JP2677421B2 - Fuel injection amount control method for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In a fuel injection amount control method for an internal combustion engine, a fuel injection amount control method for injecting into the internal combustion engine a fuel amount according to the amount of air that passes through a throttle valve and is sucked into the internal combustion engine via an intake pipe is described. The basic injection amount is calculated based on the intake pipe pressure at the calculation timing, and the first state quantity related to the air flow rate passing through the throttle valve is calculated based on the value corresponding to the opening of the throttle valve and the intake pipe pressure. Then, the second state quantity, which changes with the time delay of the first state quantity, is obtained and is related to the flow rate of the air supplied to the internal combustion engine, and is calculated from the difference between the first state quantity and the second state quantity. A third state quantity related to the time rate of change of the intake pipe pressure is obtained, and a correction value related to the sum of the time Δt1 from the calculation timing to the timing at which the intake valve closes and the filter processing time Δt2 of the output of the intake pressure detector. , The third Obtain a correction amount by the state quantity by determining the amount of fuel injected from said correction amount and the basic injection quantity, good response, and to realize a high-precision fuel injection amount control.

TECHNICAL FIELD The present invention relates to a fuel injection amount control method for controlling the fuel injection amount of an internal combustion engine.

2. Description of the Related Art In a so-called electronically controlled fuel injection device, a so-called L-JETRO method, in which an intake air flow rate is mainly detected using an air flow meter and the fuel injection amount is determined according to the intake air flow rate, and an intake pipe are conventionally used. A so-called D-JETRO method, which determines the fuel injection amount based on the pressure and the rotation speed of the internal combustion engine, is used.

Problems to be Solved by the Invention In the L-JETRO method, since the intake air flow rate is detected using an air flow meter or the like provided in the intake pipe, the responsiveness is relatively good, but the cost is high and it is detected. Since it is a volumetric flow rate, there are large errors due to altitude and temperature. In order to solve this problem, for example, a configuration is conceivable in which an atmospheric pressure sensor or the like is provided upstream of the air flow meter to detect the mass flow rate of the intake air. The increased atmospheric pressure sensor increases costs.

On the other hand, in the D-JETRO method, since the fuel injection amount is determined based on the output of the intake pressure sensor that detects the intake pipe pressure and the rotation speed of the internal combustion engine, there is no obstacle in the intake path and the cost is low. However, there is a problem that the response is poor. That is, this is because the fluctuation of the intake pressure due to the opening and closing of the intake valve reaches 50 to 100 mmHg at about 4000 rpm, for example, and the delay due to the filter process performed to absorb such fluctuation is the main factor.

An object of the present invention is to provide an internal combustion engine that can be controlled with good response and high accuracy so that the fuel injection amount becomes an optimum value with respect to the intake air flow rate, and that the cost can be reduced. A fuel injection amount control method is provided.

Means for Solving the Problems The present invention provides a fuel injection amount control method for an internal combustion engine, which injects into the internal combustion engine a fuel amount according to the amount of air that passes through a throttle valve and is drawn into the internal combustion engine through an intake pipe, The basic injection amount is obtained based on the intake pipe pressure at a predetermined calculation timing, and the first injection amount related to the air flow rate passing through the throttle valve is determined based on the opening of the throttle valve and the value corresponding to the intake pipe pressure. The state quantity is obtained, the second state quantity is changed in accordance with the first state quantity with a time delay, and the second state quantity related to the flow rate of the air supplied to the internal combustion engine is obtained, and the first state quantity and the second state quantity are obtained. The third state quantity related to the time rate of change of the intake pipe pressure is obtained from the difference between the above, and is related to the sum of the time Δt1 from the calculation timing to the timing when the intake valve is closed and the filtering processing time Δt2 of the output of the intake pressure detector. correction If the calculated correction amount by the third state quantity, which is the basic injection amount and the correction amount and the fuel injection quantity control method for an internal combustion engine, wherein the determination of the amount of fuel injection from.

The present invention also provides a fuel injection amount control method for an internal combustion engine, which injects fuel into an internal combustion engine according to the amount of air that is passed through the throttle valve and drawn into the internal combustion engine via an intake pipe, wherein the opening of the throttle valve is Based on a value corresponding to the pressure in the intake pipe, a first state quantity related to the flow rate of air passing through the throttle valve is obtained, and the first state quantity is tracked and changed with a time delay and supplied to the internal combustion engine. The second state quantity related to the air flow rate is calculated, the third state quantity related to the time rate of change of the intake pipe pressure is calculated from the difference between the first state quantity and the second state quantity, and the fuel injection amount is calculated. The correction pressure related to the sum of the time Δt1 from the timing to the timing of closing the intake valve and the filter processing time Δt2 of the output of the intake pressure detector and the third state quantity is used to obtain the correction pressure, and the intake pipe at the calculation timing is calculated. Pressure and A fuel injection amount control method for an internal combustion engine, characterized in that a fuel injection amount is obtained using the corrected pressure.

Operation According to the present invention, the first state quantity related to the air flow rate passing through the throttle valve is a value that responds to the transient state of the opening / closing operation of the throttle valve with good responsiveness, and the first state quantity is the throttle state. It is calculated based on the values corresponding to the valve opening and the intake pipe pressure. The second state quantity is related to the flow rate of the air supplied to the internal combustion engine, and changes following the first state quantity with a time delay. Then, the third state quantity is obtained from the difference between the first state quantity and the second state quantity. The third state quantity is related to the time change rate of the intake pipe pressure and has a predetermined relationship with the time change rate of the intake pipe pressure. Therefore,
The correction amount is obtained by the correction value related to the sum of the time Δt1 from the fuel injection amount calculation timing to the intake valve closing timing and the filter processing time Δt2 of the output of the intake pressure detector, and the third state amount, The fuel injection amount is obtained from the correction amount and the basic injection amount obtained based on the intake pipe pressure, and the fuel injection amount thus obtained becomes the optimum fuel supply amount to the internal combustion engine.

Further, instead of obtaining the correction amount for correcting the basic injection amount, the sum of the time Δt1 from the fuel injection amount calculation timing to the intake valve closing timing and the filter processing time Δt2 of the output of the intake pressure detector is calculated. The associated correction value,
The optimum fuel injection amount to the internal combustion engine can also be obtained by obtaining the correction pressure based on the third state amount and obtaining the fuel injection amount using the intake pipe pressure at the calculation timing and the correction pressure.

Embodiment FIG. 1 is a control apparatus 1 for an internal combustion engine according to an embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration related to the above. The combustion air introduced from the intake port 2 is purified by the air cleaner 3, and the amount of inflow is adjusted via the intake pipe 4 by the throttle valve 5 interposed in the intake pipe 3, and then is supplied to the surge tank 6. Inflow. The fuel air flowing out from the surge tank 6 is mixed with the fuel injected from the fuel injection valve 8 interposed in the intake pipe 7, and is supplied to the combustion chamber 11 of the internal combustion engine 10 via the intake valve 9. An ignition plug 12 is provided in the combustion chamber 11, and the exhaust gas from the combustion chamber 11 is discharged through an exhaust valve 13, and is discharged from an exhaust pipe 14 to the atmosphere via a three-way catalyst 15.

The intake pipe 4 is provided with an intake air temperature detector 21 for detecting the temperature of intake air, a throttle valve opening detector 22 is provided in association with the throttle valve 5, and the surge tank 6 is provided with an intake pipe 7 An intake pressure detector 23 for detecting pressure is provided. Further, a cooling water temperature detector 24 is provided near the fuel chamber 11, an oxygen concentration detector 25 is provided upstream of the three-way catalyst 15 in the exhaust pipe 14, and a downstream side of the three-way catalyst 15. An exhaust temperature detector 26 is provided. The rotation speed of the internal combustion engine 10, that is, the number of rotations per unit time is a crank angle detector.
Detected by 27.

The control device 1 includes a vehicle speed detector 28 and a starter motor 33 for starting the internal combustion engine 10 together with the detectors 21 to 27.
Start detector 29 to detect if is activated
When an automobile equipped with the internal combustion engine 10 is equipped with an automatic transmission, an air-conditioning detector 30 for detecting the use of an air conditioner, etc., and whether the shift stage of the automatic transmission is in the neutral position or not. The detection result from the neutral detector 31 for detecting is input.

Further, the control device 1 is energized by a battery 34, and the control device 1 includes the detectors 21 to 31.
The fuel injection amount and the ignition timing are calculated based on the detection result of the fuel injection, the power supply voltage of the battery 34 detected by the voltage detector 20, and the like, and the fuel injection valve 8 and the spark plug are calculated.
Control 12 and so on. The control device 1 also drives the fuel pump 32 when the internal combustion engine 10 is operating.

FIG. 2 is a block diagram showing a specific configuration of the control device 1. The detection results of the detectors 20 to 25 are supplied from an input interface circuit 41 to a processing circuit 43 via an analog / digital converter 42. In addition, the detector 22, 27-3
The detection result of 1 is given to the processing circuit 43 via the input interface circuit 44. The processing circuit 43 is provided with a memory 45 for storing various control maps and learning values.The processing circuit 43 receives power from the battery 34 through a constant voltage circuit 46. Supplied via

The control output from the processing circuit 43 is derived through an output interface circuit 47, and is applied to the fuel injection valve 8 to control the amount of fuel injection, and is also applied to an ignition plug 12 via an igniter 48 for ignition. The timing is controlled, and the fuel pump 32 is driven again.

The detection result of the exhaust gas temperature detector 26 is given to an exhaust gas temperature detection circuit 49 in the control device 1. When the detection result is abnormally high, the warning lamp 51 is turned on via the drive circuit 50.

In the control device 1 configured as described above, the detection output of the intake pressure detector 23 used for calculating the fuel injection amount and the ignition timing includes the intake valve 9 as shown in FIG.
, And the fluctuation range is a large value of, for example, about 50 to 100 mmHg at 4000 rpm as described above. In order to absorb this variation and detect an accurate intake pressure, the detection output of the intake pressure detector 23 includes a control device 1
Filter processing is performed inside.

Therefore, even if the throttle valve 5 is rapidly opened as shown in FIG. 3 (2) due to the delay caused by the filtering, the pressure waveform after the filtering is, for example,
It appears as shown by reference numeral l2 after being delayed by Δt2 with respect to the change of the actual pressure waveform of the intake pipe pressure shown by reference numeral l1 in FIG. 3 (3).

Further, the amount of fuel injected from the fuel injection valve 8 needs to be an amount commensurate with the amount of air taken into the combustion chamber 11 at the end of the intake stroke. That is, it is necessary to calculate the injection amount based on the intake pipe pressure immediately before the intake valve 9 is closed. Actually, the intake valve 9 begins to open before 14 degrees crank angle (hereinafter referred to as ° CA) of the top dead center as shown in Fig. 3 (4), for example, and the bottom dead center is passed only 46 ° CA. Will be closed when Therefore, in consideration of the injection amount calculation time shown in FIG. 3 (5), as shown in FIG. 3 (6), the intake pipe pressure reading and the injection amount calculation timing are performed.
For example, t1 is set to 90 ° CA before the top dead center.

Therefore, in FIG. 3 (3), when the injection amount is calculated based on the intake pipe pressure at the calculation timing t1, the actual intake pipe at the timing t2 at which the intake valve 9 that should originally be used for the calculation of the injection amount is closed. The pressure is reduced by a pressure difference ΔP1 corresponding to the time difference Δt1 and a pressure difference ΔP2 corresponding to the filter processing time Δt2, resulting in lean combustion. Therefore, it is necessary to predict and obtain the pressure difference ΔP1 + ΔP2 corresponding to the delay of time Δt1 + Δt2, and correct the intake pipe pressure at the calculation timing t1.

As shown in FIG. 3 (3), the pressure waveform l2 after the filtering process is almost equal to the pressure waveform l1 of the actual intake pressure, and therefore the time rate of change dP / dt of the intake pipe pressure P is accurately determined. By obtaining it, it is possible to accurately correct such a delay.

The time rate of change dP / dt is determined as follows. That is, through the throttle valve 5, the surge tank 6
Qin of the intake air flow rate (related to the first state quantity) flowing to
When Qout is the flow rate of outflow air from the surge tank 6, in other words, the flow rate of air supplied to the internal combustion engine 10 (related to the second state quantity), the first value related to the time change rate dp / dt of the intake pressure The variation K1 · dp / dt related to the three state quantities is Becomes However, ΔQ is the amount of change in the intake air flow rate,
K1 is a constant. Further, the opening of the throttle valve 5 is θ,
If the rotation speed of the internal combustion engine 10 is N, Qout = K3 · η · N · P (3) where K2 and K3 are constants, η is the intake efficiency, P
₀ is atmospheric pressure. Accordingly, from the first equation, the intake pressure P for which the delay correction has been performed is: Here, Pi is the intake pressure at the above calculation timing, and K1
a = 1 / K1.

On the other hand, the time Δt1 based on the calculation timing is constant when viewed on the crank angle axis, and when the time between 180 ° CA is T, Becomes In this formula 5, Δt1 / T is a constant value, which is set as A, and Δt2 is constant with respect to the time axis.
If this is B, Note that N = 1 / T, so that However, K1b = K1a · A.

Considering B / A here, the time required from the calculation timing to the timing t2 at which the intake valve 9 is closed is, for example, 316 ° CA. Therefore, if the delay time due to the filter processing is, for example, 10 msec, Becomes Hereinafter, for simplification of description, this B / A will be described using the value of the eighth equation. Therefore, the seventh equation can be expressed as the ninth equation.

That is, regarding the calculation timing and the delay due to the filtering process, by accurately obtaining ΔQ, these corrections can be obtained with generality and high accuracy. The characteristic of the correction is proportional to the change in the air flow rate per unit rotation, and the influence of the filter processing is greatly corrected with the rotation speed.

Next, a method of calculating ΔQ / N will be described. The change in the intake air flow rate Qin when the throttle valve 5 is suddenly opened is
In FIG. 4, this is indicated by reference numeral l3. On the other hand, due to the influence of the surge tank 6, the outflow air flow rate Qout from the surge tank 6 is indicated by reference numeral 14. These flow rates Qin and Qout are expressed by the above-described second and third equations, respectively.

During steady operation of the internal combustion engine 10, Qin = Qout, and the flow rate Q
In is determined in advance by actually measuring the flow rate Qout in the steady state with the throttle valve opening θ and the intake pipe pressure P as parameters. That is, as shown in FIG. 5, the value corresponding to N · P in the above-mentioned formula 3 is the throttle valve opening degree when the intake pipe pressure P is changed while keeping the throttle valve opening θ constant. It is assumed that the product value MAP of N and P in is used.
As a result, the flow rate Qin can be expressed as in Expression 10. The graph shown in FIG. 5 is stored in the memory 45 as a map.

Qin = K3 · η · MAP… (10) Therefore, It can be expressed as.

However, in the eleventh equation, the MAP / N and P _M is
Manufacturing variations and of the internal combustion engine 10, the actual During controlled One by the secular change, and may not match in the steady state, Therefore, in this embodiment, the value Pc obtained connexion by the intake pressure P _M in the calculation Replace with Be the intake air pressure P _M is deviation occurs due to the variation as described above, the time rate of change dP / dt is substantially identical, the but similarly to the above-mentioned delay correction represented by connexion fourth equation, It can be expressed as. However, Pci is the current calculated value, and Pci _-1 is the previous calculated value. Therefore, MAP / N
(Corresponding to the first state quantity in this embodiment) and the calculated value Pc (corresponding to the second state quantity in this embodiment) always match in the steady state, and the throttle valve opening θ in the transient state. MAP / N changes abruptly with the change of, and the value Pc changes following to match it. Therefore, the 9th
From the equation, the eleventh equation, and the twelfth equation, it is possible to obtain the arithmetic expression regarding the delay correction shown in the thirteenth equation.

Here, K4 = K1b · K3 · η. Furthermore, the value Pc is the first
Based on the four formulas, for example, the approximation calculation is performed every 4 msec.

However, K5 = K1 · K3 · η.

6 to 9 are flow charts for explaining the operations of the approximate calculation and the fuel injection amount calculation as described above.
FIG. 6 shows an operation for obtaining the rotational speed NE of the internal combustion engine 10. In step s1, the measured value measured by the crank angle detector 27 is read. This behavior is
Every 180 ° CA.

Figure 7 represents an operation for obtaining the intake air pressure P _M, the measurement result of the intake pressure detector 23 in step s11 is read into the processing circuit 43 is digitally converted by an analog / digital converter 42. This operation is performed, for example, every time a conversion operation is performed every 2 msec.

FIG. 8 is a flow chart for explaining the above-mentioned approximation calculation. For example, every time the analog / digital conversion operation of the throttle valve opening θ detected by the throttle valve opening detector 22 is performed every 4 msec. Done in Step s2
In step 1, the throttle valve opening θ is read, and in step s22, the throttle valve opening θ obtained in step s21 and the value Pc obtained in step s31 described later, that is, the intake pipe 7
The map value MAP is read out from the value corresponding to the pressure of the above, based on the graph shown in FIG.

At step s23, the value MAP is divided by the rotational speed NE to obtain the first state quantity. Steps
At s24, the value Pc which is the second state quantity is calculated from the division result.
Is subtracted. At step s25, the sign for the approximate correction of the value Pc at step s31 described later is set according to whether the result of the subtraction at step s24 is positive or negative. In step s26, it is determined whether or not the set sign is positive. Move to s28.

At step s28, the third state quantity which is the subtraction result at step s24 is multiplied by the rotation speed NE. In step s29, the coefficient K5a is read from the map shown in FIG. 10 based on the detection result of the cooling water temperature detector 24. Although K5 = K1 · K3 · η (constant) in the above formula 14, this coefficient K5 is assumed to be a value K5a that changes depending on the cooling water temperature. This is because the value Pc is M at low temperature.
By slowing the speed that follows the AP / N value, the corrected injection amount TM, which will be described later, is made to act larger and longer than room temperature, and to cope with the shortage of the correction amount due to the adherence of fuel to the pipe wall. Is.

In step s30, this coefficient K5a is multiplied by the calculation result obtained in step s28, and the value Pc is updated based on the sign set in step s25 in step s31 using this multiplication result. In this way,
The approximation calculation of the value Pc represented by the above-described fourteenth equation is performed.

FIG. 9 shows the operation for obtaining the actual fuel injection amount TAU, which is performed, for example, every 360 ° CA. At step s41, the basic injection amount TP is read from the rotational speed NE obtained at step s1 and the intake pressure P _M obtained at step s11. At step s42, a part of the calculation in the equation 13 is performed using the rotation speed NE. Step
At s43, from the rotation speed NE and the values MAP and Pc, the 13th
The other parts of the expression are calculated. In step s44, the calculation result of steps s42, s43 and the conversion constant K6 to the fuel injection amount including the constant K4 are multiplied to obtain the corrected injection amount.
TM is required. In step s45, the actual fuel injection amount TAU is calculated from the basic injection amount TP obtained in step s41 and the corrected injection amount TM obtained in step s44.

In this way, the response delay due to the delay time Δt1 due to the calculation timing and the delay time Δt2 due to the filter processing, as shown in FIGS. 3 and 4, is absorbed by the detected output after the delay. Since the actual detection output of the atmospheric pressure detector 23 is corrected based on the time change rate dP / dt, the transient response when the throttle valve 5 is suddenly opened can be improved. In addition, since the present embodiment is basically a so-called D-dietro system, it has steady stability and high accuracy, and can be realized with a relatively simple configuration. Such a problem can be solved. Furthermore, since the correction uses a relatively versatile arithmetic expression, the correction can be used in common for different types of internal combustion engines.

In the above-mentioned embodiment, the basic injection amount TP and the corrected injection amount TM
Although the actual fuel injection amount TAU is obtained from the above, as another embodiment of the present invention, the actual fuel injection amount TAU is actually obtained based on the corrected intake pressure P and the rotational speed NE of the internal combustion engine 10 shown in the equation (13). The fuel injection amount TAU may be directly obtained.

The processing in this case is shown in FIG. This process is also the 9th
It is executed every 360 ° CA as in the figure. First, in step s51, a part of the calculation in the equation (13) is performed using the rotation speed NE obtained in step s1, and the calculation result is stored in the register A1. Next, in step s52, another part of the equation (13) is calculated from the rotation speed NE and the values MAP and Pc, and the calculation result is stored in the register A2.

At step s53, the corrected pressure P _MC is obtained based on the constant K4 and the values of the registers A1 and A2. In step s54,
Yotsute this corrected pressure P _MC, the pressure P obtained by correcting the measured value P _M obtained in the step s11 is determined. From the pressure P and the rotational speed NE thus obtained, the actual fuel injection amount TAU is calculated in step s55.

As described above, according to the fuel injection amount control method of claim (1) of the present invention, the first state quantity related to the air flow rate passing through the throttle valve and the air flow rate supplied to the internal combustion engine. The third state quantity related to the time rate of change of the intake pipe pressure is calculated from the difference with the second state quantity related to the time Δt1 from the fuel injection amount calculation timing to the intake valve closing timing and the intake detector The correction amount is obtained from the correction value related to the sum of the output filtering time Δt2 and the third state amount. Therefore, the first state quantity with good transient response, and
Since the correction amount is obtained by using the second state amount that follows the first state amount with a time lag, the correction amount of the fuel can be accurately obtained even during a transient period when the throttle valve is suddenly opened and closed. Therefore, the fuel injection amount can be obtained with high accuracy by using this correction amount and the basic injection amount. Further, since the correction amount is obtained in consideration of the filter processing time of the output of the intake pressure detector, the correction amount can be obtained more accurately.

According to the fuel injection amount control method of claim (2) of the present invention, instead of obtaining the correction amount of the basic injection amount of fuel, the time from the calculation timing of the fuel injection amount to the timing at which the intake valve is closed. The correction value related to the sum of Δt1 and the filtering time Δt2 of the output of the intake pressure detector,
The control amount is sought by the state quantity. Therefore,
By obtaining the fuel injection amount using the intake pipe pressure at the calculation timing and the correction pressure, the optimum fuel injection amount can be obtained with high accuracy. Further, also in this control method, since the correction pressure is obtained in consideration of the filter processing time of the output of the intake pressure detector, the correction pressure can be obtained more accurately.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a control device 1 of an internal combustion engine according to an embodiment of the present invention and a configuration related thereto, and FIG. 2 is a block diagram showing a specific configuration of the control device 1. FIG. 3 is a timing chart for explaining the operation at the transition when the throttle valve opening is changed, and FIG. 4 is a graph showing the relationship between the intake air flow rate Qin to the surge tank 6 and the outflow air flow rate Qout. Fig. 5 shows the intake pressure P, Pc at each throttle valve opening θ.
6 to 9 are flow charts for explaining the operation, and FIG. 10 is a correction coefficient of the calculated intake pressure Pc with respect to the change of the cooling water temperature.
FIG. 11 is a flow chart for explaining the operation of another embodiment of the present invention, which is a graph showing changes in K5. DESCRIPTION OF SYMBOLS 1 ... Control device, 4,7 ... Intake pipe, 5 ... Throttle valve, 6 ... Surge tank, 8 ... Fuel injection valve, 10 ... Internal combustion engine, 14 ... Exhaust pipe, 20-31 ... Detector, 43 Processing circuit, 45 Memory

 ─────────────────────────────────────────────────── ───Continued from the front page (56) Reference JP-A 63-215848 (JP, A) JP-A 1-216054 (JP, A) JP-A 62-162750 (JP, A) JP-A 63- 289237 (JP, A) JP-A-2-136531 (JP, A) JP-A 1-216041 (JP, A) JP-A 58-211535 (JP, A) JP-A 59-201937 (JP, A) Actual Kaihei 1-160148 (JP, U)

Claims (2)

(57) [Claims] 1. A fuel injection amount control method for an internal combustion engine, comprising: injecting an amount of fuel corresponding to an amount of air taken into an internal combustion engine through an intake pipe through a throttle valve into an internal combustion engine; Determining a basic injection amount based on a pipe pressure, and determining a first state amount related to an air flow rate passing through the throttle valve based on an opening of the throttle valve and a value corresponding to a pressure of an intake pipe, The second state quantity related to the flow rate of the air supplied to the internal combustion engine is determined by following the first state quantity with a time delay, and the intake pipe pressure is calculated from the difference between the first state quantity and the second state quantity. The third state quantity related to the time change rate of is calculated, the correction value related to the sum of the time Δt1 from the calculation timing to the timing at which the intake valve is closed and the filtering time Δt2 of the output of the intake pressure detector, With 3 state quantities Therefore, the correction amount is obtained, and the fuel injection amount is obtained from the basic injection amount and the correction amount. 2. A fuel injection amount control method for an internal combustion engine, comprising: injecting fuel into an internal combustion engine according to an amount of air taken into the internal combustion engine through an intake pipe and passing through a throttle valve; , A first state quantity related to the flow rate of air passing through the throttle valve is obtained based on a value corresponding to the pressure of the intake pipe, and the first state quantity is changed following the time delay with the internal combustion engine. The second state quantity related to the supplied air flow rate is obtained, and the third state quantity related to the time rate of change of the intake pipe pressure is obtained from the difference between the first state quantity and the second state quantity. A correction pressure related to the sum of the time Δt1 from the calculation timing to the timing of closing the intake valve and the filter processing time Δt2 of the output of the intake pressure detector and the third state quantity is used to obtain the correction pressure, and the intake pressure at the calculation timing is calculated. Pipe pressure and A fuel injection amount control method for an internal combustion engine, characterized in that a fuel injection amount is obtained using the corrected pressure.