JP3677947B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection control technique at the time of fuel switching in an internal combustion engine that switches between homogeneous combustion and stratified combustion in accordance with engine operating conditions.
[0002]
[Prior art]
In recent years, a direct-injection spark-ignition internal combustion engine has attracted attention. In this engine, the fuel is injected into the combustion chamber by switching the combustion method according to the operating conditions of the engine, that is, by injecting fuel in the intake stroke. Is controlled to switch between homogeneous combustion, which is performed by diffusing the gas to form a homogeneous mixture, and stratified combustion, in which fuel is injected in the compression stroke to form a stratified mixture intensively around the spark plug Is generally used (see JP 59-37236 A).
[0003]
In the engine that performs the above-described combustion switching, the fuel is divided into an intake stroke and a compression stroke in a region between the stratified combustion region and the homogeneous combustion region in a map in which the combustion region is set based on the engine speed and load (torque). There is one in which a weakly stratified combustion region that is injected in two times is set.
In other words, if the equivalence ratio is set continuously so that there is no torque step when switching between the stratified combustion region and the homogeneous combustion region, the equivalence ratio will not be suitable for any combustion near the boundary between both regions. On the other hand, in the stratified combustion area near the boundary, the spark plug is excessively rich, causing misfires and increased smoke. On the other hand, in the homogeneous combustion area near the boundary, the homogeneous mixture becomes excessively lean and misfires occur or burns. May become unstable.
[0004]
Therefore, in the region set between the stratified combustion region and the homogeneous combustion region, stratified combustion is basically performed by setting the ignition timing, etc., and the fuel injection is divided into an intake stroke and a compression stroke. With this configuration, stratified combustion is performed while suppressing the mixture ratio around the spark plug from becoming excessively rich to suppress misfire and smoke, and at the same time, misfire and instability of combustion occur due to homogeneous combustion. Can be suppressed.
[0006]
[Problems to be solved by the invention]
However, since the conventional fuel injection split method is a method in which injection is performed twice even in a steady state in the specified weak stratified combustion region, the following problems have occurred.
When the injection is divided into two times, the injection amount per time decreases, so the offset error of the fuel injection valve (pulse width-drift amount of the fuel amount characteristic) becomes larger, and the air-fuel ratio control compared to the single injection method Accuracy decreases and exhaust emission characteristics and operability deteriorate.
[0007]
Since the amount of fuel injected in the intake stroke is small, the homogeneous mixture is excessively lean and the combustion flame in stratified combustion is extinguished, resulting in an increase in the amount of HC (unburned fuel) emissions. In particular, when split injection is performed in a low load region, a combustible air-fuel mixture is formed by the second injection, so that the first injection cannot be performed much, so the homogeneous portion becomes extremely lean, and this tendency increases. Since split injection is performed even during steady operation, the amount of heat generated by the drive unit that drives the fuel injection valve of the high voltage boosting type increases, and if two systems are used to satisfy the heat generation capacity, the unit becomes expensive .
The present invention has been made paying attention to such a conventional problem, and by appropriately combining the equivalence ratio control and the divided injection at the time of combustion switching, the fuel injection control of the internal combustion engine which has solved the above-mentioned problems An object is to provide an apparatus.
[0009]
[Means for Solving the Problems]
For this reason, as shown in FIG.
In a direct injection internal combustion engine that injects fuel into a cylinder,
An operating state detecting means for detecting the operating state of the engine;
Based on the detected operating state, homogeneous combustion conditions for supplying fuel so that a relatively rich equivalent ratio is obtained in the intake stroke, and stratified combustion for supplying fuel so that a relatively lean equivalent ratio is obtained in the compression stroke Combustion condition determining means for determining the condition;
An equivalence ratio switching means for gradually switching the equivalence ratio between the rich equivalence ratio and the lean equivalence ratio when the discrimination between the homogeneous combustion condition and the stratified combustion condition is switched;
Given the equivalent ratio is gradually changed over by the equivalent ratio switching means from a predetermined value or more deviations with respect to the equivalent ratio of the limit in the combustion condition before switching, based on the equivalents ratio of the limit in the combustion condition after switching Fuel split supply means for supplying fuel in both the intake stroke and the compression stroke until the deviation becomes less than the value;
It is characterized by including.
[0010]
The invention according to claim 2
The equivalence ratio switching means is characterized in that the equivalence ratio is gradually switched over time.
In the first or second aspect of the invention, the homogeneous combustion condition and the stratified combustion condition are discriminated based on the operating state of the engine, for example, the rotational speed and the load, and when the discrimination is switched, Is gradually switched over time between a relatively rich equivalent ratio in homogeneous combustion conditions and a relatively lean equivalent ratio in stratified combustion conditions.
In this way, when switching between homogeneous combustion and stratified combustion, it is possible to avoid the occurrence of a torque step by switching the equivalent ratio over time, so the homogeneous combustion area and the stratified combustion area should be adjacent to each other with a difference in equivalent ratio. As a result, stable combustion can be obtained in the vicinity of the boundary between the homogeneous combustion region and the stratified combustion region, the air-fuel ratio accuracy can be maintained high, and the occurrence of misfire and the increase in smoke can be suppressed.
[0011]
In addition, as a configuration in which fuel is injected while being divided into an intake stroke and a compression stroke at the time of switching the corresponding amount ratio, a homogeneous air-fuel mixture is provided outside of the spark plug while maintaining a moderately rich mixture ratio. By forming and burning, the combustion limit of the air-fuel ratio is expanded, and stable combustion can be obtained while preventing misfire.
Also, even if the fuel homogeneous mixture formed by the injection in the intake stroke at the time of the divided injection may become too lean, it is only temporarily generated at the time of switching, and the steady divided injection as in the conventional case. The increase in HC due to can also be suppressed.
[0012]
Further, since the split injection is temporarily performed, it is possible to suppress an increase in the heat generation amount of the drive unit, and it is not necessary to provide two boosting systems as in the case of steady split injection, and an inexpensive unit can be used. .
[0015]
In addition, by defining the execution conditions of split injection with a deviation of a predetermined value or more with respect to the equivalence ratio in the combustion conditions before and after switching, the split injection is executed in a more appropriate range to ensure combustible mixing. Can be formed, can prevent misfiring due to excessive richness or leaning, and can ensure stable combustion.
According to a third aspect of the present invention, when the homogeneous combustion condition is combustion at the stoichiometric air-fuel ratio, the predetermined value is set based on the engine speed with respect to an equivalent ratio corresponding to the stoichiometric air-fuel ratio. Features.
[0016]
Since the lean limit equivalent ratio of homogeneous combustion is determined by the engine rotation speed, it is possible to execute the divided injection in a more appropriate range by setting a deviation that defines the equivalent ratio for executing the divided injection by the engine rotation speed. .
The invention according to claim 4
In a direct injection internal combustion engine that injects fuel into a cylinder,
An operating state detecting means for detecting the operating state of the engine;
Based on the detected operating state, homogeneous combustion conditions for supplying fuel so that a relatively rich equivalent ratio is obtained in the intake stroke, and stratified combustion for supplying fuel so that a relatively lean equivalent ratio is obtained in the compression stroke Combustion condition determining means for determining the condition;
An equivalence ratio switching means for gradually switching the equivalence ratio between the rich equivalence ratio and the lean equivalence ratio by delay processing with a weighted average when the discrimination between the homogeneous combustion condition and the stratified combustion condition is switched; ,
A weight setting means for setting a weight for the current value of the weighted average in the equivalent ratio switching means based on the engine speed and the throttle opening;
A fuel split supply means for supplying fuel to both the intake stroke and the compression stroke for at least a predetermined period during the equivalence ratio switching period by the equivalence ratio switching means;
It is characterized by including.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 2 is a system diagram of a direct injection spark ignition type internal combustion engine showing an embodiment.
Air is sucked into the combustion chamber of each cylinder of the internal combustion engine 1 mounted on the vehicle under the control of the electric throttle valve 4 from the air cleaner 2 through the intake passage 3.
[0018]
The opening degree of the electronically controlled throttle valve 4 is controlled by a step motor or the like that is operated by a signal from the control unit 20.
An electromagnetic fuel injection valve (injector) 5 is provided to inject fuel (gasoline) directly into the combustion chamber.
The fuel injection valve 5 is energized to the solenoid by an injection pulse signal output in the intake stroke or the compression stroke in synchronization with the engine rotation from the control unit 20 to open the valve, and injects fuel adjusted to a predetermined pressure. It is like that. In the case of intake stroke injection, the injected fuel diffuses into the combustion chamber to form a homogeneous mixture, and in the case of compression stroke injection, a stratified mixture is intensively formed around the spark plug 6. Based on the ignition signal from the control unit 20, the ignition plug 6 ignites and burns (homogeneous combustion or stratified combustion). The combustion system is divided into homogeneous stoichiometric combustion, homogeneous lean combustion (air-fuel ratio 20 to 30), and stratified lean combustion (equivalent ratio of about 40) in combination with equivalent ratio control.
[0019]
Exhaust gas from the engine 1 is discharged from an exhaust passage 7, and an exhaust purification catalyst 8 is interposed in the exhaust passage 7.
The control unit 20 includes a microcomputer including a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like, and signals are input from various sensors.
[0020]
As the various sensors, crank angle sensors 21 and 22 for detecting rotation of the crankshaft or camshaft of the engine 1 are provided. These crank angle sensors 21 and 22 have a reference pulse at a predetermined crank angle position (predetermined crank angle position before compression top dead center of each cylinder) every crank angle 720 ° / n, where n is the number of cylinders. In addition to outputting the signal REF, the unit pulse signal POS is output every 1 to 2 °, and the engine speed Ne can be calculated from the cycle of the reference pulse signal REF.
[0021]
In addition, an air flow meter 23 for detecting the intake air flow rate Qa upstream of the throttle valve 4 in the intake passage 3, an accelerator sensor 24 for detecting an accelerator opening (accelerator pedal depression amount) ACC, and an opening TVO of the throttle valve 4 are detected. The throttle sensor 25 (including an idle switch that is turned on when the throttle valve 4 is fully closed), the water temperature sensor 26 that detects the cooling water temperature Tw of the engine 1, and the exhaust passage 7 according to the rich / lean exhaust equivalence ratio. An O ₂ sensor 27 that outputs a signal, a vehicle speed sensor 28 that detects a vehicle speed VSP, and the like are provided.
[0022]
Here, the control unit 20 performs a predetermined calculation process by a built-in microcomputer while inputting signals from the various sensors, so that the throttle opening by the electric throttle valve 4 and the fuel by the fuel injection valve 5 are processed. The injection amount and the ignition timing by the spark plug 6 are controlled.
Next, the control function at the time of combustion switching according to the first embodiment of the present invention will be described with reference to the block diagram of FIG.
[0023]
The homogeneous equivalence ratio setting unit A sets the equivalence ratio at the time of homogeneous combustion based on operating conditions such as engine speed and load.
Similarly, the stratified equivalent ratio setting unit B sets the equivalent ratio during stratified combustion based on operating conditions such as engine speed and load.
The homogeneity / stratification determination unit C determines whether to perform homogeneous combustion or stratified combustion based on the operating conditions of the engine.
[0024]
The switching unit D switches and sets the equivalent ratio set by either the homogeneous equivalence ratio setting unit or the stratified equivalent ratio setting unit based on the determination result of the homogeneity / stratification determination unit.
The delay unit E delays the equivalent ratio output from the switching unit D. This is because, when the equivalence ratio is switched stepwise in accordance with the switching of combustion, a torque step is generated due to the delay after the switching of the intake air amount, so by gradually changing the equivalence ratio according to the delay of the air amount, This is to smoothly change the torque.
[0025]
The fuel injection amount calculation unit F calculates the fuel injection amount by performing various corrections based on the water temperature, the equivalent ratio feedback correction coefficient, and the like based on the intake air amount, the engine rotation speed, and the delayed equivalent ratio.
Based on the equivalence ratio of either the switching unit D or the delay unit E, the distribution ratio calculating unit G is a fuel injection amount for homogeneous combustion injected in the intake stroke at the time of combustion switching and stratification injected in the compression stroke. The distribution ratio with the fuel injection amount for combustion is calculated.
[0026]
The intake stroke injection amount calculation unit H and the compression stroke injection amount calculation unit I calculate the total fuel injection amount per stroke calculated by the fuel injection amount calculation unit F and the distribution rate calculated by the distribution rate calculation unit G. Based on the above, the fuel injection amount in the intake stroke and the fuel injection amount in the compression stroke are distributed.
The homogeneous injection timing calculation unit J and the stratified injection timing calculation unit K calculate the fuel injection timing during homogeneous combustion and the fuel injection timing during stratified combustion, respectively.
[0027]
The injection pulse generation unit L generates a fuel injection pulse having a pulse width corresponding to the fuel injection amount in the intake stroke at the homogeneous combustion injection timing calculated by the homogeneous combustion injection timing calculation unit J. A fuel injection pulse having a pulse width corresponding to the fuel injection amount in the compression stroke is generated at the injection timing for stratified combustion calculated by the stratified combustion injection timing calculation unit K.
[0028]
Thus, at the time of combustion switching, the amount of fuel distributed at the distribution rate is injected into the intake stroke and the compression stroke at the distribution rate, and two injections are performed.
Next, a routine for setting the fuel injection amount distribution rate will be described according to the flowchart of FIG. 4 with reference to the time chart of FIG. This routine is executed every predetermined time, for example, every 10 ms.
[0029]
In step 1, either stratified combustion or homogeneous combustion is selected based on operating conditions such as engine speed and load (homogeneous / stratified determination unit).
In step 2, it is determined which combustion is selected (switching unit).
When stratified combustion is selected in step 2, the routine proceeds to step 4 where the equivalent ratio for stratified combustion is calculated by searching from the map or the like (stratified equivalent ratio calculating section).
[0030]
If the homogeneous combustion is selected in step 2, the process proceeds to step 3 to calculate the equivalent ratio for homogeneous combustion by searching from the map or the like (homogeneous equivalent ratio calculating unit).
In step 5, the weight Fload for the current value of the weighted average when the calculated equivalent ratio is delayed is mapped based on the engine operating conditions such as the engine speed N and the throttle valve opening TVO (see FIG. 6). ) Calculate by searching from.
[0031]
In step 6, using the weight Fload, the equivalence ratio Tφd is weighted and averaged according to the following equation and delayed (delay unit).
Tφd = Tφd n × Fload + Tφd n−1 × (1−Fload)
For example, when the determination is switched from stratified combustion to homogeneous combustion, as shown in FIG. 5, the equivalence ratio gradually increases from the map value for stratified combustion by the delay process and approaches the target value for homogeneous combustion.
[0032]
Returning to FIG. 4, in step 7, the fuel injection amount Te is calculated by the following equation (fuel injection amount calculation unit).
Te = Tp × Tφd × Ktr × Ktw × Kas × (α + αm)
Here, Tp is a basic fuel injection amount (= kQ / N; k is a constant) obtained from an intake air amount Q detected by an air flow meter and an engine speed N, Ktr is a transient correction coefficient, and Ktw is a water temperature correction coefficient. , Kas is a post-startup increase correction coefficient, α is an air-fuel ratio feedback correction coefficient, and αm is a learning value of the air-fuel ratio feedback correction coefficient α.
[0033]
In step 8, the fuel injection timing ITS for stratified combustion and the fuel injection timing ITH for homogeneous combustion are mapped for each combustion based on the engine speed N and load (see FIGS. 7 and 8). It is calculated by searching for
In step 9, the fuel injection timing ITH for homogeneous combustion is set.
In step 10, it is determined whether or not the delayed equivalent ratio Tφd is greater than a determination value for switching to homogeneous combustion that is smaller than a lower limit value TφH during homogeneous combustion by a predetermined value α1. If it is determined that it is greater than the determination value, the routine proceeds to step 11 where the distribution ratio to homogeneous combustion is set to 100%, and the fuel injection amount Te calculated in step 7 is all injected in the intake stroke to complete the process. Make homogeneous combustion.
[0034]
If it is determined in step 10 that the equivalent ratio Tφd is equal to or less than the determination value for homogeneous combustion switching, the process proceeds to step 12, and the determination for stratified combustion switching in which the corresponding amount ratio Tφd is larger by a predetermined value α2 than the upper limit value TφS during stratified combustion. It is determined whether it is smaller than the value. If it is determined that the ratio is smaller than the determination value, the routine proceeds to step 13, where the distribution ratio to homogeneous combustion is set to 0%, that is, the distribution ratio to stratified combustion is set to 100%, and all the fuel injection amounts Te are compressed. To inject completely stratified combustion.
[0035]
When it is determined in step 12 that the equivalent ratio Tφd is smaller than the determination value for stratified combustion switching, that is, when the equivalent ratio Tφd is in the range of TφS + α2 <Tφd <TφH−α1, the combustion switching according to the present invention is performed. In this state, it is determined that it is time to inject fuel twice in the intake stroke and the compression stroke, and the routine proceeds to step 14 and subsequent steps to execute twice injection.
[0036]
In step 14, the ratio obtained by dividing the equivalent ratio Tφd by the lower limit value TφS for stratified combustion and the upper limit value TφH for homogeneous combustion is calculated by the following equation.
Tφd internal ratio = (Tφd−TφS) / (TφH− TφS )
The internal ratio (= 0 to 1) may be calculated by dividing the equivalent ratio Tφd by the stratified combustion switching determination value TφS + α2 and the homogeneous combustion switching determination value TφH−α1.
[0037]
In step 15, based on the internal ratio of the equivalent ratio Tφd, the distribution ratio of the fuel injection amount based on the homogeneous combustion is retrieved from a table as shown in FIG. The fuel distribution ratio of the homogeneous combustion increases as the equivalence ratio Tφd increases, but is set in a range from a minimum value considerably larger than 0 to a maximum value considerably smaller than 100%. This is because the accuracy of the fuel injection amount by the fuel injection valve cannot be maintained if the fuel injection amount in the intake stroke or the compression stroke becomes too small.
[0038]
Thus, by performing split injection during the period in which the equivalence ratio is gradually switched according to switching to combustion, the combustibility during this period can be stabilized, and the occurrence of misfire can be prevented. In particular, in the present embodiment, the split injection period is set in the equivalence ratio range, and is set in the equivalence ratio range having a predetermined deviation from the equivalence ratio of combustion before and after switching. It is possible to ensure that stable combustion is ensured. In addition, when switching from stratified combustion to homogeneous stoichiometric combustion at the stoichiometric air-fuel ratio at the time of idling or the like by turning on an air conditioner load, the deviation from the equivalent ratio (= 1) corresponding to the stoichiometric air-fuel ratio is based on the engine speed. To set. This is because the lean limit equivalent ratio of homogeneous combustion is determined by the engine speed.
[0039]
Note that the throttle valve opening is controlled in accordance with the combustion switching determination (for example, in the example of FIG. 5, the throttle valve opening is controlled to be decreased when switching from stratified combustion to homogeneous combustion is controlled). Gradually changes (in the example of FIG. 5, gradually decreases). Further, the torque is maintained substantially constant by control that gradually changes the equivalence ratio in accordance with the delay in the intake air amount. In addition, since the ignition timing (advance value) basically performs stratified combustion during the divided injection period, it is set according to the stratified combustion, and is gradually changed according to the change in the equivalence ratio (in the example of FIG. It gradually retards as it approaches combustion. Then, the control is changed stepwise in synchronism with the switching to the homogeneous combustion by the split injection and the single injection (advance angle at the time of switching to the homogeneous combustion) and gradually changed during the equivalence ratio changing period at the homogeneous combustion. To do.
[0040]
Next, a fuel injection control routine executed in accordance with the fuel injection amount distribution rate calculated as described above will be described with reference to the flowchart of FIG. This routine is executed when the fuel injection timing ITH for homogeneous combustion is reached. In step 21, it is determined whether or not the distribution ratio is 100%. If it is not 100%, the process proceeds to step 22 where it is determined whether or not the distribution rate is 0%. When it is not 0%, it is a case where injection is performed twice, and the process proceeds to step 23 and thereafter.
[0041]
In step 23, the fuel injection amount (pulse width output to the fuel injection valve) Ti1 during the intake stroke is calculated by the following equation.
Ti1 = Te × distribution rate + Ts
Here, Ts is an invalid injection amount required for opening the fuel injection valve.
In step 24, the fuel injection amount Ti2 during the compression stroke is calculated by the following equation.
[0042]
Ti2 = Te × (1−allocation ratio) + Ts
Next, the routine proceeds to step 25, where the ignition timing ADVS for stratified combustion calculated in another routine is set. Since the combustion in the case of double injection is basically stratified combustion, the ignition timing ADVS for stratified combustion is used.
In step 26, the injection of the fuel injection amount Ti1 is started at the fuel injection timing ITH in the intake stroke.
[0043]
In step 27, the fuel injection timing ITS for stratified combustion is set, and in step 28, the fuel injection amount Ti2 in the compression stroke is set. Thus, fuel injection of the fuel injection amount Ti2 is started at the fuel injection timing ITS for stratified combustion in the compression stroke.
Further, when it is determined in step 21 that the distribution ratio is 100%, it is a case where complete homogeneous combustion is performed, and the routine proceeds to step 29, where fuel injection is injected in the intake stroke for homogeneous combustion as shown in the following equation. While calculating the amount Ti1, the fuel injection amount Ti2 injected in the compression stroke for stratified combustion is set to zero.
[0044]
Ti1 = Te (× 100%) + Ts
Ti2 = 0
Next, the routine proceeds to step 30, and after setting the ignition timing ADVH for homogeneous combustion calculated in another routine, the routine proceeds to the step 25 and thereafter. Thereby, ignition is performed at the ignition timing and homogeneous combustion is performed.
[0045]
If it is determined in step 22 that the distribution ratio is 0%, this is a case where complete stratified combustion is performed, and the process proceeds to step 31 and fuel injected in the intake stroke for homogeneous combustion as shown in the following equation. While setting the injection amount Ti1 to 0, the fuel injection amount Ti2 injected in the compression stroke for stratified combustion is calculated.
Ti1 = 0
Ti2 = Te (× 100%) + Ts
Next, the routine proceeds to step 25, and after setting the ignition timing ADVS for stratified combustion, ignition is performed at the ignition timing and stratified combustion is performed.
[0046]
FIG. 11 shows a flow of an ignition timing calculation routine executed every predetermined time, for example, every 10 ms. In step 31, based on the engine operating conditions, for example, the engine speed N and the load such as the basic fuel injection amount Tp, Ignition timing ADVH is calculated, and in step 32, the ignition timing ADVS for stratified combustion is calculated in the same manner.
[Brief description of the drawings]
FIG. 1 is a functional block diagram showing a configuration of the present invention.
FIG. 2 is a system diagram showing an embodiment of the present invention.
FIG. 3 is a block diagram illustrating a control function according to the embodiment.
FIG. 4 is a flowchart showing a routine for calculating a fuel amount distribution ratio between an intake stroke and a compression stroke at the same time in divided injection.
FIG. 5 is a time chart showing changes in various states when switching from stratified combustion to homogeneous combustion.
FIG. 6 is a map in which weights for weighted average calculation when the equivalence ratio is similarly changed are set.
FIG. 7 is also a map in which ignition timing for homogeneous combustion is set.
FIG. 8 is a map in which ignition timing for stratified combustion is also set.
FIG. 9 is a map in which the distribution ratio is similarly set.
FIG. 10 is a flowchart showing a fuel injection control routine.
FIG. 11 is a flowchart showing a routine for similarly calculating an ignition timing for each combustion.
[Explanation of symbols]
1 Internal combustion engine 4 Electric throttle valve 5 Fuel injection valve 6 Spark plug
20 Control unit

Claims (4)

In a direct injection internal combustion engine that injects fuel into a cylinder,
An operating state detecting means for detecting the operating state of the engine;
Based on the detected operating conditions, homogeneous combustion conditions for supplying fuel so that a relatively rich equivalence ratio is obtained in the intake stroke, and stratified combustion for supplying fuel so that a relatively lean equivalent ratio is obtained in the compression stroke Combustion condition determining means for determining the condition;
An equivalence ratio switching means for gradually switching the equivalence ratio between the rich equivalence ratio and the lean equivalence ratio when the discrimination between the homogeneous combustion condition and the stratified combustion condition is switched;
Given the equivalent ratio is gradually changed over by the equivalent ratio switching means from a predetermined value or more deviations with respect to the equivalent ratio of the limit in the combustion condition before switching, based on the equivalents ratio of the limit in the combustion condition after switching Fuel split supply means for supplying fuel in both the intake stroke and the compression stroke until the deviation becomes less than the value,
A fuel injection control device for an internal combustion engine, comprising:   2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the equivalence ratio switching means gradually switches the equivalence ratio as time elapses. When homogeneous combustion conditions are burned at the stoichiometric air-fuel ratio,該理Theory fuel ratio based on the equivalents ratio of equivalent, the predetermined value according to claim 1 or claim 2, characterized in that it is set based on the engine rotational speed A fuel injection control device for an internal combustion engine according to claim 1. In a direct injection internal combustion engine that injects fuel into a cylinder,
An operating state detecting means for detecting the operating state of the engine;
Based on the detected operating conditions, homogeneous combustion conditions for supplying fuel so that a relatively rich equivalence ratio is obtained in the intake stroke, and stratified combustion for supplying fuel so that a relatively lean equivalent ratio is obtained in the compression stroke Combustion condition determining means for determining the condition;
Equivalence ratio switching means for gradually switching the equivalence ratio between the rich equivalence ratio and the lean equivalence ratio by delay processing with a weighted average when the discrimination between the homogeneous combustion condition and the stratified combustion condition is switched; ,
Weight setting means for setting the weight for the current value of the weighted average in the equivalence ratio switching means based on the engine speed and the throttle opening;
A fuel split supply means for supplying fuel to both the intake stroke and the compression stroke for at least a predetermined period during the equivalence ratio switching period by the equivalence ratio switching means;
A fuel injection control device for an internal combustion engine, comprising:

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