WO2022021717A1 - 一种喷油方法 - Google Patents

一种喷油方法 Download PDF

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Publication number
WO2022021717A1
WO2022021717A1 PCT/CN2020/133609 CN2020133609W WO2022021717A1 WO 2022021717 A1 WO2022021717 A1 WO 2022021717A1 CN 2020133609 W CN2020133609 W CN 2020133609W WO 2022021717 A1 WO2022021717 A1 WO 2022021717A1
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WIPO (PCT)
Prior art keywords
engine
injection
fuel injection
fuel
load
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PCT/CN2020/133609
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English (en)
French (fr)
Inventor
向璐
沈惠贤
蒲运平
郑建军
曾庆强
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重庆长安汽车股份有限公司
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Priority to RU2021100672A priority Critical patent/RU2756704C1/ru
Publication of WO2022021717A1 publication Critical patent/WO2022021717A1/zh

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/38—Controlling fuel injection of the high pressure type
    • F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
    • F02D41/402—Multiple injections
    • F02D41/405—Multiple injections with post injections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/04—Introducing corrections for particular operating conditions
    • F02D41/047—Taking into account fuel evaporation or wall wetting

Definitions

  • the invention relates to an automobile engine, in particular to a fuel injection method.
  • In-cylinder direct injection is an important means to improve the fuel economy and power performance of gasoline engines.
  • liquid fuel directly collides with the cylinder liner, forming a liquid oil film on the cylinder liner. This part of the liquid oil film is moved by the piston. During the process, the piston ring will be scraped into the oil pan, causing the oil level to rise, the kinematic viscosity of the oil to drop, and the performance of the oil to be destroyed.
  • the main reasons for the rise of the oil level of the direct injection engine in the cylinder are: the unreasonable shape of the combustion chamber, the unreasonable fuel injection control method (including fuel injection pressure/fuel injection timing/fuel injection ratio), resulting in poor atomization of the oil beam and excessive penetration distance.
  • This type of fuel injection strategy has a greater risk of oil level rise under extremely cold conditions, mainly because: first, under extremely cold conditions (-30°C) The temperature of the fuel tank at low temperature is basically the same as the ambient temperature, and the fuel supply system has little effect on the fuel heating, resulting in the temperature of the oil bundle entering the combustion chamber close to the ambient temperature. The increase of the distance increases the risk of the oil beam hitting the cylinder wall to form an oil film; secondly, it is difficult for the engine to start cold under extremely cold conditions.
  • At least some embodiments of the present invention provide an oil injection method to at least partially solve the problem that the related art cannot effectively control the oil level rise of an engine in an extremely cold environment.
  • a fuel injection method comprising: when the engine is at a low load, a single injection is performed in each working cycle, and the fuel injection is completed before the exhaust top dead center; when the engine is at a low load At medium load, two injections are performed per working cycle, and the first injection is completed before the exhaust top dead center; when the engine is at high load, three injections are performed per working cycle, and the first injection is performed in the exhaust. Complete fuel injection before top dead center.
  • the second injection is initiated late in the compression stroke when the engine is at medium load.
  • the fuel injection amount of the second injection is not greater than 40% of the total fuel injection amount, the fuel injection amount of the first injection and the fuel injection amount of the second injection The sum is the total fuel injection quantity.
  • the start of the second injection is 30-50 crankshaft degrees after intake top dead center.
  • the third injection is initiated late in the compression stroke when the engine is under high load.
  • the fuel injection amount of the third injection is not greater than 40% of the total fuel injection amount, the fuel injection amount of the first injection, and the fuel injection amount of the second injection And the sum of the fuel injection quantity of the third injection is the total fuel injection quantity.
  • the fuel injection amount of the second injection accounts for 40%-50% of the remaining fuel injection amount, and the remaining fuel injection amount is the total fuel injection amount minus the first injection amount of fuel injection.
  • the single injection when the engine is at low load, the single injection is started late in the exhaust stroke; when the engine is at medium load, the first injection is started late in the exhaust stroke When the engine is at high load, at The first injection starts late in the exhaust stroke.
  • the engine speed range when the engine is at low load, the engine speed range is 800r/min-3000r/min, and the engine load range is 0bar-4bar; when the engine is at medium load, the engine speed range is 800r/min- 3000r/min, the engine load range is 3bar-10bar; when the engine is under high load, the engine speed range is 800r/min-3000r/min, and the engine load range is ⁇ 9bar.
  • At least some embodiments of the present invention take advantage of the advantage that the temperature in the cylinder of the engine exhaust stroke is higher than that of the engine intake stroke, and control part of the fuel injection process in the later stage of the exhaust stroke; on the one hand, maximize the use of the residual gas temperature in the cylinder to accelerate fuel evaporation , reducing the spray penetration distance, thereby reducing the wet wall of the cylinder liner; on the other hand, using the favorable conditions of high cylinder liner temperature in the later stage of the exhaust stroke to accelerate the evaporation of the oil film on the cylinder wall. Therefore, the present invention can greatly improve the problems of oil dilution and oil level rise of the direct injection engine under extremely cold environment. And the test results of the low temperature environment chamber show that (after the 7-cycle test, the oil level only increased by 1mm), this fuel injection method has a significant effect on controlling the oil level when the engine is in extremely cold working conditions.
  • FIG. 1 is a schematic diagram of a working area according to an embodiment of the present invention.
  • FIG. 2 is a schematic diagram of a fuel injection method according to an embodiment of the present invention.
  • an oil injection method is proposed to alleviate the problem of oil level rise in a supercharged direct injection engine under extreme cold conditions.
  • the details are as follows:
  • the fuel injection volume of the engine is small, and the injection end angle is controlled before the exhaust top dead center.
  • the simulation result shows that the wetted wall rate of the cylinder liner is 0.04%.
  • the cylinder liner under the original fuel injection strategy The wetted wall rate is 2.2%. From the simulation results, the residual exhaust gas temperature in the cylinder can reduce the wetted wall of the cylinder liner by 98%. up 1mm) This move keeps the oil level lower in this area.
  • the fuel injection amount of the first injection can be calculated according to the fuel injection pulse width completed before the exhaust top dead center.
  • the preferred method is (fuel injection start angle-360deg)*injection
  • the oil rate that is, the end angle of the first injection is before the exhaust top dead center as much as possible to inject as much fuel as possible, which can be more conducive to the atomization and evaporation of the fuel, and greatly reduce the risk of oil level rise, but also It is necessary to scan the starting angle of fuel injection through simulation, and the appropriate starting angle of fuel injection can be determined through the simulation results of the hydrocarbon overflow rate and the wet wall rate of the spark plug, so as to prevent a large amount of fuel from entering the exhaust system with the exhaust gas and causing the temperature of the three-way catalytic converter to overheat. high risk.
  • the fuel injected for the second time is the fuel that cannot be injected before the exhaust top dead center, and this part of the fuel cannot be atomized and evaporated by the residual temperature in the cylinder.
  • the temperature of the fuel entering the cylinder under cold conditions is basically the same as the ambient temperature, and the temperature in the cylinder during the intake stroke is also lower. If the fuel is injected into the cylinder during the intake stroke, it cannot be completely atomized, and the liquid fuel and the cylinder The oil film on the wall formed by the collision of the sleeve cannot be completely evaporated, and the risk of the oil level rising is great. Therefore, it is preferable to start the second injection at the end of the compression stroke.
  • the temperature in the cylinder at the end of the compression stroke is higher than that of the intake stroke.
  • the increased fuel can be atomized, and in order to ensure that the temperature at the later stage of the compression stroke can completely atomize the fuel, the fuel injection ratio of the second injection should not exceed 40% of the total fuel injection amount as much as possible, so as to reduce the oil level.
  • the sum of the injection volume of the first injection and the injection volume of the second injection is the total injection volume.
  • the preferred method is (injection Oil start angle -360deg)*fuel injection rate, that is, the injection end angle of the first injection is before the exhaust top dead center as much as possible, and the third injection starts at the end of the compression stroke, and the injection of the third injection
  • the fuel ratio should not exceed 40% as much as possible.
  • the sum of the fuel injection volume of the first injection, the fuel injection volume of the second injection and the fuel injection volume of the third injection is the total fuel injection volume.
  • the temperature in the cylinder of the intake stroke is low, and the fuel cannot be completely atomized, and the penetration distance of the oil beam is large, and the cylinder liner wet wall is easily formed. It brings the risk of oil level rising, so the starting point of the second fuel injection needs to be set at 30 to 50 degrees of the crankshaft angle after the top dead center of the intake air. At this time, the position of the piston in the cylinder is closer to the top dead center. It can effectively block the oil beam and shorten the penetration distance of the oil beam.
  • the fuel injection amount of the first injection can be calculated according to the fuel injection pulse width that completes the injection before the exhaust top dead center.
  • the preferred method is (fuel injection start angle -360deg) *
  • the fuel injection rate that is, the end angle of the first injection is before the exhaust top dead center as much as possible to inject as much fuel as possible, which can be more conducive to the atomization and evaporation of the fuel, and greatly reduce the risk of the oil level rising.
  • the hydrocarbon overflow rate and the wet wall rate of the spark plug can be used to determine the appropriate starting angle of fuel injection, so as to prevent a large amount of fuel from entering the exhaust system with the exhaust gas and causing the three-way catalysis other risks such as overheating.
  • the quantity is the total injection quantity minus the injection quantity of the first injection.
  • the single injection starts late in the exhaust stroke when the engine is at low load; the first injection starts late in the exhaust stroke when the engine is at medium load; and when the engine is at high load, The first injection begins late in the exhaust stroke.
  • the residual gas temperature in the cylinder is maximized to accelerate the evaporation of fuel, and the spray penetration distance is reduced, thereby reducing the wet wall of the cylinder liner;
  • the engine speed range when the engine is under low load, the engine speed range is 800r/min-3000r/min, the engine load range is 0bar-4bar, and the engine works within the range of region A; At medium load, the engine speed range is 800r/min-3000r/min, the engine load range is 3bar-10bar, and the engine works within the range of zone B; when the engine is under high load, the engine speed range is 800r/min-3000r/min , the engine load interval is ⁇ 9bar, and the engine works within the range of region C.
  • the overlapping part of area A and area B can be set to preferentially select the fuel injection strategy of area B, and the overlapping part of area C and area B can be set to preferentially select the fuel injection strategy of area C.
  • At least some embodiments of the present invention inject the circulating fuel injection amount into the cylinder in different proportions according to the operating conditions of the engine, so as to ensure that part or all of the fuel enters the cylinder at the later stage of the exhaust stroke, and to ensure that the part of the fuel injection process ends when the intake valve opens Before.
  • the present invention reasonably distributes the circulating fuel injection amount according to the engine operating conditions, injects part or all of the fuel into the cylinder at the later stage of the exhaust stroke, maximizes the utilization of the residual exhaust heat in the cylinder at the later stage of the exhaust stroke, and accelerates the atomization and evaporation of the fuel , reduce the fuel penetration and the wet wall of the cylinder liner, and suppress the formation of the oil film on the cylinder liner from the source.
  • the disclosed technical content can be implemented in other ways.
  • the device embodiments described above are only illustrative, for example, the division of the units may be a logical function division, and there may be other division methods in actual implementation, for example, multiple units or components may be combined or Integration into another system, or some features can be ignored, or not implemented.
  • the shown or discussed mutual coupling or direct coupling or communication connection may be through some interfaces, indirect coupling or communication connection of units or modules, and may be in electrical or other forms.
  • the units described as separate components may or may not be physically separated, and components shown as units may or may not be physical units, that is, may be located in one place, or may be distributed to multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution in this embodiment.
  • each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically alone, or two or more units may be integrated into one unit.
  • the above-mentioned integrated units can be realized in the form of hardware, and can also be realized in the form of software functional units.
  • the integrated unit if implemented in the form of a software functional unit and sold or used as an independent product, may be stored in a computer-readable storage medium.
  • the technical solution of the present invention can be embodied in the form of a software product in essence, or the part that contributes to the related technology, or all or part of the technical solution, and the computer software product is stored in a storage medium.
  • a computer device which may be a personal computer, a server, or a network device, etc.
  • the aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk and other media that can store program codes .

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

Abstract

一种喷油方法，在发动机处于低负荷时，每个工作循环进行单次喷射，并在排气上止点之前完成喷油；在发动机处于中负荷时，每个工作循环进行两次喷射，第一次喷射在排气上止点之前完成喷油；在发动机处于高负荷时，每个工作循环进行三次喷射，第一次喷射在排气上止点之前完成喷油。该喷油方法利用发动机排气行程缸内的温度高于发动机进气行程的优势，将部分喷油过程控制在排气行程后期；一方面，最大化利用缸内残余气体温度加速燃油蒸发，降低喷雾贯穿距，从而降低缸套湿壁；另一方面，利用排气行程后期缸套温度高的有利条件加速气缸壁面上油膜的蒸发。因此，该喷油方法能够大幅度改善极寒环境下直喷发动机机油稀释和机油液面上升问题。

Description

一种喷油方法 技术领域
本发明涉及汽车发动机，具体涉及一种喷油方法。
背景技术
缸内直喷(GDI)是提高汽油机燃油经济性、动力性的重要手段，但是，缸内直喷发动机存在液态燃油直接碰撞气缸套，在缸套上形成液态油膜，这部分液态油膜在活塞运动过程中会被活塞环刮入油底壳，导致机油液面上升，机油运动粘度下降，机油的使用性能被破坏，发动机高速运动部件润滑油膜的建立受到影响，造成发动机整体可靠性的降低。缸内直喷发动机油液面上升的原因主要有：燃烧室形状不合理，喷油控制方法(包括喷油压力/喷油时刻/喷油比例)不合理导致油束雾化不良、贯穿距过大，活塞气环与气缸配合不合理、气缸壁面与液态燃油温度低不易于蒸发、油气分离器以及曲轴箱通风系统设计不合理。对于增压直喷发动机(喷油量较大)，缸套油膜量更高，机油液面上升的风险更大。
研究表明，在环境温度极低的情况下，机油液面上升问题更加突出，因为壁面油膜的蒸发速度与气缸壁的金属温度和燃油温度紧密相关，一般情况下，通过优化发动机热管理系统将燃烧室壁面温度控制在合适范围内有利于壁面油膜的蒸发。但是，在环境温度极低(-30℃)的情况下，发动机热管理系统无法将燃烧室壁面温度控制在利于燃油蒸发的范围内，导致缸套上已经形成的油膜无法快速蒸发，机油液面上升问题很难得到控制。
相关技术大部分将喷油过程控制在发动机进气及压缩行程，此类喷油策略在极寒条件下机油液面上升风险较大，主要是因为：首先，极寒条件下(-30℃)下的燃油箱温度与环境温度基本一致，而供油系统对燃油加热效果甚微，导致进入燃烧室内油束的温度接近环境温度，低温下燃油液滴蒸发、破碎、雾化困难导致油束贯穿距增大，增加了油束撞击气缸壁面形成油膜的风险；其次，极寒条件下发动机冷启动困难，ECU(Electronic Control Unit)采取加浓混合气的策略实现发动机快速启动，喷油量增大进一步加剧了缸套油膜的形成；而且，当发动机处于极寒工作条件时，冷却系统升温慢，发动机水温一直维持在较低范围，导致壁面温度低，不利于气缸套上油膜的蒸发。因此，基于相关技术无法有效控制极寒环境下发动机的机油液面上升问题。
发明内容
本发明至少部分实施例提供了一种喷油方法，以至少部分地解决相关技术无法有效控制极寒环境下发动机的机油液面上升的问题。
在本发明其中一实施例中，提供了一种喷油方法，包括：在发动机处于低负荷时，每个工作循环进行单次喷射，并在排气上止点之前完成喷油；在发动机处于中负荷时，每个工作循环进行两次喷射，第一次喷射在排气上止点之前完成喷油；在发动机处于高负荷时，每个工作循环进行三次喷射，第一次喷射在排气上止点之前完成喷油。
在一个可选实施例中，在发动机处于中负荷时，在压缩行程后期开始第二次喷射。
在一个可选实施例中，在发动机处于中负荷时，第二次喷射的喷油量不大于总喷油量的40％，第一次喷射的喷油量和第二次喷射的喷油量之和为总喷油量。
在一个可选实施例中，在发动机处于高负荷时，第二次喷射始点在进气上止点后30-50度曲轴转角处。
在一个可选实施例中，在发动机处于高负荷时，在压缩行程后期开始第三次喷射。
在一个可选实施例中，在发动机处于高负荷时，第三次喷射的喷油量不大于总喷油量的40％，第一次喷射的喷油量、第二次喷射的喷油量以及第三次喷射的喷油量之和为总喷油量。
在一个可选实施例中，在发动机处于高负荷时，第二次喷射的喷油量占剩余喷油量的40％-50％，剩余喷油量为总喷油量减去第一次喷射的喷油量。
在一个可选实施例中，在发动机处于低负荷时，在排气行程后期开始单次喷射；在发动机处于中负荷时，在排气行程后期开始第一次喷射在发动机处于高负荷时，在排气行程后期开始第一次喷射。
在一个可选实施例中，在发动机处于低负荷时，发动机转速区间为800r/min-3000r/min，发动机负荷区间为0bar-4bar；在发动机处于中负荷时，发动机转速区间为800r/min-3000r/min，发动机负荷区间为3bar-10bar；在发动机处于高负荷时，发动机转速区间为800r/min-3000r/min，发动机负荷区间为≥9bar。
本发明至少部分实施例利用发动机排气行程缸内的温度高于发动机进气行程的优势，将部分喷油过程控制在排气行程后期；一方面，最大化利用缸内残余气体温度加速燃油蒸发，降低喷雾贯穿距，从而降低缸套湿壁；另一方面利用排气行程后期缸套温度高的有利条件加速气缸壁面上油膜的蒸发。因此，本发明可以大幅度改善极寒环境下直喷发动机机油稀释和机油液面上升问题。并且低温环境舱试验结果表明(7个 循环的试验结束后，机油液面只上涨了1mm)此喷油方法针对当发动机处于极寒工作条件下控制机油液面具有显著效果。
附图说明
图1是根据本发明其中一实施例的工况区域示意图。
图2是根据本发明其中一实施例的喷油方法的示意图。
具体实施方式
下面结合附图对本发明作进一步说明。
如图1和图2所示，在本发明其中一实施例中，提出了一种喷油方法，用于缓解极寒条件下增压直喷发动机机油液面上升的问题，具体如下：
如图1所示，当发动机的工况处于区域A时，发动机运转在低负荷区域，极寒条件(-30℃)下的燃油箱温度与环境温度基本一致，而供油系统对燃油加热效果甚微，导致进入燃烧室内油束的温度接近环境温度，而当发动机处于该区域时燃油温度更低，因此发动机工作在区域A范围内时每个工作循环进行单次喷射，并在排气上止点(CA＝360deg.)之前完成喷油；通过最大化利用发动机燃烧后缸内工质的温度大幅度雾化液态燃油，达到尽可能严格控制油束贯穿距的目的，从而确保液态燃油在碰撞缸套壁面之前已大部分雾化完成，降低油束运动至缸套壁面形成缸套油膜的概率，缸内残余工质的温度也可加速缸套油膜的蒸发。
当发动机工作在区域A范围内时，发动机的喷油量较小，喷油结束角控制在排气上止点之前，仿真结果缸套湿壁率为0.04％，原喷油策略下的缸套湿壁率为2.2％，从仿真结果来看，缸内残余的排气温度可将缸套湿壁降低98％，低温环境舱试验结果也表明(7个循环的试验结束后，机油液面只上涨了1mm)此举措可使该区域的机油液面处于较低水平。
如图1所示，当发动机的工况处于区域B时，发动机运转在中负荷区域，此区域发动机喷油量随着负荷的增大而增加，极寒条件(-30℃)下时，为了能最大化利用缸内残余温度雾化燃油，期望在排气上止点前完成全部喷射，但是当发动机处于区域B时喷油量较区域A大，无法在排气上止点前完成全部喷射，所以每个工作循环需要进行两次喷射。
发动机的工况处于区域B时，第一次喷射的喷油量可根据在排气上止点前完成喷射的喷油脉宽来计算，优选方法为(喷油起始角-360deg)*喷油速率，也即是第一次 喷射结束角在排气上止点之前的前提下尽量多喷油，就能够更有利于燃油的雾化蒸发，大幅度降低机油液面上涨的风险，但也需通过仿真扫描喷油起始角，通过仿真结果碳氢溢出率以及火花塞的湿壁率可确定合适的喷油起始角，以防止大量燃油随废气进入排气系统造成三元催化器温度过高的风险。
发动机的工况处于区域B时，第二次喷射的燃油是因为无法在排气上止点前喷完的燃油，此部分燃油不能通过缸内残余温度来雾化蒸发，如前所述，极寒条件下进入缸内的燃油温度与环境温度基本一致，并且进气行程时气缸内的温度也较低，燃油若在进气行程被喷射入缸内，则无法雾化完全，液态燃油与气缸套碰撞形成的壁面油膜也无法蒸发完全，机油液面上涨的风险极大，因此优选在压缩行程后期开始第二次喷射，如图2所示，压缩行程后期缸内的温度较进气行程有所增加，燃油能够得到雾化，并且为了保证压缩行程后期的温度能够将燃油雾化完全，所以第二次喷射的喷油比例尽量不要超过总喷油量的40％，以此降低机油液面上涨的风险，第一次喷射的喷油量和第二次喷射的喷油量之和为总喷油量。
如图1所示，当发动机的工况处于区域C时，发动机运转在高负荷区域，随着负荷的进一步增大，喷油量也大幅增加，若沿用区域B的两次喷射策略，则在压缩行程后期进行的最后一次喷射存在因喷油持续期过长导致部分燃油随着排气门开启后进入排气系统。因此，当发动机运转在区域C时每个工作循环需要进行三次喷射，第一次喷射的喷油量可根据在排气上止点前完成喷射的喷油脉宽来计算，优选方法为(喷油起始角-360deg)*喷油速率，即是第一次喷射结束角在排气上止点之前的前提下尽量多喷油，压缩行程后期开始第三次喷射，第三次喷射的喷油比例尽量不要超过40％，第一次喷射的喷油量、第二次喷射的喷油量以及第三次喷射的喷油量之和为总喷油量。
当发动机的工况处于区域C时，由于在极寒环境下(-30℃)，进气行程的缸内温度较低无法将燃油雾化完全，油束贯穿距较大易形成缸套湿壁带来机油液面上涨的风险，所以第二次喷油始点需要设置在进气上止点后30～50度曲轴转角处，此时活塞在气缸里所处的位置离上止点较近，可以有效的阻挡油束，缩短油束的贯穿距。
当发动机的工况处于区域C时，第一次喷射的喷油量可根据以在排气上止点前完成喷射的喷油脉宽来计算，优选方法为(喷油起始角-360deg)*喷油速率，也即是第一次喷射结束角在排气上止点之前的前提下尽量多喷油，就能够更有利于燃油的雾化蒸发，大幅度降低机油液面上涨的风险，但也需通过仿真扫描喷油起始角，通过仿真结果碳氢溢出率以及火花塞的湿壁率可摸底确定合适的喷油起始角，以防止大量燃油随废气进入排气系统造成三元催化器温度过高等其他风险。在一个可选实施例中，第二次喷射的喷油量与第三次喷射的喷油量在第一喷射的喷油量(一喷喷油量＝喷油起始 角-360deg)*喷油速率)确定好以后，第二次喷射的喷油量占剩余喷油量的40％-50％，第三次喷射的喷油量占剩余喷油量的50％-60％，剩余喷油量为总喷油量减去第一次喷射的喷油量。
在一个可选实施例中，在发动机处于低负荷时，在排气行程后期开始单次喷射；在发动机处于中负荷时，在排气行程后期开始第一次喷射；在发动机处于高负荷时，在排气行程后期开始第一次喷射。一方面，最大化利用缸内残余气体温度加速燃油蒸发，降低喷雾贯穿距，从而降低缸套湿壁；另一方面利用排气行程后期缸套温度高的有利条件加速气缸壁面上油膜的蒸发。
如图1所示，在本实施例中，在发动机处于低负荷时，发动机转速区间为800r/min-3000r/min，发动机负荷区间为0bar-4bar，发动机工作在区域A范围内；在发动机处于中负荷时，发动机转速区间为800r/min-3000r/min，发动机负荷区间为3bar-10bar，发动机工作在区域B范围内；在发动机处于高负荷时，发动机转速区间为800r/min-3000r/min，发动机负荷区间为≥9bar,发动机工作在区域C范围内。在具体实施时，在区域A和区域B重合的部分可以设置成优先选择区域B的喷油策略，在区域C和区域B重合的部分可以设置成优先选择区域C的喷油策略。
本发明至少部分实施例根据发动机运转工况将循环喷油量按照不同比例喷射入气缸内，确保在排气行程后期部分或全部燃油进入气缸，并保证该部分喷油过程结束于进气门打开之前。本发明根据发动机运转工况将循环喷油量进行合理分配，在排气行程后期将部分或全部燃油喷入气缸，最大化利用排气冲程后期的缸内残余废气热量，加速燃油雾化及蒸发，减少燃油贯穿及缸套湿壁，从源头上抑制气缸套上油膜的形成。
在本申请所提供的几个实施例中，应该理解到，所揭露的技术内容，可通过其它的方式实现。其中，以上所描述的装置实施例仅仅是示意性的，例如所述单元的划分，可以为一种逻辑功能划分，实际实现时可以有另外的划分方式，例如多个单元或组件可以结合或者可以集成到另一个系统，或一些特征可以忽略，或不执行。另一点，所显示或讨论的相互之间的耦合或直接耦合或通信连接可以是通过一些接口，单元或模块的间接耦合或通信连接，可以是电性或其它的形式。
所述作为分离部件说明的单元可以是或者也可以不是物理上分开的，作为单元显示的部件可以是或者也可以不是物理单元，即可以位于一个地方，或者也可以分布到多个单元上。可以根据实际的需要选择其中的部分或者全部单元来实现本实施例方案的目的。
另外，在本发明各个实施例中的各功能单元可以集成在一个处理单元中，也可以是各个单元单独物理存在，也可以两个或两个以上单元集成在一个单元中。上述集成 的单元既可以采用硬件的形式实现，也可以采用软件功能单元的形式实现。
所述集成的单元如果以软件功能单元的形式实现并作为独立的产品销售或使用时，可以存储在一个计算机可读取存储介质中。基于这样的理解，本发明的技术方案本质上或者说对相关技术做出贡献的部分或者该技术方案的全部或部分可以以软件产品的形式体现出来，该计算机软件产品存储在一个存储介质中，包括若干指令用以使得一台计算机设备(可为个人计算机、服务器或者网络设备等)执行本发明各个实施例所述方法的全部或部分步骤。而前述的存储介质包括：U盘、只读存储器(ROM，Read-Only Memory)、随机存取存储器(RAM，Random Access Memory)、移动硬盘、磁碟或者光盘等各种可以存储程序代码的介质。
以上所述仅是本发明的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也应视为本发明的保护范围。

Claims (9)

  1. 一种喷油方法，包括：
    在发动机处于低负荷时，每个工作循环进行单次喷射，并在排气上止点之前完成喷油；
    在发动机处于中负荷时，每个工作循环进行两次喷射，第一次喷射在排气上止点之前完成喷油；
    在发动机处于高负荷时，每个工作循环进行三次喷射，第一次喷射在排气上止点之前完成喷油。
  2. 根据权利要求1所述的喷油方法，其中，在发动机处于中负荷时，在压缩行程后期开始第二次喷射。
  3. 根据权利要求1所述的喷油方法，其中，在发动机处于中负荷时，第二次喷射的喷油量不大于总喷油量的40％，第一次喷射的喷油量和第二次喷射的喷油量之和为总喷油量。
  4. 根据权利要求1所述的喷油方法，其中，在发动机处于高负荷时，第二次喷射始点在进气上止点后30-50度曲轴转角处。
  5. 根据权利要求1所述的喷油方法，其中，在发动机处于高负荷时，在压缩行程后期开始第三次喷射。
  6. 根据权利要求1所述的喷油方法，其中，在发动机处于高负荷时，第三次喷射的喷油量不大于总喷油量的40％，第一次喷射的喷油量、第二次喷射的喷油量以及第三次喷射的喷油量之和为总喷油量。
  7. 根据权利要求6所述的喷油方法，其中，在发动机处于高负荷时，第二次喷射的喷油量占剩余喷油量的40％-50％，剩余喷油量为总喷油量减去第一次喷射的喷油量。
  8. 根据权利要求1所述的喷油方法，其中，在发动机处于低负荷时，在排气行程后期开始单次喷射；在发动机处于中负荷时，在排气行程后期开始第一次喷射在发动机处于高负荷时，在排气行程后期开始第一次喷射。
  9. 根据权利要求1所述的喷油方法，其中，在发动机处于低负荷时，发动机转速区间为800r/min-3000r/min，发动机负荷区间为0bar-4bar；在发动机处于中负荷时， 发动机转速区间为800r/min-3000r/min，发动机负荷区间为3bar-10bar；在发动机处于高负荷时，发动机转速区间为800r/min-3000r/min，发动机负荷区间为≥9bar。
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