The present invention relates to an oil separator for de-oiling crankcase ventilation gases of an internal combustion engine with the oil separator comprising a cyclone encompassing a gas inlet connected to the crankcase of the internal combustion engine, a gas outlet connected to the suction passage of the internal combustion engine, and an oil outlet connected to a crankcase sump of the internal combustion engine.
An oil separator of the kind mentioned above is known from DE 42 14 324 C2. In this oil separator a single cyclone is used which is dimensioned such that it may cope with the maximal amount of ventilation gases. An essential feature of this known oil separator is that a downward duct is connected to the oil outlet of the cyclone with the mouth thereof arranged below the oil level of the crankcase sump of the associated internal combustion engine, that a float valve which is normally open and arranged in a lower casing section at the side of the cyclone prevents a backwards flow out of the crankcase sump of the internal combustion engine, and that the complete oil separator as a construction unit is detachably connected to the downward pipe. These specific features of the oil separator have to take care that when the operating conditions of the associated internal combustion engine will certainly and strongly change, e.g., when full speed is achieved following an idle run, no oil from the crankcase sump of the internal combustion engine is transported into the interior of the cyclone because extremely large pressure differences will result from the change of the operating conditions.
The problem mentioned which is dealt with in the above document is solved by the oil separator described therein, however, this oil separator with the single cyclone has the disadvantage that no optimal oil separation is attained across the total range of operating conditions of the internal combustion engine which occur in practical operation. The occurring different operating conditions of the internal combustion engine on the one hand lead to different flow rates of ventilation gases out of the crankcase, and on the other hand to a different oil load of these ventilation gases. As a cyclone will operate only in a definite relative small range of operation conditions of the internal combustion engine, non-required oil volumes will occur in the gases out of the cyclone and fed to the suction air of the internal combustion engines during operation conditions outside of this optimal operating range.
Therefore it is the object of the present invention to provide a generic oil separator avoiding the mentioned disadvantages and ensuring an optimal, i.e., complete or almost complete separation of oil from the crankcase ventilation gases in particular across a very large range of practical operation conditions of the internal combustion engine.