JP2010071271A - Fuel concentration measuring device, fuel concentration measuring method, and method of preparing calibration curve therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel concentration measuring device and a fuel concentration measuring method capable of measuring a fuel concentration under proper measuring conditions utilizing SIBS (Spark Induced Breakdown Spectroscopy ) and a method of preparing a calibration curve for the device and the method. <P>SOLUTION: This fuel concentration measuring device includes a discharge device 104 for generating a spark discharge, a spectrograph 112 and a detector 113 for obtaining the intensity values of light in predetermined two wavelength ranges by dispersing the light produced by the spark discharge, an emitting light intensity ratio calculation part 123 for calculating the intensity ratio of the light in the two wavelength ranges, a conversion part 125 for outputting a fuel concentration corresponding to the intensity ratio using a calibration curve 124 prepared beforehand, and a time difference controller 115 for controlling the time of measurement by the detector 113. The time difference controller 115 selects the time of measurement from the time of discharge by the discharge device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel concentration measuring apparatus and a fuel concentration measuring method using an optical technique, and a calibration curve preparing method therefor, and in particular, spark induced breakdown spectroscopy (hereinafter referred to as “SIBS”). TECHNICAL FIELD The present invention relates to a fuel concentration measuring device and a fuel concentration measuring method using a laser, and a calibration curve preparation method therefor.

  SIBS is a measurement technique in which information about the components of a sample is obtained by exciting or ionizing the sample by discharge and spectroscopically analyzing the resulting light. For a long time, this technique has been widely applied to solid samples in the fields of steel, metallurgy, etc., but in recent years, it has been tried to apply to qualitative and quantitative analysis of trace gas components in gas samples (for example, Patent Document 1).

  In machines that handle combustion, such as combustion engines and combustion devices, spark discharge using spark plugs has been used for ignition for a long time. In addition, it is known that the fuel concentration in the part that performs ignition greatly affects the success or failure of combustion, etc. Fuel consumption, higher efficiency, improved exhaust gas, output characteristics, exhaust characteristics Need to understand and control. For this reason, various attempts have been made to apply SIBS to light generated at the time of ignition by spark discharge and obtain knowledge about fuel concentration and the like.

  For example, Patent Document 2 discloses a combustion control apparatus that performs SIBS using a spark plug having an optical fiber penetrated through a center electrode. This apparatus generates a spark discharge with the spark plug during an intake process, an exhaust process, or ignition, and condenses the resulting light with an optical fiber. This light is incident on a spectrophotometer, and composition analysis of oxygen, nitrogen oxides, carbon monoxide, hydrocarbons, etc. is performed by spectroscopy.

  Patent Document 3 discloses a local air-fuel mixture concentration measurement method in which spectrum analysis of ignition emission is performed for OH band at a wavelength of 306 nm and CN band at a wavelength of 390 nm. In this method, the values obtained by removing the emission intensity of NO2 at the base portion from the emission intensity of OH band and CN band are defined as CN intensity and OH intensity, respectively, and the ratio between CN intensity and OH intensity is obtained, Estimate the concentration of the air-fuel mixture around the spark plug at the timing.

Japanese Patent Laid-Open No. 2005-147887 JP-A-6-167240 JP 11-237315 A

  The devices described in Patent Document 1 and Patent Document 2 perform composition analysis, qualitative analysis, and the like on chemical components in the atmosphere in which discharge is performed. However, composition analysis and qualitative analysis must perform spectrum matching. Therefore, it takes time to calculate and verify the signal. Therefore, it is difficult to apply to an internal combustion engine or the like in which repeated combustion is performed, such as a spark ignition type piston engine, because the calculation amount is too large.

  In the apparatus described in Patent Document 3, the concentration of the air-fuel mixture is estimated from the ratio of the intensities of the two wavelength band components, OH band and CN band. However, as pointed out in Patent Document 3, the spectrum of light during spark discharge changes significantly with the progress of time. According to Patent Document 3, although it is sufficient to perform the measurement at an appropriate timing, it is not disclosed at which timing the measurement should be performed concretely and its means.

  Thus, the measurement of fuel concentration using SIBS is insufficiently optimized for measurement conditions.

  The present invention has been proposed in view of the above circumstances, and a fuel concentration measuring device and a fuel concentration measuring method capable of performing fuel concentration measurement under appropriate measurement conditions using SIBS, and for the same It is intended to provide a method for preparing a calibration curve.

  In order to solve the above-described problems and achieve the object, a fuel concentration measuring device according to the present invention has any one of the following configurations.

[Configuration 1]
A discharge device for generating a spark discharge; a measuring means for dispersing light generated by the spark discharge to obtain light intensity values of two predetermined wavelength bands; and calculating a light intensity ratio of the two wavelength bands. Using a calibration curve prepared in advance, a conversion means for outputting the fuel concentration corresponding to the intensity ratio, and a control means for controlling the measurement timing by the measurement means, the control means comprising: The measurement time by the measuring means is selected from the discharge period by the discharge device.

  The intensity of the light of the wavelength component corresponding to the emission of the chemical species that is considered to have a relationship with the fuel concentration (or equivalent ratio) depends greatly on the time evolution of the discharge from the start of the discharge, and is delayed until the start of measurement. The dependency changes depending on the time and the measurement period. By selecting the measurement time from the discharge period of the discharge device, it becomes possible to select and measure a time zone highly dependent on the fuel concentration.

[Configuration 2]
In the fuel concentration measurement device having the configuration 1, the discharge device performs capacity discharge at the start of discharge, and the control means selects the measurement start time and end time so that the capacity discharge period is included in the period between them. It is characterized by this.

  Since the energy applied per hour is high during the capacitive discharge period, the plasma energy state is high, recombination between other atoms is likely to occur, and the emission intensity depends greatly on the fuel concentration. By selecting the measurement time so as to include this capacitive discharge period, it is possible to obtain a good measurement result of the fuel concentration.

[Configuration 3]
In the fuel concentration measuring apparatus having the configuration 2, the control means selects a period from the spark discharge start time to 50 microseconds as the measurement time.

  The capacitive discharge generally ends in about 50 microseconds and often shifts to another discharge form such as induction discharge. The spectral pattern differs greatly between light in capacitive discharge and light in induction discharge. By selecting the measurement time from the start of discharge to 50 microseconds, it becomes possible to perform measurement in a time zone in which a measurement result highly dependent on the fuel concentration is obtained.

[Configuration 4]
In the fuel concentration measuring device having the configuration 2 or the configuration 3, the interval between the discharge gaps of the discharge means is 3 mm or more.

  When the gap of the discharge gap is 3 mm or more, the discharge is started at a high breakdown voltage. This increases the applied energy per time. Since the plasma energy state is high and recombination between other atoms easily occurs, a good measurement result having high dependence on the fuel concentration can be obtained.

[Configuration 5]
In the fuel concentration measuring device having any one of Configurations 1 to 4, one of the two wavelength bands includes a wavelength band of CN emission, and the other includes a wavelength band of NH emission.

  The intensity ratio between CN emission and NH emission is more dependent on the fuel concentration than the intensity ratio between CN emission and OH emission according to the prior art. Therefore, if the wavelength band of CN emission and the wavelength band of NH emission are selected as the wavelength bands used for fuel concentration measurement, the accuracy of fuel concentration measurement is improved.

[Configuration 6]
In the fuel concentration measuring device having any one of Configurations 1 to 4, one of the two wavelength bands includes a hydrogen atomic emission wavelength band, and the other includes an oxygen atomic emission wavelength band. Is.

  It is possible to measure the fuel concentration from the fuel component and the air component contained in the air-fuel mixture instead of products such as radicals that are secondarily generated as a result of plasma generation by discharge. This contributes to improvement in measurement accuracy. In addition, since atomic emission measurement, which has conventionally used laser measurements such as laser-induced breakdown spectroscopy (LIBS), can be performed with SIBS, atomic emission can be achieved at a small size and at low cost without using a special device such as a laser light source. Measurement based on can be performed.

[Configuration 7]
In the fuel concentration measuring device having any one of Configurations 1 to 6, the control means controls the measurement timing by blocking the optical path.

[Configuration 8]
In the fuel concentration measurement device having any one of Configurations 1 to 6, the measurement means detects light by a detector that photoelectrically converts light in two wavelength bands, and the control means controls the drive timing of the detector. It is characterized by doing.

[Configuration 9]
In the fuel concentration measuring device having any one of Configurations 1 to 6, the measurement means detects light in two wavelength bands by a detector that sequentially photoelectrically converts, and the control means includes signals output from the detector. In this case, a feature corresponding to the measurement time is extracted and given to the calculation means.

[Configuration 10]
In the fuel concentration measurement device having any one of Configurations 1 to 9, the discharge device is a spark ignition device.

  By using a spark ignition device as the discharge device, ignition and fuel concentration measurement can be performed at the same position and at the same time. Therefore, it is possible to appropriately measure the fuel concentration in a portion that greatly affects the success or failure of combustion.

[Configuration 11]
In the fuel concentration measurement device having any one of Configurations 1 to 10, the discharge device performs spark discharge with energy less than the minimum ignition energy to be measured.

  By discharging with energy less than the minimum ignition energy, the fuel concentration can be measured without igniting the measurement target. This is useful, for example, when fuel concentration measurement before ignition is required.

[Configuration 12]
In the fuel concentration measurement device having any one of Configurations 1 to 11, further, an optical for suppressing incidence of light from the outside of a measurement region including a spark discharge generation position and a predetermined range in the vicinity thereof to the measurement unit. It is characterized by comprising a system.

  By suppressing the incidence of light from the outside of the measurement region to the measurement means by the optical system, the locality of measurement is enhanced. That is, it is possible to accurately measure the fuel concentration at a part that greatly affects combustion.

[Configuration 13]
The fuel concentration measuring device having any one of Configurations 1 to 12, further comprising means for irradiating an electromagnetic wave toward a spark discharge generation position to supply energy to charged particles generated by the spark discharge. It is what.

  When the electromagnetic wave is irradiated toward the position where the spark discharge is generated, the plasma generated by the spark discharge receives energy. As a result, the plasma region is enlarged, and light emission occurs in a wide range. That is, the measurement range can be expanded.

  The fuel concentration measuring method according to the present invention has the following configuration.

[Configuration 14]
A discharge device that generates a spark discharge, a measuring unit that splits light generated by the spark discharge to obtain an intensity value of light in two wavelength bands, a calculation unit that calculates an intensity ratio of light in two wavelength bands, and a preparation in advance Using the calibration curve thus obtained and controlling the conversion means for outputting the fuel concentration corresponding to the input intensity ratio so as to measure the fuel concentration, wherein the measurement timing by the measuring means is determined by the discharge device. It is characterized by selecting from within the discharge period.

  The calibration curve preparation method according to the present invention has the following configuration.

[Configuration 15]
A calibration curve preparation method according to any one of Configurations 1 to 14, wherein a first step of introducing a premixed gas with a known fuel concentration in the vicinity of a discharge electrode, and generating a spark discharge using the discharge electrode A second step of splitting the light generated by the spark discharge and obtaining a light intensity value of the two wavelength bands generated at the position where the spark discharge is generated at the measurement time, and the intensity of the light of the two wavelength bands A fourth step of calculating the ratio; and a fifth step of recording the fuel concentration in the first step and the intensity ratio in the fourth step in correspondence with each other.

  According to the configuration 1, the control unit selects the measurement timing by the measurement unit from the discharge period by the discharge device. Therefore, it is possible to measure the fuel concentration with appropriate and high accuracy.

  According to Configuration 2, it is possible to obtain a good measurement result from light emission during the capacitive discharge period.

  According to the configuration 3, it is possible to perform measurement in a time zone in which a measurement result highly dependent on the fuel concentration is obtained.

  According to Configuration 4, it is possible to start discharging at a high breakdown voltage and obtain a good measurement result that is highly dependent on the fuel concentration.

  According to Configuration 5, the accuracy of fuel concentration measurement is improved by selecting the wavelength band of CN emission and the wavelength band of NH emission as wavelength bands.

  According to the configuration 6, it becomes possible to measure the fuel concentration from the fuel component and the air component contained in the air-fuel mixture, and the measurement accuracy is improved. In addition, if atomic emission measurement, which generally uses laser measurement such as LIBS, is performed by SIBS, measurement based on atomic emission can be performed at a small size and at low cost without using a special device such as a laser light source.

  According to Configuration 7, the measurement time can be optically selected by blocking the optical path. This contributes to simplification of the signal processing system.

  According to Configuration 8, the measurement time can be selected by controlling the drive time of the detector. That is, the measurement time can be appropriately selected without depending on the time resolution of the signal processing system.

  According to the configuration 9, since the measurement time is selected by extracting the signal used for the calculation from the output signal of the detector, the measurement time can be selected electrically or logically without depending on the mechanical measurement time selection. Is possible.

  According to the configuration 10, it is possible to appropriately measure the fuel concentration in a portion that greatly determines the success or failure of combustion.

  According to Configuration 11, the fuel concentration can be measured without igniting the measurement target.

  According to the configuration 12, the locality of measurement is improved, and the fuel concentration at a part that greatly affects combustion can be accurately measured.

  According to Configuration 13, the measurement range can be expanded.

  According to the configuration 14, the discharge device, the measurement unit that divides the light generated by the spark discharge and obtains the intensity value of the light in the two wavelength bands, the calculation unit that calculates the intensity ratio of the light in the two wavelength bands, By using the prepared calibration curve and operating the conversion means for outputting the fuel concentration corresponding to the input intensity ratio by this method, the measurement time by the measurement means is selected from the discharge period by the discharge device. This makes it possible to measure the fuel concentration with appropriate and high accuracy.

  According to the configuration 15, the calibration curve according to any one of the configurations 1 to 14 can be obtained.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[First Embodiment]
FIG. 1 shows a schematic configuration of a fuel concentration measuring apparatus 100 according to the present embodiment in the form of a block diagram. The fuel concentration measuring apparatus 100 has a configuration for performing spark discharge. That is, the ignition controller 101 for generating an ignition signal 151 indicating the start and end of energy input for generating a spark discharge in response to a predetermined external input 150, the DC power source 102, and the DC power source 102 are connected. An ignition coil 103 and a spark plug 104 connected to the ignition coil 103 are provided. The ignition controller 101 may be, for example, an engine control unit (ECU) in an internal combustion engine. Specifically, the DC power supply can be a 12-volt battery for automobiles, a 20-volt DC stabilized power supply, or the like. Both the ignition coil 103 and the spark plug 104 may be general for an internal combustion engine. The gap between the center electrode of the spark plug 104 and the ground electrode (hereinafter, this gap is referred to as “discharge gap”) is set to 3 mm or more. The spark plug is disposed so that the discharge gap is exposed in an environment where fuel and air exist. For example, it is disposed in the vicinity of the gas ejection hole of the burner or in the combustion chamber. The spark plug 104 is generally used for ignition, and the spark plug 104 may be disposed at any position where the spark plug is generally disposed.

  The fuel concentration measuring apparatus 100 further includes a condensing optical system 110 disposed at a position facing the discharge gap of the spark plug 104 and light emitted from the discharge gap and passing through the condensing optical system from one end to the other end. A light guide 111 that leads to the light source, a spectrometer 112 that emits the wavelength-resolved incident light from the other end of the light guide 111, a detector 113 that photoelectrically converts the light emitted from the spectrometer for each wavelength band, and a detector And a signal processor 114 that performs processing such as amplification, A / D conversion, and association with a wavelength band on the signal obtained as a result of photoelectric conversion by, and outputs a spectrum signal 170 of incident light to the spectrometer. .

  The condensing optical system 110 condenses light from an object point of the condensing optical system 110 on a predetermined image point. Specifically, it is a lens, a mirror, or an optical system combining them. The condensing optical system 110 may be configured by combining a plurality of mirrors such as a Cassegrain optical system and a Maxtoff optical system. These optical systems can focus light with high locality, particularly in the direction of the straight line (optical axis direction) connecting the object point and the image point, while suppressing the incidence of light from areas other than the discharge generation position. Become. Note that a plurality of mirrors may be filled with a translucent medium and integrated. Further, a condensing optical system may be incorporated in the electrode, insulator, outer conductor, or the like of the spark plug 104.

  In addition, this condensing optical system needs to have a transmission characteristic to the ultraviolet region up to about 310 nm on the short wavelength side. In addition, it is necessary to maintain good optical characteristics under a high heat and high pressure environment in the combustion chamber of the internal combustion engine in which the spark plug 104 can be installed. Therefore, when the condensing optical system 110 includes a light-transmitting component such as a lens, they are made of a material such as artificial quartz, sapphire, or the like, or optical glass having optical and mechanical characteristics similar thereto. It is desirable that

  Specifically, the light guide path 111 may be an optical fiber. The light guide path 111 is also required to have an ultraviolet transmission characteristic like the condensing optical system 110. If the incident end of the light guide 111 can be disposed sufficiently close to the position where the discharge occurs, the incident end itself of the light guide 111 may be used as a condensing optical system. For example, the light guide 111 may pass through the electrode, the insulator, the outer conductor, or the like of the spark plug 104 in order to arrange the incident end sufficiently close to the position where the discharge is generated.

  The spectroscope 112 is specifically a diffraction grating type spectroscope, and the traveling direction of the emitted light is deflected according to the wavelength. The detector 113 is specifically an ICCD camera, and the exposure start time and the exposure time are controlled by an external trigger signal 162. The operation of the ICCD camera itself is well known, and description thereof will not be repeated here. The spectroscope 112, the detector 113, and the signal processor 114 have various forms and systems. Any of these various types can be used. For example, the spectroscope 112 may use a prism, or may be a filter bank type using a filter such as an interference filter or a dichroic mirror. The detector 113 is not limited to the ICCD, and may be a CMOS, a photodiode, a photomultiplier tube, or the like. What is necessary is just to select the signal processor 114 according to the detector 114 suitably.

  The fuel concentration measuring device 100 further includes a calculator 120 connected to receive the output signal 170 of the signal processor 114. As will be apparent from the following description, the arithmetic unit 120 is specifically realized by general computer hardware and programs and data that operate on the hardware. The operation and functions of the computer itself are well known, and description thereof will not be repeated here.

  The computing unit 120 includes the following functional units. That is, the first signal extraction unit 121 that extracts and outputs the light intensity value of the first wavelength band from the spectrum signal 170, and the light intensity value of the predetermined second wavelength band is extracted from the spectrum signal 170 and output. A second signal extraction unit 122 that calculates the ratio of the intensity values of the two input lights, and a calibration curve that represents the correspondence between the emission intensity ratio and the fuel concentration. A calibration curve storage unit 124, and a conversion unit 125 that reads out and outputs the fuel concentration corresponding to the input signal of the emission intensity ratio from the configuration curve storage unit 124.

  In the present embodiment, the first signal extraction unit 121 extracts the intensity value in the wavelength band near the wavelength of 336 nm. This is a wavelength band corresponding to NH radical emission (NH emission). The second signal extraction unit 122 extracts the intensity value in the wavelength band near the wavelength of 388 nm. This is a wavelength band corresponding to CN radical emission (CN emission). The calibration curve is information in which the emission intensity ratio and the fuel concentration are made to correspond one-to-one, and the form thereof may be a function, or may be a conversion table or a group of similar data. A method for preparing the calibration curve will be described later.

  The fuel concentration measuring apparatus 100 is further connected to receive the output signal 151 of the ignition controller 101, and a time difference that gives a predetermined gate signal 162 to the detector 113 when a preset time elapses with the time when the signal is received as a base point. A controller 115 is provided. Specifically, the time difference controller 115 may be a delay pulse generator or the like.

  The fuel concentration measuring apparatus 100 operates as follows. That is, when the external signal 150 is given in a state where the air-fuel mixture to be measured exists between the discharge gaps, the ignition controller 101 outputs the ignition signal 151. The ignition signal 151 is a gate signal for a predetermined time. The ignition coil 103 receives power from the DC power supply 102 during the period in which the ignition signal 151 is applied, boosts the voltage at the end of the application of the ignition signal 151, and applies the boosted DC voltage to the spark plug 104.

  When the spark plug 104 receives a DC voltage, discharge occurs in the discharge gap. The discharge form of the spark plug 104 is constituted by a capacitive discharge in which several thousand to several tens of thousands of volts are applied to the gas in several microseconds, and an induction discharge in which a voltage of several hundred volts is applied from the end of the capacity discharge to the completion of the discharge. The amount of energy applied differs between the capacitive discharge period and the induction discharge period.

  During the period in which the discharge occurs, the measurement target existing in this portion is turned into plasma between the discharge gaps, and as a result, light emission occurs. The light collecting optical system 110 collects the emitted light. The condensed light enters the spectroscope 112 through the light guide 111 and is wavelength-resolved. The detector 113 receives the wavelength-resolved light 161.

  On the other hand, the time difference controller 115 operates in response to the application end time of the ignition signal 151 and gives a trigger signal 162 to the detector. This trigger signal 162 corresponds to the start time of photoelectric conversion by the detector 113 and the end time of photoelectric conversion. The detector 113 operates during a period between the start time and the end time of photoelectric conversion, and photoelectrically converts the light received during that period for each wavelength band.

  That is, the time from the application end time of the ignition signal 151 to the start time of photoelectric conversion is the measurement delay time for the discharge, and the time during which the detector 113 is operating is the time during which the measurement is performed. In the following description, the time during which this measurement is performed may be referred to as “exposure time”. In the present embodiment, the time difference controller 115 gives the trigger signal 162 to the detector 113 so that the delay time is 0 microseconds and the exposure time is 50 microseconds. The signal 163 generated by the photoelectric conversion is subjected to signal processing to generate a spectrum signal 170 representing the light intensity for each wavelength.

  When the computing unit 120 receives the spectrum signal 170, the first signal extraction unit 121 extracts the intensity ratio of the wavelength band near the wavelength of 336 nm, and the second signal extraction unit 122 calculates the intensity value of the wavelength band near the wavelength of 388 nm. Extract. These two extracted intensity values are given to the emission intensity ratio calculation unit 123. The light emission intensity ratio calculation unit 123 calculates and outputs a ratio of intensity values. The conversion unit 125 reads the fuel concentration corresponding to the emission intensity ratio from the configuration curve storage unit 124 and outputs this as the measurement result 180.

  There is a clear difference in intensity between the capacitive discharge period and the induction discharge period. This difference is considered to be influenced by the energy state of the plasma. During the period of capacitive discharge, energy of several millijoules is applied to the gas within a few microseconds, causing dielectric breakdown of the gas molecules and generating plasma. At this time, since the energy state is high and immediately after dielectric breakdown, the abundance of CN radicals, which are recombination of atoms existing in a high energy state, is large. In contrast, in the case of induction discharge, weak energy is applied to the gas as compared with capacity discharge of 1 millijoule or less. Considering that the discharge continues, the plasma state remains the same, but the energy state of the plasma is low. In this state, it is difficult to sustain the CN radical, and the excited state is maintained as a stable molecule. The N2 emission overlaps in the wavelength band corresponding to the CN radical emission, and the band head has a wavelength of 391 nm. Since a large amount of stable N2 exists in this low energy state, the emission intensity gradually increases at a low equivalent ratio. Therefore, in the induction discharge period, the spectrum is widely distributed over the wavelength range of 250 nm to 800 nm, and the spectrum shape is not atomic emission showing an independent line spectrum, but molecular emission having a continuous spectrum shape is dominant. Since the induction discharge period lasts long, if spectral analysis is performed in a state where the entire plasma light generated by the discharge is integrated in the time direction, light emission caused by the induction discharge becomes dominant.

  Looking at the emission spectrum when the equivalent ratio representing the mixing ratio of fuel and air is changed, the emission intensity and the spectrum shape change in the wavelength bands near 310 nm, 340 nm, and 390 nm in response to the change of the equivalent ratio. Each wavelength band is a wavelength band including a wavelength corresponding to OH radical emission (307 nm), a wavelength corresponding to NH radical emission (336 nm), and a wavelength corresponding to CN radical emission (388 nm). Looking at the emission intensity obtained by integrating the regions containing OH radicals, NH radicals, and CH radicals with respect to the equivalent ratio, OH radicals and NH radicals show a decreasing tendency as the fuel concentration increases. The emission of OH radicals increases as the equivalence ratio increases regardless of the exposure time and delay time of the detector 162, and tends to decrease after the equivalence ratio of 0.6. NH radicals decrease almost linearly with increasing equivalence ratio under the measurement conditions of an exposure time of 50 microseconds and a delay time of 0 microseconds, but no change is seen under other measurement conditions. CN radicals show no difference in intensity at low equivalent ratios under conditions other than the exposure time of 50 microseconds and the delay time of 0 microseconds.

  Intensity ratio with respect to equivalent ratio under conditions of exposure time of 50 microseconds and delay time of 0 microseconds The intensity ratio of CN radical emission and OH radical emission is a constant intensity ratio with respect to an increase in equivalent ratio as described in Patent Document 3. Increases in both, confirming the dependence of the strength ratio on the equivalence ratio. Similarly, the intensity ratio between the emission of CN radicals and the emission of OH radicals is also seen in both cases where a constant intensity ratio increases with respect to the increase in equivalent ratio, and the dependence of the intensity ratio on the equivalent ratio can be confirmed. Here, when the intensity ratio of the former is compared with the intensity ratio of the latter, the latter intensity ratio is more dependent on the equivalent ratio, and increases more strongly as the equivalent ratio increases. This is due to the fact that the emission of NH radicals decreases linearly with increasing equivalent ratio.

  As described above, in the measurement in the time zone including the period in which the capacitive discharge with the exposure time of 50 microseconds and the delay time of 0 microsecond occurs, the energy state of the plasma is high and the dependence on the radical emission and the fuel concentration can be confirmed.

  The calibration curve in the above-described embodiment prepares a measurement target with a known fuel concentration, performs measurement on this sample using the fuel concentration measurement device 100, and calculates the intensity ratio output from the emission intensity calculation unit 123. What is necessary is just to make it memorize | store in the calibration curve memory | storage part 124 corresponding to a fuel concentration.

[Second Embodiment]
In the above-described embodiment, the light intensity values of the wavelength components corresponding to the NH radical and the CN radical are extracted, but the present invention is not limited to such a case. For example, in the fuel concentration measuring apparatus 100, the wavelength band targeted for extraction by the first signal extraction unit 121 is a band including a wavelength of 656 nm, and the wavelength band targeted for extraction by the second signal extraction unit 122 is a wavelength of 777 nm. It is good also as a zone | band containing.

  A wavelength band including a wavelength of 656 nm is a wavelength band corresponding to emission of hydrogen atoms, and a wavelength band including a wavelength band of 777 nm is a wavelength band corresponding to emission of oxygen atoms. In general, it is difficult to confirm these atomic emission from the light emission caused by the spark discharge. However, when the gap of the discharge gap is opened to about 3 mm in the spark plug 104, the dielectric breakdown voltage is 1.3 times that of a general spark plug. It increases about twice. By using such a spark plug 104, therefore, a lot of energy is applied to the measurement target. As a result, a lot of atomic emission can be obtained. In addition, if the shape of the ground electrode is sharpened, the surface charge density is high, and the electric field strength is increased, the kinetic energy of the cations colliding with the ground electrode increases, resulting in secondary electron emission (γ action). The number of collision ionization increases and the generation of atoms can be promoted.

  Thus, when discharge in which atomic emission can be confirmed is performed, emission of hydrogen atoms and oxygen atoms can be detected. The intensity ratio of the wavelength band corresponding to these emission also depends on the fuel concentration and shows a high correlation with the equivalent ratio. Therefore, by converting this intensity ratio into the fuel concentration, the fuel concentration can be measured satisfactorily.

  Atomic emission is effective for fuel concentration measurement because the proportional relationship of emission intensity to input amount is clear. Moreover, it is also possible to measure simultaneously the measurement similar to 1st Embodiment of the wavelength band corresponding to radical light emission, and the measurement shown to this embodiment. This simultaneous measurement has the advantage that fuel concentration can be measured from both plasma products and substances.

[Other variations]
In each of the above-described embodiments, the discharge at the spark plug 104 may give the measurement target with sufficient energy to ignite the measurement target. In this way, ignition and fuel concentration measurement can be performed simultaneously and at the same position.

  Further, in each of the above-described embodiments, the discharge at the spark plug 104 may give the measurement target energy that is less than the ignition target (that is, energy equal to or lower than the minimum ignition energy) by discharge. This makes it possible to measure the fuel concentration without igniting the measurement target at a timing that is not directly related to ignition, such as before ignition.

  In the above-described embodiment, the measurement timing is controlled by the delay time of the operation of the detector 113 and the exposure time, but the present invention is not limited to this. For example, a shutter or the like may be provided on any one of the optical paths from the discharge gap to the detector 113, and the measurement timing may be controlled by driving the shutter. Alternatively, the measurement timing may be controlled by causing the detector 113 to perform photoelectric conversion continuously or sequentially and performing gate processing in the time direction on the signal during signal processing. Alternatively, the photoelectric conversion is performed continuously or sequentially by the detector 113, and the signal is accumulated and stored on the arithmetic unit 120, and only the portion corresponding to the measurement time is included in the first signal. You may make it give to the extraction part 121 and the 2nd signal extraction part 122. FIG.

  In each of the above-described embodiments, the calculation unit 120 extracts two wavelength bands by calculation, and obtains intensity values of these wavelength bands. However, the present invention is not limited to this. The detector 113 may photoelectrically convert only the light in the two wavelength bands described above.

  In each of the above-described embodiments, plasma is generated by spark discharge and the light is dispersed, but energy may be supplied to the plasma by irradiating the microwave with the plasma. By doing in this way, the energy density of the area | region where a plasma arises by discharge can be adjusted. This also makes it possible to sustain a plasma with a high energy density such as plasma during capacitive discharge for a long time. It is also possible to enlarge the area to be converted into plasma.

  Although the time difference controller 115 selects the measurement timing based on the timing of the ignition signal 115, the present invention is not limited to this. You may select measurement time on the basis of the first time when light emission was detected.

  The embodiment disclosed this time is merely an example, and the scope of the present invention is not limited to only the above-described embodiments. The scope of the present invention is indicated by each claim in the claims after considering the description of the specification and the drawings, and includes all modifications within the meaning and scope equivalent to the words described therein. It is a waste.

It is a block diagram showing a schematic structure of a fuel concentration measuring device concerning an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Ignition controller 102 DC power supply 103 Ignition coil 104 Spark plug 110 Condensing optical system 111 Light guide path 112 Spectrometer 113 Detector 114 Signal processor 115 Time difference controller 120 Calculator 121 First signal extraction part 122 2nd signal Extraction unit 123 Light emission intensity ratio calculation unit 124 Calibration curve storage unit 125 Conversion unit

Claims (15)

A discharge device for generating a spark discharge;
Measurement means for obtaining light intensity values of two predetermined wavelength bands by dispersing light generated by the spark discharge;
Computing means for calculating the intensity ratio of the light in the two wavelength bands;
Conversion means for outputting a fuel concentration corresponding to the intensity ratio using a calibration curve prepared in advance,
Control means for controlling the measurement time by the measurement means,
The fuel concentration measurement device, wherein the control means selects a measurement time by the measurement means from a discharge period by the discharge device. The discharge device performs capacity discharge at the start of discharge,
The fuel concentration measuring device according to claim 1, wherein the control unit selects the measurement start time and end time so that the capacity discharge period is included in a period between them. The fuel concentration measuring device according to claim 2, wherein the control means selects a period from the start time of the spark discharge to 50 microseconds as the measurement time. The fuel concentration measuring device according to claim 2 or 3, wherein an interval between discharge gaps of the discharge means is 3 mm or more. The fuel concentration measuring device according to any one of claims 1 to 4, wherein one of the two wavelength bands includes a wavelength band of CN emission, and the other includes a wavelength band of NH emission. The fuel concentration according to any one of claims 1 to 4, wherein one of the two wavelength bands includes a wavelength band of atomic emission of hydrogen, and the other includes a wavelength band of atomic emission of oxygen. Measuring device. The fuel concentration measurement device according to any one of claims 1 to 6, wherein the control unit controls the measurement timing by blocking an optical path. The measuring means detects light by a detector that photoelectrically converts light of the two wavelength bands,
The fuel concentration measuring device according to any one of claims 1 to 6, wherein the control unit controls a driving timing of the detector. The measurement means detects the light of the two wavelength bands by a detector that sequentially photoelectrically converts,
The said control means extracts the thing corresponding to the said measurement time among the signals which the said detector outputs, and gives it to the said calculation means. The said any one of Claim 1 thru | or 6 characterized by the above-mentioned. Fuel concentration measuring device. The fuel discharge measuring device according to any one of claims 1 to 9, wherein the discharge device is a spark ignition device. The fuel concentration measuring device according to any one of claims 1 to 10, wherein the discharge device performs the spark discharge with an energy less than a minimum ignition energy to be measured. The optical system for suppressing the incidence of light on the measurement means from the outside of the measurement region consisting of the spark discharge occurrence position and a predetermined range in the vicinity thereof. The fuel concentration measuring device according to any one of the above. The apparatus according to any one of claims 1 to 12, further comprising means for irradiating an electromagnetic wave toward a position where the spark discharge is generated and supplying energy to charged particles generated by the spark discharge. Fuel concentration measuring device. A discharge device that generates a spark discharge; a measurement unit that splits light generated by the spark discharge to obtain an intensity value of light in two wavelength bands; a calculation unit that calculates an intensity ratio of light in two wavelength bands; A method for operating a fuel concentration by controlling a conversion means for outputting a fuel concentration corresponding to an input intensity ratio using a prepared calibration curve,
The fuel concentration measurement method, wherein a measurement time by the measurement means is selected from a discharge period by the discharge device. A method for preparing a calibration curve according to any one of claims 1 to 14,
A first step of introducing a premixed gas with a known fuel concentration in the vicinity of the discharge electrode;
A second step of generating a spark discharge using the discharge electrode;
A third step of spectroscopically analyzing light generated by the spark discharge and obtaining intensity values of light in two wavelength bands generated at the position where the spark discharge is generated at the measurement time;
A fourth step of calculating the intensity ratio of the light in the two wavelength bands;
A calibration curve preparation method, comprising: a fifth step of recording the fuel concentration in the first step in correspondence with the intensity ratio in the fourth step.

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