Abstract: To provide a cellulose ester film formed by casting, which minimizes degradation of optical properties as well as exhibits sufficient mechanical strength generated by the enhancement of tear strength, and further to provide a production method of the same. A cellulose ester film characterized in comprising flat particles.

Abstract: In a decompression unit including a decompression arm, a decompression unit for internal combustion engine is provided in which the followability in the opening-and-closing operation of the air intake valve or the exhaust valve with respect to the cam at high-revolution speeds is satisfactory without increasing the equivalent inertia weight of the valve driving system, and for lowering the cost. A decompression unit includes a first decompression cam that takes the operating position when the number of revolutions of the engine is not more than the predetermined number of revolution during startup. A second decompression cam is provided that takes the operating position by manual operation. A decompression arm includes first and second abutting portions that abut against first and second decompression cams, respectively.

Abstract: A crankshaft support structure for an engine. An inner race forming a part of a main bearing is loosely fitted onto a bearing seat of a shaft. A direction of thrust is fixed by a flange of a timing sprocket which is press-fitted onto the shaft. The outer diameter R1 of the timing sprocket and the outer diameter R3 of the flange are respectively set so that they are smaller than the outer diameter R4 of the inner race. An outer race of the main bearing is press-fitted and fixed to the side of a left crankcase and a roller is integrated. When the shaft enters the inside of the roller, the timing sprocket and the flange pass through the inside of the roller, and the inner race is fitted to the roller. As a result, the inner diameter R2 of the inner race can be made smaller than the outer diameter R1 of the timing sprocket. Thus the main bearing supporting the crankshaft is miniaturized and lightened.

Abstract: To lighten and miniaturize a piston and form a piston for a high-speed revolution. A top ring groove and an oil ring groove are formed on the periphery of a crown and a lubricator is provided inside the oil ring groove. A pair of piston pin bosses are provided continuously under the crown in opposite positions and a skirt is provided apart by 90°. The lower end of the skirt is located on the upside of the lower end of the piston pin boss and a lubricator is provided in an upper part of the skirt, under and in the vicinity of the oil ring groove.

Abstract: A lubrication structure of an engine arranged so as to reduce the size and weight of an engine. A lubrication structure that utilizes a lead valve and a strainer that are placed close together and divided by a partition, prevents air from being sucked into a strainer at the same time as reducing the amount of air in the engine oil. In this structure the oil is supplied to the oil pan from an oil exhaust port open to a small partition partitioned by a rib. The oil exhaust port communicates with an oil reservoir in a lower part of a crankcase via a lead valve. Oil sent from the oil exhaust port includes air. However, the air is separated by providing the rib. The oil in the oil pan is sucked through the strainer by the oil pump.

Abstract: A relief valve is interposed in an oil supply passage, and the relief valve internally includes a bottom passage for supplying oil from one oil supply passage to another oil supply passage. Since any branched oil passage for a relief valve is not required to be provided, it is possible to reduce the machining steps and machining cost. Further, since a space for disposing a branched oil passage is not required and the increase in space for disposing the relief valve can be reduced, the engine can be miniaturized.

Abstract: A lubrication structure of an engine arranged so as to reduce the size and weight of an engine. A lubrication structure that utilizes a lead valve and a strainer that are placed close together and divided by a partition, prevents air from being sucked into a strainer at the same time as reducing the amount of air in the engine oil. In this structure the oil is supplied to the oil pan from an oil exhaust port open to a small partition partitioned by a rib. The oil exhaust port communicates with an oil reservoir in a lower part of a crankcase via a lead valve. Oil sent from the oil exhaust port includes air. However, the air is separated by providing the rib. The oil in the oil pan is sucked through the strainer by the oil pump.

Abstract: A power unit has a power case which includes a crankcase portion integrally formed with a transmission case portion. The crankcase portion forms a crankcase in which the crankshaft of a 4-cycle internal combustion engine is received. The transmission case portion forms a transmission case in which a wet type multiple disc friction clutch for transmitting the torque of the crankshaft is received. A partition wall makes the crankcase independent of the transmission case, and thus separates the lubrication system of the internal combustion engine from the lubrication system of the friction clutch. The lubrication structure of the present invention can improve the durability of the friction clutch and make the friction clutch compact, and secure good connection performance of the friction clutch by separating the lubrication system of an internal combustion engine from the lubrication system of friction clutch.

Abstract: To lighten and miniaturize a piston and form a piston for a high-speed revolution. A top ring groove and an oil ring groove are formed on the periphery of a crown and a lubricator is provided inside the oil ring groove. A pair of piston pin bosses are provided continuously under the crown in opposite positions and a skirt is provided apart by 90°. The lower end of the skirt is located on the upside of the lower end of the piston pin boss and a lubricator is provided in an upper part of the skirt, under and in the vicinity of the oil ring groove.

Abstract: A crankshaft support structure for an engine. An inner race forming a part of a main bearing is loosely fitted onto a bearing seat of a shaft. A direction of thrust is fixed by a flange of a timing sprocket which is press-fitted onto the shaft. The outer diameter R1 of the timing sprocket and the outer diameter R3 of the flange are respectively set so that they are smaller than the outer diameter R4 of the inner race. An outer race of the main bearing is press-fitted and fixed to the side of a left crankcase and a roller is integrated. When the shaft enters the inside of the roller, the timing sprocket and the flange pass through the inside of the roller, and the inner race is fitted to the roller. As a result, the inner diameter R2 of the inner race can be made smaller than the outer diameter R1 of the timing sprocket. Thus the main bearing supporting the crankshaft is miniaturized and lightened.

Abstract: In an internal combustion engine, a pair of suction ports are formed on left and right sides of the rear of the cylinder head with respect to the vehicle body. A pair of exhaust ports is formed on left and right sides on the front side of the cylinder head. Suction poppet valves and exhaust poppet valves for opening and closing the suction ports and the exhaust ports are slidably fitted in guide tubes, respectively. In addition, a valve gear includes a camshaft and a rocker arm pivotally supported on a rocker arm shaft. The rocker arm is formed with a bifurcated end, which crosses an ignition plug on the exhaust poppet valve side. The suction poppet valves are directly driven to open and close by the camshaft.

Abstract: In a decompression unit including a decompression arm, a decompression unit for internal combustion engine is provided in which the followability in the opening-and-closing operation of the air intake valve or the exhaust valve with respect to the cam at high-revolution speeds is satisfactory without increasing the equivalent inertia weight of the valve driving system, and for lowering the cost. A decompression unit includes a first decompression cam that takes the operating position when the number of revolutions of the engine is not more than the predetermined number of revolution during startup. A second decompression cam is provided that takes the operating position by manual operation. A decompression arm includes first and second abutting portions that abut against first and second decompression cams, respectively.

Abstract: A projection is formed on the outer circumference of an annular member and a stopping member is attached to a cylinder head supporting a camshaft thereon. A side surface of the projection comes into contact with a side surface of the stopping member to restrain a decompression cam from turning when the camshaft rotates in the normal direction. The stopping member does not apply any pressure to the annular member in a radial direction and the annular member does not exert any force on the camshaft. Consequently, frictional resistance against the rotation of the camshaft can be reduced and a loss in the output of the engine can be suppressed.

Abstract: In an internal combustion engine, a pair of suction ports are formed on left and right sides of the rear of the cylinder head with respect to the vehicle body. A pair of exhaust ports is formed on left and right sides on the front side of the cylinder head. Suction poppet valves and exhaust poppet valves for opening and closing the suction ports and the exhaust ports are slidably fitted in guide tubes, respectively. In addition, a valve gear includes a camshaft and a rocker arm pivotally supported on a rocker arm shaft. The rocker arm is formed with a bifurcated end, which crosses an ignition plug on the exhaust poppet valve side. The suction poppet valves are directly driven to open and close by the camshaft.

Abstract: A power unit has a power case which includes a crankcase portion integrally formed with a transmission case portion. The crankcase portion forms a crankcase in which the crankshaft of a 4-cycle internal combustion engine is received. The transmission case portion forms a transmission case in which a wet type multiple disc friction clutch for transmitting the torque of the crankshaft is received. A partition wall makes the crankcase independent of the transmission case, and thus separates the lubrication system of the internal combustion engine from the lubrication system of the friction clutch. The lubrication structure of the present invention can improve the durability of the friction clutch and make the friction clutch compact, and secure good connection performance of the friction clutch by separating the lubrication system of an internal combustion engine from the lubrication system of friction clutch.

Abstract: A crankshaft rotation structure for a four cycle engine has a radial ball bearing fitted into a first main bearing section of a crankcase and a radial roller bearing fitted into a second main bearing section of the crankcase. The crankshaft is rotatably supported by the radial ball bearing and radial roller bearing. Furthermore, an oil jet nozzle for cooling a piston is provided in the second main bearing section. The diameter of the shafts for attachment of the bearings can be made the same, even if the outer diameter of the radial roller bearing is decreased compared to the outer diameter of the radial ball bearing. Accordingly, even if the oil jet nozzle is provided in the second main bearing section into which the radial roller bearing is fitted, the distance from the crankshaft center to the attachment position of the oil jet can be decreased and the engine itself can be reduced in size.

Abstract: An oil sump for lubricating oil is provided at a lower part of a crank chamber of a dry sump-type four-cycle engine. A reed valve is provided at an outlet of the oil sump which opens when pressure in the crank chamber is high. Furthermore, an oil passage slopes upwards from the outlet of the oil sump, with an outlet of the oil passage being provided above an oil surface level of oil accumulated within the engine. Oil from the outlet of the oil passage is smoothly discharged from the outlet of the oil passage without being discharged into the collected oil. Furthermore, oil mixed with air within the crank chamber is not directly mixed into the collected oil and oil oxidation is therefore prevented. Since there is no direct contact with high-temperature blow-by gas, etc., oil deterioration is suppressed.

Abstract: A motorcycle engine having an exhaust passage air introduction system. Each cylinder includes two exhaust passages which are joined at a point displaced from the engine. Air is introduced into one of the exhaust passages of the two so as to more fully combust the unburned gasses within the exhaust passage and then to more fully combust the unburned exhaust in the joined passage. The timing of the valves associated with each exhaust passage is such that the valve associated with the passage having the air inlet has advance timing. A chain tensioner for the timing chain includes a tensioner cylinder hydraulically actuated by the engine oil. A gasket having an orifice therein is positioned between components in the oil passageway extending to the tensioner cylinder. The oil cooling system of the engine includes an oil filter and an oil cooler which are displaced from one another and mounted to a common base which is in turn mounted to the engine.

Abstract: A motorcycle engine having an exhaust passage air introduction system. Each cylinder includes two exhaust passages which are joined at a point displaced from the engine. Air is introduced into one of the exhaust passages of the two so as to more fully combust the unburned gasses within the exhaust passage and then to more fully combust the unburned exhaust in the joined passage. The timing of the valves associated with each exhaust passage is such that the valve associated with the passage having the air inlet has advance timing. A chain tensioner for the timing chain includes a tensioner cylinder hydraulically actuated by the engine oil. A gasket having an orifice therein is positioned between components in the oil passageway extending to the tensioner cylinder. The oil cooling system of the engine includes an oil filter and an oil cooler which are displaced from one another and mounted to a common base which is in turn mounted to the engine.