Fuel supply system

Abstract

The objective of this invention is to provide a fuel supply system capable of appropriately controlling the discharge flow rate of fuel from a supply pump. A fuel supply system includes: a supply pump for discharging fuel from a fuel tank to a low-pressure line; an intake manifold injection valve for supplying fuel to an engine from the low-pressure line; a pressure regulator for adjusting the fuel pressure of the fuel discharged to the low-pressure line by causing a portion of the fuel discharged to the low-pressure line to flow back to the fuel tank, so as to ensure that the fuel pressure does not exceed a constant fuel pressure; and a control device that performs feedforward control of the fuel discharge flow rate of the supply pump using a feedforward term, instead of performing feedback control based on the actual fuel pressure supplied to the intake manifold injection valve.

Description

Technical Field

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

[0002] There are fuel supply systems that have a supply pump that discharges fuel to the engine but do not have a fuel pressure sensor for detecting the fuel pressure supplied to the fuel injection valve (for example, see Patent Document 1).

[0003] Patent Document 1: Japanese Patent Application Publication No. 2005-330907 Summary of the Invention

[0004] Because a fuel pressure sensor is not installed, it is impossible to control the fuel discharge flow rate of the supply pump, for example, by feedback control based on the actual fuel pressure supplied to the intake manifold injection valve. Therefore, it is possible that the fuel discharge flow rate of the supply pump cannot be properly controlled.

[0005] Therefore, the object of the present invention is to provide a fuel supply system capable of appropriately controlling the discharge flow rate of fuel from the supply pump.

[0006] The aforementioned objective can be achieved by a fuel supply system comprising: a supply pump that discharges fuel from a fuel tank to a low-pressure line; an intake manifold injection valve for supplying fuel from the low-pressure line; a pressure regulator that adjusts the fuel pressure of the fuel discharged to the low-pressure line by causing a portion of the fuel discharged to the low-pressure line to flow back to the fuel tank, so as to ensure that the fuel pressure does not exceed a constant fuel pressure; and a control device that, instead of performing feedback control based on the actual fuel pressure supplied to the intake manifold injection valve, performs feedforward control of the fuel discharge flow rate of the supply pump using a feedforward term, the control device calculating based on the required injection quantity of the intake manifold injection valve. The feedforward term is calculated using the basic discharge flow rate, the fuel draw-delay flow rate corresponding to the insufficient fuel discharge amount corresponding to the draw-delay time, the annual variation reduction flow rate of the supply pump, and the fuel leakage flow rate from the pressure regulator to the fuel tank. The draw-delay time is the time from when the speed command value of the supply pump is increased until the discharge flow rate from the supply pump becomes the discharge flow rate corresponding to the increased speed command value. The control device calculates the draw-delay flow rate to a larger value when the increase rate of the basic discharge flow rate is greater, and calculates the annual variation reduction flow rate and the leakage flow rate to predetermined fixed values.

[0007] Invention Effects

[0008] A fuel supply system is provided that can appropriately control the discharge flow rate of fuel supplied to the pump. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the structure of a hybrid vehicle.

[0010] Figure 2 This is a schematic diagram of the fuel supply system.

[0011] Figure 3 This is a flowchart illustrating the discharge flow control of the supply pump. Detailed Implementation

[0012] [Brief Structure of Hybrid Vehicles]

[0013] Figure 1 This is a schematic structural diagram of a hybrid vehicle 1. The hybrid vehicle 1 includes: an engine 10; a first motor 61; a second motor 62; a power distribution mechanism 63; a transmission mechanism 64; drive wheels 70; a PCU 80; a battery 90; and an Electronic Control Unit (ECU) 100. The engine 10, the first motor 61, and the second motor 62 are equipped as the driving source for the hybrid vehicle 1.

[0014] The first motor 61 and the second motor 62 are connected to the battery 90 via the PCU 80. The first motor 61 and the second motor 62 function as motors that generate driving force for the vehicle based on power supplied from the battery 90. Furthermore, the first motor 61 and the second motor 62 also function as generators that produce electricity by generating regenerative power to charge the battery 90 based on power transmitted from the engine 10 or the drive wheels 70. The power supplied between the first motor 61 and the second motor 62 and the battery 90 is adjusted by the PCU 80. The PCU 80 is controlled by the ECU 100. The PCU 80 converts DC voltage from the battery 90 to AC voltage, or converts AC voltage from the first motor 61 or the second motor 62 to DC voltage.

[0015] The power distribution mechanism 63 mechanically connects the crankshaft of the engine 10, the rotating shaft of the first motor 61, and the output shaft of the power distribution mechanism 63. The power distribution mechanism 63 is, for example, a planetary gear mechanism comprising a sun gear, a planet carrier, a pinion, and a ring gear. The output shaft of the power distribution mechanism 63 is connected to the transmission mechanism 64. Furthermore, the rotating shaft of the second motor 62 is also connected to the transmission mechanism 64. Through the transmission mechanism 64, the driving force of the engine 10 or each of the first motor 61 and the second motor 62 is transmitted to the drive wheels 70.

[0016] ECU100 is an electronic control unit that includes arithmetic processing circuits for various calculations involved in vehicle driving control and a memory storing control programs or data. ECU100 is an example of a control device.

[0017] In ECU 100, vehicle speed sensor 101, crankshaft angle sensor 102, and coolant temperature sensor 103 are electrically connected. Vehicle speed sensor 101 detects the driving speed of hybrid vehicle 1. Crankshaft angle sensor 102 detects the engine speed. Coolant temperature sensor 103 detects the temperature of the coolant cooling engine 10.

[0018] [Brief Structure of the Fuel Supply System]

[0019] Figure 2 This is a schematic diagram of the fuel supply system A. The fuel supply system A includes a fuel tank 21, a supply pump 22, a pressure regulator 23, a branch pipe 24, a low-pressure pipe 25, a low-pressure delivery pipe 26, a high-pressure delivery pipe 36, a fuel pressure sensor 38, and a high-pressure fuel pump 40.

[0020] Engine 10 is a spark-ignition four-cylinder gasoline engine equipped with in-cylinder injection valves 37 that inject fuel into each intake port and intake manifold injection valves 27 that inject fuel into each intake passage. Furthermore, engine 10 is equipped with a camshaft 15 that drives the intake valves or exhaust valves in conjunction with the crankshaft.

[0021] Fuel tank 21 stores fuel. Supply pump 22 pressurizes the fuel in fuel tank 21 and discharges it to low-pressure line 25. A portion of the fuel discharged to low-pressure line 25 is supplied to intake manifold injection valve 27 via low-pressure distribution line 26. Thus, supply pump 22 discharges fuel to engine 10. Furthermore, the remaining portion of the fuel discharged to low-pressure line 25 is also supplied to high-pressure fuel pump 40 via high-pressure line 25a, which branches off from low-pressure line 25. High-pressure fuel pump 40 pressurizes the fuel supplied from branch line 25a and discharges it to high-pressure distribution line 36. The fuel pressurized by high-pressure fuel pump 40 is supplied to cylinder injection valve 37 via high-pressure delivery line 36.

[0022] A branch pipe 24, which branches out into the fuel tank 21, is connected to the low-pressure pipe 25. A pressure regulator 23 is provided on the branch pipe 24. The pressure regulator 23 adjusts the fuel pressure of the discharged fuel by causing a portion of the fuel discharged by the supply pump 22 into the low-pressure pipe 25 to flow back into the fuel tank 21, so that it does not exceed a constant fuel pressure (e.g., 530 kPa).

[0023] Fuel pressure sensor 38 detects the fuel pressure within the high-pressure delivery pipe 36. ECU 100 acquires the detection value from fuel pressure sensor 38.

[0024] The ECU 100 adjusts the intake manifold injection rate and the in-cylinder injection rate according to the operating range of the engine 10. The intake manifold injection rate is the ratio of the total fuel injection quantity from the intake manifold injection valve 27 and the in-cylinder injection valve 37 to the fuel injection quantity from the intake manifold injection valve 27. The in-cylinder injection rate is the ratio of the fuel injection quantity from the in-cylinder injection valve 37 to the total fuel injection quantity.

[0025] The high-pressure fuel pump 40 includes a cylinder 41, a plunger 42, a pressurization chamber 43, an intake passage 45, an exhaust passage 47, a pressure relief passage 49, an intake valve 50, an exhaust valve 47a, and a pressure relief valve 49a. The plunger 42 moves up and down within the cylinder 41 by the rotation of a cam CP that rotates together with the camshaft 15. The volume of the pressurization chamber 43 increases or decreases by the movement of the plunger 42. The pressurization chamber 43 is defined by the cylinder 41 and the plunger 42.

[0026] The intake passage 45 connects the high-pressure pipe 25a, which branches off from the low-pressure pipe 25, to the pressurization chamber 43. A pulsation damper 44 is provided in the intake passage 45 to suppress fuel pressure pulsation.

[0027] The pressure relief passage 49 connects the pressurization chamber 43 and the high-pressure distribution pipe 36. The discharge passage 47 bypasses the pressure relief valve 49a and connects to the pressure relief passage 49. The discharge valve 47a allows the flow of fuel in the discharge passage 47 from the pressurization chamber 43 side to the high-pressure delivery pipe 36 side, but restricts the flow in the opposite direction. The pressure relief valve 49a allows the flow of fuel in the pressure relief passage 49 from the high-pressure delivery pipe 36 side to the pressurization chamber 43 side, but restricts the flow in the opposite direction.

[0028] The intake valve 50 is a solenoid valve controlled by the ECU 100. When the intake valve 50 opens, the plunger 42 descends, and fuel is filled from the high-pressure pipe 25a into the pressurization chamber 43 via the intake passage 45. Then, the intake valve 50 closes, the plunger 42 rises, and the fuel in the pressurization chamber 43 is pressurized. Next, when the force of the fuel pressure acting on the discharge valve 47a from the pressurization chamber 43 side exceeds a predetermined pressure, the discharge valve 47a opens, and the pressurized fuel is supplied to the high-pressure delivery pipe 36. The pressure relief valve 49a opens if the fuel pressure in the high-pressure delivery pipe 36 rises excessively.

[0029] [Discharge flow control of the supply pump]

[0030] The discharge flow control of the supply pump 22 is explained. Figure 3 This is a flowchart illustrating the discharge flow control of the supply pump performed by ECU 100. This control is executed repeatedly. ECU 100 obtains the required injection quantity of the intake manifold injection valve 27 (step S1). The required injection quantity of the intake manifold injection valve 27 is calculated as an amount that increases with the required torque to the engine 10.

[0031] Next, ECU100 calculates the target discharge flow rate of supply pump 22 based on the required injection quantity of intake manifold injection valve 27 (step S2). The detailed calculation method for the target discharge flow rate will be described later.

[0032] Next, ECU100 controls the rotational speed of supply pump 22 so that the discharge flow rate of supply pump 22 becomes the target discharge flow rate (step S3). In this way, the discharge flow rate of supply pump 22 is controlled to the target discharge flow rate.

[0033] [Method for calculating target discharge flow rate]

[0034] The target discharge flow rate is calculated using the following formula.

[0035] Target discharge flow rate = FF term

[0036] The details of the FF (feedforward) term will be described later, but it is mainly calculated as the amount that increases as the required torque to engine 10 increases. In the control of the discharge flow rate of the supply pump 22, feedback control based on the deviation obtained by subtracting the actual fuel pressure from the target fuel pressure, which is the fuel pressure supplied to the intake manifold injection valve 27, is not used. This is because a fuel pressure sensor for detecting the actual fuel pressure supplied to the intake manifold injection valve 27 is not provided. Therefore, manufacturing costs are suppressed.

[0037] ECU100 calculates the FF term at specified time intervals according to the following formula.

[0038] FF = Basic discharge flow + Extraction delay flow + Annual variation decrease in flow + P / R leakage flow

[0039] The basic discharge flow rate is calculated based on the required injection volume of the intake manifold injection valve 27. The calculation shows that the larger the required injection volume, the larger the basic discharge flow rate will be.

[0040] The draw-delay flow rate is the flow rate corresponding to the insufficient fuel discharge amount corresponding to the draw-delay time, which is the time from the start of the increase in the speed command value of the supply pump 22 until the discharge flow rate from the supply pump 22 becomes the discharge flow rate corresponding to the increased speed command value. The aforementioned insufficient discharge amount is obtained by subtracting the increase in discharge amount during the draw-delay time when the draw-delay occurs from the ideal increase in discharge amount corresponding to the draw-delay time when the draw-delay does not occur. When the basic discharge flow rate is less than a specified value, the draw-delay is approximately not generated, and the draw-delay flow rate is considered to be zero. When the basic discharge flow rate is above the specified value, the draw-delay flow rate is calculated as a value other than zero. Furthermore, when the basic discharge flow rate is above the specified value, the greater the increase rate of the basic discharge flow rate, the larger the calculated draw-delay flow rate. This is because the greater the increase in the basic discharge flow rate per unit time, the greater the draw-delay flow rate. The ECU 100 calculates the draw-delay flow rate at specified time intervals based on the increase rate of the basic discharge flow rate through a specified mapping or formula.

[0041] The annualized decrease in flow rate is the reduction in discharge flow rate due to the annual variation of the supply pump 22. This annualized decrease in flow rate is set to a fixed value based on experimental or simulation results. Here, when the supply pump 22 is not subject to annual variation, the FF term is calculated as larger by summing the annualized decrease in flow rate. However, given the inherent function of the pressure regulator 23, which prevents excessive increases in fuel pressure within the low-pressure line 25, a larger FF term is not a significant issue. Furthermore, from the viewpoint of ensuring that the discharge flow rate in the supply pump 22 does not perform feedback control, it is preferable to calculate a larger FF term rather than a smaller one.

[0042] The P / R leakage flow rate is the flow rate of fuel leaking from the pressure regulator 23 to the fuel tank 21. Here, the pressure regulator 23 returns a portion of the fuel in the low-pressure line 25 to the fuel tank 21 to prevent further rise in fuel pressure when the fuel pressure in the low-pressure line 25 has become constant. The aforementioned P / R leakage flow rate refers to the flow rate of fuel that is not returned to the fuel tank 21 by the pressure regulator 23 as intended, but rather the flow rate of fuel that accidentally leaks from the pressure regulator 23 to the fuel tank 21. The P / R leakage flow rate is set to a fixed value based on experimental or simulation results.

[0043] As described above, the FF term is calculated based on the basic discharge flow rate, the suction delay flow rate, the annual variation decrease flow rate, and the P / R leakage flow rate. Therefore, the discharge flow rate of the supply pump 22, which does not perform feedback control, can be appropriately controlled.

[0044] The fuel supply system A in the above embodiment is installed in the hybrid vehicle 1, but it is not limited to this and can also be installed in a vehicle that only has an engine as a driving power source.

[0045] 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.

[0046] Symbol Explanation

[0047] 1-Hybrid vehicle, A-Fuel supply system, 10-Engine, 22-Supply pump, 23-Pressure regulator, 27-Intake manifold injection valve, 100-ECU (Control Unit).

Claims

1. A fuel supply system, characterized in that, have: The supply pump discharges fuel from the fuel tank to the low-pressure line; The intake manifold injection valve of the engine that supplies fuel from the low-pressure pipe; A pressure regulator that adjusts the fuel pressure of the fuel discharged to the low-pressure line by causing a portion of the fuel discharged to the low-pressure line to flow back to the fuel tank, so that the fuel pressure does not exceed a constant fuel pressure. and The control device does not perform feedback control based on the actual fuel pressure supplied to the intake manifold injection valve, but instead uses a feedforward term to perform feedforward control on the fuel discharge flow rate of the supply pump. The control device calculates the feedforward term based on the basic discharge flow rate calculated from the required injection quantity of the intake manifold injection valve, the fuel draw-delay flow rate corresponding to the insufficient fuel discharge quantity with respect to the draw-delay time, the annual variation reduction flow rate of the supply pump, and the fuel leakage flow rate from the pressure regulator to the fuel tank. The draw-delay time is the time from when the speed command value of the supply pump is increased until the discharge flow rate from the supply pump becomes the discharge flow rate corresponding to the increased speed command value. The control device calculates the draw-delay flow rate to a larger value when the increase rate of the basic discharge flow rate is greater, and calculates the annual variation decrease flow rate and the leakage flow rate to a predetermined fixed value respectively.

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