Wheel bearing device

Abstract

To reduce a weight of a fourth generation wheel bearing device.SOLUTION: A wheel bearing device 20 is configured such that a hub wheel 23 and an outside joint member 31 are coupled in a state where first and second inside raceway surfaces 23a1, 23a2 facing first and second outside raceway surfaces 22a1, 22a2 formed on an inner peripheral surface of an outward member 22 are respectively formed on outer peripheral surfaces of the hub wheel 23 and the outside joint member 31, and a shaft part 33 of the outside joint member 31 is fitted into an inner periphery of the hub wheel 23. In the wheel bearing device, when a ball diameter of a ball 24 rolling on the second inside raceway surface 23a2 is defined as d and a thickness of the ball 24 in a contact angle direction at a portion of the outside joint member 31 where the second inside raceway surface 23a2 is formed is defined as T, 0.6d≤T≤1.3d.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a wheel bearing device that supports a drive wheel of a vehicle such as an automobile so as to be rotatable relative to a vehicle body. [Background technology]

[0002] Wheel bearing devices are based on a structure called the first generation, which uses double-row rolling bearings, and have since progressed through the second and third generations, with up to the fourth generation now on the market. Second-generation wheel bearing devices have a structure in which a vehicle body mounting flange is integrally provided on the outer member of a rolling bearing having a double-row outer raceway surface, while third-generation wheel bearing devices have a structure in which one of the double-row inner raceway surfaces is integrally provided on the outer periphery of a hub wheel having a wheel mounting flange. Furthermore, fourth-generation wheel bearing devices, as described in Patent Document 1 below, for example, One of the double row inner raceways is formed on the outer peripheral surface of the hub ring, and the other is formed on the outer peripheral surface of the outer joint member of the constant velocity universal joint, eliminating the need for a dedicated inner ring (the function of the inner ring is given to the hub ring and the outer joint member), and A part or the whole of the shaft portion of the outer joint member is formed to be hollow. It has some major features such as: Due to this characteristic configuration, the fourth generation wheel support bearing device is lighter and more compact than the third generation wheel support bearing device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3875432 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, electric vehicles using electric motors as a driving source are rapidly becoming popular. In particular, battery electric vehicles (BEVs) do not have an engine as a driving source, and run by driving an electric motor with electricity stored in a storage battery (only), it is essential to reduce the weight of various parts and devices attached to the vehicle body, including the wheel bearing device, in order to increase the cruising distance. Of course, even in hybrid vehicles (HEVs, PHEVs) that use both an engine and an electric motor as a driving source, it is preferable to reduce the weight of various parts and devices attached to the chassis as much as possible in order to increase the cruising distance. Therefore, there is a demand for further weight reduction in fourth-generation wheel bearing devices, which can be significantly lighter than third-generation wheel bearing devices.

[0005] In view of the above circumstances, an object of the present invention is to provide a fourth-generation wheel bearing device that is further lightened in weight. [Means for solving the problem]

[0006] an outer member having first and second outer raceways spaced apart in the axial direction and a vehicle body mounting flange; a hub ring having a wheel mounting flange; and a fixed constant velocity universal joint including an outer joint member; a first inner raceway surface opposing the first outer raceway surface is formed on an outer peripheral surface of the hub wheel, and a second inner raceway surface opposing the second outer raceway surface is formed on an outer peripheral surface of the outer joint member, In a wheel bearing device in which an outer joint member and a hub wheel are coupled together with a shaft portion of the outer joint member fitted onto an inner periphery of the hub wheel, The present invention is characterized in that, when a ball diameter of the balls rolling on the second inner raceway is d and a wall thickness in a contact angle direction of the balls of a portion of the outer joint member where the second inner raceway is formed is T, 0.6d≦T≦1.3d is satisfied.

[0007] As described above, in the wheel bearing device according to the present invention, the thickness in the contact angle direction of the balls in the portion where the second inner raceway surface is formed among the outer joint members constituting the fixed constant velocity joint is suppressed to the minimum range that can secure the mechanical strength required based on the ball diameter. Thereby, while ensuring the desired durability, it is possible to reduce the weight of the outer joint member of the fixed constant velocity joint, and thus the wheel bearing device.

[0008] In the above configuration, when the minimum thickness in the radial direction (the direction orthogonal to the axial direction) in the portion of the outer joint member where the second inner raceway surface is formed is set as t, it can be set as 0.6d ≦ t ≦ d.

[0009] In the above configuration, when the axial distance between the mounting surface of the wheel mounting flange provided on the hub ring with respect to the wheel and the joint center of the fixed constant velocity joint is La, and the axial distance between the center of the ball rolling on the second inner raceway surface and the above mounting surface is Lb, it is preferable to satisfy the relational expression of 1.4Lb ≦ La ≦ 2.1Lb. Thereby, it becomes possible to make the wheel bearing device compact in the axial direction and reduce its weight.

[0010] In the above configuration, when the pitch circle diameter of the balls rolling on the first outer raceway surface and the first inner raceway surface is P1, and the pitch circle diameter of the balls rolling on the second outer raceway surface and the second inner raceway surface is P2, the present invention can be applied to either a wheel bearing device in which P1 = P2 or a wheel bearing device in which P1 < P2.

[0011] In the wheel bearing device according to the present invention, the diameter of the outer peripheral fitting surface of the outer member that is fitted to the inner periphery of the vehicle body side member in a state where the vehicle body mounting flange is attached and fixed to the annular vehicle body side member is made larger than the maximum outer diameter of the fixed constant velocity joint. Thereby, the wheel bearing device, and thus the drive shaft including the same, can be easily attached to the knuckle as the vehicle body side member.

[0012] The hub wheel and the outer joint member that constitute the wheel bearing device according to the present invention can be joined, for example, by forming the shaft portion of the outer joint member that is fitted onto the inner circumference of the hub wheel into a hollow shaft, and partially expanding this shaft portion (the hollow portion) or partially reducing the diameter of the hub wheel and crimping the hub wheel and the shaft portion. Effect of the Invention

[0013] As described above, according to the present invention, a fourth-generation wheel bearing device that is further lightened in weight can be provided. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing an overall configuration of a drive shaft including a wheel bearing device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a partially enlarged view of FIG. 1, showing a longitudinal cross-section of the wheel bearing device. [Diagram 3] FIG. 3 is a partially enlarged view of FIG. 2, showing one of two seals provided in the wheel support bearing; [Figure 4] 3 is a partially enlarged view of FIG. 2, showing the other of the two seals provided in the wheel support bearing; FIG. [Diagram 5] FIG. 11 is a vertical sectional view of a wheel support bearing device according to another embodiment of the present invention. [Figure 6] 13 is a modified example of a seal provided in a wheel support bearing. [Figure 7] 13 is a modified example of a seal provided in a wheel support bearing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] 1 is a schematic diagram showing the overall configuration of a drive shaft A including a wheel bearing device 20 according to an embodiment of the present invention, and more specifically, a schematic diagram showing a state in which constant velocity universal joints 1, 30 constituting the drive shaft A have no operating angle of 0°. This drive shaft A is arranged so that its longitudinal direction is aligned with the vehicle width direction of the automobile, and transmits rotational power output from a drive source mounted on the chassis to the drive wheels, and is equipped with a wheel bearing device 20 including a sliding constant velocity universal joint 1 arranged on the drive source side (also called the inboard side, on the right side of the paper in FIG. 1) and a fixed constant velocity universal joint 30 arranged on the wheel side (also called the outboard side, on the left side of the paper in FIG. 1), and a shaft member 10 connecting the two constant velocity universal joints 1, 30 so as to be able to transmit torque. Hereinafter, the terms "axial direction," "radial direction," and "circumferential direction" used in explaining directionality refer, unless otherwise specified, to the direction along the central axis of the shaft member 10 (the left-right direction on the paper in FIG. 1), the radial direction of a circle centered on the central axis, and the circumferential direction of a circle centered on the central axis, respectively.

[0017] First, a brief description will be given of the sliding type constant velocity universal joint 1. The sliding type constant velocity universal joint 1 in the illustrated example is a so-called tripod type constant velocity universal joint including an outer joint member 2 having a cylindrical cup portion 3 with a bottom, and a tripod unit as a joint internal part disposed in the internal space of the cup portion 3. The tripod unit includes a tripod member 5, a plurality of needle rollers 6, and an annular roller 7 as a torque transmission member.

[0018] The tripod member 5 integrally comprises a cylindrical boss portion 5a in which an axial hole 5b is formed, and three trunnions 5c that are disposed at equal intervals (120° pitch) in the circumferential direction and extend radially outward from the outer circumferential surface of the boss portion 5a. A spline is formed on the inner circumferential surface of the boss portion 5a (the inner wall surface of the axial hole 5b), and the inboard end of the shaft member 10 is spline-fitted to this spline. A roller 7 is rotatably fitted to the outer periphery of each trunnion 5c via a plurality of needle rollers 6. Each needle roller 6 is disposed so as to be able to roll on the outer circumferential surface of the trunnion 5c in the circumferential direction of the trunnion 5c.

[0019] Three track grooves 4, each of which accommodates a roller 7, are provided at equal intervals in the circumferential direction on the inner periphery of the cup portion 3 of the outer joint member 2. Each track groove 4 has a pair of roller guideways that face each other and guide the outer circumferential surfaces of the rollers 7, and is formed in a straight line extending in the axial direction including the roller guideways.

[0020] A lubricant such as grease is sealed in the internal space of the cup portion 3 of the outer joint member 2. In order to prevent the lubricant from leaking out and foreign matter from entering the internal space, a boot 11 made of a rubber material or a resin material and formed into a cylindrical shape is attached between the outer joint member 2 (the cup portion 3 of the outer joint member 2) and the shaft member 10. The boot 11 integrally has a large diameter cylindrical portion 11a, a small diameter cylindrical portion 11b, and a bellows portion 11c interposed between the two cylindrical portions, and the large diameter cylindrical portion 11a is fixed to the outer peripheral surface of the cup portion 3 of the outer joint member 2 by using a boot band 12, and the small diameter cylindrical portion 11b is fixed to the outer peripheral surface of the shaft member 10 by using a boot band 13. When the tripod member 5 (the shaft member 10 connected to the tripod member 5) is angularly displaced and / or axially displaced relative to the outer joint member 2, the bellows portion 11c elastically bends and expands and contracts in response to this.

[0021] The wheel bearing device 20 will be described below with reference to Fig. 2, which shows an enlarged view of a portion of Fig. 1. The wheel bearing device 20 is a so-called fourth-generation wheel bearing device, and is configured by combining a fixed constant velocity universal joint 30 (an outer joint member 31 constituting the joint), an outer member 22, and a wheel bearing 21 including a hub wheel 23.

[0022] The fixed type constant velocity universal joint 30 in the illustrated example comprises an outer joint member 31 and an inner joint member 34, a plurality of balls 35 that transmit torque between the two joint members 31, 34 while allowing relative angular displacement between the two joint members 31, 34, and a cage 36 that holds the balls 35.

[0023] The outer joint member 31 integrally has a cup-shaped mouth portion 32 and a shaft portion 33 extending axially outward (outboard side) from the bottom of the mouth portion 32. A plurality of track grooves 32a corresponding to the number of balls 35 are formed on the inner peripheral surface of the mouth portion 32 at equal circumferential intervals. The shaft portion 33 is formed as a hollow shaft having an axial through hole 33a, and the inboard end of the through hole 33a opens into the internal space of the mouth portion 32.

[0024] The inner joint member 34 is ring-shaped as a whole, and has an outer circumferential surface on which a plurality of track grooves 34a are formed at equal intervals in the circumferential direction, facing the track grooves 32a of the outer joint member 31. A spline is formed on an inner circumferential surface (inner wall surface of the shaft hole) of the inner joint member 34, and the outboard end of the shaft member 10 is spline-fitted into this spline.

[0025] The plurality of balls 35 are interposed between pairs of track grooves 32a, 34a, and transmit torque between the outer joint member 31 and the inner joint member 34. The number of balls 35 is generally six or eight, but may be ten or twelve.

[0026] The cage 36 is made of a metal or resin material and is formed in an annular shape, and is disposed between the inner circumferential surface of the outer joint member 31 and the outer circumferential surface of the inner joint member 34. The cage 36 is formed with a plurality of pockets 36a at equal intervals in the circumferential direction, which open onto the outer circumferential surface and the inner circumferential surface, and each pocket 36a individually holds a ball 35.

[0027] A lubricant such as grease is sealed in the internal space of the mouth portion 32 of the outer joint member 31. In order to prevent the lubricant from leaking out and foreign matter from entering the internal space of the mouth portion 32, a cylindrical boot 14 made of a rubber material or a resin material is attached between the outer joint member 31 (the mouth portion 32 of the outer joint member 31) and the shaft member 10. The boot 14 integrally has a large diameter cylindrical portion 14a, a small diameter cylindrical portion 14b, and a bellows portion 14c interposed between both cylindrical portions 14a, 14b. The large diameter cylindrical portion 14a is fixed to the outer peripheral surface of the mouth portion 32 by using a boot band 15, and the small diameter portion 14b is fixed to the outer peripheral surface of the shaft member 10 by using a boot band 16.

[0028] In this embodiment, the shaft portion 33 of the outer joint member 31 is formed as a hollow shaft having an axial through hole 33a, and the inboard end of the through hole 33a opens into the internal space of the mouth portion 32, so that a bottomed cylindrical seal plate 37 is fixed to a portion of the inner diameter surface of the outer joint member 31 adjacent to the outboard side of the inner joint member 34. This prevents the lubricant from leaking to the outside through the through hole 33a and prevents foreign matter from entering the internal space of the mouth portion 32.

[0029] The wheel bearing 21 has as its constituent elements a part of the outer joint member 31 which is a component of the fixed constant velocity universal joint 30 described above, and in addition thereto, its constituent elements include an outer member 22, a hub wheel 23, a plurality of balls 24, a cage 25, etc. which will be described below.

[0030] The outer member 22 integrally includes a cylindrical tube portion 22a and a vehicle body mounting flange 22b extending radially outward from the outer peripheral surface of the tube portion 22a, and a plurality of bolt mounting holes 22c are formed circumferentially at intervals through the vehicle body mounting flange 22b. A first outer raceway surface 22a1 and a second outer raceway surface 22a2 each having an arc shape are formed on the inner peripheral surface of the tube portion 22a at intervals in the axial direction. In this embodiment, of the two outer raceway surfaces 22a1 and 22a2, the second outer raceway surface 22a2 located on the inboard side is formed radially outward from the first outer raceway surface 22a1 located on the outboard side.

[0031] The hub wheel 23 integrally includes a cylindrical portion 23a having an axial through hole 23c, and a wheel mounting flange 23b extending radially outward from the outer circumferential surface of the cylindrical portion 23a and having a plurality of bolt mounting holes 23d formed at intervals in the circumferential direction. The wheel mounting flange 23b is located on the outboard side of the vehicle body mounting flange 22b. The outer circumferential surface of the cylindrical portion 23a of the hub wheel 23 is formed with a circular arc-shaped first inner raceway surface 23a1 facing the first outer raceway surface 22a1, and the outer circumferential surface of the outer joint member 31 constituting the fixed type constant velocity universal joint 30 is formed with a second inner raceway surface 23a2 facing the second outer raceway surface 22a2. Of the two inner raceway surfaces 23a1, 23a2, the second inner raceway surface 23a2 located on the inboard side is formed radially outward of the first inner raceway surface 23a1 located on the outboard side. A plurality of balls 24 are interposed between the opposing outer raceway surface 22a1 and inner raceway surface 23a1, and between the opposing outer raceway surface 22a2 and inner raceway surface 23a2. As described above, in the wheel bearing device 20 of this embodiment, the pitch circle diameter (=P2) of the balls 24 rolling on the second outer raceway surface 22a2 and second inner raceway surface 23a2 on the inboard side is larger than the pitch circle diameter (=P1) of the balls 24 rolling on the first outer raceway surface 22a1 and first inner raceway surface 23a1 on the outboard side.

[0032] The ball 24 on the outboard side ball track is in contact with the first outer raceway surface 22a1 and the first inner raceway surface 23a1 in a direction inclined with respect to the axial direction (see the dashed line passing through the center of the ball 24 in FIG. 2). That is, the ball 24 on the outboard side ball track is in contact with the first outer raceway surface 22a1 and the first inner raceway surface 23a1 with a contact angle. The ball 24 on the inboard side ball track is also in contact with the second outer raceway surface 22a2 and the second inner raceway surface 23a2 in a direction inclined with respect to the axial direction (see the dashed line passing through the center of the ball 24 in FIG. 2). That is, the ball 24 on the inboard side ball track is also in contact with the second outer raceway surface 22a2 and the second inner raceway surface 23a2 with a contact angle.

[0033] The multiple balls 24 are spaced apart circumferentially by an annular retainer 25 disposed between the inner surface of the outer member 22 and the opposing outer surfaces of the hub wheel 23 and outer joint member 31.

[0034] The internal space of the wheel bearing 21 is filled with a lubricant such as grease, and seals 26, 27 to prevent the lubricant from leaking out and foreign matter from entering the bearing internal space are provided at the openings at both ends of the outer member 22. The seal 26 arranged at the opening on the outboard side of the outer member 22 has multiple rubber seal lips (three in the illustrated example) that come into contact with the hub wheel 23 with its outer diameter end attached and fixed to the inner circumferential surface of the cylindrical portion 22a of the outer member 22, as shown in Figure 3. As shown in FIG. 4, the seal 27 arranged at the inboard opening of the outer member 22 comprises a first seal member 27a having an outer diameter end portion fixed to the inner circumferential surface of the tubular portion 22a of the outer member 22 and a second seal member 27b having an inner diameter end portion fixed to the outer circumferential surface of the outer joint member 31 of the constant velocity universal joint 30, and the first seal member 27a comprises multiple (three in the illustrated example) rubber seal lips in contact with the second seal member 27b (its metal portion) and the outer joint member 31.

[0035] The shaft portion 33 of the outer joint member 31 formed on a hollow shaft is fitted into the inner circumferential surface (inner wall surface of the through hole 23c) of the cylindrical portion 23a of the hub wheel 23, and a crimped portion 28 that joins (plastically joins) the hub wheel 23 and the shaft portion 33 of the outer joint member 31 is formed between the inner circumferential surface of the cylindrical portion 23a and the outer circumferential surface of the shaft portion 33. Although not shown in the drawings, the crimped portion 28 is formed, for example, by pressing a crimping jig into the inner periphery (through hole 33a) of the shaft portion 33 with the shaft portion 33 of the outer joint member 31 fitted into the inner periphery of the cylindrical portion 23a of the hub wheel 23, and plastically deforming the shaft portion 33 (a part of it in the axial direction) by expanding its diameter. The crimped portion 28 can be formed by plastically deforming the cylindrical portion 23a of the hub wheel 23 to reduce its diameter, but it is not easy to precisely deform (a part of) the hub wheel 23 to reduce its diameter without degrading the shape and dimensional accuracy of the first inner raceway surface 23a1 and the wheel mounting flange 23b provided on the hub wheel 23. Therefore, the crimped portion 28 is usually formed by deforming the shaft portion 33 of the outer joint member 31 to expand its diameter.

[0036] When forming the crimped portion 28, a concave-convex portion such as a screw groove or spline is provided in advance on either the outer circumferential surface of the shaft portion 33 or the opposing inner circumferential surface of the cylindrical portion 23a of the hub wheel 23, and when the shaft portion 33 is deformed and expanded in diameter, the material of the other is caused to bite into the concave-convex portion. This results in the crimped portion 28 which firmly joins the hub wheel 23 and the shaft portion 33 of the outer joint member 31.

[0037] In this embodiment, an end plate 29 is fixed to the outboard end of the cylindrical portion 23a of the hub wheel 23, closing the through hole 23c of the cylindrical portion 23a and the outboard opening of the through hole 33a of the shaft portion 33 of the outer joint member 31. This more reliably prevents the lubricant from leaking out through the through hole 33a, and also prevents foreign matter from entering the crimped portion 28.

[0038] The wheel bearing device 20 having the above configuration is attached and fixed to an annular vehicle body side member (not shown) (specifically, a knuckle extending from a suspension device attached to the vehicle body) using a bolt member (not shown) screwed into a bolt mounting hole 22c of a vehicle body mounting flange 22b of the outer member 22. Therefore, when the outer member 22 is attached and fixed to the knuckle, the tubular portion 22a of the outer member 22 (the portion of it that is inboard of the vehicle body mounting flange 22b) is fitted to the inner periphery of the knuckle. Of the outer periphery of the tubular portion 22a of the outer member 22, the diameter Da of an outer periphery fitting surface 22d that fits to the inner periphery of the knuckle is set to be equal to or smaller than the inner diameter of the knuckle and larger than the maximum outer diameter of the fixed type constant velocity universal joint 30 and the maximum outer diameter of the sliding type constant velocity universal joint 1. The above diameter Da is set to, for example, 89 mm.

[0039] In this embodiment, the maximum outer diameter of the fixed type constant velocity universal joint 30 is the outer diameter of the boot band 15 used to attach (tighten) and fix the large diameter tubular portion 14a of the boot 14 to the outer peripheral surface of the mouth portion 32 of the outer joint member 31 having the outer diameter Db. The outer diameter Db of the mouth portion 32 is set to, for example, 77 mm. The maximum outer diameter of the sliding type constant velocity universal joint 1 is the outer diameter of the boot band 12 used to attach (tighten) and fix the large diameter tubular portion 11a of the boot 11 to the outer peripheral surface of the cup portion 3 of the outer joint member 2. The maximum outer diameter of the fixed type constant velocity universal joint 30 is larger than the maximum outer diameter of the sliding type constant velocity universal joint 1.

[0040] Due to such dimensional relationships, the drive shaft A including the wheel bearing device 20 is assembled to the vehicle body in the completed state shown in Fig. 1. Specifically, the drive shaft A is assembled to the vehicle body from the outside in the vehicle width direction by passing the sliding type constant velocity universal joint 1, shaft member 10, and fixed type constant velocity universal joint 30 through the inner circumference of the knuckle in this order, and then the outer member 22 (of the vehicle body mounting flange 22b) of the wheel bearing device 20 is fixed to the knuckle using bolt members not shown. A driving wheel (not shown) is attached to the wheel bearing device 20 of the drive shaft A assembled to the vehicle body using bolt members attached to the bolt mounting holes 23d of the hub wheel 23.

[0041] The wheel bearing device 20 of the present embodiment described above has the following characteristic configuration.

[0042] In the wheel bearing 21, the ball diameter of the ball 24 rolling on the inboard side second inner raceway surface 23a2 is defined as d, and the thickness in the contact angle direction of the ball 24 at the portion where the second inner raceway surface 23a2 is formed (on the outer peripheral surface) of the outer joint member 31 of the fixed constant velocity universal joint 30 is defined as T. T is set so as to satisfy the relational expression 0.6d≦T≦1.3d.

[0043] In this way, the thickness T of the portion of the outer joint member 31 constituting the fixed type constant velocity universal joint 30 where the second inner raceway surface 23a2 of the wheel support bearing 21 is formed is kept within the minimum range that ensures the required mechanical strength. This makes it possible to partially thin the outer joint member 31, thereby reducing the weight of the wheel support bearing device 20 including the outer joint member 31.

[0044] In addition, in the wheel bearing device 20 of this embodiment, when the ball diameter of the ball 24 rolling on the inboard side second inner raceway surface 23a2 is taken as d and the minimum radial thickness of the portion of the outer joint member 31 where the second inner raceway surface 23a2 of the wheel bearing 21 is formed is taken as t, t is set so as to satisfy the relational expression 0.6d≦t≦d.

[0045] In this way, the minimum radial thickness t of the portion of the outer joint member 31 constituting the fixed type constant velocity universal joint 30 where the second inner raceway surface 23a2 of the wheel support bearing 21 is formed is kept within the minimum range that can ensure the required mechanical strength. This makes it possible to partially thin the outer joint member 31, thereby reducing the weight of the wheel support bearing device 20 including the outer joint member 31.

[0046] Note that the above-mentioned (1) relational equation between the ball diameter d and the thickness T of the portion of the outer joint member 31 where the second inner raceway surface 23a2 is formed in the contact angle direction of the ball 24, and (2) relational equation between the ball diameter d and the minimum radial thickness t of the portion of the outer joint member 31 where the second inner raceway surface 23a is formed, are both set based on the results obtained by performing stress analysis.

[0047] In the wheel bearing device 20 of this embodiment, the axial distance between the mounting surface (outboard end surface of the wheel mounting flange 23b) 23e of the hub wheel 23 relative to the wheel and the joint center of the fixed constant velocity universal joint 30 is La, and the axial distance between the center of the ball 24 rolling on the second inner raceway surface 23a2 and the mounting surface 23e is Lb, so that the relational expression of 1.4Lb≦La≦2.1Lb is satisfied. This makes it possible to make the wheel bearing device 20 more compact in the axial direction and reduce its weight. The values ​​of La and Lb can be, for example, La=90 mm and Lb=50.1 mm.

[0048] In addition to the above La and Lb, in the wheel bearing device 20 of this embodiment, the axial distance Lc between the mounting surface (the inboard end surface of the vehicle body mounting flange 22b) 22e of the outer member 22 relative to the knuckle and the mounting surface 23e of the hub wheel 23 relative to the wheel is 42 mm, and the axial distance between the center of the ball 24 rolling on the first inner raceway surface 23a1 (and the first outer raceway surface 22a1) and the mounting surface 23e of the hub wheel 23 relative to the wheel is 26.3 mm.

[0049] With the above configuration, the wheel support bearing device 20 of this embodiment has the features of being lightweight and compact in the axial direction. Therefore, the wheel support bearing device 20 of this embodiment can be suitably applied to electric vehicles such as HEVs, PHEVs, and BEVs equipped with an electric motor as a drive source. That is, in this type of electric vehicle, it is essential to reduce the weight of the wheel support bearing device in order to maximize the driving distance that can be achieved only by electricity, and it is also essential to make the wheel support bearing device compact because the installation space of the wheel support bearing device may be eroded due to changes in the layout of various parts and devices mounted on the vehicle body, including the wheel support bearing device, and the adoption of a drive unit called E-Axle that unitizes an electric motor, a reducer (transmission), and an inverter.

[0050] Although the wheel bearing device 20 according to one embodiment of the present invention and the drive shaft A including the same have been described above, the embodiment of the present invention is not limited to this.

[0051] 5 is a longitudinal sectional view of a wheel support bearing device 20 according to another embodiment of the present invention. The wheel support bearing device 20 of this embodiment differs from the wheel support bearing device 20 described above mainly in that the pitch circle diameter (=P2) of the balls 24 rolling on the inboard side second outer raceway surface 22a2 and the second inner raceway surface 23a2 is equal to the pitch circle diameter (=P1) of the balls 24 rolling on the outboard side first outer raceway surface 22a1 and the first inner raceway surface 23a1 (P1=P2). Other configurations are substantially the same as those of the wheel support bearing device 20 shown in FIG. 2, so common reference numerals are used and repeated explanations are omitted.

[0052] In addition, the seals 26, 27 provided at the openings at both ends of the outer member 22 constituting the wheel bearing device 20 can be replaced with other seals. Figure 6 shows a modified example of the outboard side seal 26, and Figure 7 shows a modified example of the inboard side seal 27.

[0053] The seal 26 shown in Fig. 6 is composed of a first seal member 26a attached and fixed to the outer member 22 and a second seal member 26b attached and fixed to the hub wheel 23. The first seal member 26a has two rubber seal lips that contact the second seal member 26b, and forms a labyrinth seal as a non-contact seal between the first seal member 26a and the second seal member 26b at a position farther from the bearing internal space than these seal lips. The seal 26 shown in Fig. 6 has a reduced number of seal lips that form a so-called contact seal compared to the seal 26 shown in Fig. 3, which contributes to lowering the torque of the wheel support bearing 21. The reduction in sealing performance caused by the reduction in the number of seal lips is compensated for by adding a labyrinth seal.

[0054] The seal 27 shown in Fig. 7 is composed of a first seal member 27a attached and fixed to the outer member 22 and a second seal member 27b attached and fixed to the joint member 31. The first seal member 27a has two rubber seal lips that contact the second seal member 27b, and forms a labyrinth seal as a non-contact seal between the first seal member 27a and the second seal member 27b at a position farther from the bearing internal space than these seal lips. The seal 27 shown in Fig. 7 has a reduced number of seal lips that form a so-called contact seal compared to the seal 27 shown in Fig. 4, which contributes to reducing the torque of the wheel support bearing 21. The reduction in sealing performance caused by the reduction in the number of seal lips is compensated for by adding a labyrinth seal.

[0055] The hub wheel 23 and the shaft portion 33 of the outer joint member 31 can also be joined by a method other than the above, in which the crimped portion 28 is formed between the inner peripheral surface of the cylindrical portion 23a of the hub wheel 23 and the outer peripheral surface of the shaft portion 33. Although not shown in the drawings, for example, the free end (outboard end) of the shaft portion 33 is made to protrude outward from the outboard end of the hub wheel 23, and this protruding portion is bent (plastically deformed) radially outward by swing crimping, thereby joining the hub wheel 23 and the shaft portion 33 of the outer joint member 31. In this case, the shaft portion 33 of the outer joint member 31 does not have to have an axial through hole 33a as shown in FIG. 2, and a part of the shaft portion 33 (for example, a portion adjacent to the protruding portion to be swing crimped) may be formed solid in the axial direction. The hub wheel 23 and the shaft portion 33 of the outer joint member 31 can also be joined by a method other than the above-mentioned plastic joining, for example, bolt-nut fixing. In this case, the shaft portion 33 of the outer joint member 31 is, for example, one in which the end portion on the outboard side is formed solid and the remaining portion is formed hollow.

[0056] Although the embodiment of the present invention has been described above, the embodiment of the present invention is not limited to this, and can be embodied in various other forms without departing from the scope of the present invention. That is, the scope of the present invention is defined by the claims, and further includes the equivalent meanings described in the claims, and all modifications within the scope of the claims. [Explanation of symbols]

[0057] 1. Sliding constant velocity universal joint 10 Shaft member 20 Wheel bearing device 21 Wheel bearings 22 Outer member 22a1,22a2 Outer raceway surface 22b Vehicle mounting flange 23 Hub wheel 23a1,23a2 Inner raceway surface 23b Wheel mounting flange 30 Fixed constant velocity joint 31 Outer joint member 33 Shaft A. Drive shaft d ball diameter P1 Pitch Circle Diameter P2 Pitch Circle Diameter T Thickness t Thickness

Claims

1. an outer member having first and second outer raceways spaced apart in the axial direction and a vehicle body mounting flange; a hub wheel having a wheel mounting flange; and a fixed constant velocity universal joint including an outer joint member; a first inner raceway surface opposing the first outer raceway surface is formed on an outer peripheral surface of the hub wheel, and a second inner raceway surface opposing the second outer raceway surface is formed on an outer peripheral surface of the outer joint member, In a wheel bearing device in which the hub wheel and the outer joint member are coupled together with a shaft portion of the outer joint member fitted into an inner periphery of the hub wheel, a ball diameter of the balls rolling on the second inner raceway surface is defined as d, and a wall thickness of the outer joint member, at a portion where the second inner raceway surface is formed, in a contact angle direction of the balls is defined as T, such that 0.6d≦T≦1.3d.

2. 2. The wheel bearing device according to claim 1, wherein 0.6d≦t≦d is satisfied, where t is a minimum radial thickness of a portion of the outer joint member where the second inner raceway surface is formed.

3. 2. A wheel bearing device as described in claim 1, wherein the axial distance between the mounting surface of the wheel mounting flange relative to the wheel and the joint center of the fixed constant velocity universal joint is La, and the axial distance between the center of the ball rolling on the second inner raceway surface and the mounting surface is Lb, 1.4Lb≦La≦2.1Lb.

4. The pitch circle diameter of the balls rolling on the first outer raceway surface and the first inner raceway surface is P １ , the pitch circle diameter of the balls rolling on the second outer raceway surface and the second inner raceway surface is P ２ , then P １ =P ２ The wheel bearing device according to any one of claims 1 to 3, wherein:

5. The pitch circle diameter of the balls rolling on the first outer raceway surface and the first inner raceway surface is P １ , the pitch circle diameter of the balls rolling on the second outer raceway surface and the second inner raceway surface is P ２ , then P １ <P ２ The wheel bearing device according to any one of claims 1 to 3, wherein:

6. 2. A wheel bearing device as claimed in claim 1, wherein the diameter of the outer peripheral fitting surface of the outer member which is fitted onto the inner periphery of the annular vehicle body side member when the vehicle body mounting flange is attached and fixed to the vehicle body side member is made larger than the maximum outer diameter of the fixed type constant velocity universal joint.

7. 2. The wheel bearing device according to claim 1, wherein the shaft portion of the outer joint member fitted onto the inner circumference of the hub wheel is formed into a hollow shaft, and the hub wheel and the outer joint member are joined by partially expanding the diameter of the shaft portion or partially reducing the diameter of the hub wheel to crimp the hub wheel and the shaft portion.

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