JPH02201247A - Optical fiber sensor - Google Patents

Abstract

PURPOSE:To enable the obtaining of a clear signal with a quick response by laminating split pieces formed in such a shape as to contact between one another's surfaces in plurality to make a swelling member. CONSTITUTION:A swelling member 15 is formed in a hollow cylinder and doughnut-shaped split pieces 16 are laminated in three layers. The surfaces 18 of the split pieces 16 are so formed as to contact one another in the lamination thereof. When an object to be detected enters a detection hole 10 of a case 5, it penetrates into the surfaces 18 of the split pieces 16 passing through an object passage hole 19 of the swelling member so that the split pieces 16 start to expand eventually causing the swelling member 15 to expand rapidly. Thus, a stress imparting member 2 is energized so strongly that an optical fiber 1 is deformed on the side of a receiving member 3 to increase a transmission loss thereby enabling detection of the presence of the object to be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a micro-bending type optical fiber sensor that detects water intrusion, oil leakage, etc.

"Prior Art" FIG. 3 shows a conventional micro-bending type optical fiber sensor.

In this optical fiber sensor, a stress applying member 2 is brought into contact with one side of the optical fiber l in the radial direction, a support member 3 is arranged on the other side, and the stress applying member 2 is attached to the optical fiber l. The swelling member 4 is arranged on the side opposite to the side on which the swelling member 4 is arranged, and these are housed in a case 5. The case 5 is provided with a detection hole lO that communicates the location where the swelling member 4 is disposed with the outside.

A pressing portion 7 that bulges out in a chevron shape is formed on the optical fiber L side of the stress applying member 2, and a swelling member 4 is formed on the back side of the pressing portion 7.
A swelling material accommodating portion 8 is formed in which the swelling material is accommodated. Further, a guide member 6 is disposed around the outer periphery of the stress applying member 2 for guiding the operation of the stress applying member 2 in a direction orthogonal to the optical fiber 1.

The swelling member 4 is formed of a swelling material that has the property of swelling when it comes into contact with a fluid object to be detected such as water or oil. And with conventional optical fiber sensors,
The swelling member 4 was formed by integrally molding a swelling material to a size that fits in the swelling material storage portion 8 of the stress applying member 2.

Next, the operating principle of this optical fiber sensor will be explained.

When the object to be detected enters through the detection hole IO of the case 5, the swelling member 4 is expanded by the object to be detected. Then, the stress applying member 2 is moved toward the optical fiber I. As a result, the optical fiber 1 is bent by being pushed by the stress applying member 2. Since transmission loss increases when the optical fiber l is bent, the presence or absence of an object to be detected can be detected by measuring this transmission loss.

"Problems to be Solved by the Invention" The conventional optical fiber sensor has a problem in that the swelling member 4 has a slow swelling speed and takes time to detect.

In order to deal with this problem, the present inventors have considered storing particulate swelling material in the swelling material accommodating portion 8 of the stress applying member 2 to form the swelling member 4. In this case, part of the swelling amount is consumed to fill the spaces between the particles, and the conversion efficiency into the force that moves the stress applying member 2, that is, the force that deforms the optical fiber l, is poor, making clear detection difficult. There was a problem where it was difficult to get a signal.

``Object of the Invention'' The present invention was made in view of the above circumstances, and an object of the present invention is to provide an optical fiber sensor that has a quick response and can obtain a clear detection signal.

"Means for Solving the Problems" In the optical fiber sensor of the present invention, the above-mentioned problems have been solved by stacking a plurality of divided pieces formed into shapes that are in close contact with each other on the surface to form a swelling member.

"Operation" In the optical fiber sensor having such a configuration, since the swelling member is divided into a plurality of parts, the object to be detected also enters between the divided pieces of the swelling member. The object to be detected is absorbed by the swelling member from a wide area.

Since each divided piece is closely stacked, the swelling of the divided piece is entirely i! of the entire swelling member. appears and strongly urges the stress applying member.

"Example" Hereinafter, the optical fiber sensor of the present invention will be described in detail with reference to the drawings. Note that the same components as those in the conventional example are given the same reference numerals to simplify the explanation.

FIGS. 1 and 2 show an embodiment of the optical fiber sensor of the present invention, and reference numeral 15 in the figures indicates a swelling member.

This expansion member 15 is formed into a hollow cylindrical shape. The expansion member 15 is made up of three donut-shaped divided pieces 16 stacked one on top of the other, and the divided pieces 16 are stacked from the optical fiber I side toward the detection hole 10 side. The surfaces 18 of each divided piece 16 are formed flat so that they come into close contact with each other when the divided pieces 16 are stacked.

A hole in the center of the swelling member 15 is a detection object passage hole 19, and is formed to communicate with the detection hole 10 of the case 5. Further, the diameter of the detection object passage hole 19 is set to a size that does not block the detection object passage hole 19 even after the swelling member 15 swells.

In this optical fiber sensor, the object to be detected is the detection hole in case 5! When it enters from 0, it passes through the sensing object passage hole 19 of the swelling member 15 and penetrates between the surfaces 18 of each divided piece 16 .

Then, due to the object to be detected that has penetrated from each surface 18...
Each divided piece 16... starts to expand, and the expansion member 15 rapidly expands.

In this way, the optical fiber sensor of this example has the divided pieces 16 and 16.
Since the swelling member 15 is formed by laminating three sheets, the surface area of the swelling member 15 into which the object to be detected permeates is large. Therefore, according to this optical fiber sensor, the swelling speed of the swelling member 15 increases and the detection time is shortened.

Moreover, in this optical fiber sensor, since the divided pieces 16 are in close contact with each other at the surfaces 18 .
The swelling amount of ... is not wasted and the divided piece 1
All of the swelling of 6... results in expansion of the entire swelling member 15 and strongly urges the stress applying member 2.

Therefore, in this optical fiber sensor, a strong load is applied to the optical fiber 1, and a clear detection signal can be obtained.

Further, since the donut plate-shaped divided pieces 16 forming the swelling member 15 of the optical fiber sensor in this example are thin, they can be manufactured by punching a sheet-like material.

Therefore, the swelling member 15 of this optical fiber sensor has good productivity and has small manufacturing variations.

Furthermore, when replacing the swelling member 15 in order to reuse the optical fiber sensor of this example, the swollen swelling member 15 is removed from the swelling material accommodating portion 8 of the stress applying member 2 by the dividing pieces 16...
・Can be withdrawn individually.

Therefore, in this optical fiber sensor, the swelling member 15 can be easily replaced and reused.

In addition, in the optical fiber sensor of this example, since the swollen member 15 is provided with the detection object passing hole 19, the object to be detected that enters through the detection hole 10 of the case 5 quickly penetrates deep into the swellable member 15. Therefore, in this optical fiber sensor,
Detection time can be further shortened.

Note that the optical fiber sensor of the present invention is not limited to the above embodiments. For example, in the above embodiment, the swelling member 1
5 shows a case 5 divided along a plane perpendicular to the center line of the detection hole IO, but the swelling member 15 is separated from the detection hole IO.
It can also be divided along a plane parallel to the center line of O.

Further, in the optical fiber sensor of the above embodiment, the swelling member 15
The detection object passage hole 19 is provided in the case 5, but the detection hole lO of the case 5 is
The swelling member 15 can be formed to have approximately the same size as the opening of the swelling material accommodating portion 8 of the stress applying member 2 and closed with a coarse mesh, and also by providing a groove in the peripheral wall of the stress applying member 2.
This makes it easier for the object to be detected to reach the deep part of the body.

"Effects of the Invention" As explained above, the optical fiber sensor of the present invention uses a swelling member in which a plurality of divided pieces formed in a shape that is in close contact with each other is stacked, so that the object to be detected can penetrate. The surface area of the swelling member is large, and the swelling rate of the swelling member is fast. Therefore, the optical fiber sensor of the present invention has a fast response speed.

Moreover, in the optical fiber sensor of the present invention, since the divided pieces are in close contact with each other on their surfaces, all the swelling of the divided pieces appears as expansion of the entire swollen member, strongly urging the stress applying member. Therefore, in the optical fiber sensor of the present invention, a strong load is applied to the optical fiber during detection, and a clear detection signal can be obtained.

Further, in the optical fiber senna of the present invention, when the swelling member is replaced and reused, the swollen member can be pulled out segment by segment from the swelling material accommodating portion of the stress applying member. Therefore, in the optical fiber sensor of the present invention, the swelling member can be easily replaced and reused.

[Brief Description of the Drawings] Fig. 1 is a sectional view showing an embodiment of the optical fiber sensor of the present invention, Fig. 2 is a perspective view showing the main parts of the embodiment, and Fig. 3 is a conventional optical fiber sensor. FIG.

Claims (1)

[Scope of Claims] An optical fiber in which a stress applying member is brought into contact with an optical fiber, and a swelling member that swells due to an object to be detected is arranged on the side of the stress applying member opposite to the side on which the optical fiber is arranged. An optical fiber sensor, wherein the swelling member is formed by stacking a plurality of segmented pieces that are shaped so that their surfaces are in close contact with each other.