Patent ID: 8171922

Claim:
A blow-by gas recirculation system for an internal combustion engine to separate oil from blow-by gas introduced from an inside of an engine body into an oil separation space and then supply the blow-by gas to a region of an intake passage downstream of a throttle valve in an intake system, comprising: an intake unit provided with the throttle valve and the intake passage and disposed on the side of one of opposite sidewalls of the engine body; an oil separation cover attached to the one sidewall of the engine body to define the oil separation space in cooperation with the one sidewall; and a gas passage which provides communication between the oil separation space and the region of the intake passage downstream of the throttle valve of the intake unit, the gas passage being formed inside the oil separation cover and the intake unit, wherein the oil separation cover has a rim wall formed as an attaching flange and an intake unit mounting portion, the oil separation cover being fastened to the engine body at a plurality of positions through the attaching flange, the intake unit mounting portion is integrally formed with a region of the attaching flange, said intake unit mounting portion has a mounting seat surface for mounting the intake unit; and the intake unit has a contact surface formed on a gas passage-adjacent portion thereof located adjacent to a region of the gas passage formed thereinside, the intake unit being fastened to the oil separation cover under a condition that the contact surface is in contact with the mounting seat surface of the oil separation cover; and the gas passage is formed to penetrate through the contact surface.