JP2014231746A - Internal combustion engine fuel supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit recurrence of vapor after the end of a feed fuel pressure increase control to increase a pressure (feed fuel pressure) of fuel fed from a low pressure pump (fuel pump).SOLUTION: If a state in which vapor occurs in fuel is determined, a feed fuel pressure increase control is executed to control a low pressure pump 12 to increase a feed fuel pressure up to a high-pressure-side target fuel pressure so as to inhibit occurrence of vapor. Thereafter, when the feed fuel pressure increase control is canceled to transition into a normal feed pressure control, a normal target fuel pressure is offset to a higher fuel pressure than execution of the feed fuel pressure increase control, and a fuel pressure offset control is executed to control the low pressure pump 12 to gradually lower the feed fuel pressure down to the post-offset normal target fuel pressure. Thus, in the normal feed fuel pressure control executed after the end of the feed fuel pressure increase control, the low pressure pump 12 is controlled so as to keep the feed fuel pressure equal to the post-offset normal target fuel pressure.

Description

  The present invention relates to a fuel supply device for an internal combustion engine that controls the pressure (feed fuel pressure) of fuel supplied from a fuel pump.

  In an internal combustion engine, when the fuel supplied from the fuel pump becomes high temperature, the vapor pressure of the fuel becomes higher than the fuel pressure (fuel pressure), and vapor (bubbles) may be generated in the fuel. When vapor is generated in the fuel, the control accuracy of the fuel injection is lowered, and there is a possibility that problems such as instability of the idle rotation speed or misfiring may occur.

  Therefore, for example, as described in Patent Document 1 (Japanese Patent Laid-Open No. 2012-122403), vapor is generated in the fuel based on the fluctuation amount of the pressure (feed fuel pressure) of the fuel supplied from the fuel pump. It is determined whether or not it is in a state, and when it is determined that vapor is generated, control is performed to increase the feed fuel pressure to a fuel pressure higher than the fuel pressure at normal time to suppress the generation of vapor. There is something like that.

JP 2012-122403 A

  However, in the technique of the above-mentioned Patent Document 1, control for increasing the feed fuel pressure to a fuel pressure higher than the fuel pressure at normal time (feed fuel pressure increase control) is executed to suppress the generation of vapor, and then the feed fuel pressure is controlled to increase the feed fuel pressure. To the same fuel pressure as before. For this reason, after the end of the feed fuel pressure increase control, the vapor pressure of the fuel may become higher than the feed fuel pressure again depending on the fuel temperature or the like, and the vapor may recur. For this reason, the frequency with which the feed fuel pressure increase control is repeatedly executed increases, and the durability performance of the fuel pump may deteriorate early.

  Therefore, the problem to be solved by the present invention is to provide a fuel supply device for an internal combustion engine that can prevent the vapor from recurring after the end of the feed fuel pressure increase control.

  In order to solve the above-mentioned problem, the invention according to claim 1 performs normal feed fuel pressure control for controlling the pressure of fuel supplied from the fuel pump (12) (hereinafter referred to as “feed fuel pressure”) to a predetermined normal target fuel pressure. In the fuel supply device for the internal combustion engine to be executed, the vapor determination means (38) for determining whether or not the vapor is generated in the fuel, and the feed fuel pressure when it is determined that the vapor is generated The fuel pressure increase control means (38) for executing the feed fuel pressure increase control for increasing the fuel pressure to a higher target fuel pressure higher than the normal target fuel pressure, and the normal target when the feed fuel pressure increase control is canceled and the control shifts to the normal feed fuel pressure control. A fuel pressure offset that offsets the fuel pressure to a higher fuel pressure than before execution of the feed fuel pressure increase control and lowers the feed fuel pressure to the normal target fuel pressure after the offset. Is obtained by the fuel pressure offset control means for executing the door control and (38) configured to include a.

  In this configuration, when it is determined that the vapor is generated, the feed fuel pressure is controlled by increasing the feed fuel pressure to the high target fuel pressure higher than the normal target fuel pressure, so that the feed fuel pressure is reduced to the fuel vapor. The generation of vapor can be suppressed by setting the pressure sufficiently higher than the pressure.

  Furthermore, when the feed fuel pressure increase control is canceled and the routine shifts to the normal feed fuel pressure control, the normal target fuel pressure is offset to a fuel pressure higher than that before execution of the feed fuel pressure increase control, and the feed fuel pressure is reached to the normal target fuel pressure after the offset. Execute fuel pressure offset control to reduce Thereby, in the normal feed fuel pressure control executed after the end of the feed fuel pressure increase control, the feed fuel pressure is controlled to the normal target fuel pressure after the offset (the fuel pressure higher than the normal target fuel pressure before the execution of the feed fuel pressure increase control). . For this reason, the feed fuel pressure after shifting from the feed fuel pressure increase control to the normal feed fuel pressure control can be made higher than before the execution of the feed fuel pressure increase control, so that the vapor pressure of the fuel is less likely to be higher than the feed fuel pressure. It is possible to prevent the vapor from recurring after the end of the feed fuel pressure increase control. As a result, the frequency with which the feed fuel pressure increase control is repeatedly executed can be reduced to suppress early deterioration of the durability performance of the fuel pump.

FIG. 1 is a diagram showing a schematic configuration of a fuel supply system for a direct injection engine according to an embodiment of the present invention. FIG. 2 is a flowchart showing the flow of processing of the feed fuel pressure control routine. FIG. 3 is a time chart showing an execution example of feed fuel pressure control.

Hereinafter, an embodiment embodying a mode for carrying out the present invention will be described.
First, a schematic configuration of a fuel supply system of a cylinder injection engine (internal combustion engine) will be described with reference to FIG.

  A low pressure pump 12 (fuel pump) that pumps up the fuel is installed in the fuel tank 11 that stores the fuel. The low-pressure pump 12 is driven by an electric motor (not shown) that uses a battery (not shown) as a power source. The fuel discharged from the low pressure pump 12 is supplied to the high pressure pump 14 through the fuel pipe 13. The fuel pipe 13 is provided with a low-pressure fuel pressure sensor 15 for detecting the pressure of fuel supplied from the low-pressure pump 12 (hereinafter referred to as “feed fuel pressure”) and a fuel temperature sensor 16 for detecting fuel temperature (fuel temperature). ing.

  The high-pressure pump 14 is a piston pump that sucks / discharges fuel by reciprocating a piston 19 (plunger) in a cylindrical pump chamber 18. The piston 19 is a cam 21 fitted to a camshaft 20 of the engine. It is driven by the rotational movement of.

  A fuel pressure control valve 23 is provided on the suction port 22 side of the high-pressure pump 14. The fuel pressure control valve 23 is a normally open type electromagnetic valve, and includes a valve body 24 that opens and closes the suction port 22, a spring 25 that urges the valve body 24 in the valve opening direction, and a valve body 24 in the valve closing direction. And a solenoid 26 that is electromagnetically driven.

  During the intake stroke of the high-pressure pump 14 (when the piston 19 is lowered), the valve body 24 of the fuel pressure control valve 23 is opened and fuel is sucked into the pump chamber 18, and the discharge stroke of the high-pressure pump 14 (when the piston 19 is raised). , The energization of the solenoid 26 of the fuel pressure control valve 23 is controlled so that the valve body 24 of the fuel pressure control valve 23 is closed and the fuel in the pump chamber 18 is discharged. At that time, the energization start timing of the fuel pressure control valve 23 (solenoid 26) is controlled to set the closing period of the fuel pressure control valve 23 (the crank angle section in the closed state from the valve closing start timing to the top dead center of the piston 19). By controlling, the discharge amount of the high-pressure pump 14 is controlled to control the fuel pressure (fuel pressure). The energization start timing of the fuel pressure control valve 23 is set by a crank angle from a predetermined reference crank angle position (for example, a crank angle position corresponding to the top dead center of the piston 19).

  For example, when the fuel pressure is increased, the energization start timing of the fuel pressure control valve 23 is advanced to advance the valve closing start timing of the fuel pressure control valve 23, thereby extending the valve closing period of the fuel pressure control valve 23 and increasing the pressure. The discharge amount of the pump 14 is increased. Conversely, when the fuel pressure is decreased, the closing period of the fuel pressure control valve 23 is shortened by delaying the energization start timing of the fuel pressure control valve 23 and delaying the closing start timing of the fuel pressure control valve 23. The discharge amount of the high-pressure pump 14 is reduced.

  On the other hand, a check valve 28 for preventing the backflow of discharged fuel is provided on the discharge port 27 side of the high-pressure pump 14. The fuel discharged from the high-pressure pump 14 is sent to the delivery pipe 30 through the high-pressure fuel pipe 29, and the high-pressure fuel is distributed from the delivery pipe 30 to the fuel injection valve 31 attached to each cylinder of the engine. The delivery pipe 30 (or the high-pressure fuel pipe 29) is provided with a high-pressure fuel pressure sensor 32 that detects the pressure of fuel in the high-pressure fuel system such as the high-pressure fuel pipe 29 and the delivery pipe 30 (hereinafter referred to as “high-pressure fuel pressure”). It has been. The delivery pipe 30 is provided with a relief valve 33, and a discharge port of the relief valve 33 is connected to the fuel tank 11 (or the low-pressure side fuel pipe 13) via a relief pipe 34.

  Further, the engine is provided with an air flow meter 36 for detecting the amount of intake air and a crank angle sensor 37 for outputting a pulse signal at every predetermined crank angle in synchronization with rotation of a crankshaft (not shown). Based on the output signal of the crank angle sensor 37, the crank angle and the engine speed are detected.

  Outputs of the various sensors described above are input to an electronic control unit (hereinafter referred to as “ECU”) 38. The ECU 38 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount and the ignition timing are determined according to the engine operating state. The throttle opening (intake air amount) and the like are controlled.

  At that time, the ECU 38 executes normal feed fuel pressure control for controlling the low-pressure pump 12 so that the actual feed fuel pressure detected by the low-pressure fuel pressure sensor 15 is maintained at a predetermined normal target fuel pressure. Further, a high-pressure pump calculates a target high-pressure fuel pressure according to the engine operating state (for example, engine speed, engine load, etc.) and matches the actual high-pressure fuel pressure detected by the high-pressure fuel pressure sensor 32 with the target high-pressure fuel pressure. The high-pressure fuel pressure feedback control (high-pressure fuel pressure control) for feedback-controlling the discharge amount of 14 (the energization timing of the fuel pressure control valve 23) is executed.

  By the way, when the fuel supplied from the low-pressure pump 12 becomes high temperature, the vapor pressure of the fuel becomes higher than the feed fuel pressure, and vapor (bubbles) may be generated in the fuel. When vapor is generated in the fuel, the control accuracy of the fuel injection is lowered, and there is a possibility that problems such as instability of the idle rotation speed or misfiring may occur.

  In this embodiment, therefore, the ECU 38 executes a feed fuel pressure control routine shown in FIG. 2 to be described later, whereby vapor is generated in the fuel (for example, the vapor is generated to the extent that it adversely affects fuel injection). When it is determined whether or not vapor is generated, feed fuel pressure increase control is executed to increase the feed fuel pressure to a higher target fuel pressure higher than the normal target fuel pressure. Thereby, the feed fuel pressure is made sufficiently higher than the vapor pressure of the fuel to suppress the generation of vapor.

  However, if the feed fuel pressure is returned to the same fuel pressure as before the execution of the feed fuel pressure increase control after the feed fuel pressure increase control is executed and the vapor generation is suppressed, the fuel vapor pressure is fed again depending on the fuel temperature, etc. Vapor may recur when the fuel pressure is higher. For this reason, the frequency with which the feed fuel pressure increase control is repeatedly executed increases, and the durability performance of the low-pressure pump 12 may deteriorate early.

  As a countermeasure, in this embodiment, when the feed fuel pressure increase control is canceled and the routine shifts to the normal feed fuel pressure control, the normal target fuel pressure is offset to a higher fuel pressure than before the execution of the feed fuel pressure increase control, and after the offset Fuel pressure offset control is executed to reduce the feed fuel pressure to the normal target fuel pressure. Thereby, in the normal feed fuel pressure control executed after the end of the feed fuel pressure increase control, the feed fuel pressure is controlled to the normal target fuel pressure after the offset (the fuel pressure higher than the normal target fuel pressure before the execution of the feed fuel pressure increase control). . This makes it difficult for the vapor pressure of the fuel to become higher than the feed fuel pressure, and prevents the vapor from recurring after the end of the feed fuel pressure increase control.

Hereinafter, the processing content of the feed fuel pressure control routine of FIG. 2 executed by the ECU 38 in this embodiment will be described.
The feed fuel pressure control routine shown in FIG. 2 is repeatedly executed at a predetermined cycle during the power-on period of the ECU 38 (for example, during the ON period of the ignition switch). When this routine is started, first, in step 101, it is detected whether or not the vapor is generated in the fuel, for example, the actual high pressure detected by the high pressure fuel pressure sensor 32 during execution of the high pressure fuel pressure feedback control. The determination is made based on whether or not the system fuel pressure Ph is lower than the target high-pressure system fuel pressure Phtg by a predetermined value or more for a predetermined time.

  When the vapor is generated in the fuel, the fuel discharge efficiency of the high-pressure pump 14 is lowered. Therefore, the actual high-pressure fuel pressure Ph can be increased to the target high-pressure fuel pressure Phtg even if the high-pressure fuel pressure feedback control is executed. become unable. Therefore, when the state where the actual high pressure fuel pressure Ph is lower than the target high pressure fuel pressure Phtg by a predetermined value or more continues for a predetermined time or more, it can be determined that the fuel is in a vaporized state. The processing in step 101 serves as a vapor determination means in the claims.

  Thereafter, the process proceeds to step 102, and it is determined whether or not vapor is generated based on the determination result of step 101. If it is determined in step 102 that the vapor is not generated, the process proceeds to step 112 and normal feed fuel pressure control is executed. In this normal feed fuel pressure control, the drive voltage (or drive current) of the low pressure pump 12 is controlled so that the actual feed fuel pressure Pf detected by the low pressure fuel pressure sensor 15 is maintained at the normal target fuel pressure Pftg.

  On the other hand, if it is determined in step 102 that the vapor has been generated, the process proceeds to step 103 to execute feed fuel pressure increase control. In this feed fuel pressure increase control, the drive voltage (or drive current) of the low-pressure pump 12 is quickly increased so that the actual feed fuel pressure Pf detected by the low-pressure fuel pressure sensor 15 is rapidly increased to the high-pressure side target fuel pressure Pftgh higher than the normal target fuel pressure Pftg. To control. Here, the high-pressure side target fuel pressure Pftgh is set to, for example, a fuel pressure (a fuel pressure higher than the vapor pressure of the fuel at the current fuel temperature) necessary to suppress the generation of vapor. The processing in step 103 serves as fuel pressure increase control means in the claims.

Thereafter, the routine proceeds to step 104 where the fuel temperature detected by the fuel temperature sensor 16 is stored as the fuel temperature T1 at the start of the feed fuel pressure increase control.
Thereafter, the process proceeds to step 105, in which it is determined whether or not the execution time of the feed fuel pressure increase control (elapsed time since the start of the feed fuel pressure increase control) is within a specified time. Here, the specified time is set to, for example, an allowable upper limit value of the execution time of the feed fuel pressure increase control.

  If it is determined in step 105 that the execution time of the feed fuel pressure increase control is within the specified time, the process proceeds to step 106 and the current fuel temperature T2 detected by the fuel temperature sensor 16 is read. The difference between the fuel temperature T1 at the start of the feed fuel pressure increase control and the current fuel temperature T2 (T1-T2) is equal to or greater than a predetermined value ΔT (that is, the fuel temperature from the start of the feed fuel pressure increase control). Whether or not has decreased by a predetermined value ΔT or more.

  If it is determined in step 107 that the difference (T1−T2) between the fuel temperature T1 at the start of the feed fuel pressure increase control and the current fuel temperature T2 is smaller than the predetermined value ΔT, the process returns to step 105. .

On the other hand, if it is determined in step 107 that the difference (T1−T2) between the fuel temperature T1 at the start of the feed fuel pressure increase control and the current fuel temperature T2 is greater than or equal to the predetermined value ΔT, step 108 is executed. Then, whether or not the difference (Phtg−Ph) between the target high-pressure fuel pressure Phtg and the actual high-pressure fuel pressure Ph is equal to or smaller than a predetermined value ΔPh (that is, in a state where the actual high-pressure fuel pressure Ph has increased to the vicinity of the target high-pressure fuel pressure Phtg). Whether or not there is).
If it is determined in step 108 that the difference (Phtg−Ph) between the target high-pressure fuel pressure Phtg and the actual high-pressure fuel pressure Ph is larger than the predetermined value ΔPh, the process returns to step 105.

  Thereafter, in step 107, it is determined that the difference (T1−T2) between the fuel temperature T1 at the start of the feed fuel pressure increase control and the current fuel temperature T2 is equal to or greater than a predetermined value ΔT, and in step 108, the target high pressure When it is determined that the difference (Phtg−Ph) between the system fuel pressure Phtg and the actual high-pressure system fuel pressure Ph is equal to or less than the predetermined value ΔPh, it is determined that no vapor is generated, and the process proceeds to step 109. Then, the feed fuel pressure increase control is terminated (released).

On the other hand, if it is determined in step 105 that the execution time of the feed fuel pressure increase control has exceeded the specified time, the process proceeds to step 109 to end (release) the feed fuel pressure increase control.
Thereafter, in steps 110 and 111, fuel pressure offset control is executed. In this fuel pressure offset control, the normal target fuel pressure Pftg is offset to a fuel pressure higher than that before execution of the feed fuel pressure increase control, and the actual feed fuel pressure Pf is gradually reduced to the normal target fuel pressure Pftg after the offset. The drive voltage (or drive current) is controlled.

  First, at step 110, the normal target fuel pressure Pftg is offset to a higher fuel pressure than before the execution of the feed fuel pressure increase control. In this case, after shifting to the normal feed fuel pressure control, the normal target fuel pressure Pftg is offset so that the pulsation lower limit value of the feed fuel pressure becomes higher than the vapor pressure of the fuel. Specifically, the difference obtained by subtracting the pulsation lower limit of the feed fuel pressure during the previous normal feed fuel pressure control from the vapor pressure obtained from the fuel vapor pressure curve is obtained as an offset amount, and this offset amount is added to the normal target fuel pressure. Thus, the normal target fuel pressure is offset to obtain the normal target fuel pressure after the offset. Alternatively, based on the descending speed of the piston 19 of the high-pressure pump 14 and the low-pressure system volume (for example, the volume of the fuel pipe 13), the amount of decrease in the feed fuel pressure when the piston 19 descends is obtained as an offset amount. The normal target fuel pressure may be offset by adding to the target fuel pressure, and the normal target fuel pressure after the offset may be obtained.

  The offset amount may be calculated in advance based on test data or design data and stored in the ROM of the ECU 38, or may be calculated by the ECU 38 when fuel pressure offset control is executed. Further, the offset amount may be increased every time the fuel pressure offset control is executed.

  Thereafter, the process proceeds to step 111, and the drive voltage (or drive current) of the low-pressure pump 12 is controlled so as to reduce the actual feed fuel pressure Pf detected by the low-pressure fuel pressure sensor 15 to the normal target fuel pressure Pftg after offset. At this time, the actual feed fuel pressure Pf is gradually decreased at a predetermined change rate (for example, a change rate that is slower than the change rate when the actual feed fuel pressure Pf is increased to the high-pressure side target fuel pressure by the feed fuel pressure increase control). The processing of these steps 110 and 111 serves as fuel pressure offset control means in the claims.

Next, an execution example of the feed fuel pressure control of this embodiment will be described with reference to FIG.
During engine operation, normal feed fuel pressure control is performed to control the low pressure pump 12 so that the actual feed fuel pressure Pf detected by the low pressure fuel pressure sensor 15 is maintained at the normal target fuel pressure Pftg, and also detected by the high pressure fuel pressure sensor 32. High-pressure fuel pressure feedback control is performed to feedback-control the high-pressure pump 14 so that the actual high-pressure fuel pressure Ph matches the target high-pressure fuel pressure Phtg.

  If the actual high-pressure fuel pressure Ph is lower than the target high-pressure fuel pressure Phtg by a predetermined value or more during the high-pressure fuel pressure feedback control for a predetermined time or longer, vapor is generated at the time t1. And the feed fuel pressure increase control for increasing the actual feed fuel pressure Pf to the high target fuel pressure Pftgh is executed. As a result, the actual feed fuel pressure Pf can be made sufficiently higher than the vapor pressure of the fuel to suppress the generation of vapor.

  After the start of the feed fuel pressure increase control, it is determined that the difference (T1−T2) between the fuel temperature T1 at the start of the feed fuel pressure increase control and the current fuel temperature T2 is equal to or greater than a predetermined value ΔT, and the target high pressure fuel pressure At the time t2 when the difference between Phtg and the actual high-pressure fuel pressure Ph (Phtg-Ph) is determined to be equal to or less than the predetermined value ΔPh, it is determined that no vapor is generated, and the feed fuel pressure increase control is terminated. (To release.

  When the feed fuel pressure increase control is canceled and the routine shifts to the normal feed fuel pressure control, the normal target fuel pressure Pftg is offset to a fuel pressure higher than that before execution of the feed fuel pressure increase control until the normal target fuel pressure Pftg after the offset. Fuel pressure offset control for reducing the actual feed fuel pressure Pf is executed. Thereby, in the normal feed fuel pressure control executed after the end of the feed fuel pressure increase control, the actual feed fuel pressure Pf is held at the normal target fuel pressure Pftg after offset (fuel pressure higher than the normal target fuel pressure before execution of the feed fuel pressure increase control). Thus, the low pressure pump 12 is controlled. As a result, the actual feed fuel pressure Pf after the shift from the feed fuel pressure increase control to the normal feed fuel pressure control is made higher than before the execution of the feed fuel pressure increase control, so that the fuel vapor pressure is less likely to be higher than the actual feed fuel pressure Pf. It is possible to prevent the vapor from recurring after the end of the feed fuel pressure increase control. Thereby, the frequency with which feed fuel pressure increase control is repeatedly executed can be reduced, and early deterioration of the durability performance of the low-pressure pump 12 can be suppressed.

  In this embodiment, the actual feed fuel pressure Pf is gradually reduced at a predetermined change rate during the fuel pressure offset control. As a result, even when vapor is generated in the middle of reducing the actual feed fuel pressure Pf during the fuel pressure offset control, the rapid increase in the fuel injection is suppressed and the fuel injection control accuracy changes suddenly. Can be prevented.

  Further, in this embodiment, the normal target fuel pressure Pftg is offset so that the pulsation lower limit value of the feed fuel pressure becomes higher than the vapor pressure of the fuel after shifting to the normal feed fuel pressure control. As a result, the normal target fuel pressure Pftg is set so that the vapor pressure of the fuel does not exceed the feed fuel pressure (lower limit value) even when the feed fuel pressure becomes the lower limit value due to the pulsation of the feed fuel pressure after shifting to the normal feed fuel pressure control. Can do.

  Further, when vapor is generated in the fuel, the actual high-pressure fuel pressure Ph cannot be raised to the target high-pressure fuel pressure Phtg even if high-pressure fuel pressure feedback control is executed. Focusing on this point, in the present embodiment, during execution of the high-pressure fuel pressure feedback control, whether or not the actual high-pressure fuel pressure Ph is lower than the target high-pressure fuel pressure Phtg by a predetermined value or more continues for a predetermined time or more. Since it is determined whether or not the vapor is generated in the fuel, the generation of the vapor can be accurately detected based on the high-pressure fuel pressure.

  The method for determining whether or not vapor is generated in the fuel is not limited to the method described in the above embodiment, and may be changed as appropriate. For example, the amount of change in the feed fuel pressure (peak value) Whether or not vapor is generated in the fuel may be determined based on the difference between the value and the bottom value.

  In the above embodiment, the fuel discharged from the low-pressure pump 12 is supplied to the high-pressure pump 14 and the fuel discharged from the high-pressure pump 14 is supplied to the fuel injection valve 31 (for example, the fuel of the direct injection engine). Although the present invention is applied to the supply system, the present invention is not limited to this. For example, a system that supplies fuel discharged from a fuel pump to a fuel injection valve without using a high-pressure pump (for example, fuel supply for an intake port injection engine) The present invention may be applied to a system.

  In addition, the present invention can be implemented with various modifications without departing from the gist, such as appropriately changing the configuration of the high-pressure pump and the configuration of the fuel supply system.

  DESCRIPTION OF SYMBOLS 12 ... Low pressure pump (fuel pump), 14 ... High pressure pump, 38 ... ECU (Vapor determination means, fuel pressure increase control means, fuel pressure offset control means)

Claims (4)

In a fuel supply device for an internal combustion engine that executes normal feed fuel pressure control for controlling a pressure of fuel supplied from a fuel pump (12) (hereinafter referred to as “feed fuel pressure”) to a predetermined normal target fuel pressure,
Vapor determining means (38) for determining whether or not vapor is generated in the fuel;
Fuel pressure increase control means (38) for performing feed fuel pressure increase control for increasing the feed fuel pressure to a higher target fuel pressure higher than the normal target fuel pressure when it is determined that the vapor is generated;
When the feed fuel pressure increase control is canceled and the routine shifts to the normal feed fuel pressure control, the normal target fuel pressure is offset to a fuel pressure higher than that before execution of the feed fuel pressure increase control until the normal target fuel pressure after the offset. And a fuel pressure offset control means (38) for performing fuel pressure offset control for reducing the feed fuel pressure.   The fuel supply device for an internal combustion engine according to claim 1, wherein the fuel pressure offset control means (38) gradually decreases the feed fuel pressure at a predetermined change rate during the fuel pressure offset control.   The fuel pressure offset control means (38) offsets the normal target fuel pressure so that the pulsation lower limit value of the feed fuel pressure becomes higher than the vapor pressure of the fuel after shifting to the normal feed fuel pressure control. The fuel supply device for an internal combustion engine according to claim 1 or 2. Applied to a system for supplying fuel discharged from the fuel pump (12) to a high-pressure pump (14) and supplying fuel discharged from the high-pressure pump (14) to a fuel injection valve;
The vapor determining means (38) controls the high pressure pump (14) so that the pressure of the fuel supplied from the high pressure pump (14) (hereinafter referred to as “high pressure fuel pressure”) matches the target high pressure fuel pressure. It is determined that the vapor is generated when a state in which the high-pressure fuel pressure is lower than a target value by a predetermined value or more with respect to the target high-pressure fuel pressure continues for a predetermined time or longer during execution of the high-pressure fuel pressure control. The fuel supply device for an internal combustion engine according to any one of claims 1 to 3.

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