Heat-insulating engine structure.

摘要

In order to improve the suction efficiency and the cycle efficiency, a heat-insulating engine structure (10) of the invention has a planar and thin-walled piston head surface portion (4) of a ceramics material to be exposed to combustion gases. A combustion chamber (15) is formed not on the side of the piston head but on the side of a cylinder head. Namely, the piston head is defined by the cooperation of a cylinder head bottom wall portion (26) having a lowered central portion and a raised outer peripheral portion (18) and a cylinder liner upper portion (28) including an upper tubular part of a substantially square cross-section and a lower cylindrical part. The cylinder head bottom wall portion has an inclined surface radially upwardly extending from the central portion to the outer peripheral portion. Intake and exhaust valves (21, 27) are associated with valve seats formed in the inclined surface. A fuel injection nozzle (25) is disposed substantially centrally of the cylinder head bottom wall portion. The sides of the square tubular part are operative to agitate a swirl to facilitate uniform mixture of fuel and air thereby assuring that the fuel and air are mixed instantaneously in a zone adjacent to the top dead center of the piston.