The invention relates to a stretching type
compression ratio variable device, and belongs to the technical field of internal
combustion engines. The stretching type
compression ratio variable device comprises an air cylinder, a cylinder cover, a
piston, a first piton ring, a second
piston ring, a connecting rod, a volume cavity, a
moving body and a spring, wherein the cylinder cover is arranged at the upper end of the air cylinder; the
piston is arranged inside the air cylinder; a
combustion chamber is formed by the air cylinder, the cylinder cover and the piston together; the first
piston ring and the second
piston ring are respectively arranged on the top of the piston; the connecting rod is connected with the piston together; the volume cavity is arranged on the top of the piston; the
moving body is arranged inside the volume cavity; the two ends of the spring are respectively connected with the lower end face of the
moving body and the lower end face of the volume cavity. Under a high-speed working condition, when the pressure inside the
combustion chamber is maximum and the combustion pressure is higher, the moving body moves downwards, and the volume of the
combustion chamber becomes larger; under a low-speed working condition, when the pressure inside the
combustion chamber is maximum and the combustion pressure is lower, the moving body moves upwards, and the volume of the
combustion chamber becomes smaller. The stretching type
compression ratio variable device is reasonable in structure and simple in design, and is suitable for the
optimal design of the compression ratio of an engine.