JP2005319889A - Bearing device for driving wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device for a driving wheel improving working efficiency in assembly and disassembly without requiring a special exclusive tool. <P>SOLUTION: In the bearing device for the driving wheel, an outside joint member 14 is detachably coupled to a hub wheel 1, a preload is applied to a serration fitting part of a shaft part 18 and the hub wheel 1 by providing a helical angle inclined in a predetermined angle to the axis line on the serration 18a of the shaft part 18, and a plurality of independent circular groove 21 is formed on the serration 7 of the hub wheel 1. The backlash in the peripheral direction of the serration fitting part is eliminated, the occurrence of noise is prevented to make the feeling good in starting of the vehicle, the volume of the serration 7 is elastically reduced and the pressing force can be reduced even if the preload is applied to the serration fitting part. Therefore, the outside joint member 14 can be easily drawn into the hub wheel 1 to improve workability of assembly. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a drive wheel bearing device that supports a drive wheel of a vehicle such as an automobile, and more specifically, a drive wheel (front wheel of an FF vehicle, rear wheel of an FR vehicle or RR vehicle, and 4WD mounted on an independent suspension type suspension). The present invention relates to a drive wheel bearing device in which a wheel bearing and a constant velocity universal joint are unitized in order to rotatably support a vehicle (all wheels) with respect to a suspension device and to drive and drive the drive wheel.

  A power transmission device that transmits engine power of a vehicle such as an automobile to a wheel transmits power from the engine to the wheel, and also causes radial or axial displacement from the wheel that occurs when the vehicle bounces or turns when traveling on a rough road. For example, as shown in FIG. 7, one end of the drive shaft 100 interposed between the engine side and the drive wheel side is connected to the sliding type constant velocity universal joint 101. The other end is connected to a drive wheel 105 via a drive wheel bearing device 104 including a fixed type constant velocity universal joint 103.

  Various types of drive wheel bearing devices 104 have been proposed in the past, and for example, one shown in FIG. 6 is known. This drive wheel bearing device 104 is connected to a hub wheel 106 for mounting the drive wheel 105 at one end thereof, a double row rolling bearing 107 for rotatably supporting the hub wheel 106, and a hub wheel 106 to drive the drive wheel 105. A fixed type constant velocity universal joint 103 that transmits shaft power to the hub wheel 106 is provided.

  A large torque is applied to the drive wheels 105 (see FIG. 7) of the vehicle from the engine via the sliding type constant velocity universal joint 101 when the engine rotates at a low speed, for example, when the vehicle starts, and the drive shaft 100 is twisted. It is known. As a result, the inner ring 109 of the double row rolling bearing 107 that supports the drive shaft 100 is also twisted. In this way, when a large twist occurs in the drive shaft 100, the circumference is between the serration 110 of the hub wheel 106 and the serration 111 of the outer joint member 108 constituting the constant velocity universal joint 103 fitted inside the hub wheel 106. If there is a clearance in the direction, a stick-slip sound due to a sudden slip is generated on the contact surface between the outer joint member 108 and the inner ring 109.

  As a countermeasure, it is common practice to provide a torsion angle on the serration 111 of the outer joint member 108, and to close the backlash in the circumferential direction between the serrations 110 and 111 to apply a preload to the fitting portion. However, when the serration 111 is provided in the serration 111 of the outer joint member 108, a large pressure input is required to pull the outer joint member 108 into the hub wheel 106 in order to elastically deform the serrations 110 and 111 to be fitted. However, there is a problem that workability is lowered and manufacturing costs are increased.

As a solution to these problems, a drive wheel bearing device as shown in FIG. 5 is known. In this drive wheel bearing device 112, an inner ring 114 is formed by a caulking portion 115 formed by externally fitting an inner ring 114 to a small diameter step portion 113a of a hub wheel 113 and plastically deforming an inner end portion of the small diameter step portion 113a in a radial direction. Is fixed in the axial direction, and the stem portion 118 of the outer joint member 117 is fitted through the serration 116. Here, the inner end portion of the screw rod 120 is screwed into the screw hole 119 formed in the distal end surface of the stem portion 118, and the stem portion 118 and the screw flange 120 are coupled and fixed. Next, by rotating the tension jig 121 in a state where the inner end face of the tension jig 121 and the outer end face of the hub wheel 113 are brought into contact with the screw collar 120, the screw collar 120 is caused to have a strong force. The stem portion 118 can be easily pulled into the serration hole 122.
JP 2002-337504 A

  However, in such a drive wheel bearing device 112, the screw rod 120 can be pulled with a strong force by rotating the pulling jig 121, and the stem portion 118 can be easily pulled into the serration hole 122, but the screw There is still a problem that a dedicated assembly jig 123 such as the rod 120 and the tension jig 121 is required and the work becomes complicated, and it takes time to assemble and disassemble.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a drive wheel bearing device that does not require a special dedicated jig and has improved workability during assembly and disassembly. .

  In order to achieve such an object, the invention according to claim 1 of the present invention integrally has an outer member having a double row outer rolling surface formed on the inner periphery, and a wheel mounting flange at one end, A cylindrical small-diameter step portion extending in the axial direction is formed on the outer periphery, and a hub ring having serrations formed on the inner periphery, and press-fitted into the small-diameter step portion of the hub ring, and the outer circumferential surface of the double row on the outer periphery. An inner member composed of at least one inner ring formed with opposing inner rolling surfaces, a rolling element rotatably accommodated between the both rolling surfaces, and a constant velocity universal joint, An outer joint member integrally including a shaft portion fitted through a serration, wherein the hub wheel and the outer joint member are detachably coupled to each other. A preload is applied to the serration fitting portion of the hub wheel and Adopting a configuration in which the circumferential groove is formed in the configuration.

  Thus, in the drive wheel bearing device in which the outer joint member of the constant velocity universal joint is detachably coupled to the hub wheel constituting the wheel bearing device, the serration fitting between the hub wheel and the shaft portion of the outer joint member is performed. Preload is applied to the part, and a circumferential groove is formed in the serration of the hub wheel, so the backlash in the circumferential direction of the serration fitting part is closed to prevent the generation of abnormal noise. The ring can be improved, and even if a preload is applied to the serration fitting portion, the volume in which the serration is elastically deformed is reduced, and the pressure input can be reduced. As a result, the outer joint member can be easily pulled into the hub wheel, and a special dedicated jig as in the prior art is not required, and the workability during assembly and disassembly can be improved.

  According to a second aspect of the present invention, there is provided a serration fitting portion between the shaft portion and the hub wheel by providing the serration of the shaft portion of the outer joint member with a torsion angle inclined by a predetermined angle with respect to the axis. Since the preload is applied to the serration fitting part, it is possible to provide a highly reliable preload means to the serration fitting part, preventing abnormal noises during sudden acceleration / deceleration of the vehicle, and loosening of the joint part due to circumferential play. Can be suppressed. Therefore, fretting wear of the serration fitting portion can be further prevented.

  Further, the circumferential groove of the serration may be a plurality of circumferential grooves independent in the axial direction as in the invention described in claim 3, or as in the invention described in claim 4. It may be a spiral groove.

  Further, the invention according to claim 5 is provided with a fitting portion on the outer peripheral surface of the shaft portion, and is fitted to the small-diameter step portion of the hub wheel via a predetermined radial clearance. It has high rigidity with respect to a bending moment to be applied and can improve durability.

  The bearing device for a drive wheel according to the present invention has an outer member in which a double row outer rolling surface is formed on the inner periphery, a wheel mounting flange at one end, and a cylindrical shape that extends in the axial direction on the outer periphery. A hub ring having a small diameter step portion and a serration formed on the inner periphery, and an inner rolling surface that is press-fitted into the small diameter step portion of the hub wheel and faces the outer surface of the double row on the outer periphery. An inner member composed of at least one inner ring, a rolling element rotatably accommodated between both the rolling surfaces, and a constant velocity universal joint are configured, and are fitted into the hub ring via serrations. In a drive wheel bearing device comprising an outer joint member integrally having a shaft portion, wherein the hub wheel and the outer joint member are detachably coupled, preload is applied to a serration fitting portion between the shaft portion and the hub wheel. And a circumferential groove in the serration of the hub wheel. As a result, the backlash in the circumferential direction of the serration fitting portion can be reduced to prevent the generation of abnormal noise, the feeling at the start of the vehicle can be improved, and a preload is applied to the serration fitting portion. Even so, the volume in which the serration is elastically deformed is reduced, and the pressure input can be reduced. As a result, the outer joint member can be easily pulled into the hub wheel, and a special dedicated jig as in the prior art is not required, and the workability during assembly and disassembly can be improved.

  A vehicle body mounting flange is integrally formed on the outer periphery, an outer member having a double row outer rolling surface formed on the inner periphery, a wheel mounting flange is integrally formed on one end, and the double row outer rolling is formed on the outer periphery. A hub ring having one inner rolling surface facing the running surface, a cylindrical small-diameter stepped portion extending in the axial direction from the inner rolling surface, and serrations formed on the inner periphery, and a small diameter of the hub ring An inner member formed of an inner ring that is press-fitted into a stepped portion and has the other inner rolling surface opposed to the outer rolling surface of the double row on the outer periphery, and is rotatably accommodated between the both rolling surfaces. A rolling element and an outer joint member that forms a constant velocity universal joint and has a shaft portion that is fitted into the hub wheel via a serration are integrally provided, and the hub wheel and the outer joint member are detachably coupled. In the drive wheel bearing device, the serration of the shaft portion is By providing a twist angle inclined at a predetermined angle, said with preload serration fitting portion of the shaft portion and the hub wheel is applied, a plurality of circumferential grooves separate the serrations of the hub wheel is formed.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a bearing device for a drive wheel according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a first embodiment of a drive wheel bearing device according to the present invention, and FIG. 2 is an enlarged view of a main part showing a serration portion of a hub wheel.

  This drive wheel bearing device comprises a hub wheel 1, a double row rolling bearing 2 and a constant velocity universal joint 3 as a unit. In the following description, the side closer to the outside of the vehicle in the state assembled to the vehicle is referred to as the outboard side (left side in the drawing), and the side closer to the center is referred to as the inboard side (right side in the drawing).

  The hub wheel 1 integrally has a wheel mounting flange 4 for mounting a wheel (not shown) at an end portion on the outboard side, and an outer rolling surface on the outboard side of the double row rolling bearing 2 on the outer periphery. 1a and a cylindrical small diameter step portion 1b extending in the axial direction from the inner rolling surface 1a are formed. And the inner ring 5 in which the inner rolling surface 5a on the inboard side of the double row rolling bearing 2 is formed is press-fitted into the small diameter step portion 1b, and the end portion of the small diameter step portion 1b is plastically deformed in the radial direction. Thus, a caulking portion 6 is formed. The inner ring 5 is fixed in the axial direction with respect to the hub wheel 1 by the caulking portion 6 to form a so-called self-retain structure. As a result, it is not necessary to control the preload by tightening firmly with a nut or the like as in the prior art, so that the weight and size can be reduced and the strength and durability of the hub wheel 1 can be improved and long. The amount of preload can be maintained for a period.

  A serration (or spline) 7 described later is formed on the inner periphery of the hub wheel 1. The hub wheel 1 is formed of medium carbon steel containing 0.40 to 0.80 wt% of carbon such as S53C, and the outer peripheral surface thereof is inwardly rolled from the base on the inboard side of the wheel mounting flange 4 serving as a seal land. A hardened layer is formed with a surface hardness of 58 to 64 HRC over the surface 1a and the small-diameter step portion 1b. As the heat treatment, local heating is preferable, and quenching by high-frequency induction heating that can set the hardened layer depth relatively easily is preferable. Here, the caulking portion 6 is not hardened with a surface hardness of 25 HRC or less. On the other hand, the inner ring 5 is made of a high carbon chrome bearing steel such as SUJ2, and is hardened in the range of 54 to 64 HRC to the core portion by quenching.

  The double row rolling bearing 2 includes an outer member 8, an inner member 9, and double row rolling elements (balls) 10, 10. The outer member 8 is attached to a vehicle body (not shown) on the outer periphery. A vehicle body mounting flange 8b is integrally formed, and double-row outer rolling surfaces 8a and 8a are formed on the inner periphery. Here, the inner member 9 refers to the hub wheel 1 and the inner ring 5. Double row rolling elements 10, 10 are accommodated between the rolling surfaces 8a, 1a and 8a, 5a, respectively, and are held by the retainers 11, 11 so as to be freely rollable. Further, seals 12 and 13 are attached to the end portion of the outer member 8 to prevent leakage of lubricating grease sealed inside the bearing and intrusion of rainwater and dust from the outside into the bearing. .

  The outer member 8 is formed of medium carbon steel containing carbon of 0.40 to 0.80 wt% such as S53C, and extends over the mating surfaces of the double row outer rolling surfaces 8a and 8a and the seals 12 and 13. The hardened layer is formed with a surface hardness in the range of 58 to 64 HRC. As the heat treatment, local heating is preferable, and quenching by high-frequency induction heating that can set the hardened layer depth relatively easily is preferable. Here, the double-row rolling bearing 2 is exemplified as a double-row angular ball bearing in which the rolling elements 10 and 10 are balls. However, the double-row rolling bearing 2 is not limited to this and may be a double-row tapered roller bearing using a tapered roller as the rolling element. good.

  In the present embodiment, an inner rolling surface 1a and a cylindrical small-diameter step portion 1b extending in the axial direction from the inner rolling surface 1a are formed on the outer periphery of the hub wheel 1, and the inner ring 6 is formed on the small-diameter step portion 1b. However, the present invention is not limited to this, but not shown in the figure, but a so-called first generation or second generation structure in which a pair of inner rings are press-fitted into the small-diameter step portion of the hub wheel is not illustrated. It may be a wheel bearing device.

  The constant velocity universal joint 3 includes an outer joint member 14, a joint inner ring 15, a cage 16, and a torque transmission ball 17. The outer joint member 14 integrally includes a cup-shaped mouth portion 14a, a shoulder portion 14b that forms the bottom of the mouth portion 14a, and a shaft portion 18 that extends in the axial direction from the shoulder portion 14b. The shaft portion 18 has a serration (or spline) 18a formed on the outer peripheral surface thereof, and a male screw 18b formed on an end portion of the serration 18a. Here, the serration 18a is provided with a twist angle inclined at a predetermined angle with respect to the axis. The outer joint member 14 is made of medium carbon steel containing 0.40 to 0.80 wt% of carbon such as S53C, and includes a track groove formed on the inner periphery of the mouth portion 14a and the shoulder portion 14b. A hardened layer having a surface hardness in the range of 58 to 64 HRC is formed by induction hardening over the base portion of the shaft portion 18.

  Then, the shaft portion 18 of the outer joint member 14 is fitted and inserted into the hub wheel 1 until the shoulder portion 14b contacts the inner end surface of the crimping portion 6 of the hub wheel 1, and the serration of the shaft portion 18 is inserted into the serration 7 of the hub wheel 1. 18a is press-fitted. Thereby, a desired preload can be given to the fitting part of the serrations 7 and 18a, and the play of the circumferential direction can be killed. Finally, the fixing nut 20 is screwed through the plate 19 that is in contact with the outer end surface 1c of the hub wheel 1 to couple the hub wheel 1 and the outer joint member 14 in the axial direction.

  Here, a plurality of circumferential grooves 21 are formed in the serration 7 of the hub wheel 1 beyond the tooth bottom of the serration 7 as shown in an enlarged view in FIG. Thus, when the serration 18a of the shaft portion 18 is press-fitted into the serration 7 of the hub wheel 1, the volume in which the serration 7 is elastically deformed is reduced even if a torsion angle is formed in the serration 18a of the shaft portion 18. , Pressure input can be reduced. The outer joint member 14 can be easily pulled into the hub wheel 1 simply by tightening the fixing nut 20 into the male screw 18 b of the shaft portion 18. Therefore, it is possible to improve workability during assembly and disassembly without requiring a special special jig as in the prior art.

  Here, the example in which a plurality of independent circumferential grooves 21 are formed in the serration 7 of the hub wheel 1 is illustrated, but for example, although not illustrated, a circumferential groove such as a spiral groove may be used. . In addition, a predetermined twist angle is provided in the serration 18a of the shaft portion 18 and preload is applied to the fitting portion with the serration 7 of the hub wheel 1. However, the present invention is not limited to this. For example, the serration 18a of the shaft portion 18 is provided. The tooth thickness of the serrations 7 of the hub wheel 1 may be tightly fitted, and the serrations 7 and 18a may be press-fitted to apply a preload to the fitting portion.

  FIG. 3 is a longitudinal sectional view showing a second embodiment of the drive wheel bearing device according to the present invention. This embodiment is different from the above-described embodiment only in the coupling means of the hub wheel and the outer joint member, and the same components and parts are denoted by the same reference numerals and detailed description thereof is omitted.

  The outer joint member 22 integrally includes a cup-shaped mouth portion 14a, a shoulder portion 14b that forms the bottom of the mouth portion 14a, and a shaft portion 23 that extends in the axial direction from the shoulder portion 14b. The shaft portion 23 has a fitting portion 23a and a serration 18a that are fitted to the small-diameter step portion 1b of the hub wheel 1 through a predetermined radial clearance, and a female screw 23b at the end portion. Yes. The depth of the female screw 23b is set to at least the length of the serration 18a.

  Then, the shaft portion 23 of the outer joint member 22 is fitted and inserted into the hub wheel 1 until the shoulder portion 14b contacts the inner end surface of the crimping portion 6 of the hub wheel 1, and the serration of the shaft portion 23 is inserted into the serration 7 of the hub wheel 1. 18a is press-fitted. Finally, the hub wheel 1 and the outer joint member 14 are coupled in the axial direction by screwing the fixing bolt 25 into the female screw 23b of the shaft portion 23 via the plate 24 that contacts the outer end surface 1c of the hub wheel 1. The

  In the present embodiment, the fitting portion 23a is provided on the outer peripheral surface of the shaft portion 23, and the fitting portion 23a is fitted to the small-diameter step portion 1b of the hub wheel 1 via a predetermined radial clearance. It has high rigidity against moment and can improve durability. Further, since the depth of the female screw 23b of the shaft portion 23 is set to at least the length of the serration 18a, the outer joint can be simply pressed into the hub wheel 1 by tightening the fixing bolt 25. The member 22 can be easily pulled into the hub wheel 1 and the assembly work can be further simplified.

  FIG. 4 is a longitudinal sectional view showing a third embodiment of the drive wheel bearing device according to the present invention. This embodiment is different from the above-described embodiment (FIG. 3) only in the coupling means for the hub wheel and the outer joint member, and the same components and parts are denoted by the same reference numerals and detailed description thereof is omitted.

  The outer joint member 26 integrally includes a cup-shaped mouth portion 14a, a shoulder portion 14b that forms the bottom of the mouth portion 14a, and a shaft portion 27 that extends in the axial direction from the shoulder portion 14b. The shaft portion 27 has a fitting portion 23a and a serration 18a that are fitted to the small-diameter step portion 1b of the hub wheel 1 via a predetermined radial clearance, and an annular groove 27a at an end portion of the shaft portion 27. ing.

  Then, the shaft portion 27 of the outer joint member 26 is fitted into the hub wheel 1 until the shoulder portion 14b contacts the inner end surface of the crimping portion 6 of the hub wheel 1, and the serration of the shaft portion 27 is inserted into the serration 7 of the hub wheel 1. 18a is press-fitted. Finally, by attaching the retaining ring 28 to the annular groove 27a of the shaft portion 27, the hub wheel 1 and the outer joint member 26 are coupled in the axial direction.

  In the present embodiment, the hub wheel 1 and the outer joint member 26 can be coupled in the axial direction only by the retaining ring 28, and not only the device is lighter and more compact, but also the number of parts and the number of processing steps can be reduced and the assembly can be performed.・ The disassembling workability is improved and the cost can be further reduced.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and is merely an example, and various modifications can be made without departing from the scope of the present invention. Of course, the scope of the present invention is indicated by the description of the scope of claims, and further, the equivalent meanings described in the scope of claims and all modifications within the scope of the scope of the present invention are included. Including.

  A bearing device for a driving wheel according to the present invention is a bearing for a driving wheel in which a constant velocity universal joint and a wheel bearing device having a first to third generation structure for rotatably supporting a driving wheel with respect to a suspension device are unitized. Applicable to equipment.

It is a longitudinal section showing a 1st embodiment of a bearing device for drive wheels concerning the present invention. It is a principal part enlarged view which shows the serration part of a hub wheel same as the above. It is a longitudinal cross-sectional view which shows 2nd Embodiment of the bearing apparatus for drive wheels which concerns on this invention. It is a longitudinal cross-sectional view which shows 3rd Embodiment of the bearing apparatus for drive wheels which concerns on this invention. It is a longitudinal cross-sectional view which shows the conventional bearing apparatus for drive wheels. It is a longitudinal cross-sectional view which shows the conventional other bearing apparatus for drive wheels. It is a longitudinal cross-sectional view which shows an example of the power transmission device incorporating the drive wheel bearing device same as the above.

Explanation of symbols

1 ... hub wheel 1a, 5a ... inner rolling surface 1b ...・ Small diameter stepped portion 1c ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Outer end surface 2 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Double row rolling bearing 3 …… ・ ・... Constant velocity universal joint 4 ... Wheel mounting flange 5 ... Inner ring 6 ·············································· 7 Member 8a ... Outer rolling surface 8b ... Car body mounting flange 9 ...・ ・ ・ ・ Inner member 10 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Rolling element 11 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Retainer 12 13 ··········· Seals 14, 22 and 26 ··· Outer joint member 14a ····················· Mouse portion 14b・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Shoulder 15 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Fitting inner ring 16 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Cage 17 ・ ・ ・··············· Torque transmission balls 18, 23, 27 ······ Shaft portion 18b ·····················・ ・ ・ ・ ・ ・ Plate 20 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Nut 21 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Circumferential groove 23a ·············· Fitting portion 23b ························ .......... annular groove 28 ............... stop 100 ... Drive shaft 101 ... Sliding type constant velocity universal joint 102 ...・ Differential 103 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Fixed constant velocity universal joint 104 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Wheel bearing device 105 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ Drive wheel 106 ・ ・ ・ ・ ・ ・ ・ ・ Hub wheel 107 ・ ・ ・ ・ ・ ・ ・ ・ Double row rolling bearing 108 ・ ・ ・ ・ ・ ・ ・ ・... outer joint member 109 ... inner rings 110, 111, 116 ... serrations 112 ... drive wheels Bearing device 113 ... hub wheel 113a ... small diameter step 114 ... inner ring 115 ... ····························································· Outer joint member 118 ... ········································································· ............... ... Serration hole 123 ... Assembly jig

Claims (5)

An outer member having a double row outer raceway formed on the inner periphery, a wheel mounting flange at one end, and a cylindrical small diameter step portion extending in the axial direction are formed on the outer periphery. A hub ring in which serrations are formed, and an inner member comprising at least one inner ring press-fitted into a small diameter step portion of the hub ring and having an inner rolling surface facing the outer rolling surface of the double row on the outer periphery. A rolling element rotatably accommodated between both the rolling surfaces, and an outer joint member that forms a constant velocity universal joint and integrally includes a shaft portion that is fitted into the hub wheel via serrations. A drive wheel bearing device in which the hub wheel and the outer joint member are detachably coupled,
A drive wheel bearing device, wherein a preload is applied to a serration fitting portion between the shaft portion and the hub wheel, and a circumferential groove is formed in the serration of the hub wheel.   The drive wheel bearing device according to claim 1, wherein the serration of the shaft portion of the outer joint member is provided with a torsion angle inclined by a predetermined angle with respect to the axis.   The bearing device for a drive wheel according to claim 1 or 2, wherein a plurality of the circumferential grooves are formed independently in the axial direction.   The bearing device for a drive wheel according to claim 1, wherein the circumferential groove is a spiral groove.   The drive wheel bearing device according to any one of claims 1 to 4, wherein a fitting portion is provided on an outer peripheral surface of the shaft portion, and the fitting portion is fitted to a small diameter step portion of the hub wheel via a predetermined radial clearance. .

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