COMBUSTION CONTROL DEVICE FOR AN ENGINE

摘要

A fuel-air mixture cooling chamber (20) is formed between a main piston (4) and a sub-piston (19) by supporting the sub-piston (19) on an upper surface of the main piston (4) in such a manner as to vertically move freely, and this fuel-air mixture cooling chamber (20) is caused to communicate with a peripheral portion of a combustion chamber (12). The sub-piston (19) is connected to a cam member (23) supported on a crank shaft (7) via a sub-connecting rod (21), and the volume of the fuel-air mixture cooling chamber (20) is increased or decreased as the crank shaft (7) rotates. The volume of the fuel-air mixture cooling chamber (20) is increased from a compression stroke to just after an ignition, and the occurrence of knocking is prevented by cooling fuel-air mixture filled therein. The volume starts to be decreased just after the ignition and fuel-air mixture in the fuel-air mixture cooling chamber (20) is forced out into the combustion chamber (12) for combustion. Thus, knocking is less apt to occur even if thermal efficiency is improved by increasing a compression ratio and advancing the ignition timing.