WHEEL END

CROSS REFERENCED TO RELATED APPLICATION

This application derives and claims priority from U.S. provisional application Serial No. 60/762,307, filed 26 January 2006, and from U.S. provisional application 60/841 ,762, filed 1 September 2006, both of which are incorporated herein by reference. TECHNICAL FIELD

This invention relates in general to wheel ends for automotive vehicles.

BACKGROUND 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.

The typical wheel end has a housing that is bolted against a steering knuckle or other suspension upright, a hub provided with a flange to which a 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 housing for the typical wheel end itself has a flange that bears against the suspension system component to which it is secured at three or four locations, normally with machine bolts that pass through the suspension component and thread into the flange. These bolts secure the entire wheel end to its suspension system component. In order to accommodate the bolts, the flange occupies space that might otherwise be utilized for some other component at the wheel end, such

as a brake assembly. In other words, the flange enlarges the entire wheel end.

Moreover, the forces exerted on any wheel of an automotive vehicle, particularly on the front wheels, if known can be employed to enhance safety. Electrical signals representing wheel forces can provide electronic braking and powertrain controls with information about vehicle loading and road conditions, enabling those controls to conform the operation of the vehicle to best accommodate the forces.

Also, it is often difficult for a driver to detect reduced level of friction of the vehicles tires on a roadway surface caused by ice formation or hydroplaning until loss of control occurs. Early warning of such dangerous conditions would enhance safety. DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a wheel end constructed in accordance with and embodying the present invention;

FIG. 2 is a transverse sectional view of the wheel end taken along 2-2 of Fig. 1;

FIG. 3 is a longitudinal half-cross sectional view of an alternative wheel end having the capacity to provide signals that reflect moments, forces and driving conditions;

FIG. 4 is a perspective view of a pair of mounting studs sectioned midlength;

FIG. 5 is a transverse sectional view of another alternative wheel end; FIG. 6 is a top view of the alternative wheel end of Fig. 5;

FIG. 7 is a one-half sectional view taken along line 7-7 of Fig. 5;

FIG. 8 is a sectional view of an overload ear and stud taken along line 8-8 of Fig. 5;

FIG. 9 is a perspective view of one of the mounting studs for the wheel end of Fig. 5; and

FIG. 10 is a fragmentary perspective view of the mounting studs for the wheel end of Fig. 5.

DESCRIPTION OF BEST MODE FOR CARRYING OUT INVENTION

Referring to the drawings, a wheel end A (Figs. 1 & 2), 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 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.

The housing 2, which is a fixed member, includes a generally cylindrical body 10, which is tubular, and two lugs or ears 12 that project radially from the body 10 generally midway between the ends of the body 10 and 180° apart. The ears 12 are preferably oriented vertically. The inboard segment of the body 10 is received in the suspension system component S such that the two ears 12 come against the component S, to which they secured with cap screws 14 that pass through the component S and thread into bores 16 in the ears 12. Thus, the wheel end A is attached to the suspension system component S at the ears 12 of its housing 2.

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

- A -

The spindle 20 merges with the flange 22 at an enlarged region

30 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. 1) 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. Apart from the two outer raceways 40 and 52, 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 in 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 end of the raceway 44, the bearing 6 has a shoulder 48 that faces away from the flange 22 and toward the inside face 38 of the formed end 36.

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 a raceway 52 that is presented outwardly toward the inboard outer raceway 42 on the housing 2 and tapers in the same direction, downwardly toward the middle of the housing 2. 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 and an integral extension 60 that leads toward the shoulder 48 on the enlarged region 30.

Completing the bearing 6 are rolling elements in the form of tapered rollers 62 organized in two rows, one located between and contacting the outboard raceways 40 and 44 and the other located between and contacting the inboard raceways 42 and 52. The rollers 62 of each row are on apex. Thus, the conical envelopes in which the outboard raceways 42 and 46 and outboard rollers 62 lie have their apices at a common point along the axis, and likewise the conical envelopes in which the inboard raceways 42 and 50 and the inboard rollers 62 lie have their apices at another common point along the axis X. The rollers 62 of each row are separated by a cage 64 that maintains the proper spacing between the rollers 62 and further retains 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 spindle 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 extension 60 bears against the shoulder 48 at the end of the enlarged region 30 of the spindle 20. The length of the cone extension 60 determines the setting for the bearing 6, and that is one of light preload. Thus, the bearing 6 contains no internal clearances.

The housing 2 at its ends contains seals 68 which 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.

Owing to the presence of only two lugs or ears 12 for securing the wheel end A to the suspension system component S ₁ more space exists around the housing 2 for appliances that typically accompany wheel ends, such as a brake assembly that operates against the brake disk 28 and a speed sensor.

A slight modification provides a wheel end B that produces electrical signals that reflect forces and moments exerted on the wheel end B, which in turn reflect driving conditions, and conditions where the wheel R contacts a road surface (Figs. 3 & 4). The modification involves shifting the two ears 12 axially on the cylindrical body 10 toward the outboard end of the body 10 and coupling the ears 12 to the suspension system component S through mounting studs 70. To this end, the ears 12 are provided with bores 72, while the suspension system component S has aligned bores 74, each to receive an end of one of the studs 70. Moreover, the cylindrical body 10 of the housing 2 fits into the suspension system component S somewhat loosely, that is to say, a clearance exists between the body 10 and the component S.

Each mounting stud 70 includes a shank 76 that lies between an outboard shoulder 78 and an inboard shoulder 80 and for the most part is reduced in cross section between the shoulders 78 and 80. In addition, each has an outboard cylindrical end 82 that projects beyond the outboard shoulder 78 and an inboard cylindrical end 84 that projects beyond the inboard shoulder 80. The outboard end 82 is shorter than the ears 12 are thick, and it is provided it with a threaded bore 86. The inboard end 88 is shorter than the suspension system component S is thick at the bore 74 in it, and it contains another threaded bore 88.

The outboard end 82 of the stud 70 fits into the bore 72 in one of the ears 12 of the housing 2 with an interference fit and is secured firmly in that bore 72, with the outboard shoulder 78 firmly abutting the ear 12, by a cap screw 90 that threads into the threaded bore 86 of the end 82 and bears against the opposite face of the ear 12. The inboard end 84 fits into the aligned bore 74 in the suspension system component S with

and interference fit and with the inboard shoulder 80 firmly against the component S. It is secured with another cap screw 92 that threads into the bore 88 and bears against the opposite face of the component S.

Thus, the studs 70 provide firm connections between the housing 2 and the suspension system component S, with that much of the vehicle weight carried by the suspension system component S being transferred to the wheel end B through the studs 70 of the wheel end B. Horizontally directed forces, both lateral along the axis Y of the studs 70 and longitudinal parallel to the longitudinal axes of the vehicle, transfer between the suspension system component S and the wheel R through the studs 70 as well — and the studs 70 in their shanks 76 flex in response to those forces. Thus, the studs 70 should be formed from a metal that is highly fatigue resistance, chrome-vanadium alloy steel being one such metal. The shank 76 of each stud 70 may be rectangular in cross section, with two of its faces being oriented horizontally and the other two being oriented vertically. To each of these faces is attached a strain sensor 94 that is oriented to sense the magnitude of strains in the direction of the axis Y of the stud 70, which axis lies parallel to the axis X of the bearing 6. The sensors 94 have wires 96 extending from them and along with the shank 76 are encapsulated in an overmold 96 formed from a polymer.

In the operation of the modified wheel end B ₁ the sensors 94 detect moments about a horizontal axis H (Fig. 4) that extends longitudinally of the vehicle and about a vertical axis V. And moments do exist because the horizontal offset between the region where the wheel R contacts the road surface and the attachment of the wheel end B to the suspension system component S. The two studs 70 account for some of that offset and will flex when subjected to moments. In this regard, a vertical load exerted downwardly on the wheel R through the wheel end B will create moments within the shanks 76. The upper sensor 94 in the shank 76 of each stud 70 will detect an contraction,

whereas the lower sensor 94 will detect a extension, each with respect to the condition that existed before the imposition of the vertical load, provided the sensors 94 are properly located with a slight offset from the axis H to account for a double bending tendency of the shanks 76 with the polarity of the moments changing on each side of the axis H. A longitudinally directed load, such as from drive traction, either braking or an acceleration delivered through the wheel R, will create a moment about the vertical axis V. During braking the forward sensor 94 will detect an extension, while the rear sensor 94 will detect a contraction. Lateral forces, such as those encountered in negotiating a turn, create extensions and contractions in the shanks 76 of the studs 70. Thus, as to the two studs 70 for the wheel end A on the outside of a turn upper stud 70 will experience an extension while the lower stud 70 will experience a contraction, this owing to the moment created by the offset of the axis X from the region where the wheel R contacts the road surface. The studs 70 for the wheel end B at the inside of the turn will experience the opposite. The sensors 94 on the shanks 76 of the studs 70 for those two wheel ends B will detect the contractions and extensions. The left and right front wheels R of a vehicle do not revolve about parallel axes X. On the contrary, the axes X are misaligned slightly to create so-called "toe". This misalignment produces inwardly directed lateral forces on the wheels R, and the sensors 94 on the studs 70 for the wheel ends B detect these forces. A loss of the inwardly directed forces will most often represent a loss of friction where the front wheels R contact pavement, and that diminished friction may be the result of ice or hydroplaning.

The strain sensors 94 are connected to amplifiers that are sensitive to both the differential mode signal between opposing strain sensors 94 and therefore bending strain, and the common mode signal that indicates axial strain. The electronics may occupy the overmolds 98 around the studs 78, with the wires 96 providing connection to the

vehicle control system. After assembly of the wheel end B to the suspension system component S the wheel end B is loaded to simulate combinations of vertical, longitudinal, and lateral wheel loads to calibrate the system response. The characteristic system response is modeled during development of the application and a set of parameters/coefficients are selected to best describe the sensor response. The actual values of these coefficients for the specific part are written to a programmable memory in the stud overmold 98 which are read by the system to allow the control system to interpret the sensor response and determine the loads. The response calibration is a combination of both a primary response, explained previously, and unintended response. An example of this would be response to vertical load. The primary response is bending along the horizontal axis H, but some response would also be observed along the vertical axis V. The vertical axis V response is the unintended response.

The shank of each stud 70 may be circular or some other cross- sectional configuration with the sensors mounted on the top, bottom and sides of the shank.

Another alternative wheel end C (Figs. 5 - 10) isolates braking forces, other than the inertial forces experienced where the road wheel R contacts the road surface, and thereby provides a truer representation of conditions at the road surface when brakes are applied. The wheel end C includes a housing 102 that differs from the housing 2 of the wheel end A in several respects, but even so includes a hub 4 and bearing 6 that are essentially the same as their counterparts on the wheel end B. The bearing 6 defines the axis X of rotation for the wheel end C.

The housing 102 includes (Figs. 5 - 7) a generally cylindrical body 104 having two mounting ears 106 that project away from the body at 180° with respect to the axis X. The ears 106 are oriented vertically and are offset axially toward the outboard end of the body 104. Each contains an axially directed bore 108. The housing 102 also has brake

mountiπg formations in the form of lugs 110 that project laterally from one side of the body 104 and are configured to support a brake caliper assembly, the pads of which lie along the brake disk 28 and clamp down on the disk 28 when the assembly is actuated. Finally, the housing 102 has a pair of overload ears 112 that project laterally from it between the mounting ears 106, and these are offset at 90° with respect to the mounting ears 106. Each overload ear 112 has (Fig. 8) a bore 114 that opens out of its inboard face and a counterbore 116 that opens out of its outboard face, there being an abutment shoulder 118 between the two. The housing 102 attaches to the suspension system component

S through two mounting studs 120 that extend between the bores 108 in the mounting ears 106 and the bores 74 in the component S. Each stud 120 lies along a stud axis Y and includes (Figs. 7 & 9) a shank 122 that flares outwardly at its ends into an outboard shoulder 124 and an inboard shoulder 126. Each also includes a cylindrical segment 128 that projects from the outboard shoulder 124 and another cylindrical segment 130 that projects from the inboard shoulder 126. The segments 128 and 130 are centered with respect to their respective shoulders 124 and 126 and with respect to the shank 122 as well. Finally, each stud 120 has threaded ends 132 that project axially from the cylindrical segments 128 and 130, but are slightly smaller in diameter.

The outboard cylindrical segments 128 for the two studs 12 fit into the bores 108 in the mounting ears 106 with interference fits, and when so fitted the outboard shoulders 124 abut the back faces of the ears 106, while the threaded ends 132 or the cylindrical segments 128 project beyond the front faces of the ears 106. Those ends 132 have nuts 134 threaded over them and against the ears 106 to attach the stud 120 firmly to the housing 102. The inboard cylindrical segments 130 fit into the bores 74 in the suspension system component S with interferences fits and with the inboard shoulders 126 abutting the suspension system component S. The threaded ends 132 that project from the segments 130 project out of the component S, and there more nuts 134 are

threaded over them, thus securing the studs 120 firmly to the suspension system component S. The cylindrical segments 128 and 130 have keys 136 that fit into keyways in the bores 108 and 74 of the mounting ears 106 and suspension system component S to properly orient the studs 120 and to keep them from turning.

The shank 122 of each stud 120 has (Figs. 9 & 10) concave surfaces 138 that are presented upwardly and downwardly. At their centers, the studs 120 are much wider then they are thick, that is to say, their dimensions parallel to the horizontal axis H of the vehicle are greater than their dimensions along the vertical axis V. To the concave surfaces 138 are applied strain sensors 140 which are oriented to sense strains that are parallel to the axes Y of the studs 120 and likewise parallel to the axis X of the bearing 6.

The overload ears 112 in their bores 114 and centerbores 116 receive (Fig. 8) overload studs 150, each having a positioning shoulder 152 and a threaded end 154 that threads into the suspension system component S, with the shoulder 152 against the component S. Thus, the position shoulder 152 fixes the axial position of the stud 150. Each stud 150 passes through the bore 114 of its overload ear 112 with a radial gap or clearance. Each stud 150 also has an abutment shoulder 156 that is presented toward the abutment shoulder 118 in the overload ear 112 through which the stud 150 extends, yet is spaced a slight distance from the shoulder 118, so that a gap or clearance exists between the two shoulders 118 and 156. On each side of its abutment shoulder 156, the stud 150 carries an O-ring 158, and the O-rings 158 wipe the surfaces of the bore 114 and counterbore 116. A corrosion preventative composition fills the annular space between the two O-rings 158.

The axial centerlines V of the two mounting studs 120 lie in a plane, vertical or near vertical, that passes through the center of the tire patch, which is where the road wheel R contacts the road surface, and also through the axis X of rotation for the bearing 6. The shanks 122 of

the studs 120 possess their thinnest cross section midway between their shoulders 124 and 126, and here the cross section is substantially longer in the horizontal direction of the axis H than in the vertical direction of the axis V. The suspension system component S lies inboard of the midportions of the stud shanks 122, whereas the center of the tire patch, where the wheel contacts the road surface, lies outboard. Thus, that much of the weight of the vehicle that is transferred through suspension system components S imparts moments to the two studs the 120, as do traction forces, such as acceleration delivered through the road wheel R and braking exerted through friction applied to the brake disk 28. Insofar as braking is concerned, the moments reflect true deceleration, because the brake assembly is mounted on the housing 102 and is isolated from the suspension system component S. The stud shanks 122 also transfer lateral forces. The moments and forces cause the stud shanks 122 to flex, and that flexure is detected by the strain sensors 140. To best monitor the moments and forces, each mounting stud 120 on each of the concave surfaces 138 of its shank 122 has four strain sensors 140 — two outboard of the midportion of the shank 122 and two inboard of the midportion. Moreover, two lie on one side of the axial centerline Y for the shank 122 and two lie on the other side of the axial centerline Y. The arrangement is such that two of the sensors 140 are directly across the thickness of the shank 122 (e.g., at locations m and n); two more are diagonally located on the same concave surface 138 (e.g., at locations n and p); and two more are located at the same positions on the shanks 122 of the two studs 120 (e.g., at locations m and p).

The strain sensors 140 have contact pads of a flexible circuit soldered to them. The flexible circuit contains bridge completion resistors, an analog-to-digital converter, power management circuitry and communication circuitry. The stud shanks 122 along with the sensors 140 on them and the contact pads and flexible circuit are

encapsulated in a protective molding that provides strain relief for a cable through which signals flow for further processing.

The overload studs 150 restrict the flexure of the mounting studs 120 to prevent the mounting studs 120 in their shanks 122 from undergoing excessive stresses beyond the yield strength of the metal from which the studs 120 are formed. For example, should the road wheel R strike a curb, the housing 102 of the wheel end B will only deflect far enough to bring the abutment shoulders 118 and 156 or one of the overload ears 112 and its overload stud 150 together, thus retarding further deflection. Likewise, small clearance between the overload studs 150 and the surfaces of the bores 114 in the overload ears 112 prevent the housing 102 from displacing upwardly or downwardly or forwardly and rearwardly on the suspension system component S, notwithstanding the capacity of the mounting studs 120 to flex.

To reduce the number of strain sensors 140 and thereby simplify the circuitry and electronic component for monitoring them, the sensors 140 may be reduced to four in number, all installed on one face of the shank 122 for only one of the two mounting studs 120, preferably the bottom stud 120. This arrangement provides good sensitively to all three forces acting on the road wheel R, although not as precise as four sensors mounted on each of the concave surfaces 138 of both mounting studs 120. The greatest compromise resides in greater sensitivity to offset drift in the sensors 140, inasmuch as the offset, such as that caused by temperature variations, is not cancelled by another sensor. But the offset drift is not overly important in fleeting dynamic events.

In another alternative embodiment the wheel R is attached to a hub that provides the outer race or member. The inner race is located around a spindle that emerges from two ears 12 that are attached to the suspension system component S through two studs 70 or 120, thus providing an inner member.

The bearing 6 need not be a double row tapered roller bearing, but may be another other antifriction bearing having inclined raceways for transferring both radial and axial loads, such as angular contact ball bearings and spherical roller bearings. The outboard inner raceway 44 may be on a separate cone somewhat similar to the cone 50.