JP2007192638A - Gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor for measuring the concentration of the gas to be sensed in a gaseous atmosphere on the basis of a change in the intensity of infrared rays transmitted through the gaseous atmosphere being a measuring target by constituting a small-sized precise optical system. <P>SOLUTION: The gas sensor includes a cylindrical gas introducing part 1 having a plurality of holes 5, in which a gas to be measured flows, provided to its side surface, the mirror 2 provided to one end part of the gas introducing part 1 and held so as to be brought into contact with the inner wall of the gas introducing part 1 and a lens unit 3 wherein two optical fibers 4, which are composed of the floodlight projection pipe 4a provided to the other end part of the gas introducing part 1, held to the inner wall of the gas introducing part 1 in a contact state and projecting infrared rays into the cylinder of the gas introducing part 1 and the light receiving pipe 4b for receiving the infrared rays reflected by the mirror 2 to be emitted outside from the gas introducing part 1, is joined to a single lens 30. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gas detector that measures the concentration of a gas to be detected in a gas atmosphere based on a change in the intensity of infrared light transmitted through the gas atmosphere to be measured.

Methane gas is the main component of gas as fuel such as city gas. By detecting methane gas having a predetermined concentration or more, gas leakage can be detected. Gases such as methane gas, carbon dioxide, acetylene, and ammonia have the property of absorbing light of a specific wavelength according to the rotation of molecules and vibration between constituent atoms. In recent years, an optical gas sensor using this property has been developed. For example, Patent Document 1 showing a source described below describes such a gas sensor.
In Patent Document 1, the light of a semiconductor laser having a single wavelength is guided to a gas cell containing methane gas via an optical fiber for the forward path, and the light transmitted through the gas cell is transmitted to the light receiving element via the optical fiber for the backward path. A leading gas sensor is disclosed. This is because the intensity of the light absorbed by the methane gas in the gas cell is determined by the difference in intensity between the light irradiated by the semiconductor laser and the light received by the light receiving element, and the concentration of the methane gas can be determined from this intensity. .
Japanese Patent Laid-Open No. 4-326041 (paragraphs 48 to 50, FIG. 1)

FIG. 14 schematically shows a configuration example of a gas sensor similar to that described in Patent Document 1. Irradiation light from a semiconductor laser (not shown) is guided to the gas cell 201 via the optical fiber 204a for the forward path and the lens 203. The light transmitted through the gas cell 201 is guided to a light receiving element (not shown) through the lens 202 and the optical fiber 204b. As shown in the figure, since the lenses 203 and 202 are opposed to each other with the gas cell 201 interposed therebetween, the two optical fibers 204 for incidence and emission are respectively connected to both ends of the gas cell 201. For this reason, when wiring the two optical fibers 204, it is necessary to bend one side largely like the Z section in the figure and align it with the other.
However, the optical fiber cannot be bent with a small diameter, and it is not preferable to apply stress by excessive bending. For this reason, in order to protect this mechanically, a big case may be needed and the member which guides wiring may be needed. As a result, the structure of the gas sensor itself is increased in size, the number of parts is increased, and this increases the cost. Further, when the gas sensor is increased in size, it may be difficult to install it on a gas pipe or the like.

  The present invention has been made in view of the above problems, and constitutes a small and accurate optical system, and is detected in a gas atmosphere on the basis of a change in the intensity of infrared light transmitted through the gas atmosphere to be measured. An object of the present invention is to provide a gas detection device for measuring the concentration of gas.

In order to achieve the above object, according to the present invention, a gas detection apparatus for measuring the concentration of a gas to be detected in the gas atmosphere based on an intensity change of infrared light transmitted through the gas atmosphere to be measured has the following characteristic configuration Is provided.
A cylindrical gas introduction part provided with a plurality of holes through which the gas to be measured flows on a side surface, and provided at one end of the gas introduction part and held in contact with the inner wall of the gas introduction part A mirror, and a light projecting tube provided at the other end of the gas introduction unit, held in contact with an inner wall of the gas introduction unit, and projecting the infrared light into a cylinder of the gas introduction unit; and A lens unit in which two optical fibers of a light receiving tube that receives the infrared rays reflected from the mirror and emitted from the gas introduction portion to the outside of the cylinder are joined to a single lens. .

  According to this characteristic configuration, the infrared light projected into the cylinder of the gas introduction part is reflected by the mirror and goes out of the cylinder of the gas introduction part again. Since the infrared rays reciprocate in the cylinder, the distance transmitted through the gas atmosphere to be measured is approximately twice the length of the gas introduction part. That is, if the transmission distance is the same, the length can be reduced to about half that of a conventional simple transmission gas sensor (see FIG. 14). Since the transmission distance is almost proportional to the amount of infrared absorption by the gas to be detected, the sensitivity can be improved if the gas detector is of the same size, and the gas detector can be made smaller if the sensitivity is the same. Can be Of course, if the number of reflections is increased, the sensitivity can be further improved or the size can be reduced.

  Moreover, since the two optical fibers are provided at the end portion on the same side of the gas introduction portion, it is possible to wire them straight in a state where they are aligned. As a result, it is not necessary to bend the optical fiber with a small diameter, and stress due to excessive bending can be suppressed. Furthermore, the two optical fibers can be simultaneously protected with a very small volume in the vicinity of the joint between the gas introduction part and the optical fiber.

  Furthermore, since two optical fibers and a single lens are joined to form a lens unit, no connection parts are required and the number of parts is small. Moreover, by being configured as a lens unit, the optical fiber that functions as a light projecting tube and the optical fiber that functions as a light receiving tube can be optically accurately arranged. Further, since the lens unit and the mirror are held in contact with the inner wall of the gas introduction unit, the optical system is held with high accuracy.

  Thus, according to this characteristic configuration, the concentration of the gas to be detected in the gas atmosphere is configured based on the change in the intensity of the infrared light transmitted through the gas atmosphere to be measured by configuring a small and accurate optical system. It is possible to provide a gas detection device that measures the above.

  In the gas detector according to the present invention, both end portions of the inner wall of the gas introduction portion have a larger inner diameter than the center portion, and a boundary portion between the both end portions side and the center portion side is the gas portion. It has two step portions that are orthogonal to and parallel to the axis of the introduction portion, and locks the mirror and the lens unit at these step portions, and toward the inside of the cylinder along the axis. It has a pressing part which presses at least one of the mirror and the lens unit.

The two step portions formed on both ends of the gas introduction part have surfaces that are orthogonal to and parallel to the axis of the gas introduction part. Therefore, the lens unit locked to one of these two surfaces is attached to the gas introduction unit with the optical axis aligned with the axis of the gas introduction unit, or at least with the optical axis parallel to the axis. Similarly, the mirror locked to the other of these two surfaces is attached to the gas introducing portion with the reflecting surface orthogonal to the axis of the gas introducing portion. Therefore, since the reflecting surface of the mirror is attached perpendicularly to the optical axis of the lens unit, an extremely accurate optical system can be configured.
In addition, since at least one of the mirror and the lens unit is pressed toward the inside of the cylinder along the axis of the gas introduction part, it is possible to reliably hold the optical system attached with high accuracy.

  The gas detection device according to the present invention is characterized in that a contact portion of at least one of the mirror and the lens unit that contacts the inner wall of the gas introduction portion is formed in a convex shape.

  Depending on the component accuracy of each member of the mirror, the lens unit, and the gas introduction unit, the accuracy of optical axis adjustment may be impaired. As in the above characteristic configuration, fine adjustment is possible when the contact portion of at least one of the mirror and the lens unit that contacts the inner wall of the gas introduction portion is formed in a convex shape. For example, the angle between the reflecting surface of the mirror and the axis of the gas introducing portion can be finely adjusted around 90 degrees. The same applies to the lens unit.

  Moreover, the gas detection device according to the present invention is characterized in that the perforation direction of one of the holes and the perforation direction of the other hole are provided so as not to be on a straight line.

  If the drilling directions of the two holes are on a straight line, the gas to be detected that has flowed into the gas introduction part from one hole may not stay in the gas introduction part and may come out of the cylinder from the other hole. is there. Such a problem can be suppressed when the holes are provided so that the drilling direction of one hole and the drilling direction of the other hole do not lie on a straight line, as in the above characteristic configuration.

  The gas detector according to the present invention is characterized in that the gas introduction part has a porous part.

  When the gas detector of the present invention is used outdoors, water such as rain may flow into the gas introduction part. If the gas introduction part is made of a porous material as in the above characteristic configuration, the gas to be measured is gas even if the hole is made small or the hole of the gas introduction part is completely invisible from the outside. It can flow into the introduction part. On the other hand, water such as rain does not flow into the gas introduction unit 1.

  In the gas detection device according to the present invention, the porous part is a porous film that covers the outside of the gas introduction part.

  As in this characteristic configuration, when the porous portion is a porous film covering the outside of the gas introduction portion, the porous portion can be made removable. If the porous part is detachable, gas diffusion to the gas introduction part can be secured by replacement or removal when the porous film (porous part) is clogged.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of a gas detection device according to the present invention.
The gas detection device 10 of the present invention measures the concentration of a gas to be detected in a gas atmosphere based on a change in the intensity of infrared light transmitted through the gas atmosphere to be measured. For example, when detecting methane gas contained in air, nitrogen, etc., these air-fuel mixtures are gases to be measured, and methane gas is a gas to be detected. Methane gas has the property of absorbing light of a specific wavelength. Therefore, the wavelength of the light source is matched with the vicinity of the methane gas absorption line (wavelength λ = 1.6537 μm) in the infrared region, and this light is transmitted through the gas atmosphere of the measurement object. If the content of methane gas is large in this gas atmosphere, the intensity of transmitted light is attenuated by infrared absorption. By detecting this attenuation amount, the concentration of the gas to be detected in the gas atmosphere to be measured is measured.

As shown in FIG. 1, the gas detection device 10 includes a cylindrical gas introduction unit 1, a disk-shaped mirror 2, and a lens unit 3 in which two optical fibers 4 are bonded to a single lens 30. Prepare.
As long as the gas introduction part 1 is cylindrical, such as a cylinder, a square cylinder, a triangular cylinder, a hexagonal cylinder, and an octagonal cylinder, the shape of the cross section is not particularly limited. However, in this example, a cylindrical shape will be described as an example. The mirror 2 is provided at one end of the gas inlet 1 and is held in contact with the inner wall of the gas inlet. The lens unit 3 is provided at the other end of the gas introduction unit 1, that is, the end opposite to the mirror 2, and is held in contact with the inner diameter of the gas introduction unit 1. The lens unit 3 includes a light projecting tube 4a that projects infrared light into the cylinder of the gas introduction unit 1, and a light receiving tube 4b that receives the infrared light reflected from the mirror 2 and emitted from the gas introduction unit 1 to the outside of the tube. It has two optical fibers 4. These two optical fibers 4 are joined to a lens 30 that is a single collimator lens to constitute a lens unit 3.

A plurality of holes 5 are provided on the side surface of the gas introduction unit 1. The hole 5 can take various shapes such as a round hole shape, a long hole shape, and a slit shape. Due to the plurality of holes 5, the gas to be measured existing around the gas detection device 10 flows into the gas introduction unit 1. When the gas to be detected includes a gas to be detected such as methane gas, the gas to be detected flows into the gas introduction unit 1 through the holes 5 by natural diffusion.
If this hole 5 is provided immediately before the lens 30 of the lens unit 3 or immediately before the mirror surface 21 of the mirror 2, if the surface of the lens 30 or the mirror 2 is dirty, a hole (cleaning hole 51) for wiping off the dirt with a cotton swab or the like. , 52).

  If the hole 5 as a natural diffusion hole is large, the speed at which the gas to be measured flows into the gas introduction part 1 is increased, which contributes to the improvement in the detection speed as the gas detection device 10. However, structurally, since it is weak against external force, the optical axis is likely to be shaken. According to the inventors' experiments, it has been found that the case where the total area of the inner wall side openings of the holes 5 is 10 to 70% with respect to the surface area of the inner wall of the gas introduction part 1 is practical. That is, at this ratio, the natural diffusion rate is effective as the gas detection device 10, and the structural strength can be maintained.

  The lens unit 3 including the two optical fibers 4 (the light projecting tube 4a and the light receiving tube 4b) and the mirror surface 21 of the mirror 2 are opposed to each other with the gas introduction part 1 interposed therebetween. Infrared light emitted from the light projecting tube 4a through the lens 30 is reflected by the mirror surface 21, and is again guided to the light receiving tube 4b through the lens 30. In this reciprocating path, infrared rays pass through the gas atmosphere of the measurement object, and if the gas to be detected is contained in this gas atmosphere, much energy is absorbed. Therefore, the concentration of the gas to be detected can be detected by detecting the difference in intensity between the infrared light projected from the light projecting tube 4a and the infrared light returned to the light receiving tube 4b.

  FIG. 2 is an exploded cross-sectional view showing the configuration of the gas detection device 10. The inner wall of the gas introduction part 1 has a larger inner diameter at both ends than at the center part. The boundary portion between the both end sides and the central portion side has two step portions 6 and 7 which are surfaces orthogonal to the axis X of the gas introduction portion 1 and parallel to each other. Surfaces (reference numerals 61 and 71, cutting surfaces described later) of these step portions 6 and 7 facing the outside of the cylinder restrict movement of the mirror 2 and the lens unit 3 in the in-cylinder direction and lock them. Moreover, it has the press parts 8 and 9 which press at least one of the mirror 2 and the lens unit 3 toward the inside of a cylinder along the axial center X, These are pressed against the cutting surfaces 61 and 71 reliably, and are hold | maintained. .

When the cylindrical gas introduction part 1 is provided, the inner walls 12a and 12b of the gas introduction part 1 are rotationally cut from the end to the inside around the axis X of the gas introduction part 1 to increase the inner diameter of the end. . The end portion on the side where the mirror 2 is provided is cut until the inner diameter is slightly larger than the outer diameter of the mirror 2. The end on the side where the lens unit 3 is provided is cut until the inner diameter is slightly larger than the outer diameter of the lens unit 3. Of course, if the outer diameters of the mirror 2 and the lens unit 3 are the same in consideration of dimensional tolerances, both ends are cut to have the same inner diameter.
By this cutting, step portions 6 and 7 are formed at both ends. The cutting surfaces 61 and 71 of the step portions 6 and 7 that are both orthogonal to the axis X are orthogonal to the axis X with very high accuracy. Accordingly, the cutting surfaces 61 and 71 facing the outside of the gas introduction part 1 are parallel to each other.

  In this example, the mirror surface 21 is a single plane. Therefore, the mirror 2 positioned at the peripheral portion of the mirror surface 21 and attached to the gas introduction unit 1 directs the projected infrared light toward the light receiving tube 4b when the peripheral portion of the mirror surface 21 is orthogonal to the axis X. The most efficient reflection. The mirror 2 is attached to the gas introduction unit 1 with high accuracy by the cutting surface 61 cut with high accuracy as described above engaging the peripheral portion of the mirror surface 21. Further, as will be described later, the mirror 2 is pressed by a mirror pressing member 8 (pressing portion) that presses the gas introduction portion 1 from the endmost portion toward the in-cylinder direction. Thereby, the mirror 2 is reliably hold | maintained in the state attached to the gas introduction part 1 with high precision.

  The lens 30 of the lens unit 3 has a convex reference surface 31 only on the central portion on one side and a flat reference surface 31 on the periphery thereof. When the reference plane 31 is perpendicular to the axis X with the lens unit 3 attached to the gas introduction unit 1, the axis X and the optical axis of the lens 30 coincide. Alternatively, at least the axis X and the optical axis of the lens 30 are parallel. As described above, the cutting surface 71 of the stepped portion 7 cut with high accuracy locks the reference surface 31, whereby the lens unit 3 is attached to the gas introduction portion 1 with high accuracy. As will be described later, a lens pressing portion 9 (pressing portion) that presses the lens unit 3 in the in-cylinder direction from the endmost portion of the gas introducing portion 1 may be provided so as to be held more securely.

  In addition, if both ends are cut simultaneously, the step portions 6 and 7 can be provided at both ends at once. If the cutting is performed one side at a time, the cutting conditions are almost the same, so that the parallelism between the cutting surfaces 61 and 71 at both ends becomes easy to cut.

  FIG. 3 is an explanatory diagram showing a method of attaching the mirror 2 to the gas introduction unit 1. From the end of the gas introduction unit 1, the mirror 2 having only one surface finished as the mirror surface 21 is inserted into the cylinder until the mirror surface 21 is locked by the cutting surface 61. Subsequently, the end 13 of the gas inlet 1 is bent in the direction A in the figure. Then, the mirror pressing member 8 is attached to the end of the gas introduction part 1. The mirror pressing member 8 includes a spring 82 (for example, a leaf spring), and the spring 82 presses the mirror 2 along the axis of the gas introduction unit 1 toward the inside of the cylinder. A hook 81 is formed on the mirror pressing member 8, and the mirror pressing member 8 is engaged with the end portion 13 of the gas introducing portion 1 by engaging the hook 81 with the bent end portion 13 of the gas introducing portion 1. Retained. As a result, the mirror 2 is securely held in a state of being attached to the gas introduction unit 1 with high accuracy. Of course, the mirror 2 may be fixed to the gas introduction part 1 using an adhesive or laser welding.

4 and 5 are explanatory views showing an optical relationship between the lens 30, the optical fiber 4, and the reflecting surface (mirror surface 21) and an optical axis adjusting method. FIG. 6 is an explanatory diagram showing a method of attaching the lens unit 3 to the gas introduction unit 1.
Two optical fibers 4 are arranged side by side in the vicinity of the end face 33 of the lens 30 that does not have a convex shape, and the optical axis is adjusted so that the coupling efficiency between the optical fibers 4a and 4b is maximized. In other words, the end faces of the two optical fibers 4 are aligned, and infrared rays are projected from the light projecting tube 4a, and the infrared rays received by the light receiving tube 4b are reflected by the reflecting surface (mirror surface 21). And fine adjustment is performed and the position which shows the maximum output is determined.

Next, as shown in FIG. 5, the end face 33 of the lens 30 is heated and softened by arc discharge, and the two optical fibers 4 are pushed into the lens focal point position 32 at the same time. Due to the difference in softening point and expansion coefficient between the optical fiber 4 and the lens 30, the optical fiber 4 and the lens 30 are directly joined by fusion. Further, fixing is performed using a UV curable resin 11 or the like.
Then, as shown in FIG. 6, the end portion 14 of the gas introduction unit 1 is bent in the direction B in the drawing as necessary, and the lens unit 3 is pressed toward the inside of the cylinder so as not to come out of the gas introduction unit 1. Therefore, the end portion 14 functions as the lens pressing portion 9 (pressing portion). Of course, the lens unit 3 may be fixed to the gas introduction unit 1 using an adhesive. Further, in order to prevent excessive bending of the optical fiber 4, a rubber cover 41 is provided from a joint portion between the lens 30 and the optical fiber 4 to a portion covering the coating 42 of the optical fiber 4 (see FIG. 1).

FIG. 7 is an explanatory diagram in a case where the optical axes of the lens 30A, the optical fiber 4, and the reflecting surface (mirror surface 21) are adjusted by a method different from that shown in FIGS.
In this method, a transparent UV curable adhesive 11 </ b> A is used for fixing the lens 30 </ b> A and the optical fiber 4. As shown in FIG. 7, the position adjustment is performed while measuring light is put into the optical fiber 4 in a state where the adhesive 11 </ b> A is not cured. In other words, the end faces of the two optical fibers 4 are aligned and the measurement light is projected from the light projecting tube 4a. Then, the amount of light reflected by the reflecting surface (mirror surface 21) and received through the light receiving tube 4b is monitored. The position adjustment is finished at the position where the amount of light is maximized (corresponding to the focal position 32), UV light is applied to cure the adhesive 11A, and the lens 30A and the optical fiber 4 are fixed. The adhesive 11A has a refractive index that is the same as that of the lens 30A or the optical fiber 4 or an intermediate value thereof, so that reflection on the adhesive surface is less likely to occur.

The lens unit 3 may be prepared by separately preparing a jig and adjusted independently of the gas introduction unit 1 and the mirror 2, or the gas introduction unit assembled as the gas detection device 10 as follows. It may be calibrated and manufactured in combination with 1 or mirror 2. That is, after the mirror 2 is first attached and fixed to the gas introduction unit 1, the lens 30 (30A) is attached and fixed. Thereafter, the optical axis may be adjusted, and the optical fiber 4 may be bonded to the lens 30 (30A).
In the former case, as long as the tolerance of each part falls within a range that satisfies the performance standard of the gas detector 10 as a product, it can be manufactured as a single part, thus contributing to improvement in productivity.
In the latter case, adjustment is performed for each gas detection device 10 as a product, so that highly accurate optical axis adjustment can be expected, and this method contributes to improvement in performance.

[Another embodiment 1]
In the above description, the mirror 2 has the mirror surface 21 locked to the cutting surface 61 of the step portion 6, and the lens unit 3 has the reference surface 31 of the lens 30 (30 </ b> A) locked to the cutting surface 71 of the step portion 7. By doing so, it is positioned. When the lens unit 3 is manufactured for each gas detection device 10 that is a product, the optical axis adjustment is performed with relatively high accuracy because the lens unit 3 is individually adjusted. However, when the gas detection device 10 is assembled using the lens unit 3 manufactured independently, the accuracy of the optical axis adjustment may be impaired due to tolerances or the like.
Therefore, in another embodiment shown in FIG. 8, at least one of the mirror 2 and the lens unit 3 is formed in a convex shape in contact with the inner wall 12 of the gas introduction unit 1.
With such a convex shape, for example, the angle between the mirror surface 21 of the mirror 2 and the axis X of the gas introduction unit 1 can be finely adjusted about 90 degrees. The same applies to the lens unit 3.

[Another embodiment 2]
In the above embodiment, for example, as shown in FIG. 1, the drilling direction of one hole 5 and the drilling direction of the other hole 5 are on a straight line. For this reason, there is a possibility that the gas to be detected that has flowed from the hole 5 does not stay in the gas introduction part 1 and comes out of the cylinder.
As shown in FIGS. 9 and 10, such a problem is suppressed when the hole 5 is provided so that the drilling direction of one hole 5 and the drilling direction of the other hole 5 do not lie on a straight line. be able to. As shown in FIG. 10, when the hole 5 is provided so that the hole 5 faces the inner wall in the drilling direction, the drilling direction of one hole 5 and the drilling direction of the other hole 5 do not lie on a straight line. Can be.
In addition, as shown in FIG. 11, the same effect can be obtained even if the hole 5 is provided by tilting the drilling direction in a direction not orthogonal to the axis X. Here, when the hole 5 is used not only as a natural diffusion hole but also as the cleaning holes 51 and 52, only the cleaning holes 51 and 52 may have a drilling direction orthogonal to the axis X as illustrated.

[Another embodiment 3]
When the gas detection device 10 of the present invention is used outdoors, water such as rain may flow into the gas introduction unit 1. Therefore, as shown in FIG. 12, a cylindrical water-repellent porous film 15 (porous portion) is detachably attached around the gas introduction portion 1. If comprised in this way, water, such as rain, does not flow into the gas introduction part 1. FIG. Even if submerged due to water increase or the like, if there is no water in the interior and there is no surrounding water, the inflow of the gas to be measured is resumed.
As shown in FIG. 12, in addition to providing the removable film 15, the gas introduction part 1 may be made of a porous material. In this case, the gas introduction part 1 also serves as a porous part. When the detachable film 15 is provided, when the film 15 is clogged, the diffusion of the gas to the gas introduction unit 1 can be ensured by replacing or removing the film 15.
The porous portion (including the porous film 15) can be configured using a sintered metal.

[Usage example]
When a combustible gas (for example, methane gas) is supplied to a facility or equipment in a factory or the like, the gas pipe may be doubled as shown in FIG. 13 for safety. Methane gas is passed through the inner inner tube 100, and nitrogen is sealed as an inert gas between the inner tube 100 and the outer tube 200. Then, in order to detect whether a gas leak has occurred in the inner pipe 100 and methane gas has leaked between the outer pipe 200 and the inner pipe 100, the gas detector 10 is provided in the outer pipe 200 as shown in the figure. May be installed.

  The gas detection device 10 of the present invention is an infrared method with higher sensitivity than a heat conduction method or the like. In order to further increase the sensitivity of the infrared method, it is preferable to lengthen the length of the gas introduction unit 1, that is, to lengthen the infrared light path. Since the gas detection device 10 of the present invention is a reflection type, the optical path can be lengthened. In addition, in the case of a pump suction type that sucks the gas to be measured and returns the exhaust gas to the gas pipe after measurement, oxygen-containing air may be mixed when returning the exhaust gas, and the detection unit has an explosion-proof structure. There is a need to. However, in the gas detection device of the present invention, it is not necessary to adopt an explosion-proof structure, and gas leakage can be detected.

Sectional drawing which shows the structure of the gas detection apparatus which concerns on this invention Exploded sectional view showing the configuration of the gas detector according to the present invention Explanatory drawing showing how to attach the mirror to the gas inlet Explanatory drawing which shows the optical relationship between a lens, an optical fiber, and a reflective surface Explanatory drawing which shows the optical axis adjustment method of a lens, an optical fiber, and a reflective surface Explanatory drawing showing how to attach the lens unit to the gas inlet Explanatory drawing which shows another optical axis adjustment method of a lens, an optical fiber, and a reflective surface Sectional drawing which shows the other structural example of a gas detection apparatus The perspective view which shows the other example of formation of the hole provided in a gas introduction part Sectional drawing of the gas introduction part which shows an example of FIG. Sectional drawing of the gas introduction part which shows the other example of FIG. Sectional drawing which shows the other structural example of a gas detection apparatus Explanatory drawing which shows the usage example of the gas detection apparatus which concerns on this invention Explanatory drawing which shows the structural example of the conventional gas detection apparatus

Explanation of symbols

1: Gas introduction part 2: Mirror 3: Lens unit 30: Lens, 30A: Lens 4: Optical fiber 4a: Projection tube, 4b: Light receiving tube 5: Hole 6: Step part 8: Mirror pressing member (pressing part)
9: Lens pressing part (pressing part)
10: Gas detector 12: Inner wall 15: Porous cover (porous part)
X: axis

Claims (6)

A gas detection device for measuring the concentration of a gas to be detected in the gas atmosphere based on an intensity change of infrared light transmitted through the gas atmosphere of the measurement object,
A cylindrical gas introduction part having a plurality of holes through which the gas to be measured flows on the side surface;
A mirror provided at one end of the gas inlet, and held in contact with the inner wall of the gas inlet;
Provided at the other end of the gas introduction part, held in contact with the inner wall of the gas introduction part, and projecting the infrared rays into the cylinder of the gas introduction part, and the mirror A gas detection apparatus comprising: a lens unit in which two optical fibers of a light receiving tube that receives the infrared rays reflected and emitted from the gas introduction unit to the outside of the cylinder are joined to a single lens.   The inner wall of the gas introduction part has a larger inner diameter at both end sides than the center part, and boundary portions between the both end parts side and the center part side are orthogonal to and parallel to the axis of the gas introduction part. It has two stepped portions that become surfaces, and the stepped portion locks the mirror and the lens unit and presses at least one of the mirror and the lens unit toward the inside of the cylinder along the axis. The gas detection device according to claim 1, further comprising a pressing portion that performs the operation.   3. The gas detection device according to claim 1, wherein at least one of the mirror and the lens unit is formed with a convex shape in a contact portion that contacts an inner wall of the gas introduction portion.   The said hole is a gas detection apparatus as described in any one of Claims 1-3 provided so that the drilling direction of one hole and the drilling direction of another hole may not get on a straight line.   The gas detector according to any one of claims 1 to 4, wherein the gas introduction part has a porous part.   The gas detection device according to claim 5, wherein the porous part is a porous film that covers an outside of the gas introduction part.

Images