WO2022202530A1

WO2022202530A1 - Vehicle wheel bearing device

Info

Publication number: WO2022202530A1
Application number: PCT/JP2022/011885
Authority: WO
Inventors: 知樹松下; 誠関; 雄太中辻
Original assignee: Ntn株式会社
Priority date: 2021-03-24
Filing date: 2022-03-16
Publication date: 2022-09-29
Also published as: JP2022148781A

Abstract

The purpose of the present invention is to provide a vehicle wheel bearing device with which it is possible to increase the strength of a recessed part formed in an inner member and improve fatigue strength.　Provided is a vehicle wheel bearing device (1) provided with an outer ring (2) having a double-row outer raceway surface (2c) on the inner circumference thereof, a hub ring (3) having a double-row inner raceway surface (3d) on the outer circumference thereof, and double-row tapered rollers (5a, 5b) accommodated so as to be able to roll between the respective raceway surfaces of the hub ring (3) and the outer ring (2), wherein: the hub ring (3) has a recessed part (13) provided between the inner raceway surface (3d) and a flange surface (3f) that is outward relative to the inner raceway surface (3d); and the recessed part (13) is subjected to treatment for hardening the surface thereof using quenching, and is subjected to grinding by means of a grinding stone (20).

Description

Wheel bearing device

The present invention relates to a wheel bearing device.

Conventionally, a wheel bearing device that rotatably supports a wheel in a suspension system of an automobile or the like is known. This wheel bearing device includes an outer member having a vehicle body mounting flange, an inner member in which one inner ring is fitted to a hub wheel, and raceway surfaces of the outer member and the inner member. A third-generation structure composed of a plurality of rolling elements interposed in the main body is the mainstream. For example, tapered roller bearings in which the rolling elements are tapered rollers so as to withstand the load are used for bearings of vehicles with a relatively large body weight, such as pickup trucks and large SUVs (Sports Utility Vehicles).

For example, the wheel bearing device disclosed in Patent Document 1 is intended to improve the durability of the recessed portion by applying a laser peening treatment that imparts residual stress to the surface layer of the recessed portion.

Further, in the wheel bearing device disclosed in Patent Document 2, the portion where the inner raceway surface formed on the inner side of the inner member intersects with the inner side flange surface of the inner raceway surface, and the outer ring of the inner member. An inner side relief processing portion and an outer side relief processing portion are provided at portions where the inner raceway surface formed on the side and the outer side flange surface of the inner raceway surface intersect. As a result, the relationship Ri<Ro is satisfied, where Ri is the radius of curvature of the inner side relief processing portion and Ro is the curvature radius of the outer side relief processing portion. According to such a wheel bearing device, it is possible to prevent stress from concentrating on the outer-side recessed portion.

JP 2018-162817 A Japanese Patent No. 6448693

However, as described in Patent Document 1, in the third-generation wheel bearing device of the double-row tapered roller bearing, stress concentrates on the relief portion. Therefore, in Patent Document 1, although it is a configuration that aims to improve durability by applying residual stress by laser peening, it is an off-line processing outside the current line, which requires the introduction of new equipment and the recessed part. Masking the surroundings increases the manufacturing cost and is not a realistic countermeasure from the viewpoint of cost effectiveness. Therefore, there is a demand for a technique capable of improving the strength of the relief portion at low cost.

In addition, in the wheel bearing device disclosed in Patent Document 2, the range of the R dimension of the recessed portion is specified, but the finishing method of the recessed portion is not clearly specified. For example, in the case of turning (finishing), the edge of the cutting tool may not form a smooth R-shaped part, and stress concentrates on this part, which easily causes metal fatigue. On the other hand, for example, in the case of grinding (grinding finish), since there is no grinding relief for the grinding wheel to escape from the smoothing portion, the processing time is greatly increased, and the processing cannot be performed at low cost. Therefore, it is required to grind the recessed portion without spending processing time to prevent stress from concentrating on the recessed portion, thereby realizing a highly robust structure.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wheel bearing device capable of improving the fatigue strength by improving the strength of the relief portion formed in the inner member. .

A first invention comprises an outer member having a double-row outer raceway surface on the inner circumference, an inner member having a double-row inner raceway surface on the outer circumference, and raceways of the inner member and the outer member. and double-row rolling elements housed between the surfaces so as to be free to roll, wherein the inner member comprises the inner raceway surface and a collar surface on one side of the inner raceway surface. A relief portion is provided between the two, and the surface of the relief portion is hardened by quenching and ground by a whetstone.

According to the present invention, by turning the recessed portion whose surface has been hardened by quenching, the strength of the recessed portion can be improved, and the fatigue strength of the inner member can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows the whole structure in 1st embodiment of a wheel bearing apparatus. FIG. 4 is a cross-sectional view showing the hub ring during grinding; FIG. 4 is a cross-sectional view showing a recessed portion and its surroundings when grinding. Sectional drawing which shows the modification of a recessed part. FIG. 10 is a cross-sectional view showing a relief turned with a single radius of curvature; FIG. 6 is an explanatory view for explaining a case where the relief portion shown in FIG. 5 is ground by a whetstone;

A wheel bearing device 1, which is a first embodiment of a wheel bearing device, will be described below with reference to FIGS. 1 to 3. FIG. In the following description, the inner side indicates the vehicle body side of the wheel bearing device 1 when attached to the vehicle body, and the outer side indicates the wheel side of the wheel bearing device 1 when attached to the vehicle body. .

As shown in FIG. 1, a wheel bearing device 1 rotatably supports a wheel in a suspension system of a vehicle such as an automobile. A wheel bearing device 1 includes an outer ring 2 , a hub ring 3 , an inner ring 4 , double-row tapered rollers 5 a and 5 b , an inner seal member 6 and an outer seal member 7 .

As shown in FIG. 1, the outer ring 2, which is an outer member, supports the hub ring 3 and the inner ring 4. An inner side opening 2a into which the inner side seal member 6 can be fitted is provided at the inner side end portion of the outer ring 2 . An outer-side opening 2b into which the outer-side seal member 7 can be fitted is provided at the outer-side end of the outer ring 2 . On the inner peripheral surface of the outer ring 2, an inner-side outer raceway surface 2c and an outer-side outer raceway surface 2d, which are formed in a tapered shape that expands toward the outside, are provided so as to be parallel to each other in the circumferential direction. It is An outer peripheral surface of the outer ring 2 is integrally provided with a vehicle body attachment flange 2e for attachment to a knuckle of a suspension system (not shown).

The inner member is composed of a hub ring 3 and an inner ring 4. The hub wheel 3 rotatably supports a vehicle wheel (not shown). The hub wheel 3 is formed in a substantially cylindrical shape and is made of, for example, medium-to-high carbon steel such as S53C. A small-diameter stepped portion 3a having a reduced diameter is provided on the outer peripheral surface of the inner side end portion of the hub wheel 3 . A wheel mounting flange 3b for mounting a wheel is integrally provided on the outer side end of the hub wheel 3. As shown in FIG. A hub bolt 3c is press-fitted into the wheel mounting flange 3b for fastening the hub wheel 3 and the wheel or the brake device. Further, on the outer peripheral surface of the hub wheel 3 on the outer side, an inner raceway surface 3d that is annular and tapered in the circumferential direction is provided.

The inner ring 4 is press-fitted into the small-diameter stepped portion 3a of the hub ring 3. An inner raceway surface 4 a is provided on the outer peripheral surface of the inner ring 4 . In other words, the inner raceway surface 4 a is formed by the inner ring 4 on the inner side of the hub wheel 3 .

The inner side tapered rollers 5a and the outer side tapered rollers 5b, which are two rows of rolling elements, support the hub wheel 3 and the inner ring 4 rotatably. A plurality of inner tapered rollers 5a and outer tapered rollers 5b are annularly retained by a retainer. The inner side tapered rollers 5a are rollably sandwiched between the inner raceway surface 4a of the inner ring 4 and the inner side outer raceway surface 2c of the outer ring 2 . The outer-side tapered rollers 5b are rollably sandwiched between the inner raceway surface 3d of the hub wheel 3 and the outer-side raceway surface 2d of the outer ring 2 . That is, the inner side tapered rollers 5a and the outer side tapered rollers 5b support the hub wheel 3 and the inner ring 4 with respect to the outer ring 2 so as to be rotatable.

As shown in FIG. 1, the outer seal member 7 closes the outer open end of the annular space formed by the outer ring 2, the hub wheel 3 and the inner ring 4. As shown in FIG.

As shown in FIG. 1, the inner side seal member 6 closes the inner side open end of the annular space formed by the outer ring 2, the hub wheel 3 and the inner ring 4. As shown in FIG.

[First embodiment]
Next, using FIGS. 2 and 3, a detailed description will be given of the recessed portion 13 of the hub wheel 3 and the grinding process for the recessed portion 13 in the wheel bearing device 1. FIG.

As shown in FIGS. 2 and 3, the hub wheel 3 has a flange surface 3f for receiving and guiding the large end surface 5b1 (see FIG. 1) of the tapered roller 5b in order to avoid interference with the tapered roller 5b on the outer side. is provided. The flange surface 3f is a flat surface formed substantially perpendicular to the inner raceway surface 3d. The hub wheel 3 is formed with a recessed curved relief portion 13 along the circumferential direction at a corner portion where the flange surface 3f and the inner raceway surface 3d on the outer side intersect. The relief portion 13 is recessed in a substantially arcuate shape when viewed in cross section.

The relief portion 13 has a first arcuate surface 13a having a substantially arcuate cross-sectional view and a second arcuate surface 13b having a substantially arcuate cross-sectional view connected to the first arcuate surface 13a. The first circular arc surface 13a is connected to the radially inner end of the flange surface 3f. The second circular arc surface 13b is connected to the outer side end of the inner raceway surface 3d. The first arcuate surface 13a has a substantially arcuate shape, and the radius of curvature of this substantially arcuate shape is defined as a "curvature radius Rx". The second arcuate surface 13b has a substantially arcuate shape, and the radius of curvature of this substantially arcuate shape is defined as "curvature radius Ry". That is, the recessed portion 13 has a first arcuate surface 13a having a two-step curvature radius Rx and a second arcuate surface 13b having a curvature radius Ry. In the first arc surface 13a and the second arc surface 13b having the two-step curvature radii Rx and Ry, the start position of the second arc surface 13b (the outer end of the second arc surface 13b) is shown in FIG. This is the position indicated by symbol P. The second arcuate surface 13b is a grinding relief provided so as to prevent interference (contact) with a tapered grindstone outer diameter surface 20a provided at the radially inner end of the grindstone 20, which will be described later, during grinding.

Here, for example, like the conventional relief portion shown in FIGS. On the other hand, when the entire inner side of the relief portion is ground, when the grindstone 20 is rapidly approached toward the outer side at a predetermined approach angle with respect to the axial direction, the portion E, which is the inner side end portion of the relief portion , it interferes (contacts) with the grindstone outer diameter surface 20a of the grindstone 20. Therefore, in order to prevent interference between the grinding wheel outer diameter surface 20a of the grinding wheel 20 and the inner ring (the portion E that is the inner end portion of the relief portion), the grinding process should be started from a position spaced apart from the portion E of the relief portion. I had to start. Therefore, the grindstone 20 cannot be rapidly approached to the vicinity of the relief portion in a short period of time (also called rapid contact). Therefore, the grindstone 20 must be slowly advanced to the vicinity of the relief portion, and the processing time of the grindstone 20 for the relief portion is greatly increased, which may reduce productivity.

Therefore, in the wheel bearing device 1 of the first embodiment of the present invention, first, the surface of the relief portion 13 is hardened in advance by induction hardening. As a result, the relief portion 13 has a quench-hardened layer on the surface thereof. Next, in the relief portion 13 according to the first embodiment, the grinding process (grinding finish) is performed not on the entire inner side of the relief portion 13 but only on the outer side region inside the relief portion 13 . That is, the relief portion 13 has a ground surface to be ground by the whetstone 20 . Specifically, in the relief portion 13, it is located on the outer side of a plane S (straight line indicated by a two-dot chain line in FIG. 3) passing through the radially outer end portion 3f1 of the flange surface 3f and perpendicular to the axial direction. A region including a portion of the first circular arc surface 13a and the flange surface 3f is a range (grinding range) to be ground by the grindstone 20. As shown in FIG. That is, a region including a portion of the first circular arc surface 13a located on the outer side of the plane S in the relief portion 13 and the flange surface 3f has a ground surface. That is, the relief portion 13 is ground to a position corresponding to the end portion 3f1 on the other side (inner side) of the flange surface 3f in the axial direction. Further, in the relief portion 13 , a region on the inner side of the plane S is a range (non-grinding range) that is not ground by the grindstone 20 . That is, in the non-grinding range, only turning (turning finishing) performed when forming the relief portion 13 is performed without grinding. That is, the second circular arc surface 13b does not have a ground surface. The non-grinding range of the relief portion 13 includes the inner end portion of the first arcuate surface 13a, the starting position P of the second arcuate surface 13b, and the second arcuate surface 13b. By grinding the quenched relief portion 13 in this manner, the effect of the built-up cutting edge of the turning tool that occurs during turning finishing of the relief portion 13 is eliminated, so that the surface of the relief portion 13 has a smooth radius. shape. As a result, the reduction in strength of the relief portion 13 can be suppressed, and the robustness can be enhanced. Furthermore, since compressive residual stress can be imparted by grinding the relief portion 13, the strength of the relief portion 13 can be increased. As a result, even when a large turning load is input to the hub wheel 3, the repeated fatigue strength is improved, so that the life of the hub wheel can be further extended.

The outer side portion of the radially inner peripheral portion of the grindstone 20 is formed in the same shape as the first circular arc surface 13a and the flange surface 3f. As a result, the grindstone 20 is moved along the direction of the approach angle α with respect to the axial direction and brought into contact with the first arcuate surface 13a and the flange surface 3f, whereby the surfaces of the first arcuate surface 13a and the flange surface 3f are ground. be.

In addition, since the wheel bearing device 1 of the first embodiment of the present invention has the second arcuate surface 13b that serves as a grinding relief, the grindstone 20 moves in the axial direction toward the relief portion 13 during grinding. On the other hand, even if the hub wheel 3 moves in the direction of the approach angle α, the wheel hub 3 does not interfere (contact) with the grinding wheel outer diameter surface 20a of the grinding wheel 20, and the grinding wheel 20 is made to approach immediately before the machining part of the relief part 13. Therefore, the processing time can be shortened and the productivity can be improved.

The surface of the relief portion 13 is hardened by, for example, induction hardening before being ground. That is, the relief portion 13 is ground after the surface is quenched.
Further, as for the hardening of the relief portion 13, hardening by a known heat treatment can be applied in addition to induction hardening. Specifically, the quenching treatment includes carburizing quenching in which only the surface of the hub wheel 3 is hardened by carburizing and the core portion is not quenched, and full hardening quenching in which the entire hub wheel 3 including the core portion is hardened. can be adopted.

Also, the curvature radius Rx of the first circular arc surface 13a is preferably 0.4 mm or more and 1.2 mm or less. For example, if the radius of curvature Rx is less than 0.4 mm, stress concentration is likely to occur, resulting in reduced strength. If the radius of curvature Rx is larger than 1.2 mm, the area of the end portion 3f1 becomes small, so that a large axial load cannot be received, and the size of the bearing device needs to be increased. Further, in the wheel bearing device 1, since the strength can be increased by grinding the relief portion 13, it is possible to provide the relief portion with a smaller radius of curvature than conventional ones. For example, conventionally, a relief portion having a radius of curvature of at least about 0.6 mm was required in order to ensure strength. However, it is possible to prevent the strength of the relief portion 13 from being lowered up to the lower limit value of about 0.4 mm.

Furthermore, it is preferable that the radius of curvature Ry of the second arcuate surface 13b be larger than the radius of curvature Rx of the first arcuate surface 13a. In this case, since the first circular arc surface 13a is arranged in the non-ground area of the relief portion 13, the stress in the non-ground area of the relief portion 13 can be relieved, and the durability of the relief portion 13 can be improved. can be done. Moreover, it is preferable that at least the second arcuate surface 13b is not ground by the grindstone 20 . As a result, the machining time can be shortened, and productivity can be improved.

Also, the approach angle α of the grindstone 20 with respect to the axial direction with respect to the relief portion 13 is preferably 0° or more and 20° or less. For example, if the approach angle .alpha.

[Second embodiment]
Next, a relief portion 13A, which is a modified example of the relief portion 13 of the hub wheel 3 in the wheel bearing device 1, will be described with reference to FIG. Since the configuration other than the relief portion 13A of the second embodiment is the same as that of the first embodiment, the same reference numerals are used and the description thereof is omitted.

First, the surface of the relief portion 13A is hardened in advance by induction hardening. As a result, the relief portion 13 has a quench-hardened layer on the surface thereof. Next, in the relief portion 13A according to the second embodiment, the grinding process is performed not on the entire inner side of the relief portion 13, but limited to the outer region inside the relief portion 13A. That is, the relief portion 13A has a ground surface to be ground by the whetstone 20. As shown in FIG. Specifically, in the relief portion 13A, a plane S (a straight line indicated by a two-dot chain line in FIG. 4) that passes through the radially outer end portion 3f1 of the flange surface 3f and is orthogonal to the axial direction becomes an outer side region. The arcuate surface 13A1 having a predetermined radius of curvature is the range (grinding range) to be ground by the grindstone 20. As shown in FIG. That is, a region including the arcuate surface 13A1 positioned on the outer side of the plane S in the relief portion 13A and the flange surface 3f has a ground surface. That is, the relief portion 13A is ground to a position corresponding to the end portion 3f1 on the other side (inner side) of the flange surface 3f in the axial direction.

In addition, the relief portion 13A has a tapered surface 13A2 which is a linear inclined surface in a cross-sectional view and which is connected to the arcuate surface 13A1 and which is located on the inner side of the plane S. That is, the relief portion 13A has a tapered surface 13A2 from a position corresponding to the inner side end of the collar surface 3f in the axial direction to the outer side end of the inner raceway surface 3d. In the relief portion 13A, the tapered surface 13A2, which is the inner side area of the flat surface S, is not ground by the grindstone 20 (non-grinding range). That is, the tapered surface 13A2 does not have a ground surface. The tapered surface 13A2 is provided so as to form an inclination angle β with respect to the axial direction. When the grindstone 20 approaches the relief portion 13A, if the approach angle of the inner peripheral edge of the grindstone 20 with respect to the axial direction is α, the relationship between the approach angle α and the inclination angle β can satisfy the relationship α>β. preferable. By satisfying this relationship, the tapered surface 13A2 becomes a grinding relief provided so that the grindstone outer diameter surface 20a of the grindstone 20 does not interfere (contact). As a result, even if the grindstone 20 moves in the direction of the approach angle α, the tapered surface 13A2 does not interfere (contact) with the grindstone outer diameter surface 20a of the grindstone 20, and the grindstone 20 can be moved up to just before the grinding portion of the relief portion 13. can be rapidly approached, the machining time can be shortened and the productivity can be improved.

As described above, in the wheel bearing device 1 of the first embodiment, the recessed portion 13 whose surface is hardened by quenching is subjected to lathe turning to improve the strength of the recessed portion 13. The fatigue strength of the wheel 3 can be improved. As a result, the fatigue strength of the hub wheel 3 can be improved without enlarging the wheel bearing device, so that the weight and size of the wheel bearing device can be reduced.

Further, in the wheel bearing device 1, the relief portions 13, 13A are provided at least halfway between the radially outer end portion 13c of the relief portions 13, 13A, which is the boundary with the flange surface 3f, and the inner raceway surface 3d. 20 is preferably applied. As a result, the processing time can be shortened compared to grinding the entire inner side of the relief portions 13, 13A, so that the productivity can be improved.

Further, as in the wheel bearing device 1 of the present embodiment, when the hub wheel 3 of the third generation structure receives an axial load on the flange surface 3f, the stress concentrates on the relief portion 13, so that the second circular arc It is preferable that the starting position P of the surface 13b be provided on the inner side (right side of the paper surface) of the position receiving the axial load (the position of the two-dot chain line in FIG. 3).

In order to prevent stress from concentrating at the joint between the grinding range and the non-grinding range (the portion only turned) in the relief portion 13, an axis corresponding to at least the radially outer end portion 3f1 of the flange surface 3f receiving an axial load is provided. It is preferable to perform grinding up to the directional position (position indicated by two-dot chain lines in FIGS. 3 and 4). Further, it is more preferable to perform the grinding process to the inner side (right side of the paper surface) of the axial position. As a result, the strength of the relief portion 13 is further improved.

As described above, the wheel bearing device 1 according to the present embodiment is for a third-generation wheel structure in which the inner raceway surface 3d of the double-row tapered rollers 5a and 5b, which are rolling elements, is directly formed on the outer periphery of the hub wheel 3. Although described as a bearing device, it is not limited to this, and may be, for example, a second-generation inner ring rotating structure in which a pair of inner rings 4 are press-fitted into a hub wheel 3 and fixed. Moreover, the above-described embodiment merely shows a typical form of the present invention, and various modifications can be made without departing from the gist of the present invention.

The present invention can be used for wheel bearing devices.

1 wheel bearing device 2 outer ring 2c outer raceway surface 2d outer raceway surface 3 hub ring 3a small diameter stepped portion 3d inner raceway surface 3f flange surface 4 inner ring 4a inner raceway surface 5a tapered roller 5b tapered roller 13 relief portion 20 grindstone

Claims

an outer member having a double-row outer raceway surface on its inner circumference;
an inner member having a double-row inner raceway surface on the outer periphery;
A wheel bearing device comprising double-row tapered rollers rollably accommodated between the raceway surfaces of the inner member and the outer member,
The inner member is
a relief portion provided between the inner raceway surface and a flange surface on one side of the inner raceway surface;
The bearing device for a wheel, wherein the relief portion has a quench-hardened layer whose surface is hardened by quenching and a ground surface whose surface is ground by a whetstone.
The wheel bearing device according to claim 1, wherein the ground surface is formed at least halfway between the boundary between the relief portion and the flange surface and the inner raceway surface.
The wheel bearing device according to claim 1 or 2, wherein the ground surface is formed up to a position corresponding to the other end of the flange surface in the axial direction.
The wheel bearing device according to any one of claims 1 to 3, wherein the relief portion has a grinding relief that does not interfere with the grindstone during the grinding process.
The relief portion includes a first arcuate surface having a substantially arcuate shape in cross section and having a curvature radius Rx connected to the flange surface, and a second arcuate surface having a substantially arcuate cross section and having a curvature radius Ry connected to the other side of the first arcuate surface. The wheel bearing device according to any one of claims 1 to 4, comprising:
When the grindstone approaches the relief portion, the approach angle of the grindstone with respect to the axial direction is α,
The relief portion has a tapered surface that is linear in cross section from a position corresponding to the other end of the flange surface in the axial direction to the inner raceway surface,
When the inclination angle of the tapered surface with respect to the axial direction is β,
The wheel bearing device according to any one of claims 1 to 4, wherein the relationship α>β is satisfied.
The wheel bearing device according to claim 5, wherein the curvature radius Rx of the first circular arc surface is 0.4 mm or more and 1.2 mm or less.
6. The wheel bearing device according to claim 5, wherein the curvature radius Ry of the second arcuate surface is larger than the curvature radius Rx of the first arcuate surface, and at least the second arcuate surface does not have the ground surface. .
The wheel bearing device according to claim 6, wherein the approach angle α of the grindstone is 0° or more and 20° or less.