Internal-combustion engines – Lubricators – Crankcase – pressure control
Reexamination Certificate
1999-10-04
2001-03-13
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Lubricators
Crankcase, pressure control
C123S311000
Reexamination Certificate
active
06199532
ABSTRACT:
BACKGROUND OF THE INVENTION
A four-stroke combustion engine is disclosed in German patent publication 30 22 901. The intake channel opens exclusively into the crankcase whereby the mixture drawn into the crankcase during the downward movement of the piston is conveyed via a transfer channel into a valve housing from where it flows through the intake valve into the combustion chamber. This mixture passage ensures that the entire air-fuel-lubricant mixture, before entering the combustion chamber, flows through the crankcase and the connecting channels so that the moving parts are lubricated. However, this guiding of the mixture has the disadvantage of causing undesirable heating of the mixture resulting in efficiency losses because of the volumes to be conveyed.
German patent publication 34 38 031 describes a four-stroke engine in which the intake channel of the intake valve is connected directly to the mixture-preparation device. A mixture conduit branches off the intake channel to the crankcase which is connected to the valve housing via a further connecting line parallel to the cylinder wall. The valve housing, in turn, is connected by a connecting channel to the intake channel so that a closed, mixture-conveying circulation is provided, which includes the crankcase and the valve housing. For controlling the mixture-conveying circuit, the mixture conduit to the crankcase is provided with an intake valve, and the connecting channel between the valve housing and the intake channel has a throttle flap. The resulting control of the mixture-conveying lubricant circuit is complex.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an oil-in-fuel lubricated four-stroke engine of the above kind so that the lubrication of all moving parts is ensured while maintaining good output characteristics and having a mechanically simple design.
The oil-in-fuel lubricated four-stroke engine of the invention includes: a cylinder; a piston movably mounted in the cylinder; the cylinder and the piston conjointly delimiting a combustion chamber; the cylinder having an intake opening and an intake valve for opening and closing the intake opening; the cylinder having an exhaust opening and an exhaust valve for opening and closing the exhaust opening; a valve housing connected to the cylinder; the intake valve and the exhaust valve movably mounted in the valve housing; a crankcase connected to the cylinder and communicating with the valve housing; a crankshaft rotatably journalled in the crankcase; a connecting rod interconnecting the piston and the crankshaft; the piston reciprocating in the cylinder to rotatingly drive the crankshaft via the connecting rod and alternately generate an overpressure and an underpressure in the crankcase; a valve drive assembly driven by the crankshaft for actuating the intake valve and the exhaust valve; a mixture-preparation device for supplying an air/fuel-lubricant mixture; an intake channel conducting the mixture to the intake valve; a connecting channel connecting the valve housing to the intake channel; and, the crankcase communicating with the mixture-preparatioil device exclusively via the valve housing, the connecting channel and the intake channel to facilitate movement of at least a portion of the mixture between the crankcase and the intake channel via the valve housing in response to the overpressure and underpressure.
Surprisingly, it was found that a branch line from the intake channel via the valve housing to the crankcase is sufficient to ensure lubrication of all moving parts. The reciprocating piston acts as a suction and pressure pump which discharges a drawn-in air-fuel-lubricant mixture via the connecting channel into the intake channel or takes in a fresh mixture via the connecting channel from the intake channel. Due to the dynamics in the crankcase, the mixture present will mix with fresh mixture components and thus maintain its lubricating properties over the entire service life of the combustion engine. Deterioration of the mixture present in the valve housing and the crankcase is reliably prevented.
Even during sudden accelerations, the mixture is supplied in sufficient amounts to the combustion chamber because, simultaneous to the opening of the intake valve and the intake of a fresh mixture, the mixture drawn by a previous engine stroke into the crankcase and the valve housing is discharged via the connecting channel into the intake channel and flows directly into the combustion chamber. Accordingly, the mixture lubricated four-stroke engine will exhibit a powerful response even for sudden throttle activation. A responsive power output is observed over the entire rpm range.
The flow connection between the crankcase and the valve housing is preferably realized by the valve drive channel so that additional connecting lines are unnecessary.
The flow connections from the crankcase via the valve drive channel to the valve housing and via the connecting channel to the intake channel are free of valves and control elements. The cross section of the connecting channel can be smaller than the intake channel cross section; that is, the cross section of the connecting channel advantageously is approximately 30% to 50%, especially 40%, of the intake channel cross section.
The connecting channel opens into the intake channel in the vicinity of the intake valve so that, especially during acceleration, a readily combustible mixture is present upstream of the intake valve during the intake stroke.
In order to ensure a reliable lubrication of all moving parts independently of the operating position of the engine, the volume of the valve housing and the exchange volume flowing through the connecting channel are adjusted relative to one another such that, during idle operation, fresh mixture components are continuously mixed into the air-fuel-lubricant mixture in the valve housing. This ensures satisfactory lubrication over the entire period of operation.
For such a configuration of the mixture lubricated combustion engine, the amount of the lubricant component of the mixture can be significantly reduced, for example, to a lubricant/fuel ratio of 1:60, 1:100, or less.
REFERENCES:
patent: 3022901 (1981-12-01), None
patent: 3438031 (1986-04-01), None
Becker Georg
Haberlein Jurgen
Andreas Stihl AG & Co.
Kamen Noah P.
Ottesen Walter
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