Filter element, oil separator, and method for controlling prevailing pressure in crankcase ventilation system

1. An oil separator for a crankcase ventilation system, comprising:

at least one filter element configured to separate oil from fluid, including:

at least one filter medium that is configured to separate oil from aerosol, the at least one filter medium having a covering surface extending parallel to a direction of flow of the fluid flowing through the filter medium; and

a cover element formed as an annular end plate, fixed onto and covering an axial end surface of the at least one filter medium; and

a tubular projection formed by the annular end plate on an axially outer surface of the annular end plate, the tubular projection projecting axially outwardly away from the filter medium, the tubular projection having an open interior which opens through the annular end plate into an interior of the at least one filter medium, wherein the tubular projection is a clean fluid discharge element configured to remove cleaned fluid from the oil separator;

wherein an axially outer end of the tubular projection of the filter element has an annular sealing surface forming a valve seat; and

wherein the oil separator includes:

a valve closing body that operates in conjunction with the valve seat of the filter element, the valve closing body sealing against the sealing surface of the tubular projection when the pressure control valve is in a closed state;

a flexible membrane surrounds the valve closing body and is connected to the valve closing body; and

a return spring arranged above the flexible membrane and the valve closing body, the return spring apply a closing force to the valve closing body, wherein the flexible membrane and the valve closing body are arranged between the return spring and fluid in the oil separator, such that the return spring is protected from contamination by the fluid in the oil separator;

wherein the sealing surface of the filter element forms the valve seat for the valve closing body a first housing part; and a second housing part; wherein the first housing part includes at least one oil separator clean fluid outlet configured to remove the cleaned fluid; and wherein the pressure control valve is accommodated in the first housing part; wherein the annular end plate comprises: an annular seal arranged on an outer circumference the annular end plate, the annular seal contacting against the first housing part and the second housing part in an interior of the oil separator; wherein the annular seal seals a pre-filtration side of the filter element from a post filtration side of the filter element; wherein the annular seal is arranged between and seals the first housing part to the second housing part.

2. The oil separator according to claim 1 , wherein

the elastic valve closing body sealing element is formed out of at least one elastomer;

wherein the at least one elastomer are selected from the set: ethylene acrylate rubber (EAR) and/or from acrylate rubber and/or from hydrogenated nitrile rubber (H)NBR.

3. The oil separator according to claim 1 , wherein

the elastic valve closing body sealing element is connected fixedly, non-releasably to the valve closing body;

wherein the elastic valve closing body sealing element is applied onto the valve closing body by a spray process.

4. The oil separator according to claim 1 , wherein

the valve closing body is flat or level on the region thereof that faces the valve seat and contacts with the annular contact surface of the valve seat of the tubular projection of the filter element.

5. The oil separator according to claim 1 , further comprising:

an elastic valve closing body sealing element arranged on at outer circumference of the valve closing body, the elastic valve closing body sealing element having an annular contact surface which seals the valve closing body against the sealing surface of the tubular projection when the pressure control valve is in a closed state.