JP4120557B2 - Infrared gas analyzer - Google Patents

Description

  The present invention relates to an infrared gas analyzer for measuring a sample gas concentration (concentration of a specific gas species) using a gas flow caused by a gas pressure fluctuation accompanying infrared spectrum absorption of an infrared active component gas, Specifically, the present invention relates to a configuration of a detection unit that is used with gas filled therein.

  Many of the heteronuclear molecules composed of two or more different atoms undergo vibrational and rotational kinetic energy level transitions specific to the chemical species when irradiated with infrared light having a wavelength of 1 to 20 μm, and a specific infrared spectrum. This causes thermodynamic changes such as an increase in internal energy, volume or pressure. A non-dispersive infrared gas analyzer (hereinafter referred to as NDIR) is an analytical instrument that measures the concentration by utilizing such characteristics of gas components.

  FIG. 6 shows the configuration of a single-beam NDIR equipped with a hot-wire flow sensor that detects a gas flow due to gas pressure fluctuations as a detector. As shown in the figure, this type of NDIR generally includes a light source unit 20 for generating infrared light, a cell unit 30 into which a sample gas (gas to be measured) is introduced, and infrared light that has passed through the cell unit 30. It is composed of three units of a detection unit 40 that finally measures the sample concentration by measuring the intensity. The light source unit 20 is responsible for the generation of infrared light, and is used to intermittently make the infrared light incident on the cell unit 30 and the detector unit 40 and a heater (light source) 21 that is a generation source for generating infrared light. And a chopper 22.

  The chopper 22 includes, for example, a two-bladed rotating disk formed with a notch partly cut out so as to allow light from the light source 21 to pass, and a motor that rotationally drives the rotating disk. It consists of and. By rotating the rotating disk with a motor, when the uncut portion (light shielding portion) of the rotating disk is positioned in front of the light source 21, the infrared light from the light source 21 is shielded and the notched portion. Is positioned in front of the light source 21, infrared light from the light source 21 passes through and is irradiated to the cell unit 30.

The cell part 30 is a part into which a sample gas is introduced, and the front and rear ends of the pipe 31 are sealed with an infrared transmissive window plate 32 such as glass or CF _{2 that} can transmit infrared rays in a wide spectral range. A gas outlet / inlet hole 33 is formed on the side surface of the pipe 31 so that the gas flows from one end to the other end. The inner surface of the pipe 31 is mirror-finished or coated with gold or the like in order to efficiently reflect infrared light.

The detection unit 40 includes a metal block 47, and a front chamber 41 and a rear chamber 42 in which a gas (sensitive gas) is sealed are formed in the block 47. In the front chamber 41 and the rear chamber 42, the boundaries between the chambers are partitioned by window plates 32, 45, and 46.
The gas sealed in the front chamber 41 and the rear chamber 42 is diluted with a high-concentration gas such as CO ₂ or an inert gas such as Ar, He, or N _{2 to} be measured by NDIR. Filled with gas.

  In NDIR, infrared light that has passed through the cell unit 30 into which the sample gas has been introduced enters the front chamber 41 and the rear chamber 42 of the detection unit 40, and the gas enclosed in the two front and rear chambers rises with infrared light. The gas is expanded by heating to increase the pressure. At this time, the front chamber 41 side is more pressurized than the rear chamber 42 side. By arranging a sensor 44 such as a flow sensor for detecting a pressure difference between the two front and rear chambers in a communication passage 43 that communicates with the front chamber 41 and the rear chamber 42, the pressure difference is detected by the sensor 44. This pressure difference depends on the intensity of infrared rays that pass through the sample gas. Since the intensity of infrared rays that have passed through the sample gas depends on the concentration of the infrared absorbing gas in the sample gas, the sample is based on the pressure difference detected by the sensor. The concentration of infrared absorbing gas in the gas can be measured.

  By the way, it is necessary to enclose gas (sensitive gas) in the front chamber 41 and the rear chamber 42 as described above. For this reason, the front chamber 41 and the rear chamber 42 are filled with gas so as to penetrate the wall surface of the block 47. Gas-filled flow paths 48 and 49 for the above are formed.

By the way, the gas filling into the front chambers 41 and 42 is performed as follows. Copper pipes 50 and 51 are bonded to the outer wall side of the gas-filled flow channels 48 and 49, and the copper pipes 50 and 51 are connected to a vacuum pump (not shown) and a gas cylinder for the sensitive gas.
First, the inside of the front chamber 41 and the rear chamber 42 is evacuated from the copper pipes 50 and 51 by a vacuum pump, and when the evacuation is finished, the gas (sensitive gas) is subsequently introduced into the front chamber 41 and the rear chamber 42 from the gas cylinder side. ).

  When the gas is filled, the copper pipes 50 and 51 are cut off at the outer positions 52 and 53 of the block 47. As a result, a gas having a specified concentration is sealed in the front chamber 41 and the rear chamber 42.

However, in the method of cutting and sealing the pipe, a load is applied to the bonding surface between the copper pipes 50 and 51 and the block 47 at the time of cutting and leakage tends to occur from there.
Further, even if no leakage occurs at the time of pressure cutting, since the protruding portion of the pipe remains, the leakage is likely to occur by colliding and breaking.
In addition, since the protruding portion is easily affected by the outside air temperature, a change in the gas volume due to the outside air temperature is supposed to deteriorate the performance of the analyzer.

Therefore, as another conventional example, as shown in FIG. 7, the balls 54 and 55 are press-fitted into the gas flow paths of the copper pipes 50 and 51 instead of being cut off and sealed. And is sealed. When sealing the ball by press-fitting, it is not sealed with the protruding copper pipe part, but in the circular hole (gas-filled flow path) formed by cutting in the metal case (block), the inner diameter of the hole It has been disclosed to press-fit a smooth hard ball having a surface having a larger diameter than that of a metal and having a hardness higher than that of a metal using a press (see, for example, Patent Document 1).
JP 2000-28520 A

As described above, by sealing the ball by press-fitting the ball into the gas-filled flow path formed in the block, there is no protruding copper pipe part, so there is no leakage caused by the copper pipe, and the influence of the outside air temperature. It becomes difficult to receive.
However, when the ball is press-fitted into the gas-filled flow path, the ball and the gas-filled flow path are in line contact, and if the gas-filled flow path at the contact portion is dirty or has a slight flaw, leakage is likely to occur. .
In addition, when the ball is suddenly pushed into the gas-filled flow path, the ball moves while the flow path is closed, and the pressure in the front chamber and the rear chamber changes. At this time, pressure shock is applied to the sensor. It will be. If a sensitive sensor such as a highly sensitive flow sensor is used, the sensor may be damaged when the ball is pressed.
In addition, when the ball moves in a state where the flow path is closed, the sealed gas pressure is increased.

Accordingly, an object of the present invention is to provide an infrared gas analyzer including a detection unit that is less likely to cause leakage of enclosed gas (sensitive gas) and is not easily affected by outside air temperature.
It is another object of the present invention to provide an infrared gas analyzer (NDIR) provided with a detection unit that does not easily change the pressure of the sealed gas during gas filling and does not damage the sensor or the like.

The infrared gas analyzer of the present invention made to solve the above problems is a measurement cell in which a sample gas is introduced into an infrared optical path guided from a light source, and a block formed adjacent to the measurement cell and passed through the measurement cell. An infrared gas analyzer including a detection unit for detecting infrared rays, wherein the detection unit includes a front chamber and a rear chamber surrounded by a wall surface of the block, a communication path communicating these two chambers, and a communication path And a sensor that detects a pressure difference between the front chamber and the rear chamber, and a gas passage that passes through the wall surface of the block and is closed after gas is sealed in the front chamber and the rear chamber. The gas-filled flow path has a step portion to which the plug is fixed, the outer surface is closed by a cylindrical plug, and the plug has a cylindrical shape on the outer surface and a hole is formed on the upper surface. Main body and fitting member to be fitted into the hole The outer diameter of the plug body is slightly smaller than the inner diameter of the gas-filled flow path when the fitting member is not fitted, and the outer face of the plug body is gas-filled with the fitting member fitted in the hole. It is to so that is formed so as to abut against the road inner surface.

According to this invention, the plug having the cylindrical outer surface is inserted into the gas-filled flow path that penetrates the wall surface of the block of the detection unit. As a result, since the gas-filled flow path and the outer surface of the plug are in surface contact, even if there is a place where the gas-filled flow path has dirt or slight scratches, it can be sealed in other places, A structure in which gas leakage is less likely to occur can be achieved.
In addition, there is a slight gap between the inner wall of the gas filling passage and the outer surface of the plug when the plug body is placed in the gas filling flow path, so that the sealed gas can escape from the gap, so that pressure shocks are generated in the front and rear chambers. No impact is applied to the communication path sensor. After inserting the plug body into the gas-sealed sealing path, the fitting member is fitted into the hole, so that the plug body expands in the radial direction and the outer diameter of the plug body increases to close the gas-filled flow path. .
Furthermore, by fixing the plug at the step portion, the movement in the axial direction can be completely prevented.

Moreover, you may make it an unevenness | corrugation be formed in a plug outer surface so that the part which contacts the inner wall of a gas enclosure flow path, and the non-contact part may be formed alternately.
According to this, the inner wall of the gas sealing channel and the outer surface of the plug are in contact with each other than the case where the entire outer surface is in surface contact due to the multiple sealing effect caused by the unevenness between the inner wall of the gas sealing channel and the outer surface of the plug. The sealing performance of the portion to be improved is improved, and a structure in which leakage does not easily occur can be achieved.

The plug and the block may be made of the same material or materials having substantially the same thermal expansion coefficient.
According to this, even if a temperature change occurs, the thermal expansion coefficients of the plug and the block are the same or substantially equal, so that the influence of heat at the seal portion is reduced, and the sealing performance is improved.
As a case where the thermal expansion coefficients are substantially equal, for example, a difference of about copper-SUS is sufficiently acceptable.

The hole on the upper surface of the plug body may have a tapered shape.
As a result, when the fitting member is fitted, the plug body effectively spreads in the radial direction and hardly moves in the axial direction, so that a pressure impact on the sensor is not further generated.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of an infrared gas analyzer (NDIR) according to an embodiment of the present invention.
The NDIR in FIG. 1 is roughly composed of a detection unit 10, a light source unit 20, and a cell unit 30. Among them, the light source unit 20 and the cell unit 30 are the same as those in the conventional example shown in FIG. Also, with respect to the detection unit 10, the same components as those in FIG.

The detection unit 10 includes an aluminum block 11. The block is not limited to aluminum but may be a metal such as copper or stainless steel.
In the block 11, a front chamber 41 and a rear chamber 42 are formed from the side close to the cell 30. The front chamber 41 is partitioned by window plates 32 and 45, and the rear chamber 42 is partitioned by window plates 45 and 46. These window plate 32,45,46 are CaF ₂ is used to transmit infrared.

  A communication passage 43 that communicates from the front chamber 41 to the rear chamber 42 is formed on the wall surface 42 of the block 11, and a sensor 44 is attached in the middle of the communication passage 43. The sensor 44 may be any sensor as long as it can detect a pressure difference between the two chambers. For example, a thin film type hot wire flow sensor is suitable.

Gas-filled flow channels 12 and 13 are formed so as to penetrate the wall surface of the block 11 from the front chamber 41. The inner diameter a of the gas sealing channel 13 is larger than the inner diameter b of the gas sealing channel 12, and a step is formed at the boundary between the gas sealing channel 13 and the gas sealing channel 12.
Similarly, the gas filling channels 14 and 15 are formed so as to penetrate the wall surface of the block 11 from the rear chamber 42, and the inner diameter c of the gas sealing channel 15 is made larger than the inner diameter d of the gas sealing channel 14. A step is formed at the boundary between the gas sealing channel 15 and the gas sealing channel 14.

  After the gas (sensitive gas) is sealed from the gas sealing channels 12 and 13 and the gas sealing channels 14 and 15 into the gas sealing channels 13 and 15, cylindrical plugs 16 and 17 are fitted, The flow path is closed.

  The plugs 16 and 17 are preferably made of the same material as that of the block 11 from the viewpoint of eliminating the influence of thermal expansion. For example, in the case of an aluminum block, an aluminum plug is preferably used. In addition, you may use materials with a similar thermal expansion coefficient like copper and SUS.

  When the plugs 16 and 17 are installed in the gas-filled flow channels 13 and 25, if the tips of the plugs 16 and 17 are brought into contact with the stepped portion of the flow channel, the volume of the sealed space becomes constant, The gas pressures in the front chamber 41 and the rear chamber 42 are desirable because they can be set with good reproducibility.

  The cylindrical plugs 16 and 17 can be easily sealed if a plug having an outer diameter slightly larger than the inner diameter a of the gas-filled flow path 13 is press-fitted. Therefore, when there is no particular influence on the sensor or the like, sealing can be performed without any problem even with this method.

However, since a pressure shock is applied to the sensor 44 when the plug is inserted, the sensor 44 may be damaged when the sensor 44 that is weak against pressure fluctuation is used.
Therefore, an embodiment of a plug sealing method that prevents pressure shock from being applied to the sensor 44 and an embodiment of the plug shape at that time will be described below.

  FIG. 2 is an enlarged cross-sectional view of a plug according to an embodiment of the present invention. The plug 18 includes a plug main body 1 having a cylindrical outer surface and a hole 2 formed on the upper surface, and an insertion member 3 that can be fitted into the hole 2 of the plug main body 1.

  The shape of the inner surface of the hole 2 and the shape of the outer surface of the fitting member 3 can be fitted to each other. The fitting member 3 expands the plug body 1 when the fitting member 3 is fitted into the hole 2 and plug body The dimensional relationship is such that the diameter of 1 slightly expands.

  In this embodiment, the inner surface shape of the hole 2 is a tapered hole, and the fitting member 3 has a tapered rod shape corresponding to the tapered hole. This is because the hole 2 and the fitting member 3 are formed into a tapered hole and a tapered rod shape so that the fitting member can be smoothly inserted into the plug body 1 when fitted.

  Further, a through hole 4 for venting gas is formed at the center of the fitting member 3 so that the gas is not confined when the fitting member 3 is fitted into the hole 2.

Next, a procedure for attaching the plug 18 shown in FIG. 2 to the gas-filled flow paths 13 and 15 will be described with reference to the drawings. 3 and 4 are diagrams for explaining a state when the plug 18 is inserted into the gas-filled flow path. When the plug 18 is inserted, as shown in FIG. 3, a sealing jig 60 comprising a container 61 in which a piping port 62 connected to the vacuum exhaust line and a piping port 63 connected to the gas filling line are formed. Is used.
In the container 61, the plug body 1 used for sealing and the fitting member 3 are held by a manipulator (not shown) in a separated state. By the operation of the manipulator, the plug body 1 and the fitting member 3 are sequentially placed in the gas-filled flow path. Can be pushed into.

The container 61 is brought into contact with the outer wall surface of the block 11 so as to cover the gas filling channels 13 and 15 (the gas filling channel 15 side is not shown).
The inside of the container 61 and the gas-filled flow paths 13 and 12, the front chamber 41, the communication path 43, and the rear chamber 42 are evacuated by a vacuum exhaust line connected to the piping port 62.

  When the evacuation is finished, the evacuation line is closed, the gas filling line is opened, and the gas (sensitive gas) is slowly introduced. Care should be taken not to cause large pressure fluctuations at this time. When the gas is filled to the desired pressure, the gas fill line is closed.

Subsequently, as shown in FIG. 4A, the manipulator is driven to send the plug body 1 into the gas-filled flow passages 13 and 15 so as to abut on the stepped portion as shown in FIG. 4B. At this time, since the outer diameter of the plug body 1 is smaller than the inner diameters of the gas-filled flow paths 13 and 15, a gap is generated between the inner wall of the gas-filled flow path 12 and the plug body 1, and the gap is interposed therebetween. Therefore, the pressure behind the gas-filled flow path 2 does not fluctuate.
Moreover, the pressure difference of both chambers does not arise by performing the above sealing process about the flow paths 13 and 15 simultaneously.

  Subsequently, in a state where the plug body 1 is fixed at the step portion, the manipulator is driven and inserted into the hole 2 of the plug member 3 plug body 1. As a result, as shown in FIG. 4C, the plug body 1 is expanded in the radial direction, and the outer surface of the plug body 1 and the inner wall surfaces of the gas-filled flow passages 13 and 15 are brought into surface contact with each other to cause leakage. A difficult seal is formed.

  FIG. 5 is an enlarged cross-sectional view of a plug body obtained by further improving the plug body 1 in FIG. In the plug body 5, a cylindrical tapered hole is formed, and a plurality of grooves 7 are cut in the circumferential direction on the outer surface of the hole 6. When the plug body 5 is inserted into the gas sealing flow paths 13 and 15 of FIG. 1 and the fitting member 3 of FIG. 2 is inserted into the hole 6, the inner walls of the gas sealing flow paths 13 and 15 and the uneven surface of the plug main body 19 are engaged. As a result, the sealing performance can be further improved.

  The present invention can be used when manufacturing an NDIR (infrared gas analyzer) in which leakage of gas sealed in the detection unit is unlikely to occur.

The block diagram of the infrared gas analyzer which is one Example of this invention. Sectional drawing of the plug used for the infrared gas analyzer which is another Example of this invention. The figure explaining the state when inserting a plug in a gas enclosure flow path. The figure explaining the state when inserting a plug in a gas enclosure flow path. Sectional drawing of the plug used for the infrared gas analyzer which is another Example of this invention. The block diagram of the conventional infrared gas analyzer. Conventional infrared gas analyzer detector.

Explanation of symbols

1: Plug body 2: Hole (tapered hole)
3: Insertion member (tapered rod)
5: Plug body 6: Hole 7: Groove 10: Detection unit 11: Block 20: Light source unit 30: Cell unit 41: Front chamber 42: Rear chambers 12, 13, 14, 15: Gas-filled flow channels 16, 17, 18, 19: Plugs 32, 45, 46: Window plate 43: Communication path 44: Sensor 60: Sealing jig 61: Container

Claims (4)

An infrared gas analyzer comprising a measurement cell in which a sample gas is introduced onto an infrared optical path guided from a light source, and a detection unit that is formed in a block adjacent to the measurement cell and detects infrared light that has passed through the measurement cell. And
A detection unit including a front chamber and a rear chamber surrounded by a wall surface of the block; a communication path communicating these two chambers; a sensor in the communication path for detecting a pressure difference between the front chamber and the rear chamber; A gas passage that passes through the wall of the gas chamber and is closed after the gas is sealed in the front chamber and the rear chamber,
The gas-filled flow path has a step portion to which the plug is fixed, the outer surface is closed by a cylindrical plug, the plug has a cylindrical shape on the outer surface, and a hole is formed on the upper surface. The plug body is inserted into the hole, and the outer surface diameter of the plug body is slightly smaller than the inner diameter of the gas-filled flow path when the insertion member is not inserted, and the insertion member is fitted in the hole. infrared gas analyzer outer surface of the plug body is characterized that you have been formed so as to contact the gas charging passage inner surface. 2. The infrared gas analyzer according to claim 1, wherein unevenness is formed on the outer surface of the plug so that a portion in contact with an inner wall of the gas-filled channel and a non-contact portion are alternately formed. The infrared gas analyzer according to claim 1, wherein the plug and the block are made of a material having the same thermal expansion coefficient. The infrared gas analyzer according to claim 1 , wherein the hole on the upper surface of the plug body has a tapered shape.

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