Filter Element and Filter System with a Filter Element

Abstract

A filter element has a filter body with a first end face and a second end face opposite the second end face in a direction of a longitudinal axis of the filter body. A first open end plate is arranged at the first end face. A second closed end plate is arranged at the second end face. The second end plate has a sealing structure and the sealing structure is adapted to seal, when the filter element is installed in a housing, a region between the second end plate and a cover of the housing relative to an interior space of the housing. The sealing structure is a ring surrounding an outside circumference of the second end plate and has a sealing surface directed in radial direction outwardly.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of German patent application Nos. 10 2013 014 488.4, filed Sep. 2, 2013; 10 2013 014 489.2, filed Sep. 2, 2013; 10 2013 014 507.4, filed Sep. 2, 2013; 10 2013 014 492.2, filed Sep. 2, 2013; 10 2013 014 491.4, filed Sep. 2, 2013; and 10 2013 014 493.0, filed Sep. 2, 2013. The entire contents of the aforesaid German patent applications being incorporated herein by reference and to the fullest extent of the law.

This application claims the benefit of U.S. provisional patent application Nos. 62/038,312, filed: Aug. 17, 2014; 62/038,575, filed: Aug. 18, 2014; 62/038,601, filed: Aug. 18, 2014; 62/038,920, filed: Aug. 19, 2014; 62/038,672, filed: Aug. 18, 2014 and 62/038,869, filed Aug. 19, 2014. The entire contents of the aforesaid provisional patent applications being incorporated herein by reference and to the fullest extent of the law.

BACKGROUND OF THE INVENTION

The invention relates to a filter element, in particular for use as an air filter for an internal combustion engine as well as a filter system for installation of such a filter element.

DE 29780439 U1 discloses air filter constructions, in which the filter element and the housing are constructed so that a “precleaning” process takes place, which already removes coarser dirt from the air before it comes in contact with the filter element. For example, housings have been designed for an air stream deflected therein so that the air stream is first deflected (or circumscribing it) in a circular flow or a helical pattern around the filter element and larger particles of dirt or suspended particulate matter is deposited based on a cyclone effect.

In conventional systems, a substantial amount of turbulence is associated with the air stream at the inlet opening into the system. Such turbulence can have an extremely negative effect on the efficiency of a preliminary separation. In some systems, the housing therefore encloses an interior structure to prevent this. This can cause premature clogging of the filter medium with larger suspended particles. Furthermore, the suspended particles may damage the filter element when they are carried past the filter medium at a high speed.

DE 29780439 U1 also provides an entire filter array comprising a housing, a removable and replaceable filter element, essentially as described above, and a precleaning configuration that is constructed and arranged in such a way that the air is guided tangentially when it enters the housing, i.e., in a circular or helical flow pattern, which flows around the filter element or is guided essentially around the filter element, at least at the beginning.

One object of the invention is to create a filter element having improved flow properties that will permit effective pre-separation of coarser particles of dirt.

Another object of the invention is to create a filter system for accommodating such a replaceable filter element having improved flow properties, which will permit effective pre-separation of larger particles of dirt.

SUMMARY OF THE INVENTION

According to one aspect of the invention, the aforementioned objects are achieved with a filter element that has a second end plate with a sealing structure so that, when the filter element is installed in a housing, a region between the second end plate and a cover of the housing can be sealed with respect to an interior space of the housing.

Favorable designs and advantages of the invention are derived from the additional claims, the description, and the drawings.

A filter element is proposed comprising a filter body with a longitudinal axis, a first end plate that is open or closed and is arranged on an end face and a second end plate arranged on the opposing end face. The second end plate has a sealing structure so that, when the filter element is installed in a housing, a region between the second end plate and a cover of the housing can be sealed with respect to an interior space of the housing. The first end plate is preferably designed to be open, i.e., has a central opening for discharging filtered fluid, and the second end plate is designed to be closed. However, the invention is also conceivable with a design having two open end plates or having a single sealing structure or an additional sealing structure on a first open end plate.

The filter element, whose filter body is designed to be permeable for the medium to be filtered as intended and which is closed by end plates at both ends with one of the end plates usually being impermeable for the medium to be filtered, is advantageously arranged in a filter system in such a way that the medium to be filtered, i.e., dust-laden air, for example, flows through an inlet into the housing and is passed tangentially by the filter element. Due to the tangential oncoming flow of the filter element, the flow is guided in a rotating motion around the filter element, a so-called cyclone motion. In this cyclone pre-separation, centrifugal forces caused by the rotation of the flow act on any larger particles of dust and dirt that might be present in the air and it is therefore possible to separate most of these particles in advance. In the prior art, the medium to be filtered can flow through the region between the closed end plate of the filter element and the cover of the housing so that, first of all, turbulence may be created in the interior space of the housing, which can reduce the efficacy of the cyclone effect. On the other hand, some of the coarser dirt may be deposited in the region of the end plate. According to the invention, the end plate therefore has a sealing structure which seals the region between the end plate and the cover of the housing from the remaining interior space of the housing when the filter element is installed.

The sealing structure may be designed as an elastic ring, for example, which is in contact with the exterior circumference of the filter body directly below or at the level of the end plate. If the cover of the housing is placed on the housing over the filter element, then a suitably designed interior contour of the cover in the form of an interior cover flange will slide over the sealing structure and will thus seal the space over the sealing structure, i.e., in the region of the end plate, with respect to the remaining interior space of the filter system. This sealing structure in the form of a ring may be connected by individual webs to the end plate to thereby ensure that, even with a narrow tolerance situation in placement of the cover, the sealing structure cannot be shifted downward and impair the sealing effect.

To achieve a reliable sealing effect of the sealing structure, it is expedient when the outside diameter of the sealing structure is designed to be larger than the inside diameter of the interior cover flange, wherein coverage of a few tenths of a millimeter is sufficient, depending on the choice of material. The sealing structure in the form of a sealing lip, for example, is then in close contact with the contour of the interior cover flange. Flow can no longer pass around the region between the end plate and the cover, and the turbulence in the medium to be filtered is reduced. The degree of preliminary separation achieved by the filter system is therefore fortunately always increased substantially because the flow can follow the desired cyclone movement better and the larger particles of dirt can be deposited on the exterior wall of the housing and can be discharged through a dirt outlet. Since the region between the end plate and the cover is outside of the flow path, eddies that occur there and deflections of the air flow rotating in the housing contribute only unnecessarily to the pressure drop of the filter system. The kinetic energy of the rotating flow at this location cannot be utilized efficiently for separation of contaminants.

In order to achieve the aforementioned effects and advantages, it may be in particular sufficient when the sealing action of the sealing structure is dust-proof. A completely flow-proof or waterproof seal is therefore advantageous but is not absolutely necessary technically.

The sealing structure can advantageously enclose a circumference of the second end plate in the form of a ring. For example, the sealing structure may enclose the end plate in the form of an O ring which sits on the radially outside circumference of the end plate. There can therefore be a very reliable and uniform sealing action of the region between the end plate and the cover of the housing. The fit of the filter element relative to the inside diameter of the cover may be adjusted in a suitable way by the thickness of the O ring in order to achieve easy assembly of the cover over the housing and/or of the filter element and also to achieve a reliable seal, on the other hand.

Furthermore, the sealing structure may be interrupted and comprised of segments, either regularly or irregularly. Such an arrangement may prove advantageous when the assembly of the cover turns out to be too difficult. Assembly can be facilitated by such an interrupted sealing structure and nevertheless the flow around the region between the end plate and the cover with the medium to be filtered can be suppressed as effectively as with the continuous arrangement.

In an advantageous embodiment, the sealing structure has a sealing surface, which is directed radially outward, in particular for sealing on a skirt or a wall section of the cover that is retracted in the direction of the interior of the housing (displaced inwardly). This has the advantage that no permanent axial force that is to be built up by tension on the filter element in the housing is necessary on the sealing structure during operation, which would additionally increase the axial load on the filter element.

In another advantageous embodiment, the sealing structure is formed by a sealing lip running peripherally in a ring shape (annular) around the radial outside circumference of the end plate. The sealing lip preferably extends radially beyond the circumference of the filter body and/or the radial outside surface of the end plate.

The sealing structure may advantageously be integrally molded on the second end plate. This facilitates assembly of the filter element because the sealing structure cannot be lost during storage or displaced during assembly in this way. In any case, a sealing structure that fits the filter element is also present during assembly and cannot be misplaced. Due to the fact that the sealing structure can be attached by molding later on, the material may be selected with a suitable elasticity for the sealing effect and is not limited to the material of the end plate.

On the other hand, in another advantageous embodiment, the sealing structure may also be embodied in one piece (monolithic) with the second end plate. If the material of the end plate should have an elasticity that is suitable for the sealing effect, the sealing structure with the end plate may also be integrally molded onto the filter body in one operation and thus embodied in one piece (monolithic) with the end plate. This is a very inexpensive way to implement an additional sealing structure. The advantages mentioned above, namely that the sealing structure cannot be lost and also cannot be inadvertently switched, also apply here.

The first and/or second end plate is/are preferably made of a casting compound that can be processed in casting molds such as, for example, polyurethane or preferably polyurethane foam. The filter body can then be embedded in the end plate material in the casting operation. The external shape of the sealing structure can be predetermined easily by the casting mold in the radially outer region of the end plate to be formed.

In an advantageous embodiment, the filter body may consist, for example, of filter bellows with zigzag folding (pleating), designed to be closed in the shape of a ring. The pleating can be produced, for example, by knife pleating for longer filter bodies or rotary pleating. The filter bellows may be made, for example, of paper or cellulose or of a fiber blend of synthetic fiber and cellulose. The filter bellows may also be embodied with a smooth surface, rolled and/or with a surface shaped with various embossed shapes for reinforcement and/or to create cavities for deposition of dust. The filter bellows may have a coating and/or impregnation to repel moisture. Alternatively, it may also be coated with nanofibers. The filter body may furthermore be reinforced structurally with a fiber wrapping. The use of these materials as the filter medium constitutes a very economical option for implementing such a filter element. At the same time, the shaping described here offers a stable configuration so that a self-supporting design of the filter body and thus favorable assembly properties are provided.

The filter element may expediently be used as an air filter, in particular as an air filter for an internal combustion engine. The reliable operation of internal combustion engines is also based on reliable and favorable filtering of the intake air for the combustion operation. The filter element described here represents an economical possibility for doing so.

Use of the filter element as a particle filter, in particular as a particle filter for an internal combustion engine is also advantageous. Here again, reliable assembly and economical replaceability of the filter element described here are of crucial importance.

According to another aspect, the invention relates to a filter system having an inventive filter element comprising a housing which is constructed essentially to be concentric about a longitudinal axis, a cover that seals the housing and is also constructed to be concentric about the longitudinal axis, an inlet arranged on the housing and/or cover for supplying the medium to be filtered, in particular air, wherein an outlet for discharging the filtered medium is provided on the housing so that it is concentric with the longitudinal axis, a skirt or a wall section that is retracted (displaced inwardly) in the direction of the interior of the housing on the cover or on the housing with which the sealing structure of the filter element is in contact so that the volume region formed axially between the end plate and the cover or the housing is separated from the flow-through region of the housing which surrounds the filter body in a ring shape.

Thus a sealing contour which corresponds to a radial seal on the first end plate of the filter element is provided on the housing in the region of the outlet, so that the filter element is arranged interchangeably in the housing of the filter system. The important advantage of such a filter system lies in the secure and stable assembly of the filter element as well as a very economical interchangeability of the filter element in a service situation. Rapid replaceability is extremely important especially for short service lives as in the case of use in agricultural and construction machinery.

A cyclone separator may advantageously be provided in the region of the inlet of the filter system and a dirt outlet may be provided on the housing or on the cover. This cyclone separator comprises a guiding geometry, which induces rotation of the medium to be filtered. An inlet is preferably directed tangentially into the interior of the housing, preferably at the outlet end of the housing so that the flow is forced into a rotational movement around the filter element. Due to this rotation, the dirt is concentrated in the region of the housing wall and is discharged through a dirt outlet at a suitable location, for example, on the housing cover on the end of the housing opposite the outlet end. Due to the pre-separation of most of the dirt out of the air to be filtered, the service life of the actual filter element can be prolonged significantly.

The sealing structure preferably forms a seal with respect to a so-called skirt radially. The skirt is defined as a cylindrical tubular wall, which extends axially from the cover of the housing (or from the other housing part in the region of the outlet) over a portion of the length of the filter element (for example, between 20% and 40% of the length of the filter element) into the housing interior and preferably surrounds the filter element coaxially. Between the skirt and the outside wall of the housing and/or of the cover, an annular flow region is thus formed in which the fluid can rotate freely. The skirt surrounds the filter element at a slight distance, preferably less than 10 mm, especially preferably less than 5 mm. The sealing structure is preferably in contact with the skirt radially, in particular forming a seal, It has surprisingly been found that the seal thereby obtained for the region situated between the end plate and the cover and thus the separation of the region from the flow-through region of the housing results in an improvement in the cyclone pre-separation performance.

In comparison with a filter system without a skirt extending along the filter body, in which there is also rotation of the flow in a region situated between the end plate and the cover, there is also a positive effect due to the seal according to the invention when the skirt or a wall section of the cover, which is retracted in the direction of the interior of the housing or a wall section of the other housing part, extends up to the end plate of the filter element, so that the sealing structure is in contact with the skirt.

According to another embodiment of the invention, a secondary element may be arranged in the interior of the filter element. The secondary element, which may consist of a load-bearing structure of a cylindrical configuration, which is lined with a permeable filter medium, for example, a nonwoven, has the function of keeping the outlet of the filter system closed when replacing the filter element so that no dirt can penetrate into this region while the filter element is being cleaned or replaced. The secondary element, which may be arranged in the interior of the filter element concentrically with the longitudinal axis of the filter system, is connected to the housing by means of a screw connection, for example, and is provided with a seal with respect to the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional advantages are derived from the following description of the drawings. The drawings illustrate exemplary embodiments of the invention. The drawings, the description and the claims contain numerous features in combination. Those skilled in the art will expediently also consider the features individually and combine them into appropriate additional combinations.

FIG. 1 is a perspective view of a filter system according to one exemplary embodiment of the invention with a tangential inlet, a central outlet, and a dirt outlet at the bottom.

FIG. 2 is a longitudinal section through a filter system according to one exemplary embodiment of the invention.

FIG. 3 shows a filter element with a sealing structure according to one exemplary embodiment of the invention, integrally molded on the second end plate.

FIG. 4 is a section through the cover part of a filter system according to one exemplary embodiment of the invention, having a sealing structure integrally molded on the second end plate.

In the Figures, same or similar components are labeled with the same reference numerals. The Figures merely show examples and are not to be understood as limiting.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a perspective view of a filter system 100 according to one exemplary embodiment of the invention, which may be used, for example, as an air filter for an internal combustion engine, having a tangential inlet 102, a central outlet 104 on one end of the housing, and a dirt outlet 106 on the bottom. This shows a round filter structure, which consists of a housing 108 that is sealed with a cover 110, for example, with a screw closure or a bayonet closure. In use as an air filter system, dust-laden air flows into the inlet 102 that is arranged tangentially to the air filter element installed in the interior so that a rotational movement is induced in the air in the interior of the housing 108 by a flow guard on the filter element. The filter element and the oncoming flow guard are not shown in the drawing. Centrifugal forces act on the dust particles in the flowing air due to the cyclone effect induced by rotational movement of the air so that the dust particles are partially separated on the housing wall and can flow out of the filter system 100 through the dirt outlet 106. The filter element is therefore under reduced load and the service life of the filter element is increased. The cleaned air can be discharged out of the housing 108 through the central outlet 104.

FIG. 2 shows a longitudinal section through a filter system 100 according to one exemplary embodiment of the invention with a tangential inlet 102, a central outlet 104, and a dirt outlet 106 at the bottom. The housing 108 of the filter system 100 is closed with a cover 110 on one front face 120. A filter element 10 consists essentially of a filter body 12 which is concentric around the longitudinal axis L and is sealed at the two opposing end faces 15, 17 with a first open end plate 16 and a second end plate 18 which may be made of polyurethane foam or an elastomer. The filter body 12 may consist of filter bellows folded in a zigzag pattern (pleated) and closed to form a ring. The pleating may be produced, for example, by knife pleating for longer filter bodies 12 or by rotational pleating. The filter bellows may be made of paper, cellulose or of a fiber blend of synthetic fiber and cellulose, for example, and may be finished with a smooth surface, with a surface designed to be rolled and/or embossed in various forms for reinforcement and/or creation of cavities for dust deposition. The filter bellows may have a coating and/or impregnation to repel moisture. Alternatively it may also be coated with nanofibers. The filter body 12 may also be reinforced structurally with a filament winding.

The second end plate 18 has supporting nubs 20 which are preferably arranged at a regular distance relative to each other in a circular arrangement around the longitudinal axis L and extend axially away from the axial outer surface of the second end plate; when installed in the receiving housing 108, the nubs 20 are supported axially on the cover 110 on an inner surface, for example, on an inner contour 114 of the cover 110. A support pipe 14, which is permanently mounted on the housing, is arranged concentrically around the longitudinal axis L in the interior 50 of the filter element 10 and is permanently connected to the housing 108 at the outlet end of the support pipe 14. The surface of the second end plate 18 facing the support pipe 14 rests on the open end of the support pipe 14, which faces the end plate 18. When the inner cover contour 114 of the cover 110 is pressed onto the end plate 18, this force is transferred through the supporting nubs 20 into the end plate 18 which remains supported on the support pipe 14. The filter element 10 is stressed axially against the cover 110 in this way and thus against the housing 108 by means of the second end plate 18 and thereby experiences a secure support on the end face 17, i.e., the end of the filter element 10 facing the cover. Since the supporting nubs 20 keep the end plate 18 spaced apart from the cover 110, an open region 119 is formed between the cover 110 and the end plate 18; this region 119 is not filled with material and is also known as dead volume.

In addition, rib-shaped elevations 112 are provided in the interior contour 114 of the cover, with which the elastic material of the second end plate 18 can interlock or in which it can be anchored so that the filter element 10 is thereby secured against possible turning caused by vibrations during operation. In addition, recesses 22, which permit additional interlocking or anchoring of the support pipe 14 with the end plate 18, are also conceivable on the end of the support pipe 14 facing the end plate 18 to thereby ensure a further anti-rotation locking action of the filter element 10 to protect from vibration-caused turning.

A radial seal 26, which corresponds to the sealing contour 116 of the housing 108, i.e., is in sealing contact therewith, is provided on the opposing end face 15 of the filter element 10 on the first end plate 16. The filter element 10 can seal the filtered air space from the unfiltered air space by means of this sealing contour.

Dust-laden air can flow in the direction of the arrow 40 through the inlet 102, which in this case is depicted as a tangential inlet and facilitates cyclone operation due to the rotational motion of the air created by means of a cyclone separator 36. Due to the rotational movement, dust particles may be deposited on the interior housing wall and discharged out of the filter system 100 due to the force of gravity through the dirt outlet 106 when the filter housing 108 is installed horizontally. This pre-separation takes place in an interior space 118 of the housing, preferably on the inside wall of the housing 108 in which the dust-laden air can flow freely. Region 119 is arranged between the second end plate 18 and the cover 110 of the housing 108 and can also be referred to as a dead volume. The region 119 is sealed by a sealing structure 24 which is formed in one piece (monolithic) with the second end plate 18 and made of the same material so that there cannot be any circulating flow in the region 119. This sealing structure 24 may be applied in the form of a ring, for example, on the circumference of the end plate 18.

On the other hand, in order to suppress the circulating flow in the region 119, it is not absolutely necessary for the sealing structure 24 to be sealed continuously with the housing 108 and/or cover 110 over the circumference of the end plate 18. The sealing structure 24 may also be interrupted and comprised of segments in order to suppress the circulating flow. As shown in FIG. 2, the sealing structure preferably forms a radial seal with respect to a so-called skirt 240. The skirt 240 is a cylindrical tubular wall which extends axially from the cover 110 of the housing 108 (or also from the other housing part 108 in the region of the outlet 104) over a portion of the length of the filter element 10 (for example, between 20% and 40% of the length of the filter element 10) into the housing interior and thereby surrounds the filter element 10, preferably coaxially. Thus, an annular flow region is formed between the skirt 240 and the exterior wall of the housing 108 and/or of the cover 110 so that the fluid can rotate freely in this annular region. The skirt 240 surrounds the filter element 10 at a slight distance, preferably less than 10 mm, especially preferably less than 5 mm. The sealing structure 24 is preferably in sealing contact radially with the skirt 240. It has surprisingly been found that the resulting seal of the region 119 situated between the end plate 18 and the cover 110 and thus the separation of the region 119 from the flow-through region of the housing 108 leads to an improvement in the cyclone pre-separation efficiency.

After partial separation of the dust particles during operation, the air then flows further through the filter body 12 in the direction of the arrows 42, 44 into the interior 50 of the filter element. Dust particles above a certain size, depending on the filter medium, still remain caught in the filter medium. Depending on the dust input, the filter element 10 must therefore be replaced after a certain service life. The filtered air flows out through the outlet 104 in the direction of the arrow 46.

A secondary element 28 is mounted in the interior 50 of the filter element 10. This secondary element consists essentially of a load-bearing structure, i.e., the body 52, and a relatively permeable filter medium, for example, a nonwoven. When the filter element 10 in the housing 108 is replaced, the secondary element 28 remains behind to protect the downstream air passage, for example, of an internal combustion engine, from dust particles and other objects penetrating into it. The secondary element 28 is inserted at the open end 54 into a housing seat 58 on the outlet part of the housing 108. The second end plate 18 of the filter element 10 sits on the closed end 55 of the secondary element 28 so that, when the housing cover 110 is closed, a force can be directed through the supporting nubs 20 on the end plate 18 into the closed end of the secondary element 28 and the secondary element 28 is thereby tightly pressed into its housing seat 58. The closed end of the secondary element 28 is designed as a handle 56 with which the element 28 can be removed again from the housing seat 58 and thus from the housing 108.

Filter systems such as those illustrated in FIGS. 1 and 2 are usually used in construction machines and in the field of agricultural machines. They are characterized by a great robustness and have a short service life because of the high filtration load. A filter system with a loaded filter element must tolerate an increase in weight of 10 kg or more.

FIG. 3 shows a view of the filter element 10 according to FIG. 2 with a sealing structure 24 designed in one piece (monolithic) with and made of the same material as the second end plate 18 according to one exemplary embodiment of the invention. The filter element 10 consists of a filter body 12 which is sealed with the end plates 16, 18 at the two end faces 15, 17. The second end plate 18 has supporting nubs 20 on the top side for axial bracing and radial support in a housing when the filter element 10 is inserted and the housing is sealed from the outside with a cover where the filter element 10 can interlock and be tensioned by means of the supporting nubs 20 on the end plate 18. The sealing structure 24 is represented in FIG. 3 as a radial sealing ring which is designed in one piece (monolithic) with the end plate 18 and is made of the same material. However, the sealing structure 24 may also be integrally molded with the end plate 18 by an injection molding process, for example, in a two-component injection molding process, in which the sealing structure 24 is integrally molded as a soft component around a hard, injection-molded end plate 18. In addition, the sealing structure 24 could also be implemented as an interrupted structure because a complete seal is not required for suppressing the circulating flow on the end plate 18 in the region between the end plate 18 and the cover 110 of the housing.

FIG. 4 shows a section through the cover part of a filter system 100 according to one exemplary embodiment of the invention, in particular through the filter system shown in FIG. 1 with a filter element as shown in FIGS. 2 and 3, wherein a sealing structure 24 that is designed in one piece and is made of the same material as the second end plate 18 is shown. Illustrated is a portion of the filter element 10 consisting of the filter body 12 and the second end plate 18 as well as, in the interior of the filter element 10, the support pipe 14 mounted in the housing and also a secondary element 28 mounted also in a housing seat. After mounting the filter element 10 in the housing 108 and closing the cover 110 on the front face 120, the cover 110 presses on the second end plate 18 via the supporting nubs 20. On the other side, the end plate 18 presses on the end of the support pipe 14 that is facing the end plate 18 and also presses on the closed end 55 of the secondary element 28 provided with the handle 56. The drawing shows the cover 110, the support pipe 14, and the secondary element 28 penetrating into the end plate 18. Since the material of the end plate 18 is expediently polyurethane foam or a similar elastic material, the end plate 18 is actually compressed between the cover 110, support pipe 14, and secondary element 28 and thereby transmits the force from the cover 110 to the support pipe 14 and the secondary element 28. The filter element 10 is securely clamped via the end plate 18 in this way and is thus held securely. Furthermore, the end plate 18 also presses the secondary element 28 securely into its housing seat.

The sealing structure 24 mounted on the end plate 18 can be seen between the end plate 18 and the cover 110. The sealing structure 24 is responsible for sealing the interior space of the housing against the region 119 between the end plate 18 and the cover 110 to thereby prevent a circulating flow of unfiltered medium around the region 119. Therefore, soiling of the region 119 is prevented, on the one hand. Furthermore, an increased preliminary deposition of dirt particles is achieved by means of the cyclone effect due to a substantially homogenized flow of the unfiltered medium in the interior space of the housing.

The sealing structure 24 may be embodied, for example, as an elastic ring, which rests on the exterior circumference of the filter body 12 directly beneath or at the level of the end plate 18. When the cover 110 of the housing 108 is placed onto the housing 108 over the filter element 10, a suitably designed interior contour of the cover 110, for example, in the form of an interior cover flange, slides over the sealing structure 24 and therefore seals the space above the sealing structure 24, i.e., in the region of the end plate 18, with respect to the remaining interior 50 of the filter system 100. This sealing structure 24 in the form of a ring may be connected to the end plate 18 by means of individual webs to thereby ensure that even with a very tight tolerance situation, the sealing structure 24 cannot be displaced downward when placing the cover 110 in position and cannot cancel or impair the sealing effect. The detail view of FIG. 4 shows clearly that the sealing structure 24, as shown, is preferably designed in one piece (monolithic) with the end plate 18 which is closed and preferably cast of a polyurethane or polyurethane foam.

The sealing structure in this case is formed by a sealing lip that extends in an annular shape around the radial outside circumference of the end plate 18. Its axial extension amounts to only a fraction of the thickness of the end plate 18 in the axial direction. The axial extension of the sealing lip, referred to below as the width, preferably amounts to less than 10 mm, especially preferably less than 5 mm. The sealing lip preferably extends radially beyond the circumference of the filter body 12 and/or the radial outside surface of the end plate 18; the radial extension is preferably between 1 mm and 10 mm.

While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

Claims

1. A filter element comprising:

a filter body comprising a first end face and a second end face opposite the second end face in a direction of a longitudinal axis of the filter body;

a first open end plate arranged at the first end face;

a second closed end plate arranged at the second end face;

wherein the second end plate comprises a sealing structure and the sealing structure, when the filter element is installed in a housing, is adapted to seal a region between the second end plate and a cover of the housing relative to an interior space of the housing.

2. The filter element according to claim 1, wherein the sealing structure is a ring surrounding an outside circumference of the second end plate.

3. The filter element according to claim 1, wherein the sealing structure has a sealing surface directed in radial direction outwardly.

4. The filter element according to claim 3, wherein the sealing structure is a sealing lip in the form of a ring surrounding a radial outside circumference of the second end plate.

5. The filter element according to claim 4, wherein the sealing lip extends radially beyond a circumference of the filter body.

6. The filter element according to claim 4, wherein the sealing lip extends radially beyond a radial outside surface of the second end plate.

7. The filter element according to claim 4, wherein the sealing lip extends radially beyond a circumference of the filter body and beyond a radial outside surface of the second end plate.

8. The filter element according to claim 1, wherein the sealing structure is interrupted and comprised of segments.

9. The filter element according to claim 1, wherein the sealing structure is integrally molded on the second end plate.

10. The filter element according to claim 1, wherein the sealing structure and the second end plate form a monolithic piece.

11. The filter element according to claim 10, wherein the sealing structure and the second end plate are made of polyurethane or polyurethane foam cast in a casting mold.

12. The filter element according to claim 1, wherein the filter body is folded in zigzag pleats and is formed as a closed ring.

13. The filter element according to claim 12, wherein the filter body is made of paper; or cellulose; or of a fiber blend of synthetic fiber and cellulose; or is comprised of a cellulose fiber layer and a synthetic fiber layer.

14. The filter element according to claim 1 as an air filter.

15. The filter element according to claim 1 as an air filter for an internal combustion engine.

16. A filter system comprising:

filter element according to claim 1;

a housing comprising a housing wall configured to be essentially concentric about a longitudinal axis of the housing;

a cover attached to the housing and sealing the housing, the cover configured to be essentially concentric about the longitudinal axis of the housing;

an inlet arranged on the housing or on the cover and adapted to supply a medium to be filtered to the housing;

a skirt or a wall section disposed in a radial direction inwardly relative to the housing wall and disposed on the cover or on the housing;

wherein the sealing structure of the filter element contacts the skirt or the wall section so that a volume region formed axially between the second end plate of the filter element and the cover or the housing is separated from a flow-through region of the housing which surrounds the filter body annularly.

17. The filter system according to claim 16, further comprising an outlet arranged on the housing and adapted to discharge the medium that has been filtered, wherein the outlet is concentric to the longitudinal axis, wherein the housing has a sealing contour in the vicinity of the outlet, wherein the sealing contour corresponds with a radial seal provided on the first end plate, wherein the filter element is adapted to be replaceably disposed in the housing.

18. A method for improving a pre-separation efficiency of a filter system, the filter system comprising a cylindrical housing with a cover and a cylindrical filter element that is in the form of a ring and comprises two end plates at opposite end faces, wherein inflowing fluid supplied into an annular flow region between a housing wall of the cylindrical housing and the filter element is induced to rotate, the method comprising:

arranging, on the cover or on the housing, a skirt or a wall section in a radial direction inwardly relative to the housing wall;

providing a sealing structure on an end plate of the filter element;

separating the annular flow region from a volume region, formed axially between the end plate with the sealing structure and the housing or the cover, by contacting the skirt or the wall section with the sealing structure.