JPH0544554B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an air-fuel ratio learning control device for an automobile internal combustion engine having an electronically controlled fuel injection device with an air-fuel ratio feedback control function. The present invention relates to an air-fuel ratio learning control device that can respond well to density changes.

<Prior art> Conventionally, in an internal combustion engine having an electronically controlled fuel injection device having an air-fuel ratio feedback control function, Japanese Patent Application Laid-Open No. 60-90944 and Japanese Patent Application Laid-Open No. 61-190142 have been disclosed.
An air-fuel ratio learning control device as shown in the above publication is employed.

This is a signal from an O ₂ sensor installed in the engine exhaust system that indicates the basic fuel injection amount, which is calculated from functional operating state parameters related to the amount of air taken into the engine (for example, engine intake air flow rate and engine speed). The standard for the feedback correction coefficient during air-fuel ratio feedback control in systems that calculate the fuel injection amount by correcting it with a feedback correction coefficient set by proportional/integral control based on the air-fuel ratio and feedback control the air-fuel ratio to the target air-fuel ratio The deviation from the value is learned for each predetermined area of the engine operating state to determine a learning correction coefficient, and when calculating the fuel injection amount, the basic fuel injection amount is corrected by the area-specific learning correction coefficient to provide feedback. The base air-fuel ratio obtained from the fuel injection amount calculated without correction by the correction coefficient is made to match the target air-fuel ratio, and during air-fuel ratio feedback control, this is further corrected by the feedback correction coefficient to calculate the fuel injection amount. It is something.

According to this, it is possible to eliminate the follow-up delay of the feedback control during the transient operation during the air-fuel ratio feedback control, and it is possible to accurately obtain the desired air-fuel ratio when the air-fuel ratio feedback control is stopped.

In addition, a system that determines the basic fuel injection amount Tp from the throttle valve opening α and the engine speed N (for example, calculates the intake air flow rate Q from α and N with reference to a map, Tp = K・Q/N (K is a constant)
Alternatively, an air flow meter is used to detect the intake air flow rate Q, and based on this and the engine speed N, the basic fuel injection amount Tp=K・
In systems that calculate Q/N and use a flap type (volume flow rate detection type) air flow meter, changes in air density are not reflected in the calculation of the basic fuel injection amount. For example, as long as learning progresses satisfactorily, changes in air density due to altitude or intake temperature can be accommodated.

<Problems to be Solved by the Invention> However, if we consider the case of suddenly climbing to a high altitude (mountain), we will notice that when driving up a mountain, there is a transient driving pattern, so the method of learning by area of the engine operating state is difficult to learn. The area for learning is not determined, and even if learning is possible, the area is limited, and in the majority of areas, learning hardly progresses. This results in
When you start driving normally on flat ground near the top of a mountain,
Due to the control delay in the air-fuel ratio feedback control, the base air-fuel ratio deviates significantly from the target air-fuel ratio when the air-fuel ratio feedback control is stopped, resulting in poor drivability.

This requires correcting changes in air density by learning from the deviation from the reference value of the feedback correction coefficient during air-fuel ratio feedback control, but some of the learned deviations include Because it includes deviations in the base air-fuel ratio that depend on engine operating conditions due to variations, etc., it is impossible to separate them from air density changes. If you suddenly climb to a high altitude, you will not be able to study each area.
This is because real learning does not progress.

In view of these conventional problems, the present invention provides an air-fuel ratio learning control for an internal combustion engine that can quickly learn air density changes and perform air-fuel ratio learning control well when driving up a mountain. The purpose is to provide equipment.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides a uniform learning supplementary system coefficient for uniformly learning air density changes mainly for altitude correction as a learning correction coefficient; This is divided into area-specific learning correction coefficients for learning parts variations, etc. for each area, and the conditions are such that only the air density changes can be learned, that is, the area where the system does not vary with respect to throttle valve opening changes. , in the region where the intake air flow rate hardly changes due to changes in throttle valve opening at each engine speed (hatched area in Figure 10), the change in air density is uniformly learned and the learning correction coefficient is uniformly rewritten. , in other areas, parts variations and the like are learned for each area and the learning correction coefficient for each area is rewritten.

Therefore, the air-fuel ratio learning control device according to the present invention is configured to include the following means A to L, as shown in FIG.

(A) An engine operating state detection means that detects the engine operating state including at least parameters related to the amount of air taken into the engine. (B) An air detector that detects engine exhaust components and thereby detects the air-fuel ratio of the engine intake mixture. Fuel ratio detection means (C) Basic fuel injection amount setting means for setting the basic fuel injection amount based on the parameters detected by the engine operating state detection means (D) Setting the basic fuel injection amount for all areas of the engine operating state. A rewritable uniform learning correction coefficient storage means (E) that stores a uniform learning correction coefficient for uniform correction.A rewritable uniform learning correction coefficient storage means (E) stores a learning correction coefficient for each area for correcting the basic fuel injection amount for each area of the engine operating state. Rewritable area-based learning correction coefficient storage means (F) Area-based learning correction for searching the area-based learning correction coefficient of the area of the corresponding engine operating state from the area-based learning correction coefficient storage means based on the actual engine operating state. Coefficient search means (G) A feedback correction coefficient for comparing the air-fuel ratio detected by the air-fuel ratio detection means with a target air-fuel ratio and correcting the basic fuel injection amount so as to bring the actual air-fuel ratio closer to the target air-fuel ratio. Feedback correction coefficient setting means (H) for increasing or decreasing by a predetermined amount the basic fuel injection amount set by the basic fuel injection amount setting means, the uniform learning correction coefficient stored in the uniform learning correction coefficient storage means, Fuel injection amount calculation means (I) for calculating the fuel injection amount based on the area-specific learning correction coefficient searched by the area-specific learning correction coefficient search means and the feedback correction coefficient set by the feedback correction coefficient setting means; Fuel injection means (J) that injects fuel into the engine on and off in response to a drive pulse signal corresponding to the fuel injection amount calculated by the calculation means. Uniform learning area detection means (K) for detecting a predetermined area in which a change in intake air flow rate is less than a predetermined ratio with respect to a change in throttle valve opening at each engine speed; uniform learning correction coefficient correction for learning the deviation of the feedback correction coefficient from a reference value and correcting and rewriting the uniform learning correction coefficient of the uniform learning correction coefficient storage means in a direction to reduce the deviation when a certain thing is detected; Means (L) When the uniform learning area detection means does not detect that the area is in the predetermined area, the deviation from the reference value of the feedback correction coefficient is learned for each area of the engine operating state, and the deviation from the reference value is reduced. Area-specific learning correction coefficient correction means for correcting and rewriting the area-specific learning correction coefficient in the area-specific learning correction coefficient storage means <Operation> The basic fuel injection amount setting means C sets the basic fuel injection amount corresponding to the target air-fuel ratio to the engine. The area-specific learning correction coefficient detection means F detects the area-specific learning correction coefficient of the area corresponding to the actual engine operating state from the area-specific learning correction coefficient storage means E. The feedback correction coefficient setting means G compares the actual air-fuel ratio with the target air-fuel ratio and sets the feedback correction coefficient based on, for example, proportional/integral control so as to bring the actual air-fuel ratio closer to the target air-fuel ratio. Set by increasing or decreasing the amount. Then, the fuel injection amount calculation means H is
By correcting the basic fuel injection amount with the uniform learning supplementary coefficient stored in the uniform learning correction coefficient storage means D, correcting it with the area-specific learning correction coefficient, and further correcting it with the feedback correction coefficient, the fuel injection amount can be adjusted. calculate. Then, the fuel injection means I is actuated by a drive pulse signal corresponding to this fuel injection amount.

On the other hand, the uniform learning area detecting means J detects a predetermined value at which the intake air flow rate does not substantially change with respect to a change in throttle valve opening at each engine speed above a comparative throttle valve opening predetermined according to the engine speed. If it is in the predetermined area, the uniform learning correction coefficient correction means K learns the deviation of the feedback correction coefficient from the reference value, and performs uniform learning in the direction of decreasing this. The correction coefficients are corrected and the data in the learning correction coefficient storage means D is uniformly rewritten. In this way, under the condition that only the air density change can be learned, that is, the intake air flow rate in response to the throttle valve opening change at each engine speed is a region where there is no variation in the system with respect to the throttle valve opening change. In the region where it is almost desired to change (the hatched part in FIG. 10), the air density change is given priority and learned uniformly. Although this region is not free from component variations, it is a high throttle valve opening range, and compared to a low opening range, the main component variation is the fuel injector pulse width - injection flow rate. Variations in characteristics and intake air amount characteristics relative to throttle valve opening are extremely small, and can be absorbed and learned based on air density.

If the area is outside the predetermined area, the area-specific learning correction coefficient correction means L learns the deviation of the feedback correction coefficient from the reference value for each area of the engine operating state, and adjusts the area of the functional operating state in a direction to decrease this deviation. The area-by-area learning correction coefficient corresponding to the area-by-area learning correction coefficient is corrected and the data in the area-by-area learning correction coefficient storage means E is rewritten. In this way, parts variations and the like are learned for each area.

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

In Figure 2, the engine 1 includes an air cleaner 2,
Air is drawn in via the throttle body 3 and intake manifold 4.

A throttle valve 5 that operates in conjunction with an accelerator pedal (not shown) is provided within the throttle body 3, and a fuel injection valve 6 serving as fuel injection means is provided upstream of the throttle valve 5. The fuel injection valve 6 is an electromagnetic fuel injection valve that opens when a solenoid is energized, and closes when the energization is stopped.The fuel injection valve 6 opens when energized by a drive pulse signal from a control unit 14 (not shown), which will be described later. Fuel is injected and supplied from the fuel pump and adjusted to a predetermined pressure by the pressure regulator. Although this example is a single-point injection system, it may be a multi-point injection system in which a fuel injection valve is provided for each cylinder in a branch of an intake manifold or in an intake port of an engine.

An ignition plug 7 is provided in the combustion chamber of the engine 1. A high voltage generated by an ignition coil 8 is applied to the ignition plug 7 via a distributor 9 based on an ignition signal from a control unit 14, thereby igniting a spark to ignite and burn the air-fuel mixture.

Exhaust gas is exhausted from the engine 1 via an exhaust manifold 10, an exhaust duct 11, a three-way catalyst 12, and a muffler 13.

The controller unit 14 includes a CPU, ROM,
Equipped with a microcomputer that includes RAM, an A/D converter, and an input/output interface, it receives input signals from various sensors, processes them as described later, and controls the fuel injection valve 6 and ignition coil 8. Control operation.

As the various sensors mentioned above, a potentiometer-type throttle sensor 15 is provided on the throttle valve 5, and outputs a voltage signal corresponding to the opening degree α of the throttle valve 5. Also provided within the throttle sensor 15 is an idle switch 16 that is turned on when the throttle valve 5 is in the fully closed position.

Further, a crank angle sensor 17 is provided built into the distributor 9 to detect the crank angle.
Position signals every 2 degrees and every 180 degrees of crank angle (4
outputs a reference signal (in the case of a cylinder).
Here, the engine rotation speed N can be calculated by measuring the number of pulses of the position signal or the cycle of the reference signal per unit time.

Further, a water temperature sensor 18 that detects the engine cooling water temperature Tw, a vehicle speed sensor 19 that detects the vehicle speed VSP, and the like are provided.

These throttle sensor 15, crank angle sensor 17, etc. are means for detecting the engine operating state.

In addition, an O ₂ sensor 20 is installed in the exhaust manifold 10.
is provided. This O ₂ sensor 20 is a known sensor whose electromotive force suddenly changes when the air-fuel mixture is combusted near the stoichiometric air-fuel ratio, which is the target air-fuel ratio. Therefore, the O ₂ sensor 20 detects the air-fuel ratio (rich).
lean) detection means.

Furthermore, the control unit 14 is equipped with a battery 2 as its operating power source and for detecting the power supply voltage.
1 is connected via an engine key switch 22. In addition, in the control unit 14
As the operating power source for the RAM, a battery 21 is connected via a suitable stabilized power source without using the engine key switch 22 in order to retain the memory contents even after the engine key switch 22 is turned off.

Here, the CPU of the microcomputer built in the control unit 14 is
The program on the ROM (fuel injection amount calculation routine, feedback control zone determination routine, proportional/integral control routine, K _ALT learning subroutine, K _MAP learning subroutine, initialization routine) shown in the flowcharts in Figs. It then performs arithmetic processing and controls fuel injection.

In addition, as a basic fuel injection amount setting means, an area-based learning correction coefficient search means, a feedback correction coefficient setting means, a fuel injection amount calculation means, a uniform learning area detection means, a uniform learning correction coefficient correction means, and an area-specific learning correction coefficient correction means. The functions are accomplished by said program. In addition, as a uniform learning correction coefficient storage means and an area-based learning correction coefficient storage means,
Use RAM.

Next, the arithmetic processing of the microcomputer in the control unit 14 will be explained with reference to the flowcharts shown in FIGS. 3 to 9.

In the fuel injection amount calculation routine shown in FIG. The engine speed N calculated based on the signal from the engine is read.

In step 2, the intake air flow rate Q corresponding to the throttle valve opening α and the engine speed N is determined in advance through experiments, etc., and is referred to a stored map in the ROM to search for Q corresponding to the actual α and N. and load it.

In step 3, a basic fuel injection amount Tp=K·Q/N (K is a constant) corresponding to the amount of intake air per unit rotation is calculated from the intake air flow rate Q and the engine speed N. Here, steps 1 to 3 correspond to basic fuel injection amount setting means.

In step 4, the rate of change in the throttle valve opening α detected based on the signal from the throttle sensor 15 or from the ON of the idle switch 16 is determined.
Acceleration correction coefficient due to switching to OFF, water temperature correction coefficient according to the engine cooling water temperature Tw detected based on the signal from the water temperature sensor 18, engine rotation speed N
Various correction coefficients COEF including a mixture ratio correction coefficient and the like are set according to the basic fuel injection amount (load) Tp and the basic fuel injection amount (load) Tp.

At step 5, the uniform learning correction coefficient _KALT stored at a predetermined address in the RAM serving as uniform learning correction coefficient storage means is read. Note that the uniform learning correction coefficient _KALT is stored as an initial value of 0 at the time when learning has not started, and this is read.

In step 6, the area-specific learning correction coefficient _KMAP is stored in the RAM as an area-specific learning correction coefficient storage means corresponding to the engine speed N representing the engine operating state and the basic fuel injection amount (load) Tp. Refer to the map and find the K _MAP corresponding to the actual N, Tp.
Search and load. This part corresponds to the area-specific learning correction coefficient search means. The map of the area-specific learning correction coefficient K _MAP divides the areas of the engine operating state into grids of about 8 x 8, with the horizontal axis representing the engine speed N and the vertical axis representing the basic fuel injection amount Tp. Area-specific learning correction coefficients K _MAP are stored, and all initial values are stored as 0 when learning has not started.

In step 7, the feedback correction coefficient LAMBOA set by the proportional/integral control routine shown in FIG. 5, which will be described later, is read. Note that the reference value of this feedback correction coefficient LAMBOA is 1.

In step 8, a voltage correction amount Ts is set based on the voltage value of the battery 21. This is to correct changes in the injection flow rate of the fuel injection valve due to changes in battery voltage.

In step 9, the fuel injection amount Ti is calculated according to the following equation. This part corresponds to the fuel injection amount calculation means.

Ti=Tp・COEF・(LAMBDA +K _ALT +K _MAD ) +Ts In step 10, the calculated Ti is set in the output register. As a result, at a predetermined fuel injection timing synchronized with the engine rotation (for example, every 1/2 rotation), a drive pulse signal having a pulse width of Ti is applied to the fuel injection valve 6, and fuel injection is performed.

FIG. 4 shows a feedback control zone determination routine, which basically performs air-fuel ratio feedback control when the rotation is low and the load is low, and stops the air-fuel ratio feedback control when the rotation is high or the load is high.

In step 21, a comparison Tp is searched from the engine speed N, and in step 22, the actual basic fuel injection amount Tp is searched.
(actual Tp) and comparison Tp are compared.

If actual Tp≦comparison Tp, that is, if the rotation is low and the load is low, proceed to step 23 to reset the delay timer (which is counted up by the clock signal), then proceed to step 26 to set λcont.
Set flag to 1. This is to perform air-fuel ratio feedback control when the engine speed is low and the load is low.

If actual Tp>comparison Tp, that is, if the rotation is high or the load is high, the process proceeds to step 27 and the λcont flag is set to 0. This is to stop the air-fuel ratio feedback control, separately obtain a rich output air-fuel ratio, control the rise in exhaust temperature, and prevent the engine 1 from seizing and the catalyst 12 from burning out.

Here, even in the case of high rotation or high load,
By comparing the value of the delay timer with a predetermined value in step 24, after shifting to high rotation or high load, until a predetermined time (for example, 10 seconds) has elapsed,
Proceeding to step 26, the λcont flag is continued to be set to 1, and air-fuel ratio feedback control is continued. This is to increase the opportunity to learn about the uniform learning correction coefficient K _ALT since mountain climbing is performed in a high load area.

However, if the engine speed N exceeds a predetermined value (for example, 3800 rpm) as determined in step 25, or if this exceeding condition continues for a predetermined period of time, the air-fuel ratio feedback control is stopped for safety reasons.

FIG. 5 shows a proportional/integral control routine, which is executed at predetermined intervals (for example, 10 ms), thereby establishing a feedback correction coefficient LAMBDA. Therefore, this routine corresponds to feedback correction coefficient setting means.

In step 31, the value of the λcont flag is determined and set to 0.
If so, this routine ends. in this case,
The feedback correction coefficient LAMBDA is clamped to the previous value (or reference value 1), and the air-fuel ratio feedback control is stopped.

If the λcont flag is 1, proceed to step 32 and read the output voltage V ₀₂ of the O ₂ sensor 20, and in the next step 33, calculate the slice level voltage corresponding to the stoichiometric air-fuel ratio.
Determine whether the air-fuel ratio is rich or lean by comparing it with V _ref . When the air-fuel ratio is lean (V ₀₂ < V _ref ), proceed from step 33 to step 34, and at the time of reversal from rich to lean (immediately after reversal). Determine whether there is
When inverted, the process proceeds to step 35, where the feedback correction coefficient LAMBDA is increased by a predetermined proportionality constant P relative to the previous value. Otherwise, the process proceeds to step 36, where the feedback correction coefficient LAMBDA is increased by a predetermined integral constant of 1 minute relative to the previous value, and thus the feedback correction coefficient LAMBDA is increased at a constant slope. Note that P>>I.

When the air-fuel ratio is rich (V ₀₂ >V _ref ), the process proceeds from step 33 to step 37, where it is determined whether or not it is the time of reversal from lean to rich (immediately after the reversal).
At the time of reversal, the process proceeds to step 38, where the feedback correction coefficient LAMBDA is decreased by a predetermined proportionality constant P from the previous value. Otherwise, the process proceeds to step 39, where the feedback correction coefficient LAMBDA is decreased by a predetermined integral constant of 1 minute from the previous value, and thus the feedback correction coefficient LAMBDA is decreased at a constant slope.

FIG. 6 shows a learning routine, FIG. 7 shows a K _ALT learning subroutine, and FIG. 8 shows a K _MAP learning subroutine.

In step 41 of FIG. 6, the value of the λcont flag is determined, and if it is 0, the routine proceeds to step 42, where the count values C _ALT and C _MAP are cleared, and then this routine ends. This is because learning cannot be performed when air-fuel ratio feedback control is stopped.

When the λcont flag is 1, that is, during air-fuel ratio feedback control, the process proceeds to step 43 and subsequent steps to learn about the uniform learning correction coefficient _KALT (hereinafter referred to as _KALT) .
(hereinafter referred to as "K MAP learning") and learning about the area-specific learning correction coefficient K _MAP (hereinafter referred to as "K _MAP learning").

In other words, K _ALT learning is performed in a predetermined high load region (hereinafter referred to as Q Since K _MAP learning is performed in other areas, the comparison _α1 is searched from the engine speed N in step 43, and the actual throttle valve opening α (actual α) is searched in step 44. Compare with α ₁ .
These steps 43 and 44 correspond to uniform learning area detection means.

As a result of comparison, actual α≧comparison α ₁ (Q flat region)
In this case, as a general rule, proceed to steps 48 and 49.
After clearing the count value C _MAP , K _ALT in Figure 7
Execute the learning subroutine.

However, in the case of a single-point injection system, in the region where the throttle valve opening is extremely large, the intake flow velocity becomes slow and the distribution to each cylinder deteriorates. Assign this to prohibit K _ALT learning at throttle valve openings greater than that. Therefore, in step 45, a comparison α ₂ is searched from the engine speed N, and in a step 46, the actual α and the comparison α ₂ are compared.
If actual α > comparison α ₂ , proceed to steps 50 and 51, clear the count value _CALT , and then proceed as shown in Figure 8.
K Move to _MAP learning subroutine.

In addition, in the case of a single point injection system, the distance from the fuel injection valve 6 to the combustion chamber of the engine 1 is long, and during rapid acceleration, due to the influence of wall flow variables,
Accurate K _ALT learning is not possible, so when accelerating suddenly, wait for a predetermined time, that is, until the wall flow becomes steady.
K _ALT study. Therefore, it is determined in step 47 whether a predetermined time has elapsed after acceleration, and if it has not, the process proceeds to steps 50 and 51, and after clearing the count value C _ALT , the K _MAP shown in Figure 8 is executed. Move to learning subroutine.

If the determination at step 44 is that actual α<comparison α ₁ , the process proceeds to steps 50 and 51, and after clearing the count value _CALT , the process proceeds to the _KMAP learning subroutine shown in FIG.

Next, the _KALT learning subroutine shown in FIG. 7 will be explained. This _KALT learning subroutine corresponds to a uniform learning correction coefficient correction means.

In step 61, it is determined whether the output of the O ₂ sensor 20 has been reversed, that is, the direction of increase/decrease of the feedback correction coefficient LAMBDA has been reversed, and when this subroutine is repeated and reversed, the count value _CALT representing the number of reversals is set to 1 in step 62. For example C _ALT
-3, step 63 to step 64
Go to the current feedback correction factor
Deviation of LAMBDA from reference value 1 (LAMBDA−
Temporarily store 1) as ΔLAMBDA ₁ and start learning.

When C _ALT =4 or more, the process proceeds from step 63 to step 64, where the deviation (LAMBDA-1) of the feedback correction coefficient LAMBDA from the reference value 1 at that time is temporarily stored as ΔLAMBDA ₂ . ΔLAMBDA ₁ and ΔLAMBDA ₂ stored at this time are the deviations from the reference value 1 of the feedback correction coefficient LAMBDA from the previous (e.g., third) reversal to the current (e.g., fourth) reversal, as shown in FIG. These are the upper and lower peak values of .

In this way, the feedback correction coefficient
Once the upper and lower peak values ΔLAMBDA ₁ and ΔLAMBDA ₂ of deviation from the standard value 1 of LAMBDA are determined, the process proceeds to step 66 to find their average value (see the following equation).

= (ΔLAMBDA ₁ +
ΔLAMBDA ₂ )/2 Next, the process advances to step 67 and the current uniform learning correction coefficient K _ALT stored at a predetermined address in the RAM is
(Initial value 0) is read.

Next, the process proceeds to step 68, and a new uniform learning correction coefficient K _ALT is calculated by adding a predetermined percentage of the average value of the deviation from the reference value of the feedback correction coefficient to the current uniform learning correction coefficient K _ALT according to the following formula. is calculated, and the uniform learning correction coefficient data at a predetermined address in the RAM is corrected and rewritten.

K _ALT ← K _ALT + M _ALT (M _ALT is an addition ratio constant, 0<M _ALT <1) After this, in step 69, ΔLAMBDA ₂ is substituted into ΔLAMBDA ₁ for the next learning.

Then, at step 70, increase the K _ALT learning count to 1.
rise. This K _ALT learning count is set to 0 by the initialization routine shown in FIG. 9, which is executed when the engine key switch 22 (or start switch) is turned on. I am counting the number of times I have learned K _ALT since then.

Next, the K _MAP learning subroutine shown in FIG. 8 will be explained. This K _MAP learning subroutine corresponds to area-specific learning correction coefficient correction means.

In step 81, it is determined whether the engine speed N, which represents the engine operating state, and the basic fuel injection amount Tp are in the same area as last time, and if the area has changed,
After proceeding to step 82 and clearing the count value _CMAP , this subroutine ends.

If it is the same area as last time, turn O ₂ in step 83.
It is determined whether the output of the sensor 20 has been reversed, that is, the direction of increase or decrease of the feedback correction coefficient LAMBDA has been reversed, and each time this subroutine is repeated and the output is reversed, a count value representing the number of times of reversal is set in step 84.
When C _MAP is increased by 1 and C _MAP = 3, for example, the process proceeds from step 85 to step 86, and the deviation (LAMBDA - 1) of the current feedback correction coefficient LAMBDA from the reference value 1 is temporarily stored as ΔLAMBDA ₁ . and start learning.

When C _MAP =4 or more, the process proceeds from step 85 to step 87, where the deviation (LAMBDA-1) of the feedback correction coefficient LAMBDA from the reference value 1 at that time is temporarily stored as ΔLAMBDA ₂ .

In this way, the feedback correction coefficient
Once the upper and lower peak values ΔLAMBDA ₁ and ΔLAMBDA ₂ of the LAMBDA deviation from the reference value 1 have been determined, the process proceeds to step 88 and their average value is determined.

Next, the process proceeds to step 89, where the area-specific learning supplement coefficient K _MAP (initial value 0) stored in the map on the RAM corresponding to the current area is retrieved and read out.

Next, proceed to step 90 to compare the value of the _KALT learning counter with a predetermined value, and if it is less than the predetermined value, then proceed to step 91 to set the addition ratio constant (weighting constant) M _MAP to 0.
Set to a relatively small value M ₀ containing . Also,
If the value is greater than the predetermined value, the addition ratio constant (weighting constant) M _MAP is set to a relatively large value M ₁ (where M ₁ << M _ALT ) in step 92.

Next, proceed to step 93, and add a predetermined percentage of the average value of the deviation from the reference value of the feedback correction coefficient to the current area-specific learning correction coefficient K _MAR according to the following formula to create a new area-specific learning correction coefficient. K _MAP is calculated, and the area-specific learning correction coefficient data for the same area of the map on RAM is corrected and rewritten.

K _MAR ←K _MAP +M _MAP・After this, in step 94, ΔLAMBDA ₂ is substituted into ΔLAMBDA ₁ for the next learning.

Regarding the addition rate constant (weighting constant) mentioned above, the reason for setting M _ALT >> M _MAP is to proceed with K _ALT learning related to air density changes first, and then perform K _MAP learning for each area. . Furthermore, changing the M _MAP value according to the number of times K _ALT learning is performed after the engine key switch 22 (or start switch) is turned on suppresses the progress of K _MRF learning until K _ALT learning is experienced, and prevents extreme If M _MAR = 0,
This is to prohibit K _MAP learning.

<Effects of the Invention> As explained above, according to the present invention, since air density changes are learned with uniform priority in the Q flat region, air density changes can be learned at high speed, such as when climbing a steep mountain. However, the effect of enabling good air-fuel ratio learning control can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing the configuration of the present invention.
Fig. 2 is a system diagram showing an embodiment of the present invention, Figs. 3 to 9 are flowcharts showing the contents of calculation processing, Fig. 10 is a diagram showing the learning area for uniform learning correction coefficients, Fig. 11 FIG. 2 is a diagram showing how the feedback correction coefficient changes. 1... Engine, 5... Throttle valve, 6... Fuel injection valve, 14... Control unit, 15...
... Throttle sensor, 17... Crank angle sensor, 20... O ₂ sensor.

Claims (1)

[Scope of Claims] 1. Engine operating state detection means for detecting an engine operating state including at least a parameter related to the amount of air taken into the engine; an air-fuel ratio detection means for detecting; a basic fuel injection amount setting means for setting a basic fuel injection amount based on the parameter detected by the engine operating state detection means; and a basic fuel injection amount setting means for setting the basic fuel injection amount for all areas of the engine operating state. a rewritable uniform learning correction coefficient storage means that stores a uniform learning correction coefficient for uniformly correcting the amount of fuel; and a learning correction coefficient for each area for correcting the basic fuel injection amount for each area of the engine operating state. a rewritable area-specific learning correction coefficient storage means; and an area-specific learning correction coefficient for retrieving an area-specific learning complement coefficient of an area in a corresponding engine operating state from the area-specific learning correction coefficient storage means based on the actual engine operating state. a search means; and a predetermined feedback correction coefficient for comparing the air-fuel ratio detected by the air-fuel ratio detection means with a target air-fuel ratio and correcting the basic fuel injection amount so as to bring the actual air-fuel ratio closer to the target air-fuel ratio. a feedback correction coefficient setting means for increasing or decreasing the amount of the basic fuel injection amount set by the basic fuel injection amount setting means, the uniform learning correction coefficient stored in the uniform learning correction coefficient storage means, and the area-specific learning. a fuel injection amount calculation means for calculating a fuel injection amount based on the area-based learning correction coefficient searched by the correction coefficient search means and the feedback correction coefficient set by the feedback correction coefficient setting means; a fuel injection means that injects fuel into the engine on and off in response to a drive pulse signal corresponding to a fuel injection amount corresponding to the fuel injection amount; uniform learning region detection means for detecting a predetermined region in which a change in intake air flow rate is equal to or less than a predetermined ratio with respect to a change in the opening degree of the throttle valve; uniform learning correction coefficient correction means for correcting and rewriting the uniform learning correction coefficient of the uniform learning correction coefficient storage means in a direction to learn and reduce the deviation of the feedback correction coefficient from the reference value; When the region detecting means does not detect that the area is in the predetermined region, the area-specific learning correction coefficient storage means learns the deviation of the feedback correction coefficient from the reference value for each area of the engine operating state, and decreases the deviation from the reference value. An air-fuel ratio learning control device for an internal combustion engine, comprising: area-specific learning correction coefficient correction means for correcting and rewriting the area-specific learning correction coefficient;