A NEW WOBBLE DRIVE WITH PARTICULAR APPLICATION IN A STIRLING ENGINE

Swash plate or wobble mechanisms used in engine drives commonly require gearing, slides and/or spherical bearings to connect the piston rods to the transfer mechanism and react to the torque produced. This paper briefly reviews the literature on this class of engine mechanism and presents the theory and form design of a new wobble yoke mechanism which achieves single degree of freedom rotational motion for all bearings, enabling the use of sealed rolling element bearings and eliminating the need for sliding surfaces or gears. The mechanism has been first applied in a liquefied petroleum gas-fuelled integrated Stirling engine electric generator system for battery charging. The hermetically sealed system gives 200 watt d.c. electrical output and is configured for charging 12 volt batteries. A square four-cylinder double-acting configuration is used, with pistons equispaced and parallel to the output shaft. The mechanism is easily parametrically sealed to different engine sizes. It also has potential application in compressors, pumps, other Stirling cycle machines or Otto cycle engines. Development of mechanical design features and thermodynamic and electrical development of the Stirling engine generator are to be described in a subsequent paper, to be published in the next Part C issue.