JPH0862099A - Air/fuel ratio measuring instrument - Google Patents

Abstract

PURPOSE: To provide an air/fuel ratio measuring instrument which can accurately measure the air/fuel ratio (A/F) from the measurement value of an exhaust constituent concentration and can eliminate such error factors as the change in dehumidification capacity of an analyzer also for a fuel whose property greatly differs. CONSTITUTION: The title item is provided with an exhaust analyzer 100 for detecting each content (PCO', PCO2 ', and PHC) of carbon monoxide, carbon dioxide, and hydrocarbon contained in an unloaded gas, a carbon/water ratio setting equipment 140 for setting the carbon/water ratio (Z) of a used fuel, an equipment 150 for setting the amount of remaining water for setting the amount of remaining water content (Hx) when detecting each content of the carbon monoxide and carbon dioxide of the exhaust analyzer 100, and a means 160 for calculating the air/fuel ratio (A/F) and/or oxygen concentration (PO2 ) based on the measurement values (PCO', PCO2 ', and PHC) of the exhaust analyzer 100 and the setting value (Z', Hx) of the equipment 150 for setting the amount of remaining water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio measuring apparatus for an internal combustion engine, and it is possible to accurately measure the air-fuel ratio (A / F) can be calculated, and
The present invention relates to an air-fuel ratio measuring device capable of eliminating an error factor such as a change in dehumidifying ability of an analyzer.

[0002]

2. Description of the Related Art As a conventional air-fuel ratio measuring device for an internal combustion engine, there is one proposed in JP-A-55-128135. In this conventional example, each content (concentration) of carbon monoxide (CO), carbon dioxide (CO ₂ ) and hydrocarbon (HC) contained in the exhaust gas is detected by a sensor, and an analog type calculator is used. The air-fuel ratio (A / F) is calculated based on each detected content (analog value). That is, an approximate expression for a specific fuel (coal water ratio 1.85; equivalent to regular gasoline) is derived, and the analog type arithmetic unit is configured to calculate the air-fuel ratio (A / F).

[0003]

However, in such a conventional air-fuel ratio measuring device, carbon monoxide (C
O), carbon dioxide (CO ₂ ) and hydrocarbon (HC) concentration information only, the air-fuel ratio (A / F) is calculated, so the measurement accuracy deteriorates except for specific fuels. Even with gasoline fuel, an error of about 0.3 A / F occurs between regular and high octave, and there is a problem that an approximate expression must be provided for each fuel type in order to eliminate the error.

Also, it is difficult to accurately calculate the approximate expression from the air-fuel ratio (A / F) in the latch to the air-fuel ratio (A / F) in the lean, and further, carbon monoxide (CO). Moreover, since the influence of the residual water content is not taken into consideration in the sensor for measuring the concentration of carbon dioxide (CO ₂ ), there is a problem that the accuracy deteriorates.

The present invention has been made in view of the above-mentioned conventional problems, that is, from gasoline to natural gas (CN).
Even for fuels whose properties are significantly different from G), the air-fuel ratio (A / F) can be measured with high accuracy from the measured values of exhaust gas component concentrations.
Another object of the present invention is to provide an air-fuel ratio measuring device capable of eliminating error factors such as changes in the dehumidifying ability of the analyzer.

In order to solve the above-mentioned problems, the air-fuel ratio measuring apparatus according to claim 1 of the present invention is shown in FIG.
As shown in Fig. 5, the carbon monoxide, carbon dioxide and hydrocarbon contents (PCO ', PC
An exhaust gas analyzer 100 for detecting O ₂ ', PHC), a coal water ratio setter 140 for setting the coal water ratio (Z) of the fuel used,
The residual water content setting device 150 for setting the residual water content (Hx) in the detection of each content of carbon monoxide and carbon dioxide of the exhaust gas analyzer 100, and the measured values (PCO ′, PCO ₂ ′) of the exhaust gas analyzer 100. , PHC) and the set values (Z,
Hx) and an air-fuel ratio (A / F) and / or an oxygen concentration (PO ₂ ) are calculated.

Further, the air-fuel ratio measuring device according to claim 2 is
The air-fuel ratio measuring apparatus according to claim 1, wherein the calculating means 160 measures the carbon monoxide and carbon dioxide content values (PCO ', PC) in the exhaust gas analyzer 100.
O ₂ '), and the oxygen concentration (PO ₂ ) is calculated based on the set values (Z, Hx) of the coal water ratio setting device 140 and the residual water content setting device 150.

The air-fuel ratio measuring device according to claim 3 is
The air-fuel ratio measuring device according to claim 1 or 2,
As shown in, the exhaust gas analyzer 500 detects the content of nitrogen oxides (PNO).

The air-fuel ratio measuring apparatus according to claim 4 is
The air-fuel ratio measuring device according to claim 3, wherein the calculating means 560 is configured to measure carbon monoxide in the exhaust gas analyzer 500,
Measured content of carbon dioxide and nitrogen oxides (PC
O ′, PCO ₂ ′, PNO) and the coal water ratio setter 14
0 and the set value of the residual water content setter 150 (Z, Hx)
Based on the above, the oxygen concentration (PO ₂ ) is calculated.

[0009]

The air-fuel ratio measuring device according to the present invention (claim 1)
Is the content of carbon monoxide, carbon dioxide and hydrocarbon contained in the exhaust gas measured by the exhaust gas analyzer 100 (PC
O ', PCO ₂ ', PHC) are detected, and the coal water ratio setter 1
40, the coal water ratio (Z) of the fuel used is set, and the residual water content setter 150 sets and calculates the residual water content (Hx) in the detection of each content of carbon monoxide and carbon dioxide in the exhaust gas analyzer 100. In the means 160, the measured values (PCO ′, PCO ₂ ′, PHC) of the exhaust gas analyzer 100 and the coal water ratio setter 14
0 and the set value of the residual water content setter 150 (Z, Hx)
Based on the above, the air-fuel ratio (A / F) and / or the oxygen concentration (PO ₂ ) are calculated. In other words, a theoretical formula containing the coal-water ratio (Z) representing the fuel property and the oxygen concentration information is used, and the oxygen concentration does not require a new oxygen analyzer, and the content of carbon monoxide and carbon dioxide is included. the amount measured value (PCO ', PCO _2') is calculated based on, and,
By taking into consideration the information (Hx) of the residual water content in the detection of each content of carbon monoxide and carbon dioxide,
The air-fuel ratio (A / F) is also measured with high accuracy for gasoline and fuel with properties greatly different from natural gas (CNG). In addition, error factors such as changes in the dehumidification capacity of the analyzer can be eliminated.

Further, in the air-fuel ratio measuring apparatus according to the present invention (claim 2), the oxygen concentration (PO ₂ ) of the calculating means 160 is calculated by the measured values of the carbon monoxide and carbon dioxide contents in the exhaust gas analyzer 100 ( PCO ′, PCO ₂ ′) and the set values (Z, Hx) of the coal-water ratio setter 140 and the residual water content setter 150.

Further, in the air-fuel ratio measuring apparatus according to the present invention (claim 3), as shown in FIG. 5, the exhaust analyzer 500 also detects the content of nitrogen oxides (PNO), and it is included in the exhaust gas. The calculation accuracy is improved by incorporating the information of the nitrogen oxides to be included in the calculation of the oxygen concentration (PO ₂ ) and the air-fuel ratio (A / F).

Further, air-fuel ratio measuring apparatus according to the present invention (Claim 3), as shown in FIG. 5, in calculating means 560, the measurement value of the exhaust analyzer _{500 (PCO ', PCO 2'} , PH
C, PNO) and the set values (Z, Hx) of the charcoal-water ratio setting device 140 and the residual water content setting device 150, the oxygen concentration (PO ₂ ) is calculated. Thus, by incorporating the information of nitrogen oxides contained in the exhaust gas into the calculation, the oxygen concentration (PO ₂ ) and the air-fuel ratio (A
The calculation accuracy of / F) is further improved.

[0013]

Embodiments of the air-fuel ratio measuring device of the present invention will be described below.
[Embodiment 1] and [Embodiment 2] will be described in detail with reference to the drawings.

[Embodiment 1] FIG. 1 is a configuration diagram of an air-fuel ratio measuring apparatus according to Embodiment 1 of the present invention. In the figure, the air-fuel ratio measuring apparatus according to the first embodiment shows that each content of carbon monoxide, carbon dioxide and hydrocarbon (PC
Exhaust gas analyzer 10 for detecting O ', PCO ₂ ', PHC)
0, a charcoal-water ratio setter 140 for setting the charcoal-water ratio (Z) of the fuel used, and a residual water content (Hx) in the detection of each content of carbon monoxide and carbon dioxide of the exhaust gas analyzer 100. Residual water content setting device 150 and exhaust gas analyzer 100
Measurements _{(PCO ', PCO 2',} PHC) and Sumisui ratio setter 140 and the set value of the residual water amount setting unit 150 (Z, Hx) based on the air-fuel ratio (A / F) and oxygen concentration (PO ₂ ) A computing unit 160 as a computing means for computing
And a display 170 for displaying the result.

[0015] The exhaust analyzer 100, the content of carbon monoxide, carbon dioxide and hydrocarbons contained in the exhaust gas _{(PCO ', PCO 2',} PHC) to respectively detect carbon monoxide (CO) Analyzer 110, carbon dioxide (C
O ₂ ) analyzer 120 and hydrocarbon (HC) analyzer 13
It has 0.

The arithmetic unit 160 includes an interface 161, a CPU (central processing unit) 162, and a memory 1.
It is equipped with 63.

An outline of the operation of the above configuration will be described. First, the signals of the carbon monoxide analyzer 110, the carbon dioxide analyzer 120, and the hydrocarbon analyzer 130 which analyze the gas sampled from the exhaust pipe (not shown) of the engine are input to the interface 161 of the calculator 160. . Further, in the coal water ratio setting device 140 for inputting the coal water ratio of the fuel used, a digital switch capable of setting a coal water ratio in the range of 1.00 to 9.99 is usually used. In the residual water content setting device 150, the residual water content in the carbon monoxide analyzer 110 and the carbon dioxide analyzer 120 is input and set. The signal of each setter is input to the interface 161. The computing unit 160 uses the calculation program stored in the memory 163 to calculate C based on each input signal input to the interface 161.
The PU 162 operates and the air-fuel ratio is calculated. The calculation result is output by the display 170 as a digital signal or an analog signal.

Next, the principle and operation of the air-fuel ratio measuring apparatus of this embodiment will be described. The air-fuel ratio (A / F) is the weight of air drawn into the engine (Ga) and the weight of fuel (Gf)
It is generally well known that it is represented by the ratio of the exhaust gas concentration and the exhaust gas component concentration. The equation is shown in Equation 1.

[0019]

[Equation 1]

There are two problems when using this formula.
It One is oxygen (O₂) Information on concentration is required.
The other is carbon monoxide (CO) concentration and carbon dioxide.
(CO ₂) Concentration needs to include the water content in the exhaust.
Is Rukoto.

First, the oxygen (O ₂ ) concentration can be obtained from the carbon monoxide (CO) concentration and the carbon dioxide (CO ₂ ) concentration. FIG. 2 is an explanatory diagram of the relationship between the carbon monoxide (CO) concentration, the carbon dioxide (CO ₂ ) concentration, the oxygen (O ₂ ) concentration, and the excess air ratio (λ). Explaining with reference to this figure, the oxygen (O ₂ ) concentration is the excess air ratio λ = 1.
When it is (theoretical air-fuel ratio), it is “0”, and the concentration becomes higher toward the lean side. Further, the carbon dioxide (CO ₂ ) concentration is a mountain shape having the maximum value when the excess air ratio λ = 1, and becomes lower toward the lean side. Therefore, the oxygen (O ₂ ) concentration PO ₂
Can be expressed by the relationship of Equation 2.

[0022]

[Equation 2]

KO of equation (3)₂Is the conversion factor
As a result, the BCO ₂Is required.
In the equation (4), x is the average of hydrocarbons (HC)
It is the carbon number, and KHC is the emission factor of hydrocarbons (HC).
Depends on HC emission concentration. Also, λS is the HC emission concentration
Is the theoretical excess air ratio that depends on the
The influence of the hydrocarbon (HC) concentration that cannot be reached is preferably small.

FIG. 3 is an explanatory diagram showing the relationship between the carbon monoxide (CO) concentration, the carbon dioxide (CO ₂ ) concentration, the oxygen (O ₂ ) concentration and the excess air ratio (λ) obtained by the calculation. Examining the influence degree of hydrocarbon (HC) concentration using the same figure, 0 [ppm] and normal emission level 4000 [pp
The difference in BCO _{2 in} m] is about 0.01 [%], which is a negligible range. Therefore, in the equation (4), the emission coefficient KHC = 0, the theoretical excess air ratio λS = 1 (that is, HC
May be treated as the theoretical excess air ratio when = 0).

In the equation (3), the conversion coefficient KO ₂
Depends on the coal-water ratio of the fuel, and has a good linear relationship as shown in the explanatory diagram of the relationship between the oxygen (O ₂ ) conversion coefficient KO ₂ and the coal-water ratio in FIG. Therefore, it can be calculated by the following equation. KO ₂ = 1 + 0.3Z (5)

Here again, although it is slightly affected by the hydrocarbon (HC) concentration, the degree of influence is 0 [ppm] and 4000.
Oxygen (O ₂ ) is about 0.02 [%] in [ppm], which is a negligible range.

Next, the residual water content in the carbon monoxide analyzer 110 and the carbon dioxide analyzer 120 will be described.
Carbon monoxide analyzer 110 and carbon dioxide analyzer 120
In the measurement principle, water is removed (dehumidified) and its volume ratio is measured, but it is not completely dehumidified and there is a small amount of residual water Hx, which affects the calculation of the air-fuel ratio (A / F). Exert. Therefore, analyzer measurement values (PCO ', PCO ₂ ')
Is corrected with Hx. PCO "= PCO '/ (1 -Hx) ... (6) PCO 2" = PCO 2' / (1-Hx) ... (7)

By this correction, the completely dehumidified carbon monoxide (CO) concentration and the carbon dioxide (CO ₂ ) concentration are obtained, and the dehumidified water amount PH ₂ O at this time is obtained by the equation 3.

[0029]

(Equation 3)

Therefore, the concentration before dehumidification (concentration of carbon monoxide (CO) and carbon dioxide (CO ₂ ) including moisture)
Are calculated by the following equations. PCO = (1-PH ₂ O) · PCO ″ (9) PCO ₂ = (1-PH ₂ O) · PCO ₂ ″ (10)

From the above, the measured value PCO 'of the carbon monoxide analyzer 110 and the measured value P of the carbon dioxide analyzer 120 are obtained.
Based on the CO ₂ ′, the actual discharge concentrations PCO and PCO ₂ are calculated by correcting the residual water content Hx. Further, the oxygen (O ₂ ) concentration is obtained from the equation (3) using the values of the actual emission concentrations PCO and PCO ₂ . Therefore, the air-fuel ratio A / F can be obtained by Equation 4 by substituting each constant into the equations (1) and (2).

[0032]

[Equation 4]

As described above, in the air-fuel ratio measuring apparatus of the first embodiment, by using the formula for calculating the air-fuel ratio A / F based on the theoretical formula, it is possible to easily deal with various fuels, and the air-fuel ratio for each fuel ( It has become possible to improve the measurement accuracy of A / F).

Further, in the air-fuel ratio measuring apparatus of the first embodiment, the oxygen (O ₂ ) concentration can be calculated without adding a new analytical instrument, and the influence of the change in the combustion state (unburned HC level) is almost eliminated. Accurately requested without receiving. In a general automobile exhaust gas analyzer, this is useful as an oxygen (O ₂ ) concentration calculation display device because the carbon monoxide analyzer 110 and the carbon dioxide analyzer 120 are integrally configured.

[Embodiment 2] Next, FIG. 5 is a configuration diagram of an air-fuel ratio measuring apparatus according to Embodiment 2 of the present invention. In the figure, the air-fuel ratio measuring apparatus according to the present embodiment is the same as the air-fuel ratio measuring apparatus according to the first embodiment except that a means for detecting the nitrogen oxide content (PNO) is added to the exhaust gas analyzer 500.

[0036] That exhaust analyzer 500, carbon monoxide contained in the exhaust gas, carbon dioxide, each amount of hydrocarbons and nitrogen monoxide _{(PCO ', PCO 2',} PHC, P
Carbon monoxide (CO) analyzer 1 for detecting NO) respectively
10, a carbon dioxide (CO ₂ ) analyzer 120, a hydrocarbon (HC) analyzer 130 and a nitric oxide (NO) analyzer 580. Therefore, a terminal for taking in a signal from the nitric oxide analyzer 580 is also added to the interface 561 of the calculator 560.

Next, the principle and operation of the air-fuel ratio measuring apparatus of the second embodiment will be described. Actual exhaust gas contains a small amount of nitrogen oxides (NOx) in addition to unburned hydrocarbons (HC). 90% or more of this nitrogen oxide (NOx) is usually in the state of nitric oxide (NO) when it is discharged from the engine. Considering the influence of the concentration PNO of this nitric oxide (NO), oxygen is (O ₂ ) PO ₂ is
In the formula (3), PO ₂ = KO ₂ · {BCO ₂ − (PCO ₂ + PCO)} − PNO (12). Oxygen (O ₂ ) concentration is measured (calculated) with higher accuracy by this equation (12).

The influence of the discharge of nitric oxide (NO) on the calculation of the air-fuel ratio (A / F) is only the change in oxygen (O ₂ ) concentration. The reason is that NO generation is N ₂ + O ₂ =
Since it is 2NO, the two molecules are only two different molecules, and there is no change in the total number of exhaust components produced. Carbon monoxide (CO) concentration, carbon dioxide (CO ₂ ) concentration, and hydrocarbon (HC) There is no bounce back to concentration. Therefore (1
Equation 5 obtained by adding the nitric oxide (NO) concentration PNO to the equation (1) may be used.

[0039]

(Equation 5)

In other words, there is no influence on the calculation of the air-fuel ratio (A / F) even if there is no information on the measured value of nitric oxide (NO). However, the measured value of the nitric oxide (NO) concentration is effective for improving the calculation accuracy of the oxygen (O ₂ ) concentration.

As described above, in the air-fuel ratio measuring apparatus according to the second embodiment, the accuracy of calculating the oxygen (O ₂ ) concentration can be improved by incorporating the information of nitric oxide (NO) in the exhaust gas. .

[0042]

As described above, the air-fuel ratio measuring apparatus (Claim 1) of the present invention detects the contents of carbon monoxide, carbon dioxide and hydrocarbons contained in the exhaust gas by the exhaust gas analyzer. Then, set the charcoal-water ratio of the fuel to be used with the charcoal-water ratio setter, set the residual water content in detecting the carbon monoxide and carbon dioxide contents of the exhaust gas analyzer with the residual water content setter, and use the calculation method. Since the air-fuel ratio and / or the oxygen concentration are calculated based on the measured values of the exhaust gas analyzer and the set values of the charcoal-water ratio setter and the residual water content setter, highly precise fuels with greatly different properties can be obtained. It is possible to provide an air-fuel ratio measuring device capable of measuring the air-fuel ratio (A / F) and eliminating error factors such as changes in the dehumidifying ability of the analyzer.

In the air-fuel ratio measuring apparatus (claim 2) of the present invention, the oxygen concentration is calculated by measuring the carbon monoxide and carbon dioxide contents measured by the exhaust gas analyzer, the charcoal-water ratio setter and the residual water content. Since it is performed based on the set value of the quantity setter, the air-fuel ratio (A / F) can be measured with high accuracy even for fuels with greatly different properties, and error factors such as changes in the dehumidification capacity of the analyzer can be eliminated. It is possible to provide a possible air-fuel ratio measuring device.

Further, the air-fuel ratio measuring apparatus of the present invention (claim 3) also detects the nitrogen oxide content by the exhaust gas analyzer, so that the calculation accuracy is improved.

Further, in the air-fuel ratio measuring device of the present invention (claim 4), the calculating means calculates the air-fuel ratio based on the measured value of the exhaust gas analyzer and the set values of the coal water ratio setting device and the residual water content setting device. / Or oxygen concentration is calculated, especially the oxygen concentration is calculated by measuring the content of carbon monoxide, carbon dioxide and nitrogen oxides in the exhaust gas analyzer and the set values of the coal water ratio setting device and the residual water content setting device. Since the information on the nitrogen oxides contained in the exhaust gas is incorporated into the calculation, the calculation accuracy of the oxygen concentration and the air-fuel ratio can be further improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an air-fuel ratio measuring device according to a first embodiment of the present invention.

FIG. 2 Carbon monoxide (CO) concentration, carbon dioxide (C
O ₂ ) concentration, oxygen (O ₂ ) concentration and excess air ratio (λ)
FIG.

FIG. 3 is an explanatory diagram of a relationship between a carbon monoxide (CO) concentration, a carbon dioxide (CO ₂ ) concentration, an oxygen (O ₂ ) concentration, and an excess air ratio (λ) obtained by calculation.

FIG. 4 is an explanatory diagram of a relationship between an oxygen (O ₂ ) conversion coefficient KO ₂ and a coal water ratio.

FIG. 5 is a configuration diagram of an air-fuel ratio measuring device according to a second embodiment of the invention.

[Explanation of symbols]

100,500 exhaust analyzer 110 CO analyzer 120 CO ₂ analyzer 130 HC analyzer 140 coal water ratio setter 150 residual water content setter 160,560 calculator (calculation means) 161,561 interface 162 CPU 163 memory 170 display Instrument 580 NO analyzer

Claims (4)

[Claims] 1. An exhaust gas analyzer for detecting respective contents of carbon monoxide, carbon dioxide and hydrocarbons contained in exhaust gas, a coal water ratio setter for setting a coal water ratio of fuel used, and the exhaust gas. A residual water content setting device for setting the residual water content in detecting each content of carbon monoxide and carbon dioxide of the analyzer;
An air-fuel ratio measuring device having a calculating means for calculating an air-fuel ratio and / or an oxygen concentration based on the measured values of the exhaust gas analyzer and the set values of the coal-water ratio setting device and the residual water content setting device. . 2. The calculating means calculates the oxygen concentration based on the measured values of the carbon monoxide and carbon dioxide contents in the exhaust gas analyzer and the set values of the coal-water ratio setting device and the residual water content setting device. The air-fuel ratio measuring device according to claim 1. 3. The air-fuel ratio measuring device according to claim 1, wherein the exhaust gas analyzer detects the content of nitrogen oxides. 4. The calculation means is based on the measured values of carbon monoxide, carbon dioxide and nitrogen oxide contents in the exhaust gas analyzer, and the set values of the coal water ratio setter and the residual water content setter. The air-fuel ratio measuring device according to claim 3, wherein the oxygen concentration is calculated.