JP2002114006A - Bearing device for driving wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the service life by restricting the deflection inside a bearing due to deformation of an inner ring and a hub wheel by a load in the contact angle direction. SOLUTION: This bearing device for driving wheel is formed of an outer ring 5 formed with double row raceway surfaces 12 and 13 in the inner peripheral surface thereof, a hub wheel 1 formed with raceway surfaces 7 and 8 opposite to the raceway surfaces 12 and 13 of the outer ring 5 in the outer peripheral surface thereof and having a wheel fitting flange 9 in the outer peripheral surface thereof, an inner ring 2, double row conical rollers 3 and 4 interposed between the raceway surfaces of the outer ring 5, the hub wheel 1 and the inner ring 2, and a constant velocity universal joint 6 having a shoulder part 28 fitted to an end surface of the inner ring 2 so as to abut thereon and provided with a joint outer ring 21 having a shaft part 23 fitted in the hub wheel 1 and the inner ring 2 freely to transmit the torque. This bearing device for driving wheel supports the wheels freely to be rotated in relation to a car body. A pilot part 32 is provided between a root part 31 of a shaft part of the joint outer ring 21 and an end of the hub wheel 1, and a clearance (a) of the pilot part is formed at 0.4 mm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive wheel bearing device, and more particularly to a drive wheel bearing device for rotatably supporting a drive wheel of an automobile on a vehicle body.

[0002]

2. Description of the Related Art Various types of bearing devices for driving wheels of automobiles have been proposed according to their uses. For example, FIG. 3 shows a drive wheel bearing device suitable for a heavy-duty automobile, and includes a hub wheel 1 and an inner ring 2 as inner members, double-row rolling elements (taper rollers) 3, 4, and an outer member. The outer race 5 and the constant velocity universal joint 6 are main components.

The hub wheel 1 has a track surface 7 on the outboard side formed on an outer peripheral surface thereof, and a wheel (not shown).
Is provided with a wheel mounting flange 9 for mounting.
Hub bolts 10 for fixing the wheel disc are implanted at equal intervals in the circumferential direction of the wheel mounting flange 9. The inner ring 2 is fitted to a small-diameter step portion 11 formed on the outer peripheral surface of the inboard end of the hub wheel 1, and an inboard-side raceway surface 8 is formed on the outer peripheral surface of the inner ring 2.

[0004] The inner ring 2 is press-fitted with an appropriate interference to prevent creep. The raceway surface 7 on the outboard side formed on the outer peripheral surface of the hub wheel 1 and the raceway surface 8 on the inboard side formed on the outer peripheral surface of the inner ring 2 constitute a double row raceway surface. The inner ring 2 is press-fitted into the small-diameter step portion 11 of the hub wheel 1, and the outer ring 21 of the constant velocity universal joint 6 inserted from the inboard side of the hub wheel 1 is fastened to the hub wheel 1. The shoulder 28 of the joint outer ring 21 prevents the inner ring 2 from coming off and provides a preload.

The outer ring 5 has track surfaces 12, 13 facing the track surfaces 7, 8 of the hub wheel 1 and the inner ring 2 on its inner peripheral surface, and a vehicle body mounting flange 14 for mounting to a vehicle body (not shown). It has. This body mounting flange 14
Is bolted to a knuckle extending from a suspension (not shown) of the vehicle body.

The bearing portion 15 has a double row tapered roller bearing structure, and has raceway surfaces 7, 8 formed on the outer peripheral surfaces of the hub wheel 1 and the inner ring 2 and raceway surfaces 12, 8 formed on the inner peripheral surface of the outer ring 5. Thirteen
And rolling elements (taper rollers) 3 and 4 are interposed therebetween, and the rolling elements 3 and 4 in each row are supported at equal intervals in the circumferential direction by retainers 16 and 17.

A pair of seals 18 and 19 for sealing the annular space between the outer ring 5 and the hub ring 1 and the inner ring 2 are fitted into the opening at both ends of the bearing part 15 at the inner diameter of the end of the outer ring 5 to fill the inside. The grease is prevented from leaking and water or foreign matter from the outside is prevented from entering.

The constant velocity universal joint 6 has a drive shaft 39.
And a joint outer ring 21 having a track groove 20 formed on an inner peripheral surface thereof, and a track groove 20 of the joint outer ring 21.
A ball 4 incorporated between the track groove 20 of the joint outer ring 21 and the track groove 40 of the joint inner ring 41, and a joint inner ring 41 having a track groove 40 facing the
2 and a retainer 43 that supports the ball 42 between the joint outer ring 21 and the joint inner ring 41.

The joint outer ring 21 has a mouth portion 22 accommodating the joint inner ring 41, the ball 42 and the retainer 43, and extends integrally from the mouth portion 22 in the axial direction, and a serration portion 24 is formed on the outer peripheral surface. It has a shaft portion 23. The shaft portion 23 is inserted into the through hole of the hub wheel 1, and both are fitted by serration portions 24 and 25 formed on the outer peripheral surface of the shaft portion 23 and the inner peripheral surface of the through hole, and formed at the shaft end. The constant velocity universal joint 6 is fixed to the hub wheel 1 by tightening a nut 27 to the male screw portion 26 thus formed.

A conventional drive wheel bearing device includes a hub wheel 1.
The pilot portion 30 is provided between the small-diameter step portion 11, that is, the end portion on the inboard side and the shaft portion root portion 29 of the joint outer ring 21. The pilot portion 30 is formed by making the inner diameter of the small-diameter step portion 11 of the hub wheel 1 larger than that of the serration portion 25. By thus forming the pilot portion 30 and providing the pilot portion clearance A, when the constant velocity universal joint 6 is assembled, the shaft portion 23 of the joint outer ring 21 and the hub wheel 1 are aligned, and the shaft portion 2 is formed.
3 is easily inserted into the through hole of the hub wheel 1. In addition,
The pilot clearance A is the small diameter step 1 of the hub wheel 1.
1 means the difference between the inner diameter of the end portion and the outer diameter of the shaft root portion 29 of the joint outer ring 21.

[0011]

The rolling elements 3,
In the drive wheel bearing device of FIG. 3 using tapered rollers in No. 4, the contact angle is smaller than that of the drive wheel bearing device having a structure using balls as rolling elements. Here, the contact angle is
It means the angle formed by the acting direction of the force transmitted to the rolling elements 3 and 4 by the raceway surfaces 7 and 8 with respect to a plane (radial plane) perpendicular to the bearing center axis.

Generally, in a bearing device for a drive wheel using a ball for a rolling element, a contact angle is about 35 °.
The load acting in the contact angle direction of the inner ring 2 is, as shown in FIG.
The shoulder 28 of the joint outer ring 21 and the inner ring 2 face in the direction of the butt surface.

On the other hand, in a drive wheel bearing device using tapered rollers for the rolling elements 3 and 4, the contact angle is generally set to a small value of about 16 to 18 ° in order to obtain a high load capacity. The load acting in the contact angle direction is directed toward the pilot portion 30 between the small-diameter step portion 11 of the hub wheel 1 and the shaft base portion 29 of the joint outer ring 21.

Therefore, as described above, when the clearance A of the pilot portion is large, the assembling property is improved, but the deformation of the small-diameter step portion 11 of the hub wheel 1 and the raceway surface 8 of the inner ring 2 due to the load in the contact angle direction is large. Become. In other words, when the amount of deformation of the raceway surface 8 of the inner race 2 increases, the rolling life decreases and the raceway surface 8
, And the axial force (preload) is easily lost due to fretting between the inner ring 2 and the shoulder 28 of the joint outer ring 21.

Further, when the amount of deformation of the small-diameter step portion 11 of the hub wheel 1 is increased, the breakage of the hub wheel 1 and fretting between the hub wheel 1 and the inner ring 2 are likely to occur. When the small-diameter step portion 11 of the hub wheel 1 and the raceway surface 8 of the inner ring 2 are easily deformed in this way, the inside of the bearing may be distorted, and the life of the bearing device may be shortened.

Accordingly, the present invention has been proposed in view of the above-mentioned problems, and an object of the present invention is to suppress distortion inside a bearing caused by deformation of a hub wheel and an inner ring due to a load in a contact angle direction to reduce the life. An object of the present invention is to provide a drive wheel bearing device that can be improved.

[0017]

SUMMARY OF THE INVENTION As a technical means for achieving the above object, the present invention provides an outer member having a double row of track surfaces formed on an inner peripheral surface, and a track surface of the outer member. An opposing raceway surface is formed on the outer peripheral surface, an inner member having a wheel mounting flange on the outer peripheral surface, and a double row of rolling elements interposed between the respective raceways of the outer member and the inner member, A constant velocity universal joint having a joint outer ring having a shoulder portion which is abutted against the end surface of the inner member in abutting state, and a shaft portion which is internally fitted to the inner member so as to be capable of transmitting torque; In a drive wheel bearing device for rotatably supporting a wheel with respect to a vehicle body, a pilot portion is provided between a root portion of a shaft portion of the joint outer ring and an end portion of the inner member. The thickness is set to 4 mm or less (claim 1).

According to the first aspect of the present invention, a pilot portion is provided between a root portion of a shaft portion of the joint outer ring and an end portion of the inner member, and a clearance of the pilot portion is set to 0.4 m.
By setting m or less, the deformation of the end of the inner member due to the load in the contact angle direction can be suppressed, and the life of the bearing device can be easily improved.

According to the present invention, a double-row raceway surface is
In addition, the present invention is applicable to a drive wheel bearing device having a structure in which an outer member having a vehicle body mounting flange integrally formed on an outer peripheral surface thereof is provided.

The present invention also provides a hub wheel having a wheel mounting flange, one raceway surface and a small diameter step formed on an outer peripheral surface,
The present invention is applicable to a drive wheel bearing device having a structure including an inner member that is fitted to the small-diameter step portion and includes a separate inner ring having the other raceway surface formed on the outer peripheral surface (claim 3).

According to a fourth aspect of the present invention, a pilot portion is formed between an end of the inner ring of the third aspect, which is abutted against a shoulder of the outer ring of the joint, and a shaft base portion of the outer ring of the joint. Features. Since the pilot portion is formed between the end portion of the inner ring and the root portion of the shaft portion of the joint outer ring as described above, deformation of the raceway surface of the inner ring due to the load in the contact angle direction can be suppressed, and the bearing device It is easy to achieve a long life.

The pilot portion formed by the inner ring of the two pilot portions formed between the root portion of the shaft portion of the joint outer ring and the end portions of the hub wheel and the inner ring. It is desirable to set the clearance smaller than the clearance of the pilot portion formed by the hub wheel.

The present invention is preferably applied to a drive wheel bearing device having a structure in which the rolling elements are tapered rollers (claim 6).

Preferably, a hardened surface layer is formed in a region extending from the base of the wheel mounting flange to an end of the inner member, and the hardened surface layer is stopped near the end surface of the inner member. 7). In this case, by increasing the surface hardness including the raceway surface of the inner member, the rolling fatigue life can be improved and fretting can be reduced.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a drive wheel bearing device according to the present invention will be described in detail below. The same parts as those in FIG. 3 are denoted by the same reference numerals.

The drive wheel bearing device of the embodiment shown in FIG. 1 includes, for example, a hub wheel 1 and an inner ring 2, which are inner members, double-row rolling elements (taper rollers) 3, 4, and an outer ring which is an outer member. 5. The constant velocity universal joint 6 is a main component.

The hub wheel 1 has one raceway surface, that is, a raceway surface 7 on the outboard side, formed on the outer peripheral surface thereof, and has a wheel mounting flange 9 for mounting wheels (not shown). I have. Hub bolts 10 for fixing the wheel disc are implanted at equal intervals in the circumferential direction of the wheel mounting flange 9. The inner ring 2 is fitted to a small-diameter step portion 11 formed on the outer peripheral surface of the inboard end of the hub wheel 1, and the other race surface, that is, the inboard race surface 8, is fitted to the outer peripheral surface of the inner ring 2. Is formed.

The inner ring 2 is press-fitted with an appropriate interference to prevent creep. The raceway surface 7 on the outboard side formed on the outer peripheral surface of the hub wheel 1 and the raceway surface 8 on the inboard side formed on the outer peripheral surface of the inner ring 2 constitute a double row raceway surface. The inner ring 2 is press-fitted into the small-diameter step portion 11 of the hub wheel 1, and the outer ring 21 of the constant velocity universal joint 6 inserted from the inboard side of the hub wheel 1 is fastened to the hub wheel 1. The shoulder 28 of the joint outer ring 21 prevents the inner ring 2 from coming off and provides a preload.

The outer ring 5 has track surfaces 12 and 13 formed on the inner peripheral surface thereof facing the track surfaces 7 and 8 of the hub wheel 1 and the inner ring 2, and a vehicle body mounting flange 14 for mounting to a vehicle body (not shown). It has. This body mounting flange 14
Is bolted to a knuckle extending from a suspension (not shown) of the vehicle body.

The bearing portion 15 has a double-row tapered roller bearing structure, and has raceway surfaces 7, 8 formed on the outer peripheral surfaces of the hub wheel 1 and the inner ring 2 and raceway surfaces 12, 8 formed on the inner peripheral surface of the outer ring 5. Thirteen
And rolling elements (taper rollers) 3 and 4 are interposed therebetween, and the rolling elements 3 and 4 in each row are supported at equal intervals in the circumferential direction by retainers 16 and 17.

A pair of seals 18 and 19 for sealing the annular space between the outer ring 5 and the hub ring 1 and the inner ring 2 are fitted into the opening at both ends of the bearing part 15 at the inner diameter of the end of the outer ring 5 to fill the inside. The grease is prevented from leaking and water or foreign matter from the outside is prevented from entering.

The constant velocity universal joint 6 includes a drive shaft 39
And a joint outer ring 21 having a track groove 20 formed on an inner peripheral surface thereof, and a track groove 20 of the joint outer ring 21.
A ball 4 incorporated between the track groove 20 of the joint outer ring 21 and the track groove 40 of the joint inner ring 41, and a joint inner ring 41 having a track groove 40 facing the
2 and a retainer 43 that supports the ball 42 between the joint outer ring 21 and the joint inner ring 41.

The joint outer ring 21 has a mouth portion 22 accommodating the joint inner ring 41, the ball 42 and the retainer 43, and extends integrally from the mouth portion 22 in the axial direction, and a serration portion 24 is formed on the outer peripheral surface. It has a shaft portion 23. The shaft portion 23 is inserted into the through hole of the hub wheel 1, and both are fitted by serration portions 24 and 25 formed on the outer peripheral surface of the shaft portion 23 and the inner peripheral surface of the through hole, and formed at the shaft end. The constant velocity universal joint 6 is fixed to the hub wheel 1 by tightening a nut 27 to the male screw portion 26 thus formed. In addition,
The serrations 24 and 25 include splines other than serrations.

In the driving wheel bearing device of the embodiment using the tapered rollers for the rolling elements 3 and 4, the contact angle is 16 to 18 °.
The load acting in the contact angle direction is
It goes toward the small diameter step portion 11 of the hub wheel 1 and the shaft root portion 29 of the joint outer ring 21. Therefore, in this embodiment,
The pilot portion 32 is provided between the shaft base portion 31 of the joint outer ring 21 and the small-diameter step portion 11 which is the end of the hub wheel 1.

The pilot portion 32 enlarges the inside diameter of the small-diameter step portion 11 of the hub wheel 1 more than the serration portion 25,
Further, the outer diameter of the shaft base portion 31 of the joint outer ring 21 is formed to be larger than that of the serration portion 24. The pilot portion 32 is formed in this manner, and the pilot portion clearance a is set to 0.4 mm or less. Here, the pilot portion clearance a means a difference between the inner diameter of the end portion of the small diameter step portion 11 of the hub wheel 1 and the outer diameter of the shaft root portion 31 of the joint outer ring 21.

By providing the pilot portion 32 and setting the pilot portion clearance a to 0.4 mm or less, the deformation of the small-diameter step portion 11 of the hub wheel 1 due to the load in the contact angle direction can be suppressed. Prevention of breakage of the hub wheel 1 and reduction of fretting between the hub wheel 1 and the inner ring 2 can be achieved, and the life of the bearing device can be improved. If the clearance a is larger than 0.4 mm, the desired effect of suppressing deformation of the small-diameter step portion 11 of the hub wheel 1 cannot be obtained.

FIG. 2 shows another embodiment of the present invention. In the drive wheel bearing device of this embodiment, the aforementioned pilot portion 32 is formed by connecting the shaft base portion 31 of the joint outer ring 21 and the hub wheel 1 to each other. A pilot portion 33 is formed between the small-diameter step portion 11 and a portion between the end portion of the inner ring 2 abutted against the shoulder portion 28 of the joint outer ring 21 and the shaft root portion 31 of the joint outer ring 21. The latter pilot portion 33 expands the diameter of the shaft base portion 31 of the joint outer ring 21 so as to extend to the gap between the end face of the small-diameter step portion 11 of the hub wheel 1 and the shoulder 28 of the joint outer ring 21. It is formed by this.

As described above, since the pilot portion 33 is formed between the end of the inner ring 2 and the base portion 31 of the shaft of the joint outer ring 21, the raceway surface 8 of the inner ring 2 is caused by the load in the contact angle direction.
Deformation of the bearing, the rolling life can be improved, the temperature rise can be suppressed, and the axial force (preload) can be prevented from coming off by reducing fretting between the inner ring 2 and the shoulder 28 of the joint outer ring 21. The service life can be improved.

Here, the shaft root portion 31 of the joint outer ring 21
Of the two pilot portions 32 and 33 formed between the inner ring 1 and the end portions of the hub wheel 1 and the inner ring 2, the pilot portion clearance b formed with the inner ring 1 is changed to the pilot portion formed with the hub wheel 1. Set smaller than the clearance a.

That is, as described above, while the pilot clearance a formed between the small-diameter step portion 11 of the hub wheel 1 and the shaft base portion 31 of the joint outer ring 21 is set to 0.4 mm or less, The pilot gap b formed between the shaft base 31 of the joint outer ring 21 and the end of the inner ring 2 is set to 0.05.
mm or less. This pilot section clearance b is 0.05
If it is larger than mm, the desired effect of suppressing deformation of the raceway surface 8 of the inner race 2 cannot be obtained. Two pilots 33, 3
2, the deformation of the inner wheel 2 is suppressed by one of the pilot portions 33, and when a larger load is applied, the deformation of the hub wheel 1 is suppressed by the other pilot portion 32.

In the above-described embodiment, the hardened surface layer 34 is formed in a region extending from the base of the wheel mounting flange 9 to the small-diameter stepped portion 11 of the hub wheel 1. The structure is stopped near the end face of the portion 11. The base of the wheel mounting flange 9 is the outer peripheral surface of the hub wheel 1 with which the seal lip of the seal 18 mounted on the outboard side end of the outer ring 5 slides, that is, the seal land portion, and the seal land portion extends from the raceway surface. Small-diameter step 1 after 7
The surface hardened layer 34 is formed in one region.

In each part of the surface hardened layer 34 and the seal land, the seal lip of the seal 18 slides, so that abrasion resistance is required. On the raceway surface 7, the rolling element 3 rolls, so that the life resistance is required. Since the small-diameter step portion 11 is fitted with the inner ring 2, creep resistance and fretting resistance are required.

The heat treatment for forming the surface hardened layer 34 is suitably induction hardening. The high frequency heat treatment as the surface hardening treatment makes it possible to freely select the surface hardened layer 34 by effectively utilizing the characteristics of the induction heating, to provide abrasion resistance and improve the fatigue strength. Induction heating is a method in which electric energy is directly converted into heat energy in a metal using electromagnetic induction to generate heat, and high-frequency heat treatment using this method has many features. In particular, local heating is possible,
The depth of the hardened layer can be freely selected, and the hardened layer can be controlled so as not to significantly affect the heat except for the hardened layer, so that the performance of the base material can be maintained.

[0044]

EXAMPLES For example, when a turning life test was performed due to a difference in dimensions of a pilot portion clearance, the following test results were obtained. Small-diameter stepped portion 11 of hub wheel 1 and outer ring 2 of joint
A pilot gap a of 0.4 mm is formed between the inner ring 2 and the outer ring 2 of the joint.
In the embodiment (see FIG. 2) in which the pilot portion clearance b of 0.05 mm was formed between the shaft portion root portion 31 of FIG. 1 and the life test result of operation time: 165 hours, temperature rise: 50 ° C. or less was obtained. Was.

On the other hand, a pilot gap A of 2 mm is formed between the small-diameter step portion 11 of the hub wheel 1 and the shaft root portion 29 of the joint outer ring 21, and the end of the inner ring 2 and the joint outer ring In the comparative example (see FIG. 3) in which a pilot gap B of 8.75 mm was formed between the base portion 29 of the shaft 21 and the shaft portion 29 (see FIG. 3), only life test results of operation time: 52 hours, temperature rise: 72 to 90 ° C. were obtained. I couldn't.

From the test results, it is clear that the operation time of the drive wheel bearing device of the embodiment is three times or more that of the comparative example and the temperature rise is suppressed, so that the life of the bearing device can be easily improved. It is.

[0047]

According to the present invention, the contact angle is reduced by providing a pilot portion between the base portion of the shaft portion of the joint outer ring and the end of the inner member, and setting the clearance of the pilot portion to 0.4 mm or less. The deformation of the end of the inner member due to the load in the direction can be suppressed, the breakage of the inner member can be prevented, the fretting of the inner member can be reduced, and the life of the bearing device can be improved and the long life can be achieved. Therefore, it is possible to provide a high-quality drive wheel bearing device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an embodiment of the present invention and showing a structural example of a bearing device for a drive wheel.

FIG. 2 is a cross-sectional view illustrating a structural example of a drive wheel bearing device according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a structural example of a conventional drive wheel bearing device.

[Explanation of symbols]

 Reference Signs List 1 inner member (hub ring) 2 inner member (inner ring) 3, 4 rolling element (taper roller) 5 outer member (outer ring) 7, 8 track surface 9 wheel mounting flange 12, 13 track surface 21 joint outer ring 23 shaft Part 28 Shoulder part 31 Shaft base part 32, 33 Pilot part a, b Pilot part clearance

Continuation of the front page (72) Inventor Takayasu Takubo 1578 Higashikaizuka, Iwata-shi, Shizuoka F-term in NTN Corporation (reference) 3J101 AA16 AA25 AA32 AA43 AA54 AA62 AA72 BA70 DA03 EA02 FA31 GA03

Claims (7)

[Claims] An inner member having a double-row raceway surface formed on an inner circumferential surface, a raceway surface facing the raceway surface of the outer member formed on an outer circumferential surface, and an inner member having a wheel mounting flange on the outer circumferential surface. And a double row rolling element interposed between the respective raceway surfaces of the outer member and the inner member, and a shoulder abutted against the end surface of the inner member, A drive wheel bearing device comprising: a constant velocity universal joint having a joint outer ring provided with a shaft portion that is internally fitted to the inner member so as to be capable of transmitting torque; and the drive wheel bearing device rotatably supporting a wheel with respect to a vehicle body. A bearing device for a drive wheel, wherein a pilot portion is provided between a root portion of a shaft portion of an outer ring and an end portion of the inner member, and a clearance of the pilot portion is set to 0.4 mm or less. 2. The wheel bearing device according to claim 1, wherein the outer member has a double-row raceway surface on an inner peripheral surface thereof and a vehicle body mounting flange integrally on an outer peripheral surface thereof. . 3. The inner member is fitted with a wheel mounting flange, a hub wheel having one raceway surface and a small-diameter stepped portion formed on an outer peripheral surface, and the small-diameter stepped portion, and the other raceway surface is formed on an outer peripheral surface. 2. An inner ring formed as a separate body.
Or the bearing device for a drive wheel according to 2. 4. The drive according to claim 3, wherein a pilot portion is formed between an end portion of the inner ring abutted against a shoulder portion of the outer ring of the joint and a shaft base portion of the outer ring of the joint. Bearing device for wheels. 5. A pilot portion clearance formed between an inner ring and a hub portion of the two pilot portions formed between a shaft root portion of the joint outer ring and end portions of a hub wheel and an inner ring. The drive wheel bearing device according to claim 4, wherein the clearance is set smaller than the formed pilot portion clearance. 6. The drive wheel bearing device according to claim 1, wherein the rolling element is a tapered roller. 7. A hardened surface layer is formed in a region extending from a base of the wheel mounting flange to an end of the inner member, and the hardened layer is stopped near an end surface of the inner member. 7. The drive wheel bearing device according to any one of 1 to 6.