Bearing device for wheels

Abstract

To provide a bearing device for wheels capable of reducing a hoop stress that is generated in an inner ring.SOLUTION: A bearing device 1 for wheels consists of an outer ring 2 including outside trajectory faces 2c and 2d, a hub ring 3 including a small diameter step 3a, and an inner ring 4 which is press-fitted into the small diameter step 3a. The inner ring 4 is fixed in an axial direction by an inner member including inside trajectory faces 3c and 4a opposed to the outside trajectory faces 2c and 2d, a plurality of ball trains 5 and 6 accommodated between both the trajectory faces of the outer ring 2 and the inner member, and a caulking part 3h which is formed by plastically deforming one end of the small diameter step 3a on one side in the axial direction to the side of an outer diameter. In the bearing device 1 for wheels, the inner ring 4 includes an inner peripheral surface 4d, an inner-side end face 4b, and an inner diameter chamfering part 4f which connects the inner peripheral surface 4d and the inner-side end face 4b and has the diameter expanding toward one side in the axial direction. The caulking part 3h is a non-annealed part, to which annealing is not applied, and includes an annular groove 31 which is separated from the inner ring 4.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Conventionally, there has been known a wheel bearing device that rotatably supports a wheel in a suspension system of an automobile, etc. In some wheel bearing devices, an inner ring is press-fitted into a small-diameter stepped portion of a hub wheel, which is an inner member, and the inner ring is fixed in the axial direction by a crimped portion formed by plastically deforming one end of the small-diameter stepped portion toward the outer diameter.

[0003] In this way, in a wheel bearing device in which a crimped portion is formed in the small diameter step portion of the hub wheel, when one end of the small diameter step portion is plastically deformed toward the outer diameter, hoop stress is generated in the inner ring, and the inner diameter of the inner ring may be pushed outward.

[0004] In addition, an outer diameter chamfer is formed at one end in the axial direction of the outer peripheral surface of the inner ring, and if a dent is present in this outer diameter chamfer, the hoop stress generated in the inner ring will promote stress concentration at the dent, causing cracks to form in the inner ring starting from the dent, which may reduce the durability of the wheel bearing device.

[0005] In order to prevent cracks from occurring originating from dents in the outer diameter chamfer of the inner ring, it is conceivable to increase the axial and radial lengths of the inner ring to reduce the hoop stress generated in the inner ring. However, increasing the axial and radial lengths of the inner ring is not desirable because it increases the weight of the wheel support bearing assembly, which can be a factor in reducing the fuel efficiency of the vehicle.

[0006] Therefore, in the past, as disclosed in Patent Document 1, the outer diameter chamfered portion of the inner ring was machined after heat treatment to form a re-machined surface, thereby removing dents on the outer diameter chamfered portion of the inner ring. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 4471150 Summary of the Invention [Problem to be solved by the invention]

[0008] However, even after dents are removed by cutting after heat treatment, dents may still occur in the outer diameter chamfered portion of the inner ring, and if dents do occur again, there is still a risk of cracks occurring due to the hoop stress generated in the inner ring.

[0009] Furthermore, when the inner diameter of the inner ring is expanded by hoop stress, the inner ring expands toward the outer diameter, changing the dimensions of the inner raceway surface formed on the inner ring, reducing the accuracy of the gap between the inner raceway surface of the inner ring and the rolling elements, which may shorten the life of the wheel bearing device.

[0010] The present invention has been made in consideration of the above circumstances, and provides a wheel bearing device that can reduce hoop stress generated in an inner ring in a configuration in which the inner ring is fixed by a crimped portion of a hub ring. [Means for solving the problem]

[0011] That is, the wheel bearing device comprises an outer member having a double-row outer raceway surface on its inner circumference, a hub ring having a small-diameter step portion extending axially on its outer circumference, and at least one inner ring press-fitted into the small-diameter step portion of the hub ring, an inner member having a double-row inner raceway surface opposing the double-row outer raceway surface, double-row rolling elements accommodated so as to be free to roll between the raceway surfaces of the outer member and the inner member, and a crimped portion formed by plastically deforming one axial end of the small-diameter step portion toward the outer diameter, the inner ring having an inner circumferential surface, an end face on one axial side of the inner ring, and an inner diameter chamfered portion that connects the inner circumferential surface of the inner ring to the end face on one side of the inner ring and that expands in diameter towards one axial side, the crimped portion being an unhardened portion that has not been hardened, and having an annular groove spaced apart from the inner ring. [Effects of the Invention]

[0012] According to the present invention, it is possible to reduce the hoop stress generated in the inner ring. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a side cross-sectional view showing a wheel bearing device. [Figure 2] 3 is a side cross-sectional view showing the vicinity of a caulking portion of a hub ring in a wheel bearing device. FIG. [Figure 3] 10 is a side cross-sectional view showing a wheel bearing device in a state where a crimped portion is not formed on a small diameter stepped portion of a hub wheel. FIG. [Figure 4] 10 is a side cross-sectional view showing a small diameter step portion in a state where a crimped portion is not formed, in which the outer side end of the annular groove is located on the outer side of the boundary point P3 of the inner ring. FIG. [Figure 5] 10 is a side cross-sectional view showing a small diameter step portion in a state where a crimped portion is not formed, in which the outer side end of the annular groove and the boundary point P3 of the inner ring are located at the same position. FIG. [Figure 6]1A and 1B are diagrams showing stress distribution in the crimped portion and the inner ring, where FIG. 1A is a diagram showing the case where the crimped portion does not have an annular groove, and FIG. 1B is a diagram showing the case where the crimped portion has an annular groove. [Figure 7] FIG. 3 is a cross-sectional side view showing an inner diameter chamfered portion of the inner ring. [Figure 8] FIG. 4 is a cross-sectional side view showing the outer chamfered portion of the inner ring. [Figure 9] FIG. 4 is a cross-sectional side view showing the relationship between the axial length of a straight surface of the inner ring and the radial length of the inner ring. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0015] [Wheel bearing device] A wheel bearing device 1 shown in FIG. 1 is one embodiment of a wheel bearing device according to the present invention, and supports a wheel rotatably in a suspension system of a vehicle such as an automobile.

[0016] In the following description, the axial direction refers to the direction along the rotational axis X of the wheel support bearing device 1, the radial direction refers to the direction perpendicular to the rotational axis X of the wheel support bearing device 1, and the circumferential direction refers to the direction along an arc centered on the rotational axis X of the wheel support bearing device 1. Additionally, the inner side refers to one side in the axial direction, which is the side facing the vehicle body when the wheel support bearing device 1 is attached to the vehicle body, and the outer side refers to the other side in the axial direction, which is the side facing the wheel when the wheel support bearing device 1 is attached to the vehicle body.

[0017] The wheel bearing device 1 has a configuration known as the third generation, and includes an outer ring 2 as an outer member, a hub ring 3 and an inner ring 4 as inner members, two rolling rows of inner ball rows 5 and outer ball rows 6, an inner sealing member 9, and an outer sealing member 10.

[0018] An inner side opening 2a is formed at the inner side end of the outer ring 2, into which an inner side seal member 9 can be fitted. An outer side opening 2b is formed at the outer side end of the outer ring 2, into which an outer side seal member 10 can be fitted.

[0019] An inner side seal member 9 is fitted into the inner side opening 2a, which is the inner side opening end of the annular space S formed by the outer ring 2 and the hub ring 3, and an outer side seal member 10 is fitted into the outer side opening 2b, which is the outer side opening end of the annular space S, thereby sealing the annular space S inside the bearing.

[0020] An inner-side outer raceway surface 2c and an outer-side outer raceway surface 2d are formed on the inner peripheral surface 2p of the outer ring 2. A vehicle body mounting flange 2e for mounting the outer ring 2 to a vehicle body member is formed integrally on the outer peripheral surface 2o of the outer ring 2. The vehicle body mounting flange 2e is provided with bolt holes into which fastening members (here, bolts) are inserted to fasten the outer ring 2 to the vehicle body member.

[0021] A small diameter step 3a having a smaller diameter than the outer end is formed at the inner end of the outer peripheral surface 3o of the hub wheel 3. A shoulder 3e is formed at the outer end of the small diameter step 3a of the hub wheel 3.

[0022] A wheel mounting flange 3b for mounting a wheel is formed integrally with the outer end of the hub wheel 3. A plurality of bolt holes 3f are formed in the wheel mounting flange 3b. Hub bolts 3i for fastening the hub wheel 3 to a wheel or brake component can be press-fitted into the bolt holes 3f.

[0023] An outer inner raceway surface 3c is provided on the outer peripheral surface 3o of the hub wheel 3 so as to face the outer outer raceway surface 2d on the outer ring 2. In other words, the inner raceway surface 3c is formed on the outer side of the inner member by the hub wheel 3. A seal land portion 3d with which the seal lip of the outer seal member 10 slides is formed on the base side of the wheel mounting flange 3b of the hub wheel 3.

[0024] An inner ring 4 is provided on the small diameter step 3a of the hub ring 3. The inner ring 4 is fixed to the small diameter step 3a of the hub ring 3 by press fitting and crimping. The inner ring 4 applies preload to the inner ball row 5 and outer ball row 6, which are the rolling rows.

[0025] The inner ring 4 has an inner end face 4b at its inner end and an outer end face 4c at its outer end. The inner end face 4b is an example of an end face on one side of the inner ring, located on one side of the inner ring in the axial direction.

[0026] A crimped portion 3h is formed on the inner end of the small diameter step portion 3a of the hub wheel 3, and is crimped to the inner end face 4b of the inner ring 4. The inner ring 4 is fixed in the axial direction by the crimped portion 3h.

[0027] The crimped portion 3h is formed by plastically deforming the inner end portion, which is one axial end of the small diameter step portion 3a, toward the outer diameter side. The crimped portion 3h of the hub ring 3 and the inner end face 4b of the inner ring 4 are in planar contact in the axial direction.

[0028] An inner-side inner raceway surface 4a is provided on the outer peripheral surface 4o of the inner ring 4 so as to face the inner-side outer raceway surface 2c of the outer ring 2. In other words, the inner ring 4 forms the inner raceway surface 4a on the inner side of the inner member.

[0029] The inner ball row 5 and the outer ball row 6, which are rolling rows, are configured by a plurality of balls 7, which are rolling elements, being held by a cage 8.

[0030] The inner ball row 5 is 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 ball row 6 is rollably sandwiched between the inner raceway surface 3c of the hub ring 3 and the outer-side outer raceway surface 2d of the outer ring 2. In other words, the inner ball row 5 and the outer ball row 6 are rollably housed between the raceway surfaces of the outer member and the inner member.

[0031] In the wheel bearing device 1, a double-row angular contact ball bearing is formed by the outer ring 2, hub ring 3, inner ring 4, inner ball row 5, and outer ball row 6. Note that the wheel bearing device 1 may be formed as a double-row tapered roller bearing instead of the double-row angular contact ball bearing.

[0032] [Configuration of the caulking part of the inner ring and hub ring] As shown in Fig. 2, the inner ring 4 has an inner peripheral surface 4d that is a surface parallel to the axial direction, and an inner diameter chamfered portion 4f that connects the inner peripheral surface 4d and the inner end face 4b. The inner diameter chamfered portion 4f increases in diameter as it approaches the inner side. The inner peripheral surface 4d of the inner ring 4 is an example of an inner ring inner peripheral surface.

[0033] The outer peripheral surface 4o of the inner ring 4 has a straight surface 4e that is a surface parallel to the axial direction. The straight surface 4e is disposed on the inner side of the inner raceway surface 4a and is located at the inner end of the outer peripheral surface 4o. The inner periphery of an inner-side seal member 9 is fitted onto the straight surface 4e of the inner ring 4.

[0034] The inner ring 4 has an outer diameter chamfered portion 4g that connects the straight surface 4e and the inner end face 4b. The straight surface 4e is located adjacent to the outer diameter chamfered portion 4g. The diameter of the outer diameter chamfered portion 4g decreases toward the inner side.

[0035] The outer diameter chamfered portion 4g is formed by cutting a portion of the inner ring 4 corresponding to the outer diameter chamfered portion 4g, heat treating the portion, and then cutting the portion again after the heat treatment. In other words, the outer diameter chamfered portion 4g is a re-cut surface that is cut after the heat treatment.

[0036] The hub ring 3 has its surface hardened by induction hardening or the like over a range from the base of the wheel mounting flange 3b to the inner raceway surface 3c on the outer side and the middle of the small diameter step portion 3a in the axial direction.

[0037] Therefore, a hardened layer is formed on the surface of the hub wheel 3 in the range from the base of the wheel mounting flange 3b to the inner raceway surface 3c on the outer side and to the middle of the small diameter step portion 3a in the axial direction.

[0038] On the other hand, the crimped portion 3h of the hub ring 3 (the shaded portion in FIG. 2) is an unhardened portion that has not been hardened. In other words, the crimped portion 3h retains the hardness of the raw material surface after forging.

[0039] The crimped portion 3h of the hub ring 3 has a first outer peripheral surface 32 that faces the inner peripheral surface 4d of the inner ring 4, a second outer peripheral surface 33 that faces the inner diameter chamfered portion 4f of the inner ring 4, and a third outer peripheral surface 34 that faces the inner side end face 4b of the inner ring 4. The first outer peripheral surface 32 is an example of a crimped portion outer peripheral surface that faces the inner peripheral surface of the inner ring.

[0040] The first outer peripheral surface 32 of the crimped portion 3h has an annular groove 31 that is recessed toward the inner diameter side and spaced apart in the radial direction from the inner peripheral surface 4d of the inner ring 4. The annular groove 31 is formed along the circumferential direction, and is formed over the entire circumference of the first outer peripheral surface 32.

[0041] The first outer peripheral surface 32, except for the annular groove 31, is in contact with the inner peripheral surface 4d of the inner ring 4. The second outer peripheral surface 33 is in contact with the inner diameter chamfered portion 4f of the inner ring 4. The third outer peripheral surface 34 is in contact with the inner side end face 4b of the inner ring 4.

[0042] [Small diameter step on hub before crimping] As shown in FIGS. 3 and 4, in the hub wheel 3, the small diameter stepped portion 3a before the crimped portion 3h is formed extends further inward than the inner end face 4b of the inner ring 4.

[0043] Before the crimped portion 3h is formed, an annular groove 30 is formed on the outer peripheral surface of the small diameter step portion 3a. The annular groove 30 is formed along the circumferential direction, and is formed over the entire circumference of the outer peripheral surface of the small diameter step portion 3a.

[0044] The annular groove 30 has an outer end P1 and an inner end P2 in the axial direction.

[0045] An outer end P1 of the annular groove 30 is located axially outer than a boundary point P3 between the inner circumferential surface 4d and the inner diameter chamfered portion 4f of the inner ring 4. An inner end P2 of the annular groove 30 is located axially inner than the boundary point P3. In other words, the annular groove 30 is located axially across the inner circumferential surface 4d of the inner ring 4 and the inner diameter chamfered portion 4f.

[0046] [Effects of the annular groove in the crimped portion] The crimped portion 3h is formed by plastically deforming the inner end of the small diameter step portion 3a, where the annular groove 30 is formed, toward the outer diameter side. Since the small diameter step portion 3a has the annular groove 30 before the crimped portion 3h is formed, the formed crimped portion 3h has the annular groove 30, and therefore the annular groove 31, which is spaced apart from the inner ring 4.

[0047] When the inner end of the small diameter step portion 3a is plastically deformed toward the outer diameter to form the crimped portion 3h, hoop stress is generated in the inner ring 4. However, since the crimped portion 3h has an annular groove 31 that is radially spaced away from the inner ring 4, it is possible to suppress the load applied to the inner ring 4 and reduce the hoop stress generated in the inner ring 4.

[0048] This reduces the amount of expansion of the inner ring 4 toward the outer diameter side caused by crimping the small diameter step portion 3a, suppresses dimensional changes to the inner raceway surface, and improves the accuracy of the gap between the inner raceway surface of the inner ring and the rolling elements, thereby extending the life of the wheel bearing device.

[0049] In addition, by reducing the hoop stress generated in the inner ring 4, even if there is a dent in the outer diameter chamfered portion 4g of the inner ring 4, it is possible to prevent cracks from occurring due to the hoop stress generated in the inner ring 4.

[0050] In this case, it is preferable that the radial groove depth d of the annular groove 30 formed in the small diameter step portion 3a is set to 0.2 mm to 0.9 mm.

[0051] This is because if the groove depth d of the annular groove 30 exceeds 0.9 mm, stress will concentrate at locations on the inner ring 4 that correspond to the ends of the annular groove 31 formed in the crimped portion 3h, which could result in cracks due to the stress concentration in the inner ring 4. Furthermore, if the groove depth d of the annular groove 30 is less than 0.2 mm, the annular groove 31 will not be formed when the crimped portion 3h is formed, making it difficult to effectively reduce hoop stress.

[0052] Furthermore, since the outer end P1 of the annular groove 30 in the small diameter step portion 3a before the crimped portion 3h is formed is located on the outer side of the boundary point P3 of the inner ring 4, when the small diameter step portion 3a is plastically deformed to form the crimped portion 3h, the annular groove 31 can be formed in a position facing the inner surface 4d of the inner ring 4.

[0053] In this way, by forming the annular groove 31 at a position facing the inner surface 4d of the inner ring 4, it is possible to effectively suppress the load from being applied to the inner ring 4 and reduce the hoop stress generated in the inner ring 4.

[0054] In this embodiment, the annular groove 31 of the crimped portion 3h faces the inner peripheral surface 4d of the inner ring 4 entirely from the outer side end to the inner side end, but a portion of the inner side may overlap the inner diameter chamfered portion 4f of the inner ring 4. In other words, the annular groove 31 may be formed across the inner peripheral surface 4d of the inner ring 4 and the inner diameter chamfered portion 4f.

[0055] 4, in this embodiment, the outer end P1 of the annular groove 30 in the small diameter step portion 3a before the crimped portion 3h is formed is located closer to the outer side than the boundary point P3 of the inner ring 4, but as shown in FIG. 5, the annular groove 30 can also be arranged so that the outer end P1 is located at the same position in the axial direction as the boundary point P3 of the inner ring 4. In the above case, the annular groove 31 is formed so that the crimped portion 3h is spaced apart from the inner diameter chamfered portion 4f when the small diameter step portion 3a is crimped. Therefore, the annular groove 31 is formed so that the crimped portion 3h and the inner diameter chamfered portion 4f are spaced apart in both the radial and axial directions.

[0056] However, if the annular groove 30 is positioned so that the outer side end P1 is located on the inner side of the boundary point P3 of the inner ring 4, it becomes difficult to form the annular groove 31 in the crimped portion 3h, and the effect of reducing the hoop stress of the inner ring 4 cannot be expected, which is not desirable.

[0057] [Stress distribution in the crimped part and inner ring] FIG. 6(a) shows the stress distribution in the crimped portion 3h and the inner ring 4 in the case where the crimped portion 3h formed on the small diameter step portion 3a does not have the annular groove 31.

[0058] In FIG. 6(a), the stress distribution at the outer diameter chamfered portion 4g of the inner ring 4 is high due to the hoop stress generated in the inner ring 4.

[0059] In this way, when the stress distribution in the outer diameter chamfered portion 4g of the inner ring 4 is high and a dent is present in the outer diameter chamfered portion 4g, stress concentration at the dent is promoted, and there is a risk that a crack will occur in the inner ring 4 starting from the dent.

[0060] Moreover, the stress distribution is relatively high on the straight surface 4e and the inner raceway surface 4a of the inner ring 4.

[0061] In this way, if the stress distribution on the straight surface 4e and inner raceway surface 4a of the inner ring 4 is high, the dimensions of the inner raceway surface 4a will change, reducing the accuracy of the gap between the inner raceway surface 4a of the inner ring 4 and the balls 7, and there is a risk that the sealing torque of the inner side seal member 9 fitted to the straight surface 4e will change.

[0062] On the other hand, FIG. 6(b) shows the stress distribution in the crimped portion 3h and the inner ring 4 when the crimped portion 3h formed in the small diameter step portion 3a has an annular groove 31 as in this embodiment.

[0063] When the crimped portion 3h has an annular groove 31, when the inner end portion of the small diameter step portion 3a is plastically deformed toward the outer diameter side, the annular groove 31 reduces the load applied to the inner ring 4, thereby reducing the hoop stress generated in the inner ring 4.

[0064] Therefore, in the inner ring 4 shown in Figure 6(b), the stress distribution in the outer diameter chamfered portion 4g is lower than in the case where the annular groove 31 is not formed in the crimped portion 3h shown in Figure 6(a). As a result, even if a dent is present in the outer diameter chamfered portion 4g of the inner ring 4, it is possible to suppress the occurrence of cracks due to hoop stress generated in the inner ring 4.

[0065] In addition, in Figure 6(b), the stress distribution on the straight surface 4e and the inner raceway surface 4a of the inner ring 4 is lower than when the annular groove 31 is not formed in the crimped portion 3h shown in Figure 6(a).

[0066] In this way, by keeping the stress distribution on the straight surface 4e and the inner raceway surface 4a of the inner ring 4 low, the dimensional change of the inner raceway surface 4a is reduced, improving the gap precision between the inner raceway surface 4a and the balls 7 and stabilizing the sealing torque of the inner-side seal member 9 fitted to the straight surface 4e.

[0067] [Inner ring inner diameter chamfer] 7, the inner diameter chamfered portion 4f of the inner ring 4 has an inner diameter tapered surface 41 and an inner diameter arcuate surface 42. The inner diameter tapered surface 41 extends from the inner axial end of the inner circumferential surface 4d of the inner ring 4 toward the inner side, which is one axial side. The inner diameter tapered surface 41 is located at the outer end of the inner diameter chamfered portion 4f.

[0068] The inner diameter tapered surface 41 is inclined with respect to the axial direction and increases in diameter as it goes inward. The inner diameter tapered surface 41 is formed linearly when viewed in the circumferential direction. The inclination angle θ1 of the inner diameter tapered surface 41 with respect to the axial direction is set to be equal to or greater than 5 degrees and equal to or less than 25 degrees.

[0069] The inner arcuate surface 42 is located between the inner tapered surface 41 and the inner end face 4b. The inner tapered surface 41 and the inner end face 4b are connected by the inner arcuate surface 42. The inner arcuate surface 42 expands in diameter as it approaches the inner side. When viewed in the circumferential direction, the inner arcuate surface 42 is formed in an arc shape that is convex toward the inner diameter side.

[0070] Since the inner diameter chamfered portion 4f of the inner ring 4 has an inner diameter tapered surface 41 at the outer end, the amount of protrusion of the inner diameter chamfered portion 4f toward the inner diameter side can be reduced compared to when the inner diameter chamfered portion 4f is formed in an arc shape overall.

[0071] Therefore, when the small diameter step portion 3a of the hub wheel 3 is crimped to the inner ring 4, the inner ring 4 can be securely fixed to the small diameter step portion 3a while the load applied to the inner ring 4 can be kept to an appropriate level, thereby reducing the hoop stress generated in the inner ring 4.

[0072] If the inclination angle θ1 of the inner diameter tapered surface 41 is less than 5 degrees, it may not be possible to sufficiently reduce the hoop stress generated in the inner ring 4. On the other hand, if the inclination angle θ1 of the inner diameter tapered surface 41 is greater than 25 degrees, it may be possible to impair stable fixation of the inner ring 4 to the small diameter step portion 3a. Therefore, it is preferable that the inclination angle θ1 of the inner diameter tapered surface 41 be greater than or equal to 5 degrees and less than or equal to 25 degrees.

[0073] [Outer chamfer of inner ring] As shown in Fig. 8, the outer chamfered portion 4g of the inner ring 4 has an outer tapered surface 43 and an outer arcuate surface 44. The outer tapered surface 43 extends from the inner end in the axial direction of the straight surface 4e of the inner ring 4 toward the inner side, which is one side in the axial direction. The outer tapered surface 43 is located at the outer end of the outer chamfered portion 4g.

[0074] The outer tapered surface 43 is inclined with respect to the axial direction, and its diameter decreases toward the inner side. The outer tapered surface 43 is formed linearly when viewed in the circumferential direction. The inclination angle θ2 of the outer tapered surface 43 with respect to the axial direction is set to be equal to or greater than 10 degrees and equal to or less than 20 degrees.

[0075] The outer arcuate surface 44 is located between the outer tapered surface 43 and the inner end surface 4b. The outer tapered surface 43 and the inner end surface 4b are connected by the outer arcuate surface 44.

[0076] The outer arcuate surface 44 has a diameter that decreases toward the inner side. When viewed from the circumferential direction, the outer arcuate surface 44 is formed into an arc shape that is convex toward the outer diameter side. The radius of curvature R of the outer arcuate surface 44 is set to be equal to or greater than 1.0 mm and equal to or less than 2.0 mm.

[0077] Since the outer chamfered portion 4g of the inner ring 4 has an outer tapered surface 43 at the outer end, the amount of protrusion of the outer chamfered portion 4g toward the outer side can be reduced compared to when the outer chamfered portion 4g is formed into an arc shape overall.

[0078] This reduces the weight of the inner ring 4, thereby reducing the weight of the wheel bearing device 1. Furthermore, compared to when the outer chamfered portion 4g is formed in an arc shape overall, stress concentration at the outer chamfered portion 4g is alleviated, making it possible to prevent cracks from occurring in the inner ring 4.

[0079] Furthermore, since the outer chamfered portion 4g has an outer diameter tapered surface 43, the circularity of the inner side seal member 9 fitted to the inner ring 4 can be maintained and the interference between the inner side seal member 9 and the inner ring 4 can be stabilized, thereby suppressing an increase in torque of the wheel bearing device 1 due to the inner side seal member 9.

[0080] If the inclination angle θ2 of the outer diameter tapered surface 43 is less than 10 degrees, it may be difficult to sufficiently reduce the weight of the wheel bearing device 1. On the other hand, if the inclination angle θ2 of the outer diameter tapered surface 43 is greater than 20 degrees, it may be difficult to sufficiently alleviate the stress concentration that occurs in the outer diameter chamfered portion 4g. Therefore, it is preferable that the inclination angle θ2 of the outer diameter tapered surface 43 be equal to or greater than 10 degrees and equal to or less than 20 degrees.

[0081] Furthermore, if the radius of curvature R of the outer arcuate surface 44 is smaller than 1.0 mm, it may be impossible to sufficiently alleviate the stress concentration that occurs in the outer chamfered portion 4g. On the other hand, if the radius of curvature R of the outer arcuate surface 44 is larger than 2.0 mm, the range in the outer chamfered portion 4g where the outer tapered surface 43 is formed becomes smaller, and it may be impossible to fully achieve the effect of forming the outer tapered surface 43. Therefore, it is preferable that the radius of curvature R of the outer arcuate surface 44 be 1.0 mm or more and 2.0 mm or less.

[0082] [Relationship between the axial length of the straight surface of the inner ring and the radial length of the inner ring] 9, the axial length of the straight surface 4e of the inner ring 4 is s, and the radial length between the straight surface 4e and the inner peripheral surface 4d of the inner ring 4 is t.

[0083] In the inner ring 4, the axial length s of the straight surface 4e and the radial length t between the straight surface 4e and the inner peripheral surface 4d are set to satisfy the relationship 0.25≦(s / t)≦0.95. The axial length s of the straight surface 4e is set to be 3 mm or more and 11 mm or less.

[0084] In the inner ring 4, when the radial length t becomes smaller relative to the axial length s, the generated hoop stress tends to increase. Also, when the radial length t becomes larger relative to the axial length s, the weight of the wheel bearing device 1 increases, which tends to reduce the fuel efficiency of the vehicle.

[0085] In particular, when (axial length s / radial length t) is greater than 0.95, the increase in hoop stress generated in the inner ring 4 becomes significant, and when (axial length s / radial length t) is less than 0.25, the increase in weight of the wheel bearing device 1 becomes significant.

[0086] Therefore, by setting the axial length s and the radial length t to satisfy the relationship 0.25≦(s / t)≦0.95, it is possible to reduce the hoop stress generated in the inner ring 4 and suppress an increase in the weight of the wheel bearing device 1. This makes it possible to optimize the magnitude of the hoop stress generated in the inner ring 4 and the weight of the wheel bearing device 1.

[0087] Furthermore, in the inner ring 4, as the axial length s of the straight surface 4e becomes smaller, the generated hoop stress tends to increase, and as the axial length s of the straight surface 4e becomes larger, the weight of the wheel bearing device 1 tends to increase, resulting in a decrease in vehicle fuel efficiency.

[0088] In particular, when the axial length s is smaller than 3 mm, the increase in the generated hoop stress becomes significant, and when the axial length s is larger than 11 mm, the increase in the weight of the wheel bearing device 1 becomes significant.

[0089] Therefore, by setting the axial length s in the range of 3 mm or more and 11 mm or less, it is possible to reduce the hoop stress generated in the inner ring 4 and suppress an increase in the weight of the wheel bearing device 1. This makes it possible to optimize the magnitude of the hoop stress generated in the inner ring 4 and the weight of the wheel bearing device 1.

[0090] In this embodiment, the wheel bearing device 1 for a driving wheel has been described, but the present invention can also be applied to a wheel bearing device for a driven wheel.

[0091] Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, which are merely examples, and it goes without saying that the present invention can be embodied in various other forms without departing from the spirit of the present invention. The scope of the present invention is indicated by the claims, and further includes the equivalent meanings set forth in the claims, and all modifications within the scope of the claims. [Explanation of symbols]

[0092] 1 Wheel bearing device 2 outer ring 2c (inner side) outer raceway 2d (Outer side) outer raceway 3 Hub Wheel 3a Small diameter stepped section 3c (hub ring) inner raceway 3h Crimping part 4. Inner Circle 4a (inner ring) inner raceway 4b Inner end face 4d inner surface 4e Straight surface 4f Inner diameter chamfer 4g Outer diameter chamfer 5 Inner ball row 6 Outer ball row 7 Ball 31 Annular groove 32 First outer peripheral surface 41 Inner diameter tapered surface 42 Inner diameter arc surface 43 Outer diameter tapered surface 44 Outer diameter arc surface θ1 (inner diameter tapered surface) inclination angle θ2 (Outer diameter tapered surface) inclination angle R (radius of curvature of outer arc surface) s Axial length (of straight surface) t Radial length (between the straight surface and inner peripheral surface of the inner ring)

Claims

1. an outer member having a double-row outer raceway surface on its inner periphery; an inner member including a hub ring having an axially extending small diameter stepped portion on its outer periphery and at least one inner ring press-fitted into the small diameter stepped portion of the hub ring, the inner member having double row inner raceway surfaces facing the double row outer raceway surfaces; double-row rolling elements rollably accommodated between the raceway surfaces of the outer member and the inner member; a crimping portion formed by plastically deforming one end of the small diameter step portion in the axial direction toward the outer diameter side, the inner ring being fixed in the axial direction; the inner ring has an inner peripheral surface, one end face of the inner ring in the axial direction, and an inner diameter chamfered portion connecting the inner peripheral surface of the inner ring to the one end face of the inner ring and increasing in diameter toward one side in the axial direction, The crimped portion is an unhardened portion that has not been hardened, and has an annular groove that is spaced apart from the inner ring.

2. the crimped portion has an outer circumferential surface facing the inner circumferential surface of the inner ring, 2. The wheel bearing device according to claim 1, wherein the annular groove is formed on the outer peripheral surface of the crimped portion and is spaced apart from the inner peripheral surface of the inner ring.

3. the inner diameter chamfered portion has an inner diameter tapered surface extending from an inner circumferential surface of the inner ring toward one side in the axial direction, and an inner diameter arcuate surface located between the inner diameter tapered surface and one end face of the inner ring, 3. The wheel bearing device according to claim 1, wherein the angle of inclination of the inner diameter tapered surface relative to the axial direction is between 5 degrees and 25 degrees.

4. the inner ring has an inner ring outer peripheral surface and an outer diameter chamfered portion connecting the inner ring outer peripheral surface to one end face of the inner ring and decreasing in diameter toward one side in the axial direction, the outer diameter chamfered portion has an outer diameter tapered surface extending from the outer peripheral surface of the inner ring toward one side in the axial direction, and an outer diameter arcuate surface located between the outer diameter tapered surface and one end face of the inner ring, 3. The wheel bearing device according to claim 1, wherein the inclination angle of the outer diameter tapered surface relative to the axial direction is 10 degrees or more and 20 degrees or less, and the radius of curvature of the outer diameter arcuate surface is 1.0 mm or more and 2.0 mm or less.

5. the inner ring outer peripheral surface has a straight surface parallel to the axial direction located adjacent to the outer diameter chamfered portion, The axial length s of the straight surface is 3 mm or more and 11 mm or less, the axial length s and the radial length t between the straight surface of the inner ring and the inner peripheral surface of the inner ring, 0.25≦(s / t)≦0.95 3. The wheel bearing device according to claim 1, wherein the following relationship is satisfied:

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