High-pressure fuel supply system without energy storage volume and with adjustable injection pressure and control method

Abstract

The invention discloses a high-pressure fuel oil supply system without energy storage volume and with adjustable injection pressure and a control method, and belongs to the field of engines, the system is a system without energy storage volume, and comprises an oil tank, a low-pressure oil pipe, a low-pressure oil pump, a fuel oil filter, a high-pressure oil pump, a high-pressure oil pipe and an oil injector, the proportional electromagnetic valve can achieve adjustment of different opening degrees, and the throttling valve can reduce the pressure drop impact bearing strength of the inlet valve of the high-pressure oil pump. Whether target injection pressure is reached or not is judged according to signals collected by a pressure sensor on a high-pressure oil pipe, the oil pumping process of the high-pressure oil pump is divided into two stages including the oil pumping stage I and the oil pumping stage II, the oil pumping stage I is the pressure building process, and the pressure building starting point of oil pumping is affected by the target injection pressure and other factors; and the oil pumping stage II is a pumping and spraying combined process, and the fuel injection pressure can be adjusted and the pressure can be stabilized in the pumping and spraying combined process by adjusting different opening degrees of a valve.

Description

Technical Field

[0001] The invention belongs to the technical field of engines, and in particular relates to a high-pressure fuel supply system with no energy storage volume and adjustable injection pressure and a control method thereof. Background Art

[0002] The fuel supply system is the basis for the normal operation of the engine and a key factor in improving fuel efficiency. At present, most fuel supply systems are common rail systems, including high-pressure common rail fuel systems, GDI fuel systems, etc. The common rail system uses the common rail pipe as a storage container for high-pressure fuel. The pumping process and the injection process are independent of each other. The amount of pumped oil entering the common rail pipe is adjusted by controlling the on-off time of the oil pump solenoid valve, and the amount of injection is adjusted by controlling the on-off time of the injector solenoid valve. The size of the common rail pipe volume affects the fluctuation of the injection pressure during the injection process. The larger the common rail pipe volume, the smaller the injection pressure fluctuation.

[0003] However, if the common rail is too large, it cannot meet the requirements of high compactness. If the common rail is too small, the injection pressure will fluctuate greatly. The separation of the pumping and injection process will also cause large pressure fluctuations during the injection process. At the same time, only controlling the opening and closing time of the oil pump valve cannot accurately adjust the pumping amount. Therefore, it is particularly important to study the control method of the non-energy storage volume system and the combination of pumping and injection. Summary of the invention

[0004] The purpose of the present invention is to solve the above problems. The present invention provides a high-pressure fuel supply system and control method without energy storage volume and with adjustable injection pressure, which eliminates the common rail pipe in the common rail system and can realize the combination of oil pumping and oil injection.

[0005] The oil supply system comprises an oil tank, a low-pressure oil pipe, a low-pressure oil pump, a fuel filter, a high-pressure oil pump, a high-pressure oil pipe, and an injector, wherein an inlet proportional solenoid valve and a throttle valve are installed at the oil inlet of the high-pressure oil pump.

[0006] Furthermore, the fuel supply system is a system without energy storage capacity, and the fuel tank, low-pressure fuel pump, and fuel filter are connected to the inlet proportional solenoid valve of the high-pressure fuel pump in sequence by a low-pressure fuel pipe, and the inlet proportional solenoid valve is connected to a throttle valve, and the oil outlet of the high-pressure fuel pump is directly connected to the oil inlet of the injector by a high-pressure fuel pipe.

[0007] Furthermore, the high-pressure oil pipe has a pressure monitoring port for installing a pressure sensor to monitor the pressure in the high-pressure oil pipe.

[0008] Furthermore, the fuel supply system uses a high-pressure fuel pump to supply fuel. Different from the switch solenoid valve used at the inlet of the fuel pump of the GDI fuel system, the inlet of the high-pressure fuel pump uses a proportional solenoid valve.

[0009] Furthermore, the proportional solenoid valve is located at the inlet end of the high-pressure oil pump. After the solenoid valve is energized, the solenoid coil generates magnetic force, which can move the plunger and control the degree of valve closing.

[0010] Furthermore, the throttle valve is located between the inlet proportional solenoid valve and the pump chamber, and the flow rate and pressure are adjusted by changing the channel cross-sectional area.

[0011] The advantages of the high-pressure fuel supply system with no energy storage volume and adjustable injection pressure provided by the present invention are: compared with the traditional GDI fuel system, the high-pressure oil pump inlet valve of the fuel supply system of the present invention can be adjusted to different opening degrees, avoiding the situation of excessive pumping oil volume caused by relying solely on valve opening and closing time control, making the control of pumping oil volume more precise; at the same time, the use of the throttle valve reduces the strength of the high-pressure oil pump inlet valve to withstand the pressure drop impact, thereby extending the service life of the valve.

[0012] The present invention also provides a control method for a high-pressure fuel supply system without energy storage volume and with adjustable injection pressure.

[0013] The control method of the present invention adjusts the opening size of the inlet valve of the high-pressure oil pump and the opening and closing state of the injector solenoid valve by monitoring the change of the pressure in the high-pressure oil pipe.

[0014] The control method of the present invention divides the oil pumping process of the high-pressure oil pump into two stages: oil pumping stage I and oil pumping stage II.

[0015] Furthermore, in the oil pumping stage I, the oil pumping starting point is determined by calibrating different target injection pressures, different injection pulse widths, different cam speeds and the duration t1 of the oil pumping stage I before pumping the oil. The target injection pressure, injection pulse width, etc. are directly determined by the actual engineering situation. During the duration t1, the inlet valve of the high-pressure oil pump is in a completely closed state. When the oil pumping stage I ends, the pressure of the high-pressure oil pipe reaches the target injection pressure.

[0016] Furthermore, in the oil pumping stage II, by adjusting the high-pressure oil pump inlet valve to different opening degrees, part of the fuel enters the high-pressure oil pipe, and part of the fuel overflows from the inlet valve back to the fuel tank, and at the same time, the injector is controlled to spray oil, and the oil pumping and injection are carried out simultaneously. The duration of the oil pumping stage II is t2, which is the same as the injection pulse width, and the time when the injector ends the injection and the valve falls is the top dead center of the plunger movement.

[0017] Furthermore, the control of different openings of the inlet proportional solenoid valve is based on the chopper control principle, which changes the control voltage of the valve to obtain different holding currents, thereby achieving control of different openings of the valve.

[0018] Furthermore, the opening of the inlet proportional solenoid valve is related to the oil pumping capacity of the high-pressure oil pump, the target fuel injection volume, etc. The larger the valve opening, the more overflow oil return and the less fuel supply; the smaller the valve opening, the less overflow oil return and the more fuel supply.

[0019] The control method of the high-pressure fuel supply system with no energy storage volume and adjustable injection pressure provided by the present invention has the advantages that: during the overflow process of the traditional oil pump, the inlet valve is fully opened, causing a sudden change in pressure in the pump chamber, and at the same time, the fuel returning to the low-pressure oil circuit will cause cavitation and a large impact. In the control method of the present invention, in the oil pumping stage II, the valve adjusts different openings, and part of the fuel returns to the low-pressure oil circuit, and part continues to be supplied to the injector, without causing a sudden change in pressure. At the same time, the common rail pipe part of the traditional fuel supply system is omitted, and the overall structure is more compact; the control method of the present invention combines oil pumping with oil injection, and injects oil during the oil pumping process, which can stabilize the pressure during the injection process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the fuel supply system

[0021] Figure 2 The schematic diagram of chopper control

[0022] Figure 3 Flow chart of the control method of the present invention

[0023] Figure 4 This is a comparison diagram of the effects of the control method of the present invention and the traditional high-pressure oil pump control method (the left figure is the effect diagram of the traditional high-pressure oil pump control method, and the right figure is the effect diagram of the control method of the present invention) DETAILED DESCRIPTION

[0024] The present invention is further described with reference to the accompanying drawings and specific embodiments.

[0025] The fuel supply system of the present invention includes Figure 1 The figure shows a schematic diagram of the fuel supply system. The fuel supply system includes: a fuel tank 1, a low-pressure fuel pump 2, a fuel filter 3, a low-pressure fuel pipe 4, a high-pressure fuel pump 5, a high-pressure fuel pipe 6, and a high-pressure fuel injector 7. The high-pressure fuel pump 5 is provided with an inlet proportional solenoid valve 8 and a throttle valve 9 at the oil inlet.

[0026] The fuel tank 1, low-pressure fuel pump 2, and fuel filter 3 of the fuel supply system of the present invention are connected in series to the proportional solenoid valve 8 at the inlet of the high-pressure fuel pump 5 by the low-pressure fuel pipe 4. A throttle valve 9 is installed between the inlet proportional solenoid valve 8 and the fuel pump chamber. At the same time, the fuel system of the present invention is a non-energy storage volume system, that is, the oil outlet of the high-pressure fuel pump 5 is directly connected to the high-pressure fuel injector 7 by the high-pressure fuel pipe 6. The high-pressure fuel pipe 6 has a pressure monitoring port for installing a pressure sensor to monitor the pressure in the high-pressure fuel pipe.

[0027] Specifically, a proportional solenoid valve 8 is used at the inlet of the high-pressure oil pump 5 in the fuel system of the present invention. The inlet proportional solenoid valve 8 changes the output voltage of the valve according to the chopper control principle to obtain different holding currents, thereby realizing the control of different valve openings. Please refer to the attached Figure 2 When the high level maintenance time of the valve output voltage accounts for 25% of the entire cycle T, and the low level maintenance time accounts for 75% of the entire cycle T, the valve opening is maintained at 25%; when the high level maintenance time of the valve output voltage accounts for 75% of the entire cycle T, and the low level maintenance time accounts for 25% of the entire cycle T, the valve opening is maintained at 75%.

[0028] Specifically, the opening of the inlet valve should be different under different working conditions. The larger the valve opening, the more overflow oil return and the less oil supply; the smaller the valve opening, the less overflow oil return and the more oil supply. If the target injection pressure is high and the injection pulse width is large, the valve opening is reduced to increase the oil supply.

[0029] Specifically, the high-pressure oil pump 5 in the fuel system of the present invention uses a throttle valve 9 between the inlet proportional solenoid valve 8 and the pump chamber to change the channel cross-sectional area, thereby achieving the purpose of regulating flow and pressure.

[0030] In the fuel supply system provided by the present invention, the inlet proportional solenoid valve 8 can be adjusted to different opening degrees, avoiding the situation where excessive pumping oil volume is caused by relying solely on valve opening and closing time control, making the control of pumping oil volume more precise; at the same time, the use of the throttle valve 9 reduces the strength of the inlet proportional solenoid valve 8 of the high-pressure oil pump 5 to withstand the pressure drop impact, thereby extending the service life of the valve.

[0031] The present invention also provides a control method, the control principle of which is: by monitoring the change of pressure in the high-pressure oil pipe, the opening size of the high-pressure oil pump inlet valve and the opening and closing state of the injector solenoid valve are adjusted.

[0032] The control method of the present invention divides the oil pumping process of the high-pressure oil pump 5 into two stages: oil pumping stage I and oil pumping stage II.

[0033] For details, please refer to the attached Figure 3 The left figure is a control method effect diagram of an energy storage volume system (rail system). The pumping process of the energy storage volume system can be divided into two stages: the pumping stage and the overflow stage. In the pumping stage: the plunger moves upward, the solenoid valve is completely closed, and the fuel in the pump chamber is squeezed into the common rail pipe. The pressure in the common rail pipe reaches the target injection pressure P 目标 ; The overflow stage: the plunger continues to move upward, the solenoid valve is fully opened, and the fuel in the pump chamber overflows back to the fuel tank. At this time, there is no obvious fluctuation in the pressure in the common rail pipe. After the pumping process of the energy storage volume system is completed, the injector solenoid valve is opened, and at the target injection pressure P 目标During the fuel injection stage, the rail pressure has an obvious downward trend, and the fuel injection law shows a slow increase and slow decrease trend.

[0034] For details, please refer to the attached Figure 3 The right figure is a control method effect diagram of the energy storage volume system of the present invention. The oil pumping process of the energy storage volume system of the present invention can be divided into two stages: oil pumping stage I and oil pumping stage II. In the oil pumping stage I: the cam pushes the plunger to move upward, the pressure in the pump chamber increases, and the pressure in the pump chamber gradually increases to squeeze the fuel into the high-pressure oil pipe 6. At this time, the proportional solenoid valve 8 at the inlet of the high-pressure oil pump 5 is in a completely closed state until the pressure in the high-pressure oil pipe 6 reaches the target injection pressure P 目标 The duration of the pumping oil phase I is t1, and the duration t1 is related to the cam profile, cam speed, and target injection pressure. Before pumping oil, the relationship between different target injection pressures and the duration of the pumping oil phase I is calibrated. Under different target injection pressures, the pumping oil starting point is different. In the pumping oil phase II, when the pressure in the high-pressure oil pipe 6 reaches the target injection pressure P 目标 When the proportional solenoid valve 8 at the inlet of the high-pressure oil pump 5 is adjusted to different openings, part of the fuel enters the high-pressure oil pipe 6, and part of the fuel overflows from the proportional solenoid valve 8 back to the fuel tank 1. At this time, the injection signal is given, and the pumping and injection are carried out simultaneously. The duration of the pumping phase II is t2, and the duration t2 is the same as the injection pulse width. The time when the injector 7 ends the injection is the top dead center of the plunger movement. The pressure of the pumping phase II during the injection process is at the target injection pressure P 目标 It fluctuates around and has no obvious downward trend. At this time, changing the size of the valve opening can change the injection pressure during the injection process, and the injection law shows a trend of rapid increase and decrease.

[0035] The control method provided by the present invention has great advantages over the energy storage volume system: the inlet valve of the traditional oil pump is fully opened during the overflow process, causing a sudden change in pressure in the pump chamber, and the return of the fuel to the low-pressure oil circuit will cause cavitation and a large impact. In the control method of the present invention, in the oil pumping process II, the valve adjusts different openings, and part of the fuel returns to the low-pressure oil circuit, and part continues to be supplied to the injector, without causing a sudden change in pressure. At the same time, the common rail pipe part of the traditional fuel supply system is omitted, and the overall structure is more compact; the control method of the present invention combines oil pumping with oil injection, and injects oil during the oil pumping process, which can stabilize the pressure during the injection process; the injection law of the system without energy storage volume shows a trend of rapid increase and decrease compared with the system with energy storage volume.

Claims

1. A high-pressure fuel supply system without energy storage volume and with adjustable injection pressure, the fuel supply system comprising a fuel tank (1), a low-pressure fuel pump (2), a fuel filter (3), a low-pressure fuel pipe (4), a high-pressure fuel pump (5), a high-pressure fuel pipe (6), and a fuel injector (7), wherein an inlet proportional solenoid valve (8) and a throttle valve (9) are installed at the fuel inlet of the high-pressure fuel pump (5); The structural features of the fuel supply system are that the fuel tank (1), the low-pressure fuel pump (2), and the fuel filter (3) are connected to the inlet proportional solenoid valve (8) of the high-pressure fuel pump (5) in sequence through a low-pressure fuel pipe (4), the inlet proportional solenoid valve (8) is connected to a throttle valve (9) to reduce the intensity of the pressure drop impact, and the oil outlet of the high-pressure fuel pump (5) and the oil inlet of the injector (7) are directly connected through a high-pressure fuel pipe (6).

2. A method for controlling a system as claimed in claim 1, characterized in that: It is determined whether the pressure in the high-pressure oil pipe (6) reaches the target injection pressure, thereby adjusting the opening size of the proportional electromagnetic valve (8) at the inlet of the high-pressure oil pump and the opening and closing state of the electromagnetic valve of the injector (7).

3. The method according to claim 2, characterized in that: The proportional solenoid valve (8) used in the inlet valve is fully closed during the fuel supply stage and the on-off timing of the solenoid valve is controlled to realize fuel supply. During the fuel injection stage, the valve opening is adjusted to realize different injection pressures.

4. The method according to claim 2, characterized in that: The oil pumping process of the high-pressure oil pump is divided into two stages: oil pumping stage I and oil pumping stage II; Oil pumping stage I: by calibrating different target injection pressures, different injection pulse widths, different cam speeds and the duration t1 of the oil pumping stage I before oil pumping, the oil pumping starting point is determined. During the duration t1, the high-pressure oil pump inlet valve (8) is in a completely closed state. When the oil pumping stage I ends, the pressure of the high-pressure oil pipe (6) reaches the target injection pressure. Pumping stage II: by adjusting the high-pressure oil pump inlet proportional solenoid valve (8) to different openings, part of the fuel enters the high-pressure oil pipe (6), and part overflows from the inlet proportional solenoid valve (8) back to the oil tank, and at the same time controls the injector (7) to spray oil, and pumping oil and spraying oil are carried out simultaneously. The duration of the pumping stage II is t2, which is the same as the injection pulse width. The valve drop time of the injector (7) after the injection ends is the top dead center of the high-pressure oil pump (5) plunger movement. The control of the opening of the inlet valve (8), the larger the valve opening, the more overflow oil returns, and the less oil supply; The valve has a small diameter, less overflow oil return and more oil supply.

Images