Variable compression-ratio reciprocating piston engine

The utility model relates to an engine with a variable compression ratio, in particular to a reciprocating piston engine with a variable compression ratio; a connecting rod (2) is connected with a connecting rod axel neck (3) on the crank shaft through an eccentric upper bearing (9) and an eccentric lower bearing (10); a slide groove and a stepped hole communicated with the slide groove are machined on a crankshaft balance weight (7) arranged on the crankshaft; wherein, a centrifugal slide block (5) is mounted in the slide groove; the centrifugal slide block (5) is connected with the eccentric lower bearing (10) through a pull rod (4); the small diameter part of the stepped hole is mounted with an adjusting bolt (11); a locking nut (12) is mounted on the adjusting bolt (11); the large diameter part of the stepped hole is mounted with a return spring (8); both ends of the return spring (8) are respectively connected with the adjusting bolt (11) and the centrifugal slide block (5). The engine with a variable compression ratio has the advantages of simple structure and small volume; the variation of the piston stroke is realized through the rotation of the eccentric upper bearing and the eccentric lower bearing arranged on the connecting rod axel neck of the crankshaft, so as to change the volume of the cylinder combustion chamber so that the compression ratio of the cylinder combustion chamber is changed.