A blow-by gas return device includes: a gas path which is configured to introduce a blow-by gas generated in a crankcase into an intake system through an inside of a head cover, a pressure control valve and a blow-by pipe; and an orifice provided to the gas path, the orifice mounted on a wall portion of an intake manifold on a cylinder head side. A passage for a blow-by gas is formed in the wall portion on the cylinder head side, and the orifice is formed on a joint pipe mounted on the passage for the blow-by gas for communicably connecting the blow-by pipe with the passage for the blow-by gas.

A hybrid vehicle includes: a crankcase extending from a lower portion of a cylinder of an engine, the crankcase including a main body portion defining a crank chamber in which a crankshaft of the engine is accommodated, the crankcase further including a breather portion projecting upwardly from the main body portion and defining a breather chamber into which blowby gas is introduced from the crank chamber; a breather tube that introduces the blowby gas from the breather chamber into the intake passage; and a drive motor disposed rearwardly of the cylinder and mounted on a top surface of the crankcase. The breather portion has a facing surface facing an outer peripheral surface of the drive motor. The facing surface of the breather portion is shaped to conform to the outer peripheral surface of the drive motor.

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.

An internal combustion engine includes: an engine main body demarcating a breather chamber that is partitioned from a crank chamber, disposed above the crank chamber, and has an inlet opening opened toward the crank chamber; a multistage transmission housed in the crank chamber and having speed change gear trains that are respectively supported by a pair of transmission shafts and mesh with each other; and a breather passage disposed above the transmission shafts and extending in an up-down direction from the crank chamber to the inlet opening of the breather chamber, the inlet opening being disposed above a half in a height direction of the breather chamber. Accordingly, the internal combustion engine can suppress the entry of splashed oil into the breather chamber more than ever before.

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.

A lubrication system for internal combustion engines, in particular for vehicles with a rideable saddle, said system comprising a crank chamber in which at least one connecting rod is accommodated, and a basin or pan for collecting a lubricating liquid, wherein said crank chamber and said collection basin or pan are put in mutual communication by means of a first opening obtained in said crank chamber, wherein the flow of said lubricating liquid through said first opening from said crank chamber into said basin is adjusted by means of a first adjusting element adapted to be switched to an open position so as to allow the discharge of said lubricating liquid from said crank chamber into said collection basin or pan at a predetermined switching gas pressure value inside said crank chamber.

A hybrid vehicle includes: a crankcase extending from a lower portion of a cylinder of an engine, the crankcase including a main body portion defining a crank chamber in which a crankshaft of the engine is accommodated, the crankcase further including a breather portion projecting upwardly from the main body portion and defining a breather chamber into which blowby gas is introduced from the crank chamber; a breather tube that introduces the blowby gas from the breather chamber into the intake passage; and a drive motor disposed rearwardly of the cylinder and mounted on a top surface of the crankcase. The breather portion has a facing surface facing an outer peripheral surface of the drive motor. The facing surface of the breather portion is shaped to conform to the outer peripheral surface of the drive motor.

A method for ventilating a crankcase of an internal combustion engine using natural gas as a fuel source may include filtering ambient air through an air filter. The method may also include heating the filtered ambient air by a jacket heat exchanger. The method may further include directing the heated ambient air through an inlet of the crankcase to purge blow-by gases including natural gas from the crankcase.

A blow-by gas treatment device includes a first blow-by gas pipe, a second blow-by gas pipe, a first pipe joint located on a first head cover, the first blow-by gas pipe being connected to the first pipe joint, a second pipe joint located on a second head cover, the second blow-by gas pipe being connected to the second pipe joint, a first union located on the first pipe joint, a second union located on the second pipe joint, and a pressure sensor connected to the first pipe joint by the first union and connected to the second pipe joint by the second union.

Methods for indicating whether a crankcase of an engine is breeched are provided. One example method comprises restricting a communication of the crankcase with atmosphere, acting to increase or decrease a crankcase pressure, and indicating whether the crankcase is breeched based on the crankcase pressure. Another example method comprises sensing a crankcase pressure component, and indicating whether the crankcase is breeched based on the crankcase pressure component, the crankcase communicating with atmosphere via a conduit, a restrictedness of the conduit responsive to one or more of a crankcase pressure and a signal from an electronic control unit of the motor vehicle. Still other examples provide more particular methods for indicating whether the crankcase is breeched, and example configurations that enable the various methods.