WO2020108567A1 - 具有低压egr***的发动机的控制策略以及车辆 - Google Patents

具有低压egr***的发动机的控制策略以及车辆 Download PDF

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WO2020108567A1
WO2020108567A1 PCT/CN2019/121626 CN2019121626W WO2020108567A1 WO 2020108567 A1 WO2020108567 A1 WO 2020108567A1 CN 2019121626 W CN2019121626 W CN 2019121626W WO 2020108567 A1 WO2020108567 A1 WO 2020108567A1
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region
engine
egr
low
control strategy
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PCT/CN2019/121626
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English (en)
French (fr)
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崔亚彬
宋东先
王立俊
常进才
马京卫
刘亚奇
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长城汽车股份有限公司
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Publication of WO2020108567A1 publication Critical patent/WO2020108567A1/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
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D41/0047—Controlling exhaust gas recirculation [EGR]
    • F02D41/0077—Control of the EGR valve or actuator, e.g. duty cycle, closed loop control of position
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/02—EGR systems specially adapted for supercharged engines
    • F02M26/04—EGR systems specially adapted for supercharged engines with a single turbocharger
    • F02M26/06—Low pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust downstream of the turbocharger turbine and reintroduced into the intake system upstream of the compressor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/10—Parameters related to the engine output, e.g. engine torque or engine speed
    • F02D2200/1002—Output torque
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/10—Parameters related to the engine output, e.g. engine torque or engine speed
    • F02D2200/101—Engine speed

Definitions

  • the present application relates to the technical field of vehicles, and in particular to a control strategy of an engine with a low-pressure EGR system and a vehicle.
  • the engine EGR system is external EGR, which leads the exhaust gas after the catalyst to the intake supercharger, and needs to pass through the supercharger, the intake intercooler, and the throttle valve to enter the engine cylinder.
  • the cooled EGR recirculated exhaust gas
  • the cooled EGR can suppress knocking when the engine is operating under medium and high loads, but when the engine is operating under small loads, especially in the external characteristic region, the addition of EGR will affect the engine's The amount of intake air, thereby reducing the power performance of the engine.
  • an object of the present application is to propose a control strategy for an engine with a low-pressure EGR system.
  • the present application also proposes a vehicle that uses the above engine and controls the engine through the above control strategy.
  • the control strategy for an engine with a low-pressure EGR system includes at least the following steps: detecting the engine speed and torque; determining and adjusting the EGR valve opening degree according to the engine speed, torque, and EGR rate map, the EGR rate
  • the map includes multiple regions, and each region corresponds to a specific EGR rate.
  • the EGR system provides a reasonable EGR amount toward the cylinder of the engine according to the engine speed, torque, and the calibrated EGR rate map.
  • the EGR rate is reasonably adjusted to achieve seamless switching between multiple EGR rate control strategies and achieve smooth driving on the basis of ensuring that the engine reduces fuel consumption.
  • the vehicle according to the embodiment of the present application includes the control strategy control of the engine having the low-pressure EGR system as described in the above embodiment.
  • FIG. 1 is a schematic diagram of a low-pressure EGR system according to an embodiment of the present application.
  • FIG. 2 is a schematic diagram of the area division of the engine operating conditions according to an embodiment of the present application.
  • Figure 3 is the transition strategy corresponding to area B in Figure 2;
  • Figure 4 is the control strategy corresponding to area A in Figure 2;
  • Figure 5 is the control strategy corresponding to area D in Figure 2.
  • Fig. 6 is the control strategy corresponding to the F area in Fig. 2.
  • the low-pressure EGR system 100 of the engine with the low-pressure EGR system 100 of this embodiment first sucks exhaust gas from the catalyst, passes through the supercharger 3, the intake intercooler 1, the EGR cooler 4, and the Only after the valve 6 can it enter the engine cylinder and mix with the oil and gas injected by the injector 2 in the cylinder.
  • the cooled EGR has a certain inhibitory effect on the knock of the engine during high-load operation, but when the engine is in a low-load operating state, it has a negative effect on combustion, especially in the external characteristics area, the addition of EGR will affect the engine The amount of intake air, which affects the power of the engine.
  • engine knocking will affect the ride comfort of the vehicle, and the decrease of the intake air amount will affect the power of the engine.
  • this embodiment is proposed to take into account the smoothness and power of the vehicle.
  • the control strategy of an engine with a low-pressure EGR system 100 includes at least the following steps: detecting the engine speed and torque; determining and according to the engine speed, torque, and EGR rate map The opening degree of the EGR valve 5 is adjusted.
  • the EGR rate map includes a plurality of regions, and each region corresponds to a specific EGR rate.
  • the operating condition of the engine is determined according to the engine speed and torque, and the opening degree of the EGR valve 5 is adjusted according to the specific EGR rate on the EGR rate map corresponding to the operating condition.
  • the optimal EGR rate is set to multiple regions within the EGR rate map, and there is a boundary line between two adjacent regions;
  • the engine speed and torque look up the corresponding area in the EGR rate map to determine the EGR rate.
  • the EGR system 100 provides a reasonable EGR amount toward the cylinder of the engine according to the engine speed, torque, and the calibrated EGR rate map. In this way, when the engine is under different loads and different torques, the EGR rate is reasonably adjusted to achieve seamless switching between multiple EGR rate control strategies and achieve smooth driving on the basis of ensuring that the engine reduces fuel consumption. Thereby improving the power of the vehicle, and effectively balance the power and smoothness of the vehicle.
  • the multiple regions include: A region-partial load region, C region-medium high load region, the EGR rate in region A is 0, and the EGR rate in region C is 10%-17%.
  • the area A is a partial load area. At this time, the combustion stability is poor, and low-pressure EGR cannot be introduced, otherwise the engine will be misfired. Therefore, the control strategy of the area A is: to suck the exhaust gas in the exhaust manifold into the cylinder, Increase the hot atmosphere in the cylinder and stabilize the combustion; the C area is a medium to high load area. At this time, a certain amount of EGR needs to be introduced to effectively suppress knocking and advance the ignition angle.
  • the EGR rate in this area is between 10% and 17% During this period, the EGR rate in this region depends on the maximum EGR rate when the combustion is stable. Therefore, the control strategy for the C region is to maintain the EGR rate between 10% and 17%, and choose it reasonably according to whether the combustion in the cylinder is stable. EGR rate.
  • the combustion habits of the oil and gas in the cylinder can be improved, and the oil and gas can be fully burned to improve power.
  • the ignition angle can be advanced and knocking can be effectively suppressed, thereby taking into account the power and smoothness of the vehicle.
  • the multiple areas further include: Area B-transition area, and Area B is provided between Area A and Area C.
  • Area B is the transition area between the area A and the area C.
  • the transition strategy of area B includes:
  • the transition strategy in area B includes: when the vehicle is under acceleration, the current torque is subtracted from the lower boundary torque to obtain the first value; if the first value is greater than zero, the first value is subtracted from the preset acceleration transition torque to obtain The second value; if the second value is greater than zero, switch to area C;
  • the current torque is subtracted from the upper boundary torque to obtain the third value; if the third value is less than zero, the third value is added to the preset deceleration transition torque to obtain the fourth value; if the fourth value Less than zero, switch to area A.
  • the EGR rate is controlled in the C region, if the third value of the actual engine torque minus the upper boundary torque in the B region is less than zero, and the third value is added to the deceleration transition torque.
  • the four values are also less than zero, and the EGR rate is controlled in the A region.
  • the EGR rate needs to be determined according to the actual torque of the engine (current torque) and the maximum torque (upper boundary torque) and the minimum torque (lower boundary torque) corresponding to the region B, so that during engine operation, It is possible to smoothly transition from area A to area C or from area C to area A.
  • valve strategy in area A is: intake valve lag, exhaust valve lag, ensure that the valve overlap angle is 0-10 °CA, and the exhaust phase is late.
  • the valve distribution strategy in area A is: intake valve lag (the intake valve opens at the latest) and exhaust valve lag (the exhaust valve closes at the latest) to ensure a small valve overlap angle (that is, the valve overlap angle is controlled at 10° Within CA).
  • the exhaust phase is late.
  • the exhaust valve is not completely closed, and part of the exhaust gas is drawn into the cylinder to maintain the temperature in the cylinder through the exhaust gas. Stable, effectively improve the combustion stability.
  • valve overlap angle refers to the sum of the intake advance angle and the exhaust lag angle.
  • the plurality of regions further include: D region-low-speed external characteristic region, and the EGR rate in the D region is 0.
  • the area D is a low-speed external characteristic area.
  • priority is given to the power performance of the engine, mainly by adjusting the overlap angle of the intake and exhaust to achieve intake scavenging, improve restart efficiency, and achieve the target torque. Therefore, the control strategy in this area is: no external EGR is introduced, and the EGR rate is zero.
  • valve allocation strategy in the D region is: intake valve advance, exhaust valve lag, and valve overlap angle is not less than 30°CA.
  • the valve distribution strategy in zone D is to make the intake valve open early and the exhaust valve close lagging to form a large valve overlap angle (that is, to control the valve overlap angle above 30°CA).
  • the intake pressure is higher than the exhaust pressure, the valve overlap angle is used reasonably, and fresh air is used to sweep the residual exhaust gas in the cylinder, and the intake capacity is improved to meet the power.
  • the plurality of regions further include: E region-medium speed external characteristic region, and the EGR rate in the E region is 5%-9%.
  • the E region is an external characteristic region of medium speed. In this region, it is necessary to increase the EGR rate to a maximum of about 7% on the premise of satisfying the power target.
  • the control strategy in the E area is: EGR is added, but the EGR rate is less than or equal to 7%, thereby suppressing knocking, improving efficiency, and reducing fuel consumption.
  • the multiple regions further include: F region-high-speed external characteristic region, and the EGR rate in F region is 1%-5%.
  • the F region is a power region.
  • the EGR rate in this region is fixed at 3%, which can reduce the mixture temperature and the exhaust temperature to a certain extent, thereby increasing power.
  • the control strategy of the F zone is to maintain the EGR rate at 3% and maintain stability.
  • control strategy of the F area is: detecting the engine speed and determining the required EGR rate; determining the actual opening degree of the EGR valve 5 according to the engine speed, the required EGR rate and the EGR valve opening map; F The area has the maximum opening degree of the EGR valve 5, and the actual opening degree of the EGR valve 5 is not greater than the maximum opening degree of the EGR valve 5.
  • control strategy of the F zone is to determine the required EGR rate according to the engine speed, and then determine the actual opening of the EGR valve 5 based on the engine speed, the required EGR rate and the EGR valve opening map.
  • the actual opening of the EGR valve 5 is less than EGR
  • the maximum opening of valve 5 is adjusted, adjust the opening of EGR valve 5 to the actual opening of EGR valve 5.
  • the actual opening of EGR valve 5 is greater than the maximum opening of EGR valve 5, adjust the opening of EGR valve 5 to the maximum opening of EGR valve 5 .
  • the control strategy of the F area is to check the EGR valve opening degree map according to the EGR rate of the calibrated power point (determined by the engine speed) to obtain the actual opening degree of the EGR valve 5, and compare the actual opening degree of the EGR valve 5 with EGR Comparing the maximum opening of valve 5, when the actual opening of EGR valve 5 is less than the maximum opening of EGR valve 5, adjust the opening of EGR valve 5 to the actual opening, when the actual opening of EGR valve 5 is greater than the maximum opening of EGR valve 5 In the opening degree, the opening degree of the EGR valve 5 is adjusted to the maximum opening degree of the EGR valve 5.
  • the exhaust temperature of the engine from being too high, thereby improving the operating stability of the engine.
  • the EGR valve opening map is obtained by the applicant after many tests and through a large number of data.
  • the actual opening of the EGR valve 5 is determined according to the engine speed, the required EGR rate and the EGR valve opening map, of course, it can also be used In other ways or methods, the actual opening degree of the EGR valve 5 corresponding to the engine speed and the required EGR rate is obtained.
  • the present application does not limit the actual opening degree of the EGR valve 5.
  • the engine operating conditions are divided into partial load conditions, medium and high load conditions, transitional conditions, low-speed external characteristic conditions, medium-speed external characteristic conditions, and high-speed external characteristic conditions.
  • partial load conditions medium and high load conditions
  • transitional conditions low-speed external characteristic conditions
  • medium-speed external characteristic conditions medium-speed external characteristic conditions
  • high-speed external characteristic conditions kinds of working conditions.
  • the combustion of oil and gas in the cylinder is different, and the amount of EGR that can be allowed to enter the cylinder is also different.
  • multiple EGR rate verifications are performed. And set the optimal EGR rate to multiple regions, so that the multiple regions correspond to the above-mentioned various operating conditions.
  • the corresponding EGR rate is selected, so that through the control strategy of this embodiment, the supply Appropriate amount of EGR into the cylinder.
  • the engine control strategy of the low-pressure EGR system 100 for different operating conditions of the engine, a plurality of optimal EGR rate regions are correspondingly provided, and according to different operating conditions, reasonable directions are provided toward the cylinder of the engine EGR amount.
  • the engine when the engine is under medium and high load, it can effectively suppress knocking and improve the smoothness of the vehicle.
  • the engine When the engine is under a small load, it can maintain the stability of the engine's intake air volume and ensure the combustion stability, thereby improving the vehicle's power. , So as to effectively balance the power and smoothness of the vehicle.
  • the vehicle according to the embodiment of the second aspect of the present application includes the engine having the low-pressure EGR system 100 as in the above embodiment, and the engine is controlled by the control strategy of the engine having the low-pressure EGR system 100 as in the above embodiment.
  • the vehicle according to the embodiment of the present application has a good balance between power performance and ride comfort, and has good ride comfort under the premise of sufficient power.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Output Control And Ontrol Of Special Type Engine (AREA)
  • Exhaust-Gas Circulating Devices (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

一种具有低压EGR***（100）的发动机的控制方法，至少包括如下步骤：检测发动机的转速和扭矩；根据发动机的转速、扭矩以及EGR率map确定并调整EGR阀（5）开度，EGR率map包括多个区域，每个区域对应特定的EGR率。该方法能在保证发动机降低油耗的基础上实现平顺性驾驶。一种包括该控制方法的车辆也被公开。

Description

具有低压EGR***的发动机的控制策略以及车辆
相关申请的交叉引用
本申请要求长城汽车股份有限公司于2018年11月30日提交的、申请名称为“具有低压EGR***的发动机的控制策略以及车辆”的、中国专利申请号“201811454564.7”的优先权。
技术领域
本申请涉及车辆技术领域，尤其是涉及一种具有低压EGR***的发动机的控制策略以及车辆。
背景技术
相关技术中，发动机EGR***为外部EGR，其是将催化器后的废气引到进气增压器前，需要经过增压器，进气中冷器以及节气门才能进入到发动机气缸内。
这样，经过冷却的EGR(再循环废气)，在发动机处于中高负荷下工作时，可以抑制爆震，但是当发动机处于小负荷下工作时，尤其是在外特性区域内，EGR的加入会影响发动机的进气量，从而降低发动机的动力性能。
发明内容
本申请旨在至少解决现有技术中存在的技术问题之一。为此，本申请的一个目的在于提出一种具有低压EGR***的发动机的控制策略。
本申请还提出了一种采用上述发动机并通过上述控制策略对发动机进行控制的车辆。
根据本申请实施例的具有低压EGR***的发动机的控制策略，至少包括如下步骤：检测发动机的转速和扭矩；根据发动机的转速、扭矩以及EGR率map确定并调整EGR阀开度，所述EGR率map包括多个区域，每个区域对应特定的EGR率。
根据本申请实施例的具有低压EGR***的发动机控制策略，根据发动机的转速、扭矩以及标定好的EGR率map，使EGR***朝向发动机的气缸内提供合理的EGR量。这样，在发动机处于不同的负荷、不同的扭矩下，合理地调整EGR率，实现在多种EGR率控制策略之间的无缝切换，在保证发动机降低油耗的基础上实现平顺性驾驶。从而提高车辆的动力性，并有效地兼顾车辆的动力性与平顺性。
根据本申请实施例的车辆，包括如上述实施例中所述的具有低压EGR***的发动机的控制策略控制。
本申请的附加方面和优点将在下面的描述中部分给出，部分将从下面的描述中变得明显，或通过本申请的实践了解到。
附图说明
图1是根据本申请实施例的低压EGR***的示意图；
图2是根据本申请实施例的发动机运行工况的区域划分示意图；
图3是图2中B区域所对应的过渡策略；
图4是图2中A区域所对应的控制策略；
图5是图2中D区域所对应的控制策略；和
图6是图2中F区域所对应的控制策略。
具体实施方式
下面详细描述本申请的实施例，所述实施例的示例在附图中示出，其中自始至终相同或类似的标号表示相同或类似的元件或具有相同或类似功能的元件。下面通过参考附图描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。
如图1所示，本实施例的具有低压EGR***100的发动机的低压EGR***100，首先由催化器吸取废气，在经过增压器3，进气中冷器1、EGR冷却器4以及节气门6后才能进入到发动机气缸内，并在气缸内与喷油器2喷出的油气混合。
其中，经过冷却的EGR对发动机中高负荷运行时的爆震具有一定抑制作用，但在发动机处于小负荷工作状态时，对燃烧起到负面作用，尤其是在外特性区域，EGR的加入会影响发动机的进气量，从而影响发动机的动力性。
也就是说，发动机爆震会影响车辆的平顺性，而进气量的下降，会影响发动机的动力性。
综上，基于上述低压EGR***100可能对发动机的运转以及车辆行驶过程中造成的不利影响，提出本实施例，以兼顾车辆的平顺性与动力性。
下面参考图1-图6描述根据本申请实施例的具有低压EGR***100的发动机的控制策略。
如图2-图6所示，根据本申请实施例的具有低压EGR***100的发动机的控制策略，至少包括如下步骤：检测发动机的转速和扭矩；根据发动机的转速、扭矩以及EGR率map确定并调整EGR阀5开度，EGR率map包括多个区域，每个区域对应特定的EGR率。
也就是说，根据发动机的转速和扭矩确定发动机所处的工况，并根据该工况所对应的EGR率map上的特定EGR率调整EGR阀5开度。
具体而言，通过针对不同的发动机运行工况进行不同EGR率的验证，将最优的EGR率设定为EGR率map内的多个区域，相邻的两个区域之间具有边界线；根据发动机的转速以及扭矩查找EGR率map中对应的区域，从而确定EGR率。
根据本申请实施例的具有低压EGR***100的发动机控制策略，根据发动机的转速、扭矩以及标定好的EGR率map，使EGR***100朝向发动机的气缸内提供合理的EGR量。这样，在发动机处于不同的负荷、不同的扭矩下，合理地调整EGR率，实现在多种EGR率控制策略之间的无缝切换，在保证发动机降低油耗的基础上实现平顺性驾驶。从而提高车辆的动力性，并有效地兼顾车辆的动力性与平顺性。
如图2和图4所示，多个区域包括：A区域-部分负荷区域、C区域-中高负荷区域，A区域的EGR率为0，C区域的EGR率为10％-17％。
其中，A区域为部分负荷区域，此时燃烧稳定性较差，不能引入低压EGR，否则会使发动机失火，因此，A区域的控制策略是：将排气歧管中的废气倒吸入缸内，增加缸内的热氛围，稳定燃烧；C区域为中高负荷区域，此时需要引入一定量的EGR，以有效地抑制爆震，并提前点火角，此区域的EGR率在10％-17％之间，此区域EGR率决定于在燃烧稳定时的最大EGR率，因此，C区域的控制策略是：使EGR率维持在10％-17％之间，并根据气缸内燃烧是否稳定，而合理选取EGR率。
由此，在根据发动机的转速以及扭矩确定发动机所处的工况，且在发动机处于部分负荷状态下运转时，可以提高气缸内的油气的燃烧稳定***顺性。
需要说明的是，本实施例中所提出的合理的控制策略是指，综合判断后，合理地调整EGR阀5的开度。
如图2所示，多个区域还包括：B区域-过渡区域，B区域设置在A区域和C区域之间。其中，B区域为A区域与C区域之间的过渡区域，通过合理的控制策略，可以实现A区域与C区域的平滑过渡，保证燃烧稳定，避免产生冲击。
如图3所示，B区域与A区域之间具有下边界扭矩，B区域与C区域之间具有上边界扭矩；B区域的过渡策略包括：
B区域的过渡策略包括：当车辆处于加速工况时，当前扭矩减去下边界扭矩以得到第一数值；若第一数值大于零，将第一数值与预设的加速过渡扭矩相减以得到第二数值；若第二数值大于零，切换到C区域；
当车辆处于减速工况时，当前扭矩减去上边界扭矩以得到第三数值；若第三数值小于零，将第三数值与预设的减速过渡扭矩相加以得到第四数值；若第四数值小于零，切换到A区 域。
也就是说，当车辆处于加速工况时，若发动机的实际扭矩(即当前扭矩)减去B区域的下边界扭矩的第一数值大于零，且第一数值与加速过渡扭矩之间的差值-第二数值也大于零，则将EGR率控制在C区域，若发动机的实际扭矩减去B区域的上边界扭矩的第三数值小于零，且第三数值与减速过渡扭矩相加得到的第四数值也小于零，则将EGR率控制在A区域。由此，在B区域内，需要根据发动机的实际扭矩(当前扭矩)以及B区域所对应的最大扭矩(上边界扭矩)、最小扭矩(下边界扭矩)确定EGR率，从而使发动机工作过程中，可以由A区域平稳地过渡到C区域或者由C区域平稳地过渡到A区域。
如图4所示，A区域的配气策略为：进气门滞后，排气门滞后，保证气门重叠角在0-10°CA，并且排气相位靠后。
A区域的配气策略为：进气门滞后(进气门最迟开启)，排气门滞后(排气门最迟关闭)，以保证小的气门重叠角(即将气门重叠角控制在10°CA之内)。
这样，不仅可以有效地减少泵气损失，做功充分，而且排气相位靠后，在发动机吸气过程中，排气门未完全关闭，将部分废气吸入缸内，以通过废气维持气缸内的温度稳定，有效地提高燃烧稳定性。
需要说明的是，气门重叠角是指：进气提前角排气滞后角的和。
如图5所示，多个区域还包括：D区域-低速外特性区域，D区域的EGR率为0。
其中，D区域为低速外特性区域，此区域以优先考虑发动机的动力性能，主要通过调整进排气的重叠角，实现进气扫气，提高重启效率，以实现目标扭矩。因此，该区域的控制策略为：不引入外部EGR，EGR率为零。
在图5所示的具体的实施例中，D区域的配气策略为：进气门提前，排气门滞后，气门重叠角不小于30°CA。
D区域配气策略为，使进气门提前开启，排气门滞后关闭，以形成大的气门重叠角(即将气门重叠角控制在30°CA之上)。
由此，使进气压力高于排气压力，合理利用气门重叠角、利用新鲜空气，将缸内残余废气扫干净，提高进气能力，从而满足动力性。
在一些实施例中，多个区域还包括：E区域-中速外特性区域，E区域的EGR率为5％-9％。
其中，E区域为中等转速的外特性区域，此区域内，需要在满足动力性目标的前提下，将EGR率提高到最大7％左右。也就是说，E区域的控制策略为：加入EGR，但EGR率小于等于7％，从而抑制爆震，提升效率，降低油耗。
如图6所示，多个区域还包括：F区域-高速外特性区域，F区域的EGR率为1％-5％。
可以理解的是，F区域为功率区域，优选地，此区域内EGR率固定在3％，可以在一定程 度上降低混合气温度，降低排气温度，从而提升功率。也就是说，F区域的控制策略为：维持EGR率为3％，并保持稳定。
需要说明的是，由于在F区域内发动机排气温度过高，此时需要降低EGR率，从而避免因EGR卡滞所造成的EGR率不足，以防止排气温度突然上升，造成增压器3损坏。
在图6所示的具体的实施例中，F区域的控制策略为：检测发动机转速并确定需求EGR率；根据发动机转速、需求EGR率和EGR阀开度map确定EGR阀5实际开度；F区域具有EGR阀5最大开度，EGR阀5实际开度不大于EGR阀5最大开度。
也就是说，F区域的控制策略为，根据发动机转速确定需求EGR率，进而根据发动机转速、需求EGR率以及EGR阀开度map确定EGR阀5实际开度，当EGR阀5实际开度小于EGR阀5最大开度时，调整EGR阀5开度到EGR阀5实际开度，当EGR阀5实际开度大于EGR阀5最大开度时，调整EGR阀5开度到EGR阀5最大开度。
换言之，F区域的控制策略为，根据所标定的功率点(由发动机转速确定)的EGR率查EGR阀开度map得到EGR阀5的实际开度，并将EGR阀5的实际开度与EGR阀5最大开度进行比较，当EGR阀5的实际开度小于EGR阀5最大开度时，将EGR阀5开度调整到实际开度，当EGR阀5的实际开度大于EGR阀5最大开度时，将EGR阀5开度调整到EGR阀5最大开度。由此，可以防止发动机的排气温度过高，从而提高发动机的工作稳定性。
需要说明的是，EGR阀开度map是申请人经过多次试验、通过大量数据得出的，根据发动机转速、需求EGR率和EGR阀开度map确定EGR阀5实际开度，当然也可以采用其他方式或方法获得发动机转速、需求EGR率对应的EGR阀5的实际开度，本申请不对EGR阀5的实际开度进行限制。
综上，针对发动机的不同工况，将发动机工况划分为部分负荷工况、中高负荷工况、过渡工况、低速外特性工况、中速外特性工况以及高速外特性工况等多种工况。
从而，根据发动机处于不同的运行工况下，油气在气缸内的燃烧状况不同，所能允许进入到气缸内的EGR的量也不同，针对不同的发动机运行工况，进行多次EGR率验证，并将最优的EGR率设定为多个区域，使多个区域与上述多种工况相对应。
进而，在发动机处于不同的运行工况下，根据发动机在此工况下所需要提供的负荷，或者该工况下的需求符合，选取对应的EGR率，从而通过本实施例的控制策略，供给到气缸内合适的EGR量。
根据本申请实施例的具有低压EGR***100的发动机控制策略，针对发动机不同的运行工况，对应设置有多个最优EGR率区域，并根据不同的运行工况，朝向发动机的气缸内提供合理的EGR量。这样，在发动机处于中高负荷下，可以有效地抑制爆震，提高车辆的平顺性，在发动机处于较小负荷下，可以维持发动机进气量的稳定，保证燃烧稳定性，从而 提高车辆的动力性，从而有效地兼顾车辆的动力性与平顺性。采用不同控制策略，实现几个技术之间的无缝切换，在保证发动机降低油耗的基础上实现平顺性驾驶。根据本申请第二方面实施例的车辆，包括如上述实施例中的具有低压EGR***100的发动机，且发动机受如上述实施例中的具有低压EGR***100的发动机的控制策略控制。
根据本申请实施例的车辆，动力性与平顺性的兼顾效果较好，在动力充沛的前提下，具有较好的平顺性。
在本说明书的描述中，参考术语“一个实施例”、“一些实施例”、“示意性实施例”、“示例”、“具体示例”、或“一些示例”等的描述意指结合该实施例或示例描述的具体特征、结构、材料或者特点包含于本申请的至少一个实施例或示例中。在本说明书中，对上述术语的示意性表述不一定指的是相同的实施例或示例。而且，描述的具体特征、结构、材料或者特点可以在任何的一个或多个实施例或示例中以合适的方式结合。
尽管已经示出和描述了本申请的实施例，本领域的普通技术人员可以理解：在不脱离本申请的原理和宗旨的情况下可以对这些实施例进行多种变化、修改、替换和变型，本申请的范围由权利要求及其等同物限定。

Claims (12)

  1. 一种具有低压EGR***的发动机的控制策略，其特征在于，至少包括如下步骤：
    检测发动机的转速和扭矩；
    根据发动机的转速、扭矩以及EGR率map确定并调整EGR阀开度，所述EGR率map包括多个区域，每个区域对应特定的EGR率。
  2. 根据权利要求1所述的具有低压EGR***的发动机的控制策略，其特征在于，多个所述区域包括：A区域-部分负荷区域，所述A区域的EGR率为0。
  3. 根据权利要求2所述的具有低压EGR***的发动机的控制策略，其特征在于，多个所述区域还包括：C区域-中高负荷区域，所述C区域的EGR率为10％-17％。
  4. 根据权利要求3所述的具有低压EGR***的发动机的控制策略，其特征在于，多个所述区域还包括：B区域-过渡区域，所述B区域设置在所述A区域和所述C区域之间。
  5. 根据权利要求4所述的具有低压EGR***的发动机的控制策略，其特征在于，所述B区域与所述A区域之间具有下边界扭矩，所述B区域与所述C区域之间具有上边界扭矩；
    所述B区域的过渡策略包括：
    当车辆处于加速工况时，当前扭矩减去所述下边界扭矩以得到第一数值；
    若第一数值大于零，将第一数值与预设的加速过渡扭矩相减以得到第二数值；
    若第二数值大于零，切换到C区域；
    当车辆处于减速工况时，当前扭矩减去所述上边界扭矩以得到第三数值；
    若第三数值小于零，将第三数值与预设的减速过渡扭矩相加以得到第四数值；
    若第四数值小于零，切换到A区域。
  6. 根据权利要求2所述的具有低压EGR***的发动机的控制策略，其特征在于，所述A区域的配气策略为：进气门滞后，排气门滞后，保证二者的气门重叠角在0-10°CA。
  7. 根据权利要求4所述的具有低压EGR***的发动机的控制策略，其特征在于，多个所述区域还包括：D区域-低速外特性区域，所述D区域的EGR率为0。
  8. 根据权利要求7所述的具有低压EGR***的发动机的控制策略，其特征在于，所述D区域的配气策略为：进气门提前，排气门滞后，保证二者的气门重叠角不小于30°CA。
  9. 根据权利要求7所述的具有低压EGR***的发动机的控制策略，其特征在于，多个所述区域还包括：E区域-中速外特性区域，所述E区域的EGR率为5％-9％。
  10. 根据权利要求9所述的具有低压EGR***的发动机的控制策略，其特征在于，多个所述区域还包括：F区域-高速外特性区域，所述F区域的EGR率为1％-5％。
  11. 根据权利要求10所述的具有低压EGR***的发动机的控制策略，其特征在于，所 述F区域的控制策略还包括：
    检测发动机转速并确定需求EGR率；
    根据发动机转速、需求EGR率确定EGR阀实际开度；
    所述F区域具有EGR阀最大开度，所述EGR阀实际开度不大于所述EGR阀最大开度。
  12. 一种车辆，其特征在于，包括权利要求1-11中任一项所述的具有低压EGR***的发动机的控制策略控制。
PCT/CN2019/121626 2018-11-30 2019-11-28 具有低压egr***的发动机的控制策略以及车辆 WO2020108567A1 (zh)

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