Injection system, engine, vehicle and injection control method

Abstract

The invention relates to an injection system, an engine, a vehicle and an injection control method. The injection system comprises a high-pressure oil pump, a main injection loop and a pre-injection loop. The high-pressure oil pump is provided with a first output end and a second output end. The main injection circuit includes a first high pressure common rail tube fluidly connected with the first output, and a main injector connected with the first high pressure common rail tube. The pre-injection circuit includes a second high pressure common rail tube fluidly connected with the second output, and a pre-injector connected with the second high pressure common rail tube. The pre-injection circuit is configured to inject at a lower pressure than the main injection circuit. Through the arrangement of the integrated oil pump, the system structure is remarkably simplified, and the manufacturing cost is reduced. Meanwhile, the pressure of the two loops is independently adjustable, flexible combination of pre-injection and main injection can be achieved, the injection atomization effect and the combustion process are optimized, and therefore the dynamic property, economical efficiency and emission performance of the engine are comprehensively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automobile parts, in particular to a spraying system, an engine, a vehicle and a spraying control method. BACKGROUND

[0002] In the field of methanol engines, in order to greatly improve the thermal efficiency and emission performance, in-cylinder direct injection technology is considered as the most potential solution. However, the high octane rating characteristics of methanol fuel make it difficult to achieve compression ignition, and if the traditional spark plug ignition scheme is adopted, it cannot withstand the high frequency airflow disturbance and extremely high cylinder pressure brought by direct injection combustion, resulting in difficult ignition. The pre-chamber ignition technology can effectively solve this problem, but its traditional implementation scheme needs to rely on two completely independent high-pressure common rail injection systems to supply oil to the pre-chamber and the main combustion chamber respectively, resulting in complex system structure, high control difficulty and high cost, which becomes the key bottleneck restricting the popularization and application of the technology. SUMMARY

[0003] To solve the above problems, the present application provides a spraying system for an engine, comprising:

[0004] a high-pressure oil pump, the high-pressure oil pump being provided with a first output end and a second output end;

[0005] a main injection circuit, comprising a first high-pressure common rail pipe in fluid connection with the first output end, and a main injector connected with the first high-pressure common rail pipe;

[0006] a pre-injection circuit, comprising a second high-pressure common rail pipe in fluid connection with the second output end, and a pre-injection injector connected with the second high-pressure common rail pipe; wherein,

[0007] the pre-injection circuit is configured to inject at a pressure lower than that of the main injection circuit.

[0008] In one embodiment, the injection pressure of the main injection circuit is configured to be 500 bar-2000 bar;

[0009] the injection pressure of the pre-injection circuit is configured to be 100 bar-1000 bar.

[0010] In one embodiment, the high-pressure oil pump comprises a plurality of plungers, the first output end is supplied by at least two plungers, and the second output end is supplied by at least one independent plunger.

[0011] In one embodiment, the high-pressure oil pump further comprises a first metering unit and a second metering unit, the first metering unit is used to adjust the fuel flow to the first output end, and the second metering unit is used to independently adjust the fuel flow to the second output end.

[0012] In one of the embodiments, the main injection circuit further comprises a first rail pressure sensor disposed on the first high-pressure common rail pipe, the first rail pressure sensor being in communication connection with the first metering unit to constitute a first closed-loop control of the main injection circuit pressure;

[0013] The pre-injection circuit further comprises a second rail pressure sensor disposed on the second high-pressure common rail pipe, the second rail pressure sensor being in communication connection with the second metering unit to constitute a second closed-loop control of the pre-injection circuit pressure; the first closed-loop control and the second closed-loop control system are independent of each other.

[0014] In one of the embodiments, the main injection circuit further comprises a first pressure relief valve disposed on the first high-pressure common rail pipe; the pre-injection circuit further comprises a second pressure relief valve disposed on the second high-pressure common rail pipe; wherein

[0015] The first pressure relief valve is an electrically controlled pressure relief valve, and the second pressure relief valve is a mechanical pressure relief valve.

[0016] In one of the embodiments, the main injector is of a structure with a return oil path; the injection system further comprises a return oil pipeline and a return oil back pressure valve disposed on the return oil pipeline; the return oil pipeline is in fluid communication with the return oil path of the main injector, and the return oil back pressure valve is configured to adjust the pressure in the return oil pipeline.

[0017] In one of the embodiments, an electronic control unit is further included, the electronic control unit being in communication connection with the high-pressure oil pump for independently controlling the output pressure of the first output end and the second output end.

[0018] The application further provides an engine, comprising:

[0019] The injection system as mentioned in any of the above embodiments;

[0020] A main combustion chamber; and

[0021] A pre-combustion chamber;

[0022] The main injector is configured to inject fuel into the main combustion chamber; and the pre-injector is configured to inject fuel into the pre-combustion chamber.

[0023] In one of the embodiments, the pre-combustion chamber is accommodated in the main combustion chamber.

[0024] The application further provides a vehicle, comprising the engine as mentioned in any of the above embodiments.

[0025] The application further provides an injection control method for an engine, applied to the engine as mentioned in any of the above embodiments, comprising:

[0026] In the engine starting stage, the pre-injection circuit is controlled to inject at a first pressure, and the main injection circuit is controlled to inject at a second pressure; wherein the second pressure is higher than the first pressure.

[0027] In one of the embodiments, in the engine starting stage, the first pressure is controlled to be in the range of 100 bar to 1000 bar, and the second pressure is controlled to be in the range of 500 bar to 2000 bar.

[0028] In one of the embodiments, the fuel amount injected by the pre-injection circuit accounts for no more than 5% of the total fuel injection amount of the engine.

[0029] In one of the embodiments, the injection strategy of the main injection circuit comprises:

[0030] When the engine load is lower than a preset threshold, the main injector is controlled to adopt a single injection mode;

[0031] When the engine load is higher than the preset threshold, the main injector is controlled to adopt a multiple injection mode, and the interval between any two adjacent injections is 10-30° of crank angle.

[0032] The technical solutions provided by the embodiments of the present application can include the following beneficial effects:

[0033] As can be seen from the above embodiments, the injection system of the present application comprises a high-pressure oil pump, a main injection circuit and a pre-injection circuit. The high-pressure oil pump is provided with a first output end and a second output end. The main injection circuit comprises a first high-pressure common rail pipe in fluid connection with the first output end, and a main injector connected with the first high-pressure common rail pipe. The pre-injection circuit comprises a second high-pressure common rail pipe in fluid connection with the second output end, and a pre-injection injector connected with the second high-pressure common rail pipe. The pre-injection circuit is configured to inject at a pressure lower than that of the main injection circuit. The present application significantly simplifies the system structure and reduces the manufacturing cost by integrating the oil pump. Meanwhile, the pressures of the two circuits are independently adjustable, which can realize flexible combination of pre-injection and main injection, optimize the injection atomization effect and combustion process, and thus comprehensively improve the power, economy and emission performance of the engine.

[0034] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments will be briefly introduced. Obviously, the drawings in the description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0036] Figure 1 A structural schematic diagram of a spray system provided in an embodiment of the present application.

[0037] Figure 2 A flowchart of a spray control method provided in an embodiment of the present application.

[0038] Reference signs:

[0039] 1, high-pressure oil pump; 10, plunger; 11, first metering unit; 12, second metering unit; 2, main injection circuit; 21, first high-pressure common rail pipe; 22, main injector; 23, main injection pipe; 24, first pressure relief valve; 3, pre-injection circuit; 31, second high-pressure common rail pipe; 32, pre-injector; 33, pre-injection pipe; 4, electronic control unit; 51, oil return pipeline; 52, oil return back pressure valve. DETAILED DESCRIPTION

[0040] The exemplary embodiments will be described in detail herein with reference to the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The modes described in the following exemplary embodiments are not intended to represent all modes consistent with the present application. Rather, they are merely examples of apparatuses consistent with some aspects of the present application as detailed in the appended claims.

[0041] As described in the background, with the increasing prominence of energy and environmental problems, developing efficient and clean internal combustion engine technology has become an important research direction of the industry. Methanol, as a low-carbon, high-octane alternative fuel, has shown great potential in improving engine thermal efficiency and reducing emissions. Among them, direct injection technology is to inject methanol fuel directly into the engine combustion chamber, which is one of the most effective solutions to achieve higher thermal efficiency and better emission performance.

[0042] However, due to its special physicochemical properties (such as high octane number and high latent heat of vaporization), it is difficult to achieve stable combustion by compression ignition, i.e. it is difficult to achieve methanol direct injection single fuel compression ignition (Homogeneous Charge Compression Ignition, HCCI), and its application faces technical challenges such as difficulty in controlling combustion phase and narrow operating load range.

[0043] To solve the problem of methanol compression ignition, the spark plug ignition scheme is usually adopted. However, when the spark plug ignition is combined with the in-cylinder direct injection of methanol, the traditional spark plug cannot reliably ignite the mixture formed by the direct injection of methanol. Since the combustion speed of methanol is fast and the in-cylinder combustion pressure is high, and the strong airflow disturbance generated by the in-cylinder direct injection will seriously interfere with the breakdown and ignition process of the spark plug, which easily leads to misfire or unstable combustion, thereby limiting the performance boundary of the engine.

[0044] Therefore, the pre-chamber ignition technology is considered as a feasible solution. The pre-chamber igniter forms flammable mixture in the pre-chamber and ignites it first, and then ignites the mixture in the main combustion chamber through the high-temperature flame jet, which is a strong and wide-ranging ignition method that is very suitable for methanol fuel. However, the implementation of this scheme relies on two independent high-pressure direct injection systems: one for injecting fuel into the pre-chamber and the other for injecting fuel into the main combustion chamber. This leads to problems such as extremely complex system structure, high manufacturing cost, and extremely difficult control strategy.

[0045] Based on this, the application provides a injection system for an engine. Referring to Figure 1 , the injection system includes a high-pressure oil pump 1, a main injection circuit 2, a pre-injection circuit 3, and an electronic control unit 4. The high-pressure oil pump 1 is provided with a first output end (not shown in the figure) and a second output end (not shown in the figure). The main injection circuit 2 includes a first high-pressure common rail pipe 21 connected to the first output end, and a main injector 22 connected to the first high-pressure common rail pipe 21. The pre-injection circuit 3 includes a second high-pressure common rail pipe 31 connected to the second output end, and a pre-injector 32 connected to the second high-pressure common rail pipe 31, and the pre-injection circuit 3 is configured to inject at a lower pressure than the main injection circuit 2. The electronic control unit 4 is in communication connection with the high-pressure oil pump 1, and is used to independently control the output pressure of the first output end and the second output end.

[0046] Specifically, the engine includes a main combustion chamber and a pre-chamber, and the main injector 22 is arranged to inject methanol fuel into the main combustion chamber to form a main mixture. The pre-injector 32 is arranged to inject methanol fuel into the pre-chamber to form a pre-mixture.

[0047] Further, referring to Figure 1 , the high-pressure oil pump 1 adopts a multi-plunger 10 structure. The multiple pump plungers 10 contained in the high-pressure oil pump 1 are divided into two groups and correspond to two output ends respectively. Among them, at least two plungers 10 work cooperatively to supply oil to the first output end together to meet the fuel demand of the main injection circuit 2 for large flow and high pressure. At the same time, at least one plunger 10 works independently and is dedicated to supplying oil to the second output end to meet the fuel demand of the pre-injection circuit 3 for medium and small flow and medium and low pressure.

[0048] In one embodiment, the high-pressure oil pump 1 comprises three pump plungers 10, one of which is in independent communication with the second output end and is dedicated to supplying fuel to the pre-injection circuit 3. The remaining two plungers 10 are in cooperative communication with the first output end and collectively supply fuel to the main injection circuit 2.

[0049] This arrangement is based on the different flow requirements of the two injection circuits. The pre-injection circuit 3 requires a small amount of fuel injection, and a single plunger 10 can meet its fuel supply requirements. The main injection circuit 2 needs to supply a large amount of fuel to the main combustion chamber, and two plungers 10 work cooperatively to ensure sufficient fuel supply. The three plungers 10 are driven by the same camshaft and maintain synchronized working rhythm.

[0050] Further, through the optimization design of the cam profile, the fuel supply phases of the three plungers 10 can be staggered, making the oil pump output more stable and reducing pressure fluctuations. At the same time, since the pre-injection circuit 3 is supplied by an independent plunger 10, its pressure build-up process is completely independent of the main injection circuit 2, avoiding pressure interference between the two circuits and ensuring the stability and independence of the two injection systems.

[0051] The present application realizes the function of the dual fuel supply system of the pre-chamber engine through a highly integrated high-pressure oil pump 1 and a dual common rail circuit design, significantly reducing the system cost and complexity. At the same time, with completely independent pressure and control strategies, the pre-chamber and the main combustion chamber can obtain optimal spray atomization and combustion organization under different working conditions, thereby effectively improving the thermal efficiency of the engine and reducing pollutant emissions.

[0052] In some embodiments, the injection pressure of the main injection circuit 2 is configured to be 500 bar - 2000 bar. The injection pressure of the pre-injection circuit 3 is configured to be 100 bar - 1000 bar. This pressure differentiation arrangement is based on the specific optimization of the different structural features and functional requirements of the pre-chamber and the main combustion chamber.

[0053] Specifically, the main injection circuit 2 uses ultra-high pressure injection of 500-2000 bar, which makes its spray particle size and atomization quality reach the level of diesel engines. The fine fuel particles greatly increase the contact area with air, accelerate the oil-gas mixing process, and form a uniform combustible mixture. This high-quality atomization effect significantly promotes the flame propagation speed, making the combustion in the main combustion chamber more complete and rapid, thereby effectively improving the thermal efficiency of the engine.

[0054] The pre-injection circuit 3 adopts a medium pressure range of 100-1000 bar, mainly based on the special structure requirements of the pre-combustion chamber. The pre-combustion chamber has a limited volume, and requires a shorter penetration distance for fuel injection to avoid direct impact of fuel particles on the wall. The medium injection pressure can not only ensure the basic atomization quality, but also effectively control the penetration ability of the spray, significantly reducing the wall risk. Especially under low temperature conditions, when the engine is cold started, the wall temperature of the pre-combustion chamber is low, and the lower injection pressure can not only ensure the required mixture for reliable ignition, but also minimize the condensation phenomenon caused by the impact of fuel on the cold wall, thereby ensuring the reliability and stability of the pre-combustion chamber ignition.

[0055] The present application provides a high-intensity ignition source in the pre-combustion chamber and a high-efficiency diffusion combustion in the main combustion chamber through the cooperative work of the two-stage pressure system. Not only does it speed up the combustion rate and shorten the combustion duration.

[0056] In some embodiments, the high-pressure oil pump 1 also integrates a first metering unit 11 and a second metering unit 12 for accurate fuel metering and pressure regulation of the two oil supply paths, respectively. The first metering unit 11 is arranged on the common oil inlet channel leading to the plurality of cooperative plungers 10, and controls the total fuel flow to the first output end by adjusting its opening degree, thereby realizing accurate regulation of the pressure of the main injection circuit 2 (500-2000 bar). The second metering unit 12 is independently arranged on the oil inlet path leading to the independent plunger 10, and controls the fuel flow to the second output end by independently adjusting its opening degree, thereby realizing independent control of the pressure of the pre-injection circuit 3 (100-1000 bar).

[0057] Further, the main injection circuit 2 further comprises a first rail pressure sensor (not shown in the figure) arranged on the first high-pressure common rail pipe 21, which is in communication connection with the first metering unit 11 to constitute a first closed-loop control of the pressure of the main injection circuit 2.

[0058] The pre-injection circuit 3 further comprises a second rail pressure sensor (not shown in the figure) arranged on the second high-pressure common rail pipe 31, which is in communication connection with the second metering unit 12 to constitute a second closed-loop control of the pressure of the pre-injection circuit 3. The first closed-loop control and the second closed-loop control system are independent of each other.

[0059] The two metering units in the present application preferably adopt proportional electromagnetic valve structure, and the opening degree of the valve core is accurately controlled by receiving the pulse width modulation (PWM) signal sent by the electronic control unit 4. The electronic control unit 4 compares the actual pressure value fed back by the pressure sensors (first rail pressure sensor and second rail pressure sensor) installed on the two common rail pipes with the preset target pressure value, and adjusts the duty cycle of the PWM signal sent to the two metering units in real time through a closed-loop control algorithm. This independent control mechanism ensures that the pressures of the two injection circuits can be independently adjusted according to the different working conditions of the engine, without interfering with each other.

[0060] Through the cooperative work of the two metering units, a truly independent dual-pressure control system is realized on a single oil pump structure. Not only does it avoid the pressure coupling problem of the traditional dual-pump system, but also significantly reduces the system complexity and manufacturing cost through integrated design. At the same time, independent pressure control enables the pre-injection circuit 3 and the main injection circuit 2 to always work in an optimal pressure state, effectively optimizing the combustion process and improving the thermal efficiency of the engine.

[0061] In some embodiments, with reference to Figure 1 , the main injection circuit 2 further comprises a first pressure relief valve 24 arranged on the first high-pressure common rail pipe 21. The pre-injection circuit 3 further comprises a second pressure relief valve (not shown in the figure) arranged on the second high-pressure common rail pipe 31. The first pressure relief valve 24 is an electronically controlled pressure relief valve, and the second pressure relief valve is a mechanical pressure relief valve.

[0062] Specifically, the electronically controlled pressure relief valve is preferably a normally closed electromagnetic valve, which is signal-connected with the electronic control unit 4 and can be quickly opened and closed according to the control instruction. It has dual functions: one is that when the engine is normally stopped or the system detects a fault, the electronic control unit 4 can actively trigger the valve to open, so that the high-pressure fuel in the main injection circuit 2 is rapidly relieved, avoiding potential safety hazards caused by slow pressure relief due to large oil volume in the main circuit; the other is that it is used as a safety valve when the system is over-pressurized, providing overpressure protection.

[0063] Specifically, the mechanical pressure relief valve is a spring-loaded structure, which works based on a preset mechanical pressure threshold. When the pressure in the pre-injection circuit 3 abnormally rises and exceeds the set value, the valve automatically opens to relieve pressure under the action of pressure difference, providing a reliable passive safety barrier for the system without external power supply.

[0064] This differentiated pressure relief arrangement fully considers the different characteristics of the two circuits. First, the main injection circuit 2 has large oil storage capacity and high pressure, and needs fast and active pressure relief capability, so an electronically controlled pressure relief valve with fast response and controllability is adopted. Second, the pre-injection circuit 3 has small volume and relatively low pressure, and the use of a mechanical pressure relief valve with simple structure, low cost and high reliability is sufficient to meet its overpressure protection requirements. This scheme realizes the optimal balance between performance and cost under the premise of ensuring system safety.

[0065] In some embodiments, referring to Figure 1 The main injector 22 is of a structure with a return oil passage, and the injection system further comprises a return oil pipeline 51 and a return oil back pressure valve 52 arranged on the return oil pipeline 51. The return oil pipeline 51 is in fluid communication with the return oil passage of the main injector 22, and the return oil back pressure valve 52 is configured to adjust the pressure in the return oil pipeline 51.

[0066] Specifically, the return oil passage is used to realize the injection and pressure control of high-pressure methanol. Since the main injection occupies a large proportion and the injection amount varies greatly at different loads, the return oil is increased to ensure the stability of the system. The pre-injection injector is a zero-return structure. Since the pre-injection occupies a small proportion and the injection amount is small, the influence on the rail pressure is small at different working conditions, and additional return oil is not needed to increase the stability of the system, thereby reducing the complexity of the system.

[0067] Further, when the electrically controlled pressure relief valve (i.e., the first pressure relief valve 24) is opened for high-pressure oil discharge, the electric control unit 4 can synchronously adjust the return oil back pressure valve 52 to appropriately increase the pressure in the return oil pipeline 51, thereby effectively inhibiting the cavitation phenomenon caused by the vaporization of methanol due to the sudden drop in pressure, and protecting the fuel system components. This arrangement significantly improves the reliability and durability of the system.

[0068] In some embodiments, referring to Figure 1 The injection system can further comprise a main injection pipeline 23 and a pre-injection pipeline 33.

[0069] Specifically, the main injection pipeline 23 is used to realize the high-pressure fuel delivery between the first output end of the high-pressure fuel pump 1 and the first high-pressure common rail pipeline 21 of the main injection circuit 2. The pipeline structure and material are designed to be able to withstand a working pressure of 500 bar to 2000 bar and have good methanol corrosion resistance.

[0070] Specifically, the pre-injection pipeline 33 is used to realize the fuel delivery between the second output end of the high-pressure fuel pump 1 and the second high-pressure common rail pipeline 31 of the pre-injection circuit 3. The pipeline specification can be set according to the working pressure requirement of 100 bar to 1000 bar.

[0071] Further, the main injection pipeline 23 and the pre-injection pipeline 33 are designed with different pipe diameters and wall thicknesses. The main injection pipeline 23 adopts a larger pipe diameter to ensure the delivery efficiency of large-flow fuel, and the pre-injection pipeline 33 adopts a relatively smaller pipe diameter to reduce the system volume and weight. Both pipelines can adopt stainless steel material to ensure long-term durability in the methanol fuel environment, and a double-sealing structure is used at the key connection parts to prevent high-pressure fuel leakage.

[0072] The application also provides an engine comprising the injection system, the main combustion chamber and the pre-combustion chamber as mentioned in any of the above embodiments. The main injector 22 in the main injection circuit 2 is installed on the top or side of the main combustion chamber, and its nozzle extends into the main combustion chamber and is configured to directly inject methanol fuel into the main combustion chamber for forming a main combustion mixture. The pre-injector 32 in the pre-injection circuit 3 is installed on the pre-combustion chamber, and its nozzle directly injects methanol fuel into the pre-combustion chamber for forming a mixture with appropriate concentration in the pre-combustion chamber.

[0073] The pre-combustion chamber is connected to the main combustion chamber through one or more flame channels. The structure design enables the high-temperature flame ignited by the spark plug in the pre-combustion chamber to be injected into the main combustion chamber at high speed through the flame channels, thereby igniting the mixture in the main combustion chamber and achieving a high-efficiency and stable combustion process.

[0074] The engine realizes independent and accurate control of fuel supply in the pre-combustion chamber and the main combustion chamber by adopting the above-mentioned injection system. During engine operation, the pre-injection circuit 3 works at a lower pressure to ensure the formation of reliable combustible mixture in the pre-combustion chamber. The main injection circuit 2 works at an ultrahigh pressure to ensure excellent fuel atomization effect in the main combustion chamber. The synergistic effect of the two makes the engine obtain optimal combustion effect in the entire operating range, significantly improves the thermal efficiency, and effectively reduces the emission of pollutants such as nitrogen oxides and soot.

[0075] The engine is particularly suitable for methanol fuel, and the design of its double independent injection system effectively solves the technical problems faced by methanol engines in compression ignition and ignition.

[0076] The application also provides a vehicle comprising the engine as mentioned in any of the above embodiments. The engine provides power for the vehicle through the synergistic effect of its double injection system (the main injection circuit 2 and the pre-injection circuit 3). The optimized combustion efficiency of the engine helps to improve the overall fuel economy of the vehicle.

[0077] The application also provides an injection control method for an engine, which is applied to the engine as mentioned in any of the above embodiments. Referring to Figure 2 , the injection control method comprises the following steps:

[0078] Step S100: during the engine starting stage, controlling the pre-injection circuit 3 to inject at a first pressure, and controlling the main injection circuit 2 to inject at a second pressure; wherein the second pressure is higher than the first pressure. Specifically, the first pressure is controlled in the range of 100-300 bar, and the second pressure is controlled in the range of 500-800 bar.

[0079] Step S200: During the engine warm-up stage, the pressures of the pre-injection circuit 3 and the main injection circuit 2 are adjusted in real time according to the coolant temperature and engine load. When the coolant temperature is detected to be above 70°C, the pre-injection circuit 3 pressure is gradually increased to a target value in the range of 100-1000 bar, while the main injection circuit 2 pressure is raised to a target value in the range of 500-2000 bar.

[0080] Step S300: During the normal engine operation stage, the pressures of the two injection circuits are independently adjusted based on the current operating condition parameters. The pre-injection circuit 3 pressure is adjusted according to the pre-chamber temperature, load changes, and emission requirements; the main injection circuit 2 pressure is adjusted according to the engine speed, load demand, and knock monitoring results.

[0081] The method further includes a spray timing control step: determining the fuel injection timing, duration, and frequency of the pre-injection and main injection according to the engine operating conditions. In low-load operating conditions, the pre-injection guided combustion mode is adopted, and in high-load operating conditions, the stratified combustion mode is adopted, and by adjusting the fuel injection parameters of the two injection circuits, a better combustion effect is achieved.

[0082] Further, the method further includes a safety protection step: real-time monitoring of the pressure data of the two injection circuits, when an abnormal pressure is detected, adjusting the metering unit opening and controlling the pressure relief valve to ensure that the system pressure is stable within a safe range.

[0083] The control method independently and cooperatively controls the working parameters of the two injection circuits, so that the engine can obtain optimal combustion effect in various operating conditions, thereby significantly improving the thermal efficiency of the engine and reducing pollutant emissions.

[0084] In some embodiments, the proportion of fuel injected through the pre-injection circuit 3 to the total fuel injection amount of the engine is not more than 5%.

[0085] The pre-chamber mainly serves as an ignition source in the engine, and the high-temperature flame jet produced after the fuel burns inside it is used to ignite the mixture in the main combustion chamber. Due to the limited volume of the pre-chamber and its non-direct participation in the power generation process, too high a fuel proportion not only cannot increase power output, but also can cause energy loss and emission deterioration. Controlling the pre-injection fuel quantity proportion below 5% can not only ensure the formation of sufficient concentration of combustible mixture in the pre-chamber, but also maximize the use of fuel for power generation in the main combustion chamber, thereby improving energy utilization efficiency.

[0086] In the implementation process, the ratio can be dynamically adjusted according to the engine operating conditions. In the cold start stage, the pre-injection amount ratio can be close to the upper limit value of 5% to ensure that sufficient concentration of mixture is formed in the pre-combustion chamber in a low temperature environment to ensure ignition reliability. As the engine temperature rises, the pre-injection amount ratio can gradually decrease to a minimum value of about 2%, at which time the pre-combustion chamber wall temperature is higher, and the fuel atomization and evaporation conditions are improved, and less fuel can form a suitable ignition mixture concentration.

[0087] The control strategy can be calculated by the electronic control unit 4 in real time to calculate the fuel amount of the pre-injection circuit 3 according to the preset ratio. The pre-injection circuit 3 performs injection according to the calculation result, and the remaining fuel is provided by the main injection circuit 2. This distribution mode not only ensures the reliability of the pre-combustion chamber ignition, but also ensures that the main combustion chamber obtains sufficient fuel supply, so that the engine can maintain optimal combustion performance in the entire working range.

[0088] By accurately controlling the pre-injection amount ratio, not only the thermal efficiency of the engine is improved, but also the combustion instability phenomenon caused by excessive fuel enrichment or lean combustion in the pre-combustion chamber is effectively reduced, and the emission of pollutants such as unburned hydrocarbons and carbon monoxide is reduced.

[0089] In some embodiments, the injection strategy of the main injection circuit 2 includes intelligent injection mode switching based on engine load: when the engine load is lower than a preset threshold (such as 30% load), the control system adopts single injection mode; when the engine load is higher than the preset threshold, the multiple injection mode is enabled, and the interval of any two adjacent injections is controlled within 10-30° crank angle range.

[0090] Specifically, the implementation of the injection strategy is realized by the electronic control unit 4 monitoring engine speed, load, temperature and other parameters in real time. In the low load condition, the single injection mode can ensure that the fuel forms a uniform mixture in the combustion chamber, and at the same time avoids the problem of uneven mixing of oil and gas caused by multiple injections. When entering the high load condition, the multiple injection mode divides the total injection amount into several injections, and by accurately controlling the phase interval (10-30° CA) between each injection, the combustion rate can be effectively controlled, and the fuel atomization effect can be optimized.

[0091] Further, the multiple injection can adopt the combination of pilot injection and main injection. The pilot injection injects a small amount of fuel to increase the combustion chamber temperature and activate the chemical reaction, creating a more favorable combustion environment for the main injection; the main injection is responsible for providing the fuel required for main work. This segmented injection strategy not only improves the combustion process, but also effectively suppresses the generation of nitrogen oxides and combustion noise.

[0092] Specifically, the interval between two adjacent injections defined in 10-30° crank angle is a preferable range based on a large number of experimental verifications: if the interval is less than 10°, the atomization quality of the subsequent injection may be affected due to the insufficient evaporation of the fuel of the previous injection; if the interval is greater than 30°, it may lead to uneven mixing of oil and gas, affecting the combustion stability. The interval range can be dynamically adjusted according to the specific working conditions, such as using a smaller interval to improve combustion efficiency under high-speed high-load conditions, and using a larger interval to optimize emission performance under low-speed conditions.

[0093] The injection control strategy can obtain good combustion effect of the engine under different load conditions by flexibly adjusting the injection mode and injection parameters, which not only ensures the power output, but also effectively reduces the pollutant emission.

[0094] The terms "first", "second", and similar terms used in the specification and claims of the present application do not denote any order, quantity, or importance, but are only used to distinguish different components. Similarly, the terms "one" or "a" and similar terms do not denote a quantity limitation, but denote the existence of at least one, and if only "one" is referred to, it will be separately stated. "Multiple" or "several" means two or more. The term "and / or" used in the present document means any or all possible combinations of one or more associated listed items.

[0095] The technical features of the above embodiments can be combined in any manner. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present specification.

Claims

1. An injection system for an engine, characterized in that, include: A high-pressure oil pump, wherein the high-pressure oil pump is provided with a first output terminal and a second output terminal; The main injection circuit includes a first high-pressure common rail pipe fluidly connected to the first output end, and a main injector connected to the first high-pressure common rail pipe. The pre-injection circuit includes a second high-pressure common rail pipe fluidly connected to the second output end, and a pre-injector connected to the second high-pressure common rail pipe; wherein, The pre-injection circuit is configured to inject at a pressure lower than that of the main injection circuit.

2. The injection system according to claim 1, characterized in that, The injection pressure of the main injection circuit is configured to be 500 bar–2000 bar; The injection pressure of the pre-injection circuit is configured to be 100 bar–1000 bar.

3. The injection system according to claim 1, characterized in that, The high-pressure oil pump includes multiple plungers, with the first output end supplied with oil by at least two of the plungers working together, and the second output end supplied with oil by at least one of the independent plungers.

4. The injection system according to claim 1, characterized in that, The high-pressure oil pump further includes a first metering unit and a second metering unit. The first metering unit is used to regulate the fuel flow rate to the first output end, and the second metering unit is used to independently regulate the fuel flow rate to the second output end.

5. The injection system according to claim 4, characterized in that, The main injection circuit also includes a first rail pressure sensor disposed on the first high-pressure common rail. The first rail pressure sensor is communicatively connected to the first metering unit to form a first closed-loop control of the pressure of the main injection circuit. The pre-injection circuit also includes a second rail pressure sensor disposed on the second high-pressure common rail. The second rail pressure sensor is communicatively connected to the second metering unit to form a second closed-loop control of the pressure of the pre-injection circuit. The first closed-loop control and the second closed-loop control system are independent of each other.

6. The injection system according to claim 1, characterized in that, The main injection circuit further includes a first pressure relief valve disposed on the first high-pressure common rail; the pre-injection circuit further includes a second pressure relief valve disposed on the second high-pressure common rail; wherein The first pressure relief valve is an electrically controlled pressure relief valve, and the second pressure relief valve is a mechanical pressure relief valve.

7. The injection system according to claim 1, characterized in that, The main injector has a structure with a return oil circuit; the injection system also includes a return oil line and a return oil back pressure valve disposed on the return oil line; the return oil line is in fluid communication with the return oil line of the main injector, and the return oil back pressure valve is configured to regulate the pressure in the return oil line.

8. The injection system according to any one of claims 1-7, characterized in that, It also includes an electronic control unit, which is communicatively connected to the high-pressure oil pump and is used to independently control the output pressure of the first output terminal and the second output terminal.

9. An engine, characterized in that, include: The injection system as described in any one of claims 1 to 8; Main combustion chamber; as well as Pre-combustion chamber; The main injector is configured to inject fuel into the main combustion chamber; the pre-injector is configured to inject fuel into the pre-combustion chamber.

10. The engine according to claim 9, characterized in that, The pre-combustion chamber is housed within the main combustion chamber.

11. A vehicle, characterized in that, Including the engine as described in claim 9 or 10.

12. A method for injection control of an engine, applied to the engine as described in claim 9 or 10, characterized in that, include: During engine start-up, the pre-injection circuit is controlled to inject at a first pressure, and the main injection circuit is controlled to inject at a second pressure; wherein the second pressure is higher than the first pressure.

13. The injection control method according to claim 12, characterized in that, During the engine start-up phase, the first pressure is controlled within the range of 100 bar to 1000 bar, and the second pressure is controlled within the range of 500 bar to 2000 bar.

14. The injection control method according to claim 12, characterized in that, The amount of fuel injected through the pre-injection circuit accounts for no more than 5% of the total fuel injection amount of the engine.

15. The control method according to claim 12, characterized in that, The injection strategy for controlling the main injection circuit includes: When the engine load is below a preset threshold, the main injector is controlled to adopt a single injection mode; When the engine load is higher than the preset threshold, the main injector is controlled to adopt a multiple injection mode, and the interval between any two adjacent injections is 10–30° crankshaft angle.

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