JP2712684B2 - Coriolis mass flowmeter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a Coriolis mass flowmeter which is easy to maintain and clean and has good earthquake resistance.

<Prior Art> FIG. 9 is an explanatory diagram of a configuration of a conventional example generally used conventionally.

In the figure, reference numeral 1 denotes a U-shaped measuring pipe having both ends attached to a pipe A.

 Reference numeral 2 denotes a mounting flange of the measuring pipe 1 to the pipe A.

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

Reference numerals 4 and 5 denote displacement detection sensors provided on both sides of the measuring tube 1, respectively.

In the above configuration, the measurement fluid is caused to flow through the measurement tube 1,
The vibrator 3 is driven. Assuming that the angular velocity “ω” in the vibration direction of the vibrator 3 and the flow velocity “V” of the measurement fluid (hereinafter, a symbol surrounded by “” represents a vector amount), Fc = −2 m “ω” × “V” The mass flow rate can be measured by measuring the amplitude of the vibration in which the Coriolis force acts and which is proportional to the Coriolis force.

However, in general, the amplitude of the vibration proportional to the Coriolis force is much smaller than the amplitude of the vibration due to the excitation, and the amplitude of the vibration proportional to the Coriolis force cannot be directly detected.

Now, when viewed from the Z-view direction in FIG. 9, when the vibration direction is divided into α and β by the vibration of the vibrator 3, depending on the direction of the flow velocity “V”, FIGS. As shown in B), since the directions of the Coriolis force are different, the phases are reversed, and the measuring tube 1 vibrates while being twisted. This is called the displacement detection sensor 4,
5.Displacement detection sensor, for example, detecting displacement with a magnetic sensor
Since the phase difference between the displacements 4 and 5 is proportional to (amplitude of vibration in proportion to Coriolis force) / (amplitude of vibration due to excitation), the mass flow rate can be obtained.

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

FIG. 11 is an explanatory view of another conventional structure generally used from the prior art.

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

<Problems to be Solved by the Invention> However, even in such a device shown in FIG. 11, the seismic resistance against external vibrations and the like is improved, but the measurement flow path is separated into two, and the cleaning of the measurement tube is difficult. It has drawbacks such as becoming difficult, and deposits tending to accumulate at the branch.

 The present invention solves this problem.

An object of the present invention is to provide a Coriolis mass flowmeter which is easy to perform maintenance cleaning and has good earthquake resistance.

<Means for Solving the Problems> In order to achieve this object, the present invention relates to a Coriolis mass flowmeter for measuring a mass flow rate using a Coriolis force, comprising: A flat plate provided in parallel with the tube axis of the measuring tube, a vibration isolating frame to which both ends of the flat plate and the measuring tube are fixed, and the measurement provided near the center of the measuring tube provided orthogonal to the tube axis. A coupling plate that couples a tube and the flat plate, and a vibration drive that is orthogonal to the tube axis and the flat plate and that is provided to face between the coupling plate and the vibration isolating frame and vibrates the measurement tube and the flat plate. A speed measuring device for measuring a displacement speed of the device and the flat plate, and a relative displacement provided near an intermediate portion between an end of the measuring tube and a mounting portion of the coupling plate for detecting a relative displacement between the measuring tube and the flat plate. A Coriolis mass flowmeter comprising a detection device Are those that you configured.

<Operation> In the above configuration, the measurement fluid in the measurement tube flows, and the vibrator is driven. The vibrator vibrates the measurement tube and the flat plate in the same direction.

Assuming that the angular velocity in the vibration direction is “ω” and the flow velocity of the measurement fluid flowing inside the measuring tube is “V”, the Coriolis force of Fc = −2 m “ω” × “V” acts. The tube is deformed by Coriolis force, and the measuring tube is deformed.

However, the flat plate is not affected by the Coriolis force. Therefore, the relative displacement due to the Coriolis force is measured by the relative displacement measuring device.

Thus, a mass signal is obtained by dividing the measured relative displacement signal by the speed measuring device.

On the other hand, with respect to the vibration of the main pipe, which acts as noise on the measured value, the measurement pipe and the flat plate are fixed near both ends by the vibration isolating frame, so that they are hardly subjected to external vibration.

 Hereinafter, a detailed description will be given based on embodiments.

<Embodiment> FIG. 1 is an explanatory view of a main part configuration of an embodiment of the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG. 3 is a sectional view taken along line BB of FIG. .

 Numeral 11 is a flange connected to the piping.

 12 is a square-shaped anti-vibration frame.

Reference numeral 13 denotes a straight measurement tube through which a measurement fluid flows, and both ends are fixed to a vibration isolating frame. In this case, the pipe has a diameter smaller than that of the pipe, and is connected to the pipe at a reduced portion and an enlarged portion.

Reference numeral 14 denotes a flat plate provided in parallel with the tube axis of the measurement tube 13, and both ends are fixed to a vibration isolating frame. The thickness of the flat plate 14 is selected so that the minimum resonance frequency is the same as that of the measurement tube 13.

15 is provided orthogonal to the tube axis of the measuring tube 13 and
Is a connecting plate for connecting the measuring tube 13 and the flat plate 14 in the vicinity of the center of the measuring tube 13.

16 and 17 are orthogonal to the measuring tube 13, the tube axis and the flat plate 14,
A vibration driving device is provided between the anti-vibration frame 12 and the vibration isolating frame 12 to vibrate the measuring tube 13 and the flat plate 14, and a speed measuring device for measuring the displacement speed of the flat plate 14.

Reference numeral 18 denotes a relative displacement detection device that is provided near an intermediate portion between the end of the measurement tube 13 and the attachment portion of the coupling plate 15, and detects a relative displacement between the measurement tube 13 and the flat plate 14.

In this case, the relative displacement detection device 18 includes a slit 181,
It comprises a light emitting device 182 and a light receiving device 183.

 FIG. 4 shows an electric circuit block diagram.

Reference numeral 21 denotes a relative displacement conversion circuit that converts the relative displacement between the flat plate 14 and the measurement tube 13 into a voltage.

The relative displacement conversion circuit 21 includes a slit 181, a light emitting device 182, a light receiving device 183, and an arithmetic circuit 22.

Reference numeral 23 denotes a speed signal circuit that outputs a voltage signal proportional to the displacement from the output of the speed measuring device 17.

24 is a smoothing circuit for smoothing the output of the relative displacement conversion circuit 21.

25 is a smoothing circuit for smoothing the output of the speed signal circuit 23.

26 is a division circuit for dividing the output of the smoothing circuits 24 and 25.

Reference numeral 27 denotes a driving circuit of the vibration driving device 16 including a coil and an iron core. The driving circuit 27 controls the frequency and magnitude by using the frequency signal of the speed signal circuit 23 and the smoothing signal of the smoothing circuit 25.

In the above configuration, the measurement fluid is caused to flow through the measurement tube 13,
The vibration driving device 16 is driven. The measurement tube 13 and the flat plate 14 vibrate in the same direction by the vibration driving device 16.

Assuming that the angular velocity in the vibration direction is “ω” and the flow velocity of the measurement fluid flowing inside the measurement tube 13 is “V”, the Coriolis force of Fc = −2 m “ω” × “V” acts. The measurement tube 13 is deformed by Coriolis force, and the measurement tube 13 is deformed.

However, the flat plate 14 is not affected by the Coriolis force. Therefore, the relative displacement due to the Coriolis force is measured by the relative displacement measuring device.

Thus, the measured relative displacement signal is transmitted to the speed measuring device 17.
By dividing by, a mass signal is obtained.

On the other hand, with respect to the vibration of the main pipe, which acts as noise on the measured value, the measurement pipe 13 and the flat plate 14 are fixed by the anti-vibration frame 12 near both ends, so that they are hardly subjected to external vibration.

 That is, FIG. 5 shows the movement of the measuring tube 13 and the flat plate 14.

When the vibration driving device 16 is driven, a periodic force is applied to the coupling plate 15 to bend and vibrate in an integrated state. Fig. 7 (A)
FIG. 7B shows the case where there is no flow of the measurement fluid, and FIG. 7B shows the case where there is a flow of the measurement fluid.

If the flow of the fluid should not, as shown in FIG. 5 (A), the displacement [delta] ₂ of the displacement [delta] ₁ and flow tube 13 of the plate 14 are matched. Therefore, the displacement δ ₂ −δ ₁ of the measuring tube 13 with reference to the flat plate 14 is zero as shown in FIG. 6 (A).

When there is a flow of the measurement fluid, a Coriolis force proportional to the mass flow rate is applied to the measurement tube 13 as shown in FIG. 5 (B), and the measurement tube 13 is distorted in upstream and downstream directions in opposite directions. Therefore, the flat plate 14
As shown in FIG. 6B, the displacement δ ₂ −δ ₁ of the measuring tube 13 changes in a sinusoidal manner as shown in FIG. 6B, which is proportional to the Coriolis force (that is, the mass flow rate).

δ ₂ −δ ₁ = kωM (υ) ω: angular velocity of the measuring tube 13 M (υ): mass flow rate Next, FIG. 8 shows the movement of the relative displacement detector 18.

 FIG. 8A shows a case where there is no relative displacement.

Light emitted from the light emitting device 182 is blocked by the slit 181, and a part of the light reaches the light receiving device 183. The light receiving device 183 has a pair of structures and receives the same amount of light when there is no relative displacement.

 FIG. 8B shows a case where there is a relative displacement.

Since the slit 181 moves, the light reaching the pair of light receiving devices 183 becomes unbalanced.

Assuming that the respective light amounts are A ₁ and A ₂ , A ₂ −A ₁ is proportional to the relative displacement.

Thus, the difference between the output voltages E (A ₁ ) and E (A ₂ ) of the light receiving device 183 is calculated by the arithmetic circuit 22 and smoothed by the smoothing circuit 24, so as to be proportional to the Coriolis force as in the following equation. A signal can be obtained.

E _D = E (A ₂ ) −E (A ₁ ) = k ₂ (A ₂ −A ₁ ) = k ₂ k ₃ (δ ₂ −δ ₁ ) = k ₁ k ₂ k ₃ ωM (υ) plate 15, a signal proportional to the mass signals by dividing the smoothed signal is obtained at the output _E υ = k ₄ ω which is proportional to the speed from the speed measuring device 17.

E _out = E _D / E _υ = (k ₁ k ₂ k ₃ ωM (υ)) / (k ₄ ω) As a result, (1) it is composed of one pipe and there is no liquid pool and no branch part Therefore, maintenance and cleaning are easy.

(2) Since the difference between the vibration of the measuring tube 13 and the vibration of the flat plate 14 is used for detecting the vibration, it is hard to receive the external vibration.

When the speed of the speed measuring device 17 is driven to be constant, the dividing circuit 26 may be omitted.

The relative displacement detecting device 18 may use an electrostatic induction type, a strain gauge type, or PZT instead of an optical type.

The speed measuring device 17 may be a method of differentiating the output of the displacement sensor or a method of integrating the output of the acceleration sensor instead of the electromagnetic induction type.

The number of relative displacement detectors 18 is set at a symmetrical position on the coupling plate 15, but the S / N ratio can be improved by performing arithmetic processing after picking up a pair of displacement signals.

If the signal of the sensor is A / D converted and calculated, the calculation accuracy can be improved.

<Effect of the Invention> As described above, the present invention relates to a Coriolis mass flowmeter that measures a mass flow rate using a Coriolis force, wherein a straight tubular measurement pipe through which a measurement fluid flows, and a pipe axis of the measurement pipe. A flat plate provided in parallel, an anti-vibration frame to which both ends of the flat plate and the measuring tube are fixed, and the measuring tube and the flat plate provided near the center of the measuring tube provided orthogonal to the pipe axis. A coupling plate to be coupled, a vibration drive device orthogonal to the tube axis and the flat plate, provided opposite the coupling plate and the vibration isolating frame, and vibrating the measurement tube and the flat plate, and displacement of the flat plate A speed measuring device for measuring a speed, and a relative displacement detecting device provided near an intermediate portion between an end of the measuring tube and a mounting portion of the coupling plate and detecting a relative displacement between the measuring tube and the flat plate. Thus, a Coriolis mass flowmeter was constructed.

As a result, (1) Since it is composed of one pipe and there is no liquid pool or branch part, maintenance and cleaning are easy.

(2) Since the difference between the vibration of the measuring tube and the vibration of the flat plate is used for detecting the vibration, it is hard to receive the external vibration.

Therefore, according to the present invention, it is possible to realize a Coriolis mass flowmeter which is easy to perform maintenance cleaning and has good seismic resistance.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a main part of an embodiment of the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1, FIG. 3 is a sectional view taken along line BB of FIG. 1, and FIG. FIG. 1 is an electric circuit block diagram, FIG. 5 to FIG. 8 are operation explanatory diagrams of FIG. 1, FIG. 9 is an explanatory diagram of a configuration of a conventional example generally used, and FIG. FIG. 11 is an operation explanatory view, and FIG. 11 is a structural explanatory view of another conventional example which has been generally used conventionally. 11 ... Flange, 12 ... Vibration isolation frame, 13 ... Measuring tube, 14 ...
Flat plate, 15 coupling plate, 16 vibration driving device, 17 speed measurement device, 18 relative displacement detection device, 181 slit, 182 light emitting device, 183 light receiving device, 21 Relative displacement circuit, 22: arithmetic circuit, 23: speed signal circuit, 24, 25
…… Smoothing circuit, 26 …… Division circuit.

Claims (1)

(57) [Claims] 1. A Coriolis mass flowmeter for measuring a mass flow rate using a Coriolis force, comprising: a straight tube-shaped measuring tube through which a measuring fluid flows; a flat plate provided in parallel with a pipe axis of the measuring tube; And a vibration isolating frame to which both ends of the measurement tube are fixed, a coupling plate that is provided orthogonal to the tube axis and couples the measurement tube and the flat plate near the center of the measurement tube, and the tube shaft. A vibration drive device provided orthogonally to the flat plate and opposed between the coupling plate and the vibration isolating frame to vibrate the measurement tube and the flat plate, and a speed measuring device for measuring a displacement speed of the flat plate; A Coriolis mass flowmeter comprising: a relative displacement detection device provided near an intermediate portion between an end of a measurement tube and a mounting portion of a coupling plate, for detecting a relative displacement between the measurement tube and the flat plate.