JP6604319B2 - Gas physical quantity measuring device - Google Patents

Description

  The present invention relates to a gas physical quantity measuring apparatus that measures a physical quantity of a gas in a combustion chamber of an internal combustion engine using an infrared absorption method.

  Conventionally, a spark ignition type in-cylinder direct injection engine including an ignition plug and an injector for injecting fuel into a combustion chamber is known. In such an engine, it becomes possible to control the timing of fuel injection, the amount of fuel injection, and the like more precisely. As a result, it has become necessary to measure the actual air-fuel ratio in the combustion chamber more precisely, and by measuring the transmittance of infrared light that has passed through the combustion chamber, A fuel concentration measuring device that calculates the concentration of a measurement gas has been proposed (see, for example, Patent Document 1).

  Conventional measurement of fuel concentration or air-fuel ratio (A / F) of an internal combustion engine using infrared rays includes various vibrations, oscillation oscillation of a light source (laser), fluctuation of light receiving sensitivity of a light receiver, electric noise, etc. in a measurement system. High frequency noise is generated due to various factors.

  FIG. 1A shows the output voltage of the photoconductive element that receives infrared light with respect to the crank angle phase, and FIG. 1B shows the power spectral density at each frequency. Since the air-fuel ratio fluctuates at a cycle proportional to the engine speed, which is about 20 Hz in the example shown in FIG. 1B, the spectral component near 20 Hz corresponding to the fluctuating cycle of the air-fuel ratio has the highest density. . On the other hand, although the component of the frequency (1 kHz-) higher than the fluctuation cycle of an air fuel ratio is also included, this is considered to be a component corresponding to the high frequency noise mentioned above. That is, it is considered that high-frequency noise is superimposed on the measurement waveform shown in FIG. 1A, and if these measurement values are used as they are, the error becomes large.

  Therefore, in order to further improve the measurement accuracy, it is necessary to remove this high-frequency noise by low-pass filter processing or the like.

JP 2004-184175 A

  However, in the prior art, in the sudden change portion where the fuel is instantly oxidized by ignition such as immediately after the ignition timing (SA) and the air-fuel ratio changes suddenly, the low-pass filter processing is performed on the air-fuel ratio calculated from the infrared transmittance. Since the influence of the value of the sudden change portion of the air-fuel ratio becomes large when the engine is operated, the calculated value of the air-fuel ratio near the ignition timing immediately before the sudden change of the air-fuel ratio is greatly shifted to the value side of the sudden change portion, resulting in a large error. There is.

  FIG. 2 shows raw data of the transmission voltage of the light receiving element with respect to the crank angle phase in the conventional measurement method, and data after the low-pass filter processing. This shows that the measured value near the ignition timing becomes larger than the raw data as the cut-off frequency of the low-pass filter processing becomes lower.

  The present invention has been made in view of such a problem, and an object of the present invention is to use measurement data up to the ignition timing in measurement of a physical quantity of gas in a combustion chamber of an internal combustion engine using an infrared absorption method. By combining the measurement data up to the ignition timing with time reversal combined as measurement data after the ignition timing, low-pass filter processing is performed on the combined data to remove high-frequency noise superimposed on the measurement data. An object of the present invention is to provide a gas physical quantity measuring apparatus capable of measuring a physical quantity of gas until ignition timing with higher accuracy than before removing high frequency noise.

  In order to solve the above problems, the present invention irradiates a combustion chamber of an internal combustion engine with infrared light, measures the transmittance of the infrared light that has passed through the combustion chamber, and measures the measured infrared light. A gas physical quantity measuring device for calculating a physical quantity of gas in the combustion chamber based on the transmittance of the gas, wherein the physical quantity of the gas with respect to the crank angle phase calculated until the ignition timing based on the measured transmittance of infrared light The first data is generated, the second data obtained by reversing the time of the first data with the ignition timing as a starting point is generated, and the second data as the data after the ignition timing is generated in the first data. Low-pass filter processing is performed on the combined data obtained by combining the data to generate third data, and a physical quantity of the gas in the combustion chamber is calculated based on the third data.

  The invention according to claim 2 is the gas physical quantity measuring device according to claim 1, wherein the wavelength of the infrared light is 3.3 to 3.5 μm, and the physical quantity of the gas is an air-fuel ratio. And

  The invention according to claim 3 is the gas physical quantity measuring device according to claim 1, wherein the wavelength of the infrared light is 1.2 to 1.4 μm, and the physical quantity of the gas is a gas temperature. And

  According to a fourth aspect of the present invention, in the gas physical quantity measuring device according to the first aspect, the wavelength of the infrared light is 4.3 to 4.5 μm, and the physical quantity of the gas is a carbon dioxide concentration. Features.

  In the measurement of the physical quantity of the gas in the combustion chamber of the internal combustion engine using the infrared absorption method, the present invention is obtained by inverting the measurement data up to the ignition timing with the measurement data up to the ignition timing as measurement data after the ignition timing. Generate combined data and perform low-pass filter processing on the combined data to remove high-frequency noise superimposed on the measurement data and measure the physical quantity of gas up to the ignition timing with higher accuracy than before removing high-frequency noise can do.

(A) is a figure which shows the permeation | transmission voltage of the photoconductive element which received the infrared light with respect to the crank angle phase, (b) is a figure which shows the power spectral density in each frequency. It is a figure which shows the raw data of the transmitted voltage of the light receiving element with respect to the crank angle phase in the conventional measuring method, and the data after a low-pass filter process. It is a figure showing composition of a gas physical quantity measuring device concerning one embodiment of the present invention. It is a flowchart explaining operation | movement of the gas physical-quantity measuring apparatus which concerns on one Embodiment of this invention. (A) is a figure which shows the 1st data of the air fuel ratio with respect to a crank angle phase produced | generated from the measured infrared transmittance, (b) is the 1st data of the air fuel ratio with respect to a crank angle phase, It is a figure which shows the combined data which combined the 2nd data which carried out time reversal from the ignition timing as the data after the ignition timing to the 1st data until the ignition timing, (c) It is a figure which shows the 3rd data produced | generated by performing a low-pass filter process. As a measurement example of one cycle, it is a figure which shows the raw data of the air fuel ratio with respect to a crank angle phase, and the air fuel ratio data with respect to the crank angle phase after the low-pass filter process of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 3 shows a configuration of a gas physical quantity measuring device according to one embodiment of the present invention. The gas physical quantity measuring device includes a light source 301 that emits infrared light having a frequency corresponding to a measured physical quantity, and an optical waveguide that guides the infrared light to the combustion chamber of the internal combustion engine and guides the infrared light that has passed through the combustion chamber to the outside. 302, a light receiving element 303 that receives infrared light transmitted through the combustion chamber and outputs the light intensity as an electric signal, and a calculation unit 304 that processes the electric signal output from the light receiving element and calculates an air-fuel ratio. I have. In the present invention, the configuration from the light source 301 other than the arithmetic unit 304 to the light receiving element 303 is not limited as long as it can output the light intensity of infrared light that has passed through the combustion chamber of the internal combustion engine as an electrical signal. Can be substituted.

  FIG. 4 is a flowchart for explaining the operation of the gas physical quantity measuring device according to the embodiment of the present invention. In the gas physical quantity measuring device in the combustion chamber of the internal combustion engine using the infrared absorption method, the transmittance of the infrared light that has passed through the combustion chamber until the ignition timing is measured (S401). From the measured infrared light transmittance, first data of air-fuel ratio with respect to the crank angle phase as shown in FIG. 5A is generated (S402). The air-fuel ratio ignition timing (SA) with respect to the calculated crank angle phase is confirmed (S403), and the first data of the air-fuel ratio with respect to the crank angle phase is time-reversed with the ignition timing as a starting point, that is, First data of the air-fuel ratio with respect to the crank angle phase is turned back at the ignition timing, and second data is generated by rearranging the air-fuel ratio so that the crank angle phase is rearranged in the reverse order starting from the ignition timing. Then, the first data up to the ignition timing is combined with the second data as data after the ignition timing to generate combined data as shown in FIG. 5B (S404). Low-pass filter processing is performed on the return data to generate third data (S405), and an air-fuel ratio from which high-frequency noise as shown in FIG. 5C is removed is calculated (S406).

  FIG. 6 shows raw data of the air-fuel ratio with respect to the crank angle phase and data after the low-pass filter processing according to the present invention of the air-fuel ratio with respect to the crank angle phase as measurement examples of one cycle. The air-fuel ratio at the ignition timing at this time was 12.6 as measured by the conventional method, but 12.3 as measured according to the present invention.

  Table 1 shows the average, variance, standard deviation, minimum value, maximum value of air-fuel ratio at the ignition timing calculated by the conventional measurement method (without low-pass filter processing) based on the data for 200 cycles and the measurement method of the present invention. Indicates the value.

  Table 1 shows that in the present invention, it is possible to perform low-pass filter processing while suppressing errors even for values in the vicinity of sudden change portions where measurement errors become large when low-pass filter processing has been performed so far, and raw data including high-frequency noise. It is shown that the air-fuel ratio can be measured with less variation than the above.

  The case where the air-fuel ratio is measured has been described so far, but the physical quantity of the gas to be measured can be changed by changing the frequency of the infrared light to be used. The wavelength suitable for measuring the air-fuel ratio is 3.3 to 3.5 μm. For example, 1.2 to 1.4 μm is used to measure the gas temperature in the combustion chamber, and the carbon dioxide concentration in the combustion chamber is measured. For this, a wavelength of 4.3 to 4.5 μm is suitable. Also in the present invention, the physical quantity of various gases can be measured by changing the frequency of the infrared light used, and the same effect can be obtained regardless of the wavelength of the infrared light used.

301 light source 302 optical waveguide 303 light receiving element 304 arithmetic unit

Claims (4)

Irradiate the combustion chamber of the internal combustion engine with infrared light to measure the transmittance of the infrared light that has passed through the combustion chamber, and based on the measured transmittance of the infrared light, determine the physical quantity of the gas in the combustion chamber. A gas physical quantity measuring device to calculate,
Generating first data that is a physical quantity of the gas with respect to a crank angle phase calculated up to an ignition timing based on the measured transmittance of infrared light, and time-reversing the first data with the ignition timing as a starting point Second data is generated, low-pass filter processing is performed on combined data obtained by combining the first data with the second data as data after the ignition timing, and third data is generated. 3. A gas physical quantity measuring device that calculates a physical quantity of gas in the combustion chamber based on the data of No. 3.   The gas physical quantity measuring device according to claim 1, wherein the wavelength of the infrared light is 3.3 to 3.5 μm, and the physical quantity of the gas is an air-fuel ratio.   2. The gas physical quantity measuring device according to claim 1, wherein the wavelength of the infrared light is 1.2 to 1.4 [mu] m, and the physical quantity of the gas is a gas temperature.   The gas physical quantity measuring device according to claim 1, wherein the wavelength of the infrared light is 4.3 to 4.5 μm, and the physical quantity of the gas is a carbon dioxide concentration.

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