Patent ID: 7685989

Claim:
A 2-cycle engine comprising: a cylinder including a cylinder chamber, wherein a piston is accommodated in the cylinder chamber; an ignition device directed so that an ignition portion is positioned in a central portion in a combustion chamber defined by the piston and an inner circumference of the cylinder chamber; an exhaust control valve that adjusts an opening of an exhaust passage connected to an exhaust port opened on an inner circumference of the cylinder chamber; a controller that controls actuations of the ignition device and the exhaust control valve, wherein the controller controls: the ignition device to activate to perform a spark ignition combustion of a mixture including air and fuel supplied into the cylinder chamber in a high load range; and the exhaust control valve to adjust the opening of the exhaust port so as to control pressure in the cylinder chamber to perform self-ignition combustion of the mixture in the combustion chamber; stratified mixture field forming means for forming a stratified mixture field where: the mixture is much distributed at a central portion of the combustion chamber; and burned gas remaining in the combustion chamber is much distributed on an outer side of the central portion of the combustion chamber, in a low load and low rotational speed range that is a low rotational speed range within the low load range; and a direct injection device that directly injects and supplies the supply fuel into the cylinder chamber, wherein the controller controls the stratified mixture field forming means to form the stratified mixture field to perform the self-ignition combustion of the mixture, in the low load and low rotational speed range, and wherein the controller controls the ignition device to perform a spark ignition combustion of a mixture forming the stratified mixture field in an extremely low load and low rotational speed range, which is a low load as well as low rotational speed range within the low load and low rotational speed range.