Abstract
After second oil shock in 1978, fuel consumption cost has become an important evaluation factor for construction machinery, many improvements have been made to increase machine efficiency [1]. Recent year, as the Kyoto Protocol get effective, further effort on fuel consumption cut or CO2 cut is required for all machine makers. As the success of the hybrid system in automobile, construction machinery makers also put a lot of force on research to apply the hybrid concept in their own machines. This paper introduced the research and development of hybrid machinery in Hitachi Construction Machinery Co. Ltd, and also discussed the problems in this field.
