HEAT ENGINE

PROBLEM TO BE SOLVED: To provide a heat engine capable of suppressing the turbulence of a liquid surface of a liquid piston.SOLUTION: A heat engine 4 forms a liquid piston on inner parts of pipe members 21, 22, 51. The liquid piston flows vibratingly with the supply and condensation of vapor. A displacement of the liquid piston is converted to a mechanical motion and output from an output part 60. A float 31 which can float on the liquid piston is arranged on the inner part of the pipe members 21, 22. The float 31 comes into contact with a seat surface 24 when being located at an upper dead center to close the inner part of the pipe member on one end. Thereby, a flow on the upper end of the liquid piston is forcibly stopped. Accordingly, turbulence on the liquid surface is forcibly suppressed. After the float 31 is seated on the seat surface 24, an excessive actuating medium in the liquid piston is discharged from discharge parts 25, 81.