Bearing device for drive wheel

Abstract

This bearing device (1) for a drive wheel comprises: an outer ring (10) that is fixed to a vehicle body-side member (2); a hub (20) to which a wheel (3) is attached; and an outer joint member (30) that has a bottomed cylindrical part (31) and a connection part (35) that is connected to the hub (20) so as to be able to transmit torque. In the outer joint member (30), a first inner raceway surface (33) provided on the outer surface of the cylindrical part (31) is disposed outside in the radial direction (Y) of an outer guide groove (32) provided to the inner surface of the cylindrical part (31), so as to overlap at least a portion of the outer guide groove (32).

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 conventional bearing device for a drive wheel. This bearing device for a drive wheel is a rolling bearing device for rotatably supporting a drive wheel, and has a structure in which a rolling bearing and a constant velocity universal joint are integrated. The rolling bearing is composed of an outer ring, a hub ring corresponding to an inner ring, a drive shaft integrated with the inner ring, rolling elements, etc., and the constant velocity universal joint is composed of a drive shaft integrated with an outer coupling member, an inner coupling member, balls, etc.

[0003] JP 2009-292275 A

[0004] In vehicles powered by electric motors or internal combustion engines, there is a demand for longer driving range and improved electricity and fuel economy. Therefore, there is a demand for lighter drive wheel bearing devices. The drive wheel bearing device of Patent Document 1 has a structure in which an inner ring raceway is provided on the outer joint member of the constant velocity joint of the drive shaft, thereby eliminating the inner ring, which is effective in reducing weight. However, further weight reduction is desired in the design of this type of drive wheel bearing device.

[0005] The present disclosure has been made in view of the above-mentioned problems, and aims to provide a technique that is effective in reducing the weight of a bearing device for a drive wheel.

[0006] One aspect of the present disclosure comprises: an outer joint member having an outer ring fixed to a vehicle body member; a hub to which a wheel is attached; a cylindrical portion having a bottom; and a connecting portion connected to the hub in a torque-transmitting manner; an inner joint member housed in the cylindrical portion of the outer joint member; a plurality of first rolling elements provided between the outer ring and the outer joint member and supporting the outer ring and the outer joint member so as to be rotatable relative to each other in a direction about the axis; a plurality of second rolling elements provided between the outer ring and the hub and supporting the outer ring and the hub so as to be rotatable relative to each other in a direction about the axis; and a plurality of third rolling elements connecting the cylindrical portion of the outer joint member and the inner joint member in a torque-transmitting manner; wherein an outer guide groove is provided on a radial inner surface of the cylindrical portion of the outer joint member to guide the third rolling elements in an axial direction; and a first inner raceway is provided on a radial outer surface of the cylindrical portion of the outer joint member to guide the first rolling elements in a circumferential direction. In the outer joint member, the first inner raceway surface is disposed radially outside the outer guide groove so as to overlap with at least a portion of the outer guide groove, or the first inner raceway surface is disposed on a vertical line perpendicular to a tangent to the outer guide groove.

[0007] In the driving wheel bearing device of the above aspect, the first inner raceway that guides the plurality of first rolling elements in the circumferential direction is provided on the radially outer surface of the tubular portion of the outer joint member, and the outer guide groove that guides the plurality of third rolling elements in the axial direction is provided on the radially inner surface of the tubular portion of the outer joint member. By using a structure in which the first rolling elements are in direct contact with the tubular portion of the outer joint member, no separate member is interposed between the first rolling elements and the outer joint member, making it possible to reduce the weight accordingly.

[0008] In addition, in the outer joint member, the first inner raceway is disposed radially outward of the outer guide groove so as to overlap at least a portion of the outer guide groove. Alternatively, in the outer joint member, the first inner raceway is disposed on a line perpendicular to a tangent to the outer guide groove. This allows the outer guide groove and the first inner raceway to be closer to each other in the axial direction. In this case, the axial dimension of the connecting portion of the outer joint member can be shortened, thereby enabling further weight reduction of the drive wheel bearing device.

[0009] According to the above-described aspect, the weight of the driving wheel bearing device can be reduced.

[0010] 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.

[0011] 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 a cross-sectional view taken along line II-II in Fig. 1, Fig. 3 is a cross-sectional view taken along line III-III in Fig. 1, Fig. 4 is a cross-sectional view showing a contact state between an outer guide groove provided on the inner surface of the cylindrical portion of the outer joint member in Fig. 1 and a first ball, Fig. 5 is a partial cross-sectional view for explaining a first lightweight structure of the bearing device for a drive wheel according to the first embodiment, Fig. 6 is a partial cross-sectional view for explaining a second lightweight structure of the bearing device for a drive wheel according to the first embodiment, Fig. 7 is a partial cross-sectional view for explaining a third and fourth lightweight structures of the bearing device for a drive wheel according to the first embodiment, and Fig. 8 is a partial cross-sectional view for explaining a fifth lightweight structure of the bearing device for a drive wheel according to the first embodiment. 12 is an axial cross-sectional view showing the eighth lightweight structure of the bearing device for a driving wheel of embodiment 1 when turning left, illustrating the eighth lightweight structure of the bearing device for a driving wheel of embodiment 1; FIG. 13 is an enlarged cross-sectional view of a portion of FIG. 12; FIG. 14 is a cross-sectional view showing a portion of a circumferential cross-section of the cylindrical portion of the outer joint member in FIG. 11 or 13; and FIG. 15 is a cross-sectional view showing a portion of a circumferential cross-section of the cylindrical portion of the outer joint member in FIG. 13.

[0012] Hereinafter, an embodiment of the above aspect will be described with reference to the drawings.

[0013] In the drawings used to explain this embodiment, unless otherwise specified, the axial direction of the drive wheel bearing device and its components is designated as the X direction, the radial direction is designated as the Y direction, the circumferential direction is designated as the Z direction, and the direction around the axis is designated as the D direction.

[0014] (Embodiment 1) 1. Overall configuration of driving wheel bearing device 1 As shown in Figure 1, a driving wheel bearing device 1 of embodiment 1 (hereinafter simply referred to as "bearing device") has a structure in which a constant velocity universal joint (constant velocity joint) 1a and a rolling bearing 1b are integrated. This bearing device 1 is mounted on a vehicle driven by an electric motor or an internal combustion engine, and transmits torque generated by the drive source to wheels 3 and supports the wheels 3 for rotation.

[0015] The constant velocity universal joint 1a is composed of multiple components including an outer joint member 30, an inner joint member 41, multiple third balls 50 which are multiple third rolling elements, and a cage 51. The constant velocity universal joint 1a is a joint of a fixed joint center type, in which the multiple third balls 50 serve as torque transmission members. The rolling bearing 1b is composed of multiple components including an outer ring 10, a hub 20, the outer joint member 30, multiple first balls 60 which are multiple first rolling elements, and multiple second balls 70 which are multiple second rolling elements.

[0016] The outer ring 10 is formed in a substantially cylindrical shape. An inner peripheral surface of the outer ring 10 is provided with annular raceway surfaces 11, 12 formed in two rows spaced apart in the axial direction X. The raceway surface 11 is a raceway surface for a plurality of first balls 60. The raceway surface 12 is a raceway surface for a plurality of second balls 70. 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."

[0017] The hub 20 is formed in an annular shape. The connecting portion 35 of the outer joint member 30 is inserted into the inner periphery of the hub 20. A plurality of bolts 22 are fixed to the hub 20, and the wheels 3, which serve as drive wheels, are attached to the hub 20 via the plurality of bolts 22.

[0018] 2. Structure of the Outer Joint Member 30 The outer joint member 30 is a member called the outer race of the constant velocity universal joint 1a. The outer joint member 30 has a cylindrical portion (joint portion) 31 with a bottom and a connecting portion 35 that is connected to the hub 20 so as to be able to transmit torque. The cylindrical portion 31 and the connecting portion 35 are integrated.

[0019] The cylindrical portion 31 of the outer joint member 30 is formed in a cup shape with a bottom surface. The cylindrical portion 31 and the hub 20 are fitted together at a fitting portion 36 by press-fitting in the axial direction X. At this time, a gap sufficient to position the hub 20 and the outer joint member 30 may be formed in the fitting portion 36. The cylindrical portion 31 has an internal space 31a and an abutment surface 31b that abuts against the hub 20 in the axial direction X. The abutment surface 31b is formed at an intermediate position between a first inner raceway surface 33 provided on the cylindrical portion 31 and a second inner raceway surface 21 provided on the hub 20. In other words, the first inner raceway surface 33 is disposed closer to the shaft 40 than the abutment surface 31b, and the second inner raceway surface 21 is disposed closer to the wheel 3 than the abutment surface 31b, with the abutment surface 31b separated therefrom. Therefore, the first ball 60 is disposed on one side in the axial direction X with respect to an imaginary plane (not shown) passing through the abutment surface 31b, and the second ball 70 is disposed on the other side in the axial direction X. The abutment surface 31b is disposed so as to overlap with the internal space 31a in the radial direction Y, i.e., so as to be located within the range of the internal space 31a in the axial direction X. Arranging the abutment surface 31b in this manner is effective in reducing the dimension of the connecting portion 35 of the outer joint member 30 in the axial direction X.

[0020] A plurality of outer guide grooves 32 that guide the plurality of third balls 50 along the axial direction X are provided on the inner surface in the radial direction Y of the cylindrical portion 31 of the outer joint member 30. The plurality of outer guide grooves 32 are formed at equal intervals in the circumferential direction Z of the cylindrical portion 31. A first inner raceway surface 33 is provided on the outer surface in the radial direction Y of the cylindrical portion 31 of the outer joint member 30 so as to overlap with the internal space 31 a in order to guide the plurality of first balls 60 in the circumferential direction Z. The first inner raceway surface 33 is formed in an annular shape in the circumferential direction Z of the cylindrical portion 31.

[0021] The connecting portion 35 of the outer joint member 30 engages with the hub 20 by so-called "spline fitting (a structure in which concave grooves on the inner circumferential surface of a spline hole or aperture engage with convex teeth on the outer circumferential surface of a spline shaft)," thereby connecting the outer joint member 30 and the hub 20 in a manner that allows torque to be transmitted between them. The connecting portion 35 is fastened and fixed to the hub 20 by a bolt 23 so as to be immovable relative to the hub 20 in the axial direction. The head 23 of the bolt 23 a abuts against the hub 20, and a male thread provided on a shaft portion 23 b extending from the head 23 a of the bolt 23 is threadedly engaged with a female thread provided in a recess 35 a of the connecting portion 35, thereby fastening and fixing the outer joint member 30 and the hub 20.

[0022] 3. Structure of the Inner Joint Member 41 The inner joint member 41 is formed in an annular shape and is fixed to the outer periphery of the shaft 40 connected to the vehicle's drive source (electric motor or internal combustion engine). The inner joint member 41 is housed in the internal space 31a of the cylindrical portion 31 of the outer joint member 30. The inner joint member 41 is tiltable relative to the outer joint member 30 around a predetermined joint center point P. In this embodiment, the angle between the central axis L1 of the outer joint member 30 and the central axis L2 of the inner joint member 41 is the joint angle. Note that FIG. 1 shows a state in which the joint angle is zero degrees.

[0023] 4. Structure of the Third Balls 50 The third balls 50 are spherical bodies of the same shape. The third balls 50 are housed in the internal space 31a of the cylindrical portion 31 of the outer joint member 30. The third balls 50 function to connect the cylindrical portion 31 of the outer joint member 30 and the inner joint member 41 so as to enable torque transmission. One third ball 50 is guided by one outer guide groove 32. The number of outer guide grooves 32 and third balls 50 is six or eight.

[0024] 5. Structure of the First Balls 60 As shown in Figures 1 and 2, the multiple first balls 60 are spherical bodies of the same shape. The multiple first balls 60 are provided between the raceway surface 11 of the outer ring 10 and the first inner raceway surface 33 of the outer joint member 30. The multiple first balls 60 have the function of supporting the outer ring 10 and the outer joint member 30 so that they can rotate relatively in the direction D around the axis (see Figure 1). The number of first balls 60 is not limited to 20 as shown in Figure 2, but may be set to any appropriate number.

[0025] 6. Structure of the Second Balls 70 As shown in FIGS. 1 and 3 , the second balls 70 are spherical bodies of the same shape. The second balls 70 are disposed between the raceway surface 12 of the outer ring 10 and the second inner raceway surface 21 of the hub 20. The second balls 70 support the outer ring 10 and the hub 20 so that they can rotate relative to each other in the direction D about the axis (see FIG. 1 ). The second inner raceway surface 21 is disposed on the outer surface of the hub 20 in the radial direction Y so as to overlap with the internal space 31 a of the cylindrical portion 31 in order to guide the second balls 70 in the circumferential direction Z. The second inner raceway surface 21 is formed in an annular shape in the circumferential direction Z of the hub 20. The number of second balls 70 is not limited to 20 as shown in FIG. 3 and may be any appropriate number.

[0026] The first ball 60 and the second ball 70 may be cylindrical rollers, needles, or conical tapered rollers, instead of spheres.

[0027] 4, each third ball 50 contacts the outer guide groove 32 at two contact positions 32a in the circumferential direction. A groove bottom 32b between the two contact positions 32a of the outer guide groove 32 forms a minute gap between the third ball 50 and the outer guide groove 32. The surface between two adjacent outer guide grooves 32 is formed by the joint inner spherical surface 34.

[0028] 5 , the cage 51 is formed in a cylindrical shape to hold the plurality of third balls 50. The outer and inner peripheral surfaces of the cage 51 are spherical, and the cage 51 is disposed between the joint inner spherical surface 34 provided on the cylindrical portion 31 of the outer joint member 30 and the joint outer spherical surface 42 provided on the inner joint member 41.

[0029] 8. Lightweight Structure of Bearing Device 1 for Drive Wheel Next, the lightweight structure characteristic of the bearing device 1 of this embodiment will be described with reference to Figures 5 to 15. The bearing device 1 does not have a separate member (such as a member called an "inner ring" or "hub inner ring") between the outer joint member 30 and the first balls 60, which is advantageous for reducing weight. The bearing device 1 of this embodiment is equipped with the following first to eighth lightweight structures to further reduce weight.

[0030] 8-1. First Lightweight Structure As shown in FIG. 5 , the first lightweight structure is a structure in which, in the outer joint member 30, the first inner raceway surface 33 is disposed radially outward of the outer guide groove 32 so as to overlap at least a portion of the outer guide groove 32. For convenience of explanation, in FIG. 5 , the region in which the outer guide groove 32 extends along the axial direction X is shown as hatched region A, and the region in which the first inner raceway surface 33 extends along the arcuate surface is shown as hatched region B. In this embodiment, region A in which the outer guide groove 32 extends along the axial direction X and region B in which the first inner raceway surface 33 extends along the arcuate surface completely overlap in the radial direction Y. Alternatively, region B may partially overlap region A in the radial direction Y.

[0031] According to the first lightweight structure, it is possible to realize a narrower structure in which the outer guide groove 32 and the first inner raceway surface 33 are closer to each other in the axial direction X than in the conventional structure. In this case, it is possible to shorten the dimension of the connecting portion 35 of the outer joint member 30 in the axial direction X. This makes it possible to reduce the weight of the bearing device 1.

[0032] 6, the second lightweight structure is a structure in which, in the outer joint member 30, the first inner raceway surface 33 is disposed on a vertical line L4 that is perpendicular to the tangent line L3 of the outer guide groove 32. The tangent line L3 is typically a tangent line to the groove bottom 32b (see FIG. 4) of the outer guide groove 32. Furthermore, this tangent line L3 may be a tangent line to the locus of the contact position 32a (see FIG. 4) of the outer guide groove 32, or may be a tangent line to the locus of the center of the third ball 50.

[0033] According to the second lightweight structure, as in the case of the first lightweight structure, the dimension of the connecting portion 35 of the outer joint member 30 in the axial direction X can be shortened, making it possible to reduce the weight of the bearing device 1.

[0034] 7, the third lightweight structure is a structure in which the angle θa between the imaginary line L5 and the central axis L1 of the outer joint member 30 is set to 60 to 80 degrees. The imaginary line L5 is a line that imaginarily connects the joint center point P of the inner joint member 41 and the center Q2 of the first ball 60.

[0035] According to the third lightweight structure, as in the case of the first lightweight structure, the dimension of the connecting portion 35 of the outer joint member 30 in the axial direction X can be shortened, thereby making it possible to reduce the weight of the bearing device 1. In particular, the greater the angle θa is set to, the greater the effect of reducing the weight of the bearing device 1.

[0036] 7, the fourth lightweight structure is a structure in which the angle θb between the imaginary line L6 and the central axis L1 of the outer joint member 30 is set to 35 to 75 degrees when the joint angle of the outer joint member 30 is zero degrees (the state shown in FIG. 1). The imaginary line L6 is a line that imaginarily connects the center Q1 of the third ball 50 and the center Q2 of the first ball 60.

[0037] According to the fourth lightweight structure, as in the case of the first lightweight structure, the dimension of the connecting portion 35 of the outer joint member 30 in the axial direction X can be shortened, thereby making it possible to reduce the weight of the bearing device 1. In particular, the greater the angle θb is set to, the greater the effect of reducing the weight of the bearing device 1.

[0038] 8-5. Fifth Lightweight Structure As shown in FIG. 8 , the fifth lightweight structure is a structure in which, in a steady state where the joint angle is within the normal range, the third ball 50 contacts the tubular portion 31 of the outer joint member 30 in a contact area C, and the contact area C is located on a vertical line L8 that is perpendicular to a tangent line L7 of the first inner raceway surface 33. The steady state here refers to when the vehicle is stopped or traveling straight. The tangent line L7 is a tangent line at the point of contact between the first inner raceway surface 33 and the third ball 50. For ease of explanation, the contact area C is shown as a hatched area in FIG. 8 .

[0039] According to the fifth lightweight structure, as in the case of the first lightweight structure, the dimension of the connecting portion 35 of the outer joint member 30 in the axial direction X can be shortened, making it possible to reduce the weight of the bearing device 1.

[0040] 9, the sixth lightweight structure is a structure in which the angle θc between an imaginary line L9 and the central axis L1 of the outer joint member 30 is set to 40 to 60 degrees. The imaginary line L9 is a line that imaginarily connects the joint center point P of the inner joint member 41 and the center Q3 of the second ball 70.

[0041] According to the sixth lightweight structure, as in the case of the first lightweight structure, the dimension of the connecting portion 35 of the outer joint member 30 in the axial direction X can be shortened, thereby making it possible to reduce the weight of the bearing device 1. In particular, the greater the angle θc is set to, the greater the effect of reducing the weight of the bearing device 1.

[0042] 9, the seventh lightweight structure is a structure in which the angle θd between an imaginary line L10 and the central axis L1 of the outer joint member 30 is set to 15 to 55 degrees when the joint angle is zero degrees (the state shown in FIG. 1). The imaginary line L10 is a line that imaginarily connects the center Q1 of the third ball 50 and the center Q3 of the second ball 70.

[0043] According to the seventh lightweight structure, as in the case of the first lightweight structure, the dimension of the connecting portion 35 of the outer joint member 30 in the axial direction X can be shortened, thereby making it possible to reduce the weight of the bearing device 1. In particular, the greater the angle θd is set to, the greater the effect of reducing the weight of the bearing device 1.

[0044] The eighth lightweight structure is a structure for reducing the weight of the bearing device 1 by reducing the thickness of the cylindrical portion 31 of the outer joint member 30 in the radial direction Y. For the eighth lightweight structure, see Figures 10 to 15.

[0045] 10 and 11 show the state of the bearing device 1 when the wheel 3 is the right front wheel and the vehicle is traveling straight. This state is a steady state in which the joint angle α is within the normal range (for example, a value of approximately 6 degrees), and the inner joint member 41 is located, for example, in the first position R1. The same applies when the vehicle is stopped. In contrast, FIGS. 12 and 13 show the state of the bearing device 1 when the wheel 3 is the right front wheel and the vehicle is turning left. This state is a variable state in which the joint angle α exceeds the normal range (for example, a value of approximately 25 degrees at most), and the inner joint member 41 is located, for example, in the second position R2.

[0046] 11 and 13, the eighth lightweight structure satisfies the condition that the inner contact direction Ea and the outer contact direction Eb do not coincide with each other in a cross section including the central axes L1, L2 of the outer joint member 30 and the inner joint member 41. That is, the inner contact direction Ea and the outer contact direction Eb do not coincide with each other not only in three dimensions but also when viewed two-dimensionally in the cross section.

[0047] The inner contact direction Ea is the contact direction of the first ball 60 on the first inner raceway surface 33 of the cylindrical portion 31 of the outer joint member 30. The first ball 60 contacts the first inner raceway surface 33 at a contact position 33a (the region shown by the substantially elliptical cross section in FIGS. 11 and 13 ) at a contact angle β (the angle with respect to an imaginary line in the radial direction Y) and inputs a load in the inner contact direction Ea to the first inner raceway surface 33. The contact angle β is, for example, approximately 40 degrees when traveling straight (see FIG. 11 ) and approximately 52 degrees when turning left (see FIG. 13 ). At this time, stress is generated in the first inner raceway surface 33 of the cylindrical portion 31 in response to the load input from the first ball 60. The inner contact direction Ea can also be referred to as the load input direction from the first ball 60.

[0048] The outer contact direction Eb is the contact direction of the third ball 50 in the outer guide groove 32 of the tubular portion 31 of the outer joint member 30. When the joint angle is α, the center of the third ball 50 is located on a line passing through the joint center point P and tilted by α / 2, which is ½ of the joint angle α, from a plane passing through the joint center point P and perpendicular to the central axis L1. The third ball 50 contacts the outer guide groove 32 at a contact angle γ (angle with respect to a virtual line in the radial direction Y) greater than α / 2 at a contact position 32a (a region indicated by a substantially elliptical cross section in FIGS. 11 and 13 ), and inputs a load in the outer contact direction Eb to the outer guide groove 32. At this time, stress is generated in the outer guide groove 32 of the tubular portion 31 in response to the load input from the third ball 50. The outer contact direction Eb can also be referred to as the load input direction from the third ball 50.

[0049] Here, if the inner contact direction Ea and the outer contact direction Eb coincide, it is expected that local stress concentration will occur in the portion of the tubular portion 31 of the outer joint member 30 where the inner contact direction Ea and the outer contact direction Eb coincide. If measures were taken to increase the thickness of the tubular portion 31 so that it could withstand this stress concentration, this could result in an increase in the weight of the bearing device 1. Therefore, in the eighth lightweight structure, the inner contact direction Ea and the outer contact direction Eb are made to not coincide with each other, thereby suppressing the occurrence of the above-mentioned stress concentration in the tubular portion 31 of the outer joint member 30. This allows the thickness of the tubular portion 31 to be reduced, thereby enabling the weight of the bearing device 1 to be reduced.

[0050] 11 and 13 , when an extension line extending from the center of a first ball 60 in the inner contact direction Ea is defined as a first extension line M1, a plurality of first extension lines M1 are formed corresponding to the number of first balls 60. Here, the first extension line M1 is a line linearly connecting the center of the first ball 60 and the contact position 33a of the first ball 60 on the first inner raceway surface 33. Furthermore, when an extension line extending from the center of a third ball 50 in the outer contact direction Eb is defined as a third extension line M3, a plurality of third extension lines M3 are formed corresponding to the number of third balls 50. Here, the third extension line M3 is a line linearly connecting the center of the third ball 50 and the contact position 32a of the third ball 50 on the outer guide groove 32.

[0051] The eighth lightweight structure is preferably a structure that satisfies the following conditions: if the multiple first extension lines M1 include one that passes through the contact position 32a of the third ball 50 in the outer guide groove 32, the third extension line M3 for the third ball 50 at that contact position 32a does not pass through the contact position 33a of the first ball 60 on the first inner raceway surface 33; and if the multiple third extension lines M3 include one that passes through the contact position 33a of the first ball 60 on the first inner raceway surface 33, the first extension line M1 for the first ball 60 at that contact position 33a does not pass through the contact position 32a of the third ball 50 in the outer guide groove 32.

[0052] 14 , for example, in this structure, one of the three first extension lines M1 passes through the contact position 32a of the third ball 50 in the outer guide groove 32, but a third extension line M3 for the third ball 50 at that contact position 32a does not pass through any of the contact positions 33a of the first balls 60 in the first inner raceway surface 33. Furthermore, one third extension line M3 passes through the contact position 33a of the first ball 60 in the first inner raceway surface 33, but the first extension line M1 for the first ball 60 at that contact position 33a does not pass through any of the contact positions 32a of the third balls 50 in the outer guide groove 32.

[0053] Furthermore, the eighth lightweight structure is preferably a structure that satisfies the condition that, during a turn in which the joint angle α exceeds the normal range (see Figures 12 and 13), the first extension line M1 of the first ball 60 that has the greatest input load on the first inner raceway surface among the multiple first balls 60 does not pass through the contact position 32a in the outer guide groove 32 of any of the multiple third balls 50.

[0054] 15 , for example, with the upper side of the drawing being the upper side of the vehicle, the first ball 60 at the first position S1, which is the highest of the three first balls 60, receives the largest load F from the vehicle compared to the first balls 60 at the second position S2 or the third position S3, which are lower than the first position S1. Therefore, the first ball 60 at the first position S1 receives the largest input load on the first inner raceway surface 33 among the three first balls 60. At this time, the first extension line M1 of the first ball 60 at the first position S1 does not pass through the contact positions 32 a in the outer guide grooves 32 of any of the multiple third balls 50.

[0055] 9. Effects According to the first embodiment described above, the following effects can be obtained.

[0056] In the bearing device 1 of embodiment 1, a first inner raceway surface 33 that guides the multiple first balls 60 in the circumferential direction Z is provided on the outer surface in the radial direction Y of the tubular portion 31 of the outer joint member 30, and an outer guide groove 32 that guides the multiple third balls 50 along the axial direction X is provided on the inner surface in the radial direction Y of the tubular portion 31 of the outer joint member 30. The structure in which the first balls 60 directly contact the tubular portion 31 of the outer joint member 30 does not require an additional member between the first balls 60 and the outer joint member 30, thereby enabling weight reduction accordingly. In addition, the bearing device 1 is provided with the first to eighth lightweight structures, thereby enabling further weight reduction of the bearing device 1.

[0057] As described above, according to the first embodiment, it is possible to reduce the weight of the bearing device 1. As a result, it is possible to extend the cruising distance of a vehicle equipped with the bearing device 1 and improve the electricity cost or fuel economy.

[0058] 10. 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.

[0059] In the above-described embodiment, an example is given of the case where the bearing device 1 is equipped with the first to eighth lightweight structures, but if necessary, a structure in which the bearing device 1 is equipped with at least one of the first to eighth lightweight structures can be adopted.

[0060] In the embodiment described above, the case where the connecting portion 35 of the outer joint member 30 and the hub 20 are connected to each other by spline fitting so as to enable torque transmission has been exemplified. However, instead of this, a connecting method other than spline fitting may be adopted.

Claims

1. An outer joint member (30) having an outer ring (10) fixed to a vehicle body side member (2); a hub (20) to which a wheel (3) is attached; a cylindrical portion (31) having a bottom and a connecting portion (35) connected to the hub so as to transmit torque; an inner joint member (41) housed in the cylindrical portion of the outer joint member; a plurality of first rolling bodies (60) provided between the outer ring and the outer joint member and supporting the outer ring and the outer joint member so as to rotate relatively in a direction around the axis (D); a plurality of second rolling bodies (70) provided between the outer ring and the hub and supporting the outer ring and the hub so as to rotate relatively in the direction around the axis (D); and a plurality of third rolling bodies (50) connecting the cylindrical portion of the outer joint member and the inner joint member so as to transmit torque. a driving wheel bearing device (1), wherein an outer guide groove (32) that guides the third rolling elements along an axial direction (X) is provided on an inner surface in a radial direction (Y) of the cylindrical portion of the outer joint member, and a first inner raceway (33) that guides the first rolling elements in a circumferential direction (Z) is provided on an outer surface in the radial direction of the cylindrical portion of the outer joint member, and the first inner raceway is disposed on the outer joint member radially outside of the outer guide groove (Y) so as to overlap at least a portion of the outer guide groove, or the first inner raceway is disposed on a vertical line (L4) that is perpendicular to a tangent (L3) of the outer guide groove.

2. A bearing device for a driving wheel as described in claim 1, wherein, in a cross section including central axes (L1, L2) of the outer joint member and the inner joint member, when the contact direction of the first rolling body on the first inner raceway surface is defined as an inner contact direction (Ea) and the contact direction of the third rolling body on the outer guide groove is defined as an outer contact direction (Eb), the inner contact direction and the outer contact direction do not coincide with each other.

3. A bearing device for a driving wheel as described in claim 2, wherein an extension line extending from the center of the first rolling body in the inner contact direction is defined as a first extension line (M1) and an extension line extending from the center of the third rolling body in the outer contact direction is defined as a third extension line (M3), if one of the multiple first extension lines passes through the contact position (32a) of the third rolling body on the outer guide groove, the third extension line of the third rolling body at that contact position does not pass through the contact position (33a) of the first rolling body on the first inner raceway surface, and if one of the multiple third extension lines passes through the contact position (33a) of the first rolling body on the first inner raceway surface, the first extension line of the first rolling body at that contact position does not pass through the contact position (32a) of the third rolling body on the outer guide groove.

4. A bearing device for a driving wheel as described in claim 3, wherein, during rotation when a joint angle (α), which is the angle between the central axis (L1) of the outer joint member and the central axis (L2) of the inner joint member, exceeds a normal range, the first extension line of the first rolling body which has the largest input load to the first inner raceway surface among the multiple first rolling bodies does not pass through any of the contact positions (32a) of the multiple third rolling bodies in the outer guide groove.

5. A bearing device for a driving wheel as claimed in any one of claims 1 to 4, wherein, in a steady state in which a joint angle (α), which is the angle between the central axis (L1) of the outer joint member and the central axis (L2) of the inner joint member, is within a normal range, the third rolling element comes into contact with the cylindrical portion of the outer joint member at a contact area (C), and the contact area is located on a vertical line (L8) perpendicular to the tangent (L7) of the first inner raceway surface.

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