JPH067323Y2 - Mass flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a mass flow meter capable of measuring a mass flow rate of a fluid with high accuracy and displaying it digitally.

<Prior Art> As a conventionally known mass flowmeter, there is, for example, “Aeronautical Engineering Course (4), Aviation Instrument” (published by Japan Aeronautical Engineering Association).

FIG. 3 is a configuration block diagram showing a conventional mass flow meter.

In FIG. 3, reference numeral 1 is a mass flow transmitter (hereinafter abbreviated as “oscillator”) which is mounted on a measuring pipe through which a measurement fluid (hereinafter abbreviated as “fluid”) Q flows. This transmitter 1
Is composed of an impeller 2 that is a rotating body, and a detection unit α including a turbine that will be described later and that is installed in a subsequent stage of the impeller 2. Here, the impeller 2 is attached to a rotation center shaft 2a located parallel to the upstream pipe axis, has a circulation port 2b in the periphery, and is driven by a power source supplied from a power source unit E, such as a synchro motor M or a gear. The rotation drive unit including the row H is given a rotational force to rotate. On the other hand, the detection unit α is the turbine 4
And a stop spring 5 for stopping the rotation of the turbine 4 to balance the turbine 4 at a displacement angle proportional to the flow rate of the fluid Q, and a magnesin 6 electrically coupled to the turbine shaft 4b. Here, the turbine 4 is the impeller 2
Is connected to the impeller 2 by a fixed disk 3 and is installed on the turbine shaft 4b which has almost the same structure as the impeller 2 and is coaxial with the rotation center shaft 2a of the impeller 2. , A fluid Q indicated by an arrow F given a rotational force (torque) according to the flow rate by the impeller 2.
To detect the flow rate of.

This will be described in more detail.

_A fluid Q indicated by an arrow F _A is given a rotational force by a synchro motor M through a flow hole 2a of an impeller 2 rotating at a constant angular velocity ω, and a turbine 4 is indicated by an arrow F _B.
Flow into the flow hole 4a and further flow out to the outlet. At this time, the rotation of the impeller 2 imparts a certain rotation speed to the fluid Q flowing through the flow hole 2a. As a result, a certain torque is applied to the fluid Q flowing into the turbine 4. When the fluid Q passes through the impeller 2, the fluid Q receives a force in the rotational direction by the impeller 2 and is given an angular momentum of inertia ratio (I) of the fluid Q × angular velocity (ω) of the impeller 2. At the same time, as a reaction, the impeller 2 obtains a load, which is a reaction torque of the angular momentum Iω, in the direction opposite to the rotation direction from the fluid Q. Although not described, this reaction torque is directly proportional to the mass flow rate. As a result, the turbine shaft 4b stops at a displacement angle in which the torque given by the fluid Q and the stop spring 5 are balanced. This displacement angle is converted into an electric signal by the pick-off coil 6a of the magnesin 6 and the rotor 6b which are electrically coupled to the turbine shaft 4b.
The electric signal converted by the magnesin 6 is sent to the coil 7a of the calibration device 7, rotates the rotor 7b, and the calibration mass flow rate is displayed by the indicator 7c which operates in conjunction with the rotation of the rotor 7b. It That is, the calibration device 7
A standard unit of an indicator that indicates an accurate value (a turbine shaft position proportional to the flow rate Q) for the output signal of the transmitter 1 to be calibrated, and a pick-off coil 6a of the magnesin 6
And the coil 7a are connected to each other. For this connection, for example, 115
An AC voltage of V400 Hz (all numerical values are taken as an example in the description of the present application) is excited from an AC power supply E, and as a result, an indicator 7c operating by the rotation of the rotor 7b is used to give an instruction. . Turbine 4
Since the torque received from the fluid detected in 1 is directly proportional to the mass flow rate, the mass flow rate of the fluid Q passed through the calibration device 7 can be accurately calibrated and displayed from the displacement angle of the turbine shaft received by the magnesin 6.

<Problems to be Solved by the Invention> By the way, the conventional mass flowmeter is required to have high accuracy as an indicator. However, in order to manufacture a highly accurate calibration device in such a calibration device, high-precision parts are required as a whole, such as a coil 7a without winding irregularities and a rotor 7b of a magnet requiring high positional accuracy. In addition, maintenance is always required to maintain reliability,
There is a problem.

The present invention has been made in view of the problems of this conventional technique, and utilizes a display means such as a commercially available synchronous digital converter (hereinafter referred to as "S / D converter"). Therefore, it is an object of the present invention to provide a highly reliable mass flowmeter having no moving parts.

<Means for Solving the Problems> In order to achieve such an object, the present invention converts the force of a stop spring that stops the rotation of a turbine to which torque is applied by a fluid to which the rotation is applied, into an electric signal. Magnesin and second harmonic component passage means for removing the fundamental frequency signal supplied to the magnesin from the combined signal obtained from the pickoff coil of the magnesin with a phase difference of 120 ° and passing only the second harmonic component; Reference signal generation means for attenuating and squaring the fundamental frequency signal to obtain a reference signal synchronized with the phase of the filtering signal output from the second harmonic component passing means, and inputting the filtering signal to a Scott transformer At the same time, a reference signal is input from the reference signal generating means, A synchro digital converter that displays a digital amount corresponding to the angle of the rotor of the shin is provided, and the mass flow rate of the fluid is converted into a digital amount by the synchro digital converter based on an electric signal obtained from the magnesin. It is characterized by converting and measuring.

<Embodiment> An embodiment of the present invention will be described in detail below with reference to the drawings.
In the following drawings, the same parts as those in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 is a block diagram showing the configuration of an embodiment of the mass flowmeter of the present invention.

In FIG. 1, the pickoff coil 6 of the magnesin 6 is shown.
An alternating voltage of, for example, 115 V 400 Hz is excited from a power source section E to a. Therefore, the output end connected to each part of the pickoff coil 6a changes with respect to the fundamental frequency of 400 Hz and the fundamental frequency from the pickoff coil 6a by the rotor 6b that rotates in conjunction with the rotational position of the turbine 4, for example. A combined signal a (individually referred to as first to third combined signals a _{1 to} a ₃ ) which is a combined voltage output of the second harmonic of 800 Hz is output. Reference numeral 8 is a means for inputting the composite signal a from the pickoff coil 6a and passing only the second harmonic component (hereinafter referred to as second harmonic component passing means). Here, it is composed of a cut filter composed of the first filter 8 ₁ , the second filter 8 ₂ and the third filter 8 _3, and the filtering signal b (individually b
_{1 to} b ₃ ) are output. Reference numeral 9 is connected to the power supply section or the pickoff coil 6a, and is a basic signal c having the above-mentioned basic frequency.
Is input to generate a reference signal for phase detection synchronized with the filtering signal b for comparison with the filtering signal b by means for displaying a calibration mass flow rate described later (hereinafter referred to as reference signal generating means). . Here, for example, an attenuator 9 ₁ that attenuates the basic signal c
In order to input the attenuation signal d from the attenuator 9 ₁ to make the fundamental frequency of 400 Hz to be the second harmonic of 800 Hz, the square circuit 9 ₂ and the square circuit 9 ₂ which square the fundamental frequency D for cutting and filtering the DC component of the squared signal e
From the C-cut filter 9 ₃ and the phase-shift circuit 9 ₄ which inputs the signal f filtered by the DC-cut filter 9 ₃ and shifts the phase to a phase synchronized with the filtering signal b and outputs the reference signal g. Become. 10 is these 2
Means for displaying the calibrated flow rate mass of the fluid Q using the signals b, g from the two means 8, 9 (hereinafter referred to as synchro digital
It is called a converter). Examples of the display means include a Scott transformer, a COS multiplier, which inputs a commercially available synchro signal to a Scott transformer and outputs an angle weight digital amount corresponding to the synchro angle.
SIN multiplier, phase shift detection circuit, reference transformer to which the reference signal is input, UP / DOW
S / D converter consisting of N counter, etc. (Detailed structure and operation are described in, for example, Electronics Digest, April 1976, "Special A / D / D / A converter application technology, pages 15 to 21"). Since this is a known technique, the description thereof will be omitted) can be used.

FIG. 2 is a signal waveform diagram for explaining the operation of FIG.

The description will be continued below with reference to FIGS. 1 and 2.

In FIG. 2 (a), (a) is the fundamental frequency c of 400 Hz, and (b) is the position of the turbine 4 at 800 Hz.
The second harmonic that changes with respect to the fundamental frequency of (c) represents the combined signal a of (a) and (b). The second harmonic of 800 Hz in the combined signals a _{1 to} a ₃ has a phase difference of 120 ° depending on the position of the rotor 6b. Second
The composite frequency of FIG. 7A has a phase difference of 120 ° from each other by passing through the _first to _third filters 81 to 83, and the second harmonic of 800 Hz as shown in FIG. 2B. Is taken out. At this time, the further filtered phase is obtained with a shift as shown in the figure. Figure 2 (c) shows 115V40
It is a basic signal c of 0 Hz. This basic waveform c is the attenuator 9
Attenuated by ₁ , for example 10V40 as shown in Fig. 2 (d)
The attenuation signal d is 0 Hz. This attenuation signal d is 800Hz
Is guided to the squaring circuit 9 ₂ to obtain the second harmonic of
The 800 Hz second harmonic signal e with the zero point shifted as shown in FIG. The DC component of the second harmonic wave e is cut and filtered by the DC cut filter 9 ₃ to obtain the filtered second harmonic signal f as shown in FIG. In order to make the phase of this second harmonic signal f the same as the phase of FIG. 2 (b), it is led to the phase shift circuit 9 ₄ to obtain the reference signal g as shown in FIG. 2 (g).
Specifically, the reference signal g is shifted so as to have the same phase as, for example, the phase of the filtering signal b ₁ of the first filter 8 ₁ which serves as a reference at this time at the position of the rotor 6b when the flow rate is zero. transfer adjusting the phase circuit 9 ₄ the phase of the second harmonic signal f as shown in FIG. 2 (g).
A reference signal g obtained from the phase shift circuit 9 ₄ By as shown in FIG. 2 (g), the reference signal g
Is the basic signal waveform of the frequency and phase of the filtering signal b. Therefore, the S / D converter 10 of the display means can digitally display the calibration mass flow rate of the fluid Q from the filtering signal b and the reference signal g.

By the way, the present invention is not limited to FIG.
For example, although 400 Hz was used as the fundamental frequency, the fundamental frequency is not limited to this, and in this case, the second harmonic is 800
Needless to say, it does not become Hz. Also, the display means is S
The / D converter may be replaced with another one having a similar function to compare the filtering signal b and the reference signal g.

<Effects of the Invention> As described above in detail with reference to the embodiments of the present invention,
According to the mass flowmeter of the present invention, it can be configured with a simple structure, does not require a movable part unlike the magnesin system, and is configured with an electronic circuit, so it is highly reliable and easy to manufacture. Therefore, an inexpensive product can be realized.
In addition, there is an effect that maintenance becomes easier.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the mass flowmeter of the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of FIG. 1, and FIG. 3 is a configuration showing a conventional mass flowmeter. It is a block diagram. DESCRIPTION OF SYMBOLS 1 ... Mass flow rate transmitter (transmitter), 2 ... Rotating body (impeller), 4 ... Turbine, 5 ... Stop spring, 8 ... 2nd harmonic component passage means, 9 ... Reference signal generation means, 1
0 ... Synchronous digital converter.

Claims (1)

[Scope of utility model registration request] 1. A magnesin that converts the force of a restraining spring that restrains the rotation of a turbine to which torque is applied by a fluid that is given a rotation into an electric signal, and a composite signal obtained from a pickoff coil of the magnesin at a phase different by 120 °. Second harmonic component passing means for removing the fundamental frequency signal supplied to the magnesin and passing only the second harmonic component; and attenuating and squaring the fundamental frequency signal to pass the second harmonic component. A reference signal generating means for obtaining a reference signal synchronized with the phase of the filtering signal output from the means, and the filtering signal is input to a Scott transformer, the reference signal is input from the reference signal generating means, and the rotor of the magnesin Synchro display that displays the digital amount corresponding to the angle of And Tal converter, the provided mass flow meter the mass flow rate of the fluid was characterized by measuring into digital amount by the synchro-to-digital converter based on the electric signal obtained from said Maguneshin.