Fuel pump and diesel engine system

Abstract

A valve unit of this fuel pump includes: a first biasing member that applies a first biasing force to a valve body so as to close a suction port; a movable member that can move between a connected position directly or indirectly connected to the valve body and an unconnected position separated from the valve body; a second biasing member that applies, to the movable member, a second biasing force which is in the opposite direction of the first biasing force and larger than the first biasing force; and a solenoid that is switched between an ON state and an OFF state to move the movable member between the connected position and the unconnected position.

Description

Fuel Pumps and Diesel Engine Systems

[0001] This disclosure relates to a fuel pump for supplying fuel to a common rail for a diesel engine, and a diesel engine system. This application claims priority to Japanese Patent Application No. 2024-088965, filed on May 31, 2024, with the Japan Patent Office, the contents of which are incorporated herein by reference.

[0002] The fuel pump includes a plurality of cylinder units, each configured to pressurize and discharge fuel for a diesel engine. Each cylinder unit includes a pump cylinder and a plunger configured to reciprocate within the pump cylinder. For example, in a fuel pump disclosed in Patent Document 1, fuel is supplied to each pump cylinder from a fuel supply pipe. The fuel pressurized by the pump cylinder is supplied to a common rail. A throttle valve is disposed in the fuel supply pipe to control the amount of fuel supplied in order to adjust the pressure within the common rail.

[0003] Furthermore, in the fuel pump disclosed in Patent Document 2, an on-off valve is provided to control the discharge amount of each pump cylinder in order to adjust the common rail pressure, which is the pressure inside the common rail. The on-off valve is a valve different from a throttle valve.

[0004] JP 2003-293888 A JP 2000-161115 A

[0005] The throttle valve can be controlled after the diesel engine is started, so the pressure in the pump cylinders can be increased immediately after startup. However, because the throttle valve is located in the fuel supply pipe that supplies fuel to each pump cylinder, there is a significant response delay between changing the throttle valve opening and changing the discharge rate from each pump cylinder. Therefore, it is difficult to control the discharge rate of the pump cylinders with good responsiveness to the common rail pressure using only the throttle valve.

[0006] Furthermore, because the on-off valves are arranged in each pump cylinder, the fuel discharge amount can be controlled immediately in accordance with the common rail pressure. However, it is necessary to recognize the crank phase before starting to control the on-off valves. Therefore, it is difficult to increase the pressure in the pump cylinders through control of the on-off valves until a certain amount of time has passed since cranking began.

[0007] However, if the throttle valve and the on-off valve are separately arranged so that they complement each other's shortcomings, the structure of the fuel pump becomes complicated.

[0008] An object of the present disclosure is to provide a fuel pump and diesel engine system that has a simple configuration and is capable of increasing the pressure in the pump cylinder immediately after starting the diesel engine and capable of responsively controlling the discharge amount in accordance with the common rail pressure.

[0009] a check valve configured to open a discharge port formed in the pump cylinder for discharging the pressurized fuel toward the common rail; and a valve unit including a valve body configured to open and close a suction port formed in the pump cylinder for drawing in the unpressurized fuel, wherein the valve unit includes: a first biasing member that applies a first biasing force to the valve body so as to close the suction port; a movable member that is movable between a connected position directly or indirectly connected to the valve body and a non-connected position spaced from the valve body; a second biasing member that applies a second biasing force to the movable member that is directed opposite to the direction of the first biasing force and is greater than the first biasing force; and a solenoid configured to switch from an off state to an on state to move the movable member from the connected position to the non-connected position.

[0010] A diesel engine system according to one embodiment of the present disclosure includes: the fuel pump; a fuel tank that stores the fuel before pressurization to be supplied to the fuel pump; the common rail that stores the pressurized fuel discharged from the fuel pump; and a diesel engine including a plurality of fuel injection devices that inject the pressurized fuel supplied from the common rail.

[0011] According to the present disclosure, it is possible to provide a fuel pump and a diesel engine system that have a simple configuration and can increase the pressure in the pump cylinder immediately after starting the diesel engine and can responsively control the discharge volume according to the common rail pressure.

[0012] FIG. 1 is a schematic diagram of an engine system according to an embodiment; FIG. 2 is a schematic diagram of a pump cylinder unit according to an embodiment; FIG. 3 is a schematic diagram of a valve unit according to an embodiment (solenoid: off state); FIG. 4 is a schematic diagram of a valve unit according to an embodiment (solenoid: on state); FIG. 5 is a schematic diagram of a plurality of graphs showing an overview of a first fuel supply operation; FIG. 6 is an explanatory diagram showing an exceptional operation in the first fuel supply operation; FIG. 7 is a schematic diagram of a control device according to an embodiment; FIG. 8 is a flowchart showing a fuel supply control process according to an embodiment; FIG. 9 is a flowchart showing first solenoid control according to an embodiment; FIG. 10 is a flowchart showing second solenoid control according to an embodiment;

[0013] Several embodiments of the present disclosure will be described below with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure and are merely illustrative examples. For example, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express relative displacements with a tolerance or angle or distance to the extent that the same function is achieved. For example, expressions expressing the equality of things, such as "same," "equal," and "homogeneous," not only express strict equality, but also express tolerance or differences to the extent that the same function is achieved. For example, expressions expressing shapes such as a square or cylindrical shape not only express shapes such as a square or cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is achieved. On the other hand, the expressions "comprise," "include," or "have" one component are not exclusive expressions that exclude the existence of other components. Note that similar components may be assigned the same reference numerals and descriptions thereof may be omitted.

[0014] <Overview of Engine System 1> FIG. 1 is a schematic diagram of an engine system (diesel engine system) 1 including an engine main body 10 according to an embodiment of the present disclosure. The engine main body 10 includes a plurality of cylinder units (not shown) and a plurality of injectors 15 provided corresponding to the plurality of cylinder units, respectively. Pressurized fuel injected from the injectors 15 is drawn into the cylinder units together with air, and then a combustion reaction occurs. The engine main body 10 converts thermal energy obtained from the combustion reaction into rotational energy to provide power to a driving device. In this example, the driving device is an emergency generator. As another example, the driving device may be a drive train mounted on a vehicle or a propeller for rotating a propeller of a ship.

[0015] The engine system 1 is provided with a fuel supply system 2 for supplying fuel to a plurality of injectors 15. The fuel supply system 2 includes a fuel tank 5 for storing unpressurized fuel, a pre-pressurized fuel supply line 6 which is a flow path for fuel discharged from the fuel tank 5, a fuel pump 3 for pressurizing the fuel supplied through the pre-pressurized fuel supply line 6, a common rail 7 for storing the pressurized fuel supplied by the fuel pump 3, and a plurality of pressurized fuel supply lines 9 for supplying the pressurized fuel discharged from the common rail 7 to the plurality of injectors 15, respectively. A low-pressure fuel pump may be provided in the pre-pressurized fuel supply line 6 for sending fuel to the fuel pump 3. A fuel filter may also be provided in the fuel supply line.

[0016] The fuel pump 3 includes a camshaft 29 and a plurality of pump cylinder units 13 aligned in the axial direction of the camshaft 29. Each pump cylinder unit 13 includes a pump cylinder 21, a plunger 22 disposed in the pump cylinder 21, and a pump cam 28 in contact with the plunger 22. The pump cylinder 21 and the plunger 22 define a pressure boost chamber C for pressurizing the fuel. The pump cam 28 is configured to rotate in conjunction with the camshaft 29. When the pump cam 28 rotates, the plunger 22 reciprocates within the pump cylinder 21. The fuel drawn into the pressure boost chamber C is pressurized and then discharged from the pump cylinder 21.

[0017] The engine system 1 also includes a crank sensor 8 for detecting the cam phase, which is the phase of the camshaft 29. In this example, the plunger 22 reciprocates twice per rotation of the camshaft 29. Therefore, in order to determine the position and direction of movement of the plunger 22 after starting the engine system 1, it is necessary to first determine the angle of the cam phase. For this purpose, the crank sensor 8 includes two different sensors. These sensors, which may be non-contact sensors, are configured to detect two rotational positions of either the camshaft 29, the pump cam 28, or a rotating body that transmits power to these. The two sensors have different detection periods for the detection targets. Therefore, the specific cam phase is determined based on the timing of the switching of the detection state of each sensor and the time lag between these two switching times. Once the specific cam phase is determined, it is possible to continuously monitor the change in the cam phase (i.e., the position and direction of movement of the plunger 22) over time by monitoring the detection result of only one sensor based on the cam phase.

[0018] The detection result of the crank sensor 8 is sent to a control device 90, which may be, for example, an ECU. The control device 90 determines the cam phase from the detection result of the crank sensor 8. This determines the position and movement direction of the plunger 22. The control device 90 is also electrically connected to a common rail pressure sensor 18 for measuring the common rail pressure, which is the pressure inside the common rail 7. If the measured common rail pressure exceeds a control target value, the control device 90 executes control to reduce the amount of fuel supplied from the fuel pump 3 to the common rail 7 (details will be described later).

[0019] 2 is a schematic diagram of the pump cylinder unit 13 according to one embodiment of the present disclosure. A discharge port 24 for discharging fuel is formed in a side wall portion of the pump cylinder 21, and the pump cylinder unit 13 is provided with a check valve 31 that can open the discharge port 24. When the boost chamber pressure, which is the pressure in the boost chamber C, becomes higher than the common rail pressure by a certain amount, the check valve 31 opens the discharge port 24. Otherwise, the check valve 31 closes the discharge port 24.

[0020] An intake port 25 for drawing in fuel is formed at one end of the pump cylinder 21. The pump cylinder 21 is equipped with a valve unit 50 for opening and closing the intake port 25. The opening and closing of the intake port 25 is performed by a valve element 55, which is a component of the valve unit 50. The valve element 55 moves between an open position where the intake port 25 is opened and a closed position where the intake port 25 is closed. The valve element 55 on the left side of FIG. 2 is in the open position, and the valve element 55 on the right side is in the closed position.

[0021] The valve unit 50 of the fuel pump 3 will be described in detail with reference to FIGS. 3 and 4 . The fuel pump 3 is illustrated schematically in both figures. The valve unit 50 further includes a first connecting member 41, an abutting member 43, and a first biasing member 51. The first connecting member 41 is a rod-shaped member having one end connected to the valve body 55. The abutting member 43 is provided at the other end of the first connecting member 41 and abuts against the first biasing member 51. The first biasing member 51 applies a first biasing force to the abutting member 43 in a direction that moves the valve body 55 from the open position (see FIG. 3 ) to the closed position (see FIG. 4 ). The first biasing force is transmitted to the valve body 55 via the first connecting member 41 as a force for closing the valve body 55. F1 in the drawings corresponds to the first biasing force.

[0022] The fuel pump 3 further includes a solenoid 60, a second connecting member 42, a movable member 58, and a second biasing member 52. The solenoid 60 includes the movable core 23. The second connecting member 42 is a rod-shaped member having one end connected to the movable core 23. The movable member 58 is provided at the other end of the second connecting member 42 and is movable together with the second connecting member 42. The second biasing member 52 applies a second biasing force to the movable member 58 that is directed in the opposite direction to the first biasing force. The second biasing force is greater than the first biasing force, and F2 shown in the drawings corresponds to the second biasing force.

[0023] The control device 90 is configured to execute energization control for the solenoid 60. By energization control, the solenoid 60 switches between an OFF state (see FIG. 3) and an ON state (see FIG. 4), and the movable core 23 moves. As a result, the movable member 58 moves between the coupled position and the uncoupled position.

[0024] The movable member 58 in the coupled position is indirectly coupled to the valve body 55 via the first connecting member 41 and the abutting member 43 (see FIG. 3). When the movable member 58 is in the coupled position, the resultant force of the second biasing force and the first biasing force acts on the valve body 55, and the valve body 55 is positioned in the open position. When the movable member 58 is in the uncoupled position, it is separated from the abutting member 43 (see FIG. 4). When the movable member 58 moves from the coupled position to the uncoupled position, the second biasing force no longer acts on the valve body 55, and the valve body 55 is moved to the closed position by the first biasing force.

[0025] As the state of the solenoid 60 switches, the valve element 55 moves between the open position and the closed position in the following manner. When the solenoid 60 switches from the off state (see FIG. 3 ) to the on state (see FIG. 4 ), the movable member 58 moves from the coupled position to the uncoupled position against the second biasing force (arrow R in FIG. 4 ). Accordingly, the valve element 55 moves from the open position to the closed position in accordance with the first biasing force. On the other hand, when the solenoid 60 switches from the on state to the off state, the movable member 58 moves from the uncoupled position to the coupled position in accordance with the second biasing force (arrow L in FIG. 3 ). Accordingly, the valve element 55 moves from the closed position to the open position in accordance with the first biasing force.

[0026] When the solenoid 60 is in the ON state, the differential pressure between the supply pressure and the boost chamber pressure, and the magnitude relationship between the differential pressure and the first biasing force, change depending on the movement direction and position of the plunger 22 (the above-mentioned supply pressure refers to the pressure in the unpressurized fuel supply line 6). In other words, even if the solenoid 60 switches from the OFF state to the ON state and the valve element 55 moves to the closed position, the valve element 55 moves between the closed position and the open position depending on the subsequent reciprocating movement of the plunger 22.

[0027] An outline of the fuel supply operation performed by the fuel pump 3 having the above configuration in response to the start of the engine body 10 will be described below. Immediately after the start of the engine body 10, it is difficult for the control device 90 to identify a specific cam phase based on the detection result of the crank sensor 8. In other words, it is difficult to identify the movement direction and position of the plunger 22 immediately after the start of the engine body 10. This is because, in order to identify the cam phase, each of the above-mentioned two sensors provided in the crank sensor 8 must properly detect the detection target, and in order for the detection target to be properly detected, the speed of the camshaft 29 that has started to rotate must reach a predetermined value.

[0028] Therefore, after starting the engine 10, the fuel pump 3 of this embodiment executes a first fuel supply operation that does not require the cam phase to be specified, and then executes a second fuel supply operation that is based on the cam phase. The first fuel supply operation and the second fuel supply operation will be described below in order.

[0029] 5 is a schematic graph showing the changes over time in the position of the plunger 22, the state of the solenoid 60, the position of the valve body 55, and the state of the check valve 31 when the first fuel supply operation is performed. "TDC" and "BDC" in the top graph indicate top dead center and bottom dead center, respectively (the same applies to FIG. 7).

[0030] In the first fuel supply operation, the solenoid 60 is switched from the OFF state to the ON state immediately after starting the engine body 10. As a result, the movable member 58 moves to the uncoupled position, and the valve body 55 moves to the closed position (θ≦θ １As the plunger 22 reciprocates between the top dead center and the bottom dead center (θ≧θ １ ), the pressure in the boost chamber in the pump cylinder 21 changes. The valve element 55 moves between a closed position and an open position in response to the pressure difference between the boost chamber pressure and the supply pressure of the unpressurized fuel supply line 6, thereby opening and closing the intake port 25.

[0031] In detail, when the plunger 22 descends from the top dead center (θ １ ≦θ≦θ ２ ), the pressure in the boost chamber falls far below the supply pressure, and the valve element 55 moves to the open position against the first biasing force. As the intake port 25 opens, fuel flows into the boost chamber C. At this time, the pressure in the boost chamber falls far below the common rail pressure, and the check valve 31 maintains the state in which the discharge port 24 is closed. Thereafter, when the plunger 22 rises from the bottom dead center (θ ２ ≦θ≦θ ３ ), the valve element 55 moves to the closed position, and the pressure in the boost chamber increases. The increase in pressure in the boost chamber causes the check valve to open the discharge port 24, and the fuel pressurized in the boost chamber C is discharged from the discharge port 24 and supplied to the common rail 7.

[0032] In this way, in the first fuel supply operation, the pump cylinder 21 can perform the intake and discharge of fuel without specifying the cam phase after the start of the engine body 10. In other words, the valve unit 50 can increase the pressure in the boost chamber C immediately after the start of the engine body 10.

[0033] While the pump cylinder 21 is discharging fuel, the common rail pressure may exceed the control target value due to some factor. In this case, the solenoid 60 exceptionally switches from the on state to the off state even during the first fuel supply operation. Figure 6 is a schematic diagram showing the state when the solenoid 60 switches to the off state during the first fuel supply operation.

[0034] At this time, the influence of the second biasing force becomes dominant, and the valve element 55 moves from the closed position to the open position, thereby opening the intake port 25. Thereafter, as the plunger 22 continues to move toward the top dead center, the fuel in the boost chamber C flows back from the intake port 25 into the pre-pressurization fuel supply line 6, and as the plunger 22 descends from the top dead center, the fuel in the pre-pressurization fuel supply line 6 is drawn into the boost chamber C.

[0035] As described above, even when the first fuel supply operation is being performed, if the common rail pressure exceeds the control target value, the solenoid 60 exceptionally remains in the OFF state. As the plunger 22 reciprocates, fuel moves back and forth between the pressurization chamber C and the pre-pressurization fuel supply line 6 (arrow J in FIG. 6 ), and the pump cylinder 21 does not discharge fuel from the discharge port 24. If the common rail pressure returns to a value equal to or lower than the control target value, the solenoid 60 returns to the ON state, and the first fuel supply operation shown in FIG. 5 is resumed.

[0036] 7 is a schematic graph showing changes over time in the position of the plunger 22, the state of the solenoid 60, the position of the valve body 55, and the state of the check valve 31 when the second fuel supply operation is performed. After the cam phase is identified, energization control of the solenoid 60 is performed in accordance with the cam phase.

[0037] When the plunger 22 descends from the top dead center (θ ａ ≦θ≦θ ｂ ), the solenoid 60 switches from the on state to the off state. The valve element 55 moves to the open position, and the intake port 25 is opened. The plunger 22 descends, reducing the pressure in the boost chamber and allowing fuel to be drawn into the boost chamber C. After that, even after the plunger 22 starts to rise from the bottom dead center (θ ｂ ≦θ≦θ ｃ ), solenoid 60 remains in the OFF state. Because intake port 25 is open, the volume of pressurized chamber C decreases and fuel flows back from intake port 25 to unpressurized fuel supply line 6. This executes the metering stroke for adjusting the amount of fuel in pressurized chamber C.

[0038] The cam phase is at a specific phase (θ ｃ), the solenoid 60 is switched on. At this time, the valve element 55 is moved to the closed position by the first biasing force, and the intake port 25 is closed. Thereafter, the check valve 31 is opened, and the metered amount of fuel is discharged from the discharge port 24 and supplied to the common rail 7. Note that, when the specific phase (θ ｃ ) may be updated in accordance with the common rail pressure obtained from the common rail pressure sensor 18. This makes it possible to control the amount of fuel discharged from the pump cylinder 21 in accordance with the common rail pressure. After the pressure in the boost chamber has risen sufficiently, the valve element is pressed to the closed position by the differential pressure between the boost chamber pressure and the supply pressure, so the solenoid 60 may be switched from the on state to the off state. In other words, θ ｃ ≦θ≦θ ｄ In this case, the timing at which the solenoid 60 switches to the OFF state is θ=θ ｄ Even in this case, the valve body 55 continues to be disposed in the closed position.

[0039] <Summary of Technical Advantages of Fuel Pump 3> With the fuel pump 3 configured as described above, after the engine body 10 is started, when the first fuel supply operation is initiated and the solenoid 60 switches from the off state to the on state, the valve element 55 opens and closes the suction port 25 in response to the pressure difference between the boost chamber pressure and the supply pressure, and fuel is drawn into the boost chamber C. Furthermore, the check valve 31 opens the discharge port 24 in response to the pressure difference between the boost chamber C and the common rail pressure, and fuel is supplied to the common rail 7. In this way, after the engine body 10 is started, the pump cylinder 21 can draw in and discharge fuel without specifying the cam phase. In other words, the valve unit 50 can increase the pressure inside the pump cylinder immediately after the engine body 10 is started.

[0040] Furthermore, after the cam phase is identified (i.e., after the position and movement direction of the plunger 22 are identified), the second fuel supply operation is initiated. The solenoid 60 switches from an OFF state to an ON state at a predetermined timing while the plunger 22 is rising from the bottom dead center. The intake port 25 is closed, allowing fuel to be immediately discharged from the pump cylinder 21. In other words, the amount of fuel discharged from the pump cylinder 21 can be quickly and precisely adjusted by controlling the energization of the solenoid 60 in accordance with the cam phase. This allows the valve unit 50 to responsively control the amount of fuel discharged from the pump cylinder 21 in accordance with the common rail pressure.

[0041] As described above, the function of increasing the pressure in the pump cylinder 21 immediately after the start of the engine body 10 and the function of responsively controlling the fuel discharge amount in accordance with the common rail pressure are realized by the valve unit 50 alone. Therefore, the configuration of the fuel pump 3 can be simplified compared to when two different valves each perform both functions.

[0042] <Control device 90> As shown in FIG. 8, the control device 90 includes a first solenoid control unit 110 involved in the first fuel supply operation, a determination unit 115 that determines whether to terminate the first fuel supply operation, and a second solenoid control unit 120 involved in the second fuel supply operation.

[0043] The first solenoid control unit 110 controls the energization of the solenoid 60 so that the solenoid 60 is maintained in the ON state regardless of the detection result of the crank sensor 8. As a result, the solenoid 60 is maintained in the ON state regardless of the position of the plunger 22 and the direction of movement of the plunger 22.

[0044] According to the above configuration, after the engine body 10 is started, the first solenoid control unit 110 controls the energization of the solenoid 60, thereby maintaining the solenoid 60 in an ON state, thereby enabling the pressure in the boost chamber to be quickly increased and enabling the driving equipment driven by the engine body 10 to be quickly started. For example, if the driving equipment is an emergency generator, the delay from the start of the engine body 10 to the start of power generation can be shortened.

[0045] The first solenoid control unit 110 also has a discharge stop control unit 113. When the common rail pressure measured by the common rail pressure sensor 18 exceeds a control target value, the discharge stop control unit 113 controls the energization of the solenoid 60 so that the solenoid 60 switches from an on state to an off state.

[0046] According to the above configuration, when the common rail pressure exceeds the control target value during the first fuel supply operation, the movable member 58 moves to the connected position, the valve element 55 moves to the open position, and the intake port 25 is opened. Therefore, even if the plunger 22 moves upward, fuel in the pressurization chamber C flows back from the intake port 25 to the unpressurized fuel supply line 6, and the check valve 31 is not opened. This stops the discharge of fuel from the discharge port 24, making it possible to avoid an excessive increase in the common rail pressure.

[0047] The description of the configuration of the control device 90 will continue. The determination unit 115 of the control device 90 determines whether the cam phase (i.e., the position of the plunger 22 and the moving direction of the plunger 22) has been identified based on the detection result of the crank sensor 8. When each of the two sensors constituting the crank sensor 8 properly detects the detection target, the determination unit 115 determines that the cam phase has been identified. At this time, the determination unit 115 also identifies the specific cam phase.

[0048] The second solenoid control unit 120 controls the energization of the solenoid 60 so that the solenoid 60 switches between an ON state and an OFF state depending on the cam phase. When the determination unit 115 determines that the cam phase has been identified, the second solenoid control unit 120 controls the energization of the solenoid 60 instead of the first solenoid control unit 110. As a result, the second fuel supply operation is performed instead of the first fuel supply operation.

[0049] According to the above configuration, after starting the engine body 10, the solenoid 60 is controlled by the first solenoid control unit 110 until the position and direction of movement of the plunger 22 are determined, thereby enabling the pressure in the boost chamber to be increased quickly. After the position and direction of movement of the plunger 22 are determined, the solenoid 60 is controlled by the second solenoid control unit 120, thereby enabling the amount of fuel discharged from the pump cylinder 21 to be optimized.

[0050] The second solenoid control unit 120 includes a quantity adjustment control unit 122 that adjusts the amount of fuel discharged from the pump cylinder 21. The quantity adjustment control unit 122 has a timing determination unit 124 and a switching control unit 126. The timing determination unit 124 determines whether the plunger 22 has reached a predetermined position between the bottom dead center and the top dead center. The timing at which the plunger 22 reaches the predetermined position is determined by the cam phase being θ ｃ When the timing determination unit 124 determines that the plunger 22 has reached the predetermined position, the switching control unit 126 switches the solenoid 60 from the OFF state to the ON state.

[0051] According to the above configuration, the solenoid 60 switches to the ON state when the amount of fuel in the pressure boost chamber C reaches a predetermined amount. This ends the metering stroke, making it possible to discharge the desired amount of fuel from the discharge port 24.

[0052] The adjustment control unit 122 further includes an update control unit 128. The update control unit 128 updates the position of the plunger 22 (i.e., the cam phase θ shown in FIG. 7 ) that serves as the determination criterion for the determination unit 115 so that the timing of switching by the switching control unit 126 changes in accordance with the common rail pressure detected by the common rail pressure sensor 18. ｃ ) to update.

[0053] More specifically, when the measured common rail pressure exceeds the target pressure, update control is executed to delay the timing of switching. ｃis updated to be larger. As a result, the amount of fuel discharged from the pump cylinder 21 decreases, and the common rail pressure decreases. On the other hand, if the measured common rail pressure is lower than the target pressure, update control is executed to advance the timing of switching. In other words, the cam phase θ ｃ is updated to be smaller. As a result, the amount of fuel discharged from the pump cylinder 21 increases, and the common rail pressure rises. ｃ is stored in the memory of the control device 90 and can be overwritten in accordance with update control.

[0054] According to the above configuration, when the common rail pressure increases, the amount of fuel discharged from the discharge port 24 decreases, and when the common rail pressure decreases, the amount of fuel discharged increases. This allows the common rail pressure to be controlled so that it falls within an allowable range.

[0055] <Control Processing> The control processing executed by the control device 90 will be described with reference to Figure 9. This control processing is executed by the processor of the control device 90, thereby sequentially executing a first fuel supply operation and a second fuel supply operation. In the following description, "step" may be abbreviated as "S".

[0056] First, the processor starts the engine body 10 and the fuel pump 3 by sending control signals to each of them (S1). Then, the processor controls the solenoid 60 to perform a first fuel supply operation (S3). Specifically, the processor executes first solenoid control to control energization of the solenoid 60 so that the solenoid 60 remains on regardless of the detection result of the crank sensor 8 (S3). The processor executing S3 is an example of the first solenoid control unit 110.

[0057] Next, the processor determines whether the cam phase has been identified based on the detection result of the crank sensor 8 (S5). The processor that executes S5 is an example of the determination unit 115. Until the cam phase is identified (S5: NO), the processor returns the process to S3, and the first solenoid control is repeatedly executed.

[0058] If it is determined that the cam phase has been identified (S5: YES), the processor controls the solenoid 60 so that the second fuel supply operation is performed instead of the first fuel supply operation (S7). Specifically, the processor executes second solenoid control that controls the energization of the solenoid 60 so that the solenoid 60 switches between an ON state and an OFF state depending on the cam phase. The processor that executes S7 is an example of the second solenoid control unit 120.

[0059] The processor determines whether to continue this control process (S9). If it is determined that this control process should be continued (S9: YES), the processor returns to S7 and executes the second solenoid control again. If it is determined that this control process should not be continued (S9: NO), the processor ends this control process.

[0060] The first solenoid control will be described in detail with reference to FIG. 10 . The processor determines whether the common rail pressure exceeds the control target value based on the measurement result of the common rail pressure sensor 18 (S11). If the measured common rail pressure is equal to or lower than the control target value (S11: NO), the processor turns on the solenoid 60 (S13) and terminates the first solenoid control. If the solenoid 60 was on before S13 was executed, control to maintain the on state is executed in S13. On the other hand, if the common rail pressure exceeds the control target value (S11: YES), the processor executes control to turn the solenoid 60 off (S15). This opens the intake port 25 and closes the check valve 31. Therefore, fuel discharge from the pump cylinder 21 is stopped. If the solenoid 60 was off before S15 was executed, control to maintain the off state is executed in S15. The processor executing S15 is an example of the discharge stop control unit 113. After execution of S15, the processor ends the first solenoid control.

[0061] The second solenoid control will be described in detail with reference to FIG. 11. At the start of this control, the solenoid 60 is in the OFF state. The processor determines whether the plunger 22 has reached a predetermined position between the bottom dead center and the top dead center based on the detection result of the crank sensor 8 (S21). When the cam phase identified by the crank sensor 8 is θ ｃ When the plunger 22 reaches the predetermined position (see FIG. 7 ), the processor that executes S21 is an example of the timing determination unit 124. The solenoid 60 is maintained in the OFF state until the plunger 22 reaches the predetermined position (S21: NO). When the plunger 22 reaches the predetermined position (S21: YES), the processor executes energization control to switch the solenoid 60 from the OFF state to the ON state (S23). The processor that executes S23 is an example of the switching control unit 126.

[0062] Next, the processor determines whether the deviation between the common rail pressure and the target pressure is large based on the measurement result of the common rail pressure sensor 18 (S25). If the deviation is small (S25: NO), the processor terminates the second solenoid control. If the deviation is determined to be large (S25: YES), the processor returns to the predetermined position (i.e., the cam phase θ ｃ ) (S27). In detail, when the common rail pressure exceeds the target pressure, the processor updates θ ｃ If the common rail pressure is lower than the target pressure, the processor updates θ ｃ The updated cam phase θ is updated so that it becomes smaller. ｃ is overwritten in the memory of the control device 90. As a result, the updated predetermined position is applied as the judgment criterion in S21 of the second solenoid control that is subsequently executed. The processor that executes S27 is an example of the update control unit 128. After executing S27, the processor ends the second solenoid control.

[0063] <Others> The valve unit 50 may not include the first connecting member 41 and the abutting member 43. In this case, the first biasing member 51 directly abuts against the valve body 55, and the movable member 58 in the coupled position is also directly coupled to the valve body 55. The valve unit 50 may also not include the second connecting member 42. In this case, the movable iron core 23 of the solenoid 60 is coupled to the movable member 58. In the example of FIG. 2 , the suction port 25 is formed in one end of the pump cylinder 21, and the discharge port 24 is formed in a side wall portion of the pump cylinder 21. Alternatively, the suction port 25 may be formed in the side wall portion, and the discharge port 24 may be formed in one end portion.

[0064] The control device 90 described above is configured by a computer and includes a processor, memory (storage medium), and an external communication interface. The processor may be a CPU, GPU, MPU, DSP, or a combination thereof. The processor according to other embodiments may be implemented by an integrated circuit such as a PLD, ASIC, FPGA, or MCU. The memory is configured to temporarily or non-temporarily store various data and may be implemented by at least one of a RAM, a ROM, or a flash memory, for example. The processor executes various control processes according to instructions from a program loaded into the memory.

[0065] <Summary> The contents described in the above-described embodiments can be understood, for example, as follows.

[0066] 1) A fuel pump (3) according to at least one embodiment of the present disclosure is a fuel pump for supplying diesel engine fuel pressurized in the pump cylinder to a common rail (7), the fuel pump comprising: a pump cylinder (21) and a plunger (22) configured to reciprocate within the pump cylinder; a check valve (31) capable of opening a discharge port (24) formed in the pump cylinder for discharging the pressurized fuel toward the common rail; and a valve unit (50) including a valve body (55) for opening and closing a suction port (25) formed in the pump cylinder for drawing in the fuel before pressurization, the valve unit comprising: a first biasing member (51) applying a first biasing force to the valve body so as to close the suction port; and a movable member (58) movable between a connected position directly or indirectly connected to the valve body and a non-connected position spaced apart from the valve body. a second biasing member (52) that applies a second biasing force to the movable member that is directed in the opposite direction to the first biasing force and is greater than the first biasing force; and a solenoid (60) that is configured to move the movable member from the coupled position to the uncoupled position by switching from an off state to an on state.

[0067] The configuration 1) above enables the following operations. That is, when the solenoid switches from an off state to an on state, the movable member can move from the coupled position to the uncoupled position against the second biasing force. Accordingly, of the first or second biasing forces, only the first biasing force acts on the valve body. The valve body can move in accordance with the first biasing force from an open position that opens the suction port to a closed position that closes it. Furthermore, when the solenoid switches from an on state to an off state, the movable member can move in accordance with the second biasing force from the uncoupled position to the coupled position. The valve body can move in accordance with the first biasing force from the closed position to the open position.

[0068] After the diesel engine starts, when the solenoid switches from its off state to its on state, the movable member moves to the uncoupled position and the valve element moves to its closed position. As the plunger reciprocates, the pressure in the boost chamber in the pump cylinder changes. The valve element opens and closes the intake port depending on the pressure difference between the boost chamber pressure and the supply pressure in the fuel supply line upstream of the intake port, allowing fuel to be drawn into the boost chamber (C) in the pump cylinder. Furthermore, the check valve opens the discharge port depending on the pressure difference between the boost chamber pressure and the common rail pressure in the common rail, allowing the pressurized fuel in the boost chamber to be supplied to the common rail. In this way, after the diesel engine starts, the pump cylinder can draw in and discharge fuel without specifying the position and direction of the plunger. In other words, the valve unit can increase the pressure in the pump cylinder immediately after the diesel engine starts.

[0069] Furthermore, after the plunger's position and movement direction are identified, the solenoid switches from its off state to its on state at a predetermined timing while the plunger is rising from bottom dead center to top dead center. The valve element moves to its closed position, allowing fuel to be immediately discharged from the pump cylinder. In other words, the amount of fuel discharged from the pump cylinder can be precisely and quickly adjusted by controlling the solenoid's current flow according to the plunger's state. This allows the valve unit to responsively control the amount of fuel discharged from the pump cylinder according to the common rail pressure.

[0070] As described above, the valve unit alone can achieve both the function of increasing the pressure in the cylinders immediately after starting the diesel engine and the function of responsively controlling the fuel discharge amount in accordance with the common rail pressure, which simplifies the configuration compared to when two separate valves each perform both functions.

[0071] 2) In some embodiments, the fuel pump described in 1) above further includes a first solenoid control unit (110) for controlling the energization of the solenoid so that the solenoid maintains the on state regardless of the position and direction of movement of the plunger.

[0072] According to the configuration 2), after the engine starts, the first solenoid control unit keeps the solenoid on, so that the pressure in the boost chamber can be increased immediately. This allows the driving device driven by the engine to start up immediately. For example, if the driving device is an emergency generator, the delay between the start of the engine and the start of power generation can be reduced.

[0073] 3) In some embodiments, in the fuel pump described in 2) above, the first solenoid control unit includes a discharge stop control unit (113) for switching the solenoid from the on state to the off state when the common rail pressure in the common rail exceeds a control target value.

[0074] According to the configuration of 3) above, when the common rail pressure exceeds the control target value, the movable member moves to the connected position and the valve element moves to the open position. Therefore, even if the plunger rises, fuel in the boost chamber flows back into the supply line upstream of the intake port, so the check valve does not open. Since fuel discharge from the discharge port stops, an excessive increase in common rail pressure can be suppressed. The control target value is a predetermined value (predetermined pressure).

[0075] 4) In some embodiments, the fuel pump described in 2) or 3) above further includes: a determination unit (115) for determining whether the position and the moving direction of the plunger have been identified; and a second solenoid control unit (120) for controlling the supply of current to the solenoid so that the solenoid switches between the on state and the off state depending on the position and the moving direction of the plunger, and when it is determined that the position and the moving direction have been identified, the second solenoid control unit controls the supply of current to the solenoid instead of the first solenoid control unit.

[0076] According to the configuration 4) above, after the diesel engine is started, the solenoid is controlled by the first solenoid control unit until the position and direction of movement of the plunger are determined, thereby enabling the pressure in the boost chamber to be increased quickly. After the position and direction of movement of the plunger are determined, the solenoid is controlled by the second solenoid control unit, thereby enabling the amount of fuel discharged from the pump cylinder to be optimized.

[0077] 5) In some embodiments, the fuel pump according to any one of 1) to 4) above further comprises a second solenoid control unit (120) for controlling the energization of the solenoid so that the solenoid switches between the off state and the on state depending on the position and movement direction of the plunger.

[0078] According to the configuration of 5) above, the second solenoid control section switches the state of the solenoid while identifying the position and moving direction of the plunger, so that the discharge amount in the pump cylinder can be optimized.

[0079] 6) In some embodiments, in the fuel pump described in 4) or 5) above, the second solenoid control unit includes a metering control unit (122) for adjusting the amount of fuel in the pump cylinder, and the metering control unit has a timing determination unit (124) for determining whether the plunger has reached a predetermined position between bottom dead center and top dead center, and a switching control unit (126) for switching the solenoid from the off state to the on state when it is determined that the plunger has reached the predetermined position.

[0080] According to the configuration of 6) above, the solenoid is switched on when the amount of fuel in the pressure boost chamber reaches a predetermined amount, thereby enabling the desired amount of fuel to be discharged from the discharge port.

[0081] 7) In some embodiments, in the fuel pump described in 6) above, the metering control unit has an update control unit (128) for updating the predetermined position that serves as the judgment criterion of the timing judgment unit so that the timing of switching by the switching control unit is delayed when the common rail pressure in the common rail exceeds a target pressure.

[0082] According to the configuration of 7) above, when the common rail pressure increases, the amount of fuel discharged from the discharge port decreases. This allows the common rail pressure to be controlled so that it falls within an allowable range. The target pressure is a specified pressure (specified value).

[0083] 8) A diesel engine system (1) according to at least one embodiment of the present disclosure comprises: a fuel pump (3) according to any one of 1) to 7) above; a fuel tank (5) for storing the fuel before pressurization to be supplied to the fuel pump; the common rail (7) for storing the pressurized fuel discharged from the fuel pump; and an engine body (10) including a plurality of injectors (15) for injecting the pressurized fuel supplied from the common rail.

[0084] The configuration 8) above provides the same technical advantages as the configuration 1).

[0085] REFERENCE SIGNS LIST 1: Engine system (diesel engine system) 2: Fuel supply system 3: Fuel pump 5: Fuel tank 6: Pre-pressurized fuel supply line 7: Common rail 8: Crank sensor 9: Post-pressurized fuel supply line 10: Engine body 13: Pump cylinder unit 15: Injector 18: Common rail pressure sensor 21: Pump cylinder 22: Plunger 23: Movable iron core 24: Discharge port 25: Intake port 28: Pump cam 29: Camshaft 31: Check valve 41: First connecting member 42: Second connecting member 43: Contact member 50: Valve unit 51: First biasing member 52: Second biasing member 55: Valve body 58: Movable member 60: Solenoid 90: Control device 110: First solenoid control unit 113: Discharge stop control unit 115: Determination unit 120: Second solenoid control unit 122: Amount adjustment control unit 124: Timing determination unit 126: Switching control unit 128: Update control unit

Claims

1. A fuel pump comprising a pump cylinder and a plunger configured to reciprocate within the pump cylinder, for supplying diesel engine fuel pressurized within the pump cylinder to a common rail, the fuel pump comprising: a check valve capable of opening a discharge port formed in the pump cylinder for discharging the pressurized fuel toward the common rail; and a valve unit including a valve body for opening and closing an intake port formed in the pump cylinder for drawing in the unpressurized fuel, the valve unit including: a first biasing member that applies a first biasing force to the valve body to close the intake port; a movable member that is movable between a connected position directly or indirectly connected to the valve body and a disconnected position spaced apart from the valve body; a second biasing member that applies a second biasing force to the movable member that is directed opposite to the direction of the first biasing force and is greater than the first biasing force; and a solenoid configured to switch from an off state to an on state to move the movable member from the connected position to the disconnected position.

2. The fuel pump according to claim 1, further comprising a first solenoid control unit for controlling the energization of the solenoid so that the solenoid maintains the ON state regardless of the position and moving direction of the plunger.

3. A fuel pump according to claim 2, wherein the first solenoid control unit includes a discharge stop control unit for switching the solenoid from the on state to the off state when the common rail pressure in the common rail exceeds a control target value.

4. A fuel pump as described in claim 2, further comprising: a determination unit for determining whether the position and the direction of movement of the plunger have been identified; and a second solenoid control unit for controlling the supply of electricity to the solenoid so that the solenoid switches between the on state and the off state depending on the position and the direction of movement of the plunger, wherein when it is determined that the position and the direction of movement have been identified, the second solenoid control unit controls the supply of electricity to the solenoid instead of the first solenoid control unit.

5. The fuel pump according to claim 1 or 2, further comprising a second solenoid control unit for controlling the energization of the solenoid so that the solenoid switches between the off state and the on state depending on the position and moving direction of the plunger.

6. A fuel pump as set forth in claim 4, wherein the second solenoid control unit includes a quantity adjustment control unit for adjusting the amount of fuel in the pump cylinder, and the quantity adjustment control unit has: a timing determination unit for determining whether the plunger has reached a predetermined position between bottom dead center and top dead center; and a switching control unit for switching the solenoid from the off state to the on state when it is determined that the plunger has reached the predetermined position.

7. A fuel pump according to claim 6, wherein the metering control unit has an update control unit for updating the predetermined position that serves as the judgment criterion for the timing judgment unit so that the timing of switching by the switching control unit is delayed when the common rail pressure in the common rail exceeds a target pressure.

8. A diesel engine system comprising: a fuel pump according to claim 1 or 2; a fuel tank for storing the fuel before it is pressurized and to be supplied to the fuel pump; a common rail for storing the pressurized fuel discharged from the fuel pump; and an engine body including a plurality of injectors for injecting the pressurized fuel supplied from the common rail.

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