FOUR-CYCLE ENGINE

摘要

A four-cycle engine (1) is adapted so that fresh air is introduced into a cylinder (1a) through an intake port (1d) opened and closed by intake valves (IN1, IN2) and so that exhaust gas is re-drawn into the cylinder (1a) through an exhaust port opened and closed by exhaust valves (EX1, EX2). The exhaust port has a first exhaust port (1p) and a second exhaust port (1e). The exhaust gas is re-drawn from the first exhaust port (1p), secondary air is drawn from the second exhaust port (1e), and as a result, in the cylinder (1a) are formed a high-temperature first temperature layer (T1) mainly composed of the exhaust gas and a low-temperature second temperature layer (T2) mainly composed of the secondary air and having a lower temperature than the first temperature layer (T1).