Abstract: In an internal combustion engine, a gasket is disposed between joining surfaces of a cylinder block and a cylinder head, and a heat radiation rib that extends in a cylinder axis direction is formed on the cylinder block or the cylinder head. In such an internal combustion engine, the gasket includes: a portion to be sandwiched that is sandwiched between the joining surfaces; and an extending portion that protrudes toward an outside from the portion to be sandwiched as viewed in a cylinder axis direction.

Abstract: In an internal combustion engine that includes a cylinder block and a cylinder head, and has a cam chain chamber on a side of the cylinder block, a beam member that traverses the cam chain chamber is disposed in the cam chain chamber.

Abstract: In an internal combustion engine that includes a cylinder block and a cylinder head, and has a cam chain chamber on a side of the cylinder block, a beam member that traverses the cam chain chamber is disposed in the cam chain chamber.

Abstract: In an internal combustion engine that includes a cylinder block and a cylinder head, and has a cam chain chamber on a side of the cylinder block, a beam member that traverses the cam chain chamber is disposed in the cam chain chamber.

Abstract: In an internal combustion engine, a gasket is disposed between joining surfaces of a cylinder block and a cylinder head, and a heat radiation rib that extends in a cylinder axis direction is formed on the cylinder block or the cylinder head. In such an internal combustion engine, the gasket includes: a portion to be sandwiched that is sandwiched between the joining surfaces; and an extending portion that protrudes toward an outside from the portion to be sandwiched as viewed in a cylinder axis direction.

Abstract: A sensor mounting structure for an engine is provided. The sensor mounting structure offers a greater flexibility in mounting a sensor which detects an operation of an actuation member disposed at an inner wall spaced apart from an outer wall of a cylinder head of a valve gear. A sensor mounting structure for an engine includes a valve gear provided at a cylinder head and a sensor detecting an operation of the valve gear. The sensor is mounted on a sensor mounting hole formed at a head inner wall of the cylinder head covered with a cylinder head cover.

Abstract: An engine oil passage structure for an engine contributing to downsizing the engine and achieving protection of an oil passage against external forces is provided. Provided is an oil passage structure for an engine installed in a small vehicle, the engine including an engine body formed of a crankcase and a cylinder block and a cylinder head stacked inclined vehicle frontward on the crankcase, the crankcase, the cylinder block, and the cylinder head being integrally fastened. The oil passage structure includes, near a bent part formed by a case front wall of the crankcase and a cylinder front wall of the cylinder block forming a valley part by an obtuse angle, a right-left direction oil passage extending in a right-left direction along the valley part.

Abstract: An engine oil passage structure for an engine contributing to downsizing the engine and achieving protection of an oil passage against external forces is provided. Provided is an oil passage structure for an engine installed in a small vehicle, the engine including an engine body formed of a crankcase and a cylinder block and a cylinder head stacked inclined vehicle frontward on the crankcase, the crankcase, the cylinder block, and the cylinder head being integrally fastened. The oil passage structure includes, near a bent part formed by a case front wall of the crankcase and a cylinder front wall of the cylinder block forming a valley part by an obtuse angle, a right-left direction oil passage extending in a right-left direction along the valley part.

Abstract: A sensor mounting structure for an engine is provided. The sensor mounting structure offers a greater flexibility in mounting a sensor which detects an operation of an actuation member disposed at an inner wall spaced apart from an outer wall of a cylinder head of a valve gear. A sensor mounting structure for an engine includes a valve gear provided at a cylinder head and a sensor detecting an operation of the valve gear. The sensor is mounted on a sensor mounting hole formed at a head inner wall of the cylinder head covered with a cylinder head cover.

Abstract: An air bleeding valve includes an annular valve element for removing air from oil contained in a hydraulic circuit of a hydraulic tensioner and for suppressing the removal of the oil. An air bleeding valve body is fitted in an air bleeding valve accommodating hole formed in the hydraulic tensioner. A circumferential groove having a rectangular cross section is formed on an outer circumferential surface of the air bleeding valve body. The annular valve element having a rectangular cross section is fitted in the circumferential groove so as to be movable in an axial direction parallel to the axis of the annular valve element, and displaceable in a radial direction toward and away from the axis of the annular valve element. Such air bleeding valve removes air in a hydraulic circuit while suppressing the removal of oil in the hydraulic circuit during starting operation of an engine.

Abstract: An internal combustion engine is equipped with a variable valve control system which is operable to selectively actuate an engine valve using one of two cams of a camshaft, by sliding a rocker arm in the axial direction of a rocker-arm shaft. The system is capable of restricting the axial-direction movement of the rocker arm within a predetermined range, using a simple structure without unduly increasing the number of component parts. Position-restriction portions are formed in a rocker arm, and abut on a trigger arm to restrict sliding movement of the rocker arm within a predetermined amount, when the trigger arm is disengaged from the rocker arm.

Abstract: An air bleeding valve includes an annular valve element for removing air from oil contained in a hydraulic circuit of a hydraulic tensioner and for suppressing the removal of the oil. An air bleeding valve body is fitted in an air bleeding valve accommodating hole formed in the hydraulic tensioner. A circumferential groove having a rectangular cross section is formed on an outer circumferential surface of the air bleeding valve body. The annular valve element having a rectangular cross section is fitted in the circumferential groove so as to be movable in an axial direction parallel to the axis of the annular valve element, and displaceable in a radial direction toward and away from the axis of the annular valve element. Such air bleeding valve removes air in a hydraulic circuit while suppressing the removal of oil in the hydraulic circuit during starting operation of an engine.

Abstract: The invention provides an internal combustion engine equipped with a variable valve control system which switches the actions of an engine valve by sliding a rocker arm in the axial direction of the rocker arm shaft, while enabling the restriction on the sliding movement of the rocker arm to be removed in accordance with the timings of the actions of the rocker arms irrespective of the engine speed. The internal combustion engine includes an actuator that moves a rocker arm shaft in its axial direction, a trigger arm that engages with a rocker arm to prohibit the sliding movement of the rocker arm, and a trigger pin which is configured to be activated by an axial movement of the rocker arm shaft to bring the trigger arm into action, and to disengage the trigger arm from the rocker arm.

Abstract: An internal combustion engine is equipped with a variable valve controlling system, in which the single actuator is disposed in a cylinder head on one side where one ends of the rocker-arm shafts are disposed, while enabling the single actuator to activate the rocker arms irrespective of the arrangement of the rocker-arm shafts. In the internal combustion engine, a hydraulic cylinder of a hydraulic actuator is disposed so as to transverse a timing chamber. Operation elements extend respectively from sidewalls of a plunger in the hydraulic cylinder, and activate respective rocker-arm shafts. In a motorcycle on which the engine is mounted, a frame member of a vehicle frame is disposed outside the hydraulic actuator.

Abstract: A fixation structure for a valve system rotation shaft of an internal combustion engine to support a camshaft with a cylinder head through the use of a lower cam holder and cam caps, which are formed separately from the cylinder head. The fixation structure eliminates the necessity of taking special vibration/noise control measures for a head cover thus preventing an increase in the cost, size, and weight of the head cover. A head external wall extends toward the head cover rather than toward a head middle surface in such a manner so as to cover the circumference of the lower cam holder fixed to a head middle surface. The connection to the holder fixation section is established with the base end of an external wall of the head cover abutted on the leading end of the head external wall.

Abstract: In an oil cooler, a heat exchange core is housed in a casing including a cylindrical sidewall part in a way that a cooling water passage is formed around a heat exchange core. The heat exchange core includes inlet-side and outlet-side oil passages, and enables oil to be delivered from the inlet-side oil passage to the outlet-side oil passage. Inlet and outlet pipes are connected to the sidewall part. The inlet pipe forms a cooling water inlet passage in communication with the cooling water passage. The outlet pipe forms a cooling water outlet passage in communication with the cooling water passage. Outward of the inlet-side oil passage, an outwardly swelling part is formed in the sidewall part of the casing. This arrangement avoids the oil cooler being constructed in a large size and avoids decreasing the heat exchange efficiency of the oil cooler, and also prevents cavitation and erosion from occurring due to the flow of cooling water in an area corresponding to the inlet-side oil passage.

Abstract: In a power unit, a counter shaft of a transmission and a crank shaft of an internal combustion engine, both located below a main shaft of the transmission, are arranged parallel to each other on a separating plane H of a crankcase. In a transmission mechanism T which drives an oil pump located below the separating plane H, a drive sprocket is placed on the main shaft of the transmission and a driven sprocket is placed on a drive shaft of the oil pump. An endless chain slidably touches a slender long chain guide along the running direction of the endless chain. The chain guide is fitted only to an end wall of an upper crankcase at its fitting part. The chain guide stretches across the end wall of the upper crankcase and an end wall of a lower crankcase, and effectively suppresses vibration of the endless chain.

Abstract: A fixation structure for a valve system rotation shaft of an internal combustion engine to support a camshaft with a cylinder head through the use of a lower cam holder and cam caps, which are formed separately from the cylinder head. The fixation structure eliminates the necessity of taking special vibration/noise control measures for a head cover thus preventing an increase in the cost, size, and weight of the head cover. A head external wall extends toward the head cover rather than toward a head middle surface in such a manner so as to cover the circumference of the lower cam holder fixed to a head middle surface. The connection to the holder fixation section is established with the base end of an external wall of the head cover abutted on the leading end of the head external wall.

Abstract: The invention provides an internal combustion engine equipped with a variable valve control system which switches the actions of an engine valve by sliding a rocker arm in the axial direction of the rocker arm shaft, while enabling the restriction on the sliding movement of the rocker arm to be removed in accordance with the timings of the actions of the rocker arms irrespective of the engine speed. The internal combustion engine includes an actuator that moves a rocker arm shaft in its axial direction, a trigger arm that engages with a rocker arm to prohibit the sliding movement of the rocker arm, and a trigger pin which is configured to be activated by an axial movement of the rocker arm shaft to bring the trigger arm into action, and to disengage the trigger arm from the rocker arm.

Abstract: An internal combustion engine is equipped with a variable valve controlling system, in which the single actuator is disposed in a cylinder head on one side where one ends of the rocker-arm shafts are disposed, while enabling the single actuator to activate the rocker arms irrespective of the arrangement of the rocker-arm shafts. In the internal combustion engine, a hydraulic cylinder of a hydraulic actuator is disposed so as to transverse a timing chamber. Operation elements extend respectively from sidewalls of a plunger in the hydraulic cylinder, and activate respective rocker-arm shafts. In a motorcycle on which the engine is mounted, a frame member of a vehicle frame is disposed outside the hydraulic actuator.