Brakes – Vehicle – Hub or disk
Reexamination Certificate
2000-03-01
2001-06-26
Butler, Douglas C. (Department: 3613)
Brakes
Vehicle
Hub or disk
C188S2180XL, C301S006100, C384S512000, C384S571000
Reexamination Certificate
active
06250431
ABSTRACT:
This invention relates to a wheel and bearing assembly whereby a minimum running clearance is retained between brake friction pads and a rotor in a brake system after a vehicle experiences centrifugal forces by utilizing a built-in end clearance in a bearing member.
BACKGROUND OF THE INVENTION
In vehicles it is a usual practice to position a wheel assembly on a bearing member located on an axle. The bearings member is designed to allow the wheel assembly to freely rotate on the axle while at the same time a rotor attached to the wheel assembly is positioned in a radial plane between friction pads of a caliper brake. A bearing member includes a plurality of rollers having a cylindrical shape or a tapered shape as disclosed in U.S. Pat. No. 5,882,123. The plurality of rollers are usually aligned in first and second rows between an outer race and an inner race. The plurality of rollers are positioned and retained in engagement with engagement surfaces on an outer race member and inner cones by trust surfaces. If the engagement with a trust surface creates too large of a retaining force on the rollers, the wheel will not rotate in a smooth manner as binding or drag occurs. Conversely, if a trust surface does not exert a sufficient retaining force on the rollers when a wheel rotates and is subjected to lateral forces it is possible to create a unstable or shimmy motion in a wheel assembly. Thus, it is desirable to position and retain the first and second rows of rollers in a bearing member in a fixed location symmetrical about a reference plane.
The bearings of as described above, which are currently in use for vehicles locate a wheel assembly on an axle and position a rotor with respect to friction pads of a caliper brake. In such vehicles, the rotor and friction pads of a caliper brake have a predetermined running clearance in order to prevent unwanted engagement that could produce additional resistance to rotation of the wheel. Unfortunately, vehicles do not always move in a linear and horizontal direction but are often subjected to centrifugal forces as when turning or negotiating curves. The centrifugal forces can often move a rotor attached to a wheel assembly into engagement with a corresponding friction pad in the caliper to essentially eliminate a running clearance between a friction pad and rotor. On termination of the centrifugal force and a return to linear and horizontal movement, should a vehicle now experience any vibratory force, the rotor and friction pad may momentarily engage each other in a manner whereby over a period of time the surface of the rotor is polished. It is possible for such polishing to distort the surfaces of a rotor to an extent that the coefficient of friction between the friction pads and rotor change and as a result surging may occur during a brake application. It should be noted that the polishing of a rotor as described above is limited to those instances when a vehicle travels for an extended period of time without an operator effecting a brake application as running clearances between the friction pads and rotor are automatically re-set through a brake application.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide a wheel and bearing assembly for a vehicle whereby a minimum running clearance is retained between a rotor secured to a wheel and friction pads carried by a caliper of a brake system after a vehicle encounters centrifugal forces prior to an operator effecting a brake application.
In more particular detail, in the present invention a bearing member is selected from a source which has a first plurality of rollers and a second plurality of rollers retained by first and second cones in a unitary outer race with preset built-in end play. The first and second cones are located on a hub of a wheel assembly with the first cone engaging a first shoulder on the hub. The hub is placed on an axle shaft of the vehicle with the second cone engaging a second shoulder on the axle shaft. The wheel assembly is secured to the axle by fasteners to hold the first and second cone members securely against the first and second shoulders. Thereafter, the unitary outer race of the bearing member is fixed to the vehicle and a rotor, which has a first peripheral face and a second peripheral face, is attached to the wheel assembly. A caliper brake is secured to the vehicle such that first and second friction disc carried by the caliper brake is aligned with the first and second peripheral faces on the rotor. The caliper brake, includes retraction structure such that a predetermined running clearance is set between the rotor and the first and second friction disc after each brake application. When the wheel assembly rotates during linear horizontal movement of the vehicle, the first plurality of rollers engage a first tapered or sloping raceway in the outer race and the second plurality of rollers engage a second tapered or sloping raceway in the outer race symmetrically with respect to a reference point such that the rotor is located in a radial plane with respect to the first and second friction disc with a desired running clearance. When the wheel assembly is subject to centrifugal forces the first and second plurality of rollers shift engagement along the first and second tapered or sloping raceways a distance corresponding to the built-in end play. This axial movement is magnified and as a result the rotor correspondingly moves friction disc to increase the running clearance a distance “y”. When the centrifugal forces terminate, the first and second plurality of rollers return to their symmetrical positions on the tapered or sloping surface on the outer race with continued horizontal linear movement of the vehicle. The first and second friction pads remain stationary and thus the movement created by the engagement with the rotor as a result the end play assures a minimum running clearance “y” is present until a brake application reestablished the desired running clearance “f”.
An advantage of this invention resides in the creation of a minimum running clearance “y” between a rotor and friction pads after a vehicle is subjected to centrifugal forces when a vehicle thereafter moves in a linear direction for an extended period of time prior to an operator instituting a brake application.
A further advantage of the brake system of this invention resides in the setting of a minimum running clearance through the selection of a bearing member having built-in end play.
REFERENCES:
patent: 5842388 (1998-12-01), Visser et al.
patent: 5882123 (1999-03-01), Lee et al.
patent: 5884980 (1999-03-01), Visser et al.
patent: 5937499 (1999-08-01), Austin et al.
Butler Douglas C.
Comstock Warren
McCormick Jr. Leo H.
Robert Bosch Corporation
Rodriguez Pamela J.
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