Wheel bearing device

Abstract

To provide a wheel bearing device which enables improvement of sealability and durability of a sealing device while keeping a contact surface pressure applied to a seal land part of a seal lip in a low state.SOLUTION: A step part 3h of a hub flange 3b linearly extends in an axial direction at a seal land part 3d side end, has a flange side straight part 3ha connected to an outer diameter side end of the seal land part 3d. An outer ring 2 has: an outer side opening 2b; and an outer ring side straight part 2ha linearly extending from an inner diameter side end of the outer side end surface 2g of the outer ring 2 toward the outer side opening 2b. A border P between the step part 3h and the seal land part 3d is located at the outer diameter side relative to the outer side opening 2b of the outer ring 2 and at the inner side relative to the outer side end surface 2g of the outer ring 2. The flange side straight part 3ha and the outer ring side straight part 2ha are arranged parallel to each other and at least partially overlapped when viewed from a radial direction.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] A wheel bearing device that rotatably supports a wheel in a suspension system of an automobile, etc. is known. The wheel bearing device is provided with a sealing device that closes an open end of an annular space formed by an outer member and an inner member to prevent foreign matter such as muddy water from entering.

[0003] The sealing device has, for example, a core bar that is fitted onto the inner circumference of an outer ring, which is the outer member, and a seal member that is integrally joined to the core bar and has a plurality of seal lips.The inner member, the hub ring, has a hub flange extending toward the outer diameter side, and a seal land portion formed at the base of the hub flange and with which the seal lip of the seal member contacts.

[0004] In this way, in a wheel bearing assembly equipped with a sealing device in which the seal lip contacts the seal land portion of the hub wheel, a step is formed between the seal land portion and the side of the hub flange, and an annular recess is formed on the inner circumference of the outer ring radially opposite the step portion, to form a labyrinth seal between the step portion of the hub wheel and the recess of the outer ring (see Patent Document 1).

[0005] By forming a labyrinth seal between the hub wheel and the outer ring, it is possible to prevent muddy water from the outside from directly penetrating into the sealing device, thereby improving the sealing performance and durability of the sealing device.

[0006] Moreover, the sealing performance of the sealing device can be improved by increasing the contact surface pressure of the seal lip of the sealing device against the seal land portion. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2009-150437 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, in recent years, as vehicles have become more electrified, there has been an increasing demand for lower torque in wheel support bearing devices, so it is preferable for the contact pressure of the seal lip against the seal land portion, which affects the rotational torque of the wheel support bearing device, to be low.

[0009] The present invention has been made in consideration of the above-mentioned circumstances, and provides a wheel bearing device which, by setting an appropriate shape for the labyrinth formed between the step portion of the hub wheel and the recessed portion of the outer ring, can further prevent foreign matter such as muddy water from entering the sealing device, and can improve the sealing performance and durability of the sealing device while maintaining a low contact surface pressure of the seal lip against the seal land portion. [Means for solving the problem]

[0010] That is, the bearing device for a wheel includes an inner member including an outer member having a double-row outer raceway on its inner circumference, a hub wheel having on its outer circumference one inner raceway surface facing the outer raceway surface and a hub flange for mounting a wheel, and a raceway surface forming member connected to the hub wheel and having on its outer circumference the other inner raceway surface facing the outer raceway surface, double-row rolling elements accommodated in a rollable manner between both raceway surfaces of the outer member and the inner member, and a sealing device fitted to the outer member and closing an opening end on one axial end side of an annular space formed by the outer member and the inner member, and the hub wheel includes a seal land portion with which the sealing device comes into contact, and a seal land portion of the hub flange on the outer diameter side of the seal land portion. a flange side surface located on one axial side of the fitting portion, and a step portion connecting the seal land portion and the flange side surface, the step portion having a flange-side straight portion extending linearly in the axial direction at an end portion on the seal land portion side and connected to the outer diameter side end of the seal land portion, the outer member having a fitting portion into which the sealing device is fitted, and an outer member-side straight portion extending linearly from an inner diameter side end of one axial end face of the outer member toward the fitting portion, the boundary between the step portion and the seal land portion being located on the outer diameter side of the fitting portion of the outer member and on the other axial side of the one axial end face of the outer member, the flange-side straight portion and the outer member-side straight portion being arranged in parallel and at least partially overlapping when viewed in the radial direction. Effect of the Invention

[0011] According to the present invention, the contact surface pressure of the seal lip against the seal land portion can be kept low, while the sealing performance and durability of the sealing device can be improved. [Brief description of the drawings]

[0012] [Figure 1] 1 is a side cross-sectional view showing a wheel bearing device. [Diagram 2] 4 is a side cross-sectional view showing an outer end portion of an outer ring and a hub flange of a hub wheel into which an outer seal member is fitted. FIG. [Diagram 3]4 is a side cross-sectional view showing a labyrinth seal formed by a recess in the outer ring and a step and seal land in the hub flange. FIG. [Figure 4] 13 is a side cross-sectional view showing a seal land portion of a hub wheel and an outer end face of an outer ring according to a second embodiment. FIG. [Diagram 5] FIG. 2 is a side cross-sectional view showing a wheel bearing device having a fourth-generation structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0014] [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.

[0015] In the following description, the axial direction refers to the direction along the rotation axis X of the wheel support bearing device 1. The outer side refers to one axial side, which is the wheel side of the wheel support bearing device 1 when mounted on a vehicle body, and the inner side refers to the other axial side, which is the vehicle body side of the wheel support bearing device 1 when mounted on the vehicle body.

[0016] The wheel bearing device 1 has a configuration called 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 seal member 9, and an outer seal member 10. The inner ring 4 is an example of a raceway surface forming member connected to the hub ring.

[0017] 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.

[0018] The inner side seal member 9 is fitted into the inner side opening 2a to close the inner side opening end of the annular space S formed by the outer ring 2 and the inner member. The outer side seal member 10 is fitted into the outer side opening 2b to close the outer side opening end of the annular space S.

[0019] The inner seal member 9 and the outer seal member 10 are sealing devices that close the open ends of the annular space S formed by the outer ring 2, which is the outer member, and the inner member. In this way, the inner seal member 9 and the outer seal member 10 close the open ends on the inner and outer sides of the annular space S, thereby achieving a sealing function that prevents foreign matter such as muddy water from entering the wheel bearing device 1.

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

[0021] The inner end of the outer circumferential surface of the hub wheel 3 is formed with a small diameter step 3a that is smaller in diameter than the outer end. A hub flange 3b for mounting a wheel is integrally formed with the outer end of the hub wheel 3. The hub flange 3b is provided with bolt holes 3f into which hub bolts 3i are press-fitted. The hub wheel 3 has a through hole 3e that penetrates in the axial direction.

[0022] An outer circumferential surface of the hub ring 3 is provided with an outer-side inner raceway surface 3c facing the outer raceway surface 2d on the outer ring 2. The inner raceway surface 3c is an example of one of the inner raceway surfaces facing the outer raceway surface. In addition, the hub ring 3 is formed at the base of the hub flange 3b with which the outer seal member 10 comes into contact.

[0023] The hub flange 3b has a flange side surface 3g that faces the inner side. The flange side surface 3g is located on the outer diameter side of the seal land portion 3d in the radial direction and on the outer side of the seal land portion 3d in the axial direction. In other words, the flange side surface 3g is located on the outer diameter side of the seal land portion 3d of the hub flange 3b and on the outer side of the seal land portion 3d.

[0024] A step 3h is formed between the flange side surface 3g and the seal land portion 3d. The step 3h connects the flange side surface 3g and the seal land portion 3d. The step 3h is bent toward the inner side as it approaches the inner diameter side, and is formed in an arc shape that is convex toward the inner diameter side.

[0025] An inner ring 4 is provided on the small diameter step portion 3a of the hub ring 3. An inner-side inner raceway surface 4a is provided on the outer peripheral surface of the inner ring 4 so as to face the inner-side outer raceway surface 2c of the outer ring 2. The inner raceway surface 4a is an example of the other inner raceway surface that faces the outer raceway surface.

[0026] The inner ball row 5 and outer ball row 6, which are rolling rows, are formed by a plurality of balls 7, which are rolling elements, being held by a cage 8. The inner ball row 5 is rollably sandwiched between the inner raceway surface 4a of the inner ring 4 and the inner outer raceway surface 2c of the outer ring 2. The outer ball row 6 is rollably sandwiched between the inner raceway surface 3c of the hub ring 3 and the outer outer raceway surface 2d of the outer ring 2.

[0027] 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. However, the wheel bearing device 1 may be formed by a double-row tapered roller bearing.

[0028] The ball 7 in the inner ball row 5 is in contact with the inner ring 4 at a contact point 41, and the contact angle of the ball 7 in the inner ball row 5 with the inner ring 4 is α. The ball 7 in the outer ball row 6 is in contact with the hub wheel 3 at a contact point 31, and the contact angle of the ball 7 in the outer ball row 6 with the hub wheel 3 is β.

[0029] A line L1 passing through the center C1 of a ball 7 in the inner ball row 5 and the contact point 41 and a line L2 passing through the center C2 of a ball 7 in the outer ball row 6 and the contact point 31 intersect at the span center SP.

[0030] The span center SP is the span center between the balls 7 in the inner ball row 5 and the balls 7 in the outer ball row 6. A span center line LC that passes through the span center SP and extends in a direction perpendicular to the axial direction intersects with the rotation axis X at an intersection point IP.

[0031] [Outer seal material] As shown in FIG. 2, the outer seal member 10 includes a core metal 11 that is fitted onto the inner periphery of the outer end portion of the outer ring 2, and a seal member 12 that is joined integrally to the core metal 11.

[0032] The core metal 11 is made of, for example, a steel plate, and has a cylindrical fitting portion 111 that fits into the inner circumference of the outer side opening 2b of the outer ring 2, and an inner portion 112 that extends from the outer side end of the fitting portion 111 toward the inner diameter side.

[0033] The seal member 12 is formed of an elastic material such as synthetic rubber, and is joined by vulcanization adhesion to the core metal 11. The seal member 12 has a grease lip 12a, a first side lip 12b, and a second side lip 12c.

[0034] The grease lip 12a extends from the inside portion 112 of the core metal 11 toward the inner diameter side and the inner side, and is in contact with the seal land portion 3d.

[0035] The first side lip 12b extends from the inner portion 112 of the core metal 11 on the outer diameter side of the grease lip 12a toward the outer side and the outer diameter side which is the hub flange 3b side. The first side lip 12b is in contact with the seal land portion 3d.

[0036] The second side lip 12c extends from an inner portion 112 of the core metal 11 toward the outer side and the outer diameter side, which is the hub flange 3b side, on the outer diameter side of the first side lip 12b. The second side lip 12c is in contact with the seal land portion 3d.

[0037] The grease lip 12a, the first side lip 12b, and the second side lip 12c are seal lips of the seal member 12, and are contact lips that come into contact with the seal land portion 3d. The second side lip 12c is the seal lip of the seal member 12 that is located on the outermost diameter side.

[0038] [Structure of hub flange and outer end of outer ring] 2 and 3, the outer diameter side end of the seal land portion 3d and the inner diameter side end of the step portion 3h are connected at a boundary P. A chamfered portion 3da is formed at the outer diameter side end of the seal land portion 3d. In the seal land portion 3d, the outer diameter side end of the chamfered portion 3da forms the boundary P.

[0039] The step portion 3h has a flange-side straight portion 3ha at its inner end portion, which is the end portion on the seal land portion 3d side, that extends linearly in an axial direction perpendicular to the circumferential direction of the hub wheel 3 and is connected to a boundary P located at the outer diameter side end of the seal land portion 3d. In this embodiment, the flange-side straight portion 3ha is formed parallel to the rotation axis X. The flange-side straight portion 3ha may be formed in the axial direction having an inclination angle with respect to the rotation axis X.

[0040] The outer ring 2 has an annular recess 2h formed by cutting out the inner circumferential surface at the outer end of the outer ring 2. The recess 2h is located between the outer end face 2g of the outer ring 2 and an outer opening 2b. The outer opening 2b is an example of a fitting portion into which a sealing device is fitted.

[0041] The inner diameter side end of the outer end face 2g of the outer ring 2 and the outer end of the recess 2h are connected at a boundary Q. A chamfered portion 2ga is formed at the inner diameter side end of the outer end face 2g. At the outer end face 2g, the inner diameter side end of the chamfered portion 2ga forms the boundary Q.

[0042] The recess 2h has an outer ring side straight portion 2ha that extends in a straight line from a boundary Q, which is the inner diameter side end of the outer side end face 2g, perpendicular to the circumferential direction of the hub wheel 3, toward the inner side, which is the side facing the outer side opening 2b. The outer ring side straight portion 2ha is an example of an outer member side straight portion. The outer ring side straight portion 2ha faces the flange side straight portion 3ha in the radial direction. In this embodiment, the outer ring side straight portion 2ha is formed parallel to the rotation axis X. The outer ring side straight portion 2ha may be formed in an axial direction having an inclination angle with respect to the rotation axis X.

[0043] A boundary P between the stepped portion 3h and the seal land portion 3d is located radially outer than the outer opening 2b of the outer ring 2, and axially inner than the outer end face 2g of the outer ring 2. The boundary P between the stepped portion 3h and the seal land portion 3d is located radially inner than the outer ring straight portion 2ha.

[0044] The flange-side straight portion 3ha is located on the inner diameter side of the outer ring-side straight portion 2ha. At least the inner-side end portion of the flange-side straight portion 3ha, which is the end portion on the side where the boundary P is located, is located on the outer diameter side of the outer-side opening 2b of the outer ring 2. In this embodiment, the entire flange-side straight portion 3ha is located on the outer diameter side of the outer-side opening 2b of the outer ring 2.

[0045] The flange side straight portion 3ha and the outer ring side straight portion 2ha are arranged parallel to each other in a direction perpendicular to the circumferential direction of the hub wheel 3. In this embodiment, the flange side straight portion 3ha and the outer ring side straight portion 2ha are both arranged parallel to the axial direction (direction of the rotation axis X). The flange side straight portion 3ha and the outer ring side straight portion 2ha may both be formed in the axial direction having an inclination angle with respect to the rotation axis X and arranged parallel to each other.

[0046] The flange side straight portion 3ha and the outer ring side straight portion 2ha overlap when viewed from the radial direction. In this embodiment, the outer ring side straight portion 2ha is set to be longer than the flange side straight portion 3ha. The flange side straight portion 3ha and the outer ring side straight portion 2ha may at least partially overlap when viewed from the radial direction.

[0047] In the wheel bearing device 1, a recess 2h formed in the outer end of the outer ring 2, and a step portion 3h and a seal land portion 3d formed in the hub flange 3b of the hub wheel 3 form a labyrinth seal LS.

[0048] In this way, by forming a labyrinth seal LS between the hub wheel 3 and the outer ring 2, the labyrinth seal LS can prevent foreign matter such as muddy water from the outside from directly penetrating into the outer seal member 10.

[0049] Furthermore, even if foreign matter such as muddy water infiltrates into the outer seal member 10, the force of the infiltrating foreign matter such as muddy water is weakened by the labyrinth seal LS, thereby reducing the impact on the seal lip of the seal member 12.

[0050] This makes it possible to improve the sealing performance and durability of the outer seal member 10. As a result, it becomes possible to extend the overall life of the wheel bearing device 1.

[0051] Furthermore, even if the contact surface pressure of the seal lip of the outer seal member 10 against the seal land portion 3d is set small, the sealing performance of the outer seal member 10 can be maintained, so that the rotational torque of the wheel support bearing device 1 can be reduced, thereby improving the fuel efficiency and electricity consumption of the vehicle on which the wheel support bearing device 1 is installed.

[0052] In this case, the boundary P between the step portion 3h and the seal land portion 3d is located on the outer diameter side of the outer opening 2b of the outer ring 2 and is located on the inner side of the outer end face 2g of the outer ring 2.

[0053] Therefore, the labyrinth seal LS is formed over the portion where the step portion 3h of the hub flange 3b faces the recess 2h of the outer ring 2, and the portion where the seal land portion 3d of the hub flange 3b faces the recess 2h of the outer ring 2, making it possible to ensure a large length for the labyrinth seal LS.

[0054] This makes it possible to further improve the sealing performance of the outer seal member 10, and increases the sealing performance and durability of the outer seal member 10 while maintaining a low contact surface pressure between the seal lip of the outer seal member 10 and the seal land portion 3d.

[0055] Furthermore, the flange side straight portion 3ha and the outer ring side straight portion 2ha are arranged parallel to each other and overlap when viewed from the radial direction, so that there is a portion in the labyrinth seal LS where the size of the gap between the hub ring 3 and the outer ring 2 is constant, making it possible to consistently demonstrate foreign object resistance performance.

[0056] Furthermore, because the flange side straight section 3ha and the outer ring side straight section 2ha are both arranged parallel to the rotational axis X of the hub wheel 3, the force of foreign matter such as muddy water flowing from above the hub flange 3b along the flange side surface 3g and step section 3h can be effectively weakened by the labyrinth seal LS.

[0057] Also, as shown in Figures 2 and 3, the axial length D1 from the outer end face 2g of the outer ring 2 to the boundary P between the step portion 3h and the seal land portion 3d is set to be 0.5 mm or more and 5 mm or less.

[0058] Setting the axial length D1 to 0.5 mm or more makes it possible to effectively exert the foreign matter resistance performance of the labyrinth seal LS formed between the hub ring 3 and the outer ring 2. Also, setting the axial length D1 to 5 mm or less makes it possible to prevent the axial length of the labyrinth seal LS from becoming too large, thereby suppressing an increase in the size of the wheel bearing device 1 in the axial direction.

[0059] Furthermore, if the axial length D1 becomes large and the outer end face 2g of the outer ring 2 protrudes too far toward the hub flange 3b, the radius of the arc shape at the step portion 3h of the hub flange 3b opposite the outer end face 2g must be reduced, which may result in stress concentration at the step portion 3h.

[0060] However, by setting the axial length D1 to 5 mm or less, the outer end face 2g does not protrude too far toward the hub flange 3b, and the radius of the arc shape at the step portion 3h can be set large, thereby preventing stress concentration at the step portion 3h.

[0061] 3, the axial length D2 of the portion where the flange-side straight portion 3ha and the outer ring-side straight portion 2ha overlap as viewed from the radial direction is set to be 1 mm or more. By setting the axial length D2 to 1 mm or more, the length of the portion where the size of the gap between the hub ring 3 and the outer ring 2 in the labyrinth seal LS is constant can be secured, making it possible to more stably exhibit foreign matter resistance performance.

[0062] As shown in FIG. 3, a radial separation distance D3 between the flange side straight portion 3ha and the outer ring side straight portion 2ha is set to be 0.4 mm or more and 0.6 mm or less.

[0063] By setting the separation distance D3 to 0.4 mm or more, a gap is secured between the outer ring 2 and the hub ring 3 at the portion where the labyrinth seal LS is formed, and interference between the hub ring 3 and the outer ring 2 can be prevented even when a turning load is applied to the wheel bearing device 1 and the hub ring 3 tilts relative to the outer ring 2.

[0064] Furthermore, by setting the separation distance D3 to 0.6 mm or less, it is possible to prevent the gap between the hub ring 3 and the outer ring 2 from becoming too large, thereby ensuring the foreign matter resistance of the labyrinth seal LS.

[0065] 1 to 3, a first arc cB having a center at an intersection IP between the span center line LC and the rotation axis X and passing through a boundary P between the stepped portion 3h and the seal land portion 3d has a radius rB. Moreover, a length of the first arc cB from the boundary P between the stepped portion 3h and the seal land portion 3d to the inner circumferential surface of the recessed portion 2h of the outer ring 2 is mB.

[0066] The radius of a second arc cA is rA, the second arc cA being centered at the intersection IP of the span center line LC and the rotation axis X and passing through a boundary Q located at the inner diameter end of the outer end face 2g of the outer ring 2. The length of the second arc cA from the boundary Q located at the inner diameter end of the outer end face 2g of the outer ring 2 to the step portion 3h of the hub ring 3 is mA.

[0067] In the labyrinth seal LS formed between the outer ring 2 and the hub wheel 3, a boundary Q located at the inner diameter end of the outer end face 2g of the outer ring 2 is located on the outer side of the wheel bearing device 1 where foreign matter such as muddy water penetrates, and a boundary P between the step portion 3h and the seal land portion 3d is located on the inner side of the wheel bearing device 1 where the infiltrating foreign matter such as muddy water leaks out toward the outer side seal member 10.

[0068] The length mB of the first circular arc cB and the length mA of the second circular arc cA satisfy the relationship mA≦mB.

[0069] In this way, by making the length mB and the length mA satisfy the relationship mA≦mB, the gap on the outer side, where the boundary Q is located, of the labyrinth seal LS formed between the outer ring 2 and the hub wheel 3 can be made smaller than the gap on the inner side, where the boundary P is located. It is more preferable to satisfy the above relationship when no turning load is applied to the wheel bearing device 1.

[0070] As a result, when no rotational load is applied to the wheel bearing device 1, the gap in the outer part of the labyrinth seal LS, which is the entrance part for foreign matter such as muddy water to enter, can be kept at its smallest state, further improving the foreign matter resistance performance.

[0071] When a turning load is applied to the wheel bearing device 1, the radius rB of the first arc cB, the length mB of the first arc cB, the radius rA of the second arc cA, and the length mA of the second arc cA satisfy the relationship (mA / rA)≦(mB / rB).

[0072] In this way, by the radius rB, length mB, radius rA, and length mA satisfying the relationship (mA / rA)≦(mB / rB), even when a turning load is applied to the wheel bearing device 1 and the hub wheel 3 tilts relative to the outer wheel 2, a relationship between the outer gap (length mA) and the inner gap (length mB) sufficient to maintain the function of the labyrinth seal LS can be maintained, ensuring resistance to muddy water.

[0073] [Second embodiment of the seal land portion of the hub ring and the outer side end surface of the outer ring] The seal land portion 3d of the hub wheel 3 and the outer end face 2g of the outer ring 2 can also be formed as shown in FIG. 4 as a seal land portion 3dA and an outer end face 2gA.

[0074] The seal land portion 3dA differs from the seal land portion 3d in that it does not include a chamfered portion 3da, and the outer end surface 2gA differs from the outer end surface 2g in that it does not include a chamfered portion 2ga.

[0075] In this way, even in a configuration in which a seal land portion 3dA and an outer end face 2gA without a chamfered portion are formed, a labyrinth seal LS can be formed by the recess 2h formed in the outer end portion of the outer ring 2 and the step portion 3h and seal land portion 3dA formed in the hub flange 3b of the hub wheel 3, just as in the case of a configuration in which a seal land portion 3d with a chamfered portion 3da and an outer end face 2g with a chamfered portion 2ga are formed.

[0076] The labyrinth seal LS formed by the recess 2h of the outer ring 2 and the step portion 3h and seal land portion 3dA of the hub wheel 3 can also improve the sealing performance and durability of the outer seal member 10 while keeping the contact surface pressure of the seal lip of the outer seal member 10 against the seal land portion 3d low.

[0077] In this embodiment, the wheel bearing device 1 is configured as a wheel bearing device 1 of a third-generation structure in which the inner raceway surface 3c is formed directly on the outer periphery of the hub wheel 3, but this is not limited to this and may be a second-generation structure in which a pair of inner rings 4 are press-fitted into the hub wheel 3.

[0078] Also, instead of forming the inner raceway surface opposing the outer raceway surface 2c of the outer ring 2 on the inner ring 4, the wheel bearing device 1 can be formed on a constant velocity universal joint that fits into the through hole 3e of the hub ring 3, resulting in a fourth-generation structure that does not include the inner ring 4. In this case, the constant velocity universal joint becomes a raceway surface forming member connected to the hub ring.

[0079] A wheel bearing device of the fourth generation structure not including an inner ring 4 can be configured, for example, as a wheel bearing device 1A shown in Fig. 5. The wheel bearing device 1A includes a constant velocity universal joint 50 connected to a hub wheel 3A, and does not include an inner ring 4. The constant velocity universal joint 50 is an example of a raceway surface forming member connected to a hub wheel.

[0080] Constant velocity universal joint 50 includes a mouth portion 52 that supports a shaft to which driving force is input from a drive source, and a stem portion 53 that extends toward the outer side from mouth portion 52. Hub wheel 3A has a through hole 3e that passes through in the axial direction, and through hole 3e and stem portion 53 are spline-fitted.

[0081] An inner raceway surface 58 that faces the inner outer raceway surface 2c of the outer ring 2 is formed on the outer peripheral surface of the outer end of the mouth portion 52. The inner raceway surface 58 is an example of the other inner raceway surface that faces the outer raceway surface. The inner ball row 5 is rollably sandwiched between the inner outer raceway surface 2c of the outer ring 2 and the inner raceway surface 58 of the mouth portion 52 of the constant velocity universal joint 50.

[0082] That is, in the wheel bearing device 1A, the constant velocity universal joint 50 having the inner raceway surface 58 opposing the outer raceway surface 2c of the outer ring 2 also serves as the inner ring.

[0083] Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, which are merely illustrative, and it goes without saying that the present invention can be embodied in various other forms without departing from the gist 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]

[0084] 1 Wheel bearing device 2 Outer ring 2b Outer side opening 2c (inner side) outer raceway 2d (Outer side) outer raceway 2g Outer end face 2h Recess 2ha Outer ring straight section 3 Hub wheel 3b Hub flange 3c Inner raceway surface 3d seal land section 3g Flange side 3h step part 3ha Flange side straight section 4. Inner Circle 4a Inner raceway surface 5 Inner ball row 6 Outer ball row 10 Outer seal member cA Second arc cB First arc h Step height mA (second arc) length mB Length (of the first arc) rA (radius of the second arc) rB (radius of the first arc) IP intersection P (Boundary between step and seal land) Q Boundary (between the outer end face of the outer ring and the recess) S Annular space SP Span center LC Span Centerline X Rotation axis

Claims

1. an outer member having a double row outer raceway surface on an inner periphery thereof; an inner member including a hub wheel having, on its outer periphery, one inner raceway surface facing the outer raceway surface and a hub flange for mounting a wheel, and a raceway surface forming member connected to the hub wheel and having, on its outer periphery, the other inner raceway surface facing the outer raceway surface; a double row of rolling elements rollably accommodated between the raceway surfaces of the outer member and the inner member; a sealing device fitted to the outer member and closing an open end on one axial end side of an annular space formed by the outer member and the inner member, the hub wheel has a seal land portion with which the sealing device comes into contact, a flange side surface located on one axial side of the seal land portion and on an outer diameter side of the hub flange from the seal land portion, and a step portion connecting the seal land portion and the flange side surface, the step portion has a flange-side linear portion that extends linearly in the axial direction at an end portion on the seal land portion side and is connected to an outer diameter side end of the seal land portion, the outer member has a fitting portion into which the sealing device is fitted, and an outer member side straight portion extending linearly from an inner diameter side end of one axial end face of the outer member toward the fitting portion, a boundary between the step portion and the seal land portion is located on an outer diameter side of the fitting portion of the outer member and on the other axial side of the one axial end face of the outer member, The flange side straight portion and the outer member side straight portion are arranged in parallel and at least partially overlap each other when viewed in a radial direction.

2. 2. The wheel bearing device according to claim 1, wherein the flange side straight portion and the outer member side straight portion are parallel to a rotational axis of the hub wheel.

3. 3. A wheel bearing device according to claim 1, wherein an axial length from the one axial end face of the outer member to the boundary between the step portion and the seal land portion is 0.5 mm or more and 5 mm or less.

4. 3. The wheel bearing device according to claim 1, wherein an axial length of an overlapping portion between the flange side straight portion and the outer member side straight portion as viewed in a radial direction is 1 mm or more.

5. 3. The wheel bearing device according to claim 1, wherein a radial separation distance between the flange side straight portion and the outer member side straight portion is not less than 0.4 mm and not more than 0.6 mm.

6. a first arc is an arc having a center at an intersection of a span center line that passes through a span center between the rolling element on one axial side and the rolling element on the other axial side, extends in a direction perpendicular to the axial direction, and a rotational axis of the hub wheel, and passes through the boundary between the step portion and the seal land portion; a length mB of the first circular arc from the boundary between the step portion and the seal land portion to an inner circumferential surface of the outer member; a second arc is defined as an arc having a center at an intersection point between the span center line and the rotation axis and passing through an inner diameter side end of the one axial end face of the outer member, The length mA of the second circular arc from the inner diameter side end of the axial end face of the outer member to the step portion of the hub wheel is, mA≦mB 3. The wheel bearing device according to claim 1, wherein the following relationship is satisfied:

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