Patent ID: 8589117

Claim:
A rotation angle detecting unit comprising a housing including a housing body having mounting openings at first and second ends thereof, respectively, and a lid covering the mounting opening at the first end, a shaft having its portion at the first end received in the housing and its portion at the second end protruding from the mounting opening of the housing at the second end, a rolling bearing rotatably supporting the shaft on the housing body, a magnetic drum fixed to an end surface of the shaft at the first end, a magnetic sensor for detecting change in magnetic flux as the magnetic drum rotates, and calculating a relative rotation angle based on the change in magnetic flux, and a circuit board carrying the magnetic sensor, wherein a board internal mounting portion is provided on a surface of the lid at the second end for mounting the circuit board, wherein the lid is configured to apply a preload to the rolling bearing by pressing an outer race of the rolling bearing and to position the magnetic sensor relative to the magnetic drum when the lid is fixed in position, wherein initial calibration parameters are configured to be written into the magnetic sensor while calibration voltage which is higher than use voltage is being supplied through a sensor power source connecting end of the circuit board, wherein a board external mounting portion is provided outside the housing to which a power source input/output board with a stabilizing circuit for stably outputting use voltage can be mounted, the rotation angle detecting unit further comprising a calibration voltage feed line extending from the sensor power source connecting end to the outside with the lid fixed in position, the calibration voltage feed line having an external connecting end which can be connected to a stabilizing output end of the power source input/output board after the initial calibration parameters have been written.