JP2003322805A - Cover opening/closing detection sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cover opening/closing detection sensor withstand against electromagnetic noise, small in the number of parts and low in cost. <P>SOLUTION: The cover opening/closing detection sensor 1 that detects the opening/closing of a hand hole cover 41 or the like is provided with an optical fiber type strain gage 31 that detects the opening/closing of the hand hole cover 41 or the like. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lid opening / closing detection sensor for detecting the opening / closing of a handhole lid or the like, and more particularly to a lid opening / closing detection sensor which uses an optical fiber type strain gauge to reduce costs. is there.

[0002]

2. Description of the Related Art As a conventional lid opening / closing detection sensor, there is an electric sensor that detects opening / closing of a handhole lid by using a magnetic coil or the like. However, the electric lid opening / closing detection sensor has a problem that it is vulnerable to electromagnetic noise.

Therefore, as a conventional lid opening / closing detection sensor,
For example, as disclosed in Japanese Patent Laid-Open No. 2001-165811, there is a lid opening / closing detection device that optically detects the opening / closing of a handhole lid using an optical fiber.

This lid opening / closing detection device detects the movement of the first movable member that moves when the handhole lid is opened and closed, the second movable member that moves in response to the movement of the first movable member, and the movement of the second movable member. It is provided with a large number of parts such as a roller for giving a bend to the optical fiber and a release cable for transmitting the movement of the first and second movable members.

In this lid opening / closing detecting device, the optical fiber is released from bending loss by preventing the roller from pushing the optical fiber when the handhole lid is closed. On the other hand, when the handhole cover is open, the roller pushes the optical fiber, thereby bending the curvature of the roller and giving a loss to the optical fiber. If the OTDR connected to the optical fiber is used for monitoring, the opening / closing of the handhole cover can be monitored using the cover opening / closing detector.

[0006]

However, the conventional lid opening / closing detecting device has a large number of parts and also has parts having a complicated structure, so that there is a problem that the cost is high.

Therefore, an object of the present invention is to provide a lid opening / closing detection sensor which is resistant to electromagnetic noise and has a small number of parts and which is inexpensive.

[0008]

The present invention was devised to achieve the above object, and the invention of claim 1 is
A lid opening / closing detection sensor for detecting opening / closing of a handhole lid or the like, the lid opening / closing detection sensor including an optical fiber type strain gauge for detecting opening / closing of a handhole lid or the like.

According to a second aspect of the present invention, a lid magnet attached to the back surface of the handhole lid, a metal plate provided below the handhole lid and deformable by opening and closing the handhole lid,
The lid opening / closing detection sensor according to claim 1, comprising an optical fiber type strain gauge attached to the surface of the metal plate.

A third aspect of the present invention is the lid opening / closing detection sensor according to the second aspect, wherein a plate magnet facing the lid magnet is attached to the surface of the metal plate when the handhole lid is closed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

First, an example of installation of the lid opening / closing detection sensor according to the present invention will be described with reference to FIG.

As shown in FIG. 4, for example, when a communication optical fiber cable is installed in the ground, the hand hole H is provided in the middle of the conduit for the purpose of pulling in the cable and connecting / branching the cable. It is an optical line facility. This handhole H is similar to a manhole, but is used in a place where the impact of heavy objects is not required and the size of the manhole is not required. A handhole lid 41 is provided above the handhole H. An optical fiber cable for communication has already been installed in the handhole H. The shape of the handhole H may be cylindrical or rectangular. Similarly, the shape of the handhole cover 41 may be a disc shape or a rectangular plate shape.

Now, the lid opening / closing detection sensor 1 according to the present invention.
Is mainly used for the purpose of monitoring the opening and closing of the handhole cover 41 and the like, and is equipped with an optical fiber type strain gauge that detects the opening and closing of the handhole cover 41 and the like. The sensor main body 2 of the lid opening / closing detection sensor 1 is located below the handhole lid 41 and above the inner wall W of the handhole H.
It is attached so as to be close to the back surface of the handhole cover 41. As the optical fiber type strain gauge, for example,
An optical fiber Bragg grating (FBG) is used.

As shown in FIG. 3, the FBG 31 is constructed such that the refractive index distribution in the longitudinal direction changes in the core 32 of the optical fiber (the high refractive index portion 33 and the low refractive index portion 34). Repetitive structure), the width Λ (= λ / (2 · n) of the refractive index distribution with respect to the incident light Li, n is the refractive index of the core 32. The refractive index n33 of the high refractive index portion 33 and the low refractive index portion 3
Since the refractive index n34 of 4 is only about 0.1,
= (N33 + n34) / 2. ), The light Lr having a wavelength λ twice as long as that in (1) is reflected, and the light Lo having another wavelength λτρ is transmitted. The clad is omitted in FIG.

When strain is applied to the FBG 31, the width Λ of the refractive index distribution changes, and the wavelength λ of the light Lr reflected corresponding to this change linearly increases as the strain increases. Change.

Therefore, the distortion applied to the FBG 31 can be obtained by making the light Li having a wide wavelength band incident on the FBG 31 and measuring the wavelength λ of the reflected light Lr. Strain measurement accuracy of FBG31 is 1μstra
The accuracy is very high, approximately in (0.0001%).

Next, the lid opening / closing detection sensor 1 will be described in more detail.

FIG. 1A shows a schematic view of the lid opening / closing detection sensor 1 when the handhole lid 41 is closed. FIG. 1B is a schematic view of the lid opening / closing detection sensor 1 when the handhole lid 41 is opened.

As shown in FIGS. 1 (a) and 1 (b), the lid opening / closing detection sensor 1 includes a sensor body 2 and a lid magnet 3 attached near the outer edge of the back surface of the handhole lid 41. ing. The sensor main body 2 is fixed to the upper part of the inner wall W of the handhole H below the handhole cover 41, and is fixed to the fixing member 4, and when the handhole cover 41 is closed, the cover magnet 3 is provided. When the handhole cover 41 is opened, the metal plate 5 bends by its own weight and the rear end portion of the front surface of the metal plate 5 on the side of the fixing member 4 is attracted to the handhole cover 41. The FBG 31 is attached along the longitudinal direction of the metal plate 5 and detects the opening and closing of the handhole cover 41 from the extension strain due to the bending of the metal plate 5. Lid magnet 3
When the handhole cover 41 is closed, faces the front end of the surface of the metal plate 5.

Although not shown in FIGS. 1 (a) and 1 (b), both ends of the FBG 31 are connected to the existing communication optical fiber cable in the handhole H. One end of the communication optical fiber cable is connected to a measuring unit that causes light having a wide wavelength band to enter the communication optical fiber cable and measures the wavelength of the reflected light from the FBG 31.

As the metal plate 5, for example, a ferromagnetic material such as iron, cobalt, nickel or an alloy containing them is used. As the lid magnet 3, in addition to a conventional magnet, for example, a plastic magnet, a rubber magnet, or the like can be used.

For example, in the case of a disc-shaped handhole cover, the length of the metal plate 5 is about 1/5 of its diameter,
In the case of a rectangular plate-shaped handhole cover, about 1/5 of its long side
The length is about the same. The length of the FBG is, for example, about 1/3 of that of the metal plate 5.

The operation of this embodiment will be described.

As shown in FIG. 1A, in the lid opening / closing detection sensor 1, when the handhole lid 41 is closed,
The metal plate 5 is attracted by the lid magnet 3,
Is horizontal to the back surface of the handhole lid 41,
No elongation strain is applied to FBG31. At this time, when the measuring means inputs light having a wide wavelength band into the optical fiber cable for communication, the light having the wavelength λ0 is reflected from the FBG 31. The measuring means stores this wavelength λ0.

On the other hand, as shown in FIG. 1 (b), when the handhole cover 41 is opened, the metal plate 5 bends downward due to its own weight, so that the FBG 31 is subject to extensional strain due to the bending of the metal plate. . At this time, similarly to the above, when light having a wide wavelength band is incident on the optical fiber cable for communication by the measuring means, light having a wavelength λ1 larger than the wavelength λ0 is reflected from the FBG 31. Therefore, by comparing the wavelengths λ0 and λ1 of the reflected light by the measuring unit, the handhole cover 4 is detected using the cover opening / closing detection sensor 1.
The opening and closing of 1 can be monitored.

As described above, the lid opening / closing detection sensor 1 according to the present invention uses the FBG 31 to optically operate the handhole lid 41.
The open / close state of the handhole cover 41 is detected. Since the open / close state of the handhole cover 41 is not electrically detected, the open / close state of the handhole cover 41 can be accurately detected.

Regarding the number of parts, the lid magnet 3,
The fixing member 4, the metal plate 5, and the FBG 31 are as few as four points, and the configuration of each component is simple, so that the cost is low.

Since the lid opening / closing detection sensor 1 is a non-contact type,
It also has the advantages of high reliability and long life.

A second embodiment will be described.

FIG. 2A is a schematic view of the lid opening / closing detection sensor 21 when the handhole lid 41 is closed. FIG. 2B is a schematic view of the lid opening / closing detection sensor 21 when the handhole lid 41 is opened.

As shown in FIGS. 2 (a) and 2 (b), the lid opening / closing detection sensor 21 has the metal plate 5 with the hand hole 41 when the hand hole 41 is closed on the surface of the metal plate 5. The plate magnet 22 facing the lid magnet 3 is attached so as to be horizontal with respect to the back surface of the plate. The plate magnet 22 may be the same as the lid magnet 3. The other configuration of the lid opening / closing detection sensor 21 is shown in FIG.
The lid opening / closing detection sensor 1 described with reference to FIGS.
The configuration is the same as that of.

In the lid opening / closing detection sensor 21, when the handhole lid 41 is closed, the metal plate 5 and the plate magnet 22 are more strongly attracted by the lid magnet 3, and the metal plate 5 is attached to the back surface of the handhole lid 41. Since it is horizontal with respect to the FBG 31, no elongation strain is applied to the FBG 31. On the other hand, when the handhole cover 41 is opened, the metal plate 5 bends downward due to its own weight and the weight of the plate magnet 22.
Stretching strain due to bending of the metal plate is applied to BG31.

This lid opening / closing detection sensor 21 has an advantage that a lid magnet or a plate magnet smaller than the lid opening / closing detection sensor 1 can be used when the same metal plate as the lid opening / closing detection sensor 1 is used. Further, when the same lid magnet as the lid opening / closing detection sensor 1 is used, there is an advantage that a metal plate which is stronger than the lid opening / closing detection sensor 1 can be used. Other operational effects of the lid opening / closing detection sensor 21 are the same as those of the lid opening / closing detection sensor 1.

In the above embodiment, the handhole cover 41 is used.
Although the example in which the metal plate 5 is horizontal when the is closed is described, the FBG 41 has extremely high accuracy, and the point is that the metal plate 5 is deformed by opening and closing the handhole cover 41. .

In the above embodiment, the lid opening / closing detection sensor 1 and the lid opening / closing detection sensor 21 according to the present invention are used.
Although the example of detecting the opening / closing of the handhole lid has been described, the present invention is not limited to this, and can be easily applied to the opening / closing detection of a door of a building, for example.

[0037]

As is apparent from the above description,
According to the present invention, the following excellent effects are exhibited.

(1) Since opening / closing of the lid is not electrically detected, opening / closing of the lid can be accurately detected without being affected by electromagnetic noise.

(2) The number of parts is small, and the structure of each part is simple.

(3) Low cost.

[Brief description of drawings]

FIG. 1 (a) is a schematic view showing a preferred embodiment of the present invention when the handhole cover is closed. Figure 1 (b)
FIG. 6 is a schematic view showing a preferred embodiment of the present invention when the handhole cover is opened.

FIG. 2A is a schematic diagram showing a second embodiment when the handhole cover is closed. FIG. 2B is a schematic view showing the second embodiment when the handhole cover is opened.

FIG. 3 is a schematic diagram of an FBG.

FIG. 4 is a cross-sectional view showing an example of installation of a lid opening / closing detection sensor according to the present invention.

[Explanation of symbols]

1 Lid opening / closing detection sensor 2 sensor body 3 Lid magnet 4 fixing members 5 metal plates 31 FBG (optical fiber strain gauge) 41 Handhole lid H hand hole W inner wall

Claims (3)

[Claims] 1. A lid opening / closing detection sensor for detecting opening / closing of a handhole lid or the like, comprising a fiber optic strain gauge for detecting opening / closing of a handhole lid or the like. 2. A lid magnet attached to the back surface of the handhole cover, a metal plate provided below the handhole cover and deformable by opening and closing the handhole cover, and an optical fiber type attached to the surface of the metal plate. The lid opening / closing detection sensor according to claim 1, which comprises a strain gauge. 3. The lid opening / closing detection sensor according to claim 2, wherein a plate magnet facing the lid magnet is attached to the surface of the metal plate when the handhole lid is closed.