JPH04155221A - Corioli's mass flowmeter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a Coriolis mass flowmeter that can shorten the pipe length and reduce the excitation force.

<Prior Art> FIG. 7 is a diagram illustrating the configuration of a conventional example that has been commonly used.

In the figure, 1 is a U-shaped measurement tube attached to piping A at both ends.

2 is a flange for attaching the measuring tube 1 to the tube HA.

Reference numeral 3 denotes a vibrator provided at the tip of the U-shaped measuring tube 1.

4.5 are displacement detection sensors provided on both sides of the measuring tube 1, respectively.

In the above configuration, the measurement fluid is flowed through the measurement tube 1, and the vibrator 3 is driven. @ Angular velocity in the vibration direction of mover 3 “ω
'', the flow velocity of the measured fluid is ``V'' (hereinafter the symbol enclosed in ``'' represents a vector quantity), then the amplitude of the vibration proportional to the Coriolika acting on the Coriolika of ``Fc--2m rωj X rV'' is measured. if,
Mass flow rate can be measured.

However, in general, the amplitude of vibrations proportional to Coriolis is extremely smaller than the amplitude of vibrations caused by excitation, and it is not possible to directly detect the amplitude of vibrations proportional to Coriolis.

Now, when viewed from the Z direction in Fig. 7, the vibration direction is divided into α and β due to the vibration of the vibrator 3, and the flow velocity r■.
As shown in FIGS. 8(A) and 8(B), the direction of Coriolis differs depending on the direction of the measuring tube 1, resulting in an opposite phase, and the measuring tube 1 vibrates while being twisted.

The displacement is detected by the displacement detection sensors 4 and 5, for example, a magnetic sensor, and the phase difference between the displacements of the displacement detection sensors 4 and 5 is (
The mass flow rate can be determined because it is proportional to the amplitude of the vibration proportional to Coriolis (@)/(amplitude of the vibration due to excitation).

Since the phase difference can be measured as the difference Δt in time at which the waveform crosses zero, Coriolis can be measured as a result.

FIG. 9 is a diagram illustrating the configuration of another conventional example that has been commonly used.

In this conventional example, the measuring tube 1 is of a two-tube type in order to further reduce noise and increase the signal.

<Problem to be solved by the invention> However, in such a Coriolis mass flowmeter, when the pipe has a large diameter, in order to vibrate the pipe,
A very large force is required, which not only makes the vibrating section and pipe fixing section large-scale, but also causes gaps in terms of durability.

The present invention solves this problem.

An object of the present invention is to provide a Coriolis mass flowmeter that can shorten the pipe length and reduce the excitation force.

Means for Solving the Problems> In order to achieve this object, the present invention provides a Coriolis mass flowmeter that measures mass flow rate using Coriolis force. a reference axis, an inner pipe provided concentrically with the reference axis, closed at both ends and fixed to the reference axis, and an inner pipe provided between the inner pipe and the reference axis to excite the inner pipe. a vibration excitation means; a displacement detection means for detecting displacement of the inner pipe and the reference shaft on both sides of the vibration excitation means;
an outer pipe provided on the outer side of the inner pipe concentrically with the reference axis and through which a measurement fluid flows between the inner pipe and the inner pipe; and a coupling plate for coupling the outer pipe and the inner pipe. This is a Coriolis mass flowmeter.

<Operation> In the above configuration, the measurement fluid is flowed between the outer pipe and the inner pipe, and the excitation means is driven.

The inner pipe vibrates by driving the vibrating means.

Assuming that the angular velocity in the vibration direction is "ω" and the flow velocity of the measurement fluid flowing inside the outer pipe is "v", Fc==-2m'ωjX
Depending on the direction of the flow rate r V J where Coriolis of rVj acts,
The inner pipe is deformed by Coriolika, and the inner pipe is deformed.

This deformation is detected by the displacement detection means, and a differential calculation is performed to measure the mass flow rate from which the influence of noise has been removed.

Hereinafter, a detailed explanation will be given based on examples.

<Example> Fig. 1 is an explanatory diagram of the main part configuration of an embodiment of the present invention, Fig. 2 is a cross-sectional view taken along line AA in Fig. 1, and Fig. 3 is a cross-sectional view taken along line B-B in Fig. 1. .

Reference numeral 11 denotes a highly rigid reference shaft provided at the center of the conduit in the direction of the conduit.

Reference numeral 12 denotes an inner pipe that is provided concentrically with the reference shaft 11 and fixed to the reference shaft 11 with both ends closed.

Reference numeral 13 denotes an excitation means that is provided between the inner pipe 12 and the reference shaft 11 and vibrates the inner pipe 12 in the Z force direction.

Reference numeral 14 denotes displacement detection means that is provided between the inner pipe 12 on both sides of the vibration excitation means 13 and the reference shaft 11, and detects the displacement of the inner pipe 12.

In this case, the displacement detection means 14 consists of a permanent magnet and a coil, and detects displacement from changes in induced electromotive force.

Reference numeral 15 denotes an outer pipe that is provided outside the inner pipe 12 concentrically with the reference axis 11 and through which the measuring fluid flows between the inner pipe 12 and the inner pipe 12 .

16 is a connecting plate that connects the outer pipe 15 and the inner pipe 12.

Reference numeral 17 denotes a case that covers the outer pipe 15 and also serves as vibration isolation.

18 is a flange for connecting to piping.

In the above configuration, the measuring fluid is caused to flow through the outer pipe 15, and the excitation means 13 is driven.

The inner bi 112 is vibrated by the driving of the vibrating means 13.

If the angular velocity in the vibration direction is "ωJ" and the flow rate of the measurement fluid flowing inside the outer pipe 15 is rVJ, then Fc = -2
Coriolis of m'(dJ x rV) acts, flow rate r
Depending on the direction of yJ, the inner pipe 12 is deformed by Coriolis, and the inner pipe 12 is deformed. This deformation is detected by the displacement detection means 14, and a differential calculation is performed to measure the mass flow rate from which the influence of noise has been removed.

That is, by driving the vibrating means 13, the inner pipe 12
vibrate to create a first-order mode resonance state with both ends fixed.

From the state where the inner pipe 12 is not deformed, due to vibration,
Consider the case of deformation as shown in FIG.

If there is no deformation of the inner pipe 12, the measured fluid particles should originally move along the vector rAAr0, as shown in FIG.
r Do an exercise like J. rArA, which is the deformation of the flow path
The force rOJ is due to the force received from the pipe, and the force rArArOJ is applied to the inner pipe 12 as a drag force.

In the vicinity of the inner pipe 12, the measuring fluid
It follows the deformation of .

That is, since the measured fluid near the inner pipe 12 has a velocity component in a direction perpendicular to the pipe axis direction, Coriolika Fc
:2ρsvω=2Qω is added to the pipe (ρ: density of the measured fluid, S: unit area, V: flow velocity of the measured fluid, ω: angular velocity around the center of rotation), from the inner pipe 12 (y,
A fluid particle with (Ry, Rz>M) in the direction (R
y.

Rz)Qωayaz=2KQω (1).

(K is determined from the diameter ratio of the inner and outer pipes, etc.

As shown in FIG. 6, the inner pipe 12 receives Coriolika Fc as shown by the arrow from the measurement fluid flowing around it, and undergoes deformation as shown by the solid line in FIG. 6 compared to when there is no flow. Since the magnitude of deformation is proportional to Coriolis Fc, the mass flow rate Q can be measured by determining K and ω from equation (1) and measuring the displacement in the Z direction.

As a result, (1) it is sufficient to vibrate the small-diameter inner pipe 12 without vibrating the large-diameter outer pipe 15, so the pipe length can be shortened even at the same resonant frequency, and downsizing can be achieved.

(2) Since the same vibration amplitude of the pipe can be obtained with a smaller force than with the large diameter outer pipe 15, the vibration excitation means 13 can be small, and a relatively large pipe fixing part is not required.

(3) Since the vibrating means 13 can be small, there is no need to apply excessive force to the pipe, and durability can be improved.

In the above-mentioned embodiment, the displacement detecting means 18 is described as being magnetic, but the displacement detecting means 18 is not limited to this. For example, between a light emitting diode and a photodiode,
An optical detection method may be used, in which a shielding plate that moves with the displacement caused by Coriolis is arranged and the displacement is determined from light intensity modulation, or a method that utilizes a change in capacitance of a capacitor; in short, any method that can detect displacement may be used.

Further, the shape of the measurement pipe may be any shape such as a U-order pipe type.

Further, the resonance mode of the pipe may be a higher-order mode higher than the second order. In that case, the vibration excitation means 13 and the displacement detection means 14
The number and position of will change as appropriate.

<Effects of the Invention> As explained above, the present invention provides a Coriolis mass flowmeter that measures mass flow rate using the Coriolis force, which includes a reference axis provided in the pipe direction at the center of the pipe, and a reference axis provided in the pipe direction at the center of the pipe. an inner pipe provided concentrically with the shaft and fixed to the reference shaft with both ends closed; an excitation means provided between the inner pipe and the reference shaft for exciting the inner pipe; displacement detection means provided between the inner pipe and the reference axis on both sides of the means to detect displacement of the inner pipe; and displacement detection means provided outside the inner pipe concentrically with the reference axis and arranged between the inner pipe and the inner pipe. A Coriolis mass flowmeter was constructed, comprising an outer pipe through which a measurement fluid flows, and a coupling plate coupling the outer pipe and the inner pipe.

As a result, (1) it is sufficient to vibrate the inner pipe with a small O diameter without vibrating the outer pipe with a large diameter, so the pipe length can be shortened even at the same resonance frequency, and miniaturization can be achieved.

(2) Compared to a large-diameter outer pipe, the same vibration amplitude of the pipe can be obtained with a smaller force, so the excitation means can be small, and a relatively large pipe fixing part is not required.

(3) Since the vibration means can be small, there is no need to apply excessive force to the pipe, and durability can be improved.

Therefore, according to the present invention, it is possible to realize a Coriolis mass flowmeter in which the pipe length can be shortened and the excitation force can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the main part configuration of an embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA in FIG. 1, FIG. 3 is a sectional view taken along BB in FIG. 1, and FIGS. 6 is an explanatory diagram of the operation of FIG. 1, FIG. 7 is an explanatory diagram of the configuration of a conventional example commonly used, and FIG.
7 is an explanatory diagram of the operation of FIG. 7, and FIG. 9 is an explanatory diagram of the configuration of another conventional example that has been generally used. 11...Reference axis, 12...Inner pipe, 13...
Vibration means, 14... Displacement detection means, 15... Outer pipe, 16... Connecting plate, 17... Case, 18...
・Flange. , Ku Agent Patent Attorney Nobuhiro Kozawa〈 Figure 3 Figure 4 Figure 1 ----↑-'-,T-,-,7,]~6,-1'@
Figure 5 /:) Figure 2 Figure S (A) (B) Figure D

Claims (1)

[Claims] A Coriolis mass flowmeter that measures mass flow rate using Coriolis force includes a reference axis provided at the center of the pipe in the direction of the pipe, and a reference axis provided concentrically with the reference axis with both ends thereof. an inner pipe closed and fixed to the reference shaft; excitation means provided between the inner pipe and the reference shaft for exciting the inner pipe; and the inner pipe on both sides of the excitation means; a displacement detection means provided between the reference axis and the inner pipe to detect displacement of the inner pipe; an outer pipe provided outside the inner pipe concentrically with the reference axis and through which a measurement fluid flows between the outer pipe and the inner pipe; A Coriolis mass flowmeter comprising: a coupling plate coupling the outer pipe and the inner pipe.