Patent ID: 8584790

Claim:
A power steering apparatus comprising: a steering shaft including an input shaft to which a rotational force is to be transmitted from a steering wheel, and an output shaft which is connected to the input shaft through a torsion bar and adapted to transmit the rotational force to steerable road wheels; a sensor coil which is disposed on an outer circumferential side of the steering shaft and detects a change in impedance value to determine an amount of relative rotation of the input shaft and the output shaft; a steering housing including a first housing surrounding the sensor coil and a second housing connected with the first housing, the first housing and the second housing being connected with each other in such a state that a first opening formed in the first housing and a second opening formed in the second housing are opposed to each other, the steering housing accommodating the steering shaft so as to extend through the first opening and the second opening, a sensor substrate which is disposed on the first housing and arranged closer to the first opening than the sensor coil so as to be exposed to the first opening; a neutral point regulating circuit which is disposed on the sensor substrate and includes a resistor connected to the sensor coil, the neutral point regulating circuit being capable of variably regulating a resistance value of the resistor so as to regulate the impedance value at a neutral point at which the amount of relative rotation of the input shaft and the output shaft is zero, and an electric motor which is driven and controlled to provide the steerable road wheels with a steering assist force in accordance with an output signal of the sensor coil which is regulated by the neutral point regulating circuit.