商用车可变气门技术VVA 

技术特点

伊顿为商用车发动机设计可变气门驱动系统VVA，例如进气门延迟关闭(LIVC)及排气门早开(EEVO)技术。为未来排放法规(如国7, 欧7)提供燃油经济性改善和排放物有效控制的方案。伊顿的LIVC与EEVO采用液压驱动或电机机械驱动，可实现快速切换气门升程。目前已经通过系统台架性能验证，在多个客户发动机平台上展开应用开发。

LIVC和EEVO都是一种连续可变气门正时策略，使进气门/排气门在特定操作条件下，延长打开的时间。其中LIVC使活塞在压缩冲程期间，将部分空气燃料混合物从气缸中推回进气歧管中，降低压缩冲程期间的活塞阻力。同时由于部分空气燃料混合物推回进气歧管中，气缸中的空气燃料混合物减少，导致膨胀比压缩比更大，从而允许从燃烧燃料中提取更多的能量，提高发动机效率和排气温度。而EEVO通过提早打开排气门使高温排气更多、更早地进入排气管加热SCR，使其在低负荷工况或者低温冷启动时可以快速升温到高效活性工作区，提高后处理装置的转换效率，从而降低排放。 

伊顿VVA是一种同时改善发动机热效率和油耗及排放的方法。主要优势如下：

提高发动机效率 – 研究结果证明，进气门延迟关闭LIVC可以把发动机在部分负载状态下的泵气损失降低40％以上，并将氮氧化物（NOx）排放减少24％

降低排放 – EEVO可以实现低温工况下排气门快速开启，解

决了SCR因工况条件限制减少高效工作范围的问题，从而进一步降低排放。

系统集成方案 – 针对发动机全工况运行范围内进排气门最优升程正时，设计整个配气系统的集成式摇臂驱动机构。

市场表现

未来国七阶段排放法规同时要求燃油经济性和排放优化，而进气门延迟关闭LIVC和排气门提早打开EEVO技术是实现其目标的发动机重要技术手段。伊顿的可变气门驱动系统可灵活的集成LIVC和EEVO功能，高效的实现了优化全工况范围内发动机效率和排放的配气需求，助力发动机满足未来更严苛的排放法规。 

Eaton design variable valve actuation system (VVA) for commercial engine, e.g. late intake valve close (LIVC) and early exhaust valve open (EEVO) technology, which can provide solution of improving fuel efficiency and effectuating emission for future emission regulation such as CN7, EU7. Eaton’s LIVC and EEVO is actuated by hydraulic or electric-mechanical actuator, can achieve quick switching of valve lift. Currently the system already successfully passed bench test, and engine platform development undergoing in many OEMs.    

LIVC and EEVO both are a kind of continuous variable valve timing strategy, which can make intake/exhaust valve lengthen open duration time at specific operation condition.

LIVC push part of mixed fuel and air gas back to intake pipe in compression stroke, to reduce piston resistance. Meanwhile, expansion ratio is higher than compression ratio due to lack of mixed gas in cylinder, then allow more engine extract from fuel, resulting to increase engine thermal efficiency and exhaust temperature.

EEVO make high temperature gas to access to exhaust pipe earlier and more, which could heat SCR quickly to the high efficient and active working scope at engine low loading or low temperature starting condition, then increase the SCR conversion efficiency, consequently decrease emission. 

Advantage

Eaton VVA is a valid solution to improve both engine efficiency and emission at the same time:

Increase Engine Efficiency – From investigation and research, LIVC can reduce > 40% pumping loss under part load condition, and reduce around 24% NOx emission.

Reduce Emission – EEVO could achieve exhaust valve quickly early open, resolving SCR limited effective work scope challenge, to reduce emission further.

Integrated System solution – Integrate all rocker arm actuation for the whole valvetrain system, aim to achieve the optimal valve timing within the engine’s overall operation condition. 

The future phase 7 emission regulation will have more stringent requirement on both fuel efficiency and emissions, so LIVC and EEVO is the engine’s significant technical method to fulfill this target. Eaton’s VVA system can integrate LIVC and EEVO function, which efficiently realize the required air management demand to optimize engine thermal efficiency and emission at overall operation scope, it will help engine satisfy future emission regulation.