Internal-combustion engines – Poppet valve operating mechanism – Lubrication
Reexamination Certificate
1999-08-26
2001-03-20
Walberg, Teresa (Department: 3742)
Internal-combustion engines
Poppet valve operating mechanism
Lubrication
Reexamination Certificate
active
06202613
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a four-stroke cycle internal combustion engine preferably used for portable working machines such as a portable trimmer, though not restricted thereto, and in particular, to a four-stroke cycle internal combustion engine equipped with an oil separator for separating lubrication oil from blow-by gas.
DESCRIPTION OF THE PRIOR ART
From the viewpoint of solving a recent problem of air pollution problem caused by exhaust gas, there has been a demand for employing a four-stroke cycle internal combustion engine even for a portable trimmer to which a two-stroke cycle internal combustion engine has generally been employed. An example of this type of four-stroke cycle internal combustion engine is disclosed, for example, in Japanese Patent Laid-open Disclosure No. 8-260926 and such engine has an oil reservoir (oil pan) for accommodating oil for lubricating portions of the engine, which is provided below the crankcase. The oil in the oil reservoir is agitated by an oil dipper formed on a big end of a connecting rod to generate oil-mist. The oil-mist is pushed out of the oil reservoir to a cam chamber by positive pressure caused by downward movement of a piston and lubricates various components in the cam chamber. When the piston moves downwardly, blow-by gas generated in the crankcase is also delivered together with the oil-mist to the cam chamber and then, the blow-by gas is separated from oil before being emitted from a breather pipe to the outside or to an air cleaner.
The reason why the oil is separated in this manner is that firstly, the oil will be used up much earlier than a predetermined oil consumption period determined for each type of portable working machine and secondly, it will pollute the environment of the working place, if blow-by gas which is not completely separated from oil is emitted to the outside or to the air cleaner. Further when the blow-by gas containing oil is returned through the air cleaner to a combustion chamber, it will cause the combustion efficiency to go down and/or a filter element to be stained.
Therefore, the object of the present invention is to provide a four-stroke cycle internal combustion engine equipped with an oil separator for separating oil from blow-by gas which is highly reliable in an operation.
SUMMARY OF THE INVENTION
The above-mentioned object can be achieved by a four-stroke cycle internal combustion engine comprising: an oil reservoir; a cam chamber; an oil dipper formed on a connecting rod and for agitating oil in the oil reservoir to generate oil mist; a carburetor; and an oil separator being provided between the cam chamber and the carburetor and for separating oil contained in oil mist from blow-by gas; the oil separator having a first passage with an upper end and a lower end and a second passage with a first end and a second end, the first passage communicating with the cam chamber at the upper end and communicating with the oil reservoir at the lower end and the second passage communicating with the lower end of the first passage at the first end and communicating with a venturi of the carburetor at the second end; whereby the engine is adapted to deliver oil mist from the oil reservoir to the cam chamber together with blow-by gas.
The four-stroke cycle internal combustion engine of the present invention functions as follows.
When a piston of the four-stroke cycle internal combustion engine of the present invention moves upwardly and downwardly, the oil dipper formed on the connecting rod agitates lubrication oil accommodated in the oil reservoir. In this way, the oil mist is generated. When the piston moves upwardly, the blow-by gas is generated in the crankcase. Then, when the piston moves downwardly, the oil mist is delivered from the oil reservoir to the camshaft chamber together with the blow-by gas. This oil mist lubricates respective members in the cam chamber. Further, the mixture of excess oil mist and the blow-by gas flows downwardly through the first passage extending in a vertical direction toward the oil reservoir. During this process, the oil contained in the oil mist falls within the first passage by its own weight, adheres to and flows downwardly along the inner wall surface of the first passage, and is separated from the blow-by gas. The separated oil returns to the oil reservoir and is recycled. Further, the blow-by gas flows from the lower end of the first passage into the one end of the second passage, and is sucked from the other end into the venturi of the carburetor so as to be combusted again. The length of the first passage may be determined so that the oil contained in the oil mist can substantially be removed by falling by its own weight while the mixture passes through the first passage.
In a four-stroke cycle internal combustion engine of the present invention, the oil separator has a simple structure which enables to assure separation of the oil from the blow-by gas. Since the separated oil is returned to the oil reservoir, the oil can be recycled, preventing unnecessary consumption of oil. Further, since only blow-by gas is returned to a combustion chamber, it is possible to prevent reduction in the combustion efficiency.
REFERENCES:
patent: 5687686 (1997-11-01), Takahashi
patent: 6039020 (2000-03-01), Kawamoto et al.
Jacobson Price Holman & Stern PLLC
Kioritz & Corporation
Patel Vinod D
Walberg Teresa
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