to 50°.

5. The radius of curvature of the aforementioned pocket surface is, The gap between the curved surface of the pocket and the rolling element held by the pocket is formed to be 0.1 mm to 0.5 mm. A wheel bearing device according to claim 1 or claim 2.

6. The column portion is divided into an outer diameter side column portion located on the outer diameter side and an inner diameter side column portion located on the inner diameter side of the outer diameter side column portion. A claw portion for holding the rolling element is formed at the tip of the outer diameter side column portion. A wheel bearing device according to claim 1 or claim 2.

7. The column portion is divided into an outer diameter side column portion located on the outer diameter side and an inner diameter side column portion located on the inner diameter side of the outer diameter side column portion. A claw portion for gripping the rolling element is formed at the tip of the inner diameter side column portion. A wheel bearing device according to claim 1 or claim 2.

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