Bearing device for wheel

Abstract

Provided is a bearing device for a wheel, the bearing device being capable of setting the distance between two rows of rolling elements in the axial direction to an appropriate value and improving the bearing rigidity when the bearing device for a wheel is increased in size. This bearing device for a wheel is provided with: an outer member (24); an inner member comprising a hub ring (31) having an inner raceway surface (29) and a wheel attachment flange (25), and an inner ring (28) connected to the hub ring (31) and having an inner raceway surface (30) on the outer diameter; and double rows of steel balls (32) which are accommodated between the respective raceway surfaces so as to be rollable, and in a side cross-sectional view, the contact angle of the steel balls on the outer side is set to be [theta] 1, and the contact angle of the steel balls on the inner side is set to be [theta] 2, the distance (f) between an imaginary straight line (L1) in the direction of a contact angle (theta1) extending from the center of the outer-side steel ball and an outer-side root (43) of the vehicle body mounting flange (23) is f > 0, and the distance (g) between an imaginary straight line (L2) in the direction of a contact angle (theta2) extending from the center of the inner-side steel ball and an inner-side root (44) of the vehicle body mounting flange (23) is g > 0.

Description

Technical Field

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

[0002] A wheel bearing device that rotatably supports a wheel is known. This wheel bearing device comprises an inner member disposed inside an outer member, with rolling elements sandwiched between the raceway surfaces of the outer and inner members. This wheel bearing device forms a rolling bearing structure, enabling the wheel mounted on the inner member to rotate freely.

[0003] Among wheel bearing devices with this type of rolling bearing structure, one known type includes a double row of rolling elements freely accommodated between the respective raceways of an inner member and an outer member (see, for example, Patent Document 1). The double row of rolling elements is arranged axially separated by a predetermined distance. As one means of extending the life of a wheel bearing device, increasing the axial distance between the double row of rolling elements and the pitch diameter of each rolling element is employed to improve rigidity. However, this structure inevitably results in an increase in the overall size of the wheel bearing device.

[0004] For example, a wheel bearing device is known in which the pitch diameter is six times larger than the diameter of the steel balls serving as rolling elements (see, for example, Patent Document 2). This configuration prevents a decrease in the pitch and reduces the bearing rigidity of the wheel bearing device. However, the increase in the steel ball diameter inevitably increases the overall size of the wheel bearing device.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-108449

[0008] Patent Document 2: U.S. Patent No. 07413349 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] Furthermore, the recent popularity of electric vehicles has been accelerating. The fact that EVs are equipped with batteries tends to increase vehicle weight, necessitating increased bearing rigidity in wheel bearing devices. Furthermore, the increased torque generated by EV motor drive has led to larger spline dimensions in constant velocity joints. This, in turn, has led to an increase in the pitch diameter of the rolling wheel in wheel bearing devices, increasing their weight.

[0011] To suppress the weight increase of the wheel bearing assembly, it is considered to reduce the axial distance between the double-row rolling elements. In addition, when the vehicle weight increases, the rotational load associated with the body mounting flange increases, and the body mounting flange needs to be thickened. However, from the perspective of suppressing weight increase, there is a limit to the thickness of the wall.

[0012] The present invention has been completed in view of the above situation, and its purpose is to provide a wheel bearing device that can set the axial distance between double-row rolling elements to an appropriate value and improve the bearing rigidity while making the wheel bearing device larger.

[0013] Means for solving problems

[0014] A wheel bearing device according to a first aspect of the present invention includes:

[0015] An outer member having a double row of outer track surfaces provided on the inner periphery and a body mounting flange for mounting on the body;

[0016] An inner member having a double row of inner raceway surfaces on the outer periphery; and

[0017] The double-row steel balls are freely accommodated between the respective track surfaces of the inner member and the outer member, wherein

[0018] The relationship between the steel ball diameter e and the center distance j between the steel balls is 0.20e<je<0.53e,

[0019] Under side sectional observation, the contact angle of the steel ball on the outer side is set to θ1, and the contact angle of the steel ball on the inner side is set to θ2. The distance f between the imaginary straight line L1 in the direction of the contact angle θ1 extending from the center of the steel ball on the outer side and the outer side root of the vehicle body mounting flange is f>0, and the distance g between the imaginary straight line L2 in the direction of the contact angle θ2 extending from the center of the steel ball on the inner side and the inner side root of the vehicle body mounting flange is g>0.

[0020] Effects of the Invention

[0021] According to the present invention, the center distance between the steel balls can be shortened, and the thickness of the outer member in the contact angle direction where the load from the bearing is greatest can be increased. Therefore, the distance between the rolling elements in the axial direction can be set to an appropriate value while increasing the bearing rigidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a cross-sectional view showing the overall structure of the first embodiment of the wheel bearing device.

[0023] Figure 2This is a partially enlarged cross-sectional view showing the distances between the components of the first embodiment of the wheel bearing device.

[0024] Figure 3 This is a side view showing the outer member of the first embodiment of the wheel bearing device.

[0025] Figure 4 It is an upper cross-sectional view showing a wheel bearing device according to a second embodiment. DETAILED DESCRIPTION

[0026] Below, use Figure 1 A wheel bearing device 1 according to a first embodiment of the wheel bearing device will be described. It should be noted that in the following description, the inner side refers to the vehicle body side of the wheel bearing device 1 when mounted on the vehicle body, and the outer side refers to the wheel side of the wheel bearing device 1 when mounted on the vehicle body.

[0027] Figure 1 A cross section of the wheel bearing device 1 is shown along a virtual plane (axial plane) including the bearing center axis. Figure 1 The wheel bearing device 1 of the illustrated embodiment comprises an outer member 24 integrally provided with a double row of raceway surfaces 21, 22 on its inner circumference and a vehicle body mounting flange 23 integrally provided on its outer circumference; a hub 31 having a wheel mounting flange 25 at one end and a cylindrical small-diameter step 26 at the other end, an inner ring 28 press-fitted into the outer diameter of this small-diameter step 26, and a raceway surface 30 formed on the press-fit inner ring 28, which faces the raceway surface 22 of the outer member 24; steel balls 32, which form a double row of rolling elements and are sandwiched between the respective raceway surfaces of the outer member 24 and the hub 31; and a retainer 33, which is sandwiched between the hub 31 and the outer member 24 and supports a plurality of steel balls 32, which serve as double row rolling elements, at equal intervals in each row along the circumferential direction. The inner member comprises the hub 31 and the inner ring 28. Furthermore, the wheel bearing device 1 has a structure in which the raceway surface 29 facing the outer raceway surface 21 on the outer side is formed directly on the outer diameter of the hub wheel 31 .

[0028] Internal and external seals 35 and 36 are attached to both ends of the inner ring 28 and outer member 24 to prevent the intrusion of foreign matter and the leakage of grease contained within. Hub bolts 37 for securing the wheel rim are mounted at evenly spaced locations along the circumference of the wheel mounting flange 25 of the hub 31. Furthermore, the vehicle body suspension system is attached to the vehicle body mounting flange 23 of the outer member 24 via a steering knuckle (not shown).

[0029] The hub 31 rotatably supports the wheel of a vehicle (not shown). The hub 31 is formed into a generally cylindrical shape and is made of medium-high carbon steel, such as S53C. A small-diameter step 26 is provided on the inner end of the hub 31, where the outer circumference is reduced. A wheel mounting flange 25 is integrally provided on the outer end of the hub 31.

[0030] The inner ring 28 is press-fitted into the small-diameter step 26 of the hub 31. A raceway 30 is provided on the outer circumference of the inner ring 28. The inner ring 28 is secured by plastically deforming (caulking) the inner end of the hub 31 radially outward. In other words, the inner ring 28 forms the inner raceway 30 on the inner side of the hub 31. The raceway 30 of the inner ring 28, located at the inner end of the hub 31, faces the inner raceway 22 of the outer member 24, while the raceway 29 on the outer side faces the outer raceway 21 of the outer member 24.

[0031] The plurality of steel balls 32 serving as rolling elements are held in place by retainers 33. The inner row of steel balls 32 is freely rotatably sandwiched between the raceway surface 30 of the inner ring 28 and the inner raceway surface 22 of the outer member 24. The outer row of steel balls 32 is freely rotatably sandwiched between the raceway surface 29 of the hub 31 and the outer raceway surface 21 of the outer member 24. In other words, the inner and outer rows of steel balls 32 are freely rotatably contained between the outer and inner raceway surfaces. The outer member 24 rotatably supports the hub 31 and inner ring 28 via the inner and outer rows of steel balls 32.

[0032] Next, use Figure 2 The distances between the components will be described. Figure 2 FIG. 1 shows a partial cross section of the wheel bearing device 1 along a virtual plane (axial plane) including the bearing center axis. Figure 2 As shown in FIG. 1 , the inner row of steel balls 32 and the outer row of steel balls 32 are arranged in parallel in the axial direction. Figure 2 As shown, the distances from various components are defined with the outer end surface of the wheel mounting flange 25 as a reference. The distance from the outer end surface of the wheel mounting flange 25 to the center of the inner steel ball 32 is defined as a. Furthermore, the distance from the outer end surface of the wheel mounting flange 25 to the inner end surface of the vehicle body mounting flange 23 is defined as b. Furthermore, the distance from the outer end surface of the wheel mounting flange 25 to the outer end surface of the vehicle body mounting flange 23 is defined as c. Furthermore, the distance from the outer end surface of the wheel mounting flange 25 to the center of the outer steel ball 32 is defined as d. Furthermore, the steel ball diameter, which is the diameter of the steel ball 32, is defined as e.

[0033] Here, when the axial distance between the centers of the steel balls 32 is defined as j, the inter-ball center distance j is the difference between a and d. Subtracting the steel ball diameter e from the inter-ball center distance j calculates the length from the axially outer end of the inner steel ball 32 to the axially inner end of the outer steel ball 32. The shorter this length, the narrower the axial width of the wheel bearing device 1 itself. On the other hand, if this length is too short, the axial thickness of the ring portion 41 of the retainer 33 cannot be fully achieved, and there is a risk that the retainer 33 will be insufficiently strong and break during bearing operation.

[0034] Therefore, in this embodiment, the relationship between the steel ball diameter e and the center distance j between the steel balls is preferably 0.20e<je<0.53e. This configuration can reduce the axial width of the wheel bearing device 1 itself while ensuring the strength of the retainer 33 during bearing operation.

[0035] Furthermore, the relationship between the distance a from the end face of the wheel mounting flange 25 to the center of the inner steel ball 32 and the distance b from the end face of the wheel mounting flange 25 to the inner end face of the vehicle body mounting flange 23 is preferably a>b. By having a>b, the vehicle body mounting flange 23 is positioned outward of the center of the inner steel ball 32, allowing the thickness of the outer member 24 to be increased in the direction extending from the inner virtual straight line L2. This allows the load from the bearing to be borne by this portion, thereby improving the bearing rigidity of the outer member 24.

[0036] Furthermore, the relationship between the distance c from the outer end surface of the wheel mounting flange 25 to the outer end surface of the vehicle body mounting flange 23 and the distance d from the outer end surface of the wheel mounting flange 25 to the center of the outer steel ball 32 is preferably c>d. By having c>d, the vehicle body mounting flange 23 is positioned inward of the center of the outer steel ball 32, and the thickness of the outer member 24 can be increased in the direction in which the outer imaginary straight line L1 extends. This portion can then bear the load from the bearing, thereby improving the bearing rigidity of the outer member 24.

[0037] The outer virtual line L1 is described below. To cope with moment loads, the outer steel balls 32 are provided as ball bearings having a contact angle θ1 with the hub 31 and the outer member 24. The rolling element contact angle θ1 is preferably 30° to 45°.

[0038] The imaginary straight line L1 is a straight line in the direction of the rolling element contact angle θ1, and is a straight line extending toward the outer diameter side as it moves toward the inner side. Here, the rolling element contact angle θ1 refers to the angle formed by the direction of the force transmitted to the steel ball 32 through the outer raceway surfaces 21 and 29 relative to the imaginary plane (radial plane) perpendicular to the bearing center axis. In side cross-sectional observation, the distance between the imaginary straight line L1 in the direction of the contact angle θ1 extending from the center of the outer steel ball and the outer root 43 of the body mounting flange 23 is set to f. Here, side cross-sectional observation refers to the angle in the direction of the contact angle θ1 extending from the center of the outer steel ball. Figure 2 The wheel bearing device 1 is viewed in the enlarged cross-sectional view shown. The outer root portion 43 is where the outer end surface 23b of the vehicle body mounting flange 23 intersects the outer peripheral surface 24a of the outer member 24. The distance f is the distance between a line tangent to the curved shape of the outer root portion 43 and parallel to θ1 and the imaginary straight line L1. It should be noted that the distance f is assumed to be positive when extending inward from the outer root portion 43.

[0039] In this embodiment, the distance f is preferably f>0. In other words, it is desirable for an imaginary straight line L1 to extend inward from the tangent line of the curved shape of the outer root portion 43. This configuration allows the outer member 24 to be thicker in the contact angle direction, where the bearing load is greatest. This allows this portion to bear the bearing load, thereby improving the bearing rigidity of the outer member 24.

[0040] Next, the inner virtual line L2 will be described. To cope with moment loads, the inner steel balls 32 are configured as ball bearings with a contact angle θ2 with the hub 31 and outer member 24. The rolling element contact angle θ2 is preferably between 30° and 45°.

[0041] The imaginary straight line L2 is a straight line in the direction of the rolling element contact angle θ2, and is a straight line extending toward the outer diameter side as it moves toward the outer side. Here, the rolling element contact angle θ2 refers to the angle formed by the direction of the force transmitted to the steel ball 32 through the inner raceway surfaces 22 and 30 relative to the imaginary plane (radial plane) perpendicular to the bearing center axis. In side cross-sectional observation, the distance between the imaginary straight line L2 in the direction of the contact angle θ2 extending from the center of the inner steel ball and the inner side root of the body mounting flange 23 is set to g. Here, side cross-sectional observation refers to the angle between the inner side and the inner side of the body mounting flange 23. Figure 2 The wheel bearing device 1 is viewed in the enlarged cross-sectional view shown. The inner root portion 44 is the intersection of the inner end surface 23c of the vehicle body mounting flange 23 and the outer peripheral surface 24b of the outer member 24. The distance g is the distance between a line tangent to the curved shape of the inner root portion 44 and parallel to θ2 and the imaginary straight line L2. It should be noted that the distance f is assumed to be positive when extending from the inner root portion 44 toward the outside.

[0042] In this embodiment, the distance g is preferably g>0. In other words, it is desirable that an imaginary straight line L2 extends outward from the tangent line of the curved shape of the inner root portion 44. This configuration increases the thickness of the outer member 24 in the contact angle direction, where the bearing load is greatest. This allows this portion to bear the bearing load, thereby improving the bearing rigidity of the outer member 24.

[0043] Furthermore, it is desirable that the distance a from the outer end surface of the wheel mounting flange 25 to the center of the inner steel ball 32 be greater than the distance b from the outer end surface of the wheel mounting flange 25 to the inner end surface of the vehicle body mounting flange 23. This configuration increases the thickness of the portion bearing the rolling element load, significantly improving rigidity.

[0044] Furthermore, it is desirable that the distance c from the outer end surface of the wheel mounting flange 25 to the outer end surface of the vehicle body mounting flange 23 be greater than the distance d from the outer end surface of the wheel mounting flange 25 to the center of the outer steel ball 32. This configuration increases the thickness of the portion bearing the rolling element load, significantly improving rigidity.

[0045] Furthermore, the intersection of the imaginary straight lines L1 and L2 is represented by P1. The vehicle body mounting flange 23 is provided with bolt mounting holes 23a for mounting bolts. The distance from the inner diameter end of the bolt when it is mounted in the bolt mounting hole 23a to the intersection P1 is represented by h. The distance h is considered negative in the inner diameter direction.

[0046] In this embodiment, the distance h is preferably h>0. That is, the intersection point P1 is located on the outer diameter side of the inner diameter side end of the bolt mounting hole 23a. By configuring in this way, the arm length of the vehicle body mounting flange 23 is inevitably shortened. The arm length of the vehicle body mounting flange 23 is Figure 3 The length of the protrusion with the bolt mounting hole 23a shown in the figure in the outer diameter direction can thereby position the mounting portion close to the axis center, reduce the moment applied to the mounting portion, and thus significantly improve the bearing rigidity of the outer member 24.

[0047] In addition, if Figure 3 As shown, the body mounting flange 23 has multiple bolt mounting holes 23a arranged concentrically around the axis when viewed axially. Ideally, the mounting center of each bolt mounting hole 23a is located between -30° and +30° circumferentially, with the side opposite the road surface at 0°. This configuration significantly improves rigidity by providing the body mounting flange 23 as a thicker portion at the upper portion, where it is most susceptible to bearing loads.

[0048] As described above, the wheel bearing device comprises: an outer member 24 having double rows of outer raceway surfaces 21 and 22 arranged on the inner periphery and a body mounting flange 23 for mounting on the body; an inner member consisting of a hub ring 31 and an inner ring 28, the hub ring 31 having an inner raceway surface 29 and a wheel mounting flange 25, the inner ring 28 being connected to the hub ring 31 and having an inner raceway surface 30 on the outer diameter; and double rows of steel balls 32, which are freely accommodated in the respective raceways of the inner member and the outer member 24. Between the surfaces, the relationship between the steel ball diameter e and the center distance j between the steel balls is 0.20e<je<0.53e. Under side section observation, the contact angle of the steel ball on the outer side is set to θ1, and the contact angle of the steel ball on the inner side is set to θ2. The distance f between the imaginary straight line L1 in the direction of the contact angle θ1 extending from the center of the steel ball on the outer side and the nearest external component surface is f>0, and the distance g between the imaginary straight line L2 in the direction of the contact angle θ2 extending from the center of the steel ball on the inner side and the nearest external component surface is g>0.

[0049] With this configuration, the axial width of the wheel bearing device 1 itself can be narrowed while ensuring the strength of the retainer 33 during bearing operation.

[0050] In addition, it is preferred that the wheel hub 31 has a wheel mounting flange 25 for being mounted on a wheel, and the relationship between the distance a from the end face of the wheel mounting flange 25 to the center of the inner side steel ball 32 and the distance b from the end face of the wheel mounting flange 25 to the inner side end face of the body mounting flange 23 is a>b, and the relationship between the distance c from the end face of the wheel mounting flange 25 to the outer side end face of the body mounting flange 23 and the distance d from the end face of the wheel mounting flange 25 to the center of the outer side steel ball 32 is c>d.

[0051] With this configuration, the vehicle body mounting flange 23 is located further outward than the center of the inner steel ball 32. This allows the outer member 24 to have a thicker wall thickness in the direction of the inner virtual line L2. This allows the load from the bearing to be borne by this portion, thereby improving the bearing rigidity of the outer member 24. Furthermore, the vehicle body mounting flange 23 is located further inward than the center of the outer steel ball 32. This allows the outer member 24 to have a thicker wall thickness in the direction of the outer virtual line L1. This allows the load from the bearing to be borne by this portion, thereby improving the bearing rigidity of the outer member 24.

[0052] Furthermore, the intersection point P1 of the imaginary straight line L1 in the contact angle θ1 direction and the imaginary straight line L2 in the contact angle θ2 direction extending from the center of each steel ball 32 is preferably located on the outer diameter side of the inner diameter side end of the bolt attachment hole 23a.

[0053] With this configuration, the arm length of the vehicle body mounting flange 23 is inevitably shortened, and thus the effect of improving the bearing rigidity of the outer member is significant.

[0054] In addition, at least one bolt attachment hole 23a of the outer member is provided within 60 degrees of the center thereof on the opposite side to the road surface.

[0055] In addition, as another embodiment, instead of the inner ring 28, the outer coupling member 61 of the CVJ having the raceway surface on the outer diameter may be used as the raceway surface forming member. Figure 4 As shown, a raceway surface 62 is formed on the outer diameter of the outer coupling member 61, facing the raceway surface 22. The outer coupling member 61 is composed of a rod portion 63 and a mouth portion 64, with the raceway surface 62 provided on the outer diameter of the outer end portion of the mouth portion 64. The outer peripheral surface of the rod portion 63 and the inner diameter of the hub wheel 31 are fixed to each other by a spline fit so as to be non-rotatable.

[0056] Furthermore, the wheel mounting flange 25 of the hub 31 is provided with bolt mounting holes 25 b , into which hub bolts 37 for fixing the wheel rim and the brake disc to the wheel mounting flange 25 are mounted.

[0057] It should be noted that in this embodiment, the wheel bearing device 1 is a third-generation structure in which an inner raceway surface 30 is formed on the outer periphery of the hub ring 31, forming a row of outer steel balls 32. However, the present invention is not limited to this. For example, the present invention may also be a second-generation structure in which a pair of inner rings are press-fitted and fixed to the hub ring 31.

[0058] Description of Reference Numerals

[0059] 1 Wheel bearing assembly

[0060] 21 Outer track surface (external side)

[0061] 22 Outer track surface (inner side)

[0062] 23 Body mounting flange

[0063] 23a Bolt mounting hole

[0064] 24 External components

[0065] 25 Wheel mounting flange

[0066] 28 inner circle

[0067] 29 Inner track surface (outer side)

[0068] 30 Inner track surface (inner side)

[0069] 31 wheel hub

[0070] 32 steel balls (rolling elements)

[0071] a Distance from the outer end face of the wheel mounting flange to the center of the inner steel ball

[0072] b Distance from the outer end surface of the wheel mounting flange to the inner end surface of the body mounting flange

[0073] c Distance from the outer side end surface of the wheel mounting flange to the outer side end surface of the body mounting flange

[0074] d Distance from the outer end surface of the wheel mounting flange to the center of the outer steel ball

[0075] e Steel ball diameter

[0076] f Distance between the imaginary straight line L1 and the outer root of the vehicle body mounting flange of the outer member

[0077] g Distance between the imaginary straight line L2 and the inner root of the vehicle body mounting flange of the outer member

[0078] L1 Imaginary straight line on the outside

[0079] L2 Imaginary straight line on the inner side

[0080] θ1, θ2 contact angles.

Claims

1. A wheel bearing device, comprising: an outer member having a double row of outer rail surfaces provided on the inner periphery and a body mounting flange for mounting on the body; an inner member composed of a hub having an inner raceway and a wheel mounting flange, and a raceway forming member connected to the hub and having an inner raceway on an outer diameter thereof; and Double rows of steel balls are accommodated between the respective track surfaces of the inner member and the outer member so as to roll freely. in, The relationship between the steel ball diameter e and the center distance j between the steel balls is 0.20e<je<0.53e, Under side sectional observation, the contact angle of the steel ball on the outer side is set to θ1, and the contact angle of the steel ball on the inner side is set to θ2. The distance f between the imaginary straight line L1 in the direction of the contact angle θ1 extending from the center of the steel ball on the outer side and the outer side root of the vehicle body mounting flange is f>0, and the distance g between the imaginary straight line L2 in the direction of the contact angle θ2 extending from the center of the steel ball on the inner side and the inner side root of the vehicle body mounting flange is g>0.

2. The wheel bearing device according to claim 1, wherein: The inner member has a wheel mounting flange for mounting on a wheel, The relationship between the distance a from the end face of the wheel mounting flange to the center of the inner side steel ball and the distance b from the end face of the wheel mounting flange to the inner side end face of the vehicle body mounting flange is a>b, and the relationship between the distance c from the end face of the wheel mounting flange to the outer side end face of the vehicle body mounting flange and the distance d from the end face of the wheel mounting flange to the center of the outer side steel ball is c>d.

3. The wheel bearing device according to claim 1, wherein: The intersection of a straight line extending from the center of each steel ball in the direction of contact angle θ1 and a straight line in the direction of contact angle θ2 exists on the outer diameter side of the inner diameter side end of the bolt mounting hole of the vehicle body mounting flange.

4. The wheel bearing device according to claim 1, wherein: The center of the bolt mounting hole of the outer member is set at least one between -30° and +30° with respect to the opposite side of the road surface.

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