JPS61275621A - Mass flowmeter - Google Patents

Abstract

PURPOSE:To take a measurement at low cost with high sensitivity by providing a detecting means which detects a Coriolis force operating fluid flowing in a tube body owing to vibration and measuring a mass flow rate proportional to the Coriolis force. CONSTITUTION:The tube body 2 forms a cantilever which is fixed on a sealed container 1 at a fulcrum, and a driving coil is arranged, nearby an opening end 51 to drive it for single vibration on a YY' axis. The vibration of this conduit is detected by a detector 4 as electric energy proportional to the amplitude. When the fluid flows as shown by an arrow and the tube body is driven as mentioned above, a Coriolis force is generated in the fluid in the tube body. The Coriolis force operates as a vector quantity in a direction proportional to the vector product of the flow vector of the fluid and the vibration vector. Then, the Coriolis force is applied onto the YY' axis in proportional to the vibration frequency and the mass flow rate of the fluid. In this case, the tube body is straight, so it is easily worked and made thin so as to improve the sensitivity, so that the inexpensive, high-sensitivity mass flowmeter is obtained.

Description

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

(2) Conventional technology When vibration is applied to the fluid flow flowing through the 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.
JP-A-54-52570 discloses a mass flowmeter that utilizes 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. A torsional vibration proportional to the Coriolis force occurs about the vertical U-shaped tube axis. 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 an increase in the area of the U-shaped tube.

This resulted in an increase in the mounting area of the flowmeter. 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 the high-pressure fluid needle side.Furthermore, the fatigue resistance of the fixed part decreases, making it unstable over a long period of time. 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.

(Example) FIG. 1 shows an example of the present invention. (A) Figure is a plan view, (B) Figure is a side view, (C) Figure is AA' of (B) figure.
A closed container 1, shown in cross section as viewed from the arrow, has an inlet 5 for a fluid to flow in from an external flow tube (not shown), a tube body 2 with an open other end 51 is inserted into the closed container, and an outlet 6 is provided. It is a container with The tubular body 2 is formed into a thin cylindrical shape, and is driven by an N moving 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. 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 point of attachment to the closed container l as a fulcrum, but a drive coil is disposed near the open end 51. , (c) Simple vibration driving is performed on the YY' axis in the figure by means described later. Note that from the viewpoint of drive energy efficiency, it is preferable to drive at a resonant frequency, and the vibration of the conduit on the ridge is detected by the detector 4 as an amount of electricity proportional to the magnitude of the amplitude. Reply 7
The rigidity is small in the direction of vibration and increases in the perpendicular direction to reduce the influence of external vibration. Assuming that the fluid flows in the direction of the arrow and 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 (c) zz′ axis, the Coriolis force is YY
' A magnitude proportional to the vibration frequency and the mass flow rate of the fluid is formed on the axis. That is, if the vibration frequency is constant, it works to reduce the amplitude in proportion to the mass flow rate.

In Figure 2, feedback is applied to eliminate changes in amplitude.

FIG. 3 is a block diagram showing a means for instructing a feedback amount proportional to a mass flow rate. The vibration of the tube body is detected as an electric quantity by the detector 4, and the phase of the detection signal is shifted by a predetermined amount by the phase shift circuit 101, so that the closed loop consisting of the amplifier 102 and the drive coil 3 is set to resonate. The phase-shifted detector outputs are resistors R,,R.

The voltage is divided by and input to the amplifier 102, but the amplifier 1
The input of 02 changes the variable resistor R, so that the amplitude of the tube body, that is, the detection signal, is kept constant. For example, a light/resistance converter 103 is used as the variable resistor R.

The light/resistance conversion element 103 is.

Comparison to amplify the deviation signal 107 obtained by comparing the DC voltage proportional to the detection signal obtained by rectifying the detection signal by the rectifier 104 and the DC voltage obtained by dividing the reference DC voltage 105 by the voltage divider 106 so as to have a desired amplitude value. It is connected to amplifier 108 as a load. When the mass flow rate increases and the tube amplitude decreases, the amount of light increases, and the resistance R3 decreases, increasing the gain of the amplifier 102 and increasing the amplitude. Since the output of the comparator amplifier 108 is proportional to the Coriolis force, the indicator 1
Display this in 09.

Although the ridge method is an 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 explanation on the ridge, 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, it is possible to reduce the influence of vibration in two-axis directions that are unnecessary for signal detection.

FIG. 3 shows another embodiment of the present invention, in which components having the same numbers as those in FIG. 1 are shown as being the same. Add the pipe body 2
1 are arranged in parallel with the tube 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 53.5 through which the tubes 2 and 21 are fixed.
4 is perforated. Also, the position of each through hole is
The drive means 3 is electromagnetically connected to the conduit openings 51 .
It is arranged in the middle part near 52.

Each tube is driven in simple harmonic motion on the YY' axis. Detectors 4 and 41 are detectors that detect the amplitude of the tubes, but if each tube vibrates with exactly the same amplitude, only one of them is needed.Normally, the same flow rate flows through each tube. When there is, this condition is met. Therefore, it is possible to apply a measuring means similar to that shown in FIG. In the embodiment shown in Fig. 3, the pipe bodies are arranged in parallel, so 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, a pipe body is provided that generates Coriolis force in the direction of fluid flow, so there is no need to bend the fluid for measurement, and installation is possible 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 drawings]

FIG. 1 shows an embodiment of the present invention, (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. Patent applicant Oval Equipment Industry Co., Ltd. Patent attorney Mori 1) Hiroshi (2 others) 'f+I! ! 1 yf32nd country 3rd m C a)

Claims (5)

[Claims] (1) A container provided with an inlet and an outlet, a main body provided with a tube inside the container, one end of which is fixed in communication with the inlet and the other end is open, and a fixing point of the tube. A method comprising: a drive means for vibrating the tube body around a nearby axis; and a detection means for detecting the Coriolis force acting on the fluid flowing inside the tube due to the vibration; and measuring a mass flow rate proportional to the Coriolis force. A mass flow meter featuring: (2) A claim characterized in that a plurality of tube bodies are arranged in parallel to form a tuning fork, and driving means for driving the tube openings in opposite phases is provided. No. (1)
Mass flow meter as described in section. (3) A mass flowmeter according to claim (1) or (2), characterized in that the pipe body has a rectangular cross-sectional shape. (4) A patent claim 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 fixation of the tube. The mass flowmeter according to any one of items (1) to (3). (5) The detection signal from the detection means is fed back to the driving means to control the driving of the tubular body. Any of the mass flowmeters described.