Patent ID: 7518273

Claim:
An electric motor comprising: a static part including an outer stator; a field magnet having a cylindrical shape; an inner rotor part having the field magnet for generating a torque around a central axis of a shaft with respect to the stator; a bearing part for supporting the inner rotor part rotatably with respect to the static part around the central axis; a sensor magnet that is a substantially ring-like rare earth anisotropic magnet and magnetized in multiple poles, the sensor magnet secured on the inner rotor part and arranged with the field magnet coaxially; a flange portion of a magnetic material disposed between the field magnet and the sensor magnet, wherein the flange portion has a radially inside part, wherein the flange portion is fixed on the shaft at the radially inside part, wherein the radially inside part has a height in the axial direction, wherein the sensor magnet is fixed on the flange portion, wherein the flange portion is spaced from the field magnet with a distance more than the height; and a sensor disposed at a radially outward portion opposed to the sensor magnet, for detecting the position of the sensor magnet.