JPH11343912A - Pilot injection controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve exhaust property by controlling the discharge of a part of fuel injected during pilot injection as an unburned component. SOLUTION: An Electronic Control Unit(ECU) 50 of a diesel engine 1 calculates the fuel injection quantity based on the engine speed calculated by the detected signals of a crank sensor 25 and a cam sensor 26 as well as the accelerator opening detected by an accelerator sensor 20. ECU 50 also calculates the timing of the fuel injection of the pilot injection based on the fuel injection quantity and the engine speed. ECU 50 controls an injector 2 and a supply pump 6 such that if the timing of the fuel injection of the pilot injection exists on the advance side, the fuel injection quantity of the pilot injection is increased and the fuel injection pressure of the pilot injection is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pilot injection control device for an internal combustion engine that executes a pilot injection prior to a main injection.

[0002]

2. Description of the Related Art In an early stage of a combustion process in a diesel engine, fuel injected into a cylinder starts burning rapidly by self-ignition, so that a change rate of a combustion pressure is large and a combustion temperature in a cylinder is extremely high. Tend to be. Therefore, in order to reduce combustion noise and nitrogen oxides (NOx) contained in exhaust gas, it is effective to suppress a rapid change in combustion pressure and an increase in combustion temperature in the initial stage of the combustion process. .

[0003] Therefore, a fuel injection system that performs so-called pilot injection has been put into practical use (for example, see "Fuel injection control device for internal combustion engine" described in JP-A-6-10552).

In this fuel injection system, a part of the fuel to be injected into the cylinder is injected (pilot injection), and then the fuel injection is temporarily stopped. Then, after the fuel injected during the pilot injection self-ignites, the remaining fuel is again injected into the self-ignited combustion gas (main injection). Therefore, the fuel injected at the time of the main injection is burned as a kind of fire using the fuel injected at the time of the pilot injection, so that the combustion pressure in the initial stage of the combustion process rises slowly, and the combustion temperature also decreases. Will begin to fall. As a result, according to the fuel injection system, the combustion noise increases and the NOx contained in the exhaust gas increases.
An increase in the amount can be suppressed.

By the way, the effect of reducing the combustion noise and the NOx amount by the pilot injection is based on the premise that the main injection is performed after the fuel injected during the pilot injection self-ignites. That is, in a situation where the pilot injection interval is shortened and the main injection is executed before the fuel injected during the pilot injection self-ignites, the fuel injected during the pilot injection no longer functions as a spark. Because it is gone. Further, the main injection is executed when the piston in the cylinder is located near the top dead center. This is because, in order to obtain a predetermined engine output, when the in-cylinder pressure becomes maximum due to the combustion of the injected fuel, the piston needs to be located near the top dead center.

Therefore, in the above fuel injection system, the pilot injection is necessarily executed when the piston is at a position away from the top dead center.

[0007]

However, as described above, when the piston is located at a position away from the top dead center, the area of the inner wall surface of the cylinder that is not covered by the piston is large. Of the fuel injected at the time, the amount of fuel adhering to the inner wall surface increases. As described above, fuel adhering to the inner wall surface of the cylinder tends to be less likely to burn than fuel floating inside the cylinder or fuel adhering to the top of the piston. The inner wall of the cylinder
Because the piston is covered by the rise of the piston thereafter, the contact time with the combustion gas is short, and since the surrounding part of the cylinder is usually cooled by cooling water, it is kept at a lower temperature than the top of the piston. is there.

Therefore, in the conventional fuel injection system, a part of the fuel adhering to the inner wall surface of the cylinder is discharged from the cylinder without completely burning, and the unburned component contained in the exhaust gas is removed. There was a risk of causing an increase.

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve exhaust characteristics by suppressing a part of fuel injected during pilot injection from being discharged as an unburned component. It is to plan.

[0010]

According to one aspect of the present invention, there is provided a pilot injection control device for an internal combustion engine which executes pilot injection prior to main injection. Fuel injection timing setting means for setting the fuel injection pressure based on the operating state of the internal combustion engine, fuel injection pressure setting means for setting the fuel injection pressure of the pilot injection based on the operating state of the internal combustion engine, and fuel injection timing setting means. And a fuel injection pressure correcting means for reducing the fuel injection pressure set by the fuel injection pressure setting means as the fuel injection timing is advanced.

According to a second aspect of the present invention, in a pilot injection control device for an internal combustion engine which executes pilot injection prior to main injection, a fuel injection timing of the pilot injection is set based on an operating state of the internal combustion engine. Injection timing setting means, fuel injection quantity setting means for setting the fuel injection amount of pilot injection based on the operating state of the internal combustion engine, and fuel injection timing set by the fuel injection timing setting means is an advanced timing. And a fuel injection amount correcting means for increasing and correcting the fuel injection amount set by the fuel injection amount setting means.

In the case where the pilot injection is executed prior to the main injection, the more the fuel injection timing of the pilot injection is set to a timing on the more advanced side, the more the piston is located at a position farther from the top dead center. Since the pilot injection is performed at a certain time, the amount of fuel adhering to the inner wall surface of the cylinder, that is, the amount of adhering to the wall surface, tends to increase, and the discharge amount of unburned components tends to increase.

In this regard, according to the configuration of the first aspect, the fuel injection pressure is reduced and corrected as the pilot injection timing of the pilot injection is advanced.
The atomization of the fuel spray injected into the cylinder is suppressed, and the diffusion of the fuel spray is suppressed, thereby reducing the amount of wall adhesion.

According to the second aspect of the present invention,
Since the fuel injection amount is increased and corrected as the fuel injection timing of the pilot injection is advanced, the penetration force of the fuel spray injected into the cylinder is increased and the diffusion of the fuel spray is suppressed. As a result, the amount of adhered wall surface is reduced.

According to a third aspect of the present invention, there is provided a pilot injection control device for an internal combustion engine for executing a pilot injection prior to a main injection, wherein a fuel injection pressure for the pilot injection is set based on an operation state of the internal combustion engine. Setting means, a fuel injection amount setting means for setting a fuel injection amount of pilot injection based on an operation state of the internal combustion engine, and a fuel injection amount setting means for setting a higher fuel injection pressure set by the fuel injection pressure setting means. And a fuel injection amount correcting means for increasing and correcting the fuel injection amount to be performed.

According to a fourth aspect of the present invention, there is provided a fuel injection control device for an internal combustion engine for executing a pilot injection prior to a main injection, wherein a fuel injection pressure of the pilot injection is set based on an operation state of the internal combustion engine. Injection pressure setting means, fuel injection amount setting means for setting the fuel injection amount of the pilot injection based on the operating state of the internal combustion engine,
A fuel injection amount correcting means for reducing the fuel injection pressure set by the fuel injection pressure setting means as the fuel injection amount set by the fuel injection amount setting means decreases.

As described above, the amount of wall surface adhesion varies depending on the fuel injection timing of the pilot injection, and also varies depending on the fuel injection amount of the pilot injection and the magnitude of the fuel injection pressure. That is, as the fuel injection amount decreases, the penetration force of the fuel spray decreases, and the fuel spray is diffused in the cylinder, so that the amount of wall adhesion increases. Also,
As the fuel injection pressure increases, the atomization of the fuel spray is promoted and the fuel spray is diffused in the cylinder, so that the amount of wall adhesion also increases.

In this regard, according to the configuration described in claim 3, since the fuel injection amount is increased and corrected as the fuel injection pressure set based on the engine operating state increases,
The diffusion of the fuel spray caused by the injection of the fuel at the relatively high fuel injection pressure is suppressed by the increase of the penetration force, so that the amount of wall adhesion is reduced.

Further, according to the configuration described in claim 4,
Since the fuel injection pressure is reduced and corrected as the fuel injection amount set based on the engine operation state decreases, if the penetration of the fuel spray is small and the fuel spray is easily diffused, the fine particles of the fuel spray are Therefore, the diffusion of the fuel spray is suppressed, and the amount of wall adhesion is reduced.

According to a fifth aspect of the present invention, in a pilot injection control device for an internal combustion engine which executes a pilot injection prior to a main injection, a fuel injection amount, a fuel injection pressure and a fuel injection timing in the pilot injection are related to the pilot injection. A basic control amount setting means for setting a basic control amount based on an operation state of the internal combustion engine; and a basic control amount based on an amount of fuel adhering to the inner wall surface of the cylinder of the fuel injected into the cylinder of the internal combustion engine by pilot injection. A wall adhesion amount estimating unit that estimates based on the basic control amount set by the setting unit; a fuel injection amount correction unit that increases and corrects the fuel injection amount set by the basic control amount setting unit as the wall adhesion amount increases, and Fuel injection pressure correction means for reducing the fuel injection pressure set by the basic control amount setting means as the amount of wall surface adhesion increases, Basic control amount correction means including a fuel injection timing correction means for correcting the fuel injection timing set by the basic control amount setting means to a more retarded timing as the wall and wall adhesion amounts increase, a fuel injection amount, a fuel injection pressure, A correction target setting unit that sets a correction target by the basic control amount correction unit so that the fuel injection timing is corrected with priority in this order.

As described above, the amount of wall surface adhesion increases as the fuel injection timing increases, the fuel injection pressure increases, and the fuel injection pressure increases. Tends to increase as the injection amount decreases.

In the structure described in claim 5, the amount of wall adhesion is estimated based on the relationship between the amount of wall adhesion and the basic control amounts such as the fuel injection timing, fuel injection pressure, and fuel injection amount. As the wall adhesion amount increases, the fuel injection amount is increased and corrected, the fuel injection pressure is reduced and corrected, and the fuel injection timing is corrected to a retarded timing. Therefore, the amount of adhered wall surface is reduced.

Further, in the above configuration, since the fuel injection amount, the fuel injection pressure, and the fuel injection timing are corrected in this order with priority, the function of the pilot injection is maintained as much as possible, The influence on the main injection by correcting the injection pressure and the fuel injection timing can be suppressed to a small value.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIGS. 1 to 1 show a first embodiment in which a fuel injection control device for an internal combustion engine according to the present invention is applied to a diesel engine.
This will be described with reference to FIG.

FIG. 1 is a schematic configuration diagram showing a fuel injection control device according to this embodiment. Diesel engine 1
Indicates a plurality of cylinders (four cylinders in this embodiment) # 1 to #
And a cylinder head 1b provided on the cylinder block 1a. In each of the cylinders # 1 to # 4, a piston 12 is accommodated so as to be able to reciprocate. The piston 12 is connected to a crankshaft (not shown) via a connecting rod 14. Also, in each cylinder # 1 to # 4,
The inner wall surfaces of these cylinders # 1 to # 4, the top surface of the piston 12,
The combustion chamber 13 is formed by being partitioned by the lower surface of the cylinder head 1b.

In the cylinder block 1a, cylinders # 1 to # 1
A water jacket 19 is formed around # 4. The cooling water flowing in the water jacket 19 cools the cylinder block 1a, especially the inner wall portions of the cylinders # 1 to # 4.

The cylinder head 1b includes cylinders # 1 to #
The injectors 2 are arranged corresponding to the four combustion chambers 13, and fuel is injected into the combustion chamber 13 from the tip of the injector 2. The injector 2 includes an electromagnetic valve 3 for injection control, and the fuel injection timing and the fuel injection amount are adjusted based on the opening and closing operation of the electromagnetic valve 3. In the diesel engine 1 of the present embodiment, the fuel injection mode by the injector 2 is switched between a pilot injection mode in which pilot injection and main injection are executed and a main injection mode in which only main injection is executed. ing.

The injector 2 is connected to a common rail 4 common to the cylinders # 1 to # 4. The common rail 4 is connected to a discharge port 6 a of a supply pump 6 via a supply pipe 5 provided with a check valve 7.

The suction port 6b of the supply pump 6 is connected to the fuel tank 8 via a filter 9. The return port 6c of the supply pump 6 and the return port 3a of the solenoid valve 3 are both connected to the return pipe 11
Is connected to the fuel tank 8.

The supply pump 6 is provided with a pressurizing chamber (not shown).
And a feed pump (not shown) for sucking fuel from the fuel tank 8 and supplying it to the pressurizing chamber, and reciprocatingly synchronize with rotation of a crankshaft (not shown) to add fuel in the pressurizing chamber. A pressure plunger (not shown).
When the operation of the diesel engine 1 is started, the fuel in the pressurized chamber pressurized by the plunger is fed to the common rail 4 from the discharge port 6a through the supply pipe 5. The fuel pumping amount of this supply pump 6 is
The pressure is adjusted based on the opening / closing operation of a pressure control valve (hereinafter abbreviated as “PCV”) 10 provided in the vicinity of the discharge port 6a.

The diesel engine 1 is provided with various sensors for detecting various state quantities related to its operation. An accelerator sensor 20 for detecting the amount of depression of the pedal 15 (accelerator opening ACCP) is provided near the accelerator pedal 15. Cylinder block 1
a is provided with a water temperature sensor 21 for detecting the temperature of the cooling water (cooling water temperature THW). Further, the common rail 4 is provided with a fuel pressure sensor 22 for detecting a fuel pressure (fuel pressure PC) inside the common rail 4. The return pipe 11 is provided with a fuel temperature sensor 23 for detecting the temperature of the fuel (fuel temperature THF). The intake passage 16 of the diesel engine 1 is provided with an intake pressure sensor 24 for detecting the pressure (intake pressure PM) of the intake air passing through the passage 16.

A crank sensor 25 is provided near the crankshaft, and a cam sensor 26 is provided near a camshaft (not shown) that rotates in synchronization with the rotation of the crankshaft. The crank sensor 25 and the cam sensor 26 are sensors for detecting the number of rotations of the crankshaft per unit time (engine speed NE) and the rotation angle of the crankshaft (crank angle CA).

The output signals of these sensors 20 to 26 are:
The electronic control unit of the diesel engine 1 (hereinafter referred to as “EC
U "). This ECU 50
Comprises a CPU, a memory, an input / output circuit, a drive circuit (all not shown), and the like. And EC
U50 is an accelerator sensor 20, a water temperature sensor 21, a fuel pressure sensor 22, a fuel temperature sensor 23, and an intake pressure sensor 2
4, the accelerator opening ACCP, the coolant temperature THW, the fuel pressure PC, the fuel temperature THF, and the intake pressure PM are respectively read. Further, the ECU 50 calculates the engine speed NE and the crank angle CA based on the output signals of the crank sensor 25 and the cam sensor 26.

Further, the ECU 50 controls the fuel injection amount, the fuel injection timing, the fuel injection pressure (fuel pressure PC), the fuel injection mode, and the like based on the various state quantities. Hereinafter, such fuel injection control will be described.

First, a procedure for calculating a basic control amount related to fuel injection control such as a fuel injection amount, a fuel injection timing, and a fuel injection pressure will be described. FIG. 2 is a flowchart showing each process of the “basic control amount calculation routine”. This routine is executed by the ECU 50 as an interruption process for each predetermined crank angle.

When the process proceeds to this routine, in step 110, the ECU 50 determines the fuel injection amount QTOTA based on the engine speed NE and the accelerator opening ACCP.
Calculate L. The fuel injection amount QTOTAL is determined by the injector 2 during one stroke from the combustion chambers 13 of the cylinders # 1 to # 4.
Is the total amount of fuel injected into the That is, when the fuel injection mode is set to the pilot injection mode, the sum of the fuel injected during the pilot injection and the main injection corresponds to this fuel injection amount QTOTAL, and when the main injection mode is set. , The amount of fuel injected at the time of the main injection corresponds to the fuel injection amount QTOTAL.

The memory of the ECU 50 stores function data defining the relationship between the fuel injection amount QTOTAL, the engine speed NE, and the accelerator opening ACCP as shown in FIG. 3, and the ECU 50 stores this function data. The fuel injection amount QTOTAL is calculated with reference to the reference.

Next, at step 112, the ECU 5
0 calculates the reference target fuel pressure PTRGB based on the engine speed NE and the fuel injection amount QTOTAL. The reference target fuel pressure PTRGB is the fuel pressure PC of the common rail 4.
And is set so as to be a pressure most suitable for the engine operating state in consideration of combustion noise, smoke concentration, and the like. The memory of the ECU 50 stores function data defining the relationship between the reference target fuel pressure PTRGB, the engine speed NE, and the fuel injection amount QTOTAL as shown in FIG. 4, and the ECU 50 refers to this function data. To calculate the reference target fuel pressure PTRGB.

Next, at step 114, the ECU 50 calculates a basic pilot injection amount QPLTB based on the engine speed NE and the fuel injection amount QTOTAL. The basic pilot injection amount QPLTB is set to be an amount most suitable for the engine operating state in consideration of combustion noise, smoke concentration, and the like.

The memory of the ECU 50 stores function data defining the relationship between the basic pilot injection amount QPLTB and the engine speed NE and the fuel injection amount QTOTAL as shown in FIG. The function data is referred to when calculating the quantity QPLTB.

In the following step 116, the ECU 50
Calculates the main injection amount QMAIN based on the following equation (1). QMAIN = QTOTAL-QPLTB (1) Next, in step 118, the ECU 50 determines the main injection timing AMAIN and the basic pilot injection timing APL based on the engine speed NE and the fuel injection amount QTOTAL.
Calculate TB.

Here, the main injection timing AMAIN is a timing at which the main injection is started. The main injection timing AMAIN is based on the compression top dead center (TDC) of each of the cylinders # 1 to # 4 to be injected with fuel. Defined as the relative angle before the point. For example, when the main injection timing AMAIN is “10 ° C.
A "(CA: Crank Angle), the main injection is started when the crank angle CA becomes 10 ° CA before the compression top dead center.

On the other hand, the basic pilot injection timing APLTB
Is defined as a relative angle before the compression top dead center with respect to the compression top dead center as in the case of the main injection timing AMAIN. For example, this basic pilot injection timing APL
When TB is “30 ° CA”, the crank angle CA
Becomes 30 ° CA before compression top dead center, pilot injection is started.

The main injection timing AMAIN, the engine speed NE and the fuel injection amount QT are stored in the memory of the ECU 50.
Function data that defines the relationship with OTAL, and function data that defines the relationship between the basic pilot injection timing APLTB, the engine speed NE, and the fuel injection amount QTOTAL are each stored. The ECU 50 refers to these respective function data when calculating the main injection timing AMAIN and the basic pilot injection timing APLTB in the above step 118.

Next, at step 120, the ECU 50 calculates an injection interval TINT based on the main injection timing AMAIN, the basic pilot injection timing APLTB, and the engine speed NE. The injection interval TINT is a time from the start of the pilot injection to the start of the main injection.

More specifically, step 12
In the process of 0, the ECU 50 calculates a crank angle interval AINT from the time when the pilot injection is started to the time when the main injection timing AMAIN is started, based on the following equation (2). AINT = APLTB-AMAIN (2) Then, the ECU 50 calculates the injection interval TINT based on the crank angle interval AINT and the engine speed NE.

After performing the processing of step 120,
The ECU 50 once ends the processing of this routine. ECU
Reference numeral 50 denotes a pilot injection timing APLT and a pilot injection amount Q based on the basic pilot injection timing APLTB and the basic pilot injection amount QPLTB calculated as described above.
PLT is calculated, and the control amounts APLT and QPLT related to the pilot injection and the control amounts AMA related to the main injection are calculated.
The fuel injection amount and the fuel injection timing are controlled based on IN and QMAIN.

That is, the ECU 50 determines that each of the control amounts APL
T, QPLT, AMAIN, QMAIN, a drive signal SINJ (O
N / OFF signal). Then, the ECU 50
The drive signal SINJ is transmitted to the ECU 50 at a predetermined timing.
, A drive current flows through the solenoid valve 3 of the injector 2 via the drive circuit. As a result, the injector 2 is driven to open and close, and fuel is injected from the injector 2 into the combustion chamber 13.

FIG. 6 is a timing chart showing an example of how the drive signal SINJ changes. As shown in the figure, the ECU 50 determines the valve opening time (pilot injection time TQP) of the injector 2 necessary for injecting the same amount of fuel from the injector 2 as the pilot injection amount QPLT.
LT) with the pilot injection amount QPLT and the common rail 4
Is calculated based on the fuel pressure PC. And the ECU 50
Outputs the drive signal SINJ “ON” for the pilot injection time TQPLT when the crank angle CA reaches the pilot injection timing APLT. Accordingly, the injector 2 is opened to perform pilot injection, and fuel is injected into each combustion chamber 13 in an amount equal to the pilot injection amount QPLT.

Next, the ECU 50 determines the main injection amount QMA
The valve opening time (main injection time TQMAIN) of the injector 2 required to inject the same amount of fuel as IN is calculated based on the main injection amount QMAIN and the fuel pressure PC, and the crank angle CA is determined by the main injection timing AMAIN.
, The drive signal SINJ is output as “ON” for the main injection time TQMAIN. Therefore,
The injector 2 is opened to perform main injection, and fuel is injected into each combustion chamber 13 in an amount equal to the main injection amount QMAIN.

The ECU 50 controls the fuel injection pressure in addition to controlling the fuel injection amount and the fuel injection timing. That is, the ECU 50 determines the reference target fuel pressure PTR
The final target fuel pressure PTRG is calculated based on GB. Then, the ECU 50 performs feedback control of the open / close state of the PCV 10 so as to adjust the amount of fuel pressure supplied from the supply pump 6 so that the fuel pressure PC detected by the fuel pressure sensor 22 matches the final target fuel pressure PTRG.

Next, a procedure for operating various control flags used in a processing routine described later will be described. FIG. 7 is a flowchart showing each process of the “control flag operation routine”. This routine
This is executed by the ECU 50 as an interruption process for each predetermined crank angle.

When the processing shifts to this routine, the ECU
At step 210, 212, 214, the pilot injection mode flag XPLT is operated. The pilot injection mode flag XPLT is a flag for determining whether or not the engine operation state is in a state where the fuel injection mode should be the pilot injection mode.

In step 210, the ECU 50
It is determined based on function data as shown in FIG. 8 whether or not the engine operation state is a state in which the fuel injection mode should be the pilot injection mode. When the engine operation state is in the low load low rotation range (for example, the engine speed NE and the fuel injection amount QT
OTAL is a predetermined value NE1, QTOT shown in FIG.
If it is AL1, the ECU 50 determines that the engine operation state is a state in which the fuel injection mode should be set to the pilot injection mode. The ECU 50 then proceeds to step 21
The process proceeds to 2 to set the pilot injection mode flag XPLT to “1”.

On the other hand, when the engine operation state is in the high load / high rotation range (for example, the engine speed NE and the fuel injection amount
OTAL is a predetermined value NE2, QTOTAL2 shown in FIG.
), The ECU 50 determines that the engine operation state is not the state in which the fuel injection mode should be set to the pilot injection mode. Then, the ECU 50 shifts the processing to Step 214 and sets the pilot injection mode flag XPLT to “0”. Thereafter, the ECU 50 shifts the processing to Step 220.

Next, the ECU 50 executes steps 216 and 2
18 and 220, the pilot injection execution flag XP
Perform LTJ operation. This pilot injection execution flag X
PLTJ is a flag for determining whether or not pilot injection is actually being executed.

After executing the processing of step 212, the ECU 50 compares the basic pilot injection amount QPLTB with a predetermined amount α in step 216. If it is determined that the basic pilot injection amount QPLTB is equal to or smaller than the predetermined amount α, the ECU 50 sets the pilot injection execution flag XPLTJ to “0” in step 220.
On the other hand, if it is determined in step 216 that the basic pilot injection amount QPLTB is larger than the predetermined amount α,
In step 218, the CU 50 sets the pilot injection execution flag XPLTJ to “1”.

Here, the predetermined amount α is preset as a minimum amount of the pilot injection amount that can stably execute the pilot injection by an experiment in consideration of the injection characteristics of the injector 2 and stored in the memory of the ECU 50. Value. For example, the basic pilot injection amount QPLT
When B is less than or equal to the predetermined amount α, stable pilot injection cannot be performed, and therefore, pilot injection execution flag XPLTJ is set to “0”. Therefore, even if the engine operation state is such that the fuel injection mode should be the pilot injection mode, the pilot injection is not executed.

After executing the processing of steps 218 and 220, the ECU 50 once ends the processing of this routine. In the present embodiment, by correcting the control amount related to the pilot injection among the basic control amounts calculated as described above, the fuel injected during the pilot injection adheres to the inner wall surfaces of the cylinders # 1 to # 4. The amount of fuel (hereinafter referred to as “wall surface adhesion amount”) is reduced. Less than,
The procedure for correcting the basic control amount will be described.

FIG. 9 is a flowchart showing each process of the "basic control amount correction routine". This routine calls E
This is executed by the CU 50 as an interrupt process for each predetermined crank angle.

When the process proceeds to this routine, in step 310, the ECU 50 calculates an injection amount correction value KQPLT based on the injection interval TINT and the engine speed NE. The injection amount correction value KQPLT is for increasing and correcting the basic pilot injection amount QPLTB so as to reduce the amount of wall surface adhesion.

The memory of the ECU 50 stores function data defining the relationship between the injection amount correction value KQPLT, the injection interval TINT and the engine speed NE as shown in FIG. 10, and the ECU 50 stores the injection amount correction value KQPLT. This function data is referred to when calculating.

As shown in the figure, the injection amount correction value KQPL
T is calculated as a relatively large value as the injection interval TINT becomes longer. This is because the longer the injection interval TINT, the more the pilot injection is performed when the piston 12 is at a position farther from the top dead center.
This is because the amount of wall adhesion increases.

Further, as shown in FIG.
QPLT is calculated as a relatively large value as the engine speed NE is lower. This is because the lower the engine speed NE, the lower the reciprocating speed of the piston 12 becomes.
This is because, as a result, the ratio of the fuel to be injected when is located away from the top dead center increases, so that the amount of wall surface adhesion increases.

After calculating the injection amount correction value KQPLT in this manner, in step 312, the ECU 50
The pilot injection amount QPLT is calculated based on the following equation (3). QPLT = QPLTB + KQPLT (3) Accordingly, the pilot injection amount QPLT is calculated as a value obtained by increasing the basic pilot injection amount QPLTB in accordance with the amount of wall surface adhesion.

Next, at step 314, the ECU 5
0 calculates an injection timing correction value △ APLT based on the injection amount correction value KQPLT and the engine speed NE. The injection timing correction value △ APLT is used to increase the fuel injection amount during pilot injection by the injection amount correction value KQPLT by correcting the basic pilot injection timing APLTB.

Next, at step 316, the ECU 5
0 is the pilot injection timing APL based on the following equation (4).
Calculate T. APLT = APLTB + △ APLT (4) Accordingly, as is apparent from the above equation (4), the pilot injection timing APLT is corrected to a timing that is more advanced than the basic pilot injection timing APLTB.

Next, at step 318, the ECU 50 calculates an injection pressure correction value KPTRG based on the injection interval TINT and the engine speed NE. The injection pressure correction value KPTRG is for reducing the reference target fuel pressure PTRGB so as to reduce the amount of wall surface adhesion.

The memory of the ECU 50 stores function data defining the relationship between the injection pressure correction value KPTRG, the injection interval TINT and the engine speed NE as shown in FIG. 11, and the ECU 50 stores the injection pressure correction value KPTRG. This function data is referred to when calculating.

As shown in the figure, the injection pressure correction value KPTR
G is calculated as a relatively large value as the injection interval TINT is longer. This is because the longer the injection interval TINT, the more the pilot injection is performed when the piston 12 is at a position farther from the top dead center, so that the amount of wall surface adhesion increases.

Further, as shown in FIG.
PTRG is calculated as a relatively large value as the engine speed NE decreases. This is because, as described above, as the engine speed NE decreases, the proportion of fuel injected when the piston 12 is located away from the top dead center increases, resulting in an increase in the amount of wall adhesion.

Next, at step 320, the ECU 5
0 determines whether or not pilot injection mode flag XPLT is set to "1". If a negative determination is made here, the ECU 50 does not need to execute the pilot injection and does not need to correct the fuel injection pressure.
Set T to “0”. Then, in the following step 323,
At 326, the fuel injection amount QTOTAL is set as the main injection amount QMAIN, and the reference target fuel pressure PTRGB is set.
Is set as the above-mentioned final target fuel pressure PTRG.

On the other hand, if the determination in step 320 is affirmative, the ECU 50 determines in step 324 whether or not the pilot injection execution flag XPLTJ is set to “1”. If a negative determination is made here, the ECU 50 proceeds to steps 322 and 32
3 and 326 are executed. On the other hand, if an affirmative determination is made in step 324, the ECU 50 proceeds to step 3
At 28, the final target fuel pressure P is calculated based on the following equation (5).
Calculate TRG. PTRG = PTRGB−KPTRG (5) Accordingly, as is apparent from the above equation (5), the final target fuel pressure PTRG is reduced by the injection pressure correction value KPTRG from the reference target fuel pressure PTRGB. .

After executing the processing of steps 326 and 328, the ECU 50 once ends the processing of this routine. The ECU 50 determines the pilot injection amount QPLT, the main injection amount QMAIN, the pilot injection timing APLT, the main injection timing AMAIN, and the final target fuel pressure PTRG obtained in the above “basic control amount calculation routine” and “basic control amount correction routine”. The fuel injection amount, the fuel injection timing, and the fuel injection pressure are controlled based on.

FIG. 12 is a timing chart showing an example of the control mode in this embodiment. FIGS. 7A and 7C show how the drive signal SINJ changes, and FIGS. 7B and 7D show how the fuel pressure PC changes. (A) and (b) show the basic pilot injection timing APLTB set at a relatively retarded timing and the injection interval TINT is relatively small. , Basic pilot injection timing APLT
B is set to a relatively advanced timing, and the injection interval TI
The change modes of the drive signal SINJ and the fuel pressure PC when NT is relatively large are shown. In FIGS. 9A and 9C, “ΔTQPLT” represents the fuel injection amount at the time of pilot injection, which is calculated by the injection amount correction value KQ.
This is a correction value related to the valve opening time of the injector 2 for increasing the amount by PLT. The correction value ΔTQPLT is calculated by the ECU 50 based on the injection amount correction value KQPLT, the engine speed NE, and the fuel pressure PC.

As shown in FIGS. 7A and 7C, according to the fuel injection control of the present embodiment, as the injection interval TINT becomes relatively longer, in other words, the pilot injection becomes relatively advanced. The injection amount correction value K
Since the QPLT is set large and more fuel is injected from the injector 2 into the combustion chamber 13, the penetration force of the fuel spray injected from the injector 2 increases, and the fuel spray is diffused (atomized). Is suppressed.

Further, as shown in FIGS. 9B and 9D, the injection pressure correction value increases as the injection interval TINT becomes relatively long and the pilot injection is executed at a relatively advanced timing. KPTRG is set large and the final target fuel pressure PT
Since the RG is largely reduced, fuel is injected from the injector 2 into the combustion chamber 13 at a lower fuel pressure PC. As a result, atomization of the fuel spray injected from the injector 2 is suppressed, and diffusion of the fuel spray is suppressed.

Since the diffusion of the fuel spray is suppressed in this way, the injector 2
Most of the fuel injected from the piston adheres to the top surface of the piston 12. The fuel adhering to the top surface of the piston 12 has a higher temperature than the inner wall surfaces of the cylinders # 1 to # 4 and is always in contact with the combustion gas in the combustion chamber 13 After that, it is quickly vaporized and completely burned. On the other hand, most of the fuel thus injected adheres to the top surface of the piston 12, so that the amount of wall surface adhesion relatively decreases. As a result, cylinder #
The amount of fuel that adheres to the inner wall surfaces of Nos. 1 to # 4 and is discharged from the combustion chamber 13 without being completely burned is greatly reduced.

(1) As a result, according to the present embodiment, a part of the fuel injected at the time of pilot injection is used as an unburned component such as carbon monoxide (HC) in the combustion chambers of the cylinders # 1 to # 4. 13 can be suppressed, and the exhaust properties can be improved.

Here, as described above, the pilot injection amount Q
When the control amount related to pilot injection such as PLT or final target fuel pressure PTRG is changed from a value based on the engine operating state such as basic pilot injection amount QPLTB or reference target fuel pressure PTRGB, the change amount, that is, injection amount correction value KQPLT If the injection pressure correction value KPTRG is set too large, there is a concern that effects of pilot injection such as reduction of combustion noise and NOx concentration may be reduced.

In this regard, in this embodiment, since both the pilot injection amount QPLT and the final target fuel pressure PTRG are changed to suppress the diffusion of the fuel spray, for example, only the pilot injection amount QPLT or the final Compared with a configuration in which only the target fuel pressure PTRG is changed to suppress the diffusion of the fuel spray, these injection amount correction values KQP
It is possible to effectively suppress the diffusion of the fuel spray while setting each of the LT and the injection pressure correction value KPTRG as small as possible.

(2) Therefore, according to this embodiment, it is possible to reliably improve the exhaust properties while maintaining the effect of the pilot injection as much as possible. [Second Embodiment] Next, a second embodiment of the present invention will be described, focusing on the differences from the first embodiment. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the first embodiment, the final target fuel pressure PTRG is changed to the reference target fuel pressure PTRG in accordance with the amount of wall surface adhesion.
By setting the injection pressure correction value KPTRG lower than B, the fuel injection pressure, that is, the fuel pressure PC is reduced. In the present embodiment, after the pilot injection is started, the reduced fuel injection pressure is increased again to a pressure based on the engine operating state (reference target fuel pressure PTRGB). Hereinafter, a control procedure related to the fuel injection pressure of the present embodiment will be described. Note that, in the present embodiment as well, it is assumed that the respective processes of the “basic control amount calculation routine” and “basic control amount correction routine” are executed by the ECU 50.

FIG. 13 is a flowchart showing each process of the "fuel injection pressure control routine". This routine
This is executed by the ECU 50 as an interruption process for each predetermined crank angle.

When the process proceeds to this routine, in step 410, the ECU 50 determines whether the current crank angle C
It is determined whether pilot injection has already been started based on A and pilot injection timing APLT. Here, if it is determined that it is after the start of the pilot injection,
The CU 50 further determines in step 412 based on the current crank angle CA and the main injection timing AMAIN.
It is determined whether or not it is before the start of the main injection. Here, if it is determined that it is after the start of the main injection, the ECU 50
Shifts the processing to step 418 described later.

On the other hand, if it is determined in step 412 that it is before the start of the main injection, in step 414, the ECU 50 corrects the final target fuel pressure PTRG to increase. That is, the ECU 50 determines the current final target fuel pressure P
A value obtained by adding a predetermined value β to TRG is set as a new final target fuel pressure PTRG. The predetermined value β is added to the final target fuel pressure PTRG so that the final target fuel pressure PTRG is changed from the pilot injection to the start of the main injection by the reference target fuel pressure PTRG.
The size is set in advance so that the pressure can be reliably increased to GB.

Next, in step 416, the ECU 50 determines whether the final target fuel pressure PTRG and the reference target fuel pressure PTR
Compare with GB. Here, when it is determined that the final target fuel pressure PTRG is higher than the reference target fuel pressure PTRG,
In step 418, the ECU 50 sets the final target fuel pressure PTRG equal to the reference target fuel pressure PTRGB. After executing the process of step 418, the ECU 5
0 ends the processing of this routine once. Similarly, when a negative determination is made in each of the above-described steps 410 and 416, the ECU 50 once ends the processing of this routine.

FIG. 14 is a timing chart showing an example of the control mode in this embodiment. FIG.
FIG. 4B shows a variation of the drive signal SINJ, and FIG. 4B shows a variation of the fuel pressure PC.

As shown in the figure, according to the fuel injection pressure control in the present embodiment, when the pilot injection is started, the final target fuel pressure PTRG is increased by a predetermined value β and is corrected. Gradually increases. Here,
At the end of the pilot injection, the fuel pressure PC is set to be relatively large as compared with the start of the pilot injection.
At the end of the pilot injection, the piston 1
2, the increase in the amount of wall adhesion due to the increase in the fuel pressure PC does not occur. The fuel pressure PC reaches the reference target fuel pressure PTRGB before the main injection is started, and thereafter, is kept equal to the reference target fuel pressure PTRGB.

Therefore, according to the present embodiment, in addition to the effects described in (1) and (2) of the first embodiment, (3) the fuel injection pressure (reference The fuel injection can be executed at the target fuel pressure PTRGB), and the diffusion of the fuel spray at the time of the main injection can be promoted to secure a favorable combustion state.

[Third Embodiment] Next, a third embodiment of the present invention will be described, focusing on differences from the first embodiment. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the present embodiment, as shown in FIG. 16, the fuel injected by the pilot injection is repeated a plurality of times (in FIG.
The first embodiment is different from the first embodiment in that a so-called split injection is performed, which is divided into two injections. Hereinafter, a control procedure related to the fuel injection in the present embodiment will be described. In this embodiment, the processes of the “control flag operation routine” described in the first embodiment and the “fuel injection pressure control routine” described in the second embodiment are executed.

FIG. 15 is a flowchart showing each process of the "basic control amount calculation routine". This routine
This is executed by the ECU 50 as an interruption process for each predetermined crank angle. It should be noted that each processing of steps 510 to 516 of this routine corresponds to steps 110 to 1 shown in FIG.
Since these processes are the same as those in step S16, description thereof is omitted.

After executing the processes in steps 510 to 516, in step 518, the ECU 50 determines the main injection timing AMAIN and the basic split injection timing APL based on the engine speed NE and the fuel injection amount QTOTAL.
Calculate TSPB. Here, the basic split injection timing APLTSPB is a reference value of a timing at which the first fuel injection is started when performing the split injection, and is similar to the main injection timing AMAIN, and is a compression top dead center (TDC).
It is defined as the previous relative angle (see FIG. 16).

The memory of the ECU 50 stores function data defining the relationship between the basic split injection timing APLTSPB and the engine speed NE and the fuel injection amount QTOTAL, and the ECU 50 calculates the basic split injection timing APLTSPB. At this time, this function data is referred to.

Next, at step 520, the ECU 5
0 is the number n of split injections based on the engine speed NE.
Is calculated. The memory of the ECU 50 stores function data defining the relationship between the number n of split injections and the engine speed NE as shown in FIG.
Refers to this function data when calculating the number n of split injections. As shown in FIG.
The number n of split injections is 1 according to the engine speed NE.
It is set between ~ 3 times. For example, when the engine speed NE is in the range of (0 ≦ NE <NE1), the number n of split injections is set to three times, and the engine speed NE is set to (N
If E1 ≦ NE <NE2), the number n of split injections is set to two. Further, the engine speed N
When E is in the range of (NE ≧ NE2), the number n of split injections is set to one.

After calculating the number n of split injections in this way, in step 522, the ECU 50 determines the basic split injection amount QPLTSPB based on equation (6).
Is calculated. QPLTSPB = QPLT / n (6) This basic split injection amount QPLTSPB is the amount of fuel injected by one split injection. For example, when the number n of split injections is “1”, the pilot It is calculated equal to the injection amount QPLT, and when the number n of split injections is “3”, the pilot injection amount QP
It is calculated equal to the amount of LT divided into three.

Next, at step 524, the ECU 5
0 calculates the injection interval TINTi (i = 1 to 3) based on the main injection timing AMAIN, the basic split injection timing APLTSPB, and the engine speed NE. The injection interval TINTi is the time from the start of each split injection to the start of the main injection (see FIG. 16). For example, a case where three split injections are executed (the number of split injections n = 3) will be described as an example.
The ECU 50 first calculates a crank angle interval AINT based on the following equation (7). AINT = APLTSPB-AMAIN (7) Then, the ECU 50 calculates an injection interval TINT1 corresponding to the first split injection based on the crank angle interval AINT and the engine speed NE.

Next, the ECU 50 calculates injection intervals TINT2 and TINT3 corresponding to the second and third split injections based on the following equation (8). TINTi = TINT1−TSPINTB × (i−1) (8) TSPINTB: Basic Split Injection Interval In the above equation, the basic split injection interval TSPINTB.
Is the time from the start of the split injection to the start of the next split injection (see FIG. 16), which is set according to the characteristics of the injector 2 and the drive circuit, and
This is a value stored in advance in the memory of U50.

After calculating each injection interval TINTi as described above, the ECU 50 once ends the processing of this routine. In the present embodiment, similarly to the first embodiment, the control amounts QMAIN and QPLT related to the pilot injection (split injection) and the main injection calculated as described above.
By correcting SPB, AMAIN, APLTSPB, and PTRGB, the amount of fuel adhering to the inner wall surfaces of the cylinders # 1 to # 4 among the fuel injected during each split injection is reduced. Hereinafter, such a correction procedure will be described.

FIG. 18 is a flowchart showing each process of the "basic control amount correction routine". This routine
This is executed by the ECU 50 as an interruption process for each predetermined crank angle.

When the processing shifts to this routine, the ECU
50 is the split injection amount correction value K at step 610 based on the injection interval TINTi and the engine speed NE.
Calculate QPLTSPi (i = 1 to 3). The split injection amount correction value KQPLTSPi is for increasing and correcting the basic split injection amount QPLTSPB in order to reduce the amount of wall surface adhesion.

The memory of the ECU 50 stores function data defining the relationship among the split injection amount correction value KQPLTSPi, the injection interval TINTi, the engine speed NE, and the number of split injections n as shown in FIG. n, respectively, and are stored in the ECU 50
Refers to this function data when calculating the split injection amount correction value KQPLTSPi.

Split injection amount correction value KQPLTSPi
Is the injection amount correction value KQPLT and the injection interval T shown in FIG.
Similar to the relationship between INT and the engine speed NE, the value is calculated as a relatively large value as the injection interval TINTi is longer and the engine speed NE is lower.

Therefore, for example, when the split injection is performed three times (split injection frequency n = 3), the injection interval TINTi is determined as (TINT1> TIN).
T2> TINT3), the split injection amount correction value KQ corresponding to each split injection
For PLTSPi, the relationship shown in the following equation (9) is always established. KQPLTSP1>KQPLTSP2> KQPLTSP3 (9) After calculating the split injection amount correction value KQPLTSPi in this manner, in step 612, the ECU 50
Based on the following equation (10), split injection amount QPLTSP
Calculate i. QPLTSPi = QPLTSPB + KQPLTSPi (10) Therefore, as is apparent from the above equation (10), the split injection amount QPLTSPi is equal to the basic split injection amount QPLT.
Split injection quantity correction value KQPLTSPi rather than SPB
It will be increased by the amount.

Next, at step 614, the ECU 5
0 calculates the injection timing correction value △ APLTSP based on the split injection amount correction value KQPLTSP1 corresponding to the first split injection and the engine speed NE. The injection timing correction value △ APLTSP is for increasing the fuel injection amount at the time of the first split injection by the split injection amount correction value KQPLTSP1 by correcting the basic split injection timing APLTSPB.

After calculating the injection timing correction value △ APLTSP in this way, in step 616, the ECU 50
Split injection timing APLTS based on the following equation (11)
Calculate P. This split injection timing ALTSP
Is the crank angle CA at the time when the first split injection is started. APLTSP = APLTSPB + △ APLTSP (11) Accordingly, the split injection timing APLTSP is an injection timing correction value △ A more than the basic split injection timing APLTSPB.
The timing is set to the advance side by the amount of PLTSP.

Next, at step 618, the ECU 50 sets the injection interval TI corresponding to the first split injection.
Injection pressure correction value KP based on NT1 and engine speed NE
Calculate TRG.

The memory of the ECU 50 stores the injection pressure correction value K
Function data that defines the relationship between the PTRG, the injection interval TINT1, and the engine speed NE is stored.
0 refers to this function data when calculating the injection pressure correction value KPTRG. Similar to the function data shown in FIG. 11, this function data has an injection pressure correction value KPTRG as the injection interval TINT1 is longer and the engine speed NE is lower.
Is set to be calculated as a relatively large value.

Next, at step 620, the ECU 5
0 determines whether or not pilot injection mode flag XPLT is set to "1". If a negative determination is made here, the ECU 50 does not need to execute the pilot injection (therefore, does not perform the split injection) and does not need to correct the fuel injection pressure. The injection amount QPLTSPi is set to “0”. Then, the following steps 623 and 62
6, the fuel injection amount QTOTAL is changed to the main injection amount Q.
MAIN and the reference target fuel pressure PTRG are set as the above-mentioned final target fuel pressure PTRG, respectively.

On the other hand, if the determination in step 620 is affirmative, the ECU 50 determines in step 624 whether or not the pilot injection execution flag XPLTJ is set to “1”. If a negative determination is made here, the ECU 50 proceeds to steps 623 and 626 described above.
Execute the processing of On the other hand, if an affirmative determination is made in step 624, the ECU 50 proceeds to step 628, where the final target fuel pressure PTR is calculated based on the aforementioned equation (5).
Calculate G.

After executing the processing of steps 626 and 628, the ECU 50 once ends the processing of this routine. The ECU 50 determines the split injection amount QPLTSPi, the main injection amount QMAIN, the split injection timing APLTSP, and the main injection timing AMA obtained in the “basic control amount calculation routine” and the “basic control amount correction routine”.
The fuel injection amount, the fuel injection timing, and the fuel injection pressure are controlled based on IN and the final target fuel pressure PTRG.

FIG. 20 is a timing chart showing an example of the control mode in this embodiment. FIG. 3A shows a variation of the drive signal SINJ for opening and closing the injector 2, and FIG. 3B shows a variation of the fuel pressure PC.

The procedure for generating drive signal SINJ will now be described with reference to this timing chart. E
The CU 50 first sets the split injection amount correction value KQPLT
Correction time TKQP based on SPi and engine speed NE
LTSPi (i = 1 to 3) is calculated. This correction time T
KQPLTSPi is a correction value related to the valve opening time of the injector 2 for increasing and correcting the fuel injection amount by the split injection amount correction value KQPLTSPi in each split injection.

Next, the ECU 50 determines the final split injection interval TSPINTj (j = 1, based on the following equation (12)).
2) is calculated. TSPINTj = TKQPLTSPj + TSPINTB−TKQPLTS P (j + 1) (12) Further, the ECU 50 determines the split injection amount QPLTSPi.
And the engine speed NE, the valve opening time TQPLTSPi (i =
1) to 3) are calculated. The ECU 50 determines the drive signal SINJ based on the valve opening time TQPLTSPi and the final split injection interval TSPINTj calculated as described above.
Generate Then, when the crank angle CA reaches the split injection timing APLTSP, the ECU 50 outputs the drive signal SINJ to the drive circuit to execute the split injection.

In the present embodiment in which the split injection is executed as described above, as shown in FIG. 11A, the injection interval TINT corresponding to each split injection is used.
As i becomes relatively longer, the valve opening time of the injector 2 (= TQPLTSPi) becomes longer (TQPLTSP1).
>TQPLTSP2> TQPLTSP3). Therefore, of the split injections performed in each time, the more the fuel is injected into each combustion chamber 13 as the split injection is performed at a relatively advanced timing, the more the fuel is injected from the injector 2. The penetration force of the fuel spray increases, and the diffusion of the fuel spray is suppressed.

Also, in this embodiment, as in the second embodiment, after the first split injection is started,
Since the final target fuel pressure PTRG increases by a predetermined value β,
As shown in FIG. 3B, the fuel pressure PC is gradually increased. Therefore, the fuel is injected at a higher fuel injection pressure as the split injection is executed at a relatively retarded timing in each split injection.

For example, when the split injection is performed three times, in the first split injection, the fuel is injected at a relatively low fuel injection pressure to suppress the increase in the amount of adhesion to the wall surface. In the third split injection, fuel is injected at a relatively high fuel injection pressure and the fuel spray is appropriately diffused, so that the combustion type of the main injection is formed earlier.

As a result, according to the present embodiment, similar to the first and second embodiments, it is possible to suppress the discharge of the unburned components, to improve the exhaust properties, and to realize a more favorable split injection. Thus, startability can be improved.

[Fourth Embodiment] Next, a fourth embodiment of the present invention will be described, focusing on the differences from the first embodiment. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In this embodiment, the final target fuel pressure PTRG
And the basic pilot injection amount Q based on the engine speed NE
The difference from the first embodiment is that the PLTB is corrected. Hereinafter, such pilot injection amount QP
The LT correction procedure will be described. In this embodiment, the processes of the “basic control amount calculation routine” and the “control flag operation routine” described in the first embodiment are respectively executed.

FIG. 21 is a flowchart showing each process of the "basic control amount correction routine". This routine
This is executed by the ECU 50 as an interruption process for each predetermined crank angle.

When the processing shifts to this routine, in step 708, the ECU 50 sets the reference target fuel pressure P calculated in the aforementioned “basic control amount calculation routine”.
TRGB is set as the final target fuel pressure PTRG. Next, in step 710, the ECU 50 calculates an injection amount correction value KQPLT based on the final target fuel pressure PTRG and the engine speed NE. This injection amount correction value KQ
The PLT is for increasing and correcting the basic pilot injection amount QPLTB so as to reduce the amount of wall surface adhesion.

The memory of the ECU 50 stores the injection amount correction value KQPLT and the final target fuel pressure PTR as shown in FIG.
The ECU 50 stores function data that defines the relationship between the injection amount correction value KQPLT and the engine speed NE.
This function data is referred to when calculating.

As shown in the figure, the injection amount correction value KQPL
T is calculated as a relatively large value as the final target fuel pressure PTRG increases. The fuel injected from the injector 2 into the combustion chamber 13 is atomized and diffused as the injection pressure increases. Therefore, the larger the final target fuel pressure PTRG is set, the larger the amount of wall surface adhesion increases. Therefore, in the present embodiment, the diffusion of the injected fuel due to the increase in the fuel injection pressure is suppressed by increasing the fuel injection amount and the penetration force of the fuel spray.

Further, as shown in FIG.
QPLT is calculated as a relatively large value as the engine speed NE decreases. This is because, as described above, as the engine speed NE decreases, the proportion of fuel injected when the piston 12 is at a position apart from the top dead center increases, and the amount of wall adhesion increases.

After calculating the injection amount correction value KQPLT in this way, in step 712, the ECU 50
The pilot injection amount QPL is calculated based on the following equation (3).
Calculate T.

Next, in step 714, the ECU 50 calculates an injection timing correction value △ APLT based on the injection amount correction value KQPLT and the engine speed NE. This injection timing correction value △ APLT is used to correct the basic pilot injection timing APLTB to thereby reduce the amount of fuel injected during pilot injection by the injection amount correction value KQ.
This is for increasing the amount by PLT. And EC
U50 calculates the pilot injection timing APLT in step 716 based on the following equation (4).

Next, the ECU 50 executes the processing after step 720. Steps 720 to 724 are performed in steps 320 to 32 shown in FIG.
4 are the same as the respective processes of FIG.

[0130] If a negative determination is made in step 724, or after the processing in step 723 is performed, the ECU 50 once ends the processing of this routine. As described above, in the present embodiment, the final target fuel pressure P
As the TRG increases, the injection amount correction value KQPLT is set to a relatively large value to increase the pilot injection amount QPLT. Accordingly, the penetration force of the fuel spray injected from the injector 2 is increased, and the diffusion of the injected fuel due to the increase in the fuel injection pressure is suppressed, so that the amount of wall adhesion can be reduced. As a result, also in the present embodiment, the same effects as the effects (1) described in the first embodiment can be obtained.

[Fifth Embodiment] Next, a fifth embodiment of the present invention will be described, focusing on the differences from the first embodiment. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In this embodiment, the pilot injection amount QPL
Reference target fuel pressure PTR based on T and engine speed NE
The difference from the first embodiment is that GB is corrected. Hereinafter, such a reference target fuel pressure PTRGB
Will be described. In this embodiment, the processes of the “basic control amount calculation routine” and the “control flag operation routine” described in the first embodiment are respectively executed.

FIG. 24 is a flowchart showing each process of the "basic control amount correction routine". This routine
This is executed by the ECU 50 as an interruption process for each predetermined crank angle.

When the processing shifts to this routine, in each of steps 810 and 811, the ECU 50 applies the basic pilot injection amounts QPLTB and APLTB calculated in the “basic control amount calculation routine” to the pilot injection amount QP
LT and pilot injection timing APLT are set.

Next, in step 812, the ECU 50 calculates an injection pressure correction value KPTRG based on the pilot injection amount QPLT and the engine speed NE. The injection pressure correction value KPTRG is for reducing the final target fuel pressure PTRG to reduce the amount of wall surface adhesion.

The memory of the ECU 50 stores the injection pressure correction value KPTRG and the pilot injection amount QP as shown in FIG.
Function data defining the relationship between LT and the engine speed NE is stored, and the ECU 50 determines the injection pressure correction value KPT
This function data is referred to when calculating RG.

As shown in the figure, the injection pressure correction value KPTR
G is calculated as a relatively large value as the pilot injection amount QPLT decreases. As the amount of the fuel injected from the injector 2 into the combustion chamber 13 decreases, the penetration force decreases and the fuel is diffused in the combustion chamber 13.
Therefore, the smaller the pilot injection amount QPLT is set, the larger the amount of fuel that adheres to the inner wall surfaces of the cylinders # 1 to # 4 among the injected fuel. Therefore, in the present embodiment, the diffusion of the fuel spray caused by the decrease in the fuel injection amount is suppressed by reducing the fuel injection pressure.

Further, as shown in the figure, also in the present embodiment, the injection pressure correction value KPTRG is calculated as a relatively large value as the engine speed NE decreases. next,
The ECU 50 executes the processing of steps 820 to 828. The processing of steps 820 to 828 corresponds to steps 320 to 820 in the flowchart of FIG.
Since the process is the same as the process of 328, the description is omitted.

As described above, in this embodiment, the smaller the pilot injection amount QPLT, the smaller the injection pressure correction value K
The PTRG is set to a relatively large value to reduce the final target fuel pressure PTRG. Therefore, the atomization of the fuel spray injected from the injector 2 is suppressed, and the diffusion of the injected fuel due to the decrease in the penetration force of the fuel spray is suppressed, so that the amount of wall surface adhesion can be reduced. As a result, also in the present embodiment, the same effects as the effects (1) described in the first embodiment can be obtained.

[Sixth Embodiment] Next, a sixth embodiment of the present invention will be described, focusing on the differences from the first embodiment. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

As described in the above embodiments,
In general, the following table 1 shows the wall adhesion amount during the pilot injection and the fuel injection timing, the fuel injection pressure, and the fuel injection amount (hereinafter, these are collectively referred to as “pilot injection control amounts”) during the pilot injection. There is a relationship as shown in

[0142]

[Table 1] As shown in this table, for the fuel injection timing, the same period should be corrected to the timing on the retard side, the fuel injection pressure should be reduced, and the fuel injection amount should be increased. Is desirable in reducing the amount of wall adhesion.

However, regarding the fuel injection timing,
If the same timing is corrected to a timing that is more retarded than the timing based on the engine operating state, the interval from the pilot injection to the execution of the main injection becomes shorter, and the pilot injection inherent in pilot injection such as reduction of combustion noise and NOx amount is reduced. Function may be reduced.

On the other hand, with respect to the fuel injection pressure, even if the injection pressure is reduced, that is, even if the fuel pressure PC in the common rail 4 is changed to a low pressure value, there is a relatively low possibility that the function of the pilot injection is reduced. Few. However, when the main injection is performed with the fuel injection pressure set low as described above, it is difficult to ensure a favorable combustion state in the main injection. Further, in order to suppress such influence on the main injection, as described in the second embodiment, the fuel pressure P
It is conceivable to increase C to a pressure value based on the engine operating state, that is, the reference target fuel pressure PTRGB. However, in order to surely increase the fuel pressure PC to the reference target fuel pressure PTRG within a short time before the main injection is started, it is necessary to use the supply pump 6 having a relatively high discharge capacity. .

On the other hand, with respect to the fuel injection amount of the pilot injection, even if the same amount is increased, the function of the pilot injection is less likely to be reduced, and the fuel injection amount of the main injection can be controlled independently. Has little effect on the main injection.

In the present embodiment, in consideration of such points, the pilot injection control amount is appropriately corrected according to the amount of adhered wall surface. Hereinafter, this correction procedure will be described. In this embodiment, the processes of the “basic control amount calculation routine” and the “control flag operation routine” described in the first embodiment are also executed.

FIG. 25 is a flowchart showing each process of the "basic control amount correction routine". This routine
This is executed by the ECU 50 as an interruption process for each predetermined crank angle.

When the process proceeds to this routine, in step 906, the ECU 50 determines whether or not the pilot injection mode flag XPLT is set to "1". If a negative determination is made here, the ECU 50 does not need to execute the pilot injection and does not need to correct the pilot injection control amount.
At 14, 920 and 926, the basic pilot injection amount QPLTB, the reference target fuel pressure PTRGB, and the basic pilot injection timing APLTB are respectively set to the pilot injection amount QPTB.
LT, final target fuel pressure PTRG, pilot injection timing A
After each setting as PLT, the processing of this routine is temporarily ended.

On the other hand, if a positive determination is made in step 906, the ECU 50 further determines in step 908 whether or not the pilot injection execution flag XPLTJ is set to "1". If a negative determination is made here, the ECU 50 proceeds to steps 914, 920,
926 are executed.

On the other hand, if a positive determination is made in step 908, the ECU 50 proceeds to step 910, where the basic pilot injection timing APLTB, the reference target fuel pressure PTRGB, and the basic pilot injection amount QPLTB are set.
Is estimated on the basis of.

More specifically, first, the ECU 50
Calculates the influence amount Ka of the fuel injection timing on the wall surface adhesion amount K. The memory of the ECU 50 stores the influence amount Ka and the basic pilot injection timing APLT as shown in FIG.
Function data defining the relationship with B is stored, and E
The CU 50 refers to this function data when calculating the influence amount Ka. As shown in FIG.
Is calculated to be larger as the basic pilot injection timing APLTB increases, in other words, as the fuel injection timing is set to a more advanced timing.

Further, the ECU 50 determines the respective influence amounts Kp, K of the fuel injection pressure and the fuel injection amount on the wall surface adhesion amount K.
Calculate p. The memory of the ECU 50 stores function data that defines the relationship between the reference target fuel pressure PTRGB and the influence amount Kp, and function data that defines the relationship between the basic pilot injection amount QPLTB and the influence amount Kq.
The ECU 50 refers to these data when calculating each of the influence amounts Kp and Kq. Here, each influence amount Kp, Kq
Is, as the reference target fuel pressure PTRG becomes higher,
The smaller the basic pilot injection amount QPLTB is, the larger the value is calculated. The basic pilot injection timing APLTB and the reference target fuel pressure PTR as shown in FIG.
GB, basic pilot injection amount QPLTB and each influence amount K
The respective relationships with a, Kp, and Kq are set in advance by experiments and the like.

Next, the ECU 50 calculates (estimates) the wall surface adhesion amount K based on the following equation (13). K = Ka + Kp + Kq (13) After estimating the wall surface adhesion amount K as described above, in step 912, the ECU 50 compares the wall surface adhesion amount K with the first wall adhesion amount.
Is compared with the judgment value K1. The first determination value K1 is
This is for determining whether or not it is necessary to correct the fuel injection amount in order to reduce the wall surface adhesion amount K to a predetermined amount or less, and is set in advance by an experiment or the like and stored in a memory. Value.

If it is determined in step 912 that the wall adhesion amount K is equal to or less than the first determination value K1, the ECU 5
0 indicates that the wall adhesion amount K is extremely small and no correction is required for the pilot injection control amount.
After sequentially executing the processes of 14, 920, and 926, the process of this routine is temporarily ended.

On the other hand, if it is determined in step 912 that the wall adhesion amount K is larger than the first determination value K1,
The CU 50 shifts the processing to Step 916, and in Step 916, calculates the pilot injection amount QPLT based on the above-mentioned equation (3). In this embodiment, the injection amount correction value KQPLT is set as a constant value.

Next, in step 918, the ECU 50 compares the wall surface adhesion amount K with the second determination value K2.
The second determination value K2 determines whether or not it is necessary to further correct the fuel injection pressure in addition to the fuel injection amount in order to reduce the wall surface adhesion amount K to a predetermined amount or less. This is a value set in advance by an experiment or the like and stored in the memory.

In this step 918, when it is determined that the wall surface adhesion amount K is equal to or smaller than the second determination value K2,
The CU 50 determines that the wall adhesion amount K can be reduced to a predetermined amount or less by correcting only the fuel injection amount, and sequentially executes the processing of step 920 and thereafter, and then temporarily ends the processing of this routine.

On the other hand, if it is determined in step 918 that the wall surface adhesion amount K is larger than the second determination value K2,
The CU 50 shifts the processing to Step 922. In Step 922, the CU 50 calculates the final target fuel pressure PTRG based on the aforementioned equation (5). In this embodiment, the injection pressure correction value KPTRG is set as a constant value.

Next, in step 924, the ECU 50 compares the wall surface adhesion amount K with the third determination value K3.
The third determination value K3 determines whether or not it is necessary to further correct the fuel injection timing in addition to the fuel injection amount and the fuel injection pressure in order to reduce the wall surface adhesion amount K to a predetermined amount or less. This is a value that is set in advance by an experiment or the like and stored in the memory.

In this step 924, if it is determined that the wall surface adhesion amount K is equal to or less than the third determination value K3,
The CU 50 executes the process of step 926, assuming that the fuel injection amount and the fuel injection pressure can reduce the wall surface adhesion amount K to a predetermined amount or less, and then terminates the process of this routine once. .

On the other hand, if it is determined in step 924 that the wall adhesion amount K is larger than the third determination value K3,
The CU 50 shifts the processing to Step 928, and in Step 928, calculates the pilot injection timing APLT based on the following equation (14). APLT = APLTB−KAPLT (14) KAPLT: Injection timing correction value In the above equation (13), the injection timing correction value KAPLT is
This is for correcting the pilot injection timing APLT to a timing on the retard side. In the present embodiment, the pilot injection timing APLT is set as a constant value similarly to the injection amount correction value KQPLT and the injection pressure correction value KPTRG. After correcting each pilot injection control amount as necessary, the ECU
50 temporarily ends the processing of this routine.

As described above, in the present embodiment, the wall surface adhesion amount K is estimated based on the pilot injection control amount such as the fuel injection timing, the fuel injection pressure, and the fuel injection amount, and the wall surface adhesion amount K is reduced. For this purpose, the pilot injection control amount is corrected according to the magnitude of the wall surface adhesion amount K.

Further, when the pilot injection control amount is corrected, if the wall surface adhesion amount K is relatively small, only the fuel injection amount is corrected, and as the wall surface adhesion amount K increases, this fuel injection amount is reduced. In addition, the fuel injection pressure and the fuel injection timing are sequentially corrected.

Therefore, according to the present embodiment, the fuel injection amount, the fuel injection pressure, and the fuel injection timing are preferentially corrected in this order, so that the function of the pilot injection is maintained as much as possible. In addition, it is possible to suppress the emission of unburned components and to improve the exhaust properties while minimizing the influence on the main injection by correcting the pilot injection control amount.

As described above, the first to sixth embodiments embodying the present invention have been described. However, each of these embodiments can be implemented by changing the configuration as follows. In the first and second embodiments, both the pilot injection amount QPLT and the final target fuel pressure PTRG are changed from values based on the engine operating state in order to suppress the diffusion of the fuel spray. , Pilot injection quantity QP
It is also possible to adopt a configuration in which only the LT or only the final target fuel pressure PTRG is changed to suppress the diffusion of the fuel spray.

In the first and second embodiments, the fuel injection amount and the fuel injection pressure are corrected according to the time from the start of the pilot injection to the start of the main injection, that is, the injection interval TINT. However, a parameter having a strong correlation with the wall adhesion amount, for example, the crank angle interval AIN
The fuel injection amount and the fuel injection pressure may be corrected based on T, pilot injection timing APLT, basic pilot injection timing APLTB, and the like.

In the first and second embodiments,
Basic pilot injection timing APLTB and engine speed NE
In addition, the pilot injection amount QPLT and the final target fuel pressure PTRG may be corrected based on the coolant temperature THW and the fuel temperature THF. This is because the ratio of the fuel discharged without complete combustion among the fuels adhered to the inner walls of the cylinders # 1 to # 4 also varies depending on the cooling water temperature THW and the fuel temperature THF. Similarly, in the third to sixth embodiments, when correcting the fuel injection amount, the fuel injection pressure, and the fuel injection timing of the pilot injection, the correction may be made based on the cooling water temperature THW or the fuel temperature THF. Good.

In the second embodiment, the fuel pressure PC in the common rail 4 is gradually increased after the start of the pilot injection. However, after the pilot injection is completed, the final target fuel pressure PTRG is corrected by the injection pressure. Value KPTRG
The fuel pressure PC may be increased at a time by increasing the fuel pressure PC by one minute.

In the sixth embodiment, the wall surface adhesion amount K
Is compared with each determination value K1 to K3, and each pilot injection control amount is corrected based on the comparison result. However, as shown in FIG. 27, the injection amount correction value KQP
LT, injection pressure correction value KPTRG, injection timing correction value KAP
Function data that defines the relationship between LT and the wall surface adhesion amount K is set in advance, and the correction values KQPLT, KPTRG, and K based on the wall surface adhesion amount K are referenced with reference to the function data.
The size of the APLT may be calculated.

The fuel injection control device in each of the above embodiments employs a configuration in which fuel is supplied from the supply pump 6 into the common rail 4 and fuel is supplied from the common rail 4 to the injector 2. It is also possible to adopt a configuration in which a so-called distribution type supply pump is used, and fuel is supplied from the pump to each injector 2.

In each of the above embodiments, the fuel injection control device according to the present invention is applied to a diesel engine. However, the fuel injection control device can be applied to a direct injection gasoline engine that injects fuel from an injector directly into a combustion chamber. .

[0172]

According to the first aspect of the present invention, since the fuel injection pressure is reduced and corrected as the fuel injection timing of the pilot injection is advanced, the fuel spray injected into the cylinder is reduced. The atomization of the fuel spray is suppressed, and the diffusion of the fuel spray is suppressed, so that the amount of wall adhesion is reduced. As a result, according to the first aspect of the invention, it is possible to suppress a part of the fuel injected at the time of pilot injection of the cylinder from being discharged as an unburned component, and to improve the exhaust property. .

According to the second aspect of the invention, the fuel injection amount is corrected to be increased as the fuel injection timing of the pilot injection is advanced, so that the penetration of the fuel spray injected into the cylinder is ensured. As the force increases and the diffusion of the fuel spray is suppressed, the amount of wall adhesion decreases.
As a result, according to the invention described in claim 2, it is possible to suppress a part of the fuel injected during the pilot injection of the cylinder from being discharged as an unburned component, and to improve the exhaust property. .

According to the third aspect of the present invention, the fuel injection amount is increased and corrected as the fuel injection pressure set based on the engine operating state increases, so that the fuel is injected at a relatively high fuel injection pressure. The diffusion of the fuel spray caused by the injection is suppressed by the increase of the penetrating force, so that the amount of wall adhesion is reduced. As a result, claim 3
According to the invention described in (1), it is possible to suppress a part of the fuel injected at the time of pilot injection of the cylinder from being discharged as an unburned component, and to improve the exhaust property.

Further, in the invention described in claim 4, the fuel injection pressure is corrected to decrease as the fuel injection amount set based on the engine operating state decreases, so that the penetration force of the fuel spray decreases. If the fuel spray is easy to spread,
Since the atomization of the fuel spray is suppressed, the diffusion of the fuel spray is suppressed, and the amount of adhesion to the wall surface is reduced. As a result, according to the fourth aspect of the present invention, it is possible to suppress a part of the fuel injected during the pilot injection of the cylinder from being discharged as an unburned component, and to improve the exhaust property. .

According to the fifth aspect of the present invention, the wall surface adhesion amount is estimated based on the basic control amounts such as the fuel injection timing, the fuel injection pressure, and the fuel injection amount of the pilot injection. However, the fuel injection amount is corrected by increasing the amount, the fuel injection pressure is corrected by reducing the pressure, and the fuel injection timing is corrected to the retarded side. Will decrease. Furthermore, since the fuel injection amount, the fuel injection pressure, and the fuel injection timing are preferentially corrected in this order, the function of the pilot injection is maintained as much as possible,
The effect on the main injection by correcting the fuel injection amount, the fuel injection pressure, and the fuel injection timing can be suppressed to be small. As a result, according to the fifth aspect of the present invention, the function of the pilot injection is maintained as much as possible, and the influence on the main injection by correcting the pilot injection control amount is suppressed to be small. It is possible to suppress exhaustion of a part of the injected fuel as an unburned component, and to improve exhaust properties.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a fuel injection control device applied to a diesel engine.

FIG. 2 is a flowchart showing a procedure for calculating a basic control amount in the first embodiment.

FIG. 3 is a graph showing a relationship between a fuel injection amount, an engine speed, and an accelerator opening.

FIG. 4 is a graph showing a relationship between a reference target fuel pressure, a fuel injection amount, and an engine speed.

FIG. 5 is a graph showing a relationship among a basic pilot injection amount, a fuel injection amount, and an engine speed.

FIG. 6 is a timing chart showing how the drive signal of the injector changes.

FIG. 7 is a flowchart showing an operation procedure of a control flag.

FIG. 8 is a graph showing a pilot injection execution region set by a fuel injection amount and an engine speed;

FIG. 9 is a flowchart showing a procedure for correcting a basic control amount in the first embodiment.

FIG. 10 is a graph showing a relationship between an injection amount correction value, an injection interval, and an engine speed.

FIG. 11 is a graph showing a relationship among an injection pressure correction value, an injection interval, and an engine speed.

FIG. 12 is a timing chart showing how the injector drive signal and the fuel pressure change.

FIG. 13 is a flowchart showing a control procedure of a fuel injection pressure.

FIG. 14 is a timing chart showing how the drive signal of the injector and the fuel pressure change.

FIG. 15 is a flowchart illustrating a calculation procedure of a basic control amount according to the third embodiment.

FIG. 16 is a timing chart showing how the drive signal of the injector changes.

FIG. 17 is a graph showing the relationship between the number of split injections and the engine speed.

FIG. 18 is a flowchart illustrating a procedure for correcting a basic control amount according to the third embodiment.

FIG. 19 is a graph showing a relationship between a split injection amount correction value, an injection interval, and an engine speed.

FIG. 20 is a timing chart showing how the drive signal of the injector and the fuel pressure change.

FIG. 21 is a flowchart showing a procedure for correcting a basic control amount in the fourth embodiment.

FIG. 22 is a graph showing a relationship among an injection amount correction value, a final target fuel pressure, and an engine speed.

FIG. 23 is a graph showing a relationship among an injection pressure correction value, a pilot injection amount, and an engine speed.

FIG. 24 is a flowchart showing a procedure for correcting a basic control amount in the fifth embodiment.

FIG. 25 is a flowchart showing a procedure for correcting a basic control amount in the sixth embodiment.

FIG. 26 is a graph showing a relationship between a pilot injection control amount and an influence amount of the control amount on a wall surface adhesion amount.

FIG. 27 is a graph showing a relationship between a pilot injection control amount and an influence amount of the control amount on a wall surface adhesion amount.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 2 ... Injector, 4 ... Common rail, 6 ... Supply pump, 8 ... Fuel tank, 13
... combustion chamber, 20 ... accelerator sensor, 50 ... ECU, # 1
~ # 4 ... Cylinder.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 37/00 F02M 37/00 C

Claims (5)

[Claims] 1. A pilot injection control device for an internal combustion engine that executes a pilot injection prior to a main injection, wherein: a fuel injection timing setting means for setting a fuel injection timing of the pilot injection based on an operation state of the internal combustion engine; Fuel injection pressure setting means for setting a fuel injection pressure for pilot injection based on an operation state of the internal combustion engine; and reducing the set fuel injection pressure as the set fuel injection timing is advanced. A pilot injection control device for an internal combustion engine, comprising: a fuel injection pressure correction unit that corrects the fuel injection pressure. 2. A pilot injection control device for an internal combustion engine that executes a pilot injection prior to a main injection, comprising: fuel injection timing setting means for setting a fuel injection timing of the pilot injection based on an operation state of the internal combustion engine; Fuel injection amount setting means for setting a fuel injection amount of pilot injection based on an operation state of the internal combustion engine; and increasing the set fuel injection amount as the set fuel injection timing is advanced. A pilot injection control device for an internal combustion engine, comprising: a fuel injection amount correction unit that corrects the fuel injection amount. 3. A pilot injection control device for an internal combustion engine that executes a pilot injection prior to a main injection, wherein: a fuel injection pressure setting means for setting a fuel injection pressure of the pilot injection based on an operation state of the internal combustion engine; Fuel injection amount setting means for setting a fuel injection amount for pilot injection based on an operation state of the internal combustion engine; and a fuel injection amount correction for increasing and correcting the set fuel injection amount as the set fuel injection pressure increases. A pilot injection control device for an internal combustion engine. 4. A pilot injection control device for an internal combustion engine that executes a pilot injection prior to a main injection, wherein: a fuel injection pressure setting means for setting a fuel injection pressure of the pilot injection based on an operation state of the internal combustion engine; Fuel injection amount setting means for setting a fuel injection amount for pilot injection based on an operation state of the internal combustion engine; and a fuel injection amount correction for reducing the set fuel injection pressure as the set fuel injection amount decreases. A pilot injection control device for an internal combustion engine. 5. A pilot injection control device for an internal combustion engine that executes a pilot injection prior to a main injection, wherein a fuel injection amount, a fuel injection pressure, and a fuel injection timing in the pilot injection are set as basic control amounts related to the pilot injection. Basic control amount setting means for setting based on an operation state of the engine; and basic control for setting an amount of fuel adhering to an inner wall surface of the cylinder of the fuel injected into the cylinder of the internal combustion engine by the pilot injection. A wall adhesion amount estimating unit that estimates based on the amount; a fuel injection amount correction unit that increases and corrects the set fuel injection amount as the estimated wall adhesion amount increases; and the estimated wall adhesion amount increases. The fuel injection pressure correction means for correcting the set fuel injection pressure to reduce the pressure, and the estimated wall adhesion amount increases as the amount increases. A basic control amount correction means including a fuel injection timing correction means for correcting the set fuel injection timing to a timing on the retard side; and the fuel injection amount, the fuel injection pressure, and the fuel injection timing are given priority in this order. And a correction target setting means for setting a correction target by the basic control amount correction means so as to be corrected in a dynamic manner.