Internal-combustion engines – Lubricators – Crankcase – pressure control
Reexamination Certificate
2000-04-18
2001-09-04
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Lubricators
Crankcase, pressure control
C184S006200
Reexamination Certificate
active
06283084
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a four-stroke cycle internal combustion engine preferably used for driving a portable working machine such as a portable trimmer, though not limited thereto, and in particular, to a four-stroke cycle internal combustion engine which is lubricated by oil in an oil reservoir provided below a connecting rod, which oil is splashed up by an oil dipper formed on a big-end of the connecting rod.
DESCRIPTION OF THE PRIOR ART
It has been known to use a portable working machine such as a portable trimmer driven by an electric spark ignition type internal combustion engine. Formerly, a two-stroke cycle internal combustion engine was generally used as an internal combustion engine for a portable working machine, but recently, there has been an increasing demand for utilizing a four-stroke cycle internal combustion engine in order to improve the air pollution problem caused by exhaust gas. Such four-stroke cycle internal combustion engine has an oil reservoir (oil pan) below a crankcase, which accommodates oil for lubricating each part of the engine. The oil in the oil reservoir is splashed up causing oil-mist by an oil dipper formed on a big-end of a connecting rod and the oil-mist is supplied to the crankcase, a chamber for a valve gear or the like to lubricate various components.
In the portable working machine, for example, in a portable trimmer, a power transmitting shaft is coupled with a front end of a crankshaft of an internal combustion engine via a centrifugal clutch, and a rotary blade for trimming is coupled with a front end of the power transmitting shaft via a gear box. An operator holds such a portable trimmer by hand and cuts weeds on the ground or trims branches of a tree above the operator's head with the rotary trimming blade driven by the internal combustion engine. Accordingly, the internal combustion engine of the portable working machine is forced, during operation, to assume a horizontal position, or an upside-down position, or some position other than a cylinder-upright position. A substantially U-shaped oil reservoir surrounding both sides and a lower side of the crankcase is disclosed, for example, in Japanese Patent Laid-open Disclosure Nos. Hei 8-260926 and Hei 10-231717. When a four-stroke cycle internal combustion engine takes various positions as described above, this type of oil reservoir allows the oil to be accommodated in oil recess areas located on the side of the crankcase to prevent the oil from flowing into the crankcase or into a cylinder area and thereby to prevent the piston from soaking in the oil or the breather from being clogged up.
However, when the internal combustion engine takes various positions as described above, the oil in the oil reservoir flows into the oil recess areas or other recess areas to prevent the oil from flowing into the crankcase or the like, while at the same time there may occur a condition where the oil dipper cannot reach the oil and thereby no oil mist is supplied to each part of the four-stroke cycle internal combustion engine.
Accordingly, the object of the present invention is to provide a four-stroke cycle internal combustion engine which can be used to drive the portable working machine, that is, which ensures the oil to be splashed up by the oil dipper even under a tilted condition or the like.
SUMMARY OF THE INVENTION
The object of the present invention described above can be achieved by a four-stroke cycle internal combustion engine comprising: a connecting rod, an oil dipper provided at a big-end of the connecting rod; a crankcase; an oil reservoir below the crankcase; a partition wall which surrounds the connecting rod to provide a separation between the crankcase and the oil reservoir; and an outer wall which is outward of and surrounds the partition wall and is connected to the partition wall at upper ends thereof so as to define an oil reservoir below the crankcase; a slit formed in the partition wall below the connecting rod to allow the oil dipper to protrude into and be withdrawn from the oil reservoir to splash oil in the oil reservoir for lubrication by the oil dipper through a swinging motion of the connecting rod; the depth of the oil reservoir being shallower at least in a part of an outer edge area thereof than that below the oil dipper so that a tip of the oil dipper reaches the oil level of the oil reservoir even when the oil flows into the outer edge area of the oil reservoir.
In the present invention, regarding the depth of the oil reservoir along the direction of the center line of the connecting rod, at least a part thereof located on an outer edge area is shallower than that located below the oil dipper. Accordingly, when the four-stroke cycle internal combustion engine is rotated and tilted about an axis intersecting with the crankshaft and thereby the oil flows into the outer edge area of the oil reservoir, the tip of the oil dipper reaches the oil level and the oil is assured to be splashed up by the oil dipper to supply the oil mist to each component in the engine.
REFERENCES:
patent: 5243937 (1993-09-01), Imagawa
patent: 5960764 (1999-10-01), Araki
patent: 10246106A (1998-09-01), None
patent: 11-2111 (1999-01-01), None
Araki Tsuneo
Liu Yumin
Nagai Noboru
Jacobson & Holman PLLC
Kamen Noah P.
Kioritz & Corporation
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