Brushless electric motor esp. for head drum of video tape recorders, hard disk drives and polygon-scanner actuators

摘要

The motor has a rotor magnet (28) with a flat surface which is magnetised in a number of polarities. A first rotary element is brought into contact with a first surface of the rotor magnet (28). The first rotary element is made from a weakly magnetic material to form a magnetic loop. A second rotary element made of a weakly magnetic material is spaced from a second surface of the rotor magnet by a predetermined air gap to absorb magnetic flux of the rotor magnet and forms a part of the magnetic loop. A spacer is inserted between the first and second rotary element to provide the air gap between the surface of the magnet and the second rotary element. A support element is arranged within the spacer to support and centre the second rotary element. A stator is arranged in the magnetic loop between the rotor magnet and the second rotary element to supply electric current to a drive coil. A locking mechanism is provided between the second rotary element and the support element to prevent opposing transfer in rotation direction between the second rotary element and the rotor magnet.