Rolling run-out measurement apparatus and method

Details Rolling run-out measurement apparatus and method Rolling run-out measurement apparatus and method

1997-06-26

2001-04-03

Hirshfeld, Andrew H. (Department: 2859)

Geometrical instruments

Gauge

Wheel

C033S203000, C033S288000

Reexamination Certificate

active

06209209

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATIONS
Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
REFERENCE TO MICROFICHE APPENDIX
Not Applicable.
BACKGROUND OF THE INVENTION
This invention relates to the vehicle alignment equipment, and more particularly with the procedures for measuring the run-out in the wheels, and/or wheel adapters, sensors, or targets in the case of a vision alignment system.
It is well known in the art of wheel alignment that it is necessary that the suspension be in a relaxed state when measuring or adjusting the alignment of a vehicle. Anti friction turnplates and anti friction skid plates (slip plates) are typically used under the front and rear axles of the vehicle respectively to achieve a relaxed condition. These devices (turnplates and skid plates) allow the vehicle wheels to move both longitudinally and laterally to relax all forces on the wheels. Such devices perform their function well, but they could be improved for certain applications.
For example, in wheel alignment it is important to measure the run-out of a wheel and/or wheel adapter, or sensor, (or a target in the case of a vision alignment system such as that shown in U.S. Pat. No. 5,535,522 to Jackson). This run-out measurement is then used when calculating the alignment angles of a wheel. Various run-out measurement schemes and devices are known. See, for example, U.S. Pat. No. 5,029,395 to Brauer et al. and the patents cited therein.
For the sake of speed it is desirable to perform this run-out measurement while rolling the vehicle, thereby eliminating the need to jack up a vehicle. When doing so, however, there are factors which can influence the run-out measurement and thereby cause errors.
As a vehicle is rolling, there may be lateral forces acting on the tires of the vehicle due to toe, camber, and/or caster. In certain cases these forces can cause errors in run-out calculations much larger than the tolerance of the required adjustment. For example, if a vehicle has an excessive amount of positive front total toe, when rolling the vehicle forward the front tires try to converge, causing the tires to scrub across the surface on which the vehicle is being rolled. This scrubbing creates lateral forces on the tires. These lateral forces can be great enough to distort suspension bushings and components which in turn change the alignment angles of each wheel. Prior art alignment machines are unable to separate the changes due to run-out from those changes due to the lateral forces on the tires. It has therefore been discovered to be necessary to eliminate these forces when conducting a run-out measurement while rolling a vehicle.
Another source of error when rolling a vehicle on a solid surface is when the rolling direction of the vehicle is reversed. When the vehicle is rolled forward (or backward) the lateral forces on the tires created by the tires scrubbing increase the forces on the suspension components causing distortion. When the direction of the vehicle is reversed these forces are relieved, changing the alignment of the wheels. For example, one prior art system involves moving the vehicle forwardly to a first position at which a first run-out measurement is taken, reversing the vehicle to move it to a second position where a second run-out measurement is taken, and then moving the vehicle forwardly back to the original position where a third run-out measurement is taken. It has been discovered that the second measurement taken with such systems is significantly in error, and that the third measurement also exhibits significant hysteresis for the reasons set forth above.
Prior art alignment equipment is not believed to be capable of either detecting these errors or compensating for them.
BRIEF SUMMARY OF THE INVENTION
Among the various objects and features of the present invention may be noted the provision of an apparatus which eliminates lateral forces on the wheels of a vehicle when measuring run-out (whether of a wheel and/or wheel adapter, sensor, or a target in the case of a vision alignment system).
Another object is the provision of such apparatus which may be used either in conjunction with or separate from a traditional turnplate for the front axle.
A third object is the provision of such apparatus which may be incorporated into new and existing lift racks or disposed in or upon the shop floor.
A fourth object is the provision of such an apparatus which includes slip plates which are restricted to lateral movement when conducting the run-out measurement.
A fifth object is the provision of a procedure for rolling run-out measurement which eliminates any effects on the vehicle alignment angles due to forces acting on the suspension and hysteresis in the suspension.
Other objects and features will be in part apparent and in part pointed out hereinafter.
Briefly, apparatus of the present invention eliminates various errors often encountered in the determination of vehicle alignment. The apparatus includes a first station at which alignment measurements for wheels of a first axle of a vehicle are made and a second station, disposed longitudinally of the first station, at which measurements for wheels of a second axle of the vehicle are made. Structure is provided for substantially eliminating lateral forces acting on the wheels at at least one of the first and second stations during measurement, that structure being fixed against longitudinal movement so as to allow the wheels of the vehicle to roll with respect to the structure.
A method of the present invention involves eliminating errors in wheel alignment measurements. It includes the steps of making a first set of wheel alignment measurements while a vehicle is disposed at a first position with substantially all lateral forces applied thereto being relieved, and making a second set of wheel alignment measurements while the vehicle is disposed at a second position with substantially all lateral forces applied thereto being relieved.


REFERENCES:
patent: 1487759 (1924-03-01), Skinner
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patent: 1927488 (1933-09-01), Christensen et al.
patent: 1950994 (1934-03-01), Musselman
patent: 3231983 (1966-02-01), Bender
patent: 3303511 (1967-02-01), Bjorn
patent: 4445278 (1984-05-01), Staudinger
patent: 5029395 (1991-07-01), Brauer et al.
patent: 5313710 (1994-05-01), Wakamori et al.
patent: 5386639 (1995-02-01), Colarelli
patent: 5535522 (1996-07-01), Jackson

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