JP2001171309A - Rolling bearing unit for supporting wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize structure having light weight, a low cost, and moreover excellent durability. SOLUTION: A cylindrical part 18b formed on the end part of a hub 2c is caulkedly expanded outward in a diameter direction to fix an inner wheel 3, in the condition wherein the wheel 3 is externally fitted to a step part 8 formed on the end part of the hub 2c. A different level part 27 is formed on the outer peripheral surface of the base end part of the part 18b, to be adopted as a starting point. A part shown by an oblique grating is hardened by heat treating, to prevent the deformation and abrasion of the part. The part 27 is not hardened to prevent damage such as a crack in a portion corresponding to the part 27 at the time of caulking work.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The rolling bearing unit for supporting wheels according to the present invention is used to rotatably support wheels of an automobile with respect to a suspension device.

[0002]

2. Description of the Related Art The wheels of an automobile are supported on a suspension system by rolling bearing units for supporting wheels. FIG. 3 shows a first example of a rolling bearing unit for supporting a wheel, which has been widely implemented conventionally. The rolling bearing unit 1 for supporting a wheel includes a hub 2, an inner ring 3, an outer ring 4, and a plurality of rolling elements 5,5. Of these, the outer end portion of the outer peripheral surface of the hub 2 (the outside refers to the side that is outwardly offset in the width direction when assembled to the automobile, and is the left side in each of the drawings except for FIG. 7. Is referred to as the inner side, and is the right side of each of the drawings except for FIG. 7).
Is formed. A first inner raceway 7 is formed on the outer peripheral surface of the intermediate portion of the hub 2, and a step 8 having a smaller outer diameter is formed on the inner end of the hub 2.

The inner ring 3 having a second inner raceway 9 formed on the outer peripheral surface thereof is fitted on the step portion 8. A male thread 10 is formed at the inner end of the hub 2, and the tip of the male thread 10 protrudes inward from the inner end surface of the inner race 3. The inner ring 3 is held at a predetermined position of the hub 2 by clamping the inner ring 3 between a nut 11 screwed to the male screw portion 10 and a step surface 12 of the step portion 8. . A locking recess 13 is formed on the outer peripheral surface of the distal end of the male screw portion 10. After tightening the nut 11 with a predetermined torque, the nut 1
The nut 11 is prevented from loosening by caulking a part of the part 1 that matches the locking recess 13 inward in the diameter direction.

A first outer raceway 14 facing the first inner raceway 7 and a second outer raceway 15 facing the second inner raceway 9 are formed on the inner peripheral surface of the outer race 4. are doing. And between the first and second inner raceways 7, 9 and the first and second outer raceways 14, 15, the rolling elements 5,
5 are provided in plurality. In the illustrated example, balls are used as the rolling elements 5 and 5. However, in the case of a heavy-weight rolling bearing unit for an automobile, tapered rollers may be used as these rolling elements.

In order to assemble the above-described rolling bearing unit 1 for supporting a wheel into an automobile, the outer ring 4 is fixed to a suspension device by a second flange 16 formed on the outer peripheral surface of the outer ring 4. The wheel is fixed to the flange 6 of.
As a result, the wheels can be rotatably supported by the suspension device.

Japanese Unexamined Patent Publication No. 11-129703 discloses a rolling bearing unit 1a for supporting a wheel as shown in FIGS.
Is described. The wheel supporting rolling bearing unit 1a of the second example of the conventional structure includes a hub 2a, an inner ring 3, an outer ring 4, and a plurality of rolling elements 5,5. A first flange 6 for supporting the wheel is formed at a portion of the outer peripheral surface of the hub 2a near the outer end. Also, this hub 2
A first inner raceway 7 is formed on the outer peripheral surface of the intermediate portion a, and a step 8 having a smaller outer diameter is formed on the inner end.

A cylindrical portion 1 for forming a caulking portion 17 for fixing the inner ring 3 is provided at the inner end of the hub 2a.
8 are formed. The thickness of the cylindrical portion 18 becomes smaller toward the distal end edge in a state before the cylindrical portion 18 is crimped outward in the diameter direction as shown in FIG. For this reason, a tapered hole 19 is formed in the inner end face of the hub 2a, the inner diameter of which gradually decreases toward the recess.

In order to fix the inner ring 3 to the inner end of the hub 2a and to widen the tip of the cylindrical portion 18 as described above, the hub 2a is fixed so as not to shift in the axial direction. Then, as shown in FIG.
Press firmly against the tip of. At the center of the tip end surface (left end surface in FIG. 5) of the pressing die 20, a truncated conical convex portion 21 which can be pushed into the inside of the cylindrical portion 18 is formed.
A concave portion 22 having an arc-shaped cross section is formed around the periphery of the convex portion 21. The cross-sectional shape of the concave portion 22 is such that the cross-sectional shape of the caulking portion 17 obtained by plastically deforming the distal end portion of the cylindrical portion 18 by the concave portion 22 is such that the thickness dimension increases from the base end portion toward the distal end portion. The composite curved surface is formed such that the radius of curvature becomes smaller toward the outer diameter side so that the thickness gradually decreases, and particularly, the thickness dimension decreases sharply at the tip end.

When the pressing die 20 having the convex portion 21 and the concave portion 22 having the above-described shape and dimensions is pressed against the distal end of the cylindrical portion 18, the distal end of the cylindrical portion 18 is swaged outward in the diameter direction. Thus, the caulking portion 17 can be formed. The inner ring 3 can be fixed to the hub 2a by clamping the inner ring 3 between the caulked portion 17 and the step surface 12 of the step 8 formed at the inner end of the hub 2a.

In order to form the caulked portion 17 by plastically deforming (caulking) the cylindrical portion 18, it is preferable to use an oscillating press device 23 as shown in FIG. The swing press device 23 includes a pressing die 20, a holding jig 24, and a holder 25. The cylindrical part 18
When the caulking portion 17 is formed by caulking and spreading, the pressing die 20 is swung and rotated while pressing the hub 2a upward through the holder 25. That is, in a state where the center axis of the pressing die 20 and the center axis of the hub 2a are inclined by the angle θ, the pressing die 20 is rocked about the center axis of the hub 2a. When the caulking portion 17 is formed by such a rocking press, a part of the pressing die 20 in the circumferential direction presses the cylindrical portion 18, and the working of the caulking portion 17 is partially performed. And proceed continuously in the circumferential direction. For this reason, the load applied to the cylindrical portion 18 during processing can be reduced as compared with the case where the caulked portion 17 is formed by general forging. The pressing jig 24 prevents the inner ring 3 and the hub 2a from swaying in the radial direction when the caulking portion 17 is processed by the pressing die 20.

Further, in the second example of the conventional structure as described above, a portion indicated by a diagonal lattice in FIG. 4 is quenched and hardened on a part of the outer peripheral surface of the hub 2b to improve the durability of the portion. This is also described in JP-A-11-129703. That is, the first inner ring raceway 7 portion, the base end portion of the first flange 6, and the base half portion of the step 8 are subjected to a quenching process, and the hardness of the portions is set to Hv550 to Hv550-9.
It is set to about 00.

Incidentally, of the portions subjected to the quenching process indicated by the diagonal lattice, the first inner raceway 7 portion receives a large surface pressure based on the contact with the rolling surface of the rolling element 5. Therefore, it is hardened to secure the rolling fatigue life. In addition, regardless of the moment load received from the first flange 6 to which the wheel is fixed,
The base is hardened to prevent deformation.
Also, the outer peripheral surface of the step portion 8 deforms regardless of the fitting pressure of the inner ring 3 and the radial load applied to the inner ring 3 from the plurality of rolling elements 5. Is hardened in order to prevent the occurrence of fretting wear on the outer peripheral surface of the step portion 8 which is a fitting portion with the inner ring 3. The stepped surface 12 of the stepped portion 8 prevents the stepped surface 12 from being deformed irrespective of an axial load applied to the inner ring 3 by a caulking operation described later. The stepped surface 12, which is a contact surface with the end surface, is cured to prevent fretting wear from occurring. Further, a corner R portion which is a continuous portion between the outer peripheral surface of the step portion 8 and the step surface 12 is hardened in order to prevent deformation due to stress concentration.

On the other hand, Japanese Unexamined Patent Publication No. 10-95203 discloses that the outer diameter of a portion of the inner end of the hub 2b protruding from the fitting portion of the inner race 3 is determined as shown in FIG. A structure smaller than the outer diameter is described. That is, the hub 2
b at the base end outer peripheral surface of the cylindrical portion 18a formed at the inner end of
A portion of the inner ring 3 slightly closer to the second inner raceway 9 than the inclined surface 26 formed at the inner end opening of the inner ring 3 has 0.02 to 1
A step 27 having a slight step H of about mm is formed. Then, a portion of the cylindrical portion 18a having a reduced outer diameter is swaged outward in the diametrical direction, and the inclined surface 2 is formed.
6 is suppressed. When the cylindrical portion 18a is swaged outward in the diametrical direction in this manner, the step portion 27 serves as a starting point of a portion that bends during the swaging operation.
For this reason, an excessive force is less likely to be applied to the cylindrical portion 18a during the swaging operation, and damage such as a crack is less likely to occur at the swaging portion.

[0014]

According to the structure of the second example shown in FIG. 4 among the conventional structures described above, a small and lightweight rolling bearing unit for supporting wheels can be realized at low cost. According to the third example of the conventional structure shown in FIG.
The yield can be improved by preventing cracking of the swaged portion. However, if the second example of the conventional structure shown in FIG. 4 and the third example of the conventional structure shown in FIG. 8 described above are combined as they are, a sufficient yield improvement effect cannot always be achieved.
Sufficient cost reduction cannot be achieved.

That is, when the second example of the conventional structure and the third example of the conventional structure are combined as they are and the step portion 27 formed on the outer peripheral surface of the cylindrical portion 18a is quenched and hardened, the cylindrical portion 18a When the caulked portion is formed by caulking and expanding the diametrically outward portion, damage such as a crack is easily generated in the step portion 27. This will be described with reference to FIG. As shown in FIG. 9 (A), when the hardened layer indicated by the oblique lattice in FIG.
Even if the cylindrical portion 18a is swaged and widened as shown in (B), the step portion 27 is hardly plastically deformed, and the obtained outer peripheral surface of the base portion of the caulking portion 17 corresponds to the portion corresponding to the step portion 27. The groove 29 as shown in FIG. 9C remains.
Then, damage such as a crack is easily generated from the groove 29. The present invention has been made in view of the above circumstances, and aims at realizing a wheel bearing rolling bearing unit that prevents damage such as cracks in a caulked portion and achieves sufficient cost reduction by a sufficient yield improving effect. It was invented.

[0016]

According to the rolling bearing unit for supporting a wheel of the present invention, a first flange is provided on the outer peripheral surface of one end portion and the outer peripheral surface of an intermediate portion is provided in the same manner as the above-mentioned conventional rolling bearing unit for supporting a wheel. A first inner raceway is formed on each of the formed hubs, a step formed on the other end of the hub, and having an outer diameter smaller than that of the portion forming the first inner raceway, and an outer peripheral surface. An inner ring that forms a second inner raceway and is externally fitted to the step, a first outer raceway facing the first inner raceway on the inner circumferential surface, and a second outer raceway facing the second inner raceway. Outer ring raceway, a second flange on the outer peripheral surface, the outer ring formed respectively, the first, the second inner raceway and the first, the second, between the outer raceway, each provided a plurality of each. Rolling elements. At the other end of the hub, a cylindrical portion formed at least at a portion protruding from the inner ring externally fitted to the step portion is swaged outward in the diametrical direction. The inner ring thus formed is pressed down toward the step surface of the step, and the inner ring externally fitted to the step is connected and fixed to the hub.

Particularly, in the rolling bearing unit for supporting a wheel of the present invention, the hub is made of carbon steel, and a surface portion of the step portion including the portion near the step surface is hardened by quenching. Things. And, on the outer peripheral surface of the cylindrical portion, a step portion having a large diameter on the step surface side and a small diameter on the distal end side of the cylindrical portion and smoothly continuing at least with the small diameter side portion is provided with a curved surface having an arc-shaped cross section. Have been.
Further, in the cylindrical portion, the quenching process is not performed on the step portion and the portion closer to the tip than the step portion.

[0018]

In the case of the rolling bearing unit for supporting a wheel of the present invention constructed as described above, the surface portion including the step is hardened by quenching, so that the surface portion is not damaged by deformation or wear. Can be prevented from occurring. In addition, since the step portion is provided on the outer peripheral surface of the cylindrical portion, when the cylindrical portion is swaged outward in the diametrical direction or when the work is spread, the damage such as a crack is less likely to occur in the swaged portion. In addition, in the case of the present invention, since the quenching process is not performed on the step portion and the portion closer to the tip than the step portion, at the time of the caulking and spreading operation, the tip portion is more advanced than the step portion and the step portion. It is possible to more effectively prevent the damage such as a crack from occurring in the shift portion. Thus, according to the present invention, the cost of the rolling bearing unit for supporting wheels can be sufficiently reduced.

[0019]

1 and 2 show an embodiment of the present invention. The feature of the present invention resides in a structure for preventing deformation and wear of each part, and for preventing a part of the hub from being damaged such as a crack when forming a caulked part. Since the structure, manufacturing method and operation of the other parts are the same as those of the prior art shown in FIGS.
Description of equivalent parts is omitted or simplified.
The following description focuses on features of the present invention and portions different from the above-described conventional technology.

Rolling bearing unit 1 for supporting wheels of the present invention
The hub 2c constituting b is made of carbon steel, and a surface portion (a diagonal lattice portion in FIG. 1) including a step portion 8 for externally fitting the inner ring 3 is hardened by a quenching process. The hardened portion is not only the base half of the step 8 but also the first inner raceway 7 to the first flange 6 in the same manner as in the conventional structure shown in FIG. It is the part that reaches the base end. The cylindrical portion 1 provided at the inner end of the hub 2c
The outer peripheral surface of 8b is provided with a step 27 having a large diameter on the base end side (left side in FIGS. 1 and 2) and a small diameter on the distal end side (right side in FIGS. 1 and 2) of the cylindrical portion 18b. The step H of the step 27 is about 0.02 to 0.12 mm. or,
The step 27 has a curved surface having an arcuate cross-section and is smoothly continuous with at least the small-diameter side portion (the outer peripheral surface of the cylindrical portion 18b near the tip).

In particular, in the case of the hub 2c constituting the wheel supporting rolling bearing unit 1b of the present invention, the cylindrical portion 1
8b, the quenching process is not performed on the step portion 27 and the portion closer to the front end than the step portion 27.
That is, the hardened and hardened portion indicated by the oblique lattice in FIG. 1 ends at a portion closer to the base end of the cylindrical portion 18b than the step portion 27 (toward the step surface 12 and to the left in FIGS. 1 and 2). .
Therefore, the carbon steel constituting the intermediate portion or the tip portion of the step portion 27 and the cylindrical portion 18b is much softer in a green or semi-green state than the hardened and hardened portion indicated by the diagonal lattice. .

In the case of the rolling bearing unit 1b for supporting a wheel of the present invention constructed as described above, the surface portion including the base end portion of the step portion 8 is hardened by quenching. Damage such as deformation or wear can be prevented from occurring in the portion. In addition, since the step portion 27 is provided on the outer peripheral surface of the cylindrical portion 18b, when the cylindrical portion 18a is swaged outward in the diametric direction, damage such as a crack is less likely to occur in the swaged portion. Moreover, in the case of the present invention, the quenching process is not performed on the step portion 27 and the intermediate portion to the tip portion of the cylindrical portion 18b which is closer to the tip than the step portion 27, so that the quenching process is not performed. At the time of caulking and spreading work, it is possible to more effectively prevent the occurrence of damage such as a crack in the step portion 27 and a portion closer to the front end than the step portion 27.

That is, at the time of the above-mentioned swaging operation, the step 27 is securely plastically deformed radially outward and closely adheres to the inner peripheral surface of the inner ring 3, as shown in FIG. 9 (C). Such a groove 29 is not formed. In particular, in the case of this example, since the step H of the step portion 27 is as small as 0.12 mm or less, it is possible to more reliably prevent the formation of the groove portion 29 which may cause a crack. Thus, according to the present invention, not only the cost reduction effect by reducing the number of parts, but also
The effect of improving the yield by reducing the occurrence rate of defective products at the time of manufacturing can be sufficiently increased, and the cost of the wheel supporting rolling bearing unit 1b can be sufficiently reduced.

[0024]

Since the present invention is constructed and operates as described above, it is possible to realize a rolling bearing unit for supporting a wheel which is lightweight, low-cost and has excellent durability.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing an example of an embodiment of the present invention before an end portion of a hub is swaged.

FIG. 2 is a half sectional view showing a state after completion.

FIG. 3 is a half sectional view showing a first example of a conventional structure.

FIG. 4 is a half sectional view showing the second example.

FIG. 5 is a partially enlarged cross-sectional view showing a state in which an inner end portion of a hub is swaged to fix an inner ring at the time of manufacturing the structure of the second example.

FIG. 6 is a partially enlarged sectional view showing a state before the inner end portion of the hub is swaged.

FIG. 7 is a longitudinal sectional view of a main part of the swing press device.

FIG. 8 is a view similar to FIG. 6, showing a third example of the conventional structure.

FIG. 9 is a partial cross-sectional view showing a state in which a defect occurs during a caulking operation in the order of steps.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1a, 1b Wheel supporting rolling bearing unit 2, 2a, 2b, 2c Hub 3 Inner ring (2nd inner ring) 4 Outer ring 5 Rolling element 6 First flange 7 First inner ring track 8 Step 9 Second Inner ring raceway 10 Male screw part 11 Nut 12 Step surface 13 Locking concave part 14 First outer raceway 15 Second outer raceway 16 Second flange 17 Caulking part 18, 18a, 18b Cylindrical part 19 Tapered hole 20 Pressing part 21 Convex part 22 Concave portion 23 Swing press device 24 Holding jig 25 Holder 26 Inclined surface 27 Stepped portion 29 Groove portion

Claims (1)

[Claims] 1. A hub formed with a first flange on one end outer peripheral surface, a first inner raceway on an intermediate outer peripheral surface, and the first inner race formed on the other end of the hub. A step portion having an outer diameter smaller than that of the portion where the track is formed, an inner ring formed with a second inner ring track on the outer peripheral surface and fitted to the step portion, and the first inner ring track on the inner peripheral surface A first outer raceway facing the second outer raceway facing the second inner raceway, an outer race formed with a second flange on the outer peripheral surface, and the first and second inner raceways, respectively. A plurality of rolling elements respectively provided between the first and second outer raceways, and formed at a portion protruding from an inner race fitted at least to the step at the other end of the hub. The crimped part formed by caulking and expanding the cylindrical part outward in the diameter direction The inner ring is pressed down toward the step surface of the step, and the inner ring externally fitted to the step is connected and fixed to the hub, and the hub is made of carbon steel. Of the above, the surface portion including the portion near the step surface is hardened by quenching treatment, and the outer peripheral surface of the cylindrical portion has a large diameter on the step surface side and a small diameter on the leading edge side of the cylindrical portion, At least a step portion which is a curved surface having an arc-shaped cross section that is smoothly continuous with the small diameter side portion is provided, and the quenching process is performed on the step portion and the portion closer to the tip than the step portion in the cylindrical portion. A rolling bearing unit for supporting wheels, which is not provided.