Fuel supply system

Abstract

To provide a fuel supply system capable of securing fuel economy through stable fuel supply in a fixed fuel pressure system.SOLUTION: A fuel supply system 100 in the present disclosure includes: a low pressure fuel pump 3 that discharges fuel stored in a fuel tank 4 to an engine via a fuel discharge passage 6 in accordance with rotational frequency; a control section 11 that controls the low pressure fuel pump 3; and a pressure regulator 5 that regulates fuel pressure of fuel to be discharged so as not to exceed fixed fuel pressure by recirculating part of fuel discharged in the fuel discharge passage 6 to the fuel tank 4. The control section 11 determines target rotational frequency obtained by adding predetermined rotational frequency to the rotational frequency of the low pressure fuel pump 3 corresponding to required injection amount in an injector 9 at the fixed fuel pressure, and controls the low pressure fuel pump 3 on the basis of the target rotational frequency.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a vehicle including a fuel pump that supplies fuel to an engine, which calculates a feed-forward operation amount corresponding to the amount of fuel injected from a fuel injection valve (injector) and a feedback operation amount based on the deviation between the actual supply pressure and the target fuel pressure, sets the target rotational speed of the fuel pump, and outputs a drive signal corresponding to the target rotational speed to the fuel pump.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] From the perspective of cost reduction, it is conceivable to eliminate the fuel pressure sensor and adopt a fixed fuel pressure system without performing feedback control. However, in the technology according to Patent Document 1, the fuel pump in the fixed fuel pressure system cannot be controlled, so there is room for consideration from the perspective of ensuring fuel efficiency by stable fuel supply in the fixed fuel pressure system.

[0005] In view of such problems, an object of the present disclosure is to provide a fuel supply system capable of ensuring fuel efficiency by stable fuel supply in a fixed fuel pressure system.

Means for Solving the Problems

[0006] The fuel supply system of the present disclosure includes: a low-pressure fuel pump that discharges the fuel stored in the fuel tank to the engine via a fuel discharge path in accordance with the rotational speed; a control unit that controls the low-pressure fuel pump; a pressure regulator that adjusts the fuel pressure of the discharged fuel so that it does not exceed a certain fuel pressure by refluxing a part of the discharged fuel in the fuel discharge path back to the fuel tank; and the control unit determines a target rotational speed obtained by adding a predetermined rotational speed to the rotational speed of the low-pressure fuel pump corresponding to the required injection amount in the injector at the certain fuel pressure, and controls the low-pressure fuel pump based on the target rotational speed.

Advantages of the Invention

[0007] According to the present disclosure, it is possible to provide a fuel supply system capable of ensuring fuel efficiency by stable fuel supply in a fixed fuel pressure system.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

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Figure 7

Modes for Carrying Out the Invention

[0009] (First Embodiment) First, the configuration of the fuel supply system 100 according to the first embodiment will be described with reference to FIG. 1. The fuel supply system 100 is mounted on a vehicle and includes an ECU (Engine Control Unit) 1, an FPC (Fuel Pump Controller) 2, a low-pressure fuel pump 3, a fuel tank 4, a pressure regulator 5, a fuel discharge path 6, a high-pressure fuel pump 7, a high-pressure delivery 8, an injector 9, and a high-pressure fuel sensor 10. Note that the ECU 1 and the FPC 2 are collectively referred to as the control unit 11 as well.

[0010] The ECU 1 acquires the fuel consumption amount (hereinafter, required fuel consumption amount) required by the internal combustion engine (engine). The required fuel consumption amount is information such as a torque value calculated from an accelerator opening corresponding to, for example, the depression amount of the accelerator pedal and the engine speed. The ECU 1 mediates the required fuel consumption amount and determines the required injection amount in the injector 9 at a constant fuel pressure (for example, 530 Kpa) based on the mediated required fuel consumption amount.

[0011] The ECU 1 determines a target rotation speed obtained by adding a predetermined rotation speed to the rotation speed of the low-pressure fuel pump 3 corresponding to the required injection amount in the injector 9 at a constant fuel pressure, and controls the low-pressure fuel pump 3 based on the target rotation speed.

[0012] Specifically, the ECU 1 determines the target discharge flow rate of the low-pressure fuel pump 3 based on the required injection amount in the injector 9 at a constant fuel pressure, determines the required discharge flow rate of the low-pressure fuel pump 3 obtained by adding a predetermined discharge flow rate to the target discharge flow rate, and determines the target rotation speed of the low-pressure fuel pump 3 corresponding to the required discharge flow rate. The predetermined discharge flow rate to be added is at least one of the discharge flow rate corresponding to the fuel leakage amount of the pressure regulator 5, the discharge flow rate due to aging deterioration, and the discharge flow rate due to load fluctuation. Then, the ECU 1 generates a Duty signal including the target rotation speed and controls the low-pressure fuel pump 3 to rotate at the target rotation speed by causing the FPC 2 to transmit the Duty signal to the low-pressure fuel pump 3.

[0013] Based on the control from the ECU1, the FPC2 controls the low-pressure fuel pump 3 by sending a Duty signal including the target rotational speed to the low-pressure fuel pump 3. The low-pressure fuel pump 3 rotates at the target rotational speed included in the Duty signal received from the FPC2, sucks in and pressurizes the fuel stored in the fuel tank 4, and discharges the fuel to the fuel discharge path 6 at a pressure P and a flow rate Q. Then, the low-pressure fuel pump 3 supplies fuel to the injector 9 provided for each cylinder of the engine via the fuel discharge path 6, the high-pressure fuel pump 7, and the high-pressure delivery 8. Note that the low-pressure fuel pump 3 is also called a feed pump.

[0014] The pressure regulator 5 is provided in a path branched from the fuel discharge path 6 and installed in the fuel tank 4. The pressure regulator 5 adjusts so that the fuel pressure of the discharged fuel does not exceed a constant fuel pressure (for example, 530 Kpa) by refluxing a part of the fuel discharged from the low-pressure fuel pump 3 in the fuel discharge path 6 to the fuel tank 4.

[0015] The high-pressure fuel pump 7 boosts the pressure of the fuel discharged from the low-pressure fuel pump 3 and discharges the pressurized fuel to the injector 9 via the high-pressure delivery 8. Here, the high-pressure fuel pump 7 boosts the pressure of the fuel based on the information of the high-pressure fuel sensor 10 provided in the high-pressure delivery 8.

[0016] Subsequently, with reference to FIGS. 2 and 3, the operation of the fuel supply system 100 according to the first embodiment will be described. As shown in FIG. 2, first, in step S101, the ECU1 acquires the required fuel consumption required by the engine. The required fuel consumption is information such as a torque value calculated from the accelerator opening corresponding to the amount of depression of the accelerator pedal, the rotational speed of the engine, and the like.

[0017] Next, in step S102, the ECU1 arbitrates the required fuel consumption. Next, in step S103, the ECU1 determines the required injection amount of the injector 9 at a constant fuel pressure (for example, 530 Kpa) based on the mediated required fuel consumption. The constant fuel pressure is not limited to 530 Kpa and can be set individually.

[0018] Next, in step S104, the ECU1 determines a target rotational speed obtained by adding a predetermined rotational speed to the rotational speed of the low-pressure fuel pump 3 corresponding to the required injection amount of the injector 9. Specifically, in steps S1041 to S1043 shown in FIG. 3, the ECU1 determines the target rotational speed.

[0019] First, in step S1041, the ECU1 determines the target discharge flow rate of the low-pressure fuel pump 3 corresponding to the required injection amount of the injector 9. Next, in step S1042, the ECU1 determines a required discharge flow rate obtained by adding a predetermined discharge flow rate to the target discharge flow rate of the low-pressure fuel pump 3. In step S1042, the ECU1 performs the following processing in detail. First, the ECU1 adds the flow rate corresponding to the fuel leakage flow rate of the pressure regulator 5 to the target discharge flow rate. For example, the ECU1 adds the flow rate that naturally leaks from the pressure regulator 5 to the fuel tank 4 or the flow rate assumed when the fuel discharged from the low-pressure fuel pump 3 is less than normal to the target discharge flow rate.

[0020] Then, the ECU1 adds the flow rate corresponding to the decrease in the discharge flow rate due to aging deterioration to the target discharge flow rate. For example, the ECU1 adds the flow rate corresponding to the decrease in the discharge flow rate of the low-pressure fuel pump 3 due to aging deterioration to the target discharge flow rate.

[0021] Finally, the ECU 1 adds the flow rate corresponding to the load fluctuation to the target discharge flow rate. For example, when the accelerator is depressed strongly, the ECU 1 adds the flow rate corresponding to the delay in the discharge of fuel from the low-pressure fuel pump 3 to the target discharge flow rate. FIG. 4 is a graph showing an example of the correspondence between the target discharge flow rate (x-axis) and the amount added to the target discharge flow rate for the load fluctuation (y-axis). For example, when the target discharge flow rate is 0 L / h to 90 L / h, the added amount is 0 L / h. When the target discharge flow rate is higher than 90 L / h, the added amount increases. Here, when the target discharge flow rate is 150 L / h, the added amount is 60 L / h.

[0022] That is, the correspondence between the target discharge flow rate and the required discharge flow rate obtained by adding the predetermined discharge flow rate in step S1042 is as shown in FIG. 5. FIG. 5 is a graph showing an example of the correspondence between the target discharge flow rate (x-axis) and the required discharge flow rate (y-axis). Q1 shows the correspondence between the required discharge flow rate and the target discharge flow rate without the added amount. Q2 shows the correspondence between the required discharge flow rate and the target discharge flow rate when the flow rate corresponding to the fuel leakage flow rate of the pressure regulator 5 and the decrease in the discharge flow rate due to aging deterioration is added to the target discharge flow rate. Q3 shows the correspondence between the required discharge flow rate and the target discharge flow rate when the flow rate corresponding to the load fluctuation is further added to Q2. For example, in Q1, when the target discharge flow rate is 150 L / h, the required discharge flow rate is 150 L / h. In Q2, when the target discharge flow rate is 150 L / h, the required discharge flow rate is 200 L / h. In Q3, when the target discharge flow rate is 150 L / h, the required discharge flow rate is 260 L / h.

[0023] Returning to the description of FIG. 3. Next, in step S1043, the ECU 1 determines the target rotation speed of the low-pressure fuel pump 3 corresponding to the required discharge flow rate.

[0024] As described above, the ECU 1 calculates the required discharge flow rate by adding the predetermined discharge flow rate to the target discharge flow rate of the low-pressure fuel pump 3. By doing so, the ECU 1 prevents the possibility that the fuel pressure of the fuel discharged from the low-pressure fuel pump 3 falls below a constant fuel pressure, that is, 530 Kpa.

[0025] Return to the description of FIG. 2. In step S105 after step S104, the ECU 1 transmits a Duty signal including the determined target rotational speed to the FPC 2, and causes the FPC 2 to control the low-pressure fuel pump 3 to rotate at the target rotational speed.

[0026] Thereafter, the low-pressure fuel pump 3 sucks and pressurizes the fuel in the fuel tank 4 at the target rotational speed, and discharges the fuel into the fuel discharge path 6. Then, the low-pressure fuel pump 3 supplies fuel to the injector 9 provided for each cylinder of the internal combustion engine via the fuel discharge path 6, the high-pressure fuel pump 7, and the high-pressure delivery 8.

[0027] Here, as shown in FIG. 6, the fuel supply system 100 according to the first embodiment is a fixed fuel pressure system that does not perform feedback control based on the deviation between the actual supply pressure and the target fuel pressure by abolishing the low-pressure fuel pressure sensor S1. The control unit 11 of the fuel supply system 100 determines a target rotational speed obtained by adding a predetermined rotational speed to the rotational speed of the low-pressure fuel pump 3 corresponding to the required injection amount in the injector 9 at a constant fuel pressure, and controls the low-pressure fuel pump 3 based on the target rotational speed. Then, the fuel pressure of the fuel discharged by the low-pressure fuel pump 3 is maintained at a constant fuel pressure by the pressure regulator 5. Therefore, in the present embodiment, the fuel supply system 100 can ensure fuel efficiency by stable fuel supply in the fixed fuel pressure system.

[0028] <Hardware Configuration> Next, with reference to FIG. 7, a hardware configuration example of a computer 1000 that realizes the control unit 11 (ECU1 and FPC2) of the fuel supply system 100 will be described. In FIG. 7, the computer 1000 has a processor 1001 and a memory 1002. The processor 1001 may be, for example, a microprocessor, an MPU (Micro Processing Unit), or a CPU (Central Processing Unit). The processor 1001 may include a plurality of processors. The memory 1002 is composed of a combination of a volatile memory and a non-volatile memory. The memory 1002 may include a storage disposed apart from the processor 1001. In this case, the processor 1001 may access the memory 1002 via an I / O interface (not shown).

[0029] Also, each configuration in the above-described embodiment is configured by hardware or software, or both, and may be configured by one piece of hardware or software, or may be configured by a plurality of pieces of hardware or software. The functions (processes) of each configuration in the above-described embodiment may be realized by a computer. For example, a program for performing the method in the embodiment may be stored in the memory 1002, and each function may be realized by executing the program stored in the memory 1002 by the processor 1001.

[0030] These programs, when loaded into a computer, include a set of instructions (or software code) for causing the computer to perform one or more of the functions described in the embodiments. The program may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, a computer-readable medium or a tangible storage medium includes random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD), or other memory technologies, CD-ROM, digital versatile disc (DVD), Blu-ray (registered trademark) disc, or other optical disc storage, magnetic cassette, magnetic tape, magnetic disk storage, or other magnetic storage devices. The program may also be transmitted on a transient computer-readable medium or a communication medium. By way of example and not limitation, a transient computer-readable medium or a communication medium includes electrical, optical, acoustic, or other forms of propagated signals.

[0031] Note that the present invention is not limited to the above embodiments and can be appropriately modified without departing from the spirit thereof.

Explanation of Reference Numerals

[0032] 1 ECU 2 FPC 3 Low-pressure fuel pump 4 Fuel tank 5 Pressure regulator 6 Fuel discharge path 7 High-pressure fuel pump 8 High-pressure delivery 9 Injector 10 High-pressure fuel sensor 11 Control unit 100 Fuel supply system 1000 Computer 1001 Processor 1002 Memory S1 Low-pressure fuel sensor

Claims

Claim 1 A low-pressure fuel pump that discharges fuel stored in a fuel tank to an engine via a fuel discharge path according to the rotational speed; A control unit that controls the low-pressure fuel pump; A pressure regulator that adjusts the fuel pressure of the discharged fuel so as not to exceed a certain fuel pressure by refluxing a part of the discharged fuel in the fuel discharge path back to the fuel tank, and; The control unit: Determines the target discharge flow rate of the low-pressure fuel pump based on the required injection amount at the injector at the certain fuel pressure, determines the required discharge flow rate of the low-pressure fuel pump obtained by adding a predetermined discharge flow rate to the target discharge flow rate, determines the target rotational speed of the low-pressure fuel pump corresponding to the required discharge flow rate, and controls the low-pressure fuel pump based on the target rotational speed; The predetermined discharge flow rate added to the target discharge flow rate is: At least one of the flow rate corresponding to the fuel leakage amount of the pressure regulator, the flow rate corresponding to the decrease in the discharge flow rate due to the secular deterioration of the low-pressure fuel pump, and the flow rate corresponding to the load fluctuation of the low-pressure fuel pump; A fuel supply system.

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