Mechanical efficiency prediction methodology of the hypocycloid gear mechanism for internal combustion engine application

Mechanical friction power loss is one of the main concerns in the internal combustion engine (ICE) systems. The piston-rod assembly and the complex motion of the connecting rod are the largest source of engine friction. A significant reduction in these losses can be achieved with ICE systems incorporating the hypocycloid gear mechanism (HGM), which ensures that the piston-rod assembly reciprocates in a perfect straight-line motion along the cylinder axis to eliminate the piston side load. This paper investigates the feasibility of an enhanced HGM for the design and development of ICE applications. It incorporates designing the planetary crank gearing system to satisfy the design specifications of ICE using the standard design procedures provided by AGMA. This is followed by building the friction model for the interacting components of the HGM engine through developing the mathematical model for the friction power loss of the internal gear train meshes, rolling bearings, and sliding bearings. The total friction power losses of the HGM engine are calculated and compared with the friction model of the conventional crank-slider engine that has been developed by Sandoval and Heywood (An Improved Friction Model for Spark-Ignition Engines. SAE Technical Paper 2003-01-0725, 2003). The comparison results show the feasibility of using the HGM for ICE applications with minimized engine friction power losses and hence higher mechanical efficiency.