JP2003048405A - Bearing device for driving wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten the fatigue resistance of a hub ring under the rotating bending condition. SOLUTION: An inner member 20 comprises a hub ring 30 having a wheel fitting flange 31 and an inner ring 40 fitted to a small diameter stepped part 32 of the hub ring 30, and a rolling surface 21 on the outboard side and a rolling surface 22 on the inboard side are formed on the outer circumference of the hub ring 30 and the outer circumference of the inner ring 40, respectively. The maximum principal stress generated in a base part of the small diameter stepped part 32 of the hub ring 30 is operated under the rotating bending condition equivalent to that in a practical application, and the shape of the inner member 20 is controlled so that the operated value reaches the regulated value or under.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device for rotatably supporting drive wheels of an automobile or the like (rear wheels of FR vehicles, front wheels of FF vehicles, all wheels of 4WD vehicles) with respect to a vehicle body. Is.

[0002]

2. Description of the Related Art A drive wheel bearing device shown in FIG. 5 is a unit in which a hub wheel 3 and a double row bearing B are unitized.
Is a double row rolling surface 1a formed on the inner periphery of the outer member 1,
A double row rolling element 5 (ball in the illustrated example) is incorporated between the double row rolling surfaces 2a and 2b formed on the outer periphery of the inner member 2. At one end of the hub wheel 3, a cylindrical small-diameter step portion 3a having a smaller diameter than the other parts is formed. The inner race 4 is press-fitted onto the outer circumference of the small-diameter step portion 3a, and the end face of the inner race 4 is brought into abutment with the shoulder surface 3b of the hub race 3, whereby the double row rolling surface
An inner member 2 having a and 2b is constructed. The bearing device of the illustrated example has one of two rows of rolling surfaces of the inner member 2 2b.
Is formed directly on the outer circumference of the hub wheel 3, and the other 2a is formed on the outer circumference of the inner ring 4.

Butt position X'of the hub wheel 3 and the inner wheel 4
Is the bearing center O '(axial center between the double-row ball centers)
Above or on the outboard side (left side of the drawing).

[0004]

Conventionally, the design of the above-mentioned bearing device for a drive wheel has been carried out mainly by examining the rolling contact fatigue life of the rolling contact surface under repeated load and the rolling contact surface strength under static maximum load. ing.

However, during actual use of the bearing device, a vertical bending moment due to a lateral load acts as the vehicle turns, and the hub wheel is repeatedly subjected to a large moment load. It is considered that the repeated load of the moment load has a great influence on the fatigue resistance of the bearing device, but conventionally, this point has not been sufficiently reflected in the design of the wheel bearing device, and there is room for improvement.

In order to confirm the influence of the repeated load of the moment load on the fatigue resistance of the hub wheel, the inventor of the present invention attached the drive wheel bearing device to the dummy knuckle,
A rotary bending fatigue test was performed by applying a moment load corresponding to the turning of the vehicle (turning condition μ = 0.7 G) to the bearing device. In this test, a radial load of 9.6 kN was applied on the wheel center, an axial load of 6.7 kN was applied to the shaft core, and a tire with a radius of 368 mm was rotated at a rotation speed of 400 r / min in this state. . Bearing center O'is 3.0m on the inboard side of the wheel center
m offset.

As a result of this test, in the test bearing device, the hub wheel is 46.9 to 50.5 h (112.6 to 1212,000 rotations), and the small diameter stepped portion 3 starts from the inner serration portion.
Broken at the base of 2. Here, the hub wheel 3 after the wheel break
Or inner race 4, or the rolling surfaces 2a, 2b, 1 of the outer member 1
The occurrence of flaking and the like was not observed even when a was observed. Therefore, it is considered that the hub wheel is fatigue-ruptured before the rolling fatigue life of the bearing is reached, and it has been found that the repeated load of the moment load has a great influence on the durability of the bearing device.

On the other hand, when the finite element analysis of the stress distribution of the inner member is carried out under the condition that the moment load is actually applied, the maximum principal stress is particularly large near the base of the small diameter step of the hub wheel, and this part is It turned out to be the weakest part of the hub wheel.

The present invention has been made based on the above findings, and an object of the present invention is to provide a drive wheel bearing device in which the fatigue resistance of the hub wheel is enhanced under the condition that an excessive moment load is applied. It is a thing.

[0010]

In order to achieve the above object, in the present invention, an outer member having a double row rolling contact surface on the inner periphery and a double row member facing the rolling contact surface of the outer member respectively. An inner member having a rolling surface, a wheel mounting flange on the outer circumference, and tooth portions for torque transmission on the inner circumference, and a double row rolling element incorporated between opposing rolling surfaces. A square member is integrally fitted with a wheel mounting flange and a small-diameter step portion, and is fitted to the small-diameter step portion of the hub wheel, and has at least an inboard side rolling surface of the double-row rolling surfaces. In a drive wheel bearing device including an inner ring, the maximum principal stress generated at the base of the small-diameter stepped portion of the hub wheel is calculated under the rotating bending condition corresponding to the time of actual use, and the calculated value becomes equal to or less than the specified value. The shape of the inner member was controlled.

As a result, the stress is relieved at the base of the small-diameter stepped portion which is the weakest portion under the so-called rotational bending condition in which a moment load is applied during the rotation of the bearing, so that the strength of the base can be increased. Therefore, the fatigue resistance of the hub wheel can be further improved. Here, the "rotational bending condition corresponding to the time of actual use" means the moment load that the hub wheel receives when turning under the turning condition of 0.5G to 0.8G.

As a result of the rotating bending fatigue test conducted by the inventor of the present invention, the maximum principal stress of the base is 30 under the turning condition of 0.7 G.
It has been found that the fatigue fracture of the hub wheel can be reliably prevented by designing the inner member to have 0 MPa. Therefore, it is desirable to set the specified value to 300 MPa.

The specified value of 300 MPa is almost equal to the swing fatigue limit of carbon steel, which is a general material for hub wheels, and therefore the specified value is determined according to the swing fatigue limit of the material of the hub wheel. It is considered possible.

By forming a surface-hardened layer by heat treatment in a region including at least the base of the small-diameter step portion on the outer periphery of the hub wheel, it is possible to further increase the strength of the weakest base. It is empirically known that when the surface hardness after heat treatment is set to 58 HRc or more, the double swing fatigue limit is almost twice as much as that of raw material. , 600 MPa is desirable.

The hub wheel and the inner wheel are arranged to face each other in the axial direction. At this time, if the abutting position of both members is offset toward the inboard side from the bearing center (axial center of the double row rolling element center), the length of the small diameter step becomes shorter and the volume of the thick part of the hub ring becomes smaller. Therefore, the stress near the base portion of the small-diameter step portion can be relaxed, and the fatigue resistance of the hub wheel can be improved.

Specifically, the center distance of the double row rolling elements is P, the distance between the abutment position of the hub ring and the inner ring and the center of the rolling element on the inboard side is L, and the rolling element diameter on the inboard side is L. It is desirable to set L ≦ 0.4P and L ≦ D as D.

Further, in the hub wheel, even if the corner portion between the shoulder surface and the outer periphery of the small-diameter step portion is formed by an arc surface formed of a ground surface, the stress of the base portion is similarly relaxed, and the fatigue resistance of the hub wheel is improved. Can be increased. In the past, since the concave shape of the grinding gutter was formed in this corner, stress concentration was likely to occur due to the notch effect, but with the above configuration, this stress concentration is alleviated.

As described above, among the double-row rolling surfaces of the inner member, the inboard-side rolling surface is formed on the outer periphery of the inner ring, while the remaining outboard-side rolling surfaces are hub wheels. Can be formed on the outer periphery of. Besides, it is also possible to fit two inner rings in a small diameter stepped portion of the hub ring in a butted state, and form rolling surfaces on the outer circumferences of both inner rings.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS.
It will be described with reference to FIG. In the following description, the side closer to the outer side of the vehicle when assembled to the vehicle is referred to as the outboard side, and the side closer to the center of the vehicle is referred to as the inboard side. 1 to 4, the left side is the outboard side and the right side is the inboard side.

FIG. 1 is a cross-sectional view of a drive wheel bearing device according to the present invention. A double row rolling element 50 is installed between an outer member 10 and an inner member 20 with a predetermined contact angle to form an inner member. This is a structure for rotatably supporting the member 20. The double row rolling elements 50 are held at equal intervals in the circumferential direction by a cage 60, and the double row rolling surfaces 11, 2 of the outer member 10 and the inner member 20 are held.
It is installed between 1 and 22. Here, the rolling element 5
Although the case where a ball is used as 0 is illustrated, a tapered roller can also be used.

The outer member 10 has a double row rolling surface 11 on the inner circumference.
And a vehicle body mounting flange 12 for mounting on a vehicle body side mounting member, for example, a knuckle extending from a suspension device. Seals 13 and 14 are attached to the openings at both ends of the outer member 10 so as to prevent leakage of the grease filled inside and intrusion of water or foreign matter from the outside.

The inner member 20 is composed of a hub wheel 30 and an inner ring 40 fitted to the outer circumference thereof. A wheel mounting flange 31 for mounting a wheel is provided on the outer periphery of the hub wheel 30.
Is integrally formed, and the hub bolt 35 embedded in the flange 31 fixes the drive wheel (not shown) to the wheel mounting flange 31 via the brake rotor.
A small-diameter step portion 32 is provided on the outer circumference of the hub wheel 30 on the inboard side, and the inner ring 40 is press-fitted to the outer circumference of the small-diameter step portion 32. Of the rolling surfaces 21, 22 of the inner member 20, the rolling surface 22 on the inboard side is formed on the outer circumference of the inner ring 40, and the rolling surface 21 on the outboard side is directly formed on the outer circumference of the hub wheel 30. There is. A through hole for attaching an outer joint member 72 of a constant velocity universal joint 70, which will be described later, is formed in the shaft core portion of the hub wheel 30.

The hub wheel 30 is formed by forging using carbon steel such as S53C, of which the portion shown by the dotted pattern in FIG. 2, that is, the wheel mounting flange 3
Starting from the vicinity of the base end portion of 1, the rolling surface 21 on the outboard side, the shoulder surface 38 in contact with the end surface of the inner ring 40, and the outer periphery of the small-diameter step portion 32 are heat-treated in a region Hv.
A surface effect layer of about 510 to 900 is formed. The quenching method can be selected from known techniques such as induction quenching, carburizing quenching, laser quenching, etc., but when the heat treatment is carried out in the above quenching pattern, induction quenching is suitable. Although illustration is omitted, the heat treatment is also applied to the entire surface of the inner ring 40. This quenching may be performed by induction quenching, or the core may be hardened by so-called zub quenching.

As shown in FIG. 1, a constant velocity universal joint 70 is assembled to this bearing device. Constant velocity universal joint 70
Applies torque from the drive shaft to the inner joint member 74
And the outer joint member 72 via the torque transmission balls 75.
Communicate to. The outer joint member 72 includes a cup-shaped mouth portion 72a having one end (outboard side) closed and the other end (inboard side) opened, and a shaft-shaped stem portion 72b, and an inner peripheral portion of the mouth portion 72a. Multiple track grooves 7
1 is formed. A plurality of ball tracks are formed by the cooperation of the track grooves 71 and a plurality of track grooves 73 provided on the outer peripheral portion of the inner joint member 74, and the torque transmitting balls 75 are arranged in the respective ball tracks. Each torque transmission ball 75 is held by a cage 76 on the bisecting plane between the two shafts.

An outer joint member 72 is provided on the inner circumference of the hub wheel 30.
The stem portion 72b is press-fitted. The hub wheel 30 and the stem portion 72b are coupled so that torque can be transmitted through a torque transmitting means for transmitting torque by meshing of tooth portions extending in the axial direction. As an example, the serration 81 is illustrated, and the serration shaft 82 is illustrated as a torque transmitting tooth portion on the outer periphery of the stem portion 72b (in addition, both can be connected by a spline).

The shoulder portion 72c of the outer joint member 72 is connected to the inner ring 40.
Press on the end surface of the inboard side of the
By screwing and tightening the nut 83 on the shaft end of b, the end surface of the inner ring 40 on the outboard side contacts the shoulder surface 38 of the hub wheel 30, and the inner ring 40 is positioned. Positioning of the inner ring 40 can also be performed by swaging the inboard side end of the hub ring 30 to the outer diameter side.

As described above, the base portion (including the shoulder surface 38 and its periphery) of the small-diameter step portion 32 of the hub wheel 30 is the weakest portion under the rotary bending condition corresponding to the actual use. In the present invention, in order to relieve the stress generated in the base portion, the maximum principal stress generated in the base portion under the rotating bending condition in actual use is calculated, and the inner member is adjusted so that the calculated value becomes smaller than the specified value. It was decided to manage 20 shapes.

FIG. 1 shows an example of this shape management. In the conventional case, the abutment position X of the hub ring 30 and the inner ring 40 on the bearing center O '(see FIG. 3B) or on the outboard side relative to this is X. Is offset toward the inboard side with respect to the bearing center O (see FIG. 7A). With this configuration, the axial length of the small-diameter step portion 32 is smaller than that of the conventional product, and therefore the volume of the thick portion of the hub wheel 30 is larger than that of the conventional product. Therefore, the maximum principal stress is reduced near the base of the small-diameter step portion 32, and the fatigue resistance of the hub wheel 30 is improved.

Specifically, as shown in FIG. 2, the distance between the centers of the double-row rolling elements 50 is P, the hub wheel 30 and the inner ring 40.
It is desirable to set L ≦ 0.4P and L ≦ D, where L is the distance between the abutting position X and the center of the rolling element 50 on the inboard side and D is the diameter of the rolling element on the inboard side. In either case where L is larger than 0.4P or when L is larger than the rolling element diameter D, the small diameter step portion 32 becomes long and the above-described effect cannot be obtained. The center of the rolling element on the inboard side is the serration 81 on the inner circumference of the hub wheel 30.
It is desirable to dispose it on the outboard side rather than the inboard side end of (E ≧ 0).

In order to confirm the stress relaxation effect of the above structure, the rotary bending condition (rotation condition μ = 0.7 G) during actual use
Was applied to the inner member 20 and the stress distribution of the inner member 20 at that time was obtained by finite element analysis. The analysis model is a bearing device integrated with the constant velocity universal joint 70 as in FIG. 1. In this analysis model, the tightening margin between the hub wheel 30 and the inner ring 40 is 25 μm, and the nut 8
The amount of deformation of the hub wheel 30 due to the tightening of No. 3 is set to 20 μm. The serration 83 on the inner circumference of the hub wheel 30 was replaced with a cylinder, and the interference between the serration 83 and the outer joint member 72 fitted to this was set to zero.

The Young's modulus of the analytical model is 20.78 × 10.
⁴ MPa, Poisson's ratio was set to 0.3, and as a constraint condition, the center of the bolt hole of the hub bolt 35 was completely restrained in the XYZ directions. The load condition is 20μ at the washer seat surface position 84.
With the displacement of m, the rolling element load under the 0.7 G turning condition was applied as a concentrated load to the corresponding nodes.

As a result of the analysis, as shown in FIG. 3 (A), in the case of the product of the present invention in which the width a of the inner ring 40 is 17 mm, the hub ring 30
The maximum principal stress was 292 MPa at the shoulder surface 38. On the other hand, as shown in FIG.
When the conventional product was analyzed under the same conditions, the maximum principal stress of the shoulder surface 3b was 374 MPa, demonstrating the stress relaxation effect of the present invention.

Next, the product of the present invention was attached to a dummy knuckle and a rotary bending fatigue test was conducted under the same conditions as in paragraph [0006]. However, the hub ring 30 was not broken, and the rolling fatigue life of the bearing was longer than that. It was confirmed to have high fatigue resistance. From the above, it is desirable to set the specified value to 300 MPa under the turning condition of 0.7 G.

By the way, the maximum principal stress is 292 MPa.
Is approximately equal to the double fatigue limit of carbon steel, which is the material of the hub wheel. Therefore, the specified value can be increased or decreased based on the double swing fatigue limit of the material. For example, when carbon steel is used in an unheated raw state, the swing fatigue limit is about 300 MPa, but when heat treatment is performed including the base of the small diameter step portion 32 to harden it to a surface hardness of 58 HRc, Since it is empirically known that the swing fatigue limit becomes about twice, the specified value in this case is set to 600 MPa.

In addition to this, as shown in FIG. 4, for the above-mentioned shape management, a corner 39 between the shoulder surface 38 of the hub wheel 30 and the outer circumference of the small-diameter step portion 32, which are abutted with the end surface of the inner ring 40, is made of a ground surface. It can also be formed by an arcuate surface 90. Traditionally,
As shown by the broken line in the figure, the nose 91 for grinding the corner 39 was formed by forging or cutting, but in the present invention, the nose 91 is eliminated and the corner 91 is shown by the solid line in the figure. Part 3
9 is formed by an arcuate surface 90 smoothly connected to the shoulder surface 38 and the outer circumference of the small-diameter step portion 32. The arcuate surface 90 is finished by grinding the shoulder surface 38 and the outer circumference of the small-diameter step portion 32 at the same time. As a result, stress concentration due to the notch effect is relaxed as compared with the case where the slime 91 is formed.
The maximum principal stress at the base of the small-diameter step portion 32 is relaxed, and the fatigue resistance of the hub wheel under rotary bending conditions can be improved.

The stress relaxation effect increases as the radius of curvature of the arc surface 90 increases (the curvature decreases).
It is desirable that the R dimension of 0 be as large as possible. In this case, it is preferable to minimize the chamfer 92 at the end portion of the outer periphery of the inner ring 40 on the outboard side in order to suppress the reduction of the abutting area of the hub ring 30 and the inner ring 40.

[0037]

As described above, according to the present invention, based on the new finding that the base of the small-diameter stepped portion of the hub wheel becomes the weakest part under the rotating bending condition corresponding to the actual use, the maximum main part of the base is obtained. The stress is kept below the specified value. Therefore, even under the condition that a high moment load is applied due to turning of the vehicle,
It is possible to ensure high fatigue resistance of the hub wheel, and it is possible to provide a drive wheel bearing device having a long durability life.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a drive wheel bearing device according to the present invention.

FIG. 2 is a cross-sectional view of the wheel bearing device before the constant velocity universal joint is assembled.

FIG. 3 is a cross-sectional view showing an inner member of the wheel bearing device,
(A) shows the product of the present invention, and (B) shows the conventional product.

FIG. 4 is an enlarged cross-sectional view near the base of the hub wheel.

FIG. 5 is a cross-sectional view of a conventional wheel bearing device for driving wheels.

[Explanation of symbols]

10 Outer member 11 Rolling surface 12 Body mounting flange 13 seal 14 seal 20 Inner member 21 Rolling surface (outboard side) 22 Rolling surface (inboard side) 30 hub wheels 31 Wheel mounting flange 32 small diameter step 35 hub bolt 38 Shoulder 39 corners 40 inner ring 50 rolling elements 60 cage 70 constant velocity universal joint 71 track groove 72 Outer joint member 72a mouse part 72b Stem part 72c shoulder 73 Track groove 74 Inner joint member 75 torque transmission ball 76 cage 81 Serration (torque transmission teeth) 82 Serration shaft (torque transmission teeth) 83 nuts 90 arc surface 91 Nusumi O bearing center X Butt position

Continued front page    F term (reference) 3J101 AA03 AA32 AA43 AA54 AA62                       AA72 BA53 BA56 DA03 EA02                       FA31 GA03

Claims (8)

[Claims] 1. An outer member having a double row rolling surface on the inner circumference, a double row rolling surface facing the rolling surface of the outer member, and a wheel mounting flange on the outer circumference for torque transmission. Each of which has inner teeth on its inner circumference, and double rows of rolling elements incorporated between opposing rolling surfaces, wherein the inner member integrally has a wheel mounting flange and a small-diameter step portion. In a drive wheel bearing device including a hub wheel and an inner ring having at least an inboard side rolling surface of a double row rolling surface that is fitted into a small-diameter step portion of the hub wheel, and is suitable for actual use. Drive wheel characterized in that the maximum principal stress generated at the base of the small-diameter step portion of the hub wheel is calculated under the rotating bending condition, and the shape of the inner member is controlled so that the calculated value is equal to or less than a specified value. Bearing device. 2. The drive wheel bearing device according to claim 1, wherein the specified value is set to 300 MPa. 3. The bearing device for a drive wheel according to claim 1, wherein a hardened surface layer is formed by heat treatment on a region including at least a base portion of the small diameter step portion on the outer periphery of the hub wheel. 4. The drive wheel bearing device according to claim 3, wherein the specified value is set to 600 MPa. 5. The drive wheel bearing device according to claim 1, wherein the hub wheel and the inner ring are butted in the axial direction, and the butted positions of both members are offset toward the inboard side with respect to the bearing center. 6. L ≦ L, where P is the distance between the centers of the double-row rolling elements, L is the distance between the abutting position and the center of the inboard rolling element, and D is the inboard rolling element diameter.
The bearing device for a drive wheel according to claim 5, wherein 0.4P and L ≦ D are set. 7. The hub wheel, wherein the corner portion between the shoulder surface and the outer circumference of the small-diameter step portion is formed by an arc surface which is a ground surface.
6. A bearing device for a drive wheel according to any one of 6 above. 8. The rolling contact surface on the outboard side of the double-row rolling surfaces of the inner member is formed on the outer circumference of the hub wheel.
7. A bearing device for a drive wheel according to any one of 7.