JPS6332128B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a vibration compensation device for a vortex flowmeter.

A vortex generator is installed in the pipe through which the fluid to be measured flows,
A vortex flowmeter is known that measures the flow rate from the frequency of the vortex generator caused when a Karman vortex street is generated downstream thereof.

However, the sensor that detects the vibration of the vortex generating body picks up not only the vibration caused by the Karman vortex, but also various vibration noises transmitted through the pipe, such as pump vibration, damper opening/closing vibration, etc.
Accurate flow measurement was difficult. In order to deal with this problem, for example, in Japanese Utility Model Application No. 57-19465 and Japanese Utility Model Application No. 57-28370, two vibration detection sensors are provided, and the output of one is used to automatically adjust the triggering level of the Schmitt trigger circuit. Adjust or
Alternatively, an apparatus has been proposed in which the above-mentioned noise is removed by combining both outputs. However, in the former case, for example, the mounting positions of the two vibration sensors are different, and therefore the noise signals collected by both sensors do not necessarily have the same waveform, which means that the above-mentioned Schmitt trigger circuit cannot be precisely adjusted. However, there is a problem in that if an external vibration larger than the vibration caused by the Karman vortex street is applied, the function will stop completely.

The present invention has been made based on the above-mentioned viewpoints, and an object of the present invention is to provide a vibration compensator for a vortex flowmeter that has a simple and easy-to-manufacture structure and can substantially completely eliminate the above-mentioned noise. It is about doing,
The gist of this is that a cylindrical first vibration sensor that vibrates together with the vortex generator is mounted on the inner wall of a lumen formed on the fixed end side of the vortex generator disposed in the pipe. A cylindrical second vibration sensor comprising a vibration sensor to which the vortex detection element is fixed and which is attached to the center hole of the first vortex detection element with a predetermined gap from the inner wall of the center hole and vibrates only due to external vibration. A detection element is provided, and a noise component in the output signal of the first vortex detection element is eliminated by the output signal of the second vibration detection element to generate a signal with a frequency corresponding only to the frequency of the vortex generator. It's about trying to get it.

Hereinafter, the details of the configuration of the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of a vortex flowmeter equipped with a vibration compensator according to the present invention, and FIG. 2 is an enlarged view of the configuration of the vibration sensor section of the vibration compensator shown in FIG. The exploded perspective views, FIGS. 3 and 4 are block diagrams showing different embodiments of the circuit configuration of the vibration compensator according to the present invention.

In FIG. 1, 1 is a pipe through which the fluid to be measured flows, 2 is a rod-shaped vortex generator installed in the pipe 1, and 3 is the fixed end side of the vortex generator 2. A first vortex detection element consisting of a hollow cylindrical vibration sensor housed in a bore 2a formed in the bore 2;
A sealing body made of glass or resin for fixing the first vortex detection element 3 to the inner wall of a, 5 is inside the center hole while maintaining a desired gap with the inner wall of the center hole of the first vortex detection element 3. Sensor storage tube to be stored, 6
7 is a second vibration detecting element made of a cylindrical vibration sensor housed in the sensor housing tube 5, and 7 is a seal made of glass or resin that fixes the second vibration detecting element 6 inside the sensor housing tube 5. It is a body. A flange 2b is formed on the fixed end side of the vortex generator 2, and this flange 2b is fixed to the side wall of the pipe line 1 with screws 8, 8. Also,
Sensor housing tube 5 housing second vibration detection element 6
A flange 5a is formed on the fixed end side of the
This flange 5a is fixed to the fixed end flange 2b of the vortex generator 2 by screws 9,9.

First vortex detection element 3 and second vibration detection element 6
The structure will be explained with reference to FIG. 2. The inner wall member of the first vortex detection element 3 is made of a cylindrical metal tube 3a, and the outer wall is surrounded by a piezoelectric element 3b. are fixed to the outer periphery of the piezoelectric element 3b, and two metal electrodes 3c, facing each other, are formed by vapor deposition, gold paste firing, dielectric material coating, etc.
3d is adhered to the metal tube 3a and the piezoelectric element 3.
One piezoelectric sensor 3p is formed by the metal tube 3a, the piezoelectric element 3b, and the electrode 3d, and another piezoelectric sensor 3q is formed by the metal tube 3a, the piezoelectric element 3b, and the electrode 3d. On the other hand, the second vibration detecting element 6 having a smaller diameter than the inner diameter of the first vortex detecting element 3 has approximately the same configuration, and a piezoelectric element 6b is fixed to surround the outer wall of a cylindrical metal tube 6a. 6b
There are two metal electrodes 6c facing each other on the outer periphery of the
6d is adhered to the metal tube 6a and the piezoelectric element 6.
One piezoelectric sensor 6p is formed by the metal tube 6a, the piezoelectric element 6b, and the electrode 6c.
d forms another voltage sensor 6q. When the first vortex detecting element 3 and the second vibration detecting element 6 are installed in the inner cavity 2a of the vortex generator 2, both the facing direction of the electrodes 3c and 3d and the facing direction of the electrodes 6c and 6d are connected to the pipe line. When viewed from the upstream or downstream side of the flow as shown in FIG.
c and 6d are also arranged to face each other on the left and right.

A sealing body 4 made of glass or resin is used to fix the first vortex detection element 3 to the inner cavity 2a of the vortex generator 2, and the second vibration detection element 6 is fixed to the inside of the sensor housing tube 5. The reason for using the sealing body 7 made of glass or resin for this purpose is not only to completely insulate the vibration sensor from the surroundings, but also to completely integrate the first vortex detection element 3 with the vortex generating body 2 and cause it to vibrate. Also, this is to allow the second vibration detection element 6 to vibrate while being completely integrated with the sensor housing tube 5.

FIG. 3 is a block diagram of a circuit that processes output signals from the first vortex detection element and the second vibration detection element configured as described above, and in the figure, 3 is a circuit that processes output signals from the piezoelectric sensors 3p and 3q. 6 is a second vibration detection element consisting of the piezoelectric sensors 6p and 6q; 10 is a charge amplifier;
1 is a low-pass filter, and 12 is a Schmitt trigger circuit.

The vibration compensator according to the present invention configured as described above operates as follows.

That is, due to the flow of the fluid to be measured, Karman vortex streets are generated alternately on the left and right downstream of the vortex generator 2 installed in the pipe line 1, and at this time, the vortex generator 2 moves in a direction approximately perpendicular to the flow. That is, it vibrates in the left-right direction in FIG.
This vibration is caused by the piezoelectric sensors 3p and 3 of the first vortex detection element 3 fixed to the inner cavity 2a of the vortex generator 2.
q, and an output signal corresponding to the frequency of the vortex generator 2 is obtained. At this time, piezoelectric sensor 3
In FIG. 3, p and 3q are connected differentially so that their polarities are opposite to each other, and therefore,
It is possible to obtain twice the output of each piezoelectric sensor. However, the output signal from the first vortex detection element 3 contains noise based on external vibrations propagating through the conduit 1 in addition to the vibrations caused by the Karman vortex street. Electrode 3 of the first vortex detection element
Since the electrodes c and 3d face each other perpendicularly to the flow direction as described above, it is difficult to detect vibrations along the flow direction, and even if they are detected, the two electrodes are differentially connected and cannot be easily detected. Although there is no risk of canceling each other out and creating noise, the vibration of the pipe in the direction perpendicular to the flow and the vortex generator propagates through the fixed end flange 2b of the vortex generator 2 and propagates to the vortex generator, creating a Karman vortex street. It is detected along with the vibration caused by the vibration.

On the other hand, the second vibration detection element 6 is adapted to detect only external vibration propagating through the conduit 1. That is, the sensor housing pipe 5 is connected to the pipe line 1 via the flange 2b of the vortex generator 2 at its flange 5a.
Since it is fixed to the inner wall of the first vortex detection element 3 and is not in contact with the inner wall of the first vortex detection element 3, only the vibration of the pipe line 1 is transmitted. Element 6 detects only external vibrations. Of the external vibrations, only the vibrations in the direction perpendicular to the flow and the vortex generator are detected.
This is similar to the first vortex detection element 3.

Therefore, as shown in FIG. 3, if the first vortex detection element 3 and the second vibration detection element 6 are connected with opposite polarities, the noise contained in the output signal of the first vortex detection element 3 can be reduced. The signal is transmitted to the second vibration detection element 6
is canceled out by the output signal from the oscillator, and only the signal due to the Karman vortex street vibration is extracted.
Since the vibration sensors 3 and 6 are high impedance elements, this output is converted into voltage fluctuation by the charge amplifier 10, high frequency components unrelated to the vibration of the vortex generator 2 are cut out by the low pass filter 11, and then the Schmitt trigger circuit 12 into a rectangular wave pulse to obtain a pulse signal that reflects only the frequency due to the Karman vortex street.
By counting these output pulses, the flow rate of the fluid to be measured is known.

Therefore, in the present invention, the first vortex detection element 3
The effects of forming the second vibration detection element 6 in a cylindrical shape are mainly the following two points. That is, first of all, since both vibration sensors are cylindrical, the second vibration detection element 6 can be housed inside the first vortex detection element 3, and therefore both can be connected to the conduit 1.
It is now possible to fix it in the exact same position on the top,
Therefore, the noise signal from conduit 1 is always collected with exactly the same waveform at both vibration sensors, regardless of the direction of vibration, etc., so that when the outputs of both vibration sensors are combined, the noise portion is completely canceled out. Is Rukoto. The second reason is that the vibration sensor can be manufactured easily. That is, in a vibration sensor using a piezoelectric element or the like, its electrode portion must be sealed with glass or the like in order to completely insulate it from the surroundings as described above. If a cylindrical vibration sensor is used as in the present invention, a glass tube or preform glass is inserted between the inner wall of the inner cavity 2a of the vortex generator and the outer wall of the first vortex detection element 3, and the glass is melted and solidified. Alternatively, it is possible to insert a glass tube or preform glass between the inner wall of the sensor housing tube 5 and the outer wall of the second vibration detection element 6 and melt and solidify the glass tube. Since the volume does not decrease any further, glass sealing can be completed in one operation, and there is no need to complicate the shape of the preform glass, making the work easier and cheaper. Can be configured.

Thus, FIG.
This shows a circuit configuration different from that shown in the figure. In FIG. 4, 3 is a first vortex detection element, 6 is a second vibration detection element, 10-1 and 10-2 are charge amplifiers,
14 is a variable gain amplifier, 13 is an addition or subtraction circuit, 11 is a low-pass filter, and 12 is a Schmitt trigger circuit. This circuit is configured to cope with the case where the output level of the first vortex detection element 3 and the output level of the second vibration detection element 6 are different. That is, although the waveform of the noise included in the output of the first vortex detection element 3 and the output waveform of the second vibration detection element 6 are the same waveform as described above, since the external dimensions etc. of both vibration sensors are different. , the output levels of the two may be different. Therefore, in the circuit shown in FIG. 4, the output of the second vibration detection element 6 is adjusted by the variable gain amplifier 14, and the charge amplifier 10-
The output level of the first vortex detection element 3 obtained through the first vortex detection element 1 is set to the same level as that of the first vortex detection element 3, and then both are combined in an addition or subtraction circuit 13 to remove noise signals. The functions of the low-pass filter 11 and the Schmitt trigger circuit 12 are similar to those described in FIG.

Since the present invention is configured as described above, the present invention has the following effects.

(a) A second cylindrical vibration detection element is built into the first hollow cylindrical vortex detection element, and the fixed ends of both detection elements are attached to the same position on the pipe, so that The noise signal becomes irrelevant to the direction of vibration, etc. in both detection elements, and therefore, when the outputs of both detection elements are combined, the noise components are canceled out.

(b) Since the vibration detecting element is cylindrical, when insulating a sensor such as a piezoelectric element, glass sealing can be achieved by melting and solidifying glass or preform glass, improving work efficiency.

Note that the configuration of the present invention is not limited to the above-mentioned embodiments, and includes, for example, the external shape of the vortex generator 2, the method of fixing it, the method of fixing the sensor housing tube 5, the cylindrical first and second The formation states of the piezoelectric elements 3b, 6b and metal electrodes 3c, 3d, 6c, 6d in the vibration sensor, the circuit configuration for combining the outputs of both vibration sensors, etc. may be changed as necessary within the scope of the purpose of the present invention. Design changes are possible, and the present invention encompasses all of them.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a vortex flowmeter equipped with a vibration compensator according to the present invention, and FIG. 2 is an enlarged view of the configuration of the vibration sensor section of the vibration compensator shown in FIG. The exploded perspective views, FIGS. 3 and 4 are block diagrams showing different embodiments of the circuit configuration of the vibration compensator according to the present invention. DESCRIPTION OF SYMBOLS 1... Pipeline, 2... Vortex generator, 2a... Inner cavity, 3... First vortex detection element, 3a... Metal tube, 3b... Piezoelectric element, 3c, 3d... Electrode, 4... Glass sealed body, 5...
Sensor housing tube, 6... second vibration detection element, 6a...
Metal tube, 6b...piezoelectric element, 6c, 6d...electrode, 7
...Glass sealed body, 10...Charge amplifier, 11...
Low pass filter, 12... Schmitt trigger circuit, 13... addition or subtraction circuit, 14... variable gain amplifier.

Claims (1)

[Scope of Claims] 1. A hollow cylindrical first vortex detection element that is fixedly attached to the wall surface of a bore formed on the fixed end side of the vortex generating body disposed in the pipe. , a cylindrical second vibration detection element that is inserted into the center hole while maintaining a predetermined gap with the inner wall of the center hole of the first vortex detection element and is attached to the attachment part of the vortex generator to the pipe line; Vibration compensator for vortex flowmeter consisting of: 2. A signal processing circuit that eliminates noise components in the output signal of the first vortex detection element using the output signal of the second vibration detection element and outputs a signal with a frequency corresponding only to the vortex signal generated by the vortex generator. A vibration compensator for a vortex flowmeter according to claim 1, comprising: