JP7552225B2 - Optical waveguide for oil leakage sensor and oil leakage sensor - Google Patents

Description

The present invention relates to an optical waveguide for an oil leak sensor and an oil leak sensor.

Patent Document 1 discloses an oil leakage sensor that reacts with oil to detect an oil leakage state. This oil leakage sensor has a pair of conductive lines formed by printing a mixture of carbonate nanotube dispersion, alkyd resin, and silver flakes onto a base film layer. When the conductive lines come into contact with oil, the alkyd resin dissolves and breaks, causing the resistance value of the conductive lines to increase. The presence or absence of oil leakage can be confirmed by detecting this change in resistance value with a controller.

Meanwhile, Patent Document 2 discloses an oil leak detection sensor that uses optical fibers. This oil leak detection sensor has a clad layer of polymer material formed around a core portion of quartz glass material, and is equipped with an optical fiber with a hole drilled in part of the clad layer. When oil adheres to the core portion exposed through this hole, the attenuation of the light propagating through the optical fiber increases. By detecting this attenuation, it is possible to confirm the presence or absence of oil leakage.

Special Publication No. 2015-528915 Utility Model Registration No. 3176191

The invention described in Patent Document 1 uses an electrical signal to check for the presence or absence of oil leakage. For this reason, in the oil leakage detection sensor described in Patent Document 1, the electrical signal may generate sparks, etc. Therefore, there is a problem that it is difficult to use an oil leakage detection sensor that uses an electrical signal for applications that detect flammable oils.

The device described in Patent Document 2 uses optical signals to check for the presence or absence of oil leakage. Therefore, the oil leakage detection sensor described in Patent Document 2 can also be used for flammable oils. However, even if water adheres to the core exposed through a hole in the cladding layer, the light propagating through the optical fiber is attenuated. For this reason, there is an issue that it cannot be used outdoors or in environments where water is used.

The object of the present invention is to provide an oil leak sensor capable of detecting oil leaks regardless of the flammability of the oil or the usage environment, and an optical waveguide for an oil leak sensor capable of realizing such an oil leak sensor.

These objects can be achieved by the present invention described below in (1) to (10).
(1) a first protective layer;
A second protective layer; and
a core layer provided between the first protective layer and the second protective layer, the core layer having a core portion including a light incident surface and a light exit surface, and a side clad portion;
Equipped with
When viewed in a thickness direction of the core layer, a side surface portion of the core portion other than the light incident surface and the light exit surface is adjacent to the side clad portion,
the shortest distance between the side surface of the core portion and the side surface of the core layer is 1 μm to 1 mm;
13. An optical waveguide for an oil leak sensor, wherein the oil resistance of said side clad portion is lower than both the oil resistance of said first protective layer and the oil resistance of said second protective layer.

(2) The core layer has an elongated shape having one end and the other end when viewed in the thickness direction,
The optical waveguide for an oil leakage sensor according to (1) above, wherein the light incident surface and the light exit surface are provided at the one end.

(3) The core portion includes a curved portion extending along a circular arc,
The optical waveguide for an oil leakage sensor according to (2) above, wherein the curved portion changes the propagation direction of light by 180° or more.

(4) A through hole penetrating the core layer,
The optical waveguide for an oil leakage sensor according to any one of (1) to (3) above, wherein the core portion includes a circumferential portion extending along the edge of the through hole.

(5) The optical waveguide for an oil leakage sensor described in (4) above, in which the core portion includes an intersection portion that intersects when viewed in the thickness direction.

(6) When the size of an interior angle adjacent to an interior angle on the through hole side among the interior angles formed by the core portions intersecting at the intersection portion is defined as an intersection angle,
The optical waveguide for an oil leakage sensor according to (5) above, wherein the crossing angle is 90° or less.

(7) Among the side surfaces of the core layer,
a sensing portion is a portion where the distance between the core portion and the side surface of the core layer is 100% or more and 200% or less of the shortest distance,
When a portion where the distance between the core portion and the side surface of the core layer is more than 200% of the shortest distance is defined as a non-sensing portion,
The optical waveguide for an oil leakage sensor according to any one of (1) to (6) above, wherein the side surface of the core layer has both the sensing portion and the non-sensing portion.

(8) The optical waveguide for an oil leak sensor described in (7) above, in which the side surface of the core layer has a plurality of the sensing portions spaced apart from each other.

(9) An optical waveguide for an oil leakage sensor according to any one of (1) to (8) above, comprising an adhesive layer provided on the side of the first protective layer opposite the core layer.

(10) An optical waveguide for an oil leakage sensor according to any one of (1) to (9) above;
a light emitting portion connected to the light incident surface;
a light receiving portion connected to the light exit surface;
A control unit that outputs a signal based on the intensity of the light received by the light receiving unit;
An oil leakage sensor comprising:

The present invention provides an oil leak sensor that can detect oil leaks regardless of the flammability of the oil or the usage environment.

The present invention also provides an optical waveguide for an oil leak sensor that can realize the above-mentioned oil leak sensor.

1 is a perspective view showing a state in which an oil leakage sensor using an optical waveguide for an oil leakage sensor according to a first embodiment is used; FIG. 2 is a cross-sectional view of the oil leakage sensor shown in FIG. 1 . FIG. 2 is a plan view illustrating the operation of the oil leakage sensor shown in FIG. 1 . FIG. 2 is a partially enlarged perspective view of the optical waveguide for the oil leakage sensor shown in FIG. 1 . FIG. 4 is a partially enlarged view of FIG. 3 . FIG. 11 is a plan view showing an optical waveguide for an oil leakage sensor according to a second embodiment. FIG. 11 is a plan view showing a first modified example of the optical waveguide for the oil leakage sensor according to the second embodiment. FIG. 8 is a cross-sectional view of FIG. FIG. 11 is a plan view showing a second modified example of the optical waveguide for the oil leakage sensor according to the second embodiment. FIG. 11 is a plan view showing an optical waveguide for an oil leakage sensor according to a third embodiment. 1 is a diagram illustrating a schematic diagram of the positional relationship between a circle C corresponding to a winding portion R, a center O of the circle C, a crossing point CP, and a core portion. 13 is a table showing, by calculation, how the distance L between the circle C and the intersection point CP changes when the intersection angle θ is changed from 45° to 120°. FIG. 11 is a partially enlarged plan view showing an optical waveguide for an oil leakage sensor according to a fourth embodiment. FIG. 13 is a partially enlarged plan view showing an optical waveguide for an oil leakage sensor according to a fifth embodiment.

The optical waveguide for an oil leak sensor and the oil leak sensor of the present invention will be described in detail below based on the preferred embodiment shown in the attached drawings.

1. Oil Leak Sensor First, an oil leak sensor 100 using an optical waveguide 1 for an oil leak sensor according to a first embodiment described below will be described.

Figure 1 is a perspective view showing the use of an oil leakage sensor 100 using the optical waveguide 1 for an oil leakage sensor according to the first embodiment. Figure 2 is a cross-sectional view of the oil leakage sensor 100 shown in Figure 1. Figure 3 is a plan view explaining the operation of the oil leakage sensor 100 shown in Figure 1. In each figure, an X-axis, a Y-axis, and a Z-axis are set as three mutually orthogonal axes, and are indicated by arrows. The base end side of the arrow is called the "negative side" of each axis, and the tip end side is called the "positive side" of each axis. The tip end side of the arrow representing the Z axis is called the "upper" side, and the base end side is called the "lower" side.

The oil leakage sensor 100 shown in Figures 1 to 3 includes an optical waveguide 1 for an oil leakage sensor, light-emitting elements 101 and 102 that emit light, light-receiving elements 103 and 104 that receive light, and a control unit 106 that outputs a detection result based on the intensity of the received light.

The optical waveguide 1 for the oil leak sensor is used in a state where it is attached to an adherend 9, as shown in Figures 1 to 3.

The adherend 9 shown in FIG. 1 comprises a main body 91 having an internal flow path, a lid 92, and four bolts 93. The bolts 93 are inserted into through holes penetrating the lid 92 and screwed into threaded holes formed in the main body 91. This presses the lid 92 against the main body 91, sealing the inside liquid-tight. As a result, oil can flow through the flow path of the main body 91.

Therefore, the adherend 9 is, for example, a structure that may have an oil leak. The optical waveguide 1 for the oil leak sensor shown in FIG. 1 is attached to the outer surface of the adherend 9 and detects the presence or absence of oil leaking onto the outer surface of the adherend 9. This allows the oil leak sensor 100 to detect the presence or absence of an abnormality in the adherend 9. The location where the optical waveguide 1 for the oil leak sensor is attached to the adherend 9 is not particularly limited, but is preferably a location that is effective for detecting oil leaks. Therefore, the location where the optical waveguide 1 for the oil leak sensor is attached is not limited to the location shown in FIG. 1, and may be, for example, the left or right surface of the adherend 9 shown in FIG. 1, or a location that spans from the left or right surface to the top or bottom surface.

Examples of oils that can be detected include crude oil, heavy oil, light oil, gasoline, lubricating oil, mineral oil, gear oil, motor oil, internal combustion engine oil, transformer oil, etc.

In the oil leak sensor 100, with the optical waveguide 1 for the oil leak sensor attached to the adherend 9, as shown in FIG. 3, incident light L1 is continuously or intermittently incident on the optical waveguide 1 for the oil leak sensor from the light emitting elements 101 and 102. The propagation direction of the incident light L1 is folded back inside the optical waveguide 1 for the oil leak sensor, and the incident light L1 is emitted as outgoing light L2. This outgoing light L2 is received by the light receiving elements 103 and 104, and the intensity is monitored by the control unit 106.

When oil leaks onto the surface of the adherend 9 while the intensity of the emitted light L2 is being monitored in this manner, the leaked oil penetrates the optical waveguide 1 for the oil leakage sensor, causing the inside to swell or dissolve. This increases the transmission loss at this location, and the intensity of the emitted light L2 becomes smaller than normal. This allows the control unit 106 to detect the decrease in the intensity of the emitted light L2, and based on this, it is possible to determine the presence or absence of oil leakage. As a result, the oil leakage sensor 100 functions as a sensor that detects oil leakage from the adherend 9.

The light emitting elements 101 and 102 emit incident light L1 into the optical waveguide 1 for the oil leakage sensor. Examples of the light emitting elements 101 and 102 include semiconductor lasers, gas lasers, and light emitting diodes.

The light receiving elements 103 and 104 receive the emitted light L2 emitted from the optical waveguide 1 for the oil leakage sensor and output a light receiving signal to the control unit 106. Examples of the light receiving elements 103 and 104 include a photodiode and a phototransistor.

The control unit 106 outputs the detection result based on the received light signal. Such a control unit 106 is composed of a device including a processor, memory, and an external interface, which are connected to each other by an internal bus, for example. The control unit 106 operates by executing a program stored in the memory on the processor. Examples of the operation include an operation to quantitatively or qualitatively report the received light intensity, and an operation to report the presence or absence of oil leakage from the adherend 9 based on the relationship between the received light intensity and an event occurring on the adherend 9, which is stored in the memory.

In addition to the above devices, the control unit 106 may also include integrated circuit elements such as a driver IC and an amplifier IC, other active elements, and various passive elements.

2. Optical Waveguide for Oil Leak Sensor 2.1. First Embodiment Next, an optical waveguide for an oil leakage sensor according to a first embodiment will be described.
FIG. 4 is a partially enlarged perspective view of the optical waveguide 1 for the oil leakage sensor shown in FIG.

As shown in Figures 2 and 4, the optical waveguide 1 for the oil leakage sensor according to this embodiment comprises a sheet body 10 in which, from below, a first protective layer 18, a clad layer 11, a core layer 13, a clad layer 12, and a second protective layer 19 are laminated in this order. Each layer extends in the XY plane. In the core layer 13, as shown in Figure 4, two elongated core portions 14 and side clad portions 15 adjacent to the side surfaces of the core portions 14 are formed.

The shape of the outer edge of the optical waveguide 1 for oil leakage sensors shown in FIG. 3 is an elongated shape, specifically a rectangle, when the core layer 13 is viewed in the thickness direction, but this shape is not particularly limited and may be a polygon such as a square or hexagon, a circle such as a perfect circle, ellipse, or oval, a ring like a ring or frame, or other shape. In the core layer 13 of the optical waveguide 1 for oil leakage sensors, both ends of the core portion 14 in the longitudinal direction are exposed on the end surface 131 that intersects with the Y axis. In other words, each core portion 14 is curved so as to be folded back 180° midway, as shown in FIG. 3.

The total length of the optical waveguide 1 for the oil leak sensor is not particularly limited, but is, for example, 10 cm or more, and may be 1 m or more and 1000 m or less. This allows the optical waveguide 1 for the oil leak sensor to be installed over a wide area. As a result, an oil leak sensor 100 that can detect oil leaks over a wide area can be realized.

The width of the optical waveguide 1 for the oil leak sensor is not particularly limited, but is preferably 0.1 cm or more and 1 m or less, and more preferably 1 cm or more and 30 cm or less.

As shown in FIG. 2, the optical waveguide 1 for the oil leak sensor is used to adhere to the adherend 9 with the underside of the first protective layer 18 as the adhesive surface 109. If necessary, an adhesive layer 2 shown in FIG. 2 may be interposed between the adhesive surface 109 and the adherend 9. The adhesiveness of the adhesive layer 2 can be utilized to fix the optical waveguide 1 for the oil leak sensor to the adherend 9. In addition, since the optical waveguide 1 for the oil leak sensor is in the form of a sheet, it can be easily attached to the surface of the adherend 9.

Each part of the optical waveguide 1 for an oil leakage sensor will be described in further detail below.
4, the side surfaces of the core 14 are surrounded by the side cladding portions 15 and the cladding layers 11 and 12. The refractive index of the core 14 is higher than the refractive indexes of the side cladding portions 15 and the cladding layers 11 and 12. This allows light to be confined in the core 14 and propagated therethrough.

In the core layer 13, the refractive index distribution in the plane perpendicular to the optical path of the core portion 14 may be any distribution, for example, a so-called step index (SI) type distribution in which the refractive index changes discontinuously, or a so-called graded index (GI) type distribution in which the refractive index changes continuously.

The cross-sectional shape of the core portion 14 in the Y-Z plane, i.e., the transverse cross-sectional shape of the core portion 14, is not particularly limited, but examples include circles such as perfect circles, ellipses, and ovals, polygons such as triangles, squares, pentagons, and hexagons, and other irregular shapes.

The average thickness of the core layer 13 is not particularly limited, but is preferably about 1 to 200 μm, more preferably about 5 to 100 μm, and even more preferably about 10 to 70 μm. This ensures the optical characteristics and mechanical strength required for the core portion 14.

As the constituent material (main material) of the core layer 13, a material that can swell or dissolve by contact with oil is used. Specifically, the constituent material of the core layer 13 includes various resin materials such as acrylic resins, methacrylic resins, polycarbonate, polystyrene, cyclic ether resins such as epoxy resins and oxetane resins, polyamide, polybenzoxazole, polysilane, polysilazane, silicone resins, fluorine resins, polyurethane, polyolefin resins, polyesters such as polybutadiene, polyisoprene, polychloroprene, polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyethylene succinate, polysulfone, polyether, and cyclic olefin resins such as benzocyclobutene resins and norbornene resins. In addition, composite materials that combine materials with different compositions are also used as the resin material. In addition, in this specification, the "main material" refers to a material that accounts for 50% or more by mass of the constituent material, and preferably refers to a material that accounts for 70% or more by mass.

Of these, cyclic ether resins or cyclic olefin resins are particularly preferred as materials for the core layer 13. These swell or dissolve moderately in oils. For this reason, they are particularly useful as materials for the core layer 13.

The core portion 14 and the side cladding portion 15 may be made of different or the same materials.

2.1.2. Clad Layer The clad layers 11 and 12 may be provided as necessary and may be omitted, but the optical waveguide 1 for the oil leakage sensor according to this embodiment has the clad layers 11 and 12. This makes it possible to form and maintain a stable refractive index difference between the core portion 14 and its outside. This makes it possible to further improve the transmission efficiency of the core portion 14. Note that the clad layers 11 and 12 are omitted in FIG. 1 for convenience of illustration.

The average thickness of the cladding layers 11 and 12 is preferably about 1 to 200 μm, more preferably about 3 to 100 μm, and even more preferably about 5 to 60 μm. This ensures that the cladding layers 11 and 12 have the optical properties and mechanical strength required.

The main material of the clad layers 11 and 12 is appropriately selected from the materials listed above as the constituent materials of the core layer 13.

In addition, either or both of the cladding layers 11 and 12 may be integral with the side cladding portion 15.

2.1.3 Protective Layer The first protective layer 18 is provided on the lower surface of the cladding layer 11. The second protective layer 19 is provided on the upper surface of the cladding layer 12. By providing such first protective layer 18 and second protective layer 19, it is possible to protect the core layer 13 and the cladding layers 11 and 12, and to suppress a decrease in the transmission efficiency of the core section 14 caused by the external environment, etc.

The average thickness of the first protective layer 18 and the second protective layer 19 is not particularly limited, but is preferably about 1 to 200 μm, more preferably about 3 to 100 μm, and even more preferably about 5 to 50 μm.

The first protective layer 18 and the second protective layer 19 may have the same configuration as each other or different configurations from each other. For example, the first protective layer 18 and the second protective layer 19 may have the same average thickness as each other or different average thicknesses from each other.

The main material of the first protective layer 18 and the second protective layer 19 may be, for example, a material containing various resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene, polyolefins such as polypropylene, polyimide, polyamide, etc.

Of these, the main material of the first protective layer 18 and the second protective layer 19 is preferably a polyimide resin. Polyimide resin has a relatively high elastic modulus and a high thermal decomposition temperature, and therefore has sufficient durability against external forces and the external environment.

The constituent materials of the first protective layer 18 and the second protective layer 19 may contain fillers, antioxidants, UV absorbers, colorants, storage stabilizers, plasticizers, lubricants, anti-deterioration agents, antistatic agents, etc., as necessary. By adding fillers, the thermal expansion coefficients of the first protective layer 18 and the second protective layer 19 can be adjusted.

The first protective layer 18 and the second protective layer 19 may have a structure that enlarges the adhesive surface, such as unevenness or embossing, to improve adhesion to the adherend 9. Furthermore, the first protective layer 18 and the second protective layer 19 may have a structure such as recesses or slits so that they can be fitted to three-dimensional curved surfaces.

2 adheres the optical waveguide 1 for an oil leak sensor to the adherend 9. The adhesive layer 2 may be provided on the adherend 9 side, or on the optical waveguide 1 for an oil leak sensor. In other words, the optical waveguide 1 for an oil leak sensor may include an uncured adhesive layer 2 provided on the lower surface of the first protective layer 18. This allows the optical waveguide 1 for an oil leak sensor to be attached to the adherend 9 efficiently.

Examples of adhesives that make up the adhesive layer 2 include acrylic adhesives, urethane adhesives, silicone adhesives, and epoxy adhesives, as well as various types of polyester-based and modified olefin-based hot melt adhesives.

The uncured adhesive layer 2 may be in a liquid, solid or semi-solid uncured state, or may be in a state where the curing reaction is partially in progress. The curing principle of the adhesive layer 2 may be thermosetting or photocuring. Furthermore, the uncured adhesive layer 2 may be provided on the entire lower surface of the first protective layer 18, or may be provided on only a portion of it. The thickness of the adhesive layer 2 after curing is not particularly limited, but is preferably 1 to 100 μm, and more preferably 5 to 60 μm.

3 has two core portions 14 each having a curved shape that is folded back 180 degrees along the way. These two core portions 14 are referred to as core portion 141 and core portion 142.

The core portion 141 has a light incident surface 1411, an incident portion 1413, a folded portion 1415, an exit portion 1417, and a light exit surface 1419.

The light incident surface 1411 is a surface on which the incident light L1 emitted from the light emitting element 101 is incident. The incident portion 1413 connects the light incident surface 1411 to the folded portion 1415. The folded portion 1415 connects the incident portion 1413 to the exit portion 1417, and is a curved portion that is folded back approximately 180 degrees. The exit portion 1417 connects the folded portion 1415 to the light exit surface 1419. The light exit surface 1419 is a surface from which the exit light L2 is emitted, and the emitted exit light L2 is received by the light receiving element 103.

The core portion 142 has a light incident surface 1421, an incident portion 1423, a folded portion 1425, an exit portion 1427, and a light exit surface 1429.

The light incident surface 1421 is a surface on which the incident light L1 emitted from the light emitting element 102 is incident. The incident portion 1423 connects the light incident surface 1421 to the folded portion 1425. The folded portion 1425 connects the incident portion 1423 to the exit portion 1427, and is a curved portion that is folded back approximately 180 degrees. The exit portion 1427 connects the folded portion 1425 to the light exit surface 1429. The light exit surface 1429 is a surface from which the exit light L2 is emitted, and the emitted exit light L2 is received by the light receiving element 104.

In this embodiment, when viewed in the thickness direction, the core layer 13 has an elongated shape having one end and the other end. The light incident surfaces 1411, 1421 and the light exit surfaces 1419, 1429 are provided on the end surface 131, which is one end.

With this configuration, the light-emitting elements 101, 102, the light-receiving elements 103, 104, and the control unit 106 can all be arranged together on the end face 131 side of the optical waveguide 1 for the oil leakage sensor. This makes it possible to distinguish between areas that use electrical signals and areas that do not use electrical signals, making it easier to prevent electrical signals from igniting oil.

In this embodiment, the light entrance surfaces 1411, 1421 and the light exit surfaces 1419, 1429 are all provided on the end surface 131, which is one end, but at least one of these may be provided on the other end.

The one end refers not only to the end face 131 but also to the area near the end face 131. Therefore, the light incident surfaces 1411, 1421 and the light exit surfaces 1419, 1429 may be, for example, a reflective surface (mirror) for converting the optical path provided at one end. This reflective surface is, for example, an inclined surface arranged at an angle to the optical path of the core portion 14, and converts the optical path of the core portion 14 by reflection. This allows the optical path of the core portion 14 to be coupled to the light emitting elements 101, 102 and the light receiving elements 103, 104 when they are arranged on the upper or lower side of the optical waveguide 1 for the oil leakage sensor. As a result, the surface mounting of the elements becomes possible. This is true not only for one end but also for the other end.

In addition, optical fibers (not shown) may be connected to the light entrance/exit surfaces 1411, 1421 and the light exit surfaces 1419, 1429. This allows the light entrance surfaces 1411, 1421 and the light exit surfaces 1419, 1429 to be coupled to the light emitting elements 101, 102 and the light receiving elements 103, 104 via the optical fibers. In this case, an optical connector (not shown) may be attached to the end surface 131.

The positions of the light entrance surfaces 1411, 1421 and the light exit surfaces 1419, 1429 are not particularly limited, and may be provided, for example, at a location other than one end or the other end.

The optical waveguide 1 for the oil leakage sensor also has a side surface 132. This side surface 132 is the side surface of the core layer 13. The core portion 14 is not exposed on this side surface 132, but the side clad portion 15 is exposed. By exposing the side clad portion 15 to the side surface 132, the transmission characteristics of the core portion 14 are maintained constant under normal conditions, that is, when no oil leakage is occurring. In other words, if the core portion 14 is exposed to the side surface 132, there is a risk that the transmission characteristics of the core portion 14 will change if, for example, moisture or the like adheres to it. However, in this embodiment, since the side clad portion 15 is exposed, such unstable factors are eliminated.

Figure 5 is a partially enlarged view of Figure 3. When the core layer 13 is viewed in the thickness direction, that is, when viewed from a position along the Z axis, the shortest distance between the core portion 14 and the side surface 132 shown in Figure 5 is designated as Sm. This side surface 132 refers to the surfaces connecting the main surfaces of the core layer 13 other than the end surface 131 described above. Therefore, the shortest distance Sm is the shortest distance among the separation distances S between the side surface 132 and the core portion 14. Furthermore, the separation distance S refers to the distance between the side surface 132 and the core portion 14 in a direction perpendicular to the contour line of the core portion 14.

In this embodiment, the shortest distance Sm is 1 μm to 1 mm. In other words, this shortest distance Sm corresponds to the thickness of the side clad portion 15 that separates the core portion 14 from the outside air. When the oil leakage sensor 100 detects oil, the oil penetrates the side clad portion 15 and reaches the core portion 14, causing the side clad portion 15 and the core portion 14 to swell or dissolve. By setting the shortest distance Sm in this range, the area that satisfies this shortest distance Sm becomes the area that allows oil to penetrate in the shortest time. Therefore, in this embodiment, the area of the side surface 132 where the separation distance S is equal to or greater than the shortest distance Sm and equal to or less than twice the shortest distance Sm2 is defined as the "sensing portion SA". Also, the area of the side surface 132 other than the sensing portion SA is defined as the "non-sensing portion N".

The sensing unit SA is usually positioned close to a location on the outer surface of the adherend 9 where oil leakage is most likely to occur. This allows the sensing unit SA to quickly detect the leaked oil in the event of an oil leak.

The shortest distance Sm is preferably 2 to 500 μm, more preferably 3 to 100 μm, even more preferably 4 to 30 μm, and particularly preferably 5 to 20 μm.

If the shortest distance Sm is below the lower limit, the length of the side clad portion 15 separating the core portion 14 and the side surface 132 becomes too short. This makes it easier for light propagating through the core portion 14 to penetrate the side clad portion 15 and leak out. Depending on the material of the side clad portion 15, the side clad portion 15 may swell or dissolve excessively due to oil, resulting in excessive sensitivity. On the other hand, if the shortest distance Sm is above the upper limit, the length of the side clad portion 15 becomes too long, and depending on the material of the side clad portion 15, it may take a long time for the oil that has entered to reach the core portion 14. This significantly reduces the sensitivity of the oil leakage sensor 100.

On the other hand, in order to allow the area that satisfies the shortest distance Sm to function as the sensing section SA, in this embodiment, the oil resistance of the side cladding section 15 is made lower than the oil resistance of the first protective layer 18 and the second protective layer 19. This makes it possible to narrow down the path through which oil can enter, thereby minimizing the variation in sensitivity for detecting oil. As a result, an oil leak sensor 100 with stable detection characteristics can be realized.

In addition, by setting the oil resistance as described above, an optical waveguide 1 for an oil leak sensor can be obtained that is less susceptible to the effects of oils from the worker's fingers and solvents contained in the adhesive layer 2, for example, when attaching the oil leak sensor 100 to the adherend 9 or when forming the adhesive layer 2. This makes it possible to realize an optical waveguide 1 for an oil leak sensor that has little variation in sensitivity regardless of the usage environment.

The oil resistance can be evaluated by the mass change rate determined based on the test method specified in JIS K 7114:2001 using test lubricant No. 3 oil specified in JIS K 6258:2016. In other words, the oil resistance of the side clad portion 15 is low when the mass change rate of the side clad portion 15 when contacted with test lubricant No. 3 oil is greater than the mass change rate of the first protective layer 18 and the second protective layer 19.

These differences are not particularly limited, but are preferably 3% or more, more preferably 5-90%, and even more preferably 10-80%. This allows the difference in oil resistance to be optimized. As a result, it is possible to increase the sensitivity of the sensing section SA to oils while providing sufficient oil resistance to the first protective layer 18 and the second protective layer 19. In other words, it is possible to achieve both ease of handling and sensitivity for the optical waveguide 1 for the oil leak sensor.

The mass change rate is the percentage of mass change before and after a test in which a test piece measuring 60 mm long x 60 mm wide x 1 mm thick was prepared from each material and immersed in the test lubricant for 168 hours.

As described above, the non-sensing portion N is a region of the side surface 132 of the core layer 13 other than the sensing portion SA. The non-sensing portion N is a region in which the separation distance S is more than 200% of the shortest distance Sm. By providing the non-sensing portion N, it becomes easier to narrow down the detection capability to the sensing portion SA.

It is particularly preferable that the non-sensing portion N has an area where the separation distance S is 500% or more of the shortest distance Sm, and more preferably 1000% or more. This ensures a sufficient difference between the sensing portion SA and the non-sensing portion N. As a result, the effect of narrowing down the detection capability to the sensing portion SA can be more significantly achieved.

In addition, when the longest distance among the separation distances S is taken as the maximum distance, there is no particular limitation on the maximum distance, but taking into consideration the miniaturization of the optical waveguide 1 for the oil leak sensor, it is preferable that the maximum distance be 30 mm or less.

As described above, the optical waveguide 1 for an oil leakage sensor according to this embodiment includes the first protective layer 18, the second protective layer 19, and the core layer 13. The core layer 13 is provided between the first protective layer 18 and the second protective layer 19, and includes a core portion 14 having light incident surfaces 1411, 1421 and light exit surfaces 1419, 1429, and a side clad portion 15. In this optical waveguide 1 for an oil leakage sensor, when viewed from the thickness direction of the core layer 13, the shortest distance Sm between the core portion 14 and the side 132 of the core layer 13 is 1 μm to 1 mm. In addition, the oil resistance of the side clad portion 15 is lower than both the oil resistance of the first protective layer 18 and the oil resistance of the second protective layer 19.

By using such an optical waveguide 1 for an oil leak sensor, oil leaks can be detected without using electrical signals. Therefore, with such an optical waveguide 1 for an oil leak sensor, it is possible to realize an oil leak sensor 100 that can detect oil leaks regardless of the flammability of the oil to be detected or the usage environment.

In addition, the optical waveguide 1 for the oil leak sensor has a shape that is thin, easy to bend, and easy to attach. This allows it to be easily attached to the substrate 9.

The core layer 13 further includes a core portion 14 and a side cladding portion 15 that covers the side of the core portion 14. Therefore, the core portion 14 is not exposed to the side 132, and therefore the occurrence of false detection due to the adhesion of moisture or foreign matter is suppressed in the optical waveguide 1 for the oil leak sensor.

The core portion 14 also has folded portions 1415, 1425 that include curved portions extending along a circular arc. That is, the folded portions 1415, 1425 according to this embodiment are each composed of a curved portion and a straight portion. The curved portion is shaped to change the light propagation direction by 180° or more. This allows the light propagation direction to be reversed while suppressing losses when the propagation direction changes, and allows the light entrance surfaces 1411, 1421 and the light exit surfaces 1419, 1429 to be concentrated on the same end surface 131. This allows the parts that use electrical signals to be concentrated on the end surface 131 side, making it possible to realize an oil leakage sensor 100 that is easy to handle and install.

Note that an arc is a portion of a circumference with an arbitrary center point. In curved sections extending along an arc, the bending radius is constant, making it easier to suppress bending loss compared to when the bending radius changes.

Among the side surfaces 132 of the core layer 13, the portion where the separation distance S between the core portion 14 and the side surface 132 of the core layer 13 is 100% to 200% of the shortest distance Sm is defined as a sensing portion SA, and the portion where the separation distance S between the core portion 14 and the side surface 132 of the core layer 13 is more than 200% of the shortest distance Sm is defined as a non-sensing portion N. In this case, the side surface 132 of the core layer 13 may be only the sensing portion SA, but in this embodiment, it has both the sensing portion SA and the non-sensing portion N.

With this configuration, a sensing section SA can be provided in a portion of the optical waveguide 1 for the oil leak sensor, and the remaining portion can be a non-sensing section N. This allows the detection capability to be narrowed down to a location where oil leakage is particularly desired. As a result, an optical waveguide 1 for the oil leak sensor can be obtained that can realize an oil leak sensor 100 that can easily narrow down the location of the oil leak.

The optical waveguide 1 for the oil leak sensor according to this embodiment has two core portions 14, a core portion 141 and a core portion 142. The core portion 141 and the core portion 142 each have a sensing portion SA. Therefore, the side surface 132 of the core layer 13 has a plurality of sensing portions SA spaced apart from each other.

With this configuration, it is possible to not only determine whether or not there is an oil leak, but also to identify the location of the oil leak. As a result, it is possible to realize an oil leak sensor 100 that can identify the location of the oil leak.

In the optical waveguide 1 for the oil leak sensor shown in FIG. 3, two sensing parts SA are arranged along the Y axis. This makes it possible to identify the location of the oil leak in the Y axis direction. The sensing parts SA may be arranged in the X axis direction as well as in the Y axis direction. Also, in FIG. 3, the sensing parts SA are provided only on the surface of the side 132 on the negative side of the X axis, but a sensing part SA may also be provided on the surface on the positive side of the X axis.

The number of cores 14 in the optical waveguide 1 for the oil leak sensor is not particularly limited, and may be one or three or more. Also, one core 14 may have multiple sensing sections SA.

The optical waveguide 1 for the oil leak sensor shown in FIG. 2 has a sheet body 10 and the above-mentioned adhesive layer 2 provided on one side of the sheet body 10. In other words, the optical waveguide 1 for the oil leak sensor has an adhesive layer 2 provided on the side of the first protective layer 18 opposite the core layer 13.

This configuration allows the optical waveguide 1 for the oil leak sensor to be attached to the substrate 9 efficiently.

The oil leakage sensor 100 according to this embodiment includes an optical waveguide 1 for an oil leakage sensor, light emitting elements 101 and 102 which are light emitting units, light receiving elements 103 and 104 which are light receiving units, and a control unit 106. The light emitting elements 101 and 102 are connected to the light incident surfaces 1411 and 1421 of the optical waveguide 1 for an oil leakage sensor. The light receiving elements 103 and 104 are connected to the light exit surfaces 1419 and 1429 of the optical waveguide 1 for an oil leakage sensor. The control unit 106 outputs a signal based on the intensity of the light received by the light receiving elements 103 and 104.

This configuration makes it possible to realize an oil leakage sensor 100 that detects oil leakage without using electrical signals. Furthermore, this oil leakage sensor 100 can detect oil leakage regardless of the flammability of the oil to be detected or the usage environment.

2.2. Second embodiment Next, an optical waveguide for an oil leakage sensor according to a second embodiment will be described.
FIG. 6 is a plan view showing an optical waveguide 1A for an oil leakage sensor according to the second embodiment.

The second embodiment will be described below, focusing on the differences from the first embodiment and omitting a description of similar points. Note that in FIG. 6, the same reference numerals as those previously described are used for configurations similar to those of the first embodiment.

The optical waveguide 1A for the oil leakage sensor shown in FIG. 6 has two through holes 3 penetrating the sheet body 10 along the Z axis. In the optical waveguide 1A for the oil leakage sensor shown in FIG. 6, the sensing section SA is set along the edge of the through hole 3. In other words, the edge of the through hole 3 is also part of the side surface 132 described above. In the optical waveguide 1A for the oil leakage sensor, the distance between the edge (side surface 132) of the through hole 3 and the core portion 14 is also the shortest distance described above. As a result, the optical waveguide 1A for the oil leakage sensor detects oil leakage by allowing oil to enter from the edge of the through hole 3.

In addition, in the optical waveguide 1A for the oil leakage sensor, the core portion 14 extends along the edge of the through hole 3. As a result, the core portion 14 shown in FIG. 6 has a winding portion R that extends around the through hole 3 along the edge of the through hole 3. In FIG. 6, the folded portions 1415 and 1425 described above each correspond to the winding portion R.

The distance S between the edge of the through hole 3 and the circumferential portion R is almost constant except for a part of the edge of the through hole 3, and satisfies the requirements of the sensing portion SA described above. As a result, in this embodiment, the sensing portion SA can be set along the edge of the through hole 3.

The sensing area SA along the edge of the through hole 3 is preferably set to 30% or more of the entire circumference of the edge of the through hole 3, and more preferably set to 50% or more. This ensures that the sensing area SA is set sufficiently wide, making it less likely that oil leakage will go undetected.

In FIG. 6, the optical waveguide 1A for the oil leakage sensor is attached so that the boundary between the body 91 and the cover 92 of the adherend 9 is visible from the through hole 3. This allows the sensing section SA to quickly capture any oil that leaks from this boundary. In addition, since the outer surface of the adherend 9 can be seen from the through hole 3 and the edge of the through hole 3 corresponds to the sensing section SA, it is easy to align the optical waveguide 1A for the oil leakage sensor when attaching it to the adherend 9. Note that this arrangement is not particularly limited, and for example, the boundary does not have to be directly visible from the through hole 3.

In addition, in this embodiment, since the sensing section SA is surrounded by the core layer 13, there is a low possibility of damaging the sensing section SA when attaching the optical waveguide 1A for the oil leak sensor. Therefore, from this perspective as well, the optical waveguide 1A for the oil leak sensor is easy to handle.

Furthermore, fastening members such as bolts or other parts can be placed in the through hole 3 as necessary. Specifically, by placing the bolt 93 inside the through hole 3, the optical waveguide 1 for the oil leakage sensor can be tightly attached to the lid 92 while avoiding the bolt 93. This makes it possible to place the sensing unit SA close to the oil leakage site, even in the case of an adherend 9 where a protruding part such as the bolt 93 can be an oil leakage site.

When the core layer 13 is viewed in the thickness direction, the through holes 3 shown in FIG. 6 are oval in shape. Such circular through holes 3 are less likely to become the starting point of cracks that occur in the sheet body 10. For this reason, circular through holes 3 are useful from the standpoint of the mechanical strength of the sheet body 10.

The shape of the through hole 3 is not particularly limited, and may be a circle other than an oval, such as an ellipse or a perfect circle, or may be another shape, such as a polygon such as a rectangle or a hexagon. The number of through holes 3 is not particularly limited, and may be one, or three or more. Although it is sufficient that the through hole 3 penetrates at least the through hole 3, it is preferable that the through hole 3 also penetrates the first protective layer 18 and the clad layer 11 located on the adherend 9 side. In this embodiment, the through hole penetrates the sheet body 10.

As described above, the optical waveguide 1A for the oil leakage sensor according to this embodiment has at least a through hole 3 penetrating the core layer 13. The core portion 14 includes a circumferential portion R that extends along the edge of the through hole 3.

With this configuration, it is possible to set the sensing portion SA along the edge of the through hole 3. Therefore, for example, when attaching the optical waveguide for an oil leakage sensor 1A to an adherend 9, the sensing portion SA is less likely to be damaged. Even if the adherend 9 is provided with a protruding portion such as a bolt, the optical waveguide for an oil leakage sensor 1A can be stably attached by arranging the protruding portion inside the through hole 3. This makes it possible to realize an oil leakage sensor 100 that can stably detect the presence or absence of oil leakage around the protruding portion.
In the second embodiment as described above, the same effects as in the first embodiment can be obtained.

7 is a plan view showing a first modified example of the optical waveguide for an oil leakage sensor according to the second embodiment, and FIG. 8 is a cross-sectional view of FIG.

The first modified example will be described below, but in the following explanation, the differences from the second embodiment will be mainly described, and explanations of similar points will be omitted.

The optical waveguide 1B for the oil leak sensor shown in FIG. 7 has the same configuration as the optical waveguide 1A for the oil leak sensor according to the second embodiment, with the addition of a covering film 4.

When viewed in the thickness direction of the core layer 13, the covering film 4 extends outward beyond the sheet body 10 as shown in FIG. 7. Therefore, the portion of the covering film 4 that protrudes beyond the sheet body 10 is directly attached to the adherend 9 as shown in FIG. 8.

By providing such a covering film 4, it is possible to prevent the sheet body 10 from being damaged or degraded by light, moisture, heat, etc. after the optical waveguide 1B for the oil leakage sensor is attached to the adherend 9. This makes it possible to maintain the condition of the sheet body 10 in good condition for a long period of time.

The covering film 4 shown in FIG. 7 is provided to cover the through-hole 3. This makes it easier for oils leaking from the adherend 9 to remain in the through-hole 3, facilitating their penetration into the sensing unit SA.

The constituent materials of the covering film 4 may be, for example, the materials listed above as the main materials of the first protective layer 18 and the second protective layer 19.

The average thickness of the coating film 4 is also set, for example, within the range of the average thickness of the first protective layer 18 and the second protective layer 19.

The second protective layer 19 shown in Fig. 8 may be expanded to have the same function as the covering film 4. In other words, the second protective layer 19 shown in Fig. 8 may be omitted, and instead, the covering film 4 shown in Fig. 8 may serve as the second protective layer 19.
In the first modified example as described above, the same effects as those of the second embodiment can be obtained.

2.2.2. Second Modification FIG. 9 is a plan view showing a second modification of the optical waveguide for an oil leakage sensor according to the second embodiment.

The second modified example will be described below, but in the following explanation, the differences from the second embodiment will be mainly described, and explanations of similar points will be omitted.

The optical waveguide 1C for an oil leak sensor shown in FIG. 9 is obtained by doubling the core portion 141 and the core portion 142 of the optical waveguide 1A for an oil leak sensor according to the second embodiment.

Specifically, the optical waveguide 1C for the oil leakage sensor shown in FIG. 9 has two core portions 141a and 141b formed by doubling the core portion 141 according to the second embodiment, and two core portions 142a and 142b formed by doubling the core portion 142.

The core portions 141a and 141b extend almost parallel to each other. The emitted light L2 emitted from these core portions 141a and 141b is received by different light receiving elements. This makes it possible to determine the difference between the time when the emitted light L2 emitted from core portion 141b is received and the time when the emitted light L2 emitted from core portion 141a is received. The control device 106 shown in FIG. 6 can estimate the time when the oil leak occurred from this time difference. Furthermore, determining the time when the oil leak occurred can contribute to factory operations and product management.

In addition, light emitted from different light-emitting elements is incident on core units 141a and 141b, and is received by one light-receiving element in a time-division manner. This increases the redundancy of core unit 14. Specifically, even if one of core units 141a and 141b is damaged for some reason, the other can be used to maintain the same functionality as core unit 14.

The core portions 142a and 142b also extend substantially parallel to each other. The core portions 142a and 142b also have the same functions and effects as the core portions 141a and 141b described above.

The second modified example is not limited to a configuration in which the core units 141 and 142 are duplicated, but may be a configuration in which the core units are tripled or more multiplexed.
In the second modified example as described above, the same effects as those of the second embodiment can be obtained.

2.3. Third embodiment Next, an optical waveguide for an oil leakage sensor according to a third embodiment will be described.
FIG. 10 is a plan view showing an optical waveguide 1D for an oil leakage sensor according to the third embodiment.

The third embodiment will be described below, focusing on the differences from the second embodiment and omitting a description of similar points. Note that in FIG. 10, the same reference numerals as those previously described are used for configurations similar to those of the second embodiment.

The optical waveguide 1D for the oil leakage sensor shown in FIG. 10 has four through holes 3 that penetrate the sheet body 10 along the Z axis. The through holes 3 shown in FIG. 10 are almost perfectly circular. The spacing between the through holes 3 may be the same or different.

The optical waveguide 1D for the oil leakage sensor shown in FIG. 10 has four core portions 14. These four core portions 14 are referred to as core portions 143, 144, 145, and 146.

Since core units 143 to 146 all have the same configuration, the following explanation will focus on core unit 143 as a representative.

The core portion 143 has a light incident surface 1431, an incident portion 1433, a folded portion 1435, an exit portion 1437, and a light exit surface 1439.

The light incident surface 1431 is a surface on which the incident light L1 emitted from the light-emitting element is incident. The incident portion 1433 connects the light incident surface 1431 to the folded portion 1435. The folded portion 1435 connects the incident portion 1433 to the exit portion 1437 and is a curved portion that folds back. The exit portion 1437 connects the folded portion 1435 to the light exit surface 1439. The light exit surface 1439 is a surface from which the exit light L2 is emitted, and the emitted exit light L2 is received by the light receiving element.

The folded portion 1435 is disposed corresponding to one through hole 3. The folded portion 1435 also includes a circumferential portion R that extends along the edge of the through hole 3.

The circumferential portion R shown in FIG. 10 surrounds the through-hole 3. This makes it possible to set the sensing portion SA over a wider area around the edge of the through-hole 3.

The core portion 143 shown in FIG. 10 includes a crossing point CP when the core layer 13 is viewed in the thickness direction. By providing the crossing point CP, it is possible to provide the winding portion R without reducing the bending radius of the core portion 143 compared to when the crossing point CP is not provided. In other words, the core portion 143 including the crossing point CP includes a curved portion extending along a circular arc, and this curved portion changes the propagation direction of the incident light L1 by 180° or more. This makes it possible to suppress an increase in bending loss.

Furthermore, among the interior angles formed by the core portions 143 intersecting at the intersection CP shown in FIG. 10, the size of the interior angle adjacent to the interior angle on the through hole 3 side is defined as the "intersection angle θ". This intersection angle θ is not particularly limited, but is preferably 90° or less, more preferably 20° to 80°, and even more preferably 30° to 60°. By setting the intersection angle θ in such a range, the distance between the intersection CP and the edge of the through hole 3 can be made particularly sufficiently short. This makes it possible to set the sensing portion SA over a wider range of the edge of the through hole 3.

Figure 11 is a schematic diagram showing the positional relationship between the circle C corresponding to the circumferential portion R, the center O of the circle C, the intersection point CP, and the core portion 143. Figure 12 is a table showing, by calculation, how the distance L between the circle C and the intersection point CP changes when the intersection angle θ is changed from 45° to 120°.

As shown in Fig. 11, the intersection angle θ is the size of the interior angle adjacent to the interior angle located on the through hole 3 side among the four interior angles formed by the core portions 143. When the intersection angle θ is set to 90° or less, it can be seen that the distance L becomes sufficiently short as shown in Fig. 12. Specifically, the ratio L/r [%] of the distance L to the radius r of the circle C is calculated to be 41.4%. Therefore, it is preferable that the ratio L/r [%] is 41.4% or less.
In the third embodiment as described above, the same effects as in the first and second embodiments can be obtained.

In FIG. 10, as in the first and second embodiments, the optical waveguide 1D for the oil leakage sensor has an elongated shape, and the light entrance and exit surfaces of the core portions 143-146 can be concentrated on one end surface. These light entrance and exit surfaces may not be concentrated on one end surface, but may be distributed to both ends in the longitudinal direction. For example, the light entrance surfaces may be concentrated on one end surface, and the light exit surfaces may be concentrated on the opposite end surface in the longitudinal direction. Even in such a case, for example, if the outer edge of the optical waveguide 1D for the oil leakage sensor is made into a ring shape, the light emitting element, light receiving element, and control unit can be concentrated in one place.

In addition, in the core portions 143 to 146, two or more light entrance surfaces may be common by merging two or more entrance portions. Even if the light entrance surface is common, if the light exit surfaces are separate, the intensity change can be detected individually in the core portions 143 to 146.

2.4. Fourth embodiment Next, an optical waveguide for an oil leakage sensor according to a fourth embodiment will be described.

Figure 13 is a partially enlarged plan view showing the optical waveguide 1E for an oil leak sensor according to the fourth embodiment.

The fourth embodiment will be described below, focusing on the differences from the third embodiment and omitting a description of similar points. Note that in FIG. 13, the same reference numerals as those previously described are used for configurations similar to those of the third embodiment.

The optical waveguide 1E for the oil leakage sensor shown in Figure 13 has a core portion 147. This core portion 147 is similar to the core portion 143 shown in Figure 10, except that it branches into three along the way.

The core section 147 has a main line 1471, a branch section 1472, three branch lines 1473, 1474, and 1475, a junction section 1476, and a main line 1477. The core section 147 also has a cross section CP.

The branch section 1472 branches the main line 1471 into three. The three branch lines 1473, 1474, and 1475 go around the through hole 3, similar to the core section 143 shown in FIG. 10. The branch line 1473 is disposed at a position closest to the through hole 3, the branch line 1475 is disposed at a position farthest from the through hole 3, and the branch line 1474 is disposed between the branch lines 1473 and 1475.

When the three branches 1473, 1474, and 1475 are arranged in this manner, the oil that penetrates from the edge (side surface 132) of the through hole 3 swells or dissolves the side cladding portion 15, and then reaches the branches 1473, 1474, and 1475 in that order. As a result, the transmission loss of the branch 1473 increases first, and the intensity of the emitted light L2 decreases accordingly. If the branch ratio is set so that the intensities after distribution are equal in the branch section 1472, and the transmission efficiency of the branch 1473 becomes zero due to the influence of the oil, the intensity of the emitted light L2 decreases to about 67% of the original intensity. By calculating the amount of this decrease, it is possible to determine whether only the branch 1473 is affected by the oil, whether both the branch lines 1473 and 1474 are affected, or whether all the branch lines 1473, 1474, and 1475 are affected. This makes it possible to realize an oil leakage sensor 100 that can identify the amount of oil that has entered.

The branching ratios in the branching sections 1472 are not particularly limited and may be equal to each other or different from each other.

For example, the branching ratio of the central branch 1474 of the branches 1473, 1474, and 1475 may be set to be smaller than the branching ratios of the branches 1473 and 1475 on either side. By setting the branching ratio in this way, even if the intensity distribution in the cross section of the incident light is not uniform, the intensity distributed to the branches 1473, 1474, and 1475 can be made equal. Specifically, for example, when a light-emitting diode is used as the light-emitting element, the intensity distribution of the incident light L1 often has a higher intensity in the center than in the peripheral areas. Therefore, by making the branching ratio of the central branch 1474 smaller than the branching ratios of the branches 1473 and 1475 on either side, it becomes possible to align the intensities distributed to the branches 1473, 1474, and 1475.

As another example, the branching ratio may be set so that the strength of the outer branch 1475 is greater than that of the inner branch 1473. By relatively increasing the strength of the outermost branch 1475, the relatively large transmission loss associated with the long optical path length can be compensated for by this difference in strength. This makes it possible to correct the variation in strength due to the difference in optical path length. As a result, the amount of oil that has entered can be determined more accurately.

In this case, the main line 1471 may be provided with a structure that repeats bending, if necessary. This structure has the effect of making the intensity distribution uniform, even when incident light L1 with a non-uniform intensity distribution is incident on the main line 1471. Therefore, the branching section 1472 can perform distribution with high accuracy according to a branching ratio determined according to the structure.

2.5. Fifth embodiment Next, an optical waveguide for an oil leakage sensor according to a fifth embodiment will be described.

Figure 14 is a partially enlarged plan view showing the optical waveguide 1F for an oil leakage sensor according to the fifth embodiment.

The fifth embodiment will be described below, focusing on the differences from the second embodiment and omitting a description of similar points. Note that in FIG. 14, the same reference numerals as those previously described are used for configurations similar to those of the second embodiment.

The optical waveguide 1F for oil leakage sensors shown in FIG. 14 is similar to the optical waveguide 1A for oil leakage sensors shown in FIG. 6, except that the light incident surface 1411 and the light exit surface 1419 are common surfaces. Specifically, the core layer 13 shown in FIG. 14 includes a branching portion BP in which the core portion 14 is branched into two. By providing the branching portion BP, the light incident surface 1411 and the light exit surface 1419 can be made common. In addition, a separation optical system (not shown) that separates the incident light L1 and the exit light L2 may be provided outside the optical waveguide 1F for oil leakage sensors. As a result, even if the light incident surface 1411 and the light exit surface 1419 are made common, the incident light L1 can be incident on the surface and the intensity change of the exit light L2 emitted from the surface can be captured. An example of a separation optical system is a three-port type optical circulator.

The core portion 14 shown in FIG. 14 includes a circulating portion R that extends along the edge of the through hole 3, similar to the second embodiment. Incident light L1 incident from the light incident surface 1411 is split into two at the branching portion BP and propagates through the circulating portion R. Then, the incident light L1 that has circulated around the circulating portion R is combined again at the branching portion BP as the outgoing light L2. The combined outgoing light L2 is then emitted from the light exit surface 1419.

With this configuration, the light entrance surface 1411 and the light exit surface 1419 can be made common, so the number of connection ports between the optical waveguide 1F for the oil leak sensor and external devices can be reduced. This reduces the man-hours required for the connection work and makes it easy to miniaturize the entire oil leak sensor 100. Note that the number of branches by the branching portion BP is not limited to two, and may be three or more.

The optical waveguide for an oil leak sensor and the oil leak sensor of the present invention have been described above based on the illustrated embodiments, but the present invention is not limited to these.

For example, the optical waveguide for an oil leak sensor and the oil leak sensor of the present invention may be such that the parts of the above-mentioned embodiments are replaced with any configuration having the same function, or any configuration may be added to the above-mentioned embodiments.

The optical waveguide for the oil leak sensor may further have a protective layer covering the adhesive layer. This protective layer is peeled off from the adhesive layer immediately before adhering the optical waveguide for the oil leak sensor to the adherend, making it possible to easily prepare a clean adhesive surface. This makes it possible to prevent foreign matter from being caught in the adhesive, and to achieve adhesion with higher adhesion.

1 Optical waveguide for oil leakage sensor 1A Optical waveguide for oil leakage sensor 1B Optical waveguide for oil leakage sensor 1C Optical waveguide for oil leakage sensor 1D Optical waveguide for oil leakage sensor 1E Optical waveguide for oil leakage sensor 1F Optical waveguide for oil leakage sensor 2 Adhesive layer 3 Through hole 4 Covering film 9 Adherend 10 Sheet body 11 Cladding layer 12 Cladding layer 13 Core layer 14 Core portion 15 Side cladding portion 18 First protective layer 19 Second protective layer 91 Main body 92 Lid body 93 Bolt 100 Oil leakage sensor 101 Light emitting element 102 Light emitting element 103 Light receiving element 104 Light receiving element 106 Control unit 109 Adhesive surface 131 End surface 132 Side surface 141 Core portion 141a Core portion 141b Core portion 142 Core portion 142a Core portion 142b Core portion 143 Core portion 144 Core portion 145 Core portion 146 Core portion 147 Core portion 1411 Light incident surface 1413 Incident portion 1415 Turned portion 1417 Exit portion 1419 Light exit surface 1421 Light incident surface 1423 Incident portion 1425 Turned portion 1427 Exit portion 1429 Light exit surface 1431 Light incident surface 1433 Incident portion 1435 Turned portion 1437 Exit portion 1439 Light exit surface 1471 Main line 1472 Branch portion 1473 Branch line 1474 Branch line 1475 Branch line 1476 Merging portion 1477 Main line BP Branch portion C Circle CP Intersecting portion L Distance L1 Incident light L2 Exit light N Non-sensing portion O Center R Circulating portion S Separation distance SA Sensing part Sm Shortest distance Sm2 Double value r Radius θ Intersection angle

Claims (10)

A first protective layer;
A second protective layer; and
a core layer provided between the first protective layer and the second protective layer, the core layer having a core portion including a light incident surface and a light exit surface, and a side clad portion;
Equipped with
When viewed from a thickness direction of the core layer, a side surface portion of the core portion other than the light incident surface and the light exit surface is adjacent to the side clad portion,
the shortest distance between the side surface of the core portion and the side surface of the core layer is 1 μm to 1 mm;
13. An optical waveguide for an oil leak sensor, wherein the oil resistance of said side clad portion is lower than both the oil resistance of said first protective layer and the oil resistance of said second protective layer. The core layer has an elongated shape having one end and the other end when viewed in a thickness direction,
2. The optical waveguide for an oil leakage sensor according to claim 1, wherein the light incident surface and the light exit surface are provided at the one end. The core portion includes a curved portion extending along a circular arc,
3. The optical waveguide for an oil leakage sensor according to claim 2, wherein the curved portion changes the propagation direction of light by 180 degrees or more. A through hole penetrating the core layer is provided,
4. The optical waveguide for an oil leakage sensor according to claim 1, wherein the core portion includes a winding portion extending along an edge of the through hole. The optical waveguide for an oil leakage sensor according to claim 4, wherein the core portion includes an intersection portion that intersects when viewed in the thickness direction. When the size of the interior angle adjacent to the interior angle on the through hole side among the interior angles formed by the core portions intersecting at the intersection portion is defined as an intersection angle,
6. The optical waveguide for an oil leakage sensor according to claim 5, wherein the crossing angle is 90 degrees or less. Among the side surfaces of the core layer,
a sensing portion is a portion where the distance between the core portion and the side surface of the core layer is 100% or more and 200% or less of the shortest distance,
When a portion where the distance between the core portion and the side surface of the core layer is more than 200% of the shortest distance is defined as a non-sensing portion,
7. The optical waveguide for an oil leakage sensor according to claim 1, wherein the side surface of the core layer has both the sensing portion and the non-sensing portion. The optical waveguide for an oil leak sensor according to claim 7, wherein the side surface of the core layer has a plurality of the sensing portions spaced apart from each other. The optical waveguide for an oil leak sensor according to any one of claims 1 to 8, further comprising an adhesive layer provided on the opposite side of the first protective layer from the core layer. An optical waveguide for an oil leakage sensor according to any one of claims 1 to 9;
a light emitting portion connected to the light incident surface;
a light receiving portion connected to the light exit surface;
A control unit that outputs a signal based on the intensity of the light received by the light receiving unit;
An oil leakage sensor comprising:

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