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.

An engine is described having a crankcase, a liner and a head assembly. The crankcase is split along a plane defining a two part crankcase, where fluid passages are passing through only one of the crankcase portions, so as to not require crossing the split line. A connecting rod also includes a tapered end, and the piston has a complementary carrier receiving the connecting rod.

An oil separator includes a case that has an inflow port, an outflow port, and an oil separation portion. The case has a first wall portion and a second wall portion that constitute a flow channel, and a partition wall portion that connects the first wall portion and the second wall portion. The partition wall portion partitions the flow channel into an upstream-side flow channel and a downstream-side flow channel. The oil separation portion has a constriction hole and a step portion. The step portion has a collision face located on the axis of the constriction hole and configured such that blow-by gas that passes through the constriction hole collides against the collision face, and allows oil that collects on the step portion to be discharged into the upstream-side flow channel through the constriction hole.

An oil mist separation mechanism of an internal combustion engine includes an oil mist separation portion being integrally provided with an internal combustion engine main body at an outer surface thereof, the oil mist separation portion for separating an oil mist included in a blow-by gas sent from the internal combustion engine main body, and an oil returning portion being connected to the oil mist separation portion, the oil returning portion returning an oil separated by the oil mist separation portion to an oil stored at a lower portion of the internal combustion engine main body.

A case for an oil mist separator comprises an inlet and an outlet through which blow-by gas flows, a separation section for separating oil mist contained in the blow-by gas, and an oil discharge section disposed at a bottom portion of the case. The oil discharge section includes a first discharge part having a first discharge hole for discharging the separated oil, and a second discharge part surrounding the first discharge hole. The second discharge part includes a reservoir for storing the oil discharged from the first discharge hole, and a second discharge hole provided at a bottom portion of the reservoir. The second discharge part further includes a passage providing fluid communication between the inside and the outside of the second discharge part.

An oil mist separator includes a case including an inflow port into which blow-by gas flows and an outflow port out of which blow-by gas flows, a separation unit arranged in the case, and an oil discharge unit arranged at a lower part of the case. The oil mist separator is configured to separate oil mist contained in blow-by gas by the separation unit and discharge oil separated by the separation unit to an outside of the case through the oil discharge unit. The oil discharge unit includes a discharge port through which oil is discharged to the outside of the case and a constriction arranged above the discharge port. The constriction is partially decreased in a small cross-sectional flow area.

To improve the oil separation performance in an oil separation device for an internal combustion engine. The oil separation device (10) comprises a gas liquid separation passage (56) internally defined by a lower wall, an upper wall and a pair of side walls, and extending in a horizontal direction, a gas inlet (54) and a gas outlet (63) provided on either end of the gas liquid separation passage, a plurality of lower partition walls (56H) projecting upward from the lower wall, and a plurality of upper partition walls (56J) projecting downward from the upper wall. The lower partition walls and the upper partition wall are tilted with respective the length wise direction in plan view so as to define a spiral passage. The lower wall is inclined with respect to a horizontal plane such that an upstream part of the lower wall is lower than a downstream part of the lower wall with respect to a direction of the swirl flow.

A breather chamber structure for an internal combustion engine wherein the breather chamber can be disposed compactly and the degree of freedom in the layout of the parts of the internal combustion engine can be raised. The breather chamber structure includes a crankcase, a cylinder body provided upwardly on the crankcase, and a breather chamber configured to separate oil from oil mist in the crankcase. The breather chamber includes a crankcase side breather chamber provided in the crankcase and open to a joining plane between the crankcase and the cylinder body, and a cylinder side breather chamber provided in the cylinder body and open to the joining plane.

An oil separator for trapping oil mist contained in blow-by gas includes a separation plate, an upstream oil-mist trapping chamber, and a downstream oil-mist trapping chamber. The upstream and downstream oil-mist trapping chambers are divided by the separation plate. The upstream oil-mist trapping chamber communicates with a flow inlet for blow-by gas. The downstream oil-mist trapping chamber communicates with the upstream oil-mist trapping chamber and communicates with a flow outlet for blow-by gas. A return port formed through the separation plate returns oil mist trapped in the downstream oil-mist trapping chamber into the upstream oil-mist trapping chamber. The return port is positioned vertically above the bottom surface of the upstream oil-mist trapping chamber and is positioned at substantially the same vertical level as the lowermost portion of the bottom surface of the downstream oil-mist trapping chamber.

An oil separating device for separating an oil mist from a blow-by gas is arranged on a flow passage of the blow-by gas. The oil separating device includes an oil separator having an inlet formed at one end thereof and an outlet formed at another end thereof opposite to the one end; a collision wall arranged at a downstream side of the oil separator, and including an uneven portion formed on a surface thereof to face the outlet of the oil separator; and a filter arranged between the oil separator and collision wall. The oil separator is formed such that the oil mist in the blow-by gas coalesces together to form a coalesced oil mist, the filter removes the coalesced oil mist from the blow-by gas, and the collision wall separates a remained oil mist remained in the blow-by gas through the filter.