JPS577562A - Rotation detector - Google Patents

Abstract

PURPOSE:To improve the low-speed rotation detecting ability of a rotation detector and enable the direction of rotation to be detected, by providing rotary and fixed gears having convex teeth of a given pitch and made of a light-transmitting material, and employing two pairs of Hall elements to detect the quantities of magnetism. CONSTITUTION:Provided are a rotary gear 2 provided with convex teeth on the peripheral part at the same pitch and made of a light-transmitting material, and fixed gers 1a, 1a', 1b, and 1b' having the same tooth pitch as the gear 2 and made of a light-transmitting material. When the gear 2 rotates, gap changes arise between said gear 2 and the fixed gears 1a-1b', and the magnetic flux changes. Consequently, a voltage signal waveform of an output A is obtained between the output terminals of a pair of Hall elements 6a and 6b', while a voltage signal waveform of an output B which is 90 deg. out of phase therewith is obtained between the output terminals of another pair of Hall elements 6b and 6b'. These elements 6a, 6b and 6a', 6b' are arranged so as to face to each other at 180 deg. respectively, and the signals therefrom are to be added. Because the quantities of magnetism are detected by such a constitution, the low-speed rotation detecting ability can be improved. In addition, because the signals which are 90 deg. out of phase with each other are obtained, the direction of rotation can be also detected.