Abstract
Changing the geometry of the crank rod linkage in an internal combustion engine leads to changes in the system kinematics and modifies the stresses which occur in such a system. For this reason, when designing an engine with variable compression ratio, kinematic and then, a dynamic calculation must be done to determine the new strength of different components. The article presents an analyze of the kinematics of system for a variable compression ratio engine with a rotating block. The modification of the engine block position leads to the geometry changing of the crank rod mechanism and in the end, to stress changes in the crank rod system. This modification can damage the engine and therefore requires a precise calculus. The kinematic calculation for any movement of the cylinder block is made with classical methods. If the engine rotates with an angle α then two sets of data changes in the formulas that describe the system kinematics: first the eccentricity of the rod-crank system and second, the position of the upper and lower dead point. The calculation of the compression ratio for an engine with variable compression ratio, depending on the cylinder block rotation.
Keywords: Variable compression ratio VCR, engine, cylinder block, rotation