An internal combustion engine including a crank chamber housing a crankshaft connected to moving parts able to supply torque to the crankshaft, a lubrication circuit, an oil sump for collecting the lubricating oil, the engine including a separating partition which separates the crank chamber from the oil sump, in which the lubrication circuit includes a first oil pump and a second oil pump, where the first oil pump is fluidically connected in aspiration to the crank chamber and in delivery to the oil sump, the second oil pump being fluidly connected in aspiration to the oil sump and in delivery to the crank chamber by means of the lubrication circuit, to re-introduce pressurised oil in the crank chamber and lubricate the moving parts.

An internal combustion engine assembly includes a crankcase and a cam housing. The crankcase includes a crankcase cavity configured to receive a counterweight. The cam housing includes a cam housing cavity configured to receive a camshaft. A pump is positioned within the cam housing. The pump is configured to draw oil from an oil reservoir defined by the cam housing cavity. A crankshaft supports the counterweight for rotation therewith. The crankshaft is rotatably supported within the cam housing and is coupled to drive the pump. A bearing supports the crankshaft between the crankcase cavity and the cam housing cavity. The bearing includes an outer race. A seal is positioned between the pump and the bearing. The seal is positioned against the outer race to block the transmission of pressure fluctuations between the crankcase cavity and the oil reservoir.

This application discloses a cylinder block structure including: a cylinder block surrounding a cylinder array formed by a plurality of cylinders lined up in a first direction; a reinforcement plate including: a first fastening portion fastened to the cylinder block; and a second fastening portion fastened to the cylinder block at a position separated from the first fastening portion in a second direction that intersects with the first direction; and an oil pump that supplies oil to the cylinder block. The oil pump is fastened to the cylinder block together with the reinforcement plate. The reinforcement plate is interposed between the cylinder block and the oil pump, and has a length that is equal to or more than half of the cylinder array in the first direction.

Oil pump and oil pump-integrated balancer device each have a pump housing formed by housing body 31 and cover member 32, pump shaft 33 having driven side helical gear 43 at which thrust force occurs when transmitting rotation force and rotating a rotor by the rotation force provided from drive side helical gear 13 that is engaged with driven side helical gear 43, first and second thrust receiving portions 47, 46 formed close to hole edges of bearing holes 32a, 31a of the cover member and the housing body, and first and second thrust limiting portions 49, 48 provided at the driven side helical gear and the pump shaft, contacting the thrust receiving portions from axis direction and limiting thrust movement of the pump shaft. With this configuration, oil pump and oil pump-integrated balancer device which are capable of securing stable support of the pump shaft are provided.

Methods and systems are provided for a cam drive system of an engine. In one example, a front end of an engine includes an idler gear assembly including an idler gear and idler pulley, the idler gear in meshing engagement with a first end of a crankshaft and the idler pulley coupled to and sharing a rotational axis with the idler gear. The front end of the engine may further include first and second camshaft pulleys positioned vertically above the idler gear assembly and a cam drive belt contacting each of the first and second camshaft pulleys and the idler pulley.

An internal combustion engine assembly includes a crankcase and a cam housing. The crankcase includes a crankcase cavity configured to receive a counterweight. The cam housing includes a cam housing cavity configured to receive a camshaft. A pump is positioned within the cam housing. The pump is configured to draw oil from an oil reservoir defined by the cam housing cavity. A crankshaft supports the counterweight for rotation therewith. The crankshaft is rotatably supported within the cam housing and is coupled to drive the pump. A bearing supports the crankshaft between the crankcase cavity and the cam housing cavity. The bearing includes an outer race. A seal is positioned between the pump and the bearing. The seal is positioned against the outer race to block the transmission of pressure fluctuations between the crankcase cavity and the oil reservoir.

In an internal combustion engine for a saddle riding vehicle, in which a gear transmission and a shift drum of a shift change device is stored in a crankcase, the gear transmission having a plurality of transmission shafts parallel to a crankshaft extending in a vehicle width direction, a single pump shaft common to first and second oil pumps is rotatably supported by the crankcase. First oil pump rotors of the first oil pump are disposed at a mating face of a pair of left and right crankcase half bodies. A second oil pump rotor of the second oil pump is disposed between a pump gear and the first oil pump and at a side surface, on a side opposite to the mating face, of one crankcase half body out of the pair of left and right crankcase half bodies, the pump gear being arranged in the pump shaft.

There is provided a lubrication structure of an internal combustion engine. A transmission chamber is arranged adjacently at the rear of a crank chamber. An oil chamber communicates with a bottom part of the transmission chamber. A feed pump supplies oil in the oil chamber to a lubrication target part. A scavenging pump sucks the oil in the crank chamber and discharges the oil to the transmission chamber. The feed pump and the scavenging pump are arranged coaxially in a width direction of the internal combustion engine. At least a part of the scavenging pump is arranged higher than a lower end of the crank chamber. A rear end of the scavenging pump is arranged at the same position as a rear end of the crank chamber or in front of the rear end of the crank chamber in a front and rear direction.

An internal combustion engine including a crank chamber housing a crankshaft connected to moving parts able to supply torque to the crankshaft, a lubrication circuit, an oil sump for collecting the lubricating oil, the engine including a separating partition which separates the crank chamber from the oil sump, in which the lubrication circuit includes a first oil pump and a second oil pump, where the first oil pump is fluidically connected in aspiration to the crank chamber and in delivery to the oil sump, the second oil pump being fluidly connected in aspiration to the oil sump and in delivery to the crank chamber by means of the lubrication circuit- to re-introduce pressurised oil in the crank chamber and lubricate the moving parts.

A rotary engine having a crankshaft, a housing provided with lobe accommodating portions arranged to surround the crankshaft, and combustion chambers communicating with the lobe accommodating portions, a rotor rotatable eccentrically with respect to the crankshaft and provided with lobes continuously accommodated in the lobe accommodating portions, a housing cover provided with a bearing portion through which the crankshaft is inserted so as to be rotatably supported, and a lubricating unit to supply oil to the bearing portion, wherein the lubricating unit includes an oil pan to accommodate oil therein, an oil pump to pump up oil filled in the oil pan, and an oil supply passage having both ends located in the oil pump and the bearing portion, respectively, is provided. This structure may allow direct and effective lubrication of the bearing portion, and can employ a journal bearing.