JP2012013648A - Coriolis mass flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a Coriolis mass flowmeter capable of generating stable vibration of a vibrating tube.SOLUTION: A Coriolis mass flowmeter measures a mass flow of measured fluid flowing through two vibrating tubes by using driving means composed of a coil and a magnet for vibrating the vibrating tubes in a mutually approaching and separating direction, and using two vibration sensors each composed of a coil and a magnet for detecting relative displacement of the vibrating tubes. The Coriolis mass flowmeter includes counterbalance means that vibrates in synchronization with the vibration of the tubes and counterbalances barycentric movement caused by flexure of the vibrating tubes.

Description

  In the present invention, two vibration tubes (sensor tubes) are vibrated in directions close to and away from each other by a driving means (excitation means) composed of a coil and a magnet, and the relative displacement of the vibration tube is composed of a coil and a magnet. The present invention relates to a Coriolis type flow meter that detects the mass flow rate of a fluid to be measured flowing through a vibration tube by detecting with two vibration sensors, and relates to a Coriolis type mass flow meter that can realize stable vibration of the vibration tube.

FIG. 2 is a configuration explanatory view showing an example of a conventional Coriolis mass flow meter.
In FIG. 2, a conventional Coriolis type mass flowmeter vibrates two vibration tubes (sensor tubes) 1 and 2 through which a fluid to be measured flows in directions close to and away from each other by a drive means (excitation means) 3. The relative displacement of the vibration tubes 1 and 2 due to the Coriolis force proportional to the flow rate is detected by the two vibration sensors 4 and 5.

  The vibrating tubes 1 and 2 are arranged in parallel on a base 6 having an inlet at one end and an outlet (not shown) at the other end, and both ends of the base 6 are connected to the inlet and the outlet. It is the tube for two connected U-shaped sensors.

  The driving means 3 and the vibration sensors 1 and 2 are both composed of a coil and a magnet. In this case, a coil is attached to one of the two sensor tubes, and a magnet is attached to the other of them.

  The driving device 3 vibrates the two vibrating tubes 1 and 2 in directions close to and away from each other, that is, vibrates symmetrically.

The Coriolis mass flow meter 10 configured as described above mainly measures the mass flow rate of the fluid to be measured as follows.
(1) The fluid to be measured flows into the two vibrating tubes 1 and 2 through the inlet of the base 6.
(2) An (alternating) current is supplied to an excitation coil or the like (not shown) of the driving means 3 to bring the two vibrating tubes 1 and 2 close to and away from each other by electromagnetic action with a magnet (not shown). Vibrate in the direction.

(3) A Coriolis force having a magnitude corresponding to the mass of the fluid to be measured acts on the vibration tubes 1 and 2. At this time, the Coriolis force of the same magnitude acts in the opposite direction on the inflow side and the outflow side of the two vibration tubes 1 and 2, thereby causing relative kinking to the two vibration tubes 1 and 2. appear.

(4) The vibration sensors 4 and 5 detect vibrations (velocities) of the two vibration tubes 1 and 2 and send the detection signals in a control device (not shown) via signal lines (not shown). It is sent to the arithmetic circuit.

(5) At this time, the vibration waveforms detected by the vibration sensors 4 and 5 (detected waveforms induced in the pair of detection coils in the sensor) are the vibration waveform A of one sensor tube 3 and the vibration waveform of the other vibration tube. This is a composite waveform (A + B) with the vibration waveform B.

(6) The arithmetic circuit in the control device calculates the mass flow rate of the fluid to be measured from the phase difference (time difference) between the combined waveform based on the detection result from the vibration sensor 4 and the combined waveform based on the detection signal from the vibration sensor 5. The result is displayed on a display means (not shown).

Thus, the conventional Coriolis mass flowmeter is transmitted to the base 6 because the drive device 3 vibrates the two vibrating tubes 1 and 2 in directions close to and away from each other (vibrates symmetrically). By canceling the vibration in the excitation direction and forming a place like a node of a tuning fork, the leakage of vibration energy is reduced (the leakage of internal vibration to the outside is reduced), and the Q value of vibration is improved.
The larger the Q value of the vibration, the more stable the vibration. If the Q value is improved, the measurement accuracy of the mass flow rate is improved accordingly.

  For example, there is Patent Document 1 below as a prior art document related to a conventional Coriolis mass flow meter.

JP 2008-209223 A

However, in the conventional Coriolis type mass flowmeter, when the driving means vibrates the two vibrating tubes symmetrically, the vibrating tube is bent, and the center of gravity of the vibrating tube is moved (for example, in the tube axis direction), causing vibration. There was a problem that energy leakage occurred.
For this reason, the improvement of the Q value of the vibration is hindered, and stable vibration of the vibration tube cannot be realized, and there is a problem that the mass flow rate cannot be measured with high accuracy.

FIG. 3 is an explanatory diagram of problems of a conventional Coriolis mass flow meter. As shown in FIG. 3, when the driving means vibrates the two vibrating tubes 1 and 2 symmetrically, the vibrating tubes 1 and 2 are bent. For this reason, when the vibration tubes 1 and 2 vibrate, the position of the center of gravity moves (for example, in the tube axis direction), and the vibration is distorted.
Then, leakage of vibration energy occurs (for example, vibration leaks to the base 6), and when the vibration returns to the vibration tubes 1 and 2 through the base 6 and the like, the vibration of the vibration tubes 1 and 2 becomes unstable. Therefore, there was a problem that accurate measurement of mass flow rate was not possible.

  The present invention solves such problems, and an object thereof is to realize a Coriolis mass flow meter capable of generating stable vibration of a vibration tube.

In order to achieve the above object, the invention described in claim 1 of the present invention is:
Two vibrating tubes are vibrated in directions close to and away from each other by driving means comprising a coil and a magnet, and the relative displacement of the vibrating tube is detected by two vibration sensors comprising a coil and a magnet. In the Coriolis type flow meter that measures the mass flow rate of the fluid to be measured flowing inside,
Coriolis mass flow rate characterized by comprising counter balance means that vibrates in synchronization with the vibration of the vibration tube and cancels all or part of vibration caused by the movement of the center of gravity caused by bending of the vibration tube. Total.

The invention according to claim 2 is the Coriolis type mass flow meter according to claim 1,
The counter balance means includes
A frame member having a hollow portion; a beam portion having elasticity crossing the hollow portion; a weight portion positioned in the hollow portion; and attached to the beam portion; and the weight portion in synchronization with vibration of the vibration tube And a weight driving means for vibrating the device.

The invention according to claim 3 is the Coriolis mass flow meter according to claim 2,
The weight portion is vibrated based on an attractive force or a repulsive force of a coil and a magnet, or the weight portion is vibrated based on an electrostatic force.

The invention according to claim 4 is the Coriolis mass flow meter according to claim 2 or 3,
When the drive current applied to the coil of the drive means is detected, drive current detection means is provided for outputting a current for vibrating the weight portion to the weight drive means.

The invention according to claim 5 is the Coriolis mass flow meter according to claim 4,
The beam portion is formed of a spring.

The invention according to claim 6 is the Coriolis mass flowmeter according to claim 4 or 5,
The drive current detection means includes
The current output to the weight driving means is controlled to bring the vibration of the vibration tube and the weight portion into a resonance state, and all or part of the vibration caused by the center of gravity movement caused by the bending of the vibration tube is counterbalanced. It is characterized in that it is canceled out by vibrations generated by the means.

  According to the present invention, the vibration tube is provided with the counter balance means that vibrates in synchronization with the vibration of the vibration tube and cancels all or part of the vibration caused by the movement of the center of gravity caused by the bending of the vibration tube. Because all or part of the vibration transmitted to the base due to the center of gravity movement caused by the bending of the vibration is canceled out, the Q value of the vibration is improved, stable vibration of the vibrating tube can be realized, and the mass flow rate is highly accurate. Can be measured.

  According to claim 4, the frame member having the hollow portion, the elastic beam portion traversing the hollow portion, the weight portion positioned in the hollow portion and attached to the beam portion, and the weight in synchronization with the vibration of the vibration tube A counter balance means that is composed of weight drive means for vibrating the part, vibrates in synchronization with the vibration of the vibration tube, and cancels the movement of the center of gravity due to the bending of the vibration tube; and when a drive current applied to the coil of the drive means is detected, Due to the provision of the drive current detection means for outputting the current for vibrating the weight portion of the counter balance means to the weight drive means, the center of gravity movement caused by the deflection of the vibration tube due to the vibration of the weight portion of the counter balance means is caused. Since all or part of the vibration transmitted to the base is canceled, the Q value of the vibration is improved, stable vibration of the vibration tube can be realized, and mass flow rate is highly accurate. It can be measured.

  According to the sixth aspect of the present invention, the drive current detection means controls the current output to the weight drive means to bring the vibration of the vibration tube and the weight portion into a resonance state, and causes all of the center of gravity movement caused by the deflection of the vibration tube. Alternatively, it is effective in that a part of vibrations can be canceled by vibrations generated by the counter balance means, so that more vibrations can be canceled than in a non-resonant state.

It is composition explanatory drawing which shows one Example of the Coriolis type | mold mass flowmeter of this invention. It is composition explanatory drawing which shows an example of the conventional Coriolis type | mold mass flowmeter. It is explanatory drawing of the problem of the conventional Coriolis type | mold mass flowmeter.

<First embodiment>
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a structural explanatory view showing an embodiment of the Coriolis mass flow meter of the present invention. The parts common to those in FIG. FIG. 1A is a configuration explanatory diagram of the entire Coriolis mass flow meter, and FIG. 1B is a configuration explanatory diagram of counter balance means.

  The difference between FIG. 1 and FIG. 2 is that a counter balance unit that vibrates in synchronization with the vibration (vibration frequency) of the vibration tube and cancels the movement of the center of gravity due to the bending of the vibration tube is provided.

(Description of configuration)
In FIG. 1, a Coriolis type mass flow meter 20 according to the present invention mainly brings two vibrating tubes (sensor tubes) 1 and 2 through which a fluid to be measured flows and the vibrating tubes 1 and 2 close to and away from each other. Drive means (excitation means) 3 for vibrating in the direction, two vibration sensors (pickups) 4 and 5 for detecting relative displacement of the vibration tubes 1 and 2 due to Coriolis force proportional to the flow rate, an inlet at one end, and the other end The base 6 such as a support tube through which a fluid having an outlet (not shown) flows, and the vibration tubes 1 and 2 vibrate in synchronization with the vibration (vibration frequency). The counter balance means 7 attached to the base 6 to cancel is provided.

  The vibrating tubes 1 and 2 are arranged in parallel on a base 6 having an inlet at one end and an outlet (not shown) at the other end, and both ends of the base 6 are connected to the inlet and the outlet. Are U-shaped two sensor tubes connected to each other.

Inside the base 6, a bifurcated inflow side flow channel branched from the inflow port and a bifurcated outflow side flow channel (not shown) gathering at the outflow port are formed, and the two vibrating tubes 1, Both ends of 2 are connected to the base 6 so as to communicate with the bifurcated inflow and outflow channels.
Therefore, the fluid to be measured supplied into the base 6 from the inflow port is equally divided by the bifurcated inflow channel and flows into the two vibrating tubes 1 and 2, and further flows from the bifurcated outflow channel. Merge at the exit and flow out.

  The drive means 3 and the vibration sensors 4 and 5 are both composed of a coil and a magnet. In this case, a coil is attached to one of the two vibration tubes 1 and 2, and a magnet is attached to the other of them.

The magnet of the drive device 3 is arranged so that the same magnetic pole is inserted into the excitation coil, for example, like the vibration sensors 4 and 5.
The (excitation) coil of the driving device 3 is supplied with an (alternative) current having a frequency substantially equal to the natural frequency of the vibration tubes 1 and 2. The attractive force and the repulsive force act, and the two vibrating tubes 1 and 2 vibrate in the directions approaching and separating from each other due to the electromagnetic interaction therebetween.

The vibration sensors 4 and 5 detect the relative displacement of the two vibration tubes 1 and 2. The vibration sensor 4 is installed on the fluid inflow side of the vibration tubes 1 and 2. 2 on the outflow side of the fluid.
The vibration sensors 4 and 5 are constituted by a detection coil and a magnet attached to a portion close to the straight tube portion of each vibration tube 1 and 2. Each magnet is arranged such that, for example, the same magnetic pole is inserted into the detection coil. When a relative displacement occurs between the detection coil and the magnet, the vibration sensors 4 and 5 cause an electromagnetic induction current to flow through the detection coil and generate a detection signal having a magnitude corresponding to the vibration (speed) of each vibration tube 1 and 2. Output.

  The counter balance means 7 is attached to the base 6 and is installed in a rectangular region that is formed, for example, as a part of the surface of the base 6 and connecting both ends of the vibration tubes 1 and 2.

  The counter balance means 7 vibrates the weight portion in synchronization with the vibration of the vibration tube and transmits the vibration to the base 6, thereby causing the base 6 caused by the movement of the center of gravity caused by the bending of the vibration tubes 1 and 2. Cancels (cancels) all or part of vibration transmitted to

  The counter balance means 7 is mainly attached to the frame member 72 having the hollow portion 71, the elastic beam portion 73 crossing the hollow portion 71, and the beam portion 73 located (internally provided) in the hollow portion 71. The weight portion 74 and weight driving means 75 for vibrating the weight portion 73 in synchronization with the vibration of the vibration tubes 1 and 2 are provided.

The beam portion 73 is configured to cross the hollow portion 71, in other words, to be bridged from one end to the other end of the periphery of the hollow portion 71, and may be any material as long as it is made of an elastic material. For example, a leaf spring or a winding spring may be used.
The weight portion 74 is made of a material having the property of being influenced by magnetic force.
The weight driving means 75 is composed of a coil and a magnet, and vibrates the weight part 73 by an attractive force or a repulsive force of the coil and the magnet based on an electric current supplied from the outside (or vibrates the weight part 73 based on an electrostatic force). It may be)
The weight driving means 75 vibrates the weight portion 73 so as to synchronize with the vibration frequency of the vibration tubes 1 and 2 based on the current supplied from the outside.

  Further, the Coriolis mass flow meter 20 according to the present invention detects the drive current output from the drive means 3 to the coil, and detects the drive current for outputting the (drive) current for vibrating the weight portion 73 to the weight drive means 75. Means 8 are also provided. The drive current detection means 8 and the weight drive means 75 are electrically connected.

The drive current detection device 8 is a drive current of the coil of the drive device 3 for vibrating the vibration tubes 1 and 2 detected by the drive current detection device 8 with a drive force (drive current) supplied to the weight drive means 75. May be controlled so as to be minimum.
That is, the drive current detection means 8 controls the current output to the weight drive means 75 to bring the vibrations of the vibration tubes 1 and 2 and the weight 73 into a resonance state, and the vibration transmitted from the vibration tubes 1 and 2 to the base 6 is detected. Alternatively, it may be canceled (cancelled) by vibration by the counter balance means 7. The resonance state is effective in that it can cancel more vibrations than the non-resonance state.

(Description of operation)
The Coriolis mass flowmeter 20 of the present invention has the configuration as described above, and mainly measures the mass flow rate of the fluid to be measured as follows.
(1) The fluid to be measured flows into the two vibrating tubes 1 and 2 through the inlet of the base 6.
(2) A current is supplied to an excitation coil or the like (not shown) of the driving means 3, and the two vibrating tubes 1 and 2 vibrate in a direction approaching and separating from each other by electromagnetic action with a magnet (not shown). Let

(3) When the drive current detection means 8 detects the drive current applied to the coil of the drive means 3, the drive current detection means 8 outputs a current for vibrating the weight portion 73 of the counter balance means 7 to the weight drive means 75.

(4) The weight driving means 75 of the counter balance means 7 vibrates the weight portion 73 in synchronization with the vibration frequency of the vibration tubes 1 and 2 based on the supplied current.

  For this reason, the vibration transmitted to the base 6 due to the movement of the center of gravity caused by the bending of the vibration tubes 1 and 2 is transmitted by the vibration by the weight portion 73 to the vibration tubes 1 and 2 through the base 6. All or a part is canceled (offset).

  The drive current detection device 8 is a drive current of the coil of the drive device 3 for vibrating the vibration tubes 1 and 2 detected by the drive current detection device 8 with a drive force (drive current) supplied to the weight drive means 75. May be controlled so as to be minimum.

(5) Coriolis force having a magnitude corresponding to the mass of the fluid to be measured acts on the vibration tubes 1 and 2. At this time, the Coriolis force of the same magnitude acts in the opposite direction on the inflow side and the outflow side of the two vibration tubes 1 and 2, thereby causing relative kinking to the two vibration tubes 1 and 2. appear.

(6) The vibration sensors 4 and 5 detect vibrations (velocities) of the two vibration tubes 1 and 2, and send the detection signals in a control device (not shown) via signal lines (not shown). It is sent to the arithmetic circuit.

(7) At this time, the vibration waveforms detected by the vibration sensors 4 and 5 (detected waveforms induced in the pair of detection coils in the sensor) are the vibration waveform A of one sensor tube 3 and the other vibration tube. This is a composite waveform (A + B) with the vibration waveform B.

(8) The arithmetic circuit in the control device calculates the mass flow rate of the fluid to be measured from the phase difference (time difference) between the combined waveform based on the detection result from the vibration sensor 4 and the combined waveform based on the detection signal from the vibration sensor 5. The result is displayed on a display means (not shown).

  As a result, the Coriolis mass flowmeter according to the present invention includes a counter balance means that vibrates in synchronization with the vibration of the vibration tube and cancels the movement of the center of gravity due to the bending of the vibration tube. Vibration can be realized.

  Further, the Coriolis mass flowmeter according to the present invention includes a frame member having a hollow portion, a beam portion having elasticity crossing the hollow portion, a weight portion positioned in the hollow portion and attached to the beam portion, and a vibrating tube. It is composed of weight drive means for vibrating the weight portion in synchronization with the vibration, and is applied to the counter balance means for oscillating in synchronization with the vibration of the vibration tube and canceling the movement of the center of gravity due to the bending of the vibration tube, and the coil of the drive means When the driving current is detected, the driving current detecting means for outputting the current for vibrating the weight portion of the counter balance means to the weight driving means is provided, so that the vibration of the vibrating tube is caused by the vibration of the weight portion of the counter balance means. Since all or part of the vibration transmitted to the base due to the movement of the center of gravity is canceled, the Q value of vibration is improved and stable vibration of the vibration tube is achieved. It can be measured mass flow rate with high accuracy.

  In the Coriolis mass flowmeter according to the present invention, the drive current detection means controls the current output to the weight drive means to bring the vibration of the vibration tube and the weight portion into a resonance state, and the center of gravity generated by the bending of the vibration tube By canceling all or part of the vibration caused by the movement with the vibration generated by the counter balance means, it is possible to cancel more vibrations than in the non-resonant state.

DESCRIPTION OF SYMBOLS 20 Coriolis mass flowmeter 1, 2 Vibrating tube 3 Drive means 4, 5 Vibration sensor 6 Base 7 Counter balance means 71 Hollow part 72 Frame member 73 Beam part 74 Weight part 75 Weight drive means 8 Drive current detection means

Claims (6)

Two vibrating tubes are vibrated in directions close to and away from each other by driving means comprising a coil and a magnet, and the relative displacement of the vibrating tube is detected by two vibration sensors comprising a coil and a magnet. In a Coriolis flow meter that measures the mass flow rate of the fluid under measurement flowing
Coriolis mass flow rate characterized by comprising counter balance means that vibrates in synchronization with the vibration of the vibration tube and cancels all or part of vibration caused by the movement of the center of gravity caused by bending of the vibration tube. Total. The counter balance means includes
A frame member having a hollow portion;
A beam part having elasticity across the hollow part;
A weight portion located in the hollow portion and attached to the beam portion;
A weight driving means for vibrating the weight portion in synchronization with the vibration of the vibration tube;
The Coriolis type mass flow meter according to claim 1, comprising: The weight driving means includes
The Coriolis mass flowmeter according to claim 2, wherein the weight portion is vibrated based on an attractive force or a repulsive force of a coil and a magnet, or the weight portion is vibrated based on an electrostatic force.   4. A drive current detection means for outputting a current for vibrating the weight portion to the weight drive means when a drive current applied to the coil of the drive means is detected. Coriolis type mass flow meter as described. The beam portion is
The Coriolis type mass flow meter according to any one of claims 2 to 4, wherein the Coriolis type mass flow meter is constituted by a spring. The drive current detection means includes
The current output to the weight driving means is controlled to bring the vibration of the vibration tube and the weight portion into a resonance state, and all or part of the vibration caused by the center of gravity movement caused by the bending of the vibration tube is counterbalanced. 6. The Coriolis mass flow meter according to claim 4, wherein the mass flow meter cancels out the vibration generated by the means.

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