JP3458425B2 - 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 the supply of fuel to an internal combustion engine.
Air-fuel ratio of the mixture to the internal combustion engine by controlling the amount
Related to an air-fuel ratio control device that controls the target air-fuel ratio
is there. [0002] 2. Description of the Related Art Conventionally, as this kind of air-fuel ratio control device,
For example, there is JP-A-5-52140. In this gazette
According to this, the half-warmed state of the air-fuel ratio sensor is detected from the sensor temperature.
And the air-fuel ratio sensor is in a semi-warmed state (sensor temperature is
(Approximately 400 ° C), the proportional / integral control process
Air-fuel ratio feedback control. Ma
In addition, from a semi-warmed state to a warmed-up state (sensor temperature is about 630)
℃), the air-fuel ratio feedback by modern control processing
Control is performed. Air-fuel ratio feedback by modern control processing
Control is based on a dynamic model of the internal combustion engine that determines the air-fuel ratio
The actual air-fuel ratio is controlled to the target air-fuel ratio when
Between the fuel supply to the internal combustion engine and the air-fuel ratio of the air-fuel mixture
Is always composed of dynamic model relationships
Need to be done. However, the air-fuel ratio sensor
Temperature (about 630 ° C), stable output cannot be obtained
Therefore, the air-fuel ratio by modern control processing until this temperature is reached
Feedback control cannot be performed. Therefore,
With conventional technology, the air-fuel ratio sensor is stable until it reaches a predetermined temperature
Output cannot be obtained, but it is limited to the output of the air-fuel ratio sensor.
Rich lean output of field current is obtained in a semi-warmed state (however,
And is not stable).
Perform air-fuel ratio feedback control by integral control processing.
I'm trying. This allows air-fuel ratio feedback control
I try to have the time to start earlier. [0004] SUMMARY OF THE INVENTION
In the conventional technology, the air-fuel ratio sensor is operated at a predetermined temperature (approximately 400
℃), proportional / integral control cannot be executed.
The air-fuel ratio control is delayed by that amount, and the emission is improved.
Has not been reached. The present invention sets the start time of the air-fuel ratio control.
Providing an air-fuel ratio control device for internal combustion engines
The purpose is to provide. [0005] SUMMARY OF THE INVENTION Accordingly, the present invention provides a method as shown in FIG.
When no operating voltage is applied as shown in
Detect only rich / lean air-fuel ratio from engine exhaust
Out and detect the air-fuel ratio when the operating voltage is applied
Air-fuel ratio sensor, and an operating voltage applied to the air-fuel ratio sensor.
Voltage applying means for applying the voltage;
Before stopping application of operating voltage to the fuel ratio sensor
Executing air-fuel ratio control based on the output of the air-fuel ratio sensor
The first air-fuel ratio control executing means and the voltage applying means
When the operating voltage is applied to the air-fuel ratio sensor
The second execution of the air-fuel ratio control based on the output of the air-fuel ratio sensor
And a signal from the air-fuel ratio sensor.
Signal determination means for determining whether or not
Activation determining means for determining whether the fuel ratio sensor is activated
And an air-fuel ratio sensor by the signal determination means.
It is determined that a signal is output from the
The air-fuel ratio sensor is not activated by the activation determination means
Is determined, the air-fuel ratio by the voltage applying means
Stop applying the operating voltage to the sensor and control the air-fuel ratio
Selecting the first air-fuel ratio control means as the control means,
The activation determination means has activated the air-fuel ratio sensor.
When it is determined that the air-fuel ratio
The operating voltage is applied to the
And selecting means for selecting the second air-fuel ratio control means.
An air-fuel ratio control device for an internal combustion engine
Offer. [0006] [Action] The air-fuel ratio sensor must be operated when no operating voltage is applied.
When the air-fuel ratio is rich or lean from the exhaust gas of the internal combustion engine
Only when the operating voltage is applied.
Detect fuel ratio. Further, the voltage application means is provided with the air-fuel ratio sensor.
The first air-fuel ratio control execution means applies an operating voltage to the
The operating voltage to the air-fuel ratio sensor by the voltage applying means.
Based on the output of the air-fuel ratio sensor when the application is stopped
Then, the air-fuel ratio control is executed. Second air-fuel ratio control execution procedure
The stage is operated by the voltage applying means to the air-fuel ratio sensor.
Pressure based on the output of the air-fuel ratio sensor.
To execute the air-fuel ratio control. [0007] Then, the selection means is provided by the air-fuel ratio sensor.
Signal determination means for determining whether a signal is output from the
Activation for determining whether the air-fuel ratio sensor is activated
Determining means for determining the air-fuel ratio by the signal determining means.
It is determined that a signal is being output from the sensor, and
The air-fuel ratio sensor is activated by the activation determination means.
When it is determined that there is no
Stop applying the operating voltage to the air-fuel ratio sensor and
Select the first air-fuel ratio control means as the fuel ratio control means
The activation determination means activates the air-fuel ratio sensor.
When it is determined that the
Apply operating voltage to air-fuel ratio sensor and control air-fuel ratio
The second air-fuel ratio control means is selected as the control means. [0008] BRIEF DESCRIPTION OF THE DRAWINGS FIG.
You. In this embodiment, a rich signal is output from the air-fuel ratio sensor.
Open control until the sensor temperature is about 300 ° C.
Activation state of air-fuel ratio sensor after rich signal is output
Until the sensor is detected (sensor temperature is about 530 ° C).
Integral control (hereinafter, in this embodiment, proportional-integral (PI) control
Control after the activation state is detected.
This controls the air-fuel ratio. FIG. 2 shows a four-cylinder four-cycle spark ignition system.
The present invention is applied to a fuel injection control system of a fuel engine (engine) 1.
Has been applied. Engine 1 operates
Below, flows into the intake pipe 20 through the air cleaner 10
Air flow through the throttle valve 20a in the intake pipe 20.
And intake manifold passing through surge tank 30
40, and this air flow is taken into the intake manifold.
Is injected into the fuel injection valve 40 by the fuel injection valves 41 to 44.
Mixes with fuel from the fuel tank to form an air-fuel mixture.
The mixture is supplied to the combustion chamber of each cylinder of the engine body 50.
To burn under the ignition of each of the spark plugs 51-54.
Through exhaust manifold 60 and three-way catalyst 70
It is discharged into the exhaust pipe 80 as exhaust gas. In addition, each ignition
Plugs 51 to 54 are ignited from distributor 90
In response to the high voltage distributed in cooperation with the circuit 100,
To fire. The three-way catalyst 70 is an intake manifold.
Harmful components (CO, HC, NO_x
Etc.). The fuel injection system includes a rotation speed sensor 110
The rotation speed sensor 110 is
The output shaft of the engine body 50 is
The actual speed (equivalent to the actual speed of the engine 1)
Detect and pulse signal at a frequency proportional to the detection result
Are sequentially generated. However, the power from the rotation speed sensor 110
The number of occurrences of the loose signal is two revolutions of the engine 1 (that is,
The number is 24 per 0 ° CA (crank angle). [0011] The throttle sensor 120 is provided with a throttle bar.
The actual opening of the lube 20a is detected and issued as an opening detection signal.
Live. Also, the throttle sensor 120 is
Switch is built-in.
This is detected when the throttle valve 20a is fully closed, and the
Issue a signal. The negative pressure sensor 130 is connected to a switch in the intake pipe 20.
Detects actual negative pressure generated downstream of the rotary valve 20a
Then, it is generated as a negative pressure detection signal. The water temperature sensor 140 cools the engine body 50.
Detects the actual cooling water temperature in the system and uses it as a water temperature detection signal
appear. The air temperature sensor 150 is a slot in the intake pipe 20.
The actual temperature of the airflow flowing upstream of the torvalve 20a
Is generated as an air temperature detection signal. First air-fuel ratio sensor
160 is upstream of the three-way catalyst 70 in the exhaust pipe 80.
The actual unburned oxygen concentration in the exhaust gas is detected and the oxygen concentration
Generated as a detection signal. At this time, this oxygen concentration detection signal is
The actual air-fuel ratio λ of the mixture supplied to the body 50 is
Take a good value. The second air-fuel ratio sensor 170 is connected to the exhaust pipe 8
0 in the exhaust gas downstream of the three-way catalyst 70
Detects unburned oxygen concentration and generates it as oxygen concentration detection signal
You. However, the oxygen concentration from the second air-fuel ratio sensor 170
The air-fuel ratio λ is the theoretical air-fuel ratio λ₀Rich against
Or lean. The microcomputer 180 has a CPU 1
81, ROM 182, RAM 183, backup RA
M184, input port 185, output port 186 and
The bus 18 comprises a bus line 187 and the like.
1 is a pulse signal from the rotation speed sensor 110, a slot
Opening detection signal and full closing detection signal from the
Signal, negative pressure detection signal from negative pressure sensor 130, water temperature sensor
The water temperature detection signal from the air temperature sensor 150
Air temperature detection signal, oxygen from first air-fuel ratio sensor 160
Oxygen from the concentration signal and the second air-fuel ratio sensor 170
The density detection signal is input to the input port 185 and the bus line 18.
7, ROM 182, RAM 183 and
The data stored in the backup RAM 184 is transferred to the bus line 1
Received through 87 and run a computer program
During this execution, the bus line 187 and the output
Each fuel injection valve 41-44 and ignition via port 186
Performs arithmetic processing necessary to drive and control the circuit 100.
U. However, the above computer program is stored in the ROM 1
82 is stored in advance. The microcomputer 180 has a battery
The power supplied from the battery Ba is divided into first and second air-fuel ratio sensors.
To the first and second air-fuel ratio sensors.
The power supply to the sensor 160 is controlled. See below for details.
You. Next, in order to perform air-fuel ratio control by modern control processing
The method that has been set will be described. First, the modeling of the controlled object will be described.
I will tell. In this embodiment, the air-fuel ratio λ of the engine 1 is controlled.
Order 1 having a dead time P = 3 in the model of the system
Using the autoregressive moving average model of
It is approximated with consideration. First, using the autoregressive average model
The model of the system that controls the air-fuel ratio λ is
Can be approximated by [0017] (Equation 1) λ (K) = a · λ (K-1) + b · FAF (K-3) However, in Equation 1, the symbol FAF is
Represents the correction coefficient. Each symbol a and b represents a constant.
The code K represents the control cycle from the start of the first sampling.
Represents a variable that indicates a number. Further, considering the disturbance d, the control system
The model of the system can be approximated by the following equation (2). [0019] Λ (K) = a · λ (K−1) + b · FAF (K
-3) + d (K-1) Step response to the model approximated as above
(360 ° CA (crank angle))
Determine each constant a and b by discretizing by pulling,
That is, obtaining the transfer function G of the system for controlling the air-fuel ratio λ is
Easy. Next, a method of displaying the state variable quantity IX (however,
IX is a vector quantity). The above number
Equation 2 is converted to a state variable quantity IX expressed by the following equation 3.
When rewritten using (K), Equation 4 and Equation 5 are obtained.
become. [0021] IX (K) = [X1 (K), X2 (K), X3
(K), X4 (K)]^T However, in Equation 3, the symbol T indicates a transposed matrix. [0022] (Equation 4) [0023] 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) Next, the design of the regulator will be described. The regulation based on the above equations (3) to (5) is performed.
When the data is designed, the feedback correction coefficient
Feedback gain IK (with vector quantity)
The following Expression 6 and Expression relating to the state variable amount IX (K)
7, and can be expressed as Expression 8. [0025] ## EQU6 ## IK = [K1, K2, K3, K4] [0026] IX^T(K) = [λ (K), FAF (K−
3), FAF (K-2), FAF (K-1)] [0027] ## EQU8 ## FAF (K) = IK.IX^T(K) = K1 · λ (K) + K2 · FAF (K-3) + K3 · F
AF (K-2) + K4 ・ (K-1) Further, in the equation (8), the
By adding the integral term ZI (K), the feedback correction coefficient
Is given by the following Equation 9. [0028] ## EQU9 ## FAF (K) = K1.lambda. (K) + K2.FAF
(K-3) + K3 · FAF (K-2) + K4 · FAF
(K-1) + Z1 (K) Note that the above integral term ZI (K) is calculated based on the target air-fuel ratio λTG and
And the deviation between the actual air-fuel ratio λ (K) and the integration constant Ka
This value is determined and is given by the following equation (10). [0029] (Equation 10) ZI (K) = ZI (K−1) + Ka · (λTG−λ
(K)) FIG. 3 shows the control of the air-fuel ratio λ for which the model is designed as described above.
1 represents a block diagram of the system. In FIG.
The feedback correction coefficient FAF (K) is calculated from FAF (K-1).
It is shown using (1 / Z) transformation to derive it.
This is based on the past feedback correction coefficient FAF (K-1).
The data is stored in the RAM 183 and read at the next control timing.
I use it. Also, in FIG.
Block P1 converts the air-fuel ratio λ (K) to the target air-fuel ratio λTG.
The state variable IX in the state of feedback control
(K), and the block P2 is an integral term Z
1 This is the part (accumulation part) for which (K) is calculated, and
P3 is the state variable IX determined in block P1.
(K) and the integral term Z1 (K) obtained in block P2.
Calculates the current feedback correction coefficient FAF (K) from
This is the part to do. Next, the optimum feedback gain IK and
The determination of the integral constant Ka will be described. Optimal feed
The back gain and the integration constant Ka are, for example,
It can be set by minimizing the evaluation function J indicated by 11.
You. [0032] [Equation 11] However, in this equation 11, the evaluation function
J controls the movement of the feedback correction coefficient FAF (K).
While reducing the deviation between the air-fuel ratio λ (K) and the target air-fuel ratio λTG.
It is intended to be small. Also, the feedback
The weight of the constraint on the lock correction coefficient FAF (K) is
It can be changed by the values of the weight parameters Q and R. Follow
Therefore, the optimal control is performed by changing the values of the weight parameters Q and R in various ways.
Repeat the simulation until the characteristic is obtained,
Determine optimal feedback gain IK and integration constant Ka
Just turn it on. Further, the optimum feedback gain IK and
And the integral constant Ka depend on the quantity model constants a and b.
You. Therefore, the fluctuation of the system that controls the actual air-fuel ratio λ (para
System stability against robustness (robustness)
In order to guarantee, the variation of each of the model constants a and b is checked.
The optimum feedback gain IK and the integration constant K
It is necessary to set a. Therefore, the simulation is performed for each model.
Stability is performed taking into account the actual possible fluctuations of numbers a and b
Feedback gain IK and integral constant satisfying
The number Ka is determined. The modeling of the control target and the state change
How to display quantity, regulator design and optimal fee
Explained the determination of the feedback gain and the integration constant
However, these are determined in advance, and in this embodiment,
Is the fuel injection control using only Equations 7 and 8 above.
Performs air-fuel ratio control in the control system. In this embodiment configured as described above,
When the fuel injection control system is in operation,
The CPU 181 of the computer 180
In step 200, the computer program
Start executing the program, and in step 300, the engine
1 generated from the rotation speed sensor 110 every 360 ° CA
In response to the pulse signal, the signals are sequentially generated from the rotation speed sensor 110
The rotational speed N of the internal combustion engine 1 according to the frequency of the shear pulse signal
_eIs calculated, and this rotation speed N_eFrom the negative pressure sensor 130
Based on the value of the negative pressure detection signal (hereinafter referred to as negative pressure PM), etc.
Basic injection of fuel into intake manifold 40
Quantity T_pAnd calculate the air-fuel ratio by computer program
Proceed to processing routine 400 (see FIG. 5). The processing executed in step 400 is
The flowchart shown is FIG. To step 400
When the air-fuel ratio calculation process (FAF setting process) is executed,
First, in step 401, the feedback condition is satisfied.
Determine whether it is standing. Where the feedback condition
This means that, for example, the cooling water temperature of the engine
℃) or more. Here, the feedback condition is satisfied.
If not, the process proceeds to step 402. And step
At 402, open control is executed. This open
FIG. 6 is a flowchart showing the control processing routine.
You. In FIG. 6, when the open control is executed,
In step 409, the feedback correction coefficient FAF is
= 1 and in the next step 410
Application F1 is set to F1 = 1. However, F1 = 1 is the current
That the air-fuel ratio control is being executed
Is shown. Thus, the FAF setting routine 40
0 ends in step 410, the CPU 181 returns to FIG.
In step 500 of 4 under the open control,
Based on equation 12, the basic injection amount T in step 300
_pIs corrected according to the correction coefficient FALL, and this is
Set as TAU. [0039] [Expression 12] TAU = FAF · T_P・ FALL On the other hand, in step 401 of FIG.
When it is determined that is established, the process proceeds to step 403,
The first air-fuel ratio sensor 160 is in the activated state (stable signal
(A temperature state in which the output can be output). less than,
A specific method of determining the activation state will be described. The first air-fuel
The present embodiment is used as a method for determining the activation state of the ratio sensor 160.
Adopts an air-fuel ratio sensor based on heater resistance.
You. FIG. 9A shows the relationship between the heater temperature and the element temperature.
It shows the relationship. In this figure, the first air-fuel
The activation temperature (530 ° C.) at which the ratio sensor 160 is activated
At this time, the heater temperature is between 600C and 680C. This case
Fluctuations result from variations in heater thermal efficiency.
You. Also, the resistance of the heater resistance of the first air-fuel ratio sensor 160
The resistance value has the characteristic that it increases as the heater temperature rises.
ing. FIG. 9B shows this characteristic. this
In the figure, when the heater resistance is 2.3Ω or more, the heater
Temperature becomes at least 680 ° C. and the first air-fuel ratio
It can be seen that the support 160 is activated. The activation of the first air-fuel ratio sensor 160
The determination method is not limited to the above method.
Of the elements having a one-to-one relationship with the element temperature of the fuel ratio sensor 160
The impedance may be directly measured. That's all
The activation state of the first air-fuel ratio sensor 160 is determined by an appropriate method.
And if it is determined that it is not in the activated state, step 404
Proceed to. In step 404, the first air-fuel ratio sensor 160
The voltage to be applied to the element is set to 0V. Thus, the applied voltage
By setting the pressure to 0 V, the air-fuel ratio sensor 160
A signal is output when the ratio is rich. Yo
When the signal is output, the air-fuel ratio is rich,
When the signal is not output, the air-fuel ratio is lean.
Can be determined. Next, proceed to step 405,
1 to determine whether a signal is output from the air-fuel ratio sensor 160.
judge. At this time, after starting the engine, it almost smells
Because the air-fuel ratio is controlled to the rich side, the output signal
Air-fuel ratio setting until rich / lean can be determined.
When the sensor 160 is activated (the sensor temperature is about 30
0 ° C.), a rich signal is output. Here, a signal is output from the air-fuel ratio sensor 160.
If not, go to step 402 and
Feedback control coefficient FAF by open control
Determine and exit this routine. Rich / lean signal
If it is, the process proceeds to step 406,
The minute control (PI control) process is executed. Hereinafter, shown in FIG.
The PI control process according to the flowchart
explain. In step 406, PI control processing is executed.
If executed, the process proceeds to step 422. At step 422
Determines whether the air-fuel ratio is rich. In this embodiment
Means that a signal is output from the air-fuel ratio sensor 160
Determines that the air-fuel ratio is rich. Here, the signal is detected.
When it is determined that the air-fuel ratio is rich
Proceed to 26. In step 426, the result is compared with the previous detection result.
Then, it is determined whether or not lean has been inverted to rich. This
Here, if it is determined that the air conditioner has changed from lean to rich,
In step 428, the feedback correction coefficient FAF−
α (α is the skip amount) is the new feedback correction coefficient
With FAF, there is no reversal from lean to rich
Is determined in step 426, step 427
And a feedback correction coefficient FAF-β (β is an integral amount, α
> Β) as a new feedback correction coefficient FAF.
Then, the process proceeds to step 429, and the modern control non-execution flag is set.
Set F1 to F1 = 1 and exit this routine. That
Thereafter, the process proceeds to step 500 in FIG.
Basic fuel injection amount T in step 300_PTo
Step 427 or step 428
Feedback correction coefficient FAF and correction coefficient FALL.
This is set as the fuel injection amount TAU. In step 422, the air-fuel ratio
When it is detected as not rich or lean
Goes to step 423. In step 423, the previous inspection
To see if it's flipped from rich to lean
to decide. When it is determined that rich has turned lean
Proceed to step 424. In step 424, the feedback
A new correction coefficient FAF + α (α is the skip amount).
The feedback correction coefficient FAF is used. To step 423
It was determined that there was no reversal from rich to lean
Sometimes, the process proceeds to step 425, where the feedback correction
The number FAF-β (β is an integral amount) is added to a new feedback
This is a positive coefficient FAF. Then, the process proceeds to step 429,
By setting the modern control non-execution flag F1 to F1 = 1,
Get out of the chin. Thereafter, the process proceeds to step 500 in FIG.
Based on Equation 12, the basic fuel injection in step 300 is performed.
Radiation T_PIn step 424 or step 425
The feedback correction coefficient FAF calculated by
The correction is made according to the positive coefficient FALL, and this is corrected by the fuel injection amount TA.
Set to U. In step 403, the first empty
When it is determined that the fuel ratio sensor 160 is in the activated state
Go to step 407. In step 407, the air-fuel ratio
For outputting a limiting current for detecting
5V) is applied to the element of the first air-fuel ratio sensor 160.
Then, in step 408, the modern control processing is executed.
Run. A flowchart showing this modern control process is shown in FIG.
8 Hereinafter, the description will be made according to this flowchart.
I do. In step 408, the flow chart
First, in step 414, when the
Set the air-fuel ratio guard according to the temperature. This air-fuel ratio
As shown in FIG.
The air-fuel ratio is taken in the range where the flow is stable.
Specifically, as the element temperature of the air-fuel ratio sensor 160 increases,
Limiting current is stable, so air-fuel ratio capture range is wide
are doing. Next, at step 415, depending on the operating state,
Set the target air-fuel ratio λTG. And the next step
At 416, the modern control non-execution flag F1 is set to F1 = 1.
It is determined whether there is. In other words, the previous air-fuel ratio control was
It is determined whether it was executed by a method other than control. here,
When the modern control non-execution flag F1 is F1 = 1, the next
Proceed to step 417 to execute the modern control process.
Make the initial settings for. Specifically, first, in step 417,
To determine the optimal feedback gain in advance
Set IKN (1,2,3,4, A) and next step
At 418, the modern control non-execution flag F1 is set to F1 = 0.
I do. At this time, the optimal feedback gain IKN is
Weight of weight parameter Q in evaluation function J of equation 11
Set the ratio (Q / R) to parameter R to (1/5)
It is determined by doing. Step 41
9, the initial value Z of the integral term is calculated based on the following equation (13).
Calculate I (K-1). [0048] ## EQU13 ## ZI (K-1) = FAF (K-1) + K2 ·
FAF (K-1) + K3 · FAF (K-2) + K4 · F
AF (K-3) -K1λ (K) However, in Equation 13, the symbol λ (K) represents the air-fuel ratio.
Represent. Equation 13 is inversely calculated from Equation 14 below.
It is what I asked for. [0049] ## EQU14 ## FAF (K) = ZI (K) + K1.lambda. (K)
-K2 • FAF (K-1) -K3 • FAF (K-2)-
K4 ・ FAF (K-3) However, in Equation 14, the code FAF is
Represents the back correction coefficient. At step 419, the initial value ZI (K
After calculating -1), the process proceeds to step 420. Also,
In step 416, the modern control non-execution flag F1 is set to F
When 1 = 1 is not satisfied, that is, when the previous air-fuel ratio control
When the control is being executed under the alternative control, step 417,
Step 4 bypassing steps 418 and 419
Go to 20. In step 420, the product is
Compute the fractional term ZI (K). And in step 421
The feedback correction coefficient FAF is calculated based on Equation 14.
Calculate. Feedback correction coefficient FAF is calculated
And in step 500 of FIG.
Basic fuel injection amount T in step 300 _pStep
421, the feedback correction coefficient FAF
The correction is made according to the positive coefficient FALL, and this is corrected by the fuel injection amount TA.
Set to U. By executing the above processing, FIG.
As shown in FIG. 5, the element temperature of the first air-fuel ratio sensor 160 is about
300 ° C., rich from the first air-fuel ratio sensor 160
・ PI control from open control when a lean signal is output
The air-fuel ratio control earlier.
Will be able to Further, the element temperature is about 530.
° C and the first air-fuel ratio sensor 160 is activated.
Switch from PI control to modern control, more accurately empty
Fuel ratio control can be performed. In this embodiment, step 40
4. Step 407 is a step for applying voltage to the voltage applying means.
Is the first air-fuel ratio control execution means, and step 408 is the second air-fuel ratio control execution means.
Step 403, Step 4
05 corresponds to the selection means and functions. Also on
In this embodiment, the air-fuel ratio sensor 1 is not activated.
When the signal is output from 60, PI control is activated.
The air-fuel ratio control is performed by modern control when
The present invention is not limited to this. For example, when the air-fuel ratio sensor is activated,
Skip amount or integration depending on the detected air-fuel ratio
Executing air-fuel ratio control by PI control that changes the amount
You may make it. [0053] According to the present invention, as described above,
Rich from air-fuel ratio sensor when no dynamic voltage is applied
Or, when a signal for detecting lean is output, the first air-fuel
Since the air-fuel ratio control is executed by the ratio control execution means,
The air-fuel ratio control should be executed earlier than the air-fuel ratio control
Can be. Furthermore, when the air-fuel ratio sensor is activated,
Executes air-fuel ratio control according to the air-fuel ratio of the ratio sensor output.
More accurate air-fuel ratio control when the air-fuel ratio sensor is activated
Can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing components of the present invention. FIG. 2 is a schematic configuration diagram of an embodiment using the present invention. FIG. 3 is a block diagram of a dynamic model in modern control theory. FIG. 4 is a flowchart of a TAU setting process executed by a CPU. FIG. 5 is a flowchart of an FAF setting process executed by the CPU. FIG. 6 is a flowchart of an open control process executed by a CPU. FIG. 7 is a flowchart of a PI control process executed by the CPU. FIG. 8 is a flowchart of a modern control process executed by the CPU. FIGS. 9A and 9B are explanatory diagrams showing a method of determining the activation state of the air-fuel ratio sensor. FIG. 10 is a graph showing an intake range of the air-fuel ratio in the relationship between the air-fuel ratio, each air-fuel ratio sensor, and the sensor temperature. FIG. 11 is a graph showing a relationship between a sensor current i and a sensor temperature of each air-fuel ratio sensor using an air-fuel ratio A / F as a parameter. [Description of Signs] 1 Engines 41 to 44 Fuel injection valve 160 First air-fuel ratio sensor 180 Microcomputer Ba Battery

Continuation of the front page (56) References JP-A-5-52140 (JP, A) JP-A-61-19800 (JP, A) JP-A-60-6037 (JP, A) JP-A-62-182645 (JP, A) JP-A-63-223347 (JP, A) JP-A-1-219327 (JP, A) JP-A-62-190840 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB Name) F02D 41/00-41/40

Claims (1)

(57) [Claim 1] When the operating voltage is not applied, only the rich or lean air-fuel ratio is detected from the exhaust gas of the internal combustion engine, and when the operating voltage is applied, the air-fuel ratio is detected. An air-fuel ratio sensor that detects an air-fuel ratio sensor, a voltage application unit that applies an operating voltage to the air-fuel ratio sensor, and an air-fuel ratio sensor that stops applying the operation voltage to the air-fuel ratio sensor by the voltage application unit. First air-fuel ratio control execution means for executing air-fuel ratio control based on the output; and air-fuel ratio based on the output of the air-fuel ratio sensor when an operating voltage is applied to the air-fuel ratio sensor by the voltage application means. Second air-fuel ratio control executing means for executing control; signal judging means for judging whether a signal is output from the air-fuel ratio sensor; and activity for judging whether the air-fuel ratio sensor is activated. When the air-fuel ratio sensor is determined to be output from the air-fuel ratio sensor by the signal determination means, and when it is determined that the air-fuel ratio sensor is not activated by the activation determination means, The application of the operating voltage to the air-fuel ratio sensor by the voltage application unit is stopped, the first air-fuel ratio control unit is selected as the air-fuel ratio control unit, and the activation determination unit activates the air-fuel ratio sensor. And an selecting means for selecting the second air-fuel ratio control means as the air-fuel ratio control means while causing the voltage application means to apply the operating voltage to the air-fuel ratio sensor when it is determined that the internal combustion engine is operating. Engine air-fuel ratio control device.