JPS58153121A - Mass flowmeter - Google Patents

Abstract

PURPOSE:To improve sensitivity, stability, and resolution, by arranging detectors in the vicinity of the positions, where the ratio between an asymmetrical deflection component, which is yielded in a pipe by a Coriolis force and a symmetrical vibration component, which is yielded in the pipe by a driving force, becomes the maximum value. CONSTITUTION:Both ends of the vibrating pipe 1 are fixed to bases 3. The detectors 61 and 62 detect the vibration of the pipe 1. The output signals e1 and e2 are inputted into a phase difference operating circuit. The mass flow rate is obtained from the phase difference. When the vibrating pipe 1 is excited, the symmetrical modes M7 and M8 are yielded by the driving force and the asymmetrical modes M9 and M10 are yielded by the Corilis' force. The detectors 61 and 62 are arranged in the vicinity of the points where the ratio between the displacement components of the asymmetrical deflection vibrations M9 and M10 and the displacement component of the symmetrical deflection vibrations M7 and M8 becomes the maximum value. Thus the sensitivity, stability, and resolution of the flowmeter are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a mass flow meter that utilizes the Coriolis force.

FIG. 1 is the ninth structural explanatory diagram illustrating the operating principle of the Coriolis flow needle. 1 is a 0-shaped tube through which the measurement fluid flows, a permanent magnet 2 is fixed at the center of its tip, and both ends of the 0-shaped tube 1 are fixed to paces 5. 04 is installed opposite to the 0-shaped tube 1. The electromagnetic drive/detection coil 5 is a support beam that supports the electromagnetic drive/detection coil at its tip, and the other end is fixed to the pace S. The υ-shaped tube 1 and the support beam 5 mutually form a tuning fork structure. In other words, the 0-shape tube 1 and the beam 5 vibrate opposite each other, just like the teeth of a tuning fork vibrate, and like a tuning fork, the pace 5 becomes a vibration node and has a configuration in which less vibrational energy is lost. It has become. 61 and 62 are round displacement detectors that detect the displacement of the rain leg of the 0-shaped tube 1.

When the O-shaped tube 1 is excited at its natural frequency by the electromagnetic force acting between the drive coil 4 and the permanent magnet 2 fixed to the O-shaped tube 1 opposing it (longitudinal vibration (symmetrical nine-deflection vibration)): 2nd figure) Ml, M2. M3 indicates each - inter-O pattern)
, a Coriolis force is generated in the fluid flowing inside the U-shaped tube 1.

The magnitude of this Rioli force is proportional to the mass and velocity of the fluid flowing inside the U-shaped tube 1, and the direction of the force corresponds to the direction of the vector product of the fluid motion direction and the angular velocity that excites the O-shaped tube 1. do. Since the direction of the fluid is reversed between the input end and the output side of the 9-U-shaped tube 10, a twisting (asymmetrical deflection) torque is generated in the 8-shaped tube 1 due to the Coriolis on the rain leg side.

This torque varies with the same frequency as the excitation frequency, and its amplitude value is proportional to the mass flow rate of the fluid. jlK2 figure Italy)
It shows the vibration mode (Coriolis vibration mode) caused by the screw sand torque of M4. M5. Me indicates the vibration pattern at each moment. Therefore, the amplitude of this torsional vibration (asymmetrical 9-way vibration) torque is detected by the displacement detector 61.
．． 62, the mass flow rate can be determined by detecting the pulse width, for example.

A mass flow needle using M coral as described above has been known for some time (for example, Japanese Patent Application Laid-Open No. 54-52570), but this has the following problems. In other words, the sensitivity of the mass flow needle is insufficient, resulting in poor 8/N and unstable output.
The drawback is that the scale ability is insufficient, making it difficult to measure minute flow rates.

The present invention has been made to eliminate the above-mentioned drawbacks.
A vibrating mass flow meter (Coriolis flowmeter) that has high sensitivity, stable output, and high resolution.The present invention is based on a Coriolis flowmeter that uses an asymmetrical nine-deflection vibration component that occurs in a pipe line due to a Coriolis force. Sensitivity can be greatly improved by placing the detector near the position where the ratio to the symmetrical 9-way vibration component generated in the pipe by the driving force is maximum, even on the WA surface below 0. 0th XS to explain the invention
a. In oll, which is a diagram showing an embodiment of the straight pipe type Coriolis flow needle of the present invention, 1 has both ends as the base jKl! Vibrating straight pipe, 61.62
Fi is a detector that detects the vibration of this pipe line 1, 7 is a detector 6
1.82 output signal 1.・Input 2 and this signal...
This is a phase difference calculation circuit that calculates the phase difference between signal 2 and signal 2. The phase difference calculation circuit 70 phase difference is proportional to the mass flow rate.

FIG. 4 is an operation explanatory diagram showing a vibration pattern shown by the conduit 1 in FIG. 1. In the figure, M7°M8 are the symmetrical 9-deflection vibration patterns that the straight pipe exhibits at each moment when excited by the driving means, Me, ln.

is a pattern of asymmetrical flexural vibrations caused by Coriolis acting on the fluid flowing in the straight pipe. In reality, the conduit 1 vibrates in a manner in which these two types of vibration patterns are superimposed. If a strain detector such as a piezoelectric element is used as the detectors 61 and 62 in Fig. The ratio ε of the strain component ε caused by the asymmetric 9-way vibration @l generated in the conduit 1 by the driving force and the strain component ε caused by the symmetric 9-deflection vibration generated in the conduit 1 by the driving force. It is approximately proportional to lε. As mentioned above, K, the phase difference is almost proportional to the mass flow rate, so the sensitivity of the flowmeter improves as the strain component ratio 'c''d increases. Figure 5 shows the relationship between strain and 1;
An example of calculation is shown for K (moment) corresponding to the moment m6 due to the driving force. The ratio of the moment m1 and the moment mc1md due to Coriolika is professional and toshi. In the figure, the moment ratio mc/ff1
The value of a shows a peak at positions C and D, but cannot be measured, so if detectors are installed at points A and B near these points at a distance t from the fixed end, the sensitivity of the flow rate needle can be increased. Particularly in the vicinity of points C and D, there is an advantage in that the sensitivity can be greatly increased by simply shifting the position of the detector slightly.

The same applies to the case where displacement detectors such as photodetecting elements are used as the detectors 61 and 62 in FIG.

The larger the ratio ac/d, the higher the sensitivity. Figure 6 shows the displacement component dct da and the displacement component ratio dc/
d.

A calculation example is shown for the displacement component ratio d as in the case of the ssO. /d, is the maximum value O neighborhood M,B
By installing a K detector, the sensitivity of the flow needle O can be greatly improved.

The same applies to the case where moderate detectors are used as the detectors 61 and 62 in FIG.

In addition, in the embodiment shown in FIG. 5, the case where the Coriolis flow needle conduit is a straight pipe is shown. ,
According to Honjitsu@, it is possible to realize a mass flow needle with high sensitivity, excellent 1it/N, stable output, and high-resolution measurement of the amount of waterfall using a simple method.

[Brief explanation of drawings]

Figure 1 is a diagram of the operating principle of the Coriolis flow needle, Figure 2 (4)
, 0) is an operation explanatory diagram of FIG. 1, and FIG. 3 is a -vI diagram of the present invention.
4IiI is a diagram explaining the operation of FIG. 5, and FIG.
6. Curve Diagram Regarding Movement and Its Ratio, No. 6 is a line diagram regarding displacement and its ratio for determining the position of the displacement detector. 1...Pipeline, 61.62...Detector, M7. M8
... Symmetrical deflection friction component (pattern), M9. M.I.
O...Asymmetric deflection friction component (pattern). ’ ) Agent Patent Attorney Nobu Isao Ozawa Figure 1

Claims (1)

[Claims] In a mass flowmeter that has a configuration in which fluid flows in a vibrating pipe, Coriolis force is generated by the flow and angular vibration of the pipe, and the pipe deforms and vibrates, the asymmetric deflection vibration component generated in the pipe by Coriolis and A mass flow rate needle characterized in that a detector is provided in the vicinity of the lid at a position where the ratio to the symmetrical deflection vibration component generated in the conduit due to the driving force is maximum to improve sensitivity.