WO2008088150A1

WO2008088150A1 - Asymmetric wheel bearing assembly

Info

Publication number: WO2008088150A1
Application number: PCT/KR2008/000212
Authority: WO
Inventors: Jung-Yang Park; Won-Rak Bae
Original assignee: Il Jin Global Co., Ltd.
Priority date: 2007-01-15
Filing date: 2008-01-14
Publication date: 2008-07-24
Also published as: KR20080067088A

Abstract

The present invention relates to a wheel bearing assembly including a hub coupled to a wheel of a vehicle and provided with a flange extending radially, an inner race formed at an exterior surface thereof, and a step portion formed at an inside of the inner race, an exterior diameter of the step portion being smaller than that of the inner race; an inner ring inserted on the step portion of the hub and having an inner race formed at an exterior surface thereof; an outer ring having outer races formed at an interior surface thereof and corresponding to the inner races; a plurality of outside rolling elements disposed between the inner race and the outer race; a plurality of inside rolling elements disposed between the inner race and the outer race; and a cage maintaining a circumferential gap between the rolling elements, wherein the diameter of the outside rolling element is smaller than that of the inside rolling element. According to the present invention, the life of the wheel bearing assembly may not be decreased, and hardness of the wheel bearing assembly may be enhanced such that tremor of a brake apparatus connected to a flange is reduced. In addition, a decrease in the life of the outside row may be minimized and the hardness may be sharply enhanced by selecting a threshold range of the life of the bearing and the hardness in accordance with the diameter of the rolling element. Since the exterior diameter of an outside outer ring can be the same as that of an inside outer ring, interference between the outer ring and other components may be minimized.

Description

ASYMMETRIC WHEEL BEARING ASSEMBLY

Technical Field

The present invention relates to a wheel bearing assembly. More particularly, the present invention relates to a wheel bearing assembly that enables the life of the wheel bearing assembly and hardness of the bearing to be increased as a consequence of the diameter of an outside rolling element being smaller than that of an inside rolling element. Background Art FIG. 1 shows a wheel bearing assembly 300, a wheel 1100 connected to a flange 317 of the wheel bearing assembly 300 by a hub bolt 350, and a tire 1200 mounted at the wheel 1100. The wheel bearing assembly 300 is connected to a vehicle by a knuckle 1300, and in a case of being mounted at the driving wheel, the wheel bearing assembly 300 is connected to a driving shaft 1400 that receives power from an engine and is rotated.

In a state in which wheel bearing assembly 300 is mounted as shown in FIG. 1, a force Fr caused by weight of the vehicle and a force Fa caused when the vehicle is turned is transmitted to the wheel bearing assembly 300 through the tire 1200. The force Fr caused by the weight of the vehicle is applied in a radial direction of the wheel bearing assembly 300, and the force Fa caused when the vehicle is turned is applied in an axial direction of the wheel bearing assembly 300, as shown in FIG. 1.

Hereinafter, as shown in FIG. 1, the right side will be called the "inside", and the left side will be called the "outside". In addition, an inner race, an outer race, and a rolling element disposed toward the inside will be generally called an "inside row", and an inner race, an outer race, and a rolling element disposed toward the outside will be generally called an "outside row".

The force Fa caused when the vehicle is turned is applied to the inside or to the outside according to a turning direction of the vehicle.

FIG. 2 is a cross-sectional view of a conventional wheel bearing assembly 100. As shown in FIG. 2, a conventional wheel bearing assembly 100 includes a hub 110, an inner ring 120, an outer ring 130, and rolling elements 140a and 140b disposed in two rows.

The hub 110 includes a flange 117 extending radially to which a hub bolt 160 is fixedly inserted, an inner race 113 formed close to the flange 117, and a step portion 115 formed at the inside of the inner race 113 and having smaller diameter than a diameter IOOD of the inner race 113. The inner ring 120 having another inner race 121 is inserted at an exterior surface of the step portion 115.

The outer ring 130 is provided with a flange portion 133 extending radially and connected to the knuckle, and has a pair of outer races 131 formed at an interior surface thereof and corresponding to the inner races 113 and 121. A plurality of rolling elements 140a and 140b are disposed respectively between the inner races 113 and 121 and the outer races 131 so as to rotatably support the hub 110 with reference to the outer ring 130. According to the conventional wheel bearing assembly 100, a diameter Do and pitch circle diameter IOOPCD of the outside rolling element 140a are respectively equal to a diameter Di and pitch circle diameter IOIPCD of the inside rolling element 140b, as shown in FIG. 2.

If expected life and displacement (y-directional displacement of "A" point in FIG. 2) of the outside row and inside row are calculated in a case in which the force Fr caused by the weight of the vehicle and the force Fa caused when the vehicle is turned are applied to the wheel bearing assembly 100 having rolling elements of predetermined diameter and pitch circle diameter, the expected life of the outside row is calculated as 440,000km, the expected life of the inside row is calculated as 340,000km, the y-directional displacement of the "A" point is about 60μm. The displacement is calculated in order to calculate hardness of the wheel bearing assembly 100, and will hereinafter be called "hardness".

If hardness of the wheel bearing assembly 100 becomes lower (the displacement of the "A" point becomes larger), there is a higher possibility of tremor occurring in a brake apparatus mounted at the flange 117. Therefore, it is of great advantage to increase the hardness (to shorten the displacement of the "A" point).

Meanwhile, if the effective life of one row between the inside and outside rows of the wheel bearing assembly 100 is expired, the wheel bearing assembly 100 cannot be used. Therefore, the effective life of the wheel bearing assembly 100 may be expired. Considering the expected life as calculated above, there are problems that the life of the outside row is inefficiently long compared with the life of the inside row according to the conventional wheel bearing assembly 100, and it is needed to enhance the hardness (to shorten the displacement of the "A" point) in order to maintain a silent driving state when the brake is operated.

Undescribed reference numeral 111 represents an interior surface where a shaft for transmitting torque is inserted, undescribed reference numeral 117a represents a flange hole where the hub bolt 160 is fixedly inserted, undescribed reference numeral 119 represents a formed portion having undergone plastic deformation for fixing the inner ring 120 that is inserted on the step portion 115 to the hub 110, undescribed reference numeral 133a represents a connecting hole for connecting the knuckle to the flange portion 133, undescribed reference numeral 145 represents a cage for maintaining a circumferential gap between the rolling elements 140a and 140b, and undescribed reference numeral 151 represents a seal mounted at a bore formed between the hub 110 and the outer ring 130, or between the inner ring 120 and the outer ring 130, and preventing intrusion of foreign substances and leakage of lubricant, in FIG. 2. In addition, 130Do represents the exterior diameter of the outside outer ring 130, and 130Di represents the exterior diameter of the inside outer ring 130. According to the conventional art, the exterior diameter 130Do of the outside is substantially the same as the exterior diameter 130Di of the inside.

FIG. 3 is a cross-sectional view of a wheel bearing assembly 200 that is suggested so as to resolve hardness problems occurring in the conventional wheel bearing assembly 100. According to such a wheel bearing assembly 200, pitch circle diameter 200PCD of an outside rolling element 240a is larger than pitch circle diameter 201PCD of an inside rolling element 240b.

In a case in which the pitch circle diameter 200PCD of the outside rolling element is larger than the pitch circle diameter 201PCD of the inside rolling element 240b, the hardness of the wheel bearing assembly 200 may increase (y-directional displacement of "A" point may be decreased in FIG. 3), but the life of the outside rolling element may increase such that a deviation of the life between the outside and the inside may further increase and the problems that the life of the outside is inefficiently long may still exist. Since the exterior diameter 230Do of the outside with reference to a flange portion 233 provided at the exterior surface of an outer ring 230 increases, deviation between the exterior diameter 230Do of the outside and the exterior diameter 230Di of the inside may increase and it may be difficult to manufacture the outer ring 230. In addition, the outside portion of the outer ring 230 may interfere with other components of a vehicle, and thus design of other components of the vehicle may need to be changed.

Undescribed reference numeral 210 represents a hub, undescribed reference numeral 220 represents an inner ring, undescribed reference numeral 250 represents a hub bolt, and undescribed reference numeral 241 represents a seal in FIG. 3. Detailed Description of Invention

The present invention is invented in order to solve the above- mentioned problems. It is an object of the present invention to provide an asymmetric bearing assembly that does not substantially decrease the life of a wheel bearing assembly but enhances hardness of the wheel bearing assembly by making the outside row have substantially the same life as the inside row, and thus decreases tremor of a brake apparatus.

In addition, it is another object of the present invention to provide a asymmetric bearing assembly that minimizes the life of an outside row and greatly increases hardness by selecting a threshold diameter range of rolling elements, and maintains the exterior diameter of an outside outer ring to be substantially the same as the exterior diameter of an inside outer ring. Brief Description of Drawings FIG. 1 is a schematic cross-sectional view of a tire, a wheel, and a wheel bearing assembly.

FIG. 2 is a cross-sectional view of a conventional wheel bearing assembly mounted at a wheel of a vehicle. FIG. 3 is a cross-sectional view of another conventional wheel bearing assembly.

FIG. 4 is a cross-sectional view of an asymmetric bearing assembly according to an exemplary embodiment of the present invention.

FIG. 5 is a cross-sectional view of an asymmetric bearing assembly according to another exemplary embodiment of the present invention.

FIG. 6 is a graph showing life of the inside and outside rows in an asymmetric bearing assembly according to an exemplary embodiment of the present invention.

FIG. 7 is a graph showing life ratio of the outside row to the inside row in accordance with a diameter change of the rolling element in an asymmetric bearing assembly according to an exemplary embodiment of the present invention.

FIG. 8 is a graph showing a reduction ratio of life of the outside row in accordance with a diameter change of the rolling element in an asymmetric bearing assembly according to an exemplary embodiment of the present invention.

FIG. 9 is a graph showing a change of bearing hardness in accordance with a diameter change of the rolling element in an asymmetric bearing assembly according to an exemplary embodiment of the present invention. * Description of Reference Numerals Indicating Primary Elements in the Drawings *

1: wheel bearing assembly 10: hub

13, 21, 23: inner race 15: step portion

20, 22: inner ring 30: outer ring 31a, 31b: outer race 33: flange portion

40a, 40b: rolling element 45a, 45b: cage

51: seal 60: hub bolt Best Mode

Hereinafter, an asymmetric bearing assembly according to exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. When the present invention is described, detailed descriptions of the same constituent elements of the conventional art will be omitted in the detailed description of the present invention, and will be given the same names as those for the conventional art.

FIG. 4 is a cross-sectional view of an asymmetric bearing assembly according to an exemplary embodiment of the present invention, FIG. 5 is a cross-sectional view of an asymmetric bearing assembly according to another exemplary embodiment of the present invention, FIG. 6 is a graph showing life of the inside and outside rows, FIG. 7 is a graph showing life ratio of the outside row to the inside row in accordance with a diameter change of the rolling element, FIG. 8 is a graph converting the graph in FIG. 7 into reduction ratio of life of the outside row, and FIG. 9 is a graph showing change of bearing hardness in accordance with diameter change of the rolling element.

As shown in FIG. 4, an asymmetric bearing assembly 1 according to an exemplary embodiment of the present invention includes a hub 10 provided with a flange 17 extending radially and connected with a wheel (not shown) by a hub bolt 60, an inner ring 20 inserted on the hub 10 and provided with an inner race 21 formed at an exterior surface thereof, an outer ring 30 provided with a flange portion 33 extending radially so as to mount a knuckle (not shown), and a plurality of rolling elements 40a and 40b disposed between the hub 10 and the outer ring 30, and between the inner ring 20 and the outer ring 30.

An inner race 13 is formed at the outside of the hub 10, and a step portion 15 that has smaller exterior diameter than the race diameter 1OD of the inner race 13 is formed at the inside of the inner race 13. The inner ring 20 is inserted on the step portion 15. As shown in FIG. 5, the long step portion 15 may be formed at the hub 10, and two inner rings 20 and 22 provided respectively with the inner races 21 and 23 may be inserted on the step portion 15.

Outer races 31a and 31b respectively corresponding to the inner race 13 or 23 and the inner race 22 are formed at an interior surface of the outer ring 30.

The outside rolling element 40a of the rolling elements 40a and 40b is disposed between the inner race 13 or 23 and the outer race 31a, and the inside rolling element 40b is disposed between the inner race 21 and the outer race 31b. Thus, the rolling elements 40a and 40b rotatably support the hub 10 with reference to the outer ring 30.

In the asymmetric bearing assembly 1 according to a preferable exemplary embodiment of the present invention, the diameter Do of the outside rolling element 40a is smaller than the diameter Di of the inside rolling element 40b. The diameter Do of the outside rolling element 40a may be 88 % to 94 % of the diameter Di of the inside rolling element 40b.

As the diameter Do of the outside rolling element 40a becomes smaller, the race diameter 1OD of the outside inner race 13 and 23 becomes larger and is therefore larger than the race diameter HD of the inside inner race 21. hi addition, the race diameter of the outside outer race 31a is smaller than or equal to that of the inside outer race 31b.

Meanwhile, as shown in FIG. 4 and FIG. 5, the pitch circle diameter IOPCD of the outside rolling element 40a may be equal to or larger than the pitch circle diameter HPCD of the inside rolling element 40b. In a case in which the pitch circle diameter IOPCD of the outside rolling element 40a is larger than the pitch circle diameter HPCD of the inside rolling element 40b in the wheel bearing assembly 1 according to the present invention, it is possible for the exterior diameter 30Do of the outside outer ring 30 to not be larger than but to be equal to the exterior diameter 30Di of the inside. Therefore, if the pitch circle diameter IOPCD increases, there is no possibility of interference with other components.

Assuming that the same forces Fr and Fa applied to the wheel bearing assembly 100 shown in FIG. 2 are applied to the wheel bearing assembly 1 according to the exemplary embodiments of the present invention, the expected life and hardness of the wheel bearing assembly 1 according to the exemplary embodiments of the present invention are calculated as follows. Here, except the diameter Do of the outside rolling element 40a, the dimensions of the wheel bearing assembly 1 according to the exemplary embodiments of the present invention are the same as those of the wheel bearing assembly 100 shown in FIG. 2. In a case in which the diameter Do of the outside rolling element 40a is the same as the diameter Di for the inside rolling element 40b, the life of the outside row is about 440,000km, the life of the inside row is about 340,000 km, and y-directional displacement of the "A" point in FIG. 4 and FIG. 5 is about 60 μ m.

In a case in which the diameter Do of the outside rolling element 40a is about 92% of the diameter Di of the inside rolling element 40b, the life of the outside row is reduced to about 370,000km, the life of the inside row is increased to about 350,000km, and the y-directional displacement of the "A" point in FIG. 4 and FIG. 5 is reduced to about 56 u m.

In addition, in a case in which the diameter Do of the outside rolling element 40a is about 83% of the diameter Di of the inside rolling element 40b, the life of the outside row is reduced to about 240,000 km, the life of the inside row is increased to about 380,000km, and the y-directional displacement of the "A" point in FIG.4 and FIG. 5 is reduced to about 55 μ m.

Above-calculated results are shown in FIG. 6 to FIG. 9. The horizontal axes in FIG. 6 to FIG. 9 represent percentage of the diameter Do of the outside rolling element 40a to the diameter Di of the inside rolling element 40b, the vertical axis in FIG. 6 represents life of the outside and inside rows, the vertical axis in FIG. 7 represents a ratio of the life of the outside row to the life of the inside row, the vertical axis in FIG. 8 represents a reduction ratio of the life of the outside row, and the vertical axis in FIG. 9 represents a change of the y-directional displacement of the "A" point shown in FIG. 4 and FIG. 5 in accordance with a change of the diameter Do of the outside rolling element 40a.

As shown in FIG. 6 to FIG. 9, the life and the hardness of the wheel bearing assembly 1 are not linearly proportionate to the diameter change of the outside rolling element 40a. The life is slowly reduced when the diameter Do of the outside rolling element 40a is reduced to about 92% of the diameter Di of the inside rolling element 40b, but the life is more quickly reduced when the diameter Do of the outside rolling element 40a is reduced from about 92% to about 83% of the diameter Di of the inside rolling element 40b, as shown in FIG. 7.

That is, as shown in FIG. 8, the life of the outside row is reduced by 6.9% when the diameter Do of the outside rolling element 40a is reduced from 100% to about 92% of the diameter Di of the inside rolling element 40b, but the life of the outside row is reduced by 19.7% when the diameter Do of the outside rolling element 40a is reduced from about 92% to about 83% of the diameter Di of the inside rolling element 40b. In addition, as shown in FIG. 6, as the diameter Do of the outside rolling element 40a is reduced, the life of the inside row is increased by a predetermined amount.

Therefore, as shown in FIG. 6 to FIG. 8, a threshold range of the diameter Do of the outside rolling element 40a apparently exists that prevents a quick reduction of the life in accordance with a reduction of the diameter Do of the outside rolling element 40a.

Meanwhile, with regard to the hardness of the wheel bearing assembly 1, the hardness is increased by 5.93% (the displacement of the "A" point is increased by 5.93% in FIG. 4 and FIG. 5) when the diameter Do of the outside rolling element 40a is reduced from 100% to about 92% of the diameter Di of the inside rolling element 40b, and the hardness is increased by 6.85% when the diameter Do of the outside rolling element 40a is reduced from about 92% to about 83% of the diameter Di of the inside rolling element 40b. In a case in which the diameter of the outside rolling element 40a is reduced, the hardness of the wheel bearing assembly 1 is increased. However, a threshold range of the diameter Do of the outside rolling element 40a exists where the hardness does not sharply increase in a case in which the diameter Do of the outside rolling element 40a is shortened, like the life of the wheel bearing assembly 1. In addition, the threshold range related to the life is substantially the same as the threshold range related to the hardness.

Therefore, in a case in which the diameter Do of the outside rolling element 40a in the wheel bearing assembly 1 is within the threshold range, it is possible to not substantially decrease the life of the wheel bearing assembly 1 (to substantially increase the life of the wheel bearing assembly 1) but to make the wheel bearing assembly 1 have sufficient hardness as a consequence of the life of the outside row being prevented from being quickly reduced and is substantially the same as the life of the inside row.

According to the above-calculated results, the diameter Do of the outside rolling element 40a is preferably set within 88% to 94% of the diameter Di of the inside rolling element 40b. When being set within the above range, the life of the inside row increases and the life of the outside row decreases, as shown in FIG. 6, such that the life of the inside row is substantially the same as that of the outside row, and thus the life of the wheel bearing assembly 1 does not decrease but increases. In addition, the hardness may be sufficiently increased.

In a case in which the diameter Do of the outside rolling element 40a is above the range, a life reduction of the outside row is small but a life increase of the inside row is not large. Therefore, the life is substantially decreased and the deviation between the life of the inside and outside rows is still large. In addition, the hardness is not sufficiently increased.

In a case in which the diameter Do of the outside rolling element 40a is below the range, the life of the outside row is quickly decreased and the life of the wheel bearing assembly 1 is decreased. In addition, the hardness is increased only a little, and thus the hardness does not sufficiently increase so as to offset the reduction of the life.

Undescribed reference numeral 11 represents an interior surface where a driving shaft (not shown) is inserted in a case of a driving wheel, undescribed reference numeral 17a represents a bolt hole where the hub bolt 60 is inserted, undescribed reference numeral 33a represents a connecting hole connecting the flange portion 33 to the knuckle (not shown), undescribed reference numerals 45a and 45b represent cages for maintaining a circumferential gap between the rolling elements 40a and 40b, and undescribed reference numeral 51 represents a seal for preventing intrusion of foreign substances and leakage of lubricant in FIG. 4 and FIG. 5. While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Industrial Applicability

According to a wheel bearing assembly of the present invention, the life of the wheel bearing assembly may not be decreased (instead, it may be substantially increased) and hardness of the wheel bearing assembly may be enhanced such that a tremor of a brake apparatus connected to a flange is reduced by making an outside row have substantially the same life as an inside low. hi addition, a decrease in the life of the outside row may be minimized and the hardness may be sharply enhanced by selecting a threshold range of the life of the bearing and the hardness in accordance with the diameter of the rolling element. Since the exterior diameter of an outside outer ring can be the same as that of an inside outer ring, interference between the outer ring and other components may be minimized.

Claims

WHAT IS CALIMED IS

1. An asymmetric bearing assembly, comprising: a hub coupled to a wheel of a vehicle and provided with a flange extending radially, an inner race formed at an exterior surface thereof, and a step portion formed at an inside of the inner race, an exterior diameter of the step portion being smaller than that of the inner race; an inner ring inserted on the step portion of the hub and having an inner race formed at an exterior surface thereof; an outer ring having outer races formed at an interior surface thereof and corresponding to the inner races; a plurality of inside and outside rolling elements disposed between the inner races and the outer races; and a cage maintaining a circumferential gap between the rolling elements, wherein the diameter of the outside rolling element is smaller than that of the inside rolling element.

2. An asymmetric bearing assembly, comprising: a hub coupled to a wheel of a vehicle, provided with a flange extending radially, and provided with a step portion formed at an exterior surface thereof; an inner ring inserted on the step portion of the hub and having an inner race formed at an exterior surface thereof; an outer ring having an outer race formed at an interior surface thereof and corresponding to the inner race; a plurality of inside and outside rolling elements disposed between the inner race and the outer race; and a cage maintaining a circumferential gap between the rolling elements, wherein the diameter of the outside rolling element is smaller than that of the inside rolling element.

3. The asymmetric bearing assembly of claim 1, wherein the diameter of the outside rolling element is 88% to 94% of that of the inside rolling element.

4. The asymmetric bearing assembly of claim 2, wherein the diameter of the outside rolling element is 88% to 94% of that of the inside rolling element.

5. The asymmetric bearing assembly of one of claims 1-4, wherein the race diameter of the outside inner race is larger than that of the inside inner race.

6. The asymmetric bearing assembly of claim 5, wherein the race diameter of the outside outer race is smaller than or equal to that of the inside outer race.

7. The asymmetric bearing assembly of claim 5, wherein pitch circle diameter of the outside rolling element is larger than or equal to that of the inside rolling element.