Active toe adjustment apparatus

• US 5,143,400 A
• Filed: 07/05/1991
• Issued: 09/01/1992
• Est. Priority Date: 08/10/1989
• Status: Expired due to Term

• Current Assignee: Michelin Recherche et Technique SA (Compagnie Generale DES Etablissements Michelin SCA)
• Original Assignee: Michelin Recherche et Technique SA (Compagnie Generale DES Etablissements Michelin SCA)
• Inventors: Miller, Gerald R., Couratier, Jean P.
• Primary Examiner(s): Marmor, Charles A.
• Assistant Examiner(s): FERRITER, KARIN L
• Application Number:
  US07/727,400
• Time in Patent Office: 424 Days
• Field of Search: 280/661, 280/91, 180/140, 180/142, 180/79.1
• US Class Current: 280/5.522
• CPC Class Codes: B62D 17/00 Means on vehicles for adjusting camber, castor, or toe-in

Abstract

The advantage of the theoretically correct Ackerman steering of land vehicles is well documented in the literature. Steering forces, vehicle handling, and tire wear are greatly improved by having correct toe angles of all steerable wheels. Adjustements in the suspension system and steering apparatus at the factory only provide first-order corrections to toe angles. A process for actively adjusting toe angles during operation of the vehicle is disclosed in this invention. Vehicle dynamics measuring devices to sense vehicle motion or position steering devices to measure toe angles are used in this process. Secondary toe angle corrections can be actively provided to account for inherent toe angle changes during maneuvers of the vehicle. An aftermarket apparatus for actively adjusting the toe angle is an embodiment of this invention. One such device includes a mechanical screw actuator apparatus, a microstepping motor with optical encoder, computer with control strategy chip and a toe angle sensing device or an onboard dynamics computer. This apparatus can be used on all land vehicles and is especially useful for modifying existing truck and bus steering systems.

Claims

1. An apparatus for use on a land vehicle having at least a pair of steerable wheels, including a slave wheel and a control wheel, with their steer angles controlled by standard steering linkages and in which each vehicle wheel rotates about an axis, said apparatus comprising:

means for sensing the steer angle of a slave steerable wheel during turning maneuvers of said vehicle;

means for calculating a turn axis of intersection between a vertical plane containing the axis of rotation of a front slave steerable wheel and a vertical plane containing the axis of rotation of a rear slave steerable or fixed wheel using the steer angles sensed by said sensing means and producing toe adjustment angle signals;

means for computing a strategy to provide electrical strategy signals as a function of said vehicle turning maneuvers and said turn axis location;

means for calculating toe adjustment angles for the steer angle of a control steerable wheel using the geometry of said standard steering wheel using the geometry of said standard steering linkages and said strategy signals such that all the axis of rotation of all steerable wheels substantially intersect said turn axis and producing toe adjustment angle signals;

means for outputting electrical control signals as a function of said toe adjustment angle signals; and

a toe adjustment apparatus attached to a standard steering linkage to effect toe adjustment angle change, said toe adjustment apparatus having an electrical motor with a power supply controlled by said electrical control signal output means, a gear box connected to said electrical motor and a mechanical actuator apparatus attached to a standard steering linkage, which has been modified to allow said attachment, and to the gear box, said mechanical actuator apparatus comprising;

a) a slidably mounted tie rod sleeve and a fixed tie rod sleeve both suitably attached to said standard steering linkage being a modified tie rod of said vehicle, said tie rod being bisected and a section removed to accommodate said two sleeves;

b) an actuator device with a screw shaft slidably mounted therein and attached at one end to said slidably mounted tie rod sleeve;

c) an actuator housing which contains said actuator device suitable attached to said fixed tie rod sleeve at one end and having an aperture in the other end to permit the slidably mounted tie rod sleeve to move in or out of said aperture as said actuator device moves said screw shaft;

d) means for rotating a gear shaft, using said electrical motor, a predetermined pusher of turns to advance said screw shaft and thereby changing the length of said tie rod, thereby adjusting the toe angle of at least one steerable wheel of said vehicle; and

e) means for detecting the actual number of turns of said screw shaft and providing feedback signals for proper control of the length of said tie rod.

2. The apparatus for use on a land vehicle as recited in claim 1, wherein the travel of said slidably mounted tie rod sleeve in said actuator housing results in the length of said tie rod for a large truck to vary by approximately 2 inches.

3. An apparatus for use on a land vehicle as recited in claim 1 wherein the sensing means further comprises:

a) means for detecting the motion of said vehicle using a vehicle dynamics device; and

b) means of outputting electrical dynamics signals from said detecting means for providing input for computing said electrical strategy signals using a computer having a geometry module and containing a strategy ship and a smart controller.