JP2018044651A - Hub unit bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure strength of an outer ring, in a hub unit bearing employing a different diameter PCD structure where a fitting flange is provided between a double row of outer ring raceways.SOLUTION: On an outer peripheral surface of an outer ring 3, a fitting flange 14 is formed between outer ring raceways 13a, 13b in an axial direction. A pitch circle diameter of a raceway row outward in the axial direction is made lager than a pitch circle diameter of a raceway row inward in the axial direction. On an inner peripheral surface of the outer ring 3, at portions of the outer ring raceways 13a, 13b, and an outer ring inclination part 15 between the outer ring raceways 13a, 13b, a continuously integrated hardening layer is formed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hub unit bearing used for rotatably supporting a wheel of an automobile with respect to a suspension device.

  The hub unit bearing supports the wheel of the automobile and the rotating rotating member for braking with respect to the suspension device. Since a large moment load is applied when the automobile turns, it is necessary to increase the moment rigidity of the hub unit bearing in order to ensure steering stability during turning. For this reason, as a hub unit bearing, a structure in which rolling elements (balls) are arranged in double rows and a preload and a back combination type (DB type) contact angle are provided to the rolling elements in each row is generally used. Has been. Furthermore, in order to ensure a larger moment rigidity while preventing an increase in size, a structure in which the pitch circle diameters of the rolling elements in each row are made different (for example, different diameter PCD structure as described in Patent Document 1). )It has been known.

  The hub unit bearing used for the front wheels of FF (front wheel drive) vehicles is both a drive wheel and a steering wheel, so the drive shaft of a CVJ (constant velocity joint) and a steering mechanism such as a steering knuckle are connected and fixed. To make the CVJ swing center close to the virtual kingpin angle of the device, it is necessary to reduce the axial dimension of the hub unit bearing and increase the axial width dimension in which the hub unit bearing and the steering knuckle overlap in the radial direction. . For this reason, it is necessary to shorten the distance (distance between flanges) between the hub flange to which the wheel or the like is fixed and the mounting flange for fixing the hub unit bearing to the knuckle of the suspension device. As a result, the mounting flange is formed on the outer side of the outer ring constituting the hub unit bearing on the outer side of the vehicle body (side closer to the hub flange) or in the axially intermediate part of the outer ring (the part between the rows). In addition, the hub unit bearing for front wheel drive that requires a large moment rigidity is difficult because the axial dimension of the hub unit bearing is restricted and the axial dimension between the double row rolling elements cannot be increased. It is conceivable to adopt a different diameter PCD structure in which the mounting flange is close.

However, when the above-described configuration is adopted, the outer ring formed with the mounting flange has a relief portion formed at the root portion of the mounting flange formed between the large diameter side track row and the small diameter side track row. Approaching the inclined part, this region (the portion between each track) becomes thin. Furthermore, the escape portion may be close to or overlap the extended line of the contact angle given to the rolling element.
Such a tendency becomes more conspicuous when the diameter of the rolling elements (balls) incorporated in the large-diameter track array is large or when the diameter difference between the pitch circle diameters of the rolling elements in each array is large.

  When the road surface reaction force during traveling is applied to the hub unit bearing described above, stress concentrates on the thin region. If the stress due to the road surface reaction force increases, the strength of the outer ring (mounting flange) may be adversely affected.

JP 2008-045674 A

  The present invention has been made in view of the above-described problems, and has a different diameter PCD configuration in which mounting flanges are provided between the outer ring raceways and the PCDs of the rolling elements incorporated in each raceway row are different. In the hub unit bearing adopting the above, the strength of the outer ring is ensured.

  The hub unit bearing of the present invention includes an outer ring having a double row outer ring raceway on the inner peripheral surface and a mounting flange on the outer peripheral surface, a double row inner ring raceway, and a hub flange for supporting and fixing the wheel. A plurality of balls in each row between the outer ring raceways and the inner ring raceways, and balls provided in a state where a contact angle of a rear combination type is provided between the outer ring raceways and the inner ring raceways. The pitch circle diameter of the track train is larger than the pitch circle diameter of the track train on the inner side in the axial direction.

Particularly, in the hub unit bearing of the present invention, the mounting flange is formed in a portion between the outer ring raceways in the axial direction, and the outer ring raceway portions and the outer ring raceways are provided on the inner peripheral surface of the outer ring. A continuous integral hardened layer is formed between the intermediate portions.
In addition, the diameter of the balls provided on the axially outer track array is larger than the diameter of the balls provided on the axially inner track array.
The cross-sectional shape of the portion between the outer ring raceways is a smoothly continuous shape.

  According to the present invention, in a hub unit bearing that adopts a different diameter PCD configuration in which mounting flanges are provided between the outer ring raceways and the PCDs of the rolling elements incorporated in each raceway row are different, Strength can be secured.

Sectional drawing of a hub unit bearing which shows embodiment of this invention.

FIG. 1 shows an embodiment of the present invention. The hub unit bearing 1 of the present embodiment includes a hub 2, an outer ring 3, and a plurality of balls 4a and 4b, each of which is a rolling element. The hub 2 has double rows (two rows) of inner ring raceways 7a and 7b formed in an intermediate portion and an inner portion in the axial direction of the outer peripheral surface, and a hub flange 8 is formed in an outer portion in the axial direction of the outer peripheral surface.
Note that “outside in the axial direction” means the outside in the width direction of the vehicle in a state assembled to the automobile, and is the left side in FIG. On the contrary, the right side in FIG. 1 which is the center side in the width direction of the vehicle is referred to as the inside in the axial direction.

  The diameter of the outer inner ring raceway 7a formed on the outer side in the axial direction is larger than the diameter of the inner inner ring raceway 7b formed on the inner side in the axial direction. A base end portion of a plurality of studs 12 is fixed to the hub flange 8 so that a wheel constituting a wheel and a braking rotator such as a disk can be supported and fixed. The hub unit bearing 1 of the present embodiment for a drive wheel has a spline hole 11 for coupling and fixing a drive shaft (not shown) while passing through the center of the hub 2 in the axial direction.

  The hub 2 is configured by combining a hub body 5 and an inner ring 6. On the outer peripheral surface of the hub body 5, an outer inner ring raceway 7 a is formed at an axially intermediate portion, and a small diameter step portion 9 is formed at an axially inner end portion. The inner ring 6 has an inner ring raceway 7 b formed on the outer peripheral surface, and is fitted and fixed to the small diameter step portion 9. The hub inclined portion 10 which is an inclined surface is provided in a portion between the outer inner ring raceway 7a and the small diameter step portion 9, thereby allowing a difference in diameter between the inner ring raceways 7a and 7b. Each of the inner ring raceways 7a and 7b has a circular cross-sectional shape (bus shape), and the outer diameter decreases as it approaches each other (towards the center in the axial direction of the hub 2).

  The outer ring 3 forms double-row (two-row) outer ring raceways 13a and 13b on the inner peripheral surface. The diameter of the outer outer ring raceway 13a formed on the outer side in the axial direction is larger than the diameter of the inner outer ring raceway 13b formed on the inner side in the axial direction. For this purpose, an outer ring inclined portion 15 is formed on the inner circumferential surface of the intermediate portion in the axial direction of the outer ring 3 between the outer ring raceways 13a and 13b. Each outer ring raceway 13a, 13b has an arcuate cross-sectional shape (bus shape), and the inner diameter becomes smaller as it approaches each other (toward the axial center of the outer ring 3).

  A plurality of balls 4a are provided between the outer inner ring raceway 7a and the outer outer ring raceway 13a, respectively, so as to be able to roll, and constitute an axially outer track train. On the other hand, a plurality of balls 4b are provided between the inner inner ring raceway 7b and the inner outer ring raceway 13b, respectively, so as to be able to roll, and constitute a track train on the inner side in the axial direction. The diameter of the balls 4a provided on the axially outer track row is larger than the diameter of the balls 4b provided on the axially inner track row. The pitch circle diameters (PCD) of the balls 4a, 4b in each track array are different from each other depending on the difference in diameter between the inner ring tracks 7a, 7b and the outer ring tracks 13a, 13b. In other words, the pitch circle diameter PCDo of each ball 4a in the axially outer track array is larger than the pitch circle diameter PCDi of each ball 4b in the axially inner track array (PCDo> PCDi).

In such a hub unit bearing 1, a contact angle (chain line Co, Ci) of a rear combination type (DB type) is given to each ball 4a, 4b arranged in a double row. Furthermore, the axially outer side surface of the hub body 5 and the axially inner side surface of the inner ring 6 are sandwiched by a CVJ (not shown) inserted through the spline hole 11 and a coupling member (nut or the like) and arranged in a double row. A preload is applied to each ball 4a, 4b. With this bearing configuration, the hub unit bearing 1 is designed to improve moment rigidity and steering stability during turning.
The axial end openings of the space where the balls 4a and 4b are installed are sealed by sealing devices 21a and 21b between the outer peripheral surface of the hub 2 and the inner peripheral surface of the outer ring 3, respectively.

  The outer ring 3 is fixed to the knuckle 30 constituting the suspension device, and does not rotate during use. In order to couple and fix the outer ring 3 to the knuckle 30, the outer ring 3 has a mounting flange 14 formed on the outer peripheral surface and a knuckle pilot section 20 formed on the inner end in the axial direction. In use, the knuckle pilot portion 20 is inserted into the fixing hole of the knuckle 30 and screwed into the mounting hole 19 with the knuckle mounting surface (the inner side surface in the axial direction) of the mounting flange 14 being in contact with the knuckle 30. The outer ring 3 is supported and fixed to the knuckle 30 by a bolt (not shown). The inner side surface in the axial direction of the mounting flange 14, which is a knuckle mounting surface, is an annular plane that is orthogonal to the central axis of the outer ring 3. The outer peripheral surface of the knuckle pilot portion 20 is a cylindrical surface concentric with the central axis of the outer ring 3.

  The mounting flange 14 is formed in a state of projecting radially outward at a portion between the outer ring raceways 13a and 13b in the axial direction. Specifically, the axially outer side surface of the mounting flange 14 is positioned axially inward from the center (center line Lo) of the arcuate outer outer ring raceway 13a, and the axially inner side surface of the mounting flange 14 ( The knuckle mounting surface is located on the outer side in the axial direction from the center (center line Li) of the arc-shaped inner outer ring raceway 13b.

The portions where the mounting flange 14 and the knuckle pilot portion 20 are connected (the radially inner end of the axial inner surface of the mounting flange 14 and the axial outer end of the outer peripheral surface of the knuckle pilot portion 20) are radially inward. A relief portion 18 that is recessed outward and in the axial direction is formed over the entire circumference of the outer ring 3. The escape portion 18 is provided to process the knuckle mounting surface and the outer peripheral surface of the knuckle pilot portion 20 with high accuracy.
The escape portion 18 is located in a range of θi ± 15 degrees with respect to the contact angle θi (the angle formed by the chain line Ci and the center line Li) of the balls 4b constituting the track array on the inner side in the axial direction (chain line Ci). (It is located in the range of ± 15 degrees on the extension line). Further, the relief portion 18 is located radially outward of the intersection point P between the chain line Ci representing the contact angle of the balls 4b constituting the axially inner raceway row and the inner peripheral surface of the inner outer ring raceway 13b (intersection point). P and the relief portion 18 overlap in the radial direction).

  The outer ring inclined portion 15 provided between the outer ring raceways 13a and 13b on the inner peripheral surface of the outer ring 3 has a smooth shape having a substantially S-shaped cross section. An outer end portion in the axial direction of the outer ring inclined portion 15 is formed in a cylindrical shape, and is continuous with an inner end portion in the axial direction of the outer outer ring raceway 13a. The axially inner end portion of the outer ring inclined portion 15 is formed in a cylindrical shape, and is continuous with the axially outer end portion of the inner outer ring raceway 13b. Between each cylindrical part formed in the axial direction both ends of the outer ring inclined part 15, it is formed in a smooth inclined surface shape that is inclined in a direction in which the inner diameter becomes smaller toward the inner side in the axial direction. Further, the both cylindrical portions and the inclined surface portion are smoothly continuous.

The outer ring 3 is made of carbon steel. The double-row outer ring raceways 13a and 13b and the outer ring inclined portion 15 are integrally formed with a hardened layer 16 (part of oblique lattice) by heat treatment over the entire circumference. Yes. The hardened layer 16 is formed by high frequency heat treatment in which the outer ring raceways 13a and 13b and the outer ring inclined portion 15 are simultaneously heated by a high frequency heating coil. Therefore, a non-cured portion 17 that has not been subjected to heat treatment exists in a peripheral portion of the cured layer 16 (a portion between the cured layer 16 and the outer peripheral surface of the outer ring 3).
The contact angles (chain line Co and chain line Ci) of the outer ring raceways 13a and 13b cross over the entire circumference inside the non-hardened portion 17 present in the radially outer portion of the outer ring inclined portion 15.

In the hub unit bearing 1 of the present embodiment configured as described above, the mounting flange 14 is provided between the outer ring raceways 13a and 13b, and the PCDs of the balls 4a and 4b incorporated in the raceway rows are different. In the hub unit bearing 1 employing the different diameter PCD configuration, the strength of the outer ring 3 can be ensured.
In this embodiment, the hardened layer 16 is integrally formed by connecting (continuously) the hardened layers of the outer ring raceways 13a and 13b and the outer ring inclined portion 15, and the outer ring inclined portion 15 is smoothly and continuously formed. It is formed in a cross-sectional shape. That is, the hardened layer (16) is continuous in a configuration in which the relief portion 18 formed at the root portion of the mounting flange 14 approaches or overlaps the contact angle (chain line Ci) of the inner outer ring raceway 13b and the outer ring inclined portion 15. If not, the stress in the radially inward portion of the relief portion 18 that has become thin increases. On the other hand, in this embodiment, by making the hardened layer 16 continuous, the contact stress of the balls 4b at the intersection point P is dispersed throughout the outer ring 3 through the hardened layer 16, and the radially inner portion of the escape portion 18 is dispersed. Prevents stress rise. Further, stress is not concentrated on a specific portion of the smoothly formed outer ring inclined portion 15. As a result, adverse effects such as a decrease in strength of the mounting flange 14 and a decrease in moment rigidity of the hub unit bearing 1 due to stress concentration on the outer ring 3 can be suppressed.

  The present invention can be applied to a hub unit bearing having a configuration other than that of the present embodiment as long as it is a hub unit bearing provided with a mounting flange in a portion between each outer ring raceway and adopting a different diameter PCD configuration.

1 Hub unit bearing 2 Hub 3 Outer ring 4a, 4b Ball 5 Hub body 6 Inner ring 7a, 7b Inner ring raceway (outer side, inner side)
8 Hub flange 9 Small diameter step 10 Hub inclined part 11 Spline hole 12 Stud 13a, 13b Outer ring raceway (outside, inside)
DESCRIPTION OF SYMBOLS 14 Mounting flange 15 Outer ring inclined part 16 Hardened layer 17 Non-hardened part 18 Escape part 19 Mounting hole 20 Knuckle pilot part 21a, 21b Sealing device 30 Knuckle

Claims (3)

An outer ring having a double row outer ring raceway on the inner peripheral surface and a mounting flange on the outer peripheral surface;
A hub having a double-row inner ring raceway and a hub flange for supporting and fixing the wheel on the outer peripheral surface;
A plurality of balls for each row between each outer ring raceway and each inner ring raceway, provided with a ball provided with a contact angle of a back combination type,
A hub unit bearing in which the pitch circle diameter of the axially outer track row is larger than the pitch circle diameter of the axially inner track row,
The mounting flange is formed in a portion between each outer ring raceway in the axial direction,
A hub unit bearing characterized in that a continuous integral hardened layer is formed on the inner peripheral surface of the outer ring at each outer ring raceway portion and between the outer ring raceways.   2. The hub unit bearing according to claim 1, wherein a diameter of the ball provided in the axially outer raceway row is larger than a diameter of the ball provided in the axially inner raceway row.   The hub unit bearing according to any one of claims 1 to 3, wherein a cross-sectional shape of a portion between the outer ring raceways is a smoothly continuous shape.

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