Abstract
The increasing concerns of air pollution and energy usage led to the electrification of the vehicle powertrain system in recent years. On the other hand, internal combustion engines were the dominant vehicle power source for more than a century, and they will continue to be used in most vehicles for decades to come; thus, it is necessary to employ advanced technologies to replace traditional mechanical systems with mechatronic systems to meet the ever-increasing demand of continuously improving engine efficiency with reduced emissions, where engine intake and the exhaust valve system represent key subsystems that affect the engine combustion efficiency and emissions. This paper reviews variable engine valve systems, including hydraulic and electrical variable valve timing systems, hydraulic multistep lift systems, continuously variable lift and timing valve systems, lost-motion systems, and electro-magnetic, electro-hydraulic, and electro-pneumatic variable valve actuation systems.
Highlights
With growing concerns on energy security and global warming, there are global efforts to develop more efficient vehicles with lower regulated emissions, including hybrid electrical vehicles, electrical vehicles, and fuel cell vehicles
The engine valve system with active control can be mainly divided into three groups: variable valve timing (VVT), variable valve lift (VVL), and camless valve system
For the variable valve timing system, the trend is to move to electrical Valve Timing (VVT) systems motivated by reducing engine cold-start emissions and significant cost reduction of electrical drive systems
Summary
With growing concerns on energy security and global warming, there are global efforts to develop more efficient vehicles with lower regulated emissions, including hybrid electrical vehicles, electrical vehicles, and fuel cell vehicles. Combustion and Need for Electronic Control of Gas Exchange time (VVT) to more sophisticated systems such as discrete variable valve lift (DVVL), continuous. There is less as homogeneous charge compression ignition (HCCI) toinimprove engine fuelengines economy and reduce demand or development on controlling gas exchange traditional diesel because of its emissions [4,5,6,7]. The associated valve lift or development on controlling gas exchange in traditional diesel engines because of its compression travel isand typically illustrated in a valveMore timing diagram For the purpose of classifying valve intake valve lift to reduce the pumping losses associated with the conventional throttle This actuation systems, the following definitions are provided: requires very close control of lift to match changes in engine speed and load conditions, which is yet. A cam-driven system utilizes cam lobes to actuate the valve lift, while a camless system does
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