JPH0322563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an area flow meter, and more particularly to a flow rate and flow rate change rate detection device suitable for simultaneously detecting the flow rate and rate of change in flow rate of a fluid flowing in a pipe. It is something.

[Conventional technology]

2. Description of the Related Art Conventional area flowmeters generally include those in which a moving body is provided inside a pipe through which fluid passes, and the displacement of this moving body is detected by electrical means.

That is, the area flow meter described in Japanese Patent Publication No. 49-41329 has a plunger made of a magnetic material provided inside an excitation coil and a differential transformer electromagnetically coupled to the excitation coil. Also, JP-A-52-
The area flow meter described in Publication No. 92554 had a core made of a magnetic material with high magnetic permeability such as soft ferrite inside a differential transformer.

[Problem to be solved by the invention]

The conventional flowmeter described above has a magnetic material installed in the movable orifice, and detects the flow rate by measuring the phase and amplitude of the AC voltage depending on the magnitude of the displacement. Therefore, it is simply used to detect only the fluid flowing inside the pipe. When a flowmeter with such a structure is applied to a hydraulic servo system and used as a detection means for feedback control, it can only perform flow rate feedback, and there is no way to measure the rate of change in flow rate. However, the control performance could not be improved. Alternatively, there is a method of measuring other physical quantities equivalent to the rate of change of flow rate and providing feedback, but this requires two detection devices and
As the device becomes more complex, various problems arise in terms of responsiveness, safety, accuracy, etc., and the reliability of measurement is impaired.

The present invention provides a highly reliable fluid flow rate and flow rate change rate detection device that can simultaneously detect the fluid flow rate and flow rate change rate with a single detection device when applied to feedback control of a servo system. The purpose is to

[Means to solve the problem]

In order to achieve the above object, the present invention includes a fixed orifice provided in a pipe through which a fluid flows;
Together with this fixed orifice, a movable orifice is formed that moves inside the tube by the differential pressure generated before and after the constriction depending on the flow rate of the fluid. a primary coil for AC excitation, and two secondary coils for detection that detect movement of the movable orifice wound on both sides of the primary coil along the outer wall of the tube, The main body of the movable orifice is formed of a ferromagnetic magnet, the protrusion forming the aperture of the movable orifice is formed of a non-magnetic material, and each induced electromotive force generated in the secondary coil is inputted. , a first subtractor that calculates a difference voltage between these voltages to obtain a fluid flow rate change rate, and two synchronous rectifiers that perform synchronous rectification by inputting the respective induced electromotive voltages generated in the secondary coil. , and a second subtractor that calculates the fluid flow rate by calculating the difference between the signals rectified by the two synchronous rectifiers.

[Effect]

The movable orifice body is formed of a ferromagnetic magnet, such as a permanent magnet, and the fixed orifice and the movable orifice protrusion are formed of a non-magnetic material. This improves the S/N ratio of the induced electromotive force induced in the secondary coil according to the displacement of the movable orifice, and prevents iron powder, etc. contained in the fluid flowing inside the pipe from adhering to the constricted part. , measurement using the aperture effect can be performed with high precision. The difference in the induced electromotive force induced in the secondary coil can be directly determined by improving the S/N ratio, and from that value the speed of the movable orifice can be determined, and at the same time, the induced electromotive voltage in the secondary coil can be synchronously rectified. From the latter difference, the magnitude and direction of the displacement of the movable orifice can be determined. The displacement of the movable orifice corresponds to the flow rate of the fluid, and the speed of the movable orifice corresponds to the rate of change in the flow rate of the fluid. Therefore, the flow rate and rate of change in flow rate can be detected simultaneously with high accuracy without the need for differentiation, which increases reliability. Improvements will be made.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of an embodiment of the device of the present invention. In this figure, a fixed orifice 2 with a shape symmetrical to the tube axis is connected to a pair of left and right rods 3A and 3B inside a stainless steel tube 1 made of a non-magnetic material through which the fluid through which the flow rate and rate of change in flow rate are to be measured passes. and is attached to supports 4A and 4B. Each support plate 4A, 4B has flow holes 5A and 5B, respectively, and is fixed to the inner wall of the tube 1. On the other hand, a movable orifice body 6 is made of a magnet made of a ferromagnetic material (that is, a permanent magnet) and is shaped to form an aperture between it and the fixed orifice 2, and a movable orifice protrusion 6B. 6 are provided so as to be movable in the left and right directions in the figure along the central axis of the tube 1 when a spring 7 acts, using the inner wall of the tube 1 as a guide.
In addition, an orifice protrusion 6B made of a specific magnetic material is provided at the tip of the movable orifice body 6A, and the orifice protrusion 6B is made of a specific magnetic material and operates integrally with the movable orifice body 6A. This is to prevent movement from being hindered.

A primary coil 8 for alternating current excitation necessary for detecting the displacement of the movable orifice 6 is provided on the outer wall surface of the tube 1 . An AC voltage source 9 is connected to the primary coil 8 . On the other hand, 1 for AC excitation
The left and right sides of the next coil 8 detect the movement of the movable orifice 6 to the right and to the left in the figure, respectively, and output signals corresponding to the amount of movement and signals corresponding to the rate of change, that is, the speed of the movable orifice 6. Secondary coils 10 and 11 for detection to output
are provided for each. Reference numeral 12 denotes an arithmetic device which extracts outputs from the secondary coils 10 and 11 for detection and separates the displacement of the movable orifice 6 and its rate of change, ie, velocity component. 13 is a flange for mounting. The arithmetic unit 12 mentioned above will be described in detail later.

In the embodiment of the device of the present invention described above, for example, hydraulic oil flows through the flow holes 5 of the support plates 4A, 4B of the pipe 1.
When the fluid flows in from A or 5B, the movable orifice 6 moves to the right or left in the figure depending on the differential pressure across the throttle caused by the flow. The displacement and speed of the movable orifice 6 due to the movement of the movable orifice body 6 made of a ferromagnetic magnet are detected by the secondary coils 10 and 11 for detection, and the displacement of the movable orifice 6 is detected by the arithmetic unit 12. and velocity components are separated. These two output signals are used as a flow rate feedback signal and a flow rate change rate feedback signal for the servo system, and are also used independently to measure the flow rate and flow rate change rate.

Next, the specific operating principle of the arithmetic unit 12 will be explained in the second section.
This will be explained with reference to FIG. FIG. 2 shows an equivalent electric circuit consisting of a primary coil 8 for AC excitation, secondary coils 10 and 11 for signal detection, a movable orifice body 6A, and a movable orifice protrusion 6B.
When the AC voltage source 9 applies an AC voltage to the primary coil 8, if the movable orifice 6 changes by x amount from the neutral position, the secondary coil 10 for detection
The induced electromotive voltages E ₁ and E ₂ generated at 11 and 11 are as follows.

E ₁ = πdnB _o dx/dt+K{1/2{(l-a)-x}dI
/dt...(1) E ₂ =-πdnB _o dx/dt-K{1/2{(l-a)+x}
dI/dt...(2) Here, d is the coil diameter, B _o is the magnetic flux density generated by the movable orifice made of a magnet, l is the total length of the movable orifice 6, and a is the coil of the secondary coils 10 and 11 for detection. I is the current flowing through the primary coil 8, and n is the coil winding of each of the secondary coils 10 and 11.

It can be seen that the first term in equations (1) and (2) corresponds to the velocity of the movable orifice 6, and the second term corresponds to the displacement component of the movable orifice 6.

FIG. 3 shows a block diagram for separating the voltages in which the displacement and velocity components of the movable orifice 6 induced in the secondary coils 10 and 11 for detection are superimposed. In this Fig. 3, the secondary coil 1 for detection
The output power of 0 and 11 is E ₁ , E ₂ as follower 14,
The movable orifice 6 is individually synchronously rectified by synchronous rectifiers 16 and 17 via 15, and both signals after the synchronization are subtracted by a subtracter 18, passed through a reduction filter 19, and amplified by an amplifier 20. A DC voltage signal of displacement can be extracted.

Next, the output signals E ₁ and E ₂ of the secondary coils 10 and 11 for detection are subtracted by a subtracter 21, passed through a reduction filter 22, and amplified by an amplifier 23. The speed can be extracted as a DC voltage signal.

By detecting the displacement and velocity of the movable orifice 6 in the tube 1 in this way, the
In order to obtain an output proportional to the flow rate and flow velocity of the fluid passing through it, the aperture area S of the diaphragm formed by the fixed orifice 2 and the movable orifice 6 must have an appropriate functional form with respect to the movement amount x of the movable orifice 6. It is necessary that Here, the relationship between the flow rate Q, the pressure receiving area A of the movable orifice 6, the moving distance x, the differential pressure ΔP at the throttle part between the fixed orifice 2 and the movable orifice 6, the flow coefficient C, and the fluid density ρ is expressed by the following equation. A relationship is established in which

AΔP=Kx …(4) (K: Spring constant) From the above equations (3) and (4) Here, in equation (5), if S(x)=β√...(6), Therefore, the displacement x of the movable orifice 6 is proportional to the flow rate Q. Further, the velocity dv/dt of the movable orifice 6 is proportional to the fluid flow velocity dQ/dt. Here, the magnitude of the speed of the movable orifice 6 is determined by the magnetic flux density of the magnet as shown in equation (1) or (2), so if the movable orifice body 6A is made of a ferromagnetic magnet, It can also detect minute speeds. Therefore, it is possible to provide a device that can detect even minute flow rates of fluid and detects flow rates and flow rate changes with high sensitivity.

In the above-described embodiment of the present invention, a restriction made of a fixed orifice 2 made of a non-magnetic material and a movable orifice main body 6A made of a ferromagnetic material is used, and the pressure difference between before and after the restriction is determined depending on the flow rate of the fluid to be measured. This constitutes a flow rate and flow rate change rate detection device that detects the flow rate value from the amount of movement of the movable orifice 6 that is displaced by the movement of the movable orifice 6, and the flow rate change rate from the velocity amount of the movable orifice 6. The calculation device 12 that separates the displacement and velocity of 6 is provided, and the output thereof is taken out as a flow rate value and a flow rate change rate value for servo system feedback control etc. using a single detector. It is possible to prevent a decrease in measurement accuracy due to uneven operation of the detection mechanism, such as in the combination of a follower and a potentiometer. Additionally, in conventional flowmeters, there was no way to measure the fluid change rate without differentiating the flow rate.
According to the present invention, a wide range of flow rates and flow rate changes from low flow rates to large flow rates can be detected. Furthermore, since the flow rate and the rate of change in flow rate can be detected with one detection device, the detection device becomes compact. In addition, since a non-magnetic throttle is attached to the protrusion of the movable orifice 6 integrally with the movable orifice body 6A, the operation of the movable orifice 6 will not be hindered by adhesion of iron powder etc. mixed in the hydraulic oil. .
Furthermore, the shape of the fixed orifice 2 is processed so that the aperture opening area and the moving amount of the movable orifice have an appropriate functional form, so that the detected value proportional to the flow rate and the detected value proportional to the flow rate change rate can be Obtainable. Therefore, the flow rate and flow rate change rate detection device according to the present invention can be widely applied not only when using these signals for feedback control of a servo system but also to measuring the flow rate and flow rate change rate of general fluids. .

〔Effect of the invention〕

As described above, according to the present invention, the flow rate and the rate of change in flow rate can be simultaneously detected with high precision using one detection device without using operations such as differentiation. As a result, a signal with small noise can be used for servo system feedback control, and can also be widely applied to measurement of flow rate change rate, etc.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the flow rate and flow rate change rate detection device of the present invention, and Fig. 2 is an equivalent electric circuit diagram of the movable orifice, primary coil, and secondary coil portion used in the present invention. , FIG. 3 is a block diagram showing an arithmetic device for separating output signals of flow rate and rate of change of flow rate. 1...Pipe, 2...Fixed orifice, 6...Movable orifice, 6A...Movable orifice body, 6B
... Non-magnetic movable orifice projection, 7 ... Spring, 8 ... Primary coil, 9 ... AC power supply, 10,
11... Secondary coil for detection, 12... Arithmetic unit, 14, 15... Follower, 16, 17... Synchronous rectifier, 18, 21... Subtractor, 19, 22...
Reduction filter, 20, 23...amplifier.

Claims (1)

[Claims] 1 A fixed orifice made of non-magnetic material provided in a pipe through which fluid flows, and a movable orifice that forms a throttle together with this fixed orifice and moves inside the pipe by the differential pressure generated before and after the throttle depending on the flow rate of the fluid. an orifice, a primary coil for alternating current excitation wound around the outer wall of the tube along the movement range of the movable orifice, and a primary coil for alternating current excitation wound around the outer wall of the tube on both sides of the primary coil. The main body of the movable orifice is formed of a ferromagnetic magnet, and the protrusion forming the aperture of the movable orifice is made of a non-magnetic material. The first step is to input the respective induced electromotive voltages generated in the secondary coil and calculate the difference voltage between these voltages to obtain the rate of change in fluid flow rate.
a subtracter, two synchronous rectifiers that perform synchronous rectification by inputting the respective induced electromotive voltages generated in the secondary coils, and a fluid by subtracting the difference between the signals rectified by the two synchronous rectifiers. 1. A flow rate and flow rate change rate detection device, comprising: a second subtractor for determining the flow rate.