JP2726151B2 - Fluidic flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention calculates a fluid by causing a fluid to be measured to flow in a fluidic element and electrically detecting the fluid vibration by a piezoelectric film sensor. In a fluidic flow meter that measures the flow rate by processing, the piezoelectric membrane sensor malfunctions due to automobile vibration, construction vibration, etc., even though there is no flow of the fluid to be measured, and an electric signal is generated. The present invention relates to a fluidic flow meter with a malfunction prevention device configured to prevent an incorrect input from being input into the device.

[Prior art] A piezoelectric membrane sensor for detecting fluid vibration in a fluidic flow meter captures a very small pressure fluctuation with a membrane and converts it into an electric signal. It may operate even when external vibration is applied.

Conventionally, as means for preventing such a malfunction, a fluid vibration detecting sensor disclosed in Japanese Utility Model Laid-Open No. 1-58119 is known.

In this sensor, a pressure chamber is divided into three chambers of a center chamber and left and right outer chambers by two piezoelectric films, the center chamber is connected to one detection hole of a detection element, and the outer chamber is connected to the other detection hole. Then, in the case of external vibration, a malfunction is prevented by canceling a signal in this case using the characteristic that two piezoelectric films are displaced in the same direction.

[Problems of the Related Art] The error motion prevention device of the above-mentioned known example is applicable to a relatively large one because it is necessary to use two piezoelectric films or to form three pressure chambers. However, when miniaturization is pursued as much as possible, these configurations become obstacles.

The present invention has been proposed in view of the above point, and an object of the present invention is to provide a malfunction prevention device that is effective when miniaturization of a fluidic flow meter is pursued as much as possible.

[Means for Solving the Problems] The configuration of the present invention is as follows.

In a fluidic flow meter that measures a flow rate by detecting and calculating a fluid vibration generated by a fluidic element by a piezoelectric membrane sensor, a flow detecting sensor that detects a flow of a fluid to be measured is attached in the flow path, Fluid flow meter incorporating a malfunction prevention circuit for canceling the output of the piezoelectric film sensor when the flow is not detected by the flow detection sensor.

In the above configuration, the type of the flow detection sensor is not particularly limited. For example, a pressure switch or a differential pressure switch is inserted into the flow path pipe of the fluid to be measured, and when pressure or differential pressure is detected in the pipe, it is determined that there is a flow and the input from the piezoelectric film sensor is received as it is. When no detection is made, the flow, that is, it is determined that no fluid is used, and the input from the piezoelectric film sensor is canceled.

The flow detection sensor has no flow when, for example, a fluidic flow meter is equipped with an emergency shutoff valve that operates during an earthquake or the like, when the shutoff valve is closed or when it is intentionally closed. Alternatively, the input from the piezoelectric film sensor may be cancelled.

[Operation] When a fluid flows through the fluidic element, the fluidic element generates fluid vibration (pressure vibration). This fluid vibration is guided to the piezoelectric film sensor and displaces the piezoelectric film. The piezoelectric film generates an electric signal by the displacement, and the electric signal enters an arithmetic processing circuit. The arithmetic processing circuit calculates the flow rate by performing arithmetic processing, and transmits the calculated flow rate to, for example, a measurement sensor by a count display or an electric signal.

On the other hand, when the fluid to be measured is not flowing, for example, when the gas appliance is not used in the case of city gas, or when the main valve of the gas is stopped during construction, the flow of the fluid to be measured is There is no. Also, when the fluidic flow meter is being transported to the installation location in the standby state, even if the piezoelectric membrane sensor is activated by external vibration such as automobile vibration,
Since the flow detection sensor does not detect the flow of the fluid to be measured, the signal that enters the arithmetic processing circuit from the piezoelectric film sensor is canceled. As a result, even if the piezoelectric film operates due to abnormal vibration and generates a flow rate signal, no measurement is made.

Embodiment FIG. 1 shows an embodiment in which a pressure switch is inserted into a flow passage in a fluidic flow meter (gas meter) to prevent malfunction.

Reference numeral 1 denotes a flow path, 2 denotes a flow rate measurement circuit including a fluidic element 3 for measuring the flow rate of gas passing through the flow path 1 and a piezoelectric film sensor 4, and 5 denotes the flow rate measurement circuit 2.
This is an arithmetic processing circuit for calculating and displaying the flow rate based on the output from.

Reference numeral 6 denotes a pressure switch inserted in the flow path 1, reference numeral 7 denotes a signal determination circuit (malfunction prevention circuit) inserted between the flow measurement circuit 2 and the arithmetic processing circuit 5, and pressure is detected by the pressure switch 6. In this case, the signal from the flow rate measuring circuit 2 is sent to the arithmetic processing circuit 5 as it is, and when the pressure is not detected, the signal is canceled and no signal is transmitted to the arithmetic processing circuit 5 side.

As a result, malfunction when there is no flow rate, that is, erroneous measurement is not performed.

FIG. 2 shows an embodiment in which a differential pressure is taken out from upstream and downstream of the flow measuring device 2 and a flow in the flow path 1 is detected by the differential pressure. , The signal determination circuit 7 passes or cancels the signal of the flow rate measuring device 2.

FIG. 3 shows an embodiment in which an emergency shut-off valve (safety valve) 9 is attached to the inlet of the fluidic flow meter. When the emergency shut-off valve 9 is ON, a signal from the flow measuring device 2 is provided. Is passed, and in the OFF state, it is canceled. 10 is an earthquake detector,
When a seismic intensity exceeding a certain level is detected, a signal is issued and the emergency shutoff valve 9 is closed. 11 is a safety circuit.

[Effect of the Present Invention] As described above, the present invention cancels the signal output from the flow rate measuring device and does not perform the arithmetic processing when the flow rate passing through the flow path (fluidic flow meter) is not detected. I made it. As a result, the following effects can be expected.

a. Even if the piezoelectric film sensor operates due to external shock vibration other than the fluid vibration from the fluidic element, all the signals transmitted from the piezoelectric film sensor are canceled.

As a result, the flow rate is not erroneously integrated when not in use.

b. Since the malfunction prevention device can be constituted by an electronic circuit, it has almost no occupied area, and thus can be applied to the miniaturization of the fluidic flow meter.

c. When a fluidic flow meter is manufactured at a factory and all are transported to the installation site in a standby state, no malfunction occurs during the transportation.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of the present invention using a pressure switch, FIG. 2 is a view showing an embodiment of the present invention using a differential pressure switch, and FIG.
The figure is an embodiment of the present invention in which the emergency shutoff valve is linked to ON and OFF. DESCRIPTION OF SYMBOLS 1 ... Flow path 2 ... Flow measuring device 3 ... Fluidic element 4 ... Piezoelectric film sensor 5 ... Arithmetic processing circuit 6 ... Pressure switch 7 ... Signal determination circuit 8 ... Differential pressure switch 9 Emergency shutoff valve 10 Earthquake detector 11 Safety circuit

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-227925 (JP, A) JP-A-64-58119 (JP, A) Jpn.

Claims (4)

(57) [Claims] 1. A fluid flow meter for measuring a flow rate by detecting a fluid vibration generated by a fluidic element by a piezoelectric membrane sensor and performing an arithmetic processing, a flow detecting sensor for detecting a flow of a fluid to be measured is provided with a flow path. A fluid flow meter including a malfunction prevention circuit that is mounted in the apparatus and cancels an output from the piezoelectric film sensor when a flow is not detected by the flow detection sensor. 2. The fluidic flow meter according to claim 1, wherein the flow of the fluid to be measured is detected by a pressure switch. 3. The fluidic flow meter according to claim 1, wherein the flow of the fluid to be measured is detected by a differential pressure switch. 4. The flow of the fluid to be measured is turned on and off by an emergency shutoff valve.
2. The fluidic flowmeter according to claim 1, wherein the fluidic flowmeter is configured to detect the condition.