In an internal combustion engine, an oil separator provided in a blowby gas passage is attached to a side wall of a cylinder block. A first communicating passage and a second communicating passage via which the inside of a crankcase is connected to the oil separator are formed in the cylinder block. An opening of the first communicating passage on the crankcase side and an opening of the second communicating passage on the crankcase side are placed to be distanced from the center of the crankcase in the extending direction of a crankshaft so as to sandwich the center of the crankcase. No passage via which the inside of the crankcase is connected to the oil separator is provided between the first communicating passage and the second communicating passage.

An attachment mechanism for electronic equipment for an engine includes a bracket configured to hold the electronic equipment and a plurality of support portions configured to elastically support the bracket with respect to a head cover of the engine. The support portions are disposed such that a maximum distance between two support portions of the support portions in a direction parallel to a shaft center of a crankshaft of the engine is longer than a maximum distance between the two support portions of the support portions in a direction perpendicular to the shaft center of the crankshaft of the engine.

In a rotation speed detecting apparatus of an internal combustion engine having a rotor supported by an end part of the crankshaft, a pulser ring that has a detected body composed of recess-projection teeth and rotates integrally with the rotor, and a detector that detects the rotation speed of the crankshaft by detecting the detected body, the detected body has a detected surface opposed to the detector, and the detected surface is inclined in such a manner as to be located closer to the outside of the crankshaft in the axial direction of the crankshaft as getting more apart from an axis line of the crankshaft in the radial direction. In the detector, an axis line of the detector is inclined with respect to the axis line of the crankshaft in such a manner that the detector is opposed to the detected surface.

A low-noise main bearing cap for an internal combustion engine is designed that includes a main bearing cap body, wherein the main bearing cap body is connected to an engine body main bearing seat. The main bearing cap body is provided with a vibration isolator A vibration isolation structure is provided between the main bearing cap body and the vibration isolator The main bearing cap body is connected with the vibration isolator through a connector The vibration isolation structure comprises an S-shaped structure and an oil film gap, and the vibration isolator is provided with an oil inlet passage which is communicated with the oil film gap. The present design solves the control problem of the main bearing vibration source caused by the main bearing load.

The two-stroke internal combustion engine has an engine crankcase including a sealing mechanism that, at all times and under all circumstances, confine the oil in the lower crankcase. The two-stroke engine uses a gaseous fuel based on dihydrogen and dioxygen, and releases only water vapor charged with unused gaseous fuel. A device for recycling the exhaust gases serves to recover the unused gaseous fuel and to reinject it at the intake opening, or the exhaust opening.

A method of operating a fan for an air-cooled internal combustion engine includes starting the air-cooled internal combustion engine, operating the fan in a first operating mode in which the fan rotates in a first direction, and operating the fan in a second operating mode in which the fan rotates in a second direction.

An engine includes: a cylinder block that has a cylinder included in a combustion chamber; a crankshaft that is placed in the cylinder block; a flywheel that is mounted to one end portion of the crankshaft; and a flywheel housing that is placed on a side of one end face of the cylinder block in a direction of the crankshaft and that houses the flywheel. The flywheel housing has a blow-by gas path through which a blow-by gas passes.

An internal combustion engine system including a cylinder block, a cylinder head attached to the cylinder block, an EGR cooler, and a coolant collector bracket is provided. The cylinder head includes a plurality of coolant passages. The coolant collector bracket is coupled to and between the cylinder head and the EGR cooler. The coolant collector bracket includes a plurality of coolant inlets directly coupled to a plurality of outlets of the plurality of coolant passages of the cylinder head. The coolant collector bracket also includes an EGR coolant outlet directly coupled to an inlet of the EGR cooler. The coolant collector bracket also includes an EGR cooler inlet directly coupled to an outlet of the EGR cooler.

A cylinder block that can be used commonly in a longitudinally mounted engine and a transversely mounted engine without increasing a manufacturing cost. The cylinder block comprises an attachment flange joined to a transmission or a transaxle, and an oil pan or the oil pan and a ladder frame are attached to a lower end thereof. The attachment flange comprises: a first flange formed on an outer periphery thereof; a first joint surface formed on the first flange to be joined to a matching surface of the transmission; a second flange extending in the inner side of the first flange; and a second joint surface formed on the second flange to be joined to a matching surface of the transaxle.

A chain cover includes a first member, which is made of a hard plastic, and a second member, which is made of a material different from the hard plastic. The first member includes a back face, which faces an engine main body. The second member is joined to the first member. Only the back face of the first member includes a groove, which receives a seal member. The seal member provides a seal between the first member and the engine main body.