JP2009243968A - Exhaust gas analyzer and analyzing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas analyzer enhanced in the measuring precision of the concentration of a component even in a case that the concentration of a predetermined component is low under a low temperature condition, and an exhaust gas analyzing method. <P>SOLUTION: The exhaust gas analyzer has a temperature sensor 55 equipped with a measuring part 5 for irradiating the exhaust gas in an exhaustion route 3, which discharges the exhaust gas of an engine 20, with a laser beam to receive the laser beam transmitted through the exhaust gas and detecting the actually measured temperature T1 of the exhaust gas in the exhaustion route 3, a difference type photodetector 64 for detecting the absorption spectrum of the laser beam absorbed into the exhaust gas from the laser beam received by the measuring part 5, a temperature calculation part 70 for calculating the theoretical temperature T2 of the exhaust gas from the absorption spectrum detected by the difference type photodetector 64 and a component concentration calculation part 73 for calculating the concentration C of the component in the exhaust gas using the actually measured temperature T1 detected by the temperature sensor 55 in a case that the concentration of a predetermined component in the exhaust gas is low or using the theoretical temperature T2 calculated by the temperature calculation part 70 in a case that the concentration of the predetermined component in the exhaust gas is high. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust gas analyzer and an exhaust gas analysis method for measuring a component concentration in exhaust gas by irradiating the exhaust gas in an exhaust path for discharging exhaust gas of an internal combustion engine with laser light and receiving the laser light transmitted through the exhaust gas. Regarding technology.

  Conventionally, in order to measure hydrocarbon (Hydro Carbon) concentration (hereinafter, component concentration) contained in exhaust gas from an internal combustion engine such as an engine, the FID (Frame Ionization Detector) method or the NDIR (Non-Dispersive Infrared Red) method 2. Description of the Related Art An exhaust gas analyzer that uses a measurement method called “K” is known.

  In particular, as a conventional on-vehicle exhaust gas analyzer, the exhaust gas in the exhaust path is irradiated with infrared laser light having a specific absorption wavelength to transmit through the exhaust gas, and the transmitted light is detected. A configuration for measuring the component concentration of is known. In such a component concentration measurement method (infrared laser absorption method) using infrared laser light, the infrared laser light from the light source is adjusted to the absorption wavelength of the hydrocarbons constituting the exhaust gas, and then the inside of the exhaust path. The light intensity of the transmitted light that is irradiated toward the exhaust gas and transmitted through the exhaust gas is detected by the light receiving sensor, and the light intensity (signal intensity) is calculated based on the absorption spectrum of the transmitted light. The component concentration is measured.

  By the way, in the exhaust gas analyzer using the infrared laser absorption method described above, the component concentration in the exhaust gas in the exhaust path is calculated based on the absorption spectrum of infrared laser light (transmitted light). Since the absorption spectrum of is affected by the temperature of the exhaust gas, the calculated concentration has an error due to these temperatures. Therefore, in order to improve the measurement accuracy of the component concentration, an exhaust gas analysis method has been proposed in which the absorption spectrum of the infrared laser beam is corrected for temperature and the component concentration is measured using the result. By the way.

For example, Patent Document 1 discloses that an infrared laser beam is irradiated toward an exhaust gas passage hole through which an exhaust gas discharged from an internal combustion engine passes through an exhaust path, and the infrared laser beam is subjected to multiple reflections by a reflecting mirror. In the exhaust gas analyzer that measures the concentration of the component in the exhaust gas by directly arranging the measurement unit that detects the infrared laser beam transmitted through the inside, H _{2 is used} as a predetermined component in the detected absorption spectrum. Disclosed is a method for calculating the component concentration in exhaust gas by calculating the temperature of exhaust gas from the light intensity (signal intensity) of the absorption spectrum of O, correcting the absorption spectrum of each molecule in the exhaust gas using the calculated temperature. Has been.
JP 2007-163422 A

Certainly, like the conventional exhaust gas analyzer disclosed in Patent Document 1, the temperature is calculated from the light intensity of the absorption spectrum of H ₂ O as a predetermined component in the exhaust gas, and the calculated temperature is used in the exhaust gas. If the method is to correct the absorption spectrum for each of the components, temperature measurement with higher response is possible, so that the component concentration can be measured with higher response.

However, when measuring the component concentration under low temperature conditions such as before engine start or immediately after engine start, the concentration of H ₂ O as a predetermined component in the exhaust gas is low (in other words, the saturated vapor pressure of H ₂ O molecules is low). Therefore, an accurate absorption spectrum of H ₂ O could not be detected, and the temperature calculation accuracy was inferior compared to when measuring the component concentration under high temperature conditions. For this reason, there has been a problem that under low temperature conditions, the absorption spectrum of each component in the exhaust gas cannot be temperature-corrected accurately, and consequently the measurement accuracy of the component concentration is lowered.

As a method for measuring the temperature of exhaust gas, in addition to the method described above, a method of measuring using a temperature sensor such as a thermocouple is known, but according to the temperature measuring method using such a temperature sensor, Under the condition where the temperature change is gentle, the measurement accuracy is high because it is an actual measurement value of the exhaust gas temperature passing through the exhaust passage, compared with the method of calculating the exhaust gas temperature from the above-described absorption spectrum of H ₂ O. However, it is difficult to measure the component concentration with a high response under conditions where the temperature changes rapidly, such as immediately after engine startup, due to a response delay due to the heat capacity of the temperature sensor itself.

  Therefore, the present invention relates to an exhaust gas analyzer and exhaust gas analysis method, which solves the above-described conventional problems, and improves the measurement accuracy of the component concentration even when the concentration of the predetermined component is low under low temperature conditions. An object of the present invention is to provide an exhaust gas analyzer and an exhaust gas analysis method.

  The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.

  That is, according to the first aspect of the invention, there is provided a measuring unit that irradiates the exhaust gas in the exhaust path for discharging the exhaust gas of the internal combustion engine with a laser beam and receives the laser beam that has passed through the exhaust gas. An exhaust gas analyzer that measures the concentration of a component in exhaust gas based on the emitted laser light, comprising temperature detection means for detecting an actual temperature of exhaust gas in the exhaust path, and laser light received by the measurement unit An absorption spectrum detecting means for detecting an absorption spectrum of laser light absorbed in the exhaust gas, a temperature calculating means for calculating a theoretical temperature of the exhaust gas from the absorption spectrum detected by the absorption spectrum detecting means, and a predetermined component in the exhaust gas. When the concentration is low, the component concentration in the exhaust gas is calculated using the measured temperature detected by the temperature detecting means, and the concentration of the predetermined component in the exhaust gas is high. The one having a component concentration calculating means for calculating a component concentration in the exhaust gas by using a theoretical temperature calculated by said temperature calculation means.

In Claim 2, the reference value calculation means for calculating a reference value based on the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component from the absorption spectrum detected by the absorption spectrum detection means, and the reference value When the reference value calculated by the calculation means is smaller than a predetermined threshold, it is determined that the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component is low, and the reference value calculated by the reference value calculation means is a predetermined value. When it is larger than the threshold value, there is a determination means for determining that the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component is high.

According to a third aspect of the present invention, the reference value calculation means calculates the area value of the absorption spectrum of H ₂ O detected by the absorption spectrum detection means as a reference value, and the determination means sets the area value to a predetermined value. When it is smaller than the threshold value, it is determined that the H ₂ O concentration in the exhaust gas is low, and when the area value is larger than the predetermined threshold value, it is determined that the H ₂ O concentration in the exhaust gas is high.

According to a fourth aspect of the present invention, the reference value calculating means calculates the light intensity of at least one peak wavelength in the absorption spectrum of H ₂ O detected by the absorption spectrum detecting means as a reference value, and When the light intensity is smaller than a predetermined threshold, it is determined that the H ₂ O concentration in the exhaust gas is low, and when the light intensity is higher than the predetermined threshold, it is determined that the H ₂ O concentration in the exhaust gas is high. To do.

According to a fifth aspect of the present invention, the reference value calculation means uses a fitting error between the measured absorption spectrum of H ₂ O detected by the absorption spectrum detection means and the predefined theoretical absorption spectrum of H ₂ O as a reference value. The determination means determines that the H ₂ O concentration in the exhaust gas is low when the fitting error is larger than a predetermined threshold, and the H in the exhaust gas when the fitting error is smaller than the predetermined threshold. It is determined that the ₂ O concentration is high.

In claim 6, the reference value calculation means calculates the theoretical temperature calculated by the temperature calculation means as a reference value, and the determination means calculates exhaust gas when the theoretical temperature is lower than a predetermined threshold value. H _{2 O} concentration is determined to be lower in the case the theoretical temperature is greater than a predetermined threshold value is to determine the high H _{2 O} concentration in the exhaust gas.

  In Claim 7, the said component density | concentration calculation means calculates the approximate component density | concentration in waste gas from the absorption spectrum detected by the said absorption spectrum detection means, and the actual temperature detected by the said temperature detection means, or the said temperature calculation Using the theoretical temperature calculated by the means, the component concentration in the exhaust gas is calculated by correcting the temperature of the approximate component concentration.

  According to an eighth aspect of the present invention, the temperature detecting means includes a temperature sensor that is disposed in the exhaust gas passage hole formed in the measurement unit and detects an actual temperature of the exhaust gas that passes through the exhaust gas passage hole.

  According to claim 9, there is provided an exhaust gas analysis method for measuring a component concentration in exhaust gas by irradiating the exhaust gas in an exhaust path for discharging exhaust gas of an internal combustion engine with laser light and receiving the laser light transmitted through the exhaust gas. A temperature detecting step of detecting an actual temperature of exhaust gas in the exhaust path, an absorption spectrum detecting step of detecting an absorption spectrum of laser light absorbed in the exhaust gas from the received laser light, and the absorption spectrum detecting step A temperature calculation step for calculating the theoretical temperature of the exhaust gas from the absorption spectrum detected by the method, and when the concentration of the predetermined component in the exhaust gas is low, the component concentration in the exhaust gas is determined using the measured temperature detected in the temperature detection step. If the concentration of the specified component in the exhaust gas is high, the component concentration in the exhaust gas is calculated using the theoretical temperature calculated in the temperature calculation step. That is one having a component concentration calculation step.

In Claim 10, from the absorption spectrum detected by the absorption spectrum detection step, a reference value calculation step of calculating a reference value based on the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component, and the reference value When the reference value calculated by the calculation step is smaller than a predetermined threshold, it is determined that the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component is low, and the reference value calculated by the reference value calculation step is a predetermined value. A determination step of determining that the concentration of H ₂ O in the exhaust gas as the concentration of the predetermined component is high when the threshold value is greater than the threshold value.

  In Claim 11, the said component concentration calculation process calculates the approximate component density | concentration in waste gas from the absorption spectrum detected by the said absorption spectrum detection process, and the measured temperature detected by the said temperature detection process, or the said temperature calculation Using the theoretical temperature calculated in the process, the component concentration in the exhaust gas is calculated by correcting the temperature of the approximate component concentration.

  As an effect of the present invention, temperature detection is possible even when the concentration of a predetermined component in exhaust gas is low, such as before the engine is started or immediately after the start, and an accurate absorption spectrum cannot be detected by the absorption spectrum detection means. By performing temperature correction of the component concentration using the measured temperature of the exhaust gas by means, it is possible to accurately correct the temperature of the absorption spectrum for each component in the exhaust gas. Can improve the measurement accuracy of the component concentration.

Next, the best mode for carrying out the invention will be described.
1 is a side view showing a state in which an exhaust gas analyzer according to an embodiment of the present invention is mounted on a vehicle, FIG. 2 is a perspective view showing a mounting structure of a measuring unit, and FIG. 3 is a perspective view of the measuring unit of FIG. FIG. 4 is a perspective view showing the configuration of the measurement unit, FIG. 5 is a functional block diagram showing the configuration of the controller, and FIG. 6 is a laser beam in a wavelength band including the detection peak of H ₂ O. FIG. 7 is a diagram showing an absorption spectrum of laser light in a wavelength band including a detection peak of H ₂ O, FIG. 8 is a functional block diagram showing the configuration of a computer device, and FIG. 9 is an absorption diagram. shows the area of each peak due to absorption of H _{2 O} which appears in the spectrum, FIG. 10 is a flowchart showing the exhaust gas analyzing method using the exhaust gas analyzer of the present embodiment, FIG. 11 appeared the absorption spectrum H each peak due to absorption of the _{2 O} FIG. 12 is a diagram showing a long light intensity, FIG. 12A is a diagram showing the area of the boundary surrounded by the measured absorption spectrum and the theoretical absorption spectrum, and FIG. 12B is a diagram showing the area of the theoretical absorption spectrum. FIG. 13 is a side view showing the mounting structure of the measuring part of another embodiment.

First, the overall configuration of the exhaust gas analyzer 1 of the present embodiment will be outlined below.
As shown in FIG. 1, the exhaust gas analyzer 1 of the present embodiment measures and analyzes the component concentration and temperature in exhaust gas discharged from an engine 20 as an internal combustion engine disposed in an automobile 2. Specifically, the exhaust gas analyzer 1 includes a plurality of measuring units 5, 5... Disposed at a plurality of locations in the exhaust path 3 described above, and a laser oscillation / light receiving controller connected to the measuring unit 5. 6 and a computer device 7 connected to the controller 6.

  The automobile 2 is provided with an exhaust path 3 for discharging exhaust gas from the engine 20 to the outside of the machine. The exhaust path 3 includes an exhaust manifold 30, an exhaust pipe 31, a first catalyst device 32, a second catalyst device 33, A muffler 34, an exhaust pipe 35, and the like are included. In addition, each component device of the exhaust path 3 is connected by a pipe 3a having a circular cross section.

  In the exhaust path 3, the exhaust gas of the engine 20 is first merged in the exhaust manifold 30, introduced into the first catalyst device 32 and the second catalyst device 33 through the exhaust pipe 31, and then into the atmosphere from the exhaust pipe 35 through the muffler 34. Released. By forming such an exhaust path 3, the exhaust gas from the engine 20 is purified by the two catalytic devices 32 and 33, muffled and decompressed by the muffler 34, and released into the atmosphere.

  The measuring units 5, 5... Are arranged at four locations in the exhaust path 3, specifically, between the engine 20 on the upstream side of the first catalyst device 32 and the exhaust pipe 31, the first catalyst device. 32 and the second catalyst device 33, between the second catalyst device 33 and the muffler 34, and at the end of the exhaust pipe 35 on the downstream side of the muffler 34. In each measuring unit 5, the controller 6 emits (infrared) laser light and receives the laser light after passing through the exhaust gas, so that the component concentration of the exhaust gas flowing through the exhaust path 3 is continuously increased. Measured in real time.

  Thus, in the exhaust gas analyzer 1 of the present embodiment, the spot exhaust gas can be measured in one section of the exhaust path 3 by each measuring unit 5. In particular, as in the present embodiment, by providing the measurement units 5 at a plurality of locations in the exhaust path 3, it is possible to instantaneously measure how the exhaust gas changes in a predetermined section of the exhaust path 3, and the exhaust gas Can be continuously measured in real time.

Next, the measurement unit 5 will be described in detail below.
In the exhaust gas analyzer 1 of the present embodiment, the measurement units 5, 5... Arranged in the exhaust path 3 are configured substantially the same. The measurement part 5 arrange | positioned between the 2nd catalyst apparatuses 33 is demonstrated.

  As shown in FIGS. 2 to 4, the measurement unit 5 of the present embodiment is formed of a rectangular thin plate material, and a circular exhaust gas passage hole 50 a through which the exhaust gas in the exhaust path 3 passes is substantially penetrated at the center. A sensor body 50 as a main body, an irradiation unit 51 for irradiating laser light for measurement toward the exhaust gas passage hole 50a, and a pair of reflecting mirrors 52 for reflecting the laser light emitted from the irradiation unit 51 in multiple reflections. 52, a light receiving unit 53 that detects laser light that has passed through the exhaust gas, a temperature sensor 55 that serves as a temperature detection unit that detects the actual temperature T1 of the exhaust gas in the exhaust path, and the like. In the measurement unit 5, laser light is irradiated from the irradiation unit 51 along one cross section orthogonal to the exhaust path 3, and the irradiated laser light is reflected a plurality of times so as to cross the exhaust path 3 between the reflecting mirrors 52. The light receiving unit 53 receives the light.

  The measuring unit 5 is fixed in a state where the sensor body 50 is sandwiched between a pair of pipe joints 36 and 36, and the pipe joints 36 and 36 are connected to the first catalyst device 32 and the second catalyst device 33, respectively. By being connected to 3a, it is disposed in the exhaust path 3. The pipe joints 36 and 36 are formed in a cylindrical shape with a through hole 36a having a circular cross section, and a flange portion 36b is provided at one opening edge. The measuring unit 5 (the sensor body 50) is sandwiched between the opening ends of the pair of pipe joints 36 and 36 on the side where the flange portion 36b is provided via the gasket 37, and the flange portions 36b and 36b are bolts 38. -It is fixed by being fastened by 38. The through hole 36a of the pipe joint 36 is formed in a circular shape having the same diameter as the pipe 3a, and the flow of exhaust gas is not hindered.

  The sensor main body 50 is composed of a thin plate-like metal member formed in a circular shape in plan view, and a circular exhaust gas passage hole 50a is formed in a substantially central portion of an opposing surface orthogonal to the exhaust gas flow direction. The sensor body 50 is assembled with the irradiation unit 51 and the light receiving unit 53 such that the light projecting surface and the light receiving surface are directed toward the center of the exhaust gas passage hole 50a, and the reflecting mirrors 52 and 52 are provided with the exhaust gas passage hole 50a. The laser beam irradiated from the irradiation unit 51 is fixed in a parallel state so as to cross the exhaust gas passage hole 50a at right angles to the exhaust passage 3 so as to face each other. Yes.

  Laser light is emitted from the irradiation unit 51 along a cross section orthogonal to the exhaust path 3, and the laser light emitted from the irradiation unit 51 is received by the light receiving unit 53. In the present embodiment, the irradiation unit 51 and the light receiving unit 53 are connected to the controller 6 described above, and the laser light emitted from the controller 6 is irradiated to the exhaust gas passage hole 50a via the irradiation unit 51 and passes through the exhaust gas. The transmitted laser light is received by the light receiving unit 53 and a light reception signal is input to the controller 6.

  The irradiation unit 51 is provided with an optical fiber 51 a for infrared transmission, and is attached so that the light projecting surface faces the center of the exhaust gas passage hole 50 a of the sensor body 50. The other end of the optical fiber 51a is connected to the controller 6 described above, and laser light emitted from the controller 6 is introduced into the exhaust gas passage hole 50a from the optical fiber 51a. Thus, the irradiation part 51 is attached to the sensor main body 50 so that the projection surface of the optical fiber 51a is opposed to the exhaust gas passage hole 50a and the laser light can be emitted toward one cross section orthogonal to the exhaust gas passage hole 50a. Yes.

  The light receiving portion 53 is provided with a detector 53a for detecting laser light, and a signal line 53b having one end connected to the detector 53a and the other end connected to the controller 6 described above, and passes through the exhaust gas. The detected laser beam is received by the detector 53a, and the received light signal is input to the controller 6 through the signal line 53b. The light receiving unit 53 is flush with the irradiation unit 6 so that the light receiving surface of the detector 53a faces the exhaust gas passage hole 50a and can receive the laser light emitted from the irradiation unit 51 toward one section orthogonal to the exhaust gas passage hole 50a. The sensor body 50 is attached so as to be positioned above.

  The reflecting mirrors 52 and 52 are configured such that the laser light emitted from the irradiation unit 51 is reflected by one reflecting mirror 52 (lower in FIG. 4) toward the other reflecting mirror 52 (upward in FIG. 4). The reflectors 52 and 52 are alternately reflected so as to reach the light receiving portion 53 on the light receiving side. As described above, the laser beam irradiated by the irradiation unit 51 is reflected by the light receiving unit 53 after being reflected a plurality of times in one cross section orthogonal to the exhaust path 3 by the pair of reflecting mirrors 52 and 52.

  As described above, in the measurement unit 5, the laser light emitted from the controller 6 is irradiated into the exhaust gas passage hole 50 a of the sensor body 50 through the optical fiber 51 a of the irradiation unit 51, and the laser light transmitted through the exhaust gas is received. Light is received by the detector 53a of the unit 53 and is input to the controller 6 via the signal line 53b.

  The temperature sensor 55 is disposed in the exhaust gas passage hole 50a of the sensor body 50, and the actual temperature T1 of the exhaust gas passing through the exhaust gas passage hole 50a is directly detected. One end of the temperature sensor 55 is connected to the computer device 7 described later, and the detected actual temperature T1 of the detected exhaust gas is input to the computer device 7 (see FIG. 3). The temperature sensor 55 of the present embodiment uses, for example, a thermocouple in which the conductor portion is covered with a heat resistant material such as enamel or ceramic. In particular, when a thermocouple is used, it may be disposed in the exhaust gas passage hole 50a while being accommodated in a metal protective tube or the like.

Next, the controller 6 will be described in detail below.
In the exhaust gas analyzer 1 of the present embodiment, the controller 6 is arranged for each of the corresponding measuring units 5, 5... Arranged in each exhaust path 3, and the measuring units 5, 5. Are supplied with the same wavelength (infrared) laser beam and receive the received light signal of the laser beam received by each of the measuring sections 5. Hereinafter, the configuration of the controller 6 connected to the measurement unit 5 will be described by focusing on one measurement unit 5 disposed between the first catalyst device 32 and the second catalyst device 33. The configuration of the controller 6 connected to the measurement unit 5 is configured in substantially the same manner.

  As shown in FIGS. 1 and 5, the controller 6 is configured as an irradiation device that irradiates laser light with a plurality of wavelengths and a light detection device that detects predetermined laser light. Specifically, a laser light source 60 that generates infrared laser light having a plurality of wavelengths, a plurality of demultiplexers 61, 61,... That demultiplex the laser light emitted from the laser light source 60, and a laser light source 60. The laser light (measurement laser light and reference laser light) emitted from the laser beam is multiplexed by the multiplexers 62 and 63 for combining the laser light of a predetermined wavelength band with the laser light of a predetermined wavelength band and received by the measurement unit 5 and transmitted through the exhaust gas. It comprises a differential photodetector 64 and the like through which attenuated measurement laser light and reference laser light are guided.

  The laser light source 60 is supplied with a signal of a predetermined frequency from a signal transmitter 65 such as a function generator to a plurality of (in this embodiment, five) laser diodes 66, 66.・ The infrared laser beam having a specific wavelength is irradiated from 66. In the laser light source 60, for example, laser light with a wavelength of about 1300 to 1330 nm and laser light with a wavelength of about 1330 to 1360 nm are emitted from one laser diode 66, respectively.

In this example, among the components contained in the exhaust gas, 5 of carbon monoxide (CO), carbon dioxide (CO ₂ ), ammonia (NH ₃ ), methane (CH ₄ ), and water (H ₂ O). The types are set as detection targets, and laser light including a wavelength band in which the peak wavelengths of the respective components exist is synthesized. Specifically, the wavelength suitable for detecting NH ₃ is around 1530 nm, the wavelength suitable for detecting CO is around 1560 nm, and the wavelength suitable for detecting CO ₂ is around 1580 nm. There is a suitable wavelength for detecting CH ₄ in the vicinity of 1650 nm. A wavelength suitable for detecting H ₂ O is around 1380 nm.

  The demultiplexer 61 is a device that demultiplexes the laser light emitted from the laser diodes 66, 66,... Of the laser light source 60 into the measurement laser light and the reference laser light. , A plurality of (in the present embodiment, five) duplexers 61, 61,... Are disposed corresponding to the laser diodes 66, 66,. The controller 6 of the present embodiment includes an exhaust gas before demultiplexing the laser light emitted from the laser diodes 66, 66... By the demultiplexer 61 into the measurement laser light and the reference laser light. A separate splitter (not shown) for splitting the laser beam is separately provided for each of the measuring units 5, 5... Constituting the analyzer 1.

  The multiplexers 62 and 63 multiplex the laser beams demultiplexed into the measurement laser beam and the reference laser beam by the demultiplexer 61 and multiplex the laser beams with a predetermined wavelength band. Thus, the measurement laser beam demultiplexed by the demultiplexer 61 is multiplexed by the multiplexer 62, and the reference laser beam demultiplexed by the demultiplexer 61 is multiplexed by the multiplexer 63. The laser light combined by the multiplexers 62 and 63 in this way is adjusted to have a wavelength band of about 700 nm to 1800 nm in accordance with a plurality of components in the exhaust gas.

  The measurement laser beam synthesized by the multiplexer 62 is guided to the irradiation unit 51 of the measurement unit 5 through the optical fiber 51a, and after being reflected by the reflection mirrors 52 and 52 in the measurement unit 5, the light receiving unit. The light is received by 53 detectors 53a and guided to a differential photodetector 64 described later via a signal line 53b. On the other hand, the reference laser beam synthesized by the multiplexer 63 is guided to the differential photodetector 64 described later via the optical fiber 63a.

  The differential light detector 64 is configured as an absorption spectrum detector that detects an absorption spectrum of the laser light absorbed in the exhaust gas from the laser light received by the measuring unit 5, and the differential light of this embodiment. The detector 64 detects the signal intensity of each input laser beam and the absorption spectrum of both laser beams. The differential photodetector 64 is connected to the signal line 53b extended from the measurement unit 5 and the optical fiber 63a extended from the duplexer 63, and passes through the exhaust gas in the measurement unit 5. The attenuated measurement laser light and the reference laser light that does not pass through the exhaust gas are input to the photodiodes 64a and 64a and converted into electrical signals, and then input as electrical signals. The signal strength is detected.

FIG. 6 shows, as an example, signal intensities of measurement laser light and reference laser light of a specific component input to the differential photodetector 64. Specifically, in the wavelength band including the detection peak of H ₂ O, FIG. 6A shows the signal intensity of the reference laser beam, and FIG. 6B shows the signal after passing through the exhaust gas. It shows the signal intensity of the laser beam for measurement (transmitted light). In particular, in the signal intensity of the laser beam for measurement after passing through the exhaust gas shown in FIG. 6B, the signal light amount decreases due to the absorption of H ₂ O at the peak wavelengths λ1, λ2, and λ3 (peaks A and B). -C) is confirmed.

Further, the differential photodetector 64 calculates the difference in light intensity between the measurement laser beam and the reference laser beam based on the input input signals of the measurement laser beam and the reference laser beam, and measures the measurement laser beam. An absorption spectrum in a predetermined wavelength band of light (transmitted light) is detected. FIG. 7 shows, as an example, absorption spectra of specific components of the measurement laser beam and the reference laser beam input to the differential photodetector 64, and the exhaust gas shown in FIG. Corresponding to the peak of the signal intensity of the measurement laser light after transmission, peaks A, B, and C accompanying absorption of H ₂ O are confirmed at peak wavelengths λ1, λ2, and λ3.

  The absorption spectrum of the laser beam detected by the differential photodetector 64 is input as an electric signal to the computer apparatus 7 to be described later via a preamplifier and an A / D converter (not shown).

Next, the computer device 7 will be described in detail below.
As shown in FIG. 8, the computer apparatus 7 of this embodiment includes a temperature calculation unit 70, a reference value calculation unit 71, a determination unit 72, a component concentration calculation unit 73, an output unit 74, and the like as will be described later. The output signal from the controller 6 is analyzed, and the component concentration C of the exhaust gas is measured based on the inputted absorption spectrum for each of the plurality of wavelength bands. In particular, in the computer device 7 of the present embodiment, the temperature of the exhaust gas is corrected by selectively using either the actually measured temperature T1 detected by the temperature sensor 55 described above or the theoretical temperature T2 calculated by the temperature calculation unit 70. The component concentration C is calculated.

  The computer device 7 is connected to the above-described differential photodetector 64 and the temperature sensor 55, and the absorption spectrum detected by the differential photodetector 64 is input as an electrical signal, and the temperature sensor 55 The detected actual temperature T1 of the detected exhaust gas is input as an electric signal.

  In the computer apparatus 7 of the present embodiment, the component concentration C in the exhaust gas is calculated using a known method. As an example, the component concentration C in the exhaust gas (corresponding to an approximate component concentration C1 to be described later) includes incident light (reference laser light) into the exhaust gas and transmitted light after passing through the exhaust gas (measurement laser light). ) Is calculated using the following mathematical formula (1).

C = −ln (I / I ₀ ) / k · L (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. That is, the component concentration C is calculated based on the ratio (I / I ₀ ) of the light intensity I of the transmitted light that is the measurement laser light to the light intensity I ₀ of the incident light that is the reference laser light. In the computer device 7, the transmitted light intensity I (signal intensity) and the incident light intensity I ₀ are calculated from the absorption spectrum detected by the differential photodetector 64, and the component concentration C is calculated.

Moreover, in the computer apparatus 7 of the present embodiment, H ₂ O water vapor that is always present in the exhaust gas is set as a predetermined component in the exhaust gas, and as will be described later, H ₂ O as the predetermined component is set. The theoretical temperature T2 of the exhaust gas is calculated from the absorption spectrum, and the temperature used for temperature correction is determined based on the magnitude of the H ₂ O concentration in the exhaust gas (see FIG. 10).

The temperature calculation unit 70 is configured as a temperature calculation unit that calculates the theoretical temperature T2 of the exhaust gas from the absorption spectrum detected by the differential photodetector 64. As a method for calculating the theoretical temperature T2 of the exhaust gas from the absorption spectrum, a known method is used. As an example, in this embodiment, since the ratio of the light intensity of two specific wavelengths depends only on the temperature, at least 2 appears in the absorption spectrum of the measurement laser light after passing through the exhaust gas shown in FIG. Using the light intensities at two peak wavelengths (for example, the light intensities I1 and I2 at the peak wavelengths λ1 and λ2), the H ₂ O concentration is calculated from Equation (1), and the two calculated H ₂ O concentrations are The target theoretical temperature T2 is calculated from the equality.

  Specifically, in Equation (1) for calculating the component concentration C described above, the absorption rate k on the right side is represented by the product of the absorption line intensity S (T) and the pressure P (k = S (T) · P ), The absorption line intensity S (T) is expressed as a function of the absorptance cross-sectional area α, the Avogadro number Na, the gas constant R, and the temperature T (S (T) = α · (Na / RT)). Based on this, the theoretical temperature T2 is calculated by substituting these into the absorptance k in Equation (1).

The reference value calculator 71 is configured as a reference value calculator that calculates a reference value based on the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component from the absorption spectrum detected by the differential photodetector 64. Yes. The “reference value based on the H ₂ O concentration in the exhaust gas” refers to a value having a correlation with the H ₂ O concentration. In this example, the area value of the absorption spectrum of H ₂ O is H ₂ O in the exhaust gas. _Since there is a correlation with the ₂ O concentration, the area value of the absorption spectrum of H ₂ O detected by the differential photodetector 64 is set as the reference value.

As shown in FIG. 9, the area value of the absorption spectrum of H 2 _O, using the absorption spectrum of the measurement laser light after passing through the flue gas shown in FIG. 7, the H _{2 O} which appears in the absorption spectrum It is calculated as the total value of the integrated values of peaks A, B, and C accompanying absorption. However, the area value of the absorption spectrum of H ₂ O may be calculated from an integrated value of a single peak (for example, an integrated value of peak A based on peak wavelength λ1) or an integrated value of two or more peaks.

The determination unit 72 determines that the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component is low when the reference value calculated by the reference value calculation unit 71 is smaller than the predetermined threshold, and the reference value calculation unit 71 When the calculated reference value is larger than a predetermined threshold value, the determination unit is configured to determine that the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component is high.

The “threshold value of H ₂ O concentration” is a threshold value when selectively using either the actual temperature T1 detected by the temperature sensor 55 or the theoretical temperature T2 calculated by the temperature calculation unit 70, as will be described later. Thus, it is appropriately set according to the exhaust gas measurement conditions, the peak wavelength detection accuracy, and the like. Further, the “reference value threshold value” is appropriately set corresponding to a preset H ₂ O concentration threshold value. For example, the threshold of the H 2 _O concentration is preset to a predetermined% concentration in the exhaust gas, the threshold reference value corresponding to the threshold of such H _{2 O} concentration is set.

The determination unit 72 according to the present embodiment determines that the H ₂ O concentration in the exhaust gas is low when the area value of the absorption spectrum of H ₂ O calculated by the reference value calculation unit 71 described above is smaller than a predetermined threshold value. When the area value is larger than the predetermined threshold value, it is determined that the H ₂ O concentration in the exhaust gas is high. Thus calculated, by using the correlation between H _{2 O} concentration in the area value and the exhaust gas of the absorption spectrum of H 2 _O, the area value of the absorption spectrum of H _{2 O} by the reference value calculating section 71 as the reference value Thus, the determination unit 72 can easily determine the magnitude of the H ₂ O concentration.

The component concentration calculation unit 73 uses the measured temperature T1 detected by the temperature sensor 55 when the H ₂ O concentration in the exhaust gas is low, or the temperature calculation unit 70 when the H ₂ O concentration in the exhaust gas is high. Is used as a component concentration calculating means for calculating the component concentration of the exhaust gas using the theoretical temperature T2 calculated by the above. Specifically, in the component concentration calculation unit 73 of the present embodiment, the approximate component concentration C1 of the exhaust gas is temporarily calculated from the absorption spectrum detected by the differential photodetector 64 and the measured temperature T1 detected by the temperature sensor 55 is calculated. Alternatively, the component concentration C is calculated by correcting the approximate component concentration C1 using the theoretical temperature T2 calculated by the temperature calculation unit 70.

  The approximate component concentration C1 of the exhaust gas is calculated from the absorption spectrum detected by the differential photodetector 64 using the above-described equation (1). The “approximate component concentration C1 of exhaust gas” is the component concentration of exhaust gas before temperature correction. Then, in the component concentration calculation unit 73, based on the determination result determined by the determination unit 72 described above, the approximate component concentration C1 of the exhaust gas is temperature-corrected using either the measured temperature T1 or the theoretical temperature T2, The component concentration C of the exhaust gas is calculated.

For example, when the determination unit 72 determines that the area value of the absorption spectrum of H ₂ O calculated by the reference value calculation unit 71 is smaller than a predetermined threshold value, and thus the H ₂ O concentration in the exhaust gas is low. The component concentration calculation unit 73 corrects the temperature of the approximate component concentration C1 using the measured temperature T1, and calculates the component concentration C in the exhaust gas. On the other hand, when the determination unit 72 determines that the area value of the absorption spectrum of H ₂ O calculated by the reference value calculation unit 71 is larger than a predetermined threshold value, and thus the H ₂ O concentration in the exhaust gas is high. The component concentration calculation unit 73 corrects the temperature of the approximate component concentration C1 using the theoretical temperature T2, and calculates the component concentration C in the exhaust gas.

  As a method of correcting the temperature of the approximate component concentration C1, a known method can be used. As an example, in this embodiment, an absorption spectrum that is an actually measured absorption spectrum of exhaust gas is defined in advance for each temperature, pressure, and concentration. The exhaust gas component concentration C is calculated by performing pattern matching with the theoretical absorption spectrum. Specifically, the shape of the absorption spectrum of the specific component shown in the above and the shape of the theoretical absorption spectrum calculated in advance are compared to obtain the closest absorption spectrum, and the component of the specific component based on this absorption spectrum The density C is calculated. In the theoretical absorption spectrum, a plurality of theoretical absorption spectra are calculated in advance for each given pressure and concentration.

  The output unit 74 is configured as an image display device such as a CTR or a liquid crystal monitor. The above-described absorption spectra are displayed as images, and the exhaust gas temperature (measured temperature T1 and theoretical temperature T2) and concentration (estimated component concentration). C1 and component concentration C) are displayed.

Next, an exhaust gas analysis method using the exhaust gas analyzer 1 of the present embodiment will be described below.
As shown in FIG. 10, the exhaust gas analysis method of the present embodiment uses the above-described exhaust gas analyzer 1 to irradiate the exhaust gas in the exhaust passage 3 for exhausting the exhaust gas of the engine 20 with laser light and transmit the exhaust gas. In this method, the component concentration C in the exhaust gas is measured by receiving light. When the measurement is started and the exhaust gas from the engine 20 is sent to the exhaust path 3, the exhaust gas analyzer 1 is activated. The exhaust gas discharged from the engine 20 eventually passes through the exhaust gas passage hole 50a formed in the sensor body 50 of the measurement unit 5.

  First, in the measurement unit 5, the exhaust gas passing through the exhaust gas passage hole 50a is irradiated with laser light, and the laser light transmitted through the exhaust gas is received (S100). Specifically, in the measurement unit 5, the laser light emitted from the controller 6 is irradiated into the exhaust gas passage hole 50 a of the sensor main body 50 through the optical fiber 51 a of the irradiation unit 51, and the pair of reflecting mirrors 52 and 52 are used. After being reflected a plurality of times within one cross section orthogonal to the exhaust path 3, the light is received by the detector 53 a of the light receiving portion 53 and input to the controller 6 through the signal line 53 b.

  In the controller 6, after the measurement laser light transmitted through the exhaust gas and attenuated by the measurement unit 5 and the reference laser light not transmitted through the exhaust gas are converted into electrical signals, differential light detection is performed as an electrical signal. The absorption spectrum is detected by input to the device 64 (S101). The absorption spectrum of the laser beam detected by the differential photodetector 64 is input to the computer device 7 (not shown) as an electrical signal.

In the computer apparatus 7, first, the theoretical temperature T2 of the exhaust gas is calculated from the absorption spectrum detected by the differential photodetector 64 (S102). In the present embodiment, the theoretical temperature T2 of the exhaust gas is calculated from the light intensity of at least two peak wavelengths expressed in the absorption spectrum of H ₂ O (see FIG. 7) set as a predetermined component in the exhaust gas. Is used to calculate. In the absorption spectrum of H ₂ O, there are three peak wavelengths λ1, λ2, and λ3 in a predetermined wavelength band, and the light intensities of at least two peak wavelengths are compared.

  Further, when the exhaust gas discharged from the engine 20 passes through the exhaust gas passage hole 50 a formed in the sensor body 50 of the measuring unit 5, the measured temperature T 1 of the exhaust gas in the exhaust path 3 is detected by the temperature sensor 55. Then, a detection signal is sent to the computer device 7 (S103).

In the present embodiment, using the temperature (measured temperature T1 or theoretical temperature T2) detected or calculated as described above, specifically, H _{2 in} the exhaust gas as the concentration of a predetermined component in the exhaust gas. The component concentration C of the exhaust gas is calculated using the measured temperature T1 when the O concentration is low, or using the theoretical temperature T2 when the H ₂ O concentration in the exhaust gas is high as the concentration of the predetermined component in the exhaust gas. Is done. This component concentration C is calculated as follows.

That is, first, a reference value based on the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component is calculated from the absorption spectrum detected by the differential photodetector 64. In this embodiment, the differential photodetector 64 is used. The area value of the absorption spectrum of H ₂ O detected by is calculated as a reference value (S104). The area value of the absorption spectrum of H ₂ O is obtained by using the absorption spectrum (see FIG. 9) of the laser beam for measurement after passing through the exhaust gas, and the peak A · associated with the absorption of H ₂ O appearing in the absorption spectrum. Calculated as the sum of the integral values of B and C.

Then, when the area value of the absorption spectra of the calculated H _{2 O} is smaller than the predetermined threshold value is determined to be low H _{2 O} concentration in the exhaust gas, the area value in the exhaust gas is greater than a predetermined threshold value It is determined that the H ₂ O concentration is high (S105). Thus, in the exhaust gas analysis method of the present embodiment, the size of the H ₂ O concentration in the exhaust gas is determined by using the area value of the absorption spectrum of H ₂ O as a reference value.

When it is determined that the area value of the absorption spectrum of H ₂ O is smaller than the predetermined threshold value, and therefore the H ₂ O concentration in the exhaust gas is low, the above-described absorption spectrum detected by the differential photodetector 64 is used. The approximate component concentration C1 of the exhaust gas is once calculated using the mathematical formula (1) (S106), and the approximate component concentration C1 is temperature-corrected using the measured temperature T1 (S107), thereby calculating the component concentration C. (S108).

On the other hand, when it is determined that the area value of the absorption spectrum of H ₂ O is larger than the predetermined threshold value, and therefore the H ₂ O concentration in the exhaust gas is high, the above-described formula ( 1) is used to temporarily calculate the approximate component concentration C1 of the exhaust gas (S109), and the approximate component concentration C1 is temperature-corrected using the theoretical temperature T2 (S110), thereby calculating the component concentration C (S111). ).

  In this embodiment, as a method of correcting the temperature of the approximate component concentration C1, the component of the exhaust gas is obtained by pattern-matching the absorption spectrum, which is an actually measured spectrum of the exhaust gas, with a theoretical absorption spectrum that is defined in advance for each pressure and concentration. The density C is calculated.

  The calculated exhaust gas temperature (measured temperature T1 and theoretical temperature T2), concentration (estimated component concentration C1 and component concentration C), and the like are output to the output unit 74 of the computer device 7 (S112).

  As described above, the exhaust gas analyzer 1 of the present embodiment includes the measuring unit 5 that irradiates the exhaust gas in the exhaust path 3 that exhausts the exhaust gas of the engine 20 with laser light and receives the laser light that has passed through the exhaust gas. An exhaust gas analyzer 1 that measures the component concentration C in the exhaust gas based on the laser light received by the measurement unit 5, and a temperature sensor 55 that detects the actual temperature T 1 of the exhaust gas in the exhaust path 3; The differential light detector 64 for detecting the absorption spectrum of the laser light absorbed in the exhaust gas from the laser light received by the measuring unit 5 and the theory of the exhaust gas from the absorption spectrum detected by the differential light detector 64 The temperature calculation unit 70 for calculating the temperature T2 and, when the concentration of the predetermined component in the exhaust gas is low, the component temperature C of the exhaust gas is calculated using the measured temperature T1 detected by the temperature sensor 55. When the concentration of the constant component is high, the engine 20 has a component concentration calculation unit 73 that calculates the component concentration C of the exhaust gas using the theoretical temperature T2 calculated by the temperature calculation unit 70. Even when the concentration of the predetermined component in the exhaust gas is low, such as immediately before the start or immediately after the start, and the differential absorption detector 64 cannot detect an accurate absorption spectrum, the actual temperature of the exhaust gas by the temperature sensor 55 is detected. By correcting the temperature of the component concentration using T1, it is possible to accurately correct the absorption spectrum of each component in the exhaust gas. As a result, the component concentration is measured even under low temperature conditions where the concentration of the predetermined component is low. The accuracy can be improved.

Further, a reference value calculation unit 71 that calculates a reference value based on the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component from the absorption spectrum detected by the differential photodetector 64, and a reference value calculation unit 71 When the calculated reference value is smaller than the predetermined threshold value, it is determined that the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component is low, and the reference value calculated by the reference value calculation unit 71 is larger than the predetermined threshold value. In this case, since the determination unit 72 determines that the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component is high, the H ₂ O that is always present in the exhaust gas is used as the predetermined component in the exhaust gas. Various calculations from the absorption spectrum detected by the differential photodetector 64 are easy, and various reference values can be set as reference values based on the H ₂ O concentration according to the analysis accuracy and the analysis purpose. .

In particular, in the exhaust gas analyzer 1 of the present embodiment, the reference value calculation unit 71 calculates the area value of the absorption spectrum of H ₂ O detected by the differential photodetector 64 as a reference value, and the determination unit 72 When the area value is smaller than the predetermined threshold, it is determined that the H ₂ O concentration in the exhaust gas is low, and when the area value is larger than the predetermined threshold, it is determined that the H ₂ O concentration in the exhaust gas is high. Therefore, the reference value calculation unit 71 can easily calculate the reference value, and the determination unit 72 can easily determine the magnitude of the H ₂ O concentration.

  Further, in the exhaust gas analyzer 1 of the present embodiment, a temperature sensor is used which is disposed in the exhaust gas passage hole 50a formed in the measurement unit 5 and detects the actual temperature T1 of the exhaust gas passing through the exhaust gas passage hole 50a. The measured temperature T1 in the exhaust gas can be detected with high accuracy with a simple configuration.

  Note that the exhaust gas analyzer 1 and the exhaust gas analysis method of the present embodiment are not limited to the configuration described above.

For example, in the exhaust gas analyzer 1 of the above-described embodiment, the area value of the absorption spectrum of H ₂ O detected by the differential photodetector 64 in the reference value calculation unit 71 in the configuration of the computer device 7 is the reference value. When the area value is smaller than a predetermined threshold value, the determination unit 72 determines that the H ₂ O concentration in the exhaust gas is low, and when the area value is larger than the predetermined threshold value, Although it is configured to determine that the H ₂ O concentration is high, the configurations of the reference value calculation unit 71 and the determination unit 72 are not limited to this. That is, as the reference value based on the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component, another value can be used as in the following examples.

For example, another embodiment will be described with reference to FIG. 11. As a reference value based on the H ₂ O concentration, at least one peak in the absorption spectrum of H ₂ O detected by the differential photodetector 64 is used. The light intensity of the wavelength may be used. Specifically, the reference value calculation unit 71 calculates the light intensity of at least one peak wavelength in the absorption spectrum of H ₂ O detected by the differential photodetector 64 as a reference value, and the determination unit 72 When the light intensity is smaller than a predetermined threshold, it is determined that the H ₂ O concentration in the exhaust gas is low, and when the light intensity is higher than the predetermined threshold, it is determined that the H ₂ O concentration in the exhaust gas is high. Is done.

Light intensity of a given peak wavelength in the absorption spectrum of H 2 _O, using the absorption spectrum of the measurement laser light after passing through the flue gas (see Fig. 11), one of the peaks due to the absorption of H 2 _O It is calculated as the light intensity of at least one peak wavelength among the wavelengths λ1, λ2, and λ3 (for example, the light intensity I1 of the peak wavelength λ1). Then, the light intensity of the predetermined peak wavelength is in a well correlated with H _{2 O} concentration in the exhaust gas and the area value of the absorption spectrum of H 2 _O, by the light intensity of the predetermined peak wavelength increases or decreases, the exhaust gas The H ₂ O concentration in the medium also increases or decreases in correlation with this.

Predetermined Thus, by utilizing the correlation between H _{2 O} concentration of the light intensity and the exhaust gas of predetermined peak wavelength in the absorption spectrum of H 2 _O, by the reference value calculating unit 71 in the absorption spectrum of H _{2 O} By calculating the light intensity at the peak wavelength as the reference value, the reference value calculation unit 71 can easily calculate the reference value, and the determination unit 72 can easily determine the magnitude of the H ₂ O concentration. .

Another example will be described with reference to FIG. 12. The reference value based on the H ₂ O concentration is defined in advance as an actually measured absorption spectrum of H ₂ O detected by the differential photodetector 64. A fitting error with the theoretical absorption spectrum of H ₂ O may be used. Specifically, in the reference-value calculating section 71, and the measured absorption spectrum of H _{2 O,} which is detected by the differential optical detector 64 (differential absorption spectrum), predefined of H _{2 O} per temperature and pressure A fitting error with the theoretical absorption spectrum is calculated as a reference value. When the fitting error is larger than a predetermined threshold value, the determination unit 72 determines that the H ₂ O concentration in the exhaust gas is low, and the fitting error is a predetermined threshold value. When it is smaller, it is determined that the H ₂ O concentration in the exhaust gas is high.

The fitting error is calculated as a relative error based on the shapes of the measured absorption spectrum of H ₂ O and the predefined theoretical absorption spectrum of H ₂ O. For example, as an example, first, the shape of the measured absorption spectrum and the shape of the theoretical absorption spectrum are compared to perform pattern matching, and the theoretical absorption spectrum that is most approximated is obtained. Next, the measured absorption spectrum and the theoretical absorption spectrum are overlapped, and the area value A1 (integrated value) (see FIG. 12A) of the boundary surrounded by the measured absorption spectrum and the theoretical absorption spectrum is determined as the area of the theoretical absorption spectrum. The fitting error is calculated by dividing by the value B1 (integral value) (see FIG. 12B).

Then, the fitting error is in well correlation with H _{2 O} concentration in the exhaust gas and the area value of the absorption spectrum of H _{2 O} as described above, since the fitting error is increased or decreased, also H _{2 O} concentration in the exhaust gas Specifically, when the fitting error increases, the H ₂ O concentration decreases. On the other hand, when the fitting error decreases, the H ₂ O concentration increases.

As described above, when the correlation between the fitting error and the H ₂ O concentration in the exhaust gas is used, the reference value calculating unit 71 calculates the fitting error as the reference value, and the determining unit 72 calculates the H ₂ O concentration. Can be easily determined.

Further, another example will be described. As the reference value based on the H ₂ O concentration, the theoretical temperature T2 calculated by the temperature calculation unit 70 may be used as the reference value. Specifically, the reference value calculation unit 71 calculates the theoretical temperature T2 calculated by the temperature calculation unit 70 as a reference value. If the determination unit 72 determines that the theoretical temperature T2 is smaller than a predetermined threshold, the exhaust gas When the H ₂ O concentration in the exhaust gas is determined to be low and the theoretical temperature T2 is higher than a predetermined threshold, it is determined that the H ₂ O concentration in the exhaust gas is high.

Theoretical temperature T2, the temperature is raised from the start of the engine 20 in the exhaust gas to be analyzed, since becomes higher also H _{2 O} concentration in the exhaust gas, and the area value of the absorption spectrum of H _{2 O} as described above Similarly, there is a correlation with the H ₂ O concentration in the exhaust gas, and when the theoretical temperature T2 increases or decreases, the H ₂ O concentration in the exhaust gas also increases or decreases in correlation with this.

In this way, if the correlation between the theoretical temperature T2 and the H ₂ O concentration in the exhaust gas is used, the temperature calculation unit 70 calculates the theoretical temperature T2 as the reference value by the reference value calculation unit 71. The theoretical temperature T2 is simply set as the reference value by the reference value calculation unit 71, and is simple. The determination unit 72 can easily determine the magnitude of the H ₂ O concentration.

  In addition to the configuration described in the above embodiment, for example, in the exhaust gas analyzer 1 of the above-described embodiment (see FIG. 3), the temperature sensor 55 is disposed in the exhaust gas passage hole 50a formed in the measurement unit 5. Thus, the actual temperature T1 of the exhaust gas passing through the exhaust gas passage hole 50a is detected, but the arrangement configuration of the temperature sensor 55 is not limited to this. That is, as shown in FIG. 13, the temperature sensor 55 is disposed in the upstream pipe 3a with respect to the target measurement unit 5 in the exhaust path 3, and the measured temperature of the exhaust gas immediately before passing through the exhaust gas passage hole 50a. It may be configured to detect T1. By adopting such an arrangement configuration, the response delay of the actual temperature T1 detected by the temperature sensor 55 is prevented, the detection accuracy of the actual temperature T1 is increased, and consequently the measurement accuracy of the component concentration C in the exhaust gas is increased. It can be improved.

  When measuring the component concentration in other exhaust gas, the controller 6 becomes a detection target by appropriately using a laser light source 60 that can irradiate infrared laser light having a wavelength that matches the number of target components. Ingredients can be added or changed.

  In the embodiment described above, the computer device 7 calculates the measured absorption spectrum from the approximate component concentration C1 calculated by the equation (1) as the method of calculating the component concentration C of the exhaust gas by the component concentration calculation unit 73. The method of calculating (temperature correction) the component concentration C by pattern matching compared with the theoretical absorption spectrum shape uniquely determined by the above has been described, but the method of calculating the exhaust gas component concentration C is not limited to this. Further, the calculation method of the theoretical temperature T2 in the temperature calculation unit 71 is not limited to the method shown in the above-described embodiment.

The side view which showed the state which mounted the exhaust gas analyzer which concerns on one Example of this invention in the vehicle. The perspective view which showed the attachment structure of the measurement part. The side view which similarly showed the attachment structure of the measurement part of FIG. The perspective view which showed the structure of the measurement part. The functional block diagram which showed the structure of the controller. It shows the signal intensity of the laser beam in a wavelength band including the detected peak of H 2 _O. It shows the absorption spectrum of the laser beam in a wavelength band including the detected peak of H 2 _O. The functional block diagram which showed the structure of the computer apparatus. It shows the area of each peak due to absorption of H _{2 O} which appears in the absorption spectrum. The flowchart which showed the exhaust gas analysis method using the exhaust gas analyzer of a present Example. It illustrates the optical intensity of each peak wavelength due to absorption of H _{2 O} which appears in the absorption spectrum. (A) is the figure which showed the area of the boundary area enclosed by the measurement absorption spectrum and the theoretical absorption spectrum, (b) is the figure which showed the area of the theoretical absorption spectrum. The side view which showed the attachment structure of the measurement part of another Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust gas analyzer 3 Exhaust path 5 Measuring part 6 Controller 7 Computer apparatus 20 Engine (internal combustion engine)
DESCRIPTION OF SYMBOLS 50 Sensor main body 50a Exhaust gas passage hole 51 Irradiation part 53 Light-receiving part 55 Temperature sensor (temperature detection means)
64 Difference type photodetector (absorption spectrum detecting means)
70 Temperature calculation part (temperature calculation means)
71 Reference value calculation unit (reference value calculation means)
72 determination unit (determination means)
73 Component concentration calculation unit (component concentration calculation means)

Claims (11)

An exhaust gas in an exhaust path for exhausting exhaust gas from an internal combustion engine is irradiated with laser light, and a measurement unit that receives the laser light transmitted through the exhaust gas is provided. The exhaust gas is emitted based on the laser light received by the measurement unit. An exhaust gas analyzer for measuring the concentration of components in
Temperature detecting means for detecting the measured temperature of the exhaust gas in the exhaust path;
An absorption spectrum detecting means for detecting an absorption spectrum of the laser light absorbed in the exhaust gas from the laser light received by the measurement unit;
Temperature calculating means for calculating the theoretical temperature of the exhaust gas from the absorption spectrum detected by the absorption spectrum detecting means;
When the concentration of the predetermined component in the exhaust gas is low, the component concentration in the exhaust gas is calculated using the measured temperature detected by the temperature detection unit, and when the concentration of the predetermined component in the exhaust gas is high, the temperature calculation unit An exhaust gas analyzing apparatus comprising: a component concentration calculating means for calculating a component concentration in the exhaust gas using the theoretical temperature calculated by the above. Reference value calculating means for calculating a reference value based on the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component from the absorption spectrum detected by the absorption spectrum detecting means;
When the reference value calculated by the reference value calculation means is smaller than a predetermined threshold, it is determined that the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component is low, and the reference calculated by the reference value calculation means The exhaust gas analyzer according to claim 1, further comprising a determination unit that determines that the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component is high when the value is larger than a predetermined threshold. The reference value calculation means calculates the area value of the absorption spectrum of H ₂ O detected by the absorption spectrum detection means as a reference value,
The determination means determines that the H ₂ O concentration in the exhaust gas is low when the area value is smaller than a predetermined threshold, and the H ₂ O concentration in the exhaust gas when the area value is larger than the predetermined threshold. The exhaust gas analyzer according to claim 2, wherein the exhaust gas analyzer is determined to be high. The reference value calculation means calculates, as a reference value, the light intensity of at least one peak wavelength in the absorption spectrum of H ₂ O detected by the absorption spectrum detection means,
The determination means determines that the H ₂ O concentration in the exhaust gas is low when the light intensity is smaller than a predetermined threshold, and the H ₂ O concentration in the exhaust gas when the light intensity is higher than a predetermined threshold. The exhaust gas analyzer according to claim 2, wherein the exhaust gas analyzer is determined to be high. In the reference value calculation means, a fitting error between the measured absorption spectrum of H ₂ O detected by the absorption spectrum detection means and a predefined theoretical absorption spectrum of H ₂ O is calculated as a reference value,
By the determination means, wherein when the fitting error is larger than a predetermined threshold value is determined to be low H _{2 O} concentration in the exhaust gas, H _{2 O} concentration in the exhaust gas when the fitting error is smaller than a predetermined threshold value The exhaust gas analyzer according to claim 2, wherein the exhaust gas analyzer is determined to be high. The reference value calculation means calculates the theoretical temperature calculated by the temperature calculation means as a reference value,
The determination means determines that the H ₂ O concentration in the exhaust gas is low when the theoretical temperature is lower than a predetermined threshold, and the H ₂ O concentration in the exhaust gas when the theoretical temperature is higher than a predetermined threshold. The exhaust gas analyzer according to claim 2, wherein the exhaust gas analyzer is determined to be high. The component concentration calculation means
Calculate the approximate component concentration in the exhaust gas from the absorption spectrum detected by the absorption spectrum detection means, and use the measured temperature detected by the temperature detection means or the theoretical temperature calculated by the temperature calculation means. The exhaust gas analyzer according to any one of claims 1 to 6, wherein the component concentration in the exhaust gas is calculated by correcting the temperature of the component concentration.   The temperature detection means includes a temperature sensor that is disposed in an exhaust gas passage hole formed in the measurement unit and detects an actual temperature of exhaust gas that passes through the exhaust gas passage hole. Item 8. The exhaust gas analyzer according to any one of Items 7. An exhaust gas analysis method for measuring a component concentration in exhaust gas by irradiating the exhaust gas in an exhaust path for discharging exhaust gas of an internal combustion engine with laser light and receiving the laser light transmitted through the exhaust gas,
A temperature detection step of detecting an actual temperature of exhaust gas in the exhaust path;
An absorption spectrum detecting step of detecting an absorption spectrum of the laser light absorbed in the exhaust gas from the received laser light;
A temperature calculating step for calculating a theoretical temperature of the exhaust gas from the absorption spectrum detected by the absorption spectrum detecting step;
When the concentration of the predetermined component in the exhaust gas is low, the component concentration in the exhaust gas is calculated using the measured temperature detected by the temperature detection step, and when the concentration of the predetermined component in the exhaust gas is high, the temperature calculation step And a component concentration calculation step of calculating a component concentration in the exhaust gas using the theoretical temperature calculated by the exhaust gas analysis method. A reference value calculation step of calculating a reference value based on the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component from the absorption spectrum detected by the absorption spectrum detection step;
When the reference value calculated by the reference value calculation step is smaller than a predetermined threshold, it is determined that the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component is low, and the reference calculated by the reference value calculation step The exhaust gas analysis method according to claim 9, further comprising a determination step of determining that the H ₂ O concentration in the exhaust gas as the concentration of the predetermined component is high when the value is larger than a predetermined threshold. The component concentration calculation step includes:
Calculate the approximate component concentration in the exhaust gas from the absorption spectrum detected by the absorption spectrum detection step, and use the measured temperature detected by the temperature detection step or the theoretical temperature calculated by the temperature calculation step. The exhaust gas analysis method according to claim 9 or 10, wherein the component concentration in the exhaust gas is calculated by correcting the temperature of the component concentration.

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