JP2991086B2 - Temperature detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature detecting device for detecting an abnormal temperature of an object to be measured.

[0002]

2. Description of the Related Art It has been conventionally considered to use an optical fiber as an effective means for detecting the temperature of an object to be measured, particularly in a noisy environment or in a place where there is a risk of explosion.

One of them is a method using a backscattered light in a so-called distributed constant temperature sensor using an optical fiber,
A method has been proposed in which a temperature-sensitive coloring tape that changes its color due to temperature is attached to a place where heat generation is likely to occur, and the color change of the tape due to a rise in temperature is confirmed using an optical fiber.

[0004] In the former case, simply, a change in backscattered light of an optical fiber accompanying a rise in the temperature of an object to be measured is detected to detect an abnormal temperature or the like of the object to be measured.
In this case, since the backscattered light of the optical fiber is very weak, there is a problem that a complicated and expensive detection means is required to detect the change, and in the latter case, a person always has to use the optical fiber. There is a problem that output must be monitored, which is very troublesome.

On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 4-355333, a device for automatically detecting a temperature rise of an object to be measured has been proposed. In addition to irradiating light from a light source through an optical fiber, and monitoring the temperature of a monitored part by receiving reflected light from a thermochromic element through an optical fiber with a color identification element, In such a configuration,
If there are a plurality of points to be monitored or measured, a plurality of optical fibers, light sources, and color identification elements must be provided, which complicates the overall configuration.

In addition, as described in Japanese Patent Application Laid-Open No. 3-92737, a temperature indicator such as a thermal paint is used as a temperature sensor for a portion to be measured, and the temperature indicator is supplied from a light source via an optical fiber for illumination. Irradiate the light beam,
The reflected light, whose color changes based on the temperature change of the temperature indicating material, is guided to the color identification light receiving element via the optical fiber for light reception, and the identification signal of the color identification light receiving element is arithmetically processed, and the alarm signal is generated as color data by the alarm generator A sensor having a structure in which a temperature indicator attached to the measurement unit is covered with a sensor unit cover housing or a temperature indicator is attached to the bottom surface in the sensor head housing so that an alarm is generated according to the alarm signal. Proposed.

[0007]

However, in the case of the apparatus described in this publication, a chemical substance that changes its color due to a temperature change, such as thermal paint, is used as the temperature indicating material. When a chemical substance that changes color between colors is used, temperature changes cannot be detected when the light source is red, so there are certain restrictions on the combination of the color of the temperature indicator and the color of the light source, and the light source can be freely selected. There is a problem that can not be.

An object of the present invention is to make it possible to easily detect an abnormal temperature of an object to be measured with a simple configuration and to freely select a light source without any restrictions.

[0009]

According to the first aspect of the present invention,
A light source, a light receiving element, first and second optical fibers connected to the light source and the light receiving element, respectively, and a third optical fiber connected to the first and second optical fibers via an optical coupler. And a temperature sensor provided at the tip of the third optical fiber, wherein the temperature sensor has a container having an open end, and a through hole in the center portion, and the container has A surfactant is filled in a space between the waterproof cap inserted therein and the waterproof cap inside the container, and the density is easily changed by light absorption / scattering with respect to light of a specific wavelength due to a rise in temperature. And a light-reflecting member provided at a position facing the distal end surface of the third optical fiber inside the container, and is inserted into the container from the opening side of the container. The tip of the third optical fiber is Is characterized in that it is introduced in a liquid-tight manner to the temperature sensing portion via the through hole of the waterproof cap.

[0010] According to such a means, the return of the reflected light from the inner surface of the container to the third optical fiber is reduced due to the change in the coloration of the surfactant in the temperature-sensitive portion due to the rise in the temperature of the object to be measured. However, since the temperature rise is detected by this decrease, the abnormal temperature of the object to be measured can be easily detected with a simple configuration without complicating the configuration. Since it becomes cloudy due to the temperature change, the temperature change can be detected irrespective of the color of the light source, and the light source can be freely selected without restriction.

At this time, it is preferable that the surfactant forming the temperature-sensitive portion is represented by the following formula (1).

According to the third aspect of the present invention, since the container itself is formed of a light reflecting material without using a light reflector, light returning to the third optical fiber due to reflection on the inner surface of the container is reduced. Therefore, it is possible to detect a temperature rise of the device under test.

Further, when air bubbles are provided in the temperature sensing portion of the temperature sensor as described in claim 4, the volume expansion of the temperature sensing portion due to a temperature rise can be reduced, and the space between the temperature sensing portion and the waterproof cap inside the container can be reduced. It is possible to prevent the temperature-sensitive part from being damaged due to expansion as in the case where the surfactant is completely filled.

Further, when the tip of the third optical fiber introduced into the temperature sensing part is cut obliquely,
The reflection at the end face of the third optical fiber can be suppressed.

By the way, as described in claim 6, the first,
The third optical fiber or the second and third optical fibers are one optical fiber, and the one optical fiber is connected to the remaining second optical fiber or the first optical fiber in the optical branching coupler. The ends may be welded, and the optical branching coupler may be an optical waveguide type or a beam splitter type.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a partial cross-sectional view of a first embodiment of the present invention, FIG. 2 is a schematic diagram, and FIG. 3 is an operation explanatory diagram.

The schematic configuration of the entire apparatus will be described.
As shown in FIG. 2, a first optical fiber 2 is connected to a light source 1 composed of an LED or other monochromatic light source or a white light source,
A second optical fiber 4 is connected to a light receiving element 3 composed of a phototransistor, a photodiode, and the like.
The second optical fibers 2 and 4 and the third optical fiber 5 are connected by an optical branching coupler (hereinafter referred to as an optical coupler) 6,
A temperature sensor 7 is provided at the tip of the third optical fiber 5.

Here, for convenience, the first, second, and third optical fibers 2, 4, and 5 are referred to. However, in this example, the first and third optical fibers 2 and 5 or the second and third optical fibers 2 and 3 are used. Optical fiber 4,5
Is an optical fiber, and the other end of the second optical fiber 4 or the first optical fiber 2 is welded to this one optical fiber in the optical coupler 6. When the optical coupler 6 is of an optical waveguide type or a beam splitter type, the three optical fibers 2, 4,
5 is connected via the optical coupler 6, and it goes without saying that such a type may be used.

The light from the light source 1 is incident on the incident end of the first optical fiber 2 and is guided to the temperature sensor 7 via the optical coupler 6 and the third optical fiber 5, and is stored in the container 9 described later. The light reflected by the light reflector 13 is received by the light receiving element 3 via the third optical fiber 5, the optical coupler 6, and the second optical fiber 4.

At this time, the light returning to the third optical fiber 5 due to the reflection on the light reflector 13 is reduced due to the light scattering accompanying the color change of the temperature sensing portion 12 in the temperature sensor 7 described later. The reflected light intensity before and after the temperature rise changes.

As shown in FIG. 1, the temperature sensor 7 has a container 9 having a concave bottom surface made of a metal such as copper or aluminum having an open end, and a container 10 having a through hole 10 in the center. The space between the waterproof cap 11 made of rubber or the like inserted through the opening 9 and the waterproof cap 11 inside the container 9 is filled with a surfactant represented by Chemical Formula 1, and is specified by a rise in temperature. Temperature sensing part 12 that changes color to a density where light absorption and scattering easily change with respect to light having a wavelength
And a light reflector 13 provided at a position facing the distal end surface of the third optical fiber 5 inside the container 9. Light from the third optical fiber 5 is Is reflected by the bottom surface of the third optical fiber 5 so as to be condensed on the distal end surface thereof.

As the surfactant to be used here, in addition to those represented by Chemical formula 1, for example, JP-A-1-113
Nonionic surfactants described in JP-A-627, ionic surfactants described in JP-A-54-123589, and the like may be used.

The light reflector 13 preferably has a high light reflectivity, such as a glossy copper plate or aluminum foil with a high surface accuracy, or a mirror.

The distal end of the third optical fiber 5 inserted into the container 9 from the opening side of the container 9 is
The temperature sensor 7 is introduced in a liquid-tight state through the through-hole 10 to the temperature sensing part 12, and such a temperature sensor 7 is arranged near the object to be measured when the object is a solid, and is arranged therein when the object is a fluid. When the temperature of the measured object rises abnormally (for example, rises to 85 ° C. or more), the color density of the surfactant of the temperature sensor 7 changes, and the specific wavelength that the light receiving element 3 receives before and after the color change is changed. Changes in the degree of light scattering, the intensity of the reflected light returning to the third optical fiber 5 changes as described above, and a rise in the temperature of the device under test is detected based on the change in the intensity of the reflected light. .

The distal end of the third optical fiber 5 introduced into the temperature sensing section 12 is cut obliquely, so that the third
The reflection at the end face of the optical fiber 5 can be suppressed.

By the way, a light source 1 is a light having a wavelength of 700 nm, and hot air of about 90 ° C. is applied to a temperature sensing portion 12 formed by filling a 5% concentration aqueous solution of a surfactant represented by the following formula (1). When the intensity of the received light is measured by a power meter instead of the element 3, the intensity of the return light to the third optical fiber 5 due to the reflection by the light reflector 13 decreases due to the temperature rise,
The change in light intensity before and after applying hot air was about 4 dB. Here, the light receiving intensity of the power meter returned to its original level after natural cooling, and it was confirmed that the temperature-sensitive portion 12 made of the surfactant had reversibility.

The relationship between the concentration of the surfactant represented by Chemical Formula 1 (= 100.x / (x + y); x is a surfactant, y is water) and the amount of change in color (attenuation) is shown below. As a result of the examination, the results are as shown in FIG. 3, and it was found that the higher the concentration of the surfactant, the larger the change amount.

Therefore, according to the first embodiment, the color change of the surfactant in the temperature sensing portion 12 due to a rise in the temperature of the object to be measured causes the light reflected by the light reflector 13 inside the container 9 to change. Since the amount of return to the optical fiber 5 of the optical fiber 3 is reduced, and a temperature rise is detected by this decrease, the abnormal temperature of the object to be measured can be easily reduced by a simple configuration without complicating the configuration unlike the related art. The temperature change can be detected irrespective of the color of the light source 1 because the surfactant of the temperature sensing part 12 becomes cloudy due to the temperature change, and the selection of the light source 1 can be freely performed without restriction. For example, an infrared LED or the like having a high emission intensity can be used.

When the tip of the third optical fiber 5 introduced into the temperature sensing section 12 is cut obliquely, reflection at the end face of the third optical fiber 5 can be suppressed, and unnecessary reflected light components can be suppressed. And the detection accuracy can be improved.

Further, since metal is used for the container 9,
The heat to the internal surfactant is well conducted, and the response to the temperature rise of the measured object is good.

The container 9 may be made of a material other than the above-mentioned metals, such as glass or plastic, and does not chemically react with the surfactant but chemically reacts with the fluid to be measured. It is only necessary to satisfy the condition that it can be used within the detection temperature range.For example, when glass is used, the thermal conductivity is lower than that of metal, so that a gentle response to temperature rise is required. Suitable for.

If the container 9 is transparent, the temperature sensing part 12
The change in white turbidity of the surfactant can be visually observed from the outside. On the other hand, if the container 9 is opaque, disturbance light from the outside can be blocked, so that the detection accuracy can be improved.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention.
It is a sectional view of a part of embodiment.

Referring to FIG. 4, FIG.
The same reference sign indicates the same or corresponding one,
The difference from FIG. 1 is that the glass, plastic,
A light reflector 15 is provided at a position facing the distal end face of the third optical fiber 5 inside the container 9 made of metal such as copper or aluminum.
Is provided.

Therefore, according to the second embodiment, the same effect as that of the first embodiment shown in FIG. 1 can be obtained.

The container 9 itself may be formed of a light absorbing material, for example, the container 9 itself may be formed of black glass.

In another embodiment, the first
Also, air bubbles may be provided in the temperature sensing part 12 in the second embodiment, and by providing such air bubbles, the volume expansion of the temperature sensing part 12 due to a temperature rise can be reduced, and the waterproof cap 11 inside the container 9 can be removed. As in the case where the surfactant is completely filled in the space between the two, the damage of the temperature sensing part 12 due to expansion can be prevented.

[0038]

As described above, according to the first aspect of the present invention, the light reflected by the light reflector inside the container accompanies a change in the coloration of the surfactant in the temperature-sensitive portion due to a rise in the temperature of the object to be measured. The return to the third optical fiber is reduced, and the temperature rise is detected by the decrease. Therefore, the abnormal temperature of the object to be measured can be easily reduced by a simple configuration without complicating the configuration unlike the related art. In addition, it can detect temperature changes regardless of the color of the light source, making it possible to freely select the light source without restriction, and easily and accurately detect the temperature rise of the DUT. Can be.

At this time, even if the container is formed of a light reflecting material, it is possible to detect an increase in the temperature of the measured object.

According to the fourth aspect of the present invention, since bubbles are provided in the temperature sensing portion of the temperature sensor, volume expansion of the temperature sensing portion due to temperature rise can be reduced, and the space between the temperature sensing portion and the waterproof cap inside the container can be reduced. As in the case of completely filling the inside with a surfactant, it is possible to prevent the temperature-sensitive part from being damaged due to expansion.

According to the fifth aspect of the present invention, since the tip of the third optical fiber introduced into the temperature sensing portion is obliquely cut, reflection at the end face of the third optical fiber can be suppressed,
Detection accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a first embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of the first embodiment of the present invention.

FIG. 4 is a partial cross-sectional view of a second embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light source 2, 4, 5 first, second, third optical fiber 3 light receiving element 6 optical coupler (optical splitter / coupler) 7 temperature sensor 9 container 10 through hole 11 waterproof cap 12 temperature sensing part 13, 15 light reflection body

Claims (7)

(57) [Claims] 1. A light source, a light receiving element, first and second optical fibers connected to the light source and the light receiving element, respectively, and the first and second optical fibers via an optical branching coupler. A third optical fiber connected thereto, and a temperature sensor provided at a tip of the third optical fiber, wherein the temperature sensor has a container having an open end, and a container having a through hole at a central portion. A space between the waterproof cap inserted into the container through the opening of the container and the waterproof cap inside the container is filled with a surfactant, and the temperature rise causes light absorption and scattering of light of a specific wavelength. A temperature-sensitive part that changes color to a density that easily changes, and a light from the third optical fiber, which is provided at a position inside the container that faces the distal end face of the third optical fiber, A light reflector that reflects to the side, The third container inserted into the container from the opening side of the container;
A temperature detecting device, wherein the tip of the optical fiber is introduced into the temperature sensing part in a liquid-tight manner through the through holes of the waterproof caps. 2. The temperature detecting device according to claim 1, wherein the surfactant forming the temperature-sensitive portion is represented by Chemical Formula 1. Embedded image 3. The temperature detecting device according to claim 1, wherein the container is formed of a light reflecting material in order to reflect light from the third optical fiber instead of the light reflecting body. . 4. The temperature detecting device according to claim 1, wherein air bubbles are provided in the temperature sensing portion of the temperature sensor. 5. The temperature detecting device according to claim 1, wherein a tip of said third optical fiber introduced into said temperature sensing part is cut obliquely. 6. The optical fiber according to claim 1, wherein the first or third optical fiber or the second or third optical fiber is a single optical fiber. 6. The temperature detecting device according to claim 1, wherein an end of the optical fiber or the first optical fiber is welded. 7. The temperature detecting device according to claim 1, wherein the optical branching coupler is of an optical waveguide type or a beam splitter type.