JPH11211693A - Method and device for measuring air-fuel ratio - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speedily obtain the results (an air ratio and an air-fuel ratio) of computations at the time when the composition of fuel is changed by simplifying computations in an air-fuel ratio measuring device as much as possible. SOLUTION: This device is provided with a table expanding means 124 to create a lean coefficient table, a strike coefficient table, and a rich coefficient table, a sensor output correcting means 126 to correct the output of an air-fuel ratio sensor through the use of a predetermined calibration gas, a region selecting means 128 to select one of a lean region, a near-strike window region, or a rich region on the basis of the corrected output from the sensor output correcting means 126, an oxygen equivalent value computing means 130 to obtain an oxygen equivalent value on the basis of a multidimensional polynomial approximate expression corresponding to the selected region, a coefficient stored in the coefficient table corresponding to the selected region, and the corrected output an air ratio computing means 132 to obtain an air ratio on the basis of the oxygen equivalent value, and an air-fuel ratio computing means 134 to obtain an air-fuel ratio on the basis of a reference constant at the time when an air ratio and an air-fuel ratio =1 to constitute this method.

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 method and an air-fuel ratio measuring apparatus, and more particularly, to a complicated fuel combustion calculation when a fuel composition changes in an internal combustion engine for an automobile or various industrial furnaces. Air-fuel ratio measurement method and air-fuel ratio measurement suitable for a measurement or control system capable of calculating the air-fuel ratio and the like of the combustion gas without delay without calculating the constant used in each multidimensional polynomial approximation formula Related to the device.

[0002]

2. Description of the Related Art Conventionally, as a method for measuring the air-fuel ratio of a combustion mixed gas in an internal combustion engine for automobiles, various industrial furnaces, and the like,
Using a so-called double-cell type air-fuel ratio sensor that combines an electrochemical cell of the oxygen concentration method and an electrochemical cell of the oxygen pump method, the correspondence between the exhaust gas component after combustion of the combustion mixed gas and the sensor output signal is determined. Based on this, there is known a method of obtaining an air-fuel ratio signal of a combustion gas, such as an air-fuel ratio (A / F) in a combustion gas, an excess oxygen ratio (λ), or an oxygen concentration (± O ₂ ) in a combustion exhaust gas. (See, for example, Japanese Patent Publication No. 6-5225 and Japanese Patent Application Laid-Open No. 4-369472).

[0003] In these techniques, when H and C of the combustion composition change, an exhaust gas component calculation after combustion of a combustion mixture gas using an oxygen excess ratio (λ) as a parameter in an air-fuel ratio measurement device is performed by air-fuel ratio measurement. The pump current value Ip of the air-fuel ratio sensor of this oxygen excess ratio (λ) is created in a calculation correspondence table, and the oxygen excess ratio (λ) using the pump current Ip signal as a reference axis is tabulated or Oxygen concentration in the combustion exhaust gas (± O ₂ ) or the oxygen pump current Ip
A calculation correspondence table with the signal is prepared, and the oxygen concentration (± O ₂ ) in the combustion exhaust gas with the pump current Ip signal as a reference axis is obtained by table lookup or interpolation calculation.

[0004]

However, in the conventional air-fuel ratio measurement, when the combustion composition changes,
Complicated calculation of each component of the combustion mixture gas inside the air-fuel ratio measuring device and creation of a correspondence table between the oxygen excess rate (λ), the oxygen concentration (± O ₂ ) and the oxygen pump current Ip are complicated. There is a problem that it takes time to perform the calculation.

A predetermined output range centered on a stoichiometric point, which is a reference output of the air-fuel ratio sensor corresponding to the air ratio = 1, is defined as a window area near the stoichiometric area, and an area with more air than the window area near the stoichiometric area is defined as a lean area. It has been found that when a region in which the fuel is more excess than the stoichiometric window region is defined as a rich region, the stoichiometric window region includes an error.

The present invention has been made in view of such problems, and simplifies the calculation in the air-fuel ratio measuring device as much as possible, and calculates the calculation results (air ratio and air-fuel ratio) when the fuel composition component changes. It is an object of the present invention to provide an air-fuel ratio measurement method and an air-fuel ratio measurement device that can be obtained quickly.

Another object of the present invention is to provide an air-fuel ratio measuring method and an air-fuel ratio measuring method capable of reducing the error in the stoichiometric window region and measuring the air ratio and the air-fuel ratio with high accuracy. It is to provide a fuel ratio measuring device.

Another object of the present invention is to provide an air-fuel ratio measuring method and an air-fuel ratio measuring method capable of greatly reducing the capacity of a memory used for calculation and promoting the miniaturization of the device configuration for measuring the air-fuel ratio. It is to provide a fuel ratio measuring device.

[0009]

An air-fuel ratio measuring method according to the present invention includes an air-fuel ratio calculating process for obtaining a target air-fuel ratio signal based on an output from an air-fuel ratio sensor for measuring combustion exhaust gas. A predetermined output range around a stoichiometric point, which is a reference output of the air-fuel ratio sensor corresponding to the air ratio = 1, is defined as a stoichiometric window region, a region with more air than the stoichiometric window region as a lean region, and a stoichiometric region. When a region in which fuel is more excess than a neighboring window region is defined as a rich region, a multidimensional polynomial approximation formula is used for the lean region, the stoichiometric neighboring window region, and the rich region in the air-fuel ratio calculation process. .

As a result, the calculation in the air-fuel ratio measuring device is simplified, and the calculation results (air ratio and air-fuel ratio) when the fuel composition component changes can be quickly obtained. Moreover,
An error in the stoichiometric vicinity window region can be reduced, and the air ratio and the air-fuel ratio can be measured with high accuracy.

In the above-mentioned measuring method, before the measurement, an information storage process for storing in advance a characteristic data group for a change in the charcoal ratio of various coefficient groups used in the multidimensional polynomial approximation formula in a storage means. And the input fuel components H and C
Based on the characteristic data group, based on the characteristic data group, based on the characteristic data group, a water / coal ratio calculation process for obtaining a water / carbon ratio based on A table expansion process for obtaining and expanding each as a coefficient table;
A sensor output correction process for determining a correction coefficient for correcting the sensitivity of the air-fuel ratio sensor using a predetermined calibration gas, and correcting the output of the air-fuel ratio sensor using the correction coefficient, and the sensor output correction process. Area selection processing for selecting any one of a lean area, a stoichiometric neighborhood window area, and a rich area based on the corrected output obtained in the above-described manner, and a multidimensional polynomial approximation formula corresponding to the area selected in the area selection processing And an oxygen equivalent value calculation process for obtaining an oxygen equivalent value based on the coefficient stored in the coefficient table corresponding to the selected region and the correction output, based on the oxygen equivalent value and at least the standard oxygen partial pressure in the atmosphere. And calculating an air-fuel ratio based on the obtained air ratio and a reference constant when the air ratio = 1. Good.

In this case, the information storage processing includes various simulations used in the multi-dimensional polynomial approximation by a theoretical combustion reaction simulation of fuel and air by a computer installed separately from an air-fuel ratio measuring device. This can be achieved by calculating a characteristic data group for the change in the water / carbon ratio of the coefficient group and storing it in the storage area.

[0013] In the table expansion processing, the coefficient in the lean area, the coefficient in the window area near the stoichiometric area, and the coefficient in the rich area corresponding to the specific water-coal ratio calculated in the water-coal ratio calculation processing are obtained from the characteristic data group. This is achieved by obtaining by an interpolation method and developing each as a coefficient table.

Further, the area selection processing selects the stoichiometric neighborhood window area when the correction output obtained in the sensor output correction processing is included in the output range corresponding to the stoichiometric neighborhood window area. When the output is equal to or greater than the output corresponding to the boundary on the high output side in the neighborhood window area, the lean area is selected, and when the output is equal to or less than the output corresponding to the boundary on the low output side in the stoichiometric neighborhood window area, the rich area is selected. Is also good.

In the sensor output correction processing, the output from the air-fuel ratio sensor is subtracted by the reference output at the stoichiometric point, and the corrected output is obtained by multiplying the output by the correction coefficient for the lean region. Is also good.

Further, the oxygen equivalent value calculation processing is achieved by obtaining an oxygen equivalent value by the following multidimensional polynomial approximation formula corresponding to the area selected in the area selection processing. [Lean Region] Oxygen equivalent value = A ₀ + A ₁ · x + A ₂ / x A _{0 to} A ₂ : Coefficient stored in the coefficient table corresponding to the lean region [Stoichiometric neighborhood window region] Oxygen equivalent value = S ₀ + S ₁ · ^{_{x + S 2 · x 2 +}} S 3 · x 3
+ S ₄ · x ⁴ + S ₅ · x ⁵ + S ₆ · x ⁶ S _{0 to} S ₆ : Coefficients stored in the coefficient table corresponding to the stoichiometric neighborhood window area [Rich area] xx = x / Km Oxygen equivalent value = R _{0 + R 1 · xx + R 2} · xx 2 + R 3 ·
xx ³ + R ₄ xx ⁴ + R ₅ xx ⁵ + R ₆ xx ⁶ Km: correction coefficient for calibration in rich area R _{0 to} R ₆ : coefficients stored in coefficient table corresponding to rich area Next, the present invention The air-fuel ratio measurement method according to the present invention includes an air-fuel ratio calculation process for obtaining a target air-fuel ratio signal based on an output from an air-fuel ratio sensor for measuring combustion exhaust gas. Using a calibration gas to determine a correction coefficient for correcting the sensitivity of the air-fuel ratio sensor,
A sensor output correction process for correcting the output of the air-fuel ratio sensor using the correction coefficient, and when the correction output obtained in the sensor output correction process indicates excess air, A first calculating process for obtaining an oxygen concentration and obtaining an air ratio based on the oxygen concentration; and, when the corrected output obtained in the sensor output correcting process indicates an excess fuel, the corrected output and the air ratio multiplying ratio are calculated. A second calculation process for obtaining an air ratio using a dimensional polynomial approximation formula, and an air ratio obtained in the first calculation process or the second calculation process and a reference constant when the air ratio = 1. Air-fuel ratio calculation processing for obtaining an air-fuel ratio.

As a result, the calculation in the air-fuel ratio measuring device is simplified, and the calculation results (air ratio and air-fuel ratio) when the fuel composition component changes can be quickly obtained. Further, the capacity of the memory used for the calculation can be significantly reduced, and the miniaturization of the device configuration for measuring the air-fuel ratio can be promoted.

In the measuring method, the first
The oxygen concentration calculation process of calculating the oxygen concentration in the gas to be measured based on the correction output from the sensor output correction process, and the theoretical calculation formula of the combustion exhaust gas for obtaining the air ratio, And an air ratio calculation process of calculating the air ratio by substituting.

On the other hand, in the second arithmetic processing, a gain using a water-carbon ratio based on the input fuel components H and C as a variable is obtained by using a multidimensional polynomial approximation formula for gain, and the correction output is obtained by the gain This is achieved by calculating the air ratio using the corrected output and the multi-dimensional polynomial approximation formula for the air ratio.

Therefore, the second arithmetic processing includes, before measurement, information storage processing in which coefficients used in the multidimensional polynomial approximation equation are stored in advance in storage means; And a C / C ratio calculation process for calculating a C / C ratio based on C and C, a gain for calculating a gain based on the multi-dimensional polynomial approximation formula for gain, the coefficient stored in the storage means, and the specific C / C ratio Calculation processing, a correction calculation processing for correcting the correction output by multiplying the correction output by the gain obtained in the gain calculation processing, a multidimensional polynomial approximation for the air ratio, the correction calculation value, and the excess fuel. Air ratio calculation processing for calculating the air ratio based on the correction coefficient on the side.

In this case, as the information storage processing, a coefficient used in the multidimensional polynomial approximation formula is obtained by simulating a theoretical combustion reaction of fuel and air by a computer installed separately from an apparatus for measuring the air-fuel ratio. , And
This can be achieved by storing in the storage means. In addition,
One defined value of 1.85 can be used as the charcoal ratio.

Further, as the second arithmetic processing, prior to the measurement, it is used in a coefficient arithmetic expression for obtaining a coefficient group used in a multidimensional polynomial approximation expression for an air ratio for obtaining an air ratio in advance. A charcoal ratio information storage process in which a characteristic data group for a change in the charcoal ratio of the coefficient group is stored in a storage unit, and a charcoal ratio calculation process for obtaining a charcoal ratio based on the input fuel components H and C. A table expansion process for a coal / coal ratio for obtaining a coefficient group of the coefficient calculation equation corresponding to the obtained specific water / coal ratio based on the characteristic data group and expanding them as a coefficient table, respectively, A coefficient calculation process for a water / coal ratio for obtaining a coefficient used in the multidimensional polynomial approximation for the air ratio based on a coefficient group stored in various coefficient tables and the specific charcoal ratio; Polynomial approximation formula and the coefficient calculation process The resulting coefficient may include an air ratio calculation processing for calculating the air ratio based on the obtained correction output by the sensor output correction process.

As a result, the calculation in the air-fuel ratio measuring device is simplified, and the calculation results (air ratio and air-fuel ratio) when the fuel composition component changes can be obtained quickly, and the air ratio can be accurately determined. And the air-fuel ratio.

In this case, as the information storage processing for the water-coal ratio, the coefficient calculation formula is used by a theoretical combustion reaction simulation of fuel and air by a computer installed separately from the apparatus for measuring the air-fuel ratio. This can be achieved by calculating a characteristic data group for the change in the coal ratio of the various coefficient groups, and storing the characteristic data group in the storage area.

The second arithmetic processing further includes an acid-carbon ratio ≠
In the case of 0, before the measurement, the coefficient arithmetic expression for obtaining the coefficient group used for the coefficient multidimensional polynomial approximation for obtaining the conversion coefficient to be converted into the output corresponding to the acid-to-carbon ratio = 0 in advance. An acid-carbon ratio information storage process for storing characteristic data groups for changes in the acid-carbon ratio of the coefficient group to be used in storage means, and an acid-carbon ratio for obtaining an acid-carbon ratio based on the input fuel components O and C. A ratio calculation process, an acid-coal ratio table expansion process for obtaining a coefficient group of the coefficient calculation formula corresponding to the obtained specific acid-carbon ratio based on the characteristic data group, and expanding each as a coefficient table; An acid-coal ratio coefficient calculation process for obtaining a coefficient used for the coefficient multidimensional polynomial approximation equation based on an arithmetic expression, a coefficient group stored in various coefficient tables, and the specific acid-carbon ratio; -Dimensional polynomial approximation and the relation for the acid-carbon ratio A conversion coefficient calculation process of calculating a conversion coefficient based on the coefficient obtained in the calculation process and the correction output obtained in the sensor output correction process, multiplying the conversion coefficient by the correction output, and A conversion process as a new correction output is included, and in the air ratio calculation process, the multi-dimensional polynomial approximation formula for the air ratio, the coefficient obtained in the coefficient calculation process, and the new value obtained in the conversion process. The air ratio may be calculated based on an appropriate correction output.

Thus, the air ratio, the air-fuel ratio, etc. of the alcohol fuel can be easily and accurately obtained, and the multi-function of the air-fuel ratio measuring process can be realized.

As the information storage processing for the acid-to-carbon ratio, the coefficient calculation formula is used by simulating the theoretical combustion reaction of fuel and air with a computer installed separately from the apparatus for measuring the air-fuel ratio. This can be achieved by calculating a characteristic data group for a change in the acid-carbon ratio of various coefficient groups and storing the characteristic data group in the storage area.

In addition to the above-described processing, the second arithmetic processing includes, before the measurement, the output of the air-fuel ratio sensor at the acid-coal ratio ≠ 0 when the water-coal ratio is a prescribed value, Ip1, When the reference output of the air-fuel ratio sensor at the coal ratio = 0 is Ip0, a correspondence table storing process of storing a correspondence table between the conversion coefficient and Ip1 in the storage means based on a relational expression of conversion coefficient = Ip0 / Ip1, A conversion coefficient calculation process for obtaining a conversion coefficient corresponding to the correction output obtained in the sensor output correction process from the correspondence table by a polygonal line approximation; multiplying the conversion coefficient by the correction output; A conversion process to be a correction output is included, and in the air ratio calculation process, the multidimensional polynomial approximation for the air ratio, a coefficient obtained in the coefficient calculation process, and a new correction obtained in the conversion process. Based on output It may be calculated air ratio.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An air-fuel ratio measuring method and an air-fuel ratio measuring apparatus according to the present invention will be described below with reference to an embodiment in which the present invention is applied to an air-fuel ratio measuring apparatus used in, for example, an internal combustion engine for automobiles and various industrial furnaces. , Which is simply referred to as an air-fuel ratio measuring device according to the embodiment) will be described with reference to FIGS. 1 to 29.

The air-fuel ratio measuring device 10 according to the present embodiment
Has an air-fuel ratio sensor 12 for measuring combustion exhaust gas and an arithmetic processing system 14 for calculating an oxygen concentration, an air ratio and an air-fuel ratio based on the output from the air-fuel ratio sensor 12, as shown in FIG. It is configured.

The air-fuel ratio sensor 12 is a ceramic substrate 20 using an oxygen ion conductive solid electrolyte such as ZrO _2.
It has a sensor element 16 including a heater section 21 using a high-temperature insulator such as alumina and a high-temperature insulator, and a control system 18 for controlling the sensor element 16.

The sensor element 16 is configured by laminating, for example, a heater section 21 composed of two alumina layers 21a and 21b and a ceramic substrate 20 composed of three solid electrolyte layers 20a to 20c.

In the ceramic substrate 20, a recess is provided between the first solid electrolyte layer 20a and the second solid electrolyte layer 20b from the bottom to form a reference oxygen partial pressure chamber 22 whose periphery is sealed. Porous platinum electrodes (a reference electrode 36 and a measurement electrode 34) are provided on the lower surface and the upper surface of the second solid electrolyte layer 20b, respectively.

A measurement chamber 26 is provided by providing a depression between the second solid electrolyte layer 20b and the third solid electrolyte layer 20c from the bottom, and a porous hole for communicating the measurement chamber 26 with an external space. A passage for the quality diffusion-controlling layer 24 is provided.

Porous platinum electrodes 28 and 30 (inner pump electrode 28 and outer pump electrode 30) are provided on the lower and upper surfaces of the third solid electrolyte layer 20c, respectively. The electrode protection layer 23 is coated with quality ZrO ₂ .

On the other hand, a heater section 40 is formed by providing a heater pattern 40 with a platinum-based cermet electrode on the first alumina layer 21a and bonding the second alumina layer 21b on the upper surface thereof.

The control system 18 includes a measurement control system 50, a heater control system 52, and a reference reference oxygen injection system 53.

The reference reference oxygen injection system 53 applies a constant voltage at the positive electrode of the reference reference oxygen partial pressure generating power supply 37 to the reference electrode 36 of the second solid electrolyte layer 20b from the bottom through a high resistance. Is connected, a current of several μA flows between the reference electrode 36 and the measurement electrode 34 to fill the reference oxygen partial pressure chamber 22 with oxygen.

Specifically, the positive electrode of the reference reference oxygen partial pressure generating power supply 37 is connected to the reference electrode 36, and the negative electrode (ground potential) is connected to the measuring electrode 34, and a small current of several μA flows. ,
By injecting a trace amount of oxygen from the measurement chamber 26 into the reference oxygen partial pressure chamber 22, a reference oxygen partial pressure is created in the reference oxygen partial pressure chamber 22.

The second solid electrolyte layer 20b, the measurement electrode 34 and the reference electrode 36 constitute an oxygen concentration cell 38 for measuring the oxygen partial pressure in the measurement chamber 26. Solid electrolyte layer 20c and inner pump electrode 28
The outer pump electrode 30 and the outer pump electrode 30 constitute an oxygen pump 32 for adjusting the oxygen partial pressure in the measurement chamber 26 via the control system 18.

The heater control system 52 raises the temperature of the measurement gas in the external space from room temperature to 950
When the temperature is changed by ° C., the applied voltage of the heater section 21 is adjusted so that the oxygen pump current Ip becomes constant, and the temperature of the measurement gas and the heater resistance ratio during operation (resistance r /
The correction amount of the heater resistance ratio of the heater unit 21 at normal temperature ro) and the heater resistance ratio at the time of reference operation (the resistance r of the heater unit 21 / the normal temperature resistance ro of the heater unit 21) and the heater supply control signal are checked. Of the heater resistance ratio (resistance r of the heater unit 21 / normal temperature resistance ro of the heater unit 21) is obtained,
The correction resistance ratio is obtained by subtracting the heater resistance ratio during operation (resistance r of the heater unit 21 / normal temperature resistance ro of the heater unit 21),
The heater 4 is controlled by PID control so that the correction resistance ratio becomes constant.
0 power control is performed (for details, see, for example, Japanese Patent No. 254647).

The measurement electrode 34 (GND) and the inner pump electrode are connected via a resistor R of several Ω to several tens Ω (hereinafter, referred to as a return resistor R).
0 is connected to the neutral point of the signal (0 mV point for ± signal) via the return resistor R.

Then, the oxygen partial pressure in the measurement chamber 26 and the oxygen partial pressure in the reference oxygen partial pressure chamber 22 are transmitted from the reference electrode 36 via a buffer amplifier (PID control circuit 54 in the example of FIG. 1). A signal obtained by adding the oxygen pump current Ip × the return resistance value R to the generated electromotive force (voltage) Va of the oxygen concentration battery 38 composed of the following (hereinafter, referred to as a concentration signal side measurement signal Vd) is measured. The generated electromotive force V of the oxygen concentration cell 38
a is an oxygen pump current Ip for oxygen injection × an internal resistance of the oxygen concentration cell 38, an irregular potential of the oxygen concentration cell 38 (mainly a temperature difference generated between the reference electrode 36 and the measurement electrode 34 of the oxygen concentration cell 38). And the theoretical electromotive force of the oxygen concentration cell 38 obtained by the Nernst equation.

The target set voltage Vb of the measurement control system 50 is the generated electromotive force of the oxygen concentration cell 38 in which the oxygen partial pressure in the measurement chamber 26 corresponds to the air ratio ≒ 1.

The measurement control system 50 converts the measurement signal Vd on the concentration cell side and the target set voltage Vb through the proportional-integral-derivative control circuit (PID control circuit) 54 and the V / I conversion circuit 56 to the outer pump electrode 30. And drives the oxygen pump 32 to change the measurement signal Vd on the concentration cell side to the target set voltage Vd.
Control is performed to match b.

The return resistance value R × the oxygen pump current Ip is the return amount of the PID control system, and the target set voltage V
Several percent to several tens of b are used to prevent oscillation of the feedback control system.

The operation of the PID control circuit 54 will now be described. The measurement signal Vd on the concentration cell side> the target set voltage Vb
At this time, the oxygen pump current Ip in the direction of returning the oxygen in the measurement chamber 26 to the external space side is passed, and the feedback control is performed by the PID operation so that the measurement signal Vd on the concentration cell side converges to the target set voltage Vb.

Conversely, when the measurement signal Vd on the concentration cell side> the target set voltage Vb, an oxygen pump current Ip in the direction of injecting oxygen flows into the measurement chamber 26 side. At this time, C on the external space side
O ₂ and H ₂ O are electrolyzed by the oxygen pump 32 at the electrode interface of the outer pump electrode 30, whereby oxygen ions move to the measurement chamber 26 side, oxygen is injected into the measurement chamber 26 side, and oxygen on the concentration cell side. Feedback control is performed by the PID operation so that the measurement signal Vd converges to the target set voltage Vb.

Output voltage signal Vp of PID control circuit 54
Represents indirectly the amount of oxygen controlled by the oxygen pump 32, which is proportional to the oxygen pump current Ip.

For example, in the measurement control system 50, for example, 350 mV is used as the level of the reference voltage Vb, and the voltage Va between the measurement electrode 34 and the reference electrode 36 is used.
Is approximately 310 when the gas to be measured is atmospheric air (excess air).
mV, about 350 mV at the stoichiometric point, and about 400 mV in the case of excess fuel. Therefore, it is preferable to select the resistance value of the return resistor R so as not to adversely affect the air-fuel ratio measurement in the downstream processing system 14 and to prevent oscillation from occurring in the measurement control system 50.

On the other hand, as shown in FIG. 1, the heater control system 52 includes a heater voltage measuring section 60 for measuring the voltage across the heater 40, and a heater current measuring section 62 for measuring the current flowing through the heater 40 through the resistor Rh. A temperature control processing unit 64 for controlling the heater temperature based on the heater voltage Vh from the heater voltage measurement unit 60 and the temperature control code Ch from the arithmetic processing system 14 based on the heater current Ih from the heater current measurement unit 62. It is configured.

The output (deviation signal) Vp from the PID control circuit 54 is supplied to an A / D converter 68 via a multiplexer 66 at the subsequent stage, and the A / D converter 68
Is converted into digital deviation data and sent to an arithmetic processing system 14 described later. This deviation data is calculated based on the voltage Vp output from the PID control circuit 54.
Is digitally converted, the pump current value Ip flowing through the oxygen pump 32 is indirectly indicated. Therefore, in the following description, the data output from the A / D converter 68 is referred to as a pump current value Ipfx. The voltage signal Vh from the heater voltage measuring section 60 and the current signal Ih from the heater current measuring section 62 are sent to the arithmetic processing system 14 via the multiplexer 66.

Next, the configuration of the arithmetic processing system 14 is shown in FIG.
This will be described with reference to FIG. The arithmetic processing system 14 includes a ROM 80 in which an arithmetic program for calculating an air ratio, an air-fuel ratio, and the like, various fixed values, and the like, and a data table group created in advance and external devices (such as a key input device 82). , A RAM 84 for storing data processed by various programs, a non-volatile memory 86 (for example, an EEPROM or a flash memory) to which necessary data is written by an arithmetic program, and inputting data to an external device. It has an input / output port 88 for performing output and a CPU (control device and logical operation device) 90 for controlling these various circuits.

The above-mentioned various circuits exchange data between the respective circuits via a data bus 92 derived from the CPU 90, and further via an address bus and control bus (neither shown) derived from the CPU 90. CPU 90 each
It is configured to be controlled by. The data bus 92 is connected to the multiplexer 66 from the PID control circuit 54.
The above-mentioned A / D converter 68 for digitally converting the output (deviation signal) Vp sent through the A / D converter is directly connected.

The input / output port 88 includes the multiplexer 66, a digital display unit 94 for digitally displaying the selected data as a numerical value, and a state (busy state, wait state, etc.) of the CPU 90. The status display unit 96, the key input device 82, the analog output system 98, and the digital communication system 100 are connected.

The analog output system 98 includes an input / output port 88
D / A converter 10 that converts digital data output through the converter into an analog signal (voltage signal or current signal)
2 and an analog output processing circuit 104 for amplifying the signal from the D / A converter 102 to a predetermined gain or adjusting the signal to a predetermined output dynamic range.

The digital communication system 100 has an input / output port 8
UART for inserting an error correction code for communication or an odd / even check code into digital data output through
For example, RC-232C interface for converting into a signal having voltage-current capable of long-distance transmission, GP-IB
And the like.

Then, the arithmetic processing means (arithmetic processing program) read from the ROM 80 is executed by the CPU 90, whereby arithmetic operations such as the air-fuel ratio are performed.

Next, three embodiments of the arithmetic processing means will be described with reference to FIGS.

First, the arithmetic processing means 110A (see FIG. 9) according to the first embodiment has a predetermined output range centered on the reference output (stoichiometric point) of the air-fuel ratio sensor 12 corresponding to the air ratio = 1. When the stoichiometric near window area, the air excess area than the stoichiometric near window area is the lean area, and the fuel excess area than the stoichiometric near window area is the rich area, the lean area, the stoichiometric near window area, the rich area , An oxygen equivalent value is determined using a multidimensional polynomial approximation formula, an air ratio and an air-fuel ratio are determined based on the oxygen equivalent value, and the oxygen equivalent value, the air ratio, and the air-fuel ratio are output.

More specifically, the arithmetic processing means 110A according to the first embodiment will be described with reference to FIGS.

First, the arithmetic processing according to the first embodiment
Before the processing means 110A is executed, as shown in FIG.
Through the information storage means 112, the multidimensional polynomial approximation
The change of the water / carbon ratio H / C of the various coefficient groups used in the equation
Characteristic data group (A₀~ A_Two, S₀~ S₆, R₀~
R₆) Is stored in the ROM 80. This information storage means 1
12 is a core installed separately from the air-fuel ratio measuring device 10.
The theoretical combustion reaction between fuel and air at the computer 114
By simulation, the multi-dimensional polynomial approximation
Characteristics of various coefficient groups used for change in H / C
Data group (A₀~ A _TwoCharacteristic table, S₀~ S₆Characteristic
Table, R₀~ R₆Characteristic table) and calculate these characteristics.
Sex data group (A₀~ A_TwoCharacteristic table, S₀~ S₆Characteristic
Table, R ₀~ R₆Characteristic table) to the arithmetic processing system
For example, the ROM writer 1
16 and burn-in. At this time,
RO (program) 110A and other fixed data
It is burned and written to M80.

The characteristic data group (A₀~ A_TwoCharacteristic table,
S₀~ S₆Characteristic table, R₀~ R ₆Characteristic table) and
The ROM 80 in which programs and the like are written is stored in the arithmetic processing unit.
Set in the science system 14 and the data in the arithmetic processing system 14
It is electrically connected to a tabus 92, an address bus and the like.

Here, the characteristic data registered in the ROM 80
Group (A₀~ A_TwoCharacteristic table, S ₀~ S₆Characteristics table
Le, R₀~ R₆4A to 4B)
This will be described with reference to FIG. 8C. This characteristic data group (A
₀~ A_TwoCharacteristic table, S₀~ S₆Characteristic table, R₀
~ R₆(Characteristic Table)
It is created for each of the window area and the rich area.

First, regarding the lean region, its multidimensional
Polynomial approximation formula is oxygen equivalent value MO_Two= A₀+ A₁・ X + A_Two/ X, A₀, A₁as well as
A_TwoChanges in A ₀Characteristic table, A₁Characteristic table
Bull and A_TwoWrite to ROM 80 as characteristic table
It is. 4A to 4C, FIG.₀Characteristic table, A₁Characteristic
Table and A_TwoChange of data registered in the characteristic table
Is shown in the form of an envelope.

For the stoichiometric neighborhood window area,
The multi-dimensional polynomial approximation formula is: MO ₂ = S ₀ + S ₁ · x + S ₂ · x ² + S ₃ · x ³ + S
Since a ^{_{4 · x 4 + S 5 ·}} x 5 + S 6 · x 6, is written in the S ₀ to S ROM 80 change of ₆ as S ₀ characteristic table to S ₆ characteristic table respectively for Mizusumihi H / C. FIGS. 5A to 5D and FIGS. 6A to 6C show changes of data registered in the S ₀ characteristic table to the S ₃ characteristic table and the S ₄ characteristic table to the S ₆ characteristic table in the form of an envelope.

For the rich region, the multidimensional polynomial approximation formula is given by: xx = x / Km (to be described later) MO ₂ = R ₀ + R ₁ xx + R ₂ xx ² + R ₃ xx
³ + since R is ^{_{4 · xx 4 + R 5 ·}} xx 5 + R 6 · xx 6, written in the R ₀ to R ROM 80 change of ₆ as R ₀ characteristic table to R ₆ characteristic table respectively for Mizusumihi H / C It is. Figure 7A~-7D and FIGS 8A~ view 8C, showing a variation of the data registered in the R ₀ characteristic table to R ₃ characteristic table and R ₄ characteristic table to R ₆ characteristic table in the form of an envelope.

Then, the operation according to the first embodiment
The processing means 110A includes, as shown in FIG.
An input for receiving the data input from 82 (see FIG. 2)
The data receiving means 120, the input fuel component H and
Water / coal ratio calculation means 12 for obtaining water / carbon ratio H / C based on C
2 and the specific water calculated by the charcoal ratio calculating means 122
Coefficient in lean region corresponding to coal ratio H / C, stoichiometric
In the window area and the rich area
Coefficient (A₀~ A_Two, S₀~ S₆, R₀~ R ₆) To R
The characteristic data group (A) stored in the OM 80₀~ A_TwoSpecial
Sex table, S ₀~ S₆Characteristic table, R₀~ R₆Characteristic
Table based on the coefficient table
Coefficient table Ta, stoichiometric coefficient table Tb,
Table exhibition developed as a rich coefficient table Tc)
Opening means 124 and the air-fuel ratio cell using a predetermined calibration gas.
Correction coefficients HM and Km for correcting the sensitivity of the sensor 12
The air-fuel ratio sensor is determined using the correction coefficients HM and Km.
A sensor output correcting means 126 for correcting the output of
The correction output obtained by the sensor output
Lean area, near stoichiometric based on Ipx
Select one of window area and rich area
Area selecting means 128 and the area selecting means 128
A multidimensional polynomial approximation corresponding to the selected region and the selected
Coefficients stored in the coefficient table corresponding to the
The oxygen equivalent value MO based on the corrected output Ipx_TwoAsk for
The oxygen equivalent value calculating means 130 and the obtained oxygen equivalent value M
O_TwoAnd at least air based on atmospheric standard oxygen partial pressure
An air ratio calculating means 132 for obtaining the ratio λ;
Reference constant ARF when ratio λ and air ratio λ = 1₀Based on
Air-fuel ratio calculating means 134 for obtaining the air-fuel ratio ARF
Oxygen equivalent value MO_Two, Air ratio λ and air-fuel ratio ARF
Digital display through input / output port 88 (see FIG. 2)
94, analog output system 98 and digital communication system 100
And output processing means 136 for outputting.
You. Here, the correction coefficient is calculated by the sensor output correction means 126.
Factors used as criteria for determining HM and Km
explain. As the correction coefficient, for example, the fuel for each sensor
Correction coefficient HM used on lean side and each sensor
Correction coefficient Km used on the fuel-rich (rich) side of
is there.

First, how to determine the correction coefficient HM will be described with reference to the flowchart of FIG. First, in step S1, setting a concentration of the calibration gas O _2. As the calibration gas, for example, 20% O ₂ gas [O ₂ / N ₂ (oxygen: about 20%)] 10% O ₂ gas [O ₂ / N ₂ (oxygen: about 10%)] 4% O ₂ gas [ O ₂ / N ₂ (oxygen: about 4%)] N ₂ gas [CO ₂ / N ₂ (carbon dioxide: about 13%)
%)], And the N ₂ gas is used to determine the calibration pump current value IpN ₂ at the stoichiometric point. Then, the calibration gas (the above-mentioned 20% O ₂ gas, 10% O ₂ gas and 4% O ₂ gas)
The oxygen concentration PO ₂ of any one of the _two gases
2 (see FIG. 2), and the non-volatile memory 86
In a predetermined storage area.

Incidentally, the oxygen concentration PO ₂ in the gas to be measured is
Is nonlinear with respect to the pump current value Ip from the sensor element 16 as shown in FIG. Therefore, if the sensitivity coefficient required for each sensor is simply processed by the ratio (one straight line) of the pump current value Ip / the oxygen concentration PO ₂ , for example, 4%
There is a large difference between the sensitivity coefficient when calibrated with O ₂ gas and the sensitivity coefficient when calibrated with atmospheric air.
There is a possibility that the measurement accuracy varies among the six individuals.

Therefore, in the present embodiment, the characteristics of the actual sensor element 16 are classified into, for example, four, and straight lines (four straight lines) for linearization are set for each of them, and are managed as linearize numbers. To do it. For example, a linearization number indicating an optimal straight line derived from the characteristics of the sensor element 16 is described in the inspection result report of the sensor element 16. The ROM 80 stores the reference sensitivity coefficient Ka.
Current value (Ipo = Ka · P) obtained based on
A correspondence table (shown as a characteristic curve in FIG. 12) between O ₂ ) and the pump current value Ipfo before linearization corresponding to each linearize number is registered. In FIG. 12, a characteristic curve a is a straight line, and a characteristic curve b is a curve having a slight curvature. The characteristic curve c has a larger curvature than the characteristic curve b, and the characteristic curve d has a larger curvature than the characteristic curve c.

More specifically, for each of the four linearization numbers LIN0 to LIN3, when the step size of the reference Ipo after the linearization is set to, for example, 0.01, the change of the reference Ipfo before the linearization is sequentially stored in the ROM 80. Register with. For example, in the case of the linearization number LIN0, the degree of change of the reference curve Ipfo before the linearization by 0.01 for the characteristic curve a in the reference curve Ipo after the linearization is the linearization number LIN0.
Is registered as a correspondence table. FIG.
In the characteristic curves corresponding to the other linearized numbers, the curve b corresponds to LIN1, the curve c corresponds to LIN2, and the curve d corresponds to LIN3.

According to this method, since the characteristics of the sensor element 16 are classified and managed by the four linearization numbers LIN0 to LIN3, variations in the measurement accuracy among the individual sensor elements 16 are reduced.

Next, in step S2 of FIG.
Calibration pump current value IpN at toy point _TwoAsk for. This place
The principle is that the gas to be measured is N_TwoFlow gas, for example digital
When the instruction on the display unit 94 becomes stable, the first calibration button
Press the tongue (not shown). At this stage, the measured values (storage
Point calibration pump current value IpN_Two) Connects the data bus 92
And stored in a predetermined storage area of the nonvolatile memory 86.
You.

Next, in step S3, the calibration gas O
Read the pump current value for ₂ . In this process, the oxygen concentration PO ₂ set in step S1 as the gas to be measured is used.
Calibration gas O ₂ is flowed, for example, when the instruction of the digital display unit 94 is stabilized, the second calibration button (not shown)
push. At this stage, the measured value (the pump current value Ips of the calibration gas) is stored in the nonvolatile memory 86 through the data bus 92.
In a predetermined storage area.

Next, in step S4, the calibration gas O
The pumping current Ipo after linearization with respect to the reference sensitivity coefficient Ka according to the _second oxygen concentration PO ₂ determined based on the following equation.

[0077] Ipo = Ka · PO ₂ Next, in step S5, the linearization prior to pumping current I to the pumping current Ipo after linearization
Find pfo. In this process, first, the key input device 82
The corresponding table corresponding to the input linearized number is read from the ROM 80. Thereafter, a pump current value Ipfo before linearization corresponding to the pump current value Ipo after linearization obtained in step S4 is obtained from the correspondence table using, for example, a reverse interpolation complementation method.

Then, in the next step S 6, the correction coefficient HM is obtained based on the following equation, and the correction coefficient HM is stored in a predetermined storage area of the nonvolatile memory 86 via the data bus 92.

HM = Ipfo / (Ips-IpN ₂ ) Ipfo: Pump current value before linearization obtained in step S5 Ips: Pump current value of calibration gas obtained in step S3 IpN ₂ : stoichiometric point obtained in step S2 Next, the correction coefficient Km of the sensor output correction means 126
Will be described with reference to the flowchart of FIG.

[0080] First, in step S101, sets the concentration PH ₂ of the calibration gas between H ₂ concentration PCO of calibration gas CO. As the calibration gas, for example, a mixed gas of three kinds [(CO + H ₂ + CO ₂ ) / N ₂ ] CO /
_{H 2 / CO 2 [6.64%} / 2.57% / 10%] is used. The concentrations PCO and PH ₂ of the calibration gases CO and H ₂ are input through the key input device 82 and stored in a predetermined storage area of the nonvolatile memory 86.

Next, in step S102, the pump current value Ipsx for the calibration gas is read. In this process, the above-mentioned three kinds of mixed gas is flowed as the gas to be measured, and when the indication on the digital display unit 94 is stabilized, for example, a third calibration button (not shown) is pressed. At this stage, the measured value (the pump current value Ipsx of the calibration gas) is stored in the data bus 9.
2 is stored in a predetermined storage area of the nonvolatile memory 86.

Next, in step S103, the correction coefficient Km is obtained based on the following equation, and the correction coefficient Km is stored in a predetermined storage area of the nonvolatile memory 86 via the data bus 92.

[0083]

(Equation 1)

KCO: Reference carbon monoxide concentration sensitivity coefficient (registered in ROM 80) KH ₂ : Reference hydrogen concentration sensitivity coefficient (registered in ROM 80) Next, calculation processing means 110A according to the first embodiment The processing operation will be described with reference to the flowcharts of FIGS.

First, in step S201, it is determined whether or not data has been input from the key input device 82 through the input data receiving means 120, and step S201 is repeated until the data is input.
That is, it waits for input data.

At this time, the operator uses the key input device 82 to enter at least the fuel components C (carbon), H (hydrogen),
Input each concentration PC, PH and PO of O (oxygen).

Next, in step S 202, the respective input densities are received by the input data receiving means 120 and stored in a predetermined storage area of the nonvolatile memory 86.

Next, in step S 203, the pump current value Ip input from the sensor element 16 via the A / D converter 68 through the sensor output correction means 126.
fx is corrected to the pump current value Ipx. This correction is performed based on the following equation.

Ipx = HM · (Ipfx−IpN ₂ ) Next, in step S204, the area selecting means 128
It is determined whether the measured gas is in the lean region, in the stoichiometric vicinity window region, or in the rich region.

In the sensor element 16 used in the air-fuel ratio measuring apparatus 10, when an excess air gas is introduced into the measuring chamber 26, the oxygen pump 32 turns the oxygen partial pressure of the measuring chamber 26 to a predetermined value. As described above, since oxygen is pumped to the reference reference oxygen partial pressure chamber 22 side, a positive pump current (+ Ip) required for the pumping flows from the V / I conversion circuit 56.

Conversely, when the fuel-excess gas is introduced into the measurement chamber 26, the oxygen pump 32 sends oxygen from the reference oxygen partial pressure chamber 22 so that the oxygen partial pressure in the measurement chamber 26 becomes a predetermined value. Since the water is pumped into the measurement chamber 26, a negative pump current (−Ip) required for the pumping flows from the V / I conversion circuit 56.

Therefore, in the determination in step S204, if the pump current value Ipx is equal to or greater than the upper limit value W1 of the stoichiometric vicinity window region, it is determined that the region is lean, and the pump current value Ipx is equal to or less than the lower limit value W2 of the stoichiometric vicinity window region. If it is, it is determined as a rich area. Also,
If the pump current value Ipx is between the upper limit value and the lower limit value of the stoichiometric vicinity window region (W2 <Ipx <W1),
It is determined as a stoichiometric vicinity window area.

In step S204, the lean area
If it is determined that the
Corresponding to the water / carbon ratio H / C through the cable deployment means 124
Coefficient A₀~ A_TwoAsk for. Specifically, FIGS. 4A to 4C
A shown in₀Characteristic table ~ A _TwoCreated in the characteristic table
Coefficient A corresponding to the charcoal ratio H / C from each coefficient group₀~ A _Two
Is determined using, for example, an interpolation method. Determined coefficient A₀~
A_TwoIs also nonvolatile through the table developing means 124
Coefficient table Ta in a predetermined storage area of the volatile memory 86.
Is stored as

Next, in step S206, the oxygen equivalent value MO ₂ in the lean region is calculated by the oxygen equivalent value calculating means 130 based on the following equation. Specifically, the coefficients A _{0 to} A ₂ of the lean coefficient table Ta stored in the non-volatile memory 86 are read, and these coefficients A _{0 to} A ₂ are substituted into the following equation for calculation. The obtained oxygen equivalent value MO ₂ is stored in a predetermined storage area of the nonvolatile memory 86 via the data bus 92.

MO ₂ = A ₀ + A ₁ · Ipx + A ₂ / Ip
x On the other hand, if it is determined in step S204 that the area is the stoichiometric neighborhood window area, the next step S207
And the water / carbon ratio H / C through the table developing means 124
The coefficient S ₀ to S ₆ corresponding to determined. Specifically, FIG.
Obtaining coefficients S ₀ to S ₆ corresponding from each coefficient group that is registered in the S ₀ characteristic table to S ₆ characteristic table water coal ratio H / C as shown in A~ Figure 6C using, for example, the interpolation method. The calculated coefficients S _{0 to} S ₆ are stored as a stoichiometric coefficient table Tb in a predetermined storage area of the nonvolatile memory 86 through the table expanding means 124.

Next, in step S208, the oxygen equivalent value MO ₂ in the stoichiometric window area is calculated by the oxygen equivalent value calculating means 130 based on the following equation. Specifically, the coefficients S _{0 to} S ₆ of the stoichiometric coefficient table Tb stored in the non-volatile memory 86 are read, and these coefficients S _{0 to} S ₆ are substituted into the following equation to perform the calculation. The obtained oxygen equivalent value MO ₂ is stored in the data bus 92
Through a predetermined storage area of the nonvolatile memory 86.

MO ₂ = S ₀ + S ₁ · Ipx + S ₂ · Ip
x ² + S ₃ · Ipx ³ + S ₄ · Ipx ⁴ + S ₅ · Ipx
⁵ + S ₆ · Ipx ⁶ On the other hand, if it is determined in step S 204 that the region is a rich region, the process proceeds to the next step S 209, and the correction output is corrected by the sensor output correction unit 126 using the correction coefficient Km.

Ipxx = Ipx / Km Next, in step S210, the table developing means 1
24, coefficients R _{0 to} R ₆ corresponding to the water / carbon ratio H / C.
Ask for. Specifically, the coefficients R _{0 to} R ₆ corresponding to the water / carbon ratio H / C are extracted from each coefficient group registered in the R ₀ characteristic table to the R ₆ characteristic table shown in FIGS. Determine using The obtained coefficients R _{0 to} R ₆ are stored as a rich coefficient table Tc in a predetermined storage area of the nonvolatile memory 86 through the table expanding means 124.

Next, in step S211, the oxygen equivalent value MO ₂ in the rich region is calculated by the oxygen equivalent value calculating means 130 based on the following equation. Specifically, the coefficients R _{0 to} R ₆ of the rich coefficient table Tc stored in the non-volatile memory 86 are read, and these coefficients R _{0 to} R ₆ are substituted into the following equation to perform the calculation. The obtained oxygen equivalent value MO ₂ is stored in a predetermined storage area of the nonvolatile memory 86 via the data bus 92.

MO ₂ = R ₀ + R ₁ · Ipxx + R ₂ · I
pxx ² + R ₃ · Ipxx ³ + R ₄ · Ipxx ⁴ + R _{5
^{· Ipxx 5 + R 6 · Ipxx}} 6 the step S206, the process proceeds to step S212 of FIG. 15 at any stage of the processing is completed in step S208 and step S211, through the air ratio calculating means 132, the oxygen equivalent value MO ₂ 0 It is determined whether it is greater than or less than 0.

If the oxygen equivalent value MO ₂ is equal to or larger than 0, the flow advances to the next step S213, and the air ratio λ is calculated based on the following equation.

[0102]

(Equation 2)

When the oxygen equivalent value MO ₂ is less than 0,
Proceeding to step S214, the air ratio λ is calculated based on the following equation.

[0104]

(Equation 3)

Step S213 or step S21
At the stage when the process in 4 is completed, the process proceeds to the next step S215, and the air ratio λ is stored in the predetermined storage area of the nonvolatile memory 86 through the air ratio calculating means 132.

Next, in step S216, the air-fuel ratio ARF is calculated by the air-fuel ratio calculation means 134 based on the obtained air ratio λ and the reference constant ARF ₀ when the air ratio λ = 1.

ARF = λ · ARF ₀ Here, the reference constant ARF ₀ is obtained from the following equation.

[0108]

(Equation 4)

Next, in step S 217, the air-fuel ratio ARF is stored in a predetermined storage area of the nonvolatile memory 86 through the air-fuel ratio calculating means 134.

Next, in step S218, the oxygen equivalent value MO ₂ and the air ratio λ stored in the predetermined storage area of the nonvolatile memory 86 are output through the output processing means 136.
And the air-fuel ratio ARF are read out, and the oxygen equivalent value MO ₂ , the air ratio λ, and the air-fuel ratio ARF are read through the input / output port 88 to the digital display unit 94 and the analog output system 98.
And output to the digital communication system 100.

When the processing in step S218 is completed, the processing operation of the arithmetic processing means 110A ends. When the fuel components H and C are input again through the key input device 82, the calculation operation is started. Processing means 1
1A will be activated by the CPU 90.

As described above, in the arithmetic processing means 110A according to the first embodiment, the relationship between the pump current value Ipx and the oxygen concentration PO ₂ is divided into a lean region, a stoichiometric vicinity window region, and a rich region, respectively. The constants used in these multidimensional polynomial approximations are calculated beforehand by performing each component calculation (complex fuel combustion reaction calculation) of the combustion mixture gas before measurement to obtain H / C
Of each constant with respect to the characteristic table group (A ₀
To A ₂ characteristic table, S ₀ to S ₆ characteristic table, R ₀ ~
R ₆ characteristic table), and stores coefficients (corresponding to three types of multidimensional polynomial approximations) corresponding to a specific H / C in a characteristic table group (A _{0 to} A ₂ characteristic table, S _{0 to} S ₆ characteristic). Table, R _{0 to} R ₆ characteristic table) using an interpolation method or the like, so that a complicated calculation (complexity) is required until the oxygen equivalent value MO ₂ corresponding to H / C characterized by data input is obtained. It is not necessary to carry out the combustion reaction calculation of the fuel), and the oxygen equivalent value MO ₂
Is very short, and as a result, the time until the air ratio λ and the air-fuel ratio ARF are also very short.

Further, based on the pump current value Ipx corrected by the sensor output correcting means 126, the arithmetic processing means 110A according to the first embodiment classifies the data into a lean area, a stoichiometric vicinity window area, and a rich area. Since the oxygen equivalent value MO ₂ is obtained using the corresponding multidimensional polynomial approximation formula, the measurement error can be greatly reduced, and the measurement accuracy of the air-fuel ratio sensor 12 can be improved. .

Here, one experimental example will be described. In this experimental example, when the oxygen concentration of the gas to be measured was changed,
The gas to be measured is processed by the arithmetic processing means 1 according to the first embodiment.
FIG. 10 shows a measurement error of the oxygen concentration when measured by the air-fuel ratio measurement device 10 using 10A.

FIGS. 16A to 16C show the experimental results. Measurement error with a normal air-fuel ratio measuring device is ± 50 ppm
In this embodiment, the measurement error is about ± 3 ppm at the maximum in the lean region (see FIG. 16A), and −8 pp at the maximum in the stoichiometric window region.
The measurement error is about m (see FIG. 16B), and the maximum measurement error is about ± 10 ppm in the rich region (see FIG. 16C), which is much smaller than that of a normal air-fuel ratio measurement device. You can see that there is.

In particular, looking at the measurement error in the stoichiometric window region shown in FIG.
The error when measuring the gas to be measured at pm is about 5 ppm (see point P), which indicates that the measurement is performed with high accuracy.

Next, an arithmetic processing means 110B according to the second embodiment will be described with reference to FIGS. Components corresponding to those in FIG. 9 are denoted by the same reference numerals, and redundant description is omitted.

As shown in FIG. 17, when the correction output Ipx from the sensor output correction means 126 indicates excess air, the arithmetic processing means 110B according to the second embodiment receives the correction output Ipx from the correction output Ipx. Oxygen concentration PO in measurement gas
₂ and a first calculating means 140 for obtaining an air ratio λ based on the oxygen concentration PO _2;
When the correction output Ipx from 26 indicates an excess fuel, the second calculation means 142 for obtaining the air ratio λ using the correction output Ipx and the multi-dimensional polynomial approximation formula for the air ratio is provided. .

The first calculating means 140 calculates the oxygen concentration PO ₂ in the gas to be measured based on the correction output Ipx from the sensor output correcting means 126, and calculates the oxygen concentration PO ₂ as the air ratio λ. The air ratio λ is determined by substituting it into the theoretical calculation formula of the combustion exhaust gas to be determined.

On the other hand, the second calculating means 142 obtains the gain G using the water / carbon ratio H / C based on the input fuel components H and C as a variable using a multidimensional polynomial approximation formula for gain, and The output Ipx is corrected by the gain G, and the air ratio λ is obtained by using the corrected output Ipx and the multidimensional polynomial approximation formula for the air ratio.

Then, the operation according to the second embodiment
Before the processing is executed, the processing unit 110B
As shown in FIG.
Multi-dimensional polynomial approximation for air ratio and multi-dimension polynomial approximation for air ratio
Coefficient a used for₀~ A_ThreeAnd b₀~ B_FourIs non-volatile
Stored in the memory 86. This information storage means 144
A computer installed separately from the air-fuel ratio measuring device 10
146, a simulation of the theoretical combustion reaction between fuel and air
Is used in the multidimensional polynomial approximation
Coefficient a₀~ A_ThreeAnd b₀~ B_FourIs calculated and the coefficient a
₀~ A_ThreeAnd b ₀~ B_FourIs used for the arithmetic processing system 14.
To the nonvolatile memory 86 to be written. Coefficient a₀~ A_ThreePassing
And b₀~ B_FourIs written in the nonvolatile memory 86
Is set in the arithmetic processing system 14, and
Connected electrically to the data bus 92, address bus, etc.
It is.

Here, the details of the coefficients a _{0 to} a ₃ and b _{0 to} b ₄ registered in the nonvolatile memory 86 will be described. Coefficients a ₀ ~a ₃ and b ₀ ~b ₄ is created and the gain for the air ratio.

First, for the air ratio, since the multidimensional polynomial approximation formula is the air ratio λ = a ₀ + a ₁ · x + a ₂ · x ² + a ₃ · x ³ , each coefficient a _{0 to} a ₃ is , A certain charcoal ratio H /
Based on C, a coefficient derived from the combustion theory calculation is selected. For example, when the water / carbon ratio H / C = 1.85, a ₀ =
0.9958, a ₁ = 0.0742, a ₂ = 0.004
6, a ₃ = 0.0001 is selected.

For the gain, the multidimensional polynomial approximation formula is given by the following equation: G = b ₀ + b ₁ · (H / C) + b ₂ · (H / C)
^{Since 2} + b ₃ · (H / C) ³ + b ₄ · (H / C) ⁴ , each of the coefficients b _{0 to} b ₄ is determined by the width of the water / carbon ratio H / C of the fuel used, For example, the charcoal ratio H
When the range of / C is 0.5 to 5.0, b ₀ = 1.8
_{44, b 1 = 0.9036, b} 2 = 0.3507, b 3
= 0.0662 and b ₄ = 0.0047 are selected.

As shown in FIG. 17, the arithmetic processing means 110B according to the second embodiment includes the first and second arithmetic means 140 and 142 as well as the first and second arithmetic means.
Arithmetic processing means 110A according to the embodiment (see FIG. 9)
Based on the input data receiving means 120, the water / carbon ratio calculating means 122, the sensor output correcting means 126, and the correction output Ipx from the sensor output correcting means 126, it is determined whether the measured gas is excessive in air or fuel. Discriminating means 15 for discriminating
0 and the first computing means 140 or the second computing means 142
Air-fuel ratio calculating means 134 for obtaining the air-fuel ratio ARF based on the air ratio λ obtained in the above and the reference constant ARF ₀ when the air ratio λ = 1, the obtained oxygen concentration PO ₂ , the air ratio λ and the air-fuel ratio ARF Through an input / output port 88, a digital display unit 94, an analog output system 98, and a digital communication system 100.
And an output processing means 136 for outputting to

The first calculating means 140 calculates the oxygen concentration PO ₂ in the gas to be measured based on the correction output Ipx from the sensor output correcting means 126.
60 and an air ratio calculating means 162 for calculating the air ratio λ by substituting the oxygen concentration PO ₂ into the theoretical calculation formula of the combustion exhaust gas for obtaining the air ratio λ.

The second calculating means 142 is based on the multidimensional polynomial approximation for gain, the coefficients a _{0 to} a ₃ and b _{0 to} b ₄ registered in the nonvolatile memory 86, and the water / carbon ratio H / C. A gain calculating means 164 for calculating the gain G by using the correction output Ipx from the sensor output correcting means 126 described above and the gain G from the gain calculating means 164 to obtain a corrected calculation value x. The air ratio λ is calculated based on the multi-dimensional polynomial approximation formula for the air ratio and the correction operation value x.
And an air ratio calculating means 168 for calculating

Next, the processing operation of the arithmetic processing means 110B according to the second embodiment will be described with reference to the flowcharts of FIGS.

First, in step S301, it is determined whether or not data has been input from the key input device 82 (see FIG. 2) through the input data receiving means 120. Until the data is input, the process proceeds to step S301. Is repeated. That is, it waits for input data.

At this time, the operator uses the key input device 82 to enter at least the fuel components C (carbon), H (hydrogen),
Input each concentration PC, PH and PO of O (oxygen).

Next, in step S302, the respective input densities are received by the input data receiving means 120 and stored in a predetermined storage area of the nonvolatile memory 86.

Next, in step S303, the pump current value Ip input from the sensor element 16 via the A / D converter 68 through the sensor output correction means 126.
fx is corrected to the pump current value Ipx. This correction is performed based on the following equation.

Ipx = HM ・ (Ipfx−IpN ₂ ) Next, in step S304, it is determined through the determination means 150 whether the gas to be measured is excessive in air or excessive in fuel. Specifically, if the pump current value Ipx is 0 or more, it is determined that the air is excessive, and if the Ipx is less than 0, it is determined that the fuel is excessive.

Then, in step S304,
If it is determined that the air is excessive, the process proceeds to the next step S305 and enters the first calculating means 140 (subroutine).

The processing operation of the first calculating means 140 is as follows. First, in step S401 of FIG.
The oxygen concentration PO ₂ in the gas to be measured is obtained from the corrected output Ipx from 26. Specifically, the pump current corresponding to the current linearization number - oxygen concentration characteristics of oxygen concentration PO ₂ is for example interpolation or the like corresponding to the pump current value Ipx from (stored as tables in the nonvolatile memory 86) Sought using.

Next, in step S 402, the oxygen concentration PO ₂ is stored in a predetermined storage area of the nonvolatile memory 86 via the oxygen concentration calculating means 160.

Next, in step S403, the air ratio λ is calculated from the following equation through the air ratio calculating means 162.

[0138]

(Equation 5)

Thereafter, in step S404, the air ratio λ is stored in a predetermined storage area of the nonvolatile memory 86 via the air ratio calculating means 162.

When the processing in step S404 is completed, the processing in the first arithmetic means 140 is completed.

On the other hand, if it is determined in step S304 in FIG. 19 that the fuel is excessive, the flow proceeds to step S306, where the second calculation means 142 (subroutine) is entered.

The processing operation of the second calculating means 142 is firstly registered in the multi-dimensional polynomial approximating equation for gain (see the following equation) and the nonvolatile memory 86 through the gain calculating means 164 in step S501 of FIG. The gain G is calculated based on the coefficients b _{0 to} b ₄ and the water / carbon ratio H / C. Since the coefficients b _{0 to} b ₄ have been described above, they are omitted here.

G = b ₀ + b ₁ · (H / C) + b ₂ · (H
/ C) ² + b ₃ · (H / C) ³ + b ₄ · (H / C) ⁴ Next, in step S502, the correction operation means 166
As shown in the following equation, the correction output Ipx from the sensor output correction means 126 is applied to the gain calculation means 16
4 is multiplied by a gain G to obtain a corrected operation value x.

X = G · Ipx Next, in step S503, the air ratio calculating means 16
8, a multidimensional polynomial approximation formula for the air ratio (see the following formula),
The air ratio λ is calculated based on the coefficients a _{0 to} a ₃ , the correction calculation value x, and the correction coefficient Km.

Λ = (a ₀ + a ₁ · x + a ₂ · x ² + a ₃
X ³ ) / Km Then, in step S 504, the air ratio λ is stored in the nonvolatile memory 8 through the air ratio calculating means 168.
6 is stored in the predetermined storage area.

When the processing in step S504 is completed, the processing in the second arithmetic means 142 is completed.

Then, as shown in FIG. 19, when the processing by the first calculating means 140 or the second calculating means 142 is completed, the process proceeds to the next step S307, where the air-fuel ratio calculating means 134 The air ratio λ and the air ratio λ obtained by the first calculating means 140 or the second calculating means 142
= 1 based on the reference constant ARF ₀ when ARF = 1
Is calculated.

ARF = λ · ARF ₀ Next, at step S308, the air-fuel ratio calculating means 13
4, the air-fuel ratio ARF is stored in a predetermined storage area of the nonvolatile memory 86.

Next, in step S309, the oxygen concentration PO ₂ , the air ratio λ, and the air-fuel ratio ARF stored in the predetermined storage area of the nonvolatile memory 86 are read out via the output processing means 136, respectively. The concentration PO ₂ , the air ratio λ, and the air-fuel ratio ARF are input / output ports 88
Are output to the digital display unit 94, the analog output system 98, and the digital communication system 100 via the

When the processing in step S309 is completed, the processing operation of the arithmetic processing means 110B is completed. However, when the fuel components H and C are input again through the key input device 82, the calculation operation is started. Processing means 1
10B will be activated by the CPU 90.

As described above, the calculation according to the second embodiment
In the processing means 110B, the measured gas is
In this case, the gain G to be applied to the correction output Ipx is
H / C specified by data input, nonvolatile memo
Coefficient b registered in Re 86₀~ B_FourAnd multi-dimensional for gain
Determined based on the polynomial approximation formula, and corrected gain G is output.
Ipx is multiplied to obtain a correction current value x.
Substitute x into the multi-dimensional polynomial approximation for air ratio, and
Coefficient a registered in the memory 86₀~ A _ThreeBased on
To obtain the air ratio λ.
86 to greatly reduce the capacity of the coefficient table to be expanded.
It is possible to reduce the amount of memory used.
Wear.

Here, a conventional air-fuel ratio sensor (comparative example) using a correspondence table between the air ratio λ and the pump current value Ip and an air-fuel ratio sensor incorporating the arithmetic processing means 110B according to the second embodiment A description will be given of a comparison of the memory capacity with the embodiment 12 (embodiment). Note that all numerical data use floating point (4 byte data).

In the comparative example using the correspondence table between the air ratio λ and the pump current value Ip, the accuracy of the correspondence table and the pump current Ip were compared.
Although there is a trade-off with the conversion speed from p to the air ratio λ, the measurement range is 0.5 with the step size of the air ratio λ being 0.001.
If it is set to １．０1.0, a set of (Ip, λ) requires 500 points, and a memory capacity of 4 bytes × 500 points × 2 = 4 kbytes is required.

On the other hand, in the air-fuel ratio sensor 12 according to the embodiment, the coefficients of the multi-dimensional polynomial approximation for gain are b _{0 to} b _4.
And the coefficients of the multi-dimensional polynomial approximation for the air ratio are a _{0 to} a ₃
Therefore, the capacity of data to be stored in the non-volatile memory 86 necessary for calculating the air ratio λ and the air-fuel ratio ARF is (5 + 4) × 4 bytes = 36 bytes.

Therefore, by using the arithmetic processing means 110B according to the second embodiment, a nonvolatile memory 86 such as an EEPROM having a small storage capacity and a one-chip CPU having a small RAM capacity can be adopted. Moreover, since a battery for backing up the RAM 84 is not required, the handling of the air-fuel ratio measuring device 10 can be facilitated and the size and weight can be reduced.

In the above example, the coefficients are written in the nonvolatile memory 86. However, if the coefficients a _{0 to} a ₃ and b _{0 to} b ₄ are registered in the ROM 80 through the information storage means 144, the nonvolatile memory 86 86 can also be omitted.

Further, the gain G is obtained by a four-dimensional polynomial approximation, and the air ratio λ is obtained by a three-dimensional polynomial approximation. A polynomial approximation such as six-dimensional may be used.

Next, an arithmetic processing means 110C according to the third embodiment will be described with reference to FIGS. Components corresponding to those in FIG. 17 are denoted by the same reference numerals.

The arithmetic processing means 110C according to the third embodiment has substantially the same configuration as the arithmetic processing means 110B (see FIG. 17) according to the second embodiment.
A point having an acid-carbon ratio calculating means 180 for obtaining an acid-carbon ratio based on the input fuel components O and C;
42 differs as follows.

That is, before the measurement, the second calculating means 142 calculates the coefficient of water-coal ratio for obtaining the coefficient group used in the multi-dimensional polynomial approximation equation for the air ratio in advance for obtaining the air ratio λ. As shown in FIG. 22, a water / carbon ratio information storage means 182 (see FIG. 23) for storing in the ROM 80 a characteristic data group for a change in the water / carbon ratio H / C of a coefficient group used in the arithmetic expression. A charcoal ratio table developing means for obtaining a coefficient group of the charcoal ratio coefficient arithmetic expression corresponding to a specific charcoal ratio H / C based on the characteristic data group and developing the coefficient group as a charcoal ratio coefficient table 184, respectively. 186, the coefficient calculation formula for the water-coal ratio, the coefficient group stored in the coefficient table for the coal-carbon ratio 184, and the multi-dimensional polynomial approximation for the air ratio based on the specific water-carbon ratio H / C. A coefficient calculating means 188 for calculating the coal / coal ratio It has an air ratio calculating means 190 for calculating an air ratio λ based on the multi-dimensional polynomial approximation formula for the air ratio, the coefficient from the coefficient calculating means 188 for the charcoal ratio and the correction output Ipx from the sensor output correcting means 126. .

In addition, the arithmetic processing means 110C according to the third embodiment is provided with the following means in addition to the above-mentioned various means, corresponding to the case where the oxidized carbon ratio is ≠ 0.

That is, an acid-carbon ratio determining means 192 for determining the presence or absence of an acid-carbon ratio O / C, and an acid-carbon ratio =
The acid-coal ratio O of the coefficient group used in the coefficient-coefficient-calculation equation used to determine the coefficient group used in the multidimensional polynomial approximation equation for the coefficient for determining the conversion coefficient KK converted into the output corresponding to 0 Acid-coal ratio information storage means 194 for storing a characteristic data group for a change in / C in ROM 80 (see FIG. 24).
And a coefficient group for the acid-carbon ratio coefficient calculation formula corresponding to a specific acid-carbon ratio O / C, based on the characteristic data group, and developed as an acid-carbon ratio coefficient table 196, respectively. Based on the expansion means 198, the coefficient arithmetic expression for the acid-coal ratio, the coefficient group stored in the coefficient table 196 for various acid-coal ratios, and the specific acid-coal ratio O / C, the multidimensional polynomial approximation expression for the coefficient is obtained. A coefficient calculating means 200 for calculating a coefficient to be used; a multidimensional polynomial approximation formula for the coefficient, a coefficient from the coefficient calculating means 200 for the acid and carbon ratio, and a correction output Ipx from the sensor output correcting means 126. Conversion coefficient calculating means 202 for calculating the conversion coefficient KK based on the conversion coefficient KK and the correction output Ipx are provided, and the conversion means 204 is provided as a new correction output Ipx.

Before the arithmetic processing means 110C according to the third embodiment is executed, as shown in FIG. 23, the arithmetic processing means 110C is used in advance in a coefficient arithmetic expression through a water / carbon ratio information storage means 182. The characteristic data group for the change in the water / carbon ratio H / C of the various coefficient groups is stored in the ROM 80. The water-coal ratio information storage means 182 is provided by a computer 206 installed separately from the air-fuel ratio measuring device 10, by a theoretical combustion reaction simulation of fuel and air, for various coefficient groups used in the multidimensional polynomial approximation formula. H / C
Is calculated, and a characteristic data group as a result of the calculation is calculated based on the R data used in the arithmetic processing system 14.
The OM 80 is burned and written using, for example, the ROM writer 208. At this time, the arithmetic processing means (program) and other fixed data are also burned and written in the ROM 80.

As shown in FIG. 24, the characteristic data group for the change in the acid / carbon ratio H / C of the various coefficient groups used in the coefficient calculation equation is stored in the ROM 80 in advance through the acid / carbon ratio information storage means 194. Is done. In the acid-coal ratio information storage means 194, the computer 210 installed separately from the air-fuel ratio measuring apparatus 10 also performs various theoretical simulations of fuel and air to simulate various kinds of equations used in the multidimensional polynomial approximation. A characteristic data group corresponding to a change in the acid-carbon ratio O / C of the coefficient group is calculated, and a characteristic data group as a result of the calculation is stored in a ROM used in the arithmetic processing system.
For example, it is burned and written in 80 using a ROM writer 212.

The ROM 80 in which the characteristic data group, the program, and the like are written is set in the arithmetic processing system 14 and is electrically connected to the data bus 92, the address bus, and the like in the arithmetic processing system 14.

Here, the details of the characteristic data group registered in the ROM 80 will be described. This characteristic data group is created for each coefficient used in the multidimensional polynomial approximation formula for air ratio and the multidimensional polynomial approximation formula for coefficients.

[0167] First, air ratio multidimensional polynomial approximation, as follows, expressed in λ = ΣA ^_i · x _i, when considering a multi-dimensional polynomial approximation up to 6 dimensions, lambda = A _{0 + A 1 · x + A 2} · x 2 + A 3 · x 3 + A 4 ·
the _{^{x 4 + A 5 · x 5}} + A 6 · x 6.

The equation for calculating the coefficient for the water / coal ratio is represented by A _i = ΣB _ij · (H / C) ^j. Considering the coefficient equation up to six dimensions, A _i = B _i0 + B _i1 · (H / C) + B _i2・ (H / C) ² + B _i3・ (H /
C) ³ + B _i4 · (H / C) ⁴ + B _i5 · (H / C) ⁵ + B _i6 · (H / C) ⁶

Specifically, when the multi-dimensional polynomial approximation formula for the air ratio is six-dimensional as described above, the coefficient calculation formula is: A ₀ = B ₀₀ + B ₀₁ · (H / C) + B ₀₂ · (H / C) ² + B ₀₃・ (H /
C) ³ + B ₀₄ · (H / C) ⁴ + B ₀₅ · (H / C) ⁵ + B ₀₆ · (H / C) ⁶ A ₁ = B ₁₀ + B ₁₁ · (H / C) + B ₁₂ · (H / C ) ² + B ₁₃・ (H /
_{^{C) 3 + B 14 · (}} H / C) 4 + B 15 · (H / C) 5 + B 16 · (H / C) 6 A 2 = B 20 + B 21 · (H / C) + B 22 · (H / C ) ² + B ₂₃・ (H /
C) ³ + B ₂₄・ (H / C) ⁴ + B ₂₅・ (H / C) ⁵ + B ₂₆・ (H / C) ⁶ A ₃ = B ₃₀ + B ₃₁・ (H / C) + B ₃₂・ (H / C ) ² + B ₃₃・ (H /
C) ³ + B ₃₄ · (H / C) ⁴ + B ₃₅ · (H / C) ⁵ + B ₃₆ · (H / C) ⁶ A ₄ = B ₄₀ + B ₄₁ · (H / C) + B ₄₂ · (H / C ) ² + B ₄₃・ (H /
_{^{C) 3 + B 44 · (}} H / C) 4 + B 45 · (H / C) 5 + B 46 · (H / C) 6 A 5 = B 50 + B 51 · (H / C) + B 52 · (H / C ) ² + B ₅₃・ (H /
C) ³ + B ₅₄ · (H / C) ⁴ + B ₅₅ · (H / C) ⁵ + B ₅₆ · (H / C) ⁶ A ₆ = B ₆₀ + B ₆₁ · (H / C) + B ₆₂ · (H / C ) ² + B ₆₃・ (H /
C) ³ + B ₆₄ · (H / C) ⁴ + B ₆₅ · (H / C) ⁵ + B ₆₆ · (H / C) ⁶ Then, each coefficient B _{00 to} B with respect to the water / carbon ratio H / C
_{06, B 10 ~B 16, B} 20 ~B 26, B 30 ~B 36, B 40 ~
Changes in B ₄₆ , B _{50 to} B ₅₆ , and B _{60 to} B ₆₆ are B ₀₀ characteristic tables to B ₀₆ characteristic tables and B ₁₀ characteristic tables to B, respectively.
₁₆ characteristic table, B ₂₀ characteristic table ~B ₂₆ characteristic table, B ₃₀ characteristic table ~B ₃₆ characteristic table, B ₄₀ characteristic table ~B ₄₆ characteristic table, B ₅₀ characteristic table ~B ₅₆ characteristic table, B ₆₀ characteristic table ~B ₆₆ is written to the ROM 80 as a characteristic table.

[0170] On the other hand, a multi-dimensional polynomial approximation is coefficient ratio as follows, expressed in KK = ΣC ^_i · x _i, when considering a multi-dimensional polynomial approximation up to 6 dimensions, KK = C _{0 + C 1 · x + C 2} · x 2 + C 3 · x 3 + C 4
· A _{^{x 4 + C 5 · x 5}} + C 6 · x 6.

The coefficient-calculation formula for the acid-to-coal ratio is expressed by C _i = ΣD _ij · (O / C) ^j , and considering the coefficient calculation formula up to six dimensions, C _i = D _i0 + D _i1 · (O / C) + D _i2 • (O / C) ² + D _i3 • (O /
C) ³ + D _i4 · (O / C) ⁴ + D _i5 · (O / C) ⁵ + D _i6 · (O / C) ⁶

Specifically, when the multidimensional polynomial approximation expression for coefficients is six-dimensional as described above, the coefficient operation expression is: C ₀ = D ₀₀ + D ₀₁ · (O / C) + D ₀₂ · (O / C ) ² + D ₀₃・ (O /
C) ³ + D ₀₄・ (O / C) ⁴ + D ₀₅・ (O / C) ⁵ + D ₀₆・ (O / C) ⁶ C ₁ = D ₁₀ + D ₁₁・ (O / C) + D ₁₂・ (O / C _{^{) 2 + D 13 · (O}} /
C) ³ + D ₁₄ · (O / C) ⁴ + D ₁₅ · (O / C) ⁵ + D ₁₆ · (O / C) ⁶ C ₂ = D ₂₀ + D ₂₁ · (O / C) + D ₂₂ · (O / C _{^{) 2 + D 23 · (O}} /
C) ³ + D ₂₄・ (O / C) ⁴ + D ₂₅・ (O / C) ⁵ + D ₂₆・ (O / C) ⁶ C ₃ = D ₃₀ + D ₃₁・ (O / C) + D ₃₂・ (O / C ) ² + D ₃₃・ (O /
C) ³ + D ₃₄ · (O / C) ⁴ + D ₃₅ · (O / C) ⁵ + D ₃₆ · (O / C) ⁶ C ₄ = D ₄₀ + D ₄₁ · (O / C) + D ₄₂ · (O / C ) ² + D ₄₃・ (O /
_{^{C) 3 + D 44 · (}} O / C) 4 + D 45 · (O / C) 5 + D 46 · (O / C) 6 C 5 = D 50 + D 51 · (O / C) + D 52 · (O / C ) ² + D ₅₃・ (O /
C) ³ + D ₅₄ · (O / C) ⁴ + D ₅₅ · (O / C) ⁵ + D ₅₆ · (O / C) ⁶ C ₆ = D ₆₀ + D ₆₁ · (O / C) + D ₆₂ · (O / C ) ² + D ₆₃・ (O /
C) ³ + D ₆₄ · (O / C) ⁴ + D ₆₅ · (O / C) ⁵ + D ₆₆ · (O / C) ⁶ Then, each coefficient D _{00 to} D with respect to the acid carbon ratio O / C
_{06, D 10 ~D 16, D} 20 ~D 26, D 30 ~D 36, D 40 ~
_{D 46, D 50 ~D 56,} D 60 changes in ~D ₆₆ respectively D ₀₀ characteristic table ~D ₀₆ characteristic table, D ₁₀ characteristic table ~D
₁₆ characteristic table, D ₂₀ characteristic table ~D ₂₆ characteristic table, D ₃₀ characteristic table ~D ₃₆ characteristic table, D ₄₀ characteristic table ~D ₄₆ characteristic table, D ₅₀ characteristic table ~D ₅₆ characteristic table, D ₆₀ characteristic table ~D ₆₆ is written to the ROM 80 as a characteristic table.

Next, the processing operation of the arithmetic processing means 110C according to the third embodiment, particularly the processing operation of the second arithmetic means 142, will be described with reference to the flowchart of FIG.

First, in step S601, the water / carbon ratio
To the water / carbon ratio H / C through the
Corresponding coefficient B₀₀~ B₀₆, B_Ten~ B₁₆, B₂₀~ B₂₆, B₃₀
~ B ₃₆, B₄₀~ B₄₆, B₅₀~ B₅₆, B₆₀~ B₆₆Ask for
You.

Specifically, B₀₀Characteristic table ~ B₀₆Characteristic
Table, B_TenCharacteristic table ~ B₁₆Characteristic table, B₂₀
Characteristic table ~ B₂₆Characteristic table, B₃₀Characteristic table ~
B₃₆Characteristic table, B₄₀Characteristic table ~ B₄₆Characteristics table
Le, B₅₀Characteristic table ~ B₅₆Characteristic table, B₆₀Characteristic
Table ~ B₆₆Water from each coefficient group registered in the characteristic table
Coefficient B corresponding to coal ratio H / C₀₀~ B₀₆, B_Ten~ B₁₆, B
₂₀~ B₂₆, B₃₀~ B₃₆, B₄₀~ B₄₆, B₅₀~ B₅₆, B₆₀
~ B₆₆Are determined using, for example, an interpolation method. Asked
Coefficient B₀₀~ B₀₆, B_Ten~ B₁₆, B₂₀~ B₂₆, B₃₀~
B₃₆, B₄₀~ B ₄₆, B₅₀~ B₅₆, B₆₀~ B₆₆Is also
Non-volatile memo through the charcoal ratio table developing means 186
The coefficient table 184 for the water and coal ratio is stored in a predetermined storage area of the memory 86.
It is memorized.

Next, in step S 602,
Through the coefficient calculating means 188 for the air ratio for the multidimensional polynomial
Coefficient A used in similar formula₀~ A₆Is calculated. concrete
Is a water / carbon ratio coefficient stored in the non-volatile memory 86.
Each coefficient B of the number table 184 ₀₀~ B₀₆, B_Ten~ B₁₆, B
₂₀~ B₂₆, B₃₀~ B₃₆, B₄₀~ B₄₆, B₅₀~ B₅₆, B ₆₀
~ B₆₆Are read out, and each of these coefficients B₀₀~ B₀₆, B_Ten~
B₁₆, B₂₀~ B₂₆, B ₃₀~ B₃₆, B₄₀~ B₄₆, B₅₀~ B
₅₆, B₆₀~ B₆₆Is substituted into the following equation to perform the operation. Profit
Coefficient A₀~ A₆Is a predetermined record of the nonvolatile memory 86.
Is stored in the storage area.

A ₀ = B ₀₀ + B ₀₁ · (H / C) + B ₀₂ · (H / C) ²
+ B ₀₃・ (H / C) ³ + B ₀₄・ (H / C) ⁴ + B ₀₅・ (H / C) ⁵ + B ₀₆・
(H / C) ⁶ A ₁ = B ₁₀ + B ₁₁ · (H / C) + B ₁₂ · (H / C) ² + B ₁₃ · (H /
_{^{C) 3 + B 14 · (}} H / C) 4 + B 15 · (H / C) 5 + B 16 · (H / C) 6 A 2 = B 20 + B 21 · (H / C) + B 22 · (H / C ) ² + B ₂₃・ (H /
C) ³ + B ₂₄・ (H / C) ⁴ + B ₂₅・ (H / C) ⁵ + B ₂₆・ (H / C) ⁶ A ₃ = B ₃₀ + B ₃₁・ (H / C) + B ₃₂・ (H / C ) ² + B ₃₃・ (H /
C) ³ + B ₃₄ · (H / C) ⁴ + B ₃₅ · (H / C) ⁵ + B ₃₆ · (H / C) ⁶ A ₄ = B ₄₀ + B ₄₁ · (H / C) + B ₄₂ · (H / C ) ² + B ₄₃・ (H /
_{^{C) 3 + B 44 · (}} H / C) 4 + B 45 · (H / C) 5 + B 46 · (H / C) 6 A 5 = B 50 + B 51 · (H / C) + B 52 · (H / C ) ² + B ₅₃・ (H /
C) ³ + B ₅₄ · (H / C) ⁴ + B ₅₅ · (H / C) ⁵ + B ₅₆ · (H / C) ⁶ A ₆ = B ₆₀ + B ₆₁ · (H / C) + B ₆₂ · (H / C ) ² + B ₆₃・ (H /
C) ³ + B ₆₄ · (H / C) ⁴ + B ₆₅ · (H / C) ⁵ + B ₆₆ · (H / C) ⁶ Next, in step S 603, the acid-coal ratio discriminating means 19
Through step 2, it is determined whether or not the acid-carbon ratio is ≠ 0. If the acid carbon ratio is ≠ 0, the process proceeds to the next step S604,
Through the oxidized carbon ratio table developing means 198, the oxidized carbon ratio O /
Factor D ₀₀ to D ₀₆ corresponding to the _{C, D 10 ~D 16, D} 20 ~
_{D 26, D 30 ~D 36,} D 40 ~D 46, D 50 ~D 56, D 60 ~D
_Ask for ₆₆ .

Specifically, D₀₀Characteristic table ~ D₀₆Characteristic
Table, D_TenCharacteristic table ~ D₁₆Characteristic table, D₂₀
Characteristic table ~ D₂₆Characteristic table, D₃₀Characteristic table ~
D₃₆Characteristic table, D₄₀Characteristic table ~ D₄₆Characteristics table
Le, D₅₀Characteristic table ~ D₅₆Characteristic table, D₆₀Characteristic
Table ~ D₆₆Acid from each coefficient group registered in the characteristic table
Coefficient D corresponding to coal ratio O / C₀₀~ D₀₆, D_Ten~ D₁₆, D
₂₀~ D₂₆, D₃₀~ D₃₆, D₄₀~ D₄₆, D₅₀~ D₅₆, D₆₀
~ D₆₆Are determined using, for example, an interpolation method. Asked
Coefficient D₀₀~ D₀₆, D_Ten~ D₁₆, D₂₀~ D₂₆, D₃₀~
D₃₆, D₄₀~ D ₄₆, D₅₀~ D₅₆, D₆₀~ D₆₆Is also
Non-volatile memos through the table expansion means 198
An acid-coal ratio coefficient table 196 is stored in a predetermined storage area of the memory 86.
It is memorized.

Next, in step S605, the coefficients C _{0 to} C ₆ used in the multi-dimensional polynomial approximation for the coefficients are calculated by the coefficient calculating means 200 for the acid-coal ratio. Specifically, the coefficients D _{00 to} D ₀₆ , D _{10 to} D ₁₆ , and D _{20 of the} acid-coal ratio coefficient table 196 stored in the nonvolatile memory 86
_{~D 26, D 30 ~D 36,} D 40 ~D 46, D 50 ~D 56, D 60 ~
D ₆₆ is read, each of these coefficients D ₀₀ ~D _06, D ₁₀ ~D
_{16, D 20 ~D 26, D} 30 ~D 36, D 40 ~D 46, D 50 ~
D ₅₆ and D _{60 to} D ₆₆ are substituted into the following equation to perform the operation.
The obtained coefficients C _{0 to} C ₆ are stored in a predetermined storage area of the nonvolatile memory 86.

C ₀ = D ₀₀ + D ₀₁ · (O / C) + D ₀₂ · (O / C) ²
+ D ₀₃・ (O / C) ³ + D ₀₄・ (O / C) ⁴ + D ₀₅・ (O / C) ⁵ + D ₀₆・
(O / C) ⁶ C ₁ = D ₁₀ + D ₁₁ · (O / C) + D ₁₂ · (O / C) ² + D ₁₃ · (O / C
C) ³ + D ₁₄ · (O / C) ⁴ + D ₁₅ · (O / C) ⁵ + D ₁₆ · (O / C) ⁶ C ₂ = D ₂₀ + D ₂₁ · (O / C) + D ₂₂ · (O / C _{^{) 2 + D 23 · (O}} /
C) ³ + D ₂₄・ (O / C) ⁴ + D ₂₅・ (O / C) ⁵ + D ₂₆・ (O / C) ⁶ C ₃ = D ₃₀ + D ₃₁・ (O / C) + D ₃₂・ (O / C ) ² + D ₃₃・ (O /
C) ³ + D ₃₄ · (O / C) ⁴ + D ₃₅ · (O / C) ⁵ + D ₃₆ · (O / C) ⁶ C ₄ = D ₄₀ + D ₄₁ · (O / C) + D ₄₂ · (O / C ) ² + D ₄₃・ (O /
_{^{C) 3 + D 44 · (}} O / C) 4 + D 45 · (O / C) 5 + D 46 · (O / C) 6 C 5 = D 50 + D 51 · (O / C) + D 52 · (O / C ) ² + D ₅₃・ (O /
C) ³ + D ₅₄ · (O / C) ⁴ + D ₅₅ · (O / C) ⁵ + D ₅₆ · (O / C) ⁶ C ₆ = D ₆₀ + D ₆₁ · (O / C) + D ₆₂ · (O / C ) ² + D ₆₃・ (O /
C) ³ + D ₆₄ · (O / C) ⁴ + D ₆₅ · (O / C) ⁵ + D ₆₆ · (O / C) ⁶ Next, in step S606, the conversion coefficient calculating means 2
02, a conversion coefficient KK based on the following multi-dimensional polynomial approximation equation for coefficients, the coefficients C _{0 to} C ₆ from the acid-coefficient-ratio coefficient calculation means 200, and the correction output Ipx from the sensor output correction means 126. Is calculated.

KK = C ₀ + C ₁ · Ipx + C ₂ · Ipx
² + C ₃ · Ipx ³ + C ₄ · Ipx ⁴ + C ₅ · Ipx ⁵
+ C ₆ · Ipx ⁶ Next, in step S607, the correction output I from the sensor output correction unit 126 is output through the conversion unit 204.
px is multiplied by the conversion coefficient KK, and the multiplied value is used as a new corrected output Ipx.

At the stage when the processing in step S607 is completed, or when it is determined in step S603 that the acid-coal ratio = 0, the process proceeds to the next step S608, and the following equation is obtained through the air ratio calculating means 190. Multi-dimensional polynomial approximation formula for air ratio and coefficient calculating means 188 for said charcoal ratio
The air ratio λ is calculated on the basis of the coefficients A _{0 to} A ₆ and the corrected output Ipx.

Λ = A ₀ + A ₁ · Ipx + A ₂ · Ipx ²
+ A ₃ · Ipx ³ + A ₄ · Ipx ⁴ + A ₅ · Ipx ⁵ +
A ₆ · Ipx ⁶ After that, in step S609, the air ratio λ is stored in the predetermined storage area of the nonvolatile memory 86 through the air ratio calculating means 190.

When step S609 is completed,
The processing by the second calculating means 142 is completed, and FIG.
The process returns to step S307 and subsequent steps.

That is, in step S307, the air-fuel ratio ARF is calculated by the air-fuel ratio calculation means 134 based on the obtained air ratio λ and the reference constant ARF ₀ when the air ratio λ = 1.

ARF = λ · ARF ₀ Next, in step S308, the air-fuel ratio calculating means 13
4, the air-fuel ratio ARF is stored in a predetermined storage area of the nonvolatile memory 86.

Next, in step S309, the oxygen concentration PO ₂ , the air ratio λ, and the air-fuel ratio ARF stored in the predetermined storage area of the nonvolatile memory 86 are read out via the output processing means 136, respectively. The concentration PO ₂ , the air ratio λ, and the air-fuel ratio ARF are input / output ports 88
Are output to the digital display unit 94, the analog output system 98, and the digital communication system 100 via the

When the processing in step S309 is completed, the processing operation of the arithmetic processing means 110C is completed. However, when at least the fuel components H and C are input through the key input device 82 again, this processing is started. The arithmetic processing means 110C according to the third embodiment is activated by the CPU 90.

As described above, in the arithmetic processing unit 110C according to the third embodiment, when the gas to be measured is in excess of fuel, each coefficient used in the multi-dimensional polynomial approximation for the air ratio is converted into a data. Based on the water / carbon ratio H / C specified by the input, the coefficient registered in the nonvolatile memory 86, and the coefficient calculation formula, the obtained coefficient and the correction output Ipx are substituted into the multi-dimensional polynomial approximation formula for the air ratio. Since the air ratio λ is obtained by the calculation, it is necessary to perform a complicated calculation (complex fuel combustion reaction calculation) before obtaining the air ratio λ and the air-fuel ratio ARF corresponding to the specific water / carbon ratio H / C. No, H / C
The time from the input of to the determination of the air ratio λ and the air-fuel ratio ARF is extremely short, and the air ratio λ and the air-fuel ratio ARF can be determined with high accuracy.

When the acid-to-carbon ratio ≠ 0, each coefficient used in the multidimensional polynomial approximation equation for coefficients is registered in the acid-to-carbon ratio O / C specified by the data input and in the nonvolatile memory 86. The conversion coefficient KK is obtained by substituting the obtained coefficient and the correction output Ipx into the multidimensional polynomial approximation equation for the coefficient, and multiplying the correction output Ipx by the conversion coefficient KK to obtain a new coefficient. Since the corrected output Ipx is used as the correction output Ipx, and the coefficient stored in the nonvolatile memory 86 is substituted into the multi-dimensional polynomial approximation for the air ratio to obtain the air ratio λ, the air-fuel ratio ARF of the alcohol fuel and the like are obtained. Can be obtained with high precision and easily, and the air-fuel ratio measuring device 1
0 multifunction can be realized.

Next, a modified example 110Ca of the arithmetic processing means 110C according to the third embodiment will be described with reference to FIGS.
This will be described with reference to FIG.

Arithmetic processing means 110Ca according to this modified example
26, as shown in FIG. 26, the table expansion means 198 for the acid-coal ratio in the second arithmetic means 142 of the arithmetic processing means 110C according to the third embodiment, the coefficient arithmetic means 2 for the acid-carbon ratio.
The difference is that the following means are provided in place of the 00 and the conversion coefficient calculating means 202.

That is, before the measurement, the output of the air-fuel ratio sensor 12 at the acid-coal ratio ≠ 0 when the water-coal ratio is a prescribed value is Ipx, and the reference output of the air-fuel ratio sensor at the acid-carbon ratio = 0. Let Ip0 be the conversion coefficient KK = Ip0 / Ipx based on the relational expression of conversion coefficient KK and Ipx.
0, which is created and stored in the ROM 80, and the sensor output correcting means 12 (see FIG. 27).
And a conversion coefficient calculating means 224 for obtaining a conversion coefficient KK corresponding to the correction output Ipx from the correspondence table 220 by, for example, a broken line approximation calculation.

Next, the arithmetic processing means 110C according to the modification example
The processing operation at a, in particular, the processing operation at the second calculating means 142 will be described with reference to FIGS. 27 and 28.

First, the arithmetic processing means 11 according to this modification example
Before the execution of 0Ca, as shown in FIG. 27, the characteristic data group with respect to the change of the water / carbon ratio H / C of the various coefficient groups used in the coefficient calculation equation is previously stored through the water / carbon ratio information storage means 182. The correction output of the air-fuel ratio sensor 12 at the acid-coal ratio ≠ 0 when the water-coal ratio H / C is a predetermined specified value is Ipx, and the acid-coal ratio = When the reference output of the air-fuel ratio sensor 12 at 0 is Ip0, the conversion coefficient KK = Ip0 / Ip
Based on the relational expression of x, the conversion coefficient KK and the correction output Ipx
Is created and stored in the ROM 80.

[0196] Then, in step S701 of FIG. 28, through the water coal ratio table deployment unit 186, the coefficient B ₀₀ .about.B ₀₆ corresponding to Mizusumihi _{H / C, B 10 ~B 16} , B 20 ~
_{B 26, B 30 ~B 36,} B 40 ~B 46, B 50 ~B 56, B 60 ~B
_Ask for ₆₆ .

Next, in step S702, the water / carbon ratio
Through the coefficient calculating means 188 for the air ratio for the multidimensional polynomial
Coefficient A used in similar formula₀~ A₆Is calculated. concrete
Is a water / carbon ratio coefficient stored in the non-volatile memory 86.
Each coefficient B of the number table 184 ₀₀~ B₀₆, B_Ten~ B₁₆, B
₂₀~ B₂₆, B₃₀~ B₃₆, B₄₀~ B₄₆, B₅₀~ B₅₆, B ₆₀
~ B₆₆Are read out, and each of these coefficients B₀₀~ B₀₆, B_Ten~
B₁₆, B₂₀~ B₂₆, B ₃₀~ B₃₆, B₄₀~ B₄₆, B₅₀~ B
₅₆, B₆₀~ B₆₆Is similar to the equation used in step S602.
The operation is performed by substituting into the expression. The obtained coefficient A₀~ A
₆Is stored in a predetermined storage area of the nonvolatile memory 86.
You.

Next, in step S703, it is determined through the oxidized-carbon ratio determining means 192 whether or not the oxidized-carbon ratio ≠ 0. If the acid-coal ratio ≠ 0, the next step S7
In step 04, a conversion coefficient KK corresponding to the correction output Ipx from the sensor output correction unit 126 is obtained from the correspondence table 220 stored in the ROM 80 by, for example, a broken line approximation calculation through the conversion coefficient calculation unit 224.

Next, in step S705, the correction output Ipx from the sensor output correction means 126 is multiplied by the conversion coefficient KK via the conversion means 204, and the multiplied value is set as a new correction output Ipx.

When the processing in step S705 is completed, or when it is determined in step S703 that the acid-to-carbon ratio is 0, the flow advances to the next step S706, and the following equation is obtained through the air ratio calculation means 190. Multi-dimensional polynomial approximation formula for air ratio and coefficient calculating means 188 for said charcoal ratio
The air ratio λ is calculated based on the coefficients A _{0 to} A ₆ obtained in the above and the correction output Ipx.

Λ = A ₀ + A ₁ · Ipx + A ₂ · Ipx ²
+ A ₃ · Ipx ³ + A ₄ · Ipx ⁴ + A ₅ · Ipx ⁵ +
A ₆ · Ipx ⁶ Thereafter, in step S 707, the air ratio λ is stored in a predetermined storage area of the nonvolatile memory 86 through the air ratio calculating means 190.

When step S707 is completed,
The processing by the second calculating means 142 is completed, and FIG.
The process returns to step S307 and subsequent steps.

As described above, in the arithmetic processing means 110Ca according to this modified example, the correspondence table 220 between the conversion coefficient KK and the pump current value Ipx is created in advance and stored in the ROM 80, and the specific acid / carbon ratio O / C Is calculated from the correspondence table 220 using a polygonal line approximation, so that a complicated calculation is required until the air ratio λ corresponding to the specific water-to-carbon ratio H / C and the acid-carbon ratio O / C is calculated. (Complex fuel combustion reaction calculation) without the need to perform
The time from the input of to the determination of the air ratio λ and the air-fuel ratio ARF becomes very short.

As a gas calibration method, there is also a method shown in FIG. 29 (a gas calibration method according to a modification) in addition to the above-described method. In the gas calibration method according to this modification, the PID control output signals Vp and D /
An IpN ₂ correction circuit 230 (±) combining an A converter (a reference voltage V _DAC for analog conversion) and an attenuator
IpN at 51.2 μA, resolution 0.1 μA / 1 bit)
₂ in the arithmetic processing system 14 so as to cancel
_Is corrected with the setting data D _N2 from. The output of the inverting amplifier 232 is changed to an attenuator 234 (R-2R type D
/ A converter: resolution 1/4096) and input to the double gain inverting amplifier 236, and output the double gain inverting amplifier 236 to the A / D converter 68 (reference voltage V for digital conversion). _ADC ). Then, the CPU 90 adjusts and outputs the attenuation (gain) of the attenuators 234 of 0 to 1 so that the specified oxygen pump current Ip is obtained at the specified oxygen concentration.

With the attenuator 234 and the inverting amplifier 236 with a gain of 2 times, the calibration gain adjustment of the oxygen pump current Ip is performed at a stage before the A / D converter 68.

In this case, the gas calibration that has been manually adjusted using a variable resistor or the like can be automatically adjusted, and the measurement time can be greatly reduced.

The air-fuel ratio measuring method and the air-fuel ratio measuring apparatus according to the present invention are not limited to the above-described embodiments, but may adopt various configurations without departing from the gist of the present invention. .

[0208]

As described above, according to the air-fuel ratio measuring method and the air-fuel ratio measuring device according to the present invention, the calculation in the air-fuel ratio measuring device is simplified, and the calculation result when the fuel composition component changes is obtained. (Air ratio and air-fuel ratio) can be obtained quickly.

Further, the error in the window region near the stoichiometry can be reduced, and the air ratio and the air-fuel ratio can be measured with high accuracy.

Further, the capacity of the memory used for the calculation can be significantly reduced, and the miniaturization of the device configuration for measuring the air-fuel ratio can be promoted.

[Brief description of the drawings]

FIG. 1 shows an embodiment in which an air-fuel ratio measuring method according to the present invention is applied to an air-fuel ratio measuring apparatus used in, for example, an internal combustion engine for an automobile or various industrial furnaces (hereinafter simply referred to as an air-fuel ratio measuring method according to the embodiment). FIG.

FIG. 2 is a block diagram showing an arithmetic processing system of the air-fuel ratio measuring device according to the present embodiment.

FIG. 3 is a configuration diagram illustrating an information storage unit in the arithmetic processing unit according to the first embodiment.

FIG. 4A is a characteristic diagram showing a change of a coefficient A ₀ with respect to a coal ratio registered in an A ₀ characteristic table, and FIG. 4B is a coefficient A _{1 with} respect to a coal ratio registered in an A ₁ characteristic table.
A characteristic diagram showing a change, FIG. 4C is a characteristic diagram showing the change of the coefficients A ₂ for water coal ratio registered in the A ₂ characteristic table.

FIG. 5A is a characteristic diagram showing a change of a coefficient S ₀ with respect to a coal ratio registered in an S ₀ characteristic table, and FIG. 5B is a coefficient S _{1 with} respect to a coal ratio registered in an S ₁ characteristic table.
FIG. 5C is a characteristic diagram showing a change in coefficient S ₂ with respect to the charcoal ratio registered in the S ₂ characteristic table, and FIG. 5D is a characteristic diagram showing the charcoal ratio registered in the S ₃ characteristic table. it is a characteristic diagram showing a change of coefficient S ₃ against.

FIG. 6A is a characteristic diagram showing a change of a coefficient S ₄ with respect to a coal ratio registered in the S ₄ characteristic table, and FIG. 6B is a coefficient S _{5 with} respect to a coal ratio registered in the S ₅ characteristic table.
FIG. 6C is a characteristic diagram showing a change in the coefficient S ₆ with respect to the water-coal ratio registered in the S ₆ characteristic table.

7A is a characteristic diagram showing a change in a coefficient R ₀ with respect to a water / coal ratio registered in the R ₀ characteristic table, and FIG. 7B is a characteristic diagram showing a coefficient R _{1 with} respect to a water / coal ratio registered in the R ₁ characteristic table.
7C is a characteristic diagram showing a change in the coefficient R ₂ with respect to the charcoal ratio registered in the R ₂ characteristic table, and FIG. 7D is a characteristic diagram showing the charcoal ratio registered in the R ₃ characteristic table. it is a characteristic diagram showing a change of coefficient R ₃ against.

FIG. 8A is a characteristic diagram showing a change in a coefficient R ₄ with respect to a coal ratio registered in the R ₄ characteristic table, and FIG. 8B is a coefficient R _{5 with} respect to a coal ratio registered in the R ₅ characteristic table.
FIG. 8C is a characteristic diagram showing a change in coefficient R ₆ with respect to the water-coal ratio registered in the R ₆ characteristic table.

FIG. 9 is a functional block diagram illustrating a configuration of an arithmetic processing unit according to the first embodiment.

FIG. 10 shows a correction coefficient HM in the sensor output correction means.
5 is a flowchart showing a processing operation until a value is obtained.

FIG. 11 is a characteristic diagram showing a relationship between an oxygen concentration in a gas to be measured and a pump current value from a sensor element.

FIG. 12 is a characteristic curve showing a correspondence table between a pump current value (Ipo = Ka · PO ₂ ) obtained based on a reference sensitivity coefficient Ka and a pump current value Ipfo before linearization corresponding to each linearization number. It is a characteristic diagram.

FIG. 13 shows a correction coefficient Km in the sensor output correction means.
5 is a flowchart showing a processing operation until a value is obtained.

FIG. 14 is a flowchart (part 1) illustrating a processing operation in an arithmetic processing unit according to the first embodiment;

FIG. 15 is a flowchart (part 2) illustrating a processing operation in the arithmetic processing unit according to the first embodiment;

FIG. 16A is a characteristic diagram showing a measurement error of the oxygen concentration in the arithmetic processing unit according to the first embodiment with respect to the gas to be measured (lean region), and FIG. FIG. 16C is a characteristic diagram showing a measurement error of the oxygen concentration in the arithmetic processing unit according to the first embodiment with respect to the gas to be measured (rich region) according to the first embodiment. FIG. 5 is a characteristic diagram showing a measurement error of the oxygen concentration in FIG.

FIG. 17 is a functional block diagram illustrating a configuration of an arithmetic processing unit according to the second embodiment.

FIG. 18 is a configuration diagram illustrating an information storage unit in the arithmetic processing unit according to the second embodiment.

FIG. 19 is a flowchart illustrating a processing operation in an arithmetic processing unit according to the second embodiment.

FIG. 20 is a flowchart showing a processing operation of the first processing means in the processing means according to the second embodiment.

FIG. 21 is a flowchart showing a processing operation of the second processing means in the processing means according to the second embodiment.

FIG. 22 is a functional block diagram illustrating a configuration of an arithmetic processing unit according to a third embodiment.

FIG. 23 is a configuration diagram showing a water / carbon ratio information storage unit in the arithmetic processing unit according to the third embodiment.

FIG. 24 is a configuration diagram showing an acid-coal-ratio information storage unit in the arithmetic processing unit according to the third embodiment.

FIG. 25 is a flowchart showing a processing operation of the second processing means in the processing means according to the third embodiment.

FIG. 26 is a functional block diagram illustrating a configuration of a modification of the arithmetic processing unit according to the third embodiment.

FIG. 27 is a configuration diagram showing a correspondence table storage unit in an arithmetic processing unit according to a modification.

FIG. 28 is a flowchart showing a processing operation in a second arithmetic unit in an arithmetic processing unit according to a modification.

FIG. 29 is a configuration diagram for explaining another example of the gas calibration method.

[Description of Signs] 10 air-fuel ratio measuring device 12 air-fuel ratio sensor 14 arithmetic processing system 16 sensor element 18 control system 50 measurement control system 52 heater control system 54 PID
Control circuit 56 V / I conversion circuit 66 Multiplexer 68 A / D converter 80 ROM 82 Key input device 86 Nonvolatile memory 94 Digital display 98 Analog output system 100 Digital communication system 110A, 110B .. 110C, 110Ca arithmetic processing means 112, 144 information storage means 122 water-carbon ratio arithmetic means 124 table expanding means 126 sensor output correcting means 128 area selecting means 130 oxygen equivalent value calculating means 132, 162, 168 190, air ratio calculating means 134, air-fuel ratio calculating means 136, output processing means 140, first calculating means 142, second
Calculation means 150 ... discrimination means 160 ... oxygen concentration calculation means 164 ... gain calculation means 166 ... correction calculation means 180 ... acid-carbon ratio calculation means 182 ... water-carbon ratio information storage means 186 ... water-carbon ratio table developing means 188 ... Water / coal ratio coefficient calculating means 192 ... acid / carbon ratio discriminating means 194 ... acid / carbon ratio information storage means 198 ... acid / carbon ratio table developing means 200 ... acid / carbon ratio coefficient calculating means 202 ... conversion coefficient calculating means 204 ... conversion Means 222: Correspondence table storage means 224: Conversion coefficient calculation means

Claims (36)

[Claims] An air-fuel ratio sensor for obtaining a target air-fuel ratio signal based on an output from an air-fuel ratio sensor for measuring a combustion exhaust gas, the air-fuel ratio sensor corresponding to an air ratio = 1 A predetermined output range centered on the stoichiometric point, which is the output, is a stoichiometric window area, an area with more air than the stoichiometric window area is a lean area, and an area with more fuel than the stoichiometric window area is a rich area. The air-fuel ratio calculation method is characterized in that the air-fuel ratio calculation process uses a multidimensional polynomial approximation for each of a lean region, a stoichiometric window region, and a rich region. 2. A method for measuring an air-fuel ratio according to claim 1, wherein before the measurement, a group of characteristic data corresponding to a change in the water-carbon ratio of various coefficient groups used in the multidimensional polynomial approximation formula is stored in the storage means. Information storage processing to be performed, a water / carbon ratio calculation processing for obtaining a water / carbon ratio based on the input fuel components H and C, a coefficient in a lean region corresponding to the obtained specific water / carbon ratio, a stoichiometric neighborhood window A table expansion process for obtaining a coefficient in a region and a coefficient in a rich region based on the characteristic data group and developing them as a coefficient table, and a correction coefficient for correcting the sensitivity of the air-fuel ratio sensor using a predetermined calibration gas. And a sensor output correction process for correcting the output of the air-fuel ratio sensor using the correction coefficient, and a sensor output correction process based on the correction output obtained in the sensor output correction process. Area selection processing for selecting one of an area, a stoichiometric neighborhood window area, and a rich area; a multidimensional polynomial approximation formula corresponding to the area selected in the area selection processing; and a coefficient corresponding to the selected area An oxygen equivalent value calculation process for obtaining an oxygen equivalent value based on the coefficient and the correction output stored in the table; and an air ratio calculation process for obtaining an air ratio based on the oxygen equivalent value and at least a standard oxygen partial pressure in the atmosphere. An air-fuel ratio calculation process for obtaining an air-fuel ratio based on the obtained air ratio and a reference constant when the air ratio = 1. 3. The air-fuel ratio measuring method according to claim 2, wherein the information storage processing is performed by simulating a theoretical combustion reaction of fuel and air with a computer installed separately from an air-fuel ratio measuring device. An air-fuel ratio measurement method, comprising calculating a characteristic data group for a change in a charcoal ratio of various coefficient groups used in a dimensional polynomial approximation expression and storing the characteristic data group in the storage area. 4. The air-fuel ratio measuring method according to claim 2 or 3, wherein the table expansion processing includes a coefficient in a lean region corresponding to a specific water-carbon ratio obtained in the water-carbon ratio calculation processing, and a stoichiometric neighborhood. An air-fuel ratio measuring method, wherein a coefficient in a window area and a coefficient in a rich area are obtained from the characteristic data group by an interpolation method and are respectively developed as coefficient tables. 5. The air-fuel ratio measuring method according to claim 2, wherein in the area selection processing, the correction output obtained in the sensor output correction processing is applied to the stoichiometric vicinity window area. Select a stoichiometric neighborhood window area when included in the corresponding output range, select a lean area if the output is equal to or greater than the output corresponding to the high output side boundary in the stoichiometric neighborhood window area, and select a low output in the stoichiometric neighborhood window area. An air-fuel ratio measuring method, wherein a rich region is selected when the output is equal to or less than the output corresponding to the boundary on the side. 6. The air-fuel ratio measuring method according to claim 5, wherein in the sensor output correction processing, an output from the air-fuel ratio sensor is subtracted by a reference output at the stoichiometric point, and a correction coefficient for calibration in a lean region side is obtained. And a correction output obtained by multiplying the air-fuel ratio. 7. The air-fuel ratio measuring method according to claim 2, wherein the oxygen equivalent value calculation processing is performed in the following multidimensional manner in accordance with the area selected in the area selection processing. An air-fuel ratio measuring method, wherein an oxygen equivalent value is determined by a polynomial approximation. [Lean Region] Oxygen equivalent value = A ₀ + A ₁ · x + A ₂ / x A _{0 to} A ₂ : Coefficient stored in the coefficient table corresponding to the lean region [Stoichiometric neighborhood window region] Oxygen equivalent value = S ₀ + S ₁ · ^{_{x + S 2 · x 2 +}} S 3 · x 3
+ S ₄ · x ⁴ + S ₅ · x ⁵ + S ₆ · x ⁶ S _{0 to} S ₆ : Coefficients stored in the coefficient table corresponding to the stoichiometric neighborhood window area [Rich area] xx = x / Km Oxygen equivalent value = R _{0 + R 1 · xx + R 2} · xx 2 + R 3 ·
xx ³ + R ₄ xx ⁴ + R ₅ xx ⁵ + R ₆ xx ⁶ Km: correction coefficient for calibration in rich region R _{0 to} R ₆ : coefficients stored in the coefficient table corresponding to the rich region 8. An air-fuel ratio calculation process for obtaining a target air-fuel ratio signal based on an output from an air-fuel ratio sensor for measuring a combustion exhaust gas, wherein the air-fuel ratio calculation process includes the steps of: A correction coefficient for correcting the sensitivity of the air-fuel ratio sensor using the correction coefficient, and a sensor output correction processing for correcting the output of the air-fuel ratio sensor using the correction coefficient; and a correction obtained in the sensor output correction processing. When the output indicates an excess of air, the first oxygen concentration in the gas to be measured is determined from the corrected output, and the air ratio is determined based on the oxygen concentration.
And a second calculation process of obtaining an air ratio using the correction output and a multidimensional polynomial approximation formula for the air ratio when the correction output obtained in the sensor output correction process indicates an excess fuel. An air-fuel ratio calculation process for obtaining an air-fuel ratio based on the air ratio obtained in the first calculation process or the second calculation process and a reference constant when the air ratio = 1. Fuel ratio measurement method. 9. The air-fuel ratio measuring method according to claim 8, wherein the first arithmetic processing is an oxygen concentration arithmetic processing for calculating an oxygen concentration in the measured gas based on a correction output from the sensor output correction processing. And an air ratio calculating process for calculating an air ratio by substituting the oxygen concentration into a theoretical calculation formula of combustion exhaust gas for obtaining an air ratio. 10. The air-fuel ratio measuring method according to claim 8 or 9, wherein the second arithmetic processing is a multidimensional polynomial for gain using a water-carbon ratio based on the input fuel components H and C as a variable. Air-fuel ratio measurement, wherein the air-fuel ratio measurement is obtained by using an approximate expression, correcting the corrected output with the gain, and obtaining the air ratio using the corrected output and the multi-dimensional polynomial approximate expression for air ratio. Method. 11. The air-fuel ratio measuring method according to claim 10, wherein the second arithmetic processing includes a step of storing coefficients used in the multidimensional polynomial approximation equation in a storage unit before measurement. A storage process; a charcoal ratio calculation process for obtaining a charcoal ratio based on the input fuel components H and C; a multidimensional polynomial approximation formula for the gain; a coefficient stored in the storage means; A gain calculation process for calculating a gain based on the charcoal ratio; a correction calculation process for correcting the correction output by multiplying the correction output by a gain obtained in the gain calculation process; and a multidimensional polynomial for the air ratio. An air-fuel ratio measuring method, comprising: an air ratio calculation process for calculating an air ratio based on an approximate expression, the correction calculation value, and a correction coefficient on an excess fuel side. 12. The air-fuel ratio measuring method according to claim 11, wherein the information storage processing is performed by simulating a theoretical combustion reaction of fuel and air with a computer installed separately from an air-fuel ratio measuring device. An air-fuel ratio measurement method, wherein a coefficient used for a dimensional polynomial approximation formula is calculated and stored in the storage means. 13. The air-fuel ratio measuring method according to claim 8, wherein one specified value of 1.85 is used as said water-to-coal ratio. . 14. The air-fuel ratio measuring method according to claim 8, wherein the second arithmetic processing is used for a multi-dimensional polynomial approximation formula for an air ratio for obtaining an air ratio in advance before measurement. A charcoal ratio information storage process for storing in the storage means a characteristic data group for a change in the charcoal ratio of the coefficient group used in the coefficient calculation formula for obtaining the coefficient group; and input fuel components H and C A water / coal ratio calculation process for obtaining a water / carbon ratio based on the calculated water / carbon ratio, and a water group for obtaining a coefficient group of the coefficient calculation formula corresponding to the obtained specific water / carbon ratio based on the characteristic data group and developing each as a coefficient table Charcoal ratio table expansion processing, and a coefficient for calculating the coefficient used in the multi-dimensional polynomial approximation for the air ratio based on the coefficient calculation formula, the coefficient group stored in the various coefficient tables, and the specific charcoal ratio. Ratio coefficient calculation processing, and the air And an air ratio calculation process for calculating an air ratio based on a coefficient obtained in the coefficient calculation process and a correction output obtained in the sensor output correction process. Air-fuel ratio measurement method. 15. The air-fuel ratio measuring method according to claim 14, wherein the water-coal ratio information storage processing is a simulation of a theoretical combustion reaction between fuel and air by a computer installed separately from an air-fuel ratio measuring device. Calculating a characteristic data group with respect to a change in the charcoal ratio of various coefficient groups used in the coefficient calculation expression, and storing the characteristic data group in the storage area. 16. The air-fuel ratio measuring method according to claim 14 or 15, wherein the second arithmetic processing further comprises: before the measurement, when the acid-carbon ratio ≠ 0,
A characteristic data group for a change in the acid-coal ratio of a coefficient group used in a coefficient operation formula for obtaining a coefficient group used for a coefficient multi-dimensional polynomial approximation expression for obtaining a conversion coefficient to be converted into an output corresponding to 0 And an acid-carbon ratio calculation process for obtaining an acid-carbon ratio based on the input fuel components O and C, and a specific acid-carbon ratio determined. An acid-coal ratio table expansion process of obtaining a coefficient group of the coefficient arithmetic expression based on the characteristic data group and expanding the coefficient group as a coefficient table, and the coefficient group stored in the coefficient arithmetic expression and various coefficient tables and the identification. An acid-carbon ratio coefficient calculation process for obtaining a coefficient used in the coefficient multidimensional polynomial approximation expression based on the acid-carbon ratio of the coefficient; The obtained coefficient and the sensor output A conversion coefficient calculation process of calculating a conversion coefficient based on the correction output obtained in the force correction process, and a conversion process of multiplying the conversion coefficient by the correction output and setting the multiplied value as a new correction output. The air ratio calculation process calculates an air ratio based on the multidimensional polynomial approximation for the air ratio, a coefficient obtained in the coefficient calculation process, and a new correction output obtained in the conversion process. An air-fuel ratio measuring method characterized by the following. 17. The air-fuel ratio measuring method according to claim 16, wherein the stoichiometric information storage processing is a simulation of a theoretical combustion reaction between fuel and air by a computer installed separately from an air-fuel ratio measuring device. Calculating a characteristic data group with respect to a change in the acid-carbon ratio of various coefficient groups used in the coefficient calculation formula, and storing the calculated characteristic data group in the storage area. 18. The air-fuel ratio measuring method according to claim 14, wherein the second arithmetic processing further includes, before the measurement, the acid-coal ratio when the water-coal ratio is a predetermined specified value. The output of the air-fuel ratio sensor at 0 is Ip1, the acid-coal ratio =
When a reference output of the air-fuel ratio sensor at 0 is Ip0, a correspondence table storing process of storing a correspondence table between the conversion coefficient and Ip1 in a storage unit based on a relational expression of conversion coefficient = Ip0 / Ip1; A conversion coefficient calculation process for obtaining a conversion coefficient corresponding to the correction output obtained in the correction process from the correspondence table by a polygonal line approximation calculation; multiplying the conversion coefficient by the correction output; and multiplying the multiplied value by a new correction output The air ratio calculation process is based on the air ratio multidimensional polynomial approximation, the coefficient obtained in the coefficient calculation process, and a new correction output obtained in the conversion process. An air-fuel ratio measuring method comprising calculating an air ratio. 19. An air-fuel ratio sensor for measuring a combustion exhaust gas, and an air-fuel ratio calculation processing system for obtaining a target air-fuel ratio signal based on an output from the air-fuel ratio sensor. A predetermined output range centered on a stoichiometric point which is a reference output of the air-fuel ratio sensor corresponding to 1 is defined as a stoichiometric near window region, a region with excess air over the stoichiometric near window region is defined as a lean region, When the fuel-excess region is defined as a rich region, the air-fuel ratio calculation processing system calculates at least an air ratio and an air-fuel ratio for each of the lean region, the stoichiometric window region, and the rich region using a multidimensional polynomial approximation formula. An air-fuel ratio measuring device, characterized in that: 20. The air-fuel ratio measuring device according to claim 19, wherein before the measurement, a characteristic data group for a change in the coal ratio of the various coefficient groups used in the multidimensional polynomial approximation formula is stored in the storage means. Means for storing information, means for calculating a charcoal ratio based on the input fuel components H and C, a coefficient in the lean region corresponding to the specified charcoal ratio, and a stoichiometric neighborhood window Table expansion means for obtaining a coefficient in a region and a coefficient in a rich region based on the characteristic data group and developing them as a coefficient table, and a correction coefficient for correcting the sensitivity of the air-fuel ratio sensor using a predetermined calibration gas. And a sensor output correcting means for correcting the output of the air-fuel ratio sensor using the correction coefficient. Area selecting means for selecting one of the area, the stoichiometric neighborhood window area, and the rich area; a multidimensional polynomial approximation formula corresponding to the area selected by the area selecting means; and a coefficient corresponding to the selected area An oxygen equivalent value calculating means for obtaining an oxygen equivalent value based on the coefficient and the correction output stored in the table; and an air ratio calculating means for obtaining an air ratio based on the oxygen equivalent value and at least a standard oxygen partial pressure in the atmosphere. An air-fuel ratio calculating device for obtaining an air-fuel ratio based on the obtained air ratio and a reference constant when the air ratio = 1. 21. The air-fuel ratio measuring apparatus according to claim 20, wherein the information storage means is configured to execute the theoretical combustion reaction simulation of fuel and air with a computer installed separately from the air-fuel ratio measuring apparatus. An air-fuel ratio measuring apparatus, wherein a characteristic data group for various coefficient groups used in a dimensional polynomial approximation formula with respect to a change in a charcoal ratio is calculated and stored in the storage area. 22. The air-fuel ratio measuring apparatus according to claim 20, wherein said table developing means includes a coefficient in a lean region corresponding to a specific water-coal ratio calculated by said water-carbon ratio calculating means, and a stoichiometric neighborhood. An air-fuel ratio measuring apparatus, wherein a coefficient in a window area and a coefficient in a rich area are obtained from the characteristic data group by an interpolation method and are developed as coefficient tables. 23. The air-fuel ratio measuring device according to claim 20, wherein the area selecting means outputs a correction output from the sensor output correcting means corresponding to the stoichiometric vicinity window area. Select a stoichiometric neighborhood window area if included in the range; select a lean area if the output is greater than or equal to the high output side boundary in the stoichiometric neighborhood window area; and select a low output side boundary in the stoichiometric neighborhood window area. An air-fuel ratio measuring device, wherein a rich region is selected when the output is equal to or less than the output corresponding to the air-fuel ratio. 24. The air-fuel ratio measuring apparatus according to claim 23, wherein the sensor output correction means subtracts an output from the air-fuel ratio sensor by a reference output at the stoichiometric point, and a correction coefficient for calibration on the lean region side. The air-fuel ratio measuring device is characterized in that a corrected output is obtained by multiplying the air-fuel ratio. 25. An air-fuel ratio measuring apparatus according to claim 20, wherein said oxygen equivalent value calculating means corresponds to the area selected by said area selecting means in the following multidimensional manner. An air-fuel ratio measuring device, wherein an oxygen equivalent value is determined by a polynomial approximation formula. [Lean region] Oxygen equivalent value = A ₀ + A 1 · x + A ₂ / x A _{0 to} A ₂ : Coefficient stored in the coefficient table corresponding to the lean region [Stoichiometric neighborhood window region] Oxygen equivalent value = S ₀ + S ₁ · x + S ^{_{2 · x 2 + S 3 ·}} x 3
+ S ₄ · x ⁴ + S ₅ · x ⁵ + S ₆ · x ⁶ S _{0 to} S ₆ : Coefficients stored in the coefficient table corresponding to the stoichiometric neighborhood window area [Rich area] xx = x / Km Oxygen equivalent value = R _{0 + R 1 · xx + R 2} · xx 2 + R 3 ·
xx ³ + R ₄ xx ⁴ + R ₅ xx ⁵ + R ₆ xx ⁶ Km: correction coefficient for calibration in rich region R _{0 to} R ₆ : coefficients stored in the coefficient table corresponding to the rich region 26. An air-fuel ratio sensor for measuring a combustion exhaust gas, and an air-fuel ratio calculation processing system for obtaining a target air-fuel ratio signal based on an output from the air-fuel ratio sensor, An arithmetic processing system for determining a correction coefficient for correcting the sensitivity of the air-fuel ratio sensor using a predetermined calibration gas, and correcting the output of the air-fuel ratio sensor using the correction coefficient; When the correction output from the sensor output correction means indicates excess air, first arithmetic processing means for obtaining an oxygen concentration in the gas to be measured from the correction output and obtaining an air ratio based on the oxygen concentration; A second arithmetic processing unit for obtaining an air ratio by using the corrected output and a multidimensional polynomial approximation formula for an air ratio when the corrected output obtained by the output correcting unit indicates an excess fuel; Processing means or second An air-fuel ratio measuring apparatus characterized by having a fuel ratio calculating means for calculating an air-fuel ratio based on the reference constant when the air ratio and the air ratio = 1 from the arithmetic processing means. 27. The air-fuel ratio measuring apparatus according to claim 26, wherein said first arithmetic processing means calculates an oxygen concentration in the gas to be measured based on a correction output from said sensor output correcting means. Means for calculating an air ratio by substituting the oxygen concentration into a theoretical calculation formula of combustion exhaust gas for obtaining an air ratio to calculate an air ratio. 28. The air-fuel ratio measuring apparatus according to claim 26, wherein the second arithmetic processing means uses a multi-dimensional gain for gain as a variable based on a water-carbon ratio based on the input fuel components H and C. An air-fuel ratio obtained by using a polynomial approximation formula, performing a correction operation on the corrected output with the gain, and obtaining an air ratio using the corrected calculation output and a multidimensional polynomial approximation expression for air ratio. measuring device. 29. An air-fuel ratio measuring apparatus according to claim 28, wherein said second arithmetic processing means stores, in a storage means, coefficients used in a multidimensional polynomial approximation in advance before measurement. Storage means; a water / coal ratio calculating means for obtaining a water / carbon ratio based on the input fuel components H and C; a multidimensional polynomial approximation for gain, a coefficient stored in the storage means, and the specific water Gain calculating means for calculating a gain based on the charcoal ratio; correction calculating means for correcting the corrected output by multiplying the corrected output by the gain obtained by the gain calculating means; and multidimensional for air ratio An air-fuel ratio measuring device comprising an air ratio calculating means for calculating an air ratio based on a polynomial approximation formula, the correction calculation value, and a correction coefficient on an excess fuel side. 30. The air-fuel ratio measuring apparatus according to claim 29, wherein the information storage means is configured to perform the theoretical combustion reaction simulation of fuel and air with a computer installed separately from the air-fuel ratio measuring apparatus. An air-fuel ratio measuring device, wherein a coefficient used for a dimensional polynomial approximation formula is calculated and stored in said storage means. 31. The air-fuel ratio measuring device according to claim 26, wherein one predetermined value 1.85 is used as the water-to-coal ratio. . 32. The air-fuel ratio measuring apparatus according to claim 26, wherein the second arithmetic processing means is used in a multi-dimensional polynomial approximation equation for an air ratio to obtain an air ratio before measurement. A charcoal ratio information storage means for storing in the storage means a characteristic data group for a change in the charcoal ratio of the coefficient group used in the coefficient calculation formula for obtaining the coefficient group; A charcoal ratio calculating means for calculating a charcoal ratio based on C; and a coefficient group of the coefficient calculation formula corresponding to the determined specific charcoal ratio based on the characteristic data group and developed as a coefficient table. A water / coal ratio table developing means, a water for obtaining a coefficient used in the air ratio multi-dimensional polynomial approximation formula based on the coefficient calculation formula, a coefficient group stored in various coefficient tables, and the specific charcoal ratio. A coefficient calculating means for the coal ratio; An air ratio calculating means for calculating an air ratio based on the air ratio multidimensional polynomial approximation formula, the coefficient obtained by the coefficient calculating means, and the correction output obtained by the sensor output correcting means; An air-fuel ratio measuring device characterized by the above-mentioned. 33. The air-fuel ratio measuring device according to claim 32, wherein the water-coal ratio information storage means is a computer and a fuel-air ratio theoretical combustion reaction simulation which is installed separately from the air-fuel ratio measuring device. An air-fuel ratio measuring apparatus characterized in that a characteristic data group for a change in the charcoal ratio of various coefficient groups used in the coefficient calculation formula is calculated by the above-mentioned method and stored in the storage means. 34. The air-fuel ratio measuring device according to claim 32, wherein the second arithmetic processing means further comprises: when the oxy-coal ratio ≠ 0, before the measurement, the oxy-coal ratio =
A characteristic data group for a change in the acid-coal ratio of a coefficient group used in a coefficient operation formula for obtaining a coefficient group used for a coefficient multi-dimensional polynomial approximation expression for obtaining a conversion coefficient to be converted into an output corresponding to 0 Information storage means for storing an oxygen-carbon ratio in a storage means, an oxygen-carbon ratio calculating means for calculating an oxygen-carbon ratio based on the input fuel components O and C, and a specific oxygen-carbon ratio determined. An acid-coal ratio table expanding means for obtaining a coefficient group of the coefficient arithmetic expression based on the characteristic data group and developing the coefficient group respectively as a coefficient table; and a coefficient group stored in the coefficient arithmetic expression and various coefficient tables and the identification. A coefficient calculating means for calculating the coefficient used for the multi-dimensional polynomial approximation for the coefficient based on the acid-carbon ratio of the coefficient; The obtained coefficient and the sensor output A conversion coefficient calculating unit that calculates a conversion coefficient based on the correction output obtained by the force correction unit; and a conversion unit that multiplies the conversion coefficient by the correction output and sets the multiplied value as a new correction output. The air ratio calculation means calculates the air ratio based on the multi-dimensional polynomial approximation formula for the air ratio, the coefficient from the coefficient calculation means, and a new correction output from the conversion means. Fuel ratio measurement device. 35. The air-fuel ratio measuring apparatus according to claim 34, wherein the oxycobalt ratio information storage means is a computer and a simulation simulation of a theoretical combustion reaction between fuel and air, which is provided separately from an air-fuel ratio measuring apparatus. An air-fuel ratio measuring apparatus characterized in that a characteristic data group for a change in the oxidized carbon ratio of various coefficient groups used in the coefficient calculation formula is calculated and stored in the storage area. 36. The air-fuel ratio measuring apparatus according to claim 32, wherein the second arithmetic processing means further comprises: before the measurement, the acid-to-carbon ratio when the water-to-carbon ratio is a predetermined specified value. The output of the air-fuel ratio sensor at ≠ 0 is Ip1, the acid-coal ratio =
Assuming that the reference output of the air-fuel ratio sensor at 0 is Ip0, a correspondence table storage means for storing a correspondence table between the conversion coefficient and Ip1 based on a relational expression of conversion coefficient = Ip0 / Ip1, and the sensor output correction means A conversion coefficient calculating means for obtaining a conversion coefficient corresponding to the correction output obtained by the linear approximation calculation, and a conversion means for multiplying the conversion coefficient by the correction output and using the multiplied value as a new correction output. The air ratio calculation means calculates the air ratio based on the multi-dimensional polynomial approximation formula for the air ratio, the coefficient from the coefficient calculation means, and a new correction output from the conversion means. Fuel ratio measurement device.