JPH0953997A - 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 similar temperature sensitive color changing member 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 equally from the surface of temperature sensitive color changing member at each temperature sensitive part and the branch ratio is varied at each branch of the optical fiber 4.

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 the same temperature-sensitive color changing material that changes color easily, and the light reflected by 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. At this time, the same temperature-sensitive color changing material is used for each of the temperature sensors, the branching ratios of a plurality of branching portions of the optical branching coupler are changed, and the reflected light accompanying the color change of the temperature-sensitive color changing material is changed. It is characterized in that a change in intensity is detected to detect a temperature rise of the object to be measured.

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. An optical branching coupler that guides each temperature sensor with a different branching ratio and guides the reflected light from each temperature sensor to the light receiving element with a different branching ratio, and the intensity of the reflected light received by the light receiving element. An identification circuit for detecting changes, each of the temperature sensors,
A container having one end opened, a temperature-sensitive color change material that is filled with a temperature-sensitive color changing material in the container, and changes in color in which light absorption / scattering easily changes with respect to light of a specific wavelength due to temperature rise; The temperature-sensitive color changing material of each of the temperature sensors is the same as that of the temperature-sensing color changing material, which is inserted into the container through the opening and has the tip of the optical fiber on the temperature sensor side introduced through the through hole in the central portion. It is characterized in that each of the optical fibers on the temperature sensor side receives the reflected light from the surface of the thermochromic material.

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, A temperature rise is detected by this change, but since the branching ratio of each branching part in the optical branching / coupling device is changed, the intensity of the reflected light from each temperature sensor received by the light receiving element is different, and the sensitivity of each temperature sensor is different. By investigating the relationship between the discolored state of the warm part and the reflected light intensity in advance, it is possible to know which temperature sensor has the discolored part from the measured reflected light intensity, and specify the temperature sensor that has changed color in this way. This makes it possible to know at which position the temperature rise has occurred in the object to be measured.

At this time, by constructing each temperature sensor as described in claim 2, a plurality of light sources,
A color identification element or the like is unnecessary, and it becomes possible to detect an abnormal temperature of the measured object with a simple configuration.

By the way, as described in claim 3, it is desirable that the distances from the respective tip surfaces of the optical fibers on the temperature sensor side to the light reflector are the same.

Further, in the invention according to claim 4, the light from the light source is guided to a plurality of temperature sensors installed in the vicinity of the object to be measured through an optical fiber, and the inside of the container constituting each of these temperature sensors. A temperature-sensitive color changing material that changes color in which light absorption / scattering easily changes with respect to light of a specific wavelength due to temperature rise is filled, and the temperature-sensitive material is reflected by the light reflectors provided in each container. The reflected light that has passed through the color changing material is received by the light receiving element via the optical fiber and the optical branching / coupling device, and the same temperature-sensitive color changing material is used for each of the temperature sensors at this time. It is characterized in that the branching ratios of the branching portions are changed and the change in intensity of the reflected light due to the color change of the temperature-sensitive color changing material is detected to detect the temperature rise of the measured object.

The invention according to claim 5 is characterized in 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 supplied. An optical branching coupler that guides each temperature sensor with a different branching ratio and guides the reflected light from each temperature sensor to the light receiving element with a different branching ratio, and the intensity of the reflected light received by the light receiving element. An identification circuit for detecting changes, each of the temperature sensors,
A container having one end opened, a temperature-sensitive color change material that is filled with a temperature-sensitive color changing material in the container, and changes in color in which light absorption / scattering easily changes with respect to 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 portion through a through hole in the center through the opening and the temperature sensing portion disposed at the bottom of the container. Configured by a light reflector that reflects the light from the optical fiber introduced into the optical fiber, the same temperature-sensitive color changing material of each temperature sensor is used, the light on the side of each temperature sensor The tip of the fiber is introduced into the temperature-sensitive color changing material so that the optical fiber receives the reflected light which is reflected by the light reflector and has passed through the temperature-sensitive color changing material.

Therefore, according to the inventions of claims 4 and 5, 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, the reflection reflected by the light reflector and passing through the temperature-sensitive color changing material. Since the intensity of light changes, the abnormal temperature of the object to be measured can be easily detected with a simple configuration as in the first and second aspects of the invention.

At this time, as described in claim 6, the distance from each tip end surface of the optical fiber on each temperature sensor side to the light reflector is made the same, and the reflectance of each light reflector is set as in claim 7. It is desirable to make them the same.

By providing an air layer in each temperature sensing part as described in claim 8, the volume expansion of the temperature sensing part due to temperature rise can be mitigated and the space inside the container between the temperature sensing part and the waterproof cap can be sensed. It is possible to prevent the temperature sensitive portion from being damaged due to expansion as in the case where the thermochromic material is completely filled.

On the other hand, as described in claim 9, when the tip of the optical fiber introduced into each temperature sensing portion is cut obliquely, 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 one which connects the light source and any one of the temperature sensors, or one optical fiber which connects 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.

[0019]

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 The end portion of the remaining optical fiber is welded to this one optical fiber by, for example, an ultrasonic welding method, and the parameters such as welding time, welding length, and welding pressure at each welding portion are adjusted as appropriate. It is possible to control and set the branching ratio of the transmitted light and the reflected light at each welded portion to different values.

The optical coupler 4 may be of a so-called optical waveguide type or beam splitter type, and in these cases, the above-mentioned optical fibers 3 and 7 are connected via the optical coupler 4. In the former optical waveguide type, by adjusting the shape of the optical waveguide and the like, and in the latter beam splitter type by adjusting the split angle respectively, the branching ratio of the incident light and the reflected light at each branching portion is controlled to different values, Can be set.

Then, the light from the light source 1 enters the incident end of the optical fiber 3 and enters 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 surface of the optical fiber 7 in each of the temperature sensors 6a, 6b, 6c, 6d and the temperature-sensitive color changing material surface 14 of each of the temperature-sensitive parts 13.
Are set to be the same, and each of these optical fibers 7 receives reflected light from each temperature-sensitive color changing material surface 14.

Each temperature sensor 6a, 6b, 6c, 6d
The tip of the optical fiber 7 introduced into the temperature-sensitive portion 13 is obliquely cut, so that reflection on 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 as well as 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.

[0027]

[Table 1]

Table 1 shows the color of the emitted light and the amount of the emitted light before and after the color change when the color of the temperature-sensitive color-changing material changes (for example, from colorless to red) while using the incident light of each color. In particular, the emitted light quantity represents a change in light quantity after color change with reference to before color change. For example, “green decrease” means that the light quantity of the green component is smaller than before change, and “green increase” means It shows 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 at high temperature as shown in Table 2, However, the material is not particularly limited to those shown in Table 2.

[0030]

[Table 2]

By the way, the branching ratio at each branching portion of the optical coupler 4 shown in FIG. 3 is set as shown in Table 3, and the change in the intensity of the reflected light is measured by the power meter in place of the light receiving element 2. As shown in Table 4. Here, Table 3 shows the branching ratios of the respective branching parts as seen from the incident side of the optical coupler 4 and the first to fourth parts.
The branching ratio of each branching portion with respect to the reflected light from each of the temperature sensors 6a, 6b, 6c, 6d is shown, and the branching ratio is such that the light intensity on the main line side is always stronger, for example, the second temperature sensor 6b. Looking at the reflected light from, the fiber designated by Y3 becomes the trunk line at the branching portion designated by X3 and Y3 in FIG. 3, and the branching ratio is such that the light intensity on this trunk side becomes larger. . The loss in Table 3 represents the loss at each branch.

[0032]

[Table 3]

[0033]

[Table 4]

From the results of Table 4, for example, the amount of change in the intensity of the reflected light received by the light receiving element 2 is 2.2 (dB).
Then, it is found that the temperature is detected only by the first temperature sensor 6a, and if the change amount of the reflected light intensity received by the light receiving element 2 is 4.4 (dB), the first, second, It can be seen that the temperature is detected by the third temperature sensors 6a, 6b, 6c, and similarly, if the variation amount of the reflected light intensity received by the light receiving element 2 is 3.3 (dB), the second and third temperatures are detected. It can be seen that the temperature is detected by the sensors 6b and 6c. However, after the natural cooling, the intensity of the reflected light returns to the state before the temperature rise, and the temperature sensors 6a, 6b, 6
It was confirmed that c and 6d exhibit reversibility.

Therefore, according to the first embodiment, since the branching ratio of each branching portion in the optical coupler 4 is changed, each temperature sensor 6a, 6b, 6 received by the light receiving element 2 is changed.
The intensities of reflected light from c and 6d are different, and each temperature sensor 6
By previously examining the relationship between the discolored state of the temperature sensitive parts 13 of a, 6b, 6c, 6d and the reflected light intensity, it is possible to know which temperature sensor temperature sensitive part 13 has changed color from the actually measured reflected light intensity. By specifying the temperature sensor that has changed color in this way, it is possible to know at which position the temperature rise has occurred, particularly when the measured object is long.

Further, each temperature sensor 6a, 6b, 6c, 6
d is composed of the container 9, the waterproof cap 11, and the temperature sensing unit 13, and the light source 1 and the light receiving element 2 and the respective temperature sensors 6a,
6b, 6c, 6d as an optical coupler 4 and optical fibers 3, 7
Since the connection is made by using the method described above, it is possible to detect an abnormal temperature of the object to be measured with a simple configuration without requiring a plurality of light sources, color identification elements and the like as in the conventional case.

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.

(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 in the temperature-sensitive color-changing material, and at the position facing the tip surface of the optical fiber 7, the same reflection made of a mirror or aluminum foil is provided. The optical fiber 7 is adapted to receive the reflected light reflected by the light reflector 15 and passing through the temperature-sensitive color changing material.

At this time, the temperature sensors 6a, 6b, 6
Light that was effectively reflected by the optical reflector 7 by the light reflector 15 before the discoloration of the temperature sensitive parts 13 of c and 6d is scattered due to the discoloration of the temperature sensitive part 13 due to the temperature rise, and the optical fiber 7 Since the amount of light returning to is less than that before the color change, the reflected light intensity is less than that before the temperature increase due to the temperature increase.

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 distance between the tip surface of the optical fiber 7 and each light reflector 15 in a, 6b, 6c, and 6d is set to be the same, and the intensity change of the reflected light is measured by a power meter instead of the light receiving element 2. It became so.

[0042]

[Table 5]

Therefore, according to the second embodiment, the same effect as in the case of FIG. 2 showing the first embodiment can be obtained.

It should be noted that 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, as described above, the container 9 can be made of metal such as copper or aluminum, 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.

[0047]

As described above, according to the inventions described in claims 1, 2, 4 and 5, the light receiving element receives each light by changing the branching ratio of each branching portion in the optical branching / coupling device. Since the intensity of the reflected light from the temperature sensor is different, the relationship between the discolored state of the temperature-sensitive part of each temperature sensor and the reflected light intensity should be investigated in advance, so that It is possible to know where the temperature has changed and to know at which position the temperature rise has occurred in the measured object. Moreover, it is possible to prevent the structure from becoming complicated as in the past, and the abnormal structure of the measured object due to the simple structure. The temperature can be detected.

By providing an air layer in each temperature sensing portion as described in claim 8, volume expansion of the temperature sensing portion due to temperature rise can be relaxed, and the space inside the container between the temperature sensing portion and the waterproof cap can be reduced. It is possible to prevent the temperature sensitive portion from being damaged due to expansion as in the case where the temperature sensitive color changing material is completely filled.

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, the same temperature-sensitive color changing material that changes color in which light absorption / scattering is likely to change is filled, and the reflected light on the surface of the temperature-sensitive color changing material of each temperature sensor is passed through the optical fiber and the optical branch coupler. Light is received by the light-receiving element, and the same temperature-sensitive color changing material is used for each of the temperature sensors at this time, and the branching ratios of the plurality of branch portions of the optical branching coupler are changed to change the color of the temperature-sensitive color changing material. A temperature detecting device, characterized in that an increase in temperature of the measured object is detected by detecting a change in the intensity of the reflected light. 2. A light source, a light receiving element, a plurality of temperature sensors, and a branching ratio in which light from the light source is connected to each of the temperature sensors by connecting the light source, the light receiving element and each of the temperature sensors with an optical fiber. From an optical branching / coupling device that guides the reflected light from each of the temperature sensors to the light receiving element with a further different branching ratio, and an identification circuit that detects the intensity change of the reflected light received by the light receiving element. And each of the temperature sensors has a container whose one end is 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 the same temperature-sensitive color changing material is used for each temperature sensor. Each of the optical fibers on the side receives the reflected light from the surface of the temperature-sensitive color changing material. 3. The distance from each end surface of the optical fiber on the temperature sensor side to the surface of the temperature-sensitive color changing material of each temperature-sensitive portion is the same.
The temperature detection device described. 4. 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 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 its color in which light absorption / scattering is likely to change is filled in, and the reflected light reflected by the light reflectors provided in the respective containers and passed through the temperature-sensitive color changing material is filled. Light is received by a light receiving element via the optical fiber and the optical branching / coupling device, and the same temperature-sensitive color changing material is used for each temperature sensor at this time, and the branching ratios of the plurality of branching parts of the optical branching / coupling device are changed. The temperature detecting device is characterized in that a change in intensity of the reflected light due to a color change of the temperature-sensitive color changing material is detected to detect a temperature rise of the object to be measured. 5. A light source, a light receiving element, a plurality of temperature sensors, an optical fiber connected to each of the light source, the light receiving element and each of the temperature sensors, and a branching ratio of light from the light source to each of the temperature sensors. From an optical branching / coupling device that guides the reflected light from each of the temperature sensors to the light receiving element with a further different branching ratio, and an identification circuit that detects the intensity change of the reflected light received by the light receiving element. And each of the temperature sensors has a container whose one end is 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 light from the optical fiber to the optical fiber, the same temperature-sensitive color changing material for each temperature sensor is used, and the tip of the optical fiber on the temperature sensor side is the temperature-sensitive material. A temperature detecting device, wherein the optical fiber is introduced into a color-changing material, and the optical fiber receives reflected light which is reflected by the light reflector and has passed through the temperature-sensitive color-changing material. 6. The temperature detecting device according to claim 1, 2, 4 or 5, wherein the distances from the respective tip surfaces of the optical fibers on the temperature sensor side to the light reflector are the same. 7. The temperature detecting device according to claim 4, wherein the light reflectors have the same reflectance. 8. The temperature detecting device according to claim 2, wherein an air layer is provided in each of the temperature sensing parts. 9. The temperature detecting device according to claim 2, 5, 6 or 7, 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. 7. 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 7, 8 or 9. 11. The temperature detecting apparatus according to claim 2, 5, 6, 7, 8 or 9, wherein the optical branching / coupling device is an optical waveguide type or a beam splitter type.