JPH07190872A - Pressure sensor - Google Patents

Abstract

PURPOSE:To obtain a pressurization sensor in which there is no fear of the influence of water or possibility of causing a spark and whose installation place is not limited by a method wherein a wirelike body is wound on an elastic optical fiber at a specific pitch and a change in the transmission amount of light at a time when the optical fiber is bent by a pressure is detected. CONSTITUTION:A wirelike body 4 having a wire diameter of 0.1 to 3mm is wound on an optical fiber 1 having an outside diameter of 0.5 to 5mm at a pitch of 0.3 to 50mm, a light source 2 such as an LED, an LD or the like is connected to one end of the fiber 1, a light-receiving body 3 such as a photodiode, a phototransistor or the like is connected to the other end, and this assembly is installed on a sensor base body 5. When a pressure is applied to the optical fiber 1, the fiber 1 is bent at a cylce of the pitch of the wirelike body 4 by a space portion which is formed by the wirelike body 4 because the wirelike body 4 is interposed between the fiber 1 and the base body 5. The output of a luminous flux which is transmitted inside the fiber 1 is dropped due to its deformation, and the light-receiving amount of the light-receiving body 3 is changed. As a result, it is possible to detect that the pressure has been applied to the fiber 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor that can be used as a pressure switch or the like.

[0002]

2. Description of the Related Art Conventionally, a switch having a mechanical movable contact structure such as a micro switch or a tape-like switch has been widely used in various mechanical devices, automobiles and the like.

A pressure conductive switch in which conductive rubber is interposed between a pair of electrodes has also been proposed (Japanese Patent Laid-Open No. 61-61).
143913).

In such a conventional pressure switch, when used outdoors, underwater, or when exposed to water, electrodes,
There is a problem that the contact is oxidized and the performance is deteriorated, and that insulation failure occurs.

Further, if waterproofing is applied to prevent the influence of water, the structure of the switch becomes complicated and the size becomes large.

Further, in other conventional pressure switches, there is a risk of being affected by electromagnetic induction and generating sparks from the contacts.

On the other hand, in order to overcome the drawbacks of the conventional pressure switch, an optical fiber is sandwiched between a pair of pressure plates having irregularities on the surface, and the pressure is detected by utilizing the microbend loss caused by the displacement of the pressure plates. A pressure sensor configured as described above is also known (for example, Japanese Patent Laid-Open No. 62-2).
No. 57037, FIG. 4).

[0008]

However, such a conventional optical fiber pressure sensor requires a pair of pressure plates having irregularities on the surface, and pressure plates must be prepared in advance according to the installation location. However, it was extremely inconvenient when it was installed in a long place or a curved surface.

Therefore, an object of the present invention is to solve the problems of the conventional pressure switch, to prevent the performance deterioration due to water, the insulation failure, and the influence of electromagnetic induction.
It is an object of the present invention to provide a pressure sensor which can be freely installed at any place without danger of spark generation from the contact.

[0010]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventor has focused on an optical fiber pressure sensor and considered to wind a linear body instead of a pressure plate. The invention was completed.

That is, the present invention is characterized in that a linear body is wound at a predetermined pitch in the longitudinal direction of an optical fiber having elasticity, and a light source is provided at one end of this optical fiber and a light receiving body is provided at the other end. It is a pressure sensor.

[0012]

The present invention utilizes development in which the amount of light transmitted through the optical fiber changes when the elastic optical fiber is deformed.

That is, when pressure is applied to the optical fiber, the linear body is interposed between the optical fiber and the sensor-installed substrate, so that the optical fiber is moved at the pitch of the linear body by the space formed by the linear body. Turn.

This deformation reduces the amount of light transmitted through the optical fiber, that is, the output of the light beam. Therefore, when light is sent from the light source provided at one end of the optical fiber to the light receiving body provided at the other end, the deformation of the optical fiber changes the amount of light received by the light receiving body, and it is detected that pressure is applied to the optical fiber. The switch may be operated according to the change in the amount of light received by the light receiver.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a schematic side view showing an example of the pressure sensor of the present invention, FIG. 2 is a cross-sectional view showing an example of an optical fiber used in the present invention, and FIG. 3 is a pressure sensor of the present invention. It is a schematic side view which shows a state.

In FIG. 1, 1 is an optical fiber, 2 is L
A light source such as an ED and an LD, 3 is a light receiving body such as a photodiode and a phototransistor, 4 is a linear body, and 5 is a sensor mounting base.

As shown in FIG. 2, the optical fiber 1 is composed of a core 6 and a clad 7 having a refractive index lower than that of the core 6. The material of the core 6 and the clad 7 is not particularly limited as long as it has elasticity enough to respond to the applied pressure. However, when the pressure is applied to the optical fiber, the optical fiber is appropriately deformed. , The core 6 is made of silicone resin or acrylic resin, and the clad 7 is
The core 6 is preferably made of a silicone resin, a fluororesin, or an elastomer having a refractive index lower than that of the material. The outer diameter of the optical fiber 1 is suitably 0.5 mm to 5 mm.

As long as a gap can be formed between the optical fiber 1 and the sensor-installed substrate 5, it can be formed of any material such as metal or synthetic resin. For example, in a place where chemical resistance is required. Fluororesin-coated electric wires are suitable for use.

The linear body 4 wound around the optical fiber 1 is
The wire diameter of the linear body is preferably 0.1 mm to 3 mm, and particularly preferably about 1 mm. Further, the winding pitch of the linear body is preferably 0.3 mm to 50 mm.
mm to 30 mm is particularly preferable.

When pressure is applied to such a pressure sensor,
As shown in FIG. 3, the optical fiber 1 bends at the portion where pressure is applied. A pressure plate may be provided above the pressure sensor. In that case, pressure is applied to the linear body 4 at a position in contact with the pressure plate, and the optical fiber 1 is deformed at that position. As a result, the amount of light received by the light receiver 3 changes,
The pressure is detected.

Now, a pressure sensor is formed by winding a fluororesin-coated electric wire with an outer diameter of 1 mm at a pitch of 20 mm around an optical fiber with an outer diameter of 2.1 mm, which has a core made of polymethylmethacrylate (PMMA) and a clad made of fluororesin. Created.

When the relationship between pressure and light output was investigated using this pressure sensor, the results shown in FIG. 4 were obtained.

As is clear from this figure, the pressure applied to the pressure sensor and the light output show a linear correlation. That is, it can be seen that as the pressure increases, the light output detected by the light receiving body 3 decreases temporarily and the light is attenuated.

Next, in the above optical sensor, the outer diameter is 0.
The relationship between the winding pitch of the linear body and the fluctuation of the light output was examined for three types of linear bodies of 6 mm, 1 mm, and 1.8 mm. The pressure was 1.9 kg.

The results are shown in FIG. 5, and it can be seen that when the outer diameter of the linear body is about 1 mm and the winding pitch is 10 to 30 mm, the fluctuation of the light output is the largest and the sensitivity is good.

[0026]

According to the pressure sensor of the present invention, even when it is used outdoors, in water, or in a place where it is exposed to water, performance deterioration and insulation failure due to the influence of water do not occur. Further, since it is not affected by electromagnetic induction and no spark is generated at the contact point, it can be safely used even in a place where there is a danger of flammability or explosion.

Further, there is no restriction on the installation place, and it is possible to cut it to an appropriate length even in a long place or a curved surface and use it as it is. Further, if an optical time domain reflectometer is used as the light source, it is possible to know which part of the pressure sensor the pressure is applied to.

The pressure sensor of the present invention can be manufactured at an extremely low cost because it is only necessary to wind the linear body around the optical fiber using an ordinary tape winding machine or the like.

[Brief description of drawings]

FIG. 1 is a schematic side view showing an example of a pressure sensor of the present invention.

FIG. 2 is a cross-sectional view showing an example of an optical fiber used in the present invention.

FIG. 3 is a schematic side view showing a state where pressure is applied to the pressure sensor of the present invention.

FIG. 4 is a graph showing the relationship between pressure and light output in the pressure sensor of the present invention.

FIG. 5 is a graph showing a relationship between a winding pitch of a linear body and a light output fluctuation.

[Explanation of symbols]

 1 Optical fiber 2 Light source 3 Photoreceptor 4 Linear body 5 Sensor installation base 6 Core 7 Cladding

Claims (5)

[Claims] 1. A pressure sensor characterized in that a linear body is wound at a predetermined pitch in the longitudinal direction of an elastic optical fiber, and a light source is provided at one end of the optical fiber and a light receiving body is provided at the other end. 2. The outer diameter of the optical fiber is 0.5 mm to 5 m.
The pressure sensor according to claim 1, wherein the pressure sensor is m. 3. The pressure sensor according to claim 1, wherein the linear body is a fluororesin-coated electric wire. 4. The winding pitch of the linear body is 0.3 mm to
The pressure sensor according to claim 3, which is 50 mm. 5. The pressure sensor according to claim 3, wherein the linear body has a wire diameter of 0.1 mm to 3 mm.