Patent ID: 7242121

Claim:
A brushless motor comprising: a stator core being wound therearound with a stator coil; a rotor including a cup-shaped rotor yoke attached on the inner peripheral side with a ring-shaped magnet being arranged to face the stator core and having magnetized a plurality of poles for driving along a circumferential direction on the inner periphery, and a shaft fixed at the center of the rotor yoke; a bearing for journaling the shaft in a freely rotating manner; a housing for holding the bearing on the inner peripheral side and holding the stator core on the outer peripheral side; a Hall element for detecting a position in a rotating direction of the magnet of the rotor; a speed detector for detecting the rotating speed of the rotor; and a circuit substrate fixed to the housing and equipped with a drive/control circuit for rotatably driving and controlling the rotor, wherein the speed detector comprises: a plurality of magnetized portions located at an end face of the magnet along a circumferential direction thereof on an open end side of the rotor; a speed detecting pattern comprising a plurality of generator wire elements connected circularly in series to be uniform along the entire circumference of the circuit substrate, at a position corresponding to the magnetized portions and on the side facing the end face of the magnet of the rotor, the generator wire elements being the same in number as poles of the magnetized portions located on the circuit substrate; and a cancel pattern located at one of the external side and the internal side of the speed detecting pattern so as to surround the speed detecting pattern, the cancel pattern being connected in series with the speed detecting pattern, the Hall element being located on a surface of the circuit substrate on the opposite side to the surface located with the speed detector, and the drive/control circuit comprises: a drive/control integrated circuit; and electronic components for surface mounting, the drive/control integrated circuit, the electronic components for surface mounting and the Hall element being all surface mounted by soldering on a surface of the circuit substrate on the side opposite to the surface located with the speed detecting pattern and the cancel pattern.