JP4566070B2 - Exhaust gas analyzer - Google Patents

Description

  The present invention relates to an exhaust gas analyzer that analyzes components contained in exhaust gas discharged from an internal combustion engine such as an automobile.

Conventionally, as this type of exhaust gas analyzer, in the high-speed measurement method of temperature, concentration, and chemical species using semiconductor laser spectroscopy described in Patent Document 1, a collimator is provided as a probe in the exhaust pipe, and a mirror is provided. The temperature and concentration of various combustion products such as H ₂ O, CO ₂ and NO contained in the exhaust gas can be measured.

  In this type of measuring device, when incident light having a wave number v is incident on the gas in the cell from the semiconductor laser, the incident light is absorbed by the gas and received by the light receiving element. Attenuates with respect to incident light according to the law. For this reason, it is possible to increase the attenuation by increasing the transmission distance of the laser light in the gas, thereby enabling accurate measurement. In order to increase the transmission distance, in this type of measuring apparatus, the laser beam is reflected in the gas a plurality of times to increase the attenuation.

  Further, there are various exhaust gas measuring devices and analyzers using NDIR (Non-Dispersive Infrared Analyzer) non-dispersive infrared spectroscopy, FID (Frame Ionization Detector) method, CLD (Chemical Luminescence Detector) method and the like. These measurement methods require a reference gas for calibration and an auxiliary gas for use in analysis in all measurement principles.

JP 2000-74830 A ([0045], [0012])

  By the way, in the exhaust gas high-speed measurement method described in Patent Document 1, exhaust gas dirt adheres to the reflective surface that reflects the laser beam for measurement, and the reflectivity decreases. As a result, the exhaust gas temperature, concentration, chemical There was a risk that the measurement accuracy of seeds and the like would be reduced, and accurate analysis could not be performed. In particular, when the measurement takes a long time, the reflectance decreases with the passage of time, and therefore, the accuracy over a long period of measurement may not be constant between the initial stage and the late stage of the measurement.

  The present invention has been made in view of such problems. The object of the present invention is to reflect a measurement laser beam that is transmitted through exhaust gas, receive the reflected light, and convert the reflected light into the reflected light. An exhaust gas analyzer that measures the temperature, concentration, chemical species, etc. of exhaust gas based on the above, and to provide an exhaust gas analyzer that stabilizes the measurement accuracy by reducing the loss of reflection by keeping the reflective surface clean. .

In order to achieve the above object, an exhaust gas analyzer according to the present invention receives laser light generating means for generating laser light, a reflecting surface for reflecting the generated laser light, and laser light reflected by the reflecting surface. And receiving the laser beam through the exhaust gas discharged from the internal combustion engine, and measuring the concentration and temperature of the components of the exhaust gas based on the received transmitted laser beam to analyze the exhaust gas The apparatus further comprises a photocatalyst layer formed on the surface of the reflecting surface, and a light beam generating means for generating a light beam for irradiating the photocatalyst layer, and a plurality of locations in the exhaust path through which the exhaust gas flows. The sensor unit includes a through hole through which exhaust gas passes, an irradiation unit that irradiates the through hole with the laser light generated from the laser light generation unit, and a light receiving unit of the light receiving unit. The exhaust gas analyzer further includes an optical switch, and the irradiation unit irradiates the laser beam generated from the laser beam generation unit and the photocatalyst layer generated from the beam generation unit. When the light intensity of the laser beam received by the light receiving means falls below a predetermined value, the light generating means is operated to generate a light beam. And the photocatalyst layer is irradiated .

  The exhaust gas analyzer of the present invention configured as described above is configured to emit a photocatalyst light beam that irradiates the photocatalyst layer even if the reflectivity decreases due to adhesion of exhaust gas components to the reflective surface that reflects the laser beam for measurement. By operating the light generating means to be generated and irradiating the reflecting surface with the light generated from this means, the dirt adhering to the reflecting surface is lifted up by the catalytic action and removed by the exhaust gas flow. The concentration of exhaust gas components, temperature, and the like can be accurately measured. The light generating means for photocatalyst may be always turned on at the time of measurement, or may be configured to turn on by detecting dirt.

Also, by installing the sensor portion having a through hole which the exhaust gas can pass into the exhaust path, configured to comprise a portion irradiated with laser light, and a light receiving portion of the laser light that has passed through the exhaust gas to the sensor unit Therefore, it can be easily installed in the exhaust route, particularly at multiple locations.

Furthermore, according to the exhaust gas analyzer of the present onset bright, for irradiating switching between light generated from the laser beam and the beam generating means for photocatalyst for measurement by the optical switch, the reflection surface is contaminated with exhaust gas components Sometimes the photocatalyst layer is irradiated by operating the photocatalyst light generating means. As a result, the exhaust gas component rises from the photocatalyst layer and is discharged out of the exhaust path by the exhaust gas flow, the reflection surface is cleaned, and the concentration and temperature of the exhaust gas component can be accurately measured.

Furthermore , according to the exhaust gas analyzer of the present invention, the exhaust gas is irradiated with laser light, reflected on the reflecting surface and then received after the exhaust gas is not circulated. When the value decreases, the light intensity of the received laser beam decreases. Then, when the received light intensity falls below a predetermined value, the light generating means is operated and the light switch is switched, so that the dirt adhering to the reflecting surface can be removed and the reflecting surface can be cleaned. .

  The exhaust gas analyzer of the present invention preferably includes a signal generator that switches the operations of the laser light generating means and the light beam generating means at a predetermined timing. With this configuration, the laser beam for measurement and the light beam for photocatalyst are generated by switching at a predetermined timing. Therefore, if dirt is deposited on the reflecting surface that reflects the laser light, the photocatalyst beam is irradiated with the photocatalyst light beam. The layer can be activated and the dirt can be lifted and removed with an exhaust gas stream. Further, the measurement laser light can be reflected on the reflective surface from which dirt has been removed and cleaned, and the transmission distance in the exhaust gas can be increased, so that the measurement accuracy can be increased.

  Moreover, in the exhaust gas analyzer of the present invention, the light beam generator may be configured to be installed in the sensor unit. According to this configuration, the measurement laser beam irradiation unit, the laser beam receiving unit that has passed through the exhaust gas, and the light generating unit that generates the photocatalyst beam are fixed to the sensor unit and fixed to the sensor unit. Since the reflecting surface can be kept clean, laser light irradiation, light reception, and cleaning of the reflecting surface can function as an integrated sensor unit.

  Furthermore, the exhaust gas analyzer of the present invention may be configured to always irradiate the light beam for the photocatalyst. With this configuration, the photocatalyst layer on the surface of the reflecting member that reflects the measurement laser beam is constantly irradiated with the photocatalyst beam to clean it, so that the measurement data such as the concentration and temperature of the exhaust gas components are reflected on the reflecting surface. Therefore, stable data acquisition is possible, and exhaust gas analysis accuracy can be improved.

  The exhaust gas analyzer of the present invention reflects the laser light transmitted through the exhaust gas in the exhaust gas, so that the transmission distance can be increased and the measurement accuracy can be improved, and the photocatalyst is formed on the surface of the reflective surface that reflects the laser light. Because the layer is formed, the photocatalyst layer can function to remove the dirt and keep it clean even if the dirt of the exhaust gas adheres to the reflective surface and the reflectivity decreases. It is possible to improve the accuracy of exhaust gas analysis.

  Hereinafter, an embodiment of an exhaust gas analyzer 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 the exhaust gas analyzer according to the present embodiment is mounted on an automobile, FIG. 2 is a main part configuration diagram in a state where the exhaust gas analyzer of FIG. 1 is installed on an engine bench, and FIG. FIG. 4 is a front view showing a detail of the sensor unit in FIG. 3 and a cross-sectional view taken along line AA. FIG. 5 is a block diagram showing an overall configuration of an exhaust gas analyzer including a main configuration of a laser oscillation / light receiving controller and a signal analyzer.

  1-5, the exhaust gas analyzer of this embodiment is an apparatus which analyzes the exhaust gas discharged | emitted from the engine 2 installed in the motor vehicle 1. In FIG. 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 composed of an exhaust manifold 3, an exhaust pipe 4, a first catalyst device 5, a second catalyst device 6, a muffler 7, and an exhaust pipe 8. Exhaust gas discharged from the engine 2 is separated by two catalyst devices 5 and 6. It is purified, muffled with a muffler 7 and depressurized and released into the atmosphere. The muffler may have two main mufflers and sub mufflers.

  The plurality of members constituting the exhaust path are connected by bolts or the like with the flange portions in contact with each other. For example, the first and second catalytic devices 5 and 6 have exhaust pipe portions connected upstream and downstream of the 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. Has been. The muffler 7 has exhaust pipes connected to the upstream and downstream sides of the large-diameter main body, and flanges F and F are fixed to the ends of the exhaust pipes. The exhaust pipe 8 at the end is fixed directly to the muffler 7 by welding or the like. In this way, the plurality of members constituting the exhaust path are connected by the flange portion, and the cross-sectional shape through which the exhaust gas passes is formed in a circle having a diameter d.

  The exhaust gas analyzer 10 of the present embodiment includes a plurality of sensor units 11 to 14 installed at 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. You may install a sensor part in the exhaust pipe for every cylinder of the upstream of the 1st sensor part 11 before merging with the exhaust manifold 3.

  The exhaust pipe 4, the first catalyst device 5, the second catalyst device 6, and the muffler 7 are connected by tightening the flange portions F and F with bolts, and the sensor portion 11 is installed between members constituting the exhaust path. , 12 and 13 are installed in a state of being sandwiched between the flange portions F and 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, and may be installed between the flanges F and F in the middle of the exhaust pipe 8 protruding from the muffler 7. In addition, what is necessary is just to set the number of installation of a sensor part arbitrarily.

  Each sensor part 11-14 is the same structure, and demonstrates the one sensor part 11 with reference to FIG. The sensor unit 11 has a sensor main body 20 formed of a rectangular thin plate material. The sensor main body has a through hole 21 having a diameter d equal to the inner diameter d of the circular cross section of the exhaust pipe portion at the center. Exhaust gas passes through the through hole. The thickness of the plate-shaped sensor body 20 is preferably as thin as possible within a range in which the laser beam irradiation part and the light receiving part can be fixed. Specifically, the thickness of the sensor body 20 is preferably about 5 to 20 mm, for example. If it exceeds 20 mm, the flue gas flow is likely to be disturbed, and if it is thinner than 5 mm, the mounting and fixing of the laser beam irradiation part for measurement and the light receiving part of the laser beam that has passed through the flue gas become complicated. Moreover, it can be easily installed as required at any location in the exhaust path. The thickness of the sensor body 20 can be set arbitrarily.

  Thus, the shape of the through hole 21 formed in the sensor main body 20 is formed in a circular shape having the same diameter as the inner diameter of the exhaust pipe portion so as not to disturb the exhaust gas flow, and the sensor main body 20 is formed thin. For this reason, even if the sensor units 11 to 14 are attached in the exhaust path, the exhaust gas flow is not disturbed, and the exhaust can be smoothly performed with little pressure loss. A metal plate or a ceramic plate is used as the plate constituting the sensor body 20, but the material is not particularly limited.

  The sensor body 20 is fixed in a state sandwiched between the flange portions F, F, and a bolt, a nut, etc., not shown in the state where the gaskets 22 are sandwiched between the flange portions F, F and the sensor body 20. It is fixed by. The gasket 22 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 body 20 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. FIG. 3 shows gaskets 22, 22 between a flange portion F welded to the downstream end of the exhaust pipe 4 and a flange portion F welded to the end of the exhaust pipe portion 5 a on the upstream side of the catalyst device 5. The structure which the sensor main body 20 is fixed on both sides is shown.

  The sensor body 20 is formed with two sensor holes 23 and 24 that penetrate the center of the plate thickness from the end surface toward the through hole. The sensor holes 23 and 24 are open toward the through hole 21 and open perpendicular to the direction in which the exhaust gas flows. The sensor unit 11 has an optical fiber 25 fixed to the sensor hole 23 as an irradiating unit for irradiating laser light, and a light receiving unit that receives the laser light irradiated from the optical fiber 25 and transmitted through the exhaust gas existing in the through hole 21. A detector 26 is fixed to the sensor hole 24. That is, the sensor unit 11 reflects the laser beam irradiated from the irradiation side optical fiber 25 so as to cross the exhaust path, is reflected by the two mirrors 30 and 31, attenuates through the exhaust gas, and is received by the detector 26. It becomes the composition which is done.

As shown in detail in FIG. 4, the two mirrors 30 and 31 are vertically moved so as to reflect the infrared laser beam for measurement and the light beam for photocatalyst on the outside of the circular through hole 21 at the center of the sensor body 20. Fixed to the installation. The mirrors 30 and 31 are detachably fixed in two insertion grooves 32 and 33 formed in parallel to the outer peripheral side of the through hole 21. The mirrors 30 and 31 are formed in the shape of a rectangular substrate having a thickness of about several millimeters. A thin film of gold or platinum is formed as a reflective surface on one surface of the substrate, and MgF ₂ or SiO _{2 is used} as a protective layer thereon. _Two thin films are formed. Note that the protective film may not be formed.

The mirrors 30 and 31 have a photocatalyst layer 35 formed on the reflection surface formed on the surface and the surface of the protective film. For example, the photocatalyst layer 35 is preferably a thin film of titanium dioxide (TiO ₂ ). The photocatalyst layer 35 is formed as a thin film on the surface of the mirror by coating or coating. When the photocatalyst layer is titanium dioxide, this thin film absorbs light for photocatalyst such as ultraviolet light and activates it, and the dirt adhering to the surface floats up. It functions to be discharged to the outside.

  The insertion grooves 32 and 33 formed on the outer periphery of the through hole 21 of the sensor body 20 are set to a size that allows the mirrors 30 and 31 to be inserted loosely. The insertion grooves 32 and 33 may penetrate the sensor body 20 and be opened on both sides, or may be formed on one side and closed on the other side. The mirrors 30 and 31 are fixed in the insertion grooves 32 and 33 by spacers 37 with mounting screws 36. If the mirror is damaged by heat shock or the like, it can be removed by loosening the mounting screw 36 to fix the new mirror. Further, when the mirror becomes dirty, it can be removed from the sensor body 20 and cleaned.

  A passage through which light can pass is formed between the inner peripheral surface of the through hole 21 and the insertion grooves 32 and 33 for fixing the mirror. As the passage, a slit that penetrates, a passage hole that penetrates, and the like are formed. In the present embodiment, slits 38 and 38 having a width of about several millimeters are formed from the inner peripheral surface of the through hole 21 to the insertion grooves 32 and 33 in a direction orthogonal to the exhaust path. With this configuration, when the measurement infrared laser light is irradiated into the through hole 21 from the optical fiber 25 that is the irradiation section, it reaches the lower mirror 31 through the lower slit 38 and is reflected upward by the lower mirror. Then, the light reaches the upper mirror 30 through the upper slit 38, is reflected downward by the upper mirror, and is reflected by the upper and lower detectors 26 after being repeatedly reflected up and down.

  The optical fiber 25 and the detector 26 are connected to a laser oscillation / light reception controller 40, and infrared laser light emitted from the laser oscillation / light reception controller 40 is irradiated into the through-hole 21 of the sensor body 20 through the optical fiber 25A, and in the exhaust gas. The infrared laser beam that has passed through is received by the detector 26 on the light receiving side, and is input to the laser oscillation / light receiving controller 40 via the signal line 28A. The intensity of light emitted from the optical fiber 25A, the intensity of light received through the exhaust gas and received by the detector 26, and the like are supplied to a personal computer 55 as an analyzer. As described above, the exhaust gas analyzer 10 includes the plurality of sensor units 11 to 14, the laser oscillation / light reception controller 40, and the personal computer 55.

  Here, the laser oscillation / light reception controller 40 will be described with reference to FIG. The laser oscillation / light reception controller 40 is an irradiation device for irradiating infrared laser beams having a plurality of wavelengths, and receives signals having a plurality of frequencies from a signal generator such as a function generator (not shown) to the plurality of laser diodes LD1 to LD5. The laser diodes LD1 to LD5 irradiate infrared laser beams having a plurality of wavelengths corresponding to the respective frequencies. A plurality of frequency signals output from the signal generator of the laser oscillation / light reception controller 40 are supplied to the laser diodes LD1 to LD5 to emit light. For example, LD1 has a wavelength of about 1300 to 1330 nm and LD2 has a wavelength of 1330 to 1360 nm. The infrared laser beam having a wavelength band in which the wavelength band in which the peak wavelength of the component gas to be detected exists is continuous is set.

The wavelength of the infrared laser beam that passes through the exhaust gas is set in accordance with the component of the exhaust gas to be detected. Carbon monoxide (CO), carbon dioxide (CO ₂ ), ammonia (NH ₃ ), methane (CH ₄ ), When detecting water (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. Further, 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 gas concentration may be detected at different wavelengths even for the same component, and may be selected from different wavelengths.

  The exhaust gas analyzer 10 of the present embodiment is configured to reflect infrared laser light for measurement by mirrors 30 and 31 to increase the transmission distance in the exhaust gas, and the photocatalyst formed on the surface of the mirror The layer 35 is provided with an LD 6 as a light generator for generating ultraviolet light that is a light for photocatalyst. That is, the LD 6 generates, for example, ultraviolet light having a wavelength of about 360 nm as a light beam having a wavelength band suitable for activating the photocatalytic layer 35. By irradiating the photocatalyst layer 35 with this ultraviolet light, the photocatalyst layer is activated and exhibits superhydrophilicity. Even if dirt such as fine particles of the exhaust gas adheres to the surfaces of the mirrors 30 and 31, the surface of the mirror 30 and 31 is caused by moisture in the exhaust gas. From the exhaust path, and can be easily removed.

  The infrared laser light emitted from each of the laser diodes LD1 to LD5 is guided to the duplexers 43 through the optical fibers 42 and is demultiplexed by the duplexers 33 according to the number of sensor units. In FIG. 5, the laser beams emitted from the laser diodes LD1 to LD5 in accordance with the three sensor units 11 to 13 are divided into three. The laser beams demultiplexed by the demultiplexers 43 are separated into signal light and measurement light by the demultiplexers 44A, 44B, 44C. The duplexers 44A are for the sensor unit 11, the duplexers 44B are for the sensor unit 12, and the duplexers 44C are for the sensor unit 13. The signal light divided by the five demultiplexers 44A for the sensor unit 11 is multiplexed by the multiplexer 45A through the optical fiber, and the combined signal light in a plurality of wavelength bands is the difference which will be described later through the optical fiber 47A. The light is guided to the mold photodetector 50A. On the other hand, the measurement light divided by the five demultiplexers 44A is multiplexed by the multiplexer 46A through the optical fiber, and is guided to the irradiation unit of the sensor unit 11 by the optical fiber 25A via the optical switch 48A. The

  Further, the infrared laser light demultiplexed by the demultiplexers 43 is divided into signal light and measurement light by the five demultiplexers 44B for the sensor unit 12, and the signal light is divided into a plurality of signals by the multiplexer 45B. The signal light is obtained by combining the wavelength bands, and is guided to the differential photodetector 50B through the optical fiber 47B. The measurement light divided by the five demultiplexers 44B is multiplexed by the multiplexer 46B and guided to the irradiation unit of the sensor unit 12 by the optical fiber 25B via the optical switch 48B. Further, the infrared laser light demultiplexed by the demultiplexers 43 is divided into signal light and measurement light by the five demultiplexers 44C for the sensor unit 13, and the signal light is divided into a plurality of signals by the multiplexer 45C. It becomes signal light in the wavelength band and is guided to the differential photodetector 50C through the optical fiber 47C. The measurement light divided by the five demultiplexers 44C is multiplexed by the multiplexer 46C and guided to the irradiation unit of the sensor unit 13 via the optical switch 25C by the optical fiber 25C.

  In FIG. 5, three sensor units 11 to 13 are shown. However, when more sensor units 14... Are installed, the demultiplexer 43 demultiplexes into more laser beams, and the demultiplexed laser beams. Are further divided into measurement light and signal light by a number of demultiplexers 44..., The signal laser light is multiplexed by a multiplexer 45, and then guided to a differential photodetector 50. Laser light for measurement is guided to more sensor units 14 through more optical switches 48.

  The photocatalyst ultraviolet light irradiated from the photocatalyst LD 6 is guided to the demultiplexer 41 through the optical fiber, and the photocatalyst ultraviolet light demultiplexed into three in accordance with the number of sensor units is optically switched. Light is guided to devices 48A, 48B, 48C. In the three optical switching devices, infrared laser light for measurement is guided by the optical fiber, and ultraviolet light for cleaning the photocatalyst is guided by the optical fiber, and the infrared laser light for measurement or the ultraviolet for the photocatalyst is used. One of the light is output to the optical fibers 25A, 25B, and 25C. For example, the built-in movable mirror is switched so that the optical axes of the one optical fiber and the output optical fiber are aligned and guided. Note that the optical switch is not limited to the one provided with the movable mirror, and other appropriate methods can be used.

  In the present embodiment, switching between the infrared laser light for measurement and the ultraviolet light for photocatalyst by the optical switching devices 48A, 48B, and 48C is performed when the mirrors 30 and 31 are confirmed to be dirty. Switch from laser light to ultraviolet light for photocatalyst and irradiate from the irradiation part. For example, when contamination on the mirrors 30 and 31 of the sensor unit 11 is detected, ultraviolet light for photocatalyst is supplied to the optical fiber 25A by the optical switch 48A, and this ultraviolet light is irradiated into the through hole 21 of the sensor body 20. The upper and lower mirrors 30 and 31 are irradiated.

  The UV light for photocatalyst has a large beam diameter and is irradiated so that it passes through the same optical path as the infrared laser light for measurement, and the surface of the mirror that reflects the infrared laser light is irradiated over a wide range. Has been. Therefore, the upper and lower mirrors 30 and 31 irradiated with the ultraviolet light irradiate the area where the measurement infrared laser light is reflected in a wide range to remove the dirt, and prevent the reduction of the reflectance in this area. be able to. It is preferable to further expand the beam shape of the ultraviolet light and irradiate the entire surface of the mirror with ultraviolet light because the entire surface of the mirror can be cleaned.

  The detectors 26A, 26B, and 26C on the light receiving side connected to the light receiving units of the sensor units 11 to 13 are connected to the differential photodetectors 50A, 50B, and 50C of the laser oscillation / light receiving controller 40 via signal lines 28A, 28B, and 28C. Connected. The signal light combined by the multiplexers 45A, 45B, and 45C is guided to the differential photodetectors 50A, 50B, and 50C through the optical fibers 47A, 47B, and 47C. The differential photodetector is configured to take the difference between the transmitted laser light that has been transmitted and attenuated through the exhaust gas and the signal laser light that has not been transmitted through the exhaust gas. The signal laser light is input to a photodiode or the like and converted into an electric signal. An electrical signal corresponding to the difference between the signal light and the reference light calculated by the differential photodetector is amplified by, for example, a preamplifier (not shown), and is passed to the personal computer 55 which is a signal analysis device via an A / D converter. Entered. The personal computer 55 analyzes the exhaust gas by calculating the concentration of the exhaust gas component and the temperature of the exhaust gas from the input signal.

  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 ), which is signal light, and the signal intensity (I / I ₀ ). Transmitted light intensity I, the detector 26A, 26B, are output through 26C, the incident light intensity _{I 0} is output optical fiber 47A, 47B, the photoelectric converter such as a photodiode differential photodetector 50 through 47C . As the incident light intensity I ₀ in the present embodiment uses a signal light intensity that does not transmit the exhaust gas.

  The operation of the exhaust gas analyzer 10 of the present embodiment configured as described above will be described below. When measuring the concentration of the exhaust gas component, the signal generator of the laser oscillation / light reception controller 40 is operated to supply a signal to each of the laser diodes LD1 to LD5, and the infrared of a predetermined wavelength is transmitted from each of the laser diodes LD1 to LD5. Laser light is emitted. The infrared laser light emitted from each of the laser diodes LD1 to LD5 reaches the duplexers 43 through optical fibers 42, and is demultiplexed according to the number of sensor units.

  Thereafter, the demultiplexed infrared laser light is demultiplexed into measurement light and signal light by demultiplexers 44A... 44B. The one sensor unit 11 will be described in detail. The signal light demultiplexed by the five demultiplexers 44A is multiplexed by the multiplexer 45A to become a signal laser beam and guided to the differential photodetector 50A. The The measurement light demultiplexed by the five demultiplexers 44A is multiplexed by the multiplexer 46A to become measurement laser light, and passes through the optical switch 25A to the irradiation unit of the sensor unit 11 through the optical fiber 25A. Light is guided. Similarly, the other sensor units 12 and 13 are demultiplexed by the demultiplexers 43, and then demultiplexed into signal light and measurement light by the demultiplexers 44B and 44C, and are multiplexed by the multiplexers 45B and 45C. Then, the signal light is guided to the differential photodetectors 50B and 50C, and the measurement light is guided to the sensor units 12 and 13.

  And the infrared laser beam for measurement irradiated from the optical fibers 25A, 25B, and 25C of the sensor units 11 to 13 is irradiated into the through hole 21 through which the exhaust gas passes. The infrared laser beam traverses the inside of the through-hole 21 which is an exhaust path, is reflected upward by the lower mirror 31, is then reflected downward by the upper mirror 30, and is repeatedly reflected to increase the transmission distance in the exhaust gas. Finally, the light is received by the detector 26. That is, the infrared laser light for measurement is transmitted through the exhaust gas and attenuated, and the attenuated transmitted light is received by the detector 26 as a light receiving unit, and the light intensity of the transmitted light (measurement light) is measured.

  In this way, the measurement infrared laser light is received across the plane perpendicular to the exhaust path in the through-hole 21 of the sensor section that constitutes the exhaust path. Concentration and temperature can be measured in spots. That is, the concentration and temperature of the exhaust gas components in a certain range along the exhaust path are not measured, but the concentration and temperature of the exhaust gas components based on a predetermined plane crossing the exhaust path are measured. Therefore, spot-like measurement is possible.

  The measurement infrared laser light that has attenuated through the exhaust gas and reached the light receiving section is output as an electrical signal by the detectors 26A, 26B, and 26C, and is supplied to the differential photodetector 50A, via the signal lines 28A, 28B, and 28C. 50B and 50C. On the other hand, the signal laser light is supplied to the differential photodetectors 50A, 50B, and 50C, and the differential photodetector detects the difference between the transmitted light (measurement light) and the signal light for each of a plurality of wavelength components, and transmits the transmitted light. The peak wavelength of the specific gas component is detected. In this way, the output from the differential photodetector is input to the personal computer 55 which is a signal analysis device. The personal computer 55 performs the concentration measurement and temperature measurement of the components of the exhaust gas based on the input peak wavelength for each of the plurality of frequency bands and analyzes it.

  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. 6a shows the signal intensity at the low temperature (= number of molecules), and FIG. 6b 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.

  Then, as shown in FIG. 7, the absorption is measured by sweeping the oscillation wavelength of the laser light with respect to one of the absorption lines, for example, the wavelength λ1. The spectrum profile is measured by taking the ratio between this waveform and the waveform of the signal laser beam. Further, the temperature measurement can be obtained by measuring the spectrum profile for two different absorption lines λ1 and λ2 and taking the area ratio A1 / A2 (or the peak height ratio P1 / P2). . In the conventional wavelength modulation method, as shown in FIG. 7a, the concentration of the exhaust gas component is calculated based on the curvature of the tip of the absorption spectrum peak. However, in the present invention, as shown in FIG. Since the concentration of the exhaust gas component is calculated, it is possible to calculate the concentration of the exhaust gas component that is not easily affected by pressure.

  In the exhaust gas analyzer 10 of the present embodiment, the infrared laser light transmitted through the exhaust gas and attenuated is detected by the detectors 26, and the concentrations and temperatures of the components of the exhaust gas are measured and analyzed. Therefore, from the output value of the detector. Decrease in the reflectivity of the mirrors 30 and 31 can be determined. That is, the infrared laser light is irradiated in a state where the exhaust gas is not passed through, the attenuation due to only reflection is detected by the detectors 26..., The exhaust gas component adheres to the surfaces of the mirrors 30 and 31, and the reflectance is a predetermined threshold (for example, several 10%), the photocatalyst LD 6 is operated, and the optical switch 48A, 48B, 48C is switched to switch to irradiate the photocatalyst ultraviolet light without irradiating the infrared laser light. Is applied to the surface of the mirror to clean the mirrors 30 and 31, and the lowered reflectance can be restored.

  When the LD 6 is operated, ultraviolet light for photocatalyst is irradiated, and when the ultraviolet light is irradiated to the surfaces of the mirrors 30 and 31 through the optical switches 48A, 48B and 48C, the photocatalyst layer 35 formed on the mirror surface is activated. Then, the exhaust gas component adhering to the mirror surface rises and flows in the exhaust gas flow, and the surfaces of the mirrors 30 and 31 are cleaned. That is, when irradiated with ultraviolet light, the photocatalyst layer 35 exhibits super hydrophilicity, adsorbs moisture in the exhaust gas, raises dirt, and is removed by the exhaust gas flow. Thereby, the reflectivity of the mirrors 30 and 31 is improved, and it is possible to measure the concentration and temperature of the exhaust gas component with high accuracy again. As described above, when the mirror surface is soiled, the LD 6 is operated and the mirror surface is cleaned by irradiating ultraviolet light, so that a state with high measurement accuracy can be maintained for a long period of time. Further, by irradiating the mirror with a beam diameter of the photocatalyst light beam, a wide area can be cleaned and the entire mirror surface can be cleaned.

  Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, the photocatalyst light beam is combined with an infrared laser beam for measurement and irradiated from the irradiation part of the sensor part into the through hole. In this embodiment, the optical switching device switches between the infrared laser light for measurement and the light beam for photocatalyst at a predetermined timing, and the infrared laser light and the light beam for photocatalyst are switched and supplied to the optical fiber as the irradiation unit. To do.

  In this embodiment, a pulse for generating a photocatalytic light beam is output from the signal generator at a fixed timing during the emission of the infrared laser light for measurement. That is, the signal generator that oscillates the laser diode is a drive pulse that generates infrared laser light having wavelength bands of concentrations of a plurality of exhaust gas components to be measured, such as the output of the photodetector shown in FIG. A driving pulse V of ultraviolet light for cleaning the photocatalyst layer is incorporated in R, and the measurement infrared laser light and ultraviolet light are switched and generated. The drive pulse V of ultraviolet light is preferably applied with a current that can generate a light intensity of about 10 mW. Then, the optical switch shown in FIG. 5 is switched at a constant timing, that is, in response to the drive pulse V of ultraviolet light.

  The exhaust gas analyzer configured in this way activates the photocatalyst layer formed on the mirror surface that reflects this infrared laser light to the infrared laser light that measures the concentration of the components in the exhaust gas and the temperature of the exhaust gas. Since ultraviolet light is incorporated as the photocatalyst beam to be used, even if the exhaust gas particles adhere to the mirror surface during exhaust gas measurement and the reflectivity decreases, the mirror surface is affected by the ultraviolet light incorporated into the infrared laser light. As the photocatalyst layer is activated, dirt such as fine particles floats up and is discharged out of the exhaust path by the exhaust gas flow, so it is possible to always prevent the mirror reflectivity from decreasing, and to measure the concentration of exhaust gas components and temperature Can be performed with stable accuracy.

  Still another embodiment of the present invention will be described in detail with reference to FIG. FIG. 9 is a front view of another embodiment of the sensor unit of the exhaust gas analyzer according to the present invention. In this embodiment, the light generating means for generating light for photocatalyst is directly installed in the sensor body of the sensor unit, and the light generating means is operated when necessary or always. It is characterized by not using an optical switch. Other substantially equivalent configurations are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, a laser diode (hereinafter referred to as LD) 60 that is a light generator that emits a light beam (ultraviolet light) that can clean the photocatalytic layer 35 formed on the surfaces of the mirrors 30A and 31 includes: The light beam for photocatalyst irradiated from the LD 60 passes through the sensor hole 61 of the sensor main body 20 into the through hole 21 and is fixed to a position facing the irradiation portion of the sensor main body 20 that irradiates the measurement infrared laser light. It becomes the structure irradiated. The LD may be located at any position on the sensor body as long as it can irradiate the mirror with a photocatalytic beam.

  In the sensor unit 15 of this embodiment, the upper mirror 30A has a reflection surface that reflects the infrared laser light at the left end in the drawing partially removed to form a reflection surface that reflects ultraviolet light. An infrared laser beam can be transmitted. As a result, the measurement laser beam passes through the left end of the mirror 30A, is reflected upward by the lower mirror 31, is reflected downward by the reflecting surface of the upper mirror 30A, and is repeatedly reflected and received by the detector 26. It is the composition which becomes. The ultraviolet light emitted from the photocatalyst LD 60 is repeatedly reflected downward by the upper mirror 30A and then reflected upward by the lower mirror 31 to irradiate the entire surface of the mirrors 30A and 31. It has become. Although not shown, the inner peripheral surface of the through hole and the reflecting surface of the mirror are configured so that infrared laser light and ultraviolet light can reach through a slit penetrating.

  In the sensor unit 15 of this embodiment configured as described above, when the mirrors 30A and 31 are soiled and it is desired to irradiate ultraviolet light for photocatalyst, when the LD 60 is operated by applying a voltage, ultraviolet light is generated from the LD 60. Then, the surfaces of the upper and lower mirrors are irradiated. A photocatalyst layer 35 is formed on the surfaces of the mirrors 30A, 31 and is activated when irradiated with ultraviolet light. The dirt adhering to the mirror surface can be lifted, and the exhaust gas component that has been lifted is dirtied. Is discharged from the exhaust path together with the exhaust gas flow. As a result, the mirror surface becomes clean, and the reflectance is restored to be high, so that the measurement accuracy of the concentration and temperature of exhaust gas components can be increased. Further, in this embodiment, an optical switch for switching between the infrared laser light for measurement and the ultraviolet light for photocatalyst is not necessary, and thus the configuration can be further simplified.

  In the case of this embodiment, the photocatalytic light beam may be always irradiated. That is, during the measurement of the concentration and temperature of the exhaust gas component, the exhaust gas always flows in the through hole 21 of the sensor unit, and the surface of the mirrors 30A and 31 that reflect the infrared laser light for measurement reflects the exhaust gas component. Since dirt such as fine particles adheres, the photocatalyst layer 35 on the mirror surface is always irradiated with ultraviolet light, so that the surfaces of the mirrors 30A and 31 can be always kept clean, and the concentration and temperature of exhaust gas components are measured. The accuracy is stable, and variations in measurement accuracy can be prevented.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the present invention described in the claims. It can be changed. For example, an example of titanium dioxide is shown as the photocatalyst layer, but other photocatalyst films such as zinc oxide (ZnO) may be used. Nitrogen oxide (NOx) can also be measured as an exhaust gas component. In this case, as a matter of course, a wavelength suitable for NOx is used as the infrared laser light that transmits 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. As a reflecting member having a reflecting surface, one mirror is arranged facing the through-hole, the infrared laser light emitted from the irradiation unit is reflected only once, and the light path length is about doubled and received by the light receiving unit. You may comprise as follows.

  Although the sensor body of the sensor unit has an optical fiber as an irradiating unit and a detector as a light receiving unit, the sensor body may be directly equipped with an irradiating unit such as a laser diode, and receives light instead of a detector such as a photodiode. It is good also as a structure which mounts the optical fiber for use. Moreover, a collimator lens may be provided in the irradiation part of an optical fiber, and you may make it irradiate a laser beam in a through-hole through a collimator lens. Further, the sensor unit may be installed between the cylinder block of the internal combustion engine and the exhaust manifold.

  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 is used for exhaust gas analysis of internal combustion engines used in ships, generators, etc. It can also be applied to. In addition to the exhaust gas analysis of a gasoline engine, exhaust gas analysis of a diesel engine can be performed, and further, it can be applied to the use of exhaust gas analysis of other internal combustion engines.

The principal part block diagram of one Embodiment which mounted the exhaust gas analyzer which concerns on this invention in the vehicle. The principal part block diagram of other embodiment which mounted the exhaust gas analyzer which concerns on this invention in the engine bench. The principal part block diagram of the exhaust gas analyzer containing the perspective view of the state which the principal part of one sensor part decomposed | disassembled. (A) is a front view of the sensor unit of FIG. 3, (b) is a cross-sectional view taken along line AA of (a), (c) is a cross-sectional view taken along line BB of (a), and (d) is (c). CC sectional view taken on line C-C. The block diagram which shows the whole structure of the exhaust gas analyzer containing the principal part structure of a laser oscillation and light reception controller, and a signal analyzer. The influence of the pressure 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. (A) is explanatory drawing which calculates the density | concentration of the component of exhaust gas from the conventional absorption spectrum, (b) is explanatory drawing which calculates the density | concentration of the component of exhaust gas from the absorption spectrum of this invention. The figure which shows the output of the photodetector which combined the infrared laser beam supplied to the irradiation part of a sensor part, and the light ray for photocatalysts. The front view of other embodiments of a sensor part.

Explanation of symbols

  1: automobile, 1A: engine bench, 2: engine, 3: exhaust manifold (exhaust path), 4: exhaust pipe (exhaust path), 5: first catalyst device (exhaust path), 6: second catalyst device (exhaust gas) Path), 7: muffler (exhaust path), 8: exhaust pipe (exhaust path), 10: exhaust gas analyzer, 11-15: sensor unit, 20: sensor body, 21: through hole, 25: optical fiber (irradiation unit) ), 26: detector (light receiving unit), 30, 30A, 31: mirror, 35: photocatalytic layer, 40: laser oscillation / light receiving controller, 43: duplexer, 44A, 44B, 44C: duplexer, 45A, 45B , 45C, 46A, 46B, 46C: multiplexer, 48A, 48B, 48C: optical switch, 50A, 50B, 50C: differential photodetector, 55: personal computer (signal analysis device), LD1 LD5: a laser diode (laser light generating means), LD6, LD60: a laser diode (light generator for photocatalyst), F: flange portion, d: the exhaust passage, the diameter of the through hole

Claims (3)

Laser light generating means for generating laser light, a reflecting surface for reflecting the generated laser light, and light receiving means for receiving the laser light reflected by the reflecting surface, the laser light being emitted from the internal combustion engine An apparatus for analyzing the exhaust gas by measuring the concentration and temperature of the components of the exhaust gas based on the received transmitted laser light.
The apparatus further includes a photocatalyst layer formed on the surface of the reflecting surface, and a light beam generating means for generating a light beam for irradiating the photocatalyst layer, and sensor units at a plurality of locations in the exhaust path through which the exhaust gas flows. Installed and configured,
The sensor unit includes a through-hole through which exhaust gas passes, an irradiation unit that irradiates the through-hole with laser light generated from the laser light generation unit, and a light-receiving unit of the light-receiving unit.
The exhaust gas analyzer further includes an optical switch, and the irradiating unit includes a laser beam generated from the laser beam generating unit and a beam for irradiating the photocatalyst layer generated from the beam generating unit, It switches and irradiates via a light switch,
The exhaust gas analysis is characterized in that when the light intensity of the laser beam received by the light receiving means falls below a predetermined value, the light generating means is operated to generate a light beam and irradiate the photocatalyst layer. apparatus. The exhaust gas analyzer according to claim 1 , further comprising a signal generator that switches operations of the laser light generator and the light generator at a predetermined timing. The exhaust gas analyzer according to claim 1 or 2 , wherein the light beam generation unit is installed in the sensor unit.