| 摘要 |
The invention provides an apparatus for controlling a power assist steering system of the type having an electric assist motor connected to a steering member such as a rack and a steering shaft including first and second coaxial shaft sections rotatable with respect to each other and connected by an elastic member. One of the shaft sections is coupled to the hand wheel and the other to the steering member. A cam operated, reversing switch is coupled across the first and second shaft sections. A drive circuit and the electric assist motor are connected to the reversing switch. A control circuit measures the relative rotation between the two shaft sections and controls the drive circuit. Relative rotation of the two steering shaft sections mechanically controls the reversing switch. The electric assist motor is (i) not electrically connected to the drive circuit when the two shaft sections are in a relative null position, (ii) electrically connected to the drive circuit in one direction when the shaft sections are relatively rotated in a first direction a predetermined amount from the null position, and (iii) electrically connected to the drive circuit in the opposite direction when the shaft sections are relatively rotated in a second direction the predetermined amount from the null position. The control circuit insures that the drive circuit outputs no electrical drive signal until the shaft sections are relatively rotated the predetermined amount. The drive potential increases thereafter as the relative rotation between the shaft sections increases above the predetermined amount. |
