Magnetic detector for rotational speed and shaft position - has toothed ring with metal plate in zone where teeth are removed and uses magneto-resistive pick=up

摘要

The magnetic detector for rotational speed and/or a given angular position of a turning shaft has a disc or ring (1) which is toothed (3) on at least part of its periphery. This toothed part has a zone (4) in which one tooth or several successive teeth have been removed. A magnetic resistance pick-up (5), with a coil (6) is placed near the teeth of the disc or ring. A metallic segment (7) such as a steel plate is placed in the zone where there are no teeth and is fixed to the disc or ring by means of screws (8) of the same material. The outer surface of the plate (7a) are withdrawn by a distance (d) w.r.t. the outer surface (3a) of the teeth. The metallic plate creates supplementary leakage flux in the zone. The distance (d) is determined experimentally such that the supplementary flux is practically equal to the drop in leakage flux resulting from the removal of the teeth. The output signal of the pick-up is no longer deformed at high speed and with sensitive pick-ups.