JP2018003610A - Fuel pressure control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel pressure control device of an internal combustion engine which can quickly lower fuel pressure in a low-pressure passage which is boosted by the decompression of the inside of a high-pressure passage.SOLUTION: A fuel pressure control device of an internal combustion engine having a port injection valve and an in-cylinder injection valve comprises: a fuel tank; a low-pressure pump; a low-pressure passage; a high-pressure pump for pressuring fuel supplied from the low-pressure passage; a high-pressure passage; a relief passage for making the high-pressure passage and the low-pressure passage communicate with each other; an electromagnetic relief valve for opening and closing the relief passage; a high-pressure system control part for decompressing the inside of the high-pressure passage by discharging fuel in the high-pressure passage into the low-pressure passage by opening the relief valve when there is a need for decompressing the inside of the high-pressure passage; and a low-pressure system control part for decompressing the inside of the low-pressure passage by stopping electricity-carrying to the low-pressure pump while injecting the fuel from at least either of the port injection valve and the in-cylinder injection valve when the inside of the high-pressure passage is decompressed.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a fuel pressure control device for an internal combustion engine.

  In a fuel pressure control device for an internal combustion engine having a port injection valve and an in-cylinder injection valve, fuel pressurized by a low pressure pump is supplied to the port injection valve via a low pressure passage, and fuel from the low pressure passage is further pumped And is supplied to the in-cylinder injection valve through the high-pressure passage. In such an apparatus, the high-pressure pump is controlled so that the fuel pressure in the high-pressure cylinder reaches the target fuel pressure, and the fuel injection amount of the in-cylinder injection valve is controlled.

  In such a configuration, when the internal combustion engine shifts to a deceleration state while the internal combustion engine is in a high load state and the high pressure passage remains in a high fuel pressure state, a fuel cut is performed, and then returns from the fuel cut. In some cases, fuel injection is performed while the high pressure passage remains in a high fuel pressure state. In this case, the target injection time calculated based on the fuel pressure in the high-pressure passage and the target injection amount is less than the minimum time during which the in-cylinder injection valve can stably perform fuel injection, and the actual injection amount is less than the target injection amount. There is a possibility that the amount of fuel injection will be higher and over-rich. For this reason, for example, in the technique of Patent Document 1, the relief passage extending from the high pressure passage to the fuel tank is opened by an electromagnetic relief valve, so that the fuel in the high pressure passage is returned to the fuel tank and the fuel pressure in the high pressure passage is reduced. It is decreasing.

JP 2010-71132 A

  However, in the technique of Patent Document 1, since the distance from the fuel tank that is the fuel supply source to the high-pressure passage that is the fuel supply destination is long, it is necessary to prepare a long relief passage. For this reason, manufacturing cost may increase.

  Therefore, for example, it is conceivable to adopt a short relief passage by returning the fuel in the high-pressure passage to the low-pressure passage located closer to the fuel tank instead of the fuel tank.

  However, if the fuel in the high-pressure passage is returned to the low-pressure passage, the fuel pressure in the low-pressure passage may increase and the fuel pressure may be maintained high. For this reason, the fuel pressure in the low-pressure passage is maintained in a state where it is higher than the target fuel pressure, and there is a possibility that the fuel injection amount from the port injection valve cannot be appropriately controlled.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel pressure control device for an internal combustion engine that can quickly reduce the fuel pressure in the low pressure passage that has risen due to the pressure reduction in the high pressure passage.

  The above object is a fuel pressure control device for an internal combustion engine comprising a port injection valve for injecting fuel into an intake port and an in-cylinder injection valve for injecting fuel into a cylinder, wherein the fuel tank stores fuel. A low pressure pump for sucking fuel from the fuel tank, a low pressure passage for discharging fuel from the low pressure pump and supplying fuel to the port injection valve, a high pressure pump for pressurizing fuel supplied from the low pressure passage, A high-pressure passage through which fuel is discharged from the high-pressure pump and supplies fuel to the in-cylinder injection valve; a relief passage that connects the high-pressure passage and the low-pressure passage; an electromagnetic relief valve that opens and closes the relief passage; and the high-pressure passage When a pressure reduction request is received, the relief valve is opened to release the fuel in the high pressure passage into the low pressure passage, thereby reducing the pressure in the high pressure passage. And when the pressure reduction in the high-pressure passage is performed, by stopping the energization to the low-pressure pump while injecting fuel from at least one of the port injection valve and the in-cylinder injection valve, This can be achieved by a fuel pressure control device for an internal combustion engine comprising a low-pressure system control unit for reducing the pressure of the engine.

  According to the above configuration, since the relief passage communicates the low pressure passage and the high pressure passage, a short relief passage can be adopted as compared with the case where the high pressure passage communicates with the fuel tank. Moreover, when the pressure reduction request | requirement in a high pressure channel | path is requested | required, the inside of a high pressure channel | path can be decompressed by opening a relief valve. Further, when the pressure in the high-pressure passage is reduced, the fuel pressure in the low-pressure passage increases, but the fuel in the low-pressure passage is consumed by fuel injection from at least one of the port injection valve and the in-cylinder injection valve. As a result, the amount of fuel discharged into the low-pressure passage is reduced. As a result, the fuel pressure in the low pressure passage that has risen due to the pressure reduction in the high pressure passage can be reduced early.

  In the above configuration, the low pressure system control unit is a fuel required to reduce the fuel pressure in the low pressure passage after the fuel in the high pressure passage is released to the target fuel pressure. A required consumption amount calculation unit for calculating the required consumption amount, and a period required to consume the fuel of the required consumption amount calculated by fuel injection of at least one of the port injection valve and the in-cylinder injection valve, And a target stop period calculation unit that calculates a target stop period that is a target period during which energization of the low-pressure pump is stopped.

  In the above configuration, a fuel pressure sensor that detects a fuel pressure in the low-pressure passage is provided, and the low-pressure system control unit until the detection value of the fuel pressure sensor decreases to a target fuel pressure value after the energization of the low-pressure pump is stopped. The structure which continues the stop of electricity supply to the said low pressure pump may be sufficient.

  The low-pressure passage includes a main passage communicating from the low-pressure pump to the port injection valve, and a branch passage branched from the main passage and communicated with the high-pressure pump, and the relief passage includes the high-pressure passage and the The structure which connects the main channel | path may be sufficient.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel pressure control apparatus of the internal combustion engine which can reduce the fuel pressure in the low-pressure channel | path raised by pressure_reduction | reduced_pressure in a high pressure channel | path early can be provided.

FIG. 1 is a schematic configuration diagram of a fuel pressure control apparatus for an internal combustion engine according to this embodiment. FIG. 2 is a flowchart illustrating an example of pressure reduction control executed by the ECU. FIG. 3 is a flowchart showing an example of the high-pressure system pressure reduction control executed by the ECU 5. FIG. 4 is a flowchart showing an example of the low-pressure system pressure reduction control executed by the ECU 5. FIG. 5 is a graph showing changes in the fuel pressure in the low-pressure system when the low-pressure system pressure reduction control is executed after the high-pressure system pressure reduction control is executed and when it is not executed. FIG. 6 is a schematic configuration diagram of a control device of a first modification. FIG. 7 is a flowchart showing an example of low-pressure system pressure reduction control executed by the ECU in the first modification. FIG. 8 is a schematic explanatory diagram of a control device according to a second modification.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a fuel pressure control device 1 for an internal combustion engine according to this embodiment. A fuel pressure control device (hereinafter referred to as a control device) 1 for an internal combustion engine includes a fuel tank 21, a low pressure pump 22, a low pressure pipe 25, a low pressure delivery pipe 26, a high pressure pipe 35, a fuel pressure sensor 38, a high pressure pump 40, and a relief passage 81. A relief valve 83, an ECU (Electronic Control Unit) 5, and the like.

  The engine 10, the downstream side of the low pressure pipe 25, the high pressure pipe 35, the fuel pressure sensor 38, the high pressure pump 40, the relief passage 81, and the relief valve 83 are housed in the engine compartment R of the vehicle on which the control device 1 is mounted. Therefore, the fuel tank 21, the low pressure pump 22, the upstream side of the low pressure pipe 25, and the ECU 5 are disposed inside the vehicle outside the engine compartment R.

  The engine 10 is a spark ignition type four-cylinder engine including an in-cylinder injection valve 37 and a port injection valve 27, and is an example of an internal combustion engine. The in-cylinder injection valve 37 injects fuel into each cylinder of the engine 10. The port injection valve 27 injects fuel into each intake port of the engine 10. In-cylinder injection valve 37 and port injection valve 27 are supplied with fuel from high-pressure delivery pipe 36 and low-pressure delivery pipe 26 of engine 10, respectively. The engine 10 includes a crankshaft 14 that is linked to a plurality of pistons, and a camshaft 15 that is linked to the crankshaft 14 and drives an intake valve or an exhaust valve. Further, a crank angle sensor 14a for detecting the rotation angle of the crankshaft 14 is provided.

  The fuel tank 21 stores gasoline as fuel. The low pressure pump 22 pressurizes the fuel and discharges it to the low pressure pipe 25 and the branch pipe 25 a branched from the low pressure pipe 25. The fuel pressurized to a predetermined pressure level by the low pressure pump 22 is regulated by a pressure regulator (not shown) and discharged to the low pressure pipe 25 and the branch pipe 25a. The relatively low pressure 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 supplied to the high pressure pump 40 via the branch pipe 25 a branched from the low pressure pipe 25. The

  The low pressure pipe 25, the branch pipe 25 a, and the low pressure delivery pipe 26 are an example of a low pressure passage through which fuel is discharged from the low pressure pump 22. The low-pressure pipe 25 and the low-pressure delivery pipe 26 are an example of a main passage that communicates from the low-pressure pump 22 to the port injection valve 27. The branch pipe 25 a is an example of a branch passage that branches from the low-pressure pipe 25 and communicates with the high-pressure pump 40.

  The high-pressure pump 40 pressurizes the fuel supplied from the branch pipe 25 a and discharges it to the high-pressure pipe 35. The relatively high pressure fuel pressurized by the high pressure pump 40 is supplied to the in-cylinder injection valve 37 via the high pressure pipe 35 and the high pressure delivery pipe 36. The high pressure pipe 35 and the high pressure delivery pipe 36 are an example of a high pressure passage through which fuel is discharged from the high pressure pump 40.

  The fuel pressure sensor 38 detects the fuel pressure in the high pressure delivery pipe 36. The ECU 5 acquires the detection value of the fuel pressure sensor 38.

  The relief passage 81 has an upstream end connected to the high pressure delivery pipe 36 and a downstream end connected to the low pressure pipe 25 so that the high pressure delivery pipe 36 and the low pressure pipe 25 communicate with each other. The relief passage 81 is provided with an electromagnetically driven relief valve 83 that opens and closes the relief passage 81. The opening and closing of the relief valve 83 is controlled by the ECU 5. Details will be described later.

  Next, the high pressure pump 40 will be described. The high pressure pump 40 is provided with a cylinder 41, a plunger 42, a pressurizing chamber 43, a suction passage 45, a discharge passage 47, a suction valve 50, and a discharge valve 60.

  The plunger 42 moves up and down in the cylinder 41 in conjunction with the driving of the engine 10. Specifically, the plunger 42 is biased by a spring toward the cam CP that rotates together with the cam shaft 15, and moves up and down in the cylinder 41 by the rotation of the cam CP.

  The pressurizing chamber 43 is defined by the cylinder 41 and the plunger 42, and the volume of the pressurizing chamber 43 decreases as the plunger 42 rises, and the volume of the pressurizing chamber 43 increases as the plunger 42 descends.

  The suction passage 45 communicates the low pressure pipe 25 and the pressurizing chamber 43. The suction passage 45 is provided with a pulsation damper 44 that suppresses fuel pressure pulsation. The discharge passage 47 communicates the pressurizing chamber 43 and the high pressure pipe 35.

  The suction valve 50 is an electromagnetically driven on-off valve that is provided on the fuel inlet side of the pressurizing chamber 43 and switches the communication state between the suction passage 45 and the pressurizing chamber 43. The suction valve 50 includes a valve body 51, a coil 55 that drives the valve body 51, and a spring 53 that constantly biases the valve body 51 in the opening direction. Energization of the coil 55 is controlled by the ECU 5. When the coil 55 is energized, the valve body 51 blocks the suction passage 45 and the pressurizing chamber 43 against the urging force of the spring 53. In the state where the coil 55 is not energized, the valve body 51 is kept open by the biasing force of the spring 53.

  The discharge valve 60 is a check valve that is provided in the discharge passage 47 and that allows the fuel to flow from the pressurizing chamber 43 side to the high-pressure pipe 35 side but restricts the 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 pipe 35 by a predetermined amount.

  In the suction stroke of the high-pressure pump 40, the suction valve 50 is opened and the plunger 42 is lowered, and fuel is charged into the pressurizing chamber 43 from the branch pipe 25a through the suction passage 45. In the pressurizing stroke, the volume of the pressurizing chamber 43 is reduced as the plunger 42 is closed and the plunger 42 is raised, and the fuel in the pressurizing chamber 43 is pressurized. In the discharge stroke, the force of the fuel pressure from the pressurizing chamber 43 acting on the discharge valve 60 is based on the resultant force of the fuel pressure from the high-pressure pipe 35 acting on the discharge valve 60 and the biasing force of the spring of the discharge valve 60. The discharge valve 60 opens. As a result, the pressurized fuel is supplied to the in-cylinder injection valve 37 via the high-pressure pipe 35 and the high-pressure delivery pipe 36.

  As described above, since high-pressure fuel is supplied to the downstream side of the discharge valve 60, the discharge passage 47, the high-pressure pipe 35, and the high-pressure delivery pipe 36 on the downstream side of the discharge valve 60 are referred to as a high-pressure system. Further, since the low pressure fuel is supplied from the low pressure pump 22 to the upstream side of the pressurizing chamber 43 of the high pressure pump 40 and the inside of the low pressure delivery pipe 26, the suction passage 45, the low pressure pipe 25, the branch pipe 25a, and the low pressure delivery pipe are provided. 26 is referred to as a low pressure system.

  The ECU 5 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The ECU 5 executes pressure reduction control, which will be described later, based on information from the sensor, information stored in the ROM in advance, and the like according to a control program stored in the ROM in advance. The pressure reduction control is executed by a high-pressure system control unit and a low-pressure system control unit that are functionally realized by a CPU, a ROM, and a RAM. Details will be described later.

  Further, the ECU 5 controls the fuel injection amounts of the port injection valve 27 and the in-cylinder injection valve 37 based on a map stored in advance in the ROM. The map defines the required injection amount for each injection valve in accordance with the operating region of the engine 10. For example, this map shows that only the port injection valve 27 injects in the low load operation region, both the port injection valve 27 and the in-cylinder injection valve 37 in the middle load operation region, and only the in-cylinder injection valve 37 in the high load operation region. Each required injection amount is defined as follows.

  Further, the ECU 5 controls the rotation speed of the low-pressure pump 22 so that the low-pressure fuel pressure becomes the low-pressure target fuel pressure value. Specifically, the target rotational speed of the low-pressure pump 22 is calculated by a map or formula corresponding to the target fuel pressure value of the low-pressure system, and energization to the low-pressure pump 22 is controlled so that the rotational speed of the low-pressure pump 22 becomes the target rotational speed. Is done. Note that the target fuel pressure value of the low pressure system is calculated by a map or a mathematical formula corresponding to the rotational speed of the engine 10 and the fuel temperature. The fuel temperature may be detected by, for example, a temperature sensor, or may be estimated based on the cooling water temperature, the oil temperature, or the like of the engine 10.

  Further, the ECU 5 controls the high pressure pump 40 so that the fuel pressure of the high pressure system, specifically, the detected value of the fuel pressure sensor 38 becomes the target fuel pressure value of the high pressure system determined according to the rotational speed and load of the engine 10. The opening / closing timing of the intake valve 50 is controlled.

  Next, the relief passage 81 and the relief valve 83 will be described. The relief valve 83 is opened for a predetermined period in high pressure system pressure reduction control, which will be described in detail later. Thereby, fuel is discharged from the high pressure system to the low pressure system via the relief passage 81, and the fuel pressure of the high pressure system is reduced.

  Here, the downstream end of the relief passage 81 is connected to the low-pressure pipe 25 as shown in FIG. 1, and the high-pressure fuel is returned into the low-pressure pipe 25. For this reason, for example, the relief passage 81 of the present embodiment may be shorter as compared with the case where the downstream end of the relief passage is connected to the fuel tank 21 or the branch pipe 25a, increasing the manufacturing cost and increasing the size of the control device 1. Is suppressed. Thus, the relief passage 81 and the relief valve 83 can be stored in the engine compartment R together with the engine 10.

  Further, the downstream end of the relief passage may be connected to the suction passage in the high-pressure pump, but it is desirable that the downstream end of the relief passage 81 is connected to the low-pressure pipe 25 as in this embodiment. This is because when the downstream end of the relief passage is connected to the suction passage in the high-pressure pump, the structure of the high-pressure pump becomes complicated and the manufacturing cost may increase. In addition, depending on the ratio of the relief passage occupied in the high-pressure pump, the pressurizing chamber needs to be miniaturized, and the fuel discharge amount of the high-pressure pump may be reduced. The above description is not intended to exclude the configuration in which the downstream end of the relief passage is connected to the suction passage in the high-pressure pump.

  The upstream end of the relief passage 81 is connected to the high pressure delivery pipe 36, but may be connected to the high pressure pipe 35. The downstream end of the relief passage 81 may be connected to the low pressure delivery pipe 26.

  Next, the decompression control executed by the ECU 5 will be described. The decompression control in this embodiment includes high pressure system decompression control and low pressure system decompression control. First, the high pressure system pressure reduction control will be described.

  In the high pressure system pressure reduction control, when there is a high pressure system pressure reduction request for lowering the fuel pressure in the high pressure system, the relief valve 83 is opened to open the relief passage 81 from the high pressure delivery pipe 36 to the low pressure pipe 25. In this control, the fuel is discharged and the high-pressure fuel pressure is reduced to the target fuel pressure value of the high-pressure system. Thereby, the fuel pressure of a high-pressure system can be reduced early. The high pressure system pressure reduction request is, for example, when there is a fuel cut request or when the target fuel pressure value of the high pressure system is smaller than the detection value of the fuel pressure sensor 38 and the difference between the target fuel pressure value and the detection value of the fuel pressure sensor 38 is a predetermined value. Occurs when exceeded.

  Next, the low pressure system pressure reduction control will be described. When the relief valve 83 is opened by the execution of the high pressure system pressure reduction control, the fuel pressure of the high pressure system decreases, but the fuel pressure of the low pressure system increases. For this reason, if the fuel pressure of the low pressure system becomes larger than the target fuel pressure value, and the fuel is continuously discharged to the low pressure system by the low pressure pump 22 in this state, the fuel pressure of the low pressure system is larger than the target fuel pressure value. May be maintained over a long period of time. For this reason, when fuel injection from the port injection valve 27 is executed in such a state, the state in which the fuel injection amount of the port injection valve 27 deviates from the required injection amount may be maintained for a long period of time. is there.

  Therefore, the ECU 5 executes the low pressure system pressure reduction control when the above-described high pressure system pressure reduction control is executed. Specifically, when the high pressure system pressure reduction control is executed, fuel injection is executed from at least one of the port injection valve 27 and the in-cylinder injection valve 37 in a state where the power supply to the low pressure pump 22 is stopped. Thereby, only the part for which the fuel pressure of the low pressure system rose by high pressure system pressure reduction control is reduced.

  Next, decompression control will be described. FIG. 2 is a flowchart showing an example of the pressure reduction control executed by the ECU 5. The ECU 5 repeatedly executes the pressure reduction control every predetermined time.

  First, the ECU 5 determines whether or not the above-described high-pressure system pressure reduction request is present (step S1). In the case of normal control when there is no high pressure system pressure reduction request, the ECU 5 ends this control. During normal control, as described above, the rotational speed of the low-pressure pump 22 is controlled so that the low-pressure fuel pressure becomes the target fuel pressure value, and the detected value of the fuel pressure sensor 38 becomes high so that the detected value of the high-pressure system becomes the target fuel pressure value. The suction valve 50 of the pump 40 is controlled.

  On the other hand, when there is a high pressure system pressure reduction request, the ECU 5 executes high pressure system pressure reduction control (step S2). The process of step S2 is a high-pressure system control for reducing the pressure in the high-pressure system by opening the relief valve 83 and releasing the fuel in the high-pressure system into the low-pressure system when there is a request for depressurization in the high-pressure system. It is an example of the process which a part performs.

  After the high pressure system pressure reduction control is executed, the ECU 5 executes the low pressure system pressure reduction control (step S3). The process of step S3 is performed by stopping energization of the low pressure pump 22 while injecting fuel from at least one of the port injection valve 27 and the in-cylinder injection valve 37 when pressure reduction in the high pressure system is executed. It is an example of the process which the low voltage | pressure system control part which pressure-reduces the inside of a system performs.

First, the high pressure system pressure reduction control will be described in detail. FIG. 3 is a flowchart showing an example of the high-pressure system pressure reduction control executed by the ECU 5. First, the ECU 5 calculates a high pressure system pressure reduction amount ΔP _h [Pa], which is a pressure reduction amount required for the high pressure system, based on the following equation (step S11).
ΔP _h = P _h −P _th (1)

Here, P _h [Pa] is a fuel pressure value of the high pressure system, and is a detected value of the fuel pressure sensor 38. P _th [Pa] is a target fuel pressure value of the high-pressure system.

Next, the ECU 5 calculates the required fuel release amount ΔV _h [mL] required for reducing the fuel pressure of the high pressure system by the calculated high pressure system pressure reduction amount ΔPh based on the following equation. (Step S13).
ΔV _h = ΔP _h × (V _h / K) (2)

V _h [mL] is the internal volume of the high-pressure system, and is stored in the ROM of the ECU 5 in advance. K [Pa] is the bulk modulus of the fuel. The volume elastic modulus of the fuel is acquired based on, for example, a map indicating the volume elastic modulus corresponding to the property of the fuel specified by a sensor that detects the property of the fuel in the ROM of the ECU 5 in advance. .

Next, the ECU 5 calculates a target valve opening period τ _er [ms] of the relief valve 83 necessary for releasing the fuel from the high pressure system by the calculated required release amount ΔV _h based on the following equation (step) S15).
τ _er = ΔV _h / Q _er (3)

Q _er [mL / ms] is the flow rate of the fuel flowing through the relief passage 81 when the relief valve 83 is opened, and is based on a map or expression corresponding to the fuel pressure difference between the high pressure system and the low pressure system. Calculated. The larger the fuel pressure difference, the larger Q _er is calculated. Specifically, the fuel pressure difference between the high pressure system and the low pressure system is the difference between the detected value of the fuel pressure sensor 38 and the target fuel pressure value of the low pressure system immediately before the relief valve 83 is opened. Q _er may be a fixed value acquired in advance through experiments.

Next, the ECU 5 opens the relief valve 83 (step S17), and determines whether or not the period that has elapsed since the relief valve 83 was opened has exceeded the target valve opening period _ter (step S19). . If the determination is negative, the ECU 5 keeps the relief valve 83 open, and if the determination is affirmative, the ECU 5 closes the relief valve 83 (step S21). Thereby, the fuel pressure of the high pressure system is reduced to the target fuel pressure, and the fuel injection amount of the in-cylinder injection valve 37 can be appropriately controlled.

Next, the low pressure system pressure reduction control will be described in detail. FIG. 4 is a flowchart showing an example of the low-pressure system pressure reduction control executed by the ECU 5. The ECU 5 considers that the fuel has been released from the high pressure system to the low pressure system by the calculated required release amount ΔV _h , and the low pressure system increase pressure amount ΔP that is the amount of increase in the low pressure fuel pressure after the fuel is released. _lu [Pa] is calculated based on the following equation (step S31).
ΔP _lu = K × (ΔV _h / V _l ) (4)
V _l [mL] is the internal volume of the low-pressure system, and is stored in advance in the ROM of the ECU 5.

Next, the ECU 5 calculates the low pressure system pressure reduction amount ΔP _ld [Pa] required for the low pressure system after the fuel is discharged from the high pressure system to the low pressure system by the required release amount ΔV _h based on the following formula. (Step S33).
ΔP _ld = P _l + ΔP _lu −P _tl (5)

P ₁ [Pa] is a target fuel pressure value of the low pressure system immediately before the relief valve 83 is opened, and is acquired by a map determined according to the rotation speed of the low pressure pump 22. Therefore, (P ₁ + ΔP _lu ) indicates the fuel pressure of the low pressure system after the fuel having the required release amount ΔV _h is released from the high pressure system to the low pressure system. P _tl [Pa] is a target fuel pressure value of the low pressure system at the present time, and is set based on the rotational speed of the engine 10 and the fuel temperature as described above.

Next, the ECU 5 calculates the required fuel consumption ΔV ₁ [mL] required to reduce the low-pressure fuel pressure by the low-pressure reduction pressure ΔP _ld based on the following equation (step S35).
ΔV _l = ΔP _ld × (V _l / K) (6)

  The processing of steps S31 to S35 is a necessary consumption for calculating the necessary consumption of fuel necessary for lowering the low-pressure fuel pressure after the high-pressure fuel is released to the low-pressure system to the target fuel pressure. It is an example of the process which a quantity calculation part performs.

Next, the ECU 5 determines whether or not the fuel is being cut (step S37). If the determination is affirmative, the process of step S37 is executed again. The purpose of the process in step S37 will be described later. In the case of negative determination, the ECU 5 determines a period required for injecting the necessary consumption amount ΔV ₁ from at least one of the port injection valve 27 and the in-cylinder injection valve 37 for a target stop period t during which the energization to the low-pressure pump 22 is stopped. [Ms] is calculated (Steps S39a, S39b, S41a to S41c). Specifically, the target stop period t is calculated according to the presence or absence of fuel injection from the port injection valve 27 and the in-cylinder injection valve 37 as follows. Specifically, the following processing is executed.

The ECU 5 determines whether or not the fuel is injected only from the port injection valve 27 (step S39a). If the determination is affirmative, the low-pressure fuel pressure system is lowered by the injection amount from the port injection valve 27. Therefore, the target stop period t is calculated based on the following formula (step S41a).
t = ΔV ₁ / {Q _pfi × τ _pfi × (Ne / 2) × #} (7)

Q _pfi [mL / ms] is the amount of fuel that each port injection valve 27 injects per millisecond at a predetermined fuel pressure, and is a fixed value determined by the design of each port injection valve 27, and is stored in advance in the ROM of the ECU 5. It is remembered. Further, τ _pfi [ms] is a valve opening period of each port injection valve 27, and indicates a required injection amount to each port injection valve 27 per fuel cycle determined according to the rotation speed and load of the engine 10. , Q _pfi . Therefore, (Q _pfi × τ _pfi ) can calculate the required injection amount of each port injection valve 27 per combustion cycle.

Ne [ms ⁻¹ ] is the rotational speed of the crankshaft 14 per millisecond and can be detected by the crank angle sensor 14a. Here, one combustion cycle is completed while the crankshaft 14 rotates twice. Therefore, (Ne / 2) corresponds to the number of combustion cycles per millisecond. Accordingly, {Q _pfi × τ _pfi × (Ne / 2)} corresponds to the required injection amount of each port injection valve 27 per millisecond.

# [−] Is the number of cylinders of the engine 10, in other words, the number of the port injection valves 27 provided, and is stored in advance in the ROM of the ECU 5. Therefore, {Q _pfi × τ _pfi × (Ne / 2) × #} can be calculated as the sum of the required injection amounts of all the port injection valves 27 per millisecond. As a result, the period required to consume the required consumption amount ΔV ₁ by the injection of the port injection valve 27 can be calculated by the equation (7), and this period is the target stop period t during which the energization to the low-pressure pump 22 is stopped. Is calculated as

If the determination in step S39a is negative, the ECU 5 determines whether fuel is being injected only from the in-cylinder injection valve 37 (step S39b). If the determination is affirmative, injection from the in-cylinder injection valve 37 is performed. The target stop period t is calculated based on the following equation, assuming that the amount of fuel is discharged from the low pressure system through the intake valve 50 to the high pressure system and the fuel pressure of the low pressure system decreases (step S41b).
t = ΔV ₁ / {Q _di × τ _di × (Ne / 2) × #} (8)

Q _di [mL / ms] is the amount of fuel that each in-cylinder injection valve 37 injects per millisecond at a predetermined fuel pressure, and is a fixed value determined by the design of each in-cylinder injection valve 37. Is stored in advance. Further, τ _di [ms] is a valve opening period of each in-cylinder injection valve 37, and the required injection to each in-cylinder injection valve 37 per one fuel cycle determined according to the rotation speed and load of the engine 10. the amount _is a value obtained by dividing the _{Q di.} Therefore, (Q _di × τ _di ) can calculate the required injection amount of each in-cylinder injection valve 37 per combustion cycle.

Similarly to the case of the port injection valve 27, {Q _di × τ _di × (Ne / 2) × #} is calculated as the sum of the required injection amounts of all the in-cylinder injection valves 37 per millisecond. it can. Therefore, the period required to consume the necessary consumption amount ΔV ₁ by the injection of the in-cylinder injection valve 37 can be calculated by the equation (8), and this period is the target stop period t during which the energization to the low-pressure pump 22 is stopped. Is calculated as

When a negative determination is made in step S39b, the ECU 5 considers that fuel is being injected from both the port injection valve 27 and the in-cylinder injection valve 37, and calculates the target stop period t based on the following equation ( Step S41c).
t = ΔV ₁ / {(Q _pfi × τ _pfi + Q _di × τ _di ) × (Ne / 2) × #} (9)

The _sum of the required injection amount of each port injection valve 27 and the required injection amount of each in-cylinder injection valve 37 in one combustion cycle can be calculated by (Q _pfi × τ _pfi + Q _di × τ _di ). Therefore, {(Q _pfi × τ _pfi + Q _di × τ _di ) × (Ne / 2) × #} represents the required injection amount of all the port injection valves 27 and in-cylinder injection valves 37 per millisecond. The total can be calculated. Therefore, the period required to consume the required consumption amount ΔV ₁ by the injection of the port injection valve 27 and the in-cylinder injection valve 37 can be calculated by the equation (9), and the energization to the low-pressure pump 22 is stopped during this period. Is calculated as a target stop period t.

  As described above, in order to depressurize the low pressure system, not only the fuel injection amount from the port injection valve 27 to which fuel is supplied from the low pressure system but also the fuel from the in-cylinder injection valve 37 to which fuel is supplied from the high pressure system. The target stop period t of the low-pressure pump 22 is calculated in consideration of the injection amount. This is because the fuel in the high-pressure system is also supplied from the low-pressure system, so that the fuel in the high-pressure system is reduced by the same amount as the fuel in the high-pressure system is consumed by the in-cylinder injection valve 37.

  In the processing of steps S41a to 41c, the low-pressure pump 22 is energized during a period required to consume the calculated amount of fuel consumed by at least one of the port injection valve 27 and the in-cylinder injection valve 37. It is an example of the process which the target stop period calculation part which calculates as the target stop period t which is the target period when is stopped is performed.

  Next, the ECU 5 stops energization of the low-pressure pump 22 (step S43), and determines whether or not the actual stop period counted after stopping energization of the low-pressure pump 22 has reached the target stop period (step S43). S45). In the case of a negative determination, the ECU 5 continues to stop energizing the low-pressure pump 22. As a result, energization of the low-pressure pump 22 is stopped while fuel is injected from at least one of the port injection valve 27 and the in-cylinder injection valve 37. If the determination in step S45 is affirmative, the ECU 5 resumes energization of the low pressure pump 22 to operate the low pressure pump 22 (step S47).

  FIG. 5 is a graph showing changes in the fuel pressure in the low-pressure system when the low-pressure system pressure reduction control is executed after the high-pressure system pressure reduction control is executed and when it is not executed. The vertical axis represents the fuel pressure in the low-pressure system, and the horizontal axis represents time. A curve P indicates the fuel pressure in the low pressure system when the low pressure system pressure reduction control is executed, and a curve Px indicates the fuel pressure in the low pressure system when the low pressure system pressure reduction control is not executed.

  When the low pressure system pressure reduction control is not executed, the rotational speed of the low pressure pump 22 does not change even after the relief valve 83 is closed. As described above, the target rotational speed of the low-pressure pump 22 is set according to the target fuel pressure value of the low-pressure system, and the target fuel pressure value of the low-pressure system is calculated by a map or mathematical formula corresponding to the rotational speed of the engine 10 and the fuel temperature. This is because the actual fuel pressure value of the low pressure system is not considered. For this reason, once the fuel pressure in the low-pressure system greatly increases, the fuel pressure in the low-pressure system may be kept high for a long period of time.

  In the case of this embodiment, while consuming fuel by fuel injection, the energization to the low-pressure pump 22 is stopped to reduce the rotational speed, and the amount of fuel discharged from the low-pressure pump 22 into the low-pressure system is reduced. Yes. As a result, the fuel pressure of the low pressure system that has been raised by the high pressure system pressure reduction control can be reduced early. Therefore, the fuel pressure of the low pressure system can be quickly restored to the fuel pressure before the high pressure system pressure reduction control is executed, and the fuel injection amount from the port injection valve 27 and the like thereafter can be appropriately controlled.

Further, the period required to consume the fuel by the necessary consumption amount ΔV ₁ required for decompression in the low-pressure system is calculated as the target stop period for energizing the low-pressure pump 22. For this reason, it is suppressed that the stop period of energization to the low-pressure pump 22 is prolonged and the fuel pressure of the low-pressure system is greatly reduced from the target fuel pressure. This also makes it possible to appropriately control the fuel injection amount from the port injection valve 27 and the like after the end of the low pressure system pressure reduction control.

In the present embodiment, the low pressure system pressure reduction control is executed after the high pressure system pressure reduction control ends, but the present invention is not limited to this. For example, the processing after step S13 of the high pressure system decompression control and the processing of steps S31 to S35 of the low pressure system decompression control may be performed simultaneously. This is because the processing in steps S31 to S35 can be performed based on the required release amount ΔV _h calculated in step S13 of the high pressure system pressure reduction control. As a result, immediately after the high-pressure system pressure reduction control is completed, the processing after step S37 can be immediately executed to depressurize the low-pressure system at an early stage.

  In step S37, it is determined whether or not the fuel is being cut. Only when the fuel is not being cut, the target stop period for energization of the low-pressure pump 22 is calculated. This is because energization of the low-pressure pump 22 has already been stopped during the fuel cut in order to suppress an excessive increase in fuel pressure. Therefore, for example, when the fuel cut is restored after it is determined in step S37 that the fuel cut is in progress, the ECU 5 continues to stop energization of the low-pressure pump 22 after the fuel cut is restored and the fuel cut is performed. The energization of the low-pressure pump 22 is stopped so that the stop period after returning from is the calculated target stop period.

In the above-described high pressure system pressure reduction control, the target valve opening period τ _er of the relief valve 83 is calculated. However, the detected value of the fuel pressure sensor 38 is high after the relief valve 83 is opened without calculating the target valve opening period τ _er. The relief valve 83 may be closed when the target fuel pressure value of the system drops. In this case, the ECU 5 counts the actual valve opening period τ _er ′ of the relief valve 83, and calculates the required release amount ΔV _h released from the high pressure system to the low pressure system based on the following equation.
ΔV _h = τ _{er ′} × Q _er (10)

Q _er [mL / ms] is the flow rate of the fuel flowing through the relief passage 81 when the relief valve 83 is opened as described above. Using the required release amount ΔV _h calculated in this way, the processing after step S31 in the low pressure system pressure reduction control may be executed.

  Next, a first modification of the above-described embodiment will be described. In addition, the overlapping description is abbreviate | omitted by attaching | subjecting the code | symbol same as the Example mentioned above. FIG. 6 is a schematic configuration diagram of the control device 1a of the first modification.

  In the control device 1a in the first modified example, a fuel pressure sensor 28 for detecting the fuel pressure in the low pressure delivery pipe 26 of the engine 10a is provided. The ECU 5 acquires the detection value of the fuel pressure sensor 28 and controls the stop period of the low-pressure pump 22 based on the detection value of the fuel pressure sensor 28.

  FIG. 7 is a flowchart showing an example of the low-pressure system pressure reduction control executed by the ECU 5a in the first modification. In the first modified example, the high-pressure system pressure reduction control is the same as that in the above-described embodiment, and thus the description thereof is omitted.

  When the high pressure system pressure reduction control is completed, the ECU 5 stops energization to the low pressure pump 22 (step S43), and determines whether or not the detected value of the fuel pressure sensor 28 has decreased to the target fuel pressure value of the low pressure system (step S43). S45a). If the determination is negative, the energization of the low-pressure pump 22 is stopped. If the determination is affirmative, the energization to the low-pressure pump 22 is resumed (step S47).

  Also by the above, the fuel pressure of the low pressure system raised by the high pressure system pressure reduction control can be reduced early. In addition, when the detection value of the fuel pressure sensor 28 is lowered to the target fuel pressure value of the low pressure system, the energization to the low pressure pump 22 is resumed, so that it is not necessary to calculate the target stop period t of the low pressure pump 22, and the ECU 5a Processing load is reduced. Further, since it is not necessary to calculate the target stop period t of the low-pressure pump 22, the energization of the low-pressure pump 22 may be stopped immediately after the relief valve 83 is closed. As a result, the low-pressure fuel pressure can be reduced early.

  FIG. 8 is a schematic explanatory diagram of a control device 1b according to a second modification. In the second modification, instead of the relief passage 81 provided outside the high-pressure pump 40, a relief passage 48 provided in the high-pressure pump 40b and a relief branch connected to the relief passage 48 and communicating with the low-pressure pipe 25 are provided. The discharge passage 47 and the low pressure pipe 25 communicate with each other by the pipe 25b. The relief passage 48 branches off from the discharge passage 47 on the downstream side of the discharge valve 60. The relief branch pipe 25b branches from the low pressure pipe 25 on the downstream side of the position where the branch pipe 25a branches from the low pressure pipe 25. The relief valve 83 is provided in the high-pressure pump 40b to open and close the relief passage 48. With such a configuration, the fuel may be discharged from the high pressure system in the high pressure pump 40b to the low pressure system outside the high pressure pump 40b.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 1 Fuel pressure control apparatus of internal combustion engine 5 ECU (High pressure system control part, Low pressure system control part, Required consumption calculation part, Target stop period calculation part)
10 Engine (Internal combustion engine)
15 Camshaft 21 Fuel tank 22 Low pressure pump 25 Low pressure pipe (low pressure passage)
25a Branch pipe (low pressure passage)
26 Low pressure delivery pipe (low pressure passage)
27 Port injection valve 28, 38 Fuel pressure sensor 35 High pressure pipe (high pressure passage)
36 High pressure delivery pipe (high pressure passage)
37 In-cylinder injection valve 40 High-pressure pump 50 Suction valve 60 Discharge valve 81 Relief passage 83 Relief valve CP cam

Claims (4)

A fuel pressure control device for an internal combustion engine comprising a port injection valve for injecting fuel into an intake port and an in-cylinder injection valve for injecting fuel into a cylinder,
A fuel tank storing fuel;
A low pressure pump for sucking fuel from the fuel tank;
A low pressure passage through which fuel is discharged from the low pressure pump to supply fuel to the port injection valve;
A high pressure pump for pressurizing fuel supplied from the low pressure passage;
A high-pressure passage through which fuel is discharged from the high-pressure pump and supplies fuel to the in-cylinder injection valve;
A relief passage communicating the high-pressure passage and the low-pressure passage;
An electromagnetic relief valve for opening and closing the relief passage;
A high-pressure system controller that depressurizes the inside of the high-pressure passage by opening the relief valve and releasing the fuel in the high-pressure passage into the low-pressure passage when there is a request for decompression in the high-pressure passage; ,
When the pressure in the high pressure passage is reduced, the pressure in the low pressure passage is reduced by stopping energization of the low pressure pump while injecting fuel from at least one of the port injection valve and the in-cylinder injection valve. A fuel pressure control device for an internal combustion engine, comprising: a low-pressure system control unit. The low-pressure system controller is
Calculation of required consumption for calculating the required consumption of fuel required to lower the fuel pressure in the low-pressure passage after the fuel in the high-pressure passage is released by discharging into the low-pressure passage to the target fuel pressure And
The period required to consume the calculated amount of fuel consumed by at least one of the port injection valve and the in-cylinder injection valve is a target period during which energization of the low-pressure pump is stopped. A fuel pressure control device for an internal combustion engine according to claim 1, further comprising a target stop period calculation unit that calculates a target stop period. A fuel pressure sensor for detecting the fuel pressure in the low pressure passage;
2. The internal combustion engine according to claim 1, wherein the low-pressure system control unit continues to stop energization of the low-pressure pump until the detection value of the fuel pressure sensor decreases to a target fuel pressure value after the energization of the low-pressure pump is stopped. Fuel pressure control device. The low-pressure passage includes a main passage communicated from the low-pressure pump to the port injection valve, and a branch passage branched from the main passage and communicated with the high-pressure pump,
The fuel pressure control device for an internal combustion engine according to any one of claims 1 to 3, wherein the relief passage communicates the high-pressure passage and the main passage.

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