Assembling piston ring

Disclosed is a combined piston ring which comprises an upper reverse torsion ring(1) and a lower torsion ring(2) which are piled up with the openings staggered at an angle of 180 degree. The section of the upper reverse torsion ring(1) is a trapezia structure with the inner edge parallel to the outer edge and the inner edge longer than the outer edge; the section of the lower torsion ring(2) is a trapezia structure with the inner edge parallel to the outer edge and the inner edge shorter than the outer edge; a circular gap(3) is arranged at the inner side of the section; the upper plane of the upper ring is parallel to the lower plane of the lower ring; the section of the piled up upper reverse torsion ring and the lower torsion ring(2) resembles a rectangle. The tortility of the lower torsion ring(2) is increased due to the structure, so the contact area of the external ring work surface of the piston ring with the cylinder wall is reduced, thus friction between the piston ring and the cylinder is reduced, the scraping and lubricating ability is increased, which is good for initial joining, reducing oil consumption and exhaust pollution.