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

Abstract

The invention describes a filter element for an oil separator of a crankcase ventilation system in which a filter element is configured to separate oil from fluid and that has a covering surface extending parallel to a direction of flow, together with at least one cover element covering surface in at least some regions. An oil separator is taught having the filter element with at least one pressure control valve controlling crankcase pressure and has a valve closing body that operates in conjunction with a valve seat.

Claims

1. A filter element for an oil separator of a crankcase ventilation system, the filter element comprising: at least one filter medium surrounding a central axis, the at least one filter medium configured to separate oil from aerosol, the at least one filter medium having an axial end surface forming a covering surface extending in a radial direction relative to the central axis; and a cover element formed as an annular end plate, fixed onto and fully covering the covering surface of the at least one filter medium; wherein the cover element forms a tubular projection on an axially outer surface of the cover element, the tubular projection projecting axially outwardly away from the at least one filter medium, the tubular projection having an open interior which opens through the cover element 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 an interior of the filter element; wherein an axially outer end of the tubular projection of the filter element has an annular sealing surface forming a valve seat; wherein the tubular projection is configured as a clean fluid discharge element that extends away from the filter element and is configured to remove cleaned fluid from an interior of the filter element to the valve seat of the cover element; wherein the valve seat of the cover element is configured as a sealing surface for a pressure control valve body of the crankcase ventilation system to sealably close against.

2. The filter element according to claim 1, wherein the filter element is oval-cylindrical; and wherein the filter element has a cavity in the interior of the at least one filter medium; wherein the fluid to be filtered flows from the outer surface of the filter medium to the cavity; and wherein the cavity is connected directly to the clean fluid discharge element in order to remove the cleaned fluid.

3. The filter element according to claim 1, wherein the clean fluid discharge element and/or the annular sealing surface is formed of at least one mechanically fixed and/or rigid material; wherein the at least one mechanically fixed and/or rigid material is a moldable material selected from the set consisting of: polyurethane, polyamide, or polyamide formed from polyamide 66 with 35% glass fiber (PA 66 GF 35).

4. The filter element according to claim 1, wherein the annular sealing surface, the clean fluid discharge element, and the cover element are integrally formed as a unitary one-piece component.

5. The filter element according to claim 1, wherein the at least one filter medium is a multi-layered non-woven wrap.

6. The filter element according to claim 1, wherein the cover element and clean fluid discharge element are continuously closed.

7. An oil separator for a crankcase ventilation system, comprising: an oil separator housing including: a first housing part; and a second housing part secured to the first housing part and enclosing a chamber therein; a filter element according to claim 1 arranged in the chamber of the oil separator housing; wherein the first housing part includes at least one oil separator clean fluid outlet configured to remove the cleaned fluid the pressure control valve is configured to limit the negative pressure applied in the crankcase ventilation system, the pressure control valve formed in combination by: the valve seat of the filter element; and a valve closing body accommodated in the first housing part that operates in conjunction with and sealably closes against the valve seat; wherein the sealing surface of the tubular projection of the cover element of the filter element forms the valve seat against which the valve closing body sealably closes when the pressure control valve is in a closed state.

8. The oil separator according to claim 7, wherein the valve closing body comprises at least one elastic valve closing body sealing element, at least on a region thereof arranged to contact with the valve seat of the filter element; and wherein the at least on a region of the at least one valve closing body is surrounded by an elastic valve closing body sealing element on the region thereof that is arranged to contact with the valve seat of the filter element.

9. The oil separator according to claim 8, wherein the 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.

10. The oil separator according to claim 7, wherein the valve closing body sealing element is connected fixedly, non-releaseably to the valve closing body; wherein the valve closing body sealing element is applied onto the valve closing body by a spray process.

11. The oil separator according to claim 7, wherein the valve closing body is flat or level on the region thereof that faces the valve seat and contacts with the valve seat of the filter element.

12. The filter element according to claim 1, wherein the annular sealing surface of the tubular projection is circular, substantially flat and free of burrs.

13. The filter element according to claim 1, wherein a circumferential edge of the annular sealing surface of the tubular projection is rounded.

14. A method for limiting the crankcase vacuum of a crankcase ventilation system to a predetermined value, comprising: providing an oil separator housing enclosing a chamber therein; providing a filter element configured to separate oil from fluid, including: at least one filter medium surrounding a central axis, the at least one filter medium configured to separate oil from aerosol, the at least one filter medium having an axial end surface forming a covering surface extending in a radial direction relative to the central axis; and a cover element formed as an annular end plate, fixed onto and fully covering the covering surface of the at least one filter medium; wherein the cover element forms a tubular projection on an axially outer surface of the cover element, the tubular projection projecting axially outwardly away from the at least one filter medium, the tubular projection having an open interior which opens through the cover element 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 an interior of the filter element; wherein an axially outer end of the tubular projection of the filter element has an annular sealing surface forming a valve seat; wherein the tubular projection is configured as a clean fluid discharge element that extends away from the filter element and is configured to remove cleaned fluid from an interior of the filter element to the valve seat of the cover element; wherein the valve seat of the cover element is configured as a sealing surface for a pressure control valve closing body of the crankcase ventilation system to sealably close against; and providing the pressure control valve configured to limit the negative pressure applied in the crankcase ventilation system, the pressure control valve formed in combination by: a valve closing body that operates in conjunction with valve seat of the cover element; wherein the sealing surface of the filter element forms the valve seat against which the valve body closes; arranging the filter element replaceably in the chamber of the oil separator housing; arranging the valve closing body of the pressure control valve in the oil separator housing such that the valve closing body is closeable against the valve seat of the filter element; operating the pressure control valve responsive to prevailing pressure in the crankcase ventilation system to limit the crankcase vacuum such that the valve closing body is moved relative to the filter element and the valve seat of the filter element to control crankcase vacuum.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) As already discussed above, there are several approaches to advantageously embodying and developing the teaching of the present invention.

(2) FIG. 1 illustrates a perspective view of an embodiment of a crankcase ventilation system according to the present invention, in which a pressure control valve thereof works according to the method of the present invention;

(3) FIG. 2 illustrates a longitudinal depiction of a crankcase ventilation system from FIG. 1, with an embodiment of an oil separator according to the present invention, in which a pressure control valve thereof works according to the method of the present invention;

(4) FIG. 3 illustrates a longitudinal view of a detail of the oil separator from FIG. 2;

(5) FIG. 4 illustrates a plan view of the oil separator from FIG. 2;

(6) FIG. 5 illustrates a perspective view of the valve closing body and the valve closing body sealing element of the pressure control valve of the oil separator from FIG. 2;

(7) FIG. 6 illustrates a longitudinal view of the valve closing body and the valve closing body sealing element from FIG. 2;

(8) FIG. 7 illustrates a perspective view of the valve closing body, a return spring, and a pressure control insert of the oil separator from FIG. 2;

(9) FIG. 8 illustrates a perspective exploded view of the components of an embodiment of a filter element according to the present invention;

(10) FIG. 9 illustrates a perspective exploded view of the components arranged in the housing cover of the crankcase ventilation system depicted in FIG. 1;

(11) FIG. 10 illustrates a detail of the pressure control valve of the crankcase ventilation system from FIG. 1, wherein the forces acting on the valve closing body are marked;

(12) FIG. 11 illustrates an embodiment of a control characteristic of the crankcase pressure as a function of the vacuum on the outlet side of the pressure control valve of the crankcase ventilation system from FIG. 1;

(13) FIG. 12 illustrates an oil separator according to the prior art; and

(14) FIG. 13 illustrates a side view of the oil separator from FIG. 12, which is configured according to the prior art.

(15) Identical or similar designs, elements, or features are provided with identical reference signs in FIG. 1 to 12.

DETAILED DESCRIPTION

(16) FIG. 1 illustrates a perspective view of a crankcase 410 (shown only schematically), which comprises an oil separator 200 of a crankcase ventilation system. The crankcase 410 is part of an internal combustion engine. The internal combustion engine may be installed in a motor vehicle. The oil separator 200 is configured as an oil separator for oil-containing air from an interior of the crankcase 410. In such applications, the oil-containing air is usually mixed with combustion gases exiting from the cylinders as leakage gas into the crankcase. This mixture is frequently also called crankcase gas, the term air still also being used for the sake of simplicity.

(17) The oil separator 200 comprises a substantially oval-cylindricalin particular, circular-cylindricalfilter housing composed of a first filter housing part 210namely, a housing coverand a second filter housing part 220namely, a housing body. The second filter housing part 220 has an inlet 222 for the oil-containing air 500. Arranged in the filter housing is a filter element 100 comprising at least one filter medium 10 made of a filter material that has been arranged in an annular shape, e.g., a circular ring shape or an oval ring shape (see FIG. 2). The filter element 100 is covered by the filter housing in FIG. 1, and therefore is marked with a dashed reference line. Within the filter housing 210, 220, the air 500 (a corresponding air flow 20 is indicated in FIG. 2 by an arrow) is filtered by means of the filter medium 10. The resulting clean air 510 is guided out of an interior 12 (FIG. 2) enclosed by the filter medium 10, through a clean air discharge element 50 of the filter element 100, to a clean air outlet 212 of the housing cover 210, and from the clean air outlet 212 back into the intake duct of the internal combustion engine. Separated oil is removed through an oil outlet 230.

(18) The oil separator 200 has a pressure control valve, in order to limit the crankcase vacuum to a defined value. The pressure control valvedepicted by way of example in FIGS. 2 and 3has a valve closing body 310 that is surrounded by a valve closing body sealing element 320, preferably by a membrane, as is illustrated here.

(19) On the end facing away from the valve closing body 310, the membrane 320 is connected to the first filter housing part 210, for example, by being clipped into the first filter housing part 210. Alternatively, the membrane 320 may also be mounted between the filter housing part 210 and the cover element 214. Preferably, the membrane is clamped between the first filter housing part 210 and an insert 350 forming even more preferably the lower stop of the spring 330, as in the presently-described embodiment. The insert 350 has openings, so that the ambient pressure can act on the membrane 320 and on the valve closing body 310.

(20) In order to be closed, the pressure control valve has a valve seat 52 arranged on the filter element 100. In contrast to the prior art illustrated in FIGS. 12 and 13, the filter element 100 illustrated in FIGS. 2, 3, 8, and 10 has a cover element 40 that is configured as an end plate and has a sealing surface 52 at the end thereof that faces away from the filter element 100, wherein this sealing surface 52 is provided in order to seal off the pressure control valve 52, 310, 320, 330, by the ability of the valve closing body sealing element 320 or the valve closing body 310 to come into sealing contact with the sealing surface 52, preferably with a contact surface 312 (see FIG. 6) of the valve closing body 310 or the membrane 320.

(21) The membrane 320 is configured to seal the clean air outlet 212 and the interior 12 of the filter medium 10 off from the ambient air pressure, and to keep the valve closing body axially movable.

(22) The valve closing body 310 can be moved relative to the valve seat 52, as illustrated in FIG. 10. The left side of the illustrated sectional view depicts the closed state of the valve, where the valve closing body 310 abuts, preferably axially (as is shown), against the sealing surface 52 with a circular ring-shaped contact surface 312 (see FIG. 6); on the right side of the view, the valve closing body 310 is spaced apart from the sealing surface 52, so that the valve is open. The pressure control valve 52, 310, 320, 330 is configured so as to control the flow rate or volume flow of the fluid flowing away through the clean fluid discharge element 50, by means of the movement of the valve closing body 310 relative to the valve seat 52, in particular, through the modification of the cross-section of the flow channel 340 formed by the gap between the sealing surface 52 and the valve closing body 310.

(23) The pressure control valve is configured such that the membrane 320 is subjected to the pressure 600 prevailing in the clean air outlet 212 on the side thereof facing the filter element 100 or the housing interior, in the region of the circular ring area A.sub.M defined by the diameters .sub.M and .sub.M, and the valve closing body 310 is subjected to the pressure 610 prevailing in the interior 12 of the filter medium 10 on the side thereof facing the filter element 100 or the housing interior, in the region of the circular area A.sub.D defined by the inner diameter .sub.0 of the sealing surface 52. On the side facing away from the filter element 100 or the housing interior, the membrane 320 and the valve closing body 310 are also subjected to the ambient pressure. Preferably also provided is a return spring 330 that subjects the membrane 320 and/or the valve closing body 310 to a force that acts in a direction of opening, i.e., is directed away from the filter element 100. At least one opening in a pressure control valve cover element 214 and/or an insert 350 causes ambient pressure to be applied to the back side of the membrane; this ventilation makes it possible for the pressure control valve to work undamped.

(24) Preferably, a return spring 330as already describedis arranged on the side of the valve closing body 310 that faces away from the filter element 100. The return spring 330 subjects the valve closing body 310 and/or the membrane 320 arranged thereon to a force 620 (see FIG. 10) oriented away from the valve seat 52. The compression spring or return spring 330 services to ensure the rest position of the valve closing body 310. The rest position corresponds to the position of the valve closing body 310 at which the force of the return spring 330 is exactly as great as the sum of the force of the crankcase pressure 610 and the force of the suction pressure 600.

(25) On the way from the interior 12 of the filter medium 10 to the clean air outlet 212, the clean fluid flows through a flow channel 340 (see FIGS. 3 and 10) that is arranged between the valve closing body 310in particular, the membrane 320 arranged on the valve closing body 310and the valve seat 52, and that preferably has the shape of an annular gap, as is provided presently. The diameter of this flow channel 340 can be changed or regulated through relative movement of the valve closing body 310 to the valve seat 52.

(26) With decreasing pressure in the clean air outlet 212 or on the exit side of the pressure control valve, the membrane 320 makes a stroke movement in the direction of the valve dome or valve seat 52, thereby reducing the cross-sectional area of the flow channel 340. This increases the flow resistance of the pressure control valve over the valve seat 52.

(27) The control behavior of the pressure control valve can be adjusted via the diameter cross-section ratios .sub.M, .sub.D of the membrane 320 and the inner diameter of the sealing surface 52 or the end surface of the clean fluid discharge element 50 that faces away from the filter element 100. FIG. 10 illustrates the cross-section diameter .sub.M of the membrane 320 (which, in the present embodiment, is defined by the roll point of the membrane 320) and the cross-section inner diameter .sub.M of the sealing surface 52.

(28) The valve closing body 310 is in the rest position (closed position) when a) the force F of the return spring 330 b) minus the differential pressure p from the atmospheric pressure and the crankcase pressure 610, multiplied by the cross-sectional area A.sub.D (defined by the inner diameter .sub.D of the valve seat 52) c) minus the differential pressure p from the atmospheric pressure and the suction pressure 600, multiplied by the cross-sectional area A.sub.M (defined by the ring between the cross-section diameter .sub.M of the membrane 320 and the inner diameter .sub.D of the valve seat 52) equals zero.
In summary, this gives:
0=F.sub.return spring 330F(.sub.(crankcase pressure 610)F(.sub.suction pressure 600)=F.sub.return spring 330p(.sub.atmospheric pressurecrankcase pressure)*A.sub.Dp(.sub.atmospheric pressuresuction pressure)*A.sub.M

(29) The return spring 330 prevents the membrane 320 from being permanently closed at small suction vacuum pressures 600 from the turbocharger or intake duct of the engine. In addition, the location of the pressure control characteristics can be varied by means of the return spring 330. This means that with a harder return spring 330, the suction vacuum pressure 600 can act more intensely on the crankcase, and the curve shifts downward.

(30) FIG. 11 illustrates an exemplary control characteristic line of a pressure control valve. The Y-axis represents the pressure prevailing in the inlet for pre-filtration fluid 222 or on the pre-filtration side 250in particular, the crankcase pressurein hectopascals [hPa]. The X-axis represents the pressure prevailing in the clean air outlet 212in particular, the suction vacuum pressurein hectopascals [hPa]. The first control characteristic line, represented in FIG. 11 with a solid line, shows the pressure ratios at a volume flow in the pressure control valve of 100 liters per minute. The second control characteristic line, represented in FIG. 11 with a dashed line, shows pressure ratios at a volume flow in the pressure control valve of 20 liters per minute. The control range of the two control characteristic linesshown by way of examplelies in the range of 2 to 28 hPa. The slope of the ranges of the two control characteristic lines marked with the reference signs 700, 702 depends on the area ratios A.sub.D and A.sub.M of the valve seat 52 and the membrane 320. The intersection of the two control characteristic lines with the Y-axis, marked with the reference signs 710, 712, shows the pressure drop with the pressure control valve is open.

(31) As depicted in FIG. 11, the pressure drop of the oil separator 200 also affects the situation of the pressure control curve, wherein when the pressure drop or volume flow increases, the situation of the pressure control curve rises. Conversely, the crankcase pressure decreases with a lower volume flow.

(32) The ratio of the cross-section diameters .sub.M and .sub.D of the membrane 320 and the sealing surface 52 influences the slope 700, 702 of the pressure control curve. If a negative pressure prevails in the crankcase relative to the atmosphere, and the pretension of the return spring 330 is overcome, then the membrane 320 moves onto the sealing surface 52, and the flow resistance increases.

(33) First, if the suction vacuum pressure 600 is large enough and the return spring 330 is compressed, this results in a curved curve, and finally in a minimum of the crankcase pressure.

(34) At even higher suction vacuum pressures, a slight increase in the pressure 610 is to be observed in the interior 12 of the filter medium, in particular, the crankcase pressure. In these operational ranges, the membrane 320 closes the suction side of the valve intermittently, and thus throttles or interrupts the volume flow. This intermediate pressure is higher than the minimum pressure, because when the valve seat 52 is closed and there is a strong suction vacuum pressure 600, the pressure 610 in the crankcase must be correspondingly higher, in order to for the membrane 320 to again be lifted off from the valve seat 52 against the suction vacuum pressure acting on the outside thereof.

(35) The oil separator 200 may have an overpressure valve 800 (FIG. 1), for safety reasons. This overpressure valve may be configured, for example, as is described in DE 10 2013 005 624 A1.

(36) FIG. 8 illustrates the components of an embodiment of a filter element 100 according to the present invention. This filter element 100 is configured for the crankcase ventilation system illustrated in FIG. 1. The filter element 100 has a cover element, in particular, an end plate 40. This end plate 40 covers the covering surface 30 (see FIG. 3) of the filter medium 10 facing the clean fluid outlet 212, and is connected sealingly thereto, so that the fluid flows through the filter medium 10 into the interior 12 of the filter medium 10. The filter element 100 is an annular coalescence element. For this purpose, the filter element 100 has, as preferred, a filter medium 10 configured as a non-woven fabric that is wrapped repeatedly and thus in a plurality of layers annularly around the central tube 70 (also called a support tube). The central tube 70 allows for flow therethrough and therefore has openings. This can be realized, for example, by a lattice-shaped configurationas shown in FIG. 8by means of a perforated plate or the like. The filter medium 10 is a non-woven wrap. For stabilization and sealing, it is preferably sealingly connected at each of the end facesfor example, by means of gluing or weldingto cover elements 40, 42 configured as end plates. The construction of the coalescence element with the wrapped non-woven fabric is thus fundamentally different from other filter elements, which are intended to separate solid particles from fluids such as air or oil and generally have a pleated filter medium.

(37) The sealing surface 52 on the clean fluid discharge element 50 is spaced apart from the axial outer surface of the cover element 40. The axial installation space required for the clean fluid outlet 212 is thereby bridged. The length of the clean fluid discharge element 50, as measured from the axial, outer surface of the cover element 40, corresponds to the diameter of the clean fluid outlet 212 of the upper housing part 210. This makes it possible to achieve a streamlined overall design with which the positioning of the sealing surface 52 on the cover element 40 or on the filter element 100 is not accompanied by disadvantages.

(38) The cover element 40 is configured as an end plate of the filter element 100, as is preferred, in the embodiment illustrated in detail in FIGS. 2, 3, and 8. The cover element is sealingly and non-releasably connected to the filter medium at an end face of the filter element, for example, by gluing or welding. The cover element 40 is preferably produced from thermoplastic polymer, preferably by injection molding.

(39) The clean fluid discharge element 50 is integrally, sealingly connectedas is preferredto the cover element 40 in the embodiment illustrated in detail in FIGS. 2, 3, and 8.

(40) The clean fluid discharge element 50 is preferably a circular-cylindrical, straight tube, as also illustrated in the drawings. This tube comprises a closed cylindrical wall and two open ends, wherein the sealing surface 52 is configured on one end that faces away from the cover element, and the other end is connected to the cover element 40, so that a fluid connection to the interior 12 of the filter medium 10 or filter body is formed. The ends are preferably oriented so as to be perpendicular to the central axis.

(41) In the embodiment illustrated in detail in FIGS. 2, 3, and 8, as is preferred, the cover element 40 is configured as an annular end plate away from which the clean fluid discharge element 50, configured as a tube, extends integrally on the side facing away from the filter medium 10. The clean fluid element and the cover element preferably form a substantially L-shaped or alternatively T-shaped cross-section, as is illustrated.

(42) The crankcase ventilation system has two spaces that must be separated from one anothernamely, the pre-filtration space or pre-filtration side 250, on which the not-yet-cleaned blow-by gas is located, and the post-filtration space or post-filtration side 240, on which the cleaned gas is located. In addition, the pre-filtration space 250 and post-filtration space 240 must also be separated from the atmosphere. To solve this problem only with a seal, the filter element 100illustrated, for example, in FIG. 8has a sealing element configured as a combination seal, namely, a filter element seal 60 that makes it possible to separate all three regions from one another.

(43) The filter element seal 60 (see FIGS. 2, 3, and 8) thus serves to seal off the pre-filtration side 250 of the filter element 100 from the post-filtration side 240 of the filter element 100, the interior of the housing upper part 210 to the ambient air pressure, and the interior of the housing lower part 220 to the ambient air pressure.

(44) A special advantage of the filter element seal 60 illustrated in FIGS. 2, 3, and 8 over filter element seals from the prior art is the functional decoupling of two sealing functions, namely, the sealing off of the interior of the filter housing 210, 220 from the environment on one hand, and the sealing off of the pre-filtration side 250 from the post-filtration side 240 on the other hand. The two sealing regions illustrated in FIGS. 2 and 8namely, the radially sealing region 64 and the axially sealing region 66are functionally independent, but integrated into one part, namely, the sealing element 60.

(45) The filter element seal 60 illustrated in FIGS. 2, 3, and 8 thus has a region 64 that is radially compressed by means of a defined force, and a region 66 that is axially compressed by means of a defined force, wherein the radially compressed region 64 and the axial compressed region 66 are connected to one another and form a continuous sealing element, which fulfills two independent sealing functions. The sealing forces are defined by a person skilled in the art, by designing the sealing parameters of Young's modulus, seal dimensions, and sealing gap dimensions.

(46) A defined radial seal can be provided in the oil separator 200 illustrated in FIGS. 2, 3, and 8 by radially compressing the filter element seal 60 by means of a defined force between the housing upper part 210 and the end plate 40. This is advantageously achieved by the extension of the housing upper art 210 to the height of the end plate 40, the end plate 40 thus being arranged over the housing edge of the housing upper part 210.

(47) The radially sealing region 64 may be configured in the manner of an O-ring (see FIGS. 2 and 3). The axially sealing region 66 is, in particular, configured in the form of a bead having a substantially rectangular cross-section, and preferably also has two opposite sealing surfaces that are in sealing contact with the housing upper part 210 and lower housing part 220, and are compressed axially between the housing parts. In this case, the filter element seal 60 is composed of an O-ring and an axial seal, which are produced in combination.

(48) In the interior 12 of the filter medium 10, a central tube 70 configured as a support element for the filter medium 10 may be arranged. The central tube supports the filter medium 10 and protects same against collapse.

(49) In order to ensure that the fluid flows through the filter medium 10 into the interior 12 of the filter medium 10, the filter element 100 has another cover element 42in particular, another end plate 42on the end thereof that faces the oil outlet 230.

(50) In order to seal off the post-filtration side of the filter element from the pre-filtration side of the filter element, another filter element seal 62configured, for example, as an O-ringmay be associated with the additional cover element 42, in order to seal off the additional cover element 42 from the housing part 220. This additional filter element seal 62 is preferably arranged radially outward on the additional cover element 42. The cover element 42 is also preferably configured as an end plate, in particular, as an open end plate having a central opening for the oil drain.

(51) FIG. 9 illustrates an exploded view of the components of pressure control arranged in the upper housing part 210. The sealing surface 52 is also a component of pressure control. Because the sealing surface 52 is arranged on the filter element 100, the sealing surface is depicted in FIG. 8.

(52) The valve closing body 310 and the membrane 320 perform a vertical stroke movement in the pressure control (see FIG. 9). In this vertical stroke movement, the valve closing body 310 and the membrane 320 are moved to the filter element 100 and away from the filter element.

(53) The components of pressure control illustrated in FIG. 9 include: the pressure control element cover element 214, which is configured to cover the first housing part 210 and has an opening to the atmosphere; the valve closing body 310; the membrane 320; preferably at least one insert 350 that is arranged between the membrane 320 and the valve closing body 310 and is configured for pressure control; the return spring 330; and the first housing part 210.

(54) The return spring 330 is arranged on the side of the valve closing body 310 that faces away from the valve seat 52, and is supported down in the insert 350, which preferably also has an opening. The return spring 330 is thus located on the atmosphere side. The valve closing body 310 preferably has at least one and particularly preferableas is presently shownthree or four continuations 311 that protrude through at least one opening of the insert 350. The return spring may thus preferably be axially mounted between the insert 350 and the continuation or continuations 311, in particular, the hooks at the end of the continuations. In this manner, the return spring 330 can exert an opening forcein particular, a force oriented away from the sealing surface 52on the valve closing body.

(55) FIGS. 12 and 13 illustrate an embodiment of an oil separator 200 of a crankcase ventilation system according to the prior art. The pressure control of this oil separator 200 is located on the side of the second housing part 220. The valve closing body 310 has the form of a dish. The valve seat 52 is here injection-molded onto the housing outside. The seal between the valve seat 52 and the valve closing body 310 happens hard to hard, in particular, through identical materials of the two components. This combination of identical materials of the valve seat 52 and the region of the valve closing body 310 that can be brought into contact with the valve seat 52 negatively affects the sealing behavior.

(56) According to an advantageous embodiment, it is provided that the return spring 330 is located on the atmosphere side in the embodiment of the present invention illustrated in FIG. 1 to 11. Preferably, the return spring is protected in a space formed by the membrane 320 and the valve closing body 310 on one side and by the pressure control valve cover element 214 on the other side. Arrangement on the outside of the fluid flow protects the spring against the influence of impurities that are contained in the fluid flow and are deposited on the spring.

(57) In contrast to the filter medium 100 illustrated in FIGS. 2 and 3, the fluid flows through the filter medium according to the prior art that is illustrated in FIG. 12 from inside to the outside. The direction of flow of the fluid is marked with an arrow.

(58) Instead of a combination seal, the crankcase ventilation system illustrated in FIG. 12 has two separated O-rings 60 in order to seal the post-filtration side 240 of the filter element 100 off from the environment and seal the pre-filtration side 250 of the filter element 100 off from the post-filtration side 240 of the filter element 100.

LIST OF REFERENCE SIGNS

(59) 10 Filter medium, in particular, non-woven wrap 12 interior or cavity enclosed by the filter medium 10 20 direction of flow of the fluid to be filtered; in particular, direction of flow of the pre-filtration fluid 500 flowing through the filter medium 10, in the present invention (see FIGS. 2 and 3) 30 Covering surface of the filter medium 10 32 Outer surface of the filter medium 10 40 Cover element of the filter medium 10; in particular, end plate of the filter medium 10 that faces the clean fluid outlet 212 42 Additional cover element of the filter medium 10; in particular, end plate of the filter element 100 that faces the oil outlet 230 44 Fastening contour of the end plate 40 configured in order to fasten the sealing element 60 46 Support contour of the end plate 40 (see FIG. 8) 50 Clean fluid discharge element; in particular, dome or nozzle configured in order to remove the clean fluidfor example, a tubular clean fluid discharge element 52 Sealing surface, in particular, valve seat of the filter element 100 of the present invention 52 Valve seat in the prior art (FIGS. 12 and 13) 60 Sealing element according to the present invention (see FIGS. 2, 3, and 8); in particular, a filter element seal, for example, to seal the pre-filtration side of the filter element 100 off from the post-filtration side of the filter element 100, and to seal the interior of the filter housing off from the environment; 60 Second embodiment for a sealing element, in particular, for a filter element seal according to the prior art (see FIG. 12) 62 Additional filter element seal; in particular, O-ring 64 Radially sealing region of the sealing element 60; in particular, a compressed region of the sealing element 60 within the filter housing 66 Axially sealing region of the sealing element 60; in particular, a compressed region of the sealing element 60 between the first housing part 210 and the additional housing part 220 70 Support element, in particular, central tube, of the filter element 100 100 Filter element; in particular, annular filter element, for example, replaceable filter element or exchangeable element 110 Longitudinal axis of the annular filter element 100 or the housing body 220 (see FIG. 8) 120 Radius of the annular filter element 100 or the housing body 220 (see FIG. 8) 130 Axis of rotation (see FIG. 2) 200 Oil separator of the crankcase ventilation system of the present invention (FIG. 1 to 4, 9, and 10) 200 Oil separator of the prior art (FIGS. 12 and 13) 210 First or upper housing part of the oil separator 200; in particular, housing cover of the filter housing of the oil separator 200 212 Clean fluid outlet of the oil separator 200 of the present invention; in particular, clean fluid outlet of the first or upper housing part 210 212 Clean fluid outlet of the oil separator of the prior art (FIGS. 12 and 13) 214 Pressure control valve cover element 220 Additional, second, or lower housing part of the oil separator 200 of the present invention (FIGS. 1 to 3 and 10); in particular, housing body of the filter housing of the oil separator 200 220 Lower housing part of the oil separator 200 of the prior art (FIGS. 12 and 13) 222 Inlet for pre-filtration fluid, in particular, for oil-containing gas, for example, for oil-containing air, of the oil separator 200 of the present invention (FIGS. 1, 2, and 4) 222 Inlet for pre-filtration fluid, in particular, for oil-containing gas, for example, for oil-containing air, of the oil separator of the prior art (FIGS. 12 and 13) 230 Oil outlet 240 Post-filtration space or post-filtration side of the filter element 100 of the present invention 240 Post-filtration space or post-filtration side of the filter element according to the prior art (see FIG. 12) 250 Pre-filtration space or pre-filtration side of the filter element 100 of the present invention 250 Pre-filtration space or pre-filtration side of the filter element according to the prior art (see FIG. 12) 310 Valve closing body, in particular, control pin, of the oil separator 200 of the present invention 310 Valve closing body, in particular, control pin, of the prior art (FIGS. 12 and 13) 311 Continuations; in particular, hook-shaped continuations which protrude upward from the valve closing body and with which the return spring 330 can engage, the continuations preferably being integral with the valve closing body 312 Contact surface of the valve closing body for contacting with the sealing surface 52 of the filter element 100, in particular, in order to close the valve 320 Valve closing body sealing element; in particular, a membrane surrounding the valve closing body 320, for example, a membrane extending between the valve closing body 310 and the first housing part 210 320 Valve closing body sealing element of the prior art (FIGS. 12 and 13) 330 Return spring of the oil separator 200 of the present invention 330 Return spring of the prior art (FIGS. 12 and 13) 340 Flow channel arranged between the valve closing body 310, in particular, the valve closing body sealing element 320, and the sealing surface 52 350 Insert configured for pressure control 410 Housing of the crankcase ventilation system 500 Pre-filtration fluid, in particular, oil-containing gas, for example, oil-containing air 510 Clean fluid, in particular, clean gas, for example, clean air 600 Force exerted through the pressure prevailing in the clean air outlet 212, in particular, suction pressure, for example, suction vacuum pressure 610 Force exerted through the pressure prevailing in the interior 12 of the filter medium 10, in particular, the crankcase pressure 620 Force exerted through the return spring 330 700 Range of the first control characteristic line where the slope thereof is dependent on the dimensions, in particular, on the area ratios A.sub.M/A.sub.D 702 Range of the second control characteristic line where the slope thereof is dependent on the dimensions, in particular, on the area ratios A.sub.M/A.sub.D 710 Point of intersection of the first control characteristic line with the Y-axis, which shows the pressure drop when the pressure control valve is open 712 Point of intersection of the second control characteristic line with the Y-axis, which shows the pressure drop when the pressure control valve is open 720 Inflection point of the first control characteristic line as a function of the compression spring or spring rate of the return spring 330 722 Inflection point of the second control characteristic line as a function of the compression spring of the return spring 330 or the spring rate of the return spring 330 800 Overpressure valve A.sub.M Cross-sectional area of the membrane 320 A.sub.D Cross-sectional area of the inner diameter .sub.D of the sealing surface 52, or the cross-sectional area of the inner diameter of the end surface of the clean fluid discharge element 50 facing away from the filter element 100 .sub.M Cross-section diameter of the membrane 320 .sub.D Cross-sectional inner diameter of the sealing surface 52 or inner diameter of the end surface of the clean fluid discharge element 50 facing away from the filter element 100