JPS6439557A - Wheel rotating speed detector - Google Patents

Abstract

PURPOSE:To securely and accurately detect a rotating speed by forming a partially cylindrical surface which has its center on the center line of rotation of a rotor as the front end surface of the detection teeth of an electromagnetic pickup facing the tooth of the rotor. CONSTITUTION:The sensor rotor 22 is cylindrical and the outer peripheral tooth part 24 of its end part is provided with teeth 26 formed at equal intervals. The electromagnetic pickup 28 is provided nearby the tooth part 34 of the rotor 22 and equipped with a permanent magnet 30 and an iron core 34 wound with a coil 32. The tip part of the iron core 34 projects toward the rotor 22 and the projection part has three detection teeth 40 formed in the circumferential direction of the rotor 22 at the same pitch as that of the teeth 26. The tip end surfaces 42 of those detection teeth 40 facing the teeth 26 form part of one partial cylindrical surface having its center on the center line of rotation of the rotor 22. Consequently, variation of magnetic flux produced by the detection teeth 40 becomes equal and generated AC voltages are all in phase. Therefore, an output obtained by one detection tooth 40 increases and has an excellent output waveform.