JPH07190864A - Temperature detection device - Google Patents

Abstract

PURPOSE:To obtain a temperature detection device which prevents the damage of an optical fiber and whose detection sensitivity is enhanced by a method wherein a low-thermal-conductivity sheath is installed on the outer circumference of a clad, a high-thermal-conductivity sheath is installed on its outer circumference, heat is made to escape to the length direction by the sheath at the outside in a local temperature rise and the heat is conducted by the sheath at the inside. CONSTITUTION:A temperature-sensitive discoloration part 11b is formed in the central part of a core 11a, a clad 11c is arranged and installed at the outer circumference of the core 11a, a low-thermal-conductivity resin sheath 11d is arranged and installed on the outer circumference of the clad 11c, and a high-thermal-conductivity metal sheath 11e is arranged and installed on its outside. When a local temperature rise is generated, heat is conducted quickly to the length direction of an optical fiber 11 by the metal sheath 11e whose thermal conductivity is good, and the damage of the core 11a is prevented. Then, the heat is conducted by the resin sheath 11d, the temperature of the optical fiber 11 is raised over a wide range, and the detection sensitivity of a temperature is enhanced.

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 using an optical fiber applied to detect the temperature of a linear elongated object.

[0002]

2. Description of the Related Art Conventionally, when detecting the temperature of a linear long object, the temperature of the linear long object can be detected in the longitudinal direction by a so-called lumped constant type temperature sensor such as a semiconductor temperature sensor. However, multiple temperature sensors must be arranged along a long linear object, many temperature sensors are required, and the circuit that processes the output of each temperature sensor becomes complicated, so the whole However, there is a problem in that a general configuration becomes complicated and a malfunction is likely to occur due to the influence of noise.

Therefore, as a temperature detecting device suitable for detecting the temperature of a long linear object, a distributed constant type temperature detecting device using an optical fiber has been proposed. It is intended to detect the abnormal temperature etc. of the linear long object by detecting the change in the backscattered light of the accompanying optical fiber, but in this case the backscattered light of the optical fiber is weak in the first place,
In order to detect the change, complicated and expensive detection means are required.

On the other hand, similarly, as a means for temperature detection using an optical fiber, as described in Japanese Utility Model Publication No. 62-3761, a temperature-sensitive color-developing layer is provided on the outer periphery of the core of the optical fiber as a color change with temperature. Is being done.

That is, as shown in FIGS. 13 (a) and 13 (b), a temperature-sensitive color forming layer 1b is provided on the outer periphery of the core 1a by vapor deposition or coating, and the cladding 1 is formed on the outer periphery of the temperature-sensitive color developing layer 1b.
c is provided, and a sheath 1d is further provided on the outer periphery thereof to form an optical fiber 1, and light from a white light source or the like is incident on the optical fiber 1 to absorb light of a specific wavelength by the thermosensitive coloring layer 1b that has developed color. The change in wavelength of the light emitted from the optical fiber 1 is detected by the attenuation effect of.

On the other hand, a temperature sensor optical cable described in Japanese Patent Laid-Open No. 62-32132 has been proposed. As shown in FIG. 14, the temperature sensor optical cable is made of aluminum and copper on the outer periphery of a temperature detecting optical fiber 3 composed of a core and a clad. , A metal coating layer 4 made of a good heat conductive metal such as silver is formed, and heat is transferred in the longitudinal direction of the optical fiber 3 by the metal coating layer 4, so that even if the temperature rises locally. The temperature rise range is widened by heat conduction in the longitudinal direction, and the sensitivity can be improved.

[0007]

However, even if the optical fiber 1 provided with the temperature-sensitive color developing layer 1b as described in the former publication is used, the temperature of the linear elongated object is locally increased and the optical fiber is increased. When the discoloration range of 1, that is, the temperature rise range is narrow, the change of the emitted light is small, so that there is a disadvantage that the abnormal temperature cannot be reliably detected.

Further, when the brightness of the light source fluctuates, or in the course of the installation path of the optical fiber 1 for temperature detection, the optical fiber 1
Even if a deformation such as bending is applied to the output, the intensity of the emitted light changes, so even if the temperature of the linear long object has not risen, this is detected as a temperature rise, causing a malfunction. There is a risk.

On the other hand, when the metal coating layer 4 is provided as described in the latter publication, since the metal coating layer 4 is directly provided on the outer circumference of the optical fiber 3, the optical fiber 3 is formed at the same time as the longitudinal direction of the optical fiber 3. Since heat is also transmitted to the center of the optical fiber 3 and the optical fiber 3 usually does not have heat resistance, the cladding and core of the optical fiber 3 are damaged by high heat until the abnormal temperature rise is detected, resulting in loss of reliability. I have a problem.

Further, since the metal coating layer 4 is formed directly on the optical fiber 3, the optical fiber 3 may be damaged, which may cause an increase in transmission loss.

Further, if the optical fiber 3 is a silica optical fiber, the metal coating layer 4 can be formed relatively easily.
It is difficult to form the metal coating layer 4 with a plastic optical fiber.

Therefore, the present invention has been made in order to solve the above problems, and an object thereof is to improve sensitivity without impairing reliability and to prevent malfunction. To do.

[0013]

The invention according to claim 1 is
An optical fiber for temperature detection, a light source which is provided at a light incident end of the optical fiber and makes light enter the optical fiber, and a light reception signal which is provided at a light emitting end of the optical fiber and corresponds to an intensity of light emitted from the optical fiber. And a core having a color-changing portion including a temperature-sensitive color-changing material that changes color in which light absorption easily changes with respect to light having a specific wavelength due to temperature rise, and a core of the core. A clad provided on the outer circumference, and a first sheath provided on the outer circumference of the clad,
It is characterized in that it is constituted by a second sheath made of a material having a higher thermal conductivity than the first sheath provided on the outer periphery of the first sheath.

Further, as described in claim 2, the temperature detection is performed on the reference optical fiber and the color changing portion including a temperature-sensitive color changing material that changes color in which light absorption is easily changed for light of a specific wavelength due to temperature rise. An optical fiber cable in which a use optical fiber is assembled and covered with a jacket to be integrated, and a light source is provided between the light source and the incident end of the optical fiber cable, and the light of the light source is branched in two directions. Optical splitters that enter the incident ends of the reference optical fiber and the temperature detecting optical fiber, respectively, and emitted lights of the reference optical fiber and the temperature detecting optical fiber that are provided at the emitting end of the optical fiber cable. And a light receiving portion for outputting a light receiving signal proportional to the light intensity of the optical fiber cable, and a sheath made of a material having a higher thermal conductivity than the outer jacket is provided on the outer circumference of the outer jacket of the optical fiber cable. There.

[0015]

According to the invention of claim 1, since the clad, the first sheath and the second sheath having a better thermal conductivity than the first sheath are formed on the outer side of the core having the discolored portion, a local temperature rise can be prevented. At the time of generation, heat is quickly transferred to the longitudinal direction of the optical fiber by the second sheath having good heat conduction, and the first sheath, which has poorer heat conduction than the second sheath in the longitudinal direction of the optical fiber, is compared to the longitudinal direction. The heat is slowly transferred, and before the cladding and core of the optical fiber are damaged, the heat is transferred in the longitudinal direction of the optical fiber and the temperature of the optical fiber rises over a wide range.

According to the second aspect of the invention, since the light from the light source is branched by the optical branching device, when the brightness of the light source fluctuates, the light intensity of the light emitted from the temperature detecting optical fiber is changed. If the change rate of the temperature is the same as the change rate of the light intensity of the output light of the reference optical fiber, and if an external force such as bending is applied, the output of the temperature detection optical fiber and the reference optical fiber When the rate of change of the light intensity of the emitted light is the same as the rate of change of the light intensity of the emitted light of the reference optical fiber, on the other hand, when the temperature rises, the temperature-sensitive color changing material of the temperature detecting optical fiber is colored, Since the color changes, the rate of change of the light intensity of the emitted light of the temperature detection optical fiber before and after the temperature rise differs from the rate of change of the light intensity of the emitted light of the reference optical fiber.

Therefore, if the ratio of the light intensity of the emitted light of the temperature detecting optical fiber and the light intensity of the emitted light of the reference optical fiber is taken, the change in the light intensity of the emitted light due to the temperature rise and the temperature rise and It is possible to clearly distinguish the variation in the light intensity of the emitted light due to other causes, and prevent malfunctions.

Also in this case, as in the case of the first aspect of the present invention, when a local temperature rise occurs, both optical fibers are separated by the sheath having good heat conduction and the jacket having poor heat conduction. A wide temperature rise range in the longitudinal direction can be obtained without being damaged by heat.

[0019]

【Example】

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

In FIG. 2 showing the overall structure, 11 is an optical fiber arranged along a linear elongated object such as an electric wire (not shown), and 12 is white light provided at the light incident end of the optical fiber 11. A light source for injecting monochromatic light into the optical fiber 11,
Reference numeral 13 denotes a light-receiving portion including a light-receiving element such as a photodiode or a phototransistor, which is provided at the light emitting end of the optical fiber 11 and outputs a light receiving signal according to the intensity of emitted light.

At this time, when the light source 12 is a monochromatic light source, a light emitting element such as a red LED or a green LED may be used.

The optical fiber 11 is constructed in detail as shown in FIG. 1, and includes a core 11a and a core 11a.
A color changing portion 11b formed in the central portion of the core 11a, which includes a temperature-sensitive color changing material that changes its light absorption with respect to a specific wavelength of light from the light source 12 to a specific wavelength, and a clad provided on the outer periphery of the core 11a. 11c, a resin sheath 11d that is the first sheath provided on the outer circumference of the clad 11c, and a metal such as aluminum, copper, or silver having a higher thermal conductivity than the resin sheath 11d provided on the outer circumference of the resin sheath 11d. And a metal sheath 11e which is a second sheath.

By the way, as an example of a method for forming the color-changing portion 11b containing the temperature-sensitive color-changing material in the central portion of the core 11a, for example, a resin tube serving as a clad 11c made of a fluorine resin having an inner diameter of 2 mm and an outer diameter of 3 mm is provided in The transparent silicone may be poured into the resin tube to form the core 11a, and then the silicone containing the temperature-sensitive color changing material may be poured into the resin tube to form the color changing portion 11b.

At this time, the silicone poured into the resin tube is difficult to proceed due to friction on the inner wall surface of the tube, and the silicone containing the temperature-sensitive color changing material subsequently poured corresponds to the center of the core 11a. The portion to be moved smoothly advances, and as a result, the structure shown in FIG. 1 is obtained.

After forming the core 11a as described above, the resin tube may be removed and the air layer or a material having a large difference in refractive index from the core 11a may be replaced with the clad 11c.

By the way, the combination of the light from the light source 12 and the temperature-sensitive color changing material is preferably as shown in Table 1, for example. In addition to the white light, the light source 12 can emit monochromatic light such as red light, green light and yellow light. It is preferable to use, and as the temperature-sensitive color changing material, as shown in Table 1, it is preferable to use a material that develops, discolors, or erases color at high temperature.

[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 the change in light quantity after color change with reference to the color before change. For example, “small green” means that the light quantity of the green component is smaller than before change, and “green large” “Indicates that the light amount of the green component increases more than before the change.

In Table 1, "before change" means room temperature and "after discoloration" means condition at high temperature of 60 ° C or higher, for example.

Further, as the material of the temperature-sensitive color change material, a material whose light absorption changes before and after the color change in relation to the light source 12 may be selected. For example, when red light is used for the light source 12, it is normally absorbed in that wavelength range. It is desirable to use a material that reversibly changes from a non-colorless or red color to a green or black color that absorbs red light. Specifically, the materials shown in Table 2 may be used. PSD-R (fluorane-based leuco compound), lauryl gallate, and toluene may be used as a material that changes from colorless to red color by the above, but the materials are not particularly limited to those shown in Table 2.

[0031]

[Table 2]

Therefore, since the optical fiber 11 for temperature detection is constructed as shown in FIG. 1, when the local temperature rise occurs, the optical fiber 1 is provided by the metal sheath 11e having good heat conduction.
1, the heat is quickly transmitted in the longitudinal direction of the optical fiber 11, and the resin sheath 11d, which has poorer heat conduction than the metal sheath 11e, transmits the heat toward the center of the optical fiber 11 more slowly than in the longitudinal direction. Before the 11a is damaged, heat is transmitted in the longitudinal direction of the optical fiber 11 and the temperature of the optical fiber 11 rises over a wide range, so that the sensitivity can be improved, and the linear long object locally has an abnormal temperature. Even when the temperature rises, the abnormal temperature can be detected reliably and reliably.

The same effect can be obtained by dispersing the temperature-sensitive color changing material in the core 11a.

(Second Embodiment) FIG. 3 is a partial sectional view of a second embodiment of the present invention.

In FIG. 3, the same symbols as in FIG. 1 indicate the same or corresponding ones, and the difference from FIG. 1 is that
A discolored portion 11f is provided on the outer periphery of the core 11a.
That is, the clad 11c is formed on the outer periphery of 1f.

As a method for forming the discolored portion 11f, as in the case of FIG. 1, for example, a syringe is used for temperature sensing by using a syringe in a resin tube as a clad 11c made of a fluororesin having an inner diameter of 2 mm and an outer diameter of 3 mm. The core 11a may be formed by pouring silicone containing a color-changing material to form the color-change portion 11f, and then pouring silicone into the resin tube using a syringe.

At this time, the silicone containing the temperature-sensitive discoloration material that was first poured into the resin tube was rubbed by the inner wall surface of the resin tube and became difficult to proceed, and the silicone that was subsequently poured was poured first. It smoothly advances through the center of the silicone resulting in the structure shown in FIG.

As described above, the discolored portion 1 is formed on the outer periphery of the core 11a.
Even if the optical fiber 11 having 1f is used, the same effect as that of the first embodiment can be obtained.

(Third Embodiment) FIG. 4 is an overall schematic view of a third embodiment of the present invention, FIG. 5 is a partial sectional view of FIG. 4, FIG.
FIG. 7 is a cross-sectional view of different parts of FIG.

As shown in FIG. 4, the light from the light source 21 is branched into two directions by the optical branching device 22, and the optical fiber cable is arranged along a linear elongated object (not shown) such as an electric wire. The light branched by the optical branching device 22 is respectively incident on the reference optical fiber 24 and the temperature detecting optical fiber 25 constituting 23, and the light emitted from both the optical fibers 24 and 25 is the first and second light receiving portions 26, Each of the light receiving portions 26 and 27 outputs a light receiving signal proportional to the light intensity of the emitted light from the both optical fibers 24 and 25. The processing circuit not shown in FIG. , 27, the ratio of the received light signals is derived, and the presence or absence of a temperature rise above a predetermined value of the linear elongated object is detected from the presence or absence of a change in this ratio.

At this time, the light source 21 may be a white light source or a monochromatic light source. When a monochromatic light source is used, a light emitting element such as a color change LED, a green LED, or a laser diode of each color may be used.

In addition, the first and second light receiving portions 26 and 27 include
It is preferable to use a light-receiving element that is easy to handle, such as a photodiode or phototransistor.

By the way, the optical fiber cable 23 is shown in FIG.
And the reference optical fiber 24, for example.
And a temperature-sensing optical fiber 25 having a color-changing portion including a temperature-sensitive color-changing material that changes color in which absorption of light of a specific wavelength is likely to change due to temperature rise inside the core, , Polypropylene, vinyl chloride or the like, both optical fibers 24 and 25 are coated and integrated with each other so that the entire optical fiber cable 23 has a circular cross section, and the outer circumference of the outer cover 28 is smaller than that of the outer cover 28. A metal sheath 29 made of a metal having a high thermal conductivity such as aluminum, copper or silver is formed.

At this time, the two optical fibers 24 and 25 may be twisted together, or may be gathered in parallel without being twisted.

The detailed structure of the reference optical fiber 24 and the temperature detecting optical fiber 25 will be described. In the reference optical fiber 24, as shown in FIG. 6, a clad 24b is formed on the outer periphery of a core 24a, and a clad 24b is formed. A resin sheath 24c is formed on the outer periphery of the core, and the temperature detecting optical fiber 25 is almost the same as that of the first embodiment. As shown in FIG. 7, a color changing portion 25b is formed near the center of the core 25a. A clad 25c is formed on the outer circumference of the core 25a, and a resin sheath 25d is formed on the outer circumference of the clad 25c.

The temperature-sensitive color changing material used for the color changing portion 25c is the same as in the first embodiment.

As described above, since the light from the light source 21 is branched by the optical branching device 22, when the brightness of the light source 21 fluctuates, the fluctuation of the light intensity of the light emitted from the temperature detecting optical fiber 25 is suppressed. When the ratio becomes equal to the ratio of the fluctuation of the light intensity of the emitted light of the reference optical fiber 24, and when an external force such as bending is applied, the temperature detection optical fiber 25 and the reference optical fiber 24 are output. The rate of change of the light intensity of the emitted light is the same as the rate of change of the light intensity of the emitted light of the reference optical fiber 24. On the other hand, when the temperature rises, the temperature detecting optical fiber 2
The thermosensitive discoloration material of No. 5 develops and discolors.

Therefore, by taking the ratio of the light intensity of the emitted light of the temperature detecting optical fiber 25 and the light intensity of the emitted light of the reference optical fiber 24, the variation of the light intensity of the emitted light due to the temperature rise and the temperature It is possible to clearly distinguish the fluctuation of the light intensity of the emitted light due to the rise and other causes, and it is possible to prevent malfunction.

Moreover, when a local temperature rise of the linear elongated object occurs, both optical fibers 2 are made by the metal sheath 29 having good thermal conductivity and the jacket 28 having poorer thermal conductivity than this.
A wide temperature rise range in the longitudinal direction can be obtained without heat damage to Nos. 4 and 25, and similar to the first embodiment, even when a local abnormal temperature rise of a linear elongated object is reliably and reliably performed. Abnormal temperature can be detected.

(Fourth to Seventh Embodiments) FIGS. 8 to 1
1 is a sectional view of the temperature detecting optical fiber of each of the fourth to seventh embodiments of the present invention, which is used in place of the temperature detecting optical fiber 25 of the third embodiment.

In the fourth embodiment, as shown in FIG.
Optical fiber 25 for temperature detection in the embodiment (see FIG. 7)
The resin sheath 25d is removed, and the optical fiber 31 for temperature detection constituted by the core 25a and the clad 25c having the discolored portion 25b in the center is used.

In the fifth embodiment, as shown in FIG.
Optical fiber 25 for temperature detection in the embodiment (see FIG. 7)
Instead of the discoloration part 25b of FIG.
The optical fiber 33 for temperature detection is used.

In the sixth embodiment, as shown in FIG. 10, the temperature detecting optical fiber 33 (see FIG. 9) in the fifth embodiment is used.
The optical fiber 34 for temperature detection in which the clad 25c and the resin sheath 25d (see (1)) are removed is used.

In the seventh embodiment, as shown in FIG. 11, the temperature detecting optical fiber 33 (see FIG. 9) in the fifth embodiment is used.
The temperature detecting optical fiber 35 from which the resin sheath 25d of (see) is removed is used.

Therefore, according to the fourth to seventh embodiments, the same effect as the third embodiment can be obtained.

(Eighth Embodiment) FIG. 12 is a sectional view of a reference optical fiber according to an eighth embodiment of the present invention, which is used in place of the reference optical fiber 24 in the third embodiment.

As shown in FIG. 12, the resin sheath 24c of the reference optical fiber 24 (see FIG. 6) in the third embodiment.
Since the reference optical fiber 36 in which is omitted is used, the same effect as that of the third embodiment can be obtained.

The reference optical fiber 36 in the eighth embodiment and the temperature detecting optical fibers 31, 33, 34, 35 in the fourth to seventh embodiments are selectively combined to form an optical fiber cable. Of course, it is okay.

In the first and second embodiments, the case where the second sheath is a metal sheath has been described, but a high thermal conductive material other than metal such as diamond or sapphire other than ceramics is used. The second sheath may be formed, and instead of the metal sheath in the third to eighth embodiments, a sheath made of a high thermal conductive material other than metal such as ceramics is formed on the outer circumference of the jacket 28. Of course, it is okay.

Furthermore, the present invention can be applied to a plastic optical fiber, and since a resin sheath and an outer cover are provided, a metal sheath and other high thermal conductivity sheaths can be easily formed.

[0061]

As described above, according to the first aspect of the invention, the clad, the first sheath and the second sheath having a higher thermal conductivity than the first sheath are provided outside the core having the discolored portion. Since it is formed, the temperature of the optical fiber for temperature detection can be raised over a wide range in the longitudinal direction of the optical fiber without damage to the cladding and core of the optical fiber for temperature detection when the temperature rises locally, and the sensitivity is improved. Therefore, it is possible to reliably and reliably detect the abnormal temperature rise of the linear long object.

According to the second aspect of the present invention, the same effects as the above can be obtained, and the light intensity of the light emitted from the temperature detecting optical fiber and the light emitted from the reference optical fiber can be obtained. By taking the ratio with the intensity, it is possible to clearly distinguish the variation in the light intensity of the emitted light due to the temperature rise from the variation in the light intensity of the emitted light due to the temperature rise and other causes.

[Brief description of drawings]

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

FIG. 2 is an overall schematic view of the first embodiment.

FIG. 3 is a partial sectional view of a second embodiment of the present invention.

FIG. 4 is an overall schematic view of a third embodiment of the present invention.

FIG. 5 is a partial cross-sectional view of the third embodiment.

6 is a cross-sectional view of a portion of FIG.

7 is a cross-sectional view of another part of FIG.

FIG. 8 is a partial sectional view of a fourth embodiment of the present invention.

FIG. 9 is a partial sectional view of a fifth embodiment of the present invention.

FIG. 10 is a partial sectional view of a sixth embodiment of the present invention.

FIG. 11 is a partial sectional view of a seventh embodiment of the present invention.

FIG. 12 is a partial sectional view of an eighth embodiment of the present invention.

FIG. 13 is a schematic view of a conventional example.

FIG. 14 is a cross-sectional view of another conventional example.

[Explanation of symbols]

 11, 25, 31, 33-35 Temperature detection optical fiber 11a Core 11b, 11f, 25b, 32 Color change part 11c Clad 11d Resin sheath (first sheath) 11e Metal sheath (second sheath) 12,21 Light source 13 Light receiving unit 22 Optical branching device 23 Optical fiber cable 24, 36 Reference optical fiber 28 Outer sheath 29 Metal sheath

Claims (4)

[Claims] 1. A temperature detecting optical fiber, a light source which is provided at a light incident end of the optical fiber and allows light to enter the optical fiber, and an outgoing light intensity of the optical fiber which is provided at a light emitting end of the optical fiber. A core having a color change portion including a temperature-sensitive color change material that changes color to a color whose light absorption easily changes with respect to light of a specific wavelength due to temperature rise. A clad provided on the outer circumference of the core, a first sheath provided on the outer circumference of the clad, and a material having a higher thermal conductivity than the first sheath provided on the outer circumference of the first sheath. And a second sheath composed of a temperature detecting device. 2. An optical fiber for reference and an optical fiber for temperature detection having a color-changing portion containing a temperature-sensitive color-changing material that changes color to a color whose light absorption is likely to change for light of a specific wavelength due to temperature rise. An optical fiber cable covered with an outer cover and integrated, a light source, and light provided from the light source and the incident end of the optical fiber cable are branched into two directions, and the reference optical fiber and An optical branching device that is incident on each of the incident ends of the temperature detecting optical fiber, and is proportional to the light intensity of the emitted light of each of the reference optical fiber and the temperature detecting optical fiber provided at the emitting end of the optical fiber cable. Two light receiving parts for outputting a light receiving signal are provided, and a sheath made of a material having a thermal conductivity higher than that of the jacket is provided on an outer periphery of the jacket of the optical fiber cable. Intelligence apparatus. 3. The temperature detecting device according to claim 1, wherein the color changing portion is provided inside the core. 4. The temperature detecting device according to claim 1, wherein the color changing portion is provided outside the core.