JP4928244B2 - Infrared gas detector - Google Patents

Description

  The present invention relates to an infrared gas detector.

At present, various types of infrared gas detectors have been proposed for detecting, for example, the concentration of carbon dioxide gas using a non-dispersive infrared absorption method.
A certain kind of such an infrared gas detector includes a gas cell having a long and narrow shape and forming a gas introduction space into which a test gas is introduced, and an infrared light source at each end position in the gas cell. And the infrared sensor element are arranged to face each other.
In the infrared type gas detector having such a configuration, the infrared light emitted from the infrared light source is periodically supplied to the infrared sensor element by, for example, an optical chopper, so that a continuous output signal is obtained. The concentration of carbon dioxide gas is calculated according to the reduction rate of the amplitude of the output signal due to the reduction of the amount of infrared light received by the infrared sensor element by the introduction of gas.

  In general, as one of requests for an infrared gas detector using a non-dispersive infrared absorption method, there is a case where the entire gas detector is configured to be sufficiently small. When the infrared gas detector is configured as a small one, it is necessary to secure a sufficient optical path length from the infrared light source to the infrared sensor element in order to prevent a decrease in sensitivity.

  In response to such demands, so-called “reflective” infrared gas detectors have been proposed in which infrared light from an infrared light source is reflected by a reflecting member such as a reflecting mirror and incident on an infrared sensor element. By adopting a reflection structure, it is said that a sufficiently large optical path length required for performing target gas detection can be secured (see, for example, Patent Document 1).

  However, in infrared gas detectors, the optical path length of infrared rays required to perform gas detection differs depending on the gas detection conditions such as the type of detection target gas and the detection concentration range, and therefore, depending on the gas detection conditions. In order to provide an infrared gas detector corresponding to each of a plurality of different gas detection conditions, a dedicated component is individually provided for each infrared gas detector. There is a problem that it must be prepared.

JP-A-9-184803

  The present invention has been made based on the circumstances as described above, and the object thereof is an infrared gas that can be configured as a sufficiently small one and can cope with a plurality of gas detection conditions. It is to provide a detector.

The infrared gas detector of the present invention is an infrared gas detector including a reflective sensor device that reflects infrared light from an infrared light source and causes the infrared sensor element to enter the infrared sensor element,
The sensor device includes a housing having a gas introduction space into which a test gas is introduced, and an infrared light source and an infrared sensor element are fixed on the same surface of the flat substrate in the gas introduction space. Arranged in a state,
A reflecting mirror for reflecting the infrared light from the infrared light source to be incident on the infrared sensor element is provided inside the housing surrounding the gas introduction space, and the reflecting mirror is used for mounting the reflecting mirror. It is arranged by being attached to any one selected among the plurality of reflector mounting parts formed in the
Other and optical path system of the optical path length different from the optical path length is formed in the optical path system from said infrared light source formed up to the infrared sensor element by the reflecting mirror is mounted to the reflector mating attachment section,
The housing has a cylindrical shape, an internal space of the housing is partitioned by a partition plate to form the gas introduction space, and the reflector mounting portion is provided in the partition plate. .

According to the infrared type gas detector of the present invention, a plurality of reflecting mirror mounting portions for mounting the reflecting mirror are formed inside the housing of the sensor device, and the number and position of mounting of the reflecting mirror are selected. Therefore, it is possible to change the optical path length of the infrared optical path, and as a result, a dedicated component is required for each gas detection condition only by changing the number and position of the reflectors. In addition, since an infrared optical path having a sufficiently large optical path length necessary for gas detection can be formed according to each of a plurality of gas detection conditions, the reflection structure can be changed while using a common component member. Can cope with a plurality of gas detection conditions, and in addition, the infrared light source and the infrared sensor element are arranged together on the same surface of the flat substrate, so that the sensor device Results that can be configured as of the type, it is possible to infrared gas detector entire miniaturized with the sensor device.
Therefore, only by changing the number of reflectors used and the arrangement position of the reflectors, the optical path from the reflection structure, that is, the infrared rays emitted from the infrared light source to the infrared sensor elements, according to each of the plurality of gas detection conditions. Since the system can be formed, the sensor device can also be configured using a common component member with respect to the component members other than the reflecting mirror, and the housing constituting the sensor device is also common. Therefore, since the peripheral connection member according to the sensor device can be shared, it is possible to easily provide an infrared gas detector having different gas detection conditions while using a common component member.

  Further, since a plurality of reflecting mirrors are provided, an infrared optical path having a sufficiently large optical path length necessary for gas detection can be formed in a state where the gas introduction space is efficiently used. The gas detector can be easily reduced in size.

  Furthermore, since the housing has a cylindrical shape, it is easy to design an infrared optical path by a reflecting mirror, and the sensor device can be configured as a small one. Therefore, the infrared gas detector can be easily downsized. it can.

FIG. 1 is a cross-sectional view schematically showing a cross section parallel to the axial direction of a housing in a state in which a reflecting mirror is not mounted in a configuration example of a sensor device constituting a gas detection unit of an infrared gas detector of the present invention. FIG. 2 is a side view of one end side showing the configuration of the sensor device when the sensor device shown in FIG. 1 is viewed from the axial direction, and FIG. 3 is a side view of the housing in the sensor device shown in FIG. It is sectional drawing for description which expands an inside and shows the state with which the reflective mirror was mounted | worn.
The sensor device 10 has a cylindrical shape as a whole, and is made of, for example, SUS, and has an inner surface that is infrared-absorbing, for example, a black housing 11. The housing 11 has an internal space, for example, the housing 11 Are partitioned in an airtight manner by a disk-shaped partition plate 12 provided so as to be orthogonal to the central axis (cylinder axis) C. Reference numeral 13 denotes a seal member made of, for example, an O-ring.

Inside the housing 11, a flat circuit board 21 penetrates the partition plate 12 in an airtight manner at a position radially displaced with respect to the central axis C of the housing 11 (see FIG. 3). It is arrange | positioned so that it may extend along a direction.
A part of the outer edge of the circuit board 21 is in contact with the inner surface of the housing 11, and one end side space on one end side (left end side in FIG. 1) in the internal space partitioned by the partition plate 12 of the housing 11 is formed. It is partitioned by the circuit board 21.

  On one surface (upper surface in FIG. 3) facing the central axis C of the housing 11 of the circuit board 21, a flashing infrared light source 22 and, for example, a short circle in a region located in one end side space of the housing 11. An infrared sensor element 23 having a columnar shape and having a sensor surface 23 </ b> A on its top surface is disposed and mounted in a state of being fixed at a position aligned in the radial direction of the housing 11, for example.

A reflecting mirror 27 is provided in a region facing one surface of the circuit board 21 where the infrared light source 22 and the infrared sensor element 23 are mounted inside the one end side space of the housing 11 (see FIG. 3). The reflecting mirror 27 is attached to any one of a plurality of (four in the illustrated example) reflecting mirror mounting portions formed for mounting the reflecting mirror 27. It is arranged.
In the example of this figure, the infrared gas detector can cope with three gas detection conditions having different required infrared optical path lengths.
For convenience of explanation, FIG. 3 shows a state in which the reflecting mirrors are mounted on all formed reflecting mirror mounting portions, and each of these four reflecting mirrors 27 is shown in FIG. Assuming “reflecting mirrors 27A to 27D” in order from the left side, for the first gas detection condition, one reflecting mirror 27 is mounted on the reflecting mirror mounting portion related to the reflecting mirror 27C, that is, the reflecting mirror 27C. As a result, an infrared light path L1 indicated by a solid arrow is formed. Further, for the second gas detection condition, one reflecting mirror 27 is mounted on the reflecting mirror mounting portion related to the reflecting mirror 27B, that is, only the reflecting mirror 27B is provided, whereby the broken arrow The infrared light path L2 indicated by is formed. Further, for the third gas detection condition, the two reflecting mirrors 27 are mounted on the reflecting mirror mounting portions related to the reflecting mirror 27A and the reflecting mirror 27D, that is, the reflecting mirror 27A and the reflecting mirror 27D are mounted. Thus, an infrared light path L3 indicated by a one-dot chain arrow is formed.

The reflecting mirror 27 is a concave mirror or a plane mirror having a plate shape as a whole, a reflecting surface 28 is formed on one surface of the reflecting mirror body, and extends in the axial direction of the housing 11 (left and right in FIG. 1). It is fixed at the reflector mounting portion.
Here, the reflecting mirror 27 has a reflecting mirror body made of a material that shows a high reflectivity in the infrared region such as aluminum, and the reflecting surface 28 is constituted by one surface that is surface-treated if necessary, or The reflective mirror body is made of, for example, a resin, and a reflective film made of a material exhibiting a high reflectance in the infrared region such as an aluminum vapor deposition film, a gold vapor deposition film, or a gold plating is formed on one surface thereof. It has been made.
In the example of this figure, the reflecting mirror 27 has an arc-shaped cross section, and has a total length adapted to the length in the axial direction (left-right direction in FIG. 1) of the region surrounding the one end side space in the housing 11. The reflecting surface 28 is formed on the inner surface.

The reflector mounting portion is provided on a member such as a side surface of the housing 11, the partition plate 12, and the circuit board 21 that surrounds the space on one end side of the housing 11, and fits a mounting portion formed on the reflector 27, for example. It has a shape.
Specifically, for example, when the mounting portion of the reflecting mirror 27 is convex, the mounting portion of the reflecting mirror has a concave shape with a hole diameter adapted to the outer diameter of the mounting portion of the reflecting mirror 27, The reflecting mirror 27 is mounted by fitting the mounting portion of the reflecting mirror 27 into the reflecting mirror mounting portion. For example, when the mounting portion of the reflecting mirror 27 is concave, the mounting portion of the reflecting mirror has a convex shape with an outer diameter that matches the hole diameter of the mounting portion of the reflecting mirror 27. The mounting part of the reflecting mirror 27 is fitted to the mounting part, and the reflecting mirror 27 is mounted, or has a concave shape with the same hole diameter as the mounting part of the reflecting mirror 27. The reflecting mirror 27 is mounted by screwing by screwing a screw into the mounting portion and the mounting portion of the reflecting mirror 27.
In the example of this figure, as shown in FIG. 4, the reflector mounting portion is provided on the partition plate 12, and is located on the partition plate 12 side of the reflector 27 formed on the partition plate 12. It is composed of two holes 30 and 30 having a hole diameter adapted to the shape of each of the projections 29 and 29 of the mounting portion formed by two cylindrical projections 29 and 29 provided at one end portion. The reflective mirror mounting part 30 is fitted with the mounting part made of the projections 29, 29 of the reflective mirror 27, and the fitting part is solidified by, for example, heat welding or soldering, so that the reflective mirror 27 reflects. It is mounted on the mirror mount.

The infrared light source 22 is composed of, for example, a lamp provided with a coil filament, and is driven to blink so that it is turned on, for example, at a frequency of 1 Hz, that is, turned on for 0.5 seconds and then turned off for 0.5 seconds.
The infrared light source 22 is formed with, for example, a light emission opening 25A as necessary, and has a configuration for blocking infrared radiation emitted in a direction other than the direction toward the light emission opening 25A. There is provided a light emission direction control member 25 (the shape of which is shown by a broken line in FIGS. 1 to 3) for controlling the infrared rays emitted from 22 to be emitted in only one direction.
Here, it is preferable that a reflection film made of a material exhibiting a high reflectance in the infrared region, such as an aluminum vapor deposition film, a gold vapor deposition film, or a gold plating, is preferably formed on the inner surface of the light emission direction control member 25.
In the example of this figure, it is preferable to provide the light emission direction control member 25 particularly when the infrared light path L3 according to the third gas detection condition is formed.

  The infrared sensor element 23 includes a band-pass filter (not shown) having a high transmittance only with respect to, for example, infrared light absorbed by the detection target gas.

  Further, the circuit board 21 is provided in a region located in the other end side space on the other end side (right end side in FIG. 1) in the internal space partitioned by the partition plate 12 of the housing 11, for example, a power supply circuit, a light source drive All electric circuits necessary for gas detection such as a circuit, a sensor circuit and a microcomputer circuit are formed.

One end side opening of the housing 11 is closed by a disk-like closing member 15. The closing member 15 has, for example, a gas introduction opening 15A formed so as to be positioned in a region surrounded by the inner surface of the housing 11 and the circuit board 21 in a cross section perpendicular to the central axis C of the housing 11. A gas introduction space S into which a test gas is introduced is formed by being blocked by a disk element 16 made of a metal.
Therefore, in this sensor device 10, the infrared light source 22 and the infrared sensor element 23 are arranged in the gas introduction space S, and the infrared sensor element is passed from the infrared light source 22 through the plurality of reflecting mirrors 27. An infrared light path reaching 23 is formed in the gas introduction space S.

  In the sensor device 10, the other end side space of the housing 11 is hermetically sealed by filling the space with, for example, a resin material 40.

Hereinafter, a configuration example of the sensor device 10 according to the present invention will be shown.
The housing 11 has, for example, an inner diameter of 20 mm, an outer diameter of 23 mm, a wall thickness of 1.5 mm, and a total length of 20 mm. The radial deviation d of the circuit board 21 with respect to the central axis C of the housing 11 is about 6 mm. The size of the internal volume of the gas introduction space S is about 2000 mm ³ .
The infrared light source 22 is, for example, a lamp having a rated voltage value of 5 V, a rated current value of 0.115 A, and a lamp height of 6.2 mm. The infrared sensor element 23 has a height of, for example, 4.8 mm and an outer diameter. The distance is φ9.2 mm, and the separation distance (center-to-center distance l) between the infrared light source 22 and the infrared sensor element 23 is, for example, about 7 mm. The optical path length of the infrared light path L1 related to the first gas detection condition is, for example, about 9 mm, the optical path length of the infrared light path L2 related to the second gas detection condition is, for example, 22.6 mm, and the infrared light related to the third gas detection condition. The optical path length of the optical path L3 is 29.5 mm, for example.

  In the infrared gas detector provided with the sensor device 10 having the above-described configuration as a gas detector, the infrared light source 22 is driven to blink at a predetermined cycle, and the infrared light emitted from the infrared light source 22 is reflected by the reflecting mirror 27. While being incident on the infrared sensor element 23, the test gas is introduced into the gas introduction space S by natural diffusion, for example. And the density | concentration of detection target gas is detected according to the extent of attenuation | damping of the infrared light quantity accompanying absorption of the infrared rays by detection target gas contained in test gas.

Thus, according to this infrared gas detector, a plurality of reflecting mirror mounting portions for mounting the reflecting mirror 27 are formed inside the housing 11 of the sensor device 10 constituting the gas detecting portion. A plurality of reflector mounting portions can be selectively used. Specifically, the number and position of the reflectors 27 can be selected, so that the optical path length of the infrared light path can be changed. Only by changing the number and position of the reflecting mirrors 27 to be mounted, for example, there is no need for a dedicated component for each different gas detection condition such as the type of detection target gas and the detection concentration range. Infrared optical path having a sufficiently large optical path length necessary for gas detection according to each of the gas detection condition, the second gas detection condition, and the third gas detection condition (specifically, the infrared light paths L1 to L3) Since it can be formed, each of these gas detection conditions is handled by changing the optical path system from the infrared light source 22 to the infrared sensor element 23 while using a common component. In addition, since the infrared light source 22 and the infrared sensor element 23 are arranged on the same surface of the same circuit board 21 and are compactly assembled, the sensor device 10 is configured to be small. As a result, the entire infrared gas detector including the sensor device 10 can be reduced in size.
Accordingly, the first gas detection condition, the second gas detection condition, and the third gas detection condition can be changed by changing the number of the reflection mirrors 27 used and the arrangement position of the reflection mirrors, and providing the light emission direction control member 25 as necessary. Since the optical path system of the infrared optical path can be formed according to each of the gas detection conditions, the sensor device 10 can be configured with components other than the reflecting mirror 27 (for example, the housing 11, the partition plate 12, the seal member 13, and the closing member 15). , The disk element 16, the circuit board 21, the infrared light source 22, the infrared sensor element 23, etc.) can also be configured using common components, and the housing 11 constituting the sensor device 10 is also common. Since the peripheral connection member related to the sensor device 10 can be shared, the three different gas detection conditions using a common component Three infrared gas detector corresponding to each can be easily provided.

  The infrared light source 22 and the infrared sensor element 23 are formed on the same surface of the same circuit board 21, and the circuit board 21 is disposed so as to extend along the axial direction of the housing 11. By arranging the circuit board 21 on which the infrared light source 22 and the infrared sensor element 23 are mounted in a predetermined positional relationship in the housing 11, the infrared light source 22 and the infrared light source 22 and Since the infrared sensor element 23 can be fixed at an intended position, an infrared gas detector can be easily manufactured.

  In addition, since the housing 11 has a cylindrical shape, it is easy to design an infrared light path by the reflecting mirror 27, and the sensor device 10 can be configured as a small one. Therefore, the infrared gas detector can be easily downsized. Can be planned.

As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment, A various change can be added.
For example, the shape of the housing is not particularly limited as long as a plurality of reflecting mirror mounting portions can be formed inside the housing, and the reflecting mirror can be disposed by these reflecting mirror mounting portions. It is not limited to.
Further, the detection target gas according to the infrared gas detector of the present invention is not particularly limited as long as it has infrared absorption characteristics, and the size of the optical path length of the infrared optical path and other specific configurations are as follows: It can change suitably according to the kind of detection object gas.
Furthermore, when high airtightness is not required for the sensor device itself, it is not necessary to have a configuration in which a partition plate is provided.

It is a cross-sectional view schematically showing a cross section parallel to the axial direction of the housing in a configuration example of the sensor device constituting the gas detection portion of the infrared gas detector of the present invention in a state where no reflecting mirror is attached. . It is a one end side view which shows the structure of a sensor apparatus when the sensor apparatus shown in FIG. 1 is seen from an axial direction. It is sectional drawing for description which shows the state in which the inside of the housing in the sensor apparatus shown in FIG. 1 was expanded and the reflective mirror was mounted | worn. It is explanatory drawing which shows the structure of the reflective-mirror mounting part provided in the partition plate in the sensor apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Sensor apparatus 11 Housing 12 Partition plate 13 Seal member 15 Closure member 15A Gas introduction opening 16 Disc element 21 Circuit board 22 Infrared light source 23 Infrared sensor element 23A Sensor surface 25 Light emission direction control member 25A Light emission opening 27, 27A, 27B, 27C, 27D Reflector 28 Reflecting surface 29 Projection 30 Hole 40 Resin material L1, L2, L3 Infrared light path S Gas introduction space

Claims (1)

An infrared gas detector provided with a reflective sensor device that reflects infrared light from an infrared light source and makes it incident on an infrared sensor element,
The sensor device includes a housing having a gas introduction space into which a test gas is introduced, and an infrared light source and an infrared sensor element are fixed on the same surface of the flat substrate in the gas introduction space. Arranged in a state,
A reflecting mirror for reflecting the infrared light from the infrared light source to be incident on the infrared sensor element is provided inside the housing surrounding the gas introduction space, and the reflecting mirror is used for mounting the reflecting mirror. It is arranged by being attached to any one selected among the plurality of reflector mounting parts formed in the
Other and optical path system of the optical path length different from the optical path length is formed in the optical path system from said infrared light source formed up to the infrared sensor element by the reflecting mirror is mounted to the reflector mating attachment section,
The housing has a cylindrical shape, an internal space of the housing is partitioned by a partition plate to form the gas introduction space, and the reflector mounting portion is provided in the partition plate. Infrared gas detector.

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