To improve lubricating performance of a double-link type piston crank mechanism.
An internal combustion engine is equipped with a piston crank mechanism 14 varying an engine compression ratio through a relative position change in a rocking center position of a control link 7 in response to the rotation of a control shaft 9. A driving force transmission mechanism part for transmitting driving force of a drive motor 20 to the control shaft 9 consists of a worm 20a and a worm wheel 21, and is arranged in a front cover chamber formed between a front wall 25 of the internal combustion engine and a front cover mounted in the front wall 25. The front cover chamber is formed to communicate with a lubricating oil passage formed in a cylinder head 26. Thus, sufficient lubricating oil is supplied to the driving force transmission mechanism part from the cylinder head 26 without influence of double links in the piston crank mechanism 14.
HIYOSHI RYOSUKE
TAKEMURA SHINICHI
Hiromichi Kobayashi
Tomioka Kiyoshi