Patent ID: 7406374

Claim:
A steering ratio control system of a vehicle comprising: a variable steering ratio mechanism that variably adjusts a steering ratio of a steer angle at left and right steered road wheels to a rotation angle of a steering wheel; a braking/driving force control unit that individually controls braking force and/or driving force of the left and right steered road wheels, the braking/driving force control unit comprising a left-and-right braking/driving force difference arithmetic calculation section that calculates a difference in braking force and/or driving force between the left and right steered road wheels; and a steering ratio control unit comprising: (a) a steering ratio decision section that determines a reference steering ratio based on a driving state of the vehicle; (b) a variable steering ratio mechanism driving section that drives the variable steering ratio mechanism depending on the reference steering ratio based on the vehicle's driving state; and (c) a steering-ratio correction value arithmetic-calculation section that calculates a steering-ratio correction value based on the difference calculated by the left-and-right braking/driving force difference arithmetic calculation section, for canceling torque steer resulting from a difference in braking force and/or driving force between the left and right steered road wheels; wherein the variable steering ratio mechanism driving section is adapted to determine a final steering ratio based on both of the reference steering ratio and the steering-ratio correction value to drive the variable steering ratio mechanism responsively to the final steering ratio.