JPS63256822A - Vortex flowmeter - Google Patents

Abstract

PURPOSE:To fix the passing band of a 2nd variable filter circuit to a specific frequency band when the air intake quantity of an engine becomes less than specific pressure, to evade the influence of noise, and to measure a correct vortex frequency by inputting the downstream air pressure signal of a throttle valve to a gate circuit provided on the output side of an F-V converting circuit. CONSTITUTION:A vortex signal generated by the vortex generation body 2 of a vortex flowmeter 1 is passed through a waveform shaping circuit 8, processed by the loop consisting of a phase comparator 9, a loop filter 10, and a voltage-controlled phase shifting circuit 7, and also inputted to a 1st variable frequency filter 12 through an LPF 11. The output of the filter 12 is processed by the 2nd variable frequency filter 13 and a waveform shaping circuit 14 and outputted. The gate circuit 16 is provided on the input side of the F-V converting circuit 15 which controls an intake air quantity with the output of the circuit 14 and the downstream air pressure signal of the throttle valve which controls the intake air quantity is inputted, thereby fixing the passing band of the filter 13 to a specific value with the output of the circuit 16 when the air pressure is lower than specific pressure.

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, a method for determining the correct vortex frequency without erroneously measuring noise that occurs when the air flow rate of the engine decreases. It is designed so that it can be detected.

[Conventional technology]

Conventionally, regarding vortex flowmeters used in engines, for example, Japanese Patent Publications No. 15045/1980, Japanese Patent Publications No. 24363/1983, Publications No. 18332/1983, Publications No. 58/58
No. 6415 is known. Fig. 1 is a block diagram showing a vortex flowmeter of the present invention, which will be described later. When explaining the [prior art], please refer to Fig. 1. . This FIG. 1 also includes a portion of the prior art.

First, in FIG. 1, the portion shown in the above-mentioned Japanese Patent Publication No. 58-56415 will be described. In this Figure 1,
An ultrasonic transmitter 4 and an ultrasonic receiver (= elements 5) are arranged facing each other through a flowmeter 1 having a vortex generator 2, and the flow of a Karman vortex street 3 generated on the downstream side of the vortex generator 2. The ultrasonic transmitter 4 is excited by the ultrasonic oscillation circuit 6 so that the ultrasonic wave is transmitted across the ultrasonic wave.

The ultrasonic wave 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 output 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.

This voltage-controlled phase shift circuit 7 maintains the high frequency stability of the ultrasonic oscillation frequency signal and 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 low-pass 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, adds the comparison result to the loop filter 10, and removes unnecessary frequency components of the comparison result from the loop filter. Remove with 10.

Depending on the output voltage of the 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.

Thereby, 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 a 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 by 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.

That is, the output of the phase comparator M9 is input to the loop filter 10, and is also input to the first variable frequency filter 12 via the low-pass filter 11.

The first variable frequency filter 12 is a high-pass filter, and passes high-frequency components of the output signal of the low-pass filter 11 to the second variable frequency filter 13.
Send to.

This second variable frequency filter 13 is a low-pass filter, and passes low frequency components to the waveform shaping circuit 14.
I am trying to output it to .

In the first and second variable frequency filters 12 and 13, the first variable frequency filter 12 serving as a high-pass filter removes noise components at frequencies below its lower limit passing frequency fL, as shown in FIG. Further, the second variable frequency filter 13, which serves as a low-pass filter, removes noise components caused by the engine having a frequency higher than its upper limit passing frequency 1. Therefore, the pass band of the first and second variable frequency filters 12.13 is between the lower limit pass frequency f and the upper limit pass frequency fu.

The noise of this engine is relatively low frequency noise caused by the pulsation of the air flow, and the so-called wind noise generated when air passes through the air valve. This is relatively high-frequency) noise, or high-output frequency noise that occurs during operations such as turbocharging.

The generation area of these noises changes, and the air miscarriage also changes depending on the instantaneous behavior of the engine, so the band amplification of the vortex frequency is quite wide, and therefore the first and second variable frequency filters 12 .13 is combined.

The vortex frequency signal that has passed through the first and second variable frequency filters 12 and 13 is waveform-shaped and amplified by a waveform-shaping amplification circuit 14, and a local frequency signal is output.

At the same time, the eddy frequency signal is frequency-voltage (hereinafter f-
The voltage is converted into a voltage corresponding to the frequency by a conversion circuit 15 (referred to as V), and the passbands of the first and second variable frequency filters 12 and 13 are controlled by this voltage.

As a result, the passbands of the first and second variable frequency filters change, and the width of the passband indicated by diagonal lines in FIG. 3 changes.

[The gap that the invention attempts to solve]

When this vortex flowmeter measures the amount of intake air in an engine equipped with a supercharger, the vortex signal wave is disturbed by the ultrasonic noise generated by the supercharger. This turbulence increases as the rotation of the supercharger increases, but normally the amount of intake air also increases, and the turbulence increases as shown in FIG. 5 (first frequency shown in al). A, as shown in FIG. 5(b), the signal B that has passed through the second variable frequency filter 13 has 1. The process is removed.

However, when the throttle valve closes suddenly, the rotation of the supercharger does not suddenly decrease due to inertia etc., even though the amount of intake air decreases. As shown in FIG. 6 fbl, the signal at the output end of the second variable frequency filter 13 has a waveform with an extremely poor S/N ratio compared to the signal at the input end of the first variable frequency filter 12.

With this waveform, noise is mistakenly judged to be a signal, and after passing through the second variable frequency filter 13, an extremely high frequency is output. This causes engine stoppage and rough idling.

This invention was made to solve this problem, and it is possible to detect the correct vortex frequency without erroneously measuring the noise that occurs when the air flow rate of the engine decreases, and is extremely excellent for the engine. The purpose is to obtain a vortex flow meter with

[Means for solving problems]

The vortex flowmeter according to the present invention includes a first variable frequency filter that high-passes the FJ signal generated in response to the flow rate of the fluid to be measured, and a second frequency variable filter that low-passes the output of the first variable frequency filter. A variable filter, a waveform shaping amplifier circuit that shapes and amplifies the output of the second variable frequency filter, and converts the vortex frequency output output from the waveform shaping amplifier circuit into a voltage to obtain the first and second frequencies. When the air pressure downstream of the frequency-voltage conversion circuit that controls the pass band of the variable filter and the throttle valve that controls the air amount of the engine becomes a predetermined amount or less, the pass band of at least the second variable frequency filter is changed to the predetermined pass band. It is provided with a means for fixing to.

[For production]

In this invention, the vortex signal generated in response to the flow rate of the fluid to be measured is introduced into the first variable frequency filter, high-passing only the high frequency components, and only the low frequency components are being passed through the second variable frequency filter. Extract only the vortex signal component that has passed and removed the noise component, waveform shape and amplify this vortex signal component to output a desired vortex signal, and convert the voltage corresponding to the frequency of this vortex signal to a frequency-voltage conversion circuit. This voltage is used to control the passbands of the first and second variable frequency filters, and when the air pressure downstream of the throttle valve becomes less than a predetermined value, the passband of at least the second variable frequency filter is controlled to a predetermined value. Fixed to passband.

〔Example〕

Embodiments of the vortex flowmeter of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of one embodiment. In FIG. 1, the description of the parts described in the ``Prior Art'' column will be omitted to avoid duplication.

In this invention, a gate circuit 16 is newly added in addition to the parts indicated by numerals 1 to 15 in FIG.
It is connected between the input terminal of the conversion circuit 15 and the input terminal of the conversion circuit 15.

A pressure signal from a pressure sensor (not shown) is input to this gate circuit 16.

This pressure sensor detects the pressure of the air flow downstream of the throttle valve (not shown), so when this pressure falls below a predetermined value, the gate circuit 16 is activated and the f-V conversion circuit 1
5 is high-passed to fix the passbands of the first and second variable frequency filters to a predetermined passband.

Next, the operation of this invention will be explained.
The operation up to the control of the passband of the frequency variable filters 12 and 13 has already been described.
Here, only the features of this invention will be explained.

Conventional problems occur only in the rapid deceleration region, so a pressure sensor is used to detect the pressure of the air flow downstream of the throttle valve.
A pressure signal from the pressure sensor is input to the gate circuit 916 when it is detected that the pressure value (absolute pressure expression) that occurs when the throttle valve is closed has become equal to or less than a predetermined value.

As a result, the gate circuit 16 high-passes the input of the f-V conversion circuit 15. Therefore, the first and second variable frequency filters 12 and 13 are fixed at low frequencies as shown in FIG.

As a result, high frequency components are forcibly removed.
The signal wave with superimposed noise as shown in ut is the first frequency variable filter! 212, a noise-free signal as shown in FIG. 4 (bl) is taken out at the output end of the second variable frequency filter 13.

FIG. 2 is a block diagram showing the configuration of main parts of another embodiment of the present invention, and portions designated by reference numerals 1 to 10 in FIG. 1 are omitted from illustration in FIG.

In the embodiment of FIG. 2, the input terminal of the f-V conversion circuit 15 is connected to the output terminal of the waveform shaping amplifier circuit 14, and the f-V
The output terminal of the conversion circuit 15 is connected to the input terminal of the reset circuit 17 and the first variable frequency filter 12. Also,
The output of the reset circuit I@17 is applied to the second variable frequency filter 13.

With this configuration, when the pressure sensor detects that the pressure of the air flow on the downstream side of the throttle valve has fallen below a predetermined value, a pressure signal is input from the pressure sensor to the reset circuit 17.

As a result, the reset circuit 917 sends a reset signal to the second variable frequency filter 13, and the f-■ conversion circuit 15
The control of the passband of the second variable frequency filter 13 is reset to fix the passband of the second variable frequency filter 13 to a predetermined band, producing the same effect as the embodiment shown in FIG. 1 above.

〔Effect of the invention〕

As explained above, when the air pressure downstream of the throttle valve that controls the amount of air in the engine falls below a predetermined level,
Since the passband of at least the second variable frequency filter is fixed to a predetermined passband, it is possible to detect the correct vortex frequency without erroneously measuring the noise generated when the air flow rate decreases as the vortex frequency. It becomes possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the vortex flowmeter of the present invention.
FIG. 2 is a block diagram showing the configuration of the main parts of another embodiment of the vortex flowmeter of the present invention, and FIG. 3 is a diagram showing the output frequency versus variable filter passing frequency for explaining the present invention and the conventional vortex flowmeter. Figure 4 is a waveform diagram of the input side and output side of the variable frequency filter of the vortex flow meter of this invention at low rotation speeds after sudden engine deceleration, and Figure 5 is a waveform diagram of the conventional waveform at high engine rotation speeds. 6rIA is a waveform diagram of the input side and output side of the variable frequency filter of a conventional vortex flowmeter at low rotation speed after sudden deceleration of the engine. be. DESCRIPTION OF SYMBOLS 1... Flowmeter, 2... Vortex generator, 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, 10
...Loop filter, 11...Low pass filter,
12...First variable frequency filter, 13...Second
variable frequency filter, 14... waveform shaping amplifier circuit,
15...f-V conversion circuit, 16... gate circuit,
17...Reset circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (3)

[Claims] (1) A detection means for detecting a vortex signal generated in response to the amount of air taken into the engine, a first frequency variable filter circuit that high-passes the output of this detection means, and a low-pass the output of this first frequency variable filter circuit. a second variable frequency filter circuit that shapes and amplifies the output signal of the second variable frequency filter to output a vortex frequency corresponding to the intake air amount of the engine; a waveform shaping amplifier circuit that receives the vortex frequency output; a frequency-voltage conversion circuit that converts the voltage into a voltage corresponding to the frequency and controls the passbands of the first and second variable frequency filter circuits using this voltage;
The invention is characterized by comprising a fixing means for fixing at least the passband of the second variable frequency filter to a predetermined passband when the air pressure downstream of the throttle valve that controls the intake air amount of the engine becomes less than a predetermined amount. Vortex flow meter. (2) The vortex flowmeter according to claim 1, wherein the fixing means is a gate circuit that high-passes the input of the frequency-voltage conversion circuit when the air pressure downstream of the throttle valve becomes lower than a predetermined value. . (3) The fixing means resets the control of the passband of the second variable frequency filter by the output of the frequency-voltage conversion circuit when the air pressure downstream of the throttle valve becomes lower than a predetermined value, and the second variable frequency filter The vortex flowmeter according to claim 1, characterized in that the vortex flowmeter is a reset circuit for fixing the flowmeter to a predetermined passband.