Heat-insulating engine with swirl chambers

In a heat-insulating engine with swirl chambers, comprising a cylinder block constituting cylinders, a cylinder head fixed to said cylinder block, swirl chamber blocks disposed inside hole portions formed in said cylinder head and constituting swirl chambers having a heat-insulating structure, pistons reciprocating inside said cylinders, main chambers formed at said piston heads of said pistons, communication ports for communicating said main chambers with said swirl chambers, formed in said swirl chamber blocks, and fuel injection nozzles having injection ports thereof opening to said swirl chambers, and sequentially operated in a cycle of an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke;

• the improvement characterized in that the heat-insulating engine with swirl chambers futher comprises:
• said communication ports including small communication ports having a small passage area and large communication ports having a large passage area, formed in said swirl chamber blocks;
• and
• control valves for opening and closing said large communication ports, said control valves closing said large communication ports during said compression stroke and opening said large communication ports at the time of the pressure rise of said swirl chambers during said expansion stroke after the injection of the fuel from said fuel injection nozzles.