JP4879005B2 - 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 order to ensure a sufficiently large optical path length, simply adopting a reflecting structure using a reflecting member, for example, an infrared sensor element emits infrared light perpendicular to the sensor surface of the infrared sensor. Since the sensitivity is the highest when incident, depending on the adjustment of the optical system, the performance of the infrared sensor element cannot be utilized with sufficiently high efficiency, and the intended gas detection must be performed. There is a problem that it may not be possible.

JP-A-9-184803

  The present invention has been made based on the circumstances as described above, and the object thereof can be configured as a sufficiently small one, and can perform desired gas detection with high reliability. An object is to provide an infrared gas 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 cylindrical housing having a gas introduction space into which a test gas is introduced. The sensor device has a flat plate shape at a position radially deviated from the central axis of the housing. The substrate is disposed so as to extend along the axial direction of the housing, and is disposed in a state where the infrared light source and the infrared sensor element are fixed in a line on the one surface facing the central axis of the housing of the flat substrate , The infrared light source is provided with a light emission direction control member for controlling the infrared light from the infrared light source to be emitted in only one direction,
In the gas introduction space, a region facing the one surface on which the infrared light source and the infrared sensor element of the circuit board are disposed has a plurality of light incident on the infrared sensor element by reflecting infrared light from the infrared light source. A reflector is disposed along the inner surface of the housing;
Wherein the incident angle of the infrared radiation is incident on each of the plurality of reflecting mirrors is less than 45 °, and the angle of incidence of infrared rays incident on the infrared sensor element is 0 ° ± 20 °.

  In the infrared type gas detector of the present invention, each of the plurality of reflecting mirrors is arranged so that the infrared light reflected by one reflecting mirror is incident on a reflecting mirror other than the reflecting mirror adjacent in the circumferential direction. Is preferred.

In infrared gas detector of the present invention, one of the plurality of linear light path portion infrared constitutes the infrared light path up to the infrared sensor element through a plurality of reflecting mirrors sequentially from the infrared light source It is preferable that there are one or more intersections in which the optical path portion intersects with other optical path portions.

  According to the infrared type gas detector of the present invention, a plurality of reflecting mirrors are provided on the inner surface of the housing of the sensor device in a state satisfying a specific arrangement condition, and the infrared light source includes an infrared ray from the infrared light source. Since the light radiation direction control member for controlling the radiation direction of the light is provided, the infrared light path having a sufficiently large light path length necessary for gas detection is used in a state where the gas introduction space is efficiently used. In addition, the infrared rays from the infrared light source can be used with high efficiency, and the infrared rays are incident on the infrared sensor element with the highest sensitivity. Therefore, the desired gas detection can be performed with high reliability, and the infrared light source and the infrared sensor element are arranged together on the same surface of the flat substrate. Since it is, the sensor device results, which may be configured as a small size, it is possible to infrared gas detector entire miniaturized with the sensor device.

  In addition, since the housing is cylindrical, it is easy to design a reflecting structure by a plurality of reflecting mirrors, and the sensor device can be configured as a small one, so that the infrared gas detector can be easily downsized. Can do.

FIG. 1 is a cross-sectional view schematically showing a cross section parallel to an axial direction including a central axis of a housing in a configuration example of a sensor device constituting a gas detection unit of an infrared gas detector of the present invention. 2 is a cross-sectional view showing an AA section shown in FIG. 1 enlarged and rotated by 90 °, and FIG. 3 is a configuration of the sensor apparatus when the sensor apparatus shown in FIG. 1 is viewed from the axial direction. FIG.
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 deviated in the radial direction with respect to the central axis C of the housing 11 (see FIG. 2). 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. 2) of the circuit board 21 facing the central axis C of the housing 11, a flashing infrared light source 22 and a short circle, for example, 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.

The infrared light source 22 is provided with a light emission direction control member 25 for controlling the infrared light emitted from the infrared light source 22 to be emitted in only one direction.
Here, the light emission direction control member 25 is arranged so as to cover the infrared light source 22, and the infrared light emitted from the infrared light source 22 is projected only forward (upward in FIG. 2) from the infrared light source 22. Control is performed by shielding infrared rays emitted in other directions.
In the example shown in the figure, the light emission direction control member 25 is generally spherical and has one light emission opening 25A, and blocks infrared rays emitted in directions other than the direction toward the light emission opening 25A. 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 formed on the inner surface thereof.

  In the inner surface of the one end side space of the housing 11, there are a plurality of (four in the example in the figure) regions facing one surface on which the infrared light source 22 and the infrared sensor element 23 of the circuit board 21 are mounted. The reflecting mirror 27 is provided.

Each of the plurality of reflecting mirrors 27 is a concave mirror or a plane mirror having a plate shape as a whole, and a reflecting surface 28 is formed on the inner surface thereof, and the reflecting surface 28 faces the central axis C of the housing 11. It is fixed by an appropriate method so as to extend in the axial direction of the housing 11 along the inner surface of the housing 11.
Here, the reflecting mirror 27 is made of a material having a high reflectance in the infrared region, such as aluminum, and the reflecting surface 28 is constituted by an inner surface that is surface-treated as necessary, or the inner surface thereof. The reflective surface 28 is formed by forming 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.
In the example of this figure, each of the plurality of reflecting mirrors 27 is a concave mirror having a different size, and is adapted to the length in the axial direction (left and 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, and one end thereof is fixed to the partition plate 12 by, for example, screwing.

The plurality of reflecting mirrors 27 reflect the infrared light path L so as to be finally incident on the infrared sensor element 23 by sequentially reflecting infrared rays (indicated by bold lines in FIG. 2) emitted from the infrared light source 22. The incident angle of infrared rays in each of the reflecting mirrors 27 is less than 45 °, and the incident angle of infrared rays to the infrared sensor element 23 is 0 ° ± 20 °, preferably 0 ° ± 10 °. It is arranged to become.
Here, in this specification, the “incidence angle of infrared rays to the infrared sensor element” is an angle at which infrared rays are incident on the infrared light receiving part of the infrared sensor element. The angle with respect to the said sensor surface 23A of the infrared rays which inject into the sensor surface 23A which is an infrared light-receiving part of the outer sensor element 23 is shown.

  Specifically, in the example of the figure, if each of the four reflecting mirrors 27 is “reflecting mirrors 27A to 27D” in order from the left side in FIG. 2, the infrared rays emitted from the infrared light source 22 are controlled in the light emission direction. After being projected by being controlled by the member 25, and incident on and reflected by the reflecting mirror 27B as indicated by the optical path portion L1, the reflected infrared rays are reflected by the reflecting mirror 27D as indicated by the optical path portion L2 and the optical path portion L3. Then, the infrared rays incident on and reflected by the reflecting mirror 27A in this order are reflected on the reflecting mirror 27C as shown by the optical path portion L4, as shown by the optical path portion L4. Although the light is incident on the sensor surface 23A of the infrared sensor element 23, each of the reflecting mirrors 27A to 27D is arranged in a state satisfying a specific positional relationship.

  Further, when there are three or more reflecting mirrors 27 constituting the sensor device 10, these reflecting mirrors 27 are infrared rays reflected by one reflecting mirror in order to satisfy the above arrangement condition. It is preferable to set the arrangement position so that the incident light enters the reflecting mirrors other than the reflecting mirrors adjacent in the circumferential direction. This makes it easy to design the infrared light path L and allows the test gas to form the infrared light path L to be The infrared light path L can be formed in a state where the introduced space is efficiently used.

Further, in order for the plurality of reflecting mirrors 27 to have a sufficiently large optical path length for the infrared optical path L, at least one of the optical path portions constituting the infrared optical path L includes the plurality of reflecting mirrors 27. Preferably, the arrangement position is set so as to have the maximum size that can be formed in the space into which the test gas to be formed and the infrared gas path L to be formed is introduced. 27 can secure a sufficiently large optical path length, and the number of components constituting the sensor device 10 as the number of reflecting mirrors 27 required to secure a sufficient optical path length decreases. Since the sensor device 10 can be configured as a small one, the entire infrared gas detector can be reduced in size.
In the example of this figure, in consideration of the positional relationship between the infrared light source 22 and the infrared sensor element 23, the longest one of the optical path portions constituting the infrared optical path L and the reflecting mirror 27D and the reflecting mirror 27D that face each other are reflected. Arrangement positions of a plurality of (four) reflecting mirrors 27 (27A to 27D) are set so that one optical path portion (specifically, an optical path portion L3) is formed between the mirror 27A.

Further, in order to make the infrared light path L have a sufficiently large optical path length, the plurality of reflecting mirrors 27 have one optical path portion among the plurality of linear optical path portions constituting the infrared light path L. It is preferable that there are one or more intersections that intersect with other optical path portions. This facilitates the design of the infrared optical path L, and allows efficient use of the space into which the test gas that should form the infrared optical path L is introduced. The infrared light path L can be formed in the state utilized for the above.
In the example of this figure, the infrared optical path L is composed of five optical path portions L1 to L5, but a total of five intersections of the optical path portions are formed by these five optical path portions L1 to L5. .

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 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 L 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 30.

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 3.3 mm. The infrared sensor element 23 has a height of, for example, 4.8 mm and an outer diameter. The distance between the infrared light source 22 and the infrared sensor element 23 (center distance 1) is, for example, about 7 mm, the optical path length of the infrared optical path L is, for example, about 65 mm (the optical path portion L1 is 12 mm, The optical path portion L2 is 15 mm, the optical path portion L3 is 16 mm, the optical path portion L4 is 12 mm, and the optical path portion L5 is 10 mm).

  In the infrared type gas detector provided with the sensor device 10 having the above-described configuration as a gas detection unit, the infrared light source 22 is driven to blink at a predetermined cycle and is emitted from the infrared light source 22, and the light emission direction control member 25. The radiation direction is controlled by, and infrared rays set in one direction are incident on the infrared sensor element 23 by the plurality of reflecting mirrors 27, while the test gas is introduced into the gas introduction space S by natural diffusion, for example. The 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, the plurality of reflecting mirrors 27 are provided on the inner surface of the housing 11 of the sensor device 10 constituting the gas detector in a state satisfying a specific arrangement condition. In addition, since the infrared light source 22 is provided with the light emission direction control member 25 for controlling the infrared radiation direction from the infrared light source 22, the infrared light having a sufficiently large optical path length necessary for gas detection. The optical path L is formed in a state where the gas introduction space S is effectively used, and the infrared light from the infrared light source 22 can be used with high efficiency, and is most sensitive to the sensor surface 23A of the infrared sensor element 23. Since the infrared rays are incident vertically, that is, the infrared rays emitted from the infrared light source 22 are used with high efficiency. Detection can be performed with high sensitivity, and as a result, desired gas detection can be performed with high reliability. In addition, the infrared light source 22 and the infrared sensor element 23 are on the same surface of the same circuit board 21. Since the sensor device 10 can be configured to be small, the entire infrared gas detector including the sensor device 10 can be downsized.

  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. The circuit board 21 on which the infrared light source 22 and the infrared sensor element 23 are mounted in a predetermined positional relationship is disposed in the housing 11 by being in a state parallel to the central axis C of the housing 11. Since the positional relationship between the infrared light source 22 and the infrared sensor element 23 with respect to the plurality of reflecting mirrors 27 disposed on the surface is fixed in an appropriate state, the infrared gas detector can be easily manufactured.

  In addition, since the housing 11 has a cylindrical shape, it is easy to design a reflecting structure by the plurality of reflecting mirrors 27, and the sensor device 10 can be configured as a small one. Therefore, the infrared gas detector can be easily downsized. Can be aimed at.

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 limited to a cylindrical shape as long as a plurality of reflecting mirrors can be disposed on the inner surface of the housing.
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.
The light emission direction control member may have a light exit opening made of a louver.
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 which shows roughly the cross section parallel to the axial direction containing the central axis of a housing in one structural example of the sensor apparatus which comprises the gas detection part of the infrared type gas detector of this invention. It is sectional drawing shown in the state which expanded the AA cross section shown in FIG. 1, and rotated 90 degrees. 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.

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 30 Resin material L Infrared light path S Gas introduction space

Claims (3)

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 cylindrical housing having a gas introduction space into which a test gas is introduced. The sensor device has a flat plate shape at a position radially deviated from the central axis of the housing. The substrate is disposed so as to extend along the axial direction of the housing, and is disposed in a state where the infrared light source and the infrared sensor element are fixed in a line on the one surface facing the central axis of the housing of the flat substrate , The infrared light source is provided with a light emission direction control member for controlling the infrared light from the infrared light source to be emitted in only one direction,
In the gas introduction space, a region facing the one surface on which the infrared light source and the infrared sensor element of the circuit board are disposed has a plurality of light incident on the infrared sensor element by reflecting infrared light from the infrared light source. A reflector is disposed along the inner surface of the housing;
The plurality of the incident angle of the infrared radiation incident on each less than 45 ° of the reflecting mirror, and infrared, wherein the angle of incidence of infrared rays incident on the infrared sensor element is 0 ° ± 20 ° Gas detector.   2. The infrared ray according to claim 1, wherein each of the plurality of reflection mirrors is arranged so that the infrared ray reflected by one reflection mirror is incident on a reflection mirror other than the reflection mirror adjacent in the circumferential direction. Gas detector. One optical path portion of a plurality of linear optical path portions constituting an infrared optical path from the infrared light source to the infrared sensor element through the plurality of reflecting mirrors sequentially passes through the other optical path portions. The infrared gas detector according to claim 1 or 2, wherein there are one or more intersections .

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