JPS5928855B2 - How to measure exhaust gas from internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring exhaust gas from an internal combustion engine, in which errors in the measured concentration of exhaust gas are corrected based on an initially determined characteristic curve.

Currently, automobile exhaust gas regulations are in place both in Japan and abroad, and all automobiles sold by manufacturers cannot be put on the market unless the exhaust gases emitted by their engines meet the above exhaust gas regulations.

For this reason, all vehicles for certification or general commercial use must be checked to see if their engines meet the above exhaust gas regulations.
, CO2, HC, NOx, etc., were measured by the following method using a non-dispersive infrared analyzer or the like.

For example, when measuring the concentration of Co, zero gas with a zero concentration of 1CO is measured using a non-dispersive infrared analyzer (not shown).

Hereinafter, it will be referred to as an analyzer. ) to adjust its output voltage to zero, then flow a span gas with a 2Co concentration of S'pμm to the analyzer and adjust its output voltage to SmV±0.3%. 3 Next, the Co concentration is B', C', D',
Flow the sample gas of E' and F' pμm into the above analyzer,
Each of these Co concentrations B', C', D', E' and F'p
As shown in FIG. 1, the output voltages B, C, D, E, and F of the analyzer with respect to μm are plotted to obtain a reference characteristic curve, and the reference characteristic curve is stored in the computer. After that, the first constant exhaust gas is passed through the analyzer and its output voltage is input to the computer.
Then, the Co concentration in the exhaust gas is determined from the reference characteristic curve.

However, the above-mentioned analyzers are generally very sensitive, and the temperature of various electronic elements of the analyzer changes during use due to changes in external temperature conditions or self-heating, and the output of the analyzer changes. Voltage drift is unavoidable.

Therefore, when measuring the concentration of CO, etc. in exhaust gas using methods 1 to 4 above, the analyzer should be warmed up sufficiently each time it is used, and then tested again using methods 1 to 3 above.
A new standard characteristic curve must be determined by performing the above operations, and each time the above operation is performed, a large amount of expensive reference gas with various concentrations that have been rigorously verified is required, which increases the measurement cost. However, there were many problems such as the fact that the measurement process was very complicated and time consuming, and required skill to perform highly accurate measurements.

On the other hand, in the process of analyzing a large amount of measured data, the inventor of the present application discovered that even if the output voltage of the above-mentioned analyzer for zero gas or the output voltage of the above-mentioned analyzer for span gas changes, the newly obtained standard characteristic curve It has been found that the linearity etc. are almost unchanged from those of the standard characteristic curve originally determined.
The present invention has been made based on the above-mentioned facts to solve the above-mentioned problems in the conventional exhaust gas measurement method for internal combustion engines. The difference (ΔVO) between the first generated voltage obtained by flowing the gas through the analyzer and the difference (ΔVO) between the generated voltage corresponding to the span gas in the above reference characteristic curve and the second generated voltage obtained by flowing the span gas through the analyzer. ΔVs) and the voltage difference change amount (
A temporary characteristic curve is obtained by proportionally distributing ΔVsΔo) to the above standard characteristic curve, and by using this temporary characteristic curve as a new standard characteristic curve, a new standard characteristic curve is recalculated for each measurement. It is an object of the present invention to provide a method for measuring exhaust gas from an internal combustion engine at a low measurement cost, which eliminates the need for an expensive reference gas, reduces the amount of expensive reference gas used, and simplifies the measurement process.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, when implementing the method of the present invention, for example, an analyzer having a basic configuration as shown in FIG. 2 can be used.

In FIG. 2, 1 is a (non-dispersive infrared) analyzer, 2 is an amplifier, 3 is an A/D converter, and 4 is a computer, and the analyzer 1 is introduced from the pipe 5a. A sample cell 5 in which exhaust gas is discharged from a pipe 5b, a control cell 6 filled with a gas containing CO at a predetermined concentration (in the case of detecting CO), and the upper parts of these sample cells 5 and control cells 6. light sources 7 and 8 that are respectively attached to and emit infrared rays downward, and a detection cell 9 that is filled with CO gas, which is the same as the component to be measured, and that converts the pressure into electricity.
It consists of a differential amplifier 11 that outputs the difference between the output voltage of the detection cell 9 and the output voltage of the detection cell 10.

The analyzer 1 emits infrared rays from a light source 7, causes absorption in a sample cell 5 according to the concentration of CO components, and then enters the infrared rays into a detection cell 9. Only the absorption wavelength is selectively absorbed, and the temperature of the enclosed CO gas is raised to increase its pressure, while infrared rays are emitted from the light source 8 and a certain amount of absorption is carried out in the control cell 6. and then input it into the detection cell 10 in the same way as above, increasing the pressure of the CO gas sealed in the detection cell 10 by a constant value determined by the CO concentration in the reference cell 6, The differential amplifier 11 detects the CO concentration of the gas in the sample cell 5 from the difference between the output voltage of the detection cell 9 and the output voltage of the detection cell 10. The output of the amplifier 11 is input to the A/D converter 3 via the amplifier 2 and converted into a digital signal, and then input to the computer 4 for data processing as described below.

The inventor of the present application used the above analyzer to first flow 1 zero gas to the above analyzer 1, as in the conventional case, and controlled the output of the differential amplifier 11 by adjusting the regulator (not shown). Voltage (
0±0.3) After adjusting to MV, the 2C0 concentration is 100p
pm span gas is passed through analyzer 1, and the above output voltage is (
100±0.3) MV, and then the CO concentration was adjusted to 6.4, 14.0, 22.0, 31.0, 40, respectively.
0,49.0,60.0,72.0 trigrams and 85.0pp
m sample gases are passed through the analyzer 1, and the output voltages of the differential amplifier 11 for these sample gases are 10.0, 30.0, 40.
．． 0, 50.0, 60.0, 70.0, 80.0 hexagrams and 90.0 mV are converted into digital signals and input into the computer 4, and a reference characteristic curve B-B7 as shown in FIG.
was stored in the computer. Thereafter, the output voltage of the differential amplifier 11 when equivalent to zero gas (hereinafter referred to as zero point).

) changes by 0 MV or (±5) MV, and the output voltage of the differential amplifier 11 when equivalent to span gas (hereinafter referred to as the span point) changes by 0 MV or (±5) MV. , the above reference characteristic curve B-B7 is converted into provisional characteristic curves A-A'', C-σ, A- as shown by thin lines in FIG. 3 corresponding to the following Table 1 while preserving its linearity. B', B-C
I assumed that it would change like 1 trigram and A-C7. Assumed above, for example, the predicted value of CO concentration based on the temporary characteristic curve A-Ck, the zero point and the span point are respectively (+
5) When calculating the error from the actual measured value of CO concentration when MVl (-5) MV changes, it was found that the total CO concentration from zero gas to span gas does not exceed 0.13% (other hypothetical Characteristic curves AN, C-σ, AB',
The same applies to B-C'VC).

Therefore, even if the zero point of the standard characteristic curve B-B originally obtained from 1 to 3 above changes by (+5) m and the MV1 span point changes by (-5) m, the standard characteristic curve B -B
′(7) While preserving the linearity, create a temporary characteristic curve A-C″
(temporary characteristic curves AN, c-σ, A-B', B
-σ can also be considered as
) MV and the difference (-10) MV from the zero point (+5) MV is C
It can be determined by proportionally distributing the reference characteristic curve B-Bk according to the O concentration.

In the present invention, based on the above facts, the zero point of the reference characteristic curve B-B'' is generally set from VO to v'o, and the span point is from Vs to v's The correction amount Δx=v'x-x of the output voltage of the differential amplifier 11 for any given CO concentration Cx is determined as follows.

From equations (1) and (2), it becomes (where, Cs is the CO concentration of the span gas, and CO is the CO concentration of the zero gas.
concentration).

Therefore, by calculating the standard characteristic curve B-B'' by the conventional operations 1 to 3 already explained, and storing the standard characteristic curve B-B7 in the computer 4, from now on, proceed as follows. Thus, the CO concentration can be detected without performing the operations 1 to 3 above again.

15 First, zero gas and span gas are passed through the analyzer 1 to detect the zero point fluctuation amount ΔVO−V−VO and the span point fluctuation amount ΔVs=V×s. , based on these fluctuation amounts ΔVO and Δs, calculate the above equation (3) to obtain the correction amount ΔX−(−X
35 Correct the reference characteristic curve B-B' by the correction amount ΔX=V'x-Vx, obtain a temporary characteristic curve, and store it in the computer 4. 45 Flow the exhaust gas to be measured into the analyzer. , C corresponding to the output voltage of the differential amplifier 11 at that time
The O concentration is detected from the temporary characteristic curve by the computer 4 and stored in the computer 4.

By doing the above, there is no need to re-determine a new reference characteristic curve using expensive reference gases with various concentrations that have been rigorously verified each time the CO concentration in exhaust gas is measured. As a result, the amount of reference gas used is reduced, and there is no need to recalculate the reference characteristic curve, which simplifies the measurement process. By implementing the present invention, it is possible to significantly reduce the cost of purchasing one reference gas. Moreover, the number of measurement steps could be reduced to about 1/3.

In the above explanation, we have explained the case of measuring CO concentration in exhaust gas, but CO2, HC and NO
Measurement of the concentration of x, etc. can also be carried out in exactly the same manner as described above.

As is clear from the above detailed explanation, the present invention is capable of proportionally changing the amount of voltage difference change (ΔVs - ΔVO) obtained from the fluctuation of the zero point and the span point with respect to the initially obtained reference characteristic curve. Since we have determined the provisional characteristic curve by allocating the data and used the provisional characteristic curve as a new standard characteristic curve to measure exhaust gas, there is no need to re-determine a new standard characteristic curve every time we measure exhaust gas, as was the case in the past. Therefore, the amount of expensive reference gas used and the number of measurement steps required in the process of determining the reference characteristic curve can be significantly reduced compared to the conventional method.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram for determining the standard characteristic curve, Fig. 2 is a diagram of the analytical device, Fig. 3 is an explanatory diagram showing changes in the standard characteristic curve assumed in advance, and Fig. 4 is the detection of a temporary characteristic curve. It is an explanatory diagram showing a method. 1...Analyzer, 2...Amplifier, 3...
... A/D converter, 4 ... Computer, 5 ... Sample cell, 6 ... Control cell,
7, 8... Light source, 9, 10... Detection cell, 11... Differential amplifier.

Claims (1)

[Claims] 1 In a non-gas measurement method for internal combustion engines that measures the content of a specified gas component based on the detected voltage value of a non-dispersive infrared analyzer, etc., the generated voltage is measured by flowing gases of various predetermined concentrations through the analyzer. After sequentially measuring the gas concentration and determining the reference characteristic curve of the voltage value, when measuring the gas to be measured, first flow the zero gas through the analyzer and read the generated voltage value at that time as the first generated voltage value. Then, after flowing span gas through the analyzer and reading the generated voltage value at that time as the second generated voltage value, the difference between the generated voltage value corresponding to the zero gas and the first generated voltage value in the reference characteristic curve (
ΔV_0) and the difference (ΔV
A temporary characteristic curve is obtained by proportionally distributing the voltage difference variation (ΔV_s - ΔV_0) between A method for measuring exhaust gas from an internal combustion engine, characterized in that a concentration value is determined based on a temporary characteristic curve, and the concentration value is used as a concentration value of a gas to be measured.