| 摘要 |
PCT No. PCT/JP84/00358 Sec. 371 Date Mar. 6, 1985 Sec. 102(e) Date Mar. 6, 1985 PCT Filed Jul. 11, 1984 PCT Pub. No. WO85/00430 PCT Pub. Date Jan. 31, 1985.Disclosed is a motor speed detecting device which comprises a first slotted disc (3) having one slot and mounted on a rotational shaft (2) of a motor (1) that is driven by a motor drive unit (7) and a second disc (4) having a plurality of slots, a first magnetic sensor (5) mounted on the first gear (3) in close proximity thereto and outputting two signals with a phase difference and a second magnetic sensor (6) mounted on the second slotted disc in close proximity thereto and outputting two signals with the phase difference and their inverted signals and a detector circuit (8) receiving the output of the first and the second magnetic sensors. The detector circuit (8) is provided, wherein two outputs from the first magnetic sensor are compared with a differential amplified voltage and a reference voltage, one pulse per one revolution of the rotational shaft (2) is output, and in addition, with the four outputs provided from the second magnetic sensor (6), differential amplification, inverting amplification, comparison and vector synthetic comparison are implemented to provide a pulse per 22.5 degrees, where the phase of the output waveform in the magnetic sensor in response to the width of the slot, resulting in a sinusoidal wave having a different phase by 90 degrees from each other, in response to the number of the slots of the second disc (4), and a square wave of as many as four times the frequencies as the number of slots of the second disc (4) and a square wave of one-fourth period of phase difference with regard to the square wave, are provided to output therewith. Thus, using the relevant device, it is applicable to a to-be-detected rotational shaft of which the rotational shaft (2) is hollow and to provide a precision of detection four times as great.
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