A positive crankcase ventilation (PCV) system includes: an oil separator separating oil from blow-by gases; a PCV valve allowing the blow-by gases from which the oil has been separated by the oil separator to flow into intake ports of a cylinder head; a PCV passage vertically extending from the PCV valve; a PCV chamber connected to the PCV passage; and a plurality of bypass passages branching off from the PCV chamber to the intake ports, respectively.

The invention relates to a cylinder head oil separator arranged in a cylinder head of an internal combustion engine. In order to reduce maintenance and simplify the oil separator, the cylinder head oil separator includes a flow channel which is constructed as a Tesla valve and which is designed such that the air-oil aerosol flows through a longer flow path in a first flow direction from the aerosol inlet at a first opening to the air outlet (separation direction) at a second opening. The air-oil aerosol flows through a shorter flow path in a ventilation direction opposite the separation direction from the inlet at the second opening to the outlet of a fluid at the first opening.

An internal combustion engine (1) includes an internal combustion engine main body (20), a head cover (11, 15) attached to an upper end part of the internal combustion engine main body, and an exhaust system (34) connected to the internal combustion engine main body, and a gas-liquid separator (45, 60) for blowby gas provided in the head cover. A part of the exhaust system is positioned adjacent to the internal combustion engine main body in a first direction (X) along a cylinder row, and the gas-liquid separator is positioned in the head cover so as to be offset in the first direction.

A cylinder head cover that prevents the gas outlet for the blow-by gas from being cooled by structural improvements so that the gas outlet does not freeze or become clogged in a cold condition. A cylinder head cover includes: a gas passage through which blow-by gas from a crankcase passes; and a gas outlet portion protruding upward from a head cover upper wall. The gas outlet portion includes a protruding case portion bulging upward from the head cover upper wall so as to form an outlet passage through which blow-by gas passes, and an air layer is formed outside the outlet passage in the protruding case portion.

A blow-by gas treating device has an oil separator. A tubular attachment portion is disposed at a discharge port of the oil separator. A PCV valve is inserted in the attachment portion. The PCV valve includes an inflow hole, a discharge hole, a flow rate regulating portion, and a stopping portion. The stopping portion is located closer to the inflow hole than to the flow rate regulating portion. The stopping portion has a dimension greater than the inner diameter of the attachment portion in a direction perpendicular to the central axis of the attachment portion. The flow rate regulating portion is surrounded by the attachment portion. The stopping portion is arranged in the space defined by the oil separator.

An air cleaner includes: an air cleaner box defining a clean chamber that is placed rearward of a dirty chamber, the clean chamber receiving air which has been introduced from front into the dirty chamber and then filtered through an air cleaner element; and funnels that are to be connected to an intake port of an internal combustion engine, the funnels protruding upward into a space within the air cleaner box from a bottom wall of the air cleaner box. The air cleaner further includes a breather chamber into which blow-by gas is introduced from the internal combustion engine, the breather chamber being placed rearward of the funnels and between the funnels and a rear wall of the air cleaner box. Accordingly, the air cleaner can further promote the air-liquid separation of blow-by gas without incurring an increase in weight of the internal combustion engine.

A head cover structured and arranged to cover at least part of a face of a cylinder head of an internal combustion engine is described. The head cover includes a chamber formation part structured and arranged to provide a chamber to restrain sound propagating through air from the cylinder head. The chamber formation part includes a partition part for partitioning the chamber from a space on a cylinder head side. The partition part has a convex part projecting into the chamber, and a through hole may be provided in the convex part that penetrates from the space on the cylinder head side to the chamber.

A cylinder head cover includes a main body and a side projection portion. The main body is provided so as to cover a cylinder head, and collects a blowby gas. The side projection portion discharges the blowby gas toward an intake passage. The cylinder head cover includes a cover gas passage through which the blowby gas flows from a main body gas passage to an outlet of the side projection portion. A minimum passage cross-sectional area portion of the cover gas passage is provided not in the side projection portion but in the main body gas passage. The main body has a hole or a projection branch passage at a position of the main body gas passage that is downstream of the minimum passage cross-sectional area portion. The main body, the side projection portion, and the hole or the projection branch passage are integrally molded.

This breather device separates engine oil included in a blow-by gas. The breather device comprises a first route, an acceleration route, a branching route, and turn-back routes. The blow-by gas flows to the first route. The acceleration route is connected to a downstream side of the first route, and has a flow channel cross-sectional area smaller than that of the first route. The branching route is connected to a downstream side of the acceleration route , configured including a wall part orthogonal to the acceleration route, and branched into two routes by the wall part. The turn-back routes are connected to one route branching at the branching route, and are turned back so as to be parallel to the acceleration route and to head in the opposite direction from a progressing direction.

A breather is provided for an internal combustion engine that is configured to be mounted to provide a compact, space efficient packaging arrangement for the internal combustion engine. The breather includes a housing with a front wall, a rear wall opposite the front wall, and a plurality of sidewalls connecting the front and rear walls. The front wall is configured for attachment to the rearward end of the valve cover.