JP3000840B2 - Temperature detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature detecting device using an optical fiber which is used for detecting the temperature of a long linear object.

[0002]

2. Description of the Related Art Conventionally, when detecting the temperature of a long linear object, the temperature of the long linear object is detected over its longitudinal direction by a so-called lumped constant type temperature sensor such as a semiconductor temperature sensor. Although it is performed, a plurality of temperature sensors must be arranged along a linear long object, a large number of temperature sensors are required, and the circuit for processing the output of each temperature sensor becomes complicated, In addition, there is a disadvantage that the general configuration is complicated and a malfunction is likely to occur due to the influence of noise.

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

On the other hand, as a means for detecting a temperature using an optical fiber, a temperature-sensitive coloring layer that changes color with temperature is provided on the outer periphery of the core of the optical fiber as described in Japanese Utility Model Publication No. 62-3761. Has been done.

More specifically, as shown in FIGS. 13A and 13B, a thermosensitive coloring layer 1b is provided on the outer periphery of the core 1a by vapor deposition or coating, and the cladding 1 is provided on the outer periphery of the thermosensitive coloring layer 1b.
c, and further, a sheath 1d is provided on the outer periphery thereof to constitute an optical fiber 1. Light from a white light source or the like is incident on such an optical fiber 1, and light having a specific wavelength is absorbed by the colored thermosensitive coloring layer 1b. , The change in the wavelength of the light emitted from the optical fiber 1 is detected.

[0006] On the other hand, JP-64 -32132 Patent temperature sensor optical cable disclosed in Japanese have been proposed which, as shown in FIG. 14, the aluminum on the outer periphery of the temperature sensing optical fiber 3 comprising a core and a cladding, copper And a metal coating layer 4 made of a good heat conductive metal such as silver or the like. The metal coating layer 4 transfers heat in the longitudinal direction of the optical fiber 3 so that even if there is a local temperature rise. In addition, 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 thermosensitive coloring layer 1b as described in the former publication is used, the temperature of the linear long object locally rises and the optical fiber If the discoloration range of 1, ie, the temperature rise range, is narrow, the change of the emitted light is very small, so that there is a disadvantage that the abnormal temperature cannot be detected reliably.

Also, when the brightness of the light source fluctuates, or when the optical fiber 1
Since the intensity of the emitted light changes even when deformation such as bending is applied to the wire, the temperature of the linear long object is detected as a temperature rise even though the temperature has not risen, and a malfunction occurs. 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 provided directly on the outer periphery of the optical fiber 3, the optical fiber 3 is simultaneously formed in the longitudinal direction of the optical fiber 3. Since the heat is also transmitted to the center of the optical fiber 3 and the optical fiber 3 does not usually have heat resistance, the cladding and the core of the optical fiber 3 are damaged by high heat before the abnormal temperature rise is detected, and the reliability is lost. There is a problem.

In addition, 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 quartz optical fiber, the metal coating layer 4 can be formed relatively easily.
In the case of a plastic optical fiber, it is difficult to form the metal coating layer 4.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to improve sensitivity without impairing reliability and prevent malfunction. I do.

[0013]

According to the first aspect of the present invention,
An optical fiber for detecting temperature, a light source provided at a light incident end of the optical fiber for inputting light to the optical fiber, and a light receiving signal provided at a light emitting end of the optical fiber and corresponding to an intensity of light emitted from the optical fiber. And a light-receiving portion that outputs a light-receiving portion, wherein the optical fiber has a discoloration portion including a thermosensitive color-change material that changes color to a color in which light absorption easily changes with respect to light of a specific wavelength due to a temperature rise, and A clad provided on the outer periphery, a first sheath coated on the outer periphery of the clad,
The first sheath closely adhered to the outer periphery of the first sheath
And a second sheath made of a material having a higher thermal conductivity than that of the second sheath.

According to a second aspect of the present invention, a color-change portion including a reference optical fiber and a thermo-sensitive color-changing material that changes color to a color whose light absorption easily changes with respect to light of a specific wavelength due to a temperature rise is detected. An optical fiber cable, which is formed by assembling optical fibers and covering them with a jacket and integrated, and provided between the light source and the light source and the incident end of the optical fiber cable to split the light of the light source in two directions. An optical splitter that enters each of the input ends of the reference optical fiber and the temperature detection optical fiber, and output lights of the reference optical fiber and the temperature detection optical fiber provided at the output end of the optical fiber cable, respectively. And two light-receiving portions that output 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 jacket is provided on the outer periphery of the jacket of the optical fiber cable. There.

[0015]

According to the first aspect of the present invention, since the clad, the first sheath, and the second sheath having better heat conduction than the first sheath are formed outside the core having the discolored portion, a local temperature rise may occur. At the time of occurrence, heat is quickly transmitted in the longitudinal direction of the optical fiber by the second sheath having good heat conduction, and the first sheath has lower heat conduction than the second sheath in the center direction of the optical fiber as compared with the longitudinal direction. The heat is transmitted slowly and heat is transmitted in the longitudinal direction of the optical fiber before the cladding and the core of the optical fiber are damaged, and the temperature of the optical fiber rises over a wide range.

According to the second aspect of the present invention, since the light from the light source is split by the optical splitter, when the brightness of the light source fluctuates, the light intensity of the light emitted from the temperature detecting optical fiber is changed. When the rate of change of the optical fiber for reference and the rate of change of the light intensity of the light emitted from the reference optical fiber become the same, and when an external force such as bending is applied, the output of the temperature detecting optical fiber and the reference optical fiber is 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 output 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 develops color, Since the color changes, the rate of change in the light intensity of the light emitted from the temperature detecting optical fiber before and after the temperature rises is different from the rate of change in the light intensity of the light emitted from the reference optical fiber.

Therefore, if the ratio of the light intensity of the light emitted from the temperature detecting optical fiber to the light intensity of the light emitted from the reference optical fiber is obtained, the fluctuation of the light intensity of the emitted light due to the temperature rise, the temperature rise, Variations in the light intensity of the emitted light due to causes other than the above can be clearly distinguished, and malfunction can be prevented.

In this case, as in the case of the first aspect of the present invention, when a local temperature rise occurs, both the optical fibers are formed 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 configuration, reference numeral 11 denotes an optical fiber disposed along a long linear object such as an electric wire (not shown), and reference numeral 12 denotes a white light or white light provided at a light incident end of the optical fiber 11. A light source for inputting monochromatic light to the optical fiber 11;
Reference numeral 13 denotes a light receiving unit including a light receiving element such as a photodiode or a phototransistor, which is provided at a light emitting end of the optical fiber 11 and outputs a light receiving signal corresponding to the intensity of the 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 configured in detail as shown in FIG. 1, and includes a core 11a and a core 11a.
A color changing portion 11b including a thermosensitive color changing material which is formed at a central portion of the core and which changes color to a color in which light absorption easily changes with respect to a specific wavelength of light from the light source 12 due to a rise in temperature; 11c and the outer periphery of the clad 11c
A resin sheath 11d which is a first sheath covered, and a second sheath made of a metal such as aluminum, copper, silver or the like having a higher thermal conductivity than the resin sheath 11d closely adhered to the outer periphery of the resin sheath 11d. Metal sheath 11e
Consists of

As an example of a method for forming a color changing portion 11b containing a thermosensitive color changing material at the center of the core 11a, for example, a resin tube serving as a cladding 11c made of a fluorine-based resin having an inner diameter of 2 mm and an outer diameter of 3 mm is placed in Transparent silicone may be poured using a syringe to form the core 11a, and subsequently, a silicone containing a thermosensitive material may be poured into the resin tube using a syringe to form the discolored portion 11b.

At this time, the silicone poured into the resin tube is hard to move forward due to friction on the inner wall surface of the tube, and the silicone containing the thermochromic material subsequently poured corresponds to the central portion of the core 11a. The structure shown in FIG. 1 is obtained as a result.

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

The combination of the light from the light source 12 and the thermochromic material is desirably, for example, as shown in Table 1. The light source 12 emits monochromatic light such as red light, green light and yellow light in addition to white light. It is preferable to use the thermosensitive color changing material which is capable of developing, discoloring and erasing at high temperatures as shown in Table 1.

[0027]

[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 thermosensitive color changing material changes (for example, from colorless to red) when the incident light of each color is used. In particular, the amount of emitted light indicates a change in the amount of light after the color change with reference to the state before the change in color. For example, “green small” indicates that the light amount of the green component is smaller than before the change, and “green large”. "Indicates that the light amount of the green component increases from before the change.

In Table 1, "before change" means a state at normal temperature, and "after discoloration" means a state at a high temperature of, for example, 60 ° C. or more.

As the material of the thermosensitive color changing 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, the light absorbing material normally absorbs light in the wavelength range. It is desirable that the colorless or red color or the like reversibly change from a colorless or red color to a green color or a black color or the like in which red light is absorbed. Specifically, materials shown in Table 2 may be used. As a material that changes color from colorless to red as a result, PSD-R (fluoran leuco compound), lauryl gallate, and toluene may be used, but the materials are not particularly limited to those shown in Table 2.

[0031]

[Table 2]

Therefore, since the temperature detecting optical fiber 11 is configured as shown in FIG. 1, when a local temperature rise occurs, the optical fiber 1 is formed by the metal sheath 11e having good heat conduction.
The heat is quickly transmitted in the longitudinal direction of the optical fiber 11, the heat is slowly transmitted to the center of the optical fiber 11 by the resin sheath 11d having lower heat conduction than the metal sheath 11e, compared to the longitudinal direction, and the cladding 11c and the core of the optical fiber 11 are formed. Before the damage to the optical fiber 11a, heat is transmitted in the longitudinal direction of the optical fiber 11 to increase the temperature of the optical fiber 11 over a wide range, thereby improving the sensitivity. Even when the temperature rises, the abnormal temperature can be detected reliably and reliably.

The same effect can be obtained by dispersing the thermochromic 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 those in FIG. 1 indicate the same or corresponding ones.
A discoloration portion 11f is provided on the outer periphery of the core 11a.
That is, the clad 11c was 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 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 using a syringe. Silicone containing a color changing material may be poured to form the color changing portion 11f, and then silicone may be poured into the resin tube using a syringe to form the core 11a.

At this time, the silicone containing the thermosensitive color-changing material first poured into the resin tube is difficult to advance due to friction on the inner wall surface of the resin tube, and the silicone poured next is poured first. Proceeding smoothly through the center of the silicone, the result is 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 formed with 1f is used, the same effect as that of the first embodiment can be obtained.

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

As shown in FIG. 4, light from a light source 21 is branched in two directions by an optical splitter 22, and an optical fiber cable disposed along a long linear object (not shown) such as an electric wire. The light branched by the optical branching device 22 is incident on the reference optical fiber 24 and the temperature detecting optical fiber 25 constituting the optical fiber 23, respectively, and the light emitted from both optical fibers 24 and 25 is transmitted to the first and second light receiving units 26 and 25. A light receiving signal proportional to the light intensity of the outgoing light from the two optical fibers 24 and 25 is output from the two light receiving units 26 and 27, respectively, and is processed by a processing circuit (not shown in FIG. 4). , 27 are derived, and the presence or absence of a change in the ratio is used to detect whether or not the temperature of the linear elongated object has risen to a predetermined value or more.

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 discolored LED, a green LED, or a laser diode for each color may be used.

The first and second light receiving sections 26 and 27 include:
It is preferable to use an easy-to-handle light receiving element such as a photodiode or a phototransistor.

The optical fiber cable 23 is shown in FIG.
The reference optical fiber 24 is configured as shown in FIG.
And a temperature detecting optical fiber 25 having a discoloration part including a thermosensitive discoloration material that changes color to a color in which light absorption easily changes with respect to light of a specific wavelength due to a rise in temperature. , Polypropylene, vinyl chloride, or the like, the two optical fibers 24 and 25 are coated and integrated so that the entire optical fiber cable 23 has a circular cross section. A metal sheath 29 made of a metal having high thermal conductivity, such as aluminum, copper, or silver, is formed.

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

The detailed configuration of the reference optical fiber 24 and the temperature detecting optical fiber 25 will be described. The reference optical fiber 24 has a clad 24b formed on the outer periphery of a core 24a as shown in FIG. A resin sheath 24c is formed on the outer periphery of the optical fiber 25. The temperature detecting optical fiber 25 is almost the same as that of the first embodiment, and a discolored portion 25b is formed near the center of the core 25a as shown in FIG. A clad 25c is formed on the outer periphery of the core 25a, and a resin sheath 25d is formed on the outer periphery of the clad 25c.

The thermochromic material used for the color changing section 25c is the same as that of the first embodiment.

As described above, since the light from the light source 21 is split by the optical splitter 22, when the brightness of the light source 21 changes, the light intensity of the light emitted from the temperature detecting optical fiber 25 changes. When the ratio and the change ratio of the light intensity of the light emitted from the reference optical fiber 24 become the same, 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 and the rate of change of the light intensity of the light emitted from the reference optical fiber 24 become the same.
The temperature-sensitive discoloring material No. 5 develops and discolors.

Therefore, the ratio between the light intensity of the light emitted from the temperature detecting optical fiber 25 and the light intensity of the light emitted from the reference optical fiber 24 is calculated, whereby the change in the light intensity of the emitted light due to a rise in temperature and the temperature Fluctuations in the light intensity of the emitted light due to the rise and other causes can be clearly distinguished, and malfunction can be prevented.

Further, when a local temperature rise of the linear long object occurs, the two optical fibers 2 are formed by the metal sheath 29 having good heat conductivity and the jacket 28 having poor heat conductivity.
4 and 25 can obtain a wide temperature rising range in the longitudinal direction without being damaged by heat, and reliably and reliably even in the case of a local abnormal temperature rise of a linear long object as in the first embodiment. Abnormal temperature can be detected.

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

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

In the fifth embodiment, as shown in FIG.
Temperature detecting optical fiber 25 in the embodiment (see FIG. 7)
Instead of the discolored portion 25b, the discolored portion 32
Is used.

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

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

Therefore, according to the fourth to seventh embodiments, the same effect as that of the third embodiment can be obtained. What
In the third embodiment, the temperature detecting optical fiber 25 itself is
The outer sheath 28 having a lower thermal conductivity than the metal sheath 29
Because it is covered, the temperature detecting optical fiber 25
Instead, as in the fourth, sixth and seventh embodiments,
Temperature detecting optical fibers 31, 34,
Even if 35 is used, the same effect as in the third embodiment can be obtained.
I can .

(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.
Is used, and the same effect as that of the third embodiment can be obtained.

An optical fiber cable is constructed by selectively combining 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. Of course, it may be possible.

In the first and second embodiments, the case where the second sheath is a metal sheath has been described. However, a high heat conductive material other than metal such as ceramics such as diamond and sapphire other than metal is used. A second sheath may be formed, and instead of the metal sheath in the third to eighth embodiments, a sheath using a high heat conductive material other than metal such as ceramics is formed on the outer periphery of the jacket 28. Of course, it may be possible.

Further, the present invention can be applied to a plastic optical fiber, and since a resin sheath and a sheath are provided, a metal sheath and other sheaths having high heat conductivity can be easily formed.

[0061]

As described above, according to the first aspect of the present invention, the clad, the first sheath and the first sheath are closely attached to the outer periphery of the core having the discolored portion and the outer periphery of the first sheath. Because the second sheath having a higher thermal conductivity is covered, when a local temperature rise occurs, the second sheath has a higher thermal conductivity than the first sheath.
Heat is generated in the longitudinal direction of the optical fiber by the second sheath having a high rate.
Is quickly transmitted, while moving toward the center of the optical fiber.
The first sheath having a lower thermal conductivity than the first sheath
Heat is transmitted more slowly than in the longitudinal direction. Accordingly, the temperature of the optical fiber can be increased over a wide range in the longitudinal direction of the optical fiber before the clad and the core of the temperature detecting optical fiber are damaged by heat , and the sensitivity can be improved, and the reliability can be improved. The abnormal temperature rise of the linear long object can be detected reliably and with high reliability.

According to the second aspect of the present invention, not only the same effects as described above can be obtained, but also the light intensity of the light emitted from the temperature detecting optical fiber and the light emitted from the reference optical fiber. By taking the ratio with the intensity, it is possible to clearly distinguish the change in the light intensity of the emitted light due to the temperature rise from the change in the light intensity of the emitted light due to the temperature rise and other causes.

[Brief description of the drawings]

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

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

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

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

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

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

FIG. 7 is a sectional view of another part of FIG. 5;

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 to 35 Temperature detecting optical fiber 11a Core 11b, 11f, 25b, 32 Discoloration portion 11c Cladding 11d Resin sheath (first sheath) 11e Metal sheath (second sheath) 12, 21 Light source 13 Light receiving unit 22 Optical splitter 23 Optical fiber cable 24, 36 Reference optical fiber 28 Jacket 29 Metal sheath

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-223632 (JP, A) JP-A-2-35323 (JP, A) JP-A-4-357427 (JP, A) 33342 (JP, U) Hikaru Hei 5-11035 (JP, U) Jiko 62-3761 (JP, Y2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01K 11/12 G02B 6 / 02

Claims (2)

(57) [Claims] 1. An optical fiber for temperature detection, a light source provided at a light incident end of the optical fiber for inputting light to the optical fiber, and an output light intensity of the optical fiber provided at a light output end of the optical fiber A light-receiving section that outputs a light-receiving signal according to the above, wherein the optical fiber has a color-changing section including a thermosensitive color-changing material that changes color to a color in which light absorption easily changes with respect to light of a specific wavelength due to temperature rise. A cladding provided on the outer periphery of the core, a first sheath coated on the outer periphery of the clad, and a thermal conductivity higher than the first sheath coated in close contact with the outer periphery of the first sheath. And a second sheath made of a high-quality material. 2. An optical fiber for reference, and an optical fiber for temperature detection having a color-changing portion including a thermosensitive color-changing material which changes color to a color whose light absorption easily changes with respect to light of a specific wavelength due to a rise in temperature. An optical fiber cable covered and integrated with a jacket, a light source, and the reference optical fiber provided between the light source and the incident end of the optical fiber cable, splitting light from the light source in two directions, An optical splitter that is incident on each of the input ends of the temperature detecting optical fiber, and is provided at an output end of the optical fiber cable, and is proportional to the light intensity of the output light of each of the reference optical fiber and the temperature detecting optical fiber. Two optical receivers for outputting a light-receiving signal, wherein an outer periphery of the jacket of the optical fiber cable is covered with a sheath made of a material having a higher thermal conductivity than the jacket. Feature Temperature sensing device.