Apparatus for determining steering positions of the front wheels of a

Abstract

An electro-optical apparatus for determining, during caster angle measurement procedures, when the front wheels of a vehicle have been turned into a first desired steering position oriented in one rotative direction from a 'straight-ahead' position and have thereafter been turned to a second desired steering position oriented in the opposite rotative direction from the 'straight-ahead' position. A multiple light beam projector and a photosensitive detector are mounted to a front wheel of the vehicle for rotation therewith, and a reflector is mounted to the rear wheel of the vehicle which is on the same side of the vehicle as the projector and detector. The projector rearwardly projects three directional beam patterns with each pattern consisting of sequentially emitted discrete beams which are projected at unique angles with respect to the plane of the front wheel. One beam pattern lies in a plane generally parallel to that of the front wheel, and the other two beam patterns are equiangularly displaced to each side of the plane of said one beam pattern, such equiangular displacements being equal to the preselected turn angles for making the caster angle measurements. The reflector is oriented parallel to the rear axle of the vehicle to direct a projected beam pattern so as to intersect the detector when the beam pattern is generally parallel to the plane of the rear wheel. The beam patterns generally provide toe angle information for the front wheel, and circuitry is provided for processing the output signals of the photosensitive detector when receiving said one beam pattern to indicate, by means of a particular output signal condition, the desired 'straight-ahead' position for the front wheel. By repeating said output signal condition when the front wheel is turned to expose the other beam patterns to the detector, the exact preselected turn angles are readily obtained.