Wheel bearing device

Abstract

To provide a wheel bearing device whose reliability is improved by restraining indentations from occurring in raceway surfaces without an increase in size.SOLUTION: A wheel bearing device comprises an outer member comprising a plurality of outside raceway surfaces in an inner periphery, an inner member comprising a plurality of inside raceway surfaces opposed to the plurality of outside raceway surfaces, and a plurality of rolling rows comprising a plurality of rolling bodies rollably housed between the raceway surfaces of both the outer member and the inner member. In at least one of the rolling rows, the rolling bodies consist of hollow balls 71 and solid balls 72.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Normally, in a wheel bearing device that constitutes a double-row angular ball bearing, in order to ensure the strength of rolling elements that locally receive loads, the hardness of the rolling elements is set higher than that of the raceway surface so that the elastic fatigue limit of the rolling elements is higher than the elastic fatigue limit of the raceway surface. Therefore, due to the input of excessive loads such as sharp turning of a vehicle or running onto a curb, the rolling elements ride onto the shoulders of the raceway surface, the area of the contact ellipse protrudes from the raceway surface, and a stress spike occurs in which the contact surface pressure rapidly increases, and there is a possibility that indentations are formed on the shoulders of the raceway surface. The indentations cause abnormal noises and lead to early peeling of the raceway surface due to stress concentration, thus reducing the reliability of the wheel bearing device.

[0003] As a countermeasure against this, for example, Patent Document 1 discloses a technique of increasing the shoulder height of the raceway surface. Thereby, it suppresses the rolling elements from riding onto the shoulders of the raceway surface.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in addition to the increase in the output and size of vehicles, the reduction of the tire profile, and the generalization of self-standing, the number of cases where the vehicle runs with a reduced tire air pressure due to insufficient management is increasing. Not only in unexpected situations such as mounting on a curb, but also in normal driving of the vehicle, the amount of deflection of the tire alone is increasing the chance that the impact load from the road surface to the wheel cannot be absorbed. In this case, an excessive load beyond expectation directly acts on the bearing device from the wheel. When the excessive load acts and exceeds the elastic limit of the raceway surface, indentations are formed on the raceway surface, which may lead to the occurrence of abnormal noises and the failure of the bearing device due to the early peeling of the raceway surface associated with the indentations.

[0006] Therefore, in order to suppress the generation of indentations on the raceway surface due to excessive load, a method of increasing the size of the bearing device itself to a size corresponding to the excessive load can be considered. However, this would go against the trend of recent vehicle weight reduction and fuel efficiency improvement, and it would be difficult to adopt due to the layout constraints on the vehicle side.

[0007] An object of the present invention is to provide a wheel bearing device with improved reliability by suppressing the generation of indentations on the raceway surface without increasing the size.

Means for Solving the Problems

[0008] The wheel bearing device of the present invention includes an outer member having a double-row outer raceway surface on its inner circumference, an inner member having a double-row inner raceway surface facing the double-row outer raceway surface, and a double-row rolling element row having a plurality of rolling elements rotatably accommodated between both raceway surfaces of the outer member and the inner member. In at least one of the rolling element rows, the rolling elements are composed of hollow balls and solid balls.

[0009] Also, the wheel bearing device of the present invention includes an outer member having a double-row outer raceway surface on its inner circumference, an inner member having a double-row inner raceway surface facing the double-row outer raceway surface, and a double-row rolling element row having a plurality of rolling elements rotatably accommodated between both raceway surfaces of the outer member and the inner member. In at least one of the rolling element rows, the rolling elements are composed of hollow balls.

Effects of the Invention

[0010] According to the present invention, in a wheel bearing device, by using a hollow ball for a rolling element that has the same surface hardness as a solid ball and can reduce the apparent Young's modulus, it is possible to effectively suppress the generation of indentations on the raceway surface without increasing the size, thereby improving the reliability.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0012] [Overall Configuration of Wheel Bearing Device] Using FIG. 1, the overall configuration of the wheel bearing device 1 will be described. In the following description, the inner side refers to the vehicle body side of the wheel bearing device 1 when attached to the vehicle body, and the outer side refers to the wheel side of the wheel bearing device 1 when attached to the vehicle body. The axial direction refers to the direction along the rotation axis A of the wheel bearing device 1.

[0013] The wheel bearing device 1 shown in FIG. 1 rotatably supports a wheel in a suspension device of a vehicle such as an automobile. The wheel bearing device 1 has a configuration called the third generation, and includes an outer ring 2 which is an outer member, a hub ring 3 and an inner ring 4 which are inner members, two rows of inner side ball rows 5 and outer side ball rows 6 which are rolling element rows, and an inner side seal member 9 and an outer side seal member 10.

[0014] The outer ring 2 supports the hub ring 3 and the inner ring 4. An inner opening 2a into which the inner seal member 9 can be fitted is formed at the inner end of the outer ring 2. An outer opening 2b into which the outer seal member 10 can be fitted is formed at the outer end of the outer ring 2. An inner outer raceway surface 2c and an outer outer raceway surface 2d are formed on the inner peripheral surface of the outer ring 2 in the circumferential direction. A vehicle body mounting flange 2e for attaching the outer ring 2 to a vehicle body member is integrally formed on the outer peripheral surface of the outer ring 2. A bolt hole 2g into which a fastening member (here, a bolt) for fastening the vehicle body member and the outer ring 2 is inserted is formed in the vehicle body mounting flange 2e.

[0015] The hub ring 3 rotatably supports a wheel and a brake rotor (or a brake drum) of a vehicle (not shown). A reduced-diameter small-diameter stepped portion 3a extending in the axial direction is provided at the inner end of the outer peripheral surface of the hub ring 3. A wheel mounting flange 3b for attaching the wheel is integrally formed at the outer end of the hub ring 3. A bolt hole 3f into which a hub bolt for fastening the hub ring 3 and the wheel or brake parts is press-fitted is formed in the wheel mounting flange 3b.

[0016] An outer inner raceway surface 3c is provided on the hub ring 3 so as to face the outer outer raceway surface 2d on the outer side of the outer ring 2. A seal land 3d with which the lip of the outer seal member 10 is in sliding contact is formed on the base side of the wheel mounting flange 3b of the hub ring 3.

[0017] The inner ring 4 is provided on the small-diameter stepped portion 3a of the hub ring 3. The inner ring 4 is fixed to the small-diameter stepped portion 3a of the hub ring 3 by press-fitting and caulking. The inner ring 4 applies preload to the inner ball row 5 and the outer ball row 6. A caulked portion 3h caulked to the inner end face of the inner ring 4 is formed at the inner end of the hub ring 3.

[0018] On the outer peripheral surface of the inner ring 4, an inner raceway surface 4a is formed. That is, on the inner side of the hub ring 3, the inner raceway surface 4a is constituted by the inner ring 4. The inner raceway surface 4a faces the outer raceway surface 2c on the inner side of the outer ring 2. On the outer peripheral surface at the inner side end of the inner ring 4, a fitting surface 4b into which the inner side seal member 9 can be fitted is formed.

[0019] The inner side ball row 5 and the outer side ball row 6, which are rolling element rows, are constituted by a plurality of balls 7, which are rolling elements, being held by a cage 8. The inner side ball row 5 is rotatably sandwiched between the inner raceway surface 4a of the inner ring 4 and the outer raceway surface 2c on the inner side of the outer ring 2. The outer side ball row 6 is rotatably sandwiched between the inner raceway surface 3c of the hub ring 3 and the outer raceway surface 2d on the outer side of the outer ring 2. That is, the inner side ball row 5 and the outer side ball row 6 are rotatably accommodated between both raceway surfaces of the outer member and the inner member.

[0020] In the wheel bearing device 1, a double row angular contact ball bearing is constituted by the outer ring 2, the hub ring 3 and the inner ring 4, the inner side ball row 5, and the outer side ball row 6.

[0021] The inner side seal member 9 and the outer side seal member 10 are seal members that close the open ends of the annular space S formed by the outer member and the inner member. The inner side seal member 9 is attached 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 10 is attached to the outer side open end formed between the outer ring 2 and the hub ring 3 in the annular space S.

[0022] [Rolling element] Figure 2 is a cross-sectional view of the ball 7 in the inner side ball row 5. In the inner side ball row 5, the ball 7 is constituted by a hollow ball 71 and a solid ball 72.

[0023] The hollow ball 71 and the solid ball 72 are made of bearing steel. The bearing steel is made of, for example, high-carbon chromium bearing steel such as SUJ2, and is hardened by quenching in the range of 62 to 67 HRC. Note that the hollow ball 71 and the solid ball 72 may be made of ceramics, but steel is cheaper than ceramics. There is no particular limitation on the manufacturing method of the hollow ball 71. For example, the manufacturing method described in JP-A-2011-58065 can be used, and instead of quenching of high-carbon chromium bearing steel, carburizing treatment can also be used.

[0024] When the hollow ball 71 and the solid ball 72 are made of the same material, the hollow ball 71 has a smaller apparent Young's modulus than the solid ball 72 while having the same surface hardness. That is, when the hollow ball 71 and the solid ball 72 are arranged between both raceway surfaces of the outer member and the inner member, the hollow ball 71 is more easily elastically deformed than the solid ball 72, and the contact ellipse with the raceway surface becomes larger. Therefore, the contact surface pressure with the outer raceway surface 2c and the inner raceway surface 4a is lower by the amount of the hollow ball 71 used than when all the balls 7 in the inner ball row 5 are made of the solid ball 72, and the same effect as when the outer diameter of the ball 7 is increased can be obtained, that is, the service life of the wheel bearing device 1 can be extended.

[0025] And even when an excessive load acts, by using the hollow ball 71 which is more easily bent than the solid ball 72, it is possible to suppress the acting of a surface pressure exceeding the elastic limit on the outer raceway surface 2c and the inner raceway surface 4a. Therefore, the generation of indentations on the outer raceway surface 2c and the inner raceway surface 4a can be suppressed. As a result, the occurrence of abnormal noise and the failure of the wheel bearing device 1 due to early peeling of the raceway surface accompanying the indentation can be suppressed, and the reliability of the wheel bearing device 1 is improved.

[0026] FIG. 3 is a diagram for explaining the sizes of the hollow ball 71 and the solid ball 72, where (a) is a cross-sectional view of the hollow ball 71 and (b) is a cross-sectional view of the solid ball 72. In order to evenly load the hollow ball 71 and the solid ball 72 when a preload is applied, within the same range as the outer diameter of the conventional ball, the outer diameter D1 of the hollow ball 71 is made larger than the outer diameter D3 of the solid ball 72. Also, when an excessive load acts, since the hollow ball 71 with a larger outer diameter receives the load first, the hollow ball 71 serves like a cushioning material and indentation is likely to be suppressed.

[0027] Specifically, when the outer diameter D1 of the hollow ball 71 and the outer diameter D3 of the solid ball 72 are 5 to 15 mm, it is preferable that the outer diameter D1 of the hollow ball 71 is larger than the outer diameter D3 of the solid ball 72 in the range of 10 μm or more and 30 μm or less. When the outer diameter D1 of the hollow ball 71 is only larger than the outer diameter D3 of the solid ball 72 by less than 10 μm, the effect of making the outer diameter D1 of the hollow ball 71 larger than the outer diameter D3 of the solid ball 72 is small. On the other hand, when the outer diameter D1 of the hollow ball 71 is larger than the outer diameter D3 of the solid ball 72 by more than 30 μm, the contact ellipse with the raceway surface of the hollow ball 71 becomes large, and due to an increase in spin slip etc., the rotational torque increases, which is not preferable.

[0028] In the inner ball row 5 of the present embodiment, 14 balls 7 are arranged, and 7 hollow balls 71 and 7 solid balls 72 are alternately arranged. Note that the number of balls 7 is not particularly limited. In the inner ball row 5, it is preferable that the ratio of the hollow balls 71 is 30% or more and 70% or less. When the ratio of the hollow balls 71 is less than 30%, the effect of using the hollow balls 71 is small. On the other hand, when the ratio of the hollow balls 71 is 70% or more, the contact ellipse with the raceway surface of the hollow balls 71 becomes large, and due to an increase in spin slip etc., the rotational torque increases, which is not preferable. Therefore, when the ratio of the hollow balls 71 is 70% or more, it is necessary to adjust the deflection amount of the hollow balls 71 by reducing the inner diameter D2 of the hollow balls 71 or using a material with a large Young's modulus.

[0029] As shown in FIG. 4, in the inner ball row 5, all the balls 7 may be composed of hollow balls 71. In this case, a plurality of types of hollow balls 71 having different outer diameters D1 and inner diameters D2 may be mixed and loaded.

[0030] Further, by using the hollow balls 71, the weight of the wheel bearing device 1 can be reduced. For example, when D1 / D2 = 1.28, the weight of the hollow ball 71 is about half of the weight of the solid ball 72. When the weight of the wheel bearing device 1 is reduced, the fuel efficiency of the vehicle is improved, and the handling stability is improved by reducing the so-called unsprung weight.

[0031] Since the configuration of the balls 7 in the outer ball row 6 is the same as the configuration of the balls 7 in the inner ball row 5, the description thereof is omitted. The inner ball row 5 and the outer ball row 6 may differ in the number of balls 7, the material of the balls 7, the pitch circle diameter, the outer diameter D1 of the hollow ball 71, the inner diameter D2 of the hollow ball 71, the outer diameter D3 of the solid ball 72, the ratio of the hollow balls 71, etc. Further, at least one of the inner ball row 5 or the outer ball row 6 may have a configuration including the hollow balls 71.

[0032] In the present embodiment, the wheel bearing device 1 for a driven wheel has been described, but the present invention can also be applied to a wheel bearing device for a driving wheel.

[0033] As described above, the wheel bearing device 1 of the present embodiment has been described as a third-generation structure wheel bearing device with an inner ring rotation in which the inner raceway surface 3c of the rolling elements is directly formed on the outer periphery of the hub ring 3, but it is not limited thereto. For example, it may be a second-generation structure of inner ring rotation in which a pair of inner rings are press-fitted and fixed to the hub ring. Further, it may be a third-generation structure or a second-generation structure of outer ring rotation. Further, it may be a first-generation structure composed of an outer ring and an inner ring. The above-described embodiment merely shows a representative form of the present invention, and various modifications can be made without departing from the gist of the present invention.

Explanation of reference numerals

[0034] 1 Wheel bearing device 2 Outer ring (outer member) 2c, 2d Outer raceway surface 3 Hub ring (inner member) 3c, 4a Inner raceway surface 4 Inner ring (inner member) 5 Inner side ball row (rolling row) 6 Outer side ball row (rolling row) 7 Ball (rolling element) 71 Hollow ball 72 Solid ball

Claims

1. An outer member having a double row of outer raceways on its inner circumference, An inner member having a double row of inner raceways facing the double row of outer raceways, A double row of rolling elements having a plurality of rolling elements rotatably accommodated between both raceways of the outer member and the inner member, In at least one of the rolling element rows, the rolling elements are composed of hollow balls and solid balls, A wheel bearing device, characterized in that the ratio of the hollow balls is different between one of the rolling element rows and the other rolling element row.

2. The wheel bearing device according to claim 1, characterized in that, in the rolling element row composed of the hollow balls and the solid balls, the ratio of the hollow balls is 30% or more and 70% or less.

3. The wheel bearing device according to claim 1 or claim 2, characterized in that, in the rolling element row composed of the hollow balls and the solid balls, the outer diameter of the hollow balls is larger than the outer diameter of the solid balls.

4. The wheel bearing device according to claim 3, characterized in that, in the rolling element row composed of the hollow balls and the solid balls, the outer diameter of the hollow balls is larger than the outer diameter of the solid balls in the range of 10 μm or more and 30 μm or less.

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