JP5339046B2 - Laser gas analyzer - Google Patents

Description

  The present invention relates to a laser-type gas analyzer, and more particularly to a laser-type gas analyzer provided with a mechanism for adjusting an optical axis between a laser beam emitted from a light projecting unit module and a light receiving element provided in the light receiving unit module.

  Laser type gas analyzers are known as analyzers for detecting various gas concentrations such as CO and NO. This analyzer utilizes the fact that laser light is irradiated into a measurement gas atmosphere and the laser light is absorbed by molecules / atoms present in the optical path of the laser light.

  A laser analyzer that realizes the laser absorption method includes a laser light source that irradiates measurement laser light into a measurement gas atmosphere, a laser light detector (light receiving element) that detects the measurement laser light transmitted through the measurement space, and And an arithmetic processing unit that processes the output signal of the laser light detector.

  As a prior art of such a laser analyzer, for example, a laser analyzer shown in FIG. 3 is known. FIG. 3 is a block diagram of a conventional laser analyzer. In FIG. 3, reference numeral 1 denotes a pipe through which the measurement gas 2 flows. In the middle of the pipeline 1, fixed flanges 3a and 3b are arranged opposite to each other through conduits 4a and 4b.

  Reference numeral 10a denotes a light projecting unit module having a mounting flange 6a fixed at one end, and is composed of an optical axis adjusting unit 7 incorporating a laser light source (LD) 5 and a light projecting side case 8. Reference numeral 10b denotes a light-receiving unit module having a mounting flange 6b fixed at one end, and includes a detector unit 11 incorporating a photodiode (PD) 7 and a light-receiving side case 9. A control unit / display unit 13 controls the output of the LD 5 and displays the output of the PD 7.

  In the above-described configuration, the measurement laser light A output from the LD 5 is applied to the measurement gas 2 flowing in the pipe 1 and enters the PD 7 that constitutes the light receiving unit module 10b disposed to face the measurement gas 2.

  In this measurement, the measurement laser beam is absorbed by gas or the like on the optical path, and the concentration or the like is detected by utilizing the fact that the amount of absorption is related to the concentration of the gas or the like. That is, the measurement laser beam is irradiated to the measurement space while continuously changing the wavelength (modulating), and the output signal of the PD 7 obtained as a result is an arithmetic processing unit (not shown) constituting the control unit. The data of the molecule / atom that is the detection target is obtained by analyzing and calculating with.

The following patent documents are known as prior art relating to such a laser gas analyzer.
JP 2002-277391 A JP 2007-170841 A JP 2008-116368 A

  By the way, the laser gas analyzer having the above-described configuration is directly installed at a location where exhaust gas flows, such as a flue, and its optical path length may be about 1 m to 10 m. It is necessary to adjust the optical axis by mechanically positioning the light emitting portion.

  Such an adjustment mechanism will be described with reference to the drawings. FIG. 4 is a configuration diagram of an adjustment mechanism of a conventional laser analyzer. As shown in FIG. 4, for example, a fixing flange 3 is fixed to a pipe wall of a duct (smoke) 1 by welding or the like via a conduit 4, and the mounting flange 6 is attached to the fixing flange 3 via an O-ring 14. Fixed.

  Thus, the presence of the O-ring 14 sandwiched and fixed between the fixed flange 3 and the mounting flange 6 causes the measurement gas 2 in the pipe (flue) 1 to leak out, or the pipe 1 Outside air is prevented from entering inside.

  The fixing flange 3 and the mounting flange 6 are attached to both sides of the light projecting unit module 10a and the light receiving unit module 10b. The LD 5 is fixed to the light projecting unit module 10a. Note that the structure shown in FIG. 4 is the simplest structure for explanation, and is omitted in the figure, but the PD 7 is the same on the light receiving unit module 10b side due to the fixing flange 3, the O-ring 14, and the mounting flange 6. The position can be adjusted by a simple mechanism.

  Next, adjustment will be described. The fixing flanges 3 on the light projecting unit module 10a side and the light receiving unit module 10b side are several meters apart and are welded to the tube wall of the pipe 1 so that the optical axes of the laser beams are perfectly aligned. It is practically impossible to fix with high accuracy.

  Therefore, it is necessary to adjust the optical axis. In this optical axis adjustment, paying attention to the fact that the mounting flange 6 can be moved by the elasticity of the O-ring 14, the mounting flange 6 is tilted in the direction of arrow B with respect to the fixed flange 3 by the adjusting screw 15, and the mounting flange is moved. The angle of the optical axis is adjusted by tilting the LD 5 and the PD 7 attached to 6 (see FIG. 3).

  However, in such an optical axis adjustment mechanism that uses the elasticity of the O-ring 14, the optical axis angle that can be tilted is only about a few degrees, so the adjustment capability is low, and in particular, the fixing flange 3 that has low mounting accuracy by welding is used as a reference. Therefore, there is a problem that the optical axis may not be aligned.

  Further, when the pipe line 1 is vibrated due to an earthquake or a collision, the adjusting screw 15 is also vibrated, and the mounting flange 6 moves to cause a deviation in the optical axis, resulting in a decrease in measurement accuracy.

  In such a laser gas analyzer, when adjusting the optical axis, it is important to align the optical axis while monitoring the amount of light transmitted from the detector. In the conventional apparatus shown in FIG. There is no unit that shows the “transmitted light amount” that can be recognized by the operator in both the unit units on the side and the light receiving side. Therefore, it is necessary for an operator to make an adjustment while another person confirms the values on the control unit and the display unit. Although there is a device that adjusts the optical axis by a visible LED, there is a problem that exact optical axis alignment cannot be performed due to a difference in refractive index because the wavelength band is different between the wavelength of the LED and the wavelength of the LD.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide an LD output unit and an LD light receiving unit in which the optical axis adjustment range is widened with a simple configuration. Furthermore, a laser-type gas analyzer that is equipped with such an LD light output unit and an LD light receiving unit to improve measurement accuracy and adjust the optical axis in the field can be operated by one person to save labor. It is to provide.

The present invention was made to solve the above problems, and in the invention of the laser type gas analyzer according to claim 1,
In the laser type gas analyzer that irradiates the measurement gas with laser light and measures the gas concentration from the change in the amount of light due to light absorption of the laser light.
A fixed flange disposed to face the pipe through which the measurement gas flows, and a light projecting unit module and a light receiving unit module fixed to the fixed flange via a mounting flange,
A connecting pipe having a predetermined length, which constitutes the light projecting module or the light receiving module and fixed to the mounting flange, and is arranged in at least one of these connecting pipes, and either the laser or the light receiving element is fixed. An inner pipe having a predetermined length,
A plurality of push screws which are screwed in from the outer periphery of the connecting pipe and support the inner pipe at a predetermined angle with respect to the longitudinal direction of the connecting pipe ;
A seal ring that is formed near both ends of the inner tube, and that tightly fixes the outer periphery of the inner tube and the inner periphery of the connection tube;
A retaining ring formed along both sides of the outer periphery of the seal ring;
An elastic member is provided in the holding ring so as to be in airtight contact with the inner periphery of the connection pipe, and the hollow portion is filled with gas .

In claim 2, in the laser type gas analyzer according to claim 1,
End The lasers of the inner tube, the other end collimating lens is disposed in an air-tight through hole for purging a gas the space formed by the collimating lens disposed on the laser and the other end Is provided.

In Claim 3, in the laser type gas analyzer of Claim 1,
Two sets of the plurality of push screws are provided at a predetermined distance on the outer periphery of the connecting pipe as a set, and each of the set of screws is located at the position where the outer periphery of the connecting pipe is equally divided. It is characterized by supporting the tube.

In claim 4 , in the laser type gas analyzer according to claim 1,
An indicator for monitoring the output of the light receiving element is provided in the light projecting unit module and the light receiving unit module.

As is apparent from the above description, according to claims 1 to 4 of the present invention, a plurality of push screws that are screwed in from the outer periphery of the connection pipe and support the connection pipe at a predetermined angle are provided.
A laser is arranged at one end of the inner tube, and a collimating lens is hermetically arranged at the other end, and a through hole for purging the space formed by the laser and the collimating lens arranged at the other end with gas is provided. Compared to the conventional example, the optical axis adjustment range can be expanded , the space between the laser and the collimating lens can be kept clean, and a highly accurate laser gas analyzer can be realized.

According to claim 4 , since the indicator for monitoring the output of the light receiving element is provided in at least one of the light projecting unit module and the light receiving unit module, the laser gas analyzer that saves the optical axis adjustment work is provided. Can be realized.

FIG. 1A and FIG. 1B show an example of an embodiment of a laser type gas analyzer of the present invention. FIG. 1A is a main part configuration diagram, and FIG. 1B is a diagram of FIG. FIG.
In these figures, the same elements as those of the conventional example shown in FIG.
In FIG. 1A, reference numeral 20a denotes a light projecting module, which is composed of a light projecting side case 18 fixed to one end of a connecting pipe 21a and a mounting flange 6a. The mounting flange 6a is attached to the fixed flange 3a. ing. Similarly, the light receiving unit module 10b is also composed of a light receiving side case 19 fixed to one end of the connecting pipe 21b and a mounting flange 6b, and the mounting flange 6a is mounted to the fixed flange 3a.

  FIG. 1B shows an enlarged cross-sectional view of the connecting tube 21a constituting the light projecting unit module 20a. In the connecting tube 21b constituting the light receiving unit module 20b, the LD is a PD, and the collimating lens is a condensing lens. The configuration is the same except that is different. Here, the configuration of the light projecting unit module 20a will be described.

  In the connecting pipe 21a, an inner pipe 22 having a predetermined length which is the same as or slightly shorter than the connecting pipe 21a is disposed near the center in the longitudinal direction. Reference numeral 23 denotes a set screw provided penetrating from the outer periphery to the inner periphery of the connection pipe 21a. In the figure, four screws are provided as a set, and two sets are provided on the outer periphery of the connection pipe 21a at a predetermined distance. Each of the screws in the set supports the inner tube 22 at a position obtained by dividing the outer periphery of the connecting tube into four equal parts.

  An LD 5 is disposed at one end of the inner tube 22 and a collimator lens 24 is disposed at the other end in an airtight manner. Reference numerals 25a and 25b denote through-holes formed on the outer periphery of the connecting pipe 21a at a predetermined distance, and reference numerals 26a and 26b denote through-holes formed on the outer periphery of the inner pipe at a predetermined distance.

  Reference numeral 27 denotes a seal ring formed on the outer periphery in the vicinity of both ends of the inner tube 22. The inner periphery of the seal ring 27 and the outer periphery of the inner tube 22 are fixed in an airtight manner. Reference numeral 28 denotes a holding ring formed along both sides of the outer periphery of the seal ring, and an elastic member (for example, rubber) 29 is disposed along the outer periphery of the seal ring 27 in the holding ring 28. The rubber 29 is formed in a hollow shape, and the hollow portion is filled with a gas. The outer periphery of the hollow rubber is disposed so as to be in airtight contact with the inner periphery of the connection pipe 21a.

  According to the above-described configuration, the angle of the inner tube 22 can be freely moved up and down and left and right by adjusting a set of four push screws arranged opposite to each other at a predetermined distance. It is. If the outer periphery of the rubber is pressed and the outer periphery of the holding ring 28 comes into contact with the inner periphery of the connecting pipe 21a and cannot be adjusted, the angle adjustment range can be expanded by injecting gas into the rubber 29 and expanding it. be able to.

  In addition, if air is injected in the direction of the arrow A through the through hole 25a formed in the outer periphery of the connection pipe 21a and discharged in the direction of the arrow B, the space formed by the LD 5 and the collimator lens 24 of the inner pipe 22 is purged and cleaned. It is possible to prevent the deterioration of accuracy caused by the entry of different gases into the space.

  FIG. 2 shows an embodiment related to claim 6. In this example, inner tubes are arranged in both the light emitting side module 20a and the light receiving side module 20b. An indicator 30 for monitoring the output of the PD (light receiving element) is provided in the light projecting module 20a and the light receiving module 20b (wiring is omitted).

  According to the configuration of FIG. 2, since the indicator 30 for monitoring the output of the PD (light receiving element) is provided in the light projecting unit module 20a and the light receiving unit module 20b, the LD5 is adjusted by adjusting the push screw 23 shown in FIG. It can be observed on both the light-projecting side and the light-receiving side whether or not the light from the laser beam is correctly irradiating the PD 7. As a result, when the optical axis is adjusted in the field, it is possible to work alone, and it is possible to realize a laser gas analyzer that saves labor.

  The above description merely shows a specific preferred embodiment for the purpose of explanation and illustration of the present invention. In FIG. 1, the inner tube 22 is provided only in the light projecting unit module 20a. However, a similar inner tube may be provided in the light receiving unit module 20b to align the optical axes in both. In FIG. 2, the indicator 30 is provided on both the light projecting unit module 20a and the light receiving unit module 20b, but it may be provided on only one side. Therefore, the present invention is not limited to the above-described embodiments, and includes many changes and modifications without departing from the essence thereof.

It is a principal part block diagram which shows an example of embodiment of the laser type gas analyzer of this invention, and a principal part cross-sectional enlarged sectional view. It is a principal part block diagram which shows the state which provided the indicator for monitoring in the light emission side module and the light reception side module. It is a principal part block diagram which shows an example of the conventional laser type gas analyzer. It is a principal part structure of the conventional optical axis alignment.

Explanation of symbols

1 Pipeline 2 Measuring gas 3 Fixed flange 4 Conduit 5 Laser diode (LD)
6 Mounting flange 7 Photodiode (PD)
8, 18 Emitting side case 9, 19 Receiving side case 10a, 20a Emitting unit module 10b, 20b Receiving unit module 11 Detector unit 14 Ring 15 Adjustment screw 21 Connection tube 22 Inner tube 23 Press screw 24 Collimating lens 25, 26 Hole 27 Seal ring 28 Retaining ring 29 Elastic body (rubber)
30 indicator

Claims (4)

In the laser type gas analyzer that irradiates the measurement gas with laser light and measures the gas concentration from the change in the amount of light due to light absorption of the laser light.
A fixed flange disposed to face the pipe through which the measurement gas flows, and a light projecting unit module and a light receiving unit module fixed to the fixed flange via a mounting flange,
A connecting pipe having a predetermined length, which constitutes the light projecting module or the light receiving module and fixed to the mounting flange, and is arranged in at least one of these connecting pipes, and either the laser or the light receiving element is fixed. An inner pipe having a predetermined length,
A plurality of push screws which are screwed in from the outer periphery of the connecting pipe and support the inner pipe at a predetermined angle with respect to the longitudinal direction of the connecting pipe ;
A seal ring that is formed near both ends of the inner tube, and that tightly fixes the outer periphery of the inner tube and the inner periphery of the connection tube;
A retaining ring formed along both sides of the outer periphery of the seal ring;
A laser-type gas analyzer comprising an elastic member disposed in the holding ring so as to be in airtight contact with the inner periphery of the connection pipe and having a hollow portion filled with gas. End The lasers of the inner tube, the other end collimating lens is disposed in an air-tight through hole for purging a gas the space formed by the collimating lens disposed on the laser and the other end The laser gas analyzer according to claim 1, wherein:   Two sets of the plurality of push screws are provided at a predetermined distance on the outer periphery of the connecting pipe as a set, and each of the set of screws is located at the position where the outer periphery of the connecting pipe is equally divided. The laser gas analyzer according to claim 1, wherein the tube is supported. The laser gas analyzer according to claim 1 , wherein an indicator for monitoring an output of the light receiving element is provided in the light projecting unit module and the light receiving unit module .

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