JPH0953996A - Temperature detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect abnormal temperature of an object to be measured easily through a simple structure and to detect the position in the object where the temperature has risen. SOLUTION: A light source 2 and a light receiving element 2 are connected through an optical fiber 3 with a photocoupler 4 which is connected with first through fourth temperature sensors 6a, 6b, 6c, 6d through an optical fiber 7. Each temperature sensor 6a, 6b, 6c, 6d comprises a case having one open end, a waterproof cap having a central through hole inserted into the case through the opening, and a temperature sensitive part where the inner space of case defined by the waterproof cap is filled with a temperature sensitive color- changing member made of similar material which changes its color to a color of which light absorption and scattering are easily changeable to a light having a specified wavelength upon temperature rise. Forward end face of the optical fiber 7 in each temperature sensor 6a, 6b, 6c, 6d is spaced apart by a different distance from the surface of temperature sensitive color changing member at each tamperature sensitive part.

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 a place where there is a risk of explosion. As described in JP-A-355333, a device for automatically detecting a temperature rise of an object to be measured has been proposed. This is a temperature-sensitive color changing element attached to a monitored part, which is connected from a light source through an optical fiber. The temperature of the monitored portion is monitored by irradiating the light and receiving the reflected light from the temperature-sensitive color changing element through the optical fiber by the color identifying element.

However, in such a configuration, if there are a plurality of points to be monitored or measured, an optical fiber, a light source,
Since a plurality of color identification elements must be provided, the overall configuration becomes complicated.

Further, as described in Japanese Patent Laid-Open No. 3-92737, a temperature indicating material such as thermal paint is used as a temperature sensor of a measured portion, and a light flux from a light source is passed through this temperature indicating material through an optical fiber for illumination. The reflected light, whose color changes depending on the temperature change of the temperature indicator, is guided to the color identification light receiving element through the optical fiber for receiving light, and the identification signal of the color identification light receiving element is processed as color data. The alarm generator generates an alarm according to the alarm signal,
It has been proposed that the temperature indicator attached to the measurement unit is covered with a sensor cover housing, or the sensor unit has a sensor unit having a structure in which the temperature indicator is attached to the bottom surface of the sensor head housing.

[0005]

However, in the case of using the temperature indicating material as described above, since there is only one temperature sensor composed of the temperature indicating material, whether the temperature of the measured object has reached the discoloration temperature of the temperature indicating material or not. Although it can be detected, it is impossible to know which part of the object to be measured has increased in temperature.

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 structure, and also to detect a temperature rising position of the object to be measured.

[0007]

According to the first aspect of the present invention,
The light from the light source is guided via an optical fiber to multiple temperature sensors installed near the object to be measured, and the temperature rises in the containers that compose each of these temperature sensors, thereby absorbing and scattering light of a specific wavelength. Is filled with a temperature-sensitive color changing material that changes its color to change easily, and the reflected light on the surface of the temperature-sensitive color changing material of each temperature sensor is received by the light receiving element via the optical fiber and the optical branching coupler, It is characterized in that the temperature change of the object to be measured is detected by detecting the intensity change of the reflected light accompanying the color change of the temperature-sensitive color changing material.

The invention according to claim 2 is such that a light source, a light receiving element, a plurality of temperature sensors, and the light source, the light receiving element and each of the temperature sensors are connected to each other by an optical fiber, and the light from the light source is received. It is composed of an optical branching / coupling device that guides each of the temperature sensors and guides the reflected light from each of the temperature sensors to the light receiving element, and an identification circuit that detects an intensity change of the reflected light received by the light receiving element. , Each of the temperature sensors is made up of a container having one end opened and a temperature-sensitive color changing material filled in the container, and the temperature changes to a color in which light absorption / scattering easily changes with respect to light of a specific wavelength. The temperature-sensitive part and a waterproof cap, which is inserted into the container through the opening of the container and has the tip of the optical fiber on the temperature sensor side introduced through the through hole in the central part, are provided on the temperature sensor side. Before It is characterized in that the optical fiber is adapted to receive the reflected light from the surface of the temperature sensitive color change materials.

Therefore, according to the first and second aspects of the present invention, the intensity of the reflected light on the surface of the temperature-sensitive color changing material changes with the color change of the temperature-sensitive color changing material of the temperature-sensitive part due to the temperature rise of the object to be measured, Since the temperature increase is detected by this change, it is possible to easily detect the abnormal temperature of the object to be measured with a simple structure without causing a complicated structure.

At this time, as described in claim 3, the temperature-sensitive color-changing material is selected such that the color of the temperature-sensitive color-changing material of each temperature-sensitive portion is different, or as described in claim 4. , The distance from each tip of the optical fiber on each temperature sensor side to the surface of the temperature-sensing color changing material may be changed. Since the reflected light intensity from each temperature sensor is different, By examining the relationship between the discoloration status and the light intensity of the reflected light in advance, it is possible to know from the intensity of the reflected light which temperature-sensitive part of the temperature sensor has changed color, and by specifying the temperature sensor that has changed color. It becomes possible to detect which part has a temperature rise.

Further, according to the invention of claim 5, the light from the light source is guided through an optical fiber to a plurality of temperature sensors installed in the vicinity of the object to be measured, and the temperature sensor is installed in a container constituting each of the temperature sensors. The temperature-sensitive discoloring material is filled with a temperature-sensitive discoloring material that discolors to a color in which light absorption / scattering easily changes with respect to light of a specific wavelength due to temperature rise, and the temperature-sensitive discoloration is reflected by a light reflector provided in each container. The reflected light that has passed through the material is received by the light receiving element through the optical fiber and the optical branching / coupling device, and the temperature change of the measured object is detected by detecting the intensity change of the reflected light due to the color change of the temperature sensitive color changing material. Is characterized in that

Further, according to the invention of claim 6, a light source, a light receiving element, a plurality of temperature sensors, and the light source, the light receiving element and each of the temperature sensors are connected to each other by an optical fiber, and the light from the light source is received. It is composed of an optical branching / coupling device that guides each of the temperature sensors and guides the reflected light from each of the temperature sensors to the light receiving element, and an identification circuit that detects an intensity change of the reflected light received by the light receiving element. , Each of the temperature sensors is made up of a container having one end opened and a temperature-sensitive color changing material filled in the container, and the temperature changes to a color in which light absorption / scattering easily changes with respect to light of a specific wavelength. A temperature sensitive part, a waterproof cap inserted into the container through an opening of the container and having a tip of the optical fiber on the temperature sensor side introduced into the temperature sensitive part through a through hole in a central part, and a bottom part of the container. Located in It is composed of a light reflector that reflects the light from the optical fiber introduced into the temperature-sensitive portion to the optical fiber, and the tip of the optical fiber on the side of each temperature sensor is introduced into the temperature-sensitive color changing material. The lever optical fiber is characterized in that it receives reflected light reflected by the light reflector and passing through the temperature-sensitive color changing material.

Therefore, according to the fifth and sixth aspects of the invention, as the temperature of the temperature-sensitive color changing material in the temperature-sensitive part changes due to the temperature rise of the object to be measured, the reflection is reflected by the light reflector and passes through the temperature-sensitive color changing material. Since the light intensity changes, it is possible to easily detect the abnormal temperature of the object to be measured with a simple configuration, as in the inventions according to the first and second aspects.

At this time, even if the reflectance of each light reflector is changed as described in claim 7, the distance from each tip surface of the optical fiber on each temperature sensor side to the light reflector is as described in claim 8. Since the reflected light intensity from each temperature sensor is different due to this, the color change occurs by investigating the relationship between the color change status of the temperature-sensitive part of each temperature sensor and the light intensity of the reflected light in advance. It is possible to specify the temperature sensor and detect which part of the object to be measured has increased in temperature.

On the other hand, as described in claim 9, when the tip of the optical fiber introduced into each temperature sensing portion is obliquely cut, reflection at the end face of the optical fiber can be suppressed.

By the way, as described in claim 10, one of the optical fibers is an optical fiber for connecting the light source and one of the temperature sensors, or one optical fiber for connecting the light receiving element and one of the temperature sensors. In the optical branching / coupling device, the end of the remaining optical fiber may be welded to this one optical fiber, and the optical branching / coupling device may be an optical waveguide type or a beam splitter. It may be a type.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

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

Explaining the schematic structure of the entire apparatus,
As shown in FIG. 1, a light source 1 including an LED or other monochromatic light source or a white light source and a light receiving element 2 including a phototransistor, a photodiode and the like are connected to an optical branching coupler (hereinafter referred to as an optical coupler) 4 by an optical fiber 3. Connected,
The optical coupler 4 includes, for example, four first, second, third and fourth
The temperature sensors 6a, 6b, 6c, 6d are connected by an optical fiber 7, respectively.

Here, of the optical fibers 3 and 7, the light source 1
And one of the temperature sensors 6a, 6b, 6c, and 6d, or one optical fiber that connects the light receiving element 2 and one of the temperature sensors 6a, 6b, 6c, and 6d, and the optical coupler 4 Inside this one optical fiber, the ends of the remaining optical fibers are welded.

When the optical coupler 4 is of the optical waveguide type or the beam splitter type, the above-mentioned optical fibers 3 and 7 are connected through the optical coupler 4, and such a type is used. Of course, the optical coupler 4 may be used.

The light from the light source 1 is incident on the incident end of the optical fiber 3 and the optical coupler 4 and the temperature sensors 6a and 6a.
The light guided to the temperature sensors 6a, 6b, 6c, 6d via the optical fibers 7 on the b, 6c, 6d side, and reflected by the surface 14 of the temperature-sensitive color changing material in the container 9 described later is reflected by the optical fibers 7, A change in the intensity of the reflected light received by the light receiving element 2 through the coupler 4 and the optical fiber 3 and received by the identification circuit 8 is detected, and the temperature rise of the measured object is detected.

By the way, each temperature sensor 6a, 6b, 6
As shown in FIG. 2, each of c and 6d has a container 9 having one end opened, a waterproof cap 11 made of rubber or the like having a through hole 10 at the center and inserted into the inside of the container 9 from the opening,
The same temperature-sensitive color changing material is used for the waterproof cap 1 inside the container 9.
It is composed of a temperature sensitive portion 13 which is filled with an air layer 12 left in the space between 1 and 1, and changes in color in which absorption and scattering of light of a specific wavelength easily change due to temperature rise. , The tip surfaces of the optical fibers 7 in the temperature sensors 6a, 6b, 6c, 6d are arranged at different distances from the temperature-sensitive color-changing material surface 14 of each temperature-sensing section 13, and each of the optical fibers 7 is The reflected light from the surface 14 of the temperature-sensitive color changing material is received.

Each temperature sensor 6a, 6b, 6c, 6d
The tip of the optical fiber 7 introduced into the temperature-sensitive portion 12 is obliquely cut, so that reflection at the end face of the optical fiber 7 can be suppressed.

Here, the combination of the light from the light source 1 and the temperature-sensitive color changing material is preferably as shown in Table 1, and the light source 1 includes white light, monochromatic light such as red light, green light and yellow light. As shown in Table 1, as the temperature-sensitive discoloring material, a material that develops, discolors or erases color when heated to a high temperature is preferable.

[0025]

[Table 1]

Table 1 shows the color of the emitted light before and after the color change and the amount of the emitted light when the color of the temperature-sensitive color-changing material changes (for example, changes from colorless to red) when the incident light of each color is used. In particular, the emitted light quantity represents the change in the light quantity after the color change with reference to the color before change. For example, “green decrease” means that the light quantity of the green component decreases compared to before the change, and “green increase” “Indicates that the light amount of the green component increases more than before the change. In Table 1, "before color change" means "at normal temperature" and "after color change" means "high temperature" of 60 ° C. or higher, for example.

As the temperature-sensitive color changing material, a material whose light absorption changes before and after the color change in relation to the light source 1 may be selected.
For example, when red light is used as the light source 1, it is desirable that the light that reversibly changes from colorless or red, which normally does not absorb in the wavelength range, to green, black, or another color in which red light is absorbed. The materials shown in Table 2 may be used, and if PSD-R (fluorane-based leuco compound), lauryl gallate, and toluene are used as the materials that change from colorless to red by the high temperature as shown in Table 2, However, the material is not particularly limited to those shown in Table 2.

[0028]

[Table 2]

Incidentally, it is assumed that the branch connection state of the optical fibers 3 and 7 in the optical coupler 4 is as shown in, for example, FIG. 3 (however, in the figure, the solid line arrow indicates the transmitted light and the broken line arrow indicates the reflected light. Shown), each temperature sensor 6a, 6b, 6
The distances between the tip surface of the optical fiber 7 and the surface 14 of the temperature-sensitive color changing material in c and 6d are 1.0 mm, 1.5 mm, and
2.0 mm and 2.5 mm, the branch ratio of one branch in the optical coupler 4 is 1: 0.8, and the loss is 0.7 dB.
As a result, the change in the intensity of the reflected light is measured by a power meter in place of the light receiving element 2, and the result is as shown in Table 3. From this, for example, the amount of change in the intensity of the reflected light received by the light receiving element 2 is 2.8 (dB). If so, it is found that the temperature is detected only by the first temperature sensor 6a, and the change amount of the reflected light intensity received by the light receiving element 2 is 4.4 (dB).
, The first, second and third temperature sensors 6a, 6
It was found that the temperature was detected by b and 6c, and similarly, the variation amount of the reflected light intensity received by the light receiving element 2 was 2.7.
If it is (dB), the second and third temperature sensors 6b,
It can be seen that the temperature is detected by 6c. However, after the natural cooling, the intensity of the reflected light returned to the state before the temperature rise, and it was confirmed that each of the temperature sensors 6a, 6b, 6c, 6d exhibited reversibility.

[0030]

[Table 3]

Therefore, according to the first embodiment, the intensity of the light reflected by the temperature-sensitive color changing material surface 14 changes with the color change of the temperature-sensitive color changing material of the temperature-sensitive part 13 due to the temperature rise of the object to be measured,
Since the temperature rise is detected by this change, it is not necessary to provide a plurality of optical fibers, light sources, and color identification elements as in the past, and the complexity of the configuration can be prevented, and the abnormal temperature of the DUT can be easily prevented by the simple configuration. It becomes possible to detect.

Further, each temperature sensor 6a, 6b, 6c, 6
Since the distances from the respective tip surfaces of the optical fibers 7 on the d side to the temperature-sensitive color changing material surface 14 are changed, the intensity of light reflected by each temperature-sensitive color changing material surface 14 is different, and the color change state of each temperature sensitive part 13 is different. By investigating the relationship with the light intensity of the reflected light in advance, it is possible to know from the intensity of the reflected light which temperature sensing part 13 of the temperature sensor has changed color, and which part of the object to be measured can be identified by specifying the temperature sensor that has changed color. It becomes possible to detect whether the temperature has risen.

Further, each temperature sensor 6a, 6b, 6c,
Since the air layer 12 is provided in the temperature sensitive portion 13 of 6d, the volume expansion of the temperature sensitive portion 13 due to the temperature rise can be mitigated by the air layer 12, and the space between the temperature sensitive portion 13 and the waterproof cap 11 inside the container 9 can be reduced. It is possible to prevent the temperature sensitive portion 13 from being damaged due to expansion as in the case where the temperature sensitive color changing material is completely filled in the space.

As described above, each temperature sensor 6a,
Instead of changing the distances from the respective tip surfaces of the optical fibers 7 on the 6b, 6c and 6d side to the surface 14 of the temperature-sensitive color changing material, as the temperature-sensitive color changing material of each temperature-sensitive portion 13, those having different colors after color change are selected. However, in this case, each temperature sensor 6a,
The distances from the respective tip surfaces of the optical fibers 7 on the 6b, 6c, and 6d sides to the temperature-sensitive color changing material surface 14 are made the same.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention.
3 is a cross-sectional view of a portion of the embodiment of FIG.

In FIG. 4, FIG. 1 showing the first embodiment is shown.
And the same sign indicates the same or equivalent,
The difference from FIG. 1 is that the above-mentioned glass, plastic,
The tip surface of the optical fiber 7 inside the container 9 made of a metal such as copper or aluminum is located inside the temperature-sensitive portion 13, and at the position facing the tip surface of the optical fiber 7, a light reflection made of a mirror, an aluminum foil, or the like. That is, the body 15 is provided.

At this time, the light projected from the front end surface of the optical fiber 7 passes through the temperature sensing portion 13 and is reflected by the light reflector 15, and the temperature sensing portion 13 of each of the temperature sensors 6a, 6b, 6c, 6d.
Before the discoloration of the optical fiber 7
The light reflected by the light is scattered along with the color change of the temperature-sensitive portion 13 due to the temperature rise, and the return light to the optical fiber 7 is reduced from before the color change. Therefore, the reflected light intensity is higher than that before the temperature rise due to the temperature rise. Decrease.

Then, as in the case of the first embodiment described above, the same temperature-sensitive color changing material of the temperature-sensitive portion 13 of each temperature sensor 6a, 6b, 6c, 6d is used, and each temperature sensor 6 is used.
The reflectance of the a, 6b, 6c, and 6d light reflectors 15 was set to 90%, 80%, 70%, and 60%, respectively, and the result of measurement of the intensity change of the reflected light by a power meter replacing the light receiving element 2 is shown in Table 4. Came to show.

[0039]

[Table 4]

Therefore, according to the second embodiment, it is possible to obtain the same effect as in the case of FIG. 2 showing the first embodiment.

As described above, each temperature sensor 6a,
Instead of changing the reflectances of the light reflectors 15 of 6b, 6c, 6d, the reflectances of the respective light reflectors 15 are made the same, and the temperature sensors 6a, 6b, 6c, 6d from the tip end surface of the optical fiber 7 respectively. The distance to the light reflector 15 may be changed. In this case, the tip end surface of the optical fiber 7 is located inside the temperature sensitive portion 13 as in the above case.

Further, the number of temperature sensors to be provided is not limited to four as described above, and it is needless to say that the number of temperature sensors may be two, three, or five or more. It may be filled with a color changing material.

Further, the container 9 can be made of metal such as copper and aluminum as described above, glass, plastic or the like. In short, the container 9 does not chemically react with the temperature-sensitive color changing material and the fluid to be measured can be measured. Any substance that does not chemically react with a substance and satisfies the condition that it can be used within the detection temperature range may be used. For example, when glass is used, the thermal conductivity is lower than that of metal, so a gradual response to temperature rise is obtained. Suitable when sex is required.

If the container 9 is transparent, the temperature sensing unit 13
The color change of the temperature-sensitive color-changing material can be visually observed from the outside, and if the container 9 is opaque, ambient light from the outside can be blocked, so that the detection accuracy can be improved.

[0045]

As described above, according to the first and second aspects of the present invention, the light reflected by the surface of the temperature-sensitive color changing material is accompanied by the color change of the temperature-sensitive color changing material of the temperature-sensitive part due to the temperature rise of the object to be measured. Intensity changes, and this change detects a temperature rise,
It is possible to easily detect an abnormal temperature of the object to be measured with a simple structure without making the structure complicated as in the conventional case.

At this time, as described in claim 3, the temperature-sensitive color changing material is selected such that the color of the temperature-sensitive color changing material of each temperature-sensitive portion is different, or as described in claim 4. , The distance from each tip of the optical fiber on each temperature sensor side to the surface of the temperature-sensing color changing material may be changed. Since the reflected light intensity from each temperature sensor is different, By investigating the relationship between the discolored state and the light intensity of the reflected light in advance, it is possible to identify the discolored temperature sensor and detect which part of the object to be measured has increased in temperature.

According to the fifth and sixth aspects of the invention, the reflection of light reflected by the light reflector and passing through the temperature-sensitive color changing material is accompanied by the color change of the temperature-sensitive color changing material of the temperature-sensitive part due to the temperature rise of the object to be measured. Since the light intensity changes, it is possible to easily detect the abnormal temperature of the object to be measured with a simple configuration, as in the inventions according to the first and second aspects.

At this time, even if the reflectance of each light reflector is changed as described in claim 7, the distance from each tip surface of the optical fiber on each temperature sensor side to the light reflector is as described in claim 8. May be changed, and since the reflected light intensity from each temperature sensor is different, it is possible to detect which part of the object to be measured has increased in temperature.

Further, as described in claim 9, by obliquely cutting the tip of the optical fiber introduced into each temperature sensing portion, reflection at the end face of the optical fiber can be suppressed and the detection accuracy is improved. be able to.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a first embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of the 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 the second embodiment of the present invention.

[Explanation of symbols]

1 light source 2 light receiving element 3,7 optical fiber 4 optical coupler (optical branching / coupling device) 6a, 6b, 6c, 6d 1st, 2nd, 3rd, 4th temperature sensor 8 identification circuit 9 container 10 through hole 11 waterproof cap 13 Temperature Sensing Part 15 Light Reflector

Claims (11)

[Claims] 1. Light from a light source is guided through an optical fiber to a plurality of temperature sensors installed in the vicinity of an object to be measured, and the temperature rises in a container forming each of these temperature sensors to convert it into light of a specific wavelength. On the other hand, a temperature-sensitive color changing material that changes color in which light absorption / scattering easily changes is filled in, and the reflected light from the temperature-sensitive color changing material surface of each temperature sensor is received through the optical fiber and the optical branching coupler. A temperature detecting device, which receives light by an element and detects a temperature rise of the object to be measured by detecting a change in intensity of the reflected light due to a color change of the temperature-sensitive color changing material. 2. A light source, a light receiving element, a plurality of temperature sensors, and each of the light source, the light receiving element and each of the temperature sensors are connected by an optical fiber to guide light from the light source to each of the temperature sensors. An optical branching / coupling device that guides the reflected light from each of the temperature sensors to the light receiving element, and an identification circuit that detects a change in intensity of the reflected light received by the light receiving element, and each of the temperature sensors, A container with one end open,
Inserted inside the container through the opening of the container and a temperature-sensitive part that is filled with a temperature-sensitive color changing material and changes color to a color whose light absorption / scattering easily changes for light of a specific wavelength due to temperature rise And a waterproof cap in which the tip of the optical fiber on the temperature sensor side is introduced through a through hole in the central portion, and each of the optical fibers on the temperature sensor side is reflected from the surface of the temperature-sensitive color changing material. A temperature detecting device characterized by being adapted to receive light. 3. The temperature detecting device according to claim 1, wherein the temperature-sensitive color changing material is selected so that the color of the temperature-sensitive color changing material of each of the temperature-sensitive parts is different. 4. The temperature detecting device according to claim 1, wherein the distance from each of the front end surfaces of the optical fibers on the temperature sensor side to the surface of the temperature-sensitive color changing material is different. 5. The light from a light source is guided through an optical fiber to a plurality of temperature sensors installed in the vicinity of the object to be measured, and a container having each of these temperature sensors converts light into light of a specific wavelength due to temperature rise. On the other hand, a temperature-sensitive color changing material that changes its color in which light absorption / scattering is likely to change is filled, and the reflected light reflected by the light reflectors provided in each of the containers is passed through the temperature-sensitive color changing material. Light is received by the light receiving element through the optical fiber and the optical branching / coupling device, and the temperature change of the measured object is detected by detecting the intensity change of the reflected light accompanying the color change of the temperature-sensitive color changing material. Characteristic temperature detection device. 6. A light source, a light receiving element, a plurality of temperature sensors, and each of the light source, the light receiving element and each of the temperature sensors are connected by an optical fiber to guide light from the light source to each of the temperature sensors. An optical branching / coupling device that guides the reflected light from each of the temperature sensors to the light receiving element, and an identification circuit that detects a change in intensity of the reflected light received by the light receiving element, and each of the temperature sensors, A container with one end open,
Inserted inside the container through the opening of the container and a temperature-sensitive part that is filled with a temperature-sensitive color changing material and changes color to a color whose light absorption / scattering easily changes for light of a specific wavelength due to temperature rise A waterproof cap in which the tip of the optical fiber on the temperature sensor side is introduced into the temperature sensing part through a through hole in the central part, and the optical fiber which is disposed in the bottom part of the container and introduced into the temperature sensing part And a light reflector that reflects the light from the optical fiber to the optical fiber, the tip of the optical fiber on the temperature sensor side is introduced into the temperature-sensitive color changing material, and the optical fiber is reflected by the light reflector. The temperature detecting device is adapted to receive reflected light that has passed through the temperature-sensitive color changing material. 7. The temperature detecting device according to claim 5, wherein the reflectances of the respective light reflectors are different from each other. 8. The temperature detecting device according to claim 5, wherein the distance from each of the tip surfaces of the optical fibers on the temperature sensor side to the light reflector is different. 9. The temperature detecting device according to claim 2, 3, 4, 6, 7, or 8, wherein a tip of the optical fiber introduced into each of the temperature sensing parts is obliquely cut. 10. Of the optical fibers, one optical fiber connects the light source to any of the temperature sensors, or one optical fiber connects the light receiving element to any of the temperature sensors. 5. The end portions of the remaining optical fibers are welded to the one optical fiber in the optical branching / coupling device.
The temperature detection device according to 6, 7, 8 or 9. 11. The temperature detecting device according to claim 2, wherein the optical branching coupler is an optical waveguide type or a beam splitter type.