Abstract: A piston cooling device includes a main body which includes a communication path communicating with an oil passage provided in the internal combustion engine, a nozzle pipe portion which includes an oil injection port for injecting an oil passing through the communication path, toward the piston, and a filter which is provided at an upstream side of the nozzle pipe portion in an oil flow path to filter the oil. The main body includes a cylindrical portion inserted into the oil passage. The filter has a bottomed cylindrical shape in which a filter side surface stands from a filter bottom surface, and is held inside the cylindrical portion. Filter holes are formed in the filter bottom surface and the filter side surface. The filter is disposed such that the filter bottom surface protrudes further upstream side in the oil flow path than a tip end of the cylindrical portion.

Abstract: A piston cooling device includes a main body which includes a communication path communicating with an oil passage provided in the internal combustion engine, a nozzle pipe portion which includes an oil injection port for injecting an oil passing through the communication path, toward the piston, and a filter which is provided at an upstream side of the nozzle pipe portion in an oil flow path to filter the oil. The main body includes a cylindrical portion inserted into the oil passage. The filter has a bottomed cylindrical shape in which a filter side surface stands from a filter bottom surface, and is held inside the cylindrical portion. Filter holes are formed in the filter bottom surface and the filter side surface. The filter is disposed such that the filter bottom surface protrudes further upstream side in the oil flow path than a tip end of the cylindrical portion.

Abstract: A power unit having a casing for rotatably supporting a driving force output power shaft and for protecting an oil seal provided between the casing and the driving force output power shaft. A first casing for rotatably supporting input power shafts and a second casing disposed at a position offset in an axial direction from the input power shafts and having an output power shaft supporting portion on which a driving force output power shaft provided in the transmission. The first and second casings are disposed adjacent each other such that the output power shaft supporting portion projects to a side farther than the first casing. A breather chamber is formed between first and second case members which cooperate with each other to configure the second casing disposed above a projection of one end portion of the driving force output power shaft from the output power shaft supporting portion.

Abstract: In an internal combustion engine for a vehicle wherein a crankshaft is supported for rotation on a crankcase and a speed change gear shaft which extends in parallel to the crankshaft and forms part of a transmission for changing the speed of rotational power from the crankshaft is supported for rotation on the crankcase such that it is disposed on one side of the crankshaft with a plurality of oil filters being mounted from the same direction to enhance the maintenance. A cover is coupled to a crankcase on one end side of a crankshaft in an axial direction, and a plurality of oil filters are attached to an outer side wall of the cover on the opposite side to a transmission with respect to the crankshaft and are disposed in an upwardly and downwardly juxtaposed relationship with each other.

Abstract: An oil supply structure of a water-cooled internal combustion engine includes an oil cooler for improving oil circulation efficiency by making an oil passage of a lubrication system short. In addition, weight of the oil cooler is reduced by reducing the number of parts. The oil supply structure of a water-cooled internal combustion engine includes an oil pump drive shaft of an oil pump that is coaxially coupled with one end of a balancer shaft placed parallel with a crankshaft and a water pump drive shaft of a water pump that is coaxially coupled with the other end of the balancer shaft. In the oil supply structure, an oil cooler is provided in the vicinity of the oil pump together with an oil filter.

Abstract: An intake port is configured such that a center position of an intake upstream side opening is offset to one side in a juxtaposition direction of intake downstream side openings with respect to a center position between the intake downstream side openings in the juxtaposition direction as viewed in plan of a cylinder head. An injector is configured such that a fuel injection center axial line is inclined to the other side in the juxtaposition direction with respect to a center axial line of the intake upstream side opening as viewed in plan of the cylinder head.

Abstract: A ball valve includes a valve hole provided in an engine body to communicate with an inner end portion of a breather hole and is open in the engine body. A valve seat is formed on an inner surface of the engine body to coaxially surround the valve hole. A guide sleeve is in coaxially communication with the valve hole and the valve seat and is secured to the engine body at one end portion. A metallic valve element, formed to be ball-like with a predetermined weight is received to be rollable in the guide sleeve for enabling the closing of the valve hole and to be prevented from falling off the other end of the guide sleeve, is provided in the engine body so that the valve hole is placed within a moving range of oil in the engine body depending on the inclination of the engine body.

Abstract: A gear transmission mechanism is provided between a crankshaft and the balancer shaft. The balancer shaft includes a pair of bearing portions supported for rotation on a crankcase and a gear wheel supporting portion formed in a tapering shape such that a diameter thereof decreases away from one bearing portion. A tubular boss portion is provided integrally on the driven gear wheel and has a tapering attachment hole in which the gear wheel supporting portion is fitted. A fitting recessed portion in which a pin which has an axial line along a radial direction of the balancer shaft and is fitted at a half portion on one end side thereof in a large diameter end portion of the gear wheel supporting portion is fitted at a half portion on the other end side thereof is provided on the boss portion on the large diameter end side of the attachment hole.

Abstract: An internal combustion engine can include a first ignition plug disposed on the inner side of a range surrounded by a plurality of intake valves and a plurality of exhaust valves with a cylinder head viewed in parallel to a cylinder axial line and standing uprightly along the cylinder axial line. A second ignition plug is inclined with respect to the cylinder axial line on the outer side of the range. The second ignition plug is disposed on the opposite side to a valve driving mechanism with respect to the cylinder axial line on the outer side of the range.

Abstract: A gear transmission mechanism is provided between a crankshaft and the balancer shaft. The balancer shaft includes a pair of bearing portions supported for rotation on a crankcase and a gear wheel supporting portion formed in a tapering shape such that a diameter thereof decreases away from one bearing portion. A tubular boss portion is provided integrally on the driven gear wheel and has a tapering attachment hole in which the gear wheel supporting portion is fitted. A fitting recessed portion in which a pin which has an axial line along a radial direction of the balancer shaft and is fitted at a half portion on one end side thereof in a large diameter end portion of the gear wheel supporting portion is fitted at a half portion on the other end side thereof is provided on the boss portion on the large diameter end side of the attachment hole.

Abstract: A power unit having a casing for rotatably supporting a driving force output power shaft and for protecting an oil seal provided between the casing and the driving force output power shaft. A first casing for rotatably supporting input power shafts and a second casing disposed at a position offset in an axial direction from the input power shafts and having an output power shaft supporting portion on which a driving force output power shaft provided in the transmission. The first and second casings are disposed adjacent each other such that the output power shaft supporting portion projects to a side farther than the first casing. A breather chamber is formed between first and second case members which cooperate with each other to configure the second casing disposed above a projection of one end portion of the driving force output power shaft from the output power shaft supporting portion.

Abstract: In an internal combustion engine for a vehicle wherein a crankshaft is supported for rotation on a crankcase and a speed change gear shaft which extends in parallel to the crankshaft and forms part of a transmission for changing the speed of rotational power from the crankshaft is supported for rotation on the crankcase such that it is disposed on one side of the crankshaft with a plurality of oil filters being mounted from the same direction to enhance the maintenance. A cover is coupled to a crankcase on one end side of a crankshaft in an axial direction, and a plurality of oil filters are attached to an outer side wall of the cover on the opposite side to a transmission with respect to the crankshaft and are disposed in an upwardly and downwardly juxtaposed relationship with each other.

Abstract: An oil supply structure of a water-cooled internal combustion engine includes an oil cooler for improving oil circulation efficiency by making an oil passage of a lubrication system short. In addition, weight of the oil cooler is reduced by reducing the number of parts. The oil supply structure of a water-cooled internal combustion engine includes an oil pump drive shaft of an oil pump that is coaxially coupled with one end of a balancer shaft placed parallel with a crankshaft and a water pump drive shaft of a water pump that is coaxially coupled with the other end of the balancer shaft. In the oil supply structure, an oil cooler is provided in the vicinity of the oil pump together with an oil filter.

Abstract: A casing structure of an automotive internal combustion engine includes an upper/lower divided crankcase structure. A crankshaft and a first transmission shaft of a pair of transmission shafts parallel to the crankshaft of a transmission are axially supported by a dividing surface of the upper crankcase and the lower crankcase. The dividing surface of the crankcase is inclined so that a second transmission shaft axially supported by the upper crankcase above the first transmission shaft is below the crankshaft. A cylinder is formed on the upper crankcase so that a cylinder axial line is orthogonal to the dividing surface.

Abstract: A ball valve includes a valve hole provided in an engine body to communicate with an inner end portion of a breather hole and is open in the engine body. A valve seat is formed on an inner surface of the engine body to coaxially surround the valve hole. A guide sleeve is in coaxially communication with the valve hole and the valve seat and is secured to the engine body at one end portion. A metallic valve element, formed to be ball-like with a predetermined weight is received to be rollable in the guide sleeve for enabling the closing of the valve hole and to be prevented from falling off the other end of the guide sleeve, is provided in the engine body so that the valve hole is placed within a moving range of oil in the engine body depending on the inclination of the engine body.

Abstract: A power unit for a vehicle includes a buffering device provided on a final shaft parallel to a countershaft of a speed change gear. The buffering device includes a damper gear wheel supported for relative rotation on the final shaft, a lifter coupled against relative rotation but for relative movement in an axial direction on the final shaft and engaged by a cam provided on one face of the damper gear wheel, a spring retainer supported at a position on the final shaft spaced apart from the lifter, and a coil spring provided between the lifter and the spring retainer for biasing the lifter toward the damper gear wheel. The buffering device is disposed on the final shaft and positioned between a pair of imaginary planes, the pair of imaginary planes extending perpendicularly to an axial line of the idle shaft and passing opposite ends of the idle shaft.

Abstract: An internal combustion engine includes: an engine body including: a crankcase for rotatably supporting a crankshaft; and a crankcase cover fastened to the crankcase by a plurality of bolts so as to cover one side of the crankcase; and a stay supporting an oil level gauge guide, the stay being mounted on the engine body, the stay having an opening receiving and supporting a tube or wire.

Abstract: A casing structure of an automotive internal combustion engine includes an upper/lower divided crankcase structure. A crankshaft and a first transmission shaft of a pair of transmission shafts parallel to the crankshaft of a transmission are axially supported by a dividing surface of the upper crankcase and the lower crankcase. The dividing surface of the crankcase is inclined so that a second transmission shaft axially supported by the upper crankcase above the first transmission shaft is below the crankshaft. A cylinder is formed on the upper crankcase so that a cylinder axial line is orthogonal to the dividing surface.

Abstract: An internal combustion engine can include a first ignition plug disposed on the inner side of a range surrounded by a plurality of intake valves and a plurality of exhaust valves with a cylinder head viewed in parallel to a cylinder axial line and standing uprightly along the cylinder axial line. A second ignition plug is inclined with respect to the cylinder axial line on the outer side of the range. The second ignition plug is disposed on the opposite side to a valve driving mechanism with respect to the cylinder axial line on the outer side of the range.

Abstract: An intake port is configured such that a center position of an intake upstream side opening is offset to one side in a juxtaposition direction of intake downstream side openings with respect to a center position between the intake downstream side openings in the juxtaposition direction as viewed in plan of a cylinder head. An injector is configured such that a fuel injection center axial line is inclined to the other side in the juxtaposition direction with respect to a center axial line of the intake upstream side opening as viewed in plan of the cylinder head.