JPH0341779B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure sensor that detects the presence of an object at a predetermined location, and particularly to a pressure sensor using an optical fiber wire.

Conventionally, sensors used for automatic opening and closing of doors, etc., are operated by a person standing on the sensor and the weight of the person sitting on the sensor, which opens and closes a contact switch to open and close the door, or by blocking a light beam to open and close an optical switch. A method such as that described above is generally used. By the way, the former gravimetric type sensor has the advantage of accurately detecting the presence of a person or object in a predetermined area, but because it is a mechanical type, it has problems with variations in sensitivity and reliability. The latter type of optical switch that blocks light rays has a problem in that it cannot reliably detect the presence of a person or object because its mounting position is limited.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to provide a novel pressure sensor that focuses on the fact that the optical transmission loss in an optical fiber strand changes due to pressurization.

The gist of the present invention to achieve the above object is to include a hard plate-like member, a soft plate-like member disposed on the hard plate-like member, and a flexible plate-like member disposed along the surfaces of both plate-like members. An optical fiber arranged in a plurality of folds, a light irradiation means for injecting light into one end of the optical fiber, and a light detector for detecting transmitted light from the light irradiation means at the other end of the optical fiber. means for applying strain to the optical fiber by pressing the soft plate-like member, causing optical transmission loss within the optical fiber, and detecting the transmitted light by the optical detection means. This feature is characterized in that pressing is detected by detecting attenuation.

Embodiments of the pressure sensor according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view for explaining one embodiment of the present invention, in which 1 is a plate-shaped hard mat made of a hard plate-like member made of iron (Fe, etc.), and 2 is a hard mat 1. 3 is a soft plate-like member made of rubber or the like and has the same shape as the hard mat 1; 4 is a light emitting element for inputting light into the optical fiber 2; 5 is a light emitting element; This is a light receiving element that receives light emitted from a fiber wire.

To describe this structure in more detail, one optical fiber wire 2 is folded back in a zigzag shape multiple times along the upper surface of the hard mat 1 to form a plurality of parallel portions in an array. It is preferable to make the parallel portions as dense as possible. This optical fiber wire 2
By placing the soft mat 3 on top of the flexible mat 3, the optical fiber 2 is sandwiched between the two plate-like members.

Both ends of the optical fiber strand 2 are led out to the outside of both plate-like members, and the light from the light emitting element 4 is input to the optical fiber strand 2 from one end, and the inside of the optical fiber 2 is guided to the other end. A light receiving element 5 is arranged to receive the transmitted light.

When the pressure sensor configured as described above is installed at a predetermined position on the passage and a pressure P is applied from above the soft mat 3 as shown in FIG. Pressure P is applied via. This pressing force causes microbending in the optical fiber 2, which causes loss in the transmitted light within the optical fiber 2. Therefore, the amount of light received by the light receiving element 5 decreases, and the output of the light receiving element 5 decreases. The amount of electricity or resistance value corresponding to this amount of change is used as a control signal for opening and closing a door, for example.

The reason why the part that supports the optical fiber strand 2 is made of a hard mat 1 is to prevent it from being deformed by pressure. If the mat 1 deforms, the optical fiber 2 will be excessively deformed, and the optical fiber 2 will be deformed. This is because there is a risk of breakage of the fiber wire 2. Therefore, the hard mat 1 prevents changes beyond microbending from occurring in the optical fiber 2.

The reason why the soft mat 3 is used to apply pressure to the optical fiber strand 2 is to prevent local loads from being applied to the optical fiber 2 due to the flexibility of the soft mat 3, and to apply pressure to the optical fiber 2 evenly over a considerable portion. This is to allow load to be applied. The soft mat 3 makes the optical fiber 2 flexible and applies pressure to the optical fiber 2, but the hard mat 1 does not cause large deformation, so the optical fiber 2 is protected.
Since microbendaine occurs widely on average,
Effective transmission light loss occurs.

The reason why microbending occurs in optical fibers is that when an optical fiber is coated with a flexible synthetic resin coating layer, such as nylon, around the optical fiber core, the coated portion becomes flat when pressed. becomes. At the boundary between this flat part and the circular part of the covered part of the unpressed part, the optical fiber core wire has a parallel step corresponding to the change in the thickness of the covering.
In other words, a curvature occurs, resulting in microbending.

The reason why the optical fiber wire 2 is folded and bent many times is to form a substantial surface sensor with dense parallel parts. As a result, loss of transmitted light occurs at many locations due to the diffusion of the pressing force of the soft mat 3, and a surface effect is obtained.

FIG. 3 is a perspective view for explaining a second embodiment of the pressure sensor according to the present invention. In FIG. 3, the pressure sensor of the present invention is equipped with a hard mat 1, an optical fiber 2, a soft mat 3, a light emitting element 4, and a light receiving element 5, as in FIG. It is characterized by its mesh-like structure. Therefore, all parts are given the same reference numerals as in FIG. 1, and their explanation will be omitted here.

In the same figure, one optical fiber strand 2 is bent in a zigzag shape multiple times along the surface of the hard mat 1 to form a plurality of parallel portions in an array, which is the same as in FIG. In this embodiment, a plurality of second parallel parts are arranged and formed by bending them in a zigzag shape multiple times perpendicularly on the first parts arranged in this way, and are arranged in a mesh lattice shape as a whole. This is what I did. Therefore, there is an intersection 21 in the optical fiber 2 of the first part and the second part.
is formed.

With the above configuration, when a pressure P as shown in FIG. 2 is applied to the optical fiber 2 and its intersection 21 through the soft mat 3, the intersection becomes more intense than in the embodiment shown in FIG. 21, greater microbending occurs. Therefore, in addition to the optical transmission loss of the embodiment shown in FIG. 1 as a whole, the transmission loss of the optical fiber strands in the cross direction and the optical transmission loss of the crossing portion 21 are added, and the optical transmission loss of the optical fiber strand 2 increases. do. The pressure sensor of this embodiment is suitable for applications where the pressurized weight is light. In this embodiment as well, both the hard mat 1 and the soft mat 3 exhibit the same effects as in the first embodiment.

In the above first and second embodiments, the surface of the hard mat 1 was described as being flat, but in order to improve sensor sensitivity, the present invention has a flat surface of the hard mat 1 on which the optical fiber 2 is arranged. rough surface or
This also includes forming it into a wave shape. In this case, since the soft mat 3 is flexible, it easily follows the surface of the hard mat 1.

The hard mat 1 is not limited to Fe, but may be other metals such as Al or other hard synthetic resins, and the soft mat 3 is not limited to rubber, but may also be a flexible synthetic resin with a small temperature coefficient.

Furthermore, although the optical fiber wire 2 has been described as one, it is also possible to combine two or more optical fiber wires.

As is clear from the above description, the pressure sensor according to the present invention has a substantial surface configuration, unlike various conventional sensors, and uses a change in weight as a change in light intensity to output objects within a predetermined area. This has great effects, such as being able to accurately identify the presence of the device, improving reliability, and making it possible to make the device thinner and more compact.

[Brief explanation of the drawing]

FIG. 1 and FIG. 3 are both perspective views for explaining an embodiment of the pressure sensor according to the present invention.
The figure shows the first embodiment, and FIG. 3 shows the second embodiment.
FIG. 2 is a side sectional view of the pressure sensor. In the figure, 1 is a hard mat, 2 is an optical fiber wire, 3 is a soft mat, 4 is a light emitting element, 5 is a light receiving element, and 21 is an intersection of the optical fiber wires.

Claims (1)

[Claims] 1. A hard plate-like member, a soft plate-like member disposed on the hard plate-like member, an optical fiber strand arranged along the surface of both the plate-like members and folded back multiple times, and the optical fiber element. A light irradiation means for injecting light into one end of the wire, and a light detection means for detecting the transmitted light from the light irradiation means at the other end of the optical fiber wire, and the flexible plate member is pressed. The strain is applied to the optical fiber strand, and the distortion causes optical transmission loss within the optical fiber strand, and the press is detected by detecting the attenuation of the transmitted light by the optical detection means. A pressure sensor characterized by: