Piston engine cylinder head with combined functions

A variable compression ratio piston engine, comprising:

• a head cylinder,
• an upper piston,
• the upper piston configured to fit horizontally and sealingly in the head cylinder and move up and down along its centerline,
• the head cylinder aligns with and connects to a main cylinder sealingly,
• the main cylinder encloses a main piston,
• the bottom face of the upper piston and the top face of the main piston defines a combustion chamber wherewithin the head cylinder and the main cylinder, the combustion chamber volume changes from its minimum to its maximum in operation, the position of the minimum combustion volume is located at a position between 15° and 75° of crank angle of the main piston,
• the spaces outside of the combustion chamber is defined as external,
• the head cylinder has a first port and a second port,
• the first port and the second port are through holes on different sides of the wall of the head cylinder,
• the upper piston has a first path and second path,
• the first path and the second path are air passages connecting the vertical sides the upper piston to the bottom face of the upper piston,
• when the first port aligns with the first path horizontally, the combustion chamber communicates with the external,
• when the second port aligns with the second path horizontally, the combustion chamber communicates with external,
• when neither the first port aligns with the first path nor the second port aligns with the second path horizontally, the combustion chamber is sealed from the external,
• the upper piston moves to its lowermost position after 20° of the crank angle of the main piston,
• wherein at least in one position from 15° to 75° crank angle of the main piston, the lowermost position of the bottom face of the upper piston is overlapped vertically with the uppermost position of the top face of the main piston at different crank angles,
• a phase shift is defined as the displacement in time between the vertical movement of the upper piston referring to its own initial position and the movement of the main piston referring to its own initial position,
• a higher compression ratio is obtained when the phase shift is leading,
• a lower compression ratio is obtained when the phase shift is lagging.

A piston engine with shifted minimum combustion chamber volume, comprising:

• a head cylinder,
• an upper piston,
• the upper piston configured to fit horizontally and sealingly in the head cylinder and move up and down along its centerline,
• the head cylinder aligns with and connects to a main cylinder sealingly,
• the main cylinder encloses a main piston,
• the bottom face of the upper piston and the top face of the main piston defines a combustion chamber wherewithin the head cylinder and the main cylinder, the combustion chamber volume changes from its minimum to its maximum in operation, the position of the minimum combustion volume is located at a position that is 20° to 75° away from 0° ATDC in crank angle of the main piston,
• the upper piston moves to its lowermost position after 20° but before 75° ATDC of the crank angle of the main piston,
• wherein at least in one position from 20° to 75° crank angle of the main piston, the lowermost position of the bottom face of the upper piston is overlapped vertically with the uppermost position of the top face of the main piston at different crank angles,
• wherein each compression stroke has a first compression stage and a second compression stage,
• the first compression stage takes place from near 180° BTDC to near 0° ATDC,
• the second compression stage takes place from near 0° ATDC to near 75° ADTC,
• the first compression stage has a combustion chamber volume Vc at 0° ATDC,
• the second compression stage has a minimum combustion chamber volume Vm after 20° ATDC,
• wherein Vm is smaller than Vc,
• wherein compression period is longer than combustion period in time.