Drive wheel bearing device

Abstract

A drive wheel bearing device (1) for rotatably supporting a drive wheel (3) of a vehicle comprises: an outer ring (10); a hub ring (20); an inner ring (30); a plurality of hub rolling bodies (40); and a plurality of inner ring rolling bodies (50). The hub ring (20) has: a hub raceway part (21) having a hub raceway surface (22); and a hub fitting part (23) that is provided closer to the vehicle body side than the hub raceway part (21) is and onto which the inner ring (30) is press-fitted. The inner ring (30) has: an inner ring raceway part (31) press-fitted onto the hub fitting part (23) and having an inner ring raceway surface (32); and an inner ring thin part (33) press-fitted onto the hub fitting part (23) together with the inner ring raceway part (31) and having a smaller thickness in the radial direction (Y) than the inner ring raceway part (31).

Description

Drive wheel bearing device

[0001] The present disclosure relates to a bearing device for a drive wheel.

[0002] Patent Document 1 below discloses a rolling bearing device. This rolling bearing device includes an outer ring having a double-row raceway surface on its inner periphery, a hub shaft which is an inner shaft having a raceway surface on its outer periphery, an inner ring which is press-fitted into a fitting portion of the hub shaft and has a raceway surface on its outer periphery, and a plurality of rolling elements arranged between the double-row raceway surface of the outer ring and the raceway surfaces of the inner shaft and inner ring.

[0003] JP 2010-133482 A

[0004] The above-mentioned rolling bearing device was constructed with the objective of suppressing the amount of contraction of the inner diameter of the spline bore while ensuring creep resistance. In the design of a driving wheel bearing device such as this one that rotatably supports the driving wheels of a vehicle, in order to suppress variation in bearing performance, a technology is required to suppress the expansion of the diameter of the inner ring raceway provided on the inner ring when the inner ring is press-fitted into the fitting portion of the hub axle.

[0005] The present disclosure seeks to provide a bearing device for a driving wheel that can suppress expansion of the diameter of the inner ring raceway surface when the inner ring is press-fitted onto the hub axle.

[0006] One aspect of the present disclosure is a driving wheel bearing device that rotatably supports a driving wheel of a vehicle, comprising: a cylindrical outer ring fixed to a vehicle body member and having a plurality of raceway surfaces on an inner periphery; a cylindrical hub ring having a hub raceway surface facing a driving wheel side raceway surface of the plurality of raceway surfaces of the outer ring and rotating together with the driving wheel; a cylindrical inner ring having an inner ring raceway surface facing a vehicle body side raceway surface of the outer ring and rotating together with the hub ring; a plurality of hub rolling elements provided between the driving wheel side raceway surface of the outer ring and the hub raceway surface of the hub ring; and a plurality of inner ring rolling elements provided between the vehicle body side raceway surface of the outer ring and the inner ring raceway surface of the inner ring, wherein the hub ring has: a hub raceway portion having the hub raceway surface; and a hub fitting portion provided closer to the vehicle body than the hub raceway portion and into which the inner ring is press-fitted, and the inner ring has: an inner ring raceway portion press-fitted into the hub fitting portion and having the inner ring raceway surface, and an inner ring thin-walled portion which is press-fitted into the hub fitting portion together with the inner ring raceway and has a radial thickness thinner than that of the inner ring raceway.

[0007] In the driving wheel bearing device of the above aspect, the inner ring is provided with an inner ring raceway portion having an inner ring raceway surface, and an inner ring thin-walled portion that is thinner in the radial direction than the inner ring raceway portion. When the inner ring is assembled to the hub wheel, both the inner ring raceway portion and the inner ring thin-walled portion of the inner ring are press-fitted into the hub fitting portion of the hub wheel. The inner ring thin-walled portion has lower rigidity during press-fitting than the inner ring raceway portion. By providing the inner ring with an inner ring thin-walled portion that has lower rigidity during press-fitting than the inner ring raceway portion, it is possible to prevent the inner ring raceway surface from expanding in the radial direction due to the load that the inner ring raceway portion receives from the hub fitting portion when the inner ring is press-fitted into the hub fitting portion of the hub wheel.

[0008] According to the above-described aspect, it is possible to provide a bearing device for a driving wheel that can suppress the inner ring raceway surface from expanding in diameter when the inner ring is press-fitted onto the hub axle.

[0009] Note that the symbols in parentheses in the claims indicate the correspondence with the specific means described in the embodiments described below, and do not limit the technical scope of the present disclosure.

[0010] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is an axial cross-sectional view of a bearing device for a drive wheel according to a first embodiment, Fig. 2 is an axial cross-sectional view showing an enlarged portion of the bearing device for a drive wheel according to Fig. 1, Fig. 3 is a cross-sectional view taken along line III-III in Fig. 1, Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 1, and Fig. 5 is an axial cross-sectional view showing an enlarged portion of the bearing device for a drive wheel according to a second embodiment.

[0011] An embodiment of the driving wheel bearing device according to the present invention will be described below with reference to the drawings. In the drawings, unless otherwise specified, the axial direction along the central axis of the outer joint member is indicated by arrow X, the radial direction perpendicular to the central axis is indicated by arrow Y, and the circumferential direction is indicated by arrow Z.

[0012] (Embodiment 1) 1. Overall Configuration of Bearing Device for Drive Wheel 1 As shown in Figure 1, a bearing device for drive wheel 1 of embodiment 1 (hereinafter simply referred to as "bearing device") 1 is mounted on a vehicle powered by an electric motor or an internal combustion engine. This bearing device 1 transmits torque generated by a drive source (not shown) and input to an outer joint member 5 of a constant velocity joint to a drive wheel 3, and rotatably supports the drive wheel 3. The bearing device 1 includes an outer joint member 5, an outer ring 10, a hub ring 20, an inner ring 30, a plurality of hub rolling elements 40, and an inner ring rolling element 50.

[0013] 2. Structure of Outer Joint Member 5 The outer joint member 5 has a cylindrical portion 6 having a bottom and a stem portion 7 extending from the center of the cylindrical portion 6 in the radial direction Y on a central axis L1 in the axial direction X. The outer joint member 5 is assembled to the hub wheel 20.

[0014] Although not shown, the housing space 6a of the cylindrical portion 6 houses a plurality of components, such as an inner joint member (not shown) fixed to the outer periphery of a shaft connected to a drive source, and a plurality of rolling elements (not shown) for connecting to the inner joint member so as to transmit torque. The inner joint member is tiltable relative to the outer joint member 5 about a predetermined joint center point P on the central axis L2.

[0015] The stem portion 7 is connected to the hub wheel 20 via spline engagement to enable torque transmission. The stem portion 7 is a splined shaft having an engagement portion 7a that engages with a splined hole 20a provided in the hub wheel 20 and a male thread portion 7b provided at the end on the drive wheel 3 side. Convex teeth provided on the outer surface of the engagement portion 7a engage with concave grooves provided on the inner circumferential surface of the splined hole 20a. This connects the stem portion 7 to the hub wheel 20. The portion where the concave grooves provided on the inner circumferential surface of the splined hole 20a engage with the convex teeth provided on the outer circumferential surface of the engagement portion 7a forms a torque transmission portion 25 that transmits torque from the outer joint member 5 to the hub wheel 20. In this embodiment, the length of the convex teeth in the axial direction X is shorter than the length of the concave grooves in the axial direction X. Therefore, the axial position of the engagement portion 7a is the axial position of the torque transmission portion 25.

[0016] The outer joint member 5 is integrally assembled to the hub wheel 20 by threading a nut (not shown) onto the male threaded portion 7b and tightening it, with the stem portion 7 inserted into the spline hole 20a of the hub wheel 20. Before assembling the outer joint member 5, the inner ring 30 is press-fitted into the hub wheel 20 to form a composite body (hereinafter referred to as the "hub assembly") in which the hub wheel 20 and the inner ring 30 are integrated. In short, in manufacturing the bearing device 1 of this embodiment, the process of press-fitting the inner ring 30 into the hub wheel 20 is carried out, and then the process of assembling the outer joint member 5 to the hub assembly is carried out.

[0017] The engaging portion 7a of the stem portion 7 does not overlap the inner ring raceway portion 31 of the inner ring 30 in the radial direction Y. This prevents the inner ring raceway surface 32 from expanding in the radial direction Y due to the load that the inner ring raceway portion 31 receives from the engaging portion 7a of the stem portion 7 when the outer joint member 5 is assembled to the hub assembly.

[0018] 3. Structure of the Outer Ring 10 The outer ring 10 is formed in a cylindrical shape. The inner periphery of the outer ring 10 is provided with a plurality of raceway surfaces 11, 12 arranged in two rows with a gap in the axial direction X. The raceway surface 11 is an annular raceway surface for a plurality of hub rolling elements 40. The raceway surface 11 is a drive wheel-side raceway surface 11 located on the drive wheel 3 side in the axial direction X with respect to the raceway surface 12. The raceway surface 12 is an annular raceway surface for a plurality of inner ring rolling elements 50. The raceway surface 12 is a vehicle body-side raceway surface 12 located on the vehicle body side in the axial direction X with respect to the raceway surface 11. The outer ring 10 is fixed to a vehicle body member 2 with bolts (not shown). The vehicle body member 2 is, for example, a member called a "knuckle." A seal mechanism 13 is interposed between the outer ring 10 and the hub wheel 20, and a seal mechanism 14 is interposed between the outer ring 10 and the inner ring 30.

[0019] 4. Structure of the hub wheel 20 The hub wheel 20 includes a cylindrical portion 20b and a flange portion 20c. The cylindrical portion 20b has a cylindrical shape with a spline hole 20a. The cylindrical portion 20b includes a hub raceway portion 21 and a hub fitting portion 23 that are adjacent to each other in the axial direction X.

[0020] The hub raceway 21 is a portion having a hub raceway surface 22 that faces the raceway surface 11 of the outer ring 10. The hub raceway surface 22 is formed in an annular shape in the circumferential direction Z on the outer peripheral surface of the hub raceway 21 of the hub wheel 20. The hub fitting portion 23 is provided closer to the vehicle body than the hub raceway 21, and is the portion into which the inner ring 30 is press-fitted.

[0021] The flange portion 20c is formed in an annular shape. A plurality of bolts 4 are fixed to the flange portion 20c, and the drive wheel 3 is attached to a flange surface 20d of the flange portion 20c via the plurality of bolts 4. This allows the hub wheel 20 to rotate together with the drive wheel 3.

[0022] 5. Structure of the Inner Ring 30 The inner ring 30 is formed in a cylindrical shape. The inner ring 30 is press-fitted into the hub ring 20 to rotate together with the hub ring 20. The inner ring 30 has an inner ring raceway portion 31 and an inner ring thin portion 33. The inner ring raceway portion 31 is a portion having an inner ring raceway surface 32 that faces the raceway surface 12 of the outer ring 10. The inner ring raceway surface 32 is formed in an annular shape in the circumferential direction Z on the outer peripheral surface of the inner ring raceway portion 31 of the inner ring 30.

[0023] The inner ring thin portion 33 is a portion that is thinner in the radial direction Y (direction perpendicular to the center axis L1) than the inner ring raceway 31. Therefore, the inner ring raceway 31 is a thick portion relative to the inner ring thin portion 33. The inner diameter of the inner ring thin portion 33 in the radial direction Y is the same as that of the inner ring raceway 31, and the outer diameter in the radial direction Y is smaller than that of the inner ring raceway 31.

[0024] When the inner ring 30 is assembled to the hub wheel 20, both the inner ring raceway 31 and the inner ring thin-walled portion 33 of the inner ring 30 are press-fitted into the hub fitting portion 23 of the hub wheel 20. The inner ring thin-walled portion 33 is provided on the inner ring 30 to prevent the inner ring raceway surface 32 from expanding in diameter in the radial direction Y due to the load that the inner ring raceway 31 receives from the hub fitting portion 23 when the inner ring 30 is press-fitted into the hub fitting portion 23 of the hub wheel 20.

[0025] 2, a detailed cross-sectional structure of the tubular portion 6 of the outer joint member 5, the hub wheel 20, and the inner ring 30 and their surroundings will be described. This cross-sectional structure includes four regions A1 to A4 in the axial direction X.

[0026] The cylindrical portion 6 of the outer joint member 5 is provided with a joint abutment surface 6b. The cylindrical portion 6 has an inclined portion 8 that extends at an angle in both the axial direction X and the radial direction Y. An inclined surface 8a of the inclined portion 8 is provided in a portion of the cylindrical portion 6 corresponding to the first region A1. The inclined surface 8a extends from the joint abutment surface 6b toward the stem portion 7. Therefore, the outer joint member 5 abuts against the inner ring 30 at the joint abutment surface 6b, which is located outside the inclined surface 8a in the radial direction Y. The inclined surface 8a is preferably a surface that extends linearly in a cross section taken along the axial direction X. This improves the workability of the inclined surface 8a. If necessary, the inclined surface 8a may be modified to a curved surface or the like.

[0027] In this embodiment, it is preferable that the thickness t of the inclined portion 8 becomes thinner toward the outside in the radial direction Y. In this case, the thickness t is defined as the dimension of the inclined portion 8 in a direction perpendicular to the inclined surface 8 a, for example. This improves formability when the outer joint member 5 is formed by forging.

[0028] The hub wheel 20 does not have a portion corresponding to the first region A1. The portion of the hub wheel 20 corresponding to the second region A2 is the hub fitting portion 23 described above. The hub fitting portion 23 is made up of a hub thick portion 23a and a hub thin portion 23b that are adjacent to each other in the axial direction X. The hub thin portion 23b is a portion that is thinner in the radial direction Y than the hub thick portion 23a and the torque transmission portion 25 described above. The hub thin portion 23b is also configured so that its inner diameter in the radial direction Y is the same as that of the hub thick portion 23a, and its outer diameter in the radial direction Y is smaller than that of the hub thick portion 23a.

[0029] In this embodiment, the hub thin portion 23b of the hub wheel 20 overlaps the inner ring raceway 31 of the inner ring 30 in the radial direction Y, but does not overlap the inner ring thin portion 33 of the inner ring 30 in the radial direction Y. Therefore, when the inner ring 30 is press-fitted into the hub fitting portion 23 of the hub wheel 20, the inner ring raceway 31 is less affected by the load from the hub wheel 20 than if the hub thin portion 23b were the same thickness as the hub thick portion 23a. Furthermore, the hub thin portion 23b is formed to be thinner in the radial direction Y than the inner ring raceway 31 of the inner ring 30. This allows the inner ring raceway 31 to be set to have higher rigidity during press-fitting than the hub thick portion 23a. This prevents the inner ring raceway surface 32 from expanding in the radial direction Y due to the load the inner ring raceway 31 receives from the hub wheel 20. As a result, variations in the bearing performance of the bearing device 1 can be reduced.

[0030] By making the inner ring raceway 31 a thicker portion than the inner ring thin portion 33, the rigidity of the hub wheel 20 can be increased compared to when the thickness of the inner ring raceway 31 in the radial direction Y is the same as the inner ring thin portion 33. This can improve the handling stability of the vehicle.

[0031] The portion of the hub wheel 20 that corresponds to the third region A3 is the hub intermediate portion 24 that overlaps with the inner ring intermediate portion 34 of the inner ring 30 in the radial direction Y. The thickness of the hub intermediate portion 24 in the radial direction Y is the same as the thickness of the hub thick portion 23 a in the radial direction Y, and is thicker than the thickness of the hub thin portion 23 b in the radial direction Y. The hub intermediate portion 24 is configured as part of the torque transmission portion 25.

[0032] In this embodiment, the torque transmission portion 25 of the hub wheel 20 overlaps with the inner ring thin portion 33 of the inner ring 30 in the radial direction Y, but does not overlap with the inner ring raceway 31 of the inner ring 30 in the radial direction Y. For this reason, when the inner ring 30 is press-fitted into the hub fitting portion 23 of the hub wheel 20, the torque transmission portion 25 is less affected by the load received from the inner ring 30 than if the inner ring thin portion 33 had the same thickness as the inner ring raceway 31. This makes it possible to prevent the torque transmission portion 25 from reducing in diameter in the radial direction Y due to the load received from the inner ring 30. As a result, variation in spline accuracy of the torque transmission portion 25 can be reduced.

[0033] The portion of the inner ring 30 corresponding to the first region A1 is a contact portion 35 that contacts the sealing mechanism 14. The contact portion 35 has a contact surface 35a and a relief surface 35b. The contact surface 35a is provided on an end face of the inner ring 30 closer to the outer joint member 5 than the inner ring raceway surface 32, and abuts against a joint contact surface 6b provided on the tubular portion 6 of the outer joint member 5. The contact surface 35a is a surface that extends in the circumferential direction Z (see FIG. 3 ). The relief surface 35b is a surface that extends from the contact surface 35a at an angle relative to the contact surface 35a. The relief surface 35b faces an inclined surface 8a provided on the inclined portion 8 of the outer joint member 5 across a gap 9.

[0034] By providing the inclined surface 8a on the outer joint member 5 and the relief surface 35b on the inner ring 30, it is possible to realize a structure that makes it easy to position the contact surface 35a of the inner ring 30 outward in the radial direction Y. This makes it possible to shorten the distance in the axial direction X from the joint center point P (see FIG. 1) of the constant velocity joint to the flange surface 20d (see FIG. 1) of the hub ring 20 without reducing rigidity against bending loads.

[0035] The portion of the inner ring 30 corresponding to the third region A3 is an inner ring intermediate portion 34 provided between the inner ring raceway portion 31 and the inner ring thin-wall portion 33. The inner ring intermediate portion 34 has an inclined surface 34a extending between the inner ring raceway surface 32 of the inner ring raceway portion 31 and the outer peripheral surface 33a of the inner ring thin-wall portion 33. A step is formed by the inclined surface 34a between the inner ring raceway surface 32 and the outer peripheral surface 33a.

[0036] In this embodiment, the thickness of the inner ring intermediate portion 34 in the radial direction Y gradually changes in the axial direction X from the inner ring raceway 31 side to the inner ring thin-walled portion 33 side. That is, the thickness of the inner ring intermediate portion 34 in the radial direction Y gradually decreases from the inner ring raceway 31 side toward the inner ring thin-walled portion 33 side, and gradually increases from the inner ring thin-walled portion 33 side toward the inner ring raceway 31 side.

[0037] As described above, the third region A3 is provided with the hub intermediate portion 24 having a portion thicker than the hub thin portion 23b of the hub wheel 20, and also with the inner ring intermediate portion 34 having a portion thicker than the inner ring thin portion 33 of the inner ring 30. In this case, the third region A3 consisting of the hub intermediate portion 24 and the inner ring intermediate portion 34 is an intermediate region between the second region A2 and the fourth region A4, and this third region A3 is provided with a high rigidity portion having higher rigidity than the second region A2 and the fourth region A4.

[0038] By providing a high rigidity portion, it is possible to set the relative rigidity balance between the hub wheel 20 and the inner ring 30 so that the hub wheel 20 is more likely to deform in the radial direction Y only at the hub thin portion 23b, and the inner ring 30 is more likely to deform in the radial direction Y only at the inner ring thin portion 33. Such a high rigidity portion is also effective in increasing the rigidity of the hub wheel 20 and improving the handling stability of the vehicle.

[0039] The portion of the inner ring 30 corresponding to the second region A2 is the inner ring raceway portion 31. The portion of the inner ring 30 corresponding to the fourth region A4 is the inner ring thin portion 33.

[0040] 6. Structure of the hub rolling elements 40 As shown in Figures 1 and 3, a plurality of hub rolling elements 40 are provided between the raceway surface 11 of the outer ring 10 and the hub raceway surface 22 of the hub wheel 20. The plurality of hub rolling elements 40 are spherical bodies (balls) of the same shape. The plurality of hub rolling elements 40 function to support the outer ring 10 and the hub wheel 20 so that they can rotate relatively about the central axis L1 (see Figure 1) of the outer joint member 5. The number of hub rolling elements 40 is not limited to that shown in Figure 3 and can be set to any appropriate number.

[0041] 7. Structure of the Inner Ring Rolling Elements 50 As shown in Figures 1 and 4, the multiple inner ring rolling elements 50 are provided between the raceway surface 12 of the outer ring 10 and the inner ring raceway surface 32 of the inner ring 30. The multiple inner ring rolling elements 50 are spherical bodies (balls) of the same shape. The multiple inner ring rolling elements 50 have the function of supporting the outer ring 10 and the outer joint member 5 so that they can rotate relatively about the central axis L1 (see Figure 1). The number of inner ring rolling elements 50 is not limited to that shown in Figure 4, and may be set to any appropriate number.

[0042] In this embodiment, the pitch circle diameter d2 (see FIG. 4) of the inner ring rolling elements 50 is greater than the pitch circle diameter d1 (see FIG. 3) of the hub rolling elements 40. The pitch circle diameter d1 corresponds to the diameter of a first pitch circle C1 formed by connecting all the center points of all the hub rolling elements 40. The pitch circle diameter d2 corresponds to the diameter of a second pitch circle C2 formed by connecting all the center points of the inner ring rolling elements 50. The second pitch circle C2 is larger in diameter than the second pitch circle C1.

[0043] By making the second pitch circle C2 larger in diameter than the first pitch circle C1, the abutment surface 35a of the inner ring 30 can be shifted outward in the radial direction Y compared to when the pitch circle diameters d1, d2 of the two pitch circles C1, C2 are the same. This increases the grip force at the abutment surface 35a of the inner ring 30 against relative slippage between the outer joint member 5 and the inner ring 30, thereby suppressing slippage. As a result, abnormal noise generated between the outer joint member 5 and the inner ring 30 can be suppressed. This abnormal noise is also called a "stick-slip noise" or a "clicking noise." Furthermore, a structure in which the abutment surface 35a of the inner ring 30 is shifted outward in the radial direction Y is easier to process than a structure in which the area of ​​the abutment surface 35a is increased.

[0044] The hub rolling elements 40 and the inner ring rolling elements 50 may be cylindrical rollers, needle-shaped rollers, or conical tapered rollers, in addition to spheres.

[0045] 8. Effects According to the first embodiment described above, the following effects can be obtained.

[0046] In the bearing device 1 of embodiment 1, the inner ring 30 is provided with an inner ring raceway portion 31 having an inner ring raceway surface 32, and an inner ring thin-walled portion 33 that is thinner in the radial direction Y than the inner ring raceway portion 31. When the inner ring 30 is assembled to the hub ring 20, both the inner ring raceway portion 31 and the inner ring thin-walled portion 33 of the inner ring 30 are press-fitted into the hub fitting portion 23 of the hub ring 20. The inner ring thin-walled portion 33 has lower rigidity during press-fitting than the inner ring raceway portion 31.

[0047] By providing the inner ring 30 with an inner ring thin portion 33 that has lower rigidity during press-fitting than the inner ring raceway 31, it is possible to prevent the inner ring raceway surface 32 from expanding in the radial direction Y due to the load that the inner ring raceway 31 receives from the hub fitting portion 23 when the inner ring 30 is press-fitted into the hub fitting portion 23 of the hub wheel 20. As a result, it is possible to reduce variations in the bearing performance of the bearing device 1. Furthermore, by keeping the load that the inner ring 30 receives from the hub fitting portion 23 low, the creep resistance of the inner ring 30 is improved.

[0048] As described above, according to the first embodiment, it is possible to provide a bearing device 1 that can prevent the inner ring raceway surface 32 from expanding in diameter when the inner ring 30 is press-fitted into the hub wheel 20 .

[0049] (Embodiment 2) Figure 5 shows a bearing device 1A of embodiment 2. The bearing device 1A differs from the bearing device 1 of embodiment 1 in the structure of the hub ring 20. The hub ring 20 of this bearing device 1A does not have a portion corresponding to the hub intermediate portion 24 in Figure 2. As a result, the inner ring intermediate portion 34 of the inner ring 30 and the hub thick portion 23a of the hub ring 20 overlap in the radial direction Y.

[0050] The other configurations of the bearing device 1A are the same as those of the bearing device 1.

[0051] According to the bearing device 1A, by increasing the dimension of the axial direction X of the hub thick portion 23a of the hub wheel 20, the effect of the load that the inner ring raceway 31 receives from the hub wheel 20 can be reduced when the inner ring 30 is press-fitted into the hub fitting portion 23 of the hub wheel 20.

[0052] 9. Modifications Although the present disclosure has been described with reference to the above-described embodiments, it is understood that the present disclosure is not limited to such embodiments or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and embodiments, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0053] In the embodiment described above, the outer joint member 5 and the hub wheel 20 are connected to each other by spline fitting so as to be able to transmit torque. However, instead of this, a connecting method other than spline fitting may be used.

Claims

1. A driving wheel bearing device (1, 1A) for rotatably supporting a driving wheel (3) of a vehicle, comprising: a cylindrical outer ring (10) fixed to a vehicle body side member (2) and having a plurality of raceway surfaces (11, 12) on its inner periphery; a cylindrical hub ring (20) having a hub raceway surface (22) facing a driving wheel side raceway surface (11) of the plurality of raceway surfaces of the outer ring and rotating together with the driving wheel; a cylindrical inner ring (30) having an inner ring raceway surface (32) facing a vehicle body side raceway surface (12) of the plurality of raceway surfaces of the outer ring and rotating together with the hub ring; a plurality of hub rolling elements (40) provided between the driving wheel side raceway surface of the outer ring and the hub raceway surface of the hub ring; and a plurality of inner ring rolling elements (50) provided between the vehicle body side raceway surface of the outer ring and the inner ring raceway surface of the inner ring, wherein the hub ring is a hub raceway portion (21) having the hub raceway surface; and a hub fitting portion (23) provided closer to the vehicle body than the hub raceway portion and into which the inner ring is press-fitted, wherein the inner ring has: an inner ring raceway portion (31) press-fitted into the hub fitting portion and having the inner ring raceway surface; and an inner ring thin-wall portion (33) press-fitted into the hub fitting portion together with the inner ring raceway portion and formed to have a thinner radial (Y) thickness than the inner ring raceway portion.

2. A bearing device for a driving wheel as described in claim 1, wherein the hub wheel has a cylindrical portion (20b), and a torque transmission portion (25) that transmits torque to the driving wheel is provided on the inner surface of the cylindrical portion, and the torque transmission portion is configured so as not to overlap with the inner ring raceway portion in the radial direction (Y).

3. A bearing device for a driving wheel according to claim 2, wherein the torque transmission portion is configured to overlap the inner ring thin portion in the radial direction.

4. A bearing device for a driving wheel as described in claim 2 or 3, wherein the hub fitting portion has a hub thin portion (23b) formed to be thinner in the radial direction (Y) than the torque transmission portion, and the hub thin portion is configured to overlap the inner ring raceway portion of the inner ring in the radial direction.

5. A bearing device for a driving wheel according to claim 4, wherein the hub fitting portion is provided with a hub thick portion (23a) having the same thickness as the torque transmission portion between the torque transmission portion and the hub thin portion.

6. A bearing device for a driving wheel according to claim 5, wherein the hub thin portion is configured so as not to overlap the inner ring thin portion of the inner ring in the radial direction.

7. A bearing device for a driving wheel according to claim 5, wherein the hub thin-walled portion is formed to have a thickness in the radial direction (Y) that is thinner than the inner ring raceway portion of the inner ring.

8. A bearing device for a driving wheel as set forth in claim 5, wherein the inner ring has an inner ring intermediate portion (34) disposed between the inner ring raceway portion and the inner ring thin portion, the radial (Y) thickness of which gradually changes in the axial (X) direction, and the hub ring has a hub intermediate portion (24) overlapping the inner ring intermediate portion of the inner ring in the radial (Y) direction, and the radial thickness of the hub intermediate portion is greater than the radial thickness of the hub thin portion.

9. A bearing device for a driving wheel as described in claim 2 or 3, comprising an outer joint member (5) assembled to the hub wheel (20), the outer joint member having an engaging portion (7a) that engages with the torque transmission portion of the hub wheel, and the engaging portion not overlapping with the inner ring raceway portion of the inner ring in the radial direction (Y).

10. A bearing device for a driving wheel as described in claim 9, wherein a pitch circle (C2) formed by connecting the center points of all of the plurality of inner ring rolling elements has a larger diameter than a pitch circle (C1) formed by connecting the center points of all of the plurality of hub rolling elements.

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