Patent ID: 8826882

Claim:
A lubricating structure of a multi-link, piston-crank mechanism for an internal combustion engine provided with an upper link with one end connected to a piston via a piston pin, a lower link connected via an upper pin to another end of the upper link while being rotatably attached to a crank pin of a crankshaft, and a control link with one end connected pivotally to an engine body while being connected with another end to the lower link via a control pin, comprising: a crank pin oil passage extending radially in the crank pin and opening with one end at an outer periphery of the crank pin for supplying a lubricating oil at a predetermined pressure; and a lower link oil passage formed in the lower link and passing through between an opposing surface opposed to either a pin boss portion of the upper link to which the upper pin is rotatably fitted or the pin boss portion of the control link to which the control pin is rotatably fitted, and a bearing shaft surface of the crank pin, wherein, at a predetermined crank angle at which the crank pin oil passage and the lower link oil passage are communicative when viewed in a direction of the crankshaft along a straight line connecting a rotation center of the crank shaft and the end of the lower link oil passage at a side of the opposing surface of the pin boss, the pin boss portion is disposed for lubrication, and wherein a recess is formed in an axial side surface which is recessed in an axial direction.