Method of coupling magnetic position detecting device with brushless dc motor and the coupling structure thereof

A method of coupling a magnetic pole position detecting device to a brushless dc motor, the dc motor having an output shaft and a motor case, and the magnetic pole position detecting device including a rotor part having an input shaft with a slit indicative of a rotor zero point, a stator part having detecting circuit means for outputting the absolute value of a relative angle between the rotor part and the stator part, and a device case with a scribed locating mark on the surface thereof, said method comprising the steps of:

• (a) determining relative angular positional relationships between the rotor part, the stator part and the device case of the magnetic pole position detecting device by
• i) providing a jig that has a shaft with a pin and a plate having ascribed mark on its surface, and mounting the detecting device to the jig by inserting the pin of the jig in the slit of the detecting device and aligning the scribed mark on the surface of the device case with the scribed mark on the plate of the jig,
• ii) then adjusting the relative angular positional relationship between the stator part and the rotor part by rotating the stator part until the detecting circuit means outputs a predetermined value, and
• iii) fixing the stator part relative to the device case;
• (b) coupling the output shaft of the motor to the rotor part of the magnetic pole position detecting device;
• (c) rotating the shaft of the motor externally;
• and
• (d) scribing another locating mark on the motor case in alignment with the mark scribed on the device case, under a condition in which the relative angular positional relationship between the motor case and the device case is such that a back E.M.F. waveform of the motor and a waveform of the absolute value output by the detecting circuit means of the detecting device are in phase.