Patent ID: 7290508

Claim:
A lower link for a piston crank mechanism of an internal combustion engine, the piston crank mechanism including an upper link having a first end connected through a piston pin with a piston, and a second end connected through an upper pin to the lower link, and a control link having a first end swingably supported by the engine and a second end connected through a control pin to the lower link, the lower link comprising: an upper section including an upper pin boss portion arranged to hold the upper pin; a lower section including a control pin boss portion arranged to hold the control pin; and a crank pin bearing section disposed between the upper section and the lower section, and mounted on a crank pin of a crank shaft; the upper section and the lower section being coupled by at least two bolts disposed to sandwich the crank pin bearing section, one of the upper section and the lower section being formed with a bolt inserting hole, the other of the upper section and the lower section being formed with an internal thread portion including an open end, one of the at least two bolts passing through the bolt inserting hole of the one of the upper section and the lower section, being screwed into the internal thread portion of the other of the upper section and the lower section, and including an end bared from the open end of the internal thread portion which is formed in a surface perpendicular to a bolt center axis, and the other of the upper section and the lower section including a recessed portion formed in the surface to divert a stress transmitting path.