Linear actuator comprising a brushless polyphase electric motor

The present invention relates to the linear actuator which consists of a ブラシレス polyphase synchronous electricity motor (2) equipped with a stator (3) and a rotator (4). The above-mentioned rotator acts on a control element (O) through the drive means (5) which can change rotational movement of the rotator into linear movement over some rotations. As for the actuator of the present invention, it is desirable to have the elasticity which can return a control element (O) to a reference position systematically at the time of generating of discontinuation of the electric power supply to a motor (2), and/or a magnetic restoration means (21). A motor (2) is equipped with the position sensing device (25, 25A) used with an electronic control unit for automatic control of the position of a rotator (4), adjustment, therefore automatic control of the position of the above-mentioned control element (O) and adjustment.