Motor-driven type power assisted steering control apparatus

Claim 1

A motor-driven power assisted steering control apparatus including a steering torque sensing means (1) for detecting a steering torque, a motor (14) connected to a steering shaft via a clutch to exert an auxiliary steering force on the steering shaft, a control means for controlling said motor in correspondence to an output from said steering torque sensing means, said apparatus being characterized by: a torque neutral point detecting means (23) for detecting a neutral point of steering torque, means (11) for sensing a current flowing in said motor, a first level detecting means (27) for detecting when said motor current exceeds a first level, and a second level detecting means (29) for detecting when said motor current exceeds a second level which is greater than the first level, means (32, 30, 21) responsive to the torque neutral point detecting means and the first level detecting means for reducing a current flowing in said clutch when the motor current exceeds the first level and the steering torque value is at other than the neutral point, and means (28, 24, 25, 26) responsive to the torque neutral point detecting means and the second level detecting means for interrupting the current flowing in said clutch and said motor when the motor current exceeds the second level and the steering torque value is at other than the neutral point.