Has the rpm sensor and the rpm sensor the electric motor type actuator

摘要

PURPOSE:To accurately detect the rotating speed of a rotary body and to position a member to be driven with high accuracy by fitting a ring magnet which has an N pole as a half periphery and an S pole as the remaining half periphery on the outer peripheral surface of the rotary body. CONSTITUTION:The half outer peripheral surface of the ring magnet 82 is the N pole and the other half outer peripheral surface is the S pole, so the magnetic polarities that a magnetic probe detects change alternately every time the rotary body 80 makes a half turn. Then when the magnetic probe is composed of a Hall IC 84, the electric signal from this Hall element has a sine waveform and a large hysteresis angle can be secured. The border of both the poles of the rotary body stops at the position of the magnetic probe and even when vibration is applied, the pulse signal from the magnetic probe has no chattering phenomenon. Consequently, the rotating speed of the rotary body in the form of a pulse signal can accurately be detected. Further, the member which is driven by the rotary body through a gear is positioned with high accuracy.