JP2002054990A - Optical sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sensor superior in chemical resistance and easy in treatment by making the most of bending performance of an optical fiber. SOLUTION: In the optical fiber 10 provided in this optical sensor, since the outside of a protective layer 12 for covering a clad is covered with a chemical resistant covering layer 13, heat when forming the chemical resistant covering layer 13 is absorbed by the protective layer 12 so that influence of the heat on the clad can be restrained. By integrating the chemical resistant layer 13 into the optical fiber 10, a conventional protective tube is not required, the number of part items is reduced, the size is reduced, and the bending performance of the optical fiber is validated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical sensor in which a sensor head is attached to the tip of an optical fiber and an optical path in the sensor head is connected to the optical fiber. The present invention relates to an optical sensor used in an environment.

[0002]

2. Description of the Related Art A conventional optical sensor of this type has a structure in which a sensor head itself is covered with a housing made of a chemical resistant resin as a structure corresponding to highly corrosive chemicals and oils. A protection tube made of a chemical-resistant resin (for example, a fluorine-based resin) was inserted through the outside of the fiber, and the end of the protection tube was heat-welded to the housing and fixed in a sealed state.

[0003]

However, in the above-mentioned conventional optical sensor, a protective tube as a member separate from the optical fiber is required. In order to secure the strength of the protective tube alone, it is necessary to use a protective tube. The wall thickness increases, and the flexibility is impaired. For this reason, the flexibility of the optical fiber cannot be utilized, and it is difficult to operate the sensor.

On the other hand, a structure in which an optical fiber is coated with a chemical-resistant coating layer (for example, a fluorine-based resin) can be considered. However, as disclosed in Japanese Patent Application Laid-Open No. 01-257906, the cladding of the optical fiber is coated. , If you coat the chemical resistant resin directly, the heat at that time,
There is a possibility that the performance of the optical fiber is degraded.

[0005] Even if the optical fiber can be coated with a chemical resistant resin while suppressing the influence of heat, if heat welding is used as a means for fixing the optical fiber to the housing, the heat generated at this time will be reduced. Therefore, there is a possibility that the performance of the optical fiber is deteriorated. Therefore, it is necessary to improve the fixing structure between the sensor head and the optical fiber.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical sensor which has excellent chemical resistance and is easy to handle by utilizing the flexibility of an optical fiber.

[0007]

According to a first aspect of the present invention, there is provided an optical sensor having a sensor head attached to a tip of an optical fiber, and an optical path in the sensor head and an optical fiber. In the optical sensor connected to the optical fiber, the outside of the protective layer covering the cladding,
It is configured by covering with a chemical resistant coating layer made of chemical resistant resin,
The sensor head is covered with a housing having chemical resistance on the outside, and the housing has a connecting tube portion into which an optical fiber is inserted extending inside, and on the outside of the connecting tube portion,
An outer cylinder member with chemical resistance is attached in a retaining state,
It is characterized in that the tapered portion formed by forming the connecting cylindrical portion into a tapered shape, and the reduced diameter portion formed by tapering the inner diameter of one end of the outer cylindrical member into a tapered shape are pressed by mounting the outer cylindrical member. Having.

According to a second aspect of the present invention, there is provided the optical fiber according to the first aspect, wherein an end of the chemical resistant coating layer is disposed at a position corresponding to the tapered portion of the connecting tubular portion of the optical fiber. By inserting the tapered portion of the connecting tube portion between the protective layers and mounting the outer tube member on the connecting tube portion, the resistance between the tapered portion of the connecting tube portion and the reduced diameter portion of the outer tube member is improved. The feature is that the chemical coating layer is crushed.

According to a third aspect of the present invention, there is provided an optical sensor in which a sensor head is attached to an end of an optical fiber and an optical path in the sensor head is connected to the optical fiber. The sensor head is covered with a chemical-resistant housing on the outside, and the housing has an optical fiber inside. The inserted connecting cylinder portion is extended, and a chemical-resistant outer cylinder member is mounted on the outer side of the connecting cylinder portion in a retaining state, and the outer cylinder member is attached to an end surface of the connecting cylinder portion. A facing receiving portion is provided, and between the receiving portion and the connecting cylinder portion,
A cylindrical packing having chemical resistance is accommodated therein, and the packing is pressed between the receiving portion and the end surface of the connecting tubular portion by the mounting of the outer tubular member, so that the packing is pressed against the optical fiber. However, it has features.

[0010]

<Operation and effect of the invention><Invention of claim 1> The optical fiber provided in the optical sensor according to the present invention has a cladding covered with a protective layer, and the outside of the protective layer is further covered with a chemical resistant coating layer. The heat when forming the chemical resistant coating layer with the chemical resin is absorbed by the protective layer, and the influence of the heat on the clad can be suppressed. By integrating the chemical resistant coating layer with the optical fiber, a conventional protective tube is not required, the number of components is reduced, the size is reduced, and the flexibility of the optical fiber is utilized.

With respect to the mounting portion between the optical fiber and the sensor head, if the optical fiber is inserted into the connecting tube and an outer tube member is attached to the outside of the connecting tube, the tapered portion provided in the connecting tube is formed. Then, the reduced diameter portion of the outer cylindrical member is pressed, and the connecting cylindrical portion is reduced in diameter. Thereby, the connecting tube portion is brought into close contact with the optical fiber to achieve waterproofing and does not require heat welding unlike the conventional one, so that the influence of heat on the optical fiber can be suppressed.

According to this structure, in addition to the functions and effects of the optical sensor according to the first aspect, the chemical-resistant coating layer of the optical fiber is formed by the tapered portion of the connecting cylindrical portion and the shrinkage of the outer cylindrical member. It is squashed between the diameter portion and serves as a sealing member, and the waterproof performance is enhanced.

<Invention of Claim 3> In the optical fiber provided in the optical sensor of the present invention, the clad is covered with a protective layer, and the outside of the protective layer is covered with a chemical-resistant coating layer. Heat at the time of forming the chemical resistant coating layer is absorbed by the protective layer, and the influence of the heat on the clad can be suppressed. By integrating the chemical resistant coating layer with the optical fiber, a conventional protective tube is not required, the number of components is reduced, the size is reduced, and the flexibility of the optical fiber is utilized.

With respect to the mounting portion between the optical fiber and the sensor head, when the optical fiber is inserted into the connecting cylindrical portion and an outer cylindrical member is mounted outside the connecting cylindrical portion, the receiving portion of the outer cylindrical member, the connecting cylindrical portion, Between the end face of the portion and the cylindrical packing, the cylindrical packing is pressed, bent inward so as to buckle, and pressed against the optical fiber. As a result, the packing is brought into close contact with the optical fiber to achieve waterproofing, and heat welding is not required unlike the conventional one, so that the influence of heat on the optical fiber can be suppressed.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment An optical sensor according to a first embodiment of the present invention will be described below with reference to FIG. In FIG. 1, reference numeral 10 denotes an optical fiber, which constitutes a wire-shaped light transmitting portion 11 by covering a center portion called a core having a high refractive index with a clad having a lower refractive index than the core. . Then, the outer surface of the clad is covered with a protective layer 12 made of, for example, polyethylene resin (PE) having excellent flexibility, and a fluororesin (for example, PFA: Tetr
afluoroethylene perfluoroalkylvinyl-ether copolyme
r) to form a chemical resistant coating layer 13. Here, since the chemical resistant coating layer 13 is formed thinly by coating as described above, it has excellent flexibility, and the flexibility of the entire optical fiber 10 is not impaired. That is, the chemical resistance is improved while the flexibility of the optical fiber 10 is maintained.

Reference numeral 20 denotes a sensor head, for example,
The housing 21 includes a non-light-transmitting fluororesin (PFA). The housing 21 includes a cylindrical main body 22 having a bottom at one end, and a front opening of the cylindrical main body 22 is sealed by welding a front lid 23 having chemical resistance and translucency. Then, the internal space becomes an optical path 24, and the optical path 2
4, a lens 24A is arranged on the front cover 23 side.

On the bottom wall 22A of the tubular main body 22, a connecting tubular portion 25 projects outward. The connecting cylinder 25 is
It is formed integrally with the bottom wall 22 </ b> A and communicates with an optical path 24 which is an internal space of the tubular main body 22. More specifically, the inner diameter of the connecting tubular portion 25 is the same as that of the chemical resistant coating layer 1 of the optical fiber 10.
3, the optical fiber 10 can be inserted into the connecting tube 25 together with the chemical-resistant coating layer 13. A protruding wall 26 is formed on the inner surface on the base end side of the connecting tubular portion 25 so as to narrow an opening to the internal space of the tubular main body 22, and is inserted into the connecting tubular portion 25. The optical fiber 10 abuts against the abutting wall 26 and is positioned. Further, the opening 26A at the center of the abutment wall 26 has substantially the same size as the outer diameter of the light transmitting portion 11 of the optical fiber 10.

A screw portion 27 is formed on the outer surface of the connecting tube portion 25 from the middle portion in the longitudinal direction to the base end, and the connecting tube portion 25 is tapered on the distal end side of the connecting tube portion 25. And a tapered portion 28 is formed. And
A connection nut 30 (corresponding to an outer tube member of the present invention) made of fluororesin (PFA) is provided on the outer surface of the connection tube portion 25 by screwing.

The thread portion 31 of the connection nut 30 is formed on the inner surface of the connection nut 30 from the axial middle portion to one end, and the other end of the connection nut 30 is formed by tapering the inner diameter of the connection nut 30. The tapered portion 32 is formed by being narrowed.

The configuration of the optical sensor according to this embodiment has been described above. Next, the operation and effect of this optical sensor will be described.

A sensor head 20 is attached to the tip of the optical fiber 10.
In order to attach the optical fiber 10, the optical fiber 10 is inserted into the connection tube 25, and the connection nut 30 is screwed to the outside of the connection tube 25. Then, the reduced diameter portion 32 of the connection nut 30 is pressed against the tapered portion 28 provided on the connection tube portion 25, and the connection tube portion 25 is reduced in diameter. This allows
The connecting tube portion 25 comes into close contact with the optical fiber 10 to achieve waterproofing. Here, in the optical sensor according to the present embodiment, when attaching the sensor head 20 to the optical fiber 10, unlike the conventional sensor, heat welding is not required, so that the influence of heat on the optical fiber 10 can be suppressed. .

The optical sensor is an optical fiber 1
It is arranged in a tank that stores, for example, highly corrosive chemicals and oils around 0. Here, the optical fiber 10
Has a chemical-resistant coating layer 13 integrally on the outer surface, so that it does not corrode even without a protective tube unlike the conventional one. In addition, since a protective tube is not required, the flexibility of the optical fiber 10 is utilized, and the optical fiber 10 can be easily handled.
In addition, since the optical fiber 10 covers the light transmitting portion 11 (specifically, the cladding) with the protective layer 12 and further covers the outside of the protective layer 12 with the chemical resistant coating layer 13, the optical fiber 10 is coated with a chemical resistant resin. The heat when forming the layer 13 is absorbed by the protective layer 12, so that the influence of the heat on the light transmitting portion 11 can be suppressed. As described above, the optical sensor according to the present embodiment is excellent in chemical resistance and can be easily handled by utilizing the flexibility of the optical fiber.

<Second Embodiment> An optical sensor according to this embodiment is shown in FIG. Hereinafter, only the configuration different from the first embodiment will be described, and the same portions will be denoted by the same reference numerals in the drawings, without redundant description.

The inside diameter of the portion where the optical fiber 10 is inserted corresponds to the outside diameter of the protective layer 12 of the optical fiber 10 in the connecting tube portion 25 provided in the sensor head 20 of the present embodiment. On the other hand, when coating the chemical-resistant coating layer 13 on the protective layer 12, the optical fiber 10 of the present embodiment has a length that is slightly shorter than the insertion amount of the optical fiber 10 into the connection tube 25, and The structure is such that the protective layer 12 is exposed from the tip and the other part is coated with the chemical resistant coating layer 13.

The sensor head 20 is attached to the tip of the optical fiber 10.
Is attached, the optical fiber 10 is inserted into the connecting cylinder 25. Then, slightly before the insertion, the chemical-resistant coating layer 13 of the optical fiber 10 rides on the tapered portion 28 and spreads, and the end of the chemical-resistant coating layer 13 is laid on the tapered portion 28. Then, when the connection nut 30 is screwed into the connection tube portion 25, the tapered portion 28 of the connection tube portion 25
Between the reduced diameter portion 32 of the connection nut 30 and the chemical resistant coating layer 1
3 is crushed, and the chemical-resistant coating layer 13 functions as a sealing member, and the waterproof performance is enhanced.

The optical sensor of this embodiment may be completed by the following manufacturing and assembling methods. That is, the optical fiber 10 has a structure in which the end to end are covered with the chemical resistant coating layer 13. Then, the chemical resistant coating layer 13 is peeled off from the protective layer 12 by a predetermined length from the tip of the optical fiber 10, and the chemical resistant coating layer 13 is removed.
Is floated from the protective layer 12. More specifically, the tapered portion 2 of the connecting tubular portion 25 of the optical fiber 10
The end of the chemical-resistant coating layer 13 is arranged at a position corresponding to 8, and the end of the chemical-resistant coating layer 13 is raised from the protective layer 12. Then, the tapered portion 28 of the connecting tube portion 25 is inserted into the gap between the chemical-resistant coating layer 13 and the protective layer 12, and the connecting nut 30 is screwed into the connecting tube portion 25. As a result, the chemical-resistant coating layer 13 is crushed between the tapered portion 28 of the connecting tubular portion 25 and the reduced-diameter portion 32 of the connecting nut 30, and the chemical-resistant coating layer 13 serves as a sealing member, and is waterproof. Performance can be enhanced.

<Third Embodiment> An optical sensor according to this embodiment is shown in FIG. Hereinafter, the same components as those of the first embodiment are denoted by the same reference numerals, and redundant description will be omitted. Only different components will be described.

The connecting cylinder 25 provided in the sensor head 20 of the first embodiment has a tapered portion 28 at the tip.
No. 0 has a structure provided with an end face 41 perpendicular to the axial direction at the tip. In the connection nut 42 of the present embodiment, a receiving portion 43 is formed so as to protrude inward at an end portion of the connection nut 42 remote from the connection tube portion 40, and faces the end surface 41 of the connection tube portion 40. . A packing 44 formed by forming a flexible chemical resistant resin into a tubular shape is accommodated between the receiving portion 43 and the connecting tubular portion 40.

In this embodiment, to attach the sensor head 20 to the optical fiber 10, a connection nut 42 is screwed to the outside of the connection tube 40 while the optical fiber 10 is inserted into the connection tube 40. Then, between the receiving portion 43 of the connecting nut 42 and the end surface 41 of the connecting cylindrical portion 40, the cylindrical packing 44 is pressed, bent inward so as to buckle, and pressed against the optical fiber 10. Thereby, the packing 44 adheres to the optical fiber 10 to achieve waterproofing,
Unlike the conventional one, heat welding is not required, so that the influence of heat on the optical fiber 10 can be suppressed.

<Other Embodiments> The present invention is not limited to the above embodiments. For example, the following embodiments are also included in the technical scope of the present invention.
In addition to the following, various changes can be made without departing from the scope of the invention.

(1) In each of the above-described embodiments, as the chemical-resistant resin, for example, a fluorine-based resin (for example, PF
Although A) was used, any resin other than a fluororesin may be used as long as the resin has chemical resistance.

(2) In each of the above embodiments, the housing 2
Although 1 and the connection nuts 30 and 42 are molded products of a chemical resistant resin, for example, they may be formed by coating a metal made of a metal with a chemical resistant resin.

(3) Connecting tube 2 described in each embodiment
The cross sections 5 and 40 are not limited to a circular shape, and the shape may be an elliptical shape, a square shape, or the like.

(4) In the first and second embodiments, the connecting cylinder 25 is reduced in diameter by the screwing operation of the connecting cylinder 25 and the connection nut 30, and is brought into close contact with the optical fiber 10. In the third embodiment, the structure in which the packing 44 is reduced in diameter so as to buckle and is closely attached to the optical fiber 10 is not limited thereto. For example, a structure in which the optical fiber is press-fitted into the connection tube portion. It may be.

(5) The optical sensor of each of the above embodiments is
Although the front cover 23 is provided, the front cover 23 may not be provided, and a structure having a cover in a portion other than the front may be employed.

(6) The optical sensor of each of the above embodiments is
Instead of the lens 24A provided in the optical path 24, a structure including a light transmitting member 49 as shown in FIG. That is, in the light transmitting member 49, the end surface on the optical fiber 10 side forms a vertical surface 49A orthogonal to the axial direction of the optical fiber 10, and the opposite surface forms an inclined surface 49B inclined with respect to the axial direction. It may have a structure. Further, as a light transmitting member, for example,
It may have a prism, or may have a structure without any translucent member.

(7) In each of the above embodiments, the connection nuts 30 and 42 as the outer cylinder members according to the present invention are attached to the respective connection cylinder parts 25 and 40 by screwing. As the outer tubular member according to the present invention, a tubular body having no screw portion is provided, and when this tubular body is fitted to the outside of the connecting tubular portion, a locking claw provided on the tubular body and the connecting tubular portion and a locked portion are provided. May be locked to each other so that the tubular body is held in the connecting tubular portion in a state of being prevented from falling off.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an optical sensor according to a first embodiment of the present invention.

FIG. 2 is a side sectional view of an optical sensor according to a second embodiment.

FIG. 3 is a side sectional view of an optical sensor according to a third embodiment.

FIG. 4 is a side sectional view of an optical sensor according to a first modification;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Optical fiber 12 ... Protective layer 13 ... Chemical resistant coating layer 20 ... Sensor head 21 ... Housing 24 ... Optical path 25, 40 ... Connection cylinder part 27, 31 ... Screw part 28 ... Taper part 30, 42 ... Connection nut (outer cylinder) 32) reduced diameter part 41 ... end face 43 ... receiving part 44 ... packing

Claims (3)

[Claims] 1. An optical sensor in which a sensor head is attached to a tip of an optical fiber and an optical path in the sensor head and the optical fiber are connected to each other. The sensor head is configured to be covered with a chemical-resistant coating layer made of a chemical-resistant resin, and the sensor head is covered on the outside with a housing having chemical resistance, and the housing has the connection tube in which the optical fiber is inserted inside. While the portion is extended, an outer cylindrical member having chemical resistance is attached to the outside of the connecting cylindrical portion in a retaining state, and a tapered portion formed by tapering the connecting cylindrical portion, An optical sensor characterized in that a reduced diameter portion formed by tapering the inner diameter of one end of the outer cylinder member into a tapered shape is pressed by mounting the outer cylinder member. 2. An end portion of the chemical resistant coating layer is disposed at a position corresponding to a tapered portion of the connection cylindrical portion of the optical fiber, and the connection between the chemical resistant coating layer and the protective layer is provided. By inserting the tapered portion of the tubular portion and mounting the outer tubular member on the connecting tubular portion, the chemical resistant coating is provided between the tapered portion of the connecting tubular portion and the reduced diameter portion of the outer tubular member. The optical sensor according to claim 1, wherein the layer is crushed. 3. An optical sensor in which a sensor head is attached to a tip of an optical fiber, and an optical path in the sensor head and the optical fiber are connected, wherein the optical fiber is provided outside a protective layer covering a clad, The sensor head is configured to be covered with a chemical-resistant coating layer made of a chemical-resistant resin, and the sensor head is covered on the outside with a housing having chemical resistance, and the housing has the connection tube in which the optical fiber is inserted inside. A portion is extended, and a chemical-resistant outer tube member is attached to the outside of the connection tube portion in a retaining state, and the outer tube member faces an end surface of the connection tube portion. A receiving portion is provided, and between the receiving portion and the connecting tubular portion, a tubular packing having chemical resistance is accommodated, and by mounting the outer tubular member, the packing becomes The receiving part and the Is compressed between the end surface of the sintered tube portion, the optical sensor being characterized in that as pressed against the optical fiber.