Abstract: In a reciprocating high-pressure fuel pump that operates a plunger while facing a cam ridge of a plunger driving cam provided on a camshaft to which power of a crankshaft of an internal combustion engine is transmitted, the cam ridge includes a cam curved surface including two apexes at a cam angle interval of 180° and two valley bottoms at a cam angle interval of 180° and alternately connecting the apexes and the valley bottoms, and a crossing angle between a first virtual line connecting the two apexes and a second virtual line connecting the two valley bottoms is not a right angle as viewed in a direction of a camshaft axis.

Abstract: In a reciprocating high-pressure fuel pump that operates a plunger while facing a cam ridge of a plunger driving cam provided on a camshaft to which power of a crankshaft of an internal combustion engine is transmitted, the cam ridge includes a cam curved surface including two apexes at a cam angle interval of 180° and two valley bottoms at a cam angle interval of 180° and alternately connecting the apexes and the valley bottoms, and a crossing angle between a first virtual line connecting the two apexes and a second virtual line connecting the two valley bottoms is not a right angle as viewed in a direction of a camshaft axis.

Abstract: An oil passageway structure for internal combustion engines includes a cylinder head having an inter-bearing wall fluid communication oil passage for providing fluid communication between a plurality of bearing walls to allow oil to flow therebetween. The cylinder head further includes a bearing wall oil passage branched from the inter-bearing wall fluid communication oil passage to supply oil to a bearing surfaces of at least one of the bearing walls. The inter-bearing wall fluid communication oil passage is defined in one of facing side walls. The bearing wall oil passageway is defined in at least one of the bearing walls. The oil passageway structure is thus made up of a reduced number of parts, can be assembled with a reduced number of man-hours, can lead to productivity growth, and is inexpensive to manufacture.

Abstract: An oil passageway structure for internal combustion engines includes a cylinder head having an inter-bearing wall fluid communication oil passage for providing fluid communication between a plurality of bearing walls to allow oil to flow therebetween. The cylinder head further includes a bearing wall oil passage branched from the inter-bearing wall fluid communication oil passage to supply oil to a bearing surfaces of at least one of the bearing walls. The inter-bearing wall fluid communication oil passage is defined in one of facing side walls. The bearing wall oil passageway is defined in at least one of the bearing walls. The oil passageway structure is thus made up of a reduced number of parts, can be assembled with a reduced number of man-hours, can lead to productivity growth, and is inexpensive to manufacture.

Abstract: A transmission driving mechanism of a transmission in an internal combustion engine is provided in which where a separate transmission driving mechanism for manual operation is not required in addition to an automatic transmission driving mechanism, whereby the number of parts is reduced, the structure is simple, no maintenance is required and the cost is reduced. The transmission transmits the rotation of a crankshaft to an output shaft at a modified speed, and includes a transmission driving mechanism which rotates a shift spindle using a shift actuator in order to automatically shift gears within the transmission and change the outputted speed of the engine. One end of the shift spindle extends through an engine case cover, and protrudes outside, and a turning tool is fitted onto a fitting portion formed at the protruding end of the shift spindle, whereby manual shifting of the transmission gears can also be achieved.

Abstract: A reverse inhibitor mechanism for a transmission of an all terrain vehicle, in which a shift drum is jounalled to a side wall opposite the transmission case so as to be rotatably supported thereon, and a reverse inhibitor arm is detachably engaged with the reverse inhibitor groove formed in the outer circumferential surface of the shift drum to regulate a reverse setting. A reverse inhibitor shaft having the reverse inhibitor arm supported at one end thereof is positioned within the transmission case. The other end of the reverse inhibitor shaft is rotatably journaled to one of the opposite side walls of the transmission case from the inside of the transmission case. A distal end of the reverse inhibitor arm which swings by the rotation of the reverse inhibitor shaft is brought into engagement with the reverse inhibitor groove during assembly of the reverse inhibitor mechanism.

Abstract: A versatile vehicle speed sensor compactly disposed on the outside in a radial direction of a gear. A motorcycle includes a power unit having a torque take-out shaft for outputting a torque generated by an internal combustion engine as a drive torque for driving a rear wheel, a torque transmission mechanism T which includes a gear pair consisting of bevel gears and a drive shaft and which transmits the drive torque to the rear wheel, and a vehicle speed sensor such that teeth of a driven gear constituting the gear pair constitute a portion to be detected. The vehicle speed sensor includes a main body portion having a detecting portion opposed to the addendum of the teeth in the direction of a normal to the addendum cone surface of the driven gear, and the main body portion extends along the normal direction.

Abstract: A crankcase structure of an internal combustion engine has a desirable shaft support achieved by maintaining the strength of a side wall of a crankcase at a high level without increasing the weight and the size of the internal combustion engine even when the internal combustion engine has an output shaft projecting from the crankcase. A crankcase structure has a crankshaft and a counter shaft that are rotatably supported on a partitioning plane of a crankcase. A main shaft is oriented in the fore-and-aft direction and is rotatably supported on opposed front and rear walls of either one of the upper and lower crankcases. An output shaft to be driven by a power of the counter shaft penetrates through the front and rear walls of one of the upper and lower crankcases by which the main shaft is not rotatably supported, and projects to the front and rear.

Abstract: An output shaft of a power unit having a driven gear for supplying a power of an internal combustion engine via a transmission mechanism and for outputting the power to an outside of a unit case. Borne members are connected respectively at each end of a cylindrical member of the output shaft. The borne members are rotatably supported by the unit case via a pair of bearings. The driven gear is fitted to one of the borne members in a position adjacent to one of the bearings. As a result, the output shaft of the power unit can be manufactured by a compact manufacturing apparatus, and the output shaft can be reduced in weight while maintaining the strength.

Abstract: In an internal combustion engine in which air-intake valves reciprocate in parallel to the direction of reciprocal motion of pistons, an air-intake structure of an internal combustion engine includes an outward projection of the air-intake port that is reduced to achieve a downsizing of a cylinder head. An air-intake structure includes air-intake valves that are supported by a cylinder head having integrally formed air-intake ports so as to reciprocate in parallel with the direction of reciprocal motion of the pistons. Fuel injection devices are formed integrally with a throttle body on intake manifolds to be connected to the air-intake ports. The air-intake ports extend toward the cylinder head cover along a recess formed on the outer surface of the cylinder head that is connected to the intake manifolds at positions just before reaching the identical plane to a mating surface between the cylinder head and the cylinder head cover.

Abstract: An internal combustion engine including a transmission for transmitting power from a crankshaft to an output shaft through speed change, with the speed change in the transmission being performed by the driving of a speed change electric motor through a speed change drive mechanism, wherein power transmission control means for controlling the transmission of power from the crankshaft to the transmission is provided at one end of the crankshaft, and at least a part of the speed change electric motor and the speed change drive mechanism is disposed on the outside of the power transmission control means. This configuration of the internal combustion engine is reduced in size because of the layout of the speed change drive mechanism and the speed change electric motor.

Abstract: To provide a clutch release mechanism which can restrain vibrations of a ball while allowing the ball to be loosely fitted when it is not in operation to ensure the engaged state of a clutch. A clutch release mechanism is configured in such a manner that a gap is defined between a clutch cam plate or a receiving plate and a ball unit so that the ball unit can slide between the clutch cam plate and the receiving plate. An urging spring is provided for urging the ball unit in the direction of being slid toward the clutch cam plate. A C-ring for restricting the ball unit from coming out from a boss member is attached to the peripheral portion of the boss member.

Abstract: To provide a pump drive structure for a water-cooled internal combustion engine in which the number of revolving shafts arranged in parallel in an internal combustion engine is reduced and a power transmission mechanism is eliminated. Thus, the internal combustion engine is downsized. The pump drive structure of a water-cooled internal combustion engine is provided in which a balancer shaft is arranged in parallel with a crankshaft at a position where crank webs of the crankshaft and balancer weights are overlapped in the axial direction. An oil pump drive shaft of an oil pump is connected coaxially at one end of the balancer shaft, and a water pump drive shaft of a water pump is connected coaxially with the other end of the balancer shaft.

Abstract: In an internal combustion engine includes an intake valve port that opens into a combustion chamber on one side of a plane containing the axis of a cylinder bore. An exhaust valve port opens into the combustion chamber on the other side of the plane. A spark plug has a tip end that fronts a substantially central portion of the combustion chamber. The spark plug is disposed between the intake valve and the exhaust valve. In order to restrain the blow-by of an unburned fuel-air mixture, and to suppress the bulging of the cylinder head to the intake system side, the operation axis of an intake valve is set to be substantially parallel to the axis of the cylinder bore. In addition, one side surface of a cylinder head is formed to be substantially parallel to the axis of the cylinder bore.

Abstract: An oil filter mounting structure in an internal combustion engine in which the outside a crankcase in the direction of a crankshaft is covered by a case cover. A spacer is interposed between the crankcase and the case cover. The spacer is formed with a lubrication system. An oil filter is mounted to an oil filter mounting surface of the spacer which is flush with a mating surface with respect to the crankcase. A part of the crankcase to which the oil filter mounting surface of the spacer faces is formed with a recess opening on top to which the oil filter is mounted. The resulting configuration provides an oil filter mounting structure in which an oil filter is reliably protected from stones. Further, oil channels are shortened to achieve a compact light-weight internal combustion engine.

Abstract: A crankcase structure of an internal combustion engine has a desirable shaft support achieved by maintaining the strength of a side wall of a crankcase at a high level without increasing the weight and the size of the internal combustion engine even when the internal combustion engine has an output shaft projecting from the crankcase. A crankcase structure has a crankshaft and a counter shaft that are rotatably supported on a partitioning plane of a crankcase. A main shaft is oriented in the fore-and-aft direction and is rotatably supported on opposed front and rear walls of either one of the upper and lower crankcases. An output shaft to be driven by a power of the counter shaft penetrates through the front and rear walls of one of the upper and lower crankcases by which the main shaft is not rotatably supported, and projects to the front and rear.

Abstract: In an internal combustion engine in which air-intake valves reciprocate in parallel to the direction of reciprocal motion of pistons, an air-intake structure of an internal combustion engine includes an outward projection of the air-intake port that is reduced to achieve a downsizing of a cylinder head. An air-intake structure includes air-intake valves that are supported by a cylinder head having integrally formed air-intake ports so as to reciprocate in parallel with the direction of reciprocal motion of the pistons. Fuel injection devices are formed integrally with a throttle body on intake manifolds to be connected to the air-intake ports. The air-intake ports extend toward the cylinder head cover along a recess formed on the outer surface of the cylinder head that is connected to the intake manifolds at positions just before reaching the identical plane to a mating surface between the cylinder head and the cylinder head cover.

Abstract: To provide a pump drive structure for a water-cooled internal combustion engine in which the number of revolving shafts arranged in parallel in an internal combustion engine is reduced and a power transmission mechanism is eliminated. Thus, the internal combustion engine is downsized. The pump drive structure of a water-cooled internal combustion engine is provided in which a balancer shaft is arranged in parallel with a crankshaft at a position where crank webs of the crankshaft and balancer weights are overlapped in the axial direction. An oil pump drive shaft of an oil pump is connected coaxially at one end of the balancer shaft, and a water pump drive shaft of a water pump is connected coaxially with the other end of the balancer shaft.

Abstract: A reverse inhibitor mechanism for a transmission of an all terrain vehicle, in which a shift drum is jounalled to a side wall opposite the transmission case so as to be rotatably supported thereon, and a reverse inhibitor arm is detachably engaged with the reverse inhibitor groove formed in the outer circumferential surface of the shift drum to regulate a reverse setting. A reverse inhibitor shaft having the reverse inhibitor arm supported at one end thereof is positioned within the transmission case. The other end of the reverse inhibitor shaft is rotatably journaled to one of the opposite side walls of the transmission case from the inside of the transmission case. A distal end of the reverse inhibitor arm which swings by the rotation of the reverse inhibitor shaft is brought into engagement with the reverse inhibitor groove during assembly of the reverse inhibitor mechanism.

Abstract: An output shaft of a power unit having a driven gear for supplying a power of an internal combustion engine via a transmission mechanism and for outputting the power to an outside of a unit case. Borne members are connected respectively at each end of a cylindrical member of the output shaft. The borne members are rotatably supported by the unit case via a pair of bearings. The driven gear is fitted to one of the borne members in a position adjacent to one of the bearings. As a result, the output shaft of the power unit can be manufactured by a compact manufacturing apparatus, and the output shaft can be reduced in weight while maintaining the strength.