JPS63277930A - Vortex flowmeter - Google Patents

Abstract

PURPOSE:To accurately remove only noises and to accurately detect a vortex frequency by setting the charging and discharging time constant of an f-V converting circuit so that charging is performed quickly at the time of the generation of a high vortex frequency and discharging is performed slowly at the time of the generation of a low frequency. CONSTITUTION:An ultrasonic wave which crosses a flow of a Karman vortex street is received by an ultrasonic wave receiver 5, whose output is inputted to a phase comparator 9 through a waveform shaping circuit 8. The output of the phase comparator 9 is sent out through a low-pass filter 11, a variable frequency filter 12, and a waveform shaping and amplifying circuit 13. This output is supplied to the f-V converting circuit 14, whose output is used to control the frequency band of the filter 12. The charging and discharging time constant of the f-V converting circuit 14 is so set that the quick charging is performed at the time of the high frequency generation and the slow discharging is performed at the time of low frequency generation.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vortex flow meter used in an engine, and in particular, the vortex output does not significantly attenuate when a high frequency occurs after a low frequency occurs, and only noise is generated. This makes it possible to remove accurately.

[Conventional technology]

Conventionally, regarding vortex flowmeters used in engines, companies have published, for example, Japanese Patent Publications No. 58-15045 and Japanese Patent Publication No. 59-24363.
Japanese Patent Publication No. 58-56415 are known. FIG. 1 is a block diagram showing the vortex flowmeter of this invention, which will be described later, and FIG. 1 will be referred to when explaining the conventional art. Figure 1 of Jin also includes parts of conventional technology.

First, I! Figure 1 shows the above-mentioned special public service No. 58-56415.
The part shown in the publication is summarized here. This first rI! In this case, an ultrasonic transmitter 4 and an ultrasonic receiver 5 are arranged facing each other via a flowmeter 1 having a vortex generator 2, and a carmine vortex street 3 generated downstream of the vortex generator 2 is arranged. The ultrasonic transmitter 4 is excited by the ultrasonic oscillation circuit 6 so that the ultrasonic wave propagates across the flow.

The ultrasonic line that crosses the flow of the Karman vortex street is phase modulated by the Karman vortex street 3, and is received by the ultrasound receiver 5. This received signal is waveform-shaped by a waveform shaping circuit 8 and then outputted to a phase comparator 9.

On the other hand, the output of the ultrasonic oscillation circuit 6 that excites the ultrasonic transmitter 4 is applied to the voltage controlled phase shift circuit 7.

The voltage controlled phase shift circuit 7 maintains high frequency stability of the ultrasonic oscillation frequency signal.

It controls only the phase shift angle. This voltage controlled phase shift circuit 7 shifts the phase of the output of the ultrasonic oscillation circuit 6 and applies it to the phase comparator 9.

The phase comparator 9, the ultrasonic oscillation circuit 6, the voltage controlled phase shift circuit 7, and the loop filter 10 constitute a phase locked loop. Note that 11 is a row/# filter. .

A phase comparator 9 compares the phases of the output of the waveform shaping circuit 8 and the output of the voltage controlled phase shift circuit 7.

The comparison result is added to the loop filter 10, and unnecessary frequency components of this comparison result are removed by the loop filter 10.

depending on the output voltage of this loop filter 10.

The voltage controlled phase shift circuit 7 controls the phase shift angle of the output signal of the ultrasonic oscillation circuit 6 and outputs it to the phase comparator 9.

As a result, the output of the voltage controlled phase shift circuit 7 is synchronized with the ultrasonic reception signal, and as a result, the output of the loop filter 10 directly becomes the phase demodulated output.

However, in the case of this publication, the vortex frequency is disturbed by noise other than the signal received by the ultrasonic receiver 5 and low-frequency undulations caused by the flow of the fluid.

To solve this problem, a "vortex flow meter" has been proposed by the same applicant as the applicant of the present invention. The vortex flowmeter of this prior application will be further described with reference to FIG. In addition to the configurations shown by reference numerals 1 to 11, the invention of this prior application has newly added parts described below.

In other words, the output of the 1st phase comparator 9 is the loop filter IOK.
In this example, the signal is input to the variable frequency filter 12 via the low/# filter 11. The output of this variable frequency filter 12 is configured to be input to a waveform shaping amplifier circuit 13. .

This waveform shaping amplifier circuit 13 outputs a Karman vortex frequency signal corresponding to the flow rate and amount of the flowmeter 1.

First, this Karman vortex frequency signal is input to a frequency-voltage (hereinafter referred to as fV) conversion circuit 14. The output of this f-4 conversion circuit 14 controls the frequency band of the variable frequency filter 12.
Ru.

With this configuration, as described above, the vortex signal, that is, the phase demodulated signal, generated in response to the flow IK of the fluid to be measured flowing through the flowmeter 1 is passed through the low/gas filter 11 to the variable frequency filter 12. is input.

The variable frequency filter 12 is a 1L band I filter.
K is designed to cut noise outside the pass band between the lower limit frequency and the upper limit frequency.

The noise of this engine is relatively low frequency noise caused by the pulsation of the air flow.The output frequency is low due to the so-called wind noise generated when air passes through the air valve, i.e. relatively high frequency noise when the flow rate is low. This is the high output frequency noise that occurs during charging and other operations.

The generation area of these noises changes, and the air flow rate also changes depending on the instantaneous behavior of the engine, so the bandwidth of the vortex frequency is quite wide. K is set so that it has the characteristics.

The vortex frequency signal that has passed through the variable frequency filter 12 is waveform-shaped and amplified by the waveform shaping and amplification circuit 13, and the vortex frequency signal is output.

At the same time, the vortex frequency signal is transmitted to the t-y conversion circuit 14,
It is converted into a voltage corresponding to that frequency, and the pass band of the single frequency variable filter 120 is controlled by this voltage.

As a result, the passband of the variable frequency filter 12 changes, and noise removal control is performed.

[Problem that the invention seeks to solve]

In this way, the pass band of the variable frequency filter 12 is controlled by the output of the f-V conversion circuit 14.
Since the output of the i-switching circuit 14 responds well to the vortex signal,
When a signal as shown in the waveform diagram shown in Fig. 3cA)K is received, the waveform becomes as shown in the output line 1!311 (to), and as a result, the output terminal of the waveform shaping amplifier circuit 13 is A waveform as shown in 0 is obtained.

In this Figure 3C), as shown by the notch,
It is attenuated compared to the waveform diagram in Figure (2). This is because in the waveform diagram of the third factor, when the output frequency of the waveform shaping amplifier circuit 13 is low, the output of the f-V conversion circuit 14 shown in part A is J. Since the output frequency is set to the same frequency, the initial waveform of the next high output frequency portion of the waveform shaping amplification circuit 13 will be greatly attenuated. For this reason, gaps occur in the output waveform after waveform shaping and amplification.

This invention was made to solve this problem, and the vortex flow rate is such that when a high frequency wave occurs after a low vortex frequency JIII wave, the vortex output is not significantly attenuated and only the noise can be reliably removed. The purpose is to obtain a measurement.

[Rounding method to solve problems]

The vortex flowmeter according to the present invention includes a variable frequency filter that receives an eddy signal generated in response to the flow rate of a fluid to be measured, a waveform shaping amplifier circuit that shapes and amplifies the output of the frequency variable filter, and a waveform shaping amplifier circuit that shapes and amplifies the output of the frequency variable filter. In addition to converting the vortex frequency output output from the circuit into voltage to control the pass band of the frequency gT variable filter, a frequency-voltage conversion circuit in which the charging time constant and discharging time constant are respectively set to predetermined values is set. It is something.

[Shoulder]

In this invention, the vortex signal t generated in response to the flow rate of the fluid to be measured is introduced into a variable local wave number filter, unnecessary noise components are removed, and the waveform is shaped and amplified by a waveform shaping amplifier circuit. The conversion circuit converts it into a voltage according to the output frequency, and the output voltage controls the passband of the variable frequency filter to superimpose it on the vortex frequency to block the passage of nine noises, as well as waveform shaping and amplification of the vortex frequency signal. It responds to the high frequency part of the signal, and responds slowly to the low frequency part.

The attenuation of the high frequency part of the vortex frequency signal output from the variable frequency filter is reduced by /j%.

〔Example〕

Hereinafter, embodiments of the vortex 1rTt it it of the present invention will be described based on the drawings. #! FIG. 1 is a block diagram showing the configuration of one embodiment.

In FIG. #S1, the description of the parts described in the [Prior Art] column will be omitted to avoid duplication.

In this invention, the configuration as a block diagram in FIG. 1 is the same as that in FIG. 1], and there is no difference, except that the f-V conversion circuit 14 is configured as shown in FIG. 2. .

In other words, 8J! Waveform shaping increase I11 in Figure 1! The output of circuit 13 passes through resistor R3 and capacitor tC2 to transistor Q.
It is designed to be entered on the page of

The emitter of the transistor Q is grounded, and the collector is connected to the power supply via a resistor R2.
The connection point between this resistor R1 and the cathode of the diode D is grounded via a capacitor C1.

By configuring the 1cf-V conversion circuit 14 in this way, the output signal of the 1813 after waveform shaping and amplification is applied to the base of the transistor Q through the resistor R3 and the capacitor C2, and if the level is below a predetermined level, the transistor Q is turned off. becomes.

When the transistor Q is turned off, the capacitor C1 is charged from the power supply via the resistor R2 and the diode Dt-.

Conversely, if the level of the output of the 1-waveform shaping amplifier circuit 13 is within a predetermined level, the transistor Q is turned on and discharged to the ground via the charge resistor R1, which had been charged in the capacitor C1, and the run resistor Q. be done.

To change the charging/failure time constant of the f-V conversion circuit 14Q,
To change the value of the resistor R2 and the discharge time constant, by changing the value of the resistor R1, the charging and discharging time constants can be set arbitrarily.
Can discharge slowly when low frequency is generated. .

Therefore, the f-V conversion circuit 14 responds to the high frequency part (Fig. 3 (2)) of the output signal of the waveform shaping layer width circuit 13, and responds to the low frequency part A (also l [Fig. 3 (2)). 2)) When K is set to respond slowly, the waveform of the output signal of the f-V conversion circuit 14 becomes as shown in FIG. The output signal of 12 is as shown in Figure 3@.

As is clear from comparing the signal in FIG. 3 (G) with the signal in FIG. 3 C), the attenuation in the high frequency part of the FIG. 3 00 signal is l! In the signal shown in Figure 3 ■, the attenuation is /j% lower. Therefore, the output wave of the waveform shaping amplifier circuit 13 will not be lost, and the vortex frequency can be detected accurately.

〔Effect of the invention〕

This invention has been explained above.j9. The charging/discharging time constant of the f-V conversion circuit was set to rapidly charge when a high frequency of the vortex frequency occurs, and discharge slowly when a low frequency occurs.
When high frequency is generated after low frequency, vortex frequency output is large 4@iKm
There is no attenuation, only noise can be accurately removed, and eddy frequencies can be detected accurately.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the eddy current meter of the present invention.
FIG. 2 is a circuit diagram showing the detailed configuration of the f-V conversion circuit in the embodiment, and FIG. 3 is a signal waveform diagram illustrating the operation of the conventional vortex flowmeter and the present invention. 1... Flow meter, 2... Vortex body, 3... Karman vortex street. 4... Ultrasonic transmitter, 5... Ultrasonic receiver, 6...
・Ultrasonic oscillation circuit, 7...Voltage control phase shift circuit, 8
...Waveform shaping circuit, 9...Phase comparator, lO...
Loop fi kfi, 11...Low pass filter, 12
. . . variable frequency filter, 13-. waveform shaping amplification circuit, 14 . -Ngin! W%1N Shun・9; Sase! Figure 2 R5~Rj:j Roaring resistance

Claims (1)

[Claims] A detection means for detecting a vortex signal generated in response to the amount of air taken into the engine, a frequency variable filter that band-passes the output of this detection means, and a waveform shaping and amplification of the output signal of this frequency variable filter to detect the intake air of the engine. a waveform shaping amplifier circuit that outputs a vortex frequency in response to the amount of vortex frequency output, and receives the vortex frequency output and converts it into a voltage corresponding to that frequency to control the passband of the variable frequency filter and adjust the charging time constant and discharging time constant. A vortex flowmeter comprising a frequency-voltage conversion circuit that suppresses attenuation of high frequency components of vortex frequencies by setting each to a predetermined value.