JPS63170532A - Air-fuel ratio control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To achieve the enhancement in acceleration and deceleration performance at a high ground, by correcting a load correction factor corresponding to a basic fuel supply quantity according to the air density. CONSTITUTION:The signals from a hot-wire type flowmeter in an intake pipe 3, and a throttle valve opening sensor 8, a and crank angle sensor 10, or the like are input into a control unit 11. In the control unit 11, an intake air quantity is calculated from a throttle valve opening and the number of revolutions, and an air density correction factor is calculated based on the calculated intake air quantity and an intake-air mass flow rate signal from a flowmeter 6. And, load correction factors at the time of acceleration and deceleration are corrected by the air density correction factor. Thus, even at a high ground or the like, the acceleration and deceleration performance can be enhanced.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an air-fuel ratio control device for an internal combustion engine for automobiles having an electronically controlled fuel injection device, etc., and particularly to cope well with changes in air density due to altitude, etc. The present invention relates to an air-fuel ratio control device capable of controlling the air-fuel ratio.

<Prior Art> Examples of conventional air-fuel ratio control devices for internal combustion engines include the following (see Japanese Unexamined Patent Publication No. 59-203828, etc.).

That is, the basic fuel injection amount corresponding to the intake air flow rate per unit rotation is determined from the mass intake air flow MQ detected by the hot wire flowmeter and the engine rotation speed N detected by the signals from the crank angle sensor and the ignition coil. Set rp. In the low rotation/low load region where the basic fuel injection amount 'rp and engine speed are below the respective set values Tp+ and Nl, the oxygen concentration in the exhaust gas is detected by the 0□ sensor installed in the exhaust system. The air-fuel ratio of the air-fuel mixture taken into the engine is detected, and feedback control is performed to bring the air-fuel ratio closer to a target air-fuel ratio (stoichiometric air-fuel ratio).

In addition, when the engine is accelerating, interrupt injection is performed simultaneously with acceleration detection or in addition to fuel injection synchronized with the engine rotation to improve responsiveness. , an increase in the amount of fuel is corrected for a response delay due to a decrease in fuel vaporization when the engine cooling water temperature is low.

On the other hand, even during deceleration, the intake air flow 1 is determined by the air flow meter.
A reduction correction for the delay in detecting the reduction, a reduction correction for the engine cooling water temperature, etc. are performed.

Incidentally, it is preferable that the various increase/decrease correction amounts of the fuel supply amount be varied depending on the load during acceleration/deceleration or just before acceleration/deceleration. Therefore, the load correction coefficient is set to 0 as shown in the following equation, and the various increase/decrease correction amounts described above are A system for use in calculating the amount of increase/decrease correction has been proposed (for example, Japanese Patent Application No. 61-219).
No. 706).

Ko = (4/4 Tp - current or Tp before acceleration/deceleration)
/ (4/4 Tp-R/LTp) However, 4/4Tp is the basic fuel injection amount Tp (determined according to the engine rotation speed N) when the throttle valve is fully open, R
/LTp is the basic fuel injection ITp of Road Load
shows. Note that the minimum basic fuel injection amount TPMIN may be used instead of R/LTp.

Here, Ko indicates the ratio of the current or before acceleration/deceleration Tp to the fluctuation of the basic fuel injection amount Tp, and is set larger as the current or before acceleration/deceleration basic fuel injection amount Tp is smaller. . Then, during acceleration, increase the increase correction amount obtained by multiplying 0 by 0, and increase it during sudden acceleration when the load (Tp) is small, and during deceleration, increase the increase correction amount obtained by multiplying by A Ko (A is a constant). It is increased during sudden deceleration when the load before deceleration is large.

<Problems to be Solved by the Invention> By the way, when the fuel increase/decrease correction amount is set in accordance with the basic fuel injection amount Tp, since the air density decreases at high altitudes, According to this 4
Even though both 4/4 Tp and R/LTp decrease (the former has a larger decrease), the above 4/4 Tp and R/LTp data used for 0 above are for flat land. On the other hand, the basic fuel injection amount 'rp at present or before acceleration/deceleration is X! according to the change in air density. A value calculated based on the intake air flow rate is used. For this reason, 0 is set relatively larger than in the case of flat land,
There is a problem in that the amount of fuel is excessively increased or decreased, resulting in a reduction in acceleration/deceleration performance.

The present invention has been made by focusing on such conventional problems, and by correcting the load correction coefficient according to the basic fuel supply amount according to the air density, it is possible to reduce the load when the air density is low, such as at high altitudes. - It is an object of the present invention to provide a fuel supply control device for an internal combustion engine that allows appropriate fuel increase/decrease correction to be performed even during deceleration operation, thereby maintaining good acceleration/deceleration performance.

Means for Solving the Problems> Therefore, as shown in FIG. 1, the present invention comprises: an intake air flow rate detection means for detecting the mass intake air flow rate of the engine; and an engine rotation speed detection means for detecting the engine rotation speed. and basic fuel supply amount setting means for setting a basic fuel supply amount based on the intake air flow rate and engine rotation speed detected by each of the detection means, and the basic fuel supply amount setting means set by the basic fuel supply amount setting means. a fuel supply amount setting means for setting the final fuel supply amount by making various corrections to the amount according to the engine operating state, or setting an interrupt supply amount of fuel under specific operating conditions; In an air-fuel ratio control device for an internal combustion engine, the air-fuel ratio control device for an internal combustion engine is equipped with a fuel supply means for supplying fuel to the engine in response to a fuel supply signal corresponding to the fuel supply amount set by the fuel amount setting means. a throttle valve opening degree detection means for detecting the opening degree of the valve; and an intake valve opening degree detected based on the engine rotation speed detected by the engine rotation speed detection means and the throttle valve opening degree detected by the throttle valve opening degree detection means. an intake air flow rate calculation means for calculating an air flow rate; a rewritable air density correction coefficient storage means for storing an air density correction coefficient; an intake air flow rate detected by the intake air flow rate detection means under predetermined operating conditions; air density correction coefficient correction means for correcting and rewriting the air density correction coefficient stored in the air density storage means based on the intake air flow rate calculated by the intake air flow rate calculation means; and an acceleration/deceleration operating state of the engine. acceleration/deceleration operation detection means for detecting acceleration/deceleration operation; and upon detection of acceleration/deceleration operation, the current or immediately preceding acceleration/deceleration basic fuel supply amount set by the basic fuel supply amount setting means and the air density correction coefficient storage means; load correction coefficient setting means for setting a load correction coefficient based on the stored air density correction coefficient; and a load correction coefficient setting means for setting an increase/decrease correction amount of the fuel supply amount when acceleration/deceleration operation is detected using the load correction coefficient.・The configuration includes a deceleration increase/decrease correction amount setting means.

(Operation) The basic fuel supply amount setting means sets the basic fuel supply amount based on the mass intake air flow rate and the engine speed.

On the other hand, the volumetric intake air flow rate is calculated by the intake air flow rate calculation means based on the engine speed and the throttle valve opening, and the air density correction coefficient correction means calculates the mass intake air flow rate and the The air density correction coefficient stored in the air density correction coefficient storage means is corrected and rewritten based on the volumetric intake air flow rate.

When the acceleration/deceleration operation state is detected by the acceleration/deceleration operation detection means, the basic fuel supply amount set at present or immediately before acceleration/deceleration and the air density correction stored in the air density correction coefficient storage means are determined. The load correction coefficient is set by the load correction coefficient setting means based on the coefficient.

As a result, the acceleration/deceleration increase/decrease correction amount setting means sets the increase/decrease correction amount of the fuel supply amount during acceleration/deceleration using the load correction coefficient, and the fuel supply amount setting means sets the increase/decrease correction amount for the fuel supply amount during acceleration/deceleration. The final fuel supply amount is set by making various corrections including the amount of fuel supplied.

The set amount of fuel is supplied to the engine by the fuel supply means to which a fuel supply signal corresponding to the set fuel supply amount is input.

In this way, during acceleration/deceleration operation at high altitudes, the load correction coefficient is corrected according to the air density, so it is possible to adjust the amount of increase/decrease in the amount of fuel supplied according to the load, and thereby・Good deceleration performance is maintained.

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

FIG. 2 shows the configuration of an air-fuel ratio control device (electronically controlled fuel injection device) for an internal combustion engine according to the present invention.

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

The intake duct 3 is provided with a hot wire flowmeter 6 that detects the mass intake air flow rate Q, and outputs a voltage signal Us corresponding to the intake air flow rate Q. In the throttle chamber 4,
A throttle valve 7 is provided which is interlocked with an accelerator pedal (not shown) to control the intake air flow rate Q. The throttle valve 7 has
A throttle valve opening sensor 8 is attached as a throttle valve opening detection means for detecting the opening θ. Intake manifold 5
An electromagnetic fuel injection valve 9 is provided for each cylinder, and the valve is driven to open by an injection pulse signal from a control unit 11 containing a microcomputer (described later), and is fed under pressure from a fuel pump (not shown) to a pressure regulator. Fuel controlled to a predetermined pressure is injected and supplied into the intake manifold 5. Furthermore, a water temperature sensor 12 is provided to detect the cooling temperature Tw in the cooling jacket 15 of the engine, and an oxygen sensor is provided to detect the air-fuel ratio in the intake air-fuel mixture by detecting the oxygen concentration in the exhaust gas in the exhaust passage 13. 14 are provided.

The control unit 11 calculates the engine rotational speed by counting for a certain period of time a crank unit angle signal outputted from a crank angle sensor 10 as an engine rotational speed detection means in synchronization with the engine rotation, or by measuring the period of a crank reference angle signal. Detect N.

The control unit 11 calculates the fuel injection amount Ti while calculating the air density correction coefficient based on the various detection signals detected as described above, and also calculates the fuel injection amount Ti based on the set fuel injection amount Ti. 9 is driven and controlled.

First, various routines for calculating the air density correction coefficient will be explained.

FIG. 3 shows a routine for averaging the mass intake air flow rate Q detected by the hot wire flowmeter 6 in order to avoid the adverse effects of intake pulsation.

In the diagram, step (denoted as S in the diagram. The same applies hereafter) ■
The output voltage Us from the hot wire flowmeter 6 is read as a digital value by the A/D converter.

In step 2, the intake air flow rate Q corresponding to the output voltage Us is searched using a map.

In step 3, the average value Qtv of the previous intake air flow rate Q
By adding +t6 with a weight of 〃 and the current detection value Q obtained with Ste Knob 2 with a weight of 2, a new average intake air flow rate Q Av++ is obtained.
Calculate 6.

FIG. 4 shows a routine that calculates the intake air flow rate based on the throttle valve opening and the engine speed, and determines the operating conditions for learning the air density correction coefficient.

In the figure, in step 11, the throttle valve opening α obtained by A/D converting the output voltage from the throttle valve opening sensor 8 is read.

In step 12, by comparing the change value Δα of the throttle valve opening α (the difference between the previous α and the current α) with the set value, it is determined whether or not the acceleration is greater than the set value. Sometimes, proceed to step 15.

If acceleration is determined in step 12, step 13
, it is determined whether or not the acceleration judgment is the first time, and if it is the first time, the process proceeds to step 21, where the timer TMACC for measuring the acceleration elapsed time is reset, and the process proceeds to step 22, where the air density correction coefficient KALTL is A flag FALTL for determining execution of learning is set to 0 indicating that no execution is to be performed.

Next, in step 23, the intake air flow t Q a N is retrieved from the three-dimensional MA knob stored in the ROM based on the engine speed N and the throttle valve opening degree α.

The function of step 23 corresponds to an intake air flow rate calculation means.

Further, after the second acceleration determination and after returning to steady state, the process proceeds to step 14, where the timer TMACC is counted up, and the process proceeds to step 15, where it is determined whether this count value has exceeded the preset value ALTLTM. , or more, the process proceeds to step 16, where the throttle valve opening degree α1 for comparison is retrieved from the two-dimensional map stored in the ROM based on the engine speed N.

In step 17, the detected value α of the throttle valve opening degree is compared with the above-mentioned α, and when α>α, the process proceeds to step 18, and if the engine rotation speed N is equal to or higher than the lower limit rotation speed NL for comparison, and It is determined whether the rotation speed is within the range of the upper limit rotation speed NM or less, and if it is within the range, the process proceeds to the steering knob 19.

In step 19, the cooling water temperature Tw is set to the set value 'l'w.

(for example, 75 degrees Celsius) or higher, and if the temperature is higher than that, proceed to step 20, set the flag FALTL to 1 indicating execution of air density correction coefficient learning, and then step 2.
Proceed to step 3 to calculate the intake air m ffi Q AN.

That is, after the set time (ALTLTM) has elapsed after acceleration, the throttle valve opening α is greater than the set value α4 for the engine speed at that time, and Nt≦N≦N.

Calculation of the air density correction coefficient KALTL is executed only under operating conditions in which the cooling water temperature is within the range of and the cooling water temperature is equal to or higher than the set value. This is because the air density correction coefficient K Al4L is calculated in a predetermined region (hereinafter referred to as the Q flat region) where the intake air flow rate Q does not substantially change with respect to a change in the throttle valve opening α for a certain engine speed N. It is. Basically, it is sufficient that the throttle valve opening α is equal to or greater than the lower limit value α1 of the throttle valve opening at which the intake air flow rate Q is approximately constant, but during acceleration, the mass of the intake air detected by the hot wire flow meter 6 is sufficient. Since the flow rate fluctuates more, it is necessary to set a predetermined time (
ALTLTM). In addition, the conditions NL≦N≦N and the conditions Tw≦Tw are KAL a.

This is a condition for selecting an area with high calculation accuracy.

FIG. 5 shows an air density correction coefficient learning routine.

In step 101, a flag FALTL for determining execution of learning is set.
is set, and if it is set, the process advances to Stellar P 102 and the current air density correction coefficient KAL? stored in the RAM is determined. L is read, and the process proceeds to step 103, where the value obtained by multiplying the intake air flow rate QAN retrieved in step 16 of the routine shown in FIG. 4 by the air density correction coefficient KALTL read in step 102 is set as A.

Next, the process proceeds to step 104 where A set in step 23 and the average mass intake air flow rate QA□ calculated in step 3 of the routine shown in FIG. 3 are calculated. Compare with.

As a result, if A=QAV□, in step 105, K
ALTL is maintained at the previous value, but if A>QAvlI6, in step 106, the value that DK has decreased by a predetermined amount (0°01%) from the previous KAt4L is updated as a new KALTL, and conversely, A<Qav* If s, step 27
The value obtained by adding the predetermined amount DK to the previous KAL is K att.
Update as t.

In other words, when going up, the air density decreases due to the increase in altitude, and since the volumetric flow rate A exceeds the mass flow rate QA, this decreases KAL increases and A falls below QAVIG, so KAL
It increases □.

As a result, the air density correction coefficient KALTL is learned so as to always have a value that corresponds well to the air density.

FIG. 6 shows a routine for determining acceleration/deceleration and setting an increase/decrease correction coefficient for fuel supply amount during acceleration/deceleration operation.

In step 31, the value α of the throttle valve opening sensor 8 is read, and in step 32, the difference from the previously read value, ie, the rate of change Δα, is calculated.

In step 33, it is determined whether the engine is in an acceleration state. Specifically, when the rate of change Δα calculated in step 32 is greater than or equal to a positive predetermined value, it is determined that the vehicle is in an accelerated state, and the process proceeds to step 34. Here, the throttle valve opening sensor 8 and the function of step 33 correspond to acceleration/deceleration detection means.

In step 34, a fuel increase correction coefficient α corresponding to the rate of change Δα is searched from a map stored in the ROM. This is set to a large value because the larger Δα, the greater the degree of acceleration.

In step 35, the fuel increase correction coefficient is determined according to the cooling water temperature Tw detected by the water temperature sensor 12. Search for W from the map stored in ROM. This is set large because the lower the water temperature, the worse the vaporization of the fuel.

In step 36, a fuel increase correction coefficient KN is set in accordance with the engine speed N detected by the crank angle sensor lO. This is set to increase as the engine speed N increases, since the effect of response delay due to calculation increases.

In step 37, it is determined whether or not fuel supply cut is performed before acceleration. If fuel supply cut is performed, the wall flow fuel amount is small, so in step 38, fuel cut correction coefficient K is determined.
Set OC to 1 or 3, and if not done, step 3
9 sets Koc to 1.

Next, the process proceeds to step 40, and the basic fuel injection 1tTp corresponding to the intake air flow rate per unit rotational speed is calculated from the average mass intake airflow fi Qav*e calculated in the routine of FIG. 2 and the engine rotational speed N. Calculated by

(Tp=-Q/NCK is a constant) The function of step 40 corresponds to the basic fuel supply amount setting means.

In step 41, the air density correction coefficient KAI4L, which has been set in the routine shown in FIG. 5 and is stored in the RAM serving as air density correction coefficient storage means, is read.

Then, in step 42, the load correction coefficient is calculated to be 0 according to the following equation.

Ko = (4/, 4 Tp-current Tp/KAL□) /
(4/4 Tp-R/LTp) This part corresponds to the load correction coefficient setting means.

Here, 4/4Tp and R/LTp store data when traveling on flat ground, but the current Tp is based on the value set in step 40 based on the mass airflow iiQ when the air density decreases at high altitudes. Since this is set, in order to avoid the influence of air density, the load is divided by the air density correction coefficient KAL□ to convert it into a load equivalent to a level ground.

In step 43, the acceleration interrupt injection amount TRINJ is set using the following formula.

TRI NJ = α・Kvw−Ks −Koc・K.

This function corresponds to acceleration/deceleration increase/decrease correction amount setting means.

In this way, TRINJ calculated in step 43
An interrupt injection signal with a pulse width corresponding to
4, and a set amount of fuel is injected.

Here, the acceleration interrupt injection amount TRINJ is set to a value that satisfactorily corresponds to the load ratio regardless of changes in air density, so it is set to an appropriate value that is neither too much nor too little, and can ensure stable acceleration performance.

FIG. 7 shows a calculation routine for the acceleration/deceleration increase/decrease correction coefficient used for calculating the fuel injection amount in the second embodiment.

In step 61, a basic fuel injection amount 'rp is calculated based on the engine speed and the intake air flow rate, and is stored as the immediately previous value T p+ when acceleration/deceleration is performed.

Read the throttle valve opening α in step 62, step 63
The rate of change Δα is calculated in step 64, and an acceleration determination is made based on Δα.

When it is determined that acceleration is occurring, flag F is set to 1 in step 65, and when it is determined that it is not acceleration, step 66
Step 67 compares Δα with a predetermined negative value to determine deceleration. If it is determined that deceleration has occurred, the process advances to step 67 and flag F is set to 0.

The throttle valve opening sensor 8 and the functions of steps 64 and 66 constitute acceleration/deceleration detection means.

If it is determined that the steady state is not deceleration, the process advances to step 68, where the increased intake air flow rate QAcc during acceleration, which will be described later.

The acceleration/deceleration increase/decrease correction coefficients Kr, Koc and the interrupt injection amount TrlNJ after regular fuel injection are set to zero.

After determining acceleration or deceleration, steps 69 to S71
Proceed to the rate of change Δα, the cooling water temperature TWl"419 function, and the increase/decrease correction coefficients corresponding to the rotational speed N, respectively, α and KTk.

After searching KN, the process proceeds to step 72, where the latest basic fuel injection amount 'rp after acceleration/deceleration is calculated, and the current value 'rp' is calculated.
Store as z.

In step 73, the air density correction coefficient KAL? L is read, and in step 74, T P + immediately before acceleration/deceleration and the air density correction coefficient K AL? The load correction coefficient KO+ is calculated based on the following equation.

Ko+= (4/4 Tp TpI /KAL?L)
/ (4/4Tp-R/LTp) In step 75, the current Tp! and air density correction coefficient KA
The load correction coefficient K is calculated by the following formula based on LTL. Calculate 2.

Koz= (4/4 Tp Tpt /KAL?L)
/ (4/4Tp-R/LTp) These steps 74 and 75 correspond to load correction coefficient setting means. In step 76, it is determined whether the flag F is 1, and if the acceleration is determined to be 1, the process proceeds to step 77, where the increased intake air flow rate during acceleration Qace + Ti, the interrupt injection amount TNINJ after completion of i, and the acceleration increase correction coefficient KF. is calculated using the following formula. Also, the deceleration reduction correction coefficient KDC is set to O.

QAce = (Kα+KN)・K, tTNINJ=α・K8・KOZ Ky=Ktw・Kα・KN'K (II In addition, when it is determined in step 76 that the flag F is O and deceleration is in progress, the process proceeds to step 78. , deceleration reduction correction coefficient KD
Set C using the following formula.

Koe= Ktw-KN (A Ko+) However, A
is a constant, and the larger the basic fuel injection amount Tp before deceleration, the greater the value. is set large.

These steps 77 and 78 correspond to an increase/decrease correction coefficient setting means.

FIG. 8 shows a fuel injection amount calculation routine that is calculated in synchronization with engine rotation or at a cycle longer than the calculation cycle shown in FIG.

In step 81, the engine speed N, the intake air flow rate Q detected from the air flow meter, and the increased intake air flow rate during acceleration QAcc set in the routine of FIG. 7 are read.

In step 82, the basic fuel injection amount 'rp is calculated using the following equation.

In step 83, the deceleration fIi amount correction correction coefficient C is read into the acceleration increase correction coefficient obtained in the routine of FIG.

In step 84, the following steps are performed: c, other water temperature correction coefficient KtW+starting correction coefficient K. , 1 for the post-idle increase correction coefficient. Various correction coefficients C0EF composed of 7, etc. are calculated as the air-fuel ratio correction coefficient.

COE F ” 1 + Ktw+ Kms
+ Km direct + Ksr + KrKtlC In step 85, it is determined whether or not the air-fuel ratio feedback condition is met. If the feedback condition is met, α is calculated based on the signal from the oxygen sensor 14 in step 86, and if it is not the feedback condition, step At step 87, β is clamped to 1 or the value at the end of the previous feedback control.

In step 8, a correction numerator s based on the battery voltage is calculated.

In step 89, the final fuel injection amount Ti is calculated using the following equation.

Ti=Tp-COEF・β+Ts This part corresponds to the fuel supply amount setting means.

An injection pulse signal having a pulse width corresponding to the fuel injection amount Ti calculated in this manner is output to the fuel injection valve 7 at a predetermined time determined by counting with a timer.

FIG. 9 shows the fuel injection control routine, step 91
It is determined whether the output of the injection pulse signal has ended or not. After the determination, in step 92, the interrupt injection amount TNINJ obtained by the routine shown in FIG.
If NJ≠0, an interrupt injection pulse signal corresponding to TNINJ is additionally output, and interrupt injection is performed.

In this way, the increase/decrease correction or interrupt injection of the fuel injection amount is performed during acceleration/deceleration, but since the load correction coefficient corrected by air density is used to set these correction amounts and interrupt injection amount, Good acceleration and deceleration performance can be obtained even at high altitudes.

<Problems to be Solved by the Invention> As explained above, according to the present invention, the fuel increase/decrease correction amount during acceleration/deceleration is set using the load correction coefficient corrected by the air density correction coefficient. Even when the air density decreases, such as at high altitudes, the fuel amount can be corrected according to the load ratio in the same way as at low altitudes, resulting in the effect that good acceleration/deceleration performance can be maintained due to a stable mixture ratio.

[Brief explanation of the drawing]

FIG. 1 is a 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 6 are flowcharts showing control details of the above embodiment, and FIGS. 9th
The figure is a flowchart showing control details of another embodiment. 1... Engine 6... Hot wire flow meter 7... Throttle valve 8... Throttle valve opening sensor 9... Fuel injection valve 10... Crank angle sensor 11... Control unit

Claims (1)

[Scope of Claims] Intake air flow rate detection means for detecting the mass intake air flow rate of the engine; engine rotation speed detection means for detecting the engine rotation speed; and intake air flow rate and engine rotation speed detected by each of the detection means. basic fuel supply amount setting means for setting a basic fuel supply amount based on the basic fuel supply amount setting means; a fuel supply amount setting means for setting a fuel supply amount or an interrupt supply amount of fuel under specific operating conditions; an air-fuel ratio control device for an internal combustion engine, comprising: a fuel supply means for supplying fuel to the engine; an intake air flow rate calculation means for calculating an intake air flow rate based on the engine rotation speed detected by the rotation speed detection means and the throttle valve opening detected by the throttle valve opening detection means; and an air density correction coefficient. Based on the stored rewritable air density correction coefficient storage means, the intake air flow rate detected by the intake air flow rate detection means under predetermined operating conditions, and the intake air flow rate calculated by the intake air flow rate calculation means. an air density correction coefficient correction means for correcting and rewriting the air density correction coefficient stored in the air density storage means; an acceleration/deceleration operation detection means for detecting acceleration/deceleration operation status of the engine; and upon detection of acceleration/deceleration operation. , a load correction coefficient is set based on the current or immediately before acceleration/deceleration basic fuel supply amount set by the basic fuel supply amount setting means and the air density correction coefficient stored in the air density correction coefficient storage means; and an acceleration/deceleration increase/decrease correction amount setting means that uses the load correction coefficient to set an increase/decrease correction amount for the fuel supply amount when acceleration/deceleration operation is detected. Air-fuel ratio control device for internal combustion engines.