JPS62218636A - Air-fuel ratio learning control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve reliability for an assumed learning, by taking both errors in an intake air quantity and a basic injection quantity into consideration when a learning correction coefficient in an operating region with a less progressed learning degree is assumed based on a learning correction coefficient in an operating region with a much progressed learning degree. CONSTITUTION:A first learning correction coefficient renewal means E for renewing a learning correction coefficient corresponding to an operating region based on a signal from an air-fuel ration feedback complement coefficient setting means B has the degree of a learning progress monitored by a learning progress degree discriminating means H. A second learning correction coefficient searching means I searches a learning correction coefficient in an operating region which is discriminate to have the same basic injection quantity and a much progressed learning degree and a third learning correction coefficient searching means K searches a learning correction coefficient in an operating region which is discriminated to have the same intake air quantity and a much progressed learning degree. A second learning correction coefficient renewal means L calculates the learning correction coefficients from the second and third learning correction coefficient searching means I, K for renewing the learning correction coefficients.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a learning control device for an air-fuel ratio feedback control system in an internal combustion engine having an electronically controlled fuel injection device.

<Prior art> A fuel injection valve used in an electronically controlled fuel injection system is opened by a drive pulse signal given in synchronization with the rotation of the engine, and during the valve opening period, fuel at a predetermined pressure is injected. It has become. Therefore, the fuel injection amount is controlled by the pulse width of the drive pulse signal, and if this pulse width is set as Ti and the control signal corresponds to the fuel injection amount, then in order to obtain the stoichiometric air-fuel ratio, which is the target air-fuel ratio, Ti is determined by the following formula. determined by.

T1=Tp−COEF·α+Ts However, Tp is a basic pulse width corresponding to the basic injection amount and is called the basic injection amount for convenience. Tp=-Q/N, K is a constant,
Q is the engine intake air flow rate, and N is the engine rotation speed. C0E
F is various correction coefficients such as water temperature correction. α is an air-fuel ratio feedback correction coefficient for air-fuel ratio feedbank control (λ control) to be described later. TS is a voltage correction element, which is used to correct changes in the injection flow rate of the fuel injection valve due to fluctuations in battery voltage.

Regarding λ control, an Otsen is installed in the exhaust system to detect the actual air-fuel ratio, and the slice level controls whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio.
For this reason, the aforementioned air-fuel ratio feedback correction coefficient α is determined, and by changing this α, the stoichiometric air-fuel ratio is maintained.

Here, the value of the air-fuel ratio feedback correction coefficient α is changed by proportional-integral (Pl) control to achieve stable control.

In other words, the output voltage of the 0□ sensor is compared with the slice level voltage, and if it is higher or lower than the slice level, the air-fuel ratio is rich (lean) without suddenly enriching or thinning the air-fuel ratio. ), first lower (raise) by P, then gradually lower (raise) 1 minute at a time.
and controls the air-fuel ratio to be lean < (rich <) (7th
(see figure).

However, under conditions where λ control is not performed, α is clamped and a desired air-fuel ratio is obtained by setting various correction coefficients COEF.

By the way, if the base air-fuel ratio under λ control conditions, that is, the air-fuel ratio when α = 1, could be set to the stoichiometric air-fuel ratio (λ = 1), feedback control would not be necessary. For example, variations in air flow meters, fuel injection valves, pressure regulators, control units), changes over time, and pulse width of fuel injection valves.
Feedback control is performed because the base air-fuel ratio deviates from λ=1 due to factors such as non-linearity of flow characteristics and changes in operating conditions and environment.

However, if the base air-fuel ratio deviates from λ=1, it takes time to stabilize the step in the base air-fuel ratio to λ=1 through feedback control when the operating range changes significantly. And for this we need the constant of proportionality and integration (P/
1 minute) increases, overshoot or undershoot occurs, resulting in poor controllability. In other words, if the base air-fuel ratio deviates from λ=1, the air-fuel ratio will be controlled within a range that deviates considerably from the stoichiometric air-fuel ratio.

As a result, the three-way catalyst is operated at a point where its conversion efficiency is poor, and not only does the cost increase due to an increase in the amount of precious metal in the catalyst, but the conversion efficiency further deteriorates as the catalyst deteriorates, forcing the catalyst to be replaced. .

Therefore, by setting the base air-fuel ratio to λ = 1 through learning, it is possible to eliminate the deviation from λ = 1 caused by the step in the base air-fuel ratio during transients, and to reduce the P/I component, improving controllability. A learning control device for air-fuel ratio that aims to improve
Japanese Patent Application No. 58-76221 (Japanese Unexamined Patent Publication No. 58-76221)
9-203828) or patent application No. 1974-1974
It was filed as No. 9.

This is because if the base air-fuel ratio deviates from the stoichiometric air-fuel ratio during air-fuel ratio feedback control, the air-fuel ratio feedback correction coefficient α becomes large to compensate for the gap.
The engine operating state and α at this time are detected, and based on α, (
A learning correction coefficient Kl is determined and stored, and when the same engine operating condition returns, the base air-fuel ratio is corrected by β to the stored learning correction coefficient so as to improve responsiveness to the stoichiometric air-fuel ratio. The storage of 1 in the learning correction coefficient here is performed for each region of a predetermined range obtained by dividing the map in the RAM into a grid according to appropriate parameters of the engine operating state such as engine speed and load.

Specifically, a map of 1 is provided in the RAM for learning correction coefficients corresponding to engine operating conditions such as engine speed and load, and when calculating the fuel injection amount Ti, the basic injection tT is calculated as shown in the following formula.
Correct p by 1 as a learning correction coefficient.

T i =Tp HC0EF-Kl ・cx+Ts Then, learning of Kl proceeds in the following steps.

i) Detect the region of the engine operating state at that time in a steady state, and detect the deviation Δα of α from the reference value α1 during that period.
(=α−αI) is detected as the average value. The reference value α is generally set to 1 as a value corresponding to λ=1.

ii) Searching for Kl that has been learned up to now corresponding to the region of the engine operating state.

1ii) Find the value of Kj2+M·Δα from Kl2 and Δα, and update the memory by using the result (learning value) as a new K Il (N). M is a constant and O<M<1.

By the way, in such a conventional learning method for air-fuel ratio feedback control, the deviation amount Δα cannot be detected accurately unless it is in a steady state, so learning is performed by detecting Δα only in a steady state. In this case, during a transient operating state, learning is not performed in an operating region where the vehicle does not operate temporarily.

For this reason, there are areas where the learning progress is large (hereinafter referred to as learning areas) and other areas where the learning progress is small (hereinafter referred to as unlearning areas). If the operating condition changes in this state, if a deviation occurs in the air-fuel ratio in the system, α and air-fuel ratio λ will change between the learning region and the unlearning region.
As a result, there is a difference in the air-fuel ratio λ when moving between the learned area and the unlearned area, leading to deterioration of exhaust emission characteristics and fuel efficiency in transient operating conditions, The effect of learning does not increase.

On the other hand, among the factors that cause the deviation of the base air-fuel ratio from λ = 1, the intake air flow i1 determined by the air flow meter is
It is thought that the measurement error of Q accounts for a fairly large proportion; for example, in the case of a hot wire type air flow meter, the progress of the measurement error becomes significant due to the adhesion of dust to the hot wire or the deterioration of the hot wire itself.

In this case, it is considered that in a region where the intake air flow rate Q is equal, the measurement error ΔQ of Q is also equal.

In view of this, the applicant of the present application detects the degree of learning progress, and the learning correction coefficient K learned in the driving region where the degree of learning progress is large.
By performing learning in a small operating region where the intake air flow i1Q is equal to the relevant operating region based on l, the reliability of the learned value is improved and the air-fuel ratio control accuracy is improved. Patent application for learning control device 1986-009
The application was filed as No. 446.

<Problems to be Solved by the Invention> However, in the case of the above learning control device, the following problems occur.

Among the factors that cause the deviation of the base air-fuel ratio from λ=1, it is thought that the deterioration of the fuel injection valve accounts for a considerable proportion, as does the measurement error of the intake air flow rate Q.

However, in this case, it appears as a change in the rising valve opening characteristic and falling valve closing characteristic with respect to the driving voltage of the fuel injector, and as in the case of the intake air flow rate Q, in the region where the basic injection amount Tp is equal, the change is caused by the deterioration of the fuel injector. Base air-fuel ratio λ=
It is considered that the amount of deviation from 1 is the same. Therefore, it cannot be said that the conventional estimation learning that takes only the intake air flow rate Q into account can provide a good estimation.

The present invention has been made in view of the above points, and improves the reliability of the estimation by estimating the learning correction coefficient for the small learning progress level by making corrections according to both the basic injection amount and the intake air flow rate. An object of the present invention is to provide an air-fuel ratio learning control device for an internal combustion engine, which improves the accuracy of air-fuel ratio control.

<Means for solving the problems> Specifically, as shown in FIG. 1, the learning control device according to the present invention includes the following means (A) to (L).

(A) Basic injection amount setting means for setting basic injection fitTp from intake air flow fiQ and engine speed N (B) Actual air-fuel ratio detected based on a signal from air-fuel ratio detection means provided in the exhaust system (C) An air-fuel ratio feedback correction coefficient setting means (C) for setting an air-fuel ratio feedback correction coefficient α by integral control by comparing the stoichiometric air-fuel ratio with the stoichiometric air-fuel ratio. Rewritable learning correction coefficient storage means (D) First learning correction coefficient retrieval means for searching the learning correction coefficient KN of the corresponding area from the learning correction coefficient storage means based on the actual engine operating state (E) Air-fuel ratio feedback A new learning correction coefficient Kl is set from the correction coefficient and the learning correction coefficient Kl searched by the learning correction coefficient retrieval means, and the learning correction coefficient Kl is used to store data of the same engine operating region in the learning correction coefficient storage means. The first step is to update
Learning correction coefficient updating means (F) Injection amount calculation means for calculating the injection amount by multiplying the basic injection tTp by the air-fuel ratio feedback correction coefficient α and the learning correction coefficient KN (G) Drive corresponding to the calculated injection amount Drive pulse signal output means (!1) that outputs a pulse signal to the fuel injection valve; learning progress that determines the degree of learning progress for each operating region based on the number of data updates for each operating region in the first learning correction coefficient updating means; degree determination means (1) The basic injection amount Tp is equal to the operating range in which the learning correction coefficient Kl is updated by the first learning correction coefficient updating means, and the learning progress degree is determined to be large by the learning progress determination means. Second learning correction coefficient search means (J) for searching the learning correction coefficient KlP of the determined driving region; adding 1° to the learning correction coefficient updated by the first learning correction coefficient updating means; Learning correction coefficient KN searched by the coefficient search means.

A learning correction coefficient deviation calculation means (K) for calculating the difference ΔKN between the learning correction coefficient Kl and the second
The learning correction coefficient K11o1. of the driving region in which the intake air flow rate Q is equal to one of the driving regions in which the learning correction coefficient KlP is searched by the learning correction coefficient searching means and in which the learning progress is determined to be high. K11p. The third learning correction coefficient search means (L) similarly searches for the learning correction coefficient Kl in the driving region where the learning correction coefficient Kn is updated and the second learning correction coefficient search means.
The data of the learning correction coefficients K l at and K l rat of the driving range in which the intake air flow IIQ is equal to the other driving range in which P is searched and in which the learning progress is determined to be small is used as the third learning correction coefficient. The learning correction coefficient for the operating region searched by the search means and having the same basic injection amount as the relevant operating region is updated with a value set based on 1゜In K IPQI and ΔK I P calculated by the learning correction coefficient deviation calculation means. The basic injection amount setting means A sets the basic injection amount Tp based on the intake air flow rate Q and the engine speed N according to a predetermined calculation formula or by searching. , the air-fuel ratio feedback correction coefficient setting means B compares the actual air-fuel ratio detected by the air-fuel ratio sensor with the stoichiometric air-fuel ratio and sets the air-fuel ratio feedback correction coefficient α by integral control II (including proportional-integral control). do.

Further, the first learning correction coefficient updating means uses the air-fuel ratio feedback correction α detected by the air-fuel ratio detection means and the learning correction coefficient Kl retrieved from the learning correction coefficient storage means C by the first learning correction coefficient retrieval means. E sets a new learning correction coefficient, and the data of the same engine operating region in the learning correction coefficient storage means C is updated with 1 as the learning correction coefficient.

While performing such learning, the injection amount calculation means F performs basic injection!
The injection amount is calculated by multiplying 1tTp by the air-fuel ratio feedback correction coefficient α and the learning correction coefficient KA, and the drive pulse signal output means G outputs a drive pulse signal corresponding to the calculated injection amount to the fuel injection valve. . As a result, the calculated amount of fuel is injected and supplied to the engine.

On the other hand, in addition to learning the searched driving range, learning based on the two-value estimation of the present invention is performed as described later.

That is, the basic injection amount Tp is determined for the operating region in which the learning correction coefficient Kl is searched by the first learning correction coefficient search means.
The second learning correction coefficient searching means I searches for the learning correction coefficient K I P in another driving region in which the learning progress determined by the learning progress determining means H is equal and the learning progress determined by the learning progress determining means H is large.

The learning correction coefficient K IF searched in this way,
The difference ΔKlP from the learning correction coefficient updated by the first learning correction coefficient updating means E is calculated by the learning correction coefficient deviation calculation means J.

Next, the operating region where the learning correction coefficient is updated to 2 and the second
The learning correction coefficient Kio of the driving region where the intake air flow rate Q is equal to one of the driving regions in which the learning correction coefficient Key is searched by the learning correction coefficient search means (■) and where the learning progress is determined to be large is determined as the first learning correction coefficient Kio. The search is performed by the learning correction coefficient search means K of No. 3.

Then, the second learning correction coefficient updating means determines that the intake air flow fiQ is equal to the other of the driving ranges in which β and β2 are searched for in the second learning correction coefficient, and that the learning progress is small. The data of the learning correction coefficient of the driving region is divided into 1 degree for the learning correction coefficient searched by the third learning correction coefficient search means K and Δ calculated by the learning correction coefficient deviation calculation means J.

The learning correction coefficient storage means C stores and updates the data of the relevant driving range.

<Example> An embodiment of the present invention will be described below.

In FIG. 2, the engine 1 includes an air cleaner 2°, an intake duct 3. Throttle chamber 4 and intake manifold 5
Air is inhaled through.

The intake duct 3 is provided with an air flow meter 6 as a means for detecting the intake air flow rate Q.
Outputs a voltage signal corresponding to the signal.

The throttle chamber 4 includes a primary throttle valve 7 and a secondary throttle valve 8 that operate in conjunction with an accelerator pedal (not shown).
is provided to control the intake air flow rate Q. Further, an auxiliary air passage 9 is provided that bypasses these throttle valves 7.8, and an idle control valve 10 is interposed in this auxiliary air passage 9. Intake manifold 5
Alternatively, a fuel injection valve 11 is provided at the intake port of the engine 1.

The fuel injection valve 11 is an electromagnetic fuel injection valve that opens when a solenoid is energized, and then closes when the energization is stopped and the valve is closed. Fuel controlled to a predetermined pressure by a regulator is injected and supplied to the engine 1.

From engine 1, exhaust manifold 12. Exhaust duct 13
．． Exhaust gas is discharged via the three-way catalyst 14 and the muffler 15.

The exhaust manifold 12 is provided with a 0□ sensor 16. This 0□ sensor 16 is the oxygen concentration in the atmosphere (constant)
outputs a voltage signal according to the ratio of the oxygen concentration in the exhaust gas and
This is a known sensor whose electromotive force changes suddenly when the air-fuel mixture is combusted at the stoichiometric air-fuel ratio. Therefore, the 02 sensor 16 is a means for detecting the air-fuel ratio of the air-fuel mixture (S.7C.Lean). The three-way catalyst 14 is a catalytic device that efficiently oxidizes or reduces CO, HC, and NOx in the exhaust gas components near the stoichiometric air-fuel ratio of the air-fuel mixture and converts them into other harmless substances.

In addition, a crank angle sensor 17 is provided.

In the crank angle sensor 17, a signal disk plate 19 is provided on the crank pulley 18, and teeth provided on the outer circumference of the plate 19 output a reference signal every 120 degrees and a position signal every 1 degree, for example. Here, the engine speed N can be calculated by measuring the period of the reference signal.

The air flow meter 6, crank angle sensors 17 and 0
□The output signals from the sensor 16 are both input to the control unit 30. Furthermore, control unit 3
The voltage of a battery 20 is directly applied to the engine 0 via an engine key switch 21 as its operating power source and for detecting the power supply voltage.

Furthermore, the control unit 30 is provided with a water temperature sensor 22 for detecting the engine cooling water temperature as required. - Throttle sensor 23 including an idle switch that detects the throttle opening of the next throttle valve 7. Vehicle speed sensor 24 that detects vehicle speed. Signals from a neutral switch 25, etc. that detect the neutral position of the transmission are manually input. The control unit 30 performs arithmetic processing based on various input signals, outputs a drive pulse signal with an optimal pulse width to the fuel injection valve 11, and obtains a fuel injection amount for obtaining an optimal air-fuel ratio.

The control unit 30, as shown in FIG.
PU31. P-ROM32. It has a CMO3-RAM 33 and an address decoder 34. Here, the RAM 33 is a rewritable storage means for learning control, and this RAM
As the operating power source of 33, a battery 20 is connected via a suitable stabilized power source without using the engine key switch 21 in order to retain the memory contents even after the engine key switch 21 is turned off.

Of the human input signals to CPU U31, air flow meter 6
．． 0□Sensor 16. Battery 20. Since the voltage signals from the water temperature sensor 22 and the throttle sensor 23 are analog signals, they are inputted via an analog input interface 35 and an A/D converter 36. The A/D converter 36 is controlled by the CPU 31 via an address decoder 34 and an A/D conversion timing controller 37. The reference signal and position signal from the crank angle sensor 17 are inputted via a one-shore multi-circuit 38. A signal from the idle switch built into the throttle sensor 23 and a signal from the neutral switch 25 are input via the digital input interface 39, and the signal from the idle switch built in the throttle sensor 23 and the signal from the neutral switch 25 are inputted via the digital input interface 39.
The signal is inputted via the waveform shaping circuit 40.

The output signal (driving pulse signal for the fuel injection valve 11 ) from the CPU 31 is sent to the fuel injection valve 11 via the current waveform control circuit 41 .

Here, the CPU 31 controls the fuel injection amount by performing input/output operations and arithmetic processing according to the program (stored in the ROM 32) based on the flowchart (fuel injection amount calculation routine) shown in FIG. .

Note that the functions of each means described in the above section ``Means for Solving the Problems'' are achieved by the program.

Next, the operation will be explained with reference to the flowcharts of FIGS. 4 and 5.

In the fuel injection amount calculation routine shown in FIG.
(31 in the figure) shows the intake air flow iQ obtained from the signal from the air flow meter 6 and the crank angle sensor 1.
The basic injection amount Tp (=-Q/N) is calculated from the engine speed N obtained from the signal from 7. This part corresponds to the basic injection amount calculation means.

In step 2, various correction coefficients C0EF are set as necessary.

In step 3, the corresponding student positive coefficient Kl is calculated from the engine speed N representing the engine operating state and the basic injection amount (load) Tp.
Search for. This part corresponds to the first learning correction coefficient search means.

Here, the learning correction coefficient KN is determined by dividing the map with the engine speed N on the horizontal axis and the basic injection amount Tp on the vertical axis using a grid of about 8 x 8, dividing the area into areas, and storing each area on the RAM 33. The learning correction coefficient KIl is stored in . therefore,
RAM33 corresponds to learning correction coefficient storage means C.

Note that at the time when learning has not started, the learning correction coefficient K
All l's are set to an initial value of 1.

In step 4, a voltage correction numerator s is set based on the voltage value of the buffer battery 20.

In step 5, it is determined whether the λ control condition is met.

Here, if the conditions are not λ control conditions, such as high rotation, high load, etc., the air-fuel ratio feedback correction coefficient α
With the value clamped to the previous value (or reference value 1), the process proceeds from step 5 to step 10, which will be described later.

In the case of the λ control condition, the output voltage of the 02 sensor 16 is set to ■ in steps 6 to 8. 2 and a slice level voltage V ref corresponding to the stoichiometric air-fuel ratio to determine whether the air-fuel ratio is rich or lean, and the air-fuel ratio feedback correction coefficient α is set by integral control or proportional-integral control. This portion corresponds to air-fuel ratio feedback correction coefficient setting means. Specifically, in the case of integral control, the air-fuel ratio -
When it is determined that the air-fuel ratio is rich (■.2>■□,), the air-fuel ratio feedback correction coefficient α is decreased by a predetermined integral (I) with respect to the previous value in step 7, and conversely, the air-fuel ratio is lean (■.

When it is determined that t<vr*t), in step 8, the feedback correction coefficient α is increased by a predetermined integral (I) with respect to the previous value. In the case of proportional-integral control, in addition to this, at the time of rich-lean reversal, a predetermined proportional amount (P) larger than the integral (1) is increased or decreased in the same direction as the integral (1) (see FIG. 6).

In the next step 9, the learning subroutine shown in FIG. 5 is executed. This will be discussed later.

Thereafter, in step 10, the fuel injection amount Ti is calculated according to the following equation. This part corresponds to the injection amount calculation means.

Ti=Tp-COEF-Kl・α+TsFuel injection amount Ti
When is calculated, a drive pulse signal having a pulse width of Ti is output at a predetermined timing in synchronization with the engine rotation, and is applied to the fuel injection valve 11 via the current waveform control circuit 41 to perform fuel injection. be exposed.

Next, the learning subroutine shown in FIG. 5 will be explained.

In step 11, it is determined whether or not the engine speed N representing the engine operating state and the basic fuel injection amount Tp are in the same range as the previous time. If it is the same area as the previous time, it is determined in step 12 whether flag F is set, and if it is not set, in step 13 the output of the 02 sensor 16 is reversed, that is, the air-fuel ratio feedback correction coefficient α is increased or decreased. It is determined whether the direction has reversed or not, and this flow is repeated and each time the direction is reversed, the count value representing the number of reversals is incremented by 1 in step 14, and when C=2, the process proceeds from step 15 to step 16. Set flag F. This flag F is set when the output of the 02 sensor 16 inverts twice in the same area, as it is assumed that a steady state has been reached. After this flag F is set, if it is determined in step 11 that the area is the same as the previous one, the process proceeds to step 17 via step 12. In steps 11 to 16, it is confirmed that: (1) the engine operating state is in one of the divided regions; (2) the direction of increase/decrease of the air-fuel ratio feedback correction coefficient α is a predetermined number of times (twice);
A steady state is detected when the above reversal occurs.

In a steady state, it is determined in step 17 whether the output of the 0□ sensor 16 has been reversed, that is, the direction of increase/decrease of the air-fuel ratio feedback correction coefficient Therefore, it is determined whether this is the third time in the same region. If it is the third time, in step 19, the deviation Δα(
=α−αI) is temporarily stored as Δα1. After that, 4
When the second reversal is detected, in step 20, the deviation Δα (=α−α1) of the current air-fuel ratio feedback correction coefficient α from the reference value α is temporarily stored as Δα2. As shown in FIG. 6, Δα1 and Δα2 stored at this time are the upper and lower peak values of Δα from the previous (for example, the third) reversal to the current (for example, the fourth) reversal.

These upper and lower peak values Δα8. Deviation Δ based on Δα2
Since one average value of α can be calculated, in step 21, the average value Δα of the deviations Δα is calculated based on the following equation.

Δα; (Δα1+Δα2)/2 Next, in step 22, the current learning correction coefficient is set to 1, the reference value α of the air-fuel ratio feedback correction coefficient α, and
By adding a predetermined percentage of the average value τi of the deviation Δα (=α−αI) from
Ml is calculated, the learning correction coefficient data of the same area is corrected and rewritten, and the learning counter LC of the area is
Increase the count value by 1. The first half of the steering knob 22 corresponds to the first learning correction coefficient retrieval means.

Next, in step 23, the learning correction coefficient KJ is set to have Tp equal to the basic injection amount Tp in the current operating region (N, Tp) searched by the first learning correction coefficient search means, and the count value of the learning counter. LC is the predetermined value LC
,The above is the learning correction coefficient for the driving area of Keio University! , (generally there are a plurality of variables, and the subscript P indicates a variable that varies depending on the area).

Here, the function of determining the learning progress level corresponds to the learning progress level determining means H, and steps 25, 26, 27, 2, which will be described later.
The same applies to the determination function No. 8), and the function of searching for the learning correction coefficient KA corresponds to the second learning correction coefficient search means I.

In step 24, the deviation ΔKl between the learning correction coefficient K l (N) updated in step 22 and the learning correction coefficient KIl□ retrieved in step 23! The function of step 24 to calculate p corresponds to the learning correction coefficient deviation calculation means J.

In step 25, the learning correction coefficient K R (Ml is updated to ensure that the intake air flow rate Q is equal to the operating region, and
A learning correction coefficient KJa+ (subscript Q, like subscript P, is a variable that differs depending on the region) of the driving region where the learning progress is high (LC≧LCo) is searched.

In step 26, in step 23, the learning correction coefficient KlP
The learning correction coefficient KIPQ! for the operating region where the intake air flow rate Q is equal to the operating region for which the search is made and the learning progress is small (L C < L Co). The data is updated with a value obtained by subtracting the deviation ΔKlP calculated in step 24 from the learning correction coefficient in the operating region where the basic injection amount Tp is equal to the operating region βpaz retrieved in step 25 by 1°.

Next, in step 27, the learning correction coefficient Klp is determined for the driving range in which the intake air flow IQ is equal to the driving range in which the learning correction coefficient Klp is searched and the learning progress is large (LC≧LCo). Search for 8.

In step 28, the learning correction coefficient K I! (N), the intake air flow rate Q is the same, and
The data of the learning correction coefficient Kloz for the driving region where the learning progress is small (LC<LCO) is searched in step 29, and Kβ
β2° for the learning correction coefficient in the operating region where the basic injection fiTp is equal to the operating region of o2.

The value obtained by subtracting the deviation ΔKlP is updated.

Here, the functions of step 25 and step 27 correspond to the third learning correction coefficient search means K, and the functions of step 26 and step 28 correspond to the second learning correction coefficient updating means.

The estimation learning from step 23 to step 28 will be explained with reference to FIG.

The learning correction coefficient K of the driving region A that has just been updated
1 (N), and the basic injection amount Tp for this region A+.
The learning correction coefficient KlP of other region B, where is equal to T p+
The deviation ΔKlP is the intake air flow rate Q measured by the air flow meter, since the errors due to deterioration of the fuel injector in these two regions /'z and B+ are equal.

This is thought to be caused mainly by the difference in the measurement error of Q2.

On the other hand, the learning correction coefficient KIQ of another operating region A2 where the intake air flow rate Q1 is equal to the region A1 and the intake air flow ffi Q t is equal to the region layer and the basic injection fJj
, TpfJ<region Bz equal in Tpt to region A1
learning correction coefficient KlP. When compared, the errors due to deterioration of the fuel injector are the same, so the difference in measurement errors of the intake air flows N Q I and Q z is the main factor, similar to the case of A+ and B+. and the same intake airflow t
For Q, since the measurement errors are considered to be almost equal, the learning correction coefficients Kin and Klr between the areas Az and BZ. The deviation ΔKlP is the deviation ΔK between the regions A + and B r
It is estimated that it is almost equal to lp.

Therefore, if one of the areas Az and Bz, for example, area A2, has a large learning progress (the area searched for in step 25), and the other area B2 has a small learning progress (
Kit in step 26. 2), the learning correction coefficient K''PQ of the area B2 is calculated by subtracting the deviation ΔKlP from the learning correction coefficient KIQI of the area At.
Z can be estimated and learned. Also, if the learning progress is reversed,
By adding the deviation ΔK12 (step 28) to the learning correction coefficient Klro+C of the area B2 (searched in step 27), 1°2 can be estimated and learned as the learning correction coefficient of the area A2.

In this way, the learning correction coefficient in the region where the learning progress is small is estimated by taking into account both the measurement error of the intake air flow rate Q by the air flow meter and the error with the basic injection amount Tp due to deterioration of the fuel injector. Since this is done, the reliability of estimation learning is improved, and the accuracy of air-fuel ratio control, especially transient response, can be improved.

In addition, in this example, the learning correction coefficient Klo of the learning progress Keio University
+ or K f p. By reducing or adding the deviation ΔKlP to 1, it becomes a learning correction coefficient for a small learning progress! ! ,.

2 or 1o is estimated to be updated, but step 2
As shown in 2, the learning correction coefficient K l before updating
Learning may also be performed in consideration of 1 pot and K lot.

<Effects of the Invention> As explained above, according to the present invention, when learning by estimation the learning correction coefficient for other areas where the learning progress is small during learning, both the intake air flow rate and the basic injection amount are Since the estimation is performed in consideration of errors, the reliability of the estimation learning can be increased and the accuracy of air-fuel ratio control can be improved as much as possible.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a configuration diagram showing an embodiment of the present invention, FIG. 3 is a block circuit diagram of the control unit in FIG. 2, and FIG. 4 and 5 are flowcharts showing the control details, FIG. 6 is a map for explaining the control details, and FIG. 7 is a control characteristic diagram. 1... Engine 6... Air flow meter 11.
...Fuel injection valve 16...0. Sensor 17...
・Crank angle sensor 30...Control unit Patent applicant Japan Electronics Co., Ltd. Agent Patent attorney Fujio SasashimaFigure 4

Claims (1)

[Claims] Basic injection amount setting means for setting the basic injection amount Tp from the intake air flow rate Q and engine speed N, and an actual injection amount detected based on a signal from an air-fuel ratio detection means provided in the exhaust system. an air-fuel ratio feedback correction coefficient setting means for setting an air-fuel ratio feedback correction coefficient α by integral control by comparing the air-fuel ratio with the stoichiometric air-fuel ratio; learning correction coefficient storage means that can be rewritten for each region; first learning correction coefficient retrieval means for searching the learning correction coefficient Kl of the corresponding region from the learning correction coefficient storage means based on the actual engine operating state; A new learning correction coefficient Kl is set from the fuel ratio feedback correction coefficient and the learning correction coefficient Kl searched by the learning correction coefficient retrieval means, and the learning correction coefficient Kl is used in the same engine operating region of the learning correction coefficient storage means. first learning correction coefficient updating means for updating the data of; injection amount calculation means for calculating the injection amount by multiplying the basic injection amount Tp by the air-fuel ratio feedback correction coefficient α and the learning correction coefficient Kl; and drive pulse signal output means for outputting a drive pulse signal corresponding to the injection amount to the fuel injection valve, the air-fuel ratio learning control device for an internal combustion engine comprising: drive pulse signal output means for outputting a drive pulse signal corresponding to the injection amount to the fuel injection valve; basic injection for the driving region in which the learning correction coefficient Kl is updated by the learning progress determining means for determining the learning progress for each driving region based on the number of data updates; and the first learning correction coefficient updating means. a second learning correction coefficient search means for searching for a learning correction coefficient Kl_p of a driving region in which the amount Tp is equal and the learning progress is determined to be large by the learning progress determining means; and a first learning correction coefficient updating means. The difference ΔKl between the learning correction coefficient Kl_(_N_) updated by and the learning correction coefficient Kl_P searched by the second learning correction coefficient searching means
learning correction coefficient deviation calculating means for calculating _P; and one of the driving range in which the learning correction coefficient Kl is updated and the driving range in which the learning correction coefficient Kl_P is searched by the second learning correction coefficient searching means and the intake air flow rate Q. equally, and
Learning correction coefficient K for the driving region where the learning progress is determined to be high
l_Q_1, Kl_P_Q_1; and a third learning correction coefficient search means for searching for l_Q_1 and Kl_P_Q_1;
When the intake air flow rate Q is equal to the other operating region in which the learning correction coefficient Kl_P is searched by the learning correction coefficient search means,
The data of the learning correction coefficients Kl_Q_2 and Kl_P_Q_2 of the driving region where the learning progress is determined to be small is searched by the learning correction coefficient search means, and the learning correction coefficient Kl_Q_1 of the driving region having the same basic injection amount Tp as that of the driving region is searched.
learning control of an air-fuel ratio of an internal combustion engine, comprising: second learning correction coefficient updating means for updating with a value set based on Kl_P_Q_1 and ΔKl_P calculated by the learning correction coefficient deviation calculation means; Device.