SU470742A1 - Device for determining the speed and direction of rotation of the shaft - Google Patents

Description

one.

The invention relates to the field of engine parameter measurements.

The known devices for determining the speed and direction of rotation of the shaft contain a frequency oscillating sensor that produces two voltages at the output, the frequency of which is proportional to the speed of rotation, and the phase difference between them is ± 90 °, the frequency-to-voltage conversion unit and the unit for determining the direction of rotation.

To improve the accuracy of determining the direction of rotation at low speeds and reduce the accuracy requirements of the sensor, the proposed device is equipped with two Schmitt triggers, the inputs of which are connected to the sensor outputs and the output of the frequency-to-voltage unit, and the outputs to the unit for determining the direction of rotation.

FIG. 1 schematically shows the proposed device; in fig. 2-voltage diagrams in known devices; in fig. 3 is the same in the proposed device.

The device contains a frequency sensor 1, the toothed rotor 2 of which is rigidly fixed on the shaft 3, and the toothed stators 4 and 5 with the signal windings 6 and 7 are fixed and shifted relative to each other; a frequency-to-average voltage conversion unit 8, threshold devices — Schmitt triggers 9 and 10, and a rotational voltage detection unit AND, a device for detecting a change in the sign of the phase shift of two voltages.

The device works as follows. With the shaft 3, the teeth of the rotor 2 modulate the magnetic flux created by the stators 4 and 5, which leads to the appearance in the signal windings 6 and 7 e. d., proportional to the rotational speed and shifted in phase relative to each other by 90 ° due to the displacement of the stators. The sign of phase deviation is determined by the direction of rotation of the shaft. Curves a, b - direct rotation, curves a, c -

reverse rotation (Fig. 2 and 3). One of the voltages is fed to the input of the frequency conversion unit 8 to the average voltage, automatically shifting the threshold for triggering the Unop threshold devices - (Schmitt trigger 9

and 10, serving as a generator of rectangular pulses (curves d, e, e in Fig. 3, fed further to block 11. At the input of the latter, thus, two sequences of pulses are obtained, the phase relations

between which they are converted into a signal defining the sign of the phase shift. The deviation of the duty cycle of the pulses of the mentioned pulse sequences from 0.5 (curves g, d, e in Fig. 2) leads to an additional

phase shift summing with the main

and reduces the accuracy of phase shift determination. The automatic shift of the trigger threshold of Schmitt triggers 9 and 10 allows maintaining a duty cycle close to 0.5 over the entire speed range. At low speeds, when the duty cycle differs significantly from 0.5, the bias voltage is small, and increasing the trigger threshold t / nop improves the shape of the curve. As the speed increases, the offset increases, the trigger threshold approaches zero and does not affect the formation of the curve. The curves g, d, e in FIG. 2 illustrates the operation of a known device that does not have an automatic displacement.

As can be seen from FIG. 2, the pulse ratio in the known device is significantly different from 0.5.

Consequently, the use of a threshold device with automatic displacement as a shaper makes it possible to extend the tolerance by

P; the preparation of the construction elements of the sensor Gi;: i the accuracy of the determined accuracy; Entailing rotation.

Subject invention

An apparatus for detecting the speed and direction of rotation of the shaft, comprising a frequency oscillating sensor that generates

The output is two voltage-shifted by 90 degrees, whose frequencies are proportional to the rotational speed, the frequency-to-voltage conversion unit, and the direction of rotation determination unit, characterized in that

increase the accuracy of determining the direction of rotation at low speeds and reduce the requirements for the accuracy of the sensor, it is equipped with two Schmitt triggers, the inputs of which are connected to the outputs of the sensor and

the output of the frequency conversion unit to the voltage, and the outputs with the unit for determining the direction of rotation.

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