Bearing device for wheel

Abstract

As a result, it is possible to reliably prevent heat treatment by quenching from affecting a bolt hole in a wheel attachment flange of a hub ring, reduce surface vibration of the wheel attachment flange, and improve the sliding torque of a hub bolt. A bearing device for a wheel is provided with: an outer ring (2); an inner member comprising a hub ring (3) having one inner raceway surface (3e) and a wheel attachment flange (3b), and an inner ring (4) connected to the hub ring and having the other inner raceway surface (4a); and double rows of rolling bodies (5, 5) housed between the outer ring and both raceway surfaces of the hub ring and the inner ring, in which the ratio (c) of the pitch circle diameter (b) of the rolling bodies to the distance (a) between the rolling bodies is 2 or more, and the wheel attachment flange has a bolt hole (3d) into which a hub bolt (3c) is inserted. The heat-affected layer of the quench-hardened layer (9) applied to the inner rail surface on the wheel attachment flange side is formed so as not to reach the bolt hole.

Description

Technical Field

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

[0002] Conventionally, a bearing device for a wheel that rotatably supports a wheel has been known. In the bearing device for a wheel, an inner member is disposed inside an outer member, and rolling elements are interposed between respective raceway surfaces of the outer member and the inner member. In this way, the bearing device for a wheel constitutes a rolling bearing structure that enables the wheel mounted on the inner member to rotate freely.

[0003] In a bearing device for a wheel having such a rolling bearing structure, a rolling bearing structure having a double row of rolling elements that are rotatably accommodated between respective raceway surfaces of the inner member and the outer member is known (for example, refer to Patent Document 1). The double row of rolling elements are arranged to be separated by a certain distance in the axial direction. As one of the means for achieving a long service life of the bearing device for a wheel, the rigidity is usually increased by increasing the distance in the axial direction of the double row of rolling elements and the pitch circle diameter (P.C.D.) of each rolling element. However, in such a structure, the overall size of the bearing device for a wheel has to be enlarged.

[0004] In addition, in recent years, the popularization of EV vehicles has been promoted. Since an EV vehicle is equipped with a storage battery and there is a tendency for the vehicle mass to easily increase, it is necessary to increase the rated load of the bearing device for a wheel.

[0005] As the vehicle mass of an EV vehicle increases, the pitch circle diameter (P.C.D.) of each rolling element is further increased compared to the past to increase the rated load. By increasing the pitch circle diameter (P.C.D.) of each rolling element, sometimes the outer side seal member also becomes larger in the radial direction, and the radial distance between the seal region portion of the hub ring forming the inner member and the bolt hole of the wheel mounting flange becomes close.

[0006] On the other hand, on the outer side raceway surface and the seal region portion of the hub ring forming the inner member, a hardened layer is formed by high-frequency quenching for the purpose of improving indentation resistance, wear resistance, and bearing life (for example, refer to Patent Document 1). In a conventional bearing device for a wheel, when high-frequency quenching is performed on the outer side raceway surface and the seal region portion, the hardened layer is prevented from being formed up to the periphery of the bolt hole of the wheel mounting flange.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2005-075135 Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] However, with the increase in the diameter of the bearing device for wheels in recent years, the radial distance between the sealing area portion of the wheel hub ring and the bolt holes of the wheel mounting flange has become closer. Therefore, sometimes the heat-hardened layer accidentally forms around the bolt holes, causing strain during the press-fitting of the wheel hub bolts and increasing the surface vibration of the wheel mounting flange. In addition, there is a concern that the sliding torque may decrease due to insufficient cutting of the wheel hub bolt serrations at the fitting portion between the wheel hub bolt and the bolt hole.

[0012] An object of the present invention is to provide a bearing device for a wheel that can reliably prevent the influence of heat treatment based on quenching on the bolt holes of the wheel mounting flange of the wheel hub ring, reduce the surface vibration of the wheel mounting flange, and achieve an increase in the sliding torque of the wheel hub bolt.

[0013] Means for solving the problem

[0014] That is, the present invention relates to a bearing device for a wheel, which includes:

[0015] An outer member having a double-row outer raceway surface on its inner circumference; an inner member composed of a wheel hub ring and a raceway surface forming member, the wheel hub ring having an inner raceway surface on the outer circumference that faces the outer raceway surface and a wheel mounting flange for mounting the wheel, the raceway surface forming member being connected to the wheel hub ring and having an inner raceway surface on the outer circumference that faces the outer raceway surface; a double-row rolling element that is rotatably accommodated between the two raceway surfaces of the outer member and the inner member; and a sealing member that seals between the outer member and the inner member, wherein,

[0016] The ratio c of the pitch circle diameter (P.C.D.) b of the rolling element to the distance a between the rolling elements is 2 or more,

[0017] The ratio k of the pitch circle diameter b to the length B from the outer side end surface of the wheel mounting flange to the inner side end portion of the outer member is 0.7 or more,

[0018] The wheel mounting flange has bolt holes,

[0019] The heat-affected layer of the quenching hardened layer applied to the inner raceway surface on the wheel mounting flange side is formed so as not to reach the bolt holes, and the axial distance d from the radial outer side end surface of the sealing area portion of the wheel mounting flange to the radial inner side surface of the bolt holes is larger than the depth e of the heat-affected layer of the quenching hardened layer.

[0020] In addition, the present invention relates to a bearing device for a wheel, which includes:

[0021] An outer member having a double-row outer raceway surface on its inner circumference; an inner member composed of a hub ring and a raceway surface forming member, the hub ring having on its outer circumference one inner raceway surface facing the outer raceway surface and a wheel mounting flange for mounting a wheel, the raceway surface forming member being connected to the hub ring and having on its outer circumference the other inner raceway surface facing the outer raceway surface; a double-row rolling element freely rotatably accommodated between the two raceway surfaces of the outer member and the inner member; and a sealing member for sealing between the outer member and the inner member, wherein,

[0022] The ratio c of the pitch circle diameter (P.C.D.) b of the rolling element to the distance a between the rolling elements is 2 or more.

[0023] The ratio k of the pitch circle diameter b to the length B from the outer side end face of the wheel mounting flange to the inner side end of the outer member is 0.7 or more.

[0024] The wheel mounting flange has bolt holes.

[0025] The heat affected zone of the quenched and hardened layer applied to the inner raceway surface on the wheel mounting flange side is formed not to reach the bolt holes. The heat affected zone of the quenched and hardened layer is formed in the thickness direction of the wheel mounting flange, and the radial distance f from the radially inner side surface of the bolt hole to the radially outermost position of the heat affected zone of the quenched and hardened layer is 2 mm or more.

[0026] In addition, in the present invention, the radial distance g from the radially outer side end face of the sealing region portion of the wheel mounting flange to the radially inner side surface of the bolt hole is formed to be 2 mm or more and 16 mm or less.

[0027] In addition, in the present invention, the ratio l of the length from the center of the bolt hole of the wheel mounting flange to the rotation axis A of the wheel bearing device to the length B from the outer side end face of the wheel mounting flange to the inner side end of the outer member is 0.65 to 1.05.

[0028] Advantages of the Invention

[0029] As an effect of the present invention, the following effects are achieved.

[0030] That is, according to the present invention, it is possible to reliably prevent the influence of heat treatment based on quenching on the bolt holes of the wheel mounting flange of the hub ring, reduce the surface vibration of the wheel mounting flange, and achieve an increase in the sliding torque of the wheel bolts. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a cross-sectional view showing a wheel bearing device.

[0032] Figure 2 It is a cross-sectional view showing a wheel bearing device according to the first embodiment.

[0033] Figure 3 It is a cross-sectional view showing a wheel bearing device according to the second embodiment.

[0034] Figure 4 It is an upper cross-sectional view showing a wheel bearing device according to the third embodiment.

[0035] Explanation of reference numerals

[0036] 1 Wheel bearing device

[0037] 2 Outer ring (outer member)

[0038] 3 Hub ring

[0039] 3a Small-diameter stepped portion

[0040] 3b Wheel mounting flange

[0041] 3c Hub bolt

[0042] 3d Bolt hole

[0043] 3e Inner raceway surface

[0044] 3f Sealing area portion

[0045] 3g Connecting portion

[0046] 4 Inner ring

[0047] 5 Rolling element

[0048] 6 Inner side seal member

[0049] 7 Outer side seal member

[0050] 9 Quenched and hardened layer

[0051] a Distance between rolling elements

[0052] b Pitch circle diameter

[0053] c Ratio of pitch circle diameter to distance between rolling elements

[0054] d Axial distance from the radially outer end face of the sealing area portion to the radially inner side face of the bolt hole

[0055] e Depth of heat affected zone of quenched and hardened layer

[0056] f Radial distance from the radially inner side face of the bolt hole to the radially outermost position of the heat affected zone of the quenched and hardened layer

[0057] The radial distance from the radially outer end face of the sealed area portion to the radially inner side face of the bolt hole

[0058] The length h from the bolt center of the wheel mounting flange to the rotation axis A of the wheel bearing device

[0059] The ratio k of the pitch circle diameter to the length from the outer side end face of the wheel mounting flange to the inner side end of the outer ring

[0060] The ratio l of the length from the bolt hole center of the wheel mounting flange to the bolt hole center of the vehicle body mounting flange to the length from the outer side end face of the wheel mounting flange to the inner side end of the outer ring

[0061] The length B from the outer side end face of the wheel mounting flange to the inner side end of the outer ring

[0062] The axial thickness C of the wheel mounting flange. Detailed implementation mode

[0063] Use Figure 1 The overall structure of the wheel bearing device 1 will be described. It should be noted that in the following description, the inner side represents the vehicle body side of the wheel bearing device 1 when installed on the vehicle body, and the outer side represents the wheel side of the wheel bearing device 1 when installed on the vehicle body. The axial direction represents the direction along the rotation axis A of the wheel bearing device 1. The radial direction represents the direction orthogonal to the rotation axis A of the wheel bearing device 1. The circumferential direction represents the direction along the arc centered on the rotation axis A of the wheel bearing device 1. The axially outer side represents the direction away from the annular space S along the rotation axis A, and the axially inner side represents the direction approaching the annular space S along the rotation axis A.

[0064] As Figure 1 As shown, the wheel bearing device 1 rotatably supports a wheel in a suspension device of a vehicle such as a motor vehicle. The wheel bearing device 1 includes an outer ring 2, a hub ring 3, an inner ring 4 as a raceway surface forming member, rolling elements 5, an inner side seal member 6, and an outer side seal member 7.

[0065] The outer ring 2 as an outer member supports the hub ring 3 and the inner ring 4. A seal fitting portion 2b for fitting the inner side seal member 6 is provided on the inner peripheral surface of the inner side end portion 2a of the outer ring 2. A seal fitting portion 2d for fitting the outer side seal member 7 is provided on the inner peripheral surface of the outer side end portion 2c of the outer ring 2. A vehicle body mounting flange 2f is integrally provided on the outer peripheral surface 2e of the outer ring 2. Fixing bolts for fastening the outer ring 2 to the steering knuckle are inserted into the vehicle body mounting flange 2f. On the inner peripheral surface of the outer ring 2, double-row outer side raceway surfaces 2g, 2h are provided along the circumferential direction on its inner side and outer side.

[0066] In addition, the outer raceway surface 2g and the outer raceway surface 2h are arranged such that their axes are aligned and they are parallel to each other in the circumferential direction. It should be noted that the pitch circle diameters of the outer raceway surface 2g and the outer raceway surface 2h may also be configured to have different sizes.

[0067] The inner member is composed of a hub ring 3 and an inner ring 4. The hub ring 3 supports a wheel (not shown) of the vehicle so as to be rotatable freely. A reduced-diameter small-diameter step portion 3a extending in the axial direction is provided at the inner side end portion of the outer peripheral surface of the hub ring 3. A wheel mounting flange 3b for mounting the wheel is integrally provided at the outer side end portion of the hub ring 3. The axial thickness C of the wheel mounting flange 3b is 7 mm to 17 mm. In addition, hub bolts 3c for fastening the hub ring 3 to the wheel or the braking device are press-fitted into the wheel mounting flange 3b.

[0068] In addition, bolt holes 3d for press-fitting the hub bolts 3c are provided in the wheel mounting flange 3b. The bolt holes 3d are holes for press-fitting the hub bolts 3c, and a plurality of them are provided in the wheel mounting flange 3b. It should be noted that the bolt holes 3d are not limited to press-fitting holes without thread teeth. For example, they may also be holes provided with thread teeth for screwing with the bolts.

[0069] In addition, an inner raceway surface 3e opposed to the outer raceway surface 2h on the outer side is provided on the outer peripheral surface on the outer side of the hub ring 3. That is, on the outer side of the inner member, the hub ring 3 constitutes the inner raceway surface 3e. A seal area portion 3f for the outer side seal member 7 to slide and contact is provided at the base side of the wheel mounting flange 3b in the hub ring 3.

[0070] The inner ring 4 is press-fitted into the small-diameter step portion 3a of the hub ring 3. The inner ring 4 applies preload to the rolling elements 5. An inner raceway surface 4a opposed to the outer raceway surface 2g on the inner side is provided on the outer peripheral surface of the inner ring 4. That is, on the inner side of the inner member, the inner ring 4 constitutes the inner raceway surface 4a. In addition, a seal fitting portion 4b for the inner side seal member 6 to be fitted is provided on the outer peripheral surface at the inner side end portion of the inner ring 4.

[0071] The rolling elements 5 are composed of balls. The inner side rolling elements 5 and the outer side rolling elements 5 are respectively held by a retainer 51. The inner side rolling elements 5 are rotatably sandwiched between the inner raceway surface 4a of the inner ring 4 and the inner side outer raceway surface 2g of the outer ring 2. The outer side rolling elements 5 are rotatably sandwiched between the inner raceway surface 3e of the hub ring 3 and the outer side outer raceway surface 2h of the outer ring 2. That is, the inner side rolling elements 5 and the outer side rolling elements 5 are rotatably accommodated between the two raceway surfaces of the outer member and the inner member.

[0072] As Figure 1As shown, the distance between the double rows of rolling elements 5 is denoted as a. The distance a between the rolling elements 5 is the distance between the centers of the balls that make up the rolling elements 5, and is also the same as the distance between the tangent centers of the raceway surfaces.

[0073] In addition, the pitch circle diameter (P.C.D) of the rolling elements 5 is denoted by b. In the present embodiment, the pitch circle diameters of the outer side rolling elements 5 and the inner side rolling elements 5 are formed to be of equal size.

[0074] The wheel bearing device 1 of the present embodiment is formed to reduce the distance a between the double rows of rolling elements 5 and increase the pitch circle diameter b of the rolling elements 5. Specifically, the ratio c of the pitch circle diameter b to the distance a is formed to be 2 or more. In the case where the pitch circle diameters of the outer side rolling elements 5 and the inner side rolling elements 5 are different, the average value of the pitch circle diameters of the outer side rolling elements 5 and the inner side rolling elements 5 may be set as b.

[0075] By configuring in this way, it is possible to increase the P.C.D. of the rolling elements 5 to form a large-diameter wheel bearing device 1, and it is possible to make the dimension in the width direction of the entire wheel bearing device 1 small. Such a large-diameter and narrow-width wheel bearing device 1 can increase the rated load and can cope with the increase in vehicle mass.

[0076] In addition, as Figure 1 shown, the length from the outer side end face of the wheel mounting flange 3b to the inner side end portion 2a of the outer ring 2 is denoted by B.

[0077] The wheel bearing device 1 in the present embodiment is formed to reduce the axial length of the wheel bearing device 1 and increase the pitch circle diameter b of the rolling elements 5. Specifically, it is formed such that the ratio k of the pitch circle diameter b to the distance B is 0.7 or more. In the case where the pitch circle diameters of the outer side rolling elements 5 and the inner side rolling elements 5 are different, the average value of the pitch circle diameters of the outer side rolling elements 5 and the inner side rolling elements 5 may be set as b.

[0078] By configuring in this way, it is possible to increase the P.C.D. of the rolling elements 5 to form a large-diameter wheel bearing device 1, and it is possible to make the dimension in the axial direction of the entire wheel bearing device 1 small. Such a large-diameter and narrow-width wheel bearing device 1 can increase the rated load and can cope with the increase in vehicle mass.

[0079] In addition, as Figure 1 shown, the length from the center of the bolt hole 3d of the wheel mounting flange 3b to the rotation axis A of the wheel bearing device 1 is denoted by h.

[0080] In the wheel bearing device 1 of this embodiment, the axial length of the wheel bearing device 1 is reduced, and the centers of the bolt holes 3d of the wheel mounting flange 3b are arranged on the outer diameter side. Specifically, it is formed such that the ratio l (h / B) of the pitch circle diameter h to the distance B is 0.65 to 1.05.

[0081] By configuring in this way, the centers of the bolt holes 3d of the wheel mounting flange 3b can be arranged at a position closer to the outer diameter side to form a large-diameter wheel bearing device 1, and the axial dimension of the entire wheel bearing device 1 can be made smaller. Such a large-diameter and narrow-width wheel bearing device 1 can increase the rated load and cope with the increase in vehicle mass.

[0082] In this way, in the wheel bearing device 1, a double-row angular contact ball bearing is constituted by the outer ring 2, the hub ring 3, the inner ring 4, and the double-row rolling elements 5. It should be noted that the wheel bearing device 1 may also be configured as a double-row tapered roller bearing instead of the double-row angular contact ball bearing.

[0083] The inner side seal member 6 and the outer side seal member 7 as seal members are seal members that block the open ends of the annular space S formed by the outer member and the inner member. The inner side seal member 6 is assembled to the inner side open end formed between the outer ring 2 and the inner ring 4 in the annular space S. On the other hand, the outer side seal member 7 is assembled to the outer side open end formed between the outer ring 2 and the hub ring 3 in the annular space S.

[0084] Next, use Figure 2 To describe the characteristic points and effects of the wheel bearing device 1 as the first embodiment.

[0085] The hub ring 3 is made of medium-high carbon steel containing 0.40 to 0.80 wt% of carbon such as S53C. The hardness of the hub ring 3 is formed to be 30 HRC or less. The outer peripheral surface of the hub ring 3 is subjected to high-frequency quenching in the heat treatment process. After the heat treatment process, a quenching hardened layer 9 based on high-frequency quenching is formed on the hub ring 3, and the surface hardness and strength are improved. As a result, not only the wear resistance of the base end side of the wheel mounting flange 3b is improved, but also sufficient mechanical strength is provided for the rotational bending load applied to the wheel mounting flange 3b, and the durability of the hub ring 3 is improved.

[0086] As Figure 2 Shown, the quenching hardened layer 9 is formed over a part of the small-diameter step portion 3a, the inner raceway surface 3e, and the seal region portion 3f. In addition, the heat-affected layer of the quenching hardened layer 9 is a portion having a hardness of 78% or more with respect to the surface hardness of the quenching hardened layer 9, and is formed by being Figure 2The portion surrounded by the slanted part is shown. The part with a surface hardness of 78% or more relative to the quenched hardened layer 9 after high-frequency quenching is defined as the heat-affected layer, and the part with a lower hardness is defined as the non-heat-affected layer without the influence of high-frequency quenching. The depth e of the heat-affected layer of the quenched hardened layer 9 is the distance from the outer peripheral surface of the wheel rim 3 to the end face of the heat-affected layer, as Figure 2 and Figure 3 shown, it is the depth from the surface to the inner surface of the quenched hardened layer 9, representing the axial depth from the radial outer diameter end face of the seal area portion 3f where the surface of the quenched hardened layer 9 is formed to the part where the surface hardness reaches 78%. The hardness of the quenched hardened layer 9 is formed to be HV500 or more.

[0087] A quenched hardened layer 9 is formed at a position radially outside the seal area portion 3f of the wheel rim 3. Let the radial distance from the radial outer end face of the seal area portion 3f to the radial inner side face of the bolt hole 3d be g. Here, the radial outer end face of the seal area portion 3f refers to the joint surface of the joint portion 3g connecting the axial inner end face of the wheel mounting flange 3b and the seal area portion 3f and the seal area portion 3f. In addition, the radial inner side face of the bolt hole 3d is the radially innermost face of the circular bolt hole 3d.

[0088] The axial distance d from the radial outer end face of the seal area portion 3f to the radial inner side face of the bolt hole 3d is larger than the depth e of the heat-affected layer of the quenched hardened layer 9. Thus, it is reliably ensured that the influence of the quenching treatment does not reach the peripheral portion of the bolt hole 3d.

[0089] In the case where the influence of the quenching treatment reaches the periphery of the bolt hole 3d, the fitting surface of the wheel hub bolt 3c and the bolt hole 3d becomes hard, and thus there may be a shortage of sliding torque caused by insufficient cutting of the teeth of the wheel hub bolt. The reason for the insufficient cutting of the teeth of the wheel hub bolt is that the relative hardness of the bolt hole 3d becomes higher than the hardness of the wheel hub bolt 3c, and it is difficult to form a serrated groove, that is, serrations, on the inner diameter of the bolt hole 3d.

[0090] On the contrary, by making the distance d larger than the depth e of the heat-affected layer, even when the quenched hardened layer 9 is formed at the radial outer end face of the seal area portion 3f, it is possible to form such that the heat-affected layer of the quenched hardened layer 9 applied to the inner raceway surface 3e on the flange side does not reach the bolt hole 3d. Therefore, the relative hardness of the bolt hole 3d can be sufficiently reduced with respect to the hardness of the wheel hub bolt 3c, and serrated grooves, that is, serrations, can be formed on the inner diameter of the bolt hole 3d, so that the sliding torque can be ensured.

[0091] In addition, if a heat-affected layer of the quenched and hardened layer 9 is formed around the bolt hole 3d, there is a possibility of a reduction in bearing life due to deterioration of crystal grain size caused by cracking or overheating. However, by making the distance d greater than the depth e of the heat-affected layer, it is possible to avoid a reduction in bearing life caused by cracking or deterioration of crystal grain size around the bolt hole 3d.

[0092] The distance g is preferably 2 mm or more and 16 mm or less.

[0093] That is, by setting the distance g to 2 mm or more, it is possible to ensure the distance required for the hardness to drop to the base material hardness from the quenched and hardened layer 9. In addition, the distance g is preferably 16 mm or less. This is obtained by the following formula based on the pitch circle diameter (P.C.D) h of the wheel bolt 3c, the hole diameter i of the wheel bolt, and the outer diameter j of the seal area portion.

[0094] h / 2-i / 2-j / 2≥g

[0095] Thereby, the quenched and hardened layer 9 can be sufficiently provided, not only improving the wear resistance on the base end side of the wheel mounting flange 3b, but also having sufficient mechanical strength for the rotational bending load applied to the wheel mounting flange 3b, and improving the durability of the wheel hub 3.

[0096] In addition, since the rigidity is increased by providing the quenched and hardened layer 9 on the inner raceway surface 3e of the wheel hub 3, deterioration of the roundness of the inner raceway surface 3e caused by the application of the load is reduced. Therefore, the steel ball load rate on the outer side of the wheel hub 3 increases, and the indentation resistance can be improved.

[0097] In addition, the characteristic points and effects of the wheel bearing device 1 in the second embodiment will be described.

[0098] As Figure 3 shown, the quenched and hardened layer 9 is formed over a part of the small-diameter step portion 3a, the inner raceway surface 3e, the seal area portion 3f, the connecting portion 3g, and a part of the wheel mounting flange 3b. In addition, the heat-affected layer of the quenched and hardened layer 9 is a portion having a hardness of 78% or more with respect to the surface hardness of the quenched and hardened layer 9, and is shown by the portion surrounded by the slanted lines Figure 3 in the figure.

[0099] The depth e of the heat-affected layer of the quenched and hardened layer 9 is the distance from the outer peripheral surface of the wheel hub 3 to the end face of the heat-affected layer, and represents the depth of the hardened layer in the direction at an angle of 30 to 45 degrees with respect to the rotation axis A. The depth e of the heat-affected layer of the quenched and hardened layer 9 is formed to vary in the axial direction. By varying the depth e of the heat-affected layer, the heat-affected layer of the quenched and hardened layer 9 is formed so as to enter inside in the axial thickness of the connecting portion 3g and the wheel mounting flange 3b. The hardness of the quenched and hardened layer 9 is formed to be HV500 or more.

[0100] Let the radial distance from the radially inner surface of the bolt hole 3d to the radially outermost position of the heat-affected layer of the quenched hardened layer 9 be f. The radially inner surface of the bolt hole 3d refers to the radially innermost surface of the circular bolt hole 3d. In addition, the radially outermost position of the heat-affected layer of the quenched hardened layer 9 refers to the position of the portion that is the most radially outer in the heat-affected layer of the quenched hardened layer 9 formed on the wheel mounting flange 3b.

[0101] The radial distance f from the radially inner surface of the bolt hole 3d to the radially outermost position of the heat-affected layer of the quenched hardened layer 9 is formed to be 2 mm or more. Thereby, it is reliably ensured that the influence of the quenching treatment does not reach the peripheral portion of the bolt hole 3d.

[0102] When the influence of the quenching treatment reaches the periphery of the bolt hole 3d, the mating surface of the wheel hub bolt 3c and the bolt hole 3d hardens, and thus there may be a shortage of slip torque caused by insufficient cutting of the wheel hub bolt serrations. The reason for the insufficient cutting of the wheel hub bolt serrations is that the relative hardness of the bolt hole 3d becomes higher than the hardness of the wheel hub bolt 3c, and it is difficult to form serrated grooves, i.e., serrations, on the inner diameter of the bolt hole 3d.

[0103] In contrast, by setting the distance f to 2 mm or more, even when a quenched hardened layer 9 based on high frequency is formed on the radially outer end surface of the seal area portion 3f, it is possible to form such that the heat-affected layer of the quenched hardened layer 9 applied to the inner raceway surface 3e on the flange side does not reach the bolt hole 3d.

[0104] That is, if the distance f is set to 2 mm or more, the distance required to decrease to the base material hardness from the quenched hardened layer 9 can be ensured.

[0105] Therefore, the relative hardness of the bolt hole 3d can be sufficiently decreased with respect to the hardness of the wheel hub bolt 3c, and serrated grooves, i.e., serrations, can be formed on the inner diameter of the bolt hole 3d, and thus the slip torque can be ensured.

[0106] In addition, if a heat-affected layer of the quenched hardened layer 9 is formed around the bolt hole 3d, there may be a reduction in bearing life due to deterioration of crystal grain size caused by burn cracking and overheating. However, by setting the distance f to 2 mm or more, it is possible to avoid a reduction in bearing life caused by burn cracking and deterioration of crystal grain size around the bolt hole 3d.

[0107] In addition, it is preferable that the radial distance g from the radially outer end surface of the seal area portion 3f to the radially inner surface of the bolt hole 3d is 2 mm or more and 16 mm or less.

[0108] That is, by setting the distance g to 2 mm or more, the distance required for the quenched and hardened layer 9 to decrease to the base material hardness can be ensured. Further, the distance g is preferably 16 mm or less. This is obtained by the following formula based on the pitch circle diameter (P.C.D) h of the wheel bolt 3c, the hole diameter i of the wheel bolt, and the outer diameter j of the seal area portion.

[0109] h / 2-i / 2-j / 2≥g

[0110] Thereby, the quenched and hardened layer 9 can be sufficiently provided, not only improving the wear resistance on the base end side of the wheel mounting flange 3b, but also having sufficient mechanical strength against the rotational bending load applied to the wheel mounting flange 3b, and improving the durability of the wheel hub 3.

[0111] In addition, since the rigidity is increased by providing the quenched and hardened layer 9 on the inner raceway surface 3e of the wheel hub 3, it is possible to reduce the deterioration of the roundness of the inner raceway surface 3e caused by the application of the load. Therefore, the steel ball load rate on the outer side of the wheel hub 3 increases, and the indentation resistance can be improved.

[0112] As described above, the wheel bearing device 1 includes: an outer ring 2 as an outer member, which has double-row outer raceway surfaces 2g and 2h on its inner circumference; an inner member composed of a wheel hub 3 and an inner ring 4, the wheel hub 3 having one inner raceway surface 3e facing the outer raceway surface 2h on its outer circumference and a wheel mounting flange 3b for mounting a wheel, and the inner ring 4 being connected to the wheel hub 3 and having the other inner raceway surface 4a facing the outer raceway surface 2g on its outer circumference; double-row rolling elements 5, 5, which are rotatably accommodated between the two raceway surfaces of the outer ring 2 and the wheel hub 3 and the inner ring 4; and seal members 6, 7, which seal between the outer ring 2 and the wheel hub 3 and the inner ring 4, wherein the ratio c of the pitch circle diameter (P.C.D.) b of the rolling elements 5, 5 to the distance a between the rolling elements is 2 or more, the ratio k of the pitch circle diameter b to the length B from the outer side end face of the wheel mounting flange 3b to the inner side end 2a of the outer ring 2 is 0.7 or more, the wheel mounting flange 3b has a bolt hole 3d into which the wheel bolt 3c is inserted, the heat affected zone of the quenched and hardened layer 9 applied to the inner raceway surface 3e on the wheel mounting flange 3b side is formed so as not to reach the bolt hole 3d, and the axial distance d from the radially outer end face of the seal area portion 3f of the wheel mounting flange 3b to the radially inner side face of the bolt hole 3d is formed to be larger than the depth e of the heat affected zone of the quenched and hardened layer 9.

[0113] By configuring in this way, the relative hardness of the bolt hole 3d can be sufficiently reduced with respect to the hardness of the wheel bolt 3c, and a serrated groove, i.e., a serration, can be formed on the inner diameter of the bolt hole 3d, and the slip torque can be ensured.

[0114] In addition, by configuring in this way, it is possible to reliably prevent the heat-affected layer of the quenched and hardened layer 9 from reaching the bolt hole 3d. Therefore, the relative hardness of the bolt hole 3d can be sufficiently reduced with respect to the hardness of the wheel bolt 3c, and serrations, i.e., sawteeth, can be formed on the inner diameter of the bolt hole 3d, so that the sliding torque can be ensured.

[0115] In addition, the heat-affected layer of the quenched and hardened layer 9 is formed in the thickness direction of the wheel mounting flange 3b, and the radial distance f from the radially inner side surface of the bolt hole 3d to the radially outermost position of the heat-affected layer of the quenched and hardened layer 9 is 2 mm or more.

[0116] By configuring in this way, even when the heat-affected layer of the quenched and hardened layer 9 is formed in the thickness direction of the wheel mounting flange 3b (as shown in the case where the depth e of the heat-affected layer is larger than the distance d), it is possible to reliably prevent the heat-affected layer of the quenched and hardened layer 9 from reaching the bolt hole 3d. Figure 3 As shown, in the case where the depth e of the heat-affected layer is larger than the distance d), it is also possible to reliably prevent the heat-affected layer of the quenched and hardened layer 9 from reaching the bolt hole 3d.

[0117] In addition, the radial distance g from the radially outer side end surface of the sealing region portion 3f of the wheel mounting flange 3b to the radially inner side surface of the bolt hole 3d is formed to be 2 mm or more and 16 mm or less.

[0118] By configuring in this way, the quenched and hardened layer 9 can be sufficiently provided, not only improving the wear resistance of the base end side of the wheel mounting flange 3b, but also having sufficient mechanical strength with respect to the rotational bending load applied to the wheel mounting flange 3b, and improving the durability of the wheel hub 3.

[0119] In addition, the ratio l of the length h from the center of the bolt hole 3d of the wheel mounting flange 3b to the rotation axis A of the wheel bearing device to the length B from the outer side end surface of the wheel mounting flange 3b to the inner side end portion 2a of the outer ring 2 is 0.65 to 1.05.

[0120] By configuring in this way, the center of the bolt hole 3d of the wheel mounting flange 3b can be arranged at a position closer to the outer diameter side to form a large-diameter wheel bearing device 1, and the axial dimension of the entire wheel bearing device 1 can be made smaller.

[0121] As described above, the wheel bearing device 1 of each embodiment has been described as a third-generation structure in which the inner ring rotates and the inner raceway surface 3e of the rolling elements 5 is directly formed on the outer periphery of the wheel hub 3, but it is not limited thereto. For example, it can also be a second-generation structure in which a pair of inner rings 4 are press-fitted and fixed to the wheel hub 3 and the inner ring rotates. In addition, it can also be a third-generation structure or a second-generation structure in which the outer ring rotates. In addition, the above-described embodiments merely show representative modes of the present invention, and various modifications can be made and implemented without departing from the gist of the present invention.

[0122] In addition, for example, as Figure 4 shown, as the orbital surface forming member, instead of the inner ring 4, the outer joint member 61 of the CVJ having an orbital surface on the outer diameter may be used. As Figure 4 shown, an orbital surface 62 opposed to the outer orbital surface 2g is formed on the outer diameter of the outer joint member 61. The outer joint member 61 is composed of a rod portion 63 and a mouth portion 64, and the orbital surface 62 is provided on the outer diameter of the outer end portion of the mouth portion 64. The inner diameter of the hub ring 3 of the outer peripheral surface of the rod portion 63 is fixed by spline fitting so as not to be able to roll.

[0123] In addition, the wheel bearing device 1 using wheel bolts instead of the hub bolts 3c may be used. Further, the hub ring 3 is made of medium-high carbon steel containing 0.40 to 0.80 wt% of carbon such as S53C, for example. The hardness of the hub ring 3 is formed to be 30 HRC or less. The outer peripheral surface of the hub ring 3 is induction hardened in the heat treatment process. A hardened layer 9 based on induction hardening is formed on the hub ring 3 after the heat treatment process, and the surface hardness and strength are improved.

Claims

1. A wheel bearing device, comprising: An outer member having a double row of outer raceway surfaces on its inner circumference; an inner member consisting of a wheel hub and a raceway surface forming member, wherein the wheel hub has an inner raceway surface on one side of its outer circumference facing the outer raceway surface and a wheel mounting flange for mounting a wheel, the raceway surface forming member being connected to the wheel hub and having an inner raceway surface on its outer circumference facing the outer raceway surface; double rows of rolling elements which are freely accommodated between the two raceway surfaces of the outer member and the inner member; and a sealing member which seals between the outer member and the inner member, characterized in that The ratio c of the pitch circle diameter (PCD) b of the rolling element to the distance a between the rolling elements is greater than 2, The ratio k of the pitch circle diameter b to the length B from the outer side end surface of the wheel mounting flange to the inner side end portion of the outer member is 0.7 or more. The wheel mounting flange has bolt holes, The heat affected layer of the quench-hardened layer applied to the inner raceway surface on the wheel mounting flange side is formed so as not to reach the bolt hole, and the axial distance d from the radially outer end surface of the sealing area portion of the wheel mounting flange to the radially inner surface of the bolt hole is greater than the depth e of the heat affected layer of the quench-hardened layer.

2. A wheel bearing device, comprising: An outer member having a double row of outer raceway surfaces on its inner circumference; an inner member consisting of a wheel hub and a raceway surface forming member, wherein the wheel hub has an inner raceway surface on one side of its outer circumference facing the outer raceway surface and a wheel mounting flange for mounting a wheel, the raceway surface forming member being connected to the wheel hub and having an inner raceway surface on its outer circumference facing the outer raceway surface; double rows of rolling elements which are freely accommodated between the two raceway surfaces of the outer member and the inner member; and a sealing member which seals between the outer member and the inner member, characterized in that The ratio c of the pitch circle diameter (PCD) b of the rolling element to the distance a between the rolling elements is greater than 2, The ratio k of the pitch circle diameter b to the length B from the outer end surface of the wheel mounting flange to the inner end of the outer member is 0.7 or more. The wheel mounting flange has bolt holes, The heat affected layer of the quench-hardened layer applied to the inner raceway surface on the wheel mounting flange side is formed so as not to reach the bolt hole, the heat affected layer of the quench-hardened layer is formed in the thickness direction of the wheel mounting flange, and the radial distance f from the radial inner side surface of the bolt hole to the radial outermost position of the heat affected layer of the quench-hardened layer is greater than 2 mm.

3. The wheel bearing device according to claim 1 or 2, characterized in that: A radial distance g from a radially outer end surface of the sealing region of the wheel mounting flange to a radially inner side surface of the bolt hole is formed to be greater than or equal to 2 mm and less than or equal to 16 mm.

4. The wheel bearing device according to claim 1, characterized in that: A ratio l of a length from a bolt hole center of the wheel mounting flange to a rotation axis A of the wheel bearing device to a length B from an outer end surface of the wheel mounting flange to an inner end portion of the outer member is 0.65 to 1.05.

Images