JPH03181831A - pressure sensor - Google Patents

Abstract

PURPOSE:To accurately detect the pressure change of a fluid by bonding an optical fiber strand to the surface of a bellows closed at the moving end thereof and having a fluid inflow port provided to the fixing end thereof and receiving the bellows in a hermetically closed casing. CONSTITUTION:An optical fiber strand 3 is bonded to the outer surface of bellows 1 closed at the moving end 1A thereof and having a fluid inflow port 2 provided to the fixing end 1B thereof and the bellows 1 is received in a hermetically closed casing 4. For example, this pressure sensor is mounted to a natural gas line so that gas flows in the bellows 1 from the inflow port 2 and, when a light pulse is sent in the strand 3 from the light pulse tester provided to one end of the strand 3, the pressure in the pipeline is lowered in such a case that the gas leaks from a part of the pipeline. As a result, the bellows 1 contracts and the curvature of the strand 3 becomes large and the transmission loss of the light pulse increases. This change of the transmission loss of the light pulse is detected by the light pulse tester and the leakage of the gas from the pipeline is detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a pressure sensor, and particularly to a pressure sensor that can accurately detect pressure changes without using a power source by using optical fiber wires. It is.

[Conventional technology]

Conventionally used pressure sensors include the following:

(1) Introducing fluid into a semicircularly curved pressure receiving pipe,
Bourdon tube type pressure sensor (2) that deforms the curvature of the pressure receiving tube and detects changes in fluid pressure based on the amount of deformation Diaphragm type pressure sensor that deforms the diaphragm depending on the pressure of the fluid and detects changes in fluid pressure based on this amount of deformation Sensor (3) Place the bellows in the casing, introduce fluid into the casing to deform the bellows, and detect changes in fluid pressure based on the amount of deformation.Bellows-type pressure sensor (4) Change the spacing between electrode plates depending on the pressure. Capacitance pressure sensor (5) that electrically detects fluid pressure changes based on the amount of change Semiconductor sensor that electrically detects fluid pressure using semiconductors [Problems to be solved by the invention] ] However, the conventional pressure sensor described above has the following problems.

That is, since the pressure sensors (1) to (3) do not themselves have a pressure transmission function, for example, when these sensors are used for remote monitoring of gas leaks from natural gas pipelines, pressure Equipment costs are high because a separate transmission line is required.

On the other hand, the pressure sensors (4) and (5) above require a power source, so although they themselves have a pressure transmission function, they require incidental equipment such as a power cord and an amplifier.
Equipment costs still apply.

Therefore, an object of the present invention is to provide a pressure sensor that can accurately detect changes in fluid pressure without requiring a separate pressure transmission path or power source.

[Means to solve the problem]

This invention is characterized by comprising a bellows with a closed moving end and a fluid inflow hole at a fixed end, an optical fiber strand pasted on the surface of the bellows, and a sealed casing for accommodating the bellows. It has the following.

Next, one embodiment of the pressure sensor of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing one embodiment of a pressure sensor of the present invention, and FIG. 2 is a partially enlarged sectional view of FIG. 1.

As shown in FIGS. 1 and 2, the pressure sensor of the present invention includes a bellows (1) whose moving end IA is closed and a fixed end (IH) having a fluid inlet hole 2, and an optical fiber attached to the outer surface of the bellows (1). It consists of a wire 3 and a closed casing 4 for housing a bellows l.

The bellows 1 is made of rubber or resin, and is given an elongation force during VT, and is compressed as the pressure inside the bellows 1 decreases.

As the optical fiber wire 3, a conventionally known one is used. The reason why the optical fiber strand 3 is attached to the outer surface of the bellows 1 is to prevent the optical fiber strand 3 from being damaged by fluid.

In this invention, the transmission loss of the optical fiber strand 3 changes according to its curvature, that is, the optical fiber strand 3
The transmission loss increases as the curvature of the optical fiber 3 increases, which is an inherent property of the optical fiber 3.

According to the pressure sensor of the present invention configured as described above, the pressure of the fluid is detected in the following manner.

For example, a plurality of pressure sensors may be installed in a natural gas vibrator line at predetermined intervals along its axial direction so that the gas flowing in the vibrator line flows into the bellows 1 from the fluid inlet hole 2 of the bellows l. , installed in series.

Then, an optical pulse is sent to the optical fiber 3 from an optical pulse tester provided at one end of the optical fiber 3, and the transmission loss of the optical pulse is measured by the optical pulse tester. At this time, the optical pulse tester is adjusted in advance so that the transmission loss of the optical pulse transmitted within the optical fiber 3 becomes zero when there is no leakage point in the pipeline.

When gas leaks from a portion of a pipeline, the pressure within the pipeline near the leak location decreases.

As a result, the bellows 1 of the pressure sensor near the leakage point contracts. When the bellows 1 contracts, the curvature of the optical fiber wire 3 attached thereto increases, and the transmission loss of optical pulses increases. Changes in the transmission loss of this optical pulse are detected by an optical pulse tester to detect gas leakage from the pipeline.

The leakage location can be detected by measuring the round trip time of the light pulse with an optical pulse tester.

〔Effect of the invention〕

As explained above, the pressure sensor of the present invention has both a sensor function and a transmission path, so it is useful in that it can accurately detect changes in fluid pressure without requiring a separate signal cable or power source. effect is brought about.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of a pressure sensor of the present invention, and FIG. 2 is a partially enlarged sectional view of FIG. 1. In the drawings: 1 - bellows, IA IB - fixed end, 2 - 3 - optical fiber 4 moving end, fluid inlet hole, casing.

Claims (1)

[Claims] (1) A bellows having a closed moving end and a fluid inflow hole at a fixed end, an optical fiber strand pasted on the surface of the bellows, and a sealed casing for accommodating the bellows. pressure sensor.