JPH0233431A - Fuel injection quantity control method for internal combustion engine - Google Patents

Abstract

PURPOSE:To aim at improving the accuracy of the air-fuel ratio control by obtaining the correcting injetion quantity at a transition time from the difference between the first state quantity calculated from the intake air quantity and the engine speed and the second state quantity which fluctuates with its delay characteristic as well as differentiating the delay characteristic depending on the first and second state quantities. CONSTITUTION:In a processing unit 31, the basic injection quantity is obtained from the rotating speed of the engine 18 calculated from the signals outputted from a crank angle detector 28 and the intake pressure detected by means of a detector 19 as well as the first state quantity is calculated from the engine speed and the intake air quantity calculated from the signals from a throttle valve aperture detector 30 and the second state quantity with the delay characteristic to the first state quantity is further calculated. The correcting injection quantity at a transition time is obtained from the difference between both these state quantities so as to correct the basic injection quantity. In this case, the delay characteristic is altered by the relations between the ratio of the first and second state quantities and the threshold value corresponding to the circulating water temperature detected by means of a sensor 24. The air-fuel ratio can be thus controlled accurately without being influenced by the tube wall adhering fuel quantity even at a transition time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of controlling the amount of fuel injected to an internal combustion engine, and more particularly to a control method of compensating the amount of fuel injected against fuel adhesion to pipe walls.

Conventional technology Conventionally, the intake pipe pressure in the intake manifold of an internal combustion engine (
Hereinafter referred to as "intake pressure". ) and the number of revolutions per unit time (hereinafter referred to as "rotational speed") of the internal combustion engine, and based on these detected values, a method is known in which the amount of fuel injection to be supplied to the internal combustion engine is calculated. This method is known as the so-called D-Jetronic method, and uses the principle that the intake pressure is approximately proportional to the amount of intake air per cycle of the internal combustion engine. This method calculates the amount of fuel that provides the stoichiometric air-fuel ratio for the intake air I that has been found, and injects the fuel from the fuel injection valve into the combustion chamber in synchronization with the rotation of the internal combustion engine.

The present inventors have made various proposals regarding compensation of the fuel injection amount during a transient period when the throttle valve opening changes suddenly. 1st
FIG. 5 is a time chart for explaining the previously proposed compensation of the fuel injection amount during a transient period. Figure 15 (1
) line 121 represents the output waveform of the throttle valve opening detector when the throttle valve opening TA suddenly changes from θ11 to θ12 at time tll. Line 122 in FIG. 15(2) represents the first state quantity. The line 123 represents a temporal change in the second state quantity, the first state quantity corresponds to the amount of intake air per cycle of the internal combustion engine,
When the intake air amount is Q and the rotational speed of the internal combustion engine is N, the first state quantity QN is expressed by the first equation.

Further, the second state quantity is a quantity that has a delay characteristic with respect to the first state quantity by a predetermined means. Then, fuel proportional to the difference between these first and second state quantities is calculated as a compensation amount for the fuel injection amount during the transient period.

In this way, the basic injection amount is determined from the rotational speed and intake pressure of the internal combustion engine, and by adding the above-mentioned correction injection amount to this basic injection amount, the mixture changes from the stoichiometric air-fuel ratio to the lean side during transient times. Prevents displacement.

Problems to be Solved by the Invention As mentioned above, the intake air amount Q and the rotational speed N of the internal combustion engine
By adding to the basic injection amount a correction injection amount that is proportional to the difference between the first state Rji obtained from It is possible to compensate for a delay in the supply of fuel injection amount during the period.

However, since the fuel injection valve injects fuel toward the intake valve body provided at the top of the cylinder, the injected fuel adheres to the intake valve body and the intake pipe wall near the intake valve body. In particular, the amount of fuel attached to the pipe wall increases as the fuel injection amount increases, and also as the temperature of the intake valve body and the intake pipe wall decreases. Even if the injection amount is compensated for, the amount of adhesion to the tube wall is not compensated for.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for controlling the fuel injection amount of an internal combustion engine, which compensates for the delay in detecting the intake air I and also compensates for the amount of pipe wall f.

Means for Solving the Problems The present invention determines the basic injection amount from the rotational speed of the internal combustion engine and the intake pipe pressure.

From the intake air amount and the rotational speed of the internal combustion engine, the first state Bj
E, find a second state quantity that follows and changes to match or almost match the first state quantity with a delay characteristic, and calculate the correction injection during the transient from the difference between the first state quantity and the second state quantity. A method for controlling a fuel injection amount of an internal combustion engine for determining a fuel injection amount supplied to the internal combustion engine based on the basic injection amount and the corrected injection amount, the method comprising: dependence between the first state quantity and the second state quantity; Due to the relationship
This is a method of controlling a fuel injection amount of an internal combustion engine, characterized in that the delay characteristics are varied.

Further, in the present invention, the control of fuel injection amount of an internal combustion engine is characterized in that the delay characteristic is varied depending on a magnitude relationship between a ratio of the first state quantity and the second state quantity and a predetermined threshold value. It's a method.

Furthermore, the present invention is a method for controlling a fuel injection amount of an internal combustion engine, characterized in that at least one of the threshold value and the delay characteristic is changed depending on the temperature of a coolant of the internal combustion engine.

Function In the present invention, the basic injection amount is determined from the rotational speed of the internal combustion engine and the intake pipe pressure. Then, a first state quantity is determined from the intake air amount and the rotational speed of the internal combustion engine, and a second state quantity is determined by giving the first state quantity a delay characteristic. Further, the delay characteristic is changed based on the dependence relationship between the first state quantity and the second state Rjl. The corrected injection amount is determined from the difference between the first state quantity and the second state quantity thus determined.

Then, the fuel injection amount to be supplied to the internal combustion engine is determined from the basic injection amount and the corrected injection amount.

Further, in the present invention, the ratio between the first state quantity and the second state quantity is determined, and the delay characteristic is changed depending on the magnitude relationship between this ratio and a predetermined threshold value.

Furthermore, in the present invention, at least one of the threshold value and the delay characteristic is changed depending on the temperature of the coolant of the internal combustion engine.

Embodiment FIG. 1 is a configuration block diagram of a fuel injection control device in which the present invention is implemented. The internal combustion engine 13 includes a plurality of combustion chambers E.
1 to Em are formed, and these combustion chambers E1 to Em
Combustion air is supplied to the intake pipe 15. A throttle valve 16 is provided in the intake pipe 15, and the combustion air flow rate is controlled according to the opening degree of the throttle valve 16. Combustion air flowing in via the throttle valve 16 is passed from a surge tank 14 that suppresses pulsation of the air flow and promotes intake of combustion air to intake pipes A1 to Am provided individually for each of the combustion chambers E1 to Em. guided by. In each of the intake pipes A1 to Am, fuel injection valves B1 to Bm are provided in the vicinity upstream of the intake valves C1 to Cm, and each combustion chamber E1 to E
In each explosion step in m, a fuel injection amount TP calculated by a processing device 31, which will be described later, is injected.

Each combustion chamber E1-Em is provided with an intake valve C1-Cm and an exhaust valve D1-Dm, respectively. In the internal combustion engine 13, for example, four thermosurge tanks 14 having spark plugs G1 to Gm are provided with one pressure detector for detecting the intake pressure P, . The intake pipe 15 is provided with a temperature detector 27 that detects intake air temperature. internal combustion engine 1
3 is provided with a crank angle detector 28 for detecting the crank angle, and a valve opening detector 30 for detecting the opening TA of the throttle valve 16. The temperature of the coolant of the internal combustion engine 13 is detected by a temperature detector 24 . An oxygen concentration detector 21 is provided in the middle of the exhaust pipe 20, and the exhaust gas is purified by a three-way catalyst 22 and discharged to the outside.

Processing bag W realized by microcomputer etc.
31 includes an input interface 32, an analog/digital converter 33 that converts an input analog signal into a digital signal, a processing circuit 34, and an output ink face 35.
and a memory 36, the memory 36 including read-only memory and random access memory. In an embodiment of the invention, the fuel injector is The fuel injection jiTP for each step injected from B1 to Bm is controlled.

The fuel injection amount TP supplied from the fuel injection valves 81 to Bm to the combustion chambers E1 to Em is determined by setting the basic injection amount as TPD, the suction efficiency as η, the injection amount conversion coefficient as J, and furthermore, the first state quantity and Letting the second state RJl be QN and QND, respectively, it is expressed by the second equation.

TP=TPD+η・J・(QN−QND)・
(2) TPD, which is the basic injection amount, is the rotational speed N of the internal combustion engine and the suction pressure P, which is the pressure inside the surge tank 14.

These relationships are stored in the memory 36 as a map. The basic injection amount TPD corresponds to the fuel injection amount when the throttle valve 16 is in a steady state, and the second term on the right side of the second equation corresponds to the corrected fuel injection amount when the throttle valve 16 is in a transient state.

As already mentioned, the amount of fuel injected into the combustion chambers E1-Em is determined to be the stoichiometric air-fuel ratio with respect to the amount of air taken into the combustion chambers E1-Em, so the amount of fuel injected is the optimal amount of fuel. In order to find the amount of intake air per cycle, it is necessary to find the amount of intake air per cycle.
seek.

FIG. 2 is a graph for estimating the intake air amount from the throttle valve opening and the second state quantity. The relationship between the throttle valve opening TA, the second state quantity QND, and the intake air, IQ shown in FIG. 2 is stored in the memory 36 as an intake air amount characteristic map, and is
When ND is given, the intake air amount Q is determined. As understood from FIG. 2, as the throttle valve opening TA increases, the intake air amount Q also increases. Note that in the initial stage when the second state quantity QND is not determined, the second state quantity is used as an initial value.

When the intake air IQ is determined from the throttle valve opening TA and the second state quantity QND, the first state WiQN is expressed by the third equation, where N is the rotational speed of the internal combustion engine determined from the output signal of the crank angle detector 28. It is required according to the following.

When the first state vAIQN is determined by the third equation, the second state vAIQN
The state quantity QND is calculated according to the fourth equation.

QND1=QNDa−++ −(QNJ−QNDJ−1
)...(4)τ Note that the subscript j of the first state quantity QN and the second state quantity QND
represents the timing at which the second state quantity QND is calculated, and the subscript j-1 is the previous calculated value.

Further, the coefficient τ is a coefficient called a rough value, and determines the delay characteristic that the second state fijlQND has with respect to the first state quantity QN. As this rough value τ increases,
The amount of delay between the second state quantity and the first state quantity increases.

Next, a description will be given of temporal changes in the first state quantity and the second state quantity determined by the third and fourth equations. FIG. 3 is a timing chart showing temporal changes in the first state quantity and the second state B quantity during the transition of the throttle valve opening. As shown in FIG. 3 (1), when the throttle valve opening TA rapidly increases from θ1 to 02 at time t1, the second
As can be understood from the figure, the intake air amount Q is estimated to increase as the throttle valve opening changes. However, the intake pressure detected by the pressure detector 19 is the combustion chamber E1~
There is a time delay with respect to changes in the amount of air taken into Em. Therefore, the processing circuit 34 converts the second state quantity QND having a predetermined delay characteristic to the first state quantity QN into a fourth state quantity QND.
Calculated according to the formula, these first state quantities QN and second state f
An amount proportional to the difference from ixQND is added to the basic injection amount TPD as a correction injection amount during a transient period, and the fuel injection amount is compensated.

FIG. 3 (2) shows the first state quantity QN and the second state quantity QN.
In the timing chart showing the temporal change of D, line 1
1 represents the first state WIQN, and line 12 represents the second state quantity Q
ND, thus, the first state quantity QN shown by line 11 and the second state ff! shown by line 12! By finding IQND and finding the compensation injection amount proportional to the difference,
It is possible to compensate for the fuel injection amount when the throttle valve opening changes suddenly. However, as described above, as the fuel injection amount increases, the amount of fuel that adheres to the pipe wall also increases. Therefore, it is necessary to compensate for the one-dimensional loss of the tube wall due to the increase in the corrected injection amount during the transient event. An area zl is partitioned by line I13 and line 11 and is shaded for convenience.

z2 indicates the compensation amount of fuel injection amount for pipe wall adhesion,
In order to compensate for this fuel injection amount, it can be easily determined by manipulating the second state quantity created in the processing circuit 34 in this embodiment.

FIG. 4 is a functional block diagram for explaining the relationship between the throttle valve opening degree, the engine rotation speed, and the first and second state quantities. The throttle valve opening TA detected by the valve opening detector 30 is the processing bag! 31 processing circuits 34
is input. The processing circuit 34 calculates the intake air I from the second state QiQND and the throttle valve opening TA shown in FIG.
The relationship for determining Q is stored in the memory 36 as an intake air amount characteristic map 36a. Using this intake air amount characteristic map 36a, the intake air amount Q is determined. In addition,
In the initial state, the second state quantity QND is not calculated, so the second state quantity QND as an initial value is stored in the memory 36 as an initial value 36b.

The intake air IQ determined in this way is
is given to the i calculation means 34a, and the angle detector 28
is divided by the detected engine rotational speed N to obtain the first state QiQN.

This first state quantity QN is given to the filter 34b in order to further obtain a second state B quantity QND.

In the filter 34b, calculation according to the fourth equation is performed, and the delay characteristic with respect to the first state quantity QN is set based on the value of the round value τ. Compensation for pipe wall adhesion in this embodiment is achieved by changing the rough value of this filter 34b according to the conditions described later, so that the corrected injection amounts in the regions zl and z2 shown in FIG. 3 are adjusted to the second state quantity QND. You can keep it on the verge.

The first shape R quantity QN and the second shape R quantity QN obtained by the above calculation
As for the state quantity QND, the corrected injection amount is obtained by calculating the difference between them as described above.

FIG. 5 is a graph showing the relationship between the engine rotational speed and the smoothed value when the absolute value of the ratio of the first and second state quantities exceeds the threshold value. That is, as shown in equation 5, the absolute value of the ratio between the first state quantity QN and the second state IQND is a predetermined threshold value LQNFLT (for example, 1.1 to 1.15
is selected. ), the rough value τ1 is selected.

FIG. 6 is a graph showing the relationship between the engine rotation speed and the smoothed value when the absolute value of the ratio of the first and second state quantities is less than or equal to the threshold value. That is, the ratio of the first state R quantity QN to the second state quantity QND is the threshold value LQ as shown in equation 6.
If it is less than NFLT, the rough value τ2 shown in FIG. 6 is selected as the rough value.

FIG. 7 shows that according to the absolute value of the ratio of the first and second state quantities,
7 is a time chart for explaining a situation in which the rough value τ is switched. FIG. 7(1) is a waveform diagram showing changes in throttle valve opening TA from the valve opening detector 30;
2) is a timing chart showing changes in the first state quantity QN and the second state quantity QND. As shown in FIG. 7 (1), the throttle valve opening TA suddenly increases at time 3,
and sharply decreases at time t4, the seventh
As shown in Figure (2), the first state quantity Q shown by line 14
N and I of the second wear amount QND represented by line 15 also increase or decrease. The selected round value τ differs depending on the absolute value of the ratio between the first state fiiQN and the second state quantity QND.

That is, during the period W2. during which the fifth equation holds true. In W4, the correction for the delay in the intake air amount with respect to the intake pressure is mainly performed, and the smoothed value τ1 is selected, and the period Wl, W during which the sixth equation holds true is determined.
3. In W5, in order to mainly correct for pipe wall adhesion, the rounded value is 2, which is a value larger than 1.
is selected.

The above-mentioned correction for pipe wall adhesion is a correction of the fuel injection amount after the internal combustion engine has been warmed up. However, when the internal combustion engine is not warmed up, the temperature of the intake valve is low, and the amount of fuel injected from the fuel injection valve is It is known that the injected fuel is vaporized in a larger amount than when it is warmed up (approximately 20% of the injected amount is deposited).Therefore, when the internal combustion engine is warmed up, It is possible to supply an amount of fuel close to the stoichiometric air-fuel ratio to the combustion chambers E1-Em by determining whether or not the temperature has reached the stoichiometric air-fuel ratio by determining whether or not the temperature has reached the stoichiometric air-fuel ratio. can.

FIG. 8 is a graph showing the relationship between the coefficient for correcting the smoothing value and the coolant temperature. FIG. 8(1) is a graph showing a change of 1 in the coefficient multiplied by the stability value τ as the coolant temperature decreases. If the coolant temperature is 80℃ or higher, the coefficient is 1.
．． 0 is selected, but when the coolant temperature is less than 80°C, the coefficient increases by 1 as the liquid temperature decreases. As the coefficient is set to a larger value of 1, the sluggish value τ becomes larger, and therefore the amount of delay between the second state quantity QND and the first state quantity QN becomes larger.

FIG. 8(2) is a graph showing the relationship between 2 and the coefficient for changing the magnitude of the threshold value LQNFLT used in the fifth and sixth equations according to the coolant temperature. in this way,
By multiplying the coefficient of threshold LQNFLT by 2,
The timing of correction for tube wall adhesion can be brought forward. When the coolant temperature is 80'C or higher, the internal combustion engine is considered to have been warmed up, so no correction is made to the threshold LQNFLT.

No. 9121 is a timing chart showing the relationship between the change in the first state quantity and the correction amount for pipe wall adhesion when the rough value τ is corrected. Line 16 in FIG. 9(1) is
FIG. 9 (2) shows a signal waveform from the valve opening degree detector 30 showing a rapid increase in the throttle valve 16 at time t5.
1 is a timing chart for explaining correction of the fuel injection amount for pipe wall adhesion when the sluggish value τ is corrected according to the coolant temperature. A hatched area z3 surrounded by line 16 and line e7, which represents the change in the first state IQN, represents the correction amount of the fuel injection amount for pipe wall adhesion, and similarly, in FIG. 9(3), , a region z4 surrounded by line p6 and line 18 has a threshold value LQNFL
It represents the correction amount of the fuel injection amount when T is changed according to the coolant temperature.

Furthermore, according to FIG. 9(4), line 16 and line 1
The area z5 surrounded by 9 represents the correction amount of the fuel injection amount for pipe wall adhesion when the rough value τ and the threshold value LQNFLT are simultaneously corrected according to the coolant temperature. By simultaneously correcting the threshold value LQNFLT and the threshold value LQNFLT, it is possible to change the correction timing and correction amount during warm-up according to the coolant temperature.

Next, a method of calculating the correction amount for the above-mentioned tube wall adhesion will be explained below using a flowchart.

FIG. 10 is a flowchart for explaining calculation of the corrected injection amount. The processing contents of each step will be explained below. In step a1, the valve opening degree detector 30
The opening degree TA of the throttle valve 16 is determined by inputting the detection signal from the
The program then proceeds to step a2, where the intake air IQ is estimated from the intake air amount characteristic map 36a stored in the memory 36. In step a3, step a
The intake air IQ determined in step 2 and the crank angle detector 28
The first state quantity QN is calculated from the rotational speed N of the internal combustion engine determined based on the detection signal from the first state quantity QN according to the third equation. When the first state quantity QN is calculated in step a3, the process proceeds to step a4, where a corrected injection amount is determined. That is,
The second item on the right side of the second equation is calculated. Note that in the first calculation, an initial value is used as the second state quantity QND.

FIG. 11 is a flowchart for explaining calculation of the basic injection amount. In step b1, the surge tank 14
The intake pressure PI9 within is detected by the pressure detector 19. In step b2, the basic injection amount TPD is determined from a map stored in the memory 36 from the intake pressures P and H and the rotational speed N of the internal combustion engine.

FIG. 12 is a flowchart 1 for explaining the reading of the coefficient for correcting the rough value and the threshold value. In step C1, the coolant temperature is detected, and 1 is set as the coefficient for the coolant temperature. It is obtained from the relationship shown in Figure 8 (1). Similarly, in step C2, a coefficient of 2 is determined from the coolant temperature based on the relationship shown in FIG. 8 (2). The process then proceeds to step C3, where the threshold value LQNFLT is corrected according to equation 7 using 2 as the coefficient determined in step C2, and a new threshold value LQNFLT is calculated.

LQNFLT, = 2・LQN F LT
(7) FIG. 13 is a flowchart for explaining the calculation of the second state at. In step d1, the absolute value of the ratio of the first and second state quantities and the threshold value LQNFL
T, which comparisons are made. If the absolute value of the ratio of the first and second state quantities is greater than the threshold LQNFLT, the process proceeds to step d2, where the coefficient τ1 is calculated from the rotational speed N of the internal combustion engine at that time based on the relationship shown in FIG. Desired.

Moreover, the absolute value of the ratio of the first and second state quantities is the threshold L
If QNFLT is less than or equal to QNFLT, proceed to step d3;
The coefficient τ2 is determined from the rotational speed N of the internal combustion engine based on the relationship shown in FIG.

The smoothed value τ1 or τ2 obtained in step d2 or step d3 is corrected by the coolant temperature in step d4. That is, as shown in Equation 8, the coefficient 1 is multiplied by the smoothed value τ, and the corrected smoothed value τ1
．． Or τ2. is calculated.

In this way, the raw value τ1. Or τ2. Once determined, the second state IQND is calculated in step d5. That is, the stability value τ1. calculated in step d4. Or τ2. is substituted into the fourth equation, the first state quantity QN that has already been found, and the second state quantity QN D , -, that has been found in the previous calculation, are substituted, and the second state quantity QND is lit. be done.

FIG. 14 is a flowchart for calculating the amount of fuel finally injected from the fuel injection valve.

In step e1, the sum of the corrected injection amount obtained in step a4 of FIG. 10 and the basic injection amount TPD obtained in step b2 of FIG. 11 is calculated to calculate the injection amount TP. In this way, the determined injection amount TP is transmitted to the fuel injection valve 8 in synchronization with the detection signal of the crank angle detector 28.
1 to Bm are injected into the combustion chambers E1 to Em.

As described above, according to this embodiment, by changing the coefficients used in the calculation formula for correcting the response delay of transient fuel injection, which is a drawback of the so-called D~dietronic system, the fuel adhering to the pipe wall can be reduced. can also be easily corrected.

Effects of the Invention As described above, according to the present invention, it is possible to compensate for the delay in detecting the intake air amount with respect to the intake pipe pressure, and by the compensation, it is possible to easily compensate for the newly increasing amount of fuel adhering to the pipe wall. Even during transient times, the internal combustion engine can be controlled near the stoichiometric air-fuel ratio.

Further, according to the present invention, the delay characteristic of the second state quantity with respect to the first state quantity is determined by the magnitude relationship between the ratio of the first state R quantity and the second state l and the predetermined threshold value. For walls, the amount of correction for wear can be accurately obtained.

Furthermore, according to the present invention, at least one of the threshold value and the delay characteristic is changed depending on the temperature of the coolant of the internal combustion engine, so that the amount of adhesion on the pipe wall that changes depending on the temperature of the internal combustion engine can be reduced. It is possible to compensate more accurately.

[Brief explanation of the drawing]

Fig. 1 is a configuration block diagram of a fuel injection control device in which the present invention is implemented, Fig. 2 is a graph for estimating the intake air amount from the throttle valve opening and the second state quantity, and Fig. 3 is the throttle valve opening. FIG. 4 is a time chart showing temporal changes in the first state quantity and the second state quantity during a transient period of . A functional block diagram, FIG. 5 is a graph showing the relationship between the engine rotation speed and the smoothed value when the absolute value of the ratio of the first and second state quantities exceeds the threshold, and the sixth
The figure is a graph showing the relationship between the engine rotation speed and the smoothed value when the absolute value of the ratio of the first and second state quantities is below the threshold, and Figure 7 is the ratio of the first and second state quantities. A time chart for explaining the situation in which the smoothed value is changed depending on the absolute value of Fig. 10 is a flowchart for explaining the calculation of the corrected injection quantity, and Fig. 11 is a flowchart for explaining the calculation of the basic injection quantity. Flowchart to explain,
Fig. 12 is a flowchart for explaining the reading of the coefficients for correcting the radius value and the threshold value, and Fig. 13 is the
Flowchart for explaining state quantity calculation, 14th
The figure is a flowchart for explaining the calculation of the injection amount injected from the fuel injection valve into the combustion chambers E1 to Ern, and FIG. 15 is a time chart for explaining the compensation of the fuel injection amount during a transient period, which has already been proposed. . 13... Internal combustion engine, 14... Surge tank, 15.
... Intake pipe, 16... Throttle valve, 19... Pressure detector, 24.27... Temperature detector, 28... Crank angle detector, 30... Valve opening detector, 31 ... Processing device, A1-Am... Intake pipe line, 81-Bm...
Fuel injection valve, E1~Em... Combustion chamber, 01~0m...
・Spark Plug Agent Patent Attorney Keishi Saikyo

Claims (3)

[Claims] (1) Determine a basic injection amount from the rotational speed of the internal combustion engine and intake pipe pressure, determine a first state quantity from the intake air amount and the rotational speed of the internal combustion engine, and give the first state quantity a lag characteristic. Find a second state quantity that follows and changes so that they match or almost match, find a correction injection amount during a transient period from the difference between the first state quantity and the second state quantity, and calculate the basic injection amount and the correction injection amount. A method for controlling a fuel injection amount of an internal combustion engine for determining a fuel injection amount supplied to the internal combustion engine based on the above, characterized in that the delay characteristic is made different depending on the first state quantity and the second state quantity. A method of controlling fuel injection amount in an internal combustion engine. (2) The fuel injection for an internal combustion engine according to claim 1, wherein the delay characteristic is varied depending on the magnitude relationship between the ratio of the first state quantity and the second state quantity and a predetermined threshold value. How to control quantity. (3) A method for controlling a fuel injection amount for an internal combustion engine according to claim 2, characterized in that at least one of the threshold value and the delay characteristic is changed depending on the temperature of a coolant of the internal combustion engine.