Patent ID: 6381527
Filing Date: 2002-04-30
Classification: B62D

Abstract:
A controller unit for a rear-wheel steering apparatus, said rear-wheel steering apparatus comprising: a motor; a rotational-force transmitting member rotatable in accordance with rotation of said motor; a pair of sliding members movable from respective central neutral positions, away from each other, to respective outward positions corresponding to a designated steering angle of rear wheels and movable from the outward positions, toward each other, back to the neutral positions; a threaded engagement section having oppositely-threaded portions and operatively connecting between said rotational-force transmitting member and said sliding members through threaded engagement in such a manner that said sliding members are caused to move away from or toward each other in response to rotation of said rotational-force transmitting member by said motor; a clutch mechanism for operatively connecting either one of said sliding members with a steering rod provided between the rear wheels; and a first stopper for defining the neutral positions of said sliding members and limiting respective inward movement of said sliding members, wherein with the one of said sliding members operatively connected with the steering rod via said clutch mechanism, the rear wheels are turned by a designated steering angle by moving said sliding members outwardly away from each other through rotation of said motor in a first direction and are returned to a straight-ahead position by moving said sliding members inwardly toward each other through rotation of said motor in a second direction reverse to said first direction,said controller unit comprising: a target-steering-angle setting section for setting a target steering angle of the rear wheels; an actual-steering-angle measurement section for measuring an actual steering angle of the rear wheels; a steering-angle adjustment section for, on the basis of the target steering angle set by said target-steering-angle setting section and the actual steering angle measured by said steering-angle adjustment section, generating a motor drive signal to control the rotation of said motor in such a manner that a difference between said target steering angle and said actual steering angle becomes zero, said steering-angle adjustment section supplying the motor drive signal to said motor so that, through the rotation of said motor based on the motor drive signal, said sliding members are moved to the outward positions when the rear wheels are to be turned by the designated steering angle or said sliding members are returned to the neutral positions when the rear wheels are to be turned back to the straight-ahead position; and a motor-deceleration-amount calculation section for, on condition that said motor is in a predetermined driving state, being activated to calculate an actual rotating speed of said motor on the basis of the actual steering angle of the rear wheels and comparing the calculated actual rotating speed of said motor and a prestored reference rotation speed, said motor-deceleration-amount calculation section calculating a motor-rotation deceleration amount when the calculated actual rotating speed is higher than the reference rotation speed, wherein said steering-angle adjustment section includes a subtracter for subtracting the motor-rotation deceleration amount from the motor drive signal.