JP2003336534A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device for an internal combustion engine capable of achieving the correction of a fuel injection period constantly based on proper fuel pressure regardless of the fuel pulsation of a high-pressure pump, and preventing nonconformity due to the control error of a fuel injection quantity. <P>SOLUTION: The average of fuel pressure P is determined for every cycle of an SGT cycle T, and for fuel injection, the fuel injection period is corrected based on average fuel pressure before two previous cycles of injection (as shown with a solid line). For the correction of the fuel injection period in the first half of a pulsation cycle, average fuel pressure determined based on fuel pressure pulsation in the first half of the pulsation cycle before 360°CA is applied. For the correction of the fuel injection period for the second half of the pulsation cycle, average fuel pressure determined based on fuel pressure pulsation in the second half of the pulsation cycle before 360°CA is applied. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an internal combustion engine (hereinafter,
It is referred to as an engine) fuel injection control device.

[0002]

2. Related Background Art For example, in a cylinder injection type gasoline engine, a considerably high fuel pressure is required to inject fuel into the cylinder during the compression stroke, and a plunger type or other high pressure pump is used to secure this fuel pressure. Has been done. This type of high-pressure pump causes fuel pressure pulsation, which causes a control error in the fuel injection amount.As a countermeasure against this, there is a process of correcting the fuel injection period based on the fuel pressure to cancel the influence of the fuel pressure pulsation. It has been implemented.

There are various methods for suppressing the control error of the fuel injection amount by the correction process of the fuel injection period. For example, Japanese Utility Model Laid-Open No. 6-58231 discloses a rail pressure of a common rail type diesel engine as a target value. Although the technique of using the average value of the rail pressure when performing the feedback control is described, this technique can be applied to the correction process. That is, as shown in FIG. 5, the fuel pressure P of the high-pressure pump is averaged every rising cycle T of the SGT signal synchronized with the fuel injection of each cylinder, and as shown by the arrow, immediately before the fuel injection (1
It is possible to correct the fuel injection period based on the average value of (before the injection cycle).

[0004]

The correction process of FIG.
It is premised that the same fuel pressure pulsation as before the injection cycle is reproduced in this injection cycle. For example, in the case of a plunger type pump that pressurizes fuel by actuating a plunger by means of a cam lobe, if the number of cam lobes corresponds to the number of cylinders, a similar fuel pressure pulsation is reproduced for each fuel injection of each cylinder. Therefore, no significant problem occurs in correcting the fuel injection period. However, some high-pressure pumps have the number of cam lobes set to half the number of cylinders in order to secure a time margin for fuel spill. Since the fuel pressure pulsation of is not reproduced, the following problems occur.

FIG. 6 is a time chart showing the correction situation of the fuel injection period of the prior art in which the number of cam peaks of the high pressure pump is set to half the number of cylinders. As shown in the figure, while the fuel pressure P of the high-pressure pump is averaged at each rising cycle T of the SGT signal, the fuel injection period is corrected based on the average value one injection cycle before, as in the case of FIG. There is. On the other hand, the fuel pressure P of the high-pressure pump pulsates in a cycle twice the cycle of the SGT signal. More specifically, the fuel pressure P increases with the pressurization by the cam ridges, reaches the maximum value according to the fuel spill (point ab in the figure), and sharply decreases by the first fuel injection (point in the figure). b-c), after that, a constant value is maintained (points cd in the figure), the fuel is further rapidly reduced by the next fuel injection (points d-e in the figure), and the above cycle is repeated.

Therefore, although a relatively high average value is calculated in the first half of the pulsation cycle, this average value is applied to the fuel injection correction performed at a relatively low fuel pressure P thereafter, and relatively in the latter half of the pulsation cycle. Although a low average value is calculated,
This average value will be applied to the subsequent correction of the fuel injection performed at the relatively high fuel pressure P. As a result, in any case, the fuel injection period is corrected based on the inappropriate fuel pressure P, the fuel injection amount is not an appropriate amount, and there is a problem that exhaust gas characteristics, fuel efficiency, drivability, etc. are deteriorated. It was

An object of the present invention is to always realize correction of a fuel injection period based on an appropriate fuel pressure regardless of fuel pressure pulsation of a high-pressure pump, and thus prevent occurrence of a problem due to inappropriate fuel injection control. An object of the present invention is to provide a fuel injection control device for an internal combustion engine that can perform the operation.

[0008]

In order to achieve the above object, the invention of claim 1 pressurizes fuel by a high-pressure pump in synchronization with the rotation of an internal combustion engine and supplies the fuel to a fuel injection valve of each cylinder for control. Fuel injection control of an internal combustion engine, in which each fuel injection valve is opened and closed by means to inject fuel into the cylinder of the corresponding cylinder, and the fuel injection period of the fuel injection valve is corrected by the correction means based on the fuel pressure of the high-pressure pump. In the apparatus, the high-pressure pump pressurizes the fuel at a cycle that is twice as long as the injection cycle of the fuel injection valve of each cylinder, and the correction means averages the fuel pressure of the pressurized fuel for each injection cycle of the fuel injection valve. The value is calculated, and the fuel injection period is corrected based on the average value of the fuel pressure calculated two injection cycles before.

For example, in a plunger type high pressure pump in which a plunger is actuated by a cam to pressurize fuel in synchronism with the rotation of an internal combustion engine, if the number of cam lobes is set to half the number of cylinders, The fuel is pressurized in a cycle that is twice the injection cycle, and fuel pressure pulsation that is in synchronization with it is generated. Therefore, the fuel pressure pulsation in the first half of the pulsation cycle is reproduced in the same first half of the pulsation cycle after two injection cycles, and the fuel pressure pulsation in the second half of the pulsation cycle is reproduced in the same second half of the pulsation cycle after two injection cycles.

Therefore, when the fuel injection period is corrected by the correction means based on the average value of the fuel pressure calculated two injection cycles before, the correction of the fuel injection period in the first half of the pulsation cycle is as follows.
Similarly, the average value of the fuel pressure in the first half of the pulsation cycle, which is two injection cycles before, is applied, and the average value of the fuel pressure in the second half of the pulsation cycle, which is also two injection cycles before, is applied to the correction of the fuel injection period in the second half of the pulsation cycle. As a result, regardless of the fuel pressure pulsation of the high-pressure pump, the fuel injection period is always corrected by the appropriate average value of the fuel pressure, and the fuel injection amount can be made an appropriate amount.

According to a first aspect of the present invention, preferably, the high-pressure pump is rotationally driven together with a camshaft on an intake side or an exhaust side of an internal combustion engine, and a phase of the camshaft with respect to a crankshaft is variable in valve timing. It is desirable to apply to an internal combustion engine that can be changed by a mechanism. In the internal combustion engine configured in this manner, the valve timing variable mechanism adjusts the phase of the camshaft with respect to the crankshaft to control the valve timing on the intake side or the exhaust side. Since the phase of is also changed, the positional relationship of fuel pressure pulsation with respect to fuel injection is deviated. In other words, the average value of the fuel pressure changes according to the control status of the valve timing, so it becomes more difficult to correct the fuel injection period based on the appropriate fuel pressure, but even in such a case, the pulsation cycle is reproduced after two injection cycles. Since it is not changed, it becomes possible to appropriately correct the fuel injection period based on the average value of the fuel pressure two injection cycles before, and the fuel injection amount can be made an appropriate amount.

According to a second aspect of the present invention, in the first aspect, the high pressure pump controls the fuel pressure based on the target fuel pressure set from the operating state of the internal combustion engine, and the correction means sets the fuel pressure of the high pressure pump and the target fuel pressure. When the difference is greater than or equal to a predetermined value, the fuel injection period is corrected based on the average value of the fuel pressure calculated one injection cycle before. When the difference between the fuel pressure of the high pressure pump and the target fuel pressure is greater than or equal to a predetermined value, it can be considered that the fuel pressure is in a transitional state in which the fuel pressure is following the target fuel pressure. The fuel pressure at this time largely changes during the pulsation cycle, and the amount of change exceeds the difference in the average value of the fuel pressure between the first half of the pulsation cycle and the second half of the pulsation cycle. Therefore, in this case, the average value of the fuel pressures calculated immediately before the immediately preceding injection cycle is based on the current fuel pressure.
By applying the average value of the fuel pressure before the injection cycle to the correction of the fuel injection period, the control error of the fuel injection amount in the transient state can be prevented.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is embodied in a fuel injection control device for a direct injection engine will be described below. FIG. 1 is an overall configuration diagram showing a fuel injection control device for an engine of the present embodiment, and an engine 1 of the present embodiment is configured as an in-line 4-cylinder direct injection gasoline engine. The cylinder head of the engine 1 is provided with an electromagnetic fuel injection valve 2 for each cylinder so as to face the inside of the cylinder, and each fuel injection valve 2 is connected to a high-pressure pump 4 via a common delivery pipe 3. . The high-pressure pump 4 is connected to the rear end of the intake camshaft 5, is driven to rotate together with the intake camshaft 5, and supplies pressurized fuel to each fuel injection valve 2 at an arbitrary fuel pressure via the delivery pipe 3.

A timing pulley 6 is provided at the front end of the intake camshaft 5, and the timing pulley 6 is rotationally driven by a crankshaft 7 via a timing belt together with a timing pulley of an exhaust camshaft (not shown), and each of the camshafts is driven. The intake / exhaust valve is opened / closed by 5 at a predetermined timing. As a result, intake air is introduced into the cylinder through an intake passage (not shown) with the opening of the intake valve, the fuel injected from the fuel injection valve 2 is ignited by the ignition plug and burned, and the exhaust gas after combustion is When the exhaust valve is opened, it is discharged through an exhaust passage (not shown), and the above cycle is repeated according to a predetermined ignition order.

A valve timing variable mechanism 8 is incorporated in the timing pulley 6 of the intake camshaft 5, and the phase of the intake camshaft 5 with respect to the timing pulley 6 is arbitrarily changed by the variable mechanism 8 and the intake valve of the intake valve is correspondingly changed. The opening and closing timing is adjusted. Various configurations have been proposed for the variable valve timing mechanism 8, so a detailed description thereof will be omitted. For example, Japanese Patent Laid-Open No. 9-60508.
As described in the publication, a vane rotor is rotatably arranged in a hydraulic chamber formed in a timing pulley 6, an intake camshaft is connected to the vane rotor, and hydraulic pressure is applied to the vane rotor to rotate the vane rotor in an arbitrary direction. By moving
It is configured to change the phase of the intake camshaft 5 with respect to the timing pulley 6. The exhaust camshaft is not provided with such a variable valve timing mechanism 8 and the exhaust valve is always opened and closed at a predetermined timing.

On the other hand, in the passenger compartment, an input / output device (not shown), a storage device (ROM, RAM, etc.) for storing control programs and control maps, and a central processing unit (CP) are provided.
U), an ECU (electronic control unit) 11 including a timer counter and the like is installed. On the input side of the ECU 11, a throttle sensor 12 for detecting the throttle opening θTH of the engine 1 and 180 of the same cycle as the fuel injection of each cylinder.
Crank angle sensor 1 that outputs an SGT signal for each CA
3. Various sensors such as a fuel pressure sensor 14 for detecting the fuel pressure P in the delivery pipe 3 are connected. Further, various devices such as the fuel injection valve 2, the high pressure pump 4, the variable valve timing mechanism 8 and the spark plug are connected to the output side.

Then, the ECU 11 determines the ignition timing, the fuel injection mode, the fuel injection period, etc. based on the detection information from each sensor, and drives and controls the ignition plug and the fuel injection valve 2. The fuel injection mode is a control mode peculiar to the cylinder injection type engine capable of injecting fuel in addition to the intake stroke. For example, the ECU 11 obtains the target average effective pressure Pe representing the engine load and the output of the crank angle sensor 13. Based on the engine speed Ne, the fuel injection mode is set according to the operating region from a preset map. Although not described in detail, in a region where the target average effective pressure Pe and the engine rotation speed Ne are high, an intake stroke injection mode in which fuel is injected in the intake stroke is set to secure engine output by uniform combustion, while the target average effective In a region where the pressure Pe and the engine rotation speed Ne are low, a compression stroke injection mode in which fuel is injected in a compression stroke is set, a lean air-fuel ratio is realized by stratified combustion, and pumping loss is reduced to improve fuel efficiency.

Further, the ECU 11 sets the target fuel pressure Ptgt according to the switching of the fuel injection mode, and controls the fuel spill of the high pressure pump 4 so that the actual fuel pressure P becomes the target fuel pressure Ptgt. This processing is intended to always drive the fuel injection valve 2 in an area of an appropriate pulse width regardless of the switching of the fuel injection mode, and thereby the injection error caused by the excessively small pulse width is generated. To prevent.

Further, the ECU 11 controls the target average effective pressure Pe.
Based on the engine rotation speed Ne, the advance amount of the intake camshaft 5 is set according to the operating region from a preset map, and the variable valve timing mechanism 8 is drive-controlled based on the set advance amount. On the other hand, the high pressure pump 4
Is configured as a plunger type pump that pressurizes fuel by operating a plunger by a cam crest connected to the rear end of the intake camshaft 5. In the present embodiment, a pair of cam crests that is half the number of cylinders They are provided at 180 ° opposite positions. Therefore, the plunger of high-pressure pump 4 is 360
The fuel is pressurized in a cycle of CA, that is, a cycle of 180 degrees CA which is the cycle of fuel injection or SGT signal of each cylinder, and fuel pressure pulsation due to this is also generated in a cycle of 360 CA.

Further, the ECU 11 controls the fuel injection amount by determining the fuel injection pulse width for determining the fuel injection period according to the operating condition detected based on the detection information from various sensors, that is, the opening of the fuel injection valve 2. The fuel injection valve 2 is drive-controlled for the period. Then, even if the fuel injection pulse width is the same, if the fuel pressure fluctuates due to pulsation of the high-pressure pump 4 or the like, the fuel injection amount also fluctuates. Therefore, the ECU 11 cancels the influence of the fuel pressure pulsation or the like of the high-pressure pump 4 on the fuel injection amount. The fuel injection pulse width is corrected based on the actual fuel pressure P (more specifically, the average fuel pressures P1ave, P2ave). The fuel injection pulse width correction processing will be described in detail below.

FIG. 2 is a time chart showing the correction situation of the fuel injection period (pulse width) of this embodiment in which the number of cam peaks of the high-pressure pump 4 is set to half the number of cylinders, and as shown in this figure. , SGT signal is output at a cycle of 180 ° CA, and fuel injection into each cylinder is performed at a predetermined timing of the same cycle based on the SGT signal. The figure shows a state in which the fuel injection mode is not switched and the fuel injection mode in either the intake stroke or the compression stroke is continued.

On the other hand, as described above, the fuel pressure P of the high pressure pump 4 is
Pulsation occurs in a 360 ° CA cycle. More specifically, the fuel pressure P increases with the pressurization by the cam ridges and reaches the maximum value according to the fuel spill (point a- in the figure).
b), the fuel consumption drops sharply at the first fuel injection (point b in the figure)
-C), and then maintain a constant value (point c- in the figure
d), the fuel consumption is reduced sharply by the next fuel injection (point de in the figure), and the above cycle is repeated.

On the other hand, the ECU 11 executes the average fuel pressure calculation routine shown in FIG. 3 at a predetermined control interval. First, in step S2, the fuel pressure P detected by the fuel pressure sensor 14 is added to the total fuel pressure ΣP, and in the subsequent step S4, SGT is performed.
It is determined whether or not it is a signal rising timing (falling timing in the case of a falling cycle). When the determination is NO (negative), the process returns to step S2 to repeat the process of adding the fuel pressure P, and when the determination is YES, the process proceeds to step S6. As a result, the total fuel pressure ΣP is calculated as the sum of the fuel pressures P during the rising or falling cycle of the SGT signal (hereinafter referred to as the SGT cycle T).

Thereafter, the average fuel pressure P1ave one injection cycle before calculated in step S6 is replaced by the average fuel pressure P2 two injection cycles before.
The value is updated to 2ave, and in the subsequent step S8, the total fuel pressure ΣP is divided by the number of additions n of the fuel pressure P to calculate the average fuel pressure P1ave one cycle before this time. Further, in step S10, the total fuel pressure Σ
After resetting P, the routine ends. Therefore, by repeating the routine, the average value of the fuel pressure P is calculated every SGT cycle T, the latest value is set as the average fuel pressure P1ave one injection cycle before, and the immediately preceding value is the average two injection cycles before. It is set as the fuel pressure P2ave.

Further, the ECU 11 executes the fuel injection period correction routine shown in FIG. 4 at a predetermined timing immediately before the fuel injection synchronized with the SGT signal, and first calculates the fuel pressure deviation ΔP in step S12. This fuel pressure deviation ΔP is used as an index as to whether or not the actual fuel pressure P is controlled following the target fuel pressure Ptgt set according to the fuel injection mode as described above. It is calculated as a difference from the average fuel pressure P1ave one injection cycle before.

In a succeeding step S14, it is determined whether or not the fuel pressure deviation ΔP is less than a preset predetermined value ΔP0. When the determination is YES, the above-mentioned 2 is performed in step S16.
A correction coefficient k is obtained from a predetermined map based on the average fuel pressure P2ave before the injection cycle (correction means). On the other hand, when the determination is NO, a predetermined map is obtained based on the average fuel pressure P1ave before the one injection cycle in step S18. The correction coefficient k is obtained from the correction coefficient k. Further, in step S20, the next fuel injection pulse width is corrected by the calculated correction coefficient k, and then the routine ends. In a fuel injection control routine (not shown), the next fuel injection is performed based on the corrected fuel injection pulse width (control means).

The correction situation of the fuel injection pulse width by the above processing of the ECU 11 will be described. First, as described above, the fuel pressure P of the high-pressure pump 4 pulsates in a 360 ° CA cycle,
As shown in FIG. 2, this pulsation cycle is 18 in the SGT cycle T.
When it is divided into 0 ° CAs, it is divided into a pulsation cycle first half where the fuel pressure is relatively high and a pulsation cycle second half where the fuel pressure is relatively low. Then, the fuel pressure pulsation in the first half of the pulsation cycle is reproduced in the same first half of the pulsation cycle after 360 ° CA, and the fuel pressure pulsation in the second half of the pulsation cycle is reproduced in the same second half of the pulsation cycle after 360 ° CA.

When the determination in step S14 is YES (ΔP <ΔP0), for example, the specific fuel injection mode is continued as shown in FIG. 2, and the fuel pressure P sufficiently follows the predetermined target fuel pressure Ptgt. The fuel injection pulse width at this time is corrected based on the average fuel pressure P2ave two injection cycles before, as indicated by the solid arrow in FIG. Therefore, to the correction of the fuel injection pulse width in the first half of the pulsation cycle, the average fuel pressure P2ave calculated from the fuel pressure pulsation in the first half of the pulsation cycle before 360 ° CA is applied, and the correction of the fuel injection pulse width in the second half of the pulsation cycle is applied. Similarly, the average fuel pressure P2ave calculated from the fuel pressure pulsation in the latter half of the pulsation cycle before 360 ° CA is applied to.

Here, 360 ° is set between the calculation of the average fuel pressure P2ave two injection cycles before and the correction of the fuel injection pulse width.
Although there is a time difference corresponding to CA, in this steady state, the increase / decrease in the fuel pressure P is relatively small, so there is almost no risk of causing a correction error. As a result, regardless of the fuel pressure pulsation of the high-pressure pump 4, the fuel injection pulse width can always be corrected by the appropriate average fuel pressure P2ave to properly control the fuel injection amount, and therefore, a problem due to a control error of the fuel injection amount, for example, exhaust gas. It is possible to prevent deterioration of characteristics, fuel consumption, drivability, and the like.

In addition, in the engine 1 of this embodiment, when the advance amount of the intake camshaft 5 is controlled by the variable valve timing mechanism 8, the phase of the cam crest of the high-pressure pump 4 with respect to the crankshaft 7 is accordingly changed, That is, the positional relationship of the fuel pressure pulsation with respect to the fuel injection in FIG. 2 shifts. That is, since the average fuel pressure changes according to the control status of the valve timing, it becomes more difficult to correct the fuel injection pulse width based on an appropriate fuel pressure, but even in such a case, the pulsation cycle is reproduced after 360 ° CA. Since this is the same, it is possible to appropriately correct the fuel injection pulse width based on the average fuel pressure P2ave two injection cycles before.

On the other hand, when the determination in step S14 is NO (ΔP ≧ ΔP0), for example, the fuel injection mode is switched, and the fuel pressure P follows the newly set target fuel pressure Ptgt. It is regarded as a certain transient state, and the fuel injection pulse width at this time is corrected based on the average fuel pressure P1ave one injection cycle before, as indicated by the broken line arrow in FIG.

That is, the fuel pressure P in the transient state is 36 in the pulsation cycle.
There is a large change between 0 ° CA, and the amount of change is the difference in the average fuel pressure between the first half of the pulsation cycle and the second half of the pulsation cycle (P1ave-P2ave).
Will be exceeded. Therefore, in this case, the average fuel pressure P1ave immediately before is based on the current fuel pressure P, so that the average fuel pressure P1ave one injection cycle before is applied to the correction of the fuel injection pulse width. By carrying out the processing, another advantage is obtained in that the inadequacy of the fuel injection amount in the transient state can be prevented in advance.

Although the embodiment has been described above, the aspect of the present invention is not limited to this embodiment. For example, in the above-described embodiment, the fuel injection control device for the in-line 4-cylinder in-cylinder injection type gasoline engine 1 is embodied. However, the number of cylinders and the type of the engine are not limited to this. The number of cam peaks of the high-pressure pump 4 may be set to three as applied to a gasoline engine. Alternatively, it may be embodied as a fuel injection control device for a common rail type diesel engine, and even in this case, a fuel pressure pulsation is inevitably used by using a high pressure pump such as a plunger type in order to secure a high fuel pressure required for in-cylinder injection. Since this occurs, it is possible to obtain exactly the same operation and effect by the correction processing similar to that of the above embodiment.

In the above embodiment, the engine 1 is provided with the valve timing variable mechanism 8 for controlling the advance amount of the intake camshaft 5, but the variable mechanism 8 is not always necessary and has this function. Not applicable to general engines.

[0035]

As described above, according to the fuel injection control device for the internal combustion engine of the invention of claim 1, the fuel injection period is always corrected based on the appropriate fuel pressure regardless of the fuel pressure pulsation of the high-pressure pump. As a result, the fuel injection amount can be controlled appropriately, and thus the occurrence of a defect due to a control error of the fuel injection amount can be prevented.

According to the fuel injection control device for the internal combustion engine of the second aspect of the present invention, in addition to the first aspect, it is possible to prevent the control error of the fuel injection amount in the transient state.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a fuel injection control device for an engine according to an embodiment.

FIG. 2 is a time chart showing a correction situation of a fuel injection period in the embodiment in which the number of cam peaks of the high-pressure pump is set to half the number of cylinders.

FIG. 3 is a flowchart showing an average fuel pressure calculation routine executed by an ECU.

FIG. 4 is a flowchart showing a fuel injection period correction routine executed by the ECU.

FIG. 5 is a time chart showing a correction situation of a fuel injection period of the related art in which the number of cam peaks of the high-pressure pump is set corresponding to the number of cylinders.

FIG. 6 is a time chart showing a correction situation of a fuel injection period of the related art in which the number of cam peaks of the high-pressure pump is set to half the number of cylinders.

[Explanation of symbols]

1 engine (internal combustion engine) 2 fuel injection valve 4 high pressure pump 11 ECU (control means, correction means)

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Claims (2)

[Claims] 1. A fuel is pressurized by a high-pressure pump in synchronism with the rotation of an internal combustion engine and supplied to a fuel injection valve of each cylinder, and each fuel injection valve is opened / closed by a control means to be in the cylinder of the corresponding cylinder. In a fuel injection control device for an internal combustion engine, which injects fuel and corrects a fuel injection period of the fuel injection valve based on a fuel pressure of the high-pressure pump, the high-pressure pump includes: The fuel is pressurized at a cycle twice as long as the injection cycle, and the correction means calculates an average value of the fuel pressure of the pressurized fuel at each injection cycle of the fuel injection valve and at the same time two injection cycles before. A fuel injection control device for an internal combustion engine, wherein the fuel injection period is corrected based on the calculated average value of the fuel pressure. 2. The high-pressure pump is controlled in fuel pressure based on a target fuel pressure set from the operating state of the internal combustion engine, and the correction means is configured such that the difference between the fuel pressure of the high-pressure pump and the target fuel pressure is a predetermined value. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel injection period is corrected based on the average value of the fuel pressure calculated one injection cycle before at the above time.