WO2008134415A1

WO2008134415A1 - Wheel end with double row bearing having dissimilar contact angles

Info

Publication number: WO2008134415A1
Application number: PCT/US2008/061403
Authority: WO
Inventors: Scott A. Warren
Original assignee: The Timken Company
Priority date: 2007-04-27
Filing date: 2008-04-24
Publication date: 2008-11-06

Abstract

A wheel end (A) for coupling a road wheel (R) to a suspension system component (S) of an automotive vehicle includes a housing (2) that is configured for attachment to the suspension system component, and a hub (4) having a drive flange (22) to which the road wheel attaches and a spindle (20) that projects from the drive flange into the housing. In addition, the wheel end has an antifriction bearing (6) located between the housing and the hub spindle to enable the hub to rotate about an axis (X). The bearing has outboard and inboard raceways (40, 44, 42, and 52) carried by the housing and hub spindle and rolling elements (60, 62) organized in outboard and inboard rows between the outboard and inboard raceways, respectively, all such that the bearing will transfer radial loads and thrust loads in both axial directions. The contact angle ( Φo) of the outboard row differs from the contact angle ( Φi) of the inboard row so as to optimize performance of the wheel end.

Description

WHEEL END WITH DOUBLE ROW BEARING HAVING DISSIMILAR

CONTACT ANGLES

CROSS REFERENCE TO RELATED APPLICATIONS This application derives and claims priority from U.S. provisional application 60/914,371 , filed 27 April 2007, which application is incorporated herein by reference. TECHNICAL FIELD

This invention relates in general to wheel ends for automotive vehicles and, more particularly, to a wheel end with dissimilar contact angles in its bearing. BACKGROUND OF ART

Automobiles and light trucks of current manufacture contain many components that are acquired in packaged form from outside suppliers. The packaged components reduce the time required to assemble automotive vehicles and further improve the quality of the vehicles by eliminating critical adjustments from the assembly line. So-called "wheel ends" represent one type of packaged component that has facilitated the assembly of automotive vehicles. A wheel end couples a road wheel to the suspension system of the vehicle and transfers both radial and thrust loads between the wheel and suspension system, all while allowing the wheel to rotate.

The typical wheel end has (Fig. 1 ) a housing that is bolted against a steering knuckle or other suspension upright, a hub provided with a drive flange to which the road wheel is attached and also a spindle that projects from the flange into the housing, and an antifriction bearing located between the housing and the hub spindle to enable the hub to rotate in the housing with minimal friction. The bearing has rolling elements organized in two rows - one outboard, the other inboard - and those rolling elements together with raceways along which they roll are configured to transfer thrust loads in both axial directions as well as radial loads. Moreover, the typical bearing is symmetrical, that is to say the rolling elements and raceways of the outboard row are identical to the rolling elements and raceways of the inboard row except for orientation, which of course enables the bearing to accommodate thrust loads in both axial directions.

But often in a wheel end one row - usually the outboard row - carries a greater radial load and a greater thrust load than the other row. To measure the difference in the loading derives from the amount of offset in the road wheel. For example, if the axial center of the tire on that road wheel does not vertically align with the space between the two rows of rolling elements, one row will carry a greater radial load than the other. When a vehicle negotiates a turn, both the outboard row for the bearing on the outside of the turn and the inboard row for the bearing on the inside of the turn transfer thrust to resist the inertial forces encountered in the turn, but the bearing in the outside of the turn transfers thrust of a magnitude greater than that transferred by the bearing on the inside of the turn. BRIEF DESCRIPTION OF THE DRAWING Fig. 1 is a longitudinal sectional view of a wheel end constructed in accordance with and embodying the present invention, with the wheel end being fitter to a suspension system component and having a road wheel secured to it; and Fig. 2 is an enlarged longitudinal sectional view of the wheel end. DESCRIPTION OF BEST MODE FOR CARRYING OUT INVENTION

A wheel end A which is in essence a bearing assembly, couples a road wheel R to a suspension system component S of an automotive vehicle, and enables the road wheel R to rotate about an axis X and to transfer both radial loads and thrust loads in both axial directions between the wheel R and, the suspension system component S. If the road wheel R steers the vehicle, the suspension system component S takes the form of a steering knuckle. If it does not steer, the suspension system component S is a simple suspension upright. The wheel end A includes a housing 2 that is bolted to the suspension system component S, a hub 4 to which the road wheel R is attached, and a bearing 6 located between the housing 2 and hub 4 to enable the latter to rotate with respect to the former about the axis X with minimal friction. Thθ housing 2, which is a fixed outer member, includes (Fig. 1 ) a generally cylindrical body 10, which is tubular, and a flange 12 that projects radially from the body 10 generally midway between the ends of the body 10. The inboard segment of the body 10 is received in the suspension system component S such that the flange comes against the component S, to which it is secured with cap screws 14 that pass through the component S and thread into the flange 12. Actually, the flange 12 has several lobes and is attached to the suspension system component S at its lobes.

The hub 4, which is a rotatable inner member, includes (Fig. 1 ) a spindle 20, which extends through the tubular body 10 of the housing 2, and a drive flange 22 that is formed integral with the spindle 20 at the outboard end of the spindle 20. The drive flange 22 is fitted with lug bolts 24 over which lug nuts 26 thread to secure a brake rotor 28 and the road wheel R to the hub 4.

The spindle 20 merges with the flange 22 at an enlarged region 30 (Fig. 2) that leads out to a cylindrical bearing seat 34 that in turn leads out to a formed end 36. The formed end 36 is directed outwardly away from the axis X and provides an inside face 38 that is squared off with respect to the axis X and is presented toward the enlarged region 30.

The bearing 6 lies between the spindle 20 of the hub 4 and the housing 2 and enables the hub 4 to rotate relative to the housing 2 about the axis X. It includes (Fig. 2) two outer raceways 40 and 42 formed on the interior surface of the tubular body 10 for the housing 2, the former being outboard and the latter being inboard. The two raceways 40 and 42 taper downwardly toward each other, so that they have their least diameters where they are closest, generally midway between the ends of the housing 2. However, the outboard raceway 40 is preferably larger than the inboard raceway 42 and lies at a greater angle with respect to the axis X. Apart from the two outer raceways 40 and 42, the bearing 6 also includes an inner raceway 44 and thrust rib 46 that are on the enlarged region 30 of the spindle 20. The raceway 44 lies at the outboard position and faces the outboard outer raceway 40, tapering the same direction downwardly toward the center of the housing 2. The thrust rib 46 extends along the large end of the raceway 44. Beyond the opposite small A-

end of the raceway 44, the enlarged region 30 assumes a cylindrical configuration and terminates at a shoulder 48 that faces away from the flange 22 and toward the inside face 38 of the formed end 36. The bearing seat 34 lies between the inside face 38 and the shoulder 48. The bearing 6 also includes an initially separate inner race in the form of a cone 50 that fits over the bearing seat 34 of the spindle 20 with an interference fit. It includes an inboard inner raceway 52 that is presented outwardly toward the inboard outer raceway 42 on the housing 2 and tapers in the same direction, downwardly toward enlarged region 30. However, it is preferably smaller in diameter than the outboard inner raceway 44 and lies at a lesser angle with respect to the axis X. At the large end of its raceway 52 the cone 50 has a thrust rib 54 that leads out to a back face 56 that is squared off with respect to the axis X. At the small end of its raceway 52 the cone 50 has a retaining rib 58 that leads toward the shoulder 48 on the enlarged region 30.

Completing the bearing 6 are (Fig. 2) rolling elements in the form of tapered rollers 60 organized in an outboard row between the outboard raceways 40 and 44 and tapered rollers 62 organized in an inboard row between the inboard raceways 42 and 52. The outboard rollers 60 along their tapered side faces contact the outboard raceways 40 and 44, whereas the inboard rollers 62 along their tapered side faces contact the inboard raceways 42 and 52. The rollers 60 and 62 of the two rows are on apex. Thus, the conical envelopes in which the outboard raceways 40 and 42 and the side faces of the rollers 60 lie have their apices at a common point along the axis X, and likewise the conical envelopes in which the inboard raceways 42 and 52 and the side faces of the inboard rollers 62 lie have their apices at another common point along the axis X. The rollers 60 and 62 of the two rows are separated by cages 64 that maintain the proper spacing between the rollers 60 and 62 and further retain them in place around their respective inner raceways 44 and 52 in the absence of the housing 2.

The cone 50 fits over the bearing seat 34 of the spindle 20 with an interference fit and there lies captured between the enlarged region 30 of the spindlθ 20 and the formed end 36 of the spindle 20. Indeed, its back face 56 bears against the inside face 38 of the formed end 36, while the front end of its retaining rib 58 bears against the shoulder 48 at the end of the enlarged region 30 of the spindle 20. The length of the retaining rib 58 determines the setting for the bearing 6, and preferably that is one of light preload. As such, the bearing 6 contains no internal clearances.

The housing 2 contains seals 66 that close the ends of the bearing 6 and prevent contaminants from entering the bearing 6, while retaining a lubricant in the bearing 6. Initially, the hub 4 does not have the formed end 36 at the inboard end of its spindle 2. Instead, it is manufactured with a deformable end that forms an extension of the bearing seat 34. It is deformed outwardly once the inboard cone 50 is fitted over it. U.S. patents 6,443,622 and 6,532,666, which are incorporated herein by reference, disclose procedures for providing the formed end 36.

Should it be necessary to monitor the rotation of the hub 4, such as in connection with the operation of an antilock braking system or a traction control system, the housing 2 may be fitted with a speed sensor 70 and the hub with a target wheel 72. The speed sensor 70 projects through the housing 2 and into the space between the two rows of tapered rollers 60 and 62 where its end is presented toward the cylindrical surface of the enlarged region 30 between the small end of the outboard inner raceway 44 and the shoulder 48. The target wheel 72 fits snugly over that portion of the enlarged region 30 where it is located opposite the inner end of the sensor 70. The target wheel 72 has discontinuities of one type or another, and the sensor 70 detects the passage of them when the hub 4 rotates.

The outboard row of rollers 60 has (Fig. 2) a pitch diameter d_0; whereas the inboard row of rollers 62 has a pitch diameter d,. Each pitch diameter d₀ and d, represents the diameter of the circle described by the centerpoints, both longitudinal and radial, of the rollers 60 and 62 for the row to which it pertains. The pitch diameter d₀ of the outboard row is preferably greater than the pitch diameter d, of the inboard row. If the outboard rollers 60 are the samθ size as the inboard rollers 62, the outboard row can hold more rollers 60 than rollers 62, and this enables the outboard row of rollers 60 to carry a greater load than the inboard row of rollers 62. On the other hand, if the outboard rollers 60 are larger than the inboard rollers 62, although perhaps equal in number, the outboard row will still carry greater loads than the inboard row. However, the bearing 6, housing 2, and hub 4 may be configured so that the pitch circle d, of the inboard row of rollers 62 is greater than the pitch circle d₀ of the outboard row of roller 60, in which event more rollers 62 may be fitted into the inboard row or the rollers 62 or the inboard row may be larger than the rollers 60 of the outboard row. In either case, the inboard row will have a greater capacity for loads than the outboard row. It all depends on where the bearing 6 will see its greatest loading.

The contact angles for the rollers 60 and 62 of the two rows also differ. In this regard, the contact angle Φ_o for the rollers 60 of the outboard row is the included angle between a line perpendicular to the axis X and a line perpendicular to the outboard outer raceway 40. The contact angle Φ, for the rollers 62 of the inboard row is the included angel between a line perpendicular to the axis X and a line perpendicular to the inboard outer raceway 42. Both are acute angles, and typically the outboard contact angle Φ_o exceeds the inboard contact angle Φ,, although the bearing 6 may be configured with the inboard angle Φ, greater than the outboard angle Φ_o . In any event, the angles Φ_o and Φ, are adjusted independently to optimize the performance of the bearing 6 with respect to load capacity, stiffness and torque, among other factors. For example, when the outboard contact angle Φ_o exceeds the inboard contact angle Φ,, the bearing 6 is better equipped to transfer thrust loads that are directed inwardly toward the suspension system component S and such loads are typically encountered by the wheels R on the outside of a turn. Of course, the bearings 6 for the wheels on the inside of a turn will experience thrust loads in the opposite direction, that is directed away from the system component S, but they are normally of a lesser magnitude. Variations are possible. For example, the outer raceways 40 and 42 may reside on separate races, called cups, that fit snugly into the housing 2. Likewise, the outboard inner raceway 44 may be on a separate race, called a cone, that fits snugly over the spindle 20 of the hub 4 as does the cone 50 on which the inboard inner raceway 52 resides. The cone 50 need not be retained by the formed end 36, but instead may be retained by the nut threaded over the end of the spindle 20 or by a snap ring or some other device engaged with the spindle 20 near its end.

Then again the bearing 6 need not be tapered roller bearing at all. Instead, it may take the form of a double row angular contact ball bearing.

The contact angle for either row of balls in such a bearing constitutes the included angel between a line perpendicular to the axis X and a line passing through the center of any ball and the centers of the contacts along which that ball transfers loading to the outer and inner raceways. Moreover, the bearing 6 may have a mixture of rolling elements - tapered rollers in one row and balls in the other.

Also, the housing 2 and suspension system component S may be formed integral.

A modified wheel end with dissimilar contact angles in its two rows of rolling elements may have a fixed spindle and a hub that rotates about that spindle, with the spindle projecting from a suspension system component and the hub attached to a road wheel. In that event, the fixed spindle would constitute an inner member and the rotatable hub an outer member.

Claims

CLAIMS:

1. A wheel end for accommodating the rotation for a road wheel, said wheel end comprising: an outer member; an inner member that projects into the outer member; and a bearing for enabling the one member to rotate relative to the other member about an axis of rotation, the bearing including outboard and inboard outer raceways carried by the outer member and being inclined in opposite directions with respect to the axis; outboard and inboard inner raceways carried by the inner member, the outboard inner raceway being presented toward the outboard outer raceway and being inclined in the same direction as the outboard outer raceway and the inboard inner raceway being presented toward the inboard outer raceway and being inclined in the same direction as the inboard outer raceways; outboard rolling elements arranged in an outboard row between the outboard raceways; inboard rolling elements arranged in an inboard row between the inboard raceway; the contact angle for the outboard row differing from the contact angle for the inboard row.

2. A wheel end according to claim 1 wherein the pitch diameter for the outboard row differs from the pitch diameter for the inboard row.

3. A wheel end according to claim 1 wherein the contact angle for the outer row is greater than the contact angle for the inboard row.

4. A wheel end according to claim 3 wherein the pitch diameter for the outboard row exceeds the pitch diameter for the inboard row.

5. A wheel end according to claim 1 wherein the outer member is a housing configured for attachment to a suspension system component or forming part of a suspension system component, and the inner member is a rotatable hub having a spindle that projects into the housing, the outer raceway being carried by the housing and the inner raceway being carried by the spindle of the hub.

6. A wheel end according to claim 5 wherein the hub also has a flange configured for attachment of a road wheel and the spindle projects from the flange and has an enlarged region where it emerges from the flange, the outboard inner raceway being on the enlarged region.

7. A wheel end according to claim 6 wherein the bearing also includes a cone that fits around the spindle and is initially separate from the spindle, and the inboard inner raceway in on the cone.

8. A wheel end according to claim 7 wherein the spindle has a formed end which projects radially outwardly behind the cone and retains the cone on the spindle.

9. A wheel end according to claim 1 wherein the raceways are tapered and the rolling elements are tapered rollers.

10. A wheel end for coupling a road wheel to a suspension system component of an automotive vehicle, said wheel end comprising: a housing configured for attachment to the suspension system component; a hub having a drive flange located beyond the outboard end of the housing and configured for attachment of the road wheel to it, the hub also having a spindle that projects from the flange into the housing; a bearing located between the housing and the hub to enable the hub to rotate about an axis, the bearing including; outboard and inboard outer raceways carried by the housing and presented inwardly toward the axis, the outboard raceway being inclined downwardly toward each other so that they have their least diameters where they are closest, outboard and inboard inner raceways carried by the hub spindle and being presented outwardly away form the axis, the outboard inner raceway being presented toward the outboard outer raceway and inclined in the same direction as the outboard outer raceway, the inboard inner raceway being presented toward the inboard outer raceway and inclined in the same direction as the inboard outer raceway, outboard rolling elements arranged in an outboard row between the outboard raceways, and inboard rolling elements arranged in an inboard row between the inboard raceways; the contact angle for the outboard row being different from the contact angle of the inboard row.

1 1 . A wheel end according to claim 10 wherein the contact angle for the outboard row is greater than the contact angle for the inboard row.

12. A wheel end according to claim 10 wherein the pitch diameter for the outboard row is greater than the pitch diameter for the inboard row.

13. A wheel end according to claim 10 in combination with a suspension system component to which the housing is attached and a road wheel that is attached to the drive flange of the hub.