Wheel bearing device

Abstract

The present invention addresses the problem of reducing stress concentration in a hub ring while ensuring the sealing properties of a sealing device in a wheel bearing device. The present invention is configured to satisfy at least one of the following relationships: 0.04 ≤ (r − h) / PCDh ≤ 0.80 where r is a radius of curvature of a stepped section (3i), h is an axial-direction length at a first boundary P1 of a boundary portion between a radial-direction inner end of the stepped section (3i) and a radial-direction outer end of a seal land section (3g) and at a second boundary P2 of a boundary portion between a radial-direction outer end of the stepped section (3i) and a radial-direction inner end of a flange side surface of an axle attachment flange (3b), and PCDh is a pitch circle diameter of a hub bolt (3f); and 0.04 ≤ (d1 − d2) / (2 × PCDh × tanθ) ≤ 0.80 where d1 is a diameter of the first boundary P1, d2 is a diameter of the second boundary P2, PCDh is a pitch circle diameter of the hub bolt (3f), and θ is an angle of a tangent with respect to the radial direction at the first boundary of the stepped section (3i).

Description

Wheel bearing device

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

[0002] 2. Description of the Related Art Wheel bearing devices that rotatably support wheels in suspension systems for automobiles and the like are known.

[0003] In recent years, fuel regulations have been imposed on vehicles that use wheel bearing devices in response to social trends such as energy conservation and decarbonization, and the trend toward electrification is progressing. Electric vehicles, which are primarily powered by on-board batteries and are expected to become more popular in the future, tend to be heavier than gasoline-powered vehicles, and their axle loads tend to increase.

[0004] Generally, as axle load increases, the rotational torque of a wheel bearing device increases, and from the perspective of strength, the size of the wheel bearing device must be increased. For example, wheel bearing devices used in electric vehicles tend to be narrow and large-diameter, with the axial distance from the outer side of the wheel mounting flange of the hub wheel to the inner end of the inner ring being smaller than the outer diameter of the inner end (pilot portion) of the outer ring. Furthermore, the mounting dimensions of wheel bearing devices have often remained largely unchanged from the past, with the steel ball arrays being closer in both radial and axial directions to the hub bolts that fasten the hub wheel to the wheel or brake components at the wheel mounting flange of the hub wheel. This has been addressed by thinning the wheel mounting flange of the hub wheel and reducing the dimensions of various components. However, thinning the wheel mounting flange of the hub wheel and reducing the dimensions of various components can potentially lead to stress concentration.

[0005] Furthermore, from the viewpoint of reducing fuel consumption, there is a demand for a wheel bearing device with lower torque. To achieve a lower torque for a wheel bearing device, for example, it is conceivable to reduce the contact force of the sliding surface caused by the lip of the sealing device between the outer ring and the hub wheel, but this may lead to a decrease in the sealing performance of the sealing device.

[0006] In Patent Document 1, the wheel bearing device includes double-row rolling elements rollably housed between the rolling surfaces of an inner member and an outer member via a cage, and a seal attached to an opening of an annular space formed between the outer member and the inner member, the base of the inner side of the wheel mounting flange being formed in an arc-shaped cross section, the outer seal of the seals being in sliding contact with this base, a step being formed between the side surface of the inner side of the wheel mounting flange and the base, the corners of this step being formed into arc-shaped surfaces with a predetermined radius of curvature, and annular recesses being formed on the inner periphery of the outer end of the outer member, and annular labyrinths having a generally L-shaped cross section facing the corners of the step with a small gap between them. In this way, the wheel bearing device of Patent Document 1 ensures the sealing performance of the sealing device, and the labyrinth prevents foreign matter such as muddy water from entering the outer seal side.

[0007] JP 2009-150437 A

[0008] However, in the wheel bearing device described above, although the labyrinth prevents the intrusion of foreign matter such as muddy water into the outer seal side while ensuring the sealing performance of the sealing device, in order to adapt it to the narrow, large-diameter wheel bearing devices of recent years, as mentioned above, it is thought that measures such as thinning the wheel mounting flange of the hub wheel and reducing the dimensions of various parts such as the radius of curvature of the stepped part of the wheel mounting flange will be necessary. And, by thinning the wheel mounting flange of the hub wheel and reducing the dimensions of various parts in this way, stress concentration can occur in the hub wheel.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wheel bearing device that can reduce stress concentration in a hub wheel while ensuring the sealing performance of a sealing device.

[0010] that is, a wheel bearing device comprising: an outer ring which is an outer member having double row outer raceway grooves on its inner circumference; a hub ring which has a small diameter step portion at the inner side end of its outer circumference, and an inner member which is made up of an inner ring provided on the small diameter step portion of the hub ring, and which has double row inner raceway grooves which face the double row outer raceway grooves; an outer side seal member which is fitted into an outer side opening formed between the outer ring and the hub ring; an inner side ball row which is rollably accommodated between the outer side outer raceway groove on the inner side of the outer ring and the inner raceway groove of the inner ring; and an outer side ball row which is rollably accommodated between the outer side outer raceway groove on the outer side of the outer ring and the inner raceway groove of the hub ring, wherein the hub ring has: a wheel mounting flange formed at the outer side end of the hub ring for mounting a wheel; a plurality of bolt holes which axially pass through the wheel mounting flange; a plurality of bolts press-fitted into each of the plurality of bolt holes; a seal land portion formed at the base of the wheel mounting flange with which the outer side seal member comes into contact; The wheel mounting flange has a flange side surface on the inner side of the wheel mounting flange, and a step portion that connects the flange side surface and the seal land portion and has a cross section formed in an arc shape, wherein the radially inner end of the step portion is connected to the radially outer end of the seal land portion, and the boundary portion between the radially inner end of the step portion and the radially outer end of the seal land portion is configured as a first boundary P1, and the radially outer end of the step portion is connected to the radially inner end of the flange side surface, and the boundary portion between the radially outer end of the step portion and the radially inner end of the flange side surface is configured as a second boundary P2, and with regard to the following conditions 1 to 5, at least one of condition 1 and condition 2 is satisfied, and condition 3 is satisfied, and at least one of condition 4 and condition 5 is satisfied.Condition 1: Where a is the length of the outer diameter of the inner end of the outer ring and b is the axial length from the outer side surface of the wheel mounting flange of the hub ring to the inner side surface of the inner ring, it satisfies 1.20≦a / b≦1.95. Condition 2: Where PCDo is the pitch circle diameter of the outer ball row and PCDh is the pitch circle diameter of the bolts of the hub ring, it satisfies 0.60≦PCDo / PCDh≦0.73. Condition 3: Where d0 is the inner diameter of a portion of the outer end of the outer ring where the outer seal member is fitted and d1 is the diameter of the first boundary P1, it satisfies d0≧d1. Condition 4: Where r is the radius of curvature of the stepped portion of the hub ring, h is the axial length between the first boundary P1 and the second boundary P2, and PCDh is the pitch circle diameter of the bolts of the hub ring, it satisfies 0.04≦(r−h) / PCDh≦0.80. The relationship between the diameter d1 of the first boundary P1, the diameter d2 of the second boundary P2, the pitch circle diameter PCDh of the bolt of the hub wheel, and the angle θ of the tangent at the first boundary P1 of the stepped portion of the hub wheel relative to the radial direction is 0.04≦(d1−d2) / (2×PCDh×tanθ)≦0.80.

[0011] The present invention has the following advantages: That is, the wheel bearing device of the present invention can reduce stress concentration in the hub wheel while ensuring the sealing performance of the sealing device.

[0012] 1 is a cross-sectional view showing a wheel bearing device according to an embodiment of the present invention; FIG. 1 is an enlarged cross-sectional view showing the structure of a wheel mounting flange of a hub ring and an outer end portion of an outer ring of the wheel bearing device; FIG. 2 is an enlarged cross-sectional view showing the structure of a wheel mounting flange of a hub ring and an outer end portion of an outer ring of the wheel bearing device; (a) a diagram showing the stress amplitude level of a stepped portion of a hub ring in the configuration of condition 4 of the wheel bearing device; (b) a diagram showing the stress amplitude level of a stepped portion of a hub ring in the configuration of condition 5 of the wheel bearing device; FIG. 2 is an enlarged view of the hub ring of the wheel bearing device as viewed from the inner side; FIG. 3 is an enlarged cross-sectional view showing the structure of a wheel mounting flange of a portion of the hub ring of the wheel bearing device where a rib is not arranged and an outer end portion of the outer ring; FIG. 4 is an enlarged cross-sectional view showing the structure of a wheel mounting flange of a hub ring of the wheel bearing device and an outer end portion of the outer ring.

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

[0014] [Wheel Bearing Apparatus] A wheel bearing apparatus 1 shown in FIG. 1 uses a sealing device according to the present invention, and supports a wheel rotatably in a suspension system of a vehicle such as an automobile.

[0015] As shown in Figures 1 and 2, the wheel bearing device 1 has a configuration known as a 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.

[0016] Here, the inner side refers to the vehicle body side of the wheel support bearing device 1 when it is attached to the vehicle body, and the outer side refers to the wheel side of the wheel support bearing device 1 when it is attached to the vehicle body. The axial direction refers to the direction along the rotation axis X of the wheel support bearing device 1, with one axial end side being the outer side and the other axial end side being the inner side. The direction perpendicular to the rotation axis of the wheel support bearing device 1 is referred to as the radial direction. In the following, the term "cross section" will be explained as referring to a cross section that passes through the rotation axis of the wheel support bearing device 1 and is parallel to the rotation axis of the wheel support bearing device 1.

[0017] An inner-side outer raceway groove 2c and an outer-side outer raceway groove 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 member is integrally formed on the outer peripheral surface of the outer ring 2. The vehicle body mounting flange 2e is provided with bolt holes into which fastening members (here, bolts) are inserted that fasten the vehicle body member and the outer ring 2. The inner end of the outer ring 2, on the inner side of the vehicle body mounting flange 2e, is configured as a cylindrical pilot portion 2g that is fitted into a vehicle knuckle.

[0018] The inner end of the outer peripheral surface of the hub wheel 3 is formed with a small-diameter step 3a that is smaller in diameter than the outer end. A wheel mounting flange 3b that extends radially outward is integrally formed with the outer end of the hub wheel 3 for mounting a wheel. A plurality of ribs 3d are formed on the wheel mounting flange 3b in the circumferential direction about the rotation axis X. An outer-side inner raceway groove 3c is provided on the outer peripheral surface of the hub wheel 3 so as to face the outer outer raceway groove 2d of the outer ring 2. In other words, the inner raceway groove 3c is defined by the hub wheel 3 on the outer side of the inner member. A plurality of bolt holes 3e are formed in the wheel mounting flange 3b, each penetrating the plurality of ribs 3d in the axial direction. A plurality of hub bolts 3f are press-fitted into the plurality of bolt holes 3e to fasten the hub wheel 3 to a wheel or brake component. In other words, the plurality of hub bolts 3f are formed in the circumferential direction about the rotation axis X.

[0019] The inner ring 4 is mounted on the small diameter step 3a of the hub ring 3. The inner ring 4 is press-fitted into the small diameter step 3a via a predetermined interference. Furthermore, the hub ring 3 and the inner ring 4 are integrated by a crimped portion formed by plastically deforming and crimping the inner end of the small diameter step 3a of the hub ring 3, preventing the inner ring 4 from slipping out of the hub ring 3 in the axial direction. The inner ring 4 applies preload to the inner ball row 5 and outer ball row 6, which form the rolling rows. An inner-side inner raceway groove 4a is formed on the outer peripheral surface of the inner ring 4 so as to face the inner-side outer raceway groove 2c of the outer ring 2. In other words, the inner ring 4 defines the inner raceway groove 4a on the inner side of the inner member.

[0020] A bearing space, which is an annular space, is formed between the outer ring 2 and the hub wheel 3. An outer seal member 10, which is a sealing device, is fitted into the outer end of the bearing space to prevent the intrusion of foreign matter such as muddy water.

[0021] An inner seal member 9, which is a sealing device, is fitted into the inner end of the bearing space between the outer ring 2 and the inner ring 4 to prevent the intrusion of foreign matter such as muddy water.

[0022] The inner ball row 5 and outer ball row 6, which are rolling rows, are rollably housed between the raceway grooves of the outer member and the inner member. The inner ball row 5 and outer ball row 6 are formed by a plurality of balls 7, which are rolling elements, held in a cage 8. The inner ball row 5 is rollably sandwiched between the outer raceway groove 2c on the inner side of the outer ring 2 and the inner raceway groove 4a of the inner ring 4. The outer ball row 6 is rollably sandwiched between the outer raceway groove 2d on the outer side of the outer ring 2 and the inner raceway groove 3c of the hub ring 3. In other words, the inner ball row 5 and outer ball row 6 are rollably housed between the raceway grooves of the outer member and the inner member. In the wheel bearing device 1, the outer ring 2, the hub ring 3 and the inner ring 4, the inner ball row 5, and the outer ball row 6 form a double-row angular contact ball bearing.

[0023] [Conditions for Axial and Radial Size of Wheel Bearing Device] The wheel bearing device 1 is configured to satisfy at least one of Condition 1 and Condition 2. Condition 1 is a condition regarding the axial and radial sizes of the wheel bearing device 1. Condition 1 satisfies the relationship of 1.20≦a / b≦1.95, where the outer diameter a of the inner end of the outer ring 2 (a cylindrical pilot portion that fits into the knuckle of a vehicle) and the axial distance b from the outer side surface of the wheel mounting flange 3b of the hub ring 3 to the inner end of the inner ring 4 are respectively. Condition 2 is a condition regarding the radial size of the wheel bearing device 1. Condition 2 satisfies the relationship of 0.60≦PCDo / PCDh≦0.73, where the pitch circle diameter PCDo of the outer ball row 6 and the pitch circle diameter PCDh of the hub bolt 3f of the hub ring 3 are respectively. In this way, by satisfying either Condition 1 or Condition 2, the wheel bearing device 1 is configured to be relatively large in the radial direction. Furthermore, by satisfying both conditions 1 and 2, the pitch circle diameter PCDo is the diameter obtained when the radial distance from the rotation axis X to the center of the outer ball is taken as the radius, and the pitch circle diameter PCDh is the diameter obtained when the radial distance from the rotation axis X to the central axis of the hub bolt 3f is taken as the radius. Also, although the present embodiment uses hub bolts 3f, wheel bolts may be used instead of hub bolts.

[0024] [Specific Configuration of Outer Seal Member] The outer seal member 10 includes a core metal 11 and a seal member 12 .

[0025] The core metal 11 is, for example, a circular ring made of steel plate, and is fitted into the outer ring 2. The core metal 11 includes an inner fitting portion and an inner portion. The inner fitting portion is a cylindrical portion that is fitted into the radially inner surface of the outer end portion of the outer ring 2. The inner portion is a donut-shaped portion that extends radially inward from the outer end portion of the inner fitting portion.

[0026] The seal member 12 is made of, for example, synthetic rubber and is configured to be elastically deformable. The seal member 12 is joined to the core metal 11 by vulcanization bonding or the like, and is configured integrally with the core metal 11. The seal member 12 has multiple seal lips that contact the seal land portion 3g. The seal member 12 has a grease lip 12a and side lips 12b and 12c.

[0027] The grease lip 12a and side lips 12b and 12c of the seal member 12 constitute the seal lips of the seal member 12. The grease lip 12a extends from the inside of the core 11 toward the inner diameter side and the inner side, and contacts the seal land portion 3g. The side lip 12b extends from the inside of the core 11 toward the outer diameter side and the outer side, radially outward of the grease lip 12a, and contacts the seal land portion 3g. The side lip 12c extends from the inside of the core 11 toward the outer diameter side and the outer side, which is the wheel mounting flange 3b side, radially outward of the grease lip 12a and the side lip 12b, and contacts the seal land portion 3g.

[0028] [Structure of the wheel mounting flange of the hub wheel and the outer end of the outer ring] A seal land 3g, with which the outer seal member 10 comes into contact, is formed at the base of the wheel mounting flange 3b of the hub wheel 3. The seal land 3g is configured in an annular shape in the circumferential direction about the rotation axis X and is connected to the inner raceway groove 3c. In a cross section passing through the rotation axis X and parallel to the rotation axis X, the seal land 3g comprises an axial surface 3ga, which is a straight surface parallel to the axial direction, an arc-shaped surface 3gb, which is convex toward the inner diameter side, and a radial surface 3gc, which is a straight surface parallel to the radial direction. The inner end of the axial surface 3ga is connected to the outer end of the inner raceway groove 3c. The inner end of the arc-shaped surface 3gb is connected to the outer end of the axial surface 3ga. The radially inner end of the radial surface 3gc is connected to the radially outer end of the arc-shaped surface 3gb.

[0029] The wheel mounting flange 3b of the hub wheel 3 has an inner flange side surface 3h. The flange side surface 3h is a flat surface parallel to the radial direction. The portion of the flange side surface 3h near the bolt hole 3e serves as a bearing surface when the hub bolt 3f is fastened. The flange side surface 3h is located radially outward and on the outer side of the seal land portion 3g.

[0030] A step portion 3i is formed between the flange side surface 3h and the seal land portion 3g of the hub wheel 3. The step portion 3i is configured in an annular shape in the circumferential direction about the rotation axis X and connects the flange side surface 3h and the seal land portion 3g. The step portion 3i bends inward as it approaches the inner diameter side, and has an overall arc-shaped cross section that is convex toward the inner diameter side. The radially inner end of the step portion 3i is connected to the radially outer end of the radial surface 3gc of the seal land portion 3g. The boundary between the radially inner end of the step portion 3i and the radially outer end of the radial surface 3gc of the seal land portion 3g is configured as a first boundary P1. The radially outer end of the step portion 3i is connected to the radially inner end of the flange side surface 3h. The boundary between the radially outer end of the step portion 3i and the radially inner end of the flange side surface 3h is configured as a second boundary P2.

[0031] The outer end face 2h of the outer ring 2 is composed of a flat surface parallel to the radial direction. The outer ring 2 also has an inclined surface 2i. The inclined surface 2i is composed of a flat surface or a curved surface that has an inclination angle with respect to the axial direction, or a combined surface of a flat surface and a curved surface. Here, when the inclined surface 2i is a curved surface or a combined surface of a flat surface and a curved surface, the inclined surface 2i is defined as having an inclination angle even when the straight line connecting the connection point between the inclined surface 2i and the outer end face 2h and the connection point between the inclined surface 2i and the portion of the outer end of the outer ring 2 where the outer seal member 10 is fitted forms an angle with respect to the axial direction.

[0032] A predetermined gap is formed between the outer end face 2h and inclined surface 2i of the outer ring 2 and the stepped portion 3i of the hub ring 3, forming a labyrinth. The outer end face 2h of the outer ring 2 and the stepped portion 3i of the hub ring 3 are configured to face each other in the axial direction. The outer end face 2h and inclined surface 2i of the outer ring 2 are located radially outward from the first boundary P1. The outer end face 2h and inclined surface 2i of the outer ring 2 are located radially inward from the second boundary P2.

[0033] The wheel bearing device 1 is configured to satisfy condition 3. Condition 3 satisfies the relationship d0≧d1 between an inner diameter d0 of a portion of the outer end of the outer ring 2 where the outer seal member 10 is fitted and a diameter d1 of a first boundary P1 that is the radially outer end of the seal land 3g. Here, the inner diameter d0 is the diameter obtained when the radial distance from the rotation axis X to the portion where the outer seal member 10 is fitted is taken as the radius, and the diameter d1 is the diameter obtained when the radial distance from the rotation axis X to the first boundary P1 is taken as the radius.

[0034] This configuration allows the radius of curvature r of the stepped portion 3i of the hub wheel 3 (the radius of curvature r of the arc-shaped portion of the stepped portion 3i) to be relatively large. Therefore, even if the wheel bearing device 1 is configured to satisfy at least one of Condition 1 and Condition 2, stress generation in the stepped portion 3i can be suppressed. Furthermore, since Condition 3 (the relationship d0≧d1 between the inner diameter d0 of the outer end of the outer ring 2 and the diameter d1 of the first boundary P1) is satisfied and a predetermined gap is formed as a labyrinth between the outer end face 2h and inclined surface 2i of the outer ring 2 and the stepped portion 3i of the hub wheel 3, foreign matter can be prevented from entering the outer seal member 10 from the outer end of the bearing space between the outer ring 2 and the hub wheel 3. Compared to when the relationship d0<d1 is satisfied, the amount and speed of muddy water flowing into the contact portion between the seal lip 12c and the radial surface 3gc can be reduced, improving muddy water resistance.

[0035] Furthermore, the wheel bearing device 1 is configured to satisfy at least one of Condition 4 and Condition 5. Condition 4 satisfies the relationship 0.04≦(r−h) / PCDh≦0.80, where r is the radius of curvature of the stepped portion 3i (the arc-shaped portion of the stepped portion 3i) of the hub ring 3, h is the axial length between a first boundary P1 that is the radially outer end of the seal land portion 3g and a second boundary P2 that is the radially inner end of the flange side surface 3h, and PCDh is the pitch circle diameter PCDh of the hub bolt 3f of the hub ring 3.

[0036] By configuring the wheel bearing device 1 to satisfy condition 4 in this way, the radius of curvature r of the stepped portion 3i of the hub ring 3 can be configured to be relatively large, reducing the stress amplitude generated at the stepped portion 3i of the hub ring 3 and improving the efficiency of discharging muddy water that has entered the labyrinth formed by the predetermined gap between the outer end face 2h and inclined surface 2i of the outer ring 2 and the stepped portion 3i of the hub ring 3 (see FIG. 4(a)). Therefore, by satisfying conditions 3 and 4, the sealing performance of the outer seal member 10 can be ensured while stress concentration at the stepped portion 3i of the hub ring 3 can be reduced.

[0037] Condition 5 requires that the following relationship be satisfied: 0.04≦(d1−d2) / (2×PCDh×tanθ)≦0.80, where d1 is the diameter of the first boundary P1, which is the radially outer end of the seal land 3g; d2 is the diameter of the second boundary P2, which is the boundary between the radially outer end of the stepped portion 3i and the radially inner end of the flange side surface 3h; d2 is the pitch circle diameter PCDh of the hub bolt 3f of the hub wheel 3; and θ is the angle θ of the tangent of the stepped portion 3i at the first boundary P1 relative to the radial direction. Here, diameter d2 is the diameter when the radial distance from the rotation axis X to the second boundary P2 is taken as the radius. The wheel bearing device 1 shown in FIG. 3 satisfies Condition 5, and the radius of curvature r of the stepped portion 3i of the hub wheel 3 is configured to be close to its upper limit. Also, as shown in FIG. 3, a tapered portion may be formed on the outer diameter surface of the outer ring 2. This allows for an appropriate distance to be maintained between the outer diameter surface of the outer ring 2 and the hub bolt 3f.

[0038] By configuring the wheel bearing device 1 to satisfy condition 5 in this way, the radius of curvature r of the step 3i of the hub ring 3 can be made relatively large, reducing the stress amplitude generated at the step 3i of the hub ring 3 and improving the efficiency of discharging muddy water that has entered the labyrinth formed by the predetermined gap between the outer end face 2h and inclined surface 2i of the outer ring 2 and the step 3i of the hub ring 3 (see FIG. 4(b)). Therefore, by satisfying conditions 3 and 5, the sealing performance of the outer seal member 10 can be ensured while stress concentration at the step 3i of the hub ring 3 can be reduced.

[0039] The wheel bearing device 1 may also be configured to satisfy conditions 4 and 5. By configuring the wheel bearing device 1 to satisfy conditions 4 and 5 in this way, the radius of curvature r of the stepped portion 3i of the hub ring 3 can be configured to be relatively large, the stress amplitude generated in the stepped portion 3i of the hub ring 3 can be reduced, and the efficiency of discharging muddy water that has entered the labyrinth formed by the predetermined gap between the outer end face 2h and inclined surface 2i of the outer ring 2 and the stepped portion 3i of the hub ring 3 can be improved. Therefore, by satisfying conditions 3, 4, and 5, the sealing performance of the outer seal member 10 can be ensured while stress concentration in the stepped portion 3i of the hub ring 3 can be reduced.

[0040] The radially inner end of the stepped portion 3i of the hub wheel 3 is connected to the radially outer end of the radial surface 3gc of the seal land portion 3g, and a tangent to the second boundary P2 of the stepped portion 3i is configured to be parallel to the flange side surface 3h.

[0041] By configuring in this manner, the radius of curvature r of the step portion 3i of the hub wheel 3 can be configured to be relatively large, thereby reducing the stress amplitude generated in the step portion 3i of the hub wheel 3. Therefore, by satisfying condition 3, the sealing performance of the outer seal member 10 can be ensured while stress concentration in the step portion 3i of the hub wheel 3 can be reduced.

[0042] The wheel bearing device 1 is configured to satisfy condition 6. Condition 6 satisfies the relationship C1≦C2, where C1 is the shortest distance between the inclined surface 2i of the outer ring 2 and the stepped portion 3i of the hub wheel 3, and C2 is the axial distance C2 between the outermost diameter portion of the outer end face 2h of the outer ring 2 and the stepped portion 3i of the hub wheel 3.

[0043] With this configuration, the inner side is narrower than the outlet side gap (gap at the radially outer end) in the predetermined labyrinth between the outer end face 2h and inclined surface 2i of the outer ring 2 and the stepped portion 3i of the hub wheel 3. This makes it possible to more reliably prevent foreign matter from entering the outer side end of the bearing space between the outer ring 2 and hub wheel 3 toward the outer side seal member 10.

[0044] 5 and 6, the seal land 3g and step 3i of the hub ring 3 are configured in an annular shape extending circumferentially relative to the axial direction, and are also formed in areas where the ribs 3d are not formed. Even in areas where the ribs 3d are not formed on the hub ring 3, a predetermined gap is formed between the outer end face 2h and inclined surface 2i of the outer ring 2 and the step 3i of the hub ring 3, forming a labyrinth. Furthermore, even in areas where the ribs 3d are not formed on the hub ring 3, the configuration is configured to satisfy Condition 6 (where C1 is the shortest distance between the inclined surface 2i of the outer ring 2 and the step 3i of the hub ring 3, and C2 is the axial distance C2 between the outermost diameter part of the outer end face 2h of the outer ring 2 and the step 3i of the hub ring 3, and the relationship C1≦C2).

[0045] With this configuration, even in parts of the hub wheel 3 where the ribs 3d are not formed, the labyrinth of predetermined gaps between the outer end face 2h and inclined surface 2i of the outer ring 2 and the stepped portion 3i of the hub wheel 3 is configured so that the inner side is narrower than the outlet side gap (gap at the radially outer end). Therefore, even in parts of the hub wheel 3 where the ribs 3d are not formed, it is possible to more reliably prevent foreign matter from entering the outer end of the bearing space between the outer ring 2 and hub wheel 3 toward the outer seal member 10.

[0046] As shown in Figure 7, the step portion 3i of the hub wheel 3 may also be configured to include an arc-shaped surface 3ia having an arc-shaped cross section that convex toward the inner diameter side, and a straight surface 3ib located radially inward of the arc-shaped surface 3ia. The radially outer end of the arc-shaped surface 3ia is connected to the flange side surface 3h. In other words, the boundary between the radially outer end of the arc-shaped surface 3ia and the radially inner end of the flange side surface 3h is configured as a second boundary P2. The radially outer end of the straight surface 3ib is connected to the radially inner side of the arc-shaped surface 3ia, and the radially inner end of the straight surface 3ib is connected to the radially outer end of the radial surface 3gc of the seal land portion 3g. In other words, the boundary between the radially outer end of the straight surface 3ib and the radially outer end of the radial surface 3gc of the seal land portion 3g is configured as a first boundary P1. In the present embodiment, the configuration may be such that the relationship C1≦C2 is satisfied for the shortest distance C1 between the inclined surface 2i of the outer ring 2 and the stepped portion 3i (arcuate surface 3ia or straight surface 3ib) of the hub wheel 3, and the axial distance C2 between the outermost diameter portion of the outer end face 2h of the outer ring 2 and the stepped portion 3i (arcuate surface 3ia or straight surface 3ib) of the hub wheel 3. Furthermore, the radially inner end of the straight surface 3ib of the stepped portion 3i may be connected to the radially outer end of the radial surface 3gc of the seal land portion 3g, and the tangent at the second boundary P2 of the arcuate surface 3ia of the stepped portion 3i may be parallel to the flange side surface 3h.

[0047] By configuring in this manner, the radius of curvature r of the step portion 3i of the hub wheel 3 can be configured to be relatively large, thereby reducing the stress amplitude generated in the step portion 3i of the hub wheel 3. Therefore, by satisfying condition 3, the sealing performance of the outer seal member 10 can be ensured while stress concentration in the step portion 3i of the hub wheel 3 can be reduced.

[0048] Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, which are merely examples, and it goes without saying that the present invention can be embodied in various other forms without departing from the spirit of the present invention. The scope of the present invention is indicated by the claims, and further includes the equivalent meanings set forth in the claims, and all modifications within the scope of the claims.

[0049] The present invention can be used in a wheel bearing device.

[0050] DESCRIPTION OF SYMBOLS 1 Wheel bearing device 2 Outer ring 2c (inner side) outer raceway surface 2d (outer side) outer raceway surface 2e Vehicle body mounting flange 2f Bolt hole 2g Inner side end (pilot portion) 2h Outer side end 2i Inclined surface 3 Hub ring 3a Small diameter step portion 3b Wheel mounting flange 3c Inner raceway surface 3d Rib 3e Bolt hole 3f Hub bolt 3g Seal land portion 3h Flange side surface 3i Step portion 4 Inner ring 4a Inner raceway surface 5 Inner side ball row 6 Outer side ball row 7 Balls 8 Cage 9 Inner side seal member 10 Outer side seal member 11 Core metal 12 Seal member 12a Grease lip 12b Side lip 12c Side lip d0 Inner diameter of outer side end of outer ring d1 Diameter of first boundary P1 d2 Diameter of second boundary P2 P1 First boundary P2 Second boundary PCDo Pitch circle diameter of outer ball row PCDh Pitch circle diameter of hub bolt of hub ring 3 r Radius of curvature of step portion h Axial length between first boundary P1 and second boundary P2

Claims

1. A wheel bearing device comprising: an outer ring which is an outer member having double row outer raceway grooves on its inner circumference; a hub ring having a small diameter step portion at the inner end of its outer circumference, and an inner member consisting of an inner ring provided at the small diameter step portion of the hub ring, the inner member having double row inner raceway grooves facing the double row outer raceway grooves; an outer seal member fitted into an outer opening formed between the outer ring and the hub ring; an inner ball row rollably housed between the outer raceway groove on the inner side of the outer ring and the inner raceway groove of the inner ring; and an outer ball row rollably housed between the outer raceway groove on the outer side of the outer ring and the inner raceway groove of the hub ring, wherein the hub ring has: a wheel mounting flange formed at the outer end of the hub ring for mounting a wheel; a plurality of bolt holes axially penetrating the wheel mounting flange; a plurality of bolts press-fitted into each of the bolt holes; a seal land formed at the base of the wheel mounting flange with which the outer seal member comes into contact; a flange side surface on the inner side of the wheel mounting flange; and a step portion connecting the flange side surface and the seal land portion and having an arc-shaped cross section, wherein a radially inner end of the step portion is connected to a radially outer end of the seal land portion, and a boundary portion between the radially inner end of the step portion and the radially outer end of the seal land portion is configured as a first boundary P1, and a radially outer end of the step portion is connected to a radially inner end of the flange side surface, and a boundary portion between the radially outer end of the step portion and the radially inner end of the flange side surface is configured as a second boundary P2, and with respect to the following conditions 1 to 5, at least one of condition 1 and condition 2 is satisfied, and condition 3 is satisfied, and at least one of condition 4 and condition 5 is satisfied.Condition 1: Where a is the length of the outer diameter of the inner end of the outer ring and b is the axial length from the outer side surface of the wheel mounting flange of the hub ring to the inner side surface of the inner ring, it satisfies 1.20≦a / b≦1.

95. Condition 2: Where PCDo is the pitch circle diameter of the outer ball row and PCDh is the pitch circle diameter of the bolts of the hub ring, it satisfies 0.60≦PCDo / PCDh≦0.

73. Condition 3: Where d0 is the inner diameter of a portion of the outer end of the outer ring where the outer seal member is fitted and d1 is the diameter of the first boundary P1, it satisfies d0≧d1. Condition 4: Where r is the radius of curvature of the stepped portion of the hub ring, h is the axial length between the first boundary P1 and the second boundary P2, and PCDh is the pitch circle diameter of the bolts of the hub ring, it satisfies 0.04≦(r−h) / PCDh≦0.

80. The relationship between the diameter d1 of the first boundary P1, the diameter d2 of the second boundary P2, the pitch circle diameter PCDh of the bolt of the hub wheel, and the angle θ of the tangent at the first boundary P1 of the stepped portion of the hub wheel relative to the radial direction is 0.04≦(d1−d2) / (2×PCDh×tanθ)≦0.

80.

2. The wheel bearing device according to claim 1, wherein the outer ring is provided with an inclined surface connected to the outer end face of the outer ring, the inclined surface being located radially inward of the outer end face of the outer ring and having an inclination angle relative to the axial direction, and a predetermined gap is formed between the outer end face and inclined surface of the outer ring and the stepped portion of the hub ring, and the following condition 6 is satisfied: Condition 6: The shortest distance C1 between the inclined surface of the outer ring and the stepped portion of the hub ring, and the axial distance C2 between the outermost diameter part of the outer end face of the outer ring and the stepped portion of the hub ring, satisfy the relationship C1≦C2.

3. A wheel bearing device as set forth in claim 2, wherein the hub ring has a plurality of ribs formed circumferentially about the rotation axis and on which the bolts are formed, the seal land portion and the step portion of the hub ring are configured in an annular shape and are formed even in parts where the ribs are not formed, and in parts of the hub ring where the ribs are not formed, a predetermined gap is formed between the outer side end face and the inclined surface of the outer ring and the step portion of the hub ring, and the device is configured to satisfy condition 6.

4. A wheel bearing device according to any one of claims 1 to 3, wherein a tangent to the second boundary P2 of the stepped portion of the hub wheel is configured to be parallel to the flange side surface.

5. A wheel bearing device as claimed in any one of claims 1 to 3, wherein the step portion of the hub wheel comprises an arc-shaped surface having an arc-shaped cross section and a straight surface arranged radially inward of the arc-shaped surface, the radially outer end of the arc-shaped surface is connected to the flange side surface, and the boundary portion between the radially outer end of the arc-shaped surface and the radially inner end of the flange side surface is configured as the second boundary P2, and the radially outer end of the straight surface is connected to the radially inner side of the arc-shaped surface, and the radially inner end of the straight surface is connected to the radially outer end of the radial surface of the seal land portion, and the boundary portion between the radially outer end of the straight surface and the radially outer end of the radial surface of the seal land portion is configured as the first boundary P1.

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