JP4576704B2 - Rolling bearing unit for wheel support - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The wheel support rolling bearing unit according to the present invention is used for rotatably supporting the wheel of an automobile with respect to a suspension device.
[0002]
[Prior art]
The wheels of the automobile are supported on the suspension device by a rolling bearing unit for supporting the wheels.
FIG. 4 shows a first example of a wheel support rolling bearing unit that has been widely used in the past. The wheel support rolling bearing unit 1 includes a hub 2, an inner ring 3, an outer ring 4, and a plurality of rolling elements 5 and 5. Of these, the outer end of the outer peripheral surface of the hub 2 (outside with respect to the axial direction refers to the side that is outward in the width direction in the assembled state in the automobile, and is the left side of each figure excluding FIG. 8. The first flange 6 for supporting the wheel is formed on the side closer to the center in the direction is called “inside” and is the right side of each figure except FIG. A first inner ring raceway 7 is formed on the outer peripheral surface of the intermediate portion of the hub 2, and a step portion 8 having a smaller outer diameter is formed on the inner end portion.
[0003]
The step 8 is fitted with the inner ring 3 having a second inner ring raceway 9 formed on the outer peripheral surface thereof. Further, a male screw portion 10 is formed at the inner end portion of the hub 2, and the tip end portion (the right end portion in FIG. 4) of the male screw portion 10 protrudes inward from the inner end surface of the inner ring 3. The inner ring 3 is clamped and fixed to a predetermined position of the hub 2 by sandwiching the inner ring 3 between a nut 11 screwed into the male threaded portion 10 and a stepped surface 12 of the stepped portion 8. . A locking recess 13 is formed on the outer peripheral surface of the distal end portion of the male screw portion 10. Then, after tightening the nut 11 with a predetermined torque, a portion of the nut 11 that is aligned with the locking recess 13 is caulked inward in the diametrical direction, thereby preventing the nut 11 from loosening. Yes.
[0004]
A first outer ring raceway 14 that faces the first inner ring raceway 7 and a second outer ring raceway 15 that faces the second inner ring raceway 9 are formed on the inner peripheral surface of the outer ring 4. ing. A plurality of the rolling elements 5 and 5 are provided between the first and second inner ring raceways 7 and 9 and the first and second outer ring raceways 14 and 15, respectively. In the example shown in the figure, balls are used as the rolling elements 5 and 5. However, in the case of a rolling bearing unit for automobiles that is heavy in weight, tapered rollers may be used as the rolling elements.
[0005]
In order to assemble the wheel support rolling bearing unit 1 as described above to the automobile, the outer ring 4 is fixed to the suspension device by the second flange 16 formed on the outer peripheral surface of the outer ring 4, and the first flange 6 Secure the wheels to the As a result, this wheel can be rotatably supported with respect to the suspension device.
[0006]
Japanese Patent Application Laid-Open No. 11-129703 discloses a wheel bearing rolling bearing unit 1a as shown in FIGS. The wheel support 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. Of these, a first flange 6 for supporting the wheel is formed in a portion near the outer end of the outer peripheral surface of the hub 2a. A first inner ring raceway 7 is formed on the outer peripheral surface of the intermediate portion of the hub 2a, and a step portion 8 having a smaller outer diameter is formed on the inner end portion.
[0007]
A cylindrical portion 18 for forming a caulking portion 17 for fixing the inner ring 3 is formed at the inner end portion of the hub 2a. The thickness of the cylindrical portion 18 becomes smaller toward the tip edge (the right edge in FIG. 7) in the state before the cylindrical portion 18 is caulked outward in the diametrical direction as shown in FIG. For this reason, a tapered hole 19 is formed in the inner end surface of the hub 2a, the inner diameter of which gradually decreases toward the inner part.
[0008]
In order to squeeze the tip of the cylindrical portion 18 as described above in order to fix the inner ring 3 to the inner end of the hub 2a, the hub 2a is fixed so that it does not move in the axial direction. As shown in FIG. 6, the pressing die 20 is strongly pressed against the tip of the cylindrical portion 18.
A frustoconical convex portion 21 that can be pushed into the inside of the cylindrical portion 18 is formed at the central portion of the tip surface (left end surface in FIG. 6) of the pressing die 20, and a circular arc section is formed around the convex portion 21. The concave portion 22 is formed so as to surround the entire circumference 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 plastic deformation of the distal end portion of the cylindrical portion 18 by the concave portion 22 has a thickness dimension as it goes from the proximal end portion toward the distal end portion. The composite curved surface has a curvature radius that becomes smaller toward the outer diameter side, so that the thickness dimension is abruptly reduced especially at the tip portion so as to gradually become smaller.
[0009]
If the pressing die 20 having the convex portion 21 and the concave portion 22 having the shape and dimensions as described above is pressed against the tip portion of the cylindrical portion 18, the tip portion of the cylindrical portion 18 is caulked outward in the diametrical direction, The caulking portion 17 can be formed. The inner ring 3 can be clamped between the caulking portion 17 and the stepped surface 12 of the stepped portion 8 formed at the inner end of the hub 2a, so that the inner ring 3 can be fixed to the hub 2a.
[0010]
In order to perform the operation of forming the caulking portion 17 by plastically deforming (caulking and expanding) the cylindrical portion 18, a swing press device 23 as shown in FIG. 8 is preferably used. The swing press device 23 includes a pressing die 20, a holding jig 24, and a holder 25. When the caulking portion 17 is formed by caulking the cylindrical portion 18, the pressing die 20 is swung and rotated while pressing the hub 2 a upward via the holder 25. That is, in a state where the central axis of the pressing die 20 and the central axis of the hub 2a are inclined by an angle θ, the pressing die 20 is rotated around the central 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 caulking portion 17 is partially processed. And continuously in the circumferential direction. For this reason, compared with the case where the said caulking part 17 is formed by a general forging process, the load added to the said cylindrical part 18 at the time of a process can be made small. The holding jig 24 prevents the hub 2a and the inner ring 3 from swinging in the radial direction when the caulking portion 17 is processed by the pressing die 20.
[0011]
[Problems to be solved by the invention]
When the second example of the conventional structure shown in FIGS. 5 to 7 is manufactured, it is preferable that the inner ring 3 is externally fitted to the step portion 8 of the hub 2a by an interference fit. The reason for this is that after the inner ring 3 is fitted on the step portion 8 and before the caulking portion 17 is formed at the inner end of the hub 2a, the position of the inner ring 3 with respect to the hub 2a is not shifted. Because of that. For example, when preload is applied to the rolling elements 5, 5, the inner ring 3 is moved relative to the stepped portion 8 in order to prevent the inner ring 3 from being displaced before the caulking portion 17 is formed. It is necessary to externally fit with an interference fit. Even in the case where no preload is applied, in order to prevent the position of the inner ring 3 from shifting and shifting before the caulking portion 17 is formed for some reason, the inner ring 3 is tightly fitted to the stepped portion 8. It is preferable to externally fit.
[0012]
In order to surely prevent the inner ring 3 from shifting and moving before the caulking portion 17 is formed, it is preferable that the tightening allowance of the inner ring 3 with respect to the step portion 8 is larger. The inner ring 3 is cracked and does not function as a wheel bearing rolling bearing unit. Moreover, the stress applied to the inner ring 3 in the state of being completed as a wheel support rolling bearing unit is not only the stress based on the interference fit but also the stress accompanying the formation of the caulking portion 17. That is, as the caulking portion 17 is formed, a force directed outward in the diameter direction is applied to the inner ring 3, so that the force based on the interference fit and the caulking portion 17 are formed on the inner ring 3. The total with the force accompanying the work is added as a tensile stress in the circumferential direction. In order to ensure the reliability and durability of the wheel support rolling bearing unit, it is necessary to prevent the inner ring 3 from cracking regardless of the total of the two types of forces as described above.
The wheel bearing rolling bearing unit of the present invention has been invented in view of such circumstances.
[0013]
[Means for Solving the Problems]
The wheel support rolling bearing unit of the present invention is formed with a first flange on the outer peripheral surface of one end and a first inner ring raceway on the outer peripheral surface of the intermediate portion in the same manner as the conventional wheel support rolling bearing unit described above. A hub, a step formed on the other end of the hub and having a smaller outer diameter than the portion forming the first inner ring raceway, and a second inner ring raceway formed on the outer peripheral surface. An inner ring externally fitted to the stepped portion, a first outer ring raceway facing the first inner ring raceway and a second outer ring raceway facing the second inner ring raceway on the inner peripheral surface, and a second outer ring raceway on the outer peripheral surface. And a plurality of rolling elements each provided between the first and second inner ring raceways and the first and second outer ring raceways. Then, at the other end of the hub, at least the cylindrical portion formed in the portion protruding from the inner ring that is externally fitted to the stepped portion is externally fitted to the stepped portion by the caulking portion that is formed by caulking outward in the diameter direction. The inner ring is pressed against the step surface of the stepped portion, and the inner ring fitted on the stepped portion is coupled and fixed to the hub.
[0014]
In particular, in the rolling bearing unit for supporting a wheel according to the present invention, the inner ring is externally fitted to the stepped portion with an interference fit. Each rolling element is preloaded with the end face of the inner ring abutting against the step surface before the cylindrical portion is caulked outward in the diametrical direction. The static friction force applied to the inner ring based on the interference fit is larger than the axial load applied to the inner ring based on the preload applied to the rolling elements, and based on the interference fit . The circumferential stress generated in the inner ring is smaller than the allowable stress in the circumferential direction of the inner ring minus the circumferential stress applied to the inner ring as the caulking portion is formed. Similarly, the tightening margin of the inner ring with respect to the stepped portion is regulated.
Further, when the present invention is carried out, it is preferable that, in the state before the cylindrical portion is caulked outward in the diametrical direction, for example, as in the second aspect of the invention, the other end portion of the hub The outer diameter of the part protruding from the part fitted with the inner ring is made smaller than the outer diameter of the part fitted with the inner ring, and the parts having different outer diameters are made continuous by the step part.
Further, when the invention described in claim 2 described above is carried out, preferably, the step size of the stepped portion is set to 0.02 to 0.12 mm as in the invention described in claim 3. .
[0015]
[Action]
According to the rolling bearing unit for supporting a wheel of the present invention configured as described above, the position of the inner ring externally fitted to the stepped portion is prevented from inadvertently shifting before the caulked portion is formed at the end of the hub. Moreover, it is possible to prevent the inner ring from cracking. Further, with the preload applied to each rolling element, the end surface of the inner ring can be kept in contact with the stepped surface of the hub regardless of the axial load based on the preload. For this reason, even when a force in an inclined direction is applied to the inner ring and the central axis of the hub as the caulking portion is formed, the outer peripheral edge of the inner ring and the outer peripheral surface of the stepped portion It is possible to prevent strong rubbing and tilting of the central axis of the inner ring with respect to the central axis of the hub.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 show a first example of an embodiment of the present invention. The feature of the present invention relates to the structure of the portion where the inner ring 3 is fitted and fixed to the step portion 8 formed on the outer peripheral surface of the inner end portion of the hub 2b. Since the entire structure and operation of the wheel-supporting rolling bearing unit 1a are the same as those of the second example of the conventional structure shown in FIG. 5 described above, description of equivalent parts will be omitted or simplified. The description will focus on the part.
[0017]
The inner ring 3 is externally fitted to the stepped portion 8 formed on the outer peripheral surface of the inner end portion of the hub 2b by an interference fit. In particular, in the case of the rolling bearing unit for supporting a wheel according to the present invention, the maximum value d _max of the tightening allowance d of the inner ring 3 with respect to the step portion 8 is regulated to prevent the inner ring 3 from cracking. ing. That is, as the inner ring 3 is externally fitted to the stepped portion 8 with a fastening allowance d (tightened), stress δ _{3 in the} circumferential direction is generated in the inner ring 3. In addition, the cylindrical portion 18 formed on the inner end portion of the hub 2b is caulked outward in the diametrical direction to form a caulking portion 17 (see FIGS. 5 to 6). Stress δ _r is applied. In the case of the rolling bearing unit for supporting a wheel according to the present invention, the sum of the stress δ ₃ applied to the inner ring 3 based on the interference fit and the stress δ _r applied to the inner ring 3 as the caulking portion 17 is formed. However, the maximum value d _max of the interference allowance d is regulated so that the allowable stress δ _{a in} the circumferential direction of the inner ring 3 becomes large (δ _a > δ ₃ + δ _r ).
[0018]
Furthermore, in the case of this example, a desired preload is applied to the rolling elements 5 and 5 with the outer end surface of the inner ring 3 abutted against the step surface 12 of the step portion 8. The static frictional force applied to the inner ring 3 based on the interference fit is made larger than the axial load applied to the inner ring 3 based on the preload applied to the rolling elements 5 and 5. Accordingly, in the state where the outer end surface of the inner ring 3 is abutted against the stepped surface 12 and a desired preload is applied to the rolling elements 5 and 5 as described above, the cylindrical portion formed at the inner end portion of the hub 2b. Even before caulking 18, the inner ring 3 is held in a position as it is (while the outer end surface of the inner ring 3 is abutted against the step surface 12).
[0019]
As described above, when the inner ring 3 is externally fitted to the step portion 8 of the hub 2b and preload is applied to each of the rolling elements 5, 5 as in the case of the prior art described above, the inner ring 3 is swung. By caulking the cylindrical portion 18 outward in the diameter direction, the caulking portion 17 as shown in FIG. 2 is formed. In particular, according to the wheel supporting rolling bearing unit of the present invention, even when the formation of the caulking portion 17, stress applied to the inner ring 3 is suppressed to less than the allowable stress [delta] _a.
[0020]
Further, according to the illustrated example, when the caulking portion 17 is formed as described above, the inner ring 3 is not displaced with respect to the hub 2b. That is, the inner ring 3 is externally fitted to the step portion 8 of the hub 2b before the caulking portion 17 is formed, and the axial direction based on the preload is applied while the rolling elements 5 and 5 are preloaded. Regardless of the load, the outer end surface of the inner ring 3 remains in contact with the stepped surface 12 formed on the outer peripheral surface of the hub 2b. Therefore, even when a force in the tilt direction is applied to the inner ring 3 with respect to the central axis of the inner ring 3 and the hub 2b as the caulking portion 17 is formed, the outer peripheral edge of the outer end opening of the inner ring 3 is There is no strong rubbing against the outer peripheral surface of the portion 8 and the central axis of the inner ring 3 is not inclined with respect to the central axis of the hub 2b.
[0021]
Further, in the illustrated example, the outer diameter of the portion protruding from the fitting portion with the inner ring 3 at the inner end portion of the hub 2b is made smaller than the outer diameter of the fitting portion. That is, the outer peripheral surface of the base end portion of the cylindrical portion 18 formed at the inner end portion of the hub 2b is formed on the inner end opening portion of the inner ring 3 more than the curved surface portion 26 having a quarter arc shape in cross section. A slightly stepped portion 27 having an arc-shaped cross section having a slight step H of about 0.02 to 0.12 mm is formed in a portion slightly approaching the second inner ring raceway 9. A portion of the cylindrical portion 18 having a reduced outer diameter is caulked and spread outward in the diametrical direction by swing caulking to suppress the curved surface portion 26. In this way, when the cylindrical portion 18 is caulked and spread outward in the diametrical direction, the stepped portion 27 becomes a starting point of a portion that is bent along with caulking and spreading work. For this reason, it is difficult to apply an excessive force to the cylindrical portion 18 with the caulking and spreading work, and damage such as cracks is less likely to occur in the caulking and spreading portion.
[0022]
Next, FIG. 3 shows a second example of the embodiment of the present invention. In the case of this example, the first inner ring raceway 7 is provided on the outer peripheral surface of the intermediate portion of the hub 2c, and a separate inner ring in which the first inner ring raceway 7 is formed on the outer peripheral surface of the intermediate portion of the hub 2c. 3a is externally fitted. In the case of the wheel support rolling bearing unit 1b shown in FIG. 3, the inner end surface of the separate inner ring 3a becomes the step surface 12a, and protrudes inward from the step surface 12a at the inner end portion of the hub 2c. This portion becomes a step portion 8a for externally fitting the inner ring 3 having the second inner ring raceway 9 formed on the outer peripheral surface. In the case of this example as well, as in the case of the first example described above, the inner ring 3 before the caulking portion 17 is formed by restricting the tightening margin of the inner ring 3 with respect to the inner end of the hub 2c. It is possible to prevent the position of 3 from being shifted inadvertently and to prevent the inner ring 3 from cracking.
[0023]
【The invention's effect】
Since the present invention is configured and operates as described above, a small and lightweight wheel support rolling bearing unit can be stably obtained.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing a first example of an embodiment of the present invention in a state before a caulking portion is formed.
FIG. 2 is a half cross-sectional view showing a state after a caulking portion is formed.
FIG. 3 is a half sectional view showing a second example of an embodiment of the present invention in a state after a caulking portion is formed.
FIG. 4 is a half sectional view showing a first example of a conventional structure.
FIG. 5 is a half sectional view showing the second example.
FIG. 6 is a partially enlarged cross-sectional view showing a state in which the inner end of the hub is caulked and spread in order to fix the inner ring to the hub when the structure of the second example is manufactured.
FIG. 7 is a partially enlarged sectional view showing a state before the inner end of the hub is caulked and spread.
FIG. 8 is a longitudinal sectional view of a main part of the swing press device.
[Explanation of symbols]
1, 1a, 1b Wheel support rolling bearing units 2, 2a, 2b, 2c Hub 3, 3a Inner ring 4 Outer ring 5 Rolling element 6 First flange 7 First inner ring raceway 8, 8a Step 9 Second inner raceway DESCRIPTION OF SYMBOLS 10 Male thread part 11 Nut 12, 12a Step surface 13 Locking recessed part 14 1st outer ring raceway 15 Second outer ring raceway 16 Second flange 17 Caulking part 18 Cylindrical part 19 Taper hole 20 Stamping die 21 Convex part 22 Concave part 23 Oscillation Press device 24 Holding jig 25 Holder 26 Curved surface portion 27 Step portion

Claims (3)

A hub formed with a first flange on the outer peripheral surface of one end and a first inner ring raceway on the outer peripheral surface of the intermediate portion, and a part formed with the first inner ring raceway formed on the other end of the hub A step portion having a smaller outer diameter, a second inner ring raceway formed on the outer peripheral surface and fitted on the stepped portion, and a first inner portion facing the first inner ring raceway on the inner peripheral surface. The outer ring raceway and the second outer ring raceway facing the second inner ring raceway, the outer ring formed with the second flange on the outer peripheral surface, the first and second inner ring raceways and the first and second A plurality of rolling elements provided between each of the two outer ring raceways, and a cylindrical portion formed at a portion projecting from at least the inner ring externally fitted to the stepped portion at the other end of the hub. The inner ring that is externally fitted to the stepped portion is formed by the caulking portion that is formed by caulking outward in the direction. In the rolling bearing unit for wheel support in which the inner ring that is externally fitted to the stepped portion is pressed against the stepped surface of the portion and fixed to the hub, the inner ring is externally fitted to the stepped portion by an interference fit Each rolling element is preloaded with the end face of the inner ring abutting against the step surface before the cylindrical portion is caulked outward in the diametrical direction, and is based on the interference fit. The circumferential friction generated in the inner ring based on the interference fit so that the static frictional force applied to the inner ring is larger than the axial load applied to the inner ring based on the preload applied to the rolling elements. For the stepped portion, the stress related to the direction is smaller than the value obtained by subtracting the circumferential stress applied to the inner ring as the caulking portion is formed from the allowable stress related to the circumferential direction of the inner ring. Tightening the inner ring Wheel support rolling bearing unit, characterized in that regulates a. Prior to caulking the cylindrical portion outward in the diametrical direction, the outer diameter of the portion of the other end of the hub that protrudes from the portion where the inner ring is fitted is larger than the outer diameter of the portion where the inner ring is fitted. The wheel bearing rolling bearing unit according to claim 1, wherein the portions having different outer diameters are continuous with each other by a stepped portion. The rolling bearing unit for wheel support according to claim 2, wherein the size of the step of the step portion is 0.02 to 0.12 mm.

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