Abstract
An air engine includes a cylinder, a piston, a gas supply and an intake-exhaust mechanism. The piston reciprocates in the cylinder. The gas supply supplies a compressed gas to move the piston. The intake-exhaust mechanism connected to the cylinder and the gas supply includes a body and an intake-exhaust assembly. The body has a chamber and an intake channel, an exhaust channel, an inlet port and an outlet port, which communicate with the chamber. The intake-exhaust assembly is rotatable within the chamber, controls the inlet port to connect to the intake channel or not and controls the outlet port to connect to the exhaust channel or not, so that the compressed gas enters the cylinder through the inlet port and the intake channel to drive the piston. After driving the piston, the compressed gas becomes an exhaust gas, which is exhausted from the cylinder via the exhaust channel and the outlet port.