Filter insert for a filter unit

Abstract

The invention relates to a filter insert (10) for a filter unit which comprises an electric supply module, wherein the filter insert (10) can be inserted into an insert receiving region of the filter unit in a plurality of insert orientations. The filter insert comprises an electrically insulating filter material (14), at least one electrically conductive polarization element (16a, 16b), to which an electric voltage can be applied in order to polarize the filter material (14), and a contacting assembly, which is connected to the at least one polarization element (16a, 16b), for producing an electric contact between the filter insert (10) and the electric supply module.

Description

[0001] Filter insert for a filter unit

[0002] The invention relates to a filter insert for a filter unit comprising an electrical supply module, wherein the filter insert can be inserted into an insert receiving area of ​​the filter unit in several insertion orientations, with an electrically insulating filter material, at least one electrically conductive polarization element to which an electrical voltage can be applied to polarize the filter material, and a contacting arrangement connected to the at least one polarization element for electrically contacting the filter insert with the electrical supply module.

[0003] Furthermore, the invention relates to a filter unit with a filter insert, an electrical supply device, an insert receiving area in which the filter insert can be inserted in several insertion orientations, and a counter contact field connected to the electrical supply device and arranged on the insert receiving area for electrically contacting the filter insert.

[0004] For rectangular filter inserts that require electrical contact and do not have an alignment or guide contour specifying a specific installation position, twisting the filter insert can lead to improper installation. Improper installation can compromise or even eliminate the electrical contact of the filter insert, thus impairing or eliminating current-supported functions, such as a polarization function, which typically results in a significant reduction in filter performance.

[0005] To prevent misalignment of the filter insert during insertion, it is already common practice for non-electrified filter inserts to apply alignment aids, such as arrows, to the filter insert. These are intended to assist the user in correctly aligning the filter insert. This can only reduce, but not eliminate, the risk of misalignment of the filter insert when inserting it into the insert receiving area of ​​the filter unit.

[0006] The object underlying the invention is therefore to eliminate or at least further reduce the risk of improper installation of the filter insert.

[0007] The object is achieved by a filter insert of the type mentioned at the outset, wherein the contacting arrangement of the filter insert according to the invention has a plurality of contacting fields each assigned to at least one insertion orientation of the filter insert, in particular contacting fields assigned to only one insertion orientation of the filter insert, via which the filter insert can be electrically contacted with a predetermined counter-contact field on the insert receiving area of ​​the filter insert in a plurality of insertion orientations of the filter insert.

[0008] The contact fields of the contact arrangement are each assigned, in particular, to an insertion orientation of the filter insert. The filter insert can have a cuboid basic shape. Due to its basic shape and the free space in the insert receiving area, the filter insert can only be inserted into the insert receptacle of the filter unit in a limited number of different insertion orientations, for example, in four. In the respective insertion orientations of the filter insert, contact is made with the filter insert via the contact field assigned to the current insertion orientation of the filter insert.The contacting arrangement can, for example, have two contact fields, each assigned to an insertion orientation of the filter insert, via which the filter insert can be electrically contacted with the predetermined mating contact field in the insert receiving area of ​​the filter unit in two insertion orientations of the filter insert. Alternatively, the contacting arrangement can, for example, have four contact fields, each assigned to an insertion orientation of the filter insert, via which the filter insert can be electrically contacted with the predetermined mating contact field in the insert receiving area of ​​the filter unit in four insertion orientations of the filter insert.

[0009] Alternatively, the contacting arrangement can have only one contact pad on each of two opposite sides. The contact pads can be designed so that they can each be contacted for two insertion orientations. For this purpose, the contact pads can be designed point-symmetrically.

[0010] For filter inserts where a required flow direction exists, for example, due to a specific sequence of media layers, it is also possible to deliberately not have assigned contact pads for some of the insertion orientations. This means that the filter insert can only be provided with contact pads for insertion orientations with the correct orientation for the flow direction. Thus, if the filter insert is installed in the incorrect insertion orientation, no electrical contact is established between the mating contact pad and a contact pad. In this case, a control system can detect the missing contact and issue a signal, for example, a visual and / or acoustic.

[0011] The filter insert can be a filter insert for a cabin air filter, particularly for a vehicle. The electrical conduction paths of the contact arrangement can be interrupted, for example, slotted, so that the electrically conductive connection to the polarization element is only established when the filter insert is inserted via a bridging conductor in the insert receiving area.

[0012] In a preferred embodiment of the filter insert according to the invention, two contact pads are arranged on the same side of the filter insert. The two contact pads arranged on the same side are located, for example, on a lateral outer surface of the filter insert. The two contact pads arranged on the same side can be located on a long side or a narrow side of the filter insert. The two contact pads arranged on the same side are located, for example, on a lateral material strip of the filter insert and / or on a side lamination of the filter insert.

[0013] The filter insert according to the invention is further advantageously developed in that the two contact pads arranged on the same side of the filter insert have the same orientation and / or a double-mirror-symmetrical structure. Due to the double-mirror-symmetrical structure of the contact pads, they can be conceptually aligned by two reflections on two mutually perpendicular mirror planes. Due to the two contact pads arranged on the same side of the filter insert, the filter insert can be electrically contacted with the predetermined mating contact pad in the insert receiving area of ​​the filter unit in two insertion orientations of the filter insert.

[0014] In a further preferred embodiment of the filter insert according to the invention, two contact pads are arranged on opposite sides of the filter insert. Preferably, a pair of contact pads is arranged on each of the opposite sides of the filter insert, so that the filter insert has a total of four contact pads.

[0015] In a further preferred embodiment of the filter insert according to the invention, the two contact pads arranged on opposite sides of the filter insert have opposite orientations and / or a simple mirror-symmetrical structure. Due to the two contact pads arranged on opposite sides of the filter insert, the filter insert can be electrically contacted with the predetermined mating contact pad on the insert receiving area of ​​the filter unit in two insertion orientations of the filter insert. Furthermore, a filter insert according to the invention is advantageous in which the contact pads each have at least one contact point for electrically contacting a mating contact point of the predetermined mating contact pad. The contact point is preferably wider and / or higher than a conduction path adjoining the contact point.The longitudinal distance between a contact point of a first contact field and a first longitudinal end of the filter insert and the longitudinal distance between a contact point of a second contact field and a second longitudinal end of the filter insert preferably correspond. The first longitudinal end can be formed, for example, by a front-side material edge or material surface of the filter insert. The second longitudinal end can be formed, for example, by a rear-side material edge or material surface of the filter insert. Alternatively or additionally, the height distance between a contact point of a first contact field and a first height end of the filter insert and the height distance between a contact point of a second contact field and a second height end of the filter insert correspond.The first height termination can be formed, for example, by a material edge or surface on the top side of the filter insert. The second height termination can be formed, for example, by a material edge or surface on the bottom side of the filter insert. The contact points can be electrically conductive contact poles accessible from the outside.

[0016] In another preferred embodiment of the filter insert according to the invention, the contact pads each have two spaced-apart contact points for electrically contacting two spaced-apart mating contact points of the predetermined mating contact pad. A first contact point of the contact pads is configured, for example, to be contacted with a positive pole of the mating contact pad. A second contact point of the contact pads is preferably configured to be contacted with a negative pole of the mating contact pad. The two contact points of the contact pads can be spaced apart longitudinally and / or vertically. Alternatively, the first or second contact point of the contact pads can be configured to be contacted with a grounding contact of the mating contact pad.Alternatively, the first or second contact point of the contact fields can be configured to be contacted with a phase contact of the counter contact field.

[0017] Furthermore, a filter insert according to the invention is advantageous in which the longitudinal distance between a first contact point of a first contact field and a first longitudinal end of the filter insert and the longitudinal distance between a first contact point of a second contact field and a second longitudinal end of the filter insert correspond. Alternatively or additionally, the longitudinal distance between a second contact point of the first contact field and a first longitudinal end of the filter insert and the longitudinal distance between a second contact point of the second contact field and the second longitudinal end of the filter insert correspond. The first longitudinal end can be formed, for example, by a front-side material edge or material surface of the filter insert. The second longitudinal end can be formed, for example, by a rear-side material edge or material surface of the filter insert.Alternatively or additionally, the height distance between a first contact point of a first contact field and a first height termination of the filter insert and the height distance between a first contact point of a second contact field and a second height termination of the filter insert are the same. Alternatively or additionally, the height distance between a second contact point of the first contact field and a first height termination of the filter insert and the height distance between a second contact point of the second contact field and the second height termination of the filter insert are the same. The first height termination can be formed, for example, by a top-side material edge or material surface of the filter insert. The second height termination can be formed, for example, by a bottom-side material edge or material surface of the filter insert.The contact points can be externally accessible, electrically conductive contact poles. In another preferred embodiment of the filter insert according to the invention, the contact pads each comprise an electrical resistor, in particular as a voltage divider. By means of the voltage divider, a supply voltage different from the required polarization voltage can be applied to the contact pads. By appropriately tapping the voltage along the resistance path of the voltage divider, the supply voltage can be reduced to the required polarization voltage.

[0018] Furthermore, a filter insert according to the invention is advantageous in which the contact fields are formed, at least in sections, by a contact foil applied, in particular glued, to a surface of the filter insert or by a contact label applied, in particular glued, to a surface of the filter insert. By using contact foils or contact labels, the contact fields can be produced with extremely low manufacturing effort. Thus, different contact field arrangements can also be produced to realize a greater variety of variants without major adaptation effort. The contact foils or contact labels preferably comprise a carrier layer to which an electrically conductive material is applied.

[0019] In a further preferred embodiment of the filter insert according to the invention, the contact pads and / or the electrical conduction paths of the contact pads are printed at least in sections. The contact pads can, for example, be printed directly onto the side lamination of the filter insert. Alternatively, the contact pads can be created by printing an electrically conductive material onto a carrier layer of the contact foils or a carrier layer of the contact labels. A printing paste that remains electrically conductive even after curing is preferably used to print the contact pads.

[0020] In another preferred embodiment of the filter insert according to the invention, the polarizing element is designed as a polarizing layer. The polarizing layer preferably runs parallel to the electrically insulating filter material and / or is in planar contact with the electrically insulating filter material. The electrically insulating filter material is preferably an electret material or comprises an electret material.

[0021] In another preferred embodiment of the filter insert according to the invention, two electrically conductive polarizing elements, each designed as a polarizing layer, are separated from one another by the electrically insulating filter material. An electrical voltage can be applied to the polarizing layers to polarize the filter material. The electrically insulating filter material and the two electrically conductive polarizing layers preferably form a pleated layer composite. The two electrically conductive polarizing elements designed as polarizing layers are preferably connected to the contacting arrangement. The connection between the polarizing layers and the contacting arrangement generates an electric field for polarizing the filter material when contacting and energizing the filter insert.

[0022] The object underlying the invention is further achieved by a filter unit of the type mentioned above, wherein the filter insert of the filter unit according to the invention is designed according to one of the embodiments described above. With regard to the advantages and modifications of the filter unit according to the invention, reference is therefore first made to the advantages and modifications of the filter insert according to the invention.

[0023] The insert receiving area, into which the filter insert can be inserted in multiple insertion orientations, is preferably arranged within a housing of the filter unit. The housing can have an insert receiving part that provides the insert receiving area. The insert receiving part can be closed with a housing cover of the housing. To insert and remove the filter insert, the housing cover is preferably opened so that the filter insert can be pulled out of the insert receiving part or pushed into the insert receiving part. Preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying drawings. In the drawings:

[0024] Fig. 1 shows a filter insert according to the invention in a perspective view;

[0025] Fig. 2 shows the filter insert shown in Fig. 1 in a further perspective view;

[0026] Fig. 3 shows a further filter insert according to the invention in a perspective view;

[0027] Fig. 4 shows the filter insert shown in Fig. 3 in a further perspective view;

[0028] Fig. 5 shows another filter insert according to the invention in a

[0029] perspective representation; and

[0030] Fig. 6 the filter insert shown in Fig. 5 in another

[0031] Perspective representation.

[0032] Figures 1 and 2 show a filter insert 10 of a filter unit that can be used in a motor vehicle. The filter unit serves, for example, as the interior air filter of the motor vehicle.

[0033] The filter insert 10 comprises a pleated layer composite 12 consisting of several layers. The layer composite 12 comprises an electrically insulating filter material 14 and two electrically conductive polarizing elements 16a, 16b. The polarizing elements 16a, 16b are designed as polarizing layers. One polarizing layer 16a is located on a first side of the filter material 14, with another polarizing layer 16b located on the other side of the filter material 14.

[0034] Material strips 18a, 18b run along the outer lateral edges of the pleated layered composite 12. The material strips 18a, 18b form the side laminations of the filter insert 10 and are integrally bonded, for example, by adhesive bonding, to the pleated layered composite 12. The filter insert 10 further comprises a contact arrangement connected to the polarization elements 16a, 16b for electrically contacting the filter insert 10 with an electrical supply module.

[0035] The filter insert 10 can be inserted into an insert receiving area of ​​the filter unit in four different insertion orientations. The contact arrangement has a total of four contact fields 20a, 20b, 22a, 22b, each assigned to an insertion orientation of the filter insert 10, via which the filter insert 10 can be electrically contacted with a predetermined mating contact field in the insert receiving area of ​​the filter unit in the four insertion orientations of the filter insert 10.

[0036] Fig. 1 shows a first insertion orientation of the filter insert 10. In this insertion orientation of the filter insert 10, the electrical contact of the filter insert 10 is made via the contact field 20a. By rotating the filter insert 10 by 180° about the transverse axis Q, the filter insert 10 can be moved into a second insertion orientation, in which the electrical contact of the filter insert 10 is made via the contact field 20b.

[0037] Fig. 2 shows the filter insert 10 in a different orientation. Starting from the orientation of the filter insert 10 shown in Fig. 1, the filter insert 10 can be moved into a third insertion orientation by rotating the filter insert 10 by 180° about the longitudinal axis L. In the third insertion orientation, the electrical contact of the filter insert 10 is made via the contact field 22a. By further rotating the filter insert 10 by 180° about the transverse axis Q, the filter insert 10 can be moved into a fourth insertion orientation, in which the electrical contact of the filter insert 10 is made via the contact field 22b.

[0038] The contact pads 20a, 20b, 22a, 22b of the contact arrangement are thus each assigned to an insertion orientation of the filter insert 10. In the respective insertion orientations of the filter insert 10, contacting of the filter insert 10 takes place via the contact pad 20a, 20b, 22a, 22b, which is assigned to the current insertion orientation of the filter insert 10. The contact pads 20a, 20b are arranged on the same side of the filter insert 10 and on the material strip 18a. The contact pads 22a, 22b are arranged on the same side of the filter insert 10 and on the material strip 18b. The two contact pads 20a, 20b form a first contact pad pair. The contact pads 22a, 22b form a second contact pad pair. The contact fields 20a, 20b of the first contact field pair and the contact fields 22a, 22b of the second contact field pair are arranged on opposite sides of the filter insert 10.

[0039] The contact pads 20a, 20b, 22a, 22b each have two spaced-apart contact points 24a, 24b for electrically contacting two spaced-apart mating contact points of the given mating contact pad. The contact points 24a, 24b are each connected via contact paths 26a, 26b to a polarizing element 16a, 16b of the layered assembly 12, designed as a polarizing layer. An electrically conductive connection is provided between the contact points 24a, 24b of the contact pads 20a, 20b, 22a, 22b and the polarizing elements 16a, 16b of the layered assembly 12 via the contact paths 26a, 26b.

[0040] The longitudinal distances L1 between the first contact points 24a of the contact fields 20a, 22a and a first longitudinal end 28a of the filter element 10 and the longitudinal distances L1 between the first contact points 24a of the contact fields 20b, 22b and a second longitudinal end 28b of the filter insert 10 are identical. The longitudinal distances L2 between the second contact points 24b of the contact fields 20a, 22a and the first longitudinal end 28a of the filter insert 10 and the longitudinal distances L2 between the second contact points 24b of the contact fields 20b, 22b and the second longitudinal end 28b of the filter insert 10 are identical.

[0041] The height distances H1 between the first contact points 24a of the contact fields 20a, 22a and a first height termination 30a of the filter insert 10 and the height distances H1 between the first contact points 24a of the contact fields 20b, 22b and a second height termination 30b of the filter insert 10 are identical. The height distances H2 between the second contact points 24b of the contact fields 20a, 20b and the first height termination 30a of the filter insert 10 and the height distances H2 between the second contact points 24b of the contact fields 20b, 22b and the second height termination 30b of the filter insert 10 are identical.

[0042] The longitudinal edge 28a is formed by the front material edges of the material strips 18a, 18b. The longitudinal edge 28b is formed by the rear material edges of the material strips 18a, 18b. The vertical edge 30a is formed by the top material edges of the material strips 18a, 18b. The vertical edge 30b is formed by the bottom material edges of the material strips 18a, 18b.

[0043] 3 and 4 show a filter insert 10, which can also be electrically contacted in four different insertion orientations with a predetermined mating contact field on the insert receiving area of ​​the filter unit. In the illustrated embodiment, the four contact fields 20a, 20b, 22a, 22b have conduction paths 32 comprising a voltage divider 34. A contact path 26a, 26b branches off along the resistance path 36 of the voltage divider 34, via which a polarization element 16a, 16b of the layered composite 12 is contacted. The voltage divider 34 allows a suitable polarization voltage to be tapped along the resistance path 36, so that a supply voltage higher than the polarization voltage required to polarize the filter material 14 can be applied to the contact points 24a, 24b.

[0044] 5 and 6 show a filter insert which also has four contact fields 20a, 20b, 22a, 22b, wherein the filter insert 10 can be electrically contacted via the four contact fields 20a, 20b, 22a, 22b in four insertion orientations with a predetermined counter contact field on the insert receiving area of ​​the filter unit.

[0045] A conducting path 32 runs along the material strips 18a, 18b formed as side lamination, extending over the entire length of the material strips 18a, 18b. The electrical conducting path is interrupted between the conducting path 32 and the contact paths 26a, 26b. The electrically conductive connection between the contact points 24a, 24b of the contact fields 20a, 20b, 22a, 22b and the polarization elements 16a, 16b is only established when the filter insert 10 is inserted into the insert receiving area of ​​the filter unit by bridging conductors in the insert receiving area. The bridging conductors in the insert receiving area can be the mating contact points of the specified mating contact field.

[0046] An alternative embodiment could be designed as shown in Figs. 5 and 6, omitting the contact paths 26a or omitting the contact paths 26b. The filter insert would thus have a large-area contact pad on each of the two material strips 18a, 18b, which would be point-symmetrical in terms of the contact points and conduction paths. Each contact pad would allow contact in two insertion orientations.

[0047] In a further alternative embodiment according to Figs. 5 and 6, omitting the contact paths 26b, the remaining contact paths 26a could also be arranged offset along the material strips 18a, 18b such that no point symmetry of the contact field results. In this case, contact between the mating contact field and the contact points would be established in two insertion orientations, for example, with the polarization element 16a facing upwards, and no contact between the mating contact field and the contact points would be established in two insertion orientations, for example, with the polarization element 16a facing downwards.

[0048] The contact pads 20a, 20b, 22a, 22b of the filter inserts 10 shown in Figs. 1 to 6 can be formed, for example, by contact foils or contact labels applied, in particular glued, to the material strips 18a, 18b. Alternatively or additionally, the contact pads 20a, 20b, 22a, 22b and / or the electrical conduction paths 32 of the contact pads 20a, 20b, 22a, 22b can be printed, wherein the printing is carried out with a printing paste that is electrically conductive after curing. Reference symbol

[0049] 10 Filter insert 12 Layer composite 14 Filter material

[0050] 16a, 16b Polarization elements 18a, 18b Material strips 20a, 20b Contact pads 22a, 22b Contact pads 24a, 24b Contact points 26a, 26b Contact paths 28a, 28b Longitudinal terminations 30a, 30b Vertical terminations 32 Conductive paths 34 Voltage divider 36 Resistor path

[0051] L Longitudinal axis

[0052] L1, L2 Longitudinal distances H1, H2 Height distances Q Transverse axis

Claims

Claims 1. A filter insert (10) for a filter unit comprising an electrical supply module, wherein the filter insert (10) can be inserted into an insert receiving area of the filter unit in a plurality of insertion orientations, comprising an electrically insulating filter material (14); at least one electrically conductive polarizing element (16a, 16b) to which an electrical voltage can be applied to polarize the filter material (14); and a contacting arrangement connected to the at least one polarizing element (16a, 16b) for electrically contacting the filter insert (10) with the electrical supply module;characterized in that the contacting arrangement has a plurality of contact fields (20a, 20b, 22a, 22b) each assigned to at least one insertion orientation of the filter insert (10), via which the filter insert (10) can be electrically contacted with a predetermined counter-contact field on the insert receiving area of the filter unit in a plurality of insertion orientations of the filter insert (10); 2. Filter insert (10) according to claim 1, characterized in that two contact fields (20a, 20b, 22a, 22b) are arranged on the same side of the filter insert (10).

3. Filter insert (10) according to claim 2, characterized in that the two contact fields (20a, 20b, 22a, 22b) arranged on the same side of the filter insert (10) have the same orientation and / or a double-mirror-symmetric structure.

4. Filter insert (10) according to one of the preceding claims, characterized in that two contact fields (20a, 20b, 22a, 22b) are arranged on opposite sides of the filter insert (10).

5. Filter insert (10) according to claim 4, characterized in that the two contact fields (20a, 20b, 22a, 22b) arranged on opposite sides of the filter insert (10) have opposite orientations and / or a simple mirror-symmetrical structure.

6. Filter insert (10) according to one of the preceding claims, characterized in that the contact fields (20a, 20b, 22a, 22b) each have at least one contact point (24a, 24b) for electrical contact with a mating contact point of the predetermined mating contact field, wherein the longitudinal distance (L1, L2) between a contact point (24a, 24b) of a first contact field (20a, 22a) and a first longitudinal end (28a) of the filter insert (10) and the longitudinal distance (L1, L2) between a contact point (24a, 24b) of a second contact field (20b, 22b) and a second longitudinal end (28b) of the filter insert (10) correspond;and / or the height distance (H1, H2) between a contact point (24a, 24b) of a first contact field (20a, 22a) and a first height termination (30a) of the filter insert (10) and the height distance (H1, H2) between a contact point (24a, 24b) of a second contact field (20b, 22b) and a second height termination (30b) of the filter insert (10) correspond.; 7. Filter insert (10) according to one of the preceding claims, characterized in that the contact fields (20a, 20b, 22a, 22b) each have two spaced-apart contact points (24a, 24b) for electrical contact with two spaced-apart mating contact points of the predetermined mating contact field.

8. Filter insert (10) according to claim 7, characterized in that the longitudinal distance (L1) between a first contact point (24a) of a first contact field (20a, 22a) and a first longitudinal end (28a) of the filter insert (10) and the longitudinal distance (L1) between a first contact point (24a) of a second contact field (20b, 22b) and a second longitudinal end (28b) of the filter insert (10) are the same; and / or the longitudinal distance (L2) between a second contact point (24b) of the first contact field (20a, 22a) and a first longitudinal end (28a) of the filter insert (10) and the longitudinal distance (L2) between a second contact point (24b) of the second contact field (20b, 22b) and the second longitudinal end (28b) of the filter insert (10) are the same;and / or the height distance (H1) between a first contact point (24a) of a first contact field (20a, 22a) and a first height termination (30a) of the filter insert (10) and the height distance (H1) between a first contact point (24a) of a second contact field (20b, 22b) and a second height termination (30b) of the filter insert (10) match; and / or the height distance (H2) between a second contact point (24b) of the first contact field (20a, 22a) and a first height termination (30a) of the filter insert (10) and the height distance (H2) between a second contact point (24b) of the second contact field (20b, 22b) and the second height termination (30b) of the filter insert (10) match.; 9. Filter insert (10) according to one of the preceding claims, characterized in that the contact fields (20a, 20b, 22a, 22b) each comprise an electrical resistor, in particular a voltage divider (34).

10. Filter insert (10) according to one of the preceding claims, characterized in that the contacting fields (20a, 20b, 22a, 22b) are formed at least in sections by a contacting film applied, in particular glued, to a surface of the filter insert (10) or by a contacting label applied, in particular glued, to a surface of the filter insert (10).

11. Filter insert (10) according to one of the preceding claims, characterized in that the contacting fields (20a, 20b, 22a, 22b) and / or the electrical conduction paths (32) of the contacting fields (20a, 20b, 22a, 22b) are at least partially printed.

12. Filter insert (10) according to one of the preceding claims, characterized in that the polarizing element (16a, 16b) is designed as a polarizing layer.

13. Filter insert (10) according to one of the preceding claims, characterized in that two electrically conductive polarizing elements (16a, 16b), each designed as polarizing layers, are separated from one another by the electrically insulating filter material (14).

14. Filter insert (10) according to claim 13, characterized in that the two electrically conductive polarizing elements (16a, 16b) designed as polarizing layers are connected to the contacting arrangement.

15. A filter unit comprising a filter insert (10); an electrical supply device; an insert receiving area into which the filter insert (10) can be inserted in several insertion orientations; and a counter-contact field connected to the electrical supply device and arranged on the insert receiving area for electrically contacting the filter insert (10); characterized in that the filter insert (10) is designed according to one of the preceding claims.

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