Patent ID: 7882924

Claim:
A motor-driven power steering system, comprising: an input shaft that is connected to a steering handle; an output shaft that is connected to a steering wheel; a torsion bar that couples the input shaft with the output shaft to make a torsional displacement in steering; a switch plate disposed to the input shaft and a resistor plate disposed to the output shaft respectively, to change selectively resistance to and polarity of electricity according the torsional displacement of the torsion bar; an input member that continuously supplies the electricity to the switch plate, the input member coupled to a first stationary member; and an output member that continuously outputs the electricity that has passed through the resistor plate, the output member coupled to a second stationary member; wherein the switch plate, comprises: a circular plate formed with a hole at the center portion thereof through which the torsion bar passes; and insulated switch electrodes radially disposed in the circular plate and exposed to the outside at both upper and lower surfaces of the circular plate; wherein the resistor plate comprises: a circular plate formed with a hole at the center portion thereof through which the torsion bar passes; a pair of first variable resistors and a pair of second variable resistors formed on the same side of the circular plate, which are electrically insulated respectively and have a shape corresponding to trajectories that are constructed when the insulated switch electrodes of the switch plate turn from a neutral position with respect to the torsion bar, the pair of the first variable resistors and the pair of the second variable resistors provided on the side facing the switch plate; and electrical plate patterns that are electrically connected with the pairs of the first variable resistors and the second variable resistors respectively and provided on the opposite side to the pairs of first resistors and second resistors, the electrical plate patterns coaxially disposed and electrically insulated; wherein the outer resistor of the first variable resistors is connected with outer one of the electrical plate patterns and inner resistor of the first variable resistors is connected with inner one of the electrical plate patterns, whereas, outer resistor of the second variable resistors is connected with inner one of the electrical plate patterns and inner resistor of the second variable resistors is connected with outer one of electrical plate patterns.