VARIABLE COMPRESSION RATIO MECHANISM FOR INTERNAL COMBUSTION ENGINE

摘要

Provided is a variable compression ratio mechanism (5) in which a control shaft (10) is rotationally driven by an electric motor (21) via a wave gear speed reducer (22). The wave gear speed reducer (22) comprises: a first internal gear member (31); an external gear member (32) arranged concentrically on the interior of the first internal gear member (31); a wave generator (33) arranged on the interior of the external gear member (32), the outer shape of said wave generator (33) having an elliptical outline; and a second internal gear member (34). The ratio of the number of teeth of a fixed gear section (35) of the first internal gear member (31) to the number of teeth of a first gear section (37) of the external gear member (32) is set to be larger than the ratio of the number of teeth of an output-side gear section (42) of the second internal gear member (34) to the number of teeth of a second gear section (38) of the external gear member (32).