JP6147125B2 - Optical pressure sensor - Google Patents

Description

  The present invention relates to an optical pressure sensor using a fiber black grating (FBG), and more particularly to an optical pressure sensor disposed in a fluid flowing in a pipeline.

  Conventionally, as a pressure sensor using FBG, as shown in FIG. 7A, an optical cable 102 and a diaphragm 103 are disposed in a case 101, and an elastic deformation amount of the diaphragm 103 due to pressure is detected by the FBG 104. It has been put into practical use (Patent Document 1). Since the FBG 104 has a characteristic that the reflected wavelength shifts depending on the amount of strain, by fixing the FBG 104 to the diaphragm 103, the amount of elastic deformation due to pressure can be converted to the wavelength shift amount of the FBG 104, and the function as a pressure sensor Can be given.

  Further, as a method for fixing the FBG to the diaphragm, as shown in FIG. 7 (b), a mode is disclosed in which the FBG 113 is fixed to a high tension wire 112 arranged vertically from the diaphragm 111 (Patent Document 2). .

Japanese Patent No. 4615076 Japanese Patent No. 3571936

  As described above, an optical pressure sensor using a general FBG has a configuration in which a diaphragm is disposed on one end surface of a substantially cylindrical container and an optical fiber is led out from the other end surface. And in order to detect the elastic deformation amount of a diaphragm, FBG formed in a part of optical fiber is being fixed directly or indirectly to the diaphragm surface.

  On the other hand, in an optical fiber, a minimum bending radius is defined in order to prevent brittle fracture of glass, and in a general optical fiber, the minimum bending radius is R30 mm. Therefore, after securing R30 mm in the path through which the optical fiber is led out of the pressure sensor, it is necessary to arrange the optical fiber constituting the path at a substantially right angle with respect to the diaphragm surface (FIG. 7A). reference).

  For this reason, the container volume of the pressure sensor becomes a value corresponding to the product of both the diameter of the diaphragm and the optical fiber storage dimension in the direction perpendicular to the diaphragm (vertical direction), and the volume of the entire sensor must be increased. .

  However, when measuring the water level in an environment with a water flow such as a river or sewer, the volume of the pressure sensor should be small so that the flow is not hindered, especially when measuring the water level in a small diameter pipe. Since it is necessary to reduce the influence on the flow as much as possible so as not to cause problems such as a decrease in pressure detection accuracy and clogging in the pipe tube, downsizing of the sensor is desired.

  An object of the present invention is to provide an optical pressure sensor that can reduce the influence on the flow as much as possible while realizing highly reliable measurement using an FBG, and is highly convenient regardless of the installation location. .

In order to achieve the above object, an optical pressure sensor according to the present invention is an optical pressure sensor that is disposed in a flow path and detects the pressure of a fluid flowing through the flow path with an optical fiber. A flat sealed container having a wall; a diaphragm attached to the bottom wall of the sealed container; and disposed substantially parallel to the bottom wall; and disposed in the sealed container and substantially parallel to the membrane of the diaphragm. A fiber black grating attached in such a manner, an optical fiber integrally connected to the fiber black grating and laid so as to be substantially parallel to the membrane of the diaphragm, and provided on a side wall of the sealed container, and a inlet and outlet for connecting to an external optically through a fiber in a side view of the closed container, the central axis of the optical fiber to be inserted into the introduction outlet, It is disposed at a position lower than the film surface of serial diaphragm and said Rukoto.

  Moreover, it is preferable that the said airtight container is formed with resin.

  The optical fiber includes a first optical fiber disposed on the upstream side of the fiber black grating and a second optical fiber disposed on the downstream side of the fiber black grating, and the first optical fiber and Both of the second optical fibers are laid substantially parallel to the diaphragm membrane.

  The central axis of the fiber black grating is preferably substantially parallel to the central axis of the optical fiber inserted through the introduction outlet.

  Preferably, a part of the bottom wall of the sealed container forms a recess recessed inward.

  Further, the sealed space formed in the sealed container includes a first space formed immediately above the diaphragm and a second space formed on the side of the diaphragm, and the second space is It is preferable that the concave portion has a flat shape.

Furthermore, a pressure correction unit that is connected to the sealed container and corrects the pressure in the sealed space formed in the sealed container is attached to the optical pressure sensor.
In order to achieve the above object, the optical pressure sensor is disposed in a flow path and detects the pressure of a fluid flowing through the flow path with an optical fiber, and is a flat-type hermetic seal having an upper wall and a bottom wall. A container, a diaphragm attached to the bottom wall of the sealed container and disposed substantially parallel to the bottom wall, and a fiber black disposed in the sealed container and attached to be substantially parallel to the membrane of the diaphragm A grating, an optical fiber integrally connected to the fiber black grating, and laid so as to be substantially parallel to the membrane of the diaphragm; provided on a side wall of the sealed container; A part of the bottom wall of the sealed container has a recessed part recessed inward, and the sealed space formed in the sealed container is A first space formed just above the Iyafuramu, is composed of a second space formed on the side of said diaphragm, said second space, characterized in that has a flat shape by the recess.

  According to the present invention, the sealed container has a flat shape, and the fiber black grating and the optical fiber are attached so as to be substantially parallel to the membrane of the diaphragm. An introduction outlet is provided on the side wall of the sealed container. As a result, the optical fiber wiring inside the optical pressure sensor can be accommodated in a plane substantially parallel to the diaphragm film while ensuring a minimum bending radius R30 mm. In addition, the volume of the optical pressure sensor is a value corresponding to the product of both the diameter of the diaphragm and the storage size of the optical fiber in a direction substantially parallel to the diaphragm, thereby greatly reducing the volume of the optical pressure sensor. It becomes possible.

It is a figure which shows schematically the structure of the optical pressure sensor which concerns on embodiment of this invention, (a) is a top view, (b) is a width direction side view. (A) is a bottom view of the optical pressure sensor of FIG. 1, (b) is a longitudinal side view. (A) is a longitudinal cross-sectional view of the optical pressure sensor along line AA in FIG. 2 (a), and (b) is an optical pressure sensor along line BB in FIG. 2 (a). FIG. It is a figure which shows the optical fiber laid in the optical pressure sensor of FIG. 1, (a) is a top view, (b) is a longitudinal direction side view. It is a figure which shows the structure of the atmospheric pressure correction unit connected to the optical pressure sensor of FIG. It is a figure which shows the example of installation in the case of installing the optical pressure sensor of FIG. (A) is a figure which shows the structure of the conventional optical pressure sensor, (b) is a figure which shows the structure of the other conventional optical pressure sensor.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  1A is a top view schematically showing the configuration of the optical pressure sensor according to the present embodiment, FIG. 1B is a side view in the width direction, FIG. 2A is a bottom view, and FIG. It is a longitudinal direction side view. 3A is a longitudinal sectional view of the optical pressure sensor taken along line AA in FIG. 2A, and FIG. 3B is taken along line BB in FIG. It is longitudinal direction sectional drawing of an optical pressure sensor. 4A is a plan view showing an optical fiber laid in the optical pressure sensor of FIG. 1, and FIG. 4B is a longitudinal side view. The optical pressure sensor of FIGS. 1 to 4 shows an example thereof, and the optical pressure sensor of the present invention is not limited to that of FIGS.

  The optical pressure sensor according to the present embodiment is arranged in a flow path and detects the pressure of a fluid flowing through the flow path with a single mode optical fiber, and employs a wavelength detection method using FBG. . The wavelength used is, for example, the 1.55 μm band.

  Specifically, the optical pressure sensor 1 is attached to the bottom wall 2a of the flat container having the bottom wall 2a and the top wall 2b, and is disposed substantially parallel to the bottom wall 2a. A diaphragm 3, a fiber black grating (FBG) 4 disposed in the hermetic container 2 and attached so as to be substantially parallel to the thin film 31 of the diaphragm 3, and the fiber black grating are integrally connected to each other. An optical fiber 5 laid so as to be substantially parallel to the thin film 31 and a side wall 2c in the width direction of the sealed container 2 for optically connecting to an external device (for example, a closure) via the optical fiber 5. The inlet 6 is provided.

  The optical pressure sensor 1 has a characteristic shape first. Specifically, the sealed container 2 has a flat shape with an aspect ratio of about 5: 1 in a side view in the longitudinal direction, and an aspect in a plan view. It has a vertically long structure with a ratio of about 2: 1. According to such a shape, even when the optical pressure sensor 1 is installed in a flow path such as a pipe rod or a side groove, the optical pressure sensor can be provided by arranging the sensor substantially parallel to the fluid flow direction. It is possible to perform pressure measurement without changing the flow state in the vicinity of 1 as much as possible.

  The hermetic container 2 includes a base portion 21 and a lid portion 22 (FIG. 1B). The base portion 21 has a bottom wall 2a and the lid portion 22 has an upper wall 2b. The base portion 21 and the lid portion 22 are fitted face to face with each other through the seal member 23 (FIG. 3A), and are fixed with bolts 24. As a result, a substantially flat sealed space is formed in the sealed container 2. This airtight sealed space is composed of a sealed space X (first space) formed immediately above the diaphragm 3 and a sealed space Y (second space) formed on the side of the diaphragm 3.

  The bottom wall 2a includes a bottom wall portion 21a that supports the diaphragm 3 and the fixing member 32, and a bottom wall portion 21b ′ for guiding the optical fiber 5 from the diaphragm 3 to the outside in a longitudinal sectional view (see FIG. 3 (a)). A sealed space X is formed immediately above the bottom wall portion 21a, and a sealed space Y is formed immediately above the bottom wall portion 21b '.

  The material of the sealed container 2 is formed of a resin such as polypropylene, and more preferably a resin having corrosion resistance. Thereby, most of the optical pressure sensor 1 can be molded with a resin, and the optical pressure sensor 1 can be manufactured at a low cost and at a lower cost than a metal sealed container. Further, when installing a plurality of optical pressure sensors 1, the burden on the operator is reduced, and the installation efficiency can be improved.

  The diaphragm 3 is supported on the bottom wall portion 21a of the sealed container 2 via a ring-shaped fixing member 32 (FIG. 3A). The diaphragm 3 is a substantially cylindrical metal member, and a thin film 31 is attached to the center thereof. And FBG4 is attached to the inner surface 31a of the thin film 31, and the center part of this thin film. When the water level in the flow path fluctuates, the pressure applied to the diaphragm 3 changes and the thin film 31 is deformed, so that the FBG 4 expands and contracts. Due to the expansion and contraction of the FBG 4, the center wavelength of the light reflected by the FBG is shifted. Using this principle, the water level, that is, the pressure is measured from the shift amount of the center wavelength.

  As shown in FIG. 4 (a), the FBG 4 is fixed to the sealed container 2 and the FBG 4a for pressure detection disposed at the center of the thin film 31 so as to be substantially parallel to the longitudinal direction of the sealed container 2, It is comprised by FBG4b for temperature detection arrange | positioned substantially parallel to FBG4a. The FBGs 4a and 4b are connected to each other via an optical fiber 5 and are connected to an external device.

  The FBG 4a is optically connected to an external device (not shown) through an optical fiber 5a. Light output from an external light source is introduced into the FBG 4a through the optical fiber 5a, and light reflected by the FBG 4a is reflected. It is led out through the optical fiber 5a. The light transmitted through the FBG 4a is introduced into the FBG 4b through the optical fiber 5b, and the light transmitted through the FBG 4b is led out to the outside through the optical fiber 5c.

  The optical fiber 5 includes an optical fiber 5a (first optical fiber) disposed on the upstream side of the FBG 4a and optical fibers 5b and 5c (second optical fiber) disposed on the downstream side of the FBG 4a. An FBG 4b is disposed between the optical fibers 5b and 5c.

  The optical fibers 5a, 5b, and 5c are arranged in this order in the sealed spaces X and Y, and all of these are laid substantially parallel to the thin film 31 of the diaphragm 3 (FIG. 4B). By laying in this way, the entire sealed space can be flattened while ensuring the minimum bending radius R30 mm of the optical fiber 5, and the space volume can be significantly reduced compared to the conventional case. .

  Further, part or all of the optical fiber 5c may be formed of a so-called bending strong fiber having high bending strength. As the bending strong fiber, for example, one conforming to “ITU-T G.657 A1” is selected, and the minimum bending radius is allowed up to R15 mm. Since the optical fiber 5c is a portion having the smallest bending radius in the sensor, the optical fiber 5c can be obtained by using a bending strong fiber (a small-diameter bending-compatible fiber) according to the widthwise dimension of the sealed container 2. Can be reliably prevented.

  Note that the fiber wiring of FIG. 4 is simplified for convenience of explanation, but the optical fiber 5a connected to the outside via the introduction outlet 6 is wound once or a plurality of times in the sealed space, and the FBG 4a. May be connected. Similarly, the optical fiber 5b may be wound once or a plurality of times and connected to the FBG 4b, and the optical fiber 5c may be wound once or a plurality of times and connected to the outside via the introduction outlet 6. .

  An inlet / outlet 6 is formed in the side wall 2c in the width direction of the sealed container 2, and a tubular connecting member 61 for connecting the optical pressure sensor 1 and an external device is fitted into the inlet / outlet substantially coaxially. ing. In the longitudinal sectional view of the sealed container 2, the central axes of the optical fibers 5a and 5c inserted through the introduction outlet 6 are lower than the inner surface 31a of the diaphragm 3 (FIG. 3 (b): H1 <H2). . Thereby, the airtight container 2 can be made into a flat shape, ensuring the attachment space of the tubular connection member 61 in the side wall 2c reliably.

  The tubular connecting member 61 is arranged so that its central axis is substantially parallel to the thin film 31 of the diaphragm 3. Optical fibers 5a and 5c are inserted into the tubular connecting member 61, and the end of each optical fiber is connected to an external device. Therefore, the central axes of the optical fibers 5 a and 5 c inserted through the tubular connecting member 61 are also substantially parallel to the thin film 31 of the diaphragm 3.

  In the present embodiment, the central axes of the FBGs 4a and 4b are arranged so as to be substantially parallel to the central axes of the optical fibers 5a and 5b inserted through the inlet / outlet 6 (FIG. 4A). Furthermore, in plan view, the central axis of the FBG 4a is arranged substantially coaxially with the central axis of the inlet / outlet 6 (FIG. 4A).

  The sealed spaces X and Y are adjusted to atmospheric pressure by a pressure correction unit as shown in FIG. 5, for example. The pressure correction unit 70 communicates with the sealed spaces X and Y and is connected to the tubular connection member 61 approximately coaxially with the optical fiber, a connection box 72 connected to the tube 71, and air to the connection box. Tube 73, expansion / contraction part 75 made of an elastic body connected to tube 73 via joint 74, expansion / contraction part 75, and expansion / contraction part accommodation box provided with air introduction port 76a 76. The expansion / contraction part 75 is expanded or contracted by the pressure (atmospheric pressure) of the air introduced from the air introduction port 76a, and the internal pressure of the expansion / contraction part 75 is kept in equilibrium with the atmospheric pressure. Therefore, by connecting the sealed spaces X and Y of the optical pressure sensor 1 and the expansion / contraction part 75, the pressure of the sealed spaces X and Y is maintained at atmospheric pressure. With this configuration, since the pressure applied to the thin film 31 of the diaphragm 3 is only the pressure received from the fluid, it is possible to accurately detect the pressure.

  Further, as described above, since the volumes of the sealed spaces X and Y are very small, the amount of air moving between the expansion / contraction part 75 and the sealed spaces X and Y is significantly reduced. Therefore, it is possible to reduce defects due to deterioration over time, and to reduce maintenance work.

  In order to further reduce the volume of the sealed space Y, as shown in FIG. 3A, the bottom wall portion 21b ′ located on the side of the diaphragm 3 may form a recess 25 having a substantially rectangular cross section in the longitudinal direction. . By forming the recess 25 so as to be recessed inward, the sealed container 2 has a raised bottom shape, and the volume of the sealed space Y becomes smaller.

  However, in the laying portion of the optical fiber 5, a recess 26 having a substantially triangular cross section in the longitudinal direction is formed in consideration of the minimum bending radius of the optical fiber (FIG. 3B). Specifically, a bottom wall portion 21b ″ that is gently inclined from the inner surface 31a of the diaphragm 3 toward the introduction outlet 6 is provided at a substantially central portion in the width direction of the base portion 21. Thus, FIGS. As shown in b), the optical fibers 5a and 5c are laid on the inclined surface of the bottom wall portion 21b ″. Therefore, the optical fibers 5a and 5c do not have the minimum bending radius R30 mm or less in the sealed space Y, and laying without causing brittle fracture can be easily performed.

  The optical pressure sensor 1 configured as described above is installed, for example, in a pipe tub serving as a water channel. As shown in FIG. 6, the optical pressure sensor 1 is fixed to the tube bottom 81 a of the tube rod 81 with an annular fixing band 91. An optical fiber cable 92 that connects the optical pressure sensor 1 and the closure 93 is fixed to the tube bottom 81a of the tube 81 with a fixing band 91, so that the optical fiber cable 92 is connected to the inside of the tube 81 and It is laid in the manhole 82. The closure 93 is fixed to the side wall 81a in the manhole 82 by a fixing tool (not shown) such as a saddle.

  When a pressure sensor is installed in such a pipe rod, it is necessary to take care not to cause problems such as a decrease in accuracy of pressure detection and clogging in the pipe rod. In this embodiment, the small and flat optical pressure sensor 1 is installed in parallel with the water flow direction F of the pipe rod 81 and is fixed to the inner peripheral surface 81a. And the influence on the water flow can be reduced as much as possible. Moreover, since the optical fiber cable 92 led out from the optical pressure sensor 1 can be laid substantially parallel to the water flow direction F, the influence on the water flow can be further reduced.

  Moreover, since there is a possibility that the combustible gas will be filled in the tube, the installation of electric wires such as metal wires may be restricted when installing the devices in the tube. In this embodiment, since the optical pressure sensor 1 and the closure 93 are connected by the optical fiber cable 92, the installation of the sensor with a high degree of freedom can be realized without being restricted by the installation in the pipe tube.

  As described above, according to the present embodiment, the sealed container 2 has a flat shape, and the FBGs 4 a and 4 b and the optical fiber 5 are attached so as to be substantially parallel to the thin film 31 of the diaphragm 3. An introduction outlet 6 is provided on the side wall 2 c of the sealed container 2. Thereby, the optical fiber wiring inside the optical pressure sensor 1 can be accommodated in a plane substantially parallel to the thin film 31 of the diaphragm 3 while ensuring a minimum bending radius R30 mm. The volume of the optical pressure sensor 1 is a value corresponding to the product of both the diameter of the diaphragm 3 and the storage size of the optical fiber 5 in a direction substantially parallel to the diaphragm 3, and the volume of the optical pressure sensor 1 is greatly increased. It is possible to reduce the size. Therefore, while realizing highly reliable measurement, the influence on the water flow can be reduced as much as possible, and the optical pressure sensor 1 with high convenience can be provided regardless of the installation location.

  Further, since the volume of the optical pressure sensor 1 can be reduced, it is possible to reduce the sealed spaces X and Y for correcting the pressure and atmospheric pressure inside the sensor when detecting the water level, that is, the pressure compensation unit.

  Further, when installed on the pipe bottom 81a of the pipe rod 81, the sensor cross-sectional area perpendicular to the water flow direction can be greatly reduced, and the optical fiber cable 92 led out of the sensor is also substantially the same as the water flow. Since it can be laid in parallel, the influence on the water flow can be greatly reduced.

  The optical pressure sensor according to the present embodiment has been described above, but the present invention is not limited to the described embodiment, and various modifications and changes can be made based on the technical idea of the present invention.

DESCRIPTION OF SYMBOLS 1 Optical pressure sensor 2 Airtight container 2a Bottom wall 2b Top wall 2c Side wall 3 Diaphragm 4 FBG
4a, 4b FBG
5 Optical fiber 5a, 5b, 5c Optical fiber 6 Inlet / outlet 21 Base part 21a Bottom wall part 21b 'Bottom wall part 21b "Bottom wall part 22 Lid part 23 Seal member 24 Bolt 25 Recessed part 26 Recessed part 31 Thin film 31a Inner surface 32 Fixing member 61 Tubular connection member 71 Tube 72 Connection box 73 Tube 74 Joint 75 Expansion / contraction part 76 Expansion / contraction part storage box 76a Air inlet 81 Pipe rod 82 Manhole 81a Tube bottom 91 Fixed band 92 Optical fiber cable 93 Closure

Claims (8)

An optical pressure sensor that is disposed in a flow path and detects the pressure of a fluid flowing through the flow path with an optical fiber,
A flat sealed container having a top wall and a bottom wall;
A diaphragm attached to the bottom wall of the sealed container and disposed substantially parallel to the bottom wall;
A fiber black grating disposed in the sealed container and attached so as to be substantially parallel to the membrane of the diaphragm;
An optical fiber integrally connected to the fiber black grating and laid so as to be substantially parallel to the membrane of the diaphragm;
Provided on the side wall of the sealed container, and an introduction outlet for optically connecting to the outside via the optical fiber ,
In a side view of the closed container, the central axis of the optical fiber to be inserted into the introduction outlet, optical pressure sensor, wherein Rukoto is disposed at a position lower than the film surface of the diaphragm.   The optical pressure sensor according to claim 1, wherein the sealed container is made of a resin. The optical fiber includes a first optical fiber disposed upstream of the fiber black grating and a second optical fiber disposed downstream of the fiber black grating;
2. The optical pressure sensor according to claim 1, wherein both the first optical fiber and the second optical fiber are laid substantially parallel to the membrane of the diaphragm. 3.   The optical pressure sensor according to claim 1, wherein a central axis of the fiber black grating is substantially parallel to a central axis of an optical fiber inserted through the introduction outlet.   The optical pressure sensor according to claim 1, wherein a part of the bottom wall of the sealed container constitutes a concave portion recessed inward. The sealed space formed in the sealed container is composed of a first space formed immediately above the diaphragm and a second space formed on the side of the diaphragm,
The optical pressure sensor according to claim 5 , wherein the second space has a flat shape due to the concave portion. 2. The optical pressure sensor according to claim 1, further comprising a pressure correction unit connected to the sealed container and configured to correct a pressure in a sealed space formed in the sealed container . An optical pressure sensor that is disposed in a flow path and detects the pressure of a fluid flowing through the flow path with an optical fiber,
A flat sealed container having a top wall and a bottom wall;
A diaphragm attached to the bottom wall of the sealed container and disposed substantially parallel to the bottom wall;
A fiber black grating disposed in the sealed container and attached so as to be substantially parallel to the membrane of the diaphragm;
An optical fiber integrally connected to the fiber black grating and laid so as to be substantially parallel to the membrane of the diaphragm;
Provided on the side wall of the sealed container, and an introduction outlet for optically connecting to the outside via the optical fiber,
A part of the bottom wall of the sealed container has a recess recessed inwardly,
The sealed space formed in the sealed container is composed of a first space formed immediately above the diaphragm and a second space formed on the side of the diaphragm,
The optical pressure sensor, wherein the second space is flattened by the recess.

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