JP2006337068A - Method and apparatus for analyzing exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of analyzing exhaust gas capable of measuring the exhaust gas condition at a plurality of locations in an exhaust route and of measuring the relative changes in the condition of the exhaust gas. <P>SOLUTION: In the exhaust gas analyzing method, sensor parts 11-14, which are equipped with optical fibers 24A, 24B, etc. (irradiation parts) for irradiating the exhaust gas with the laser beams emitted from laser diodes LD1-LD5 and detectors 25 (light-detecting parts) for detecting the laser beams transmitted through the exhaust gas irradiated with the laser beams from the irradiation parts, are attached at a plurality of the places in the exhaust route, through which the exhaust gas discharged from an engine 2 flows to measure the condition of the exhaust gas. The outputs of a plurality sensors are input to a differential photodetector 40, to be subjected to signal analysis in a personal computer 45, and the condition of the exhaust gas (the concentrations or temperatures of the component of the exhaust gas) at a plurality of the places in the exhaust routes are relatively detected, on the basis of the sensor part at one of the locations among a plurality of the places. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for analyzing exhaust gas discharged from an internal combustion engine such as an automobile, and in particular, the concentration of components contained in exhaust gas passing through the exhaust path by attaching sensor units to a plurality of locations in the exhaust path. The present invention relates to an exhaust gas analysis method and an exhaust gas analysis device that accurately and in real time measures and analyzes temperature and temperature.

  Conventionally, as this type of exhaust gas analyzer, there is an in-vehicle HC measuring device described in Patent Document 1. This measuring apparatus includes an NDIR (non-dispersive infrared spectroscopy) gas analyzer for continuously measuring the concentration of HC (hydrocarbon) in exhaust gas flowing through an exhaust pipe connected to an engine, and exhaust gas flowing through the exhaust pipe. Exhaust gas flow meter that continuously measures the flow rate of gas, and calculation processing that calculates the THC (total hydrocarbons) amount in the exhaust gas continuously by calculating the output of each of the NDIR gas analyzer and the exhaust gas flow meter The circuit can be installed in the vehicle. In addition, the measurement method such as the NDIR type gas analyzer requires a reference gas for calibration and an auxiliary gas for use in analysis in all measurement principles.

JP 2004-117259 A

  By the way, the exhaust gas analyzer of the above-mentioned structure and the conventional exhaust gas measuring device of a general internal combustion engine collect a part of the exhaust gas and introduce it into a measuring instrument, and perform measurement by mixing dilution gas or the like. It is difficult to make it on-vehicle. And since this type of device measures only the exhaust gas discharged from the muffler, it can measure only the final exhaust form to be measured, and knows the relative concentration change of exhaust gas components, temperature change, etc. Can not.

  The present invention has been made in view of such problems, and the object of the present invention is to measure the state of exhaust gas at a plurality of locations in the exhaust path and determine the relative change in those measured values. The object is to provide a method for analyzing changes in the concentration of gas components contained in exhaust gas. That is, for example, sensors are attached before and after the catalyst device or before and after the muffler in the exhaust path, and the state of the exhaust gas in the middle of the exhaust path is measured using this sensor, and the relative change is obtained and analyzed. An object is to provide an exhaust gas analysis method and an exhaust gas analyzer.

  In order to achieve the above object, an exhaust gas analysis method according to the present invention includes an irradiation unit that irradiates a laser beam generated from a laser beam generation unit in an exhaust path through which an exhaust gas discharged from an internal combustion engine flows, and the irradiation unit. An exhaust gas analysis method for measuring a state of the exhaust gas by attaching a sensor unit including a light receiving unit that receives a laser beam irradiated from the unit and passing through the exhaust gas, and based on outputs of the plurality of sensor units Thus, the state of the exhaust gas at a plurality of locations in the exhaust path is relatively detected with reference to one of the plurality of locations. That is, for example, with reference to the output of the sensor part at the most upstream part, the outputs of a plurality of sensor parts are input to a differential photodetector, and signal analysis is performed by a personal computer to check the state of the exhaust gas component concentration, temperature, etc. Is calculated and detected relatively.

  The exhaust gas analysis method of the present invention configured as described above is based on the state of the exhaust gas in the exhaust path, for example, the concentration and temperature state of the exhaust gas, based on the upstream sensor unit, for example, by the sensor units installed at a plurality of locations. Can be measured and analyzed relatively. Since the relative value of the state of the exhaust gas measured in this way is measured by, for example, laser light supplied from one reference laser light generating means, the measurement accuracy is good and the state change in the exhaust path is high. The accuracy can be verified.

  As a preferred specific mode of the exhaust gas analysis method according to the present invention, it is preferable that the laser beams supplied to the plurality of sensor units are demultiplexed and supplied from a single laser beam generating unit. And it is preferable that the said single laser beam generation means is comprised by combining the laser beam which has the absorption wavelength matched with the several component of waste gas. According to this configuration, since the state of the exhaust gas is measured using the laser light generated from the single laser light generating means, it is possible to improve the relative detection accuracy. Moreover, the state of the several component of waste gas can be measured accurately.

  In another preferred embodiment of the exhaust gas analysis method according to the present invention, the plurality of sensor units reflect the laser light generated from the laser light generation unit in the exhaust gas, and then the light receiving unit. It is characterized by receiving light. If comprised in this way, since the laser beam irradiated in waste gas will be received by the light-receiving part after reflecting with a mirror etc., the permeation | transmission distance in the waste gas of laser light can be lengthened. As a result, the amount of attenuation due to the laser light passing through the exhaust gas increases, the ratio of the transmitted light intensity to the incident light intensity increases, and the concentration of the exhaust gas component can be measured with high accuracy.

Furthermore, as another preferable specific embodiment of the exhaust gas analysis method according to the present invention, the exhaust gas analysis method relatively measures concentrations of exhaust gas components at a plurality of locations as the state of exhaust gas in the exhaust path. Analysis. According to this configuration, the concentration of the component gas (for example, CO gas, CO ₂ gas, etc.) in the exhaust gas is continuously measured by the sensor units attached to a plurality of locations in the exhaust path, and the exhaust gas in the exhaust path is measured. The concentration state of the component can be verified. In particular, when a catalyst device is installed in the exhaust path, the performance and deterioration degree of the catalyst device can be determined by measuring the concentration of exhaust gas components before and after the catalyst device.

  Further, as the state of the exhaust gas, the exhaust gas state in the exhaust path may be configured to relatively measure and analyze the exhaust gas temperatures at a plurality of locations. In the thus configured exhaust gas analysis method, the temperature of the exhaust gas can be continuously measured by the sensor units installed at a plurality of locations in the exhaust path, and the high temperature exhaust gas discharged from the internal combustion engine is exhausted. The process of lowering the temperature in the route can be relatively determined.

  An exhaust gas analyzer according to the present invention includes a plurality of sensor units attached in an exhaust path through which exhaust gas discharged from an internal combustion engine circulates, and the exhaust path based on signals output from the plurality of sensor units. An apparatus for analyzing changes in component concentration in the exhaust process of exhaust gas components that circulate, wherein the plurality of sensor units each irradiate laser light, and a laser that is irradiated from the irradiation unit and passes through the exhaust gas A light receiving unit that receives light, and the laser beam emitted from the irradiation unit is supplied to each irradiation unit after being demultiplexed from a single light source. According to this configuration, since the laser light generated from a single light source is demultiplexed and supplied to the irradiation units of the plurality of sensor units, the change in the component concentration during the exhaust gas component discharge process is accurately measured and analyzed. can do.

  The exhaust gas analysis method and the exhaust gas analyzer of the present invention can measure the state of exhaust gas discharged from an internal combustion engine in the exhaust path, for example, the concentration of exhaust gas components and the exhaust gas temperature, and analyze in real time. As a result, it is possible to analyze in real time the state change such as how much the catalyst device is disposed upstream and downstream of the catalyst device that is disposed in the exhaust path and performs exhaust gas purification. Performance evaluation etc. can be judged instantly. Further, a relative change in the temperature of the exhaust gas in the exhaust path can also be detected.

  Hereinafter, an embodiment of an exhaust gas analysis method according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a main part configuration diagram in which an exhaust gas analyzer for carrying out an exhaust gas analysis method according to this embodiment is mounted on a vehicle, and FIG. 2 is a main part configuration in a state in which the exhaust gas analyzer of FIG. 1 is installed on an engine bench. FIG. 3 is an exploded perspective view showing a main part configuration of the sensor unit of the exhaust gas analyzer, and FIG. 4 is an overall configuration of the exhaust gas analyzer including a personal computer as a main part configuration of the laser oscillation / light receiving controller and a signal analysis unit. FIG.

  In FIG. 1, an exhaust gas analyzer that performs the exhaust gas analysis method of the present embodiment is an apparatus that analyzes exhaust gas discharged from an engine 2 installed in an automobile 1. Moreover, as shown in FIG. 2, it is an apparatus which analyzes the exhaust gas of the engine 2 installed in the engine bench 1A. The exhaust gas discharged from each cylinder of the engine 2 is merged in the exhaust manifold 3, introduced into the first catalyst device 5 through the exhaust pipe 4, further introduced into the second catalyst device 6, and then through the muffler 7 to the exhaust pipe 8. From the atmosphere. The exhaust path is formed by joining the exhaust manifold 3, the exhaust pipe 4, the first catalyst device 5, the second catalyst device 6, the muffler 7, and the exhaust pipe 8, and the exhaust gas discharged from the engine 2 is converted into the first catalyst device 5. Then, after purifying with the second catalyst device 6, the muffler 7 mute and reduce the pressure and release it into the atmosphere. The muffler may have two main mufflers and sub mufflers.

  The plurality of members constituting the exhaust path are basically pipe-like tube members, and are connected by bolts or the like with the flange portions in contact with each other. For example, the first catalyst device 5 has exhaust pipe portions connected upstream and downstream of a large-diameter main body portion, and flange portions F and F are fixed to the end portions of these exhaust pipe portions by welding or the like. The second catalyst device 6 also has an exhaust pipe connected to the upstream and downstream sides of the large-diameter main body, and flanges F and F are fixed to the ends of these exhaust pipes to connect the flanges. Thus, an exhaust path is configured. The exhaust pipe 8 at the end is fixed directly to the muffler 7 by welding or the like.

  The exhaust gas analyzer 10 of the present embodiment includes a plurality of sensor units 11 to 14 attached to a plurality of locations in the exhaust path. The first sensor unit 11 is installed between the exhaust pipe 4 on the engine side upstream of the first catalyst device 5, the second sensor unit 12 is installed on the downstream side of the first catalyst device 5, and the third The sensor unit 13 is installed on the downstream side of the second catalyst device 6. The fourth sensor unit 14 is installed in the exhaust pipe 8 downstream of the muffler 7. The sensor unit 14 may be installed in the middle of the exhaust pipe or may be installed by being inserted into the opening at the end of the exhaust pipe.

  As shown in FIG. 3, the exhaust pipe 4, the first catalyst device 5, the second catalyst device 6, and the muffler 7 are connected by tightening flange portions F and F with bolts (not shown). The sensor parts 11, 12, 13 installed between the members constituting the are installed in a state of being sandwiched between the flange parts F, F. The flange portions F and F are formed at both end portions of the member constituting the exhaust path, and the joint surfaces of the flange portions intersect at right angles to the center line of the exhaust path. As a result, the sensor parts 11 to 13 are installed so as to cross the exhaust path between the flange parts F and F. The fourth sensor unit 14 performs analysis immediately before the exhaust gas is released into the atmosphere. The fourth sensor unit 14 may be installed between the flanges F and F in the middle of the exhaust pipe 8 protruding from the main muffler 7. . In addition, what is necessary is just to set the number of installation of a sensor part arbitrarily.

  The sensor units 11 to 14 attached in the exhaust path have substantially the same configuration, and one sensor unit 11 will be described in detail with reference to FIGS. The sensor portion has a sensor base 21 formed of a plate material having a thickness of about 5 to 20 mm, for example, and a through hole 22 having a diameter substantially the same as the inner diameter of the exhaust pipe portion is formed in the center portion. The exhaust gas passing through the exhaust passage passes through the through hole 22. The shape of the through hole 22 is preferably a circle having the same diameter as the inner diameter of the exhaust pipe portion so as not to disturb the exhaust flow. A metal plate or a ceramic plate is used as the plate, but the material is not particularly limited. The sensor base 21 is formed with two sensor holes 21a and 21b penetrating from the outer peripheral surface toward the through hole. A collimator 23 for condensing laser light is fixed to one sensor hole 21a, an optical fiber 24 for irradiating the laser light is connected to the collimator, and a detector such as a photodiode for receiving the laser light is connected to the other hole 21b. 25 is fixed.

  In the through hole 22 of the sensor base 21, two upper and lower reflecting plates 26 and 27 are fixed facing each other. The two reflecting plates are fixed in a parallel state, and the infrared laser light condensed and emitted from the irradiation-side optical fiber 24 through the collimator 23 is first reflected upward by the lower reflecting plate 27, and then the upper The light is reflected downward by the reflection plate 26 and is alternately reflected by the two reflection plates 26 and 27 so as to reach the detector 25 on the light receiving side. In this manner, the transmission distance of the laser light in the exhaust gas is set to be long.

The reflectors 26 and 27 are preferably formed of materials that do not deteriorate due to exhaust gas. A thin film such as gold or platinum is formed on a base plate material, and a thin film of MgF ₂ or SiO ₂ is formed thereon as a protective layer. What is done is preferable. Further, it is desirable that the reflector has a high reflectance so that infrared laser light can be efficiently reflected. Since the reflector is exposed to the exhaust gas during engine startup and becomes contaminated, it is preferable to remove the sensor base 21 from the flange portions F and F for cleaning as necessary. By wiping the protective layer covering the reflective surface, the attached dirt can be easily cleaned, and the reflectance can be improved.

  The sensor base 21 is fixed in a state where it is sandwiched between the flange portions F, F, and a bolt, a nut, etc., not shown in the state where gaskets 28, 28 are sandwiched between the flange portions F, F and the sensor base 21. It is fixed by. The gasket 28 is made of asbestos or the like, and has a through hole having the same diameter as the inner diameter of the exhaust pipe. With this configuration, even if the exhaust path is connected with the sensor base 21 sandwiched between the flange portions F and F, the exhaust gas does not leak in the middle, and the increase in the length of the exhaust path is small. In FIG. 3, between the flange portion F welded to the downstream end of the exhaust pipe 4 and the flange portion F welded to the end portion of the exhaust pipe portion 5a on the upstream side of the first catalyst device 5, the gaskets 28, In this configuration, the sensor base 21 is fixed with 28 interposed therebetween.

  An optical fiber 24 that supplies laser light to the sensor unit 11 and a detector 25 that receives laser light that has passed through the exhaust gas by the sensor unit 11 and outputs an electrical signal are connected to a laser oscillation / light reception controller 30. That is, infrared laser light emitted from a laser diode (to be described later) of the laser oscillation / light reception controller 30 is irradiated into the through hole 22 through the sensor hole 21a of the sensor base 21 through the optical fiber 24 and reflected by the reflection surfaces 26 and 27. The infrared laser light thus received is received by the detector 25 on the light receiving side through the sensor hole 21 b, and an electric signal output from the detector 25 is input to the laser oscillation / light receiving controller 30 via the cable 29.

  The light emission intensity of the reference light of the infrared laser light emitted from the laser oscillation / light reception controller 30 and the light reception intensity of the signal light transmitted through the exhaust gas and received by the detector 25 are supplied to the personal computer 45 which is a signal analysis unit. The personal computer is configured to measure and analyze the concentration and temperature of the components contained in the exhaust gas. Thus, the exhaust gas analyzer 10 includes a plurality of sensor units 11 to 14, the laser oscillation / light reception controller 30, and the personal computer 45. The exhaust gas analyzer 10 introduces exhaust gas discharged from the engine into the through hole 22 of the sensor unit, irradiates the exhaust gas with laser light through the optical fiber 24, and receives the laser light transmitted through the exhaust gas with the detector 25. In this apparatus, the concentration of exhaust gas components and the like are measured and analyzed based on the received laser beam.

  Here, the laser oscillation / light reception controller 30 will be described with reference to FIG. The laser oscillation / light reception controller 30 supplies a plurality of frequency signals from a signal generator 31 such as a function generator to a plurality of laser diodes LD1 to LD5 as a laser beam generating means for generating infrared laser beams having a plurality of wavelengths. The laser diodes LD1 to LD5 respectively generate infrared laser beams having a plurality of wavelengths corresponding to the respective frequencies. Signals of a plurality of frequencies output from the signal generator 31 of the laser oscillation / light reception controller 30 are supplied to the laser diodes LD1 to LD5 to generate laser light. For example, LD1 has a wavelength of about 1300 to 1330 nm, and LD2 has a wavelength of 1330 to It is set to generate an infrared laser beam having a wavelength band such that the wavelength band in which the peak wavelength of the component gas to be detected exists, such as 1360 nm, continues.

The wavelength of the infrared laser beam that passes through the exhaust gas is set in accordance with the exhaust gas component to be detected. Carbon monoxide (CO), carbon dioxide (CO ₂ ), ammonia (NH ₃ ), methane (CH ₄ ), water When detecting (H ₂ O), infrared laser beams having five wavelengths are used. For example, the wavelength suitable for detecting ammonia is 1530 nm, the wavelength suitable for detecting carbon monoxide is 1560 nm, and the wavelength suitable for detecting carbon dioxide is 1570 nm. The wavelength suitable for detecting methane is 1680 nm, and the wavelength suitable for detecting water is 1350 nm. As described above, it is preferable to use a laser beam obtained by combining a plurality of types of single wavelength laser beams as the infrared laser beam transmitted through the exhaust gas. Furthermore, when detecting the concentration of other exhaust gas components, infrared laser beams having different wavelengths are used in accordance with the number of exhaust gas components. The laser diodes LD1 to LD5 constitute a single laser light generating means (single light source) having a plurality of types of wavelength bands.

  Laser light emitted from each of the laser diodes LD1 to LD5 is divided into reference light and signal light by optical fibers 32. Then, the signal laser light divided by the five demultiplexers 33... Is multiplexed by the multiplexers 36 A and 36 B through the optical fiber 35 A in which an optical attenuator 34 is installed on the way, and the sensor units 11-11 through the optical fiber 24. 14 is guided to the irradiation unit 14 and irradiated through the collimator 23 into the through hole 22. Further, the reference laser light divided by the five demultiplexers 33 is multiplexed by the multiplexer 37 through the optical fiber 35B. The signal and reference laser beams are infrared laser beams obtained by combining laser beams having a plurality of wavelengths in accordance with a plurality of component gases of the exhaust gas. In the present embodiment, the optical fiber 24 constitutes an irradiation unit that emits laser light. Thus, the laser beams generated from the laser diodes LD1 to LD5 constituting the single light source are demultiplexed by the demultiplexers 33 and supplied to the irradiation units of the plurality of sensor units 11 to 14.

  In the present embodiment, the signal laser light demultiplexed by the demultiplexer 33 as described above is configured to be multiplexed through the optical attenuator 34. The optical attenuator 34 has a function of adjusting the intensity of the signal laser light that is transmitted through the exhaust gas by controlling the light intensity of the signal laser light. That is, a feedback correction amount is calculated based on the light intensity of the transmitted laser light transmitted through the exhaust gas and the light intensity of the reference laser light, and this correction amount is input to the optical attenuator 34 to input the light of the signal laser light. Adjust the strength. The optical attenuator 34 is provided with a filter capable of changing the transmittance in the optical path of the laser light, adjusting the light intensity by changing the amount of transmitted light, and placing a mirror in the optical path, and changing the reflection angle of the mirror. The thing of appropriate forms, such as what adjusts light intensity, can be used. The optical attenuator may be configured to adjust the demultiplexed reference laser beam, or may be configured to adjust both the reference laser beam and the signal laser beam.

  In FIG. 4, two sensor units 11 and 12 among the four sensor units 11 to 14 illustrated in FIG. 1 are illustrated. That is, the laser beams emitted from the laser diodes LD1 to LD5 that generate the infrared laser beams in the five wavelength bands are combined by the two multiplexers 36A and 36B, and are applied to the irradiation units of the two sensor units 11 and 12. Supplied through optical fibers 24A and 24B. When there are 5 or more sensor units, use 5 or more multiplexers, and supply the signal laser beam from each multiplexer to the irradiation unit of the sensor unit using an optical fiber or the like. To do. Then, the electrical signals output from the two sensor units 11 and 12 are input to the differential photodetector 40 described later of the laser oscillation / light reception controller 30 via the cables 29A and 29B.

  The reference laser light supplied from the reference light multiplexer 37 through the optical fiber 38 is input to the differential photodetector 40 and converted into an electric signal by a photoelectric converter such as a photodiode. The differential photodetector 40 calculates a feedback correction amount so as to make the light intensity of the signal light constant based on the electrical signal of the signal laser light transmitted through the exhaust gas and the electrical signal of the reference laser light, The signal is input to the optical attenuator 34 disposed in front of the signal multiplexers 36A and 36B through the feedback line 41.

  The feedback correction amount is calculated for each component gas, supplied to the optical attenuator 34 for each signal light of the laser diode that generates the peak wavelength of the component gas, and adjusts and controls the light intensity of the signal light. The differential photodetector 40 inputs the electrical signals output from the plurality of sensor units to a personal computer 45 as a signal analysis unit that calculates the concentration and temperature of the exhaust gas components. Note that the reference light may not be directly input to the differential photodetector, but may be input after being converted into an electrical signal via a photodiode or the like.

  The optical attenuator 34 controls the laser diodes LD1 to LD5 so that the laser light generated from the laser diode is attenuated based on the supplied feedback correction amount so that the light intensity of the laser light becomes constant. An electric signal corresponding to the difference between the signal light and the reference light calculated by the differential photodetector 40 is amplified by, for example, a preamplifier (not shown), and a personal computer 45 that is a signal analysis unit via an A / D converter. In the personal computer, the data from the differential photodetector is converted into a concentration value to calculate the concentration of the exhaust gas component and the exhaust gas temperature.

  In place of the detector 25 fixed to the sensor base 21 as the light receiving part of the sensor parts 11 to 14, a light receiving optical fiber is fixed to the sensor base 21, and the received laser light is separated by a demultiplexer for each gas component. The output voltage of each gas component may be detected by a photodiode or the like, and the concentration of the exhaust gas component may be calculated by the personal computer 45 from the reference light and the signal light.

  The exhaust gas analyzer 10 of the present invention transmits, for example, infrared laser light into exhaust gas, calculates the concentration of exhaust gas components based on the intensity of incident light and the intensity of transmitted light after passing through the exhaust gas, Is to analyze. That is, the concentration C of the exhaust gas component is calculated from the following formula (1).

C = −ln (I / I ₀ ) / kL (1)
In Equation (1), I is the transmitted light intensity, I ₀ is the incident light intensity, k is the absorptance, and L is the transmission distance. Therefore, the concentration C of the exhaust gas component is calculated based on the ratio of the transmitted light intensity (I) to the incident light intensity (I ₀ ) and the signal intensity (I / I ₀ ). The transmitted light intensity I passes through the exhaust gas through the optical fiber 24 and is output from the detector 25, and the incident light intensity I ₀ is input from the multiplexer 37 through the optical fiber 38 to the differential optical detector 40 and is shown in the figure. Output from a non-photodiode. As the incident light intensity I ₀ in the present embodiment uses a signal light intensity that does not transmit the exhaust gas.

The exhaust gas analysis method of the present embodiment configured as described above will be described below. When analyzing the exhaust gas by measuring the concentration of the exhaust gas component, etc., the signal generator 31 of the laser oscillation / light-receiving controller 30 is operated, and a drive pulse of a predetermined frequency band is supplied to each of the laser diodes LD1 to LD5, Infrared laser light having a predetermined wavelength is generated from each of the laser diodes LD1 to LD5. The infrared laser light generated from each of the laser diodes LD1 to LD5 reaches the splitters 33 through the optical fibers 32, where it is split into signal light and reference light. The signal light demultiplexed by each demultiplexer is multiplexed by the multiplexers 36A and 36B through the optical attenuator 34 and the optical fiber 35A to become signal laser light, and the optical fiber 24 is applied to the irradiation parts of the sensor units 11-14. Is guided through. Further, the reference light demultiplexed by the demultiplexers 33... Is combined by the multiplexer 37 through the optical fiber 35B to become reference laser light, and is measured by the differential photodetector 40 as the incident light intensity I _0. The

And the signal laser beam irradiated to the sensor parts 11-14 from the optical fiber 24 is irradiated into the through-hole 22 through which the exhaust gas passes. The signal laser light is repeatedly reflected by the reflecting surfaces 26 and 27 and reaches the detector 25 of the light receiving section. The signal laser light attenuated through the exhaust gas is received as the transmitted light intensity I by the detector 25 which is a light receiving unit, converted into an electric signal, and input to the differential photodetector 40. The signal laser light is repeatedly reflected, so that the distance transmitted through the exhaust gas is increased, and the attenuation amount is increased by increasing the transmission distance L in the formula (1). It is possible to measure the concentration. Thus, the signal intensity which is the ratio (I / I ₀ ) between the light intensity I ₀ of the reference laser light and the transmitted light intensity I of the signal laser light is calculated, and the components of the exhaust gas are calculated based on this signal intensity ratio. The concentration of is calculated. The signal laser light is repeatedly reflected and attenuated by the reflection surfaces 26 and 27, but the light intensity received by the detector 25 is 30% or more of the light intensity irradiated from the optical fiber 24 without exhaust gas. It is preferable. This is because if it is less than 30%, it is difficult to distinguish the noise.

  In the differential photodetector 40, an optical attenuator 34 is used to calculate a feedback correction amount from the signal laser light that has been transmitted and attenuated through the exhaust gas and adjust the light intensity of the laser diodes LD1 to LD5 corresponding to each wavelength. Feedback control. The optical attenuator 34 adjusts the light intensity for each laser diode and calibrates the signal laser light. For example, when the signal light intensity decreases due to disturbance, the light intensity can be increased by automatically detecting and reducing the attenuation rate, and a balance equivalent to the initial state can be maintained. Note that. Since the reference light has no disturbance element from the generation to the reception of the laser light, and the reference light intensity does not change unless the laser output changes, it is preferable to adjust the signal light intensity with an optical attenuator to achieve a balance.

Further, the differential photodetector 40 takes a difference between the reference laser beam and the signal laser beam and supplies a signal to the personal computer 45 for signal analysis. The personal computer 45 calculates the ratio (I / I ₀ ) between the light intensity of the reference laser light and the light intensity of the peak wavelength of the signal laser light attenuated by passing through the exhaust gas, and the sensor unit is installed. The concentration of the component contained in the exhaust gas at a position in the exhaust path is calculated. Moreover, the relative change in the concentration of the components of the exhaust gas in the exhaust path can be analyzed by the sensor units 11 to 14 installed at a plurality of locations.

  In the present embodiment, a plurality of sensor units 11 to 14 are attached in the exhaust path, and the concentration and temperature of exhaust gas components at the position of each sensor unit are measured. Therefore, the concentration and temperature of the component gas in the downstream portion of the exhaust manifold 3 and the concentration and temperature of the component of the exhaust gas on the upstream side and downstream side of the first catalyst device 5 can be measured. For example, the performance of the catalyst devices 5 and 6 is evaluated based on the temperature after passing through the catalyst devices 5 and 6 and the concentration of the exhaust gas components, and the temperature before processing in the catalyst devices 5 and 6 and the concentration of the exhaust gas components. In addition, the deterioration of the catalyst device due to, for example, aging can be detected. In particular, a laser beam generated from a single laser beam generating unit composed of a plurality of laser diodes LD1 to LD5 is demultiplexed and supplied to the irradiation units of the plurality of sensor units 11 to 14, and the component gas concentration or Since the temperature is measured, the gas concentration and the like in each sensor unit can be measured with relatively high accuracy, and accurate analysis is possible.

  Next, the operation for measuring the temperature using the exhaust gas analyzer of the present embodiment will be described. Each gas has its own absorption wavelength band, and many absorption lines exist in the absorption wavelength band, for example, as shown in FIG. FIG. 5a shows the signal intensity at the low temperature (= number of molecules), and FIG. 5b shows the signal intensity at the high temperature. Thus, since the signal intensity changes depending on the temperature, the temperature of the exhaust gas at the time of measurement can be calculated by measuring the signal intensity ratio. In FIG. 5, the horizontal axis indicates the wavelength λ, and the vertical axis indicates the signal intensity. The temperature of the exhaust gas thus calculated can also be measured with high accuracy because the infrared laser light irradiated to the exhaust gas is stable.

  In the exhaust gas analysis method of the present invention, the concentration and temperature of exhaust gas components are measured by the first sensor unit 11, and the concentration and temperature of exhaust gas components are also measured by the second sensor unit 12. The concentration and temperature of the exhaust gas components are also measured in the third to fourth sensor portions 13 and 14. As a result, it is possible to easily determine a state in which the concentration of the exhaust gas component relatively changes in the first to fourth sensor units. Further, the temperature can be easily determined by measuring the temperature at each location by the first to fourth sensor units and changing in the exhaust path. As described above, in the present embodiment, the sensor units 11 to 14 installed at the four locations can easily detect the relative values of the concentrations of the exhaust gas components and the relative values of the temperatures at the four measurement locations.

  That is, in the first sensor unit 11, the concentration of a certain component of the exhaust gas is (C1) PPM, for example, and the temperature is (T1) ° C., and in the second sensor unit 12, the concentration of the component of the exhaust gas is (C2 ) PPM, the temperature is (T2) ° C., and in the third sensor unit 13, the concentration of a certain component of the exhaust gas is (C3) PPM, the temperature is (T3) ° C., and the fourth sensor unit 14 The concentration and temperature of the exhaust gas component of each sensor unit are calculated such that the concentration of a certain component of the exhaust gas is (C4) PPM and the temperature is (T4) ° C.

  From these values, the personal computer 45 determines, for example, about 60 after passing through the first catalyst device 5 when the concentration of the exhaust gas component is 100% (reference value) at the location of the first sensor unit 11. %, And after passing through the second catalyst device 6, the relative value is calculated so as to reduce to about 10%, for example. Further, regarding the temperature that is one of the states of the exhaust gas, when the temperature in the first sensor unit 11 is, for example, 700 ° C., the temperature in the second sensor unit 12 is reduced by 50% to about 350. It can be evaluated by a relative value such that the temperature is reduced by 80% at the third sensor unit 13 to about 140 ° C., and the fourth sensor unit 14 is reduced by 95% to about 35 ° C. In addition, although the sensor part used as a reference | standard among several sensor parts is a thing on the uppermost stream side, you may make another sensor part into a reference | standard. The relative value indicating the state of the exhaust gas calculated in this way is measured by the laser beam supplied from the laser beam generating means that combines the infrared laser beams generated from the laser diodes LD1 to LD5. The accuracy is high and the state of the exhaust gas can be detected with high accuracy.

  As described above, the exhaust gas analyzing method and the exhaust gas analyzing apparatus of the present invention combine signal laser light from a plurality of laser diodes, and use the combined single laser light to output signals to a plurality of sensor units. Since the reference laser beam is supplied to the differential optical detector 40, the concentration and temperature of exhaust gas components can be measured at multiple locations using laser beams having the same phase and wavelength. Good relative exhaust gas component concentrations and temperatures can be measured, and exhaust gas analysis accuracy can be improved. Thereby, the state of exhaust gas in the entire exhaust path can be relatively analyzed, and reduction of exhaust gas, evaluation of the catalyst device, and the like can be determined instantaneously.

  Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention described in the claims. Design changes can be made. For example, nitrogen oxide (NOx) can be measured as a component gas of exhaust gas. In this case, as a matter of course, a wavelength (for example, 1800 nm) suitable for NOx is used as the infrared laser beam that passes through the exhaust gas. The laser light emitted from the irradiation unit is not limited to infrared laser light, and may be visible laser light or ultraviolet laser light.

  An example was shown in which a laser beam irradiation unit was attached to the sensor base of the sensor unit via an optical fiber, and a photodiode was fixed to the sensor base as a light receiving unit. However, an irradiation unit such as a laser diode was directly attached to the sensor base. And it is good also as a laser beam irradiation part. Alternatively, the detector that is the light receiving unit may not be directly fixed to the sensor base, but the optical fiber may be fixed and guided to the detector. The optical attenuator may be installed not on the signal laser beam side but on the reference laser beam side.

Moreover, although the example which forms the thin film of gold | metal | money or platinum as a reflective surface was shown, thin films, such as a titanium oxide, may be formed, and if it is excellent in heat resistance and can be mirror-finished, a material will not be specified. The reflecting surface may be formed directly on the inner surface of the through hole through which the exhaust gas flows without using a reflecting plate such as a mirror. In this case, after reflecting the inner peripheral surface of the through hole, the reflection surface may be formed by a technique such as plating or vapor deposition. The reflecting surface may be a gold or platinum thin film formed by polishing the inner peripheral surface of the through-hole without using a mirror or the like, and a MgF ₂ or SiO ₂ thin film is formed thereon as a protective layer. Also good. Thereby, the structure of a reflective surface can be simplified.

  In the above-described embodiment, the configuration in which the sensor unit is installed on the downstream side of the exhaust manifold is shown, but the sensor unit may be installed between the exhaust manifold and the cylinder block of the engine. If comprised in this way, the density | concentration and temperature of the component of the exhaust gas for every cylinder of an engine can be measured, for example, the cause of engine malfunction etc. can be judged for every cylinder. In particular, since the exhaust gas analyzer of the present invention detects the concentration of exhaust gas components using laser light transmission without using a reference gas or the like, it has a feature that can be measured even at high temperatures. Measurement of the concentration of the exhaust gas component at a high temperature of about 800 ° C. can be performed with high accuracy.

  As an application example of the present invention, this exhaust gas analyzer can be used for exhaust gas analysis of combustion devices such as boilers, and in addition to automobile exhaust gas analysis, it can also be applied to exhaust gas analysis applications of internal combustion engines used in ships and the like it can.

The principal part block diagram of one Embodiment which mounted the exhaust gas analyzer which implements the exhaust gas analysis method which concerns on this invention in a vehicle. The principal part block diagram of embodiment which mounted the exhaust gas analyzer of FIG. 1 in the engine bench. The disassembled perspective view which shows the principal part structure of a sensor part. The block diagram which shows the whole structure of the exhaust gas analyzer containing the principal part structure and signal analysis part of a laser oscillation and light reception controller. The influence of the temperature of an absorption spectrum is shown, (a) is explanatory drawing of signal intensity at the time of low temperature, (b) is explanatory drawing of signal intensity at the time of high temperature.

Explanation of symbols

  1: automobile, 1A: engine bench, 2: engine (internal combustion engine), 3: exhaust manifold (exhaust path), 4: exhaust pipe (exhaust path), 5: first catalyst device (exhaust path), 6: second Catalyst device (exhaust path), 7: Muffler (exhaust path), 8: Exhaust pipe (exhaust path), 10: Exhaust gas analyzer, 11-14: Sensor unit, 24A, 24B ...: Optical fiber (irradiation unit), 25 : Detector (light receiving unit), 26, 27: reflector, 29, 29A, 29B ...: cable, 30: laser oscillation / light receiving controller, 31: signal generator, 33: branching filter, 34: optical attenuator, 36A , 36B..., 37: multiplexer, 40: differential optical detector, 41: feedback line, 45: personal computer (signal analysis unit), LD1 to LD5: laser diode (laser light generating means)

Claims (7)

An irradiating unit for irradiating laser light generated from laser light generating means in an exhaust path through which exhaust gas discharged from an internal combustion engine flows, and a light receiving unit for receiving laser light irradiated from the irradiating unit and transmitted through the exhaust gas The exhaust gas analysis method for measuring the state of the exhaust gas, attached to a plurality of sensor parts comprising:
An exhaust gas analysis method, wherein, based on outputs of the plurality of sensor units, exhaust gas states at a plurality of locations in the exhaust path are relatively detected with reference to one of the plurality of locations.   The exhaust gas analysis method according to claim 1, wherein the laser beams supplied to the plurality of sensor units are demultiplexed and supplied from a single laser beam generation unit.   3. The exhaust gas analysis method according to claim 1, wherein the single laser light generation unit is configured by combining laser beams having absorption wavelengths matched to a plurality of components of the exhaust gas.   The exhaust gas according to any one of claims 1 to 3, wherein the plurality of sensor parts reflect the laser light generated from the laser light generating means in the exhaust gas and then receive the light at the light receiving part. Analysis method.   The exhaust gas analysis method according to any one of claims 1 to 4, wherein the exhaust gas analysis method performs analysis by relatively measuring concentrations of exhaust gas components at a plurality of locations as a state of the exhaust gas in the exhaust path. Analysis method.   The exhaust gas analysis method according to any one of claims 1 to 4, wherein the exhaust gas analysis method performs analysis by relatively measuring exhaust gas temperatures at a plurality of locations as a state of exhaust gas in the exhaust path. Components in the exhaust process of exhaust gas components that circulate in the exhaust path based on signals output from the plurality of sensor parts attached to the exhaust path through which the exhaust gas discharged from the internal combustion engine circulates An exhaust gas analyzer for analyzing changes in concentration,
Each of the plurality of sensor units includes an irradiation unit that irradiates a laser beam, and a light receiving unit that receives the laser beam irradiated from the irradiation unit and transmitted through the exhaust gas,
The exhaust gas analyzing apparatus, wherein the laser beam emitted from the irradiation unit is demultiplexed and supplied from the single light source to each irradiation unit.

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