| 摘要 |
PURPOSE:To suppress a malfunction at the generation of chattering by arranging two reed switches on a vehicle speed sensor with the shift of a prescribed angle and comparing vehicle speed signals outputted from the two reed switches by a control unit. CONSTITUTION:A shaft 2 and a magnet 3 are rotated through a cable 1 rotated in proportion to the speed of an automobile. Two reed switches 4, 4a are arranged oppositely to the magnet 3 so as to be shifted by a prescribed angle (112.5 deg.) from alternate magnetic fields 5, 5a generated by the magnet 3. Vehicle speed signals 6, 6a from the switches 4, 4a form waveforms having an always fixed phase difference. When one switch 4 outputs a chattering signal 9, the other switch 4a sets up the alternate magnetic field applied to the switch 4a itself on the outside of the range of hysteresis 7 generated from the switch 4a itself, so that the malfunction of the control unit can be suppressed by the vehicle speed signal 6a.
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