Patent ID: 7726439
Filing Date: 2010-06-01
Classification: B62D

Abstract:
1. An apparatus for steering a vehicle comprising: a hand steering device which a driver of the vehicle manipulates for steering road wheels; a road wheel steering device which actuates the road wheels and including a rack and pinion mechanism for transmitting steering force to the road wheels; a steering motor, which is attached to the road wheel steering device, for producing an assist force for the road wheels; a connection device for selectively disconnecting the hand steering device and the road wheel steering device during a normal steering mode and connecting the hand steering device and the road wheel steering device during a failure steering mode; and a controller which is configured to control the road wheel steering device during the normal steering mode such that a ratio of a displacement made by the hand steering device to a displacement generated by the road wheel steering device increases as a speed of the vehicle becomes greater while the vehicle is traveling in a predetermined range of speed, wherein the rack and pinion mechanism has a gear ratio which varies according to an angular position of the hand steering device; and wherein a gear ratio of the rack and pinion mechanism is configured to progressively increase with increasing rack stroke in a predetermined range of rack strokes such that a characteristic curve representing the relationship between steering angle ratio and vehicle speed for a vehicle operating in the normal steering mode has a shape which approaches, but is different from that of, a characteristic curve representing the relationship between steering angle ratio and vehicle speed for a vehicle operating in the failure steering mode during at least part of said predetermined range of speed.