JPH0762453B2 - Air-fuel ratio learning controller for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air-fuel ratio learning control device for an internal combustion engine having an electronically controlled fuel injection device having an air-fuel ratio feedback control function, and particularly to a change in air density depending on altitude and the like. The present invention relates to an air-fuel ratio learning control device that can cope with the above.

<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 Laid-Open No. 60-90
Air-fuel ratio learning control devices such as those disclosed in Japanese Laid-Open Patent Publication No. 944 and Japanese Patent Laid-Open No. 61-190142 are used.

This is a signal from the O ₂ sensor provided in the engine exhaust system, which is the basic fuel injection amount calculated from the parameters of the engine operating state related to the amount of air taken into the engine (for example, the engine intake air flow rate and engine speed). Based on the feedback correction coefficient set by proportional / integral control, etc., the fuel injection amount is calculated and the air-fuel ratio is feedback-controlled to the target air-fuel ratio. The deviation from the value is learned for each area of the engine operating state set in advance, the learning correction coefficient is determined, and when calculating the fuel injection amount, the basic fuel injection amount is corrected by the learning correction coefficient for each area, and the feedback correction coefficient is used. The base air-fuel ratio obtained from the fuel injection amount calculated without correction is made to match the target air-fuel ratio, and the air-fuel ratio During back control is intended for calculating the fuel injection amount is corrected by further feedback correction coefficient so.

According to this, the follow-up delay of the feedback control during the transient operation can be eliminated during the air-fuel ratio feedback control, and the desired air-fuel ratio can be accurately obtained when the air-fuel ratio feedback control is stopped.

Further, a system for determining the basic fuel injection amount Tp from the throttle valve opening α and the engine speed N (for example, the intake air flow rate Q is obtained by referring to the map from α and N, and Tp = K · Q / N (K
Is a constant), or an air flow meter is used to detect the intake air flow rate Q, and from this and the engine speed N, the basic fuel injection amount Tp = K.
In a system that calculates Q / N, such as one that uses a flap type (volume flow rate detection type) as an air flow meter, the change in air density is not reflected in the calculation of the basic fuel injection amount, but the above learning control For example, as long as it is premised that learning proceeds well, it is possible to cope with changes in air density due to altitude or intake air temperature.

<Problems to be Solved by the Invention> By the way, since the air-fuel ratio feedback control is performed during steady operation in which the operating characteristics of the engine are stable,
The learning control for each area is also performed during steady operation.

Therefore, for example, if an attempt is made to go downhill to a lowland while the learning control for each area is advanced in a highland, the following problems occur.

That is, during downhill travel, deceleration operation, which is an excessive operation, is frequently performed, so the air-fuel ratio feedback control is stopped and the area-based learning control does not proceed. In addition, when traveling downhill, the O ₂ sensor often becomes inactive due to a decrease in exhaust temperature due to deceleration operation or deceleration fuel cut, etc., and the accelerator pedal is accidentally depressed to enable learning control by area for other operating conditions. O ₂ even if the condition is entered
Since the deceleration operation is started before the sensor is activated, the learning control for each area is not performed, and the learning control for each area does not proceed even by this.

As a result, when the fuel injection amount is calculated based on the learning correction coefficient for each area (learning correction amount for each area) learned in the highland during downhill travel, the change in the air density that is inversely proportional to the decrease in altitude cannot be dealt with, and the base air-fuel ratio Is greatly deviated from the target air-fuel ratio (shifts to the lean side as the altitude decreases), resulting in poor drivability and, in the worst case, causing engine stall.

Further, when the air-fuel ratio feedback control is started immediately after finishing the downhill, the fuel injection amount is calculated based on the learning correction coefficient for each area learned in the highland, so that the base air-fuel ratio is set to the target air-fuel ratio due to the response delay. There is a problem similar to the above that deviates from the fuel ratio.

The present invention has been made in view of such an actual situation, and provides an air-fuel ratio learning control device capable of optimally controlling an actual air-fuel ratio even during downhill traveling in which area learning control is stopped. To aim.

<Means for Solving Problems> Therefore, the present invention is configured as shown in FIG.

That is, the engine operating condition detecting means A for detecting the actual engine operating condition including at least the parameter relating to the amount of air taken into the engine, and the engine exhaust gas component for detecting the air-fuel ratio of the engine intake air-fuel mixture. Air-fuel ratio detecting means B, basic fuel injection amount setting means C for setting a basic fuel injection amount based on the parameters detected by the engine operating state detecting means, and corresponding to engine operating state A rewritable area-based learning correction amount storage means D for storing the area-specific learning correction amount for correcting the basic fuel injection amount, which is set by the above, and the area-based learning correction amount storage means based on the actual engine operating state. Area-based learning correction amount searching means E for searching the area-based learning correction amount and the detected actual air-fuel ratio and the target air-fuel ratio are compared to determine the actual air-fuel ratio. Feedback correction amount setting means F that sets a feedback correction amount that corrects the basic fuel injection amount so as to approach the standard air-fuel ratio, and learns a deviation from the reference value of the set feedback correction amount and reduces the deviation. A new area-based learning correction amount rewriting means G for setting a new area-based learning correction amount and rewriting the area-based learning correction amount stored in the area-based learning correction amount storage means E to a new one under the same operating conditions. A rewritable advanced learning correction amount storage means H for storing an advanced learning correction amount for advanced correction of the area-specific learning correction amount, and an advanced learning correction amount for searching the advanced learning correction amount storage means H for the advanced learning correction amount. Search means I, deceleration operation state detection means J for detecting the deceleration operation state, and deceleration operation state in a predetermined period based on the detected deceleration operation state A deceleration ratio calculating means K for calculating a speed ratio, and a new altitude learning correction amount set by modifying the altitude learning correction amount according to the calculated deceleration ratio and stored in the altitude learning correction amount storage means. An altitude correction amount correction means L for rewriting the altitude correction amount to a new one, the set basic injection amount, a learned or newly set learned correction amount, and a searched or corrected altitude learning correction amount, Fuel injection amount setting means M that sets the fuel injection amount based on a parameter that includes, and drive pulse output means O that outputs a drive pulse signal corresponding to the set fuel injection amount to the fuel injection means N. I configured it.

<Operation> In this way, the altitude decrease is estimated and detected from the deceleration rate in view of the fact that the deceleration operation state occupies a large proportion of the deceleration rate during the predetermined period during downhill traveling. Then, the basic fuel injection amount is corrected by the altitude learning correction amount that is corrected according to the decrease in altitude, so that the optimum air-fuel ratio can be ensured during downhill traveling and immediately thereafter.

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

In FIG. 2, air is sucked into the engine 1 via an air cleaner 2, a throttle body 3 and an intake manifold 4.

A throttle valve 5 that interlocks with an accelerator pedal (not shown) is provided in the throttle body 3, and a fuel injection valve 6 as fuel injection means is provided upstream of the throttle valve 5. The fuel injection valve 6 is an electromagnetic fuel injection valve that is energized by a solenoid to open the valve, and deenergized to close the valve.
A valve is energized by a drive pulse signal from a control unit 14 to be described later to open the valve, and fuel is pressure-fed from a fuel pump (not shown) to inject and supply fuel adjusted to a predetermined pressure by a pressure regulator. Although this example is a single point injection system, it may be a multipoint injection system in which a fuel injection valve is provided for each cylinder in the branch portion of the intake manifold or the intake port of the engine.

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

Exhaust gas is discharged from the engine 1 through the exhaust manifold 10, the exhaust duct 11, the three-way catalyst 12, and the muffler 13.

The control unit 14 includes a CPU, ROM, RAM, a microcomputer including an A / D converter and an input / output interface, receives input signals from various sensors, and performs arithmetic processing as described later, The operation of the fuel injection valve 6 and the ignition coil 8 is controlled.

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

In addition, a crank angle sensor 17 is built in the distributor 9 and outputs a position signal for each 2 ° crank angle and a reference signal for each 180 ° crank angle (in the case of four cylinders). Here, the engine speed N can be calculated by measuring the pulse number of the position signal per unit time or the period of the reference signal.

Further, a water temperature sensor 18 for detecting the engine cooling water temperature Tw, the vehicle speed VSP
A vehicle speed sensor 19 and the like for detecting the

The throttle sensor 15, the crank angle sensor 17, etc. are the engine operating state detecting means. Also, the crank angle sensor
The idle switch 17 and the idle switch 16 are deceleration operation state detecting means.

Further, the exhaust manifold 10 is provided with an O ₂ sensor 20. The O ₂ sensor 20 is a known sensor in which the electromotive force suddenly changes when the air-fuel mixture is burned in the vicinity of the theoretical air-fuel ratio which is the target air-fuel ratio. Therefore, the O ₂ sensor 20 is an air-fuel ratio (rich / lean) detecting means.

Further, a battery 21 is connected to the control unit 14 as an operating power source for detecting the power source voltage via an engine key switch 22. Further, as the operating power source of the RAM in the control unit 14, in order to retain the stored contents even after the engine key switch 20 is turned off, the battery 21 is connected not through the engine key switch 22 but through an appropriate stabilized power source. .

Here, the CPU of the microcomputer incorporated in the control unit 14 executes a program (a fuel injection amount calculation routine, a feedback control zone determination routine, a program on the ROM shown as a flowchart in FIGS. 3 to 10).
The proportional / integral control routine, the learning routine, the K _ALT learning subroutine, the K _MAP learning subroutine, the initialization routine, the advanced learning correction routine) are operated to control the fuel injection.

The basic fuel injection amount setting means, the area-based learning correction amount search means, the feedback correction amount setting means, the fuel injection amount setting means, the advanced learning correction amount correction means, the deceleration rate calculation means, and the area-based learning correction amount rewriting means. The function is achieved by the program. RAM is used as the advanced learning correction amount storage means and the area-based learning correction amount storage means.

Next, referring to the flow charts of FIGS. 3 to 10, the state of the arithmetic processing of the microcomputer in the control unit 14 will be described.

Step 1 in the fuel injection amount calculation routine of FIG.
(Indicated as S1 in the figure. The same applies hereinafter), the throttle valve opening α detected based on the signal from the throttle sensor 15 and the engine speed N calculated based on the signal from the crank angle sensor 17 Read in.

In step 2, the intake air flow rate Q corresponding to the throttle valve opening α and the engine speed N is obtained by experiments or the like in advance and is referred to the stored map on the ROM to obtain the Q corresponding to the actual α, N.
Search for and read.

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

In step 4, the change rate of the throttle valve opening α detected based on the signal from the throttle sensor 15 or the acceleration correction amount due to the switching of the idle switch 16 from ON to OFF, and the detection based on the signal from the water temperature sensor 18 Various correction factors COEF including the water temperature correction amount according to the engine cooling water temperature Tw to be set are set.

In step 5, RAM as advanced learning correction coefficient storage means
The uniform learning correction coefficient K _ALT as the advanced learning correction amount (advanced learning correction coefficient) stored in the predetermined address of is read. The uniform learning correction coefficient K _ALT is stored as an initial value 0 when learning is not started, and is read.

In step 6, the area-based learning correction coefficient K _MAP is stored on the RAM as the area-based learning correction coefficient storage means for storing the area-specific learning correction coefficient K _MAP corresponding to the engine speed N representing the engine operating state and the basic fuel injection amount (load) Tp. Refer to the map and search and read the K _MAP corresponding to the actual N, Tp. This portion corresponds to the area-based learning correction coefficient search means. The learning correction coefficient K for each area
The map of _MAP has the engine speed N as the horizontal axis and the fuel injection amount Tp as the vertical axis, and divides the engine operating area by a grid of about 8 × 8, and stores the learning correction coefficient K _MAP for each area. The initial value 0 is stored at all when learning is not started.

In step 7, the feedback correction coefficient LAMB set by the proportional / integral control routine of FIG.
Read DA. The reference value of this feedback correction coefficient LAMBDA is 1.

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

In step 9, the fuel injection amount Ti is calculated according to the following equation.
This portion corresponds to the fuel injection amount setting 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 in synchronization with engine rotation (for example, every 1/2 rotation), a drive pulse signal having a pulse width of Ti is given to the fuel injection valve 6, and fuel injection is performed.

FIG. 4 is a feedback control zone determination routine, which basically performs feedback control of the air-fuel ratio at low and medium speeds and low and medium loads, and stops the air-fuel ratio feedback control at high speeds and loads. Is.

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

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

When actual Tp> comparison Tp, that is, when the rotation is high and the load is high, as a rule, proceed to step 27 and set the λcont flag to 0.
To This stops feedback control of the air-fuel ratio,
This is to separately obtain a rich output air-fuel ratio, suppress an increase in exhaust temperature, and prevent seizure of the engine 1 and damage to the catalyst 12.

Here, even in the case of high rotation or high load,
By comparing the value of the delay timer with a predetermined value in 24, the process proceeds to step 26 and continues to set the λcont flag to 1 until the predetermined time elapses after shifting to high rotation or high load and feedback of the air-fuel ratio. Try to keep control. This is because the mountain climbing traveling is performed in a high rotation / high load region, so that opportunities for learning about the uniform learning correction coefficient K _ALT are increased. However, when the engine speed N exceeds a predetermined value (for example, 3800 rpm) in the determination in step 25, the air-fuel ratio feedback control is stopped for safety.

FIG. 5 shows a proportional / integral control routine for a predetermined time (for example,
It is executed every 10 ms), and thereby the feedback correction coefficient (feedback correction amount) LAMBDA is set. Therefore, this routine corresponds to the feedback correction amount setting means.

In step 31, the value of the λcont flag is judged, and if it is 0, this routine is ended. In this case, the feedback correction coefficient LAMBDA is clamped to the previous value (or the reference value 1), and the air-fuel ratio feedback control is stopped.

If the λcont flag is 1, the routine proceeds to step 32, where the output voltage V ₀₂ of the O ₂ sensor 20 is read, and at the next step 33, it is compared with the slice level voltage V _ref equivalent to the theoretical air-fuel ratio to obtain a rich air-fuel ratio Judge lean.

When the air-fuel ratio is lean (V ₀₂ <V _ref ), the _routine proceeds from step 33 to step 34, where it is judged whether or not it is the time of reversal from rich to lean (immediately after reversal), and at the time of reversal, step 35
Then, the process proceeds to and the feedback correction coefficient LAMBDA is increased by a predetermined proportional constant P with respect to the previous value. Stets except when flipped
Proceeding to 36, the feedback correction coefficient LAMBDA is increased by a predetermined integration constant I with respect to the previous value, and thus the feedback correction coefficient LAMBDA is increased at a constant slope. In addition, P>
> I.

When the air-fuel ratio is rich (V ₀₂ > V _ref ), the _routine proceeds from step 33 to step 37, where it is judged whether or not the lean-to-rich reversal is occurring (immediately after the reversal).
Then, the process proceeds to and the feedback correction coefficient LAMBDA is decreased by a predetermined proportional constant P from the previous value. Stets except when flipped
Proceeding to 39, the feedback correction coefficient LAMBDA is decreased by a predetermined integration constant I with respect to the previous value, and thus the feedback correction coefficient LAMBDA is decreased with 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 0
In the case of, the routine proceeds to step 42, the count values C _ALT and C _MAP are cleared, and then this routine is ended. This is because learning cannot be performed when the feedback control of the air-fuel ratio is stopped.

When the λcont flag is 1, that is, during feedback control of the air-fuel ratio, the routine proceeds to step 43 and thereafter, learning for uniform learning correction coefficient K _ALT (hereinafter referred to as K _ALT learning) and learning for area-specific learning correction coefficient K _MAP ( (Hereinafter referred to as K _MAP learning).

That is, the K _ALT learning is performed in a predetermined high load region (hereinafter referred to as Q flat) where the intake air flow rate Q does not change with the change of the throttle valve opening α at each engine speed N as shown by hatching in FIG. Region)) and K _MAP learning is performed in other regions. Therefore, in step 43, the comparison α ₁ is searched from the engine speed N, and in step 44, the actual throttle valve opening α (actual α) is calculated. Compare with α ₁ .

As a result of the comparison, if the actual α ≧ comparison α ₁ (Q flat region), in principle, proceed to steps 48 and 49, and count value C
After clearing _MAP , the K _ALT learning subroutine of FIG. 7 is executed.

However, in the case of the single point injection system, the intake flow velocity becomes slow in the region where the stottle valve opening is extremely large, and the distribution property to each cylinder deteriorates.Therefore, the distribution deterioration region is assigned by the throttle valve opening for the engine speed. Every other time, K _ALT learning is prohibited when the throttle valve opening is larger than that. Therefore, in step 45, the engine speed N is compared α
₂ is searched and the actual α is compared with the comparative α ₂ in step 46. If the actual α is greater than the comparative α ₂ , the process proceeds to steps 50 and 51 to clear the count value C _ALT , and then FIG. Move to the K _MAP learning subroutine.

Further, in the case of the single point injection system, the distance from the fuel injection valve 6 to the combustion chamber of the engine 1 is long, and accurate K _ALT learning cannot be performed due to the effect of wall flow fuel during rapid acceleration, so when rapid acceleration is performed K _ALT learning is performed after waiting for a predetermined time, that is, until the wall flow becomes steady. Therefore, in Steps 47, it is determined whether or not a predetermined time has elapsed after acceleration. If not, the process proceeds to Steps 50 and 51, and the count value C
After clearing _ALT , shift to the K _MAP learning subroutine in FIG.

If it is determined in step 44 that actual α <comparison α ₁ , proceed to steps 50 and 51 to clear the count value C _ALT and then
The process proceeds to the K _MAP learning subroutine shown in FIG.

Next, the K _ALT learning subroutine of FIG. 7 will be described.

In step 61, it is determined whether or not the output of the O ₂ sensor 20 is inverted, that is, whether the increasing / decreasing direction of the feedback correction coefficient LAMBDA is inverted. When repeating this subroutine, the count value C _ALT indicating the number of times of inversion is set in step 62. When it is increased by 1, for example, C _ALT = 3, the process proceeds from step 63 to step 64 and the current feedback correction coefficient LAMBDA
The deviation (LAMBDA-1) from the reference value of 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 and the feedback correction coefficient LAMBDA at that time
The deviation (LAMBDA-1) from the reference value 1 of 1 is temporarily stored as ΔLAMBDA ₂ . The 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 (for example, the third) inversion to the current (for example, the fourth) inversion as shown in FIG. Is the peak value above and below.

When the peak values ΔLAMBDA ₁ and ΔLAMBDA ₂ above and below the deviation of the feedback correction coefficient LAMBDA from the reference value 1 are obtained in this way, the process proceeds to step 66, and the average value of them is calculated.
Calculate ▼ (see the following formula).

▲ ▼ = (ΔLAMBDA ₁ + ΔLAMBDA ₂ ) / 2 Next, the routine proceeds to step 67, where the current uniform learning correction coefficient K _ALT (initial value 0) stored in a predetermined address of the RAM is read.

Next, in step 68, a new uniform learning correction coefficient K _ALT is calculated by adding the average value ▲ ▼ of the deviation of the feedback correction coefficient from the reference value to the current uniform learning correction coefficient K _ALT according to the following equation by a predetermined ratio. Then, the data of the uniform learning correction coefficient in the predetermined address of the RAM is corrected and rewritten.

K _ALT ← K _ALT + M _ALT・ ▲ ▼ (M _ALT is an addition rate constant, 0 <M _ALT <1) After that, in step 69, ΔLAMBDA _{2 is changed} to ΔL for the next learning.
Substitute in AMBDA ₁ .

Then, in step 70, the K _ALT learning counter is incremented by 1. Incidentally, the K _ALT learning counter one that is to 0 by initialization routine of FIG. 9 which is executed at the time of turn-on of the engine key switch 22 (or a start switch), K _ALT from after turning of the engine key switch 22 Counting the number of learning.

Next, the K _MAP learning subroutine of FIG. 8 will be described.
This K _MAP learning subroutine corresponds to learning correction amount rewriting means for each area.

In step 81, it is determined whether the engine speed N indicating the engine operating state and the basic fuel injection amount Tp are in the same area as the previous time. If the area is changed, the process proceeds to step 82 to set the count value C _MAP . After clearing, this subroutine ends.

In the case of the same area as the previous time, it is determined in step 83 whether the output of the O ₂ sensor 20 is inverted, that is, whether the increasing / decreasing direction of the feedback correction coefficient LAMBDA is inverted, and in step 84 every time this subroutine is repeated and inverted. When the count value C _MAP indicating the number of inversions is increased by 1, and when, for example, C _MAP = 3, the process proceeds from step 85 to step 86 and the deviation of the current feedback correction coefficient LAMBDA from the reference value 1 (LAMB
Temporarily store DA-1) as ΔLAMBDA ₁ and start learning.

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

In this way, when the peak values ΔLAMBDA ₁ and ΔLAMBDA ₂ above and below the deviation of the feedback correction coefficient LAMBDA from the reference value 1 are obtained, the routine proceeds to step 88 and the average value of them is calculated.
Ask for ▼.

Next, in step 89, the learning correction coefficient for each area K _MAP (initial value 0) stored in the map on the RAM corresponding to the current area is searched and read.

Next, in step 90, the value of the K _ALT learning counter is compared with a predetermined value, and if it is less than the predetermined value, in step 91 the addition ratio constant (weighting constant) M _MAP is set to a relatively small value M ₀ including ₀ . To do. When the value is equal to or larger than the predetermined value, the addition ratio constant (weighting constant) M _{MAP is set} to a relatively large value M in step 92.
Set to ₁ (however, M ₁ << M _ALT ).

Next, in step 93, a new area-specific learning correction coefficient K _{MAP is} added to the current area-specific learning correction coefficient K _MAP according to the following equation by adding the average value ▲ ▼ of the deviation of the feedback correction coefficient from the reference value by a predetermined ratio. Is calculated, and the learning correction coefficient data for each area of the same area on the RAM is corrected and rewritten.

K _MAP ← K _MAP + M _MAP・ ▲ ▼ After this, at step 94, ΔLAMBDA _{2 is changed} to ΔL for the next learning.
Substitute in AMBDA ₁ .

Regarding the above-mentioned addition ratio constant (weighting constant), M _ALT ≧
The reason why M _MAP is used is to allow K _ALT learning related to air density change to proceed first, and then K _MAP learning for each area. In addition, changing the value of M _MAP according to the number of K _ALT learning after turning on the engine key switch 22 (or start switch) suppresses the progress of K _MAP learning until K _ALT learning is experienced, This is because M _MAP = 0 and K _MAP learning is prohibited.

In this way, the learning correction coefficient for each area K _MAP and the uniform learning correction coefficient K _ALT can be used even when climbing or moving to a highland.
Based on and, the fuel injection amount is calculated so that the air-fuel ratio becomes optimum. The uniform learning correction coefficient K _ALT becomes a negative value because the air density decreases as the altitude increases.

Next, an altitude learning correction routine that is effectively applied when traveling downhill will be described with reference to FIG. This routine is the deceleration rate calculation means, the altitude learning correction amount rewriting means, and the altitude correction amount retrieval means.

In S101, it is determined whether or not the count time counted by the timer has exceeded the set travel time T. If YES, the process proceeds to S102, and if No, it is determined that the count time of the timer is less than the set travel time T. Proceed to.

In S102, the count value of the timer is reset to the initial value and counting is started again.

In S103, the deceleration ratio X (= T _B / T × 100) is calculated from the deceleration integrated time T _B accumulated in S107 described later and the set traveling time T.
(%)) Is calculated.

In S104, the altitude increase rate K is searched from the map based on the calculated deceleration rate X. The altitude drop rate K is set to increase as the deceleration rate X increases.

Here, the deceleration rate decreases to, for example, 20% when traveling on a flat land such as a general urban area, while it decreases to 60% when traveling on a downhill.
It has become as large as%. Therefore, the increase rate K is set to 0 when the deceleration rate X is around 20%, and is set to increase in the region where the deceleration rate X exceeds 20%. That is, the deceleration accumulated time T _B occupying within the set traveling time T
It is estimated that the higher the ratio of
The increase rate K is set accordingly.

In S105, the uniform learning correction coefficient K _ALT is retrieved from the RAM.

In S106, a new uniform learning correction coefficient is obtained by adding the searched altitude increase rate K to the searched uniform learning correction coefficient K _ALT.
K _ALT is calculated, the data in the RAM is corrected to a new uniform learning correction coefficient K _ALT , and rewritten.

Further, in S107, when the idle switch 16 is in the ON state and the engine speed exceeds the idle speed, a predetermined value (for example, 15
00R.Pm) detected by determining a deceleration operation when the above the deceleration operation is detected time integrated by the timer determining the deceleration integration time T _B in within the set running time T.

In this way, if the uniform learning correction coefficient K _ALT is learning-controlled according to the deceleration rate X corresponding to the deceleration operation state during downhill traveling, for example, uniform learning will be performed corresponding to the air density that changes during downhill traveling. The correction coefficient K _ALT can be changed.

Therefore, if the fuel injection amount is calculated based on the uniform learning correction coefficient K _ALT and the area-specific learning correction coefficient K _MAP , even if the air density changes during downhill traveling, the air density change The base air-fuel ratio (air-fuel ratio) can be brought close to the target air-fuel ratio, and thus the operating performance of the engine can be maintained excellent.

Further, even if the air-fuel ratio feedback control is started immediately after finishing the downhill, the air-fuel ratio can be brought close to the target air-fuel ratio with good responsiveness, and the operating performance of the engine can be kept excellent.

Incidentally, in the embodiment, the uniform learning correction coefficient K _ALT for learning control of the air density change and the like when climbing to a high altitude is subjected to the advanced learning control according to the deceleration rate X, but such uniform learning correction coefficient K _ALT is set. An altitude learning correction coefficient (advanced learning correction amount) according to the deceleration rate X may be provided without providing. In this case, since the altitude learning control can be performed corresponding to the air density when the vehicle is in the highland and the area-specific learning control is progressing to the lowland, the air-fuel ratio can be brought close to the target air-fuel ratio.

<Effects of the Invention> As described above, in the present invention, the altitude learning correction amount is corrected according to the deceleration rate, so that the air-fuel ratio is set to a target value when traveling downhill from a highland or immediately after shifting to a lowland. It is possible to approach the air-fuel ratio, so that the operating performance of the engine can be maintained well.

[Brief description of drawings]

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 10 are flowcharts showing arithmetic processing contents, and FIG. 11 is uniform learning. FIG. 12 is a diagram showing a learning region for the correction coefficient, and FIG. 12 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, 16 …… Idle switch, 17 …… Crank angle sensor, 20 …… O ₂ sensor

Claims (1)

[Claims] Claim: What is claimed is: 1. An engine operating condition detecting means for detecting an actual engine operating condition including at least a parameter relating to the amount of air taken into the engine; Air-fuel ratio detecting means for detecting the basic fuel injection amount setting means for setting the basic fuel injection amount based on the parameters detected by the engine operating state detecting means, and the basic fuel injection amount setting means set in correspondence with the engine operating state. A rewritable area-based learning correction amount storage unit that stores the area-based learning correction amount for correcting the fuel injection amount, and an area-based learning correction amount from the area-based learning correction amount storage unit based on the actual engine operating state. Area-based learning correction amount search means for searching and comparing the detected actual air-fuel ratio with the target air-fuel ratio to bring the actual air-fuel ratio close to the target air-fuel ratio Feedback correction amount setting means for setting a feedback correction amount for correcting the amount of fuel injection, and a new learning correction amount for each area to learn the deviation from the reference value of the set feedback correction amount and reduce it. Area-based learning correction amount rewriting means for rewriting the area-based learning correction amount stored in the area-based correction amount storage means to a new one under the same operating condition, and altitude learning correction for altitude-correcting the basic fuel injection amount Rewritable advanced learning correction amount storage means for storing the amount, advanced learning correction amount search means for searching the advanced learning correction amount storage means for advanced learning correction amount, and deceleration operation state detection means for detecting the deceleration operation state A deceleration ratio calculation means for calculating a deceleration ratio occupied by the deceleration operation state in a predetermined period based on the detected deceleration operation state; In accordance with the above, the advanced learning correction amount is modified to set a new advanced learning correction amount, and the advanced learning correction amount stored in the advanced learning correction amount storage means is rewritten with a new advanced learning correction correction means. , A fuel injection for setting a fuel injection amount based on a parameter including the set basic fuel injection amount, a learned or newly learned correction amount for each area, and a searched or corrected advanced learning correction amount A control device for learning the air-fuel ratio of an internal combustion engine, comprising: an amount setting means; and a drive pulse output means for outputting a drive pulse signal corresponding to the set fuel injection amount to the fuel injection means. ..