Patent ID: 8836321
Filing Date: 2014-09-16
Classification: G01P

Abstract:
1. A motor speed detection apparatus configured to detect rotational speed of a motor, the apparatus comprising: a frequency generation coil and a magnet that are configured to be relatively moved with rotation of the motor, the frequency generation coil outputting an alternating-current signal to be sampled by the apparatus; an A/D converter configured to convert the alternating-current signal output from the frequency generation coil into a digital signal; an integrator configured to perform time integration on the digital signal output from the A/D convertor; a first determiner configured to determine which one of plural threshold ranges includes an integration value obtained by the integrator; a second determiner configured to determine whether change of the integration value is increase or decrease; and a logical product calculator configured to produce a binary signal showing a logical product of determination results of the first and second determiners, wherein the apparatus is configured to calculate the rotational speed based on a production cycle of the binary signal.