Wheel Bearing Device

Abstract

A wheel bearing device has a vehicle-body-mounting flange 5b with a plurality of ears 10 discontinuously formed in a circumferential direction on an outer circumferential surface of the outer member 5. An outer circumferential surface 11 on the outer side of the outer member is tapered and formed such that a diameter of the outer member gradually decreases in a direction to an outer side. Ridges 16 protrude from a fitting surface 12 toward the outside in a radial direction. The ridges 16 are formed between the plurality of ears 10. The ridges 16 are forged to smoothly connect to the outer circumferential surfaces of the plurality of ears 10. Ribs 15 are forged on inner-side outer circumferential surfaces of the plurality of ears 10.

Claims

1. A wheel bearing device, comprising: an outer member including a vehicle-body-mounting flange integrally formed on an outer circumference of the outer member, the vehicle-body-mounting flange is to be mounted to a knuckle of a suspension, double-row outer raceway surfaces are integrally formed on an inner circumference of the outer member; an inner member outer circumference includes double-row inner raceway surfaces facing the double-row outer raceway surfaces; double-row rolling elements are rollably accommodated between the raceway surfaces of the inner member and the outer member; a plurality of tapped holes, that receive fastening bolts, is formed in the vehicle-body-mounting flange; and a plurality of ears is formed on the vehicle-body-mounting flange, the plurality of ears is discontinuously formed in a circumferential direction on an outer circumferential surface of the outer member, the plurality of ears protrudes toward an outside in a radial direction, an outer circumferential surface on the outer side of the outer member is tapered and formed such that a diameter of the outer member gradually decreases in a direction to an outer side of the outer member, a cylindrical fitting surface is to be fit into the knuckle is formed on an inner side of the outer member, the plurality of ears is interposed between the outer circumferential surface and the fitting surface, ribs are formed, by a forging process, on inner-side outer circumferential surfaces of the plurality of ears.

2. The wheel bearing device according to claim 1, wherein ridges are formed between the plurality of ears on the outer member, the ridges are formed by a forging process so as to be smoothly connected to the outer circumferential surfaces of the plurality of ears, and inner-side side surfaces of the ridges and inner-side side surfaces of the plurality of ears are flattened by a cutting process.

3. The wheel bearing device according to claim 1, wherein arc-shaped corners are formed by a forging process at portions where the plurality of ears and the ridges of the outer member meet the outer circumferential surface on the outer side, and the ribs of the plurality of ears have a thickness larger than a thickness of the ridges.

4. The wheel bearing device according to claim 1, wherein arc-shaped corners are formed by a forging process at portions where the plurality of ears and the ridges of the outer member meet the outer circumferential surface on the outer side, and the ribs of the plurality of ears have a thickness less than a thickness of the ridges.

Description

DRAWINGS

[0021] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[0022] FIG. 1 is a longitudinal sectional view of a wheel bearing device according to an embodiment of the present disclosure.

[0023] FIG. 2 is a perspective view of an outer member as a single item illustrated in FIG. 1.

[0024] FIG. 3 is a longitudinal sectional view of a conventional wheel bearing device.

[0025] FIG. 4 is an enlarged view of main parts in FIG. 3 and illustrates a modification.

DETAILED DESCRIPTION

[0026] A wheel bearing device includes an outer member with a vehicle-body-mounting flange integrally formed on an outer circumference of the outer member. The flange is to be mounted to a knuckle of a suspension. Double-row outer raceway surfaces are integrally formed on an inner circumference of the outer member. An inner member includes a wheel hub with a wheel-mounting flange to mount a wheel. The wheel-mounting flange is integrally formed on an end portion of the wheel hub. An inner raceway surface on the wheel hub outer circumference faces one of the double-row outer raceway surfaces. A cylindrical portion extends from the inner raceway surface in an axial direction. An inner ring is press-fit on the cylindrical portion of the wheel hub. Another inner raceway surface, facing the other double-row outer raceway surface, is on an outer circumference of the inner ring. Double-row rolling elements are rollably accommodated between the raceway surfaces of the inner member and the outer member. A plurality of tapped holes, to receive fastening bolts, is formed in the vehicle-body-mounting flange. The vehicle-body-mounting flange is formed with a plurality of ears. The ears are discontinuously formed in a circumferential direction on an outer circumferential surface of the outer member. The ears protrude toward the outside in a radial direction. The outer circumferential surface on the outer side is tapered. A diameter of the outer member gradually decreases in a direction to an outer side of the outer member. A cylindrical fitting surface, to be fit into the knuckle, is formed on an inner side. The plurality of ears is interposed between the outer circumferential surface and the fitting surface. Ridges protrude from the fitting surface toward the outside in the radial direction. The ridges are formed between the plurality of ears. The ridges are formed by a forging process to be smoothly connected to the outer circumferential surfaces of the plurality of ears. Ribs are formed, by a forging process, on inner-side outer circumferential surfaces of the plurality of ears.

[0027] An embodiment of the present disclosure will now be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view of a wheel bearing device according to an embodiment of the present disclosure. FIG. 2 is a perspective view of an outer member illustrated in FIG. 1. In the following description where the wheel bearing device is assembled with the vehicle, the outside of the vehicle is referred to as an outer side (left-hand side in FIG. 1). A central side of the vehicle is referred to as an inner side (right-hand side in FIG. 1).

[0028] The wheel bearing device illustrated in FIG. 1 is referred to as a third-generation wheel bearing device for a driven wheel. It includes an inner member 3, with a wheel hub 1 and an inner ring 2, and an outer member 5. The outer member 5 is mounted around the inner member 3 with double-row rolling elements (balls) 4 interposed between the two.

[0029] The wheel hub 1 includes a wheel-mounting flange 6 to mount a wheel (not illustrated). The wheel mounting flange 6 is integrally formed on an outer-side end portion. Hub bolts 6a are inserted in the wheel-mounting flange 6 at regular intervals about the circumference. An (outer-side) inner raceway surface 1a is formed on an outer circumference on the wheel hub 1. A cylindrical portion 1b axially extends from the inner raceway surface 1a. The inner ring 2 has another (inner-side) inner raceway surface 2a formed on its outer circumference. The inner ring 2 is press-fit onto the cylindrical portion 1b with a predetermined amount of interference. An end of the cylindrical portion 1b is plastically deformed radially toward the outside. This forms a caulked portion 1c. The caulked portion 1c enables fixation in the axial direction in a state where a bearing preload is applied. This forms a so-called self-retaining structure.

[0030] The outer member 5 is made of medium- or high-carbon steel containing 0.40 to 0.80 wt % carbon, such as S53C. It includes a vehicle-body-mounting flange 5b integrally formed on its outer circumference. The flange 5b is to be mounted to a knuckle (not illustrated) of a suspension. Double-row outer raceway surfaces 5a face the double-row inner raceway surfaces 1a and 2a. The outer raceway surfaces 5a are integrally formed on an inner circumference of the outer member. The outer raceway surfaces 5a are hardened in the range from 58 to 64 HRC by induction hardening. The double-row rolling elements 4 are rollably accommodated between the outer raceway surfaces 5a of the outer member 5 and the double-row inner raceway surfaces 1a and 2a that face the outer raceway surfaces 5a. The rolling elements 4 are retained by cages 7. Seals 8 and 9 are attached in openings forming an annular space between the outer member 5 and the inner member 3. The seals prevent lubricating grease sealed inside the bearing from leaking out. The seals prevent, for example, rainwater and dust from entering into the inside of the bearing from the outside.

[0031] The vehicle-body-mounting flange 5b of the outer member 5 is discontinuously formed in the circumferential direction on an outer circumferential surface. It is formed with ears 10 (here, four ears) protruding in the radial direction. The ears 10 each have a tapped hole 13, described later. The outer member 5 is to be fastened to the knuckle by using fastening bolts passing through the ears 10, not illustrated.

[0032] The wheel hub 1 is made of medium- or high-carbon steel containing 0.40 to 0.80 wt % carbon, such as S53C. Surfaces of portions ranging from a seal land portion, in sliding contact with the outer-side seal 8, to the cylindrical portion 1b, including the inner raceway surface la, are hardened in the range from 58 to 64 HRC by induction hardening. The caulked portion 1c is a non-hardened portion. It has a surface hardness of less than 25 HRC after forging. Thus, the stiffness of the wheel hub 1 is improved. Fretting wear of a fitting surface where the inner ring 2 fits onto the hub can be prevented. Thus, the durability of the wheel hub 1 is improved. Workability when the caulked portion 1c is plastically deformed is improved. Accordingly, the occurrence of cracks, for example, is prevented during the process. Thus, the reliability and quality is improved.

[0033] The inner ring 2 is made of high-carbon chromium bearing steel, such as SUJ2. It is hardened in the range from 58 to 64 HRC to its core by quenching, with coolant. The rolling elements 4 are made of high-carbon chromium bearing steel, such as SUJ2. They hardened in the range from 62 to 67 HRC to their core by quenching, with coolant.

[0034] The wheel bearing device described herein, by way of example, includes a double-row angular contact ball bearing that uses balls as the rolling elements 4. The wheel bearing device, however, is not limited and may include a double-row tapered roller bearing that uses tapered rollers as the rolling elements. According to the embodiment, a third-generation structure is described. The embodiment, however, is not limited and may be used, for example, on a second- or fourth-generation structure.

[0035] According to the embodiment, the outer member 5 has an outer circumferential surface 11. The surface 11 is tapered and formed such that the diameter of the outer member 5 gradually decreases in the direction to the outer side. A cylindrical fitting surface 12, to be fit into the knuckle, is formed on the inner side of the ears 10. The ears 10, forming the vehicle-body-mounting flange 5b, are interposed between the outer circumferential surface 11 and the fitting surface 12. An outer-side side surface 10a and an inner-side side surface 10b of the ears 10 are formed so as to be parallel to each other.

[0036] As illustrated in FIG. 2, ribs 15 are formed on the inner-side outer circumferential surface of the ears 10 (on the side of the fitting surface 12). Ridges 16 are formed between the ears 10. The ridges 16 protrude from the fitting surface 12. The ridges 16 are formed by a forging process to be smoothly connected to the outer circumferential surface of the ears 10. The ridges 16 enable the strength and stiffness of the outer member 5 to be improved. Also, they ensure the area of contact with the knuckle so that a pressure applied to the vehicle-body-mounting flange 5b can be decreased.

[0037] Large-arc-shaped corners 14 are formed by a forging process. They are formed at portions where the ears 10 meet the outer circumferential surface 11 on the outer side. Arc-shaped corners 17 are also formed by a forging process. They are formed at portions where the ridges 16 meet the outer circumferential surface 11 (see FIG. 1). An inner-side side surface 16a of the ridges 16 that comes in contact with the knuckle, and the inner-side side surface 10b of the ears 10 are flattened by a cutting process. The tapped holes 13 are formed through the ears 10. The outer member 5 is to be fastened to the knuckle in a manner where fastening bolts (not illustrated) are inserted into the tapped holes 13 from the side of the fitting surface 12.

[0038] The ribs 15 are formed on the inner-side outer circumferential surface of the ears 10, forming the vehicle-body-mounting flange 5b. The ridges 16 protrude from the fitting surface 12 and are formed between the ears 10, by a forging process. The weight of the outer member 5 can be decreased without changing the length of the tapped holes 13 and the contact area between the inner-side side surface 10b of the ears 10 and the knuckle. In other words, a desired outer diameter of the ears 10 can be maintained and the contact area with the knuckle can be ensured. An excess thickness of an outer circumferential portion of the ears 10 is decreased to a minimum by a forging process. Thus, the weight of the outer member 5 can be reduced. In addition, the number of cutting processes is decreased as much as possible. The wheel bearing device can be provided at a reduced cost.

[0039] Here, W1≧W2 holds. W1 represents the thickness of the ribs 15 of the ears 10. W2 represents the thickness of the ridges 16. This decreases a stress applied to the corners 14 between the ears 10 and the outer circumferential surface 11 in the case where a large moment load is applied to the outer member 5. Thus, the durability of the outer member 5 can be increased. In the case where W1<W2 holds, a stress applied to the corners 17 between the ridges 16 and the outer circumferential surface 11 can be decreased. Thus, the strength and stiffness of the outer member 5 can be increased.

[0040] A wheel bearing device according to the present disclosure can be used on any one of the wheel bearing devices having second- to fourth-generation structures that include a vehicle-body-mounting flange integrally formed on the outer circumference of the outer member forming the bearing and that is to be mounted to the knuckle.

[0041] Although the embodiment of the present disclosure is described above, the present disclosure is not limited to the embodiment, which is described by way of example. The present disclosure can be naturally carried out in various modes without departing from the spirit and scope of the present disclosure. The scope of the present disclosure is shown by claims and contains all modifications having the same content and scope as the claims or their equivalents.