Homogeneous charge compression ignition engine

A homogeneous charge compression ignition engine having a combustion chamber and an intake passage which is connected to the combustion chamber, wherein the engine allows the combustion mode to be switched between spark ignition combustion and homogeneous charge compression ignition combustion through a switching period, the engine provides a negative overlap period in an operation during homogeneous charge compression ignition combustion, the negative overlap period being a period during which an intake valve and an exhaust valve are both closed when a piston is in the vicinity of the top dead center in the exhaust stroke, so that burned gas remains inside the combustion chamber, and the engine comprises:

• a throttle for adjusting the amount of air supplied to the combustion chamber;
• an adjusting section for adjusting the amount of fuel supplied to the intake passage at a point upstream from the throttle;
• and
• a control section for controlling the throttle and the adjusting section, wherein, during the switching period in which the spark ignition combustion is switched to the homogeneous charge compression ignition combustion, the control section controls the throttle such that the opening degree of the throttle increases to the opening degree at the time of the steady operation at the homogeneous charge compression ignition combustion from the opening degree at the time of steady operation at the spark ignition combustion, and controls the adjusting section such that the amount of fuel supplied to the intake passage becomes greater than the amount at the time of the steady operation at the spark ignition combustion.