Various embodiments of the present invention are directed toward a linear combustion engine, comprising: a cylinder having a cylinder wall and a pair of ends, the cylinder including a combustion section disposed in a center portion of the cylinder; a pair of opposed piston assemblies adapted to move linearly within the cylinder, each piston assembly disposed on one side of the combustion section opposite the other piston assembly, each piston assembly including a spring rod and a piston comprising a solid front section adjacent the combustion section and a gas section; and a pair of linear electromagnetic machines adapted to directly convert kinetic energy of the piston assembly into electrical energy, and adapted to directly convert electrical energy into kinetic energy of the piston assembly for providing compression work during the compression stroke.

The present invention provides a system and method for economically using compressed air as automobile power source, comprising: a compressed air power device, which includes automobile air storage tubes (1) to store a sufficient amount of high-pressure compressed air and a cylinder-combined engine consisting of the first and second cylinders (9)(10), and which can make full use of the compressed air to produce driving power; a mechanism to produce, store and provide high-pressure compressed air, which includes a boiler-type high-pressure compressed air producing and storing device, abbreviated as boiler-type HCAPS device (4), to be able to use electricity during periods of low energy demand (off-peak) such as at night simultaneously recovering the by-produced heat for central heating, and pressurizing and inflating into the automobile air storage tubes (1) during daytimes; brake energy recovery and regeneration devices, which include a spring reserving-releasing device and/or a compressed air reserving-releasing device to save the compressed air in the automobile air storage tubes (1) for saving the driving power; an inner gear ring assembly, which includes an inner gear ring (2) gearing meshing with inner acting gears (45), with the first and second accelerating gears (72)(92), with a flywheel front inner meshing gear (48) and reset gears (46), for transmitting torque and mixing/outputting power; some clutch transmission devices and a controller, which controls orderly coordinated operation of devices and mechanisms.

A free piston device, comprises a housing with a cylindrical inner wall having a first wall opening and a second wall opening; a cylindrical piston movable in axial direction and rotatable around its longitudinal axis; the piston comprising a first skirt forming a first chamber, said first skirt having at least a first opening in the form of a hole through the wall of the skirt for allowing passage of a fluid directly into or out of said chamber; control means for controlling axial and angular movement of said piston; sensing means for providing signals related to the axial position and/or the angular position of the piston; a digital control unit for rotating the piston around its longitudinal axis in synchronism with its axial movement.

A free piston device, comprises a housing with a cylindrical inner wall having a first wall opening and a second wall opening; a cylindrical piston movable in axial direction and rotatable around its longitudinal axis; the piston comprising a first skirt forming a first chamber, said first skirt having at least a first opening in the form of a hole through the wall of the skirt for allowing passage of a fluid directly into or out of said chamber; control means for controlling axial and angular movement of said piston; sensing means for providing signals related to the axial position and/or the angular position of the piston; a digital control unit for rotating the piston around its longitudinal axis in synchronism with its axial movement.

An internal combustion engine for providing a linear reciprocating movement of an output shaft along a longitudinal axis. The engine has a double sided cylinder that is bounded by an engine head at each side of the cylinder. An exhaust unit is positioned at each side of the cylinder. A piston is positioned within a cylinder inner space and freely slides with respect to the cylinder along the longitudinal axis. Two piston rods are aligned with the longitudinal axis. Each piston rod is connected at a different side of the piston. Each of the piston rods has exhaust openings.

A linear reciprocating engine may include an engine block, a cylinder having combustion chambers at opposing ends, cylinder heads located at an end of the respective combustion chambers, respectively, and a double-faced piston. The engine may further include piston rod portions extending from both faces of the piston through the combustion chambers. The engine may further include an exhaust outlet in a peripheral cylinder wall and elongated channels in the piston rod portions being configured to serve as an intake inlet for gas from a location external to the cylinder. When the piston is in a combustion stage in a first combustion chamber, the piston blocks the exhaust outlet from communicating with the first chamber with the first channel access opening outside the first chamber, while simultaneously the exhaust outlet is in communication with a second combustion chamber with the second channel access opening within the second chamber.

An internal combustion engine may include an engine block, a cylinder within the engine block, and a piston within the cylinder. The piston may have an outer peripheral wall, and a groove in the outer peripheral wall of the piston may have a first edge and a second edge spaced from the first edge. The piston may have a piston ring in the groove, and the piston ring may have a shape that meanders within the groove, such that the shape of the piston ring differs from a shape of the groove and such that the piston ring does not substantially fill the groove. The piston ring may be constructed of a material that when subjected to heat causes a shape of the meanderings to change, thereby enabling the piston ring to expand in an axial direction of the piston, between the edges of the groove.

A linear reciprocating engine may include a cylinder having a first combustion chamber at one end and a second combustion chamber at an opposing end, first and second cylinder heads located at an end of the first and second combustion chambers, respectively, and a double-faced piston slidably mounted within the cylinder. The engine may further include a first piston rod portion extending from a first face of the double-faced piston through the first combustion chamber, and a second piston rod portion extending from a second face of the piston through the second combustion chamber. Passageways in the piston rod portions may be configured to communicate gases between the combustion chamber and a location outside the cylinder and configured to prevent gases from being exchanged between the cylinder and a location outside the cylinder via a path that crosses both face of the piston.

A linear power generator has a gas pressure cylinder structure which causes reciprocating motion of a piston in an axial direction by supplying a high-pressure gas alternately to a left gas chamber and a right gas chamber of a cylinder which includes an electromotive coil, and alternately applying a gas pressure in the left gas chamber and a gas pressure in the right gas chamber to the piston which includes a permanent magnet in the cylinder, and which induces power generation of the electromotive coil by way of reciprocating motion of the piston which has the permanent magnet in the axial direction. The linear power generator encourages movement of the piston by supplying a first high-pressure gas into the left gas chamber and the right gas chamber, and keeps moving the piston by supplying a second high-pressure gas for supplementing the first high-pressure gas into the left gas chamber and the right gas chamber.

A linear reciprocating engine may include a cylinder having first and second combustion chambers at opposing ends, first and second cylinder heads at an end of the first and second combustion chambers, respectively, and a double-faced piston slidably mounted within the cylinder. The engine may further include an exhaust port located in a peripheral cylinder wall and at least one combustion gas inlet in a location other than the peripheral cylinder wall. The combustion gas inlet and the exhaust port may be configured to cooperate such that combustion gases introduced through the inlet are evacuated from the cylinder through the exhaust port. The double-faced piston may have an axial length from one face to an opposite face of the piston less than or equal to of a distance from at least one of the first cylinder head and the second cylinder head to the exhaust port.