Camless Engine

Topics: Internal combustion engine, Variable displacement, Camshaft Pages: 11 (3324 words) Published: August 18, 2012
PERUNDURAI , ERODE -638052 Tamil Nadu. (Approved by AICTE, New Delhi)


V.PIRANESH, Second Year Mechanical Engineering, ph:9597848518

R.YOGESHWARAN Second Year Mechanical Engineering , ph :9894882579

ABSTRACT Presented within is a synopsis of the conceptual design, analysis and testing of a camless engine (CLE) with an electro hydraulic valve train. The system makes use of a piezoelectric controlled hydraulic actuator. This actuator serves as a replacement for the camshaft in an internal combustion engine (ICE). In essence, the actuator is an electro hydraulic device capable of producing engine valve displacement at typical automotive demands. The goals for maximum displacement and frequency are 10 mm and 50 Hz, respectively for a typical engine speed of 6000 RPM. The system design utilizes a customized piezoelectric stack and hydraulic spool valve combined with an in-house designed hydraulic amplifier. Control is facilitated by a function generator, and feedback is monitored with an oscilloscope. The resulting system is capable of displacing an engine valve to nearly 11 mm, and frequencies up to 500 Hz have been obtained. The system makes use of a magnetic or Hall Effect crankshaft position sensor in place of the conventional chain and sprocket timing drive. Valve timing can be varied by varying the input voltage signal to the piezoelectric stacks and electronic control also facilitates cylinder shut down. The electro hydraulic valve train therefore effectively implements variable valve timing and variable cylinder management.



Since the origination of the automobile, the internal combustion engine has evolved considerably. However, one constant has remained throughout the decades of ICE development. The camshaft has been the primary means of controlling the valve actuation and timing, and therefore, influencing the overall performance of the vehicle. The camshaft is attached to the crankshaft of an ICE and rotates relative to the rotation of the crankshaft. Therefore, as the vehicle increases is velocity, the crankshaft must turn more quickly, and ultimately the camshaft rotates faster. This dependence on the rotational velocity of the crankshaft provides the primary limitation on the use of camshafts. As the camshaft rotates, cam lobes, attached to the camshaft, interface with the engine’s valves. This interface may take place via a mechanical linkage, but the result is, as the cam rotates it forces the valve open. The spring return closes the valve when the cam is no longer supplying the opening force. Since the timing of the engine is dependent on the shape of the cam lobes and the rotational velocity of the camshaft, engineers must make decisions early in the automobile development process that affect the engine’s performance. The resulting design represents a compromise between fuel efficiency and engine power. Since maximum efficiency and maximum power require unique timing characteristics, the cam design must compromise between the two extremes.

engines that are governed by the rotation of a camshaft. This rotation, the speed of which is proportional to the engine’s speed, determines the timing of the engine valves. For this reason, automotive engineers must make a decision early in the design process that dictates the performance of the automobile. The engine will either have powerful performance or increased fuel economy, but with the existing technology it is difficult to achieve both simultaneously. In response to the needs of improved engines, some manufacturers have designed mechanical devices to achieve some variable valve timing. These devices are essentially camshafts with multiple cam lobes or engines with multiple camshafts. For example, the Honda VTEC uses three lobes, low, mid, and high to...
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