DC motor unit with a rotational speed detector

摘要

A d.c. motor unit with a rotational speed detector comprising a d.c. motor (1) having an output end and an idle end, and a rotational speed detector (14) water-tightly attached to the motor output end. The d.c. motor (1) comprises a motor frame (2) including an output end and an idle end, a mounting bracket (9) attached to the output end of the motor frame (2) and a rotary shaft (4) having an idle end rotatably supported by the motor frame (2) and an output end rotatably supported by and extending outwardly through the mounting bracket (9). The rotational speed detector (14) comprises a rotary portion mounted on the output end of the rotary shaft (4) and a stationary portion mounted to the mounting bracket at the output end of the motor frame (2). The rotational speed detector (14) comprises a substantially elastic permanent magnet plate (20) for generating a magnetic flux ( phi ) extending through a closed magnetic circuit including contact surfaces which are in pressure contact with the permanent magnet plate (20).