Fuel supply system for internal combustion engines

Abstract

To provide a fuel supply device of an internal combustion engine which can close a relief valve for lowering the fuel pressure of a high-pressure delivery pipe.SOLUTION: A fuel supply device of an internal combustion engine having a high-pressure pump for pressurizing fuel which is sucked into a pressurization chamber, and pressure-sensing it to a high-pressure passage, a discharge valve for making the pressurization chamber and the high-pressure passage communicate with each other by opening it, and a suction valve for making a low-pressure passage and the pressurization chamber communicate with each other by opening it, comprises: a relief pipe connected to the high-pressure passage and the low-pressure passage; and a relief valve which is opened by a rise of the fuel pressure in the high-pressure passage to valve-opening pressure or higher to make the high-pressure passage and the low-pressure passage communicate with each other, is closed by the lowering of the fuel pressure in the high-pressure passage to valve-closing pressure or lower to prohibit the movement of fuel between the high-pressure passage and the low-pressure passage. At the opening of the relief valve, the fuel supply device continues to open the suction valve until the relief valve is closed even if the fuel pressure in the high-pressure passage is equal to or lower than a target fuel pressure (Step S8).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a fuel supply device that injects pressurized fuel into cylinders of an internal combustion engine. [Background technology]

[0002] Patent Document 1 describes a high-pressure pump configured to increase the opening speed of a relief valve that relieves fuel from a high-pressure delivery pipe that stores pressurized fuel in a pressurization chamber to the pressurization chamber. The relief valve includes a valve element that receives fuel pressure from the high-pressure delivery pipe at its tip and a shaft that is integrated with the rear end of the valve element and is biased in a valve-closing direction by a spring. A notch is formed in a portion of the outer periphery of the shaft. The shaft also has a recess formed along the axial direction that communicates with the pressurization chamber, and a flow path that connects the recess and the notch. Therefore, when the valve element separates from the valve seat, the high-pressure delivery fuel pressure acts on the end face of the shaft excluding the notch, thereby increasing the load pressing against the shaft and increasing the opening speed of the relief valve. The pump also includes an intake valve that switches between a communication state and a non-communication state between the fuel tank and the pressurization chamber. The intake valve is electrically controlled to open and close in response to the rotation angle of the crankshaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-211598 Summary of the Invention [Problem to be solved by the invention]

[0004] The high-pressure pump described in Patent Document 1 is provided with a relief valve that relieves fuel from the high-pressure delivery pipe to the pressurization chamber. Therefore, the difference between the fuel pressure acting to open the valve element and the fuel pressure acting to close the valve element is relatively small, allowing the spring load to be set to a small value. Therefore, even if the relief valve opens once, the relief valve can be closed by a slight decrease in fuel pressure in the high-pressure delivery pipe or a slight increase in fuel pressure in the pressurization chamber.

[0005] However, if a relief valve is configured to relieve fuel from the high-pressure delivery pipe to a low-pressure section upstream of the intake valve, for example, to reduce the size of the high-pressure pump, the fuel pressure acting in the direction to close the relief valve becomes extremely low. This necessitates a high spring force to prevent the relief valve from opening while pumping fuel from the pressurization chamber to the high-pressure delivery pipe. Furthermore, if a relief valve is configured to increase the load acting on the valve element, including the stem, in the valve opening direction when the relief valve is open, as in the relief valve described in Patent Document 1, the fuel pressure in the high-pressure delivery pipe must be reduced to a level greater than the fuel pressure in the high-pressure delivery pipe when the relief valve begins to open in order to close the opened relief valve. Therefore, the fuel pressure in the high-pressure delivery pipe may fall below the target fuel pressure. In this case, fuel continues to be pumped to the high-pressure delivery pipe via the pressurization chamber by opening and closing the intake valve. Therefore, if the relief valve opens, a relatively large load continues to act in the direction to open the relief valve, preventing the relief valve from closing and potentially preventing the fuel pressure in the high-pressure delivery pipe from increasing.

[0006] The present invention has been made in light of the above technical problems, and aims to provide a fuel supply device for an internal combustion engine that can close a relief valve that reduces the fuel pressure in a high-pressure delivery pipe. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a fuel supply device for an internal combustion engine, comprising: a high-pressure pump that pressurizes fuel drawn into a pressurizing chamber as an output shaft rotates and sends the pressurized fuel to a high-pressure passage; a discharge valve that opens to communicate between the pressurizing chamber and the high-pressure passage when the fuel pressure in the pressurizing chamber is greater than the fuel pressure in the high-pressure passage by a predetermined pressure or more; and an intake valve that opens to communicate between a low-pressure passage and the pressurizing chamber, wherein the fuel supply device comprises a relief pipe connected to the high-pressure passage and the low-pressure passage; and a relief pipe that opens to communicate between the high-pressure passage and the low-pressure passage when the fuel pressure in the high-pressure passage reaches a predetermined valve-opening pressure or more, and communicates between the high-pressure passage and the low-pressure passage, and when the fuel pressure in the high-pressure passage falls below a predetermined valve-closing pressure or less. and a controller for controlling the suction valve, wherein, when the relief valve is closed, if the fuel pressure in the high-pressure passage is equal to or lower than a predetermined target fuel pressure, the controller opens and closes the suction valve to supply fuel from the low-pressure passage into the pressurization chamber and pressurize the fuel supplied to the pressurization chamber to force the fuel into the high-pressure passage, and when the relief valve is open, the controller keeps the suction valve open until the relief valve closes, even if the fuel pressure in the high-pressure passage is equal to or lower than the target fuel pressure.

[0008] In the present invention, the engine may further include an injection device that injects fuel from the high-pressure passage, and the controller may be configured to control the injection device to inject fuel from the high-pressure passage when the relief valve is open.

[0009] In the present invention, the internal combustion engine may further include a first injection device that injects fuel from the high-pressure passage and a second injection device that injects fuel from the low-pressure passage, and the controller may be configured to control the first injection device and the second injection device so that, when the relief valve is open, the amount of fuel injected from the first injection device relative to the total amount of fuel injected into a cylinder of the internal combustion engine is greater than when the relief valve is closed.

[0010] In the present invention, the relief valve may be formed so that a pressure-receiving area that receives fuel pressure from the high-pressure passage when the relief valve is open is larger than the pressure-receiving area when the relief valve is closed. [Effects of the Invention]

[0011] According to the present invention, the relief valve is configured to open when the fuel pressure in the high-pressure passage exceeds the valve opening pressure, thereby communicating the high-pressure passage with the low-pressure passage. While the relief valve is open, the intake valve remains open until the fuel pressure in the high-pressure passage falls below the valve closing pressure and the relief valve closes. This prevents the intake valve from opening and closing, thereby pressurizing fuel in the pressurization chamber, i.e., pumping fuel from the pressurization chamber to the high-pressure passage, even when the fuel pressure in the high-pressure passage exceeds the relief valve closing pressure. In other words, this prevents fuel from being pumped to the high-pressure passage, preventing the fuel pressure from dropping below the relief valve closing pressure and the relief valve from closing. As a result, the relief valve can be closed, preventing a situation in which the fuel pressure in the high-pressure passage cannot be increased to the target fuel pressure. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram for explaining an example of a fuel supply device for an internal combustion engine according to an embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional view schematically illustrating an example of the configuration of a relief valve. [Figure 3] 3 is a flowchart for explaining control and behavior changes in a fuel supply system of an internal combustion engine. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described based on the embodiments shown in the drawings. Note that the embodiments described below are merely examples of specific embodiments of the present invention and are not intended to limit the present invention.

[0014] FIG. 1 shows an example of a fuel supply system for an internal combustion engine according to an embodiment of the present invention. The fuel supply system 1 shown in FIG. 1 is configured to supply fuel to direct injection injectors (DI) 2 provided in cylinders of the internal combustion engine and injecting fuel directly into the cylinders, and to port injection injectors (PFI) 3 provided in an intake pipe and injecting fuel toward an intake port. The fuel supply system 1 shown in FIG. 1 is configured to supply fuel to a four-cylinder internal combustion engine, and therefore has four direct injection injectors 2 and four port injection injectors 3. The direct injection injectors 2 correspond to the "injector" or "first injector" in the embodiment of the present invention, and the port injection injectors 3 correspond to the "second injector" in the embodiment of the present invention. The direct injection injectors 2 and the port injection injectors 3 can be configured similarly to the direct injection injectors and port injection injectors provided in conventional internal combustion engines.

[0015] The fuel supply device 1 includes a fuel tank 4 that stores fuel, a low-pressure pump 5 that pumps up the fuel from the fuel tank 4, and a high-pressure pump 6 that pressurizes the fuel pumped up by the low-pressure pump 5. The low-pressure pump 5 is configured similarly to a pump provided in a conventional internal combustion engine, and a low-pressure fuel pipe 7 is connected to its output port.

[0016] A low-pressure delivery pipe 9 is connected to the low-pressure fuel pipe 7 via a fuel filter 8 that removes foreign matter from the fuel. A port injector 3 is provided in the low-pressure delivery pipe 9, and fuel stored under pressure in the low-pressure delivery pipe 9 is injected toward the intake port by opening the port injector 3. The low-pressure delivery pipe 9 is provided with a fuel pressure sensor 10 that detects the internal pressure.

[0017] A branch pipe 11 is connected to the low-pressure fuel pipe 7 downstream of the fuel filter 8, and a high-pressure pump 6 is connected to the branch pipe 11. The high-pressure pump 6 is configured to further increase the pressure of the input fuel (hereinafter referred to as fuel pressure) and output it to a high-pressure delivery pipe 12 in which the direct injection injector 2 is provided. That is, the high-pressure pump 6 and the high-pressure delivery pipe 12 are connected via a high-pressure pipe 13. In the example shown in FIG. 1 , an orifice 14 is provided downstream of the high-pressure pipe 13, and a fuel pressure sensor 15 that detects the internal pressure is provided in the high-pressure delivery pipe 12. The high-pressure pipe 13 and the high-pressure delivery pipe 12 correspond to the "high-pressure passage" in the embodiment of the present invention.

[0018] The high-pressure pump 6 shown in FIG. 1 is configured to pressurize fuel in conjunction with the rotation of a crankshaft (not shown). Specifically, it includes a pump cam 17 mounted on a camshaft (not shown) for opening and closing intake and exhaust valves, and a lifter 18 that moves up and down with the rotation of the pump cam 17. A chain 16 is wound around the camshaft and crankshaft. Therefore, the camshaft rotates in conjunction with the rotation of the crankshaft, and as a result, the phase of the rotational direction of the pump cam 17 changes, causing the lifter 18 to move up and down. This crankshaft corresponds to the "output shaft" in this embodiment of the present invention.

[0019] The pump cam 17 shown in FIG. 1 is formed in a rectangular shape. In other words, the distance from the center of rotation to the outer edge is formed non-uniformly. A lifter 18 is provided above the pump cam 17 so as to be able to move up and down and contact the outer edge of the pump cam 17. Therefore, as the pump cam 17 rotates, the distance from the center of rotation of the pump cam 17 to the contact point with the lifter 18 varies, causing the lifter 18 to move up and down. Note that a compression spring 20 is provided between the pump body 19 and the lifter 18 that constitute the high-pressure pump 6, pressing the lifter 18 toward the pump cam 17, so that the lifter 18 and the pump cam 17 can be maintained in contact with each other.

[0020] A plunger 22 extending toward a pressurizing chamber 21 formed in a pump body 19 is integrated with the lifter 18. Therefore, when the lifter 18 rises, the plunger 22 protrudes into the pressurizing chamber 21, reducing the volume of the pressurizing chamber 21, thereby pressurizing the fuel drawn into the pressurizing chamber 21 and sending it under pressure to the high-pressure delivery pipe 21.

[0021] A suction port 23 for taking in low-pressure fuel is formed in the pressurized chamber 21, and a suction pipe 24 is connected to the suction port 23. The suction pipe 24 is configured so that low-pressure fuel is supplied from a damper chamber 25 connected to the branch pipe 11. That is, the upstream end of the suction pipe 24 is connected to the damper chamber 25.

[0022] A pulsation damper 26 is provided in the damper chamber 25. This pulsation damper 26 is configured similarly to a conventional pulsation damper, and is configured to attenuate fluctuations in pressure when pressure acts on the fuel in the intake pipe 24 due to backflow from the pressurizing chamber 21.

[0023] As described above, the low-pressure fuel pumped by the low-pressure pump 5 can be supplied to the pressurization chamber 21 via the low-pressure fuel pipe 7, the branch pipe 11, the damper chamber 25, and the suction pipe 24. Meanwhile, the plunger 22 is configured to pressurize the fuel by moving up and down in conjunction with the rotation of the crankshaft. Therefore, an intake valve 27 is provided in the intake port 23 to switch whether or not fuel is supplied to the pressurization chamber 21 depending on whether or not fuel pressurization is required. That is, by opening the intake valve 27, low-pressure fuel is supplied from the suction pipe 24 to the pressurization chamber 21, and by closing the intake valve 27, fuel flow from the pressurization chamber 21 to the suction pipe 24 is blocked, thereby pressurizing the fuel in the pressurization chamber 21. The low-pressure fuel pipe 7, the branch pipe 11, the damper chamber 25, and the suction pipe 24 correspond to the "low-pressure passage" in this embodiment of the present invention.

[0024] The intake valve 27 is a normally-open control valve that includes a valve element 28 made of a magnetic material and abutting against the intake port 23, a solenoid 29 for actuating the valve element 28, and a spring (not shown) for pressing the valve element 28 in the valve-opening direction. Therefore, when there is no demand for fuel to be pumped to the high-pressure delivery pipe 12, the solenoid 29 is de-energized to open the intake valve 27. That is, even when the plunger 22 is rising, keeping the intake valve 27 open allows fuel to flow back from the pressurization chamber 21, thereby preventing fuel from being pumped from the pressurization chamber 21 to the high-pressure delivery pipe 12. Conversely, when there is a demand for fuel to be pumped to the high-pressure delivery pipe 12, the supply of electricity to the solenoid 29 is controlled to open and close the intake valve 27 in conjunction with the rotation angle of the crankshaft, i.e., the up and down movement of the plunger 22. That is, when the plunger 22 descends, the solenoid 29 is de-energized and the intake valve 27 is opened, thereby supplying fuel to the pressurized chamber 21, and when the plunger 22 ascends, the solenoid 29 is energized and the intake valve 27 is closed, thereby suppressing backflow from the pressurized chamber 21, and as a result, fuel is pressurized from the pressurized chamber 21 to the high-pressure delivery pipe 12.

[0025] Furthermore, a discharge pipe 31 is connected to an output port 30 of the pressurized chamber 21, and the high-pressure piping 13 is connected to the discharge pipe 31. The discharge pipe 31 is provided with a discharge valve 32 that opens to communicate between the pressurized chamber 21 and the high-pressure delivery pipe 12 when the pressure acting from the pressurized chamber 21 is higher by a predetermined pressure or more than the pressure acting from the high-pressure delivery pipe 12 side. That is, the discharge valve 32 is composed of a valve element 33 that abuts against a valve seat formed in the pressurized chamber 21, and a spring 34 that presses the valve element 33 toward the valve seat. By adjusting the pressure-receiving area of ​​the valve element 33 on the pressurized chamber 21 side, the pressure-receiving area on the high-pressure delivery pipe 12 side, and the spring force of the spring 34, the discharge valve 32 is configured to open when the difference between the fuel pressure on the pressurized chamber 21 side and the fuel pressure on the high-pressure delivery pipe 12 side becomes a predetermined difference or more.

[0026] Furthermore, a relief path 35 is provided to prevent the fuel pressure in the high-pressure delivery pipe 12 from exceeding a predetermined upper limit pressure. The fuel supply device 1 shown in Fig. 1 is configured to relieve the fuel in the high-pressure delivery pipe 12 upstream of the intake valve 27. Specifically, a relief pipe 36 is provided that is connected to the discharge pipe 31 and the intake pipe 24, and a relief valve 37 is provided in the relief pipe 36.

[0027] The relief valve 37 shown in Fig. 1 is composed of a valve element 38 that abuts against a valve seat formed on the high-pressure delivery pipe 12 side, and a spring 39 that presses the valve element 38. Fig. 2 is an enlarged view schematically showing the tip of the valve element 38, with Fig. 2(a) showing the closed state and Fig. 2(b) showing the open state.

[0028] As shown in FIG. 2, the valve element 38 is formed in a cylindrical shape with a closed end and a bottom. The center of the end of the valve element 38 is formed with an abutment portion 41 that protrudes toward the valve seat 40. That is, when the valve element 38 abuts against the valve seat 40 as shown in FIG. 2(a), the tip of the abutment portion 41 receives fuel pressure from the high-pressure delivery pipe 12 acting from the right side in the figure. When the valve element 38 moves away from the valve seat 40 as shown in FIG. 2(b), the tip of the abutment portion 41 and the circular tip portion of the valve element 38 receive fuel pressure from the high-pressure delivery pipe 12. That is, when the relief valve 37 is open, the pressure-receiving area that receives fuel pressure from the high-pressure delivery pipe 12 is larger than when the relief valve 37 is closed. Therefore, the load acting on the valve element 38 when the valve is open is greater than the load (dynamic pressure) acting on the valve element when the valve is closed. A spring 39 is provided to press against the rear end or hollow portion of the valve element 38. Therefore, the opening pressure of the relief valve 37 is the pressure obtained by dividing the closing load, which is the spring force added to the load corresponding to the fuel pressure in the intake pipe 24 and the pressure-receiving area that receives the fuel pressure in the intake pipe 24, by the pressure-receiving area of ​​the abutment portion 41, and the closing pressure of the relief valve 37 is the pressure obtained by dividing the above-mentioned closing load by the sum of the pressure-receiving areas of the abutment portion 41 and the tip of the valve body 38.

[0029] An electronic control unit (hereinafter referred to as ECU) 42 is provided for controlling the above-mentioned low-pressure pump 5, intake valve 27, direct injector 2, and port injector 3. Like ECUs that control various devices in conventional internal combustion engines, this ECU 42 is mainly composed of a microcomputer, and is configured to output signals to the low-pressure pump 5, intake valve 27, direct injector 2, and port injector 3 based on signals input from various sensors and pre-stored arithmetic expressions, maps, etc. This ECU 42 corresponds to the "controller" in this embodiment of the present invention.

[0030] In the example shown in FIG. 1, signals are input to the ECU 42 from the fuel pressure sensors 10 and 15, a crank angle sensor 43 that detects the rotation angle of the crankshaft, an accelerator opening sensor (not shown) that detects the power required by the internal combustion engine, and an A / F sensor (not shown) that detects the air-fuel ratio of the internal combustion engine.

[0031] When a flag for pressure reduction control, which will be described below, is off, the ECU 42 outputs a signal to the solenoid 29 to open or close the intake valve 27 based on, for example, the crank angle detected by the crank angle sensor 43 and the fuel pressure detected by the fuel pressure sensor 15. Specifically, when the fuel pressure detected by the fuel pressure sensor 15 is equal to or lower than a target fuel pressure, the ECU 42 increases the fuel pressure in the high-pressure delivery pipe 12. That is, the ECU 42 determines the position or operating direction of the plunger 22 based on the crank angle detected by the crank angle sensor 43, and outputs a signal to the solenoid 29 to close the intake valve 27 when the position or operating direction (upward direction) of the plunger 22 is such that the fuel in the compression chamber 21 can be compressed. Conversely, when the position or operating direction of the plunger 22 is such that the fuel is taken into the compression chamber 21 (downward direction), the ECU 42 outputs a signal to the solenoid 29 to open the intake valve 27. Furthermore, when there is no demand to increase the fuel pressure in the high-pressure delivery pipe 12, the solenoid 29 is de-energized as described above, and the intake valve 27 is always open.

[0032] In addition, based on signals detected by the accelerator opening sensor, the A / F sensor, and the crank angle sensor 43, the amount of fuel to be injected into the internal combustion engine and its timing, or the fuel ratio between the amount of fuel injected from the direct injection injector 2 and the amount of fuel injected from the port injection injector 3, etc. are calculated, and signals are output to the direct injection injector 2 and the port injection injector 3 based on these fuel amounts, timing, fuel ratio, etc.

[0033] When the fuel pressure detected by the fuel pressure sensor 10 is equal to or lower than a predetermined pressure, a signal for driving the low-pressure pump 5 is output.

[0034] The fuel supply system for an internal combustion engine according to the embodiment of the present invention is configured to control the intake valve 27 and the direct injector 2 so as to appropriately close the relief valve 37. For the sake of convenience, Fig. 3 shows the control and changes in behavior as a single flowchart. The behavior is indicated by a dashed frame.

[0035] In the example shown in FIG. 3, first, when a transient operating state in which fuel injection is stopped while the plunger 22 is moving up and down, such as when a fuel cut control is executed to stop fuel supply while the internal combustion engine is running at a high speed, is entered (step S1), and the direct injection injector 2 is stopped (step S2). On the other hand, the energization control for opening and closing the intake valve 27 may be controlled based on a signal (data) different from that used for the fuel cut control and may have a different control cycle than that used for the fuel cut control. In such a case, even when the fuel cut control ends, in other words, when the direct injection injector 2 is stopped, the intake valve 27 may still be controlled to pressure-feed fuel from the pressurization chamber 21 to the high-pressure delivery pipe 12. Therefore, the fuel pressure in the high-pressure delivery pipe 12 and the fuel pressure at the output of the high-pressure pump 6, i.e., the high-pressure pipe 13, increase (step S3).

[0036] Next, it is determined whether the fuel pressure in the high-pressure delivery pipe 12 (high-pressure delivery pressure) is higher than a predetermined pressure (step S4). If the fuel pressure in the high-pressure delivery pipe 12 is equal to or lower than the predetermined pressure and the determination in step S4 is negative, the process returns to step S3. Conversely, if the fuel pressure in the high-pressure delivery pipe 12 is higher than the predetermined pressure and the determination in step S4 is positive, the pressure reduction control flag is switched on (step S5). The predetermined pressure can be the maximum fuel pressure set during normal operation.

[0037] Simultaneously with, or before or after, step S4, the fuel pressure in high-pressure delivery pipe 12 becomes higher than the valve opening pressure (relief valve opening pressure) of relief valve 37 (step S6), and relief valve 37 opens (step S7). Therefore, the fuel pressure in high-pressure delivery pipe 12 decreases.

[0038] When the pressure reduction control flag is on as described above, if the fuel pressure detected by fuel pressure sensor 15 decreases, pressure reduction control is executed to quickly reduce the fuel pressure in high-pressure delivery pipe 12 to a pressure at which relief valve 37 can close (step S8). Specifically, even if the fuel pressure detected by fuel pressure sensor 15 is equal to or lower than the target fuel pressure, intake valve 27 continues to be open until the detected value decreases to a fuel pressure at which it can be determined that relief valve 37 has closed. Note that, until the pressure reduction control in step S8 is executed, when the fuel pressure detected by fuel pressure sensor 15 is equal to or lower than the target fuel pressure, as described above, intake valve 27 is opened or closed depending on the position or movement direction of plunger 22 in order to increase the fuel pressure in high-pressure delivery pipe 12.

[0039] Furthermore, in the pressure reduction control, fuel may be injected from the direct injector 2 at a timing when fuel is available from the direct injector 2 in order to quickly reduce the fuel pressure in the high-pressure delivery pipe 12. For example, when the fuel cut control ends before the pressure reduction control ends and fuel injection is requested, the amount of fuel injected from the direct injector 2 relative to the total amount of fuel injected into the cylinders of the internal combustion engine may be set to be larger than when the pressure reduction control is not being executed. In other words, the proportion of the fuel amount injected from the direct injector 2 may be set to be higher than the proportion of the fuel amount injected from the port injector 3, compared to when the pressure reduction control is not being executed (i.e., when the relief valve 37 is closed).

[0040] By executing the pressure reduction control as described above, fuel flows from the high-pressure delivery pipe 12 to the low-pressure intake pipe 24, thereby reducing the fuel pressure in the high-pressure delivery pipe 12. Furthermore, when fuel is injected from the direct injector 2 as described above, in addition to the fuel flowing into the intake pipe 24, the fuel pressure in the high-pressure delivery pipe 12 is reduced by discharging fuel from the direct injector 2 to the cylinder. Therefore, following step S8, it is determined whether the fuel pressure in the high-pressure delivery pipe 12 (high-pressure delivery pressure) has become lower than a valve-closing pressure (relief valve-closing pressure) at which the relief valve 37 can close (step S9). This determination in step S9 can be made based on the detection value of the fuel pressure sensor 15. The valve-closing pressure is a pressure based on the spring force of the spring 39 that constitutes the relief valve 37 and the fuel pressure in the intake pipe 24 (i.e., the detection value of the fuel pressure sensor 10).

[0041] If the fuel pressure in the high-pressure delivery pipe 12 is equal to or greater than the valve closing pressure of the relief valve 37 and therefore the answer to step S9 is NO, step S9 is repeatedly executed until the fuel pressure in the high-pressure delivery pipe 12 becomes lower than the valve closing pressure of the relief valve 37. In other words, the pressure reduction control is continuously executed. In this case, the relief valve 37 is maintained in an open state.

[0042] Conversely, if the fuel pressure in the high-pressure delivery pipe 12 is lower than the valve closing pressure of the relief valve 37 and therefore the answer to step S9 is YES, the relief valve 37 is closed (step S10). Therefore, the pressure reduction control flag is switched off (step S11), and this routine ends. In this case, it is assumed that the fuel pressure in the high-pressure delivery pipe 12 is lower than the target fuel pressure, and therefore, as the pressure reduction control ends, the intake valve 27 is opened and closed to pressure-feed fuel to the high-pressure delivery pipe 12.

[0043] As described above, in an internal combustion engine equipped with a relief valve 37 for relieving fuel in the high-pressure delivery pipe 12, located in the intake pipe 24 upstream of the pressurizing chamber 21 that pressure-feeds fuel to the high-pressure delivery pipe 12, when the relief valve 37 opens, the intake valve 27 is maintained open until the fuel pressure in the high-pressure delivery pipe 12 falls below the valve-closing pressure. This prevents the intake valve 27 from opening and closing, resulting in fuel being pressure-fed to the high-pressure delivery pipe 12 even when the fuel pressure in the high-pressure delivery pipe 12 is equal to or higher than the valve-closing pressure of the relief valve 37. In other words, it prevents the relief valve 37 from being unable to close due to fuel being pressure-fed to the high-pressure delivery pipe 12 even when the high-pressure delivery pipe 12 is discharging fuel through the relief valve 37. As a result, it is possible to close the relief valve 37, thereby preventing a situation in which the fuel pressure in the high-pressure delivery pipe 12 cannot be increased to a target pressure.

[0044] The fuel supply system for an internal combustion engine in the embodiment of the present invention is not limited to one equipped with a direct injector and a port injector. Therefore, in an internal combustion engine equipped with only a direct injector, when pressure reduction control is executed and fuel is injected from the high-pressure delivery pipe, fuel may be injected from the direct injector during a period when fuel injection is possible. [Explanation of symbols]

[0045] 1 Fuel supply device 2 Direct injection injectors 3-port injector 6. High-pressure pump 7 Low pressure fuel piping 9 Low pressure delivery pipe 10,15 Fuel pressure sensor 12 High-pressure delivery pipe 13 High-pressure piping 21 Pressure chamber 22 Plunger 23 Intake port 24 Suction pipe 27 Intake valve 28 Valve body 29 Solenoid 30 output ports 31 Discharge pipe 32 Discharge valve 33,38 Valve body 34,39 Spring 35 Relief Route 36 Relief pipe 37 Relief valve 40 Valve seat 41 Contact part 42 Electronic Control Unit (ECU) 43 Crank angle sensor

Claims

1. A fuel supply device for an internal combustion engine, comprising: a high-pressure pump that pressurizes fuel drawn into a pressurization chamber as an output shaft rotates and sends the pressurized fuel to a high-pressure passage; a discharge valve that opens to communicate between the pressurization chamber and the high-pressure passage when the fuel pressure in the pressurization chamber is greater than the fuel pressure in the high-pressure passage by a predetermined pressure or more; and an intake valve that opens to communicate between a low-pressure passage and the pressurization chamber, a relief pipe connected to the high-pressure passage and the low-pressure passage; a relief valve that opens when the fuel pressure in the high-pressure passage becomes equal to or higher than a predetermined valve opening pressure to communicate the high-pressure passage with the low-pressure passage, and closes when the fuel pressure in the high-pressure passage becomes equal to or lower than a predetermined valve closing pressure to prohibit fuel from moving between the high-pressure passage and the low-pressure passage; a controller for controlling the intake valve; Further provided with The controller When the relief valve is closed, if the fuel pressure in the high-pressure passage is equal to or lower than a predetermined target fuel pressure, fuel is supplied from the low-pressure passage into the pressurization chamber, and the intake valve is opened and closed to pressurize the fuel supplied to the pressurization chamber and send the fuel under pressure to the high-pressure passage. When the relief valve is opened, the intake valve is opened until the relief valve is closed, even if the fuel pressure in the high-pressure passage is equal to or lower than the target fuel pressure. A fuel supply device for an internal combustion engine.

2. 2. A fuel supply system for an internal combustion engine according to claim 1, an injection device that injects fuel from the high-pressure passage; The controller When the relief valve is open, the injection device is controlled to inject fuel from the high-pressure passage. A fuel supply device for an internal combustion engine.

3. 2. A fuel supply system for an internal combustion engine according to claim 1, a first injector that injects fuel from the high-pressure passage; a second injection device that injects fuel from the low-pressure passage, The controller When the relief valve is open, the first injection device and the second injection device are controlled so that the amount of fuel injected from the first injection device relative to the total amount of fuel injected into the cylinder of the internal combustion engine is greater than when the relief valve is closed. A fuel supply device for an internal combustion engine.

4. A fuel supply device for an internal combustion engine according to any one of claims 1 to 3, The relief valve is formed so that a pressure receiving area that receives fuel pressure from the high-pressure passage when the valve is open is larger than the pressure receiving area when the valve is closed. A fuel supply device for an internal combustion engine.

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