PURPOSE: To reduce smoke in exhaust gases by applying a system wherein a liquid fuel is heated and vaporized in a vaporizing chamber for forming a mixture of fuel and air, the vaporizing chamber is shifted to and made open in a pre-combustion chamber and the mixture is dispersed on a swirl of compressed air in the pre-combustion chamber.

CONSTITUTION: In a crank angle range of 0°W180°, a suction valve 34 opens and an exhaust valve closes, while a vapor generating valve 15 closes and a liquid fuel is supplied from a fuel feed valve 27 to an active chamber 18 and a vaporizing chamber 17 for the start of a vaporizing process assisted by a heater 21. Then, in a crank angle range of 180°W360°, each of said valves 34 and 35 closes and a compression stroke starts. Thereafter, a valve body 16 is pushed down by a rotary cam 29, just before the crank angle reaches 360°. Consequently, each of said chambers 17 and 18 is shifted to and open in a pre-combustion chamber 7, and the vapor generating valve 15 opens. At this stage, a mixture on a swirl 7a is dispersed in the pre-combustion chamber 7 and jetted into a main combustion chamber 5 via an injection hole 8.