Fuel injection system and fuel supply pump

Abstract

To inhibit fuel from flowing into a pressurization chamber side via a leak passage having a zero delivery throttle even when pressure on a suction side of a low-pressure pump becomes unintended high pressure.SOLUTION: A leak passage (65) with a zero delivery throttle (45) includes a backflow shutoff part (70) that makes a suction passage (7) side and a second low pressure passage (62) side communicate with each other when pressure in a suction passage (7) of a low-pressure pump (41) is a predetermined reference or smaller and that allows passage of fuel from the second low pressure passage (62) side to the suction passage (7) side and shutting off passage of the fuel from the suction passage (7) side to the second low pressure passage (62) side when the pressure in the suction passage (7) exceeds the predetermined reference.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fuel injection system and a fuel supply pump. [Background technology]

[0002] A known fuel injection system for injecting fuel into an internal combustion engine is an accumulator-type fuel injection system (also known as a common rail system), which supplies fuel to multiple fuel injection valves via a pressure accumulator (common rail) that accumulates pressurized fuel. A fuel supply pump used in a common rail system includes a low-pressure pump driven by the driving force of the internal combustion engine, which delivers fuel from a fuel tank to a pressurization chamber, where a plunger that moves back and forth by the driving force of the internal combustion engine pressurizes the fuel and delivers it to the common rail. This fuel supply pump is equipped with a flow control unit downstream of the low-pressure pump, which adjusts the flow rate of fuel flowing into the pressurization chamber, thereby delivering the required amount of high-pressure fuel from the pressurization chamber to the common rail.

[0003] The excess fuel that results from adjusting the flow rate of fuel flowing into the pressurization chamber is returned to the fuel tank via a return passage. Therefore, when there is no fuel to be supplied to the common rail, it is possible to prevent fuel from being pumped to the common rail by returning the fuel discharged from the low-pressure pump to the fuel tank. However, even when there is no fuel to be supplied from the fuel supply pump to the common rail, there is a risk that some fuel will flow into the pressurization chamber through the clearance of the flow control unit and then be pumped from the pressurization chamber to the common rail.

[0004] In contrast to this, there is a fuel supply pump that is configured such that a leak passage including a throttling passage, also known as a zero delivery throttle, is connected between the flow control unit and the pressurizing chamber to ensure that the amount of fuel pressure-fed to the common rail is zero, and that the fuel that has passed through the flow control unit is recovered. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-34995 Summary of the Invention [Problem to be solved by the invention]

[0006] In some fuel supply pumps, a leak passage including a throttle passage is connected to the intake passage upstream of the low-pressure pump, and the fuel that has passed through the flow control unit and been collected is returned directly to the intake side of the low-pressure pump. However, if the leak passage is connected to the intake passage, when the pressure in the intake passage rises above a predetermined level, the fuel on the intake side of the low-pressure pump may flow back through the leak passage and be supplied to the pressurizing chamber.

[0007] For example, to assist in the rapid start of an internal combustion engine, a fuel injection system may include an electric pump that forcibly sends fuel to a low-pressure pump during start-up. In this case, the pressure in the intake passage may exceed the expected level, causing fuel to be supplied to the pressurized chamber through the leak passage when it is not needed. As a result, unnecessary fuel may be supplied to the common rail, which may affect the control of the fuel pressure in the common rail (hereinafter also referred to as "rail pressure").

[0008] The present invention has been made in consideration of the above-mentioned problems, and provides a fuel injection system and a fuel supply pump that can prevent fuel from flowing into a pressurized chamber through a leak passage having a throttle passage, even if the pressure on the suction side of the low-pressure pump becomes unexpectedly high. [Means for solving the problem]

[0009] In order to solve the above problem, according to one aspect of the present invention, there is provided a low-pressure pump that sucks in and discharges fuel delivered from a fuel tank, an electric pump that is provided upstream of the low-pressure pump and delivers fuel in the fuel tank toward the low-pressure pump, a flow rate control unit that adjusts the flow rate of fuel delivered by the low-pressure pump, a pressurizing unit that pressurizes the fuel whose flow rate has been adjusted by the flow rate control unit and delivers it to a common rail, an intake passage that connects the fuel tank and an intake port of the low-pressure pump, a first low-pressure passage that connects the discharge port of the low-pressure pump and the flow rate control unit, a second low-pressure passage that connects the flow rate control unit and an intake port of the pressurizing unit, and a valve that connects the first low-pressure passage or the flow rate control unit to the common rail. The fuel injection system includes a return passage connected to a quantity control unit to return excess fuel to the fuel tank, and a leak passage connecting the second low-pressure passage and the suction passage and having a throttle passage with a reduced passage area, wherein a backflow blocker is provided in a region of the leak passage closer to the suction passage than the throttle passage, the backflow blocker connecting the suction passage side and the second low-pressure passage side when the pressure in the suction passage is equal to or lower than a predetermined standard, and allowing fuel to pass from the second low-pressure passage side to the suction passage side when the pressure in the suction passage exceeds the predetermined standard, while blocking fuel from passing from the suction passage side to the second low-pressure passage side.

[0010] Furthermore, in order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided a fuel supply system including: a low-pressure pump that sucks in and discharges fuel delivered from a fuel tank; a flow rate control section that adjusts the flow rate of the fuel delivered by the low-pressure pump; a pressurizing section that pressurizes and delivers the fuel whose flow rate has been adjusted by the flow rate control section; an intake passage connected to an intake port of the low-pressure pump; a first low-pressure passage that connects a discharge port of the low-pressure pump and the flow rate control section; a second low-pressure passage that connects the flow rate control section and an intake port of the pressurizing section; and a return passage connected to the first low-pressure passage or the flow rate control section and that discharges excess fuel. The fuel supply pump includes a leak passage connecting the second low-pressure passage and the suction passage and having a throttle passage with a reduced passage area, and further includes, in a region of the leak passage closer to the suction passage than the throttle passage, a backflow blocking unit that connects the suction passage side and the second low-pressure passage side when the pressure in the suction passage is equal to or lower than a predetermined standard, and that allows fuel to pass from the second low-pressure passage side to the suction passage side when the pressure in the suction passage exceeds the predetermined standard, while blocking fuel from passing from the suction passage side to the second low-pressure passage side. [Effects of the Invention]

[0011] As described above, according to the present invention, even if the pressure on the suction side of the low-pressure pump becomes unexpectedly high, it is possible to prevent fuel from flowing into the pressurization chamber through a leak passage having a zero delivery throttle. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a configuration diagram showing an example of a fuel injection system for an internal combustion engine according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram illustrating a configuration example of a fuel supply pump according to the present embodiment. [Figure 3] FIG. 2 is a perspective view schematically showing a backflow blocking portion provided in the fuel supply pump according to the embodiment. [Figure 4] 4 is a perspective view showing an example of the configuration of a piston of a backflow blocking unit provided in the fuel supply pump according to the embodiment; FIG. [Figure 5] 3 is a cross-sectional view showing a cross section of a piston of a backflow blocking unit provided in the fuel supply pump according to the embodiment, taken along the axis thereof; FIG. [Figure 6] 5 is an explanatory diagram showing a state of a backflow blocking portion when the pressure in the intake passage of the fuel supply pump according to the embodiment rises above a predetermined standard. FIG. [Figure 7] 5 is an explanatory diagram showing a state of a backflow blocking portion when the pressure in the intake passage of the fuel supply pump according to the embodiment rises above a predetermined standard. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0014] 1. Fuel injection system First, an example of a fuel injection system for an internal combustion engine to which a fuel supply pump according to an embodiment of the present disclosure can be applied will be described.

[0015] 1 shows an example of the configuration of a fuel injection system 1 for a diesel engine equipped with a fuel supply pump according to this embodiment. The fuel injection system 1 is constructed as a common rail system equipped with a pressure accumulator (common rail) 19. In this embodiment, the internal combustion engine is a diesel engine, but the type of internal combustion engine is not particularly limited.

[0016] The fuel injection system 1 includes a fuel tank 3, an electric pump 5 that sends fuel from the fuel tank 3 to a fuel supply pump 10, the fuel supply pump 10 that pressurizes and pumps out the fuel, a common rail 19 that stores the fuel pumped out from the fuel supply pump 10, and a fuel injection valve (injector) 30 that injects the fuel distributed by the common rail 19 into the cylinders of an internal combustion engine (not shown).

[0017] The electric pump 5 has a function of discharging fuel (diesel) from the fuel tank 3 and sending it to the fuel supply pump 10 via an intake passage 7. The intake passage 7 has a filter 9 between the electric pump 5 and the fuel supply pump 10. The electric pump 5 is driven, for example, at start-up to ensure that the low-pressure pump provided in the fuel supply pump 10 sucks in fuel, thereby assisting in the start-up of the internal combustion engine. However, the electric pump 5 may be driven constantly while the fuel injection system 1 is running.

[0018] The fuel supplied from the electric pump 5 has its flow rate controlled by a flow rate control unit 13 and is supplied to the pressurization chamber of the fuel supply pump 10. Excess fuel is discharged to a return passage 25 via an overflow valve (not shown) provided in parallel with the flow rate control unit 13, and is returned to the fuel tank 3. The fuel supply pump 10 is driven to rotate by the power of the internal combustion engine, pressurizes the fuel supplied to the pressurization chamber, and pressure-feeds it toward the common rail 19 via a high-pressure fuel passage 15.

[0019] The common rail 19 accumulates the fuel pumped from the fuel supply pump 10, raises the pressure of the fuel, and distributes it to each fuel injection valve 30 at a uniform pressure. The common rail 19 is provided with a pressure sensor 21 that detects the pressure inside the common rail 19 and a pressure regulating valve 23 that adjusts the rail pressure. The control device 17 controls the operation of the flow control unit 13 to control the flow rate of the high-pressure fuel supplied to the common rail 19, and also controls the operation of the pressure regulating valve 23 so that the rail pressure detected by the pressure sensor 21 becomes the desired pressure. The fuel discharged via the pressure regulating valve 23 is returned to the fuel tank 3 via a return passage 29.

[0020] High-pressure fuel distributed from the common rail 19 to each fuel injection valve 30 flows into a pressure control chamber (not shown) of the fuel injection valve 30. The high-pressure fuel that has flowed into the pressure control chamber biases the valve element in a direction that closes the injection hole, and by discharging a portion of the high-pressure fuel in the pressure control chamber, the biasing force of the valve element is weakened, and fuel is injected from the injection hole into the cylinder of the internal combustion engine. The control device 17 controls the operation of the fuel injection valve 30 based on the rail pressure and the target injection amount. At this time, the fuel discharged from the pressure control chamber is returned to the fuel tank 3 via a return passage (return piping) 27 connected to the fuel injection valve 30.

[0021] The above-described configuration of the fuel injection system 1 is merely an example, and the fuel injection system 1 is not limited to the above example. For example, the common rail system may be configured such that the pressure regulating valve 23 is not provided in the common rail 19, and the rail pressure is controlled by controlling the discharge amount of the fuel supply pump 10 using a flow control unit 13 provided upstream of the pressurizing chamber of the fuel supply pump 10.

[0022] <2. Fuel supply pump> Next, an example of the configuration of the fuel supply pump according to this embodiment will be described.

[0023] 2 is a schematic diagram showing an example configuration of the fuel supply pump 10. The fuel supply pump 10 includes a low-pressure pump 41, a flow control unit 13, and a pressurizing section 50. The fuel supply pump 10 also includes an intake passage 7, a first low-pressure passage 61, a second low-pressure passage 62, a return passage 63, and a leak passage 65. The intake passage 7 connects the fuel tank 3 with the intake port of the low-pressure pump 41. The first low-pressure passage 61 connects the discharge port of the low-pressure pump 41 with the flow control unit 13. The second low-pressure passage 62 connects the flow control unit 13 with the intake port of the pressurizing chamber 51.

[0024] The low-pressure pump 41 is driven by the driving force of the internal combustion engine, and sucks in and discharges fuel sent from the fuel tank 3. The low-pressure pump 41 may be, for example, a vane pump or a gear pump. The low-pressure pump 41 is driven by the driving force of the internal combustion engine, and discharges fuel toward the pressurizing unit 50 without consuming electric power.

[0025] The flow rate control unit 13 is driven by the control device 17 and adjusts the flow rate of fuel pumped by the low-pressure pump 41. For example, the flow rate control unit 13 may be a proportional control valve whose passage area is variable depending on the amount of current supplied to it. The flow rate control unit 13 is one aspect of a flow rate control section. A return passage 63 is connected to the first low-pressure passage 61. The return passage 63 is provided with a relief valve 43, and excess fuel that is not sent to the pressurizing section 50 by the flow rate control unit 13 is returned to the fuel tank 3. Note that the return passage 63 only needs to be connected upstream of the part of the flow rate control unit 13 whose passage area is variable, and the return passage 63 may be connected to the flow rate control unit 13.

[0026] The pressurizing section 50 pressurizes the fuel whose flow rate has been adjusted by the flow control unit 13 and sends it under pressure to the common rail. The pressurizing section 50 includes an intake valve 47, a discharge valve 49, a pressurizing chamber 51, a plunger 53, and a cam 55. The intake valve 47 and the discharge valve 49 are each mechanical valves that open and close based on the balance between a spring and fuel pressure. The pressurizing chamber 51 is a space formed by partitioning a hole through which the plunger 53 slides by the plunger 53, and has an intake port where the intake valve 47 is provided and an outlet port where the discharge valve 49 is provided.

[0027] The plunger 53 moves back and forth in accordance with the rotation of a cam 55, which is driven to rotate by the driving force of the internal combustion engine. When the plunger 53 moves and the volume of the pressurizing chamber 51 expands, the intake valve 47 opens, and fuel, the flow rate of which is adjusted by the flow control unit 13, flows into the pressurizing chamber 51. When the plunger 53 moves and the volume of the pressurizing chamber 51 decreases, the fuel in the pressurizing chamber 51 is pressurized, the discharge valve 49 opens, and the high-pressure fuel is pressure-fed toward the common rail 19. Note that two or more sets of pressurizing units 50 may be provided.

[0028] A leak passage 65 is connected to the second low-pressure passage 62. The leak passage 65 connects the second low-pressure passage 62 and the intake passage 7. The leak passage 65 is provided with a throttle passage 45 having a reduced passage area. The leak passage 65 having the throttle passage 45 has the function of recovering the fuel that has passed through the clearance when the flow control unit 13 is closed, and preventing the fuel from being supplied to the common rail 19.

[0029] A backflow blocking section 70 is provided in a region of the leak passage 65 closer to the suction passage 7 than the throttle passage 45. The backflow blocking section 70 connects the suction passage 7 side to the second low-pressure passage 62 side when the pressure in the suction passage 7 is equal to or lower than a predetermined standard. This allows the fuel that has passed through the flow control unit 13 to be recovered to the suction passage 7 side when the pressure in the suction passage 7 is in an expected low-pressure state.

[0030] Furthermore, backflow blocking section 70 allows fuel to pass from the second low-pressure passage 62 to the suction passage 7 when the pressure in suction passage 7 exceeds a predetermined standard, but blocks fuel from passing from the suction passage 7 to the second low-pressure passage 62. This allows fuel that has passed through flow control unit 13 to be recovered to the suction passage 7 when the pressure in suction passage 7 rises above an expected low-pressure state, and prevents fuel from flowing back from suction passage 7 to the second low-pressure passage 62. This prevents more fuel than necessary from flowing into pressurizing section 50 and supplying less fuel than required to common rail 19.

[0031] 3 to 5 are explanatory diagrams showing an example of the configuration of the backflow blocking unit 70 provided in the fuel supply pump 10 according to this embodiment. Fig. 3 is a perspective view showing a typical configuration of the backflow blocking unit 70 provided in the leak passage 65. Fig. 4 is a perspective view showing an example of the configuration of a piston 71 of the backflow blocking unit 70, and Fig. 5 is a cross-sectional view showing one cross section of the piston 71 cut along the axis.

[0032] The backflow blocking unit 70 includes a piston 71 and a spring 83. The piston 71 is slidably provided in a bypass passage 67 that is provided to intersect with the leak passage 65 and has one end connected to the suction passage 7. The bypass passage 67 has one end connected to the suction passage 7 and the other end extending further, intersecting with the leak passage 65. The piston 71 is slidably provided in the bypass passage 67 at the point where the leak passage 65 and the bypass passage 67 intersect.

[0033] The spring 83 is provided on an extension 69 formed by extending further and intersecting the leak passage 65 of the bypass passage 67. Both ends of the spring 83 are joined to an end face of the piston 71 and an end face of the extension 69. The spring 83 is a biasing member that biases the piston 71 in the bypass passage 67 toward the suction passage 7. The elastic force of the spring 83 is set according to a predetermined standard of fuel pressure that should suppress backflow of fuel from the suction passage 7 toward the second low-pressure passage 62. The biasing member is not limited to the coil spring shown in the figure, but may be a leaf spring or other elastic element.

[0034] Piston 71 is a cylindrical member having an outer circumferential surface that slides against the inner circumferential surface of bypass passage 67. One end face of piston 71 is provided with a protrusion 79 for aligning the axis of spring 83 with the axis of piston 71. In addition, a guide key 81 is provided on the outer circumferential surface of piston 71 to engage with a guide groove 68 formed on the inner circumferential surface of bypass passage 67 and prevent axial rotation of piston 71.

[0035] Of both end faces of piston 71, the end face opposite to the end face to which spring 83 is joined is subjected to the pressure of fuel in intake passage 7 supplied through bypass passage 67. When the pressure of fuel in intake passage 7 is equal to or lower than a predetermined reference level, which is an assumed low-pressure state, piston 71 is held in the first position shown in Fig. 3. On the other hand, when the pressure of fuel in intake passage 7 exceeds the predetermined reference level and becomes a high-pressure state, piston 71 receives the fuel pressure and moves to the second position against the biasing force of spring 83.

[0036] Piston 71 has first and second through holes 73 and 75, which are provided at different axial positions of piston 71, formed along a direction intersecting the axial direction of piston 71, and open at both ends. First through hole 73 becomes part of leak passage 65 when the pressure in suction passage 7 is equal to or lower than a predetermined standard. Second through hole 75 becomes part of leak passage 65 when the pressure in suction passage 7 exceeds the predetermined standard.

[0037] In other words, when the piston 71 is in the first position, the first through hole 73 is located at the intersection of the leak passage 65 and the bypass passage 67, and connects the first portion 65a of the leak passage 65 on the second low-pressure passage 62 side with the second portion 65b on the suction passage 7 side. The first through hole 73 is a through hole that is always open. The cross-sectional shape of the first through hole 73 is not limited to a rectangular shape.

[0038] Furthermore, when the piston 71 is in the second position, the second through hole 75 is located at the point where the leak passage 65 and the bypass passage 67 intersect, and connects a first portion 65a of the leak passage 65 on the second low-pressure passage 62 side with a second portion 65b on the suction passage 7 side. The second through hole 75 is provided with a blocking member 77 that opens the second through hole 75 when the pressure on the second low-pressure passage 62 side is higher than the pressure on the suction passage 7 side, and blocks the second through hole 75 when the pressure on the suction passage 7 side is higher than the pressure on the second low-pressure passage 62 side.

[0039] The second through hole 75 has a step 89 midway. The blocking member 77 is attached to the second through hole 75 using a hinge 85 so as to abut against the portion of the step 89 on the suction passage 7 side (see FIG. 5 ). The hinge 85 allows the blocking member 77 to open and close toward the suction passage 7 side, but prevents it from opening and closing toward the second low-pressure passage 62 side. Therefore, when the pressure on the second low-pressure passage 62 side is higher than the pressure on the suction passage 7 side, the pressure difference pushes the blocking member 77 toward the suction passage 7 side, thereby opening the second through hole 75. On the other hand, when the pressure on the suction passage 7 side is higher than the pressure on the second low-pressure passage 62 side, the pressure difference pushes the blocking member 77 against the step 89, thereby blocking the second through hole 75.

[0040] 4 has a concave curved surface on the suction passage 7 side and a flat surface on the second low-pressure passage 62 side. This makes the pressure-receiving area on the suction passage 7 side larger than the pressure-receiving area on the second low-pressure passage 62 side, making it easier for the blocking member 77 to block the second through hole 75 due to the pressure difference.

[0041] Furthermore, the edge of the opening of the second through hole 75 on the second low-pressure passage 62 side is formed in a flat shape. This ensures a wide opening area of ​​the second through hole 75 on the throttle passage 45 side even when only a portion of the second through hole 75 overlaps with the leak passage 65. This increases the reliability with which the shutoff member 77 is pushed open by the pressure of the fuel that has flowed out through the throttle passage 45.

[0042] <3.Operation> Next, the operation of the backflow blocking unit 70 of the fuel supply pump 10 according to this embodiment will be described.

[0043] FIG. 3 shows the state of the backflow blocking unit 70 when the pressure in the intake passage 7 is in a low-pressure state below a predetermined standard assumed for a normal operating state. In this state, the piston 71 is held in the first position. With the piston 71 held in the first position, a first portion 65a of the leak passage 65 on the second low-pressure passage 62 side and a second portion 65b on the intake passage 7 side are in communication with each other via a first through-hole 73 in the piston 71. For example, when fuel is being drawn by the low-pressure pump 41, the pressure in the intake passage 7 is relatively low, and there is no risk of fuel backflowing from the intake passage 7 side to the second low-pressure passage 62 side. Furthermore, in this state, when the amount of high-pressure fuel to be supplied to the common rail 19 is zero, the fuel that has passed through the flow control unit 13 is recovered to the intake passage 7 side through the leak passage 65, also due to the suction force of the low-pressure pump 41.

[0044] 6 and 7 show the state of the backflow blocking unit 70 when the pressure in the suction passage 7 rises above a predetermined level. For example, when the electric pump 2 is driven to ensure that the low-pressure pump 41 draws fuel during startup of the internal combustion engine, the pressure in the suction passage 7 may rise above the predetermined level. In this state, the piston 71 is held in the second position. With the piston 71 held in the second position, the first portion 65a of the leak passage 65 on the second low-pressure passage 62 side and the second portion 65b on the suction passage 7 side communicate with each other through the second through hole 75 of the piston 71. However, when the pressure on the suction passage 7 side is higher than the pressure on the second low-pressure passage 62 side, as shown in FIG. 6, the blocking member 77 blocks the second through hole 75, preventing fuel from flowing back from the suction passage 7 side to the second low-pressure passage 62 side.

[0045] On the other hand, even when piston 71 is held at the second position, if the pressure on the intake passage 7 side is lower than the pressure on the second low-pressure passage 62 side, as shown in Fig. 7, the pressure difference pushes open shutoff member 77, allowing leaked fuel to be collected from the second low-pressure passage 62 side to the intake passage 7 side. Therefore, even if the pressure in the intake passage 7 rises, if the pressure in the second low-pressure passage 62 exceeds the pressure in the intake passage 7 due to fuel passing through flow control unit 13, the leaked fuel is collected to the intake passage 7 side via the leak passage 65. This maintains the function of reducing the amount of high-pressure fuel to be supplied to common rail 19 to zero.

[0046] <4. Effects> As described above, the fuel supply pump 10 according to this embodiment includes the leak passage 65 that connects the second low-pressure passage 62 and the suction passage 7 and has the throttle passage 45 with a reduced passage area. The backflow blocking unit 70 is provided in a region of the leak passage 65 closer to the suction passage 7 than the throttle passage 45. The backflow blocking unit 70 connects the suction passage 7 side to the second low-pressure passage 62 side when the pressure in the suction passage 7 is equal to or lower than a predetermined reference level, and allows fuel to pass from the second low-pressure passage 62 side to the suction passage 7 side when the pressure in the suction passage 7 exceeds the predetermined reference level, while blocking fuel from passing from the suction passage 7 side to the second low-pressure passage 62 side. Therefore, even if the pressure on the suction side of the low-pressure pump 41 becomes unexpectedly high, fuel can be prevented from flowing into the pressurizing unit 50 via the leak passage 65 having the throttle passage 45. This prevents unwanted fuel from being supplied to the common rail 19, which would otherwise affect rail pressure control.

[0047] Furthermore, in the fuel supply pump 10 according to this embodiment, the backflow blocking portion 70 includes a piston 71 having a first through hole 73 that is displaced in response to the pressure in the suction passage 7 and that becomes part of the leak passage 65 when the pressure in the suction passage 7 is equal to or lower than a predetermined standard, a second through hole 75 that becomes part of the leak passage 65 when the pressure in the suction passage 7 exceeds the predetermined standard, and a blocking member 77 that is provided in the second through hole 75 and that opens the second through hole 75 when the pressure on the second low-pressure passage 62 side is higher than the pressure on the suction passage 7 side and blocks the second through hole 75 when the pressure on the suction passage 7 side is higher than the pressure on the second low-pressure passage 62 side. Therefore, a state in which fuel backflow is prevented from occurring from the suction passage 7 side to the second low-pressure passage 62 side as the pressure in the suction passage 7 increases can be automatically created.

[0048] Furthermore, the backflow blocking section 70 is configured to include a blocking member 77 that is provided in the second through hole 75 and opens the second through hole 75 when the pressure on the second low-pressure passage 62 side is higher than the pressure on the suction passage 7 side, and blocks the second through hole 75 when the pressure on the suction passage 7 side is higher than the pressure on the second low-pressure passage 62 side, thereby maintaining the function of reducing the amount of high-pressure fuel to be supplied to the common rail 19 to zero even when the pressure in the suction passage 7 rises.

[0049] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications or alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

[0050] For example, in the above embodiment, the low-pressure pump, flow control unit, pressurizing unit, and backflow cutoff unit are incorporated into the fuel supply pump, but the present invention is not limited to the above example. Even in a fuel injection system in which some or all of the low-pressure pump, flow control unit, pressurizing unit, and backflow cutoff unit are independent from each other, the same effects as those of the above embodiment can be obtained by providing the backflow cutoff unit in a region of the leak passage closer to the intake passage than the throttle passage. [Explanation of symbols]

[0051] 1: Fuel injection system 2: Electric pump 3: Fuel tank 5: Electric pump 7: Suction passage 10: Fuel supply pump 13: Flow control unit 15: High pressure fuel passage 41: Low pressure pump 45: Aperture passage 50: Pressure section 61: First low pressure passage 62: Second low pressure passage 63: Return passage 65: Leak passage 65a: 1st part 65b :Second part 67: Bypass passage 70: Backflow blocking section 71: Piston 73: 1st passage hole 75: 2nd passage hole 77: Blocking member 79:Protruding part

Claims

1. a low-pressure pump (41) that sucks and discharges fuel sent from a fuel tank (3); an electric pump (2) provided upstream of the low-pressure pump (41) and feeding fuel in the fuel tank (3) toward the low-pressure pump (41); a flow rate control unit (13) that adjusts the flow rate of fuel pumped by the low-pressure pump (41); a pressurizing unit (50) that pressurizes the fuel whose flow rate has been adjusted by the flow rate control unit (13) and sends it under pressure to a common rail (19); an intake passage (7) connecting the fuel tank (3) and an intake port of the low-pressure pump (41); a first low-pressure passage (61) connecting a discharge port of the low-pressure pump (41) and the flow rate control unit (13); a second low-pressure passage (62) connecting the flow rate control section (13) and an intake port of the pressurizing section (50); a return passage (63) connected to the first low-pressure passage (61) or the flow rate control section (13) for returning excess fuel to the fuel tank (3); a leak passage (65) connecting the second low-pressure passage (62) and the intake passage (7) and having a throttle passage (45) with a reduced passage area, In a region of the leak passage (65) closer to the intake passage (7) than the throttle passage (45), When the pressure in the suction passage (7) is equal to or lower than a predetermined standard, the suction passage (7) side and the second low-pressure passage (62) side are brought into a state of communication with each other, a backflow blocking section (70) that allows fuel to pass from the second low-pressure passage (62) side to the intake passage (7) side when the pressure in the intake passage (7) exceeds a predetermined standard, while blocking fuel from passing from the intake passage (7) side to the second low-pressure passage (62) side.

2. The backflow blocking section (70) It is displaced according to the pressure in the suction passage (7), a first passage hole (73) that becomes part of the leak passage (65) when the pressure in the suction passage (7) is equal to or lower than a predetermined standard; a second passage hole (75) that becomes part of the leak passage (65) when the pressure in the suction passage (7) exceeds a predetermined standard; a blocking member (77) provided in the second through hole (75), which opens the second through hole (75) when the pressure on the second low-pressure passage (62) side is higher than the pressure on the suction passage (7) side, and which blocks the second through hole (75) when the pressure on the suction passage (7) side is higher than the pressure on the second low-pressure passage (62) side; 2. The fuel injection system of claim 1, further comprising a piston (71) comprising:

3. The piston (71) is slidably provided in a bypass passage (67) that is provided so as to intersect with the leak passage (65) and has one end connected to the suction passage (7), a biasing member (83) that biases the piston (71) toward the suction passage (7), When the pressure in the suction passage (7) is equal to or lower than the predetermined standard, the piston (71) is held at a first position by the biasing member (83), and the first through hole (73) becomes a part of the leak passage (65); 3. The fuel injection system according to claim 2, wherein when the pressure in the intake passage exceeds the predetermined standard, the piston moves to a second position against the biasing force of the biasing member, and the second through hole becomes part of the leak passage.

4. a low-pressure pump (41) that sucks and discharges fuel sent from a fuel tank (3); a flow rate control unit (13) that adjusts the flow rate of fuel pumped by the low-pressure pump (41); a pressurizing unit (50) that pressurizes and pressure-feeds the fuel whose flow rate has been adjusted by the flow rate control unit (13); an intake passage (7) connected to the intake port of the low-pressure pump (41); a first low-pressure passage (61) connecting a discharge port of the low-pressure pump (41) and the flow rate control unit (13); a second low-pressure passage (62) connecting the flow rate control section (13) and an intake port of the pressurizing section (50); a return passage (63) connected to the first low-pressure passage (61) or the flow rate control section (13) to discharge excess fuel; a leak passage (65) connecting the second low-pressure passage (62) and the intake passage (7) and having a throttle passage (45) with a reduced passage area, In a region of the leak passage (65) closer to the intake passage (7) than the throttle passage (45), When the pressure in the suction passage (7) is equal to or lower than a predetermined standard, the suction passage (7) side and the second low-pressure passage (62) side are brought into a state of communication with each other, a backflow blocking section (70) that allows fuel to pass from the second low-pressure passage (62) side to the suction passage (7) side when the pressure in the suction passage (7) exceeds a predetermined standard, while blocking fuel from passing from the suction passage (7) side to the second low-pressure passage (62) side.

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