Rotational speed detector

Claim 1

A rotation speed signal detector comprising a cylindrical rotor magnet (1) having an array of n magnetic poles (1A) magnetized on one circumferential surface of said cylinder along the peripheral direction and an array of m (m > n) magnetic poles (lB) magnetized orr the other circumferential, surface of said cylinder along the peripheral direction; a stator (4) fixed opposite to said array of n magnetic poles of said rotor magnet and having a stator winding for giving a rotational force to said rotor magnet; a detection coil (5) provided with coil conductors (16, 17) having winding elements at angular positions corresponding to magnetic pole pitches of m poles of said rotor magnet and connecting in a wavy form said winding elements for detection, the electric phase difference of said coil conductors on the both surfaces of a flexible insulating sheet being made π ; a supporting member (6) for supporting said detection coil in a ring form such that said detection coil lies around said array of m poles of said rotor magnet and such that the peripheral surface of said detection coil is. made opposite to said array of m poles of said rotor magnet with a prescribed gap therebetween; and pin terminal means (8, 20a, 20b, 21, 21a, 21b) having terminal pins connected to one-side pair of the terminal conductor portions of said detection coil to lead out a rotation speed signal of said detection coil, while the other side terminal pair of conductor portions of said detection coil are electrically connected to form a short-circuit whereby the rotation speed signal of said rotor magnet is derived from said pin terminal means.