Energy and environmental issues are the driving force for researches on engine worldwide, to pursue new developments on improving engine performances. Many advanced themodynamic cycle theories and working models were born in the fields. Since the combustion process is deeply affected by the variation of working chamber volume, it is necessary to develop new power transmission device, to optimize the engine combustion process, and further its performance. The Twin-rotor Piston Engine is driven by a novel cycloidal cam combination mechanism, whose key parts are the swing plate and a spherical cam with cycloidal profiles. To achieve a good performance of the Twin-rotor Piston Engine, the cycloidal profile of the spherical cam mechanism was studied in the paper, and then the kinematics was investigated, followed by the configuration of the variation law of the working chamber volume. The relationship between the motion law of the swing plate and the cam profile was obtained through theoretical derivation, and four typical curves was applied for comparation. During the comparation, influences of rotor motions on the theoretical profile was calculated and analyzed. The main conclusions are: the rotor motion is determined by the cycloidal profile of the spherical cam mechanism, and then the engine combustion process will be confirmed. To achieve a good engine combustion performance, the rotor motions should be optimized to develop an advanced cycloidal profile of spherical cam. A better cycloidal profile of spherical cam is that there is no mutation point during the rotor motions, so that the spherical cam mechanism will work under low level of virabration and impact.
