JP6736044B2 - Strain sensor and jig for mounting the strain sensor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain sensor and a strain sensor mounting jig, and more particularly to a strain sensor that includes an optical fiber and optically detects strain of a measurement target, and a strain sensor mounting jig.

In recent years, strain sensors equipped with optical fibers have been used. This type of strain sensor acquires a strain amount based on a change in the reflection state or a change in the scattering state of light transmitted through the optical fiber according to the deformation of the optical fiber.

For example, Japanese Patent Application Laid-Open No. 2004-242242 discloses a conventional technique in which an optical fiber including an FBG (Fiber Bragg Grating) portion is fixed to a measurement target while the FBG portion is covered with an adhesive, and tension (pretension) is applied. There is disclosed a configuration in which the above optical fiber is bonded and fixed to the measurement object at two positions sandwiching the FBG portion. Further, Patent Document 1 discloses a strain sensor including a bendable elastic body and fixing an optical fiber to the elastic body in a state where pretension is applied, for the purpose of improving the accuracy of strain measurement. In this strain sensor, the elastic body is fixed to the measurement target, and the optical fiber is deformed by the deformation of the elastic body according to the strain of the measurement target.

Further, Patent Document 2 discloses a strain sensor in which an optical fiber is arranged and fixed in the diameter direction of a ring body. In this strain sensor, the optical fiber is deformed by the radial deformation of the ring body.

JP, 2005-091151, A JP, 2009-162601, A

In a configuration in which an optical fiber is fixed to an object to be measured as disclosed in Patent Document 1 as a prior art, if a proper pretension is not applied to the optical fiber, distortion in the compression direction along the optical fiber occurs. , Buckling (microbend) occurs in the optical fiber. When buckling occurs in the optical fiber, the light propagating in the optical fiber loses, which makes it difficult to accurately measure the strain.

As disclosed in Patent Document 1, such a problem can be avoided by fixing the optical fiber in a tensioned state to the measurement target. However, in order to directly fix the optical fiber in the tensioned state to the measurement object, attach a weight or the like to the other end of the optical fiber with one end of the optical fiber fixed and apply tension to the optical fiber Therefore, the complicated work of fixing the optical fiber is required. Further, when the surface to be measured is not a horizontal surface, the difficulty of fixing the optical fiber becomes high.

On the other hand, in the techniques disclosed in Patent Documents 1 and 2, since the optical fiber is fixed to the elastic body or the ring body (hereinafter, referred to as a gauge carrier), the optical fiber is gauged with an appropriate tension applied. Can be fixed to the carrier. Therefore, the strain in the compression direction can be accurately measured by fixing the gauge carrier to the measurement target.

However, in such a configuration, it is essential to secure a space for installing the gauge carrier on the measurement target. For example, when the measurement target is relatively large, such as a moving object such as a building, an aircraft, a ship, or a railway, it is easy to secure a space for installing the gauge carrier. On the other hand, when the measurement target is relatively small, such as a component that constitutes a moving body, or when the measurement target has a curved surface, it is difficult to secure a space for installing the gauge carrier. In some cases.

Further, in recent years, in a moving body, an object to be measured may be made of a material such as carbon that can be largely deformed as compared with metal. In this case, if the material of the gauge carrier is metal, for example, the range in which the strain sensor can accurately measure is limited to the range of deformation that the gauge carrier can follow. That is, when the measurement target is deformable beyond the deformation limit of the gauge carrier, the strain sensor including the gauge carrier cannot accurately measure the strain generated in the measurement target.

The present invention has been made in view of the above problems of the conventional technology, the space required for installation is smaller than the conventional one, the installation is easier than the conventional one, and the measurable strain amount is An object of the present invention is to provide a strain sensor and a jig for mounting the strain sensor, the range of which can be expanded as compared with the conventional one.

In order to achieve the above-mentioned object, the present invention employs the following technical means. First, the present invention is premised on a strain sensor using an optical fiber. The strain sensor according to the present invention includes two locking parts and a holding member provided between the two locking parts. The two locking portions are provided on the optical fiber at a predetermined interval. The holding member includes an elastic portion that applies a biasing force to the optical fiber in a direction in which the two locking portions are separated from each other, and holds the optical fiber. Further, the holding member is detached from the optical fiber after the optical fiber is fixed to the measurement object.

In the strain sensor of the present invention, the holding member holding the optical fiber is installed on the measurement target. Then, the optical fiber is fixed to the measurement object in a state in which the elastic portion of the holding member applies a biasing force to the two locking portions, that is, in a state in which tension (pretension) is applied to the optical fiber. After that, the holding member is separated from the optical fiber. As a result, the optical fiber is fixed to the measurement object in a state where tension is applied. Therefore, it is extremely easy to install on the measurement object. Further, the measurement target does not require a space for installing the gauge carrier, and the space required for installing the strain sensor can be reduced as compared with the conventional case. Therefore, it is possible to measure the distortion of a relatively small measurement target such as a component of a moving body. Further, the measurable strain amount range is not limited to the deformation limit of the gauge carrier. In addition, since the optical fiber is installed under tension, the strain in the compression direction can be accurately measured.

In this strain sensor, the holding member may be configured to hold the optical fiber in a state in which the optical fiber is biased. Alternatively, the holding member may be configured to hold the optical fiber in a state in which the biasing force is not applied to the optical fiber and generate the biasing force when the optical fiber is fixed to the measurement target.

Further, in the above strain sensor, the elastic portion can be formed by a ring spring. Further, the optical fiber may have a configuration including an FBG (Fiber Bragg Grating) portion between the two locking portions. Furthermore, it is also possible to adopt a configuration in which the holding member includes a plurality of elastic portions that hold the optical fibers arranged in different directions.

Further, in the above strain sensor, the holding member has a groove portion on the surface facing the measurement object when the optical fiber is fixed to the measurement object, and the optical fiber is arranged in the groove portion. You can also do it. It is also possible to adopt a configuration in which the contact surface of the locking portion with the measurement object and the contact surface of the holding member with the measurement object are arranged in the same plane.

On the other hand, from another point of view, the present invention can also provide a strain sensor mounting jig made of an optical fiber. That is, the strain sensor mounting jig according to the present invention includes the elastic portion and the groove portion. The elastic portion applies a biasing force to the optical fiber in a direction in which two locking portions provided at a predetermined interval in the optical fiber separate from each other. The groove is provided on the surface facing the measurement target when the optical fiber is fixed to the measurement target, and the optical fiber is accommodated therein.

According to the present invention, the space required for installing the strain sensor can be made smaller than in the conventional case, and the strain sensor can be installed more easily than in the conventional case. In addition, the range of measurable strain amount can be expanded as compared with the conventional case.

1A and 1B are schematic configuration diagrams showing an example of a strain sensor according to an embodiment of the present invention. FIG. 2A and FIG. 2B are schematic cross-sectional views showing an example of the strain sensor according to the embodiment of the present invention. 3(a) to 3(f) are diagrams showing the procedure for assembling the strain sensor according to the embodiment of the present invention. FIG. 4A and FIG. 4B are diagrams showing an example of a mounting manner of the strain sensor in the embodiment of the present invention. FIG. 5A and FIG. 5B are diagrams showing an example of how the strain sensor is attached in the embodiment of the present invention. FIG. 6A and FIG. 6B are schematic configuration diagrams showing an example of another strain sensor according to an embodiment of the present invention. FIG. 7 is a schematic configuration diagram showing an example of another strain sensor according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. Hereinafter, the present invention will be embodied as a uniaxial strain sensor (strain gauge).

1A and 1B are schematic configuration diagrams showing an example of the overall configuration of the strain sensor 1 in the present embodiment. FIG. 1A is a view showing a surface (hereinafter referred to as a contact surface) on the side fixed to the surface of the measurement target. FIG. 1B is a view showing a surface opposite to the surface shown in FIG. 1A (hereinafter referred to as a non-contact surface). 2A and 2B are schematic cross-sectional views taken along the lines AA and BB shown in FIG. 1A, respectively. 2A and 2B, the lower side in the figure corresponds to the contact surface, and the upper side in the figure corresponds to the non-contact surface. Note that FIGS. 2A and 2B are schematic diagrams, and the dimensions of each part are not expressed exactly.

As shown in FIGS. 1A, 1</b>B, 2</b>A, and 2</b>B, the strain sensor 1 includes an optical fiber 10 and a holding member 20. The optical fiber 10 is provided with two locking portions 11 and 12 at a predetermined interval, and a holding member 20 is disposed between the locking portions 11 and 12. As will be described later, the strain measurement is performed with only the optical fiber 10 fixed to the measurement target. That is, although the holding member 20 is included as a component of the strain sensor 1, the holding member 20 is detached from the optical fiber 10 after fixing the optical fiber 10 to the measurement target.

The holding member 20 includes an elastic portion 21 and a fixed portion 22. The elastic portion 21 applies a biasing force to the optical fiber 10 in a direction in which the two locking portions 11 and 12 are separated from each other. In the present embodiment, the elastic portion 21 is composed of a ring spring that generates an elastic force in the plane including the optical fiber 10. Here, the optical fiber 10 is arranged in the diameter direction of the ring spring which is the elastic portion 21. Although not particularly limited, in the present embodiment, the outer diameter of the ring spring that is the elastic portion 21 is about 5 mm.

The fixing portion 22 is used to temporarily fix the strain sensor 1 to the measurement target when fixing the optical fiber 10 to the measurement target. In this embodiment, in the ring spring which is the elastic portion 21, the fixing portion 22 is located outside of the ring spring in the plane including the optical fiber 10 at a position facing each other and in a direction perpendicular to the arrangement direction of the optical fiber 10. It is composed of a plate-shaped member extending toward. As a method of fixing the fixing portion 22 to the measurement target, any known method can be used as long as the holding member 20 can be separated from the measurement target after fixing the optical fiber 10. Here, the double-sided tape 23 is provided on the contact surface side of the fixing portion 22, and the fixing portion 22 is temporarily fixed to the measurement object by the adhesive force of the double-sided tape 23.

In the present embodiment, the holding member 20 including the elastic portion 21 and the fixed portion 22 is configured as an integral member made of a resin material or the like. As shown in FIGS. 2A and 2B, the holding member 20 is made of a plate-shaped material having a thickness larger than the diameter of the optical fiber 10. A groove portion 24 is provided on the contact surface of the elastic portion 21, and the optical fiber 10 is accommodated in the groove portion 24 without protruding toward the contact surface side of the holding member 20.

In the present embodiment, the optical fiber 10 has a structure in which a core that propagates light and a clad that surrounds the core and reflects the light that propagates in the core toward the core are sequentially arranged from the center. Further, in the present embodiment, the end surface 13 is provided at one end of the optical fiber 10. The terminal surface 13 is end-treated so that the light reflected by the terminal surface 13 does not travel backward in the optical fiber 10. Here, the end surface 13 is oriented with respect to the axial center of the optical fiber 10 so that the reflected light at the end surface 13 is incident on the boundary surface between the core and the cladding at a critical angle or more and is emitted to the outside of the core. It is composed of a surface having an inclination angle of 8 degrees. Further, on the other end side of the optical fiber 10, a portion separated from the holding member 20 by a predetermined distance or more is covered with an outer cover resin 14 that protects the core and the clad.

Further, as shown in FIGS. 1A and 1B, the optical fiber 10 (the optical fiber between the locking portion 11 and the locking portion 12) arranged inside the ring spring which is the elastic portion 21. An FBG (Fiber Bragg Grating) section 25 having a specific Bragg wavelength is arranged in the core of 10). In the figure, the FBG portion 25 is represented by black painting for the sake of convenience.

As is well known, the FBG portion reflects light having a wavelength defined by the Bragg wavelength. The FBG portion is composed of a plurality of diffraction gratings arranged at a predetermined interval in the core of the optical fiber, and the Bragg wavelength is proportional to the product of the refractive index of the optical fiber and the arrangement interval of the diffraction grating. Therefore, when the FBG portion is pulled by the distortion and the distance between the diffraction gratings forming the FBG portion is expanded, the wavelength of the light reflected by the FBG portion becomes large. Further, when the FBG portion is compressed by the distortion and the distance between the diffraction gratings forming the FBG portion is narrowed, the wavelength of the light reflected by the FBG portion becomes smaller.

On the other hand, the locking portions 11 and 12 are formed by the protrusions provided on the optical fiber 10. Although not particularly limited, the locking portions 11 and 12 are made of an ultraviolet curable resin here. As shown in FIG. 2B, in the present embodiment, the contact surfaces of the locking portions 11 and 12 with the measurement object and the contact surface of the holding member 20 with the measurement object are in the same plane. It is arranged.

Further, the optical fiber 10 is fixed to the groove portion 24 (holding member 20) with an adhesive 27 so as not to separate from the holding member 20 before being installed on the measurement target. Note that the adhesive force of the adhesive 27 used for fixing the holding member 20 and the optical fiber 10 is such that the holding member 20 can be detached from the optical fiber 10 after the optical fiber 10 is fixed to the measurement object. It is smaller than the adhesive force of the adhesive used for fixing the optical fiber 10 and the measurement object.

Next, the procedure for assembling the strain sensor 1 will be described. 3A to 3F are views showing an assembly procedure of the strain sensor 1 in the present embodiment. First, the locking portions 11 and 12 are formed in the optical fiber 10. When the locking portions 11 and 12 are formed, as shown in FIG. 3A, the optical fiber 10 is formed on the substrate 30 having a horizontal surface at the positions where the locking portions 11 and 12 are formed. Are placed in contact with a horizontal plane. The FBG portion 25 is arranged between the formation position of the locking portion 11 and the formation position of the locking portion 12.

Next, as shown in FIG. 3B, the ultraviolet curable resin, which is the material for forming the locking portions 11 and 12, is placed at the position where the locking portions 11 and 12 are formed. At this time, the ultraviolet curable resin is arranged so that the distance between the locking portion 11 and the locking portion 12 becomes a predetermined distance L. Such an arrangement can be realized by, for example, arranging a spacer or the like between the locking portion 11 and the locking portion 12 to regulate the position of the ultraviolet curable resin. The spacers and the like are removed from between the locking portions 11 and 12 after the ultraviolet curable resin is cured. Note that, as shown in FIG. 3C, the outer diameter R of the ring spring, which is the elastic portion 21, when there is no load is slightly larger than the distance L between the locking portion 11 and the locking portion 12. ..

When the holding member 20 is arranged between the locking portion 11 and the locking portion 12, the ring spring which is the elastic portion 21 is arranged in the arrangement direction of the optical fiber 10 as shown by a solid arrow in FIG. Elastically deformed in the compression direction. As a result, the outer diameter of the ring spring in the direction along the arrangement direction of the optical fiber 10 becomes the distance R1 smaller than the distance L. Although not particularly limited, in the configuration of the holding member 20 of the present embodiment, such elastic deformation causes the ring spring to be perpendicular to the arrangement direction of the optical fiber 10 as shown by a dashed arrow in FIG. It can be realized by spreading it in any direction. In this example, a concave portion 28 that enters the fixed portion 22 side is provided at the base end portion of the fixed portion 22 that constitutes the inner surface of the ring spring that is the elastic portion 21. Then, for example, the elastic deformation described above is realized by applying a force toward the fixed portion 22 side to the concave portion 28 in the state where the rod-shaped member is in contact with the concave portion 28.

With the ring spring elastically deformed as described above, the ring spring is inserted between the locking portion 11 and the locking portion 12 on the substrate 30 as shown in FIG. The fiber 10 is housed in the groove 24 (see FIGS. 2A and 2B). Thereafter, when the elastic deformation of the ring spring is released, the outer diameter of the ring spring in the direction along the arrangement direction of the fiber 10 returns to the distance R, as shown in FIG. While abutting on the portion 11 and the locking portion 12, a biasing force is applied to the optical fiber 10 in a direction in which the two locking portions 11 and 12 are separated from each other. That is, the optical fiber 10 is held by the holding member 20 in a state where tension (pretension) is applied. The magnitude of the urging force applied to the optical fiber 10 depends on the distance between the locking portion 11 and the locking portion 12, the difference between the outer diameter of the ring spring, which is the elastic portion 21, and the ring. It is determined by the elastic modulus of the spring.

The optical fiber 10 and the holding member 20 assembled as described above are separated from the substrate 30. Then, as described above, the optical fiber 10 is fixed to the holding member 20 by the adhesive 27 having a relatively weak adhesive force. According to the above assembly procedure, the contact surface of the locking portions 11 and 12 with the measurement object and the contact surface of the holding member 20 with the measurement object can be arranged in the same plane (Fig. 2(b)).

Hereinafter, the procedure for attaching the optical fiber 10 to the measurement object will be described. Any known method can be used to fix the optical fiber 10 to the measurement target. In this embodiment, the optical fiber 10 is fixed to the object to be measured with an ultraviolet curable adhesive. FIG. 4A and FIG. 4B are diagrams showing an example of an attachment mode of the strain sensor 1 according to the embodiment of the present invention.

When fixing the optical fiber 10 to the measurement object 40, first, as shown in FIG. 4A, the strain sensor 1 is measured by the double-sided tape 23 provided on the contact surface of the fixing portion 22. Temporarily fixed at 40. In this state, as shown in FIG. 4A, the adhesive 50 that covers the locking portion 11 and the adhesive 50 that covers the locking portion 12 are applied. When the curing of the adhesive 50 is completed, the holding member 20 is separated from the optical fiber 10. As described above, the adhesive force of the adhesive 27 used for fixing the holding member 20 and the optical fiber 10 is larger than the adhesive force of the adhesive 50 used for fixing the optical fiber 10 and the measuring object 40. Small. Therefore, the holding member 20 is separated from the optical fiber 10 by performing an operation of separating the holding member 20 from the measurement object 40.

After the holding member 20 is detached, the optical fiber 10 is fixed to the measurement object 40 at two points as shown in FIG. In such an attachment mode, for example, the length of the FBG portion 25 is relatively long (for example, the length that occupies most of the space between the locking portion 11 and the locking portion 12), and the strain in a relatively wide area is large. It is particularly suitable for the purpose of detection.

5(a) and 5(b) are diagrams showing another mounting mode of the strain sensor 1 in the embodiment of the present invention. In this example, similarly to the example shown in FIGS. 4A and 4B, first, the strain sensor 1 is temporarily attached to the measurement object 40 by the double-sided tape 23 provided on the contact surface of the fixing portion 22. Fixed. In this state, as shown in FIG. 5A, the adhesive 50 is applied so as to cover the FBG portion 25. When the curing of the adhesive 50 is completed, the holding member 20 is separated from the optical fiber 10.

After the holding member 20 is detached, the optical fiber 10 is fixed to the measurement object 40 at one point as shown in FIG. In such an attachment mode, for example, the FBG portion 25 has a relatively short length (for example, a length that occupies a very small portion between the locking portion 11 and the locking portion 12), and a strain in a relatively narrow region. Is particularly suitable for the purpose of detecting

In the above description, the holding member 20 holds the optical fiber 10 in a state in which the optical fiber 10 is biased. However, the holding member 20 may hold the optical fiber 10 without applying a biasing force to the optical fiber 10. In this case, when the optical fiber 10 is fixed to the object to be measured, the elastic portion 21 of the holding member 20 generates a biasing force, so that the same effect can be obtained. With such a configuration, the outer diameter of the ring spring, which is the elastic portion 21, when there is no load is made slightly smaller than the distance between the locking portion 11 and the locking portion 12, or the ring spring has no diameter. This can be achieved by making the outer diameter under load equal to the distance between the locking portion 11 and the locking portion 12.

FIGS. 6A and 6B are diagrams showing a method of mounting the strain sensor 1 when the holding member 20 holds the optical fiber 10 in a state where the holding member 20 does not apply a biasing force to the optical fiber 10. .. In this case, as shown by a solid arrow in FIG. 6A, when the holding member 20 is temporarily fixed to the measurement object 40, the ring spring, which is the elastic portion 21, extends along the arrangement direction of the optical fiber 10. Elastically deformed in the expansion direction. This increases the outer diameter of the ring spring in the direction along which the optical fiber 10 is arranged. Although not particularly limited, such elastic deformation can be realized by narrowing the ring spring along a direction perpendicular to the arrangement direction of the optical fiber 10 as shown by a dashed arrow in FIG. is there.

When fixing the optical fiber 10 to the measurement object 40, as shown in FIG. 6( b ), the above-mentioned structure is provided on the contact surface of the fixing portion 22 while maintaining the elastic deformation shown in FIG. 6( a ). The holding member 20 is temporarily fixed to the measurement object 40 by the double-sided tape 23. For example, by providing recesses on the non-contact surface sides of the fixing portions 22 on both sides, and inserting a regulator that maintains the distance between the recesses to be narrower than the distance between the recesses when there is no load, The elastically deformed state described above can be maintained.

In this state, as shown in FIG. 6B, the adhesive 50 that covers the locking portion 11 and the adhesive 50 that covers the locking portion 12 are applied. When the curing of the adhesive 50 is completed, the holding member 20 is separated from the optical fiber 10. Even in this case, the optical fiber 10 will be fixed to the measurement object while the tension is applied.

As described above, in the strain sensor 1, the holding member 20 holding the optical fiber 10 is installed on the measurement target. Then, the optical fiber 10 is measured in a state in which the elastic portion 21 of the holding member 20 applies a biasing force to the locking portion 11 and the locking portion 12, that is, in a state in which tension (pretension) is applied to the optical fiber 10. It is fixed to the object. After that, as a result of the holding member 20 being detached from the optical fiber 10, the optical fiber is fixed to the measurement object in a state where tension is applied. Therefore, it is extremely easy to install on the measurement object.

In addition, the space for installing the gauge carrier is not required for the measurement object, unlike the prior art, and the space required for installing the strain sensor can be made smaller than in the prior art. Therefore, it is possible to measure the distortion of a relatively small measurement target such as a component of a moving body. Further, the measurable strain amount range is not limited to the deformation limit of the gauge carrier. In addition, since the optical fiber 10 is installed in a state where tension is applied, it is possible to accurately measure the strain in the compression direction.

When the strain is measured with the above configuration, it is preferable to perform temperature correction in order to remove the influence of the deformation of the optical fiber 10 due to the influence of the ambient temperature. For the temperature correction, a known method can be adopted. That is, the amount of wavelength shift caused by the ambient temperature is acquired by the strain sensor arranged on the sample of the same material as the measurement target, and the wavelength shift amount of the strain sensor arranged on the measurement target is measured using the wavelength shift amount. Correct it.

The above-described embodiment does not limit the technical scope of the present invention, and various modifications and applications are possible within the scope of the present invention, other than those already described. For example, in the above embodiment, the case where the present invention is applied to a uniaxial strain sensor has been described, but the present invention can also be applied to a Rosetta strain sensor that detects the direction of strain along with the amount of strain. In this case, as shown in FIG. 7, the holding member 70 may include a plurality of elastic portions 21 that hold the optical fibers 10 arranged in different directions. In the example of FIG. 7, the FBG portion 25 is arranged at the central portion of each side of the optical fibers 10 arranged in a regular triangle shape, and the two locking portions 11 and 12 provided with the FBG portions 25 sandwiched therebetween. The elastic portion 21 is arranged between the two. In this configuration, the fiber portions facing different directions may be configured by changing the direction of one optical fiber, or may be configured by three independent optical fibers. In the former case, the Bragg wavelengths of the FBG units 25 are set to different wavelengths.

Further, in the above-described embodiment, the configuration in which the strain is detected by the wavelength variation of the reflected light in the FBG unit 25 has been described as a particularly preferable form, but the strain detection method is not particularly limited. Although there is a possibility that the size of the sensor will increase, it is also possible to employ a distributed strain detection configuration, such as detecting strain by measuring fluctuations in the backscattered light of the optical fiber.

Further, in the above-described embodiment, the elastic portion 21 is formed of a circular ring spring as a particularly preferable form, but the elastic portion may have any structure as long as it can generate the biasing force described above.

Further, in the above-described embodiment, the optical fiber 10 and the holding member 20 are fixed by the adhesive 27 as a particularly preferable form, but a cover, a tape or the like that is detached when the optical fiber 10 and the holding member 20 are attached to the object to be measured should be arranged on the contact surface. The unintended disconnection of the optical fiber 10 may be prevented. Further, the holding member 20 may hold the optical fiber 10 only by the biasing force generated by the elastic portion 21.

Furthermore, in the above-described embodiment, the locking portions 11 and 12 are made of ultraviolet curable resin as a particularly preferable form, but the locking portions 11 and 12 can be formed by adhering and fixing a member formed by a separate process or the like to the optical fiber 10. May be configured. Further, it is not essential that the contact surfaces of the locking portions 11 and 12 with the measurement object and the contact surface of the holding member 20 with the measurement object are arranged in the same plane.

In addition, in the above embodiment, the present invention has been described as the strain sensor 1 including the optical fiber 10 and the holding member 20, but only the holding member 20 may be used as a mounting jig. That is, the optical fiber 10 including the locking portions 11 and 12 and the holding member 20 that is a mounting jig are separately prepared, and when the optical fiber 10 is installed on the measurement target, the optical fiber 10 is set on the spot as shown in FIG. The configuration may be such that the holding member 20 holds the optical fiber 10 by the procedure shown in c) to FIG. Even with such a configuration, it is possible to obtain the same effect as that of the strain sensor 1 described above.

According to the present invention, the space required for installation is smaller than in the past, the installation is easier than in the past, and the range of measurable strain amount can be widened as compared with the conventional strain sensor. It is useful as a mounting jig for strain sensors.

DESCRIPTION OF SYMBOLS 1 Strain sensor 10 Optical fiber 11, 12 Locking part 13 End surface 14 Skin resin 20, 70 Holding member 21 Elastic part 22 Fixing part 23 Double-sided tape 24 Groove 25 FBG part 27 Adhesive 28 Concave 30 Substrate 40 Measuring object 50 Adhesion Agent

Claims (9)

A strain sensor using an optical fiber,
Two locking portions which are provided on the optical fiber at a predetermined interval and which are formed by a protrusion provided on the outer peripheral surface of the optical fiber ;
A holding member which is detachably fixed to the optical fiber between the two locking portions, and which is fixed to the measurement object and then is separated from the optical fiber;
Equipped with
The holding member,
An elastic portion that abuts on the two locking portions and applies a biasing force to the optical fiber in a direction in which the two locking portions separate;
When fixing the optical fiber to the measurement object, a fixing portion used for temporary fixing to the measurement object,
Ruyugami sensor equipped with. The strain according to claim 1, wherein the holding member is fixed to the optical fiber in a state in which the elastic portion applies the biasing force to the optical fiber, and in the state, the optical fiber is fixed to the measurement target. Only sensor. The holding member, the strain seen sensor according to claim 1, wherein the optical fiber when it is fixed to the measurement object, and generates the biasing force by the deformation of the elastic portion extending in the axial direction of the optical fiber. The elastic portion is formed of a ring spring , and the fixing portion is a ring spring in a plane including the optical fiber in a direction perpendicular to the arrangement direction of the optical fiber at positions facing each other in the ring spring. strain sensor according to any one of claims 1 to 3 that will be configured by extending out a plate-like member outward from. The strain sensor according to any one of claims 1 to 4, wherein the optical fiber includes an FBG (Fiber Bragg Grating) portion between the two locking portions. The strain sensor according to any one of claims 1 to 5, wherein the holding member includes a plurality of elastic portions that are fixed to respective optical fibers arranged in different directions. The elastic portion of the holding member includes a groove portion on a surface facing the measurement object when the optical fiber is fixed to the measurement object, and the optical fiber is arranged in the groove portion. The strain sensor according to claim 6. The strain sensor according to any one of claims 1 to 7, wherein a contact surface of the locking portion with the measurement object and a contact surface of the holding member with the measurement object are arranged in the same plane. A jig for mounting a strain sensor consisting of an optical fiber,
Provided at a predetermined interval before Symbol optical fiber, in contact with the two locking portions formed by protrusions provided on the outer peripheral surface of the optical fiber, with respect to the optical fiber, the two An elastic portion that applies a biasing force in a direction in which the locking portion separates,
When fixing the optical fiber to the measurement target, a fixing unit used for temporary fixing to the measurement target,
Wherein the elastic portion, provided in the measurement object surface facing the when the optical fiber is secured to the measurement object mounting jig of the strain sensor comprising a groove and said optical fiber is housed.

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