Electric motor having a Hall sensor

摘要

The Hall sensor is acted on by the magnetic field of permanent magnets in the rotor and produces a control signal, which indicates the respective position of the rotor, for speed regulation or commutation. Interference magnetic fields, in particular from the motor coils of the stator, also act on the sensors. The signal to noise ratio at the output of the sensor is thus frequently unsatisfactory. The object is to improve the signal to noise ratio at the sensor without any significant additional cost (complexity). The permanent magnets (3) are shaped on their side facing the Hall sensor (4) such that the size of the magnetic lines of force which pass from the magnets (3) to the sensor (4) is increased. The edge is preferably provided with a chamfer (8) which is at right angles to the line connecting the edge of the magnet (3) to the sensor (4). Particularly for speed regulation or electronic commutation of a capstan motor in a video recorder. <IMAGE>