Fuel supply system

Abstract

The present invention addresses the problem of providing a fuel supply system capable of appropriately controlling the amount of fuel supplied from a high-pressure pump to an in-cylinder injection valve of an engine in accordance with a change in the operating state of the engine. A fuel supply system is provided with: a high-pressure pump for supplying fuel stored in a fuel tank from a low-pressure fuel passage to an in-cylinder injection valve of an engine; and a control device that controls the high-pressure pump, the high-pressure pump including: a pressurizing chamber that pressurizes fuel in accordance with reciprocating motion of a plunger in conjunction with rotation of the engine; a suction passage communicating the low-pressure fuel passage and the pressurizing chamber; a discharge passage that communicates with the pressurizing chamber and the in-cylinder injection valve; an electromagnetic suction valve that adjusts the amount of fuel sucked into the pressurizing chamber from the low-pressure fuel passage; and a discharge valve which is provided in the discharge passage and which permits the flow of fuel from the pressurizing chamber side to the in-cylinder injection valve side but restricts the flow in the opposite direction.

Description

Technical Field

[0001] This invention relates to a fuel supply system. Background Technology

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

[0003] Patent Document 1: Japanese Patent Application Publication No. 2016-217315 Summary of the Invention

[0004] In the aforementioned technology, the target valve opening timing is calculated only once before the intake valve opens. Therefore, if the engine operating state changes after the target valve opening timing is calculated but before the intake valve opens, the intake valve will open at the target valve opening timing calculated before the engine operating state changed. Consequently, it may be impossible to properly control the amount of fuel supplied from the high-pressure pump to the engine's in-cylinder injection valves according to changes in the engine operating state.

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

[0006] This can be achieved by a fuel supply system comprising: 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 an engine; and a control device that controls the high-pressure pump, the high-pressure pump comprising: a pressurization chamber that pressurizes the fuel 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 pressurization chamber; an exhaust passage connecting the pressurization 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 pressurization chamber; and an exhaust valve disposed on the exhaust... The control device includes: a calculation unit that calculates a target value for the opening timing of the intake valve multiple times at each predetermined calculation timing according to the engine operating state before the intake valve opens; an update unit that performs an update process to update the target opening timing of the storage unit at each predetermined update timing before the intake valve opens; and 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 storage unit.

[0007] If the interval between the target valve opening timing updated in the storage unit and the target valve opening timing newly calculated by the calculation unit after the target valve opening timing is updated in the storage unit is less than the resolution of the timing when the suction valve can be opened, the updating unit may not perform the update process.

[0008] The updating unit may not perform the updating process during the opening of the intake valve.

[0009] If the target valve opening timing calculated by the calculation unit after updating the target valve opening timing in the storage unit is earlier than the current timing, the updating unit does not perform the update process.

[0010] When the intake valve is controlled in a special drive mode, the update unit may not perform the update process, and the special drive mode does not depend on the target valve opening timing calculated by the calculation unit based on the engine's operating state.

[0011] Invention Effects

[0012] According to the present invention, a fuel supply system is provided that can appropriately control the amount of fuel supplied from a high-pressure pump to the in-cylinder injection valve of the engine according to changes in the engine's operating state. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the fuel supply system.

[0014] Figure 2 This is a flowchart illustrating the intake valve opening control executed by the ECU.

[0015] Figure 3 This is a timing diagram illustrating the opening control of the intake valve. Detailed Implementation

[0016] [Brief Structure of the Fuel Supply System]

[0017] Figure 1 This 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 distribution pipe 26, a high-pressure distribution pipe 36, fuel pressure sensors 28 and 38, a fuel temperature sensor 39, a high-pressure pump 40, and an electronic control unit (ECU) 100. The fuel supply system 1 is, for example, installed in a vehicle powered by the engine 10, but is not limited to this.

[0018] Engine 10 is a spark-ignition four-cylinder gasoline engine equipped with cylinder injection valves 37 for injecting fuel into each cylinder and intake manifold injection valves 27 for injecting fuel into each intake manifold. However, engine 10 is not limited to this; for example, it can be a diesel engine, an alcohol engine, or even a so-called direct injection engine without intake manifold injection valves 27 or low-pressure distribution pipes 26. Furthermore, engine 10 includes a camshaft 15 that drives the intake or exhaust valves in conjunction with a crankshaft that is linked to multiple pistons.

[0019] Gasoline, a liquid fuel, is stored in fuel tank 21. If engine 10 is a diesel engine, the liquid fuel is light oil. If engine 10 is an alcohol engine, the liquid fuel is alcohol. Low-pressure pump 22 pressurizes the fuel and discharges it into low-pressure pipe 25. The fuel discharged into low-pressure pipe 25 is supplied to intake manifold injection valve 27 via low-pressure distribution pipe 26, and also to high-pressure pump 40 via branch pipe 25a branching from low-pressure pipe 25. Low-pressure pipe 25 and branch pipe 25a are examples of low-pressure fuel passages.

[0020] High-pressure pump 40 pressurizes the fuel supplied from branch pipe 25a and discharges it to high-pressure distribution pipe 36. The fuel pressurized by high-pressure pump 40 is supplied to cylinder injection valve 37 via high-pressure distribution pipe 36.

[0021] Fuel pressure sensors 28 and 38 detect the fuel pressure in the low-pressure distribution pipe 26 and the high-pressure distribution pipe 36, respectively. Fuel temperature sensor 39 detects the fuel temperature in the high-pressure distribution pipe 36. ECU 100 acquires the detection values ​​from fuel pressure sensors 28 and 38, as well as fuel temperature sensor 39.

[0022] The ECU 100 includes a Central Processing Unit (CPU), Random Access Memory (RAM), Read Only Memory (ROM), and an erasable non-volatile memory 101. The CPU executes a program stored in the ROM to perform the intake valve opening control, which will be described later. The intake valve opening control is performed by a calculation unit, an update unit, and a control unit, which are functionally implemented using the CPU, ROM, RAM, and memory 101. Details will be described later.

[0023] Furthermore, the ECU 100 adjusts the in-cylinder injection rate according to the operating region of the engine 10. The in-cylinder injection rate is the ratio of the amount of fuel injected from the in-cylinder injection valve 37 to the total amount of fuel injected. For example, when the engine 10 is operating in a low-load region, the in-cylinder injection rate is 0%, in a high-load region it is 100%, and in a medium-load region it is set to an intermediate value.

[0024] [Brief Structure of a High-Pressure Pump]

[0025] The high-pressure pump 40 is described below. The high-pressure pump 40 is equipped with a cylinder 41, a plunger 42, a pressurization chamber 43, a suction channel 45, a discharge channel 47, a pressure relief channel 49, a suction valve 50, a discharge valve 60, and a pressure relief valve 70.

[0026] The plunger 42 reciprocates within the cylinder 41 in a drive linkage with the engine 10. Specifically, the plunger 42 is pushed by a spring toward the cam CP, which rotates together with the camshaft 15, and reciprocates within the cylinder 41 by the rotation of the cam CP. The cam CP is a roughly square shape with four vertices.

[0027] The pressurization chamber 43 is defined by the cylinder 41 and the plunger 42. The volume of the pressurization chamber 43 decreases as the plunger 42 rises and increases as the plunger 42 falls.

[0028] The intake passage 45 connects to a branch pipe 25a branching from the low-pressure pipe 25 and the pressurization chamber 43. A pulsation damper 44 to suppress fuel pressure pulsations is provided in the intake passage 45. The pressure relief passage 49 connects to the pressurization chamber 43 and the high-pressure distribution pipe 36. The discharge passage 47 connects to both the pressure relief passage 49 located further from the discharge valve 60 than the side of the pressurization chamber 43 and the pressure relief passage 49 located further from the discharge valve 60 than the side of the high-pressure distribution pipe 36. That is, the discharge passage 47 bypasses the pressure relief valve 70.

[0029] The intake valve 50 is located on the fuel inlet side of the pressurization chamber 43 and is an electromagnetic on / off valve that switches the connection between the intake passage 45 and the pressurization 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 provides a preload force in the opening direction to the valve body 51. The energization of the coil 55 is controlled by the ECU 100. If the coil 55 is energized, the valve body 51 resists the preload force of the spring 53 and cuts off the intake passage 45 and the pressurization chamber 43. When the coil 55 is not energized, the valve body 51 remains open due to the preload force of the spring 53.

[0030] The discharge valve 60 is a check valve located on the discharge passage 47, allowing fuel to flow from the pressurization chamber 43 to the high-pressure distribution pipe 36, but restricting flow in the opposite direction. Specifically, the discharge valve 60 opens when the fuel pressure in the pressurization chamber 43 is higher than the fuel pressure in the high-pressure distribution pipe 36 by a specified amount.

[0031] During the suction stroke of the high-pressure pump 40, the suction valve 50 opens, the plunger 42 descends, and fuel is filled into the pressurization chamber 43 from the branch pipe 25a via the suction passage 45. During the pressurization stroke, the suction valve 50 closes, and as the plunger 42 rises, the volume of the pressurization chamber 43 decreases, and the fuel in the pressurization chamber 43 is pressurized. During the discharge stroke, when the fuel pressure acting on the discharge valve 60 from the pressurization chamber 43 side is greater than the sum of the fuel pressure acting on the discharge valve 60 from the high-pressure distribution pipe 36 side and the preload of the discharge valve 60 spring, the discharge valve 60 opens, supplying pressurized fuel to the high-pressure distribution pipe 36.

[0032] The pressure relief valve 70 is located on the pressure relief passage 49 and allows fuel to flow from the high-pressure distribution pipe 36 side to the pressurized chamber 43 side, but restricts flow in the opposite direction. The pressure relief valve 70 opens in case the fuel pressure in the high-pressure distribution pipe 36 rises excessively to the point that an abnormality may occur in the high-pressure distribution pipe 36 or the in-cylinder injection valve 37, thereby preventing abnormalities in these components.

[0033] [Suction valve opening control]

[0034] ECU100 performs the following control on the opening of the intake valve. Figure 2 This is a flowchart illustrating the intake valve opening control executed by ECU 100. ECU 100 repeats this control at predetermined intervals during ignition on-time. ECU 100 determines whether the high-pressure pump 40 is in a special drive mode (step S1).

[0035] The driving mode of the high-pressure pump 40 is switched to either a normal driving mode or a special driving mode. As described later, the normal driving mode is as follows: the target opening timing of the intake valve 50 is calculated based on 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.

[0036] The special drive mode is one in which the intake valve 50 is controlled independently of the target valve opening timing calculated based on 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 one in which, for example, to supply high-pressure fuel to the in-cylinder injection valve 37 as early as possible during engine 10 startup, the opening period of the intake valve 50 is controlled to be longer than in the normal drive mode. The silent mode is one in which, for example, the closing noise of the intake valve 50 is suppressed by reducing the energizing current of the intake valve 50 to a lower level than in the normal drive mode. The stop mode is one in which, for example, the opening of the intake valve 50 is stopped when a fuel cut-off request is received. If "Yes" is selected in step S1, the update process described later is not performed, and this control ends.

[0037] If "No" is received in step S1, i.e., in normal drive mode, ECU100 determines whether the target value for the opening timing of the intake valve 50 is the calculated timing (step S2). The calculated timing may be set to each specified time, but is not limited to this; for example, it may also be set to each specified crankshaft angle.

[0038] If "Yes" is selected in step S2, the ECU 100 executes a calculation process (step S3) to determine the target valve opening timing based on the operating state of the engine 10. In this calculation process, the target valve opening timing is calculated based on the engine speed and load, and the fuel pressure within the high-pressure distribution pipe 36. The target valve opening timing is calculated as the crankshaft angle of the engine 10.

[0039] If the answer in step S2 is "No", or after executing step S3, the ECU 100 determines whether it is an update time for the target valve opening timing stored in the memory 101 (step S4). The update time is set, for example, for each specified crankshaft angle.

[0040] If "yes" is received in step S4, ECU100 determines whether the update conditions for the target valve opening timing are met (step S5). The update conditions include conditions 1 to 3.

[0041] 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 suction valve 50 can open. This is because if the interval is less than the resolution, even if the update process described later is performed, the actual opening timing of the suction valve 50 will be the same. For example, if the target valve opening timing updated in memory 101 is 166°CA, and the newly calculated target valve opening timing in step S3 is 164°CA, with a resolution of 5°CA, then since the interval between the target valve opening timings is 2°CA and less than the resolution, it is determined as "No" in step S5, and the update process is not performed.

[0042] The second condition is that the current timing is before the opening of the suction valve 50. This is because even if an update process is performed during the opening of the suction valve 50, the opening timing of the suction valve 50 cannot be changed. In this case, the result is determined as "No" in step S5, and the update process is not performed.

[0043] The third condition is that the newly calculated target valve opening timing is after the current timing. This is because if the newly calculated target valve opening timing is earlier than the current timing, even if the timing is updated to the newly calculated target valve opening timing through the update process, the intake valve 50 cannot be opened at that timing. This is because, for example, the newly calculated target valve opening timing may be earlier due to a decrease in fuel pressure in the high-pressure distribution pipe 36 or an increase in the target fuel injection quantity. In this case, it is determined as "No" in step S5, and the update process is not performed.

[0044] As described above, if any one of the conditions 1 to 3 is not met, the result is determined as "no" in step S5, and the update process is not performed.

[0045] If all conditions 1 to 3 are met, the result is "yes" in step S5, and ECU100 performs an update process (step S6). The update process is to overwrite the target valve opening timing stored in memory 101 with the newly calculated target valve opening timing in step S3.

[0046] If the result in step S4 or S5 is "No", or after executing step S6, ECU 100 determines whether the current timing is the target valve opening timing updated in memory 101 (step S7). If the result in step S7 is "No", the control ends. If the result in step S7 is "Yes", ECU 100 opens the intake valve 50 (step S8).

[0047] By repeatedly executing the above-described intake valve opening control at predetermined intervals until the intake valve 50 opens, the target valve opening timing is calculated multiple times according to each predetermined calculation timing, and the memory 101 is updated with the target valve opening timing according to each predetermined update timing. This allows for appropriate control of the fuel supply from the high-pressure pump 40 to the in-cylinder injection valve 37 of the engine 10 based on changes in the engine 10's operating state. Furthermore, the above-described intake valve opening control needs to be repeated at time intervals shorter than the intervals between the calculated timings or the update timings. While the update process increases the processing load on the ECU 100, as described above, the update process is not performed if "yes" is indicated in step S1 or "no" is indicated in step S5. This reduces the processing load on the ECU 100.

[0048] Figure 3 This is a timing diagram illustrating the opening control of the intake valve. Figure 3 The diagram shows the calculated changes in the processing, update processing, and the state of the suction valve 50. Figure 3 In the diagram, the horizontal axis represents the crankshaft angle. Additionally, in... Figure 3The diagram shows plunger 42 at top dead center (TDC1) and then at top dead center (TDC2). The interval between TDC1 and TDC2 is the crankshaft angle obtained by dividing 720° by the number of the cam CP's apex (4). This is because the cam CP rotates 360° for every 720° crankshaft rotation. The interval between TDC1 and TDC2 corresponds to one cycle of plunger 42.

[0049] Before TDC1, a calculation process (crankshaft angle C1) is performed, followed by an update process (crankshaft angle C2). Then, a calculation process (crankshaft angle C3) is performed again, followed by an update process (crankshaft angle C4). Then, an update process (crankshaft angle C5) is performed again, but no calculation process is performed between the previous update process and this update process, so the target valve opening timing is updated to the value calculated in crankshaft angle C3. That is, the target valve opening timing is updated to the same value in memory 101. Then, a calculation process (crankshaft angle C6) is performed, but no update process is required, to open the intake valve 50 (crankshaft angle C7) at the target valve opening timing updated in memory 101. Furthermore, no update process is performed during the opening of the intake valve 50. A calculation process (crankshaft angle C8) is also performed during the opening of the intake valve 50, followed by an update process (crankshaft angle C9). The target valve opening timing, calculated in crankshaft angle C8 and updated in crankshaft angle C9, is used for the valve opening control of the intake valve 50 before it opens from TDC2 to TDC3 (not shown), when the plunger 42 becomes top dead center again.

[0050] In the above example, even if the operating state of the engine 10 changes between the execution of the first calculation process (crankshaft angle C1) and the execution of the second calculation process (crankshaft angle C3), the corresponding target valve opening timing (crankshaft angle C3) is calculated and updated in the memory 101 (crankshaft 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 according to the changes in the operating state of the engine 10.

[0051] Furthermore, for example, if the structure is configured such that the target valve opening timing is calculated only once before the intake valve 50 opens, and this calculated timing is the aforementioned crankshaft angle C3, it can correspond to changes in the operating state of the engine 10 in the same way as in this embodiment. However, if the target valve opening timing is calculated only once before the intake valve 50 opens, and the crankshaft angle C3 is the calculated timing, sometimes the target valve opening timing is calculated at an earlier time than the crankshaft angle C3. In this case, since the calculated timing has already passed the target valve opening timing, it may be impossible to properly control the opening timing of the intake valve 50. Therefore, as in this embodiment, it is preferable that at least one of the multiple calculated timings is before the moment when the plunger 42 is at top dead center (TDC1) before the intake valve 50 opens.

[0052] In addition, Figure 3 In the example, no update process is performed after the intake valve 50 is closed and until it becomes TDC2, but it can still be performed.

[0053] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific embodiments described above. Various modifications and alterations can be made within the scope of the spirit of the present invention as set forth in the claims.

[0054] Symbol Explanation

[0055] 1-Fuel supply system, 10-Engine, 21-Fuel tank, 25-Low-pressure pipe (low-pressure fuel passage), 25a-Branch pipe (low-pressure fuel passage), 36-High-pressure distribution pipe, 37-In-cylinder injection valve, 40-High-pressure pump, 42-Plunger, 43-Pressure chamber, 45-Intake passage, 47-Exhaust passage, 50-Intake valve, 60-Exhaust valve, 100-ECU (Calculation unit, Update unit, Control unit), 101-Memory (Storage unit).

Claims

1. A fuel supply system, characterized in that, have: A high-pressure pump supplies fuel stored in the fuel tank from the low-pressure fuel passage to the engine's in-cylinder injection valves; and Control device, which controls the high-pressure pump The high-pressure pump includes: The pressurization chamber pressurizes the fuel through the reciprocating motion of the plunger, which is linked to the rotation of the engine. An intake passage that connects the low-pressure fuel passage and the pressurization chamber; An exhaust passage connects the pressurization 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 pressurization chamber; and A discharge valve, disposed on the discharge passage, allows fuel to flow from the pressurized chamber side to the in-cylinder injection valve side, but restricts flow in the opposite direction. The control device includes: The calculation unit calculates the target value of the valve opening time, i.e. the target valve opening time, multiple times according to the engine's operating state before the intake valve opens. The updating unit, before the intake valve opens, performs an updating process that updates the storage unit with the target valve opening timing at each predetermined updating timing; and A control unit controls the suction valve so that the opening timing of the suction valve becomes the target opening timing updated in the storage unit.

2. The fuel supply system according to claim 1, characterized in that, If the interval between the target valve opening timing updated in the storage unit and the target valve opening timing newly calculated by the calculation unit after the target valve opening timing is updated in the storage unit is less than the resolution of the timing when the suction valve can be opened, the updating unit does not perform the update process.

3. The fuel supply system according to claim 2, characterized in that, The updating unit does not perform the updating process during the opening of the intake valve.

4. The fuel supply system according to claim 3, characterized in that, If the target valve opening timing calculated by the calculation unit after updating the target valve opening timing in the storage unit is earlier than the current timing, the updating unit does not perform the update process.

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

Images