Free-piston regenerative hot gas hydraulic engine

A free-piston regenerative engine comprising:

• a piston chamber including an upper portion, a lower portion and a bottom;
• a displacer piston slidably mounted to move through a stroke within said upper portion of said piston chamber, said displacer piston including a top surface area and a bottom surface area;
• a heater, a regenerator and a cooler in communication with said piston chamber and being referenced to the top surface area and the bottom surface area of said displacer piston;
• means for imparting motion to the displacer piston;
• an inertial piston slidably mounted within said piston chamber;
• a diaphragm positioned to move through a stroke at a lower portion of said piston chamber wherein a fluid chamber is defined between the diaphragm and said bottom of said piston chamber;
• whereby fluid is supplied to and discharged from said fluid chamber in response to the movement of said displacer piston;
• and
• said displacer piston remaining stationary for a predetermined period of time at the end of said stroke to allow the diaphragm to complete its stroke prior to reversing the motion of said displacer piston, and wherein varying said predetermined period of time varies the engine frequency and output power.