Advanced valve technology

　　Nissan Motors has introduced a new engine technology that delivers a balance of responsiveness and power, fuel efficiency and low emissions.

　　The new system conbines the technologies behind Nissan’s newly developed variable valve event and lift (VVEL) and continuous valve timing control (C-VTC) to deliver enhanced performance.

　　VVEL can reduce carbon dioxide emissions by up to 10 per cent. C-VTC and VVEL combine to control the valve phases and its valve events and lifts , allowing free-control of the valve timing and lift. This results in more efficient airflow through the cylinder and significantly improves responsiveness , optimising the balance between power and environmental performance.

　　The new engine technology offers a number of advantages depending on driving range. At low-to-mid load ranges ,the system controls air intake at the intake-valve, immediately before it enters the combustion chamber, in contrast with conventional engine air intake via a throttle valve. This leads to increased efficiency by easing airflow through the cylinder. In the low and medium-rpm ranges, intake-valve lift is kept low to reduce camshaft friction and speed up intake flow, resulting in more efficient full combustion.

　　Controlling air intake at the intake-valves improves acceleration response by allowing more dense air into the cylinders from the start of acceleration.

　　In the low –rpm range, the intake-valves open for a shorter period, preventing blowback of the air-fuel mixture and improving torque. While ,in the high range ,greater intake-valve lift allows increased air intake to deliver greater torque outputs.

　　Intake-valve timing is optimised on startup, when the engine is still cool, to quickly raise the temperature of exhaust gases and more quickly activate the catalytic converter.

　　The VVEL improves fuel efficiency most effectively in the low-to-medium operating range, thus it is best matched to the multiple-cylinder and higher displacement engines, which typically operate within that range.

　　For multiple-cylinder, high-displacement engines , Nissan will combine VVEL technology with the direct-injection system.

　　With the VVEL system, a rocker arm and two types of links close the intake-valves by transferring the rotational movement of a drive shaft with an eccentric cam to the output cam. The movement of the output cam can be varied by rotating the control shaft within the DC motor and changing the fulcrums of the links. This makes a continuous adjustment.

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　　日前，日产汽车公司引进了一种新的引擎技术，该技术使得敏感度与动力性、燃油经济性与排放性能实现了更好的平衡。

　　该系统结合了日产公司新近开发的可变气正时与行程控制系统（Variable Valve Event and Lift, VVEL）以及连续可变气门正时控制系统（Continuous Valve Timing Control, C-VTC）的技术，极大地提高了引擎性能。

　　VVEL技术可以汽车尾气中二氧化碳的排放量降低十个百分点，C-VTC和VVEL系统的相互结合，可以自由控制气门的相位以及行程，这带来了更好的进气效率，极大提升了引擎的响应速度，使得其动力性和环保性能之间的平衡得到进一步的优化。

　　这项新的引擎技术可以依据不同的车辆行驶速度提供一系列的性能优化。常规的引擎通常由节气门来控制进气量，而在中低转速下，VVEL则直接控制气门的行程，以减缓进气流量来达到更佳的油耗，与此同时，较低的气门行程也能减少凸轮轴摩擦，加快进气速度，从而进一步增强引擎燃烧过程的经济性。

　　（另一方面，）通过进气阀门处的气流控制，该技术可以提高加度行程中的进气端空气密度，以达到更迅速的油门反应。

　　在低转速时，VVEL技术缩短气门的开启时间，以防止油气回流，同时改善扭力表现；在高转速下，VVEL则提高气门行程，以增加进气流量，来达到最大的扭力输出。

　　该项技术可以在引擎发动时，将气门正时调整至最佳化，以快速提高排气端的废气温度，同时使触媒转化器提升至工作温度，以迅速的发挥作用。

　　VVEL技术在中低转速下运作能够发挥最大的节油效能，因此对于多气缸，或大排气量等经常以中低转速运转的引擎，VVEL将会是其最佳的选择。

　　对多气缸车型，日产计划将VVEL技术与缸内直喷等系统联合搭载使用。

　　在VVEL系统中，引擎摇杆臂与进气阀门处的两个连接件可以通过一个偏心凸轮将驱动轴的旋转运动传递至输出凸轮，输出凸轮的运动可以通过直流电机控制轴的旋转和连接件支点的变化而改变，因此实现了对气门正时和升程的连接调节。