| 摘要 |
PROBLEM TO BE SOLVED: To enable an electric motor to generate required torque even if a steering gear ratio is changed, without making a power source voltage circuit portion large in scale. SOLUTION: A microcomputer portion 51 changes the steering gear ratio by controlling rotations of the electric motor 31 through a driving circuit 53. A microcomputer portion 61 assists rotating operation of a steering wheel 11 of a driver by drive-controlling the electric motor 31 through a driving circuit 63. A target voltage computing portion 61e calculates target voltage according to the steering gear ratio calculated by a gear ratio computing portion 51 and the steering speed of the steering wheel 11, and controls power source voltage for the driving circuit 63 by a boosting circuit 62 according to the target voltage. A temperature estimating portion 61g estimates the temperature of electric components structuring the boosting circuit 62, and a gear ratio change instructing portion 61h instructs the change of the steering gear ratios when the estimated temperature becomes high. COPYRIGHT: (C)2006,JPO&NCIPI |
