JPS6014290B2 - Flow velocity flow measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flow rate measuring device that utilizes Karman vortices.

More specifically, the present invention relates to a flow rate measuring device that detects the alternating force acting on an object due to Karman vortices, extracts it as a vortex signal, and measures the flow rate or flow rate.

FIG. 1 shows a conventional example of a flow rate measuring device that has been commonly used.

In the figure, 1 is a cylindrical conduit, and 11 is a cylindrical nozzle provided at right angles to the conduit 1.

Reference numeral 2 denotes a columnar force-receiving body inserted perpendicularly into the conduit 1 through the nozzle 11. One end is supported by the conduit 1 with a screw 3, and the end is fixed to the nozzle 11 at the flange portion 21 by screws or welding. has been done.

22 is a recess provided on the flange portion 21 side of the force receiving body 2.

Reference numeral 4 denotes a disk-shaped stress detection section provided in the recess 22, and its central axis coincides with the center axis of the force receiving body 2.

In this case, the stress detection section 4 consists of a disk-shaped element body 41 and electrodes 42, 43, and 44, as shown in FIG. The electrode 42 has a thin disk shape and is provided on one side of the element body 41. On the other hand, the electrodes 43 and 44 have a substantially arcuate shape,
sandwiching the center of the element body 41 on the other side of the element body 41,
It is provided symmetrically in the direction perpendicular to the direction of the pipe line. In this case, the element body 41 is made of lithium niobate (LiNb0
3) A piezoelectric element consisting of the following is used. Reference numeral 5 denotes a sealing body made of an insulating material and sealing the stress detection part 4 in the recess 22 while insulating it from the force receiving body 2. In this case, a glass material is used.

In the above configuration, when the measurement fluid flows in the pipe line 1, an alternating force F as shown by the arrow in FIG. 1 acts on the force receiving body 2 due to a Karman vortex.

This alternating force F is transmitted to the stress detection section 4 via the sealing body 5. In this case, stress changes occur in the force-receiving body 2 in opposite directions across the central axis of the force-receiving body 2, as shown in FIG. Therefore, the electrode 42-electrode 43 of the stress detection section 4, the electrode 4
An electric signal (
For example, a change in charge) occurs. By detecting the number of times this change occurs, the vortex generation frequency can be detected. Thus, by differentially processing the electrical output between the electrodes 42 and 43 and between the electrodes 42 and 44, twice the electrical output can be obtained. Such a configuration in which the stress detection section 4 of the force receiving body 2 is sealed with glass has various advantages.

However, [1-] The softening point of glass is around 400q0, and the softening point that can actually be used is about 300q0.

If glass with a high softening point is used, the sealing temperature will be high.
Shoden Element's Curie - surpasses one point. Alternatively, it has a small expansion coefficient and is not suitable for sealing a piezoelectric element to the force receiving body 2. {21 The thickness 1 of the glass on the closing side of the recess 22 needs to be a certain thickness in order to sufficiently increase the sensitivity of the force detection part 4, but the difference in the expansion and expansion will occur in the case of sudden heat shock or high temperature. This causes cracks in the glass, so the thickness is limited to a degree that does not cause cracks, and high sensitivity cannot be obtained. It needs to be equal, so
When using a piezoelectric element made of lithium niobate (LiNb03), the Z plate has a characteristic that the sensitivity is 1'3 compared to the Y plate.

It has the following disadvantages.

The present invention solves these problems.

The purpose of the present invention is to be able to measure up to high temperature range, to have high sensitivity,
An object of the present invention is to provide a flow rate measuring device that has excellent earthquake resistance and is robust.

FIG. 3 is an explanatory diagram of the configuration of an embodiment of the present invention.

In the figure, the same symbols as in FIG. 1 represent the same functions.

Hereinafter, only the differences from FIG. 1 will be explained.

2 is a force receiving body, and as will be described later, at position B where the alternating bending moment Mv based on the Karman vortex becomes zero, the bending moment MQ based on the disturbance force is increased by the increase in the bending moment MQ due to the appendage ΔMQ The structure is such that the bending moments have the same sign.

As shown in FIG. 4, 4b is a stress detection section placed at a position B where the bending moment Mv is approximately zero, and 4a is placed near the stress detection section 4b, so that the bending moment Mv is equal to the increase ΔMQ. (Hereinafter, when stress detection parts 4a and 4b are collectively referred to as "
It is called "stress detection section 4".

) 6a, 6b, and 6c (hereinafter collectively referred to as "6") are disc-shaped insulators arranged on both sides of the stress detection section 4, and in this case, ceramic is used. A fixing body 7 presses and fixes the stress detection part 4 and the insulator 6 into the recess 22, and in this case, stainless steel material is used.

One end side of the fixed body 7 is fixed to the force receiving body 2, and in this case,
Welded. Therefore, the depth L of the recess 22 is selected so as to satisfy the following equation.

(QK-qp) (L-ts-tL) = Qp (tS + tL) - Q8tS - QLtL'1' where 1, QP; expansion coefficient of force receiving body 2 QK; fixed body 7 〃 〃 Qs; insulator 6 ″ 〃 QL; Stress detection unit 4 〃 〃 ts; Sum of the thicknesses of insulators 6a, 6b, and 6c tL; Thickness of stress detection unit 4, that is, the thickness of force receiving body 2, force detection unit 4, and insulator The depth L of the recess 22 is set so that the difference in thermal expansion between the force receiving body 2 and the fixed body 7 can be exactly canceled out.

FIG. 5 is a block diagram of the electrical circuit 8 of FIG. 3 (not shown in FIG. 3). In the figure, 81 is a first input processing circuit that amplifies the output of the stress detection section 4a.

A second input processing circuit 82 amplifies the output of the stress detection section 4b, and is configured to have a variable gain.

83 is a differential amplifier that differentially processes the outputs of the first and second input processing circuits 81 and 82.

In such things, changes in ambient temperature can cause
The compressive force applied to the force detection unit 4 does not change, and the fixed body 7 maintains the initial compressed state that was initially applied.

Therefore, it is possible to measure the fluid to be measured up to a high temperature range. Further, in this device, if the fixed body 7 applies an initial compressive force to the force detecting section 4 to some extent, the sensitivity of the force detecting section 4 increases.

Note that, in practice, it is not possible to strictly make both sides of equation '11 equal, so the left side is set so that the right side is slightly larger than the right side.

In this way, compressive force is always applied and sensitivity can be prevented from decreasing at high temperatures. However, it is necessary to set the compressive force including the initial compressive force so that it does not exceed the allowable stress of the force detection section 4.

According to experiments conducted by the present inventors, the initial compression force was set to 0.
28k9/side 2, and an output sensitivity three times that of the conventional glass-sealed one was obtained.

In addition, lithium niobate (LiNb0
3), since a Y plate can also be used, the sensitivity can be tripled compared to the case where a Z plate is used.

In this way, if the device of the present invention is used, ○' Can also be used for measuring fluids of 300qo or more.

(According to experiments, it is possible to measure a measuring fluid of 500 qo.) [2] Sensitivity can be increased.

[3] Defects such as glass cracks and poor sealing do not occur during the manufacturing process, improving yields and reducing costs.

'4- Large furnaces and other equipment required for glass sealing work are not required, making mass production easier.

In addition, {5- In order to reduce the heat capacity of the force-receiving body 2 during glass sealing, the columnar part on the conduit 1 side of the force-receiving body 2 is manufactured separately, and then attached to the main body after glass sealing. The troublesome manufacturing process of fixing is also eliminated.

Next, the entire pipe line vibrates due to the influence of vibration noise propagating through the pipe line, for example, vibration noise caused by opening and closing of pumps, compressors, dampers, etc.

Due to this vibration, an alternating bending moment MQ based on the mass distribution of the force receiving body 2 acts on the force receiving body 2 in the direction in which the aforementioned alternating force F acts. Bending moment MQ of this alternation
The stress generated in the force receiving body 2 is detected as noise by the stress detection section 4. FIG. 4 shows this bending moment MQ, where MQ is an alternating bending moment (object to be measured) caused by vortex generation.

When actually using the device of the present invention, as shown in FIG. A cable connection pipe E, a transmission cable F for transmitting signals, etc. are installed.

These are located outside the point where the force receiving body 2 is fixed to the conduit 1 and are mainly fixed to the conduit 1, so even if the entire conduit sways, there is no effect on the force receiving body 2. Generally considered. However, since the pipe 1 is not an ideal rigid body, it has been confirmed through experiments by the inventors that the pipe itself vibrates and the vibrations are amplified by the mounted objects.

As a result, the bending moment MQ is as shown in FIG.
Bending moment MQ based on force receiving body 2 alone, . , and the bending moment MQ,2 based on the case C, bracket D, connection pipe 8, and transmission cable F are combined to form a bending moment MQI.

Therefore, the position where the bending moment MQ, becomes zero is A
, and the position A where the bending moment MQ becomes zero will move. In some cases, the position A may coincide with the position B where the bending moment Mv is zero. Alternatively, there may be a case where the weight of the loaded object such as the case C is heavy, the bending moment MQ2 exhibits a characteristic as shown in FIG. 8, and the position A does not exist at all. In the case of the conventional example in which one stress detection section 4 is used, it is sufficient to arrange it at a position where the bending moment MQ is zero, that is, at position A, so as not to detect noise, but as described above, position A is moved. , conditions such as positions A and B match and no measurement signal can be detected, or position A does not exist, will actually result in the detection of noise.

Further, it is practically difficult to accurately arrange the stress detection section 4 at a position where the bending moment MQ is zero. For this reason,
In order to minimize the increase in the bending moment MQ2 caused by the loaded objects, etc., the subordinate structure reduces the bending moment MQ generated in the force-receiving body 2 by reducing the weight of the case C, etc., and by providing bellows or the like to absorb vibrations. Efforts were made to reduce the size.

This results in drawbacks such as a complicated structure and impossibility to make it robust. Thus, the case C, bracket D, connecting pipe E, etc. are assembled in the factory during the manufacture of this device, but the transmission cable F, etc. are added at the instrumentation site.

However, its mass depends on the measurement conditions at the instrumentation site. On the other hand, the bending moment Mv is not affected by the load.

In the present invention, the stress detection section 4a detects the stress based on the bending moments Mv and MQ, and
b, the stress based on the bending moment MQ is detected.

Then, the second input processing circuit 82 adjusts the gain of the detected value in the stress detecting section 4b so that it becomes the same as the detected value based on the bending moment MQ in the stress detecting section 4b, and the gain is adjusted in the difference amplifier 83. I decided to cancel it. As a result, only the signal to be measured is detected without detecting noise components based on pipe vibration.

Moreover, by adjusting the second input processing circuit 83, it is possible to obtain a signal whose level does not fluctuate. Further, a mechanism for reducing the influence of pipe vibration noise is not required, and the device can be made inexpensive and robust. Furthermore, for example, the weight of the loaded items such as the case C can be made sufficiently larger than the expected weight of the transmission cable F, etc., and the influence of the loaded weight can be ignored, and there is no limit to the weight of the loaded items, making it easier to design. A large degree of freedom can be obtained.

FIG. 9 is an explanatory diagram of the main part configuration of another embodiment of the present invention.

In this embodiment, a spacer 9a is placed between the stress detection parts 4a and 4b with insulators 60 and 6Q interposed therebetween.

The spacer ga is made of the same material as the fixed body 7 in this case. In such a device, it is possible to freely select the interval between the stress detecting portions 4a and 4b. This is particularly effective when, as a result of calculation, the thickness of the insulator 6b becomes thinner, the stress detection section 4a approaches the position A, and the measurement signal value based on the bending moment Mv cannot be obtained large. FIG. 10 is an explanatory diagram of the main part configuration of another embodiment of the present invention.

In this embodiment, one surface side of each of the stress detection sections 4a, 4b is brought into contact with the bottom surface of the recess 22 and the bottom surface of the fixed body 7, and the electrodes on one surface side of the stress detection sections 4a, 4b are omitted. This simplifies the configuration.

FIG. 11 is an explanatory diagram of the main part configuration of another embodiment of the present invention.

In this embodiment, a smoother 9b is disposed on the bottom surface of the recess 22, a flange TI is provided on the circumferential surface of the fixed body 7, and a flexible portion 7 consisting of a ring-shaped groove is provided in the coin portion 71.
11.

When pressing and fixing the stress detection part 4 to the force receiving body 2, the recess 2
The flatness required for the bottom surface of the recess 22 can be easily obtained by placing a spacer 9b whose flatness is precisely made in advance, and the recess 22 does not need to be finished with such precision. Therefore, it is easy to finish the flatness of the flatness plate 9b with high accuracy, so manufacturing is easy.
It can be made cheaply. Further, since the movable portion 711 is provided, it is possible to prevent excessive thermal steering and force from being generated due to variations in dimensions of each component. FIG. 12 is an explanatory diagram of the main part configuration of another embodiment of the present invention.

In this embodiment, the stress detection section 4, the insulator 6, and the fixed body 7 are configured in a cylindrical shape and a disk shape, respectively, and an electrode 61 is configured on the insulator 6 side, and the lead wire 62 is centered from the electrode. It is designed to be pulled out from a hole formed in the saddle, making it easy to take out the lead wire.

In addition, in the above-mentioned embodiment, the case where one end of the force-receiving body 2 is fixed to the conduit 1 and the other end is supported is explained, but even if both ends are fixed to the conduit 1, good.

In addition, the element body 41 is made of lithium niobate (LiNb0
3) It was explained that a piezoelectric element consisting of
The present invention is not limited to this, and for example, a ceramic pressure fin element such as zircon lead titanate (PZT) may be used, and in short, any Shoelectric element may be used.

Furthermore, although it has been explained that the insulator 6 is made of ceramic,
The material is not limited to this, and may be made of an insulating material.

Furthermore, although it has been explained that the in-phase noise components detected by the stress detection sections 4a and 4b are differentially processed by the difference amplifier 83 and the noise components are canceled, the polarization of the piezoelectric element body 41 of the stress detection section 4b or by reversely connecting the wire taken out from the stress detection section 4b to the second input processing circuit 82, the output of the stress detection section 4b is set in opposite phase to the output of the stress detection section 4b. It is also possible to cancel the noise component by adding both outputs.

In this way, it is not necessary to electrically reverse the phase of one of the outputs of the stress detection sections 4a and 4b, so that the cost can be reduced. Furthermore, although it has been explained that the gain of the second input processing circuit 82 is adjusted, if the detected value based on the bending moment MQ can be canceled in the differential amplifier 83, the gain adjustment circuit in the second input processing circuit 82 can be eliminated. Good too.

In addition, the stress detection section 4 includes a disk-shaped element body 41 and an electrode 42.
, 43, 44, but the electrodes 42, 43,
Of course, 44 may be a separate body.

In addition, in the above-mentioned embodiment, it was explained that the stress detection unit 4b is arranged at the position B of the force receiving body where the bending moment Mv is almost zero, but the position near the almost zero position is the position where the bending moment Mv is almost zero when the gain is adjusted. However, the signal amount is not limited to almost zero, and the stress detection unit 4
Of course, b may be provided at the first position where the stress caused by the disturbance force has the same sign as the increased stress increased by the appendix.

Furthermore, in the above embodiment, a case was explained in which the influence of disturbance vibration is increased by increasing the amount of added weight, but since the device has resonance characteristics due to a change in disturbance vibration frequency, the weight is substantially increased Of course, the same applies to cases where the same effect is achieved.

As described above, according to the present invention, it is possible to realize a flow rate measuring device that can measure up to a high temperature range, has high sensitivity, has excellent earthquake resistance, and is robust.

[Brief explanation of the drawing]

Fig. 1 is a conventionally commonly used flow rate measuring device, Fig. 2 is an explanatory diagram of the parts of Fig. 1, Fig. 3 is an explanatory diagram of the configuration of an embodiment of the present invention, and Fig. 4 is Fig. 3. Fig. 5 is a block diagram of the electric circuit shown in Fig. 3, Fig. 6 is an explanatory diagram of the overall configuration of the actual usage example of Fig. 3, Fig. 7, Fig. 8
This figure is an explanatory view of the operation of FIG. 3, and FIGS. 9 to 12 are explanatory views of the configuration of other embodiments of the present invention. 1... Conduit, 2... Force receiving body, 22...
...Concavity, 4a...Second stress detection section, 4b...First
Stress detection section, 41...Element body, 42, 43, 44
...Electrode, 6...Insulator, 7...
Fixed body, 8... Electric circuit, 81... First input processing circuit, 82... Second input processing circuit,
83... Differential amplifier, F... Alternating force, P.
...Disturbance force, Mv...Bending moment based on Karman vortex, MQ...Bending moment based on disturbance force, L...Depth of recess 22. Figure 11 Purple 12 Figure 1 Figure 2 Figure 3 Sagimu Figure 5 Traditional 6 Figure Purple 7 Figure 8 Figure 9 Figure 10

Claims (1)

[Claims] 1 In a flow rate measuring device that measures the flow velocity or flow rate by detecting the alternating force acting on the force receiving body due to the Karman vortex,
a columnar force receiving body inserted perpendicularly into the pipe and configured such that the stress due to the disturbance force has the same sign as the increased stress increased by the appendix at the first position; a first stress detection section disposed in the recess and provided at the first position; and a first stress detection section disposed in the recess and provided at a position where the stress due to the disturbance force has the same sign as the increased stress. an adder/subtractor that adds or subtracts the outputs of the second stress detector and the first stress detector, and a second stress detector that is fixed to the force receiving body and presses and fixes the stress detector in the recess. and an insulator that insulates the stress detection section, and the depth of the recess in the axial direction increases between the force receiving body, the stress detection section, and the insulator as the temperature changes. 1. A flow rate measuring device, characterized in that the depth is set such that a difference in thermal expansion occurring between the force receiving body and the fixed body is canceled out by a difference in thermal expansion between the force receiving body and the fixed body.