TH48210A - Hand-held four-stroke engine - Google Patents

Abstract

DC60 (30/05/44) In a handheld four-stroke engine, the valve actuation mechanism consists of a camshaft supported to rotate within the cylinder head for opening and closing the intake and exhaust valves, and a camshaft transmission assembly mounted on one side outside the main engine body, establishing a connection between the crankshaft and camshaft. A centrifugal clutch for power output is mounted on the crankshaft on the opposite side outside the main engine body. The camshaft transmission assembly and centrifugal clutch positioned at both ends of the crankshaft improve weight balance, allowing the engine's center of gravity to be as close as possible to the center of the crankshaft. Combined with reduced weight, this increases engine performance. In a handheld four-stroke engine, the valve actuation mechanism consists of a camshaft supported to rotate within the cylinder head for opening and closing the intake and exhaust valves, and a camshaft transmission assembly mounted on one side outside the main engine body, establishing a connection between the crankshaft and camshaft, and a centrifugal clutch for power output. The output power is mounted on the crankshaft on opposite sides outside the main engine body. The camshaft and centrifugal clutch assembly, positioned at both ends of the crankshaft, improves weight balance by bringing the engine's center of gravity as close to the center of the crankshaft as possible. Combined with this reduced weight, this enhances engine performance.

Claims (15)

1. A handheld four-stroke engine consists of: the main engine body, which comprises the engine block with the crankcase; the cylinder block with the cylinders; and the cylinder head with the intake and exhaust ports; the crankshaft, supported within the engine body and housed within the crankcase; the piston, assembled in the cylinders and connected to the crankshaft; the intake and exhaust valves for opening and closing the intake and exhaust ports, which are mounted in the cylinder head; the valve actuator, which can act in conjunction with the crankshaft rotation to open and close the intake and exhaust valves; the power output mechanism, provided on one end of the crankshaft protruding from the main engine body; and the fuel tank. The valve actuator mechanism here comprises: a camshaft, supported to rotate within the cylinder head for opening and closing the intake and exhaust valves; a camshaft transmission assembly, mounted externally on the opposite side of the power output mechanism and working to establish a connection between the crankshaft and the camshaft; and the flywheel, which is mounted on the crankshaft between the main engine body and the fuel tank. The power output mechanism, the flywheel, consists of a cooling fan for directing cooling air to the engine main body and has a diameter larger than the diameter of the power output mechanism, and where the fuel tank is supported by the engine main body on the same side as the main body, as is the camshaft transmission assembly. 2. A four-stroke, handheld engine under claim 1, in which the camshaft drive assembly is dry and separated from the crankcase. 3. A handheld four-stroke engine under either claim 1 or 2, in which the oil tank for storing lubricating oil for internal lubrication of the engine's main body is positioned outside the camshaft drive assembly in a connected state. 4. A four-stroke, handheld engine pursuant to claim 1, in which the valve actuation mechanism consists of a camshaft transmission unit connected to one end of the crankshaft and a cam system for transmitting the rotational force of the follow side of the camshaft transmission unit to the intake and exhaust valves for opening and closing; the first valve actuation chamber containing the camshaft transmission unit is provided as a single unit with the oil reservoir; the second valve actuation chamber containing at least part of the cam system is formed in the cylinder head; and a pair of oil stirrers for agitating and dispersing the oil stored in the oil reservoir for the formation of oil mist which will be directed to the second valve actuation chamber; and the crankcase is attached to the crankshaft in a condition in which the camshaft transmission unit is placed between the pair of stirrers. 5. A handheld four-stroke engine pursuant to claim paragraph 4, in which a through hole through which oil mist generated in the oil reservoir is transferred to the crankcase, shall be provided on the crankshaft, and the open end of the through hole in the oil reservoir shall be located between the camshaft transmission assembly and the oil agitator. 6. A handheld four-stroke engine under claim 4 in which the camshaft transmission assembly is protruding into the oil tank, the belt guide housing the camshaft transmission assembly is provided as a single unit with the oil tank, and the open end of the belt guide inside the oil tank protrudes toward the center of the oil tank in a position where the open end is above the fluid level of the stored oil, regardless of whether the engine is mounted upside down or on its side. 7. A four-stroke, handheld engine pursuant to claim paragraph 4, in which the end of the crankshaft is extended into the oil tank, and the camshaft actuator assembly is connected to the crankshaft inside the oil tank, and the camshaft actuator assembly is lubricated by the oil inside the oil tank. 8. A four-stroke, handheld engine under claim 7, where the cooling fan is incorporated and mounted to the crankshaft, and the cooling fan has a diameter larger than the diameter of the power output mechanism. 9. A four-stroke, handheld engine pursuant to claim paragraph 7, in which a cam system for transmitting the rotation of the driven side of the camshaft to the intake and exhaust valves for opening and closing force is arranged in a second valve acting chamber provided in the cylinder head, and an oil misting device for generating oil mist inside the oil reservoir is connected to the crankshaft, with the oil mist being delivered to the valve acting chambers. 10. A handheld four-stroke engine pursuant to claim paragraph 4, in which the camshaft transmission of the valve actuation mechanism is constructed as a swivel assembly with a swivel component, the drive side of the swivel component protruding into the oil tank. An oil misting device for the generation of oil mist for lubricating the camshaft transmission by atomizing the oil stored in the oil tank is provided in the oil tank, and an oil droplet wall is provided protruding from the inner wall of the oil tank, which guides and causes the adhering oil droplets to drip onto the part of the camshaft transmission protruding into the oil tank when the engine is placed horizontally. 11. A handheld four-stroke engine pursuant to claim 1, in which the valve actuation mechanism is provided above an external oil reservoir containing the lubricant. The first valve acting chamber is formed upwards from the oil reservoir, and the second valve acting chamber is formed in the cylinder head. The oil reservoir and crankcase are connected through a through hole. The crankcase and the second valve acting chamber are connected by an external oil feed pipe. The second valve acting chamber and the oil reservoir are connected by an oil return pipe. The oil reservoir contains an oil atomizing device for atomizing the stored oil by stirring and dispersing it, and a delivery device for delivering the oil atomizer from the oil reservoir to the oil feed pipe through the crankcase. The crankcase is connected to the oil feed pipe so that the valve actuation mechanism within the first valve acting chamber is lubricated by the oil dispersed within the oil reservoir, and the valve actuation mechanism within the second valve acting chamber is lubricated by the oil atomizer delivered from the oil feed pipe to the second valve acting chamber. 12. A handheld four-stroke engine pursuant to claim 11, in which the transmission device contains a valve that closes the oil supply pipe when the crankcase pressure is negative and opens it when the pressure is positive. 13. A handheld four-stroke engine under either claim 11 or 12, where the oil feed and oil return lines are connected by a bypass. 14. A four-stroke, handheld engine according to claim 1, in which the valve actuation mechanism consists of a camshaft drive assembly with a rotating drive assembly connected to the crankshaft and a cam system for transmitting the rotational force of the rotating drive assembly of the camshaft drive assembly to the intake and exhaust valves for opening and closing forces; the first valve acting chamber and the oil reservoir are provided on one side of the main body of the engine; the first valve acting chamber contains the camshaft drive assembly; the oil reservoir contains an oil atomizing device for atomizing oil from the stored oil; and the lower end of the first valve acting chamber is open inside the oil reservoir; the second valve acting chamber, containing the cam system, is provided on the upper part of the main body of the engine in alignment with the first valve acting chamber; the first lubrication system consists of the first and second oil passages, which are positioned side-by-side and make contact between the oil reservoir and the crankcase, and the first oil feed device for circulating the atomized oil from the oil reservoir through the first oil passage, the crankcase, and the second oil passage, and then back to the oil reservoir; The secondary lubrication system consists of a third oil passage connecting the first valve acting chamber and the second valve acting chamber, a fourth oil passage connecting the second valve acting chamber and the crankcase, a second oil passage, and a second oil feeder for circulating the oil mist generated inside the oil tank from the oil tank through the first valve acting chamber, the third oil passage, the second valve acting chamber, the fourth oil passage, the crankcase, and the second oil passage, and then back to the oil tank. 15. A handheld four-stroke engine according to claim 14, in which the first oil supply device contains a first one-way valve provided in the second oil passage, which is closed when the crankcase pressure is reduced and open when the pressure is increased, and the second oil supply device contains a second one-way valve provided in the third oil passage, which is closed when the crankcase pressure is reduced and open when the pressure is increased.