JPH0313692Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a fluidic flowmeter using a polymeric piezoelectric film as a detection element.

BACKGROUND ART A fluidic flowmeter is known as a flowmeter for measuring the flow rate of fluids including gas and liquid.

Fluidytsk flow meter is Coanda
A fluid oscillator is configured by utilizing this effect, and the oscillation frequency is designed to be proportional to the main jet flow, and the flow rate of the fluid is measured from the oscillation frequency. The Coanda effect is when a jet blows into a narrow space surrounded by walls, the jet mixes up the surrounding fluid, and this entrainment phenomenon mediates the interference between the jet and the wall, causing the jet to flow in one direction. This is a phenomenon in which the jet becomes stable by adhering to a wall (wall adhesion phenomenon), and a fluid oscillator generates a jet from a jet nozzle that has less energy than the main jet from a control nozzle installed on the side of the flow. It is constructed by combining the amplification effect of a type of switch element, which can change the adhesion wall of the main jet by blowing out fluid, and a suitable feedback mechanism. Typical examples of this are the feedback oscillation type (Figure 1), in which a part of the jet adhering to the wall is returned to the control nozzle for oscillation, and the relaxation oscillation type, in which the control nozzle is connected to the control nozzle to oscillate. (Figure 2).

Referring to FIG. 1, this feedback oscillation type fluidic flowmeter has a fluid flow path to be measured provided by a piping 2 having a constriction part 1, on the downstream side of the constriction part 1.
A columnar object (target) 3 extending in a direction substantially perpendicular to the flow path (thickness direction in the drawing) is disposed, and a pair of opposing pipe walls downstream of the columnar object placement section is provided with a vibration control device. Fluid inlets 4a, 4b for
and an outlet 5 on the pipe wall immediately after the constriction part.
a, 5b are opened, and a pair of return channels 6a, 6b are formed between these.

When the fluid to be measured flows in the direction of the arrow 7 in such a configuration, at the time shown in Fig. 1, the main jet that has passed through the constriction part 1 adheres to one (the upper side in the figure) of the pipe wall due to the Coanda effect. It stabilizes and progresses as shown by arrow 8a, but a part of it progresses as shown by arrow 1.
8a, it passes through the return flow path 6a and flows out through the opening 5a immediately after the constriction part, exerting a thrust on the main jet flow. Due to this thrust and the inertia of the fluid, at the next point in time, the main jet changes its flow along the lower pipe wall as shown by arrow 8b, and eventually flows while oscillating between arrows 8a and 8b.

In addition, the relaxation oscillation type fluidic flowmeter shown in FIG.
a and 15b are opened, and these openings are connected by a bypass conduit 16; other points are substantially the same as the configuration shown in FIG. 1. Also, unlike the thrust force in the case of FIG. 1, the flow of the vibration control fluid through the pipe line 16 is performed mainly by the suction force against the opening 15a or 15b by the main jet that has passed through the constriction part. This is done based on almost the same principle as the mold, and fluid vibration occurs between arrows 8a and 8b.

The fluidic flow meter utilizes the fact that the fluid flow rate is approximately proportional to the frequency of the fluid vibration described above, and the fluid flow rate is measured by measuring the fluid vibration frequency with a suitable detection element. In the cases shown in FIGS. 1 and 2, the columnar object 3 is not necessarily essential, but it is effective for causing fluid vibration to occur quickly and stably.
It can also be used as a holding member for arranging a vibration detection element (Japanese Unexamined Patent Publication No. 57-66313).

In addition, the control fluid flow can be actively driven and vibrated by a method such as inserting a solenoid valve into the bypass flow paths 6a, 16a shown in FIG. 1 or 2 or a bypass flow path provided with a separate inlet. It is also possible to generate fluid vibrations more reliably and stably by synchronizing the fluid vibrations of the main jet flow with the detection element (Japanese Patent Laid-Open No. 59-68624).

In such a fluidic flow meter,
Needless to say, a fluid detection element that can reliably detect fluid vibrations is desired. Conventionally, hot wire current meters, strain gauges, magnetostrictive or electrostrictive elements, piezoelectric elements, etc. have been proposed as such detection elements, but none of them are necessarily satisfactory in terms of ease of arrangement or detection sensitivity. isn't it. Among them, the one that shows the best sensitivity is the hot wire type detector, but in this case it is not necessarily easy to arrange, requires an external energy supply, and is not used with corrosive or flammable fluids. There is a problem in applying it to etc. The use of piezoelectric elements is also considered (Japanese Patent Laid-Open No. 57-66313), but what is being considered here is a rigid piezoelectric element that forms part of a columnar object, that is, a ceramic such as PZT. Since it is a piezoelectric material, there are problems with its placement, particularly low measurement accuracy on the high frequency side, and problems with mechanical strength.

Purpose of the invention The purpose of the present invention is to provide a fluidic flowmeter that includes a detection element that is highly sensitive, has high mechanical strength, and is easy to configure.

Summary of the invention As a result of research for the above-mentioned purpose, the inventors found that by using a polymeric piezoelectric film as a detection element, it can be easily placed by adhering it to a desired location, and it can be easily molded. It has been found that a detection element with excellent mechanical durability and a sensitivity comparable to that of a hot wire can be obtained.

The fluidic flowmeter of the present invention is based on such knowledge, and more specifically, it consists of a fluid flow path piping to be measured having a constriction section, and a polymer piezoelectric film disposed downstream of the constriction section of the flow path. The present invention is characterized in that fluid vibration in a direction perpendicular to the flow direction downstream of the throttle portion is detected, and a fluid flow rate corresponding to the frequency of the fluid vibration is measured.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

Embodiment FIG. 3 is a schematic sectional view in the direction of the flow path showing a schematic configuration of an embodiment in which the present invention is applied to the feedback oscillation type fluidic flowmeter shown in FIG. 1.

In this example, a fluidic flowmeter is constructed of a piping 2 having a constriction part 1 and has a columnar target 3 provided downstream of the constriction. By adhering a polyvinylidene fluoride (PVDF) piezoelectric film to the wall (sensor B), or by gluing one end of the PVDF film to the downstream side of target 3 and arranging it like a windsock (sensor C), three A sensor system was constructed. used
A 9 μm thick PVDF membrane with A1 electrodes on both sides was cut into 6 mm x 18 mm.

Using air as the fluid, we varied the flow rate and connected the output signals from each sensor to a spectrum analyzer and plotter to observe the frequency and waveform.

In addition, both sensors A and C are made of the above PVDF.
This is the output voltage based on the difference in pressure applied to the membrane, and in the case of sensor B, the PVDF membrane is deflected from side to side (for convenience, it is shown as vibrating up and down in the figure, but in reality, due to its characteristics, it is caused by the lateral vibration). The output voltage generated between the double-sided electrodes was measured using the method (which is more preferable).

The frequency characteristic measurement results are shown in FIG. 4 together with the output measurement results using the hot wire in the control loop.

In either sensor, output disturbance occurs at 6 to 8 Hz, which corresponds to the transition region between the laminar region and the turbulent region, but exhibits good frequency characteristics in other regions. In addition, it has been confirmed that sensors A and C are capable of measuring from 1 Hz or less to 40 Hz (measurements at higher frequencies were not possible due to limitations of the experimental equipment), and sensor B's measurement frequency was The upper limit was around 20 Hz, but this can be improved by reducing the length of the PVDF membrane in the flow path direction. On the other hand, Sensor B, which actively utilizes the flexibility of this polymer piezoelectric film, has a sensor B that is approximately 30 times larger than other sensors.
It can be seen that the measurement sensitivity is particularly excellent.

Effects of the invention As described above, according to the invention, a piezoelectric polymer film that is easy to mold, has excellent mechanical durability, and can be easily installed at a desired location by adhesive is used as a fluid detection element. By placing this on the downstream side of the throttle in the fluid flow path to be measured, a fluidic flowmeter that includes a fluid sensor system that exhibits maximum sensitivity but is comparable to hot wire sensors that have problems in placement etc. is configured. Also
Compared to the case of using ceramic piezoelectric materials such as PZT, pressure can be applied to the entire surface without disturbing the flow, and high sensitivity can also be obtained in this respect.

[Brief explanation of drawings]

1 and 2 are schematic sectional views in the flow path direction of feedback oscillation type and relaxation oscillation type fluidic flowmeters, respectively, and FIG. 3 is a schematic sectional view in the flow path direction showing an example in which the present invention is applied to a fluidic flowmeter. The cross-sectional view and FIG. 4 are graphs showing the frequency characteristics of the output signal according to the embodiment. 1... Throttle section, 2... Channel piping, 3... Columnar object (target), A, B, C... PVDF membrane.

Claims (1)

[Claims for Utility Model Registration] 1. Consisting of a fluid flow path piping to be measured having a constriction portion and a polymer piezoelectric film disposed downstream of the constriction portion of the flow path, the pipe is perpendicular to the flow direction downstream of the constriction portion. A fluidic flow meter that detects fluid vibration in a direction of vibration and measures a fluid flow rate corresponding to the frequency of the fluid vibration. 2. The flowmeter according to claim 1, wherein a columnar object extending substantially perpendicular to the flow path is disposed approximately at the center of the flow path of the fluid to be measured downstream of the constriction portion. 3. The flowmeter according to claim 1 or 2, wherein a polymer piezoelectric film is attached to the expanding tube wall downstream of the constriction portion of the fluid flow path piping to be measured. 4. The flowmeter according to claim 2, wherein a polymer piezoelectric film is attached to a wall portion of the columnar object that is substantially parallel to the fluid flow path to be measured. 5. The flowmeter according to claim 2, wherein a polymeric piezoelectric film is attached in the form of a windsock to the downstream wall of the measured fluid flow path of the columnar object. 6. The flowmeter according to any one of claims 1 to 5, wherein the polymeric piezoelectric film has a bimorph form. 7. Any one of claims 1 to 5 for registering a utility model in which the outlet of the vibration control fluid flow path is opened at a pair of opposing locations on the pipe wall immediately after the constriction part of the fluid flow path piping to be measured. Flow meter as described. 8. The pair of vibration control fluid flow paths communicate with each of a pair of fluid inlets opened in the pipe wall downstream of the polymer piezoelectric membrane arrangement portion, and constitute a feedback oscillation type fluidic flowmeter. A flowmeter according to claim 7 of the utility model registration claim. 9. The utility model registration claim No. 9 constitutes a relaxation oscillation type fluidic flow meter, in which the pair of vibration control fluid flow paths are connected by a single pipe line that bypasses the main flow path of the fluid to be measured. Flow meter described in item 7.