Some aspects concerning the geometry of a hinged engine with a variable compression ratio

Abstract

An improvement in automotive fuel consumption has been for many years the most important challenge in engine development. In a century of automotive spark ignition engine development, only two parameters were subject to automatic control: the air-fuel ratio and spark advance. Ever since, a wide range of technologies has been developed in order to improve fuel economy further. The following strategy was used: the identification of the sources of losses in the conventional spark ignition engine and then the attempt to reduce them one by one. The potential of these technologies needs to be evaluated by a cost and consumption benefit trade-off and all these, of course, without affecting the power level. In this context, the authors are about to develop a variable geometrical compression ratio engine, in order to overcome the main drawback of the spark ignition engine: the continuous variation of the real rate of compression, caused by the load control. The concept of the variable geometrical compression ratio (VCR) engine is the subject of a patent and consists of a hinged mechanism. It is an intrinsic, automatic self-regulation system with a fast response time and at the same time is a natural development of the classic engine. So far, two prototypes have been designed and tested. The paper presents some specific features regarding hinge position choice. The following are taken into consideration: the upper block rotational angle, added angle of the piston, tipping torque, and relative motion of the camshaft with respect to the crankshaft.