JP2623703B2 - Fuel injection amount control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection amount control device for an internal combustion engine, and more particularly to a device for controlling a fuel injection amount by predicting an amount of air taken into an engine combustion chamber. The present invention relates to a fuel injection amount control device for an internal combustion engine.

[Conventional technology]

Conventionally, the amount of air passing upstream of the throttle valve or the absolute pressure of the intake pipe downstream of the throttle valve (hereinafter referred to as the intake pipe pressure) is sampled at predetermined intervals, and based on this sampled value and the detected value of the engine rotational speed. The fuel injection time is calculated by correcting the basic fuel injection time with the intake air temperature, the engine cooling water temperature, etc. to obtain the fuel injection time, and the fuel injection valve is opened for a time corresponding to the fuel injection time to obtain the fuel. BACKGROUND ART A fuel injection amount control device for an internal combustion engine that controls an injection amount is known. The above-mentioned air quantity and the physical quantity of the intake pipe pressure both correspond to the air quantity taken into the engine combustion chamber. In order to supply the amount of fuel required by the engine to the engine combustion chamber, sampling of the physical quantity at the time when the amount of air to be drawn into the engine combustion chamber is determined, that is, near the intake valve closing time including when the intake valve is closed The fuel injection amount may be controlled using the value. However, a predetermined time is required to calculate the fuel injection time, and a predetermined flight time is required until the fuel injected from the fuel injection valve reaches the combustion chamber, and the amount of air taken into the combustion chamber is required. When the fuel injection amount is calculated and injected when the value is determined, the injected fuel is not supplied to the engine combustion chamber due to a time delay.

For this reason, conventionally, the pressure in the intake pipe at the time when the injected fuel reaches the combustion output is predicted and predicted according to the following expression determined in consideration of the second-order differential term of the macrolein-expanded polynomial. The fuel injection amount is calculated using the intake pipe pressure PMF thus calculated and injected (JP-A-60-169647, JP-A-62-157244).

PMF = 2.5PM-2.0PM360 + 0.5PM720 where PM is the current intake pipe pressure sampled and PM
360 is the intake pipe pressure sampled 360 ° C. (crank angle) before the present, and PM720 is the intake pipe pressure sampled 720 ° CA before the present.

However, in the above-described technology, if the period between the time point to be predicted (prediction destination) and the time point actually predicted is long, the predicted value and the actual value may differ from each other due to a change in the operating state after predicting the intake pipe pressure and the like. For example, when acceleration is performed after predicting the intake pipe pressure or the like, the amount of air actually sucked into the combustion chamber becomes larger than the predicted value, so that the air-fuel ratio becomes lean, and drivability and exhaust emission are reduced. Worsens.
In order to solve this problem, a direct fuel injection device for directly injecting fuel into a cylinder is provided in addition to the main fuel injection device as disclosed in JP-A-63-75325, and detection by an air flow meter is conventionally performed. The fuel injection amount is calculated from the intake air amount and the engine rotation speed detected by the crank angle sensor, and the shortage of the fuel injection amount is calculated, the fuel is injected from the main fuel injection device, and the shortage of the fuel injection amount is directly determined by the fuel. Injection is performed directly from an injection device into a cylinder.

[Problems to be solved by the invention]

However, in the above prior art, since the fuel injection amount is calculated based on the detected intake air amount, at the time of rapid acceleration, the detected intake air amount in the fuel injection amount calculation and the intake air amount near the intake valve closing are calculated. The difference becomes large, so that the shortage of the fuel injection amount increases, and there is a possibility that the entire shortage amount cannot be injected before ignition. In addition, there is a problem that the production cost is increased because a direct fuel injection device is required in addition to the main fuel injection device.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and does not increase the number of fuel injection valves normally provided in the engine, and minimizes the shortage to minimize the fuel supply amount during sudden acceleration or the like. It is an object of the present invention to provide a fuel injection amount control device for an internal combustion engine that prevents deterioration of exhaust emission.

[Means for solving the problem]

In order to achieve the above object, the present invention provides, as shown in FIG. 1, a sampling means A for sampling a physical quantity related to an air quantity taken into an engine combustion chamber at a predetermined cycle,
A prediction unit B that predicts a future physical quantity that is a predicted value of the physical quantity at a prediction time point that is a predetermined period ahead of the present based on a current sampling value and a past sampling value;
A fuel amount calculating means C for calculating a fuel amount to be supplied to the engine combustion chamber based on the future physical amount; a fuel amount determined based on the future physical amount; and a fuel amount determined based on a sampling value at the prediction time. Amount calculating means D for calculating the amount of fuel shortage to be supplied to the engine combustion chamber from the engine
And a fuel injection means E for injecting the amount of fuel calculated by the fuel amount calculation means C at the fuel injection timing and immediately injecting the shortage of fuel calculated by the shortage amount calculation means. It is composed.

[Action]

Hereinafter, the operation of the present invention will be described. Sampling means A
Samples a physical quantity related to the amount of air drawn into the engine combustion chamber (for example, the amount of air passing upstream of the throttle valve, the pressure of the intake pipe downstream of the throttle valve, etc.) at predetermined intervals. The prediction means B predicts a future physical quantity, which is a predicted value of a physical quantity at a prediction time point a predetermined period ahead of the present, based on the current sampling value and the past sampling value. This future physical quantity is preferably an air quantity existing in the engine combustion chamber when the intake valve is closed, that is, an air quantity contributing to combustion.
The predicted value of the physical quantity at a predetermined point in time from the time when the intake valve is closed (or in the vicinity thereof) is a value that does not pose any practical problem. The fuel amount calculating means C calculates the fuel amount to be supplied to the engine combustion chamber based on the future physical quantity (the predicted value predicted by the predicting means B). The shortage amount calculating means D calculates a fuel amount determined based on a future physical quantity predicted by the predicting means B and a fuel amount determined based on a sampling value at the time of prediction (a sampling value near the intake valve closing). The shortage of the amount of fuel to be supplied to the engine combustion chamber is calculated. Then, the amount of fuel calculated by the fuel amount calculating means C is injected from the fuel injection means E at the fuel injection timing, and the shortage of fuel calculated by the shortage calculating means is immediately injected. As described above, the prediction means B predicts a future physical quantity, and injects an amount of fuel corresponding to the predicted value of the physical quantity at the fuel injection timing, and immediately injects a shortage of fuel. The difference between the predicted value and the actual sampling value corresponding to this predicted value can be minimized, thereby minimizing the shortage of the fuel amount and supplying the entire shortage to the combustion chamber in a short time. it can. Further, since the fuel injection means E injects the fuel amount to be supplied to the engine combustion chamber and the shortage of the fuel amount,
There is no need to provide new fuel injection means.

〔The invention's effect〕

As described above, according to the present invention, it is possible to prevent the deterioration of the exhaust emission and the like due to the shortage of the fuel supply amount at the time of rapid acceleration without increasing the number of fuel injection valves and minimizing the shortage of the fuel injection amount. Can be obtained.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, the present invention is applied to a four-cylinder engine to perform fuel injection control independently for four cylinders. FIG. 2 schematically shows an internal combustion engine (engine) provided with a fuel injection amount control device to which the present invention can be applied.

This engine is controlled by an electronic control circuit such as a micro computer. A throttle valve 8 is disposed downstream of an air cleaner (not shown). The throttle valve 8 is in a fully closed state. An idle switch 10 to be turned on is attached, and a surge tank 12 is provided downstream of the throttle valve 8. A semiconductor type pressure sensor 6 is attached to the surge tank 12. The pressure sensor 6 has a small time constant (for example, 3 to 5 msec) for removing a pulsating component of the intake pipe pressure, and is a filter (third filter) composed of a CR filter or the like having a good response.
(Fig.) This filter may be built in the pressure sensor. A bypass passage 14 is provided so as to bypass the throttle valve 8 and connect the surge tank 12 upstream of the throttle valve and the surge tank 12 downstream of the throttle valve.
Is provided. The ISC whose opening is adjusted by a pulse motor 16A having a 4-pole stator
(Idle speed control) Valve 16B is installed. The surge tank 12 is connected to a combustion chamber of the engine 20 via an intake manifold 18 and an intake port 22. And this intake manifold 18
A fuel injection valve 24 is attached to each cylinder so as to protrude inside.

The combustion chamber of the engine 20 is connected to a catalyst device (not shown) filled with a three-way catalyst via an exhaust port 26 and an exhaust manifold 28. The exhaust manifold 28 is provided with an O ₂ sensor 30 that outputs a signal inverted at the stoichiometric air-fuel ratio. A cooling water temperature sensor 34 is attached to the engine block 32 so as to penetrate the engine block 32 and protrude into the water jacket. The coolant temperature sensor 34 detects the engine coolant temperature and outputs a coolant temperature signal, and the coolant temperature signal represents the engine temperature. The engine oil temperature may be detected to represent the engine temperature.

An ignition plug 38 is attached to each cylinder so as to penetrate the cylinder head 36 of the engine 20 and protrude into the combustion chamber. The ignition plug 38 is connected via a distributor 40 and an igniter 42 to an electronic control circuit 44 composed of a micro computer or the like. In the distributor 40, a cylinder discriminating sensor 46 and a rotation angle sensor 48 each composed of a signal rotor fixed to the distributor shaft and a pickup fixed to the distributor housing are mounted. The cylinder discrimination sensor 46 outputs a cylinder discrimination signal, for example, every 720 ° CA, and the rotation angle sensor 48 outputs an engine speed signal, for example, every 30 ° CA.

As shown in FIG. 3, the electronic control circuit 44 includes a microprocessing unit (MPU) 60, a read-only memory (ROM) 62, a random access memory (RAM) 64, and a back-up program (BU-RAM). 66, an input / output port 68, an input port 70, output ports 72, 74 and 76, and a bus 75 such as a data bus and a control bus connecting these. An analog-digital (A / D) converter 78 and a multiplexer 80 are sequentially connected to the input / output port 68. The multiplexer 80 is connected to the pressure sensor 6 via a CR filter 7 and a buffer 82 each composed of a resistor R and a capacitor C, and to the cooling water temperature sensor 34 via a buffer 84. The multiplexer 80 is connected to the idle switch 10. MPU6
To 0, the multiplexer 80 and the A / D converter 78 are controlled to sequentially convert the output of the pressure sensor 6, the output of the idle switch 10, and the output of the cooling water temperature sensor 34 input via the CR filter 7 into digital signals. Store in RAM64.
This A / D conversion can be performed every 180 ° CA, but may be performed every predetermined time. Therefore, multiplexer 80,
The A / D converter 78, the MPU 60 and the like function as sampling means for sampling the pressure sensor output at a predetermined crank angle (at a predetermined cycle). The input port 70 is connected to the O ₂ sensor 30 via a comparator 88 and a buffer 86, and also connected to a cylinder discriminating sensor 46 and a rotation angle sensor 48 via a waveform shaping circuit 90. The output port 72 is connected to the igniter 42 via the drive circuit 92, and the output port 74
Is connected to the fuel injector 24 via a drive circuit 94 having a down counter, and the output port 76 is connected to the pulse motor 16A of the ISC valve via a drive circuit 96. In addition, 98 is a clock and 99 is a timer. In the ROM 62, a control routine program and the like described below are stored in advance.

FIG. 4 shows an asynchronous fuel injection execution routine executed every 180 ° CA. In step 140, the intake pipe pressure which is A / D converted at a predetermined cycle (every 2 to 4 msec) and stored in the RAM. Captures the current sampling value PM of In the next step 142, the fuel injection amount corresponding to the current sampling value PM, that is, the actual fuel injection time tTAU representing the actual fuel injection amount actually requested by the engine is calculated according to the following equation.

tTAU = PM · KINJ · FWL (1) where KINJ is a conversion coefficient for converting the intake pipe pressure into the fuel injection time, and FWL is a correction coefficient determined according to the engine cooling water temperature. In the next step 144, the actual fuel injection time t
The asynchronous fuel injection time is calculated by subtracting the predicted fuel injection time TAUR (calculated in step 162 in FIG. 5) from TAU.
Calculate TAUASY. At step 146, the asynchronous fuel injection time TAUASY is compared with the minimum fuel injection time TAUMIN (minimum fuel amount that can be injected by the fuel injector) determined by the characteristics of the fuel injection valve, and if TAUASY> TAUMIN, the routine proceeds to step 148. The asynchronous fuel injection is executed by immediately executing the fuel injection. Then, after calculating the predicted intake pipe pressure PMF in step 150, the process returns after inverting the flag XTAUCAL in step 152. In addition,
The calculation of the predicted intake pipe pressure PMF will be described later.

FIG. 5 shows the fuel injection time TAU calculation routine. In step 160, it is determined whether or not the flag XTAUCAL is reset. When the flag XTAUCAL is reset, the predicted fuel injection time TAUR is calculated in step 162 according to the following equation.

TAUR = PMF · KINJ · FWL · FAF ... (2) However, FAF is an air-fuel ratio fed back correction coefficient for fed back controlling the air-fuel ratio to the stoichiometric air-fuel ratio based on the O ₂ sensor output.

Here, the flag XTAUCAL is set to 180 ° C in step 152.
The fuel injection time TAUR is 360 ゜ C
The calculation is performed for each A. In step 164, the increment TAUW based on the amount of fuel adhering to the intake pipe wall surface (the amount of manifold wetness) is calculated based on the following equation (3). In step 166, the fuel injection time for actually opening the fuel injection valve is calculated. The TAU is calculated according to the following equation (4) and stored in the RAM. The details of the following equations (3) and (4) will be described later.

_{TAUW = K2 (TAUR-TAUI i} + TAUI i) ... (3) TAU = TAUR + TAUW ... (4) Figure 6 is shows a fuel injection routine, step 17
At 0, it is determined whether or not it is the fuel injection timing. At the time of the fuel injection timing, the fuel injection time TAU stored in the RAM is taken in step 172, and the fuel injection valve is opened for a time corresponding to the fuel injection time TAU in step 174. To execute synchronous fuel injection. If there is a request for asynchronous fuel injection during execution of synchronous fuel injection, the synchronous fuel injection time TAU is extended by a time corresponding to the asynchronous fuel injection time TAUASY. FIG. 7 shows the timings of the synchronous fuel injection and the asynchronous fuel injection under the control as described above.

Hereinafter, the calculation principle of the predicted intake pipe pressure PMF will be described. X ° C
Assuming that the function indicating the intake pipe pressure at A is f (x) and the intake pipe pressure at m ° CA is predicted, the intake pipe pressure at the prediction destination is represented by a function f (x + m). When this function is Taylor-expanded, the following equation (5) is obtained.

Here, f (x + m) ≡PMF is replaced with the current intake pipe pressure f
(X) Assuming that the intake pipe pressure PMa before ≡PM, a ゜ CA, and the intake pipe pressure PM2a before 2a ゜ CA, Therefore, the above equation (5) becomes the following equation (8).

The third term or less (ΔΔPM or less) on the right side of the above equation (8) is represented by k · ΔPM + ΔΔ, where k is a fitting constant determined by experiment.
When approximated by PM, the following equation (9) is obtained.

In the control device for controlling the fuel injection amount based on the intake pipe pressure and the engine rotation speed, the value obtained by processing the output of the pressure sensor by the CR filter and the digital soft filter is employed as the sampling value. Intake pipe pressure PMF
Is delayed by the processing in the filter. Therefore, it is necessary to correct the adaptation constant k in consideration of the delay caused by the filter. If the time constant of the filter is T and the engine speed is NE, it is necessary to correct T · NE / 60000. Also, the fuel injection method (simultaneous injection or independent injection) for the predicted crank angle
Needs to be adapted accordingly. For this reason, a new adaptation constant taking into account the correction of the filter delay and the prediction destination crank angle, etc. is k1, and Therefore, when Equation (9) is modified by these, the following is obtained.

There is a relationship shown in FIG. 8 between the terms of the above equation (11), which includes the rate of change ΔPM, so that the number of times of sampling is small and the intake pipe pressure is low as in the case of low rotation or rapid acceleration. When ΔPM increases due to the change, the predicted intake pipe pressure PMF will overshoot. In addition, under rapid deceleration, the vehicle undershoots. For this reason, in the present embodiment, as shown in FIG. 12, the difference (rate of change) ΔP between the current sampling value PM and the previous sampling value PMa
The predicted intake pipe pressure PMF is calculated by the following formula using a compression value DPM obtained by correcting the difference ΔPM and compressing the difference ΔPM so that the absolute value of the difference ΔPM becomes smaller as the absolute value of M increases. I do.

In the case of a four-cylinder engine, there are a case where fuel is injected simultaneously with four cylinders once per engine revolution and a case where fuel is injected independently with four cylinders. In the case of simultaneous injection with four cylinders, FIG. When fuel is injected at the timings shown, the cylinder in which the injected fuel is most ingested is the first cylinder # 1, and the amount of air which is taken into the combustion chamber of the first cylinder at this time is the intake valve of the first cylinder closed. It is determined by the intake pipe pressure at the time of valve. Therefore, it is sufficient to predict the intake pipe pressure 360 ° CA ahead of the present. In the above description, the predicted crank angle is determined assuming that the injected fuel is most often taken into the first cylinder. However, the predicted crank angle is preferably determined experimentally because the injected fuel is also taken into other cylinders. At this time, as described above, the adaptation constant k1 is corrected. In the case of four-cylinder independent injection, as shown in FIG. 9 (2), the fuel calculated at the present time and injected at the injection timing is sucked into the first cylinder # 1, and at this time, the fuel enters the engine combustion chamber. Since the amount of air to be taken in is determined by the intake pipe pressure when the intake valve of the first cylinder is closed, the intake pipe pressure 360 ° CA ahead of the present may be predicted.

In the case of a four-cylinder engine, the fluctuation cycle due to the pulsation of the intake pipe pressure is considered to be every 180 ° CA. Therefore, if the intake pipe pressure is sampled every 180 ° CA, the influence of the fluctuation due to the pulsation can be minimized. it can.

Therefore, in the case of a four-cylinder engine, the intake pipe pressure may be sampled every 180 ° CA, and the intake pipe pressure 360 ° CA ahead of the present may be predicted. Therefore, in the case of a four-cylinder engine, a = 18
If 0, m = 360, the predicted intake pipe pressure PMF is as follows.

PMF = PM360 + (4 + k1) DPM (13) In the case of a six-cylinder engine, FIGS. 10 (1) and (2)
As understood from the timing of fuel injection shown in
Since it is sufficient to sample every 120 ° CA and predict the intake pipe pressure 360 ° CA ahead of the present, a = 120, m
If = 360, the predicted intake pipe pressure PMF is as follows.

PMF = PM240 + (5 + k1) · DPM (14) The same applies to the case where the amount of air passing upstream of the throttle valve is used as the physical quantity related to the amount of air taken into the engine combustion chamber.

FIG. 11 shows a detailed routine of step 150 in FIG. 4 of the present embodiment for calculating the predicted intake pipe pressure PMF in accordance with the above principle. In step 100, the current intake pipe pressure PM, 180 ° CA By taking the intake pipe pressure PM180 and the intake pipe pressure PM360 before 360 ° CA from the RMA, the current sampling value, the previous sampling value, and the sampling value before the previous sampling are taken. In step 102, the intake pipe pressure change rate ΔPM is calculated by subtracting the intake pipe pressure PM180 180 ° CA before the current intake pipe pressure PM from the current intake pipe pressure PM. Rate of change ΔPM
Is positive for acceleration and negative for deceleration. In the next step 104, it is determined whether or not the transition state is a transient state by determining whether or not the absolute value | ΔPM | of the rate of change is equal to or greater than a predetermined value α. If it is determined that the state is a transient state, the first
The compression value DPM corresponding to the change rate ΔPM is calculated from the table of the change rate ΔPM and the compression value DPM shown in FIG. This compression value DPM
Is compressed so that the absolute value of the change rate ΔPM increases as the absolute value of the change rate increases, so that the absolute value decreases. As a result, the curve of DPM = ΔPM is logarithmically compressed. Note that the degree of ΔPM compression is not necessarily required to be the same in the region where ΔPM> 0 (during acceleration) and in the region where ΔPM <0 (during deceleration), and may be determined according to the characteristics of the engine.

In the next step 108, the engine speed NE shown in FIG.
Is calculated from the table of the adaptation constant k1 determined in accordance with the above. The adaptation constant k1 is set so as to increase as the engine speed increases, with 0 as an initial value. 2+
k1 may be used as the adaptation constant. In step 110, the above (1
3) Calculate the predicted intake pipe pressure PMF according to the equation shown in the equation,
In steps 112 and 114, the intake pipe pressure PM180 before 180 ° CA is replaced by the intake pipe pressure PM360 before 360 ° CA, and the current intake pipe pressure PM is replaced by the intake pipe pressure before 180 ° CA, and then the process proceeds to step 152. .

On the other hand, when it is determined in step 104 that the absolute value of the change rate | ΔPM | is less than the predetermined value α and the engine operation state is determined to be the steady operation state, the intake pipe pressure PM180 and the change rate ΔPM
, The predicted intake pipe pressure PMF is calculated according to the following equation, and in steps 120 and 122, the intake pipe pressure PM180 before 180 ° CA is converted to the intake pipe pressure before 360 ° CA, and the predicted intake pipe pressure PMF is calculated by 180 °. After replacing with the intake pipe pressure before CA, respectively, the process proceeds to step 152.

In step 122, the predicted intake pipe pressure PMF is changed to the intake pipe pressure.
Since the predicted intake pipe pressure PMF is calculated based on the above equation (15) instead of PM180, when the previously calculated predicted intake pipe pressure is PMF ₀ and the above equation (15) is modified, the following equation (1) is obtained.
6) As shown in the equation.

As understood from the above equation (16), the predicted intake pipe pressure PMF in the steady state is obtained by increasing the weight of the previous predicted intake pipe pressure PMF ₀ and the current intake pipe pressure PM and the previous predicted intake pipe pressure PMF _0. By calculating a weighted average of Such a weighted average value can be obtained by digital filtering processing.

 Next, the above equations (3) and (4) will be described in detail.

Α of the fuel injection amount TAU to be injected this time adheres to the wall surface, TAU · (1−α) is sucked into the engine, and the wall surface adhesion amount Q
Is left on the wall surface and Q · (1−β) is sucked into the engine, the adhesion amount Q _i and the suction amount F _i are as follows.

Adhesion amount Q _i = α · TAU + β · Q _i-1 ... (17) Inhalation amount F _i = TAU · (1-α) + Q _i-1 · (1-β) ... (18) Inhalation amount sucked into the engine F _i is TP ・ FWL ・ FAF ・ ・ ・ ・ ＝
It is sufficient to determine the TAU to be equal to TAUR, so (1
8) is as follows.

F _i = TAUR = TAU · (1−α) + Q _i−1 · (1−β) (19) Solving for TAU, From equation (17), since Q _i−1 = α · TAU _i−1 + β · Q _i−2 , Becomes

Here, assuming that TAUW = TAU-TAUR and the increment by the manifold wett, the increment TAUW is as follows.

Here, considering the second term of equation (23), Q _i-1 −Q _i−2 = α · (TAU _i−1 −TAU _i−2 ) + β · (Q _i−2 −Q _i−3 ) Substituting this into equation (23) gives here と β ^j · ΔTAUI _ij = TAUI _i , TAUI _i-2 = TAUO _i ,
Equation (25) is as follows.

TAUW = K2 ｛(TAUR−TAU _i-1 ) + TAUI _i … ... (26) TAUI _i = K3 ｛｛(TAU _i-1 -TAUO _i ) + TAUI _i-1 … ... (27) TAUO _i = TAUI _{i- 2} … (28) K3 = β (30) Accordingly, the TAU to be injected is the sum of the TAUR desired to be drawn into the engine combustion chamber and the wet TAUW adhering to the manifold, as shown in equation (31).

TAU = TAUR + TAUW (31) Next, another embodiment of the present invention will be described. This embodiment deals with a case where the change in the intake pipe pressure of 180 ° CA is extremely large, such as in full-open racing.

FIG. 14 shows a routine executed every predetermined time (for example, 4 msec). In step 180, A / D conversion is started, and the A / D conversion value of the pressure sensor output is sampled at the current sampling of the intake pipe pressure. Store it in RAM as the value PM (Step 1
82). In the next step 184, the current sampling value PM
Is subtracted from the value stored in the register PMINJ to calculate the rate of change ΔPM.
It is determined whether M is equal to or greater than a predetermined value A. If .DELTA.PM.gtoreq.A, the current sampling value PM is stored in the register PMINJ in step 188, the asynchronous fuel injection time TAUSY is calculated in step 190 according to the following equation, and then the asynchronous fuel injection is executed in step 192.

TAUASY = ΔPM · KINJ · (1 + FWL + FASE) (32) FIG. 15 shows a routine executed at every 360 ° CA to calculate the predicted intake pipe pressure PMF. Calculate PMF, step 1
At 96, the predicted intake pipe pressure PMF according to the following equation (32)
After calculating the fuel injection time TAU by using the formula (1), in step 198, the predicted intake pipe pressure PMF is stored in the register PMINJ.

TAU = PMF / KINJ / FEV / FAF / (1 + FWL + FASE) (33) FIG. 16 shows the execution timing of the asynchronous fuel injection under the control as described above. As described above, after the predicted intake pipe pressure PMF is stored in the register PMINJ, the current sampling value is stored in the register PMINJ every time A / D conversion is started. The first asynchronous fuel injection is performed when the difference from the value is equal to or greater than a predetermined value A, and thereafter, each time the rate of change of the sampling value, that is, the rate of change of the intake pipe pressure, exceeds a predetermined value, the asynchronous fuel injection is performed. . Therefore, since the shortage of the fuel injection amount is obtained for each A / D conversion and the asynchronous fuel injection is executed, the fuel injection amount can be made close to the value required by the engine.

[Brief description of the drawings]

FIG. 1 is a block diagram corresponding to the claims of the present invention, FIG. 2 is a schematic diagram of an internal combustion engine provided with a fuel injection amount control device to which the present invention can be applied, and FIG. 3 is a control diagram of FIG. FIG. 4 is a block diagram showing details of the circuit, FIG. 4 is a flowchart showing an asynchronous fuel injection routine in the embodiment of the present invention, FIG. 5 is a flowchart showing a fuel injection time calculation routine in the above embodiment, and FIG.
The figure is a flowchart showing the synchronous fuel injection routine of the above embodiment,
FIG. 7 is a diagram showing timings of the asynchronous fuel injection and the synchronous fuel injection in the above embodiment, and FIG. 8 is a current intake pipe pressure sampling value PM, a sampling value before a predetermined crank angle.
9 (1) and 9 (2) are diagrams showing the relationship between PMa and the intake pipe pressure PM2a before a predetermined crank angle, and FIGS. 9 (1) and 9 (2) are diagrams for explaining the injection timing of a four-cylinder engine. 1) and (2) are diagrams for explaining the injection timing of a six-cylinder engine, FIG. 11 is a flowchart showing details of step 150, FIG. 12 is a diagram showing a table of compression values DPM, FIG.
FIG. 3 is a diagram showing a change in the adaptation constant K1, FIG. 14 is a flowchart showing an asynchronous fuel injection routine in another embodiment of the present invention, and FIG. 15 is a flowchart showing a predicted intake pipe pressure calculation routine of the above embodiment. FIG. 16 is a diagram showing the asynchronous fuel injection timing of the other embodiment.

Claims (1)

(57) [Claims] 1. A sampling means for sampling a physical quantity related to an amount of air taken into an engine combustion chamber at a predetermined cycle, and a sampling means for a predetermined time period ahead of a present time based on a current sampling value and a past sampling value. Prediction means for predicting a future physical quantity, which is a predicted value of the physical quantity; fuel quantity calculation means for calculating a fuel quantity to be supplied to the engine combustion chamber based on the future physical quantity; determined based on the future physical quantity An insufficiency calculating means for calculating an insufficiency of the fuel amount to be supplied to the engine combustion chamber from the fuel amount and the fuel amount determined based on the sampling value at the time of the prediction, and a fuel amount calculated by the fuel amount calculating means. Fuel injection means for injecting the fuel at the fuel injection timing and immediately injecting the shortage calculated by the shortage calculation means. Injection amount control device.