Laser-based wheel alignment system

• US 5,274,433 A
• Filed: 01/22/1992
• Issued: 12/28/1993
• Est. Priority Date: 07/07/1989
• Status: Expired due to Term

• Current Assignee: Miradco
• Original Assignee: Miradco
• Inventors: Madey, John M. J., Madey, Julius M. J.
• Primary Examiner(s): EVANS, FANNIE L
• Application Number:
  US07/823,632
• Time in Patent Office: 706 Days
• Field of Search: 356/154, 356/155, 33/288
• US Class Current: 356/155
• CPC Class Codes: G01B 11/275 for testing wheel alignment
• CPC Class Codes: G01B 2210/283 Beam projectors and related sensors
• CPC Class Codes: G01B 2210/303 fixed to the ground or to the measuring station
• CPC Class Codes: G01B 2210/306 Mirror, prism or other reflector

Abstract

A device and method to align the wheels of motor vehicles. A beam of collimated light from a low power visible laser is split into two generally parallel beams by a partially transmitting mirror and a series of plane front surface mirrors positioned in front and along side the vehicle being serviced. The two beams are reflected from a set of plane mirrors attached to the rims of the wheels to be aligned. The vertical and horizontal angles of each of the wheel-mounted mirrors are set by calibrated lead-screws to cancel the angular displacement of the wheels expected when the wheels are properly aligned. The reflected beams are imaged through a large aperture beam combiner on a common viewing screen. Correct toe-in and camber settings are indicated when the laser beams reflected from the wheel-mounted mirrors overlap at the center of the viewing screen. The caster settings of the front wheels are measured by observing the angle at which the reflected spots travel across the screen when the steering wheel is turned. The system can be used to align the front wheels only, or alternatively all four wheels simultaneously.

Claims

1. Apparatus for use in setting desired toe-in and camber angles on at least one pair of wheels on a vehicle, comprising:

a plane mirror associated with each wheel;

means for adjustably mounting each mirror to its associated wheel at a selected relative angular orientation that corresponds to the desired toe-in and camber angles for that wheel such that when the wheels are set to the desired toe-in and camber angles, the mirrors are vertical and parallel to each other and face outwardly;

means for generating first and second beams, said beams in the aggregate containing at least two visibly distinct color components;

incident beam transport means for directing said beams toward respective outer surfaces of the wheels to be aligned so as to impinge on said mirrors, said beams being parallel to each other and in a reference plane when they impinge on said mirrors;

reflected beam transport means for directing the beams reflected from said mirrors to a common region, said reflected beam transport means operating such that the reflected beams overlap at the common region when the toe-in and camber angles are correct; and

wavelength selective means for causing at least two reflected beams to have different ones of the visibly distinct color components.

2. The apparatus of claim 1 wherein said first and second beams are associated with opposite sides of the vehicle.

3. The apparatus of claim 1 wherein said means for generating first and second beams comprises:

a laser for generating a single beam; and

a beam splitter disposed in the path of said single beam to provide said first and second beams.

4. The apparatus of claim 1 wherein said incident beam transport means comprises first and second sets of plane deflection mirrors, disposed in the paths of said first and second beams, respectively.

5. The apparatus of claim 4 wherein said reflected beam transport means comprises at least some of the same deflection mirrors as are in said first and second sets of deflection mirrors.

6. The apparatus of claim 1 wherein said means for mounting comprises:

a reference plate;

means for registering said reference plate to the associated wheel in a plane substantially parallel to the plane of the associated wheel;

means for holding said reference plate in said registered position; and

a kinematic mount for mounting the associated mirror to said reference plate while allowing vertical and horizontal angular displacements therebetween.

7. The apparatus of claim 6 wherein said registering means includes at least three pins extending perpendicular to said reference plate.

8. The apparatus of claim 6 wherein said holding means comprises a plurality of permanent magnets mounted to said reference plate at locations commensurate with the wheel'"'"'s studs.

9. The apparatus of claim 1, and further comprising:

a viewing screen located at the common region.

10. The apparatus of claim 1 wherein said first and second beams are associated with opposite sides of the vehicle, the vehicle has a front wheel and a rear wheel on each side, and said incident beam transport means comprises, for each of said first and second beams:

first and second plane deflection mirrors disposed in the path of the associated beam and oriented to direct respective first and second portions of the associated beam toward the front and rear wheels on the associated side for impingement along parallel axes.

11. The apparatus of claim 10 wherein said reflected beam transport means comprises, for each of said first and second beams:

the same first and second deflection mirrors as are in said incident beam transport means; and

a lens, disposed in the path of said second beam portion only, said lens being at a location and having a focal length so as to cause the beams reflected from the front and rear wheels to overlap at the common region, even if the vehicle is skewed relative to the apparatus.

12. Apparatus for use in setting desired toe-in and camber angles on at least one pair of wheels on a vehicle, comprising:

a plane mirror associated with each wheel;

means for adjustably mounting each mirror to its associated wheel at a selected relative angular orientation that corresponds to the desired toe-in and camber angles for that wheel such that when the wheels are set to the desired toe-in and camber angles, the mirrors are vertical and parallel to each other and face outwardly; and

means for generating a set of laser reference beams that impinge on said mirrors, are reflected from said mirrors, and are brought to a common region, said reference beams being parallel to each other and in a reference plane when they impinge on said mirrors such that the reference beams overlap each other at the common region when the toe-in and camber angles of the wheels are correct, at least two of said reference beams being of visibly distinct colors.