Fuel supply system

Abstract

The objective is to provide a fuel supply system that can appropriately control the fuel discharge flow rate of a feed pump. [Solution] A fuel supply system comprising: a feed pump that discharges fuel from a fuel tank to a low-pressure pipe; a port injection valve of an engine to which fuel is supplied from the low-pressure pipe; a pressure regulator that adjusts the fuel pressure of the fuel discharged to the low-pressure pipe so as not to exceed a certain fuel pressure by returning a portion of the fuel discharged to the low-pressure pipe to the fuel tank; and a control device that performs feedforward control of the fuel discharge flow rate of the feed pump using a feedforward term without performing feedback control based on the actual fuel pressure supplied to the port injection valve.

Description

Technical Field

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

Background Art

[0002] There is a fuel supply system that includes a feed pump for discharging fuel to an engine and is not provided with a fuel pressure sensor for detecting the fuel pressure supplied to a fuel injection valve (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Since a fuel pressure sensor is not provided, for example, it is not possible to control the fuel discharge flow rate of the feed pump by feedback control based on the actual fuel pressure supplied to a port injection valve. Therefore, there is a risk that the fuel discharge flow rate of the feed pump cannot be appropriately controlled.

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

Means for Solving the Problems

[0006] The above objective is to provide a feed pump that discharges fuel from a fuel tank to a low-pressure pipe, a port injection valve of an engine to which fuel is supplied from the low-pressure pipe, a pressure regulator that adjusts the fuel pressure of the fuel discharged to the low-pressure pipe so as not to exceed a certain fuel pressure by returning a portion of the fuel discharged to the low-pressure pipe to the fuel tank, and a control device that performs feedforward control of the fuel discharge flow rate of the feed pump using a feedforward term without performing feedback control based on the actual fuel pressure supplied to the port injection valve, wherein the control device calculates a basic discharge flow rate based on the required injection amount of the port injection valve, This can be achieved by a fuel supply system in which the feedforward term is calculated based on the feedforward term calculated based on the fuel delay flow rate corresponding to the amount of fuel discharged for the shortfall corresponding to the delay time from when the rotational speed command value to the feed pump increases until the discharge flow rate from the feed pump becomes the discharge flow rate corresponding to the increased rotational speed command value, the decrease in flow rate due to aging of the feed pump, and the fuel leakage flow rate from the pressure regulator to the fuel tank, and the control device calculates the delay flow rate as a larger value the greater the rate of increase of the basic discharge flow rate, and calculates the decrease in flow rate due to aging and the leakage flow rate as predetermined fixed values. [Effects of the Invention]

[0007] This system provides a fuel supply system that can appropriately control the fuel discharge flow rate of a feed pump. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of a hybrid vehicle. [Figure 2] This is a schematic diagram of the fuel supply system. [Figure 3] This is a flowchart illustrating the discharge flow rate control of a feed pump. [Modes for carrying out the invention]

[0009] [Overall configuration of a hybrid vehicle] Figure 1 is a schematic diagram of the hybrid vehicle 1. The hybrid vehicle 1 includes an engine 10, a first motor 61, a second motor 62, a power split mechanism 63, a transmission mechanism 64, drive wheels 70, a PCU 80, a battery 90, and an ECU (Electronic Control Unit) 100. The engine 10, the first motor 61, and the second motor 62 are mounted as the drive sources for the hybrid vehicle 1.

[0010] 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 the driving force of the vehicle in response to power supplied from the battery 90. Furthermore, the first motor 61 and the second motor 62 also function as generators that generate regenerative power to charge the battery 90 in response to power transmission from the engine 10 and the drive wheels 70. The power exchanged between the first motor 61 and the second motor 62 and the battery 90 is regulated by the PCU 80. The PCU 80 is controlled by the ECU 100. The PCU 80 converts the DC voltage from the battery 90 to AC voltage, or converts the AC voltage from the first motor 61 or the second motor 62 to DC voltage.

[0011] The power split 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 split mechanism 63. The power split mechanism 63 is a planetary gear mechanism, for example, equipped with a sun gear, planetary carrier, pinion gear, and ring gear. The output shaft of the power split mechanism 63 is connected to the transmission mechanism 64. The rotating shaft of the second motor 62 is also connected to the transmission mechanism 64. The driving forces of the engine 10, the first motor 61, and the second motor 62 are transmitted to the drive wheels 70 via the transmission mechanism 64.

[0012] The ECU100 is an electronic control unit comprising an arithmetic processing circuit that performs various calculations related to vehicle driving control, and a memory that stores control programs and data. The ECU100 is an example of a control device.

[0013] The ECU 100 is electrically connected to a vehicle speed sensor 101, a crank angle sensor 102, and a water temperature sensor 103. The vehicle speed sensor 101 detects the driving speed of the hybrid vehicle 1. The crank angle sensor 102 detects the engine speed. The water temperature sensor 103 detects the temperature of the coolant that cools the engine 10.

[0014] [Outline configuration of the fuel supply system] Figure 2 is a schematic diagram of the fuel supply system A. The fuel supply system A includes a fuel tank 21, a feed 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.

[0015] Engine 10 is a spark-ignition type four-cylinder gasoline engine equipped with port injection valves 27 that inject fuel into each intake port and in-cylinder injection valves 37 that inject fuel into each cylinder. Engine 10 also includes a camshaft 15 that is linked to the crankshaft and drives the intake valve or exhaust valve.

[0016] The fuel tank 21 stores fuel. The feed pump 22 pressurizes the fuel in the fuel tank 21 and discharges it into the low-pressure pipe 25. A portion of the fuel discharged into the low-pressure pipe 25 is supplied to the port injection valve 27 via the low-pressure delivery pipe 26. In this way, the feed pump 22 discharges fuel to the engine 10. The remaining fuel discharged into the low-pressure pipe 25 is also supplied to the high-pressure fuel pump 40 via the high-pressure pipe 25a, which branches off from the low-pressure pipe 25. The high-pressure fuel pump 40 pressurizes the fuel supplied from the high-pressure pipe 25a and discharges it into the high-pressure delivery pipe 36. The fuel pressurized by the high-pressure fuel pump 40 is supplied to the in-cylinder injection valve 37 via the high-pressure delivery pipe 36.

[0017] A branch pipe 24 branched within the fuel tank 21 is connected to the low-pressure pipe 25. A pressure regulator 23 is provided in the branch pipe 24. The pressure regulator 23 adjusts the fuel pressure discharged by refluxing a part of the fuel discharged from the feed pump 22 in the low-pressure pipe 25 back to the fuel tank 21 so that the fuel pressure does not exceed a certain fuel pressure (for example, 530 Kpa).

[0018] The fuel pressure sensor 38 detects the fuel pressure in the high-pressure delivery pipe 36. The ECU 100 acquires the detected value of the fuel pressure sensor 38.

[0019] The ECU 100 changes the port injection rate and the in-cylinder injection rate according to the operating region of the engine 10. The port injection rate is the fuel injection ratio from the port injection valve 27 with respect to the total fuel injection amount from the port injection valve 27 and the in-cylinder injection valve 37. The in-cylinder injection rate is the ratio of the fuel injection amount from the in-cylinder injection valve 37 with respect to the total fuel injection amount.

[0020] The high-pressure fuel pump 40 includes a cylinder 41, a plunger 42, a pressurizing chamber 43, a suction passage 4, a discharge passage 47, a relief passage 49, a suction valve 50, a discharge valve 47a, and a relief valve 49a. The plunger 42 moves up and down in the cylinder 41 by the rotation of a cam CP that rotates together with the camshaft 15. The volume of the pressurizing chamber 43 increases and decreases due to the up and down movement of the plunger 42. The pressurizing chamber 43 is defined by the cylinder 41 and the plunger 42.

[0021] The suction passage 45 communicates the high-pressure pipe 25a branched from the low-pressure pipe 25 with the pressurizing chamber 43. A pulsation damper 44 for suppressing fuel pressure pulsation is provided in the suction passage 45. The relief passage 49 communicates the pressurizing chamber 43 with the high-pressure delivery pipe 36. The discharge passage 47 bypasses the relief valve 49a and communicates with the relief passage 49. The discharge valve 47a allows the flow of fuel from the pressurizing chamber 43 side to the high-pressure delivery pipe 36 side in the discharge passage 47 but regulates the reverse flow. The relief valve 49a allows the flow of fuel from the high-pressure delivery pipe 36 side to the pressurizing chamber 43 side in the relief passage 49 but regulates the reverse flow.

[0022] The intake valve 50 is a solenoid valve controlled by the ECU 100. When the intake valve 50 opens and the plunger 42 descends, fuel is filled into the pressurizing chamber 43 from the high-pressure pipe 25a through the intake passage 45. Next, when the intake valve 50 closes and the plunger 42 ascends, the fuel in the pressurizing chamber 43 is pressurized. Next, when the fuel pressure acting on the discharge valve 47a from the pressurizing chamber 43 side reaches a predetermined pressure or higher, the discharge valve 47a opens, and the pressurized fuel is supplied to the high-pressure delivery pipe 36. The relief valve 49a opens when the fuel pressure in the high-pressure delivery pipe 36 rises excessively.

[0023] [Discharge Flow Rate Control of Feed Pump] The discharge flow rate control of the feed pump 22 will be described. FIG. 3 is a flowchart illustrating the discharge flow rate control of the feed pump executed by the ECU 100. This control is repeatedly executed. The ECU 100 acquires the required injection amount of the port injection valve 27 (step S1). The required injection amount of the port injection valve 27 is calculated so as to increase as the required torque to the engine 10 increases.

[0024] Next, the ECU 100 calculates the target discharge flow rate of the feed pump 22 based on the required injection amount of the port injection valve 27 (step S2). The detailed calculation method of the target discharge flow rate will be described later.

[0025] Next, the ECU 100 controls the rotational speed of the feed pump 22 so that the discharge flow rate of the feed pump 22 becomes the target discharge flow rate (step S3). In this way, the discharge flow rate of the feed pump 22 is controlled to the target discharge flow rate.

[0026] [Calculation Method of Target Discharge Flow Rate] The target discharge flow rate is calculated based on the following formula. Target discharge flow rate = FF term The FF (feedforward) term, as will be explained in more detail later, is calculated to increase as the required torque to the engine 10 increases. Feedback control based on the deviation obtained by subtracting the actual fuel pressure from the target fuel pressure supplied to the port injection valve 27 is not used to control the discharge flow rate of the feed pump 22. This is because there is no fuel pressure sensor to detect the actual fuel pressure supplied to the port injection valve 27. As a result, manufacturing costs are kept down.

[0027] The ECU100 calculates the FF term at predetermined time intervals based on the following formula. FF term = Basic discharge flow rate + delayed pumping flow rate + aging-induced decrease in flow rate + P / R leakage flow rate The basic discharge flow rate is calculated based on the required injection volume of the port injection valve 27, and is calculated so that the basic discharge flow rate increases as the required injection volume increases.

[0028] The delayed pumping flow rate is the flow rate corresponding to the amount of fuel being discharged that is insufficient, corresponding to the delayed pumping time from when the rotational speed command value to the feed pump 22 increases until the discharge flow rate from the feed pump 22 reaches the discharge flow rate corresponding to the increased rotational speed command value. The amount of discharged insufficient mentioned above is obtained by subtracting the increase in discharge volume during the delayed pumping time when a delayed pumping occurs from the ideal increase in discharge volume corresponding to the delayed pumping time when no delayed pumping occurs. If the basic discharge flow rate is less than a predetermined value, a delayed pumping delay does not occur and the delayed pumping flow rate is considered to be zero. If the basic discharge flow rate is greater than or equal to the predetermined value, the delayed pumping flow rate is calculated to be a value other than zero. Furthermore, when the basic discharge flow rate is greater than or equal to the predetermined value, the larger the rate of increase in the basic discharge flow rate, the larger the delayed pumping flow rate will be calculated to be. This is because the greater the increase in the basic discharge flow rate per unit time, the greater the delayed pumping flow rate will also be. The ECU 100 calculates the delayed pumping flow rate at predetermined time intervals using a map or calculation formula defined based on the rate of increase of the basic discharge flow rate.

[0029] The aging-induced decrease in flow rate is the discharge flow rate that decreases due to the aging of the feed pump 22. The aging-induced decrease in flow rate is set to a predetermined fixed value based on experimental and simulation results. Here, when the feed pump 22 is not aging, the FF term is calculated to be higher due to the addition of the aging-induced decrease in flow rate. However, since the original function of the pressure regulator 23 prevents the fuel pressure in the low-pressure pipe 25 from becoming excessively high, there is little problem even if the FF term is calculated to be higher. Furthermore, it is preferable to calculate the FF term to be higher than it is preferable to calculate it to be lower, from the standpoint of ensuring the discharge flow rate of the feed pump 22 where feedback control is not performed.

[0030] The P / R leak rate is the amount 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 pipe 25 to the fuel tank 21 in order to suppress any further increase in fuel pressure once the fuel pressure in the low-pressure pipe 25 reaches a certain level. The P / R leak rate mentioned above is not the amount of fuel returned to the fuel tank 21 by the intended function of the pressure regulator 23, but rather the amount of fuel that unintentionally leaks from the pressure regulator 23 to the fuel tank 21. The P / R leak rate is set to a predetermined fixed value based on experimental and simulation results.

[0031] As described above, the FF term is calculated based on the basic discharge flow rate, as well as the delayed pumping flow rate, the flow rate decrease due to aging, and the P / R leakage flow rate. Therefore, the discharge flow rate of the feed pump 22, which does not perform feedback control, can be appropriately controlled.

[0032] In the above embodiment, the fuel supply system A is installed in the hybrid vehicle 1, but is not limited to this, and may also be installed in a vehicle that has only an engine as a driving power source.

[0033] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of Symbols]

[0034] 1. Hybrid vehicle A Fuel supply system 10 Engines 22 Feed pump 23 Pressure Regulator 27-port injection valve 100 ECUs (Control Units)

Claims

[Claim 1] A feed pump that discharges fuel from the fuel tank into a low-pressure pipe, A port injection valve of an engine to which fuel is supplied from the aforementioned low-pressure pipe, A pressure regulator that adjusts the fuel pressure of the fuel discharged to the low-pressure pipe so that it does not exceed a certain fuel pressure by recirculating a portion of the fuel discharged to the low-pressure pipe back to the fuel tank, The system includes a control device that performs feedforward control of the fuel discharge flow rate of the feed pump using a feedforward term, without performing feedback control based on the actual fuel pressure supplied to the port injection valve, The control device calculates the feedforward term based on the basic discharge flow rate calculated based on the required injection amount of the port injection valve, the delayed fuel flow rate corresponding to the fuel discharge amount for the shortage corresponding to the delayed pumping time from when the rotational speed command value to the feed pump increases until the discharge flow rate from the feed pump becomes the discharge flow rate corresponding to the increased rotational speed command value, the flow rate of the feed pump that decreases over time, and the fuel leakage flow rate from the pressure regulator to the fuel tank. The control device calculates the delayed pumping flow rate as a larger value the greater the rate of increase of the basic discharge flow rate, and calculates the aging-induced decrease flow rate and the leakage flow rate as predetermined fixed values, in a fuel supply system.

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