JPH03197846A - Infrared gas sensor - Google Patents

Abstract

PURPOSE:To reduce the size of the sensor and prevent a light source, gas to be measured, and an infrared detection part from deviating in position relation by interposing the gas cell between the light source and infrared detection part and integrally assembling a light source block, the gas cell, and a support member. CONSTITUTION:The light source 20 is put in the light source block 18 and its tip part is put opposite a through hole 19, and positioned and shielded by a blocking plate 21. While the gas cell 12 is mounted on the block 18 and transparent glass 15 is set opposite the through hole 19, the cell is fixed to the block 18 with a screw 22. The cell 12 is covered with a support plate 9, which is fixed to the cell 12 with a screw 23. Only a gas intake 16 and an outlet 17 are exposed through cut parts 25 of the cell 12. The infrared detector 1 is previously soldered to a substrate 8. The substrate 8 has the detector 1 inserted into a support plate 9 through an insertion hole 10 and fixed to the support plate 9 with a screw 26. Thus, the sensor A is reduced in size and the light source 20, through hole 15, and detector 1 can easily be positioned on one straight line.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to an infrared gas sensor that measures the concentration of gas by utilizing the property that infrared rays emitted from a light source are absorbed and attenuated by gas.

(b) Conventional technology Infrared gas sensors are used in gas concentration meters, etc. that measure gas concentration without contact by detecting the amount of infrared rays that reach the gas to be measured without being absorbed. The elements used for this are generally differential input type, and a pyroelectric element is a typical example.

A conventional infrared gas sensor 100 is shown in FIG. The sensor 100 is composed of an infrared detection section S made of a pyroelectric element, a chopper 104 made of a metal disk 103 having a notch 101 and rotated by a motor 102, and a position detector 105 of the metal disk 103. An alternating current signal having the same frequency as that at which the metal disk 103 interrupts the incident infrared rays U is generated in accordance with the amount.

(c) Problems to be Solved by the Invention According to the above configuration, since the motor 102 and the metal disc 103 are included, the entire device becomes large and requires a very large installation volume, and the sensor cannot be installed. There was a problem in that the design restrictions for the entire device that was used were increased.

The present invention aims to solve this problem.

(d) Means for Solving the Problems The present invention provides an infrared gas sensor that obtains an output by irradiating an infrared detection unit with infrared rays that have passed through a gas to be measured. A block, a gas cell having an infrared transmitting part through which gas to be measured flows, and a support member to which an infrared detecting part is attached are prepared, and the gas cell is interposed between the light source block and the infrared detecting part. A light source block, a gas cell, and a support member are assembled together.

(E) Function According to the present invention, the overall size of the infrared gas sensor can be extremely reduced, and a structure can be created in which no misalignment occurs in the positional relationship between the light source, the gas to be measured, and the infrared detection section.

(f) Example Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of an infrared gas sensor A of the present invention.
Further, FIG. 2 shows a longitudinal sectional view thereof. Furthermore, FIG. 3 shows an exploded perspective view of a so-called modulation type pyroelectric infrared detector 1 developed in recent years. The detection S1 houses the above-mentioned infrared detection section S in a shield box 2, and a chopper C consisting of a slit member 4 driven by a piezoelectric bimorph vibrator 3 is placed at a position corresponding to a through hole (not shown) formed in the shield box 2. The entire body is covered by a case 6 in which a through hole 5 is formed at a corresponding position. The slit member 4 is constructed by attaching two plates with slits formed in an overlapping relationship as shown in FIG. The slit is opened and closed, and the infrared ray U that enters through the through hole 5 and reaches the infrared detection section S is intermittent, and an output corresponding to the amount of infrared rays is generated as an alternating current signal of the same frequency as the input frequency of the chopper C.

With this configuration, the infrared detector 1 can be made very small and can be mounted on a printed circuit board. After the signal from the infrared detector 1 is rectified and A/D converted, it is input to a microcomputer (not shown) and is subjected to arithmetic processing as data for controlling and displaying the gas concentration.

The infrared gas sensor A is used, for example, to measure carbon dioxide gas concentration, and has a through hole 5 fitted with a sapphire glass window 7 that transmits infrared rays.

Next, in FIGS. 1 and 2, 8 is a printed circuit board for mounting the infrared detector I, and 9 is a support plate for supporting the board 8. The support plate 9 is formed into a box shape from a thin stainless steel plate having a diameter of about 8, and is open downward and has an insertion hole 10 formed in its upper surface. Also,
Other electronic components 11 to which the infrared detector 1 is electrically connected are also attached to the substrate 8.

Reference numeral 12 denotes a gas cell formed into a rectangular shape by machining brass or aluminum, inside which passages 13 are formed on the left and right sides through which carbon dioxide gas, which is the gas to be measured, flows; Through-holes 14 are formed in the upper and lower portions thereof, and the upper and lower portions are sealed with sapphire glasses 15 and 15.

Further, 16 and 17 are gas inlets and outlets to which tubes (not shown) for introducing gas are connected.

Reference numeral 18 is a light source block formed into a rectangular shape by machining brass or aluminum, and is hollow inside, with a through hole 19 communicating with the upper surface.

20 is a light source consisting of an electric heater that emits infrared rays;
The tip generates heat of approximately 600°C and emits infrared rays.

Next, the assembly procedure of each part will be explained. The light source 20 is housed inside the light source block 18, and is positioned and shielded by a closing plate 21 with its tip corresponding to the through hole 19. Next, gas cell 1
2 is placed on the light source block 18, and with the transparent glass 15 corresponding to the through hole 19, it is fixed to the light source block 18 from the upper surface of the gas cell 12 with screws 22 and 22. Furthermore, cover the support plate 9 from above the gas cell 12, and screw the screws 23 from both sides.
It is fixed to the gas cell 12 at 23. At this time, the support plate 9 contains the gas cell 12, and the gas population 16 is contained in the notch 25.
Only the exit 17 faces the outside. The depth of the notch 25 can be determined by placing the screw holes of the support plate 9 and the screws 23 of the gas cell 12 in such a relationship that the deepest part thereof is in contact with the gas port 16 or the outlet 17, so that positioning is possible. It becomes very easy.

The infrared detector 1 is soldered to the board 8 in advance. The board 8 is then fixed to the support plate 9 with screws 26 and 26 with the detection 51 inserted into the support plate 9 through the insertion hole 1o. At this time, both screw holes are formed in such a positional relationship that the through hole 5 of the infrared detector 1 corresponds to the transparent glass 15.

By assembling the light source block 18, gas cell 12, and support plate 9 together with the gas cell 12 interposed between the light source block 18 and the infrared detector 1 in this manner, the entire infrared gas sensor A can be miniaturized. At the same time, the light source 20, the through hole 15.15 and the infrared detector 1 can be positioned in a straight line very easily. Furthermore, since the heat emitted from the light source 20 is dissipated in the process of being conducted through the support plate 9, it is possible to prevent the infrared detection section S from deteriorating due to the heat. Furthermore, the support plate 9 has a shape that seals the infrared detector 1, thereby preventing dust and light from entering from the outside, and preventing changes in the amount of infrared rays incident on the infrared detecting section S, thereby ensuring good infrared detection. I'm trying to do it in a state.

The infrared rays emitted from the light source 20 enter the passage 1 of the gas cell 12.
It is absorbed and attenuated in the process of passing through the gas to be measured flowing through the detector 1, and the remainder reaches the infrared detection section S of the detector 1. The amount of infrared rays absorbed by this gas changes depending on the gas concentration, so as a change in the output of the AC signal mentioned above,
Gas concentration can be captured and used as information for display and concentration control.

In addition, although the sensor of the present invention was applied to detect carbon dioxide gas in the embodiment, the sensor is not limited thereto and can be applied to other types of gas. In that case, the material of the window 7 should be changed depending on the type of gas.

(g) Effects of the Invention According to the present invention, the overall size of the infrared gas sensor can be extremely reduced, so that design constraints are eliminated, especially in small-sized devices. Furthermore, since the positions of the light source, the gas to be measured, and the infrared detection section are very close to each other, it becomes easy to position the champion, and defects caused by positional deviation can be eliminated.

[Brief explanation of drawings]

Figures 1 to 4 show embodiments of the present invention, with Figure 1 being a perspective view of an infrared gas sensor, Figure 2 being a longitudinal sectional view of the same, and Figure 3 being a modulation type pyroelectric infrared detector. FIG. 4 is a perspective view of a slit member, and FIG. 5 is a perspective view of a conventional infrared detector. 1... Infrared detector, 8... Printed circuit board, 9
...Support plate, 12...Gas cell, 18...Light source block, 20...Light source, A...Infrared type gas sensor, S...Infrared detection section.

Claims (1)

[Claims] 1) In a device that obtains an output by irradiating an infrared detection section with infrared rays that have passed through a gas to be measured, it has a light source block that houses the light source for generating the infrared rays, and an infrared transmission section, the inside of which is to be measured. It consists of a gas cell through which gas flows and a support member to which the infrared detection section is attached, and the light source block, gas cell, and support member are assembled integrally with the gas cell interposed between the light source block and the infrared detection section. An infrared gas sensor consisting of