Wheel bearing device

Abstract

To provide a wheel bearing device capable of improving the strength of a relief part formed in an inward member to improve fatigue strength.SOLUTION: In a wheel bearing device comprising an outer ring having a double-row outside raceway surface on its inner periphery, a hub wheel 3 having a double-row inside raceway surface on its outer periphery, and double-row conical rollers rollably housed between the raceway surfaces of the hub ring 3 and the outer ring, the hub wheel 3 has a relief part 13 provided between the inside raceway surface 3d and a flange surface 3f on the outer side of the inside raceway surface 3d, and the surface of the relief part 13 is hardened by quenching and ground by a grindstone 20.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a wheel bearing device.

Background Art

[0002] Conventionally, a wheel bearing device that rotatably supports a wheel in a suspension device of an automobile or the like is known. This wheel bearing device mainly has a third-generation structure including an outer member having a vehicle body mounting flange, an inner member in which one inner ring is fitted to a hub ring, and a plurality of rolling elements interposed between the respective raceway surfaces of the outer member and the inner member. For example, for bearings of vehicles with relatively large vehicle body weights such as pickup trucks or large SUVs (Sports Utility Vehicles), tapered roller bearings with tapered rollers are used so as to withstand the load.

[0003] For example, the wheel bearing device disclosed in Patent Document 1 is provided with laser peening treatment for applying residual stress to the surface layer of the theft prevention portion to improve the durability of the theft prevention portion.

[0004] In addition, in the wheel bearing device disclosed in Patent Document 2, at each of the portions 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 portions where the inner raceway surface formed on the outer side of the inner member intersects with the outer side flange surface of the inner raceway surface, inner side theft prevention processed portions and outer side theft prevention processed portions are provided. Thereby, when the radius of curvature of the inner side theft prevention processed portion is Ri and the radius of curvature of the outer side theft prevention processed portion is Ro, it is configured to satisfy the relationship of Ri < Ro. According to such a wheel bearing device, it is configured to prevent stress from concentrating on the outer side theft prevention processed portion.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, as described in Patent Document 1, stress concentrates in the recessed portion of a third-generation wheel bearing device in a double-row tapered roller bearing. Therefore, Patent Document 1 proposes a configuration in which residual stress is applied by laser peening to improve durability, but this is an offline process outside of the current production line, necessitating the introduction of new equipment, and masking the area around the recessed portion increases manufacturing costs, making it an unrealistic solution from a cost-effective perspective. Therefore, a technology is needed that can improve the strength of the recessed portion at low cost.

[0007] Furthermore, the wheel bearing device disclosed in Patent Document 2 specifies the range of the radius of the recessed portion, but does not clearly specify the finishing method for the recessed portion. For example, in the case of turning (turning finish), the recessed portion may not have a smooth radius due to the built-up cutting edge of the turning tool, which causes stress to concentrate in this area and makes metal fatigue more likely. On the other hand, in the case of grinding (grinding finish), for example, the recessed portion does not have a grinding relief for the grinding wheel, which significantly increases the processing time and makes it difficult to process at low cost. Therefore, there is a need to perform grinding on the recessed portion without increasing the processing time, thereby preventing stress concentration in the recessed portion and achieving a highly robust structure.

[0008] The present invention has been made in view of the above circumstances, and has as its object to provide a wheel bearing device that can improve fatigue strength by improving the strength of the recessed portion formed in the inner member. [Means for solving the problem]

[0009] The first invention is a wheel bearing device comprising an outer member having a double-row outer raceway surface on its inner periphery, an inner member having a double-row inner raceway surface on its outer periphery, and double-row rolling elements accommodated in a rollable manner between the raceway surfaces of the inner member and the outer member, wherein the inner member has a recessed portion provided between the inner raceway surface and a flange surface on one side of the inner raceway surface, and the recessed portion is surface-hardened by quenching and then ground with a grinding wheel. The recess has a grinding surface, and the recess has a grinding relief that does not interfere with the grindstone during the grinding process. [Effects of the Invention]

[0010] According to the present invention, by performing turning on the recessed portion whose surface has been hardened by quenching, the strength of the recessed portion can be improved, thereby improving the fatigue strength of the inner member. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing an overall configuration of a wheel bearing device according to a first embodiment; [Figure 2] FIG. 4 is a cross-sectional view showing the hub ring when grinding is performed. [Figure 3] FIG. 4 is a cross-sectional view showing a recessed portion and its surroundings when performing grinding. [Figure 4] FIG. 10 is a cross-sectional view showing a modified example of the recessed portion. [Figure 5] A cross-sectional view showing a recessed area that has been turned with a single radius of curvature. [Figure 6] FIG. 6 is an explanatory diagram illustrating a case where the recessed portion shown in FIG. 5 is subjected to grinding processing using a grindstone. DETAILED DESCRIPTION OF THE INVENTION

[0012] A wheel bearing device 1, which is a first embodiment of the wheel bearing device, will be described below with reference to Figures 1 to 3. In the following description, the inner side refers to the vehicle body side of the wheel bearing device 1 when attached to the vehicle body, and the outer side refers to the wheel side of the wheel bearing device 1 when attached to the vehicle body.

[0013] 1, a wheel bearing device 1 rotatably supports a wheel in a suspension system of a vehicle such as an automobile. The wheel bearing device 1 includes an outer ring 2, a hub ring 3, an inner ring 4, double-row tapered rollers 5a, 5b, an inner seal member 6, and an outer seal member 7.

[0014] As shown in Figure 1, the outer ring 2, which is the outer member, supports the hub ring 3 and the inner ring 4. An inner side opening 2a is provided at the inner side end of the outer ring 2, into which an inner side seal member 6 can be fitted. An outer side opening 2b is provided at the outer side end of the outer ring 2, into which an outer side seal member 7 can be fitted. The inner peripheral surface of the outer ring 2 is provided with an inner side outer raceway surface 2c and an outer side outer raceway surface 2d, which are tapered so that their diameter increases outward and are parallel to each other in the circumferential direction. A vehicle body mounting flange 2e is provided integrally with the outer peripheral surface of the outer ring 2 for mounting to a knuckle of a suspension system (not shown).

[0015] The inner member is made up of a hub ring 3 and an inner ring 4. The hub ring 3 rotatably supports a vehicle wheel (not shown). The hub ring 3 is formed in a roughly cylindrical shape and is made of medium- to high-carbon steel such as S53C. The inner end of the hub ring 3 is provided with a small-diameter step 3a, which is a reduced diameter portion, on the outer peripheral surface. The outer end of the hub ring 3 is integrally provided with a wheel mounting flange 3b for mounting a wheel. Hub bolts 3c for fastening the hub ring 3 to a wheel or a brake device are press-fitted into the wheel mounting flange 3b. In addition, the outer peripheral surface of the outer side of the hub ring 3 is provided with a circumferentially annular, tapered inner raceway surface 3d.

[0016] The inner ring 4 is press-fitted into the small diameter step 3a of the hub ring 3. An inner raceway surface 4a is provided on the outer peripheral surface of the inner ring 4. In other words, on the inner side of the hub ring 3, the inner raceway surface 4a is formed by the inner ring 4.

[0017] The two rows of rolling elements, inner tapered rollers 5a and outer tapered rollers 5b, rotatably support the hub ring 3 and inner ring 4. The multiple inner tapered rollers 5a and outer tapered rollers 5b are held in an annular shape by a cage. The inner tapered rollers 5a are rollably sandwiched between the inner raceway surface 4a of the inner ring 4 and the inner outer raceway surface 2c of the outer ring 2. The outer tapered rollers 5b are rollably sandwiched between the inner raceway surface 3d of the hub ring 3 and the outer outer raceway surface 2d of the outer ring 2. In other words, the inner tapered rollers 5a and outer tapered rollers 5b support the hub ring 3 and inner ring 4 rotatably relative to the outer ring 2.

[0018] 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 ring 3, and the inner ring 4.

[0019] As shown in FIG. 1, the inner seal member 6 closes the inner open end of the annular space formed by the outer ring 2, the hub ring 3, and the inner ring 4.

[0020] [First embodiment] Next, the recessed portion 13 of the hub ring 3 in the wheel bearing device 1 and the grinding process for the recessed portion 13 will be described in detail with reference to FIGS.

[0021] As shown in Figures 2 and 3, the hub ring 3 is provided with a rib surface 3f that receives and guides the large end faces 5b1 (see Figure 1) of the tapered rollers 5b to avoid interference with the outer tapered rollers 5b. The rib surface 3f is a flat surface formed in a direction approximately perpendicular to the inner raceway surface 3d. The hub ring 3 is formed with a concavely curved recess 13 along the circumferential direction at the corner where the rib surface 3f and the outer inner rolling surface 3d intersect. The recess 13 is recessed in a substantially arc shape in cross section.

[0022] The recessed portion 13 has a first arcuate surface 13a that is generally arcuate in cross section and a second arcuate surface 13b that is generally arcuate in cross section and connected to the first arcuate surface 13a. The first arcuate surface 13a is connected to the radially inner end of the rib surface 3f. The second arcuate surface 13b is connected to the outer end of the inner raceway surface 3d. The first arcuate surface 13a has a generally arcuate shape, and the radius of curvature of this generally arcuate shape is defined as "radius of curvature Rx." The second arcuate surface 13b also has a generally arcuate shape, and the radius of curvature of this generally arcuate shape is defined as "radius of curvature Ry." That is, the recessed portion 13 has a first arcuate surface 13a with a two-step curvature radius Rx and a second arcuate surface 13b with a curvature radius Ry, where two continuous rounded surfaces form a single step. In the first arcuate surface 13a and the second arcuate surface 13b each having two radii of curvature Rx and Ry, the starting position of the second arcuate surface 13b (the outer end of the second arcuate surface 13b) is the position indicated by the symbol P in Fig. 3. The second arcuate surface 13b is a grinding relief provided so that a tapered grinding wheel outer diameter surface 20a at the radially inner end of the grinding wheel 20, which will be described later, does not interfere with (contact with) the second arcuate surface 13b during grinding.

[0023] For example, when using an annular grinding wheel 20 to grind the entire inside of a conventional undercut, which has a generally arc-shaped cross section and a single radius of curvature R, as shown in FIGS. 5 and 6 , the grinding wheel 20 approaches the outer ring at a predetermined approach angle toward the axial direction. This causes interference (contact) with the grinding wheel outer diameter surface 20a of the grinding wheel 20 at the inner end portion E of the undercut. Therefore, to prevent interference between the grinding wheel outer diameter surface 20a of the grinding wheel 20 and the inner ring (the inner end portion E of the undercut), it is necessary to start grinding from a position away from the undercut. This makes it impossible to rapidly approach the undercut (also called "rapid contact") in a short time. Therefore, the grinding wheel 20 must be advanced slowly to the undercut, significantly lengthening the time required to process the undercut using the grinding wheel 20, potentially reducing productivity.

[0024] Therefore, in the wheel bearing device 1 according to the first embodiment of the present invention, the surface of the recess 13 is first hardened by induction hardening. As a result, the surface of the recess 13 has a quench-hardened layer obtained by quench-hardening. Next, in the recess 13 according to the first embodiment, grinding (finishing by grinding) is performed not on the entire inside of the recess 13, but only on the outer region inside the recess 13. That is, the recess 13 has a grinding surface that is ground by the grindstone 20. Specifically, the area of ​​the recess 13 that is ground by the grindstone 20 includes a part of the first arcuate surface 13a located on the outer side of a plane S (shown by a two-dot chain line in FIG. 3 ) that passes through the radially outer end 3f1 of the flange surface 3f and is perpendicular to the axial direction and includes the flange surface 3f. That is, the area of ​​the recess 13 including a part of the first arcuate surface 13a located on the outer side of the plane S and the flange surface 3f has a ground surface. That is, the recess 13 is ground up to a position corresponding to the end 3f1 on the other side (inner side) of the flange surface 3f in the axial direction. Also, the area of ​​the recess 13 that is inner than the plane S is a range (non-grinding range) that is not ground by the grindstone 20. That is, the non-grinding range is not ground, and only the turning (turning finish) performed when forming the recess 13 is performed. That is, the second arcuate surface 13b does not have a ground surface. The non-grinding range of the recess 13 includes the inner end 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 hardened recess 13 in this way, the recess 13 is no longer affected by the built-up cutting edge of the turning tool that occurs when the recess 13 is finished by turning, and the surface of the recess 13 has a smooth R-shape. This prevents a decrease in strength of the recess 13 and increases robustness. Furthermore, grinding the recess 13 imparts compressive residual stress, thereby increasing the strength of the recess 13. Consequently, repeated fatigue strength is improved even when a large turning load is applied to the hub wheel 3, further extending the life of the hub wheel.

[0025] The outer portion of the radially inner periphery of grinding wheel 20 is formed in the same shape as first arcuate surface 13a and flange surface 3f. As a result, by moving grinding wheel 20 in the axial direction along the approach angle α and bringing it into contact with first arcuate surface 13a and flange surface 3f, the surfaces of first arcuate surface 13a and flange surface 3f are ground.

[0026] Furthermore, the wheel bearing device 1 of the first embodiment of the present invention has a second arc surface 13b that serves as a grinding relief, so even if the grinding wheel 20 moves in the direction of the approach angle α relative to the axial direction toward the recess portion 13 during grinding, the hub wheel 3 does not interfere with (contact with) the grinding wheel outer diameter surface 20a of the grinding wheel 20, and the grinding wheel 20 can be brought quickly close to just before the processing portion of the recess portion 13, thereby shortening the processing time and improving productivity.

[0027] The surface of the recess 13 is hardened in advance by, for example, induction hardening before being ground. That is, the surface of the recess 13 is hardened before being ground. Furthermore, other known heat treatments besides induction hardening can be used to harden the recessed portion 13. Specifically, the hardening treatment can be carburizing hardening, in which only the surface of the hub ring 3 is hardened by carburizing and the core is left unhardened, or full hardening hardening, in which the entire hub ring 3 including the core is hardened.

[0028] Furthermore, the curvature radius Rx of the first arcuate surface 13a is preferably 0.4 mm or more and 1.2 mm or less. For example, if the curvature radius Rx is less than 0.4 mm, stress concentration is likely to occur, resulting in reduced strength. Furthermore, if the curvature radius Rx is greater than 1.2 mm, the area of ​​the end portion 3f1 becomes smaller, making it unable to withstand large axial loads and requiring an increase in the size of the bearing device. Furthermore, in the wheel bearing device 1, the strength can be increased by grinding the recess 13, making it possible to provide a recess with a smaller curvature radius than conventional recesses. For example, while a minimum curvature radius of approximately 0.6 mm was previously required to ensure strength, the recess 13 of this embodiment can prevent a decrease in strength of the recess 13 even if the first arcuate surface 13a is smaller than 0.6 mm, down to the lower limit of approximately 0.4 mm.

[0029] Furthermore, it is preferable that the radius of curvature Ry of the second arcuate surface 13b is larger than the radius of curvature Rx of the first arcuate surface 13a. In this case, since the first arcuate surface 13a is disposed in the non-grinding range of the recessed portion 13, stress in the non-grinding range of the recessed portion 13 can be alleviated, thereby improving the durability of the recessed portion 13. It is also preferable that at least the second arcuate surface 13b is not subjected to grinding processing with the grindstone 20. This shortens the processing time, thereby improving productivity.

[0030] Furthermore, the approach angle α of the grinding wheel 20 relative to the axial direction of the recess 13 is preferably set to be equal to or greater than 0° and equal to or less than 20°. For example, if the approach angle α is set to be greater than 20°, grinding the recess 13 becomes difficult.

[0031] [Second embodiment] Next, a description will be given of a recessed portion 13A, which is a modified example of the recessed portion 13 of the hub ring 3 in the wheel bearing device 1, with reference to Figure 4. Since the configuration of the second embodiment is the same as that of the first embodiment except for the recessed portion 13A, the same reference numerals are used and the description thereof will be omitted.

[0032] First, the surface of the recess 13A is hardened in advance by induction hardening. As a result, the recess 13 has a quench-hardened layer on its surface. Next, in the recess 13A according to the second embodiment, grinding is performed not on the entire inside of the recess 13 but only on the outer region of the inside of the recess 13A. That is, the recess 13A has a grinding surface that is ground by the grindstone 20. Specifically, in the recess 13A, a circular arc surface 13A1 with a predetermined radius of curvature that is located on the outer side of a plane S (shown by a two-dot chain line in FIG. 4 ) that passes through the radially outer end 3f1 of the flange surface 3f and is perpendicular to the axial direction is the range that is ground by the grindstone 20 (grinding range). That is, the region of the recess 13A that includes the circular arc surface 13A1 located on the outer side of the plane S and the flange surface 3f has a grinding surface. That is, the recessed portion 13A is ground up to a position corresponding to the end 3f1 on the other side (inner side) of the flange surface 3f in the axial direction.

[0033] The recess portion 13A also has a tapered surface 13A2, which is a linear inclined surface in cross section and is connected to the arcuate surface 13A1 and is located in a region on the inner side of the plane S. That is, the recess portion 13A has the tapered surface 13A2 between a position corresponding to the inner end of the flange surface 3f in the axial direction and the outer end of the inner raceway surface 3d. In the recess portion 13A, the tapered surface 13A2, which is located in a region on the inner side of the plane S, is a range (non-grinding range) that is not ground by the grinding wheel 20. 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 grinding wheel 20 approaches the recess portion 13A, the approach angle α of the inner peripheral edge of the grinding wheel 20 with respect to the axial direction is defined as α. It is preferable that the relationship between the approach angle α and the inclination angle β satisfy the relationship α > β. By satisfying this relationship, the tapered surface 13A2 becomes a grinding relief provided so as not to interfere with (contact with) the grinding wheel outer diameter surface 20a of the grinding wheel 20. As a result, even when the grinding wheel 20 moves in the direction of the approach angle α, the tapered surface 13A2 does not interfere with (contact with) the grinding wheel outer diameter surface 20a of the grinding wheel 20, and the grinding wheel 20 can be brought close to just before the grinding processing portion of the recessed portion 13, thereby shortening the processing time and improving productivity.

[0034] As described above, in the wheel bearing device 1 of the first embodiment, by performing turning on the recessed portion 13 whose surface has been hardened by quenching, it is possible to improve the strength of the recessed portion 13 and thereby improve the fatigue strength of the hub ring 3. Furthermore, since the fatigue strength of the hub ring 3 can be improved without increasing the size of the wheel bearing device, it is possible to make the wheel bearing device lighter and more compact.

[0035] Furthermore, in the wheel bearing device 1, it is preferable that the recesses 13, 13A are ground with the grindstone 20 at least from the radially outer end 13c of the recesses 13, 13A, which is the boundary with the flange surface 3f, to the middle of the way to the inner raceway surface 3d. This shortens the processing time compared to grinding the entire inside of the recesses 13, 13A, thereby improving productivity.

[0036] Furthermore, in the case of a third-generation structure hub ring 3, such as the wheel bearing device 1 of this embodiment, when an axial load is applied to the flange surface 3f, stress is concentrated in the recessed portion 13, so it is preferable to set the starting position P of the second arc surface 13b on the inner side (to the right of the page) of the position where the axial load is applied (the position indicated by the two-dot chain line in Figure 3).

[0037] In addition, to prevent stress concentration at the boundary between the ground and non-ground areas (areas that are only turned) in the recess 13, it is preferable to perform grinding at least up to the axial position (the position indicated by the two-dot chain line in FIGS. 3 and 4) that corresponds to the radially outer end 3f1 of the flange surface 3f that receives the axial load. It is more preferable to perform grinding further inward (to the right side of the drawing) than the axial position. This further improves the strength of the recess 13.

[0038] The wheel bearing device 1 according to this embodiment has been described above as a wheel bearing device of a third-generation structure in which the inner raceway surfaces 3d of the double-row tapered rollers 5a, 5b, which are rolling elements, are formed directly on the outer periphery of the hub ring 3, but the present invention is not limited to this and may, for example, be an inner-ring-rotating second-generation structure in which a pair of inner rings 4 are press-fitted and fixed into the hub ring 3. Furthermore, the above-described embodiment merely shows a typical form of the present invention, and various modifications can be made within the scope of the gist of the present invention. [Explanation of symbols]

[0039] 1 Wheel bearing device 2 outer ring 2c Outer raceway surface 2d outer raceway 3 Hub Wheel 3a Small diameter stepped section 3d inner raceway surface 3f Tsubamen 4. Inner Circle 4a Inner raceway surface 5a Tapered roller 5b Tapered roller 13 Stealing 20 Grindstone

Claims

1. an outer member having a double-row outer raceway surface on its inner periphery; an inner member having a double-row inner raceway surface on its outer periphery; a double-row tapered roller housed between the raceway surfaces of the inner member and the outer member so as to be able to roll freely, The inner member is a recessed portion provided between the inner raceway surface and a flange surface on one side of the inner raceway surface, The recessed portion has a quench-hardened layer that is subjected to a surface hardening treatment by quenching, and a ground surface that is subjected to a grinding process by a grinding stone, The recessed portion has a grinding relief that does not interfere with the grinding stone during the grinding process.

2. 2. The wheel bearing device according to claim 1, wherein the ground surface is formed at least partway from the boundary between the recessed portion and the flange surface to the inner raceway surface.

3. 3. The wheel bearing device according to claim 1, wherein the ground surface is formed up to a position corresponding to the other end of the flange surface in the axial direction.

4. 4. The wheel bearing device according to claim 1, wherein the recessed portion has a first arcuate surface that is generally arcuate in cross section and connected to the flange surface and has a radius of curvature Rx, and a second arcuate surface that is generally arcuate in cross section and connected to the other side of the first arcuate surface and has a radius of curvature Ry.

5. When the grinding wheel is brought close to the recessed portion, an approach angle of the grinding wheel with respect to the axial direction of the grinding wheel is defined as α, the recessed portion has a tapered surface that is linear in cross section from a position corresponding to the other end of the rib 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 claim 1 , wherein the relationship α>β is satisfied.

6. 5. The wheel bearing device according to claim 4, wherein the radius of curvature Rx of the first arcuate surface is equal to or greater than 0.4 mm and equal to or less than 1.2 mm.

7. 5. The wheel bearing device according to claim 4, wherein the radius of curvature Ry of the second arcuate surface is larger than the radius of curvature Rx of the first arcuate surface, and at least the second arcuate surface does not have the ground surface.

8. 6. The wheel bearing device according to claim 5, wherein an approach angle α of the grindstone is set to be equal to or greater than 0° and equal to or less than 20°.

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