JP2004176746A - Double row tapered roller bearing unit for supporting wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent edge load from applying to a double row tapered roller bearing unit for supporting a wheel which fixes inner rings by caulked parts by making appropriate crownings applied to inner ring raceways irrespective of the elastic deformation of the inner rings caused by the forming operation of the caulked parts. <P>SOLUTION: The crowing top point of the inner row inner ring raceway 20a is shifted to a small diameter side relative to the crowning top point of the outer row inner raceway 20a. The large-diameter side drop amount hiL of the inner row inner ring raceway 20b is formed larger than the large-diameter side drop amount hoL of the outer row inner ring raceway 20a (hiL > HoL). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement of a double row tapered roller bearing unit for supporting wheels for rotatably supporting wheels of a relatively heavy automobile such as a light truck or a large passenger car with respect to a suspension device.
[0002]
[Prior art]
A double-row tapered roller bearing unit for supporting wheels is used to rotatably support the wheels of an automobile with respect to a suspension device. This type of double-row tapered roller bearing unit for supporting wheels is generally a double-row tapered roller bearing having one double-row outer ring and two inner rings, and is used for a knuckle or the like constituting a suspension device. And a structure in which an inner ring is fitted to a hub for fixing wheels is known. As means for fixing the inner ring fitted to the hub in the axial direction, it is also known that the shaft end of the hub is plastically deformed outward in the radial direction and caulked.
[0003]
Double rows of tapered rollers are interposed between the outer raceway and the inner raceway so as to roll freely. Each track is crowned so that no edge load is applied to the contact portion of the tapered roller with the rolling surface. The cross-sectional shape of the conventional standard crowning, as shown somewhat exaggeratedly in FIG. 4, is that the intermediate portion 2 in the axial direction is a convex arc having a large radius of curvature R, and both ends 4 in the axial direction are small. It is a convex arc having a radius of curvature r. The centers of curvature of the radii of curvature R and r of the two portions 2 and 4 are all on the center line α, which is a straight line orthogonal to the inner raceway at the axial center of the inner raceway.
[0004]
That is, the distances X0 from the center line α where the center of curvature is present to the axial ends of the intermediate portion 2 and the distances Y0 from the center line α to the end edges of both ends 4 are made equal to each other. Therefore, the drop amounts of the intermediate portion 2 and the both end portions 4 (lengths at which the portions are displaced inward in the radial direction with respect to the tangent to the inner raceway, perpendicular to the center line α) δ0 and δ1 are the inner races. It coincides with each other at both ends of the track.
[0005]
[Patent Document 1]
JP-A-2002-168246 (paragraphs 0006 and 0007, FIG. 3)
[0006]
[Problems to be solved by the invention]
In the manufacturing process of the double-row tapered roller bearing unit for wheel support having a configuration as outlined above, a large force directed outward in the radial direction is applied to the inner end of the inner ring along with the forming operation of the caulking portion. In addition, the inner end elastically deforms radially outward. In the case of elastic deformation, the cross-sectional shape of the inner raceway formed on the outer peripheral surface of the inner race deviates from a desired shape, and an edge load occurs on a part of the contact portion of the inner raceway with the rolling surface of the tapered roller. It will be easier.
[0007]
In other words, the shape of the crowning applied to prevent the edge load from occurring on the track collapses, making it difficult to achieve the purpose of preventing the edge load. Specifically, of the crowning applied to the inner raceway, the drop amount in the portion near the inner end in the axial direction decreases or disappears. As a result, a high contact pressure based on the edge load is likely to be applied to the contact portion between the inner end of the inner raceway and the inner end of the rolling surface of the tapered roller. Such a high surface pressure based on the edge load is not preferable because it causes a reduction in the rolling fatigue life of the inner raceway.
[0008]
Each time a rolling element passes over a raceway surface, compressive, tensile and shear stresses are generated near the raceway and rolling surface surfaces. The fatigue phenomenon of the material due to the repeated stress is called rolling fatigue. Although it does not appear in the initial stage, residual stress and changes in the microstructure occur, and fine cracks occur. This progresses to pitching and flaking, making the bearing unusable.
[0009]
An object of the present invention is to provide a double-row tapered roller bearing unit for wheel support that has solved the above-mentioned problems.
[0010]
[Means for Solving the Problems]
The present invention provides an outer ring 10 having a double-row outer raceway 10a, 10b on the inner circumference, a hub 20 having a double-row inner raceway 20a, 20b on the outer circumference, outer raceways 10a, 10b, and inner raceways 20a, 20b. The hub 20 includes a hub body 22 having a flange 24 and a supporting step 23 for fixing wheels on the outer periphery, and a hub body 22 having a plurality of rows of tapered rollers 30 rotatably interposed therebetween. A pair of inner races 26, 28 fitted to the support step, the inner races 20a, 20b are formed on the outer peripheral surface of each inner race 26, 28, and at least the inner row inner race 20b is crowned; The inner rings 26 and 28 are caulked by plastically deforming a step surface 29 present at the outer end of the supporting step 23 and a cylindrical portion 25 provided at the inner end of the hub body 22 outward in the radial direction. 27, the crowning apex of the inner row inner raceway 20b is shifted to the smaller diameter side with respect to the crowning apex of the outer row inner raceway 20a, and the inner row inner race is fixed. The large diameter side drop amount hiL of the track 20b is set to be larger than the large diameter side drop amount hoL of the outer row inner ring track 20a.
[0011]
The present invention also provides an outer ring 10 having a double row of outer raceways 10a, 10b on the inner periphery, a hub 20 'having a double row of inner raceways 20a, 20b on the outer periphery, outer raceways 10a, 10b and inner raceway 20a. , 20b with a double row of tapered rollers 30 rotatably interposed therebetween, wherein the hub 20 'is provided with a flange 24 for fixing wheels on the outer periphery, an outer row inner raceway 20a, and a supporting step 23'. , And an inner ring 28 fitted on the supporting step portion of the hub body 22 'and having an inner row inner raceway 20b formed on the outer peripheral surface. At least the inner row inner raceway 20b is crowned. The inner ring 28 is formed by plastically deforming a step surface 29 ′ present at the outer end of the supporting step 23 ′ and a cylindrical portion 25 provided at the inner end of the hub body 22 ′ radially outward. Clenched In the double row tapered roller bearing unit for wheel support fixed between the outer row inner ring raceway 20a and the crowning vertex of the inner row inner ring raceway 20b, the crowning vertex of the inner row inner ring raceway 20b is shifted to the small diameter side. The large diameter side drop amount hiL of the inner raceway 20b is larger than the large diameter side drop amount hoL of the outer row inner raceway 20a.
[0012]
The track width Li of the inner row inner ring track 20b can be equal to or slightly smaller than the track width Lo of the outer row inner ring track 20a.
[0013]
According to the present invention, the cylindrical portion 25 provided at the inner ends of the hub bodies 22 and 22 ′ is plastically deformed radially outward to form the caulking portion 27, so that the inner ring 28 inside the separate body 28 is formed. Even when the end portion is elastically deformed radially outward, the function of crowning the inner row inner ring raceway 20b provided on the outer peripheral surface of the inner ring 28 can be secured even at the inner end portion of the inner row inner ring raceway 20b. For this reason, it becomes difficult for an edge load to be applied to the contact portion between the inner row inner raceway 20b and the inner end edge of the rolling surface of the tapered roller 30, and the inner row inner raceway 20b, and consequently, the double row cone for supporting the wheels. The rolling fatigue life of the roller bearing unit is improved.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the basic configuration of a double row tapered roller bearing unit for supporting wheels will be described with reference to FIGS. 2 and 3, and then the embodiment of the present invention will be described with reference to FIG.
[0015]
As shown in FIG. 2, the double-row tapered roller bearing unit for supporting wheels includes an outer ring 10, a hub 20, and a plurality of tapered rollers 30. The outer race 10 has an outer row of outer races 10a and an inner row of outer races 10b each having a conical concave shape formed on an inner circumferential surface, and a mounting portion 12 for fixing to a suspension device on the outer circumference. Here, of the double-row tracks, the outer row when assembled to the vehicle is called an outer row, and the inner row is called an inner row. Similarly, “inside” and “outside” mean inside and outside as viewed in the width direction of the vehicle assembled to the vehicle.
[0016]
The hub 20 is located concentrically with the outer ring 10 on the inner diameter side of the outer ring 10. The hub 20 includes a hub body 22 and a pair of inner rings 26 and 28. The hub body 22 has a flange 24 at the outer end of the outer periphery for fixing the wheel. Further, a support step 23 is formed in a portion from an intermediate portion of the outer peripheral surface of the hub body 22 to an inner end portion. A pair of inner rings 26 and 28 are press-fitted into the support step 23 by interference fitting. The outer inner ring 26 forms an outer row inner ring track 20a on the outer peripheral surface. The inner inner ring 28 forms an inner row inner ring track 20b on the outer peripheral surface. A plurality of tapered rollers 30 are provided between the outer raceways 10a and 10b and the inner raceways 20a and 20b in such a manner as to be freely rolled by retainers 32 made of synthetic resin or metal.
[0017]
The inner end surface of the second inner ring 28 is pressed by a caulking portion 27 formed by plastically deforming a cylindrical portion 25 provided at the inner end portion of the hub body 22 radially outward, and the pair of inner rings 26, 28 are caulked. The pair of inner rings 26 and 28 are fixed to the hub main body 22 by being sandwiched between the support step 27 and a step surface 29 existing at the outer end of the support step 23. Further, by pressing the inner end surface of the inner ring 28 by the caulking portion 27, a preload is applied to the bearing portion constituted by the tapered rollers 30 and the tracks 10a, 10b, 20a, 20b.
[0018]
As shown in FIG. 3, the double row tapered roller bearing unit for supporting a wheel according to the present invention has a structure in which an inner raceway 20a is formed directly on an outer peripheral surface of an intermediate portion of a hub body 22 'constituting a hub 20'. Things are also included. In this case, a support step 23 'for press-fitting one inner ring 28 is provided only at the inner end of the outer peripheral surface of the hub main body 22', and the support step 23 'exists at the outer end of the support step 23'. The outer end surface of the inner ring 28 is brought into contact with the step surface 29 '.
[0019]
Further, seal rings (combined seal rings) 14 and 16 are provided on the inner peripheral surfaces of both ends of the outer ring 10 to close the openings at both ends of the bearing space 34 including the tapered rollers 30. Since the illustrated example is a double-row tapered roller bearing unit for driving wheel support, a spline hole 21 is provided in the center of the hub bodies 22, 22 '.
[0020]
When assembling the double row tapered roller bearing unit for wheel support having the above-described configuration to an automobile, the mounting portion 12 of the outer ring 10 is fixed to a knuckle or the like constituting a suspension device, and the wheel is fixed to the flange 24. As a result, the wheels are rotatably supported by the suspension device. Then, by inserting and fixing a spline shaft attached to a constant velocity universal joint (not shown) into the spline hole 21 of the hub body 22, torque can be transmitted to the wheels via the hub body 22.
[0021]
Subsequently, the embodiment shown in FIG. 1 will be described. This is because an inner row inner ring raceway 20b formed on the outer peripheral surface of the inner ring 28 by a radially outward force applied to the inner end of the inner ring 28 with the forming operation of the caulking portion 27 (see FIGS. 2 and 3). The function of the crowning applied to the inner row inner ring raceway 20b is not impaired even when the shape of the inner row changes.
[0022]
FIG. 1 shows the inner row inner ring raceway surface shape and the outer row inner ring raceway surface shape in an overlapped manner, and the solid line shows the inner row inner ring raceway surface shape (see the B section in FIGS. 2 and 3). The chain line indicates the outer race inner ring raceway surface shape (see A portion in FIGS. 2 and 3). Note that the right side of the drawing is the large diameter side, and the left side is the small diameter side.
[0023]
As can be understood from FIG. 1, the crowning vertex of the inner row inner race 20b is shifted to the smaller diameter side by Δ with respect to the crowning vertex of the outer row inner race 20a. The outer race inner ring raceway surface 20a is crowned with a radius of curvature Ro from the center of curvature Oo, as indicated by the two-dot chain line. They are connected by a radius RoL (<Ro). As shown by the solid line, the inner row inner ring raceway surface 20b is crowned with a radius of curvature Ri from the center of curvature Oi, and the radius of curvature RiL (<L at the large-diameter end portion of the raceway width Li. Ri). The amount of drop of the crowning on the small diameter side is the same for both the outer and the inner (hoS = hiS), but the amount of drop of the crowning on the large diameter side is larger than that of the outer (hoL <hiL).
[0024]
The above is summarized as follows.
Track width: (Li ≦ Lo)
Large-diameter drop amount: (hiL> hoL)
Small diameter drop amount: (hiS = hoS)
According to the double row tapered roller bearing unit for wheel support having the above-described configuration, the cylindrical portion 25 provided at the inner end portion of the hub body 22 is plastically deformed radially outward to form the caulking portion 27 (see FIGS. 2 to 3). As a result, even when the inner end of the inner row inner raceway 20b is elastically deformed radially outward, an appropriate crowning function can be ensured even at the inner end of the inner row inner raceway 20b. For this reason, it becomes difficult for an edge load to be applied to the contact portion between the inner row inner raceway 20b and the inner edge of the rolling surface of the tapered roller 30, and the rolling fatigue life of the inner row inner raceway 20b is improved.
[0025]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the rolling fatigue life of an inner row inner ring raceway is improved, and therefore the double row tapered roller bearing unit for wheel support which has excellent durability can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a track of a double-row tapered roller bearing unit for supporting wheels, showing an embodiment of the present invention.
FIG. 2 is a sectional view of a double-row tapered roller bearing unit for supporting wheels.
FIG. 3 is a cross-sectional view of another wheel supporting double row tapered roller bearing unit.
FIG. 4 is a sectional view similar to FIG. 1 showing a conventional technique.
[Explanation of symbols]
Reference Signs List 10 outer ring 10a outer row outer ring track 10b inner row outer ring track 12 mounting portion 14 seal ring 16 seal ring 20, 20 'hub 20a outer row inner ring track 20b inner row inner ring track 21 spline holes 22, 22' hub bodies 23, 23 'support Step portion 24 Flange 25 Cylindrical portion 26 Inner ring 27 Caulking portion 28 Inner ring 29, 29 ′ Step surface 30 Tapered roller 32 Cage 34 Space hoL Larger diameter side drop amount of crowning of outer row inner ring track hiL Larger crowning of inner row inner ring track Diameter drop amount

Claims (3)

An outer ring having a double-row outer ring track on the inner periphery,
A hub having a double row of inner ring raceways on the outer periphery,
Equipped with double-row tapered rollers that are rotatably interposed between the outer raceway and the inner raceway,
The hub is composed of a hub body having a flange and a supporting step for fixing a wheel on the outer periphery, and a pair of inner rings fitted to the supporting step of the hub body, wherein the inner ring raceway is provided on the outer peripheral surface of each inner ring. Is formed, and at least the inner row inner ring raceway is crowned,
The inner ring is fixed between a step surface present at an outer end of the support step and a caulking portion formed by plastically deforming a cylindrical portion provided at an inner end of the hub body radially outward. In the double-row tapered roller bearing unit for wheel support,
The crowning apex of the inner row inner ring raceway is shifted to the smaller diameter side with respect to the crowning apex of the outer row inner ring raceway, and the large diameter side drop amount of the inner row inner ring raceway is larger than the large diameter side drop amount of the outer row inner ring raceway. A double row tapered roller bearing unit for supporting wheels. An outer ring having a double-row outer ring track on the inner periphery,
A hub having a double row of inner ring raceways on the outer periphery,
Equipped with double-row tapered rollers that are rotatably interposed between the outer raceway and the inner raceway,
A hub body having a flange, an outer row inner ring raceway, and a support step portion for fixing the wheel to the outer periphery, and an inner ring having an inner row inner ring raceway formed on the outer peripheral surface by fitting to the support step portion of the hub body. It has been crowned at least in the inner row inner ring raceway,
The inner ring is fixed between a step surface present at the outer end of the supporting step and a caulking portion formed by plastically deforming a cylindrical portion provided at the inner end of the hub body radially outward. In the double row tapered roller bearing unit for wheel support,
The crowning apex of the inner row inner ring raceway is shifted to the smaller diameter side with respect to the crowning apex of the outer row inner ring raceway, and the large diameter side drop amount of the inner row inner ring raceway is larger than the large diameter side drop amount of the outer row inner ring raceway. A double row tapered roller bearing unit for supporting wheels. The double-row cone for supporting wheels according to claim 1 or 2, wherein the track width of the inner row inner raceway is equal to or slightly shorter than the track width of the outer row inner raceway. Roller bearing unit.

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