Patent ID: 8579071

Claim:
A power steering system comprising: a housing having: a first housing section which is formed by resin material and has a coil housing portion thereinside and an opening portion at an axial direction side thereof; and a second housing section which is combined with the first housing section and which closes the opening portion of the first housing section; a steering shaft having: an input shaft to which a turning force from a steering wheel is transmitted; and an output shaft which is connected to the input shaft through a torsion bar and transmits the turning force to steered road wheels, the steering shaft rotatably housed in the housing; a sensor coil housed in the coil housing portion and positioned at an outer periphery of the steering shaft, the sensor coil outputting a relative rotation amount between the input shaft and the output shaft as an impedance change by application of an excitation signal; a coil bobbin having: a coil holding part which holds the sensor coil; and a flange part which is provided so as to protrude from the coil holding part in a radially outward direction, the coil bobbin formed by the resin material and housed in the coil housing portion; a first held section provided at the flange part of the coil bobbin; a sensor board housed in the housing and electrically connected to the sensor coil, an electronic element that outputs the excitation signal to the sensor coil being mounted on the sensor board; a second held section provided at the sensor board; a first riveting portion formed by the resin material and provided at the first housing section, the first riveting portion fixing the coil bobbin to the first housing section by a first structure in which a first holding section that engages with and holds the first held section is formed at the first riveting portion in a molten state; a second riveting portion formed by the resin material and provided at the first housing section, the second riveting portion fixing the sensor board to the first housing section by a second structure in which a second holding section that engages with and holds the second held section is formed at the second riveting portion in the molten state; and an electric motor driven and controlled according to an output signal of the sensor coil and providing a steering assist force to the steered road wheels, and one of the flange part of the coil bobbin and the sensor board being located at a second housing section side with respect to the other of the flange part of the coil bobbin and the sensor board in an axial direction of the steering shaft, and one of the first and second riveting portions, which is provided at the other of the flange part and the sensor board, being disposed so as to overlap the one of the flange part and the sensor board in a direction orthogonal to the steering shaft.