Hypocycloid Gear Mechanism Versus Slider-Crank Mechanism in Engines

Abstract

This effort investigates the feasibility of using the Hypocycloid Gear Mechanism (HGM) as an alternative to the conventional slider-crank mechanism for Internal Combustion Engine (ICE) applications. Engines incorporating the conventional slider-crank mechanism are subjected to high frictional power losses mainly due to the piston-rod assembly and the associated complex motion of the connecting rod. The unique HGM engine provides the means for the piston-rod assembly to reciprocate in a straight-line motion along the cylinder axis, thus eliminating the piston side-thrusting into the cylinder wall. To analyze the performance advantages of the HGM engine, a Matlab/Simulink model is developed for the simulation of a single-cylinder HGM engine from the throttle to the crankshaft output. The model integrates several sub-models for combustion, gas flow, heat transfer, and friction power loss of the internal gear train meshes, rolling bearings, and sliding bearings. The design of the planetary crank gearing system to satisfy the design specifications of ICE, has been derived using standard design procedures provided by AGMA. Calculated efficiency and power diagrams are plotted and compared with the performance of conventional engines in the literature. The results show that the HGM can satisfy modern ICE design requirements, achieve better engine performance characteristics, and minimize the frictional power losses. The HGM engine achieved lower frictional power losses by an average 33% of the conventional engine losses while its mechanical efficiency is enhanced by up to +24% with respect to the conventional engine.

Performance study of the hypocycloid gear mechanism for internal combustion engine applications

“…A methodology for predicting the mechanical efficiency of the HGM was developed in previous works. 23,24 The methodology considered the three major elements of the HGM: the internal gear mesh losses, the carrier rolling bearing losses, and the sliding bearings losses. It should be noted that the HGM frictional losses comprise both mechanical and spin power losses; however, the model proposed includes only the mechanical power losses.…”

“…Therefore, the piston side thrusting into the cylinder walls is eliminated and the piston frictional losses are minimized allowing for increased engine brake power. 23,24 In addition, there is no need for the wrist pin bearing and the piston skirt, allowing for a shorter and lower weight piston without concerns of chocking or piston slap. More importantly, the kinematic features of the HGM engine ensured that the piston dwells at both the TDC and BDC allowing for the constant-volume combustion process at one end and more time for a full cylinder intake charge at the other.…”