Crankcase ventilation in an internal combustion engine

Details Crankcase ventilation in an internal combustion engine Crankcase ventilation in an internal combustion engine

1999-12-03

2001-04-10

McMahon, Marguerite (Department: 3747)

Internal-combustion engines

Charge forming device

Crankcase vapor used with combustible mixture

Reexamination Certificate

active

06213107

ABSTRACT:

The present invention relates to an internal combustion engine with a crankcase containing oil, a ventilation arrangement for evacuating blow-by gases from the crankcase and a wheel rotating when the engine operates, said wheel being enclosed in a space which communicates with the crankcase.
It is a known fact that it is not possible that the piston rings between the pistons in the surrounding cylinder walls of the cylinders in an internal combustion engine will achieve a one hundred percent seal between the combustion chambers and the engine crankcase. A small amount of combustion gases, so-called blow-by gases, always slip past the piston rings and flow down into the engine crankcase. In order to prevent excessive overpressure due to the blow-by gases in the crankcase, the crankcase must be ventilated by venting the gases away, leaving only a small over-pressure in the crankcase.
There are two types of crankcase ventilation, viz. open and closed ventilation. An engine with open ventilation can quite simply have, in the valve cover for example, a downwardly directed pipe, which is connected to an opening in the engine and which opens into the surrounding atmosphere. In an engine with closed crankcase ventilation, the blow-by gases are conducted from the crankcase to the engine intake manifold and are mixed with the intake air.
When evacuating blow-by gases from the crankcase it has hitherto been unavoidable that a certain amount of oil mist will accompany the blow-by gases. The amount of oil accompanying the blow-by gases depends on the placement of the ventilation outlet and on any filters or oil traps used in the crankcase ventilation. Regardless of whether the engine has open or closed crankcase ventilation, it is desirable to keep the amount of oil in the evacuated blow-by gases to a minimum.
In the former case, the negative environmental impact is to be kept as small as possible, and the engine oil consumption is to be minimized. In the latter case, it is intended to prevent oil coating or deposits on the components of the engine intake system, for example, oil coating on the blades of the compressor of a turbo-charged engine or oil deposits in the charge air-cooler in engines with charge air-cooling.
The purpose of the present invention is to achieve an engine of the type described by way of introduction, in which the amount of oil mist evacuated with the blow-by gases via crankcase ventilation is very small.
This is achieved according to the invention by virtue of the fact that the ventilation arrangement comprises an outlet from said space, said outlet being disposed to one side of a lateral surface of the rotating wheel and with at least the major portion thereof within the periphery of the wheel.
In a preferred embodiment of the engine according to the invention, a highly placed gear in the engine camshaft drive train is used. The outlet, in the form of a short pipe is preferably fixed in an opening in the drive train casing directly opposite the center of the gear.
It has been found that the rotating gear to one side of the outlet has such a centrifugal effect that practically all of the oil mist can be separated from the blow-by gases in the vicinity of the outlet. For example, comparative trials when driving under extreme conditions and extraction of excess power in a test rig revealed that an engine with conventional open crankcase ventilation emitted a large amount of oil in one 24 hour period, while the same engine with the ventilation arrangement according to the invention mounted, reduced the amount of oil emitted by more than 99%. In other words, practically one hundred percent separation of oil from the evacuated blow-by gas was achieved.


REFERENCES:
patent: 1872609 (1932-08-01), Schittke
patent: 5937836 (1999-08-01), Yonezawa et al.
patent: 6029638 (2000-02-01), Funai et al.
patent: 423 791 (1926-01-01), None
patent: 2 103 061 (1971-08-01), None
patent: 0 736 673 (1996-10-01), None
patent: 1 014 746 (1965-12-01), None

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