JPH0515552Y2 - - Google Patents

Description

[Detailed description of the invention] <Field of industrial application> The present invention relates to an air-fuel ratio learning control device for an automobile internal combustion engine that has 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, there have been disclosed Japanese Patent Application Laid-Open No. 60-90944 and Japanese Patent Application Laid-open No. 61-190142.
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 engine 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 learning correction coefficient and the feedback correction coefficient is calculated. The base air-fuel ratio obtained from the fuel injection amount calculated without correction by be.

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> By the way, the premise of learning is that air-fuel ratio feedback control is being performed, but conventionally, air-fuel ratio feedback control has been performed as an air-fuel ratio feedback control area as shown in Fig. 12. This is done only in the set low rotation and low load range. This is because if feedback control is performed to the stoichiometric air-fuel ratio, which is the target air-fuel ratio, in a high rotation or high load region, there is a risk of engine seizure or catalyst burnout due to a rise in exhaust temperature. This is to clamp the engine and obtain a rich output air-fuel ratio to prevent engine seizure.

Therefore, when climbing from a lowland to a highland (mountain), in addition to operating mainly in a high load region, the air pressure is lower at the same throttle valve opening, so the apparent amount of air is lower compared to a lowland. The basic fuel injection amount Tp set for the air amount increases,
Moreover, in order to maintain the same power performance as at low altitudes, it is necessary to press the accelerator pedal and increase the throttle valve opening to increase the amount of air, which further increases the basic fuel injection amount Tp, as shown in Figure 12. It goes out of the fuel ratio feedback control area. For this reason, the higher the altitude, the narrower the air-fuel ratio feedback control area becomes, resulting in a problem in that the rate at which air-fuel ratio feedback control is performed is extremely reduced, reducing the chance of learning.

In view of these conventional problems, the present invention has been developed to develop an air-fuel ratio for an internal combustion engine that can maintain a sufficient learning function by ensuring an appropriate air-fuel ratio feedback control area even when the air density changes. The purpose is to provide a learning control device.

<Means for solving the problem> In order to achieve the above objectives, the present invention uniformly learns the air density changes for all areas of the engine operating state and determines a uniform learning correction coefficient. Based on the rotational speed and basic fuel injection amount corrected by a uniform learning correction coefficient, the air-fuel ratio feedback control area, which is a low rotation and low load area, is detected and an air-fuel ratio feedback control command is output. It is.

Therefore, the air-fuel ratio learning control device according to the present invention, as shown in FIG. 1, includes the following means A to J.

(A) 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) Detects engine exhaust components and thereby detects the air-fuel ratio of the engine intake mixture. air-fuel ratio detection means (C); basic fuel injection amount setting means (D) for setting a basic fuel injection amount based on the parameters detected by the engine operating state detection means; and (D) for uniformly correcting the basic fuel injection amount. A rewritable uniform learning correction coefficient storage means (E) that stores a uniform learning correction coefficient; a uniform learning correction coefficient stored in the uniform learning correction coefficient storage means that stores the basic fuel injection amount set by the basic fuel injection amount setting means; basic fuel injection amount correction means (F) for correcting the engine speed in the low rotation and low load region based on the engine speed detected by the engine operating state detection means and the basic fuel injection amount corrected by the basic fuel injection amount correction means; an air-fuel ratio feedback control region detection means (G) for detecting an air-fuel ratio feedback control region and outputting an air-fuel ratio feedback control command; feedback correction coefficient setting means (H) for increasing or decreasing by a predetermined amount a feedback correction coefficient for correcting the basic fuel injection amount so that the actual air-fuel ratio approaches the target air-fuel ratio by comparing the actual air-fuel ratio with the target air-fuel ratio; Fuel injection is performed based on 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 feedback correction coefficient set by the feedback correction coefficient setting means. a fuel injection amount calculation means (I) for calculating the fuel injection amount; a fuel injection means (J) for injecting fuel into the engine on and off in response to a drive pulse signal corresponding to the fuel injection amount calculated by the fuel injection amount calculation means; Uniform learning correction coefficient correction for correcting and rewriting the uniform learning correction coefficient of the uniform learning correction coefficient storage means in the direction of learning and decreasing the deviation of the feedback correction coefficient from the reference value while outputting the fuel ratio feedback control command. Means (Function) The basic fuel injection amount setting means C sets the basic fuel injection amount corresponding to the target air-fuel ratio based on parameters related to the amount of air taken into the engine, While the air-fuel ratio feedback control command is being output, the feedback correction coefficient setting means G compares the actual air-fuel ratio with the target air-fuel ratio and performs, for example, proportional/integral control on the feedback correction coefficient so as to bring the actual air-fuel ratio closer to the target air-fuel ratio. Set by increasing/decreasing a predetermined amount based on. Then, the fuel injection amount calculation means H calculates the fuel injection amount by correcting the basic fuel injection amount with the uniform learning correction coefficient stored in the uniform learning correction coefficient storage means D, and further correcting it with the feedback correction coefficient. do. Then, the fuel injection means I is actuated by a drive pulse signal corresponding to this fuel injection amount.

During output of an air-fuel ratio feedback control command by the air-fuel ratio feedback control region detecting means F, the uniform learning correction coefficient modifying means J learns the deviation of the feedback correction coefficient from a reference value under predetermined conditions, modifies the uniform learning correction coefficient in a direction to reduce this deviation, and rewrites the data in the uniform learning correction coefficient storing means D.

Here, the air-fuel ratio feedback control region detecting means F detects an air-fuel ratio feedback control region that is a low rotation and low load region based on the engine speed and the basic fuel injection amount, and outputs an air-fuel ratio feedback control command. However, as the basic fuel injection amount for detecting the control region, the basic fuel injection amount corrected by the basic fuel injection amount correction means E using a uniform learning correction coefficient is used. As a result, even at high altitudes, the air-fuel ratio feedback control area is not narrowed and is properly secured.

<Example> An example of the present invention will be described below. In this example, the learning correction coefficient is mainly used for altitude correction, and a uniform learning correction coefficient _KALT is used to uniformly learn air density changes, and a uniform learning correction coefficient KALT is used to uniformly learn changes in air density. The area-based learning correction coefficient K _MAP is divided into two parts and is configured to be learned separately.

In FIG. 2, the engine 1 includes an air cleaner 2, a throttle body 3, and an intake manifold 4.
Air is inhaled through.

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 control 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 according 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
Programs on the ROM shown as flowcharts in Figures to Figure 9 (fuel injection amount calculation routine, feedback control zone determination routine, proportional/integral control routine, learning routine, _KALT learning subroutine, _KMAP learning subroutine, initialization routine) ) to control fuel injection.

The functions of the basic fuel injection amount setting means, the basic fuel injection amount correction means, the air-fuel ratio feedback control region detection means, the feedback correction coefficient setting means, the fuel injection amount calculation means, and the uniform learning correction coefficient correction means are performed by the above program. achieved. In addition, RAM is used as a uniform learning correction coefficient storage means.
Use.

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, the intake air flow rate Q and engine speed N
The basic fuel injection amount Tp=K·Q/N (K is a constant) corresponding to the intake air amount per unit rotation is calculated from. 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 such as a mixture ratio correction coefficient COEF are set according to the basic fuel injection amount (load) Tp and the basic fuel injection amount (load) Tp.

In 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 RAM is stored in which area-specific learning correction coefficients K _MAP are stored corresponding to the engine rotation speed N that represents the engine operating state and the basic fuel injection amount (load) Tp.
Refer to the map above and correspond to the actual N and Tp.
Search and load K _MAP . 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. Learning correction coefficients K _MAP for each area are stored, and all initial values 0 are stored when learning has not started.

In step 7, the feedback correction coefficient LAMBDA 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 LAMBDA 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 _MAP )
+Ts In step 10, the calculated Ti is set in the output register. As a result, at a predetermined fuel injection timing synchronized with 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.

Next, in step 22, the actual basic fuel injection amount Tp (actual Tp) is uniformly corrected by the learning correction coefficient _KALT according to the following equation to obtain a correction Tp. This portion corresponds to the basic fuel injection amount correction means. Note that at high altitudes, the learning correction coefficient K _ALT is a negative value, so the correction Tp becomes smaller than the actual Tp.

Correction Tp=Actual Tp・(1+ _KALT ) Next, in step 23, the correction Tp and the comparison Tp are compared.

If correction Tp≦comparison Tp, that is, if the rotation is low and the load is low, proceed to step 24 and reset the delay timer (counted up by the clock signal), then proceed to step 27 and set the λcont flag to 1. do. This is to perform air-fuel ratio feedback control when the engine speed is low and the load is low. Therefore, step 21,
Portions 23 and 27 correspond to air-fuel ratio feedback control area detection means that detects an air-fuel ratio feedback control area that is a low rotation and low load area and outputs an air-fuel ratio feedback control command.

If correction Tp>comparison Tp, that is, if the rotation is high or the load is high, the process proceeds to step 28 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, suppress 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 25, after shifting to high rotation or high load, until a predetermined time (for example, 10 seconds) has elapsed,
Proceeding to step 27, 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 changes in air density since mountain climbing is mainly done in high load areas.

However, if the engine speed N exceeds a predetermined value (for example, 3800 rpm) as determined in step 26, 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 setting the 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.

When the λcont flag is 1, that is, while the air-fuel ratio feedback control command is being output, the process advances to step 32 to read the output voltage V _p2 of the O ₂ sensor 20, and in the next step 33, the slice level voltage V _ref corresponding to the stoichiometric air-fuel ratio is determined. The rich/lean air-fuel ratio is determined by comparing with

When the air-fuel ratio is lean (V _p2 <V _ref ), the process proceeds from step 33 to step 34, where it is determined whether or not it is the time of reversal from rich to lean (immediately after reversal).
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 I with respect 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 _p2 > 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 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 I 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.

If the λcont flag is 1, that is, while the air-fuel ratio feedback control command is being output, proceed to step 43 and onwards to learn about the uniform learning correction coefficient _KALT (hereinafter referred to as _KALT learning) and the area-specific learning correction coefficient.
Switching between learning about K _MAP (hereinafter referred to as K _MAP learning).

In other words, K _ALT learning learns only the change in air density, so the system is in an area where there is no variation in the opening degree of the throttle valve 5, as shown by hatching in Fig. 10. K MAP learning is performed preferentially in a predetermined region (hereinafter referred to as the "Q flat region") where the intake air flow rate Q hardly changes with changes in the throttle valve opening α at engine speed N, and K _MAP learning is performed in other regions. , in step 43, a comparison α ₁ is searched from the engine speed N,
In step 44, the actual throttle valve opening α (actual α)
Compare with α ₁ .

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 sudden acceleration, the wall flow of fuel causes
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 learning shown in Figure 8 is performed. Move to subroutine.

If the judgment at step 44 is that actual α<comparison _α1 , 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 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, a count value _CALT representing the number of times of reversal is determined in step 62. 1 up, for example
When C _ALT = 3, proceed from step 63 to step 64 and calculate the current feedback correction coefficient.
Deviation of LAMBDA from reference value 1 (LAMBDA−
1) is temporarily stored as ΔLAMBDA ₁ and learning is started.

When C _ALT =4 or more, the process proceeds from step 63 to step 65, 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 the LAMBDA deviation from the reference value 1 have been determined, the process proceeds to step 66 and their average value (see the following equation) is determined.

= (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 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 KALT according to the following formula. _ALT is calculated, and the uniform learning correction coefficient data at a predetermined address in 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, in step 70, set the K _ALT learning counter to 1.
rise. This K _ALT learning counter 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.

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 correction 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 _MAP 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 _MAP ←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. . In addition, 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 _MAP learning until K _ALT learning is experienced, and prevents extreme In this case, set M _MAP = 0.
This is to prohibit K _MAP learning.

In addition, when using the basic fuel injection amount Tp, which is one of the parameters for determining the air-fuel ratio feedback control region, as in the present invention, the one corrected by the uniform learning correction coefficient _KALT , that is, the correction Tp,
It is also preferable to use the correction Tp when setting the mixture ratio correction coefficient among the various correction coefficients COEF for obtaining the output air-fuel ratio outside the air-fuel ratio feedback control region.

<Effects of the invention> As explained above, according to the invention, even if the air density changes at high altitudes, the air-fuel ratio feedback control area does not narrow, and an appropriate air-fuel ratio feedback control area is ensured. This provides sufficient learning opportunities and improves the accuracy of learning control.

[Brief explanation of drawings]

Figure 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 arithmetic processing contents, Fig. 10 is a diagram showing a learning area for uniform learning correction coefficients, Fig. 11 12 is a diagram showing how the feedback correction coefficient changes, and FIG. 12 is a diagram showing the air-fuel ratio feedback control region. 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 Claim for Utility Model Registration] Engine operating state detection means for detecting the engine operating state including at least parameters related to the amount of air taken into the engine; an air-fuel ratio detection means for detecting a fuel ratio; 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 uniform correction for the basic fuel injection amount. a rewritable uniform learning correction coefficient storage means that stores a uniform learning correction coefficient for the uniform learning correction coefficient storage means; a basic fuel injection amount correction means that corrects by a coefficient; and a low rotation and low load area based on the engine rotation speed detected by the engine operating state detection means and the basic fuel injection amount corrected by the basic fuel injection amount correction means. an air-fuel ratio feedback control region detecting means for detecting an air-fuel ratio feedback control region and outputting an air-fuel ratio feedback control command; while outputting the air-fuel ratio feedback control command;
The air-fuel ratio detected by the air-fuel ratio detection means is compared with a target air-fuel ratio, and a feedback correction coefficient for correcting the basic fuel injection amount is increased or decreased by a predetermined amount so that the actual air-fuel ratio approaches the target air-fuel ratio. 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 feedback correction coefficient setting means a fuel injection amount calculation means for calculating a fuel injection amount based on a set feedback correction coefficient; and a fuel injection amount calculation means for injecting and supplying fuel to the engine on and off in response to a drive pulse signal corresponding to the fuel injection amount calculated by the fuel injection amount calculation means. a fuel injection means for outputting the air-fuel ratio feedback control command;
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 of learning and reducing the deviation of the feedback correction coefficient from a reference value; An air-fuel ratio learning control device for an internal combustion engine, characterized in that: