JP2927074B2 - Air-fuel ratio control device for internal combustion engine - Google Patents

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 control device suitable for controlling an air-fuel ratio of an air-fuel mixture to an internal combustion engine to a target air-fuel ratio by controlling a fuel supply amount to the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, an air-fuel ratio control device of this type includes an air-fuel ratio detecting means for detecting an air-fuel ratio of an air-fuel mixture to an internal combustion engine as disclosed in Japanese Patent Application Laid-Open No. 1-110853. Determining the control amount of the fuel supply amount control means based on the detected air-fuel ratio, and setting the actual air-fuel ratio of the mixture to a target air-fuel ratio. Air-fuel ratio control means for controlling, the air-fuel ratio control means calculating the control amount of the fuel supply amount control means based on a dynamic model of the internal combustion engine for determining the air-fuel ratio by utilizing modern control theory. In some cases, the actual air-fuel ratio of the air-fuel mixture is controlled to a target air-fuel ratio.

[0003]

By the way, in such a configuration, the above-mentioned model is a dynamic model that is well established between the amount of fuel supplied to the internal combustion engine and the air-fuel ratio of the air-fuel mixture. It must always be structured with relationships. However, in the air-fuel ratio sensor constituting the air-fuel ratio detecting means, as shown in FIG. 7, while the oxygen concentration sensor that generates a normal rich output or lean output is activated at about 300 (° C.), The rich lean output of the limit current, which is the output of the fuel ratio sensor, starts from 400 (° C.). Normally, the limit temperature must be used at a stable temperature. Therefore, when trying to measure the air-fuel ratio over this range, the element temperature needs to be about 630 (° C.). Feedback can not be started. As a result, the start timing of the feedback is considerably delayed as compared with the feedback of the air-fuel ratio by the ordinary oxygen concentration sensor, and a problem occurs that HC in the exhaust gas deteriorates.

As a countermeasure, a method of immediately starting feedback when the limit current starts to be output can be considered, but the output characteristics of the air-fuel ratio sensor are not stable in the above-mentioned half-warmed state of the air-fuel ratio sensor. For this reason, the dynamic model relationship between the fuel injection amount and the air-fuel ratio is broken, and as a result, the control of the air-fuel ratio expected by utilizing the modern control theory cannot be properly realized. In particular, in the air-fuel ratio control device having the above-described configuration, the air-fuel ratio control becomes more and more unstable due to high responsiveness, which may cause a hunting phenomenon. In order to address the above-described problems, the present invention selectively utilizes control arithmetic processing based on modern control theory and proportional / integral control arithmetic processing (PI control arithmetic processing) in an air-fuel ratio control apparatus for an internal combustion engine. Thus, the air-fuel ratio control based on the feedback of the detected air-fuel ratio can always be satisfactorily performed regardless of whether the air-fuel ratio sensor is activated or not.

[0005]

In order to solve the above-mentioned problems, a structural feature of the present invention is, as exemplified in FIG. 1, that a fuel mixture to be supplied to an internal combustion engine is specified for specifying an air-fuel mixture to be supplied to the internal combustion engine. Fuel supply amount control means 1 for controlling a supply amount according to a control amount, an air-fuel ratio sensor for detecting an actual air-fuel ratio of the air-fuel mixture based on exhaust gas of an internal combustion engine, and a control amount of the fuel supply amount control means 1 And an air-fuel ratio control means 2 for controlling an actual air-fuel ratio of the air-fuel mixture to a target air-fuel ratio in accordance with the detected air-fuel ratio to specify the output signal of the air-fuel ratio sensor. Stability of what starts to appear
Semi- warm-up state determining means 3 for determining a non- warm-up state
And the air-fuel ratio control means 2 responds to the determination of the semi-warmed-up state by the semi-warmed-up state
A first air-fuel ratio correction coefficient determination means 2a for determining a first air-fuel ratio correction coefficient of the mixture of the previous SL target air-fuel ratio in the proportional-integral control arithmetic operation such that a predetermined value based on the ratio, a semi-warm machine state determination section 3 by the non-semi-warm-up state of the response to determining the target air-fuel ratio of the detected air-fuel ratio control all rather internal combustion according to
And and a second air-fuel ratio correction coefficient determination means 2b for determining a second air-fuel ratio correction coefficient of the air-fuel mixture at the current cash control calculation processing based on the dynamic model of the engine, a fuel supply amount controller 1
When the air-fuel ratio sensor is in a semi-warmed state,
According to the first air-fuel ratio correction coefficient,
In the non-semi-warmed state, the determination is made according to the second air- fuel ratio correction coefficient.

[0006]

According to the present invention , a semi-warm-up is achieved.
The provided machine state determination section 3, before Kisora ratio sensor output signal
When to determine the constant semi warm-up state not stable but begins to appear, the air-fuel ratio control means 2, proportional front <br/> Symbol target air-fuel ratio on the basis of the detected air-fuel ratio to the predetermined value -The first air-fuel ratio correction coefficient of the air-fuel mixture is determined by the first air-fuel ratio correction coefficient determination means 2a in the integral control calculation process. Further, the semi-warm-up state determining means 3, the air-fuel ratio sensor is determined not to half-warm-up state, the air-fuel ratio control means 3, the target air-fuel ratio control all rather internal combustion engine according to the detected air-fuel ratio Dynamic mode
By the second air-fuel ratio correction coefficient determination means 2b at current cash control calculation processing based on Dell determining a second air-fuel ratio correction coefficient of the air-fuel mixture. Then, the air-fuel ratio control means 3 changes the control amount of the fuel supply amount control means 1 to a half-warm-up state of the air-fuel ratio sensor.
In the case of, according to the first air-fuel ratio correction coefficient,
If the air-fuel ratio sensor is determined according to the second air- fuel ratio correction coefficient when the air-fuel ratio sensor is in a non-semi-warmed state , the fuel supply amount control means 1
The fuel supply amount to the internal combustion engine is controlled according to the determined control amount.

[0007]

As a result, when the air-fuel ratio sensor is in a semi-warmed-up state, a control amount based on the first air-fuel ratio correction coefficient determined based on the proportional / integral control calculation processing is used.
The fuel injection amount to the internal combustion engine is controlled to control the air-fuel ratio of the air-fuel mixture to the predetermined value.On the other hand, when the air-fuel ratio sensor is not in a half-warmed state, the dynamic model of the internal combustion engine is
With the control amount based on the second air-fuel ratio correction coefficient determined on the basis of the control processing by the current cash control theory based, air-fuel ratio the detected air-fuel ratio of the mixture to control the fuel injection quantity to the internal combustion engine Therefore, even if the air-fuel ratio sensor is in a semi-warmed state, feedback control of the air-fuel ratio is performed. Therefore, the start timing of the feedback control of the air-fuel ratio in such air-fuel ratio control system can be advanced as compared with the conventional, so that, on the basis of the detected air-fuel ratio by the air-fuel ratio sensor, equivalent
From the half-warmed state of the air-fuel ratio sensor, proper air-fuel ratio control is performed.
And in can control the internal combustion engine may further promote the reduction of emissions of harmful components of the exhaust gas in the gas.

[0008]

FIG. 2 shows an example in which the present invention is applied to a fuel injection control system of a 4-cylinder 4-cycle spark ignition type internal combustion engine E. . Under its operation, the internal combustion engine E transmits air flowing into the intake pipe 20 through the air cleaner 10 to the throttle valve 20 a and the surge tank 3 in the intake pipe 20.
0, and flows into the intake manifold 40, and the inflow airflow is mixed with fuel from the fuel tanks injected by the fuel injection valves 41 to 44 into the intake manifold 40 to form an air-fuel mixture. The air-fuel mixture is supplied to the combustion chamber of each cylinder of the engine main body 50 and each ignition plug 5
The fuel is burned under the ignition of 1 to 54 and discharged through the exhaust manifold 60 and the three-way catalyst 70 into the exhaust pipe 80 as exhaust gas. In addition, each of the ignition plugs 51 to 54
It ignites by receiving a high voltage distributed from the distributor 90 in cooperation with the ignition circuit 100. Further, the three-way catalyst 70 plays a role in reducing harmful components (CO, HC, NOx, etc.) in the exhaust gas from the intake manifold 60.

The fuel injection control system includes a rotational speed sensor 1
The rotational speed sensor 110 is provided in the distributor 90 and detects the actual rotational speed of the output shaft of the engine body 50 (corresponding to the actual rotational speed of the internal combustion engine 10). A pulse signal is sequentially generated at a frequency proportional to the detection result. However, the number of pulse signals generated from the rotation speed sensor 110 is two rotations of the internal combustion engine E (that is, 72 rotations).
24 degrees per 0 degree crank angle). The throttle sensor 120 detects the actual opening of the throttle valve 20a, and generates an opening detection signal. The throttle sensor 120 also has a built-in idle switch.
The idle switch detects this when the throttle valve 20a is fully closed and generates a fully closed detection signal. The negative pressure sensor 130 detects an actual negative pressure generated downstream of the throttle valve 20a in the intake pipe 20 and generates a negative pressure detection signal.

The water temperature sensor 140 detects an actual cooling water temperature in the cooling system of the engine body 50 and generates a water temperature detection signal. The air temperature sensor 150 generates the actual temperature of the airflow flowing into the intake pipe 20 upstream of the throttle valve 20a as an air temperature detection signal. Oxygen concentration sensor 16
0 detects the actual unburned oxygen concentration in the exhaust gas upstream of the three-way catalyst 70 in the exhaust pipe 80 and generates it as an oxygen concentration detection signal. In such a case, the oxygen concentration detection signal is the actual air-fuel ratio λ of the air-fuel mixture supplied to the engine body 50.
Takes a linear value for. The oxygen concentration sensor 170 detects the actual unburned oxygen concentration in the exhaust gas downstream of the three-way catalyst 70 in the exhaust pipe 80 and generates an oxygen concentration detection signal. However, the oxygen concentration detection signal from the oxygen concentration sensor 170 indicates whether the air-fuel ratio λ is rich or lean with respect to the stoichiometric air-fuel ratio λo.

The microcomputer 180 has a CPU 1
81, ROM 182, RAM 183, backup RA
M184, an input port 185, an output port 186, a bus line 187, and the like.
Are pulse signals from the rotation speed sensor 110 and the throttle sensor 120 according to the flowcharts shown in FIGS.
Opening detection signal and full closing detection signal from the
0, a water temperature detection signal from the water temperature sensor 140, an air temperature detection signal from the air temperature sensor 150, an oxygen concentration detection signal from the oxygen concentration sensor 160, and an oxygen concentration detection signal from the oxygen concentration sensor 170. Received through input port 185 and bus line 187, ROM 18
2, receiving the data stored in the RAM 183 and the backup RAM 184 through the bus line 187 and executing the computer program, and during this execution, each of the fuel injection valves 4 through the bus line 187 and the output port 186.
The arithmetic processing necessary for controlling the driving of the ignition circuit 100 and the ignition circuit 100 is performed. However, the above-described computer program is stored in the ROM 182 in advance.

Next, a method designed in advance to perform air-fuel ratio control in the fuel injection control system will be described. 1). Modeling of Controlled Object In this embodiment, an autoregressive moving average model of order 1 having a dead time P = 3 is used as a model of a system for controlling the air-fuel ratio λ of the engine E, and is further approximated in consideration of disturbance d. doing. First, a model of a system for controlling an air-fuel ratio λ using an autoregressive moving average model can be approximated by the following equation 1.

Λ (K) = a · λ (K−1) + b · FAF (K−3) where, in Equation 1, the symbol FAF represents an air-fuel ratio correction coefficient. Each symbol a and b represents a constant. The symbol K represents a variable indicating the number of times of control since the start of the first sampling.

Further, considering the disturbance d, the model of the control system can be approximated by the following equation (2).

Λ (K) = a · λ (K−1) + b · FAF (K−3) + d (K−1) For the model approximated as described above, the rotation cycle using the step response ( It is easy to determine the constants a and b by discretization by sampling at (360 ° crank angle) sampling, that is, to obtain the transfer function G of the system for controlling the air-fuel ratio λ.

2). How to display the state variable quantity IX (however,
IX is a vector quantity.) The above equation 2 is replaced by a state variable quantity IX expressed by the following equation 3.
When rewritten using (K), Equations 4 and 5 are obtained.

(Equation 3) However, in Equation 3, the symbol T indicates a transposed matrix.

(Equation 4)

X1 (K + 1) = aX1 (K) + bX2 (K) + d (K) = λ (K + 1) X2 (K + 1) = FAF (K-2) X3 (K + 1) = FAF (K-1) X4 ( K + 1) = FAF (K)

3). Design of Regulator When the regulator is designed based on the above equations (3) to (5), the air-fuel ratio correction coefficient becomes the optimum feedback gain IK
Expression (8) can be expressed as Expression (8) using the following Expression (6) relating to (having a vector amount) and Expression (7) relating to the state variable amount IX (K).

IK = [K1, K2, K3, K4]

(Equation 7)

(Equation 8)

Further, when an integral term ZI (K) for absorbing an error is added to the equation (8), the air-fuel ratio correction coefficient is given by the following equation (9).

## EQU9 ## FAF (K) = K1.lambda. (K) + K2.FAF (K-3) + K3.FAF (K-2) + K4.FAF (K-1) + Z1 (K) The above-mentioned integral term ZI (K) is a value determined from the deviation between the target air-fuel ratio λTG and the actual air-fuel ratio λ (K) and the integration constant Ka, and is given by the following equation (10).

## EQU10 ## ZI (K) = ZI (K−1) + Ka · (λTG−λ (K))

FIG. 6 is a block diagram of a control system of the air-fuel ratio λ designed as described above. In FIG. 5, the air-fuel ratio correction coefficient FAF (K) is represented by FAF (K−1).
Is expressed using the (1 / Z) conversion to derive from the past air-fuel ratio correction coefficient FAF (K-1) by R
It is stored in the AM 183 and read out and used at the next control timing. In FIG. 6, a block P1 surrounded by a dashed line indicates that the air-fuel ratio λ (K) is the target air-fuel ratio λ.
State variable amount I while feedback control is applied to TG
X (K), the block P2 is a part (accumulation part) for obtaining the integral term Z1 (K), and the block P3 is a state variable IX determined in the block P1.
This is a part for calculating the current air-fuel ratio correction coefficient FAF (K) from (K) and the integral term Z1 (K) obtained in the block P2.

4). Determination of Optimal Feedback Gain IK and Integral Constant Ka The optimal feedback gain and integral constant Ka can be set, for example, by minimizing an evaluation function J expressed by the following equation (11).

[Equation 11] However, in equation (11), the evaluation function J restricts the movement of the air-fuel ratio correction coefficient FAF (K) while maintaining the air-fuel ratio λ (K).
And the target air-fuel ratio λTG is intended to be minimized. The weight of the constraint on the air-fuel ratio correction coefficient FAF (K) can be changed by the values of the weight parameters Q and R. Therefore, the simulation may be repeated until the optimum control characteristics are obtained by variously changing the values of the weight parameters Q and R, and the optimum feedback gain IK and the integration constant Ka may be determined.

Further, the optimum feedback gain IK and the integration constant Ka depend on both model constants a and b. Therefore, the stability (robustness) of the system against the fluctuation (parameter fluctuation) of the system that controls the actual air-fuel ratio λ
In order to guarantee the optimum feedback gain IK and the integration constant Ka in consideration of the variation of each of the model constants a and b,
Need to be set. So the simulation is
The optimum feedback gain IK and the integration constant Ka satisfying the stability are determined by taking into account the actual fluctuations of the model constants a and b. The modeling of the control target, the method of displaying the state variable amount, the design of the regulator, and the determination of the optimal feedback gain and the integration constant have been described above. These are determined in advance, and in the present embodiment, Then, the air-fuel ratio control in the fuel injection control system is performed using only equation (8) and equation (8).

In this embodiment configured as described above,
When the fuel injection control system is in the operating state, the CPU 181 of the microcomputer 180 starts execution of the computer program in step 200 according to the flowcharts of FIGS. In response to each pulse signal generated from the rotation speed sensor 110 for each crank angle, the rotation speed Ne of the internal combustion engine E is calculated according to the frequency of the pulse signal sequentially generated from the rotation speed sensor 110, and the rotation speed Ne and the negative pressure are calculated. Sensor 13
Based on the value of the negative pressure detection signal from 0 (hereinafter, referred to as negative pressure PM) or the like, the basic fuel injection amount Tp into the intake manifold 40 is calculated, and the computer program is converted into an air-fuel ratio calculation routine 400 (see FIG. 4 and FIG. 4). (See FIG. 5).

Then, the CPU 181 starts the execution of the air-fuel ratio calculation routine 400 in step 400a, and in the next step 410, determines whether or not the feedback condition of the air-fuel ratio λ is satisfied. However, the satisfaction of this feedback condition is that the cooling water temperature in the cooling system of the engine body 50 is equal to or higher than a predetermined water temperature, the rotation speed and load of the internal combustion engine E are not high, and the temperature of the oxygen concentration sensor 160 Activation temperature of 400 (° C) (Fig. 7
See above).

If the feedback condition is not satisfied at this stage, the CPU 181 determines in step 410 the rotation speed Ne, the negative pressure PM, the value of the water temperature detection signal from the water temperature sensor 140 (hereinafter, referred to as water temperature Thw), and the like. "N
O ", and at step 410a, the air-fuel ratio correction coefficient F
AF is set to FAF = 1, and in the next step 410b, the open control determination flag F1 is set to F1 = 1. However, F1 = 1 indicates that the fuel injection control system is in open control calculation processing. When the calculation processing of the air-fuel ratio calculation processing routine 400 ends in step 400b in this manner, the CPU 181 executes step 5
At 00 (see FIG. 3), the basic injection amount Tp in step 300 is determined based on the following equation 12 under the open control.
Is corrected according to the correction coefficient FALL, and this is corrected by the fuel injection amount TA.
Set as U.

[Equation 12] TAU = FAF / Tp / FALL

On the other hand, if the feedback condition is satisfied when the computer program proceeds to step 410 as described above, in step 410, the CPU 181 determines in step 410 according to the rotational speed Ne, the negative pressure PM, the water temperature Thw, and the like. Y
ES ”, and in a step 420, it is determined whether or not the oxygen concentration sensor 160 is in a semi-warmed state. In such a case, the semi-warmed-up state of the oxygen concentration sensor 160 corresponds to a temperature state in which the output from these sensors starts but the limit current value is not stabilized (see FIG. 7). At this stage, if the temperature of the oxygen concentration sensor 160 has reached a temperature at which the limit current is stable, the CPU 181 determines at step 420 that “N
In step 420a, an air-fuel ratio guard corresponding to the temperature of the oxygen concentration sensor 160 is set as shown in FIG. 8, and in the next step 420b, the target air-fuel ratio λTG according to the operating state is set. Set. As shown in FIG. 7, this guard indicates a range where the limit current is stable at a certain element temperature.

Thereafter, in order to determine whether or not the open control was performed without satisfying the previous feedback condition, C
In step 430, the PU 181 determines whether or not the open control determination flag F1 = 1 is established. When the open control determination flag F1 = 1, that is, when the previous open control was performed, the CPU 181 determines in step 430a the optimum feedback gain by the predetermined I.
KN (1, 2, 3, 4, A), and
At b, the PI control determination flag F2 is set to F2 = 0. However, the optimal feedback gain IKN is determined by setting the ratio (Q / R) of the weight parameter Q to the weight parameter R in the evaluation function J of the above equation (11) to (1/5).

Next, the CPU 181 determines in step 430
At c, the integral term ZI (K-1) is calculated based on the following equation 13.

ZI (K-1) = FAF (K-1) + K2.FAF (K-1) + K3.FAF (K-2) + K4.FAF (K-3) -K1.lambda. (K) In Expression 13, the symbol λ (K) represents the air-fuel ratio.
Further, Expression 13 is obtained by performing an inverse operation from Expression 14 below.

FAF (K) = ZI (K) + K1.lambda. (K) -K2.FAF (K-1) -K3.FAF (K-2) -K4.FAF (K-3) where In 14, the symbol FAF represents an air-fuel ratio correction coefficient.

On the other hand, as described above, when the computer program proceeds to step 430 and the determination in this step is “NO” (F1 = 0), the CP
In step 440, U181 determines whether the previous control operation was a modern control operation instead of the PI control operation based on the PI control determination flag F2. Last time was P
If it is during the I control arithmetic processing (corresponding to F2 = 1), it is necessary to switch to the modern control arithmetic processing.
U181 determines "NO" in step 440, and performs steps 430a, 430b, and 430 in the same manner as described above.
At step c, the optimum feedback gain IKN is sequentially set, F2 = 0 is set, and the initial value ZI (K
-1), and the computer program proceeds to Step 430d.

Then, the CPU 181 determines in step 4
In step 30d, the integral term ZI (K) is calculated based on the above equation (10). In step 430e, the air-fuel ratio correction coefficient FAF is calculated based on the above equation (14).
Sets the open control determination flag F1 to F1 = 0. When the calculation of the air-fuel ratio correction coefficient FAF in step 430e is completed in this way, the CPU 181 determines the basic injection amount Tp in step 300 in step 500 (see FIG. 3) based on the above equation 12 in step 500 (see FIG. 3). The correction is made according to the air-fuel ratio correction coefficient FAF and the correction coefficient FALL, and this is set as the fuel injection amount TAU.

When the computer program proceeds to step 420 as described above, if the determination in the step is "NO", the CPU 181 sets the target air-fuel ratio λTG to substantially "1" in step 430g. Set. This means that the sensor current i of the oxygen concentration sensor 160
Is set to i = 0. Next, assuming that the target air-fuel ratio λTG is substantially “1”, the CPU 18
1 calculates the air-fuel ratio correction coefficient FAF based on the following equation 15 in step 430h.

## EQU15 ## FAF (K) = 1 + Kx (.lambda. (K)-. Lambda.TG) Equation 15 is intended to correct the deviation of the air-fuel ratio by multiplying by the integral constant Kx. In such a case, the actually obtained λ (K) is equal to each of the oxygen concentration sensors 160 and 17.
For a semi-warm-up region where the temperature changes at a temperature of 0, the integration constant Kx is made relatively small to avoid abrupt correction.

Thereafter, the CPU 181 determines in step 430
At i, the PI control determination flag F2 is set to F2 = 1, and at step 430f, F1 = 0 is set,
The computer program proceeds to step 500. Then, in step 500, the CPU 181 determines the basic injection amount T in step 300 based on the above-described equation (12).
p is the air-fuel ratio correction coefficient FAF in step 430h.
The correction is made according to the correction coefficient FALL and the fuel injection amount TAU is set.

As described above, steps 410a, 43
When the fuel injection amount TAU in step 500 is set based on the air-fuel ratio correction coefficient FAF at 0e or 430h, the CPU 181 uses the fuel injection amount TAU as a fuel injection output signal in
7 and the output ports 186, each of the fuel injection valves 41 to 4
4 is assigned. Thus, each of the fuel injection valves 41 to 44 injects fuel from the fuel tank into the intake manifold 40 in an amount corresponding to the value of the fuel injection output signal. In other words, when the oxygen concentration sensor 160 is in a semi-warmed-up state, the PI is set so that the target air-fuel ratio becomes approximately 1.
With the fuel injection amount based on the air-fuel ratio correction coefficient FAF determined based on the control calculation process, the fuel injection amount to the internal combustion engine E is controlled so that the air-fuel ratio of the air-fuel mixture becomes substantially 1; On the other hand, when the oxygen concentration sensor 160 is not in the half-warm-up state, the fuel injection amount to the internal combustion engine E is determined based on the fuel injection amount based on the air-fuel ratio correction coefficient FAF determined based on the control calculation process based on the modern control theory. The air-fuel ratio of the air-fuel mixture is controlled so as to be a target air-fuel ratio corresponding to the detected air-fuel ratio.

This means that the air-fuel ratio feedback control is performed even when the oxygen concentration sensor 160 is in a semi-warmed state. For this reason, the start timing of the feedback control of the air-fuel ratio in this type of air-fuel ratio control device can be advanced as compared with the conventional case, and as a result, the oxygen concentration sensor
Regardless of whether 0 is in the semi-warmed-up state or not, under appropriate air-fuel ratio control, it is possible to further promote the reduction of the emission of harmful components in the exhaust gas.

The present invention is not limited to the fuel injection control system, but may be applied to a secondary air control system or an EGR control system of an internal combustion engine.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to the description in the claims.

FIG. 2 is a block diagram of a fuel injection system for an internal combustion engine to which the present invention is applied.

FIG. 3 is a flowchart showing an operation of the microcomputer of FIG. 2;

FIG. 4 is a detailed flowchart showing an open control calculation process and a PI control calculation process of an air-fuel ratio correction coefficient calculation process routine of FIG. 3;

FIG. 5 is a detailed flowchart showing a part of the modern control arithmetic processing.

FIG. 6 is a block diagram of a dynamic model in modern control theory.

FIG. 7 is a graph showing a relationship between a sensor current i and a sensor temperature of each oxygen concentration sensor using an air-fuel ratio A / F as a parameter.

FIG. 8 is a graph showing an intake range of an air-fuel ratio in a relationship between an air-fuel ratio and a sensor temperature of each oxygen concentration sensor.

[Explanation of symbols]

E: internal combustion engine, 20: intake pipe, 40: intake manifold, 41 to 44: fuel injection valve, 50: engine body, 6
0: Exhaust manifold, 70: Exhaust pipe, 160
... oxygen concentration sensor, 180 ... microcomputer.

Continuation of the front page (56) References JP-A-63-223347 (JP, A) JP-A-1-10853 (JP, A) JP-A-3-145536 (JP, A) JP-A-4-370340 (JP) JP-A-2-215948 (JP, A) JP-A-4-252833 (JP, A) JP-A-63-246434 (JP, A) JP-A-64-35037 (JP, A) 4-91348 (JP, A) JP-A-2-99745 (JP, A) JP-A-59-196930 (JP, A) JP-A-58-27848 (JP, A) JP-A-59-138752 (JP, A) A) JP-A-59-65537 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/00-45/00

Claims (1)

(57) [Claims] 1. A fuel supply amount control means for controlling a fuel supply amount to an internal combustion engine in accordance with a control amount in order to specify a mixture to be supplied to the internal combustion engine, and the air / fuel mixture based on exhaust gas of the internal combustion engine. An air-fuel ratio sensor that detects the actual air-fuel ratio of the air-fuel mixture, and an air that controls the actual air-fuel ratio of the air-fuel mixture to the target air-fuel ratio in accordance with the detected air-fuel ratio so as to specify the control amount of the fuel supply amount control means. An air-fuel ratio control device provided with a fuel-ratio control means, wherein an output signal of the air-fuel ratio sensor
A half- warm-up state determining means for determining a half-warm-up state is provided, and the air-fuel ratio control means responds to the determination of the semi-warm-up state by the half-warm-up state determining means , and adjusts the detected air-fuel ratio.
A first air-fuel ratio correction coefficient determination means for determining a first air-fuel ratio correction coefficient of the air-fuel mixture in the proportional-integral control arithmetic operation such that a predetermined value before Symbol target air-fuel ratio based on the semi-warming up condition in response to determining that the non-semi-warmed up by the determination means of the control all rather internal combustion engine according to the target air-fuel ratio to the detected air-fuel ratio
And and a second air-fuel ratio correction coefficient determination means for determining a second air-fuel ratio correction coefficient of the air-fuel mixture at the current cash control calculation processing based on the dynamic model, the control amount of the fuel supply amount control means
When the air-fuel ratio sensor is in a semi-warmed state,
Depending on the fuel ratio correction coefficient, and the non-half of the air-fuel ratio sensor
An air-fuel ratio control device for an internal combustion engine, which is determined according to the second air- fuel ratio correction coefficient during a warm-up state .