JPH1062335A - Measurement cell of infrared gas analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily manufacture a measurement cell having an optical path length suitable to the concentration range of a measuring gas at low cost. SOLUTION: Denoted at IA is a first cylinder, 1B is a second cylinder, and they have natural convection holes 9 on the respective circumferential walls. A light source part 11 is arranged on the left side of the cylinder 1A, and a detection part 12 on the right side of the cylinder 1B shown by a dashed line herein. The left circumferential part of the cylinder 1B is fitted to the right circumferential part of the cylinder 1A so as to be relatively movable in the axial direction. Thus, a measurement cell. formed by mutually fitting the cylinders 1A, 1B can be continuously changed to an optical path length suitable to the concentration range of a measuring gas. When the relative positioning of each cylinder 1A, 1B is ended, the light source part 11 and the detection part 12 are installed, respectively, and fixed to a base not shown by each fixing leg 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for measuring exhaust gas from automobiles, controlling air conditioning in buildings, controlling carbon dioxide concentration in facility cultivation, controlling carbon dioxide concentration in a culture tank, etc., and sampling a measured gas by a natural convection method. The present invention relates to a measuring cell for an infrared gas analyzer which has an optical path length suitable for a concentration range of a measuring gas and which can be manufactured easily and at low cost.

[0002]

2. Description of the Related Art An infrared gas analyzer using a general conventional example (measuring cell) will be described with reference to a side view of FIG. On the left side of the measuring cell 25 through which the measuring gas flows, a synchronous motor 24 and a rotating sector 2 directly connected to the synchronous motor 24 are provided.
3, a light source unit 21 for infrared rays, and a detection unit 22 on the right side.
Are respectively arranged. Here, the rotating sector 23 and the synchronous motor 24 constitute a chopper mechanism. The measurement cell 25 is a cylindrical body whose right and left sides are each closed by a transparent plate, and has a gas inlet 26 and a gas outlet 27 near the left and right ends, respectively. The measurement gas is supplied from a gas inlet 26 using a pump and a filter (not shown), and flows through the measurement cell 25 from left to right in a form of being discharged from a gas outlet 27. The infrared light incident from the light source unit 21 is transmitted to the measurement cell 2
Since the specific wavelength portion is absorbed by molecules of the measurement gas and attenuates when the measurement gas flows through the sample gas 5, the measurement gas concentration can be obtained by measuring the attenuation rate. Usually, using a light source unit with a heating element with a wide emission wavelength band,
The intensity of light transmitted through the measurement gas is detected by a wavelength-selective detector. The wavelength selectivity of the detection unit is determined by detecting a temperature change (or pressure change) based on infrared light absorption by a gas of the same type as the measurement gas previously sealed in the detection unit, or an infrared wavelength used for measurement. It can be obtained by placing a multilayer thin film optical filter that transmits only light in front of the detection unit.

The infrared gas analyzer shown in FIG. 7 takes a form in which a measurement gas flows through a measurement cell 25 for sampling a measurement gas. For this purpose, a motor and a filter are used. Therefore, there is a disadvantage that maintenance is troublesome. A method that improves this point is a natural convection (also called natural diffusion) method. The natural convection method is a method in which the measurement gas naturally flows into and out of the measurement cell placed in the measurement gas, that is, is sampled by natural convection or diffusion. By adopting the natural convection method, troublesome maintenance work for measuring the gas concentration can be omitted, and the cost can be reduced. An infrared gas analyzer using a conventional example (measurement cell) based on the natural convection method will be described with reference to a side view of FIG. The light source unit 11 and the detection unit 12 are disposed at both ends of a cylindrical measurement cell 15 that is open on both sides, respectively. The light source unit 11 may use a chopper mechanism using a rotating sector in the same manner as in the above-mentioned general conventional example. However, here, the structure is simplified by blinking the light source itself. In addition, the light source unit 11 is provided with an inlet 13 through which a calibration gas flows into the end face opposite to the measuring cell 15 and a fixed leg 14 having a threaded hole at the lower side. The detection unit 12 is provided with the same fixed legs 14 on the lower side. These two fixed legs 1
At 4, the entire infrared gas analyzer is mounted on a base (not shown). Further, in the peripheral wall of the measurement cell 15, a plurality of holes, here three for natural convection, into which the measurement gas naturally enters and exits, are formed in this case.

[0004]

As described above, as described above,
Regarding the conventional measurement cell, whether it is of the forced once-through type or the natural convection type, its length (optical path length) is set to be long when the concentration is low and short when it is high according to the concentration range of the measurement gas. . This measuring cell is a plastic molded product such as ABS resin, which is generally excellent in heat resistance and impact resistance. To suppress the leakage of infrared light, glossy Cr plating or Ni is used.
Plating is applied. Therefore, it is necessary to prepare a large number of components of the measurement cell having different lengths (optical path lengths) so as to correspond to various specifications of the concentration range of the measurement gas, which complicates component inventory management. Not only
This has caused cost and delivery problems.

[0005] The problem to be solved by the present invention is to solve the above problems of the prior art, and to improve the optical path length suitable for the concentration range of the measurement gas so that it can be manufactured simply and at low cost. To provide a measurement cell for an infrared gas analyzer.

[0006]

The invention according to claim 1 is
A measurement cell of an infrared gas analyzer for sampling a measurement gas by a natural convection method, wherein a first cylindrical body in which a light source unit is disposed on one end side and a detection unit is disposed on one end side. The first and second cylindrical bodies are fitted with each other including the other end, and are relatively movable in the axial direction. is there.

According to a second aspect of the present invention, there is provided a measurement cell of an infrared gas analyzer for sampling a measurement gas by a natural convection method, wherein the measurement cell is a cylindrical body having a light source unit and a detection unit disposed at both ends. At each of a plurality of locations in the length direction of the cylindrical body, slits for cutting support having a narrow width and having a circumferential direction as a longitudinal direction are provided in parallel along the circumference at the location.

[0008] In the invention according to claim 2,
It is preferable that the configuration is modified as in each of the following items (1) to (3). (1) A V-shaped groove for cutting support is formed in each of a plurality of locations in the length direction of the cylindrical body along the circumference at the location, along with the slit. (2) At each of a plurality of locations in the length direction of the cylindrical body, a U-shaped groove for coupling support is formed along the circumference at the location, in such a manner that the slit row is brought close to one leg of the U-shape. It is formed including. (3) A coupling support slit orthogonal to the cutting support slit is formed so as to cross the bottom of the U-shaped groove.

Therefore, in the first aspect of the present invention, the first and second cylindrical bodies are fitted to each other including the other end, and are relatively moved in the axial direction.
The optical path length can be changed to a suitable one for the concentration range of the measurement gas. In the invention according to claim 2, the cylindrical body is cut at two selected slit portions (the slit supports cutting), and end faces of the cut portions are brought into contact with each other except for an intermediate portion thereof. Thereby, the optical path length can be changed to a suitable one for the concentration range of the measurement gas.

Further, the following method is modified according to the above items (1) to (3). (1) Cutting is performed along the V-shaped groove at the selected two slit portions, and end faces of the cut portions are brought into contact with each other except for an intermediate portion thereof. (2) At the two selected slits, cut along the wall corresponding to one of the legs of the U-shape of the U-shaped groove, and remove the hollow cylindrical body at one of the cuts except for the intermediate part. The distal end of the cylindrical stepped portion at the other cut location is fitted into the portion. (3) In the preceding paragraph (2), the cylindrical stepped portion is divided into a plurality of parts along the circumference by the slit for supporting the connection, and it is easily elastically deformed and fitted into the hollow part of the cylindrical body on the other side. Is supported.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As embodiments of the present invention, first to fourth embodiments will be described below with reference to the drawings. FIG. 1 is a side view of the first embodiment. In FIG.
1A is a first cylindrical body, 1B is a second cylindrical body, and a natural convection hole 9 is formed in each peripheral wall. Cylindrical body 1A
The light source unit 11 is on the left side of the body, and the detection unit 12 is on the right side of the cylindrical body 1B.
(Both are the same as the conventional example of FIG. 6 and are indicated by dashed lines here). The outer peripheral portion of the left side portion of the cylindrical body 1B is fitted to the inner peripheral portion of the right side portion of the cylindrical body 1A, and is relatively movable in the axial direction. Therefore, the measurement cell formed by fitting the cylinders 1A and 1B is continuously changed to an optical path length suitable for the concentration range of the measurement gas by the relative movement of the cylinders 1A and 1B. Can be. In addition, in the relative normal movement range of the cylinders 1A and 1B, the holes 9 are not closed by the other cylinder, and the sampling of the measurement gas is performed without any trouble.
In addition, the gap existing at the fitting portion of each of the cylindrical bodies 1A and 1B also functions as a natural convection, like the holes 9. When the relative positioning of the cylindrical bodies 1A and 1B is completed, the light source unit 11 and the detecting unit 12 are mounted on the cylindrical bodies 1A and 1B, respectively, and are fixed to the base (not shown) by the fixing legs 14, whereby the optical path of the measuring cell is set. The length will be set.

FIGS. 2A and 2B relate to the second embodiment, in which FIG. 2A is a side view of the basic parts, and FIG. 2B is a cross-sectional view of the joint after the optical path length is changed. The basic part of the measuring cell is the cylinder 2. A light source unit 11 and a detection unit 12 are disposed on both ends of the cylindrical body 2 as in the first embodiment. In addition, two holes for natural convection 9 are formed in the peripheral wall of the cylindrical body 2 in the same manner as in the first embodiment.
At each of four locations B, C and D, eight slits 6 for cutting assistance having a narrow width and having a circumferential direction as a longitudinal direction along the circumference at the location are provided in parallel. The row of the slits 6 corresponds to a cut line of the cylindrical body 2 and can be easily cut using a circular saw or a thread saw according to the cut line, and also serves as a natural convection hole.

When the optical path length of the measuring cell is set in accordance with the concentration range of the measuring gas, the cylindrical body 2 is formed at the row portion of two slits 6 selected from A, B, C and D.
Is cut, and the end faces of the cut portion are brought into contact with each other except for an intermediate portion thereof. That is, the basic component corresponds to the lowest density range. It is designed such that different optical path lengths can be obtained by selecting any two of A, B, C, and D and cutting the cylindrical body 2 to remove an intermediate portion. In FIG. 2 (a), each point A, B is selected as an actual cut surface, and after cutting, except for an intermediate portion between the cross section A and the cross section B,
As shown in (b), the cut surfaces A and B are brought into contact with and joined to each other, and the optical path length is set shorter than that of the basic part of the cylindrical body 2 so as to meet the specifications. When the setting of the optical path length of the cylindrical body 2 is completed, the light source unit 11 and the detection unit 12 are attached to the left and right ends, respectively, as in the first embodiment of FIG. The optical path length of the measuring cell is set by fixing it to the base. The contact / joining surfaces of the cuts A and B do not necessarily have to be bonded to each other, and may have a slight gap. This gap can perform natural convection together with the natural convection hole 9 and the slits 6 at the uncut portions C and D.

FIGS. 3A and 3B relate to the third embodiment, wherein FIG. 3A is a side view of a basic part thereof, and FIG. 3B is a cross-sectional view of a joint after an optical path length is changed. In the third embodiment, the following additional processing is performed on the second embodiment. In FIG. 3A, the cylindrical body 3 is
At each of four locations A, B, C, and D in the longitudinal direction, a V-shaped groove 7 for cutting support is formed along the circumference at the location along with the slit 6. Here, the cylindrical body 3 is cut along the V-shaped groove 7 at the slit 6 at each of the selected portions A and B, and each end face A of the cut portion is removed as shown in FIG. , B are brought into contact with each other, so that there is an advantage that the cutting operation is more accurate and easier than in the second embodiment.

FIGS. 4A and 4B relate to a fourth embodiment, in which FIG. 4A is a side view of the basic parts, and FIG. 4B is a cross-sectional view of the joint after the optical path length is changed. In the fourth embodiment, a U-shaped groove 8 for supporting the coupling is formed along each of the four points A, B, C and D in the longitudinal direction of the cylindrical body 4 as shown in FIG. Are formed in such a manner that the rows of the slits 6 are included inside the U-shaped left leg in proximity to the U-shaped left leg. Here, the cylindrical body 4 is cut at the slits 6 of the selected portions A and B so as to follow the wall surface of the U-shaped groove 8 corresponding to the left leg of the U-shape. The distal end of the cylindrical stepped portion at the right cut point B is fitted into the hollow portion of the cylindrical body at the left cut point A. Actually, the corner of the inner surface at the end of the left cylindrical body is slightly chamfered so that it can be easily fitted. In the fourth embodiment, the end portions are fitted to each other, so that the two cylindrical portions are inserted and connected.

FIGS. 5A and 5B relate to the fifth embodiment, in which FIG. 5A is a side view of a basic part thereof, and FIG. The fifth embodiment is different from the fourth embodiment in that the slit 10 for joining support orthogonal to the slit 6 for cutting support is
The difference is that additional processing is performed across the bottom of the V-shaped groove 8. The slit 10 divides the cylindrical stepped portion into eight along the circumference, and is easily elastically deformed, so that the fitting into the mating cylindrical hollow portion is facilitated.

[0017]

According to the present invention, although the optical path length suitable for the concentration range of the measurement gas generally depends on the assembly adjustment or the cutting process, it is simple from the basic part (plastic molded article). In addition, there is an excellent effect that it can be manufactured at low cost, and the number of stocked parts can be significantly reduced by standardizing the parts, and further, the management cost and the delivery time can be reduced. In particular, (1) According to the first aspect of the present invention, since the first and second cylindrical bodies are fitted and moved relatively in the axial direction, cutting processing is not required, but required. There is an advantage that only the assembly adjustment is required, and the number of processing steps can be reduced. (2) According to the second aspect of the present invention, the method is a method in which one cylindrical body, which is a basic part, is cut at two selected places and the end faces are joined to each other, so that only one standard part is required. is there. In particular, by providing the slit and the V-shaped groove together, the cutting operation becomes more accurate and easier than when only the slit is used. In addition, since the slit and the U-shaped groove are provided side by side, the shape follows the wall surface corresponding to one of the legs of the U-shape, so that the cutting becomes accurate and easy, and the cylindrical hollow portion at one of the cut portions is provided. In this case, the distal end of the cylindrical stepped portion at the other cut point is fitted into the cylindrical portion, so that the two cylindrical portions are firmly inserted and connected. Further, the slit for supporting the connection divides the cylindrical stepped portion into a plurality of pieces along the circumference, is easily elastically deformed, and supports the fitting and fitting into the hollow portion of the cylindrical body on the other side.

[Brief description of the drawings]

FIG. 1 is a side view of a first embodiment according to the present invention.

2 (a) is a side view of the basic component, and FIG. 2 (b) is a cross-sectional view of the joint after changing the optical path length.

3 (a) is a side view of the basic component, and FIG. 3 (b) is a cross-sectional view of the joint after changing the optical path length.

4 (a) is a side view of the basic component, and FIG. 4 (b) is a cross-sectional view of the joint after changing the optical path length.

5 (a) is a side view of the basic component, and FIG. 5 (b) is a cross-sectional view of the junction after changing the optical path length.

FIG. 6 is a side view of a conventional infrared gas analyzer using a natural convection method.

FIG. 7 is a side view of an infrared gas analyzer using a general conventional example.

[Explanation of symbols]

 1A cylindrical body (first) 1B cylindrical body (second) 2, 3, 4, 5 cylindrical body 6 slit (for cutting support) 7 V-shaped groove 8 U-shaped groove 9 hole (for natural convection) 10 slit (coupling support) 11) Light source 12 Detector 13 Calibration gas inlet 14 Fixed leg

Claims (5)

[Claims] 1. A measurement cell of an infrared gas analyzer for sampling a measurement gas by a natural convection method, comprising: a first cylindrical body having a light source disposed on one end side; The first and second cylindrical bodies are fitted with each other including the other end, and are relatively movable in the axial direction. A measuring cell for an infrared gas analyzer. 2. A measurement cell of an infrared gas analyzer for sampling a measurement gas by a natural convection method, comprising a cylindrical body having a light source section and a detecting section disposed at both ends, respectively, in a longitudinal direction of the cylindrical body. A slit for assisting cutting, which has a circumferential direction as a longitudinal direction and a narrow width, is arranged in parallel at each of the plurality of locations. 3. The measuring cell according to claim 2, wherein a V-shaped groove for assisting cutting is provided at each of a plurality of locations in the length direction of the cylindrical body along the circumference at the location. A measuring cell for an infrared gas analyzer formed. 4. The measuring cell according to claim 2, wherein a U-shaped groove for supporting the coupling is formed at each of a plurality of locations in the longitudinal direction of the cylindrical body along the circumference at the location, and the slit row is formed in a U-shape. Is formed so as to be included in the vicinity of one of the legs,
A measurement cell for an infrared gas analyzer, characterized in that: 5. The measurement cell according to claim 4, wherein the coupling support slit orthogonal to the cutting support slit is U-shaped.
A measurement cell for an infrared gas analyzer, wherein the measurement cell is formed so as to cross the bottom of a U-shaped groove.