JPH08184556A - Optical gas detector - Google Patents

Abstract

PURPOSE: To obtain an optical gas detector suitable for a small section. CONSTITUTION: Infrared transmitting section 7 and receiving section 8 are disposed at appropriate positions of a case 1 having multiple vents 2 and an appropriate number of infrared mirrors 3, 9 for extending the optical path are interposed between them thus constituting a sensor section 17. The transmitting section 7 and receiving section 8 at the sensor section are connected through an optical fiber 11 with a detector body 18 disposed remotely therefrom. With such structure, an ideal explosion-proof performance is realized while employing a convenient laying method of optical fiber and the cost is reduced significantly. Since the sensor section comprises no aging component, e.g. a gas sensor, and has a simple constitution, stabilized performance can be sustained for a long term so long as the installation environment is clean in some degee.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical gas detector, and more particularly to a small area optical gas detector.

[0002]

2. Description of the Related Art As a conventional gas detection device for monitoring a gas leak, a gas sensor such as a ceramic sensor or an electrochemical sensor is installed at a monitoring target location,
A diffusion type gas detection device with a measurement and alarm output unit installed in an instrument room away from the monitoring target station, and a structure in which these are connected by an electric wire, an infrared detection light transmitter and receiver, or a light transmitter and A space detection type in which a light receiving device and a reflective object are installed across a monitoring area, and the detection light emitted from the light transmitting device to the monitoring area is received by the light receiving device and gas is detected by absorption of a specific wavelength by the gas. There is a gas detector, etc.

[0003]

In the diffusion type gas detection device of the present invention, since aging deterioration and change in sensitivity of the gas sensor cannot be avoided, periodical inspection and adjustment and parts replacement are required.
There is also a problem that expensive explosion-proof wiring work is required. In the space detection type gas detection device, the gas can be one-dimensionally monitored in a linear space of a relatively wide monitoring area, but the device becomes large in size and is not suitable as a gas detection device for a small area. The present invention aims to solve such problems.

[0004]

In order to solve the above-mentioned problems, in the present invention, an infrared light transmitting section and a light receiving section are provided at appropriate places of a case having a large number of ventilation holes, and the light transmitting section and the light receiving section are received. A configuration in which a proper number of infrared mirrors for extending the optical path are installed between the parts to configure the sensor part, and the light-transmitting part and the light-receiving part of the sensor part and the detection device body installed at a distant position are connected by an optical fiber. We propose an optical gas detector.

According to the present invention, in the above structure, the light transmitting section and the light receiving section are provided on one side of the case with a space therebetween, and the infrared mirror is provided on the other side of the case and the one side of the light transmitting section and the light receiving section. Suggest to install in between.

[0006]

[Function] When the target gas flows into the case from the ventilation hole and reaches the optical path of infrared rays from the light transmitting section to the light receiving section, absorption of a specific wavelength of infrared rays occurs, and this is detected by the detection device main body via an optical fiber. By doing so, the gas can be detected at a distant position.

In the case, since the optical path between the light transmitting section and the light receiving section can be extended by the infrared mirror,
The number of times infrared rays cross the gas increases, and sensitivity can be increased.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to the accompanying FIG. Reference numeral 1 is a cylindrical container-like case whose one end side is closed, and a large number of ventilation holes 2 are formed in the middle part. A disk-shaped support 4 supporting the first infrared mirror 3 on one end side.
Are fitted and fixed. An optical block 5 is fitted and fixed to the other end side of the case 1 facing the first infrared mirror 3. The optical block 5 is a disc-shaped support 6
The light-transmitting section 7 and the light-receiving section 8 are formed at the diametrical position on the peripheral side, and the second infrared mirror 9 is supported between them so as to face the first infrared mirror 3. The light transmitting unit 7 and the light receiving unit 8 include a lens system and an optical fiber 11 in the small chamber 10.
A lens system is provided with a collimator lens 13 installed on the side facing the first infrared mirror 3, and a microlens 14 installed corresponding to the tip of the optical fiber 11. Lenses 13 and 14
It is composed of a multilayer film filter 15 installed between them.
Since the method of connecting the optical fiber 11 by the optical connector 12 is well known, detailed illustration is omitted. An air filter 16 is attached to the outer periphery of the case 1 so as to correspond to the portion where the vent hole 2 is formed. The sensor unit 17 is configured as described above, and the sensor unit 17 is installed at the gas leak detection point.

Reference numeral 18 is a detector main body, and this detector main body 18 is installed in an instrument room or the like, which is separated from the gas leakage detection point, like the conventional diffusion gas detector. The detector main body 18 includes an infrared light transmitting means 19 and a light receiving means 20, and a gas detecting means 21 that controls the infrared light transmitting means 19 and the light receiving means 20 and detects the absorption of infrared rays at a specific frequency to detect a gas. The optical fiber 11 is connected to the light transmitting means 19 and the light receiving means 20, respectively. As the above-mentioned means, any conventional means can be used.

In the above structure, the infrared rays as the detection light emitted from the light transmitting means 19 reach the sensor portion 17 through the optical fiber 11, and the microlens 14 of the light transmitting portion 7
After passing through the multilayer filter 15 and the collimator lens 13, a parallel light beam is propagated through the space inside the case 1 toward the first infrared mirror 3. The infrared light that has reached the first infrared mirror 3 is reflected here and propagates in the opposite direction in the space inside the case 1, then the second infrared mirror 9, and again the first infrared mirror 9.
After being reflected by the infrared mirror 3 of the above, it reaches the light receiving portion 8, passes through the collimator lens 13, the multilayer film filter 15 and the microlens 14 and enters the optical fiber 11,
1 to reach the light receiving means 20 of the detection device body 18. The number of multiple reflections can be adjusted by adjusting the shapes and angles of the first and second infrared mirrors 3 and 9.

A sensor section 17 installed at a gas leak detection point
If gas leaks in the vicinity of the
6 through the ventilation hole 2 into the space inside the case 1,
By traversing the infrared light flux, absorption of a specific wavelength of infrared light occurs, and the occurrence of this absorption is transmitted to the light receiving means 20 of the detection device body 18 through the optical fiber 11 and can be detected by the gas detection means.

[0012]

As described above, the present invention has the following effects. Since the sensor section and the optical fiber installed at the gas detection point have essentially no ignition energy, ideal explosion-proof performance can be obtained. Therefore, the conventional expensive explosion-proof wiring work is not required, a very simple laying method for optical fibers can be adopted, and the cost is greatly reduced. Unlike the gas sensor such as the ceramic sensor and the electrochemical sensor, the sensor part does not deteriorate with age and has a simple structure. Therefore, stable environment can be maintained for a long time if the installed environment is clean to some extent. The maintenance cost can be significantly reduced. Since the sensor unit has a simple structure, it is suitable for mass production and can be provided at low cost. By extending the optical path length in the case, the gas detection sensitivity can be increased. The distance between the sensor and the detector body can be extended practically without limit, for example, several tens of kilometers or more.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of an apparatus of the present invention.

[Explanation of symbols]

 1 Case 2 Vent 3 First Infrared Mirror 4 Support 5 Optical Block 6 Support 7 Light Transmitter 8 Light Receiver 9 Second Infrared Mirror 10 Small Chamber 11 Optical Fiber 12 Optical Connector 13 Collimator Lens 14 Microlens 15 Multilayer Filter 16 Air Filter 17 Sensor Section 18 Detector Main Body 19 Light Transmitting Unit 20 Light Receiving Unit 21 Gas Detecting Unit

Claims (2)

[Claims] 1. An infrared light transmitter and a light receiver are provided at appropriate places of a case having a large number of ventilation holes, and an appropriate number of infrared mirrors for extending an optical path are provided between the light transmitter and the light receiver. An optical gas detection device comprising a sensor part, and a light-transmitting part and a light-receiving part of the sensor part and a detection device main body installed at a distant position are connected by an optical fiber. 2. The light transmitting unit and the light receiving unit are provided on one side of the case with a space therebetween, and the infrared mirror is installed on the other side of the case and between the light transmitting unit and the light receiving unit on the one side. The optical gas detection device according to claim 1.