JPH0454895B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Industrial Application Field The present invention relates to a mass flowmeter that utilizes Coriolis force.

(2) Prior art When vibration is applied to a fluid flow flowing through a flow tube,
It is known that a Coriolis force is generated in a direction perpendicular to the direction of the fluid flow and the vibration axis of the flow tube, and that this Coriolis force is proportional to the vibration frequency and the mass flow rate of the fluid. Japanese Patent Publication No. 54-52570 discloses a mass flowmeter that utilizes the Coriolis force. This conventional example has a body shape in which a U-shaped tube having an inlet and an outlet is fixed to a support member, and fluid flows out from the inlet through the U-shaped tube. When the U-shaped tube is rotated in a direction perpendicular to the surface of the U-shaped tube about the fixation line corresponding to the fixation mentioned above, Coriolis force due to the fluid flowing through the U-shaped tube acts on the fixation line. vertical U
Torsional vibrations proportional to the Coriolis force occur about the axis of the shaped tube. This Coriolis force is determined from the time difference when the tube passes through the reference plane.

(3) Problems to be solved by the invention In the conventional example described above, the Coriolis force is detected as the torsion of the tube body, but in order to cause the torsion, the U-shaped tube body is used to pass the reciprocating path directly through the fluid. .
That is, the fluid is bent at right angles as it enters and exits the tube. In order to effectively detect the Coriolis force, it is necessary to increase the length of the arms of the tube about the fixed line axis and to increase the moment about the U-shaped tube axis. This results in increasing the area of the U-shaped tube,
This resulted in the installation area of the flowmeter being increased. Furthermore, it is advantageous to make the wall thickness of the tube thinner, but this leads to a decrease in pressure resistance, making it unsuitable for high-pressure fluid gauges.Furthermore, the fatigue resistance of fixed parts decreases, resulting in long-term stability. There are problems such as the inability to measure flow rate.

(4) Means for solving the problem The present invention has been made in order to solve the above-mentioned problems. In other words, in order to reduce the installation area of the flowmeter, the tube that vibrates the fluid is made a straight tube along the fluid pipeline, and the Coriolis force can be measured, and even if the wall thickness of the tube is made thinner, The main body shape is such that the tube is inserted into a closed container to withstand measurement of high-pressure fluid.

Embodiment FIG. 1 shows an embodiment of the present invention. Figure A shows a plan view, Figure B shows a side view, and Figure C shows a cross section taken along the AA′ arrow in Figure B. The closed container 1 has an inlet 5 for fluid to flow in from an external flow tube (not shown), a tube 2 with an open other end 51 is inserted into the closed container, and an outlet 6 is provided. The tube body 2 is formed into a thin cylindrical shape, and is driven by a drive coil on the YY′ axis in a single vibration. Therefore, when the drive is performed electromagnetically, the tube is made of a magnetic material, and a magnetic piece is fixed to the surface facing the drive coil.
If the driving means does not rely on electromagnetic force, for example, when an eccentric cam is driven by an electric motor, there is no need for a magnetic material. The tube body 2 forms a cantilever beam with the fixed point with the closed container 1 as a fulcrum, and a drive coil is disposed near the open end 51, and is driven by a simple vibration on the YY' axis in Figure C by means described later. . Note that from the viewpoint of drive energy efficiency, it is preferable to drive at a resonant frequency. The above-mentioned conduit vibration is detected by the detector 4 as an electric quantity proportional to the magnitude. The rib 7 has low rigidity in the vibration direction,
It is made larger in the right angle direction to reduce the influence of external vibrations. Assuming that the fluid flows in the direction of the arrow,
When the tube is driven as described above, a Coriolis force is generated in the fluid within the tube. The Coriolis force acts as a vector quantity whose direction is proportional to the vector product of the fluid flow vector and the vibration vector. Since the vibration vector is on the ZZ′ axis of the diagram, the Coriolis force is
It appears on the YY' axis with a magnitude proportional to the vibration frequency and the mass flow rate of the fluid. That is, if the vibration frequency is constant, it works to reduce the amplitude in proportion to the mass flow rate.

FIG. 2 is a block diagram showing a means for performing feedback so as to eliminate changes in amplitude and instructing a feedback amount proportional to the mass flow rate. The vibration of the tube body is detected as an electric quantity by the detector 4, and the vibration is detected as an electric quantity by the detector 4, and
The phase of the detection signal is shifted by a predetermined amount by
02 and the drive coil 3 is set so that it resonates. The phase shifted detector output is resistor
The voltage is divided by R ₁ and R ₂ and input to the amplifier 102, and the input to the amplifier 102 is made to keep the amplitude of the tube constant, that is, the detection signal, by changing the variable resistor R ₁ . For example, a light-to-resistance converter 103 is used as the variable resistor _R1 . The photoresistance conversion element 103 has a DC voltage proportional to the detection signal obtained by rectifying the detection signal by a rectifier 104, and a DC voltage obtained by dividing a reference DC voltage 105 by a voltage divider 106 so as to have a desired amplitude value. It is connected as a load to a comparison amplifier 108 that amplifies the compared deviation signal 107. As the mass flow rate increases and the tube amplitude decreases, the amount of light increases and the resistance R ₁ decreases, increasing the gain of amplifier 102 and increasing the amplitude. Since the output of the comparator amplifier 108 is proportional to the Coriolis force, the indicator 109 indicates this.

Although the method described above is a specific example, the instruction method is not a problem to be solved by the present application, and other means other than the above are also possible. In the above description, the cross section of the tube is circular, but by making it a rectangular cross section with long sides in the Z-axis direction, the bending rigidity of the tube can be reduced and the detection sensitivity can be increased. Furthermore, since the rigidity in the Z-axis direction is increased, the influence of vibration in the Z-axis direction that is unnecessary for signal detection can be reduced.

FIG. 3 shows another embodiment of the present invention, and components having the same numbers as those in FIG. 1 are shown as being the same. A tube body 2 having the same shape and size as the tube body 2 in the embodiment shown in FIG.
1 is added, and the tubular body 21 is arranged in parallel with the tubular body 2. Inside the closed container 1, a dividing plate 8 is fixed to the inner wall of the closed container so as to face the inflowing fluid and form a fluid chamber 9. The dividing plate 8 has equal-sized through holes 53 and 5 through which the tubes 2 and 21 are fixed.
4 is perforated. Further, it is preferable that the positions of the respective through holes be arranged at equal intervals with respect to the inlet so that the same flow rate flows into the pipe bodies 2 and 21. The driving means 3 is an electromagnet and is arranged in the intermediate part near the conduit openings 51 and 52,
Each tube is driven in simple harmonic motion on the YY′ axis. The detectors 4 and 41 are detectors for detecting the amplitude of the tube bodies, but if the tube bodies vibrate with exactly the same amplitude, only one of them may be used. Normally, this condition is satisfied when the same flow rate flows through each tube. Therefore, it is possible to apply a measuring means similar to that shown in FIG. In the embodiment shown in FIG. 3, since the pipe bodies are arranged in parallel, the pressure loss of the fluid is reduced to 1/4, which is effective. Therefore, four times the flow rate can be obtained with the same pressure loss. Similarly, if the pipe body is constructed with a large number of parallel pipes, the pressure drop effect will be further improved.

(6) Effects As explained above, according to the present invention, the pipe body that generates the Coriolis force in the direction of fluid flow is provided, so the fluid does not bend for measurement and the installation can be performed with less pressure loss. The area also becomes smaller. Furthermore, since the tube is a straight tube, it is easy to process and can be made into a thin-walled tube to increase sensitivity.Furthermore, since the tube opens into a sealed container, there is no need to worry about it being affected by fluid pressure. It is possible to provide an inexpensive and highly sensitive mass flow meter.

Furthermore, since the tube is a simple straight tube, when expanding the flow rate measurement range, it is easy to configure parallel tubes of the same shape and size, making it easy to expand the range of application.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, in which A is a plan view, B is a side view, and C is a front view. FIG. 2 is a block diagram illustrating a measuring means for implementing the present invention such as vibration and detection instructions shown in FIG. 1, and FIG. 3 shows another embodiment of the present invention. In the figure, 1 is a closed container, 2 is a tube body, 3 is a drive coil, 4 is a detector, 5 is an inlet, and 6 is an outlet.

Claims (1)

[Scope of Claims] 1. A container having an inlet and an outlet, a main body having a tube disposed in the container, one end of which communicates with and is fixed to the inlet, and the other end of which is open, and the tube. A mass flow rate proportional to the Coriolis force is provided, comprising a driving means for vibrating the tube body around an axis near the fixed point of the body, and a detection means for detecting the Coriolis force acting on the fluid flowing inside the tube due to the vibration. A mass flow meter characterized by measuring. 2. Claim 1, characterized in that a plurality of tube bodies are arranged in parallel to form a tuning fork, and a driving means for driving the tube openings in opposite phases is provided. Mass flow meter as described in section. 3. The mass flowmeter according to claim 1 or 2, wherein the tube body has a rectangular cross-sectional shape. 4. Claims characterized in that a rib connecting the tube and the container is fixed in the vibration direction of the tube and in a direction perpendicular to the vibration direction and parallel to the tube axis in the vicinity of the tube where the tube is fixed. The mass flowmeter according to any one of items 1 to 3. 5. The mass flow rate according to any one of claims 1 to 4, characterized in that the detection signal from the detection means is fed back to the driving means to control the driving of the tube body. Total.