Fuel supply system

Abstract

To provide a fuel supply system that can appropriately control the amount of fuel supplied from a high-pressure pump to the in-cylinder injection valve of an engine in response to changes in the engine's operating conditions. [Solution] The control device includes a calculation unit that calculates a target valve opening timing, which is a target value for the valve opening timing of the intake valve, multiple times at predetermined calculation timings according to the engine operating state before the intake valve opens; an update unit that performs an update process to update the target valve opening timing in a storage unit at predetermined update timings before the intake valve opens; and a control unit that controls the intake valve so that the valve opening timing of the intake valve becomes the target valve opening timing updated in the storage unit.

Description

Technical Field

[0001] The present invention relates to a fuel supply system.

Background Art

[0002] The target opening timing of the electromagnetic suction valve of a high-pressure pump that supplies fuel to an in-cylinder injection valve of an engine is calculated at a predetermined timing according to the operating state of the engine (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above technique, the target opening timing is calculated only once before the suction valve opens. Therefore, if the operating state of the engine changes after the calculation of the target opening timing and before the suction valve opens, the suction valve will open at the target opening timing calculated before the change in the operating state of the engine. Therefore, there is a possibility that the fuel supply amount from the high-pressure pump to the in-cylinder injection valve of the engine cannot be appropriately controlled according to the change in the operating state of the engine.

[0005] Therefore, an object of the present invention is to provide a fuel supply system that can appropriately control the fuel supply amount from a high-pressure pump to an in-cylinder injection valve of an engine according to a change in the operating state of the engine.

Means for Solving the Problems

[0006] The system comprises a high-pressure pump that supplies fuel stored in a fuel tank from a low-pressure fuel passage to the in-cylinder injection valve of the engine, and a control device that controls the high-pressure pump. The high-pressure pump includes a pressurizing chamber that pressurizes the fuel in accordance with the reciprocating motion of a plunger linked to the rotation of the engine, an intake passage connecting the low-pressure fuel passage and the pressurizing chamber, a discharge passage connecting the pressurizing chamber and the in-cylinder injection valve, an electromagnetic intake valve that adjusts the amount of fuel drawn from the low-pressure fuel passage into the pressurizing chamber, and a discharge valve provided on the discharge passage that allows fuel to flow from the pressurizing chamber side to the in-cylinder injection valve side but not in the reverse direction. This can be achieved by a fuel supply system that includes a discharge valve that regulates the flow of fuel, and the control device includes a calculation unit that calculates a target valve opening timing, which is a target value for the valve opening timing of the intake valve, multiple times at predetermined calculation timings according to the operating state of the engine before the intake valve opens, an update unit that performs an update process to update the target valve opening timing in a storage unit at predetermined update timings before the intake valve opens, and a control unit that controls the intake valve so that the valve opening timing of the intake valve becomes the target valve opening timing updated in the storage unit.

[0007] If the interval between the target valve opening timing updated in the memory unit and the target valve opening timing newly calculated by the calculation unit after the target valve opening timing has been updated in the memory unit is less than the resolution of the timing at which the intake valve can open, the update unit does not need to perform the update process.

[0008] The update unit does not need to perform the update process while the intake valve is open.

[0009] If the target valve opening timing newly calculated by the calculation unit after the target valve opening timing has been updated in the storage unit is in the past than the current timing, the update unit does not need to perform the update process.

[0010] If the intake valve is controlled in a special drive mode that does not depend on the target valve opening timing calculated by the calculation unit according to the operating state of the engine, the update unit does not need to perform the update process. [Effects of the Invention]

[0011] According to the present invention, a fuel supply system can be provided that can appropriately control the amount of fuel supplied from a high-pressure pump to the in-cylinder injection valve of an engine in response to changes in the engine's operating state. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram of the fuel supply system. [Figure 2] This flowchart illustrates the intake valve opening control performed by the ECU. [Figure 3] This is a timing chart illustrating the control of the intake valve opening mechanism. [Modes for carrying out the invention]

[0013] [Outline configuration of the fuel supply system] Figure 1 is a schematic diagram of the fuel supply system 1. The fuel supply system 1 includes an engine 10, a fuel tank 21, a low-pressure pump 22, a low-pressure pipe 25, a low-pressure delivery pipe 26, a high-pressure delivery pipe 36, fuel pressure sensors 28 and 38, a fuel temperature sensor 39, a high-pressure pump 40, and an ECU (Electronic Control Unit) 100, etc. The fuel supply system 1 is installed in a vehicle that uses the engine 10 as a power source, for example, but is not limited to that.

[0014] Engine 10 is a spark-ignition type four-cylinder gasoline engine equipped with in-cylinder injectors 37 that inject fuel into each cylinder and port injectors 27 that inject fuel into each intake port. However, engine 10 is not limited to this, and may be a diesel engine, an alcohol engine, or a so-called direct injection engine without port injectors 27 or low-pressure delivery pipes 26. Engine 10 also includes a camshaft 15 that drives intake valves or exhaust valves in conjunction with a crankshaft which is linked to a plurality of pistons.

[0015] The fuel tank 21 stores gasoline, which is a liquid fuel. If the engine 10 is a diesel engine, the liquid fuel is diesel oil. If the engine 10 is an alcohol engine, the liquid fuel is alcohol. The low-pressure pump 22 pressurizes the fuel and discharges it into the low-pressure pipe 25. The fuel discharged into the low-pressure pipe 25 is supplied to the port injection valve 27 via the low-pressure delivery pipe 26, and also to the high-pressure pump 40 via the branch pipe 25a that branches off from the low-pressure pipe 25. The low-pressure pipe 25 and the branch pipe 25a are examples of low-pressure fuel passages.

[0016] The high-pressure pump 40 pressurizes the fuel supplied from the branch pipe 25a and discharges it into the high-pressure delivery pipe 36. The fuel pressurized by the high-pressure pump 40 is supplied to the in-cylinder injection valve 37 via the high-pressure delivery pipe 36.

[0017] The fuel pressure sensors 28 and 38 detect the fuel pressure in the low-pressure delivery pipe 26 and the high-pressure delivery pipe 36, respectively. The fuel temperature sensor 39 detects the fuel temperature in the high-pressure delivery pipe 36. The ECU 100 acquires the detected values ​​from the fuel pressure sensors 28 and 38 and the fuel temperature sensor 39.

[0018] The ECU 100 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a rewritable non-volatile memory 101. By executing the program stored in the ROM with the CPU, the intake valve opening control described later is executed. The intake valve opening control is executed by a calculation unit, an update unit, and a control unit that are functionally realized by the CPU, the ROM, the RAM, and the memory 101. Details will be described later.

[0019] Also, the ECU 100 changes the in-cylinder injection rate, which is the ratio of the fuel injection amount injected from the in-cylinder injection valve 37 to the total fuel injection amount, according to the operating region of the engine 10. For example, when the operating region of the engine 10 is a low load region, the in-cylinder injection ratio is 0%, when it is a high load region, it is 100%, and when it is a medium load region, it is set to an intermediate value.

[0020] [Schematic Configuration of High-Pressure Pump] The high-pressure pump 40 will be described. The high-pressure pump 40 is provided with a cylinder 41, a plunger 42, a pressure chamber 43, a suction passage 45, a discharge passage 47, a relief passage 49, a suction valve 50, a discharge valve 60, and a relief valve 70.

[0021] The plunger 42 reciprocates within the cylinder 41 in conjunction with the drive of the engine 10. Specifically, the plunger 42 is biased by a spring toward the cam CP side that rotates together with the camshaft 15, and reciprocates within the cylinder 41 due to the rotation of the cam CP. The cam CP is a substantially square shape having four vertices.

[0022] The pressure chamber 43 is defined by the cylinder 41 and the plunger 42. When the plunger 42 rises, the volume of the pressure chamber 43 decreases, and when the plunger 42 descends, the volume of the pressure chamber 43 increases.

[0023] The intake passage 45 connects the branch pipe 25a, which branches off from the low-pressure pipe 25, to the pressurizing chamber 43. The intake passage 45 is equipped with a pulsation damper 44 to suppress fuel pressure pulsation. The relief passage 49 connects the pressurizing chamber 43 to the high-pressure delivery pipe 36. The discharge passage 47 connects the relief passage 49 on the pressurizing chamber 43 side of the discharge valve 60 to the relief passage 49 on the high-pressure delivery pipe 36 side of the discharge valve 60. In other words, the discharge passage 47 bypasses the relief valve 70.

[0024] The intake valve 50 is an electromagnetic on-off valve located on the fuel inlet side of the pressurizing chamber 43, which switches the communication state between the intake passage 45 and the pressurizing chamber 43. The intake valve 50 has a valve body 51, a coil 55 that drives the valve body 51, and a spring 53 that always biases the valve body 51 in the open direction. The energization of the coil 55 is controlled by the ECU 100. When the coil 55 is energized, the valve body 51 blocks the intake passage 45 and the pressurizing chamber 43 against the biasing force of the spring 53. When the coil 55 is not energized, the valve body 51 is maintained in the open state by the biasing force of the spring 53.

[0025] The discharge valve 60 is a check valve located on the discharge passage 47 that allows fuel to flow from the pressurizing chamber 43 to the high-pressure delivery pipe 36 but restricts flow in the reverse direction. Specifically, the discharge valve 60 opens when the fuel pressure in the pressurizing chamber 43 becomes higher than the fuel pressure in the high-pressure delivery pipe 36 by a predetermined amount.

[0026] During the intake stroke of the high-pressure pump 40, the intake valve 50 opens and the plunger 42 descends, filling the pressurizing chamber 43 from the branch pipe 25a through the intake passage 45. During the pressurizing stroke, the intake valve 50 closes and the volume of the pressurizing chamber 43 decreases as the plunger 42 rises, pressurizing the fuel in the pressurizing chamber 43. During the discharge stroke, when the fuel pressure force acting on the discharge valve 60 from the pressurizing chamber 43 side becomes greater due to the fuel pressure force acting on the discharge valve 60 from the high-pressure delivery pipe 36 side and the biasing force of the discharge valve 60's spring, the discharge valve 60 opens, and the pressurized fuel is supplied to the high-pressure delivery pipe 36.

[0027] The relief valve 70 is a check valve located on the relief passage 49 that allows fuel to flow from the high-pressure delivery pipe 36 to the pressurizing chamber 43 but restricts flow in the reverse direction. The relief valve 70 opens when the fuel pressure in the high-pressure delivery pipe 36 rises excessively to the point where it could cause malfunctions in the high-pressure delivery pipe 36 or the in-cylinder injection valve 37, thereby preventing malfunctions in these components.

[0028] [Inhalation valve opening control] The ECU 100 performs intake valve opening control as follows. Figure 2 is a flowchart illustrating the intake valve opening control performed by the ECU 100. The ECU 100 repeatedly performs this control at predetermined intervals while the ignition is on. The ECU 100 determines whether the high-pressure pump 40 is in a special drive mode (step S1).

[0029] The drive mode of the high-pressure pump 40 can be switched between a normal drive mode and a special drive mode. In the normal drive mode, as described later, the target opening timing of the intake valve 50 is calculated according to the operating state of the engine 10, and the intake valve 50 is controlled so that the opening timing of the intake valve 50 becomes the target opening timing.

[0030] A special drive mode is a mode in which the intake valve 50 is controlled regardless of the target valve opening timing calculated according to the operating state of the engine 10. Special drive modes include, for example, a forced mode, a silent mode, and a stop mode. The forced mode is a mode in which the opening period of the intake valve 50 is controlled to be longer than in the normal drive mode in order to supply high-pressure fuel to the in-cylinder injection valve 37 early when the engine 10 is started. The silent mode is a mode in which the seating noise when the intake valve 50 is closed is suppressed by reducing the current supplied to the intake valve 50 compared to the normal drive mode. The stop mode is a mode in which the opening of the intake valve 50 is stopped when a fuel cut request is made. If the answer to step S1 is Yes, this control ends without the update process described later being executed.

[0031] If the answer in step S1 is No, i.e., in normal drive mode, the ECU 100 determines whether or not it is the calculation timing for the target valve opening timing, which is the target value for the valve opening timing of the intake valve 50 (step S2). The calculation timing is set, for example, at predetermined time intervals, but is not limited to this, and may be set, for example, at predetermined crank angles.

[0032] If the answer in step S2 is Yes, the ECU 100 performs a calculation process to calculate the target valve opening timing according to the operating state of the engine 10 (step S3). In the calculation process, the target valve opening timing is calculated based on the rotational speed and load of the engine 10 and the fuel pressure in the high-pressure delivery pipe 36. The target valve opening timing is calculated as the crank angle of the engine 10.

[0033] If the answer in step S2 is No, or after step S3 is executed, the ECU 100 determines whether or not it is the update timing for the target valve opening timing stored in memory 101 (step S4). The update timing is set, for example, for each predetermined crank angle.

[0034] If the answer in step S4 is Yes, the ECU 100 determines whether the update conditions for the target valve opening timing are met (step S5). The update conditions include the first to third conditions.

[0035] The first condition is that the interval between the target valve opening timing updated in memory 101 and the newly calculated target valve opening timing is greater than or equal to the resolution of the timing at which the intake valve 50 can open. If the above interval is less than the resolution, even if the update process described later is executed, the timing at which the intake valve 50 actually opens will be the same. For example, if the target valve opening timing updated in memory 101 is 166°CA, and the target valve opening timing newly calculated in step S3 is 164°CA, the resolution is 5°CA. In this case, the interval between the target valve opening timings is 2°CA, which is less than the resolution, so it is determined as No in step S5, and the update process is not executed.

[0036] The second condition is that the current timing is before the intake valve 50 opens. This is because even if the update process is executed while the intake valve 50 is open, it is not possible to change the opening timing of the intake valve 50. In this case, step S5 is determined to be No, and the update process is not executed.

[0037] The third condition is that the newly calculated target valve opening timing is later than the current timing. If the newly calculated target valve opening timing is earlier than the current timing, it will be impossible to open the intake valve 50 at that timing, even if the target valve opening timing is updated by the update process. For example, the newly calculated target valve opening timing may be earlier due to a decrease in fuel pressure in the high-pressure delivery pipe 36 or an increase in the target fuel injection amount. In this case, the result is determined to be No in step S5, and the update process is not executed.

[0038] As described above, if any of the first to third conditions are not met, the result will be determined as No in step S5, and the update process will not be executed.

[0039] If all of the first to third conditions are met, the result is determined as Yes in step S5, and the ECU 100 executes the update process (step S6). The update process overwrites the target valve opening timing stored in memory 101 with the target valve opening timing newly calculated in step S3.

[0040] If the answer in step S4 or S5 is No, or after step S6 is executed, the ECU 100 determines whether the current timing has reached the target valve opening timing updated in memory 101 (step S7). If the answer in step S7 is No, this control is terminated. If the answer in step S7 is Yes, the ECU 100 opens the intake valve 50 (step S8).

[0041] As the above intake valve opening control is repeatedly executed at predetermined time intervals, the target valve opening timing is calculated multiple times at predetermined calculation timings until the intake valve 50 opens, and the target valve opening timing is updated in the memory 101 at predetermined update timings. This makes it possible to appropriately control the amount of fuel supplied from the high-pressure pump 40 to the in-cylinder injection valve 37 of the engine 10 in accordance with changes in the operating state of the engine 10. Note that the above intake valve opening control needs to be repeatedly executed at time intervals shorter than the intervals of the calculation timings and update timings described above. In addition, although the execution of the update process increases the processing load of the ECU 100, as described above, the update process is not executed if the answer in step S1 is Yes or in step S5 is No. This reduces the processing load of the ECU 100.

[0042] Figure 3 is a timing chart illustrating intake valve opening control. Figure 3 shows the calculation process, update process, and the state of the intake valve 50. In Figure 3, the horizontal axis represents the crank angle. Figure 3 shows TDC1, where the plunger 42 is at top dead center, and TDC2, where the plunger 42 is at top dead center again. The interval between TDC1 and TDC2 is the crank angle obtained by dividing 720° by 4, the number of vertices on the cam CP. This is because when the crankshaft rotates 720°, the cam CP rotates 360°. The interval between TDC1 and TDC2 corresponds to one cycle of the plunger 42.

[0043] The calculation process is performed before TDC1 (crank angle C1), followed by the update process (crank angle C2). Then the calculation process is performed again (crank angle C3), followed by the update process (crank angle C4). Then the update process is performed again (crank angle C5), but since no calculation process is performed between the previous update process and the current update process, the target valve opening timing calculated at crank angle C3 is updated. That is, the same target valve opening timing is updated in memory 101. Then the calculation process is performed (crank angle C6), but without any update processing, the intake valve 50 opens at the target valve opening timing updated in memory 101 (crank angle C7). Also, no update process is performed while the intake valve 50 is open. The calculation process is performed while the intake valve 50 is open (crank angle C8), followed by the update process (crank angle C9). The target valve opening timing, calculated using crank angle C8 and updated using crank angle C9, is used to control the opening of the intake valve 50, which opens between TDC2 and TDC3 (not shown) when the plunger 42 returns to top dead center.

[0044] In the example above, even if the operating state of the engine 10 changes between the execution of the first calculation process (crank angle C1) and the execution of the second calculation process (crank angle C3), the corresponding target valve opening timing is calculated (crank angle C3) and updated in memory 101 (crank angle C4). In this way, the amount of fuel supplied from the high-pressure pump 40 to the in-cylinder injection valve 37 of the engine 10 can be appropriately controlled in response to changes in the operating state of the engine 10.

[0045] Furthermore, if the system is configured to calculate the target valve opening timing only once before the intake valve 50 opens, and that calculation timing is the crank angle C3 described above, then it is possible to respond to changes in the operating state of the engine 10 in the same way as in this embodiment. However, if the only calculation timing before the intake valve 50 opens is the crank angle C3, the target valve opening timing may be calculated as a timing earlier than the crank angle C3. In this case, since the calculation timing has already passed the target valve opening timing, there is a risk that the valve opening timing of the intake valve 50 cannot be properly controlled. Therefore, as in this embodiment, it is preferable that at least one of the multiple calculation timings is before the time when the plunger 42 is at top dead center (TDC1) before the intake valve 50 opens.

[0046] In the example shown in Figure 3, the update process is not performed after the suction valve 50 has closed and until TDC2 is reached, but it may be performed if necessary.

[0047] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of Symbols]

[0048] 1. Fuel supply system 10 Engines 21 Fuel tank 25 Low-pressure pipe (low-pressure fuel passage) 25a Branch pipe (low-pressure fuel passage) 36 High-pressure delivery pipe 37 In-cylinder injection valve 40 High-pressure pump 42 plungers 43 Pressurized chamber 45 Suction passage 47 Discharge passage 50 Inhalation valve 60 Discharge valve 100 ECUs (Calculation Unit, Update Unit, Control Unit) 101 Memory (storage unit)

Claims

1. A high-pressure pump supplies fuel stored in the fuel tank from the low-pressure fuel passage to the in-cylinder injection valve of the engine, The system includes a control device for controlling the high-pressure pump, The aforementioned high-pressure pump is A pressurizing chamber pressurizes the fuel in accordance with the reciprocating motion of a plunger linked to the rotation of the engine. An intake passage connecting the low-pressure fuel passage and the pressurized chamber, A discharge passage connecting the pressurized chamber and the in-cylinder injection valve, An electromagnetic intake valve for adjusting the amount of fuel drawn from the low-pressure fuel passage into the pressurized chamber, and Includes a discharge valve provided on the discharge passage which allows fuel to flow from the pressurizing chamber side to the in-cylinder injection valve side but restricts flow in the reverse direction, The control device is A calculation unit calculates a target opening timing, which is a target value for the opening timing of the intake valve, multiple times at predetermined calculation timings according to the operating state of the engine, before the intake valve opens. An update unit that performs an update process to update the target valve opening timing in the storage unit at predetermined update timings before the intake valve opens, and The control unit includes a control unit that controls the intake valve so that the opening timing of the intake valve becomes the target opening timing updated in the memory unit, Fuel supply system.

2. The fuel supply system according to claim 1, wherein if the interval between the target valve opening timing updated in the memory unit and the target valve opening timing newly calculated by the calculation unit after the target valve opening timing has been updated in the memory unit is less than the resolution of the timing at which the intake valve can open, the update unit does not perform the update process.

3. The fuel supply system according to claim 2, wherein the updating unit does not perform the updating process while the intake valve is open.

4. The fuel supply system according to claim 3, wherein if the target valve opening timing newly calculated by the calculation unit after the target valve opening timing has been updated in the storage unit is in the past than the current timing, the update unit does not perform the update process.

5. The fuel supply system according to claim 4, wherein if the intake valve is controlled in a special drive mode that does not depend on the target valve opening timing calculated by the calculation unit according to the operating state of the engine, the update unit does not perform the update process.

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