JPS6370117A - Number-of-rotation detecting circuit - Google Patents

Abstract

PURPOSE:To exclude the effect due to the variation of the positional relation between a gear and a displacement detector detecting such as the whirling and levitation, etc., of a rotary shaft, by detecting the max. of min. value of the signal wave form of the displacement detector and correcting a threshold value on the basis of the variation quantity thereof. CONSTITUTION:A comparator 53 calculates the deviation DELTAEp=Ep-Epo of the peak value Ep detected this time and the peak value Epo before one cycle, that is, the variation quantity of the peak values to send out the same to an adder 54. The adder 54 adds DELTAEt=Ep to the output Eto of a reference threshold value setting device 14 as threshold value correction quantity to obtain a threshold value Et=Eto+Et. A comparator 12 binarizes a signal E on the basis of the threshold value Et to obtain a binary signal C which is, in turn, sent out to a counter 13. The counter 13 counts the signal C to obtain a speed signal Nc and the number of rotations are calculated from said signal Nc. By this method, a number-of-rotation signal Nc is obtained without being affected by the variation of detected displacement (x).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotation speed detection circuit for detecting the rotation speed of a rotating machine.

[Conventional technology] FIG. 2 shows a conventional example of this type of rotation speed detection circuit.

The gear 1 rotates together with a rotating machine (not shown), and a displacement detector 2 is installed opposite the gear 1. The driver 3 converts the displacement X detected by the displacement detector 2 into a voltage ES. If an overcurrent type displacement detector having the characteristics shown in Fig. 3 is used as the displacement detector 2, and it is placed opposite the gear 1 rotating at the rotation speed N, the displacement X will be x (t) in Fig. 3. Since the time response of the frequency f is proportional to the rotation speed N, the driver output voltage ES is also the time response of the frequency f, Es(t
). The operation of the rotation speed detection circuit 4 will be explained below.

The driver output voltage ES has noise components removed by the buffer amplifier 11 and is output as a signal E to the comparator 12. The comparator 12 outputs the output Eto of the setting device 14.
The signal E is binarized using the threshold value, and the signal C is outputted to the counter 13. The frequency f of the binary signal C is proportional to the rotation speed N of the gear, and the signal C is counted by a counter 13 to obtain the rotation speed Nc. Here, the threshold value Eta is explained using the symbols in FIG. 3, for example, the minimum displacement XIA
What is necessary is to select the average value of the driver output voltage EPL corresponding to the maximum displacement X2A and the driver output voltage EPH corresponding to the maximum displacement X2A.

[Problems to be solved by the invention] The conventional rotation speed detection circuit described above converts the displacement detector signal into two
Since the threshold value for converting into values is a constant value, if the waveform of the displacement detector signal fluctuates due to wobbling or lifting of the rotating shaft, it becomes impossible to convert into binary by the comparator, and the rotation speed cannot be detected. There was a drawback that would go away. For example, as shown in FIG. 4, when the time response of displacement I can do it, but xi(
t), since Es B (t) > Eto, C is always
(t)-'1°, and counting by the counter becomes impossible.

[Means for Solving the Problems] The present invention detects the maximum or minimum value of a signal waveform of a displacement detector installed opposite a gear that rotates integrally with a rotating machine, and detects the maximum value or minimum value of a signal waveform based on the amount of variation thereof. A circuit for correcting the threshold value is provided, the output of the circuit is used as the threshold value to binarize the displacement detector signal, and the number of revolutions is determined by counting the number of pulses of this binarized signal. .

By employing the circuit means, the threshold value is corrected in conjunction with fluctuations in the displacement detector signal due to wobbling, lifting, etc. of the rotating shaft.

[Configuration] Fig. 1 shows an embodiment of the present invention. Elements common to the conventional example shown in FIG. 2 are given the same numbers. The rotation speed detection circuit 40 according to an embodiment of the present invention includes a peak value detector 51. The threshold generation circuit 50 includes an analog memory 52, a comparator 53, an adder 54, a threshold value setter 14, and other elements, and a buffer amplifier 11, a comparator 12, a counter 13, and other elements.

[Operation] Variables necessary for a detailed explanation of the present invention are defined with reference to FIGS. 3 and 4. EPH, EPHA.

EPHB: highest value of detector signal, EPL.

EPL^, EPLB; lowest value of the detector signal, Et.

Eto: L, threshold, EP, EPO: peak value (highest value or lowest value) of detector signal, ΔEP: variation amount of peak value EP, ΔEt: I, threshold correction amount.

The peak value detector 51 will be described here as a maximum value detector because the same effect can be obtained as either a maximum value detector or a minimum value detector.

A voltage ES outputted from the driver 3 corresponding to the displacement X detected by the displacement detector 2 becomes a signal E after noise components are removed by the buffer amplifier 11. Signal E is sent to comparator 12 and also to peak value detector 51 . The peak value detector 51 detects the highest value EP of the signal E.
mll:pH is detected and sent to analog memory 52 and comparator 53. Analog memory 52 receives input signal E
The means for storing P updates the stored value at regular intervals, and its output Epo is equal to the input signal one cycle before. However, the update period is at least 1/2 of the period of the detector signal. The comparator 53 calculates the deviation ΔEP-EP-EPO between the currently detected peak value EP and the peak value IEpo one cycle before, that is, the amount of variation in the peak value, and sends it to the adder 54.

The adder 54 receives the output Et of the reference threshold setter 14.

By adding ΔEt - ΔEP as the threshold correction amount, the threshold Et - Eto + ΔEt number day 2 is obtained.
The value signal C is counted by a counter 13 to obtain a speed signal Nc.

When the detected displacement X changes as shown in FIG. 4 xA(t), the driver output voltage ES changes as shown in E S A (t), with the highest value being EPHA and the lowest value being EPI,A. At this time, the reference threshold value of the comparator 12 is Eto-(EP
Assuming that it is set to HA+EPL person)/2,
Since EP = EP O, ΔEP-0 becomes Et-Eto. Therefore, by the comparator 12, the binary signal C
(O is obtained. Here, the detected displacement
(t), Epo=EpoA%Ep-
becomes Epun, ΔEP ””EP-EP O”EP
HB-EP HA. The threshold value Et of the comparator 12 is Et-Eto+ΔEt, where ΔEP=EP HB-EP HA is the correction amount ΔEt. This is recorded in FIG. 4 as the threshold value Et according to the invention. Therefore, even if the detected displacement X changes like X B (t), a binary signal C(t) can be obtained.

Due to the above points, the rotational speed signal Nc can be obtained without being affected by fluctuations in the detected displacement X.

[Effects of the Invention] As detailed above, according to the rotation speed detection circuit of the present invention,
The rotational speed can be detected without being affected by fluctuations in the positional relationship between the gear and the displacement detector, such as whirling or lifting of the rotating shaft.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing the configuration of a rotation speed detection circuit according to an embodiment of the present invention, FIG. 2 is a circuit block diagram showing the configuration of a conventional rotation speed detection circuit, and FIGS. 3 and 4 are FIG. 3 is a diagram for explaining the effects of the present invention and the conventional example, respectively. 40... Rotation speed detection circuit, 50... Threshold generation circuit, 51... Peak value detector, 52... Analog memory, 53... Comparator, 54... Adder, 11・・・
・Buffer amplifier, 12... Comparator, 13...
-Counter, 14...Reference threshold value setter.

Claims (1)

[Claims] In a rotation speed detection device that uses the signal of a displacement detector installed opposite a gear that rotates integrally with a rotating machine as a rotation speed signal, the maximum or minimum value of the signal waveform of the displacement detector is detected and the signal is kept constant. A circuit that is equipped with a means for storing every cycle and calculates the difference between the current detected value and the previous detected value and adds this difference to a threshold value, and a binary displacement detector signal that uses the output of the circuit as a threshold value. 1. A rotational speed detection circuit comprising: a circuit for calculating the number of rotations by counting the number of pulses of the binary signal.