Wheel bearing device

Abstract

To provide a wheel bearing device capable of setting mechanical characteristics such as rolling fatigue life and rigidity within an appropriate range, and realizing low torque and light weighting.SOLUTION: In a wheel bearing device 1, an outer diameter a at an inner side end part of an outer ring 2 and an axial distance b between a flange surface 3k of a hub flange 3b and an inner side end face 4b of an inner ring 4 satisfy the relationship (a / b)>1.2, and a pitch circle diameter PCDo of balls 7 constituting an outer side ball row 6 and a pitch circle diameter PCDi of balls 7 constituting an inner side ball row satisfy the relationship PCDo<PCDi.SELECTED DRAWING: Figure 2

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 of a vehicle such as an automobile is known.

[0003] In recent years, in vehicles in which wheel bearing devices are used, fuel regulations have been imposed due to social backgrounds such as energy conservation and decarbonization, and the trend of electrification is progressing. In the future, in electric vehicles that use in-vehicle batteries as the main power source and are expected to spread, the vehicle weight is larger than that of gasoline vehicles, and the axle load tends to increase.

[0004] Generally, when the axle load increases, the rotational torque of the wheel bearing device increases, and it is necessary to increase the size of the wheel bearing device from the viewpoint of strength. For example, a wheel bearing device used in an electric vehicle has a tendency to have a narrow and large diameter in which the outer diameter at the axial end of the outer ring is larger than the axial distance between the flange surface of the hub flange in the hub ring and the axial end surface of the inner ring fitted to the hub ring, and the weight is increased compared to the wheel bearing device used in a gasoline vehicle. Therefore, in the wheel bearing device used in an electric vehicle, reduction of torque and weight are required.

[0005] In Patent Document 1, for a wheel bearing device in which the pitch circle diameter of the rolling elements in the inner rolling element row is formed larger than the pitch circle diameter of the rolling elements in the outer rolling element row, and the diameter of the rolling elements in the inner rolling element row is formed larger than the diameter of the rolling elements in the outer rolling element row, the groove bottom side and shoulder side raceway surface curvature radii on the raceway surfaces of the outer ring and the inner ring are formed larger than the raceway surface curvature radius around the contact portion of the rolling elements on the raceway surface.

[0006] With such a configuration, while ensuring the rolling fatigue life and moment rigidity, the occurrence of edge loading on the rolling surfaces of the rolling elements is suppressed, thereby improving the durability of the wheel bearing device. However, Patent Document 1 does not describe specific numerical values such as the diameter of the rolling elements, the number of rolling elements, and the contact angle of the rolling elements with respect to the raceway surface. Depending on these numerical values, it may be difficult to sufficiently obtain the rolling fatigue life and moment rigidity.

[0007] Further, Patent Document 1 describes a wheel bearing device in which the pitch circle diameter of the rolling elements in the outer rolling element row is formed larger than the pitch circle diameter of the rolling elements in the inner rolling element row.

[0008] In a wheel bearing device used for a gasoline vehicle, in many cases, the outer diameter at the axial end of the inner ring is smaller than or equal to the axial distance between the flange surface of the hub flange in the hub ring and the axial end face of the inner ring fitted to the hub ring. In order to ensure sufficient rolling fatigue life and rigidity in a limited space, a structure in which the pitch circle diameter of the outer rolling elements is larger than the pitch circle diameter of the inner rolling elements, as described in Patent Document 1, is more appropriate.

[0009] On the other hand, in a wheel bearing device for an electric vehicle in which the width is reduced and the diameter is increased as the axle load increases, since it is possible to form a large pitch circle diameter of the inner rolling elements, if the pitch circle diameter of the outer rolling elements is formed larger than or equal to the pitch circle diameter of the inner rolling elements, mechanical characteristics such as the rolling fatigue life and rigidity of the outer side may be improved more than necessary.

[0010] In addition, when the wheel bearing device becomes narrow-width and large-diameter, the axial distance from the flange surface of the hub flange to the center position of the wheel attached to the flange surface tends to increase. Moreover, since the axle load of an electric vehicle is large, the moment load and rotational torque generated in the wheel bearing device are likely to increase. Further, when the axle load increases, it is necessary to increase the pitch circle diameter of the rolling elements, the diameter of the rolling elements, and the number of rolling elements, so the weight of the wheel bearing device is likely to increase.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0012] For this reason, in a narrow-width and large-diameter wheel bearing device, if the pitch circle diameter of the outer rolling elements is formed to be larger than or equal to the pitch circle diameter of the inner rolling elements, mechanical properties such as rolling fatigue life and rigidity become excessive, while it becomes difficult to satisfy environmental performance such as low torque and weight reduction.

[0013] The present invention has been made in view of the above circumstances, and provides a wheel bearing device that can set mechanical properties such as rolling fatigue life and rigidity within an appropriate range while forming the pitch circle diameter of the inner rolling elements to be larger than the pitch circle diameter of the outer rolling elements, and can achieve low torque and weight reduction.

Means for Solving the Problems

[0014] That is, the wheel bearing device includes an outer member having a first outer raceway surface formed on one axial end side and a second outer raceway surface formed on the other axial end side with respect to the first outer raceway surface, a hub flange for attaching a wheel on one axial end side, and a hub ring having a first inner raceway surface facing the first outer raceway surface, and an inner member including an inner ring fitted to the other axial end side of the hub ring and having a second inner raceway surface facing the second outer raceway surface, a first rolling element rotatably accommodated between the first outer raceway surface and the first inner raceway surface, and a second rolling element rotatably accommodated between the second outer raceway surface and the second inner raceway surface. In the wheel bearing device, an outer diameter a at the other axial end of the outer member and an axial distance b between the flange surface of the hub flange and the other axial end side surface of the inner ring satisfy the relationship (a / b)>1.2, and a pitch circle diameter PCDo of the first rolling element and a pitch circle diameter PCDi of the second rolling element satisfy the relationship PCDo<PCDi.

Advantages of the Invention

[0015] According to the present invention, while achieving low torque and weight reduction, mechanical characteristics such as rolling fatigue life and rigidity can be set within an appropriate range.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

[0018] [Wheel bearing device] The wheel bearing device 1 shown in FIG. 1 is an embodiment of the wheel bearing device according to the present invention, and rotatably supports a wheel in a suspension device of a vehicle such as an automobile.

[0019] 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 perpendicular to the rotation axis X. Further, the outer side represents the wheel side of the wheel bearing device 1 when attached to the vehicle body at one end side in the axial direction, and the inner side represents the vehicle body side of the wheel bearing device 1 when attached to the vehicle body at the other end side in the axial direction.

[0020] The wheel bearing device 1 has a configuration called the third generation, and includes an outer ring 2 which is an outer member, a hub ring 3 and an inner ring 4 which are inner members, two rows of inner side ball rows 5 and outer side ball rows 6 which are rolling element rows, and an inner side seal member 9 and an outer side seal member 10.

[0021] An inner side opening 2a into which the inner side seal member 9 can be fitted is formed at the inner side end portion of the outer ring 2. An outer side opening 2b into which the outer side seal member 10 can be fitted is formed at the outer side end portion of the outer ring 2.

[0022] An inner side outer raceway surface 2c and an outer side outer raceway surface 2d are formed on the inner peripheral surface of the outer ring 2. The outer side outer raceway surface 2d is an example of a first outer raceway surface, and the inner side outer raceway surface 2c is an example of a second outer raceway surface. A vehicle body mounting flange 2e for mounting the outer ring 2 to a vehicle body side member is integrally formed on the outer peripheral surface of the outer ring 2. The inner side end portion of the outer ring 2 is a pilot portion that is fitted to a vehicle body side member.

[0023] At the inner side end of the outer peripheral surface 3j of the hub ring 3, a small-diameter step portion 3a having a diameter smaller than that of the outer side end is formed. At the outer side end of the hub ring 3, a hub flange 3b for attaching a wheel is integrally formed.

[0024] A plurality of bolt holes 3e are formed in the hub flange 3b. A hub bolt 3f for fastening the hub ring 3 and a wheel or a brake component is press-fitted into the bolt hole 3e. The hub flange 3b has a flange surface 3k facing the outer side. The hub ring 3 has a through hole 3i penetrating in the axial direction, and a constant velocity joint can be fitted into the through hole 3i so as to be rotatable integrally with the hub ring 3.

[0025] An inner side raceway surface 3c is provided on the outer peripheral surface 3j of the hub ring 3 so as to face the outer side raceway surface 2d on the outer side of the outer ring 2. That is, the inner side raceway surface 3c is formed by the hub ring 3 on the outer side of the inner member. The inner side raceway surface 3c of the hub ring 3 is an example of a first inner side raceway surface. In the hub ring 3, a lip sliding surface 3d with which the outer side seal member 10 slides in contact is formed on the base side of the hub flange 3b.

[0026] The inner side seal member 9 is fitted to the inner side opening end of the annular space S formed by the outer ring 2 and the hub ring 3, and closes the inner side opening end. The outer side seal member 10 is fitted to the outer side opening end of the annular space S formed by the outer ring 2 and the hub ring 3, and closes the outer side opening end.

[0027] The inner ring 4 is provided on the small-diameter step portion 3a of the hub ring 3. The inner ring 4 is fixed to the small-diameter step portion 3a of the hub ring 3 by press-fitting and caulking. The inner ring 4 applies preload to the inner side ball row 5 and the outer side ball row 6, which are rolling rows. The inner ring 4 has an inner side end face 4b at the inner side end. At the inner side end of the hub ring 3, a caulked portion 3h caulked to the inner side end face 4b of the inner ring 4 is formed. The inner ring 4 fitted to the small-diameter step portion 3a of the hub ring 3 has a fitting surface 4c with respect to the hub ring 3. The fitting surface 4c is the inner peripheral surface of the inner ring 4.

[0028] On the outer peripheral surface of the inner ring 4, an inner side inner raceway surface 4a is provided so as to face the outer side raceway surface 2c on the inner side of the outer ring 2. That is, on the inner side of the inner member, the inner side raceway surface 4a is formed by the inner ring 4. The inner side raceway surface 4a of the inner ring 4 is an example of a second inner raceway surface.

[0029] The inner side ball row 5 and the outer side ball row 6, which are rolling rows, are configured by a plurality of balls 7, which are rolling elements, being held by a cage 8. The inner side ball row 5 is rotatably sandwiched between the inner side inner raceway surface 4a of the inner ring 4 and the outer side raceway surface 2c on the inner side of the outer ring 2. The outer side ball row 6 is rotatably sandwiched between the inner raceway surface 3c of the hub ring 3 and the outer side raceway surface 2d on the outer side of the outer ring 2.

[0030] That is, the inner side ball row 5 and the outer side ball row 6 are rotatably accommodated between the raceway surfaces of both the outer member and the inner member. The balls 7 of the outer side ball row 6 are an example of a first rolling element, and the balls 7 of the inner side ball row 5 are an example of a second rolling element.

[0031] In the wheel bearing device 1, a double-row angular ball bearing is configured by the outer ring 2, the hub ring 3 and the inner ring 4, the inner side ball row 5, and the outer side ball row 6. Note that the wheel bearing device 1 may be configured as a double-row tapered roller bearing instead of the double-row angular ball bearing.

[0032] [Relationship between Dimensions of Each Part in Wheel Bearing Device] As shown in Fig. 1, the outer diameter at the inner side end of the outer ring 2 is a. Also, the axial distance between the flange surface 3k of the hub flange 3b and the inner side end face 4b of the inner ring 4 is b. The outer diameter a and the axial distance b satisfy the relationship of (a / b) > 1.2.

[0033] That is, the outer diameter a at the inner side end of the outer ring 2 is formed to be larger than 1.2 times the axial distance b between the flange surface 3k and the inner side end face 4b of the inner ring 4, and the wheel bearing device 1 is configured to be narrow-width and large-diameter. In this embodiment, it is set to (a / b) = 1.46, satisfying the relationship of (a / b) > 1.2.

[0034] The pitch circle diameter of the balls 7 constituting the inner side ball row 5 is PCDi, and the pitch circle diameter of the balls 7 constituting the outer side ball row 6 is PCDo. The pitch circle diameter PCDi of the inner side ball row 5 is the diameter of a circle centered on the rotation axis X and passing through the center Ci of the balls 7 in the inner side ball row 5. The pitch circle diameter PCDo of the outer side ball row 6 is the diameter of a circle centered on the rotation axis X and passing through the center Co of the balls 7 in the outer side ball row 6.

[0035] The pitch circle diameter PCDo of the outer side ball row 6 and the pitch circle diameter PCDi of the inner side ball row 5 satisfy the relationship of PCDo < PCDi. That is, the pitch circle diameter PCDi of the inner side ball row 5 is formed to be larger than the pitch circle diameter PCDo of the outer side ball row 6.

[0036] In this way, in the wheel bearing device 1, while forming the pitch circle diameter PCDi of the inner side ball row 5 to be larger than the pitch circle diameter PCDo of the outer side ball row 6, by forming the outer diameter a at the inner side end of the outer ring 2 to be larger than 1.2 times the axial distance b between the flange surface 3j and the inner side end face 4b of the inner ring 4, reduction of torque and weight, which are environmental performances, are achieved, and mechanical characteristics such as rolling fatigue life and rigidity are set within an appropriate range.

[0037] As shown in Fig. 2, the radius of curvature of the outer raceway surface 2d on the outer side of the outer ring 2 is Roo, the radius of curvature of the outer raceway surface 2c on the inner side of the outer ring 2 is Rio, the radius of curvature of the inner raceway surface 3c of the hub ring 3 is Roi, and the radius of curvature of the inner raceway surface 4a of the inner ring 4 is Rii. Also, the diameter of the ball 7 in the outer ball row 6 is Do, and the diameter of the ball 7 in the inner ball row 5 is Di.

[0038] The radius of curvature Roi of the inner raceway surface 3c on the outer side is set to be 51% to 53% of the diameter Do of the ball 7 in the outer ball row 6. The radius of curvature Rii of the inner raceway surface 4a on the inner side is set to be 51% to 53% of the diameter Di of the ball 7 in the inner ball row 5.

[0039] The radius of curvature Roo of the outer raceway surface 2d on the outer side is set to be 52% to 54% of the diameter Do of the ball 7 in the outer ball row 6. The radius of curvature Rio of the outer raceway surface 2c on the inner side is set to be 52% to 54% of the diameter Di of the ball 7 in the inner ball row 5.

[0040] By setting the radius of curvature of each raceway surface to such a size range, it is possible to reduce the rolling fatigue life of each raceway surface.

[0041] Also, the radius of curvature Rii of the inner raceway surface 4a on the inner side, the radius of curvature Rio of the outer raceway surface 2c on the inner side, the radius of curvature Roi of the inner raceway surface 3c on the outer side, and the radius of curvature Roo of the outer raceway surface 2d on the outer side preferably satisfy Rii < Rio or Roi < Roo within a predetermined numerical range.

[0042] By setting it in this way, it becomes possible to further reduce the rotational torque of the wheel bearing device 1. Specifically, since the circumferential length of the raceway surface is larger and the torque is more likely to increase in the outer raceway surfaces 2c and 2d than in the inner raceway surfaces 4a and 3c, by setting the radius of curvature Rii < the radius of curvature Rio, or the radius of curvature Roi < the radius of curvature Roo, the sliding surfaces of the balls 7 in the outer raceway surfaces 2c and 2d can be made smaller than the sliding surfaces of the balls 7 in the inner raceway surfaces 4a and 3c, and it becomes possible to reduce the rotational torque.

[0043] Also, the radius of curvature Rii of the inner raceway surface 4a on the inner side, the radius of curvature Rio of the outer raceway surface 2c on the inner side, the radius of curvature Roi of the inner raceway surface 3c on the outer side, and the radius of curvature Roo of the outer raceway surface 2d on the outer side preferably satisfy Roi ≤ Rii and Roo ≤ Rio within a predetermined numerical range.

[0044] By setting it in this way, it is possible to suppress the excessive decrease in the rolling life of the outer ball row 6 with respect to the inner ball row 5. Specifically, when the pitch circle diameter PCD o < the pitch circle diameter PCD i and 0.35 mm < (D i - D o) < 0.80 mm are set, if the radius of curvature Roi > the radius of curvature Rii and the radius of curvature Roo > the radius of curvature Rio, the contact surface pressure of the outer ball row 6 with a smaller ball diameter against the inner raceway surface 3c and the outer raceway surface 2d on the outer side is likely to increase excessively with respect to the contact surface pressure of the inner ball row 5 with a larger ball diameter against the inner raceway surface 4a and the outer raceway surface 2c on the inner side, and there is a risk that the life of the outer ball row 6 will decrease excessively with respect to the life of the inner ball row 5.

[0045] In this way, if the life of the outer ball row 6 decreases excessively compared to the inner ball row 5, there is a risk that the optimization of the mechanical characteristics of the outer ball row 6 and the inner ball row 5 cannot be achieved. Therefore, it is preferable to set the radius of curvature Roi ≤ the radius of curvature Rii and the radius of curvature Roo ≤ the radius of curvature Rio.

[0046] Furthermore, in order to optimize the mechanical characteristics and environmental performance, it is preferable that the radius of curvature Rii < the radius of curvature Rio, or the radius of curvature Roi < the radius of curvature Roo, and the radius of curvature Roi ≤ the radius of curvature Rii, and the radius of curvature Roo ≤ the radius of curvature Rio are satisfied.

[0047] As shown in FIG. 2, the ball 7 in the inner ball row 5 is in contact with the inner raceway surface 4a at the contact point 41, and the contact angle of the ball 7 in the inner ball row 5 with respect to the inner raceway surface 4a is αi. Also, the ball 7 in the inner ball row 5 is in contact with the outer raceway surface 2c at the contact point 21, and the contact angle of the ball 7 in the inner ball row 5 with respect to the outer raceway surface 2c is αi.

[0048] The contact angle αi is the inclination angle with respect to the radial direction of the straight line Li passing through the center Ci of the ball 7 in the inner ball row 5 and the contact points 41 and 21.

[0049] The ball 7 in the outer ball row 6 is in contact with the inner raceway surface 3c at the contact point 31, and the contact angle of the ball 7 in the outer ball row 6 with respect to the inner raceway surface 3c is αo. Also, the ball 7 in the outer ball row 6 is in contact with the outer raceway surface 2d at the contact point 22, and the contact angle of the ball 7 in the outer ball row 6 with respect to the outer raceway surface 2d is αo.

[0050] The contact angle αo is the inclination angle with respect to the radial direction of the straight line Lo passing through the center Co of the ball 7 in the outer ball row 6 and the contact points 31 and 22.

[0051] The contact angle αi of the ball 7 with respect to the inner raceway surface 4a and the outer raceway surface 2c in the inner ball row 5, and the contact angle αo of the ball 7 with respect to the inner raceway surface 3c and the outer raceway surface 2d in the outer ball row 6 satisfy the relationship αo≥αi. In the present embodiment, the contact angle αo is set to 40°, the contact angle αi is set to 35°, and the relationship αo≥αi is satisfied. Note that the contact angle αo can be set to 35° to 45°.

[0052] In the wheel bearing device 1, since the load on the outer raceway surface is larger than the load on the inner raceway surface, the rolling fatigue life of the outer raceway surface is more disadvantageous than that of the inner raceway surface.

[0053] However, by setting the contact angle αo of the inner raceway surface 3c and the outer raceway surface 2d on the outer side to be equal to or larger than the contact angle αi of the inner raceway surface 4a and the outer raceway surface 2c on the inner side, it is possible to suppress the rolling fatigue life of the inner raceway surface 3c and the outer raceway surface 2d on the outer side from decreasing more than the rolling fatigue life of the inner raceway surface 4a and the outer raceway surface 2c on the inner side.

[0054] Also, the diameter Di of the ball 7 in the inner ball row 5 is formed larger than the diameter Do of the ball 7 in the outer ball row 6 (Di>Do), and the diameter Di of the inner ball 7 and the diameter Do of the outer ball 7 satisfy the relationship 0.35mm<(Di - Do)<0.80mm. Further, the number Zi of the balls 7 in the inner ball row 5 and the number Zo of the balls 7 in the outer ball row 6 are set to the same number (Zi = Zo).

[0055] In a wheel bearing device 1 in which the pitch circle diameter PCDi of the inner side ball row 5 is formed larger than the pitch circle diameter PCDo of the outer side ball row 6, the number Zi of the inner side balls 7 and the number Zo of the outer side balls 7 are set to the same number, and further, the diameter Di of the inner side balls 7 and the diameter Do of the outer side balls 7 satisfy the relationship of 0.35 mm < (Di - Do) < 0.80 mm. By configuring in this way, it is possible to suppress the mechanical characteristics such as the rolling fatigue life and rigidity on the outer side from becoming excessive with respect to the inner side, and it is possible to set the mechanical characteristics on the outer side and the inner side within an appropriate range.

[0056] Also, a straight line Li passing through the center Ci of the ball 7 and the contact point 41 in the inner side ball row 5 passes through the fitting surface 4c of the hub ring 3 of the inner ring 4. If the straight line Li passed through the inner side of the fitting surface 4c of the inner ring 4, the hub ring 3 might not be able to sufficiently receive the load from the inner side ball 7, and the rigidity of the wheel bearing device might decrease.

[0057] However, in the wheel bearing device 1, since the straight line Li passes through the fitting surface 4c, the hub ring 3 can sufficiently receive the load from the inner side ball 7, and it is possible to ensure the rigidity of the wheel bearing device 1.

[0058] In the wheel bearing device 1, the radius of curvature of the shoulder side raceway surface 4aa located at the inner side end of the inner side raceway surface 4a of the inner side can be formed larger than the radius of curvature of the inner side raceway surface 4a near the contact point 41. The radius of curvature of the shoulder side raceway surface 3ca located at the outer side end of the inner side raceway surface 3c of the outer side can be formed larger than the radius of curvature of the inner side raceway surface 3c near the contact point 31.

[0059] The radius of curvature of the shoulder-side raceway surface 2ca located at the outer end of the outer raceway surface 2c on the inner side can be formed to be larger than the radius of curvature of the outer raceway surface 2c near the contact point 21. The radius of curvature of the shoulder-side raceway surface 2da located at the inner end of the outer raceway surface 2d on the outer side can be formed to be larger than the radius of curvature of the outer raceway surface 2d near the contact point 22.

[0060] In this way, by forming the radius of curvature of the shoulder-side raceway surface on each raceway surface to be larger than the radius of curvature near the contact point with the ball 7 on each raceway surface, it becomes possible to suppress a decrease in durability due to edge loading that occurs when the ball 7 rides up on the shoulder.

[0061] As shown in FIGS. 1 and 2, on the outer end of the hub ring 3, a wheel WH constituting a wheel is attached to the flange surface 3k of the hub flange 3b. The central position in the axial direction of the wheel WH is Wp. The wheel center distance, which is the axial distance between the flange surface 3k of the hub flange 3b and the central position Wp in the axial direction of the wheel WH attached to the flange surface 3k, is Wc.

[0062] Also, a straight line Li passing through the center Ci of the ball 7 and the contact point 41 in the inner ball row 5 and a straight line Lo passing through the center Co of the ball 7 and the contact point 31 in the outer ball row 6 intersect at the span center SP. The span center SP is the span center between the ball 7 in the inner ball row 5 and the ball 7 in the outer ball row 6. The span center distance, which is the axial distance between the flange surface 3k of the hub flange 3b and the span center SP, is Bc.

[0063] In the wheel bearing device 1, the wheel center distance Wc, the span center distance Bc, the contact angle αi of the inner ball 7 with respect to the inner raceway surface 4a, and the contact angle αo of the outer ball 7 with respect to the inner raceway surface 3c satisfy the relationship of (Bc - Wc) ≤ (-0.57×(αo - αi) + 7.15 mm). That is, it is configured such that the difference in the axial positions between the wheel center distance Wc and the span center distance Bc is within (-0.57×(αo - αi) + 7.15 mm).

[0064] For example, when αo is set to 40° and αi is set to 35°, the above relationship becomes (Bc - Wc) ≤ 4.3 mm. However, in this embodiment, when αo = 40° and αi = 35°, the wheel center distance Wc and the span center distance Bc are set such that (Bc - Wc) = -0.4 mm, satisfying (Bc - Wc) ≤ 4.3 mm.

[0065] Thus, in the wheel bearing device 1 in which the inner pitch circle diameter PCDi is formed larger than the outer pitch circle diameter PCDo, when configured such that (Bc - Wc) ≤ (-0.57×(αo - αi) + 7.15 mm), for example, with respect to a wheel bearing device in which the inner pitch circle diameter PCDi and the outer pitch circle diameter PCDo are formed to have the same diameter, the span center SP will move inward.

[0066] Thereby, the moment load applied to the wheel bearing device 1 can be reduced, and the rotational torque of the wheel bearing device 1 formed with a narrow width and a large diameter can be decreased.

[0067] In addition, when configured to satisfy the relationship of pitch circle diameter PCDo < pitch circle diameter PCDi and (Bc - Wc) ≤ (-0.57 × (αo - αi) + 7.15 mm), it is preferable to configure to simultaneously satisfy the relationship of number of teeth Zo = number of teeth Zi, the relationship of 0.35 mm < (Di - Do) < 0.80 mm, and the relationship of αo ≥ αi. By configuring in this way, while setting mechanical properties such as rolling fatigue life and rigidity within an appropriate range, it becomes possible to efficiently reduce torque and weight.

[0068] Fig. 3 shows the outer ring 2 and the hub ring 3 when the inner pitch circle diameter PCDi is formed larger than the outer pitch circle diameter PCDo as in the present embodiment by solid lines, and shows the outer ring 2 and the hub ring 3 when the inner pitch circle diameter PCDi and the outer pitch circle diameter PCDo are formed to have the same size by two-dot chain lines. In addition, light ink is applied to the region where the shapes of the outer ring 2 and the hub ring 3 shown by the solid lines are different from the shapes of the outer ring 2 and the hub ring 3 shown by the two-dot chain lines.

[0069] When calculating the increase / decrease rate of the weights of the outer ring 2 and the hub ring 3 in the present embodiment where the pitch circle diameter PCDi is formed larger than the pitch circle diameter PCDo, with the weights of the outer ring 2 and the hub ring 3 when the pitch circle diameter PCDi and the pitch circle diameter PCDo are formed to have the same size as the denominator, the weights of the outer ring 2 and the hub ring 3 in the present embodiment can be reduced by about 7% with respect to the weights of the outer ring 2 and the hub ring 3 when the pitch circle diameter PCDi and the pitch circle diameter PCDo are formed to have the same size.

[0070] The weight reduction rate of the outer ring 2 and the hub ring 3 is approximately proportional to the value of (PCDo 2 - PCDi 2 ). Therefore, forming the inner pitch circle diameter PCDi larger than the outer pitch circle diameter PCDo effectively acts on weight reduction in the wheel bearing device 1 formed with a large axial load and a narrow and large diameter as in the present embodiment.

[0071] In addition, by reducing the weights of the outer ring 2 and the hub ring 3, the materials and the grinding amount used in manufacturing the outer ring 2 and the hub ring 3 can be reduced, so that the manufacturing cost of the wheel bearing device 1 can be reduced.

[0072] [Second Embodiment of Wheel Bearing Device] The wheel bearing device 1 is configured for a driving wheel in which the inner ring 4 is caulked by the hub ring 3. However, the wheel bearing device 1 can also be configured for a driven wheel like the wheel bearing device 1A shown in FIG. 4. The wheel bearing device 1A is different from the wheel bearing device 1 in that it includes a hub ring 3A instead of the hub ring 3.

[0073] The hub ring 3A does not have a through hole 3i penetrating in the axial direction. Instead, it has a recess 3m recessed in the axial direction from the outer side. Other configurations of the hub ring 3A are the same as those of the hub ring 3.

[0074] In the wheel bearing device 1A, the relationship between the dimensions of each part can be the same as that of the wheel bearing device 1 described above. As a result, in the wheel bearing device 1A, while achieving low torque and weight reduction, it is possible to set mechanical characteristics such as rolling fatigue life and rigidity within an appropriate range.

[0075] [Third Embodiment of Wheel Bearing Device] The wheel bearing device 1 is configured for a driving wheel in which the inner ring 4 is caulked by the hub ring 3. However, as in the wheel bearing device 1B shown in FIG. 5, it can also be configured for a driving wheel in which the inner ring 4 is not caulked by the hub ring 3. The wheel bearing device 1B is different from the wheel bearing device 1 in that it includes a hub ring 3B instead of the hub ring 3.

[0076] The hub ring 3A is different from the hub ring 3 in that it does not have a caulking portion 3h for caulking the inner ring 4. Other configurations of the hub ring 3B are the same as those of the hub ring 3.

[0077] In the wheel bearing device 1B, it is possible to have the relationship of each part dimension similar to that of the wheel bearing device 1 described above. Thereby, in the wheel bearing device 1B, while achieving low torque and weight reduction, it is possible to set mechanical characteristics such as rolling fatigue life and rigidity within an appropriate range.

[0078] [Second Embodiment of Bolt Hole of Hub Flange] The bolt hole 3e formed in the hub flange 3b can also be formed as a tapped hole like the bolt hole 3eA shown in FIG. 6. A wheel bolt is fastened to the bolt hole 3eA formed by the tapped hole from the outer side.

[0079] As described above, the embodiments of the present invention have been explained. However, the present invention is not limited to such embodiments at all, and is merely illustrative. Of course, the present invention can be implemented in various other forms without departing from the gist of the present invention. The scope of the present invention is shown by the description in the claims, and further includes the equivalent meaning described in the claims and all modifications within the scope.

Explanation of Reference Numerals

[0080] 1 Wheel bearing device 2 Outer ring 2c (Inner side) outer raceway surface 2d (Outer side) outer raceway surface 3 Hub ring 3a Small diameter step portion 3b Hub flange 3c Inner raceway surface 3k Flange surface 4 Inner ring 4a Inner raceway surface 4b Inner side end face 5 Inner side ball row 6 Outer side ball row 7 Ball a Outer diameter (at the other axial end of the outer ring) b Axial distance (between the flange surface and the inner side end face of the inner ring) PCDi (Pitch circle diameter of the balls in the inner ball row) PCDo (Pitch circle diameter of the balls in the outer ball row)

Claims

1. An outer member having a first outer raceway surface formed on one axial end side, and a second outer raceway surface formed on the other axial end side of the first outer raceway surface; A hub ring having a hub flange for attaching a wheel on one axial end side, and having a first inner raceway surface facing the first outer raceway surface, and an inner member including an inner ring fitted to the other axial end side of the hub ring and having a second inner raceway surface facing the second outer raceway surface; A first rolling element rollably accommodated between the first outer raceway surface and the first inner raceway surface; A second rolling element rollably accommodated between the second outer raceway surface and the second inner raceway surface, the wheel bearing device comprising: The outer diameter a at the other axial end of the outer member, and the axial distance b between the flange surface of the hub flange and the other axial end side surface of the inner ring satisfy: (a / b) > 1.2 And satisfy the relationship of: The pitch circle diameter PCDo of the first rolling element and the pitch circle diameter PCDi of the second rolling element satisfy: PCDo < PCDi A wheel bearing device characterized by satisfying the relationship of.

2. The curvature radius Roi of the first inner raceway surface is 51% to 53% of the diameter Do of the first rolling element; The curvature radius Rii of the second inner raceway surface is 51% to 53% of the diameter Di of the second rolling element; The curvature radius Roo of the first outer raceway surface is 52% to 54% of the diameter Do of the first rolling element; The wheel bearing device according to claim 1, wherein the curvature radius Rio of the second outer raceway surface is 52% to 54% of the diameter Di of the second rolling element.

3. The number Zo of the first rolling elements accommodated between the first outer raceway surface and the first inner raceway surface is the same as the number Zi of the second rolling elements accommodated between the second outer raceway surface and the second inner raceway surface, the wheel bearing device according to claim 2.

4. The diameter Do of the first rolling element and the diameter Di of the second rolling element satisfy: 0.35 mm < (Di - Do) < 0.80 mm The wheel bearing device according to claim 2, which satisfies the relationship of.

5. The contact angle αo of the first rolling element with respect to the first inner raceway surface and the contact angle αi of the second rolling element with respect to the second inner raceway surface satisfy: αo ≥ αi The wheel bearing device according to claim 2, which satisfies the relationship of.

6. A straight line Li passing through the contact point of the second inner raceway surface with the second rolling element and the center of the second rolling element passes through the fitting surface of the inner ring with respect to the hub ring, the wheel bearing device according to claim 1.

7. The number Zo of the first rolling elements accommodated between the first outer raceway surface and the first inner raceway surface is the same as the number Zi of the second rolling elements accommodated between the second outer raceway surface and the second inner raceway surface, the diameter Do of the first rolling elements and the diameter Di of the second rolling elements satisfy the relationship of 0.35 mm < (Di - Do) < 0.80 mm, the contact angle αo of the first rolling elements with respect to the first inner raceway surface and the contact angle αi of the second rolling elements with respect to the second inner raceway surface satisfy the relationship of αo ≥ αi, a wheel center distance Wc which is an axial distance between the flange surface and the central position in the axial direction of the wheel attached to the flange surface, a span center distance Bc which is an axial distance between the flange surface and the span center of the first rolling elements and the second rolling elements, the contact angle αo of the first rolling elements with respect to the first inner raceway surface, the contact angle αi of the second rolling elements with respect to the second inner raceway surface, satisfy the relationship of (Bc - Wc) ≤ (-0.57 × (αo - αi) + 7.15 mm) The wheel bearing device according to claim 2, which satisfies the above relationship.

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