Filter insert for a filter unit

Abstract

The invention relates to 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 several insertion orientations, with 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 contact arrangement connected to the at least one polarizing element (16a, 16b) for electrically contacting the filter insert (10) with the electrical supply module.

Description

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 region of the filter unit in a plurality of insertion alignments, having an electrically insulating filter material, at least one electrically conductive polarizing element, to which an electrical voltage can be applied for polarizing the filter material, and a contacting arrangement connected to the at least one polarizing element for electrically contacting the filter insert with the electrical supply module.The invention further relates to a filter unit having a filter insert, an electrical supply device, an insert receiving region, in which the filter insert can be inserted in a plurality of insertion alignments, and a countercontact field, which is connected to the electrical supply device and arranged on the insert receiving region, for electrically contacting the filter insert.In the case of rectangular filter inserts which require electrical contact and do not have an alignment or guide contour which presets a specific installation position, the filter insert can be installed in an improper manner by rotating the filter insert. As a result of the non-intended installation, the electrical contacting of the filter insert can be impaired or not present, with the result that current-assisted functions, such as a polarization function, for example, are impaired or canceled, as a result of which a considerable reduction in the filter performance usually occurs.In order to avoid misalignment of the filter insert during insertion, it is already known from practice in non-electrified filter inserts to apply alignment aids, such as arrows, to the filter insert, which are intended to assist the user in correctly aligning the filter insert. This merely reduces the risk of a misalignment of the filter insert during insertion into an insert receiving region of the filter unit, but does not eliminate it.The object on which the invention is based is thus to eliminate or at least to further reduce the risk of an improper installation of the filter insert.The object is achieved by a filter insert of the type mentioned at the beginning, wherein the contacting arrangement of the filter insert according to the invention has a plurality of contacting fields which are each assigned to at least one insertion orientation of the filter insert, in particular contacting fields which are assigned to only one insertion orientation of the filter insert, by means of which the filter insert can be electrically contacted in a plurality of insertion orientations of the filter insert with a predetermined counter-contacting field at the insert receiving region of the filter insert.The contact fields of the contact arrangement are in particular each assigned to an insertion orientation of the filter insert. The filter insert can have a cuboidal basic shape. Due to its basic shape and the free installation space in the insert receiving region, the filter insert can only be inserted into the insert receptacle of the filter unit in a limited number, for example in four different insertion orientations of the filter insert. In the respective insertion orientations of the filter insert, the contacting of the filter insert takes place via the contact field which is assigned to the present insertion orientation of the filter insert. The contacting arrangement can have, for example, two contacting fields each assigned to an insertion orientation of the filter insert, by means of which the filter insert can be electrically contacted with the predetermined counter-contacting field at the insert receiving region of the filter unit in two insertion orientations of the filter insert. The contacting arrangement can alternatively have, for example, four contacting fields which are each assigned to an insertion orientation of the filter insert and by means of which the filter insert can be electrically contacted with the predetermined counter-contacting field at the insert receiving region of the filter unit in four insertion orientations of the filter insert.The contacting arrangement can alternatively have a contacting field only on two opposite sides. The contact fields can be designed such that they can be contacted for two insertion alignments in each case. For this purpose, the contact fields can be designed point-symmetrically.In the case of filter inserts in which a required direction of flow is present, for example due to a specific sequence of the media layers, there can also be no associated contact fields in a targeted manner for part of the insertion alignments, i.e. only contact fields for insertion alignments with the alignment correct for the direction of flow can be provided on the filter insert. Thus, when the filter insert is installed in an incorrect insertion orientation, no electrical contact is established between the counter contact field and a contact field. In this case, a controller can determine the lack of contact and emit a signal, for example an optical and / or acoustic signal.The filter insert can be a filter insert for an interior filter, in particular of a vehicle. The electrical conduction paths of the contacting arrangement can be interrupted, for example slotted, so that the electrically conductive connection to the polarization element is only produced when the filter insert is inserted through a bridging conductor at the insert receiving region.In a preferred embodiment of the filter insert according to the invention, two contact fields are arranged on the same side of the filter insert. The two contact fields arranged on the same side are located, for example, on a lateral outer surface of the filter insert. The two contact fields arranged on the same side can be located on a long side or a narrow side of the filter insert. The two contact fields arranged on the same side are located, for example, on a lateral material strip of the filter insert and / or on a side cladding of the filter insert.The filter insert according to the invention is further advantageously further developed in that the two contact fields arranged on the same side of the filter insert have the same alignment and / or a double mirror-symmetrical structure. Due to the double mirror-symmetrical construction of the contact fields, these can be notionally brought into coincidence by two reflections at two mirror planes running perpendicular to one another. By means of the two contact pads arranged on the same side of the filter insert, the filter insert can be electrically contacted with the predetermined counter contact pad at the insert receiving region of the filter unit in two insertion alignments of the filter insert.In a further preferred embodiment of the filter insert according to the invention, two contact fields are arranged on opposite sides of the filter insert. Preferably, a pair of contact fields is arranged on each of the opposite sides of the filter insert, so that the filter insert has a total of four contact fields.In a further preferred embodiment of the filter insert according to the invention, the two contact fields arranged on opposite sides of the filter insert have opposite alignments and / or a simple mirror-symmetrical structure. By means of the two contact fields arranged on opposite sides of the filter insert, the filter insert can be electrically contacted with the predetermined counter contact field at the insert receiving region of the filter unit in two insertion alignments 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 making electrical contact with a mating contact point of the predefined mating contact pad. The contacting point is preferably wider and / or higher than a conducting path adjoining the contacting point. The longitudinal distance between a contacting point of a first contacting area and a first longitudinal termination of the filter insert and the longitudinal distance between a contacting point of a second contacting area and a second longitudinal termination of the filter insert preferably correspond to one another. The first longitudinal termination can be formed, for example, by a front material edge or material surface of the filter insert. The second longitudinal termination can be formed, for example, by a material edge or material surface of the filter insert on the rear side. Alternatively or additionally, the height distance between a contacting point of a first contacting area and a first height termination of the filter insert and the height distance between a contacting point of a second contacting area and a second height termination of the filter insert correspond. The first height termination can be formed, for example, by an upper-side material edge or material surface of the filter insert. The second height termination can be formed, for example, by a material edge or material surface of the filter insert on the underside. The contact points can be electrically conductive contact poles accessible from the outside.In another preferred embodiment of the filter insert according to the invention, the contact pads each have two contact pads spaced apart from one another for making electrical contact with two counter contact pads spaced apart from one another of the predetermined counter contact pad. A first contact-making point of the contact-making fields is configured, for example, to be contacted with a positive pole of the counter contact field. A second contact point of the contact pads is preferably configured to be contacted with a negative pole of the counter contact pad. The two contact points of the contact fields can have a longitudinal distance and / or a height distance from one another. Alternatively, the first or the second contacting point of the contacting fields can be configured to be contacted with a ground contact of the counter-contacting field. Alternatively, the first or the second contacting point of the contacting fields can be configured to be contacted with a phase contact of the counter-contacting field.A filter insert according to the invention is furthermore advantageous, in which the longitudinal distance between a first contacting point of a first contacting area and a first longitudinal termination of the filter insert and the longitudinal distance between a first contacting point of a second contacting area and a second longitudinal termination of the filter insert coincide. Alternatively or additionally, the longitudinal distance between a second contacting point of the first contacting area and a first longitudinal termination of the filter insert and the longitudinal distance between a second contacting point of the second contacting area and the second longitudinal termination of the filter insert correspond. The first longitudinal termination can be formed, for example, by a front material edge or material surface of the filter insert. The second longitudinal termination can be formed, for example, by a material edge or material surface of the filter insert on the rear side. Alternatively or additionally, the height distance between a first contacting point of a first contacting area and a first height termination of the filter insert and the height distance between a first contacting point of a second contacting area and a second height termination of the filter insert correspond. Alternatively or additionally, the height distance of a second contacting point of the first contacting area and a first height termination of the filter insert and the height distance between a second contacting point of the second contacting area and the second height termination of the filter insert correspond. The first height termination can be formed, for example, by an upper-side material edge or material surface of the filter insert. The second height termination can be formed, for example, by a material edge or material surface of the filter insert on the underside. The contact points can be electrically conductive contact poles accessible from the outside.In another preferred embodiment of the filter insert according to the invention, the contact fields each comprise an electrical resistor, in particular as a voltage divider. By means of the voltage divider, a supply voltage differing from the required polarization voltage can be applied to the contact fields, wherein the supply voltage can be reduced to the required polarization voltage by a suitable tapping of the voltage along the resistance section of the voltage divider.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 an extremely low production outlay. Thus, different contact field arrangements for realizing a greater variety of variants can also be produced without great adaptation complexity. The contact foils or the contact labels preferably comprise a carrier layer to which an electrically conductive material is applied.In a further preferred embodiment of the filter insert according to the invention, the contact fields and / or the electrical conduction paths of the contact fields are printed on at least in sections. The contact fields can be printed, for example, directly onto the side cover of the filter insert. Alternatively, the contact fields can be produced by printing an electrically conductive material onto a carrier layer of the contact foils or a carrier layer of the contact labels. For printing the contact pads, a printing paste is preferably used which is also electrically conductive after curing.In another preferred embodiment of the filter insert according to the invention, the polarizing element is designed as a polarizing layer. The polarization 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.In another preferred embodiment of the filter insert according to the invention, two electrically conductive polarization elements, each designed as polarization layers, are separated from one another by the electrically insulating filter material. An electrical voltage can be applied to the polarization layers for polarizing the filter material. The electrically insulating filter material and the two electrically conductive polarization layers preferably form a pleated layer composite. Preferably, the two electrically conductive polarization elements configured as polarization layers are connected to the contacting arrangement. Due to the connection between the polarization layers and the contacting arrangement, an electric field for polarizing the filter material is generated when contacting and energizing the filter insert.The object on which the invention is based is furthermore achieved by a filter unit of the type mentioned at the beginning, wherein the filter insert of the filter unit according to the invention is formed 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 thus made first to the advantages and modifications of the filter insert according to the invention.The insert receiving region, into which the filter insert can be inserted in a plurality of insert alignments, is preferably arranged within a housing of the filter unit. The housing may include an insert receiving portion providing the insert receiving portion. The insert receiving part can be closable with a housing cover of the housing. For inserting and removing the filter insert, the housing cover is preferably to be 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 attached drawings. The following are shown: FIG. 1 shows a filter insert according to the invention in a perspective view; FIG. 2 shows the filter insert depicted in FIG. 1 in a further perspective illustration; FIG. 3 shows a perspective view of a further filter insert according to the invention; FIG. 4 shows the filter insert depicted in FIG. 3 in a further perspective illustration; FIG. 5 shows a perspective view of a further filter insert according to the invention; and FIG. 6 shows the filter insert depicted in FIG. 5 in a further perspective illustration.FIGS. 1 and 2 show a filter insert 10 of a filter unit which can be used in a motor vehicle. The filter unit serves, for example, as an interior air filter of the motor vehicle.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 16 a, 16 b. The polarization elements 16 a, 16 bare designed as polarization layers. One polarizing layer 16a is located on a first side of the filter material 14, and another polarizing layer 16b is located on the other side of the filter material 14.Material strips 18 a, 18 brun on the lateral outer edges of the pleated layer composite 12. The material strips 18 a, 18 bform the side coverings of the filter insert 10 and are connected, for example bonded, to the pleated layer composite 12 in a materially bonded manner.The filter insert 10 further comprises a contacting arrangement connected to the polarization elements 16 a, 16 bfor electrically contacting the filter insert 10 with an electrical supply module.The filter insert 10 can be inserted into an insert receiving region of the filter unit in four different insertion orientations. The contacting arrangement has a total of four contacting fields 20 a, 20 b, 22 a, 22 b, each assigned to an insertion orientation of the filter insert 10, by means of which the filter insert 10 can be electrically contacted with a predetermined counter-contacting field at the insert receiving region of the filter unit in the four insertion orientations of the filter insert 10.FIG. 1 shows a first insertion orientation of the filter insert 10. 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 contacting of the filter insert 10 takes place via the contacting field 20 b.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 contacting of the filter insert 10 takes place via the contacting field 22 a. By further turning 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 contacting of the filter insert 10 takes place via the contacting field 22 b.The contact fields 20 a, 20 b, 22 a, 22 bof 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, the contacting of the filter insert 10 takes place via the contacting field 20 a, 20 b, 22 a, 22 b, which is assigned to the present insertion orientation of the filter insert 10.The contact fields 20a, 20b are arranged on the same side of the filter insert 10 and on the material strip 18a. The contact fields 22a, 22b are arranged on the same side of the filter insert 10 and on the material strip 18b. The two contact fields 20 a, 20 bform a first contact field pair. The contact pads 22a, 22b form a second contact pad pair. The contact pads 20a, 20b of the first contact pad pair and the contact pads 22a, 22b of the second contact pad pair are arranged on opposite sides of the filter insert 10.The contact pads 20 a, 20 b, 22 a, 22 bhave in each case two contact pads 24 a, 24 b, which are spaced apart from one another, for making electrical contact with two counter contact pads, which are spaced apart from one another, of the predefined counter contact pad. The contact points 24 a, 24 bare each connected via contact paths 26 a, 26 bto a polarization element 16 a, 16 bof the layer composite 12 embodied as a polarization layer. Via the contact paths 26 a, 26 b, an electrically conductive connection is provided between the contact points 24 a, 24 bof the contact fields 20 a, 20 b, 22 a, 22 band the polarization elements 16 a, 16 bof the layer composite 12.The longitudinal distances L 1 between the first contacting points 24 aof the contacting fields 20 a, 22 aand a first longitudinal termination 28 aof the filter element 10 and the longitudinal distances L 1 between the first contacting points 24 aof the contacting fields 20 b, 22 band a second longitudinal termination 28 bof the filter insert 10 correspond to one another. The longitudinal distances L2 between the second contact points 24b of the contact pads 20a, 22a and the first longitudinal termination 28a of the filter insert 10 and the longitudinal distances L2 between the second contact points 24b of the contact pads 20b, 22b and the second longitudinal termination 28b of the filter insert 10 correspond to one another.The height distances H 1 between the first contact points 24 aof the contact pads 20 a, 22 aand a first height termination 30 aof the filter insert 10 and the height distances H 1 between the first contact points 24 aof the contact pads 20 b, 22 band a second height termination 30 bof the filter insert 10 correspond to one another. The height distances H 2 between the second contact points 24 bof the contact pads 20 a, 20 band the first height termination 30 aof the filter insert 10 and the height distances H 2 between the second contact points 24 bof the contact pads 20 b, 22 band the second height termination 30 bof the filter insert 10 correspond to one another.The longitudinal termination 28 ais formed by the front-side material edges of the material strips 18 a, 18 b. The longitudinal termination 28 bis formed by the rear material edges of the material strips 18 a, 18 b. The height termination 30 ais formed by the upper material edges of the material strips 18 a, 18 b. The height termination 30 bis formed by the underside material edges of the material strips 18 a, 18 b.FIGS. 3 and 4 show a filter insert 10 which can likewise be electrically contacted in four different insertion orientations with a predetermined mating contact field at the insert receiving region of the filter unit. In the embodiment shown, the four contact pads 20 a, 20 b, 22 a, 22 bhave conduction paths 32 having a voltage divider 34. A contact path 26 a, 26 bbranches off along the resistor section 36 of the voltage divider 34, via which contact is made with a polarization element 16 a, 16 bof the layer composite 12. The voltage divider 34 allows a suitable polarization voltage to be tapped along the resistor section 36, with the result that a supply voltage can be applied to the contact points 24 a, 24 bthat is higher than the polarization voltage required for polarizing the filter material 14.FIGS. 5 and 6 show a filter insert which likewise has four contact pads 20 a, 20 b, 22 a, 22 b, wherein the filter insert 10 can be electrically contacted via the four contact pads 20 a, 20 b, 22 a, 22 bin four insertion orientations with a predetermined mating contact pad at the insert receiving region of the filter unit.A line path 32 runs along the material strips 18 a, 18 b, which are designed as side panels, and extends over the entire length of the material strips 18 a, 18 b. The electrical conduction path is interrupted between the conduction path 32 and the contact paths 26 a, 26 b. The electrically conductive connection between the contact points 24 a, 24 bof the contact fields 20 a, 20 b, 22 a, 22 band the polarization elements 16 a, 16 bis produced only when the filter insert 10 is inserted into the insert receiving region of the filter unit by bridging conductors at the insert receiving region. The bridging conductors at the insert receiving region can be the mating contact points of the predefined mating contact array.An alternative configuration could be formed in accordance with FIGS. 5 and 6 with omission of the contact paths 26 aor with omission of the contact paths 26 b. The filter insert would thus have a large-area contact field on each of the two material strips 18 a, 18 b, which contact field would be constructed point-symmetrically with respect to the contact points and conduction paths. Each bonding pad would allow contact in two insertion orientations.In a further alternative embodiment corresponding to FIGS. 5 and 6, with omission of the contact paths 26 b, the remaining contact paths 26 ashould also be arranged offset along the material strips 18 a, 18 bsuch that no point symmetry of the contact field would result. In this case, in two insertion alignments, for example with polarizing element 16 atowards the top, contacting of the counter contact array with the contacting points would be produced, and in two insertion alignments, for example with polarizing element 16 atowards the bottom, contacting of the counter contact array with the contacting points would not be produced.The contact fields 20 a, 20 b, 22 a, 22 bof the filter inserts 10 illustrated in FIGS. 1 to 6 can be formed, for example, by contact foils or contact labels which are applied, in particular adhesively bonded, to the material strips 18 a, 18 b. Alternatively or additionally, the contact pads 20 a, 20 b, 22 a, 22 band / or the electrical conduction paths 32 of the contact pads 20 a, 20 b, 22 a, 22 bmay be printed, wherein the printing is carried out with an electrically conductive printing paste after curing.Reference numerals denote reference numerals10 Filter insert 12 Layer composite 14 Filter material 16 a, 16 b Polarisierung elements 18 a, 18 bMaterial strips 20 a, 20 bContact pads 22 a, 22 bContact pads 24 a, 24 bContact points 26 a, 26 bContact paths 28 a, 28 b Längs terminations 30 a, 30 b Höhen terminations 32 Line paths 34 Voltage dividers 36 Resistance section L Longitudinal axis L 1, L 2 Longitudinal distances H 1, H 2 Height distances Q Transverse axis

Claims

Filter insert (10) for a filter unit comprising an electrical supply module, wherein the filter insert (10) can be inserted into an insert receiving region of the filter unit in a plurality of insertion alignments, having - an electrically insulating filter material (14); - at least one electrically conductive polarization element (16a, 16b), to which an electrical voltage can be applied for polarizing the filter material (14); and - a contacting arrangement connected to the at least one polarization 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 contacting fields (20a, 20b, 22a, 22b) respectively assigned to at least one insertion alignment of the filter insert (10), via which the filter insert (10) can be electrically contacted with a predetermined counter-contacting field at the insert receiving region of the filter unit in a plurality of insertion alignments of the filter insert (10).Filter insert (10) according to claim 1, characterised in that two contact fields (20a, 20b, 22a, 22b) are arranged on the same side of the filter insert (10).Filter insert (10) according to claim 2, characterised in that the two contact fields (20a, 20b, 22a, 22b) arranged on the same side of the filter insert (10) have the same alignment and / or a double mirror-symmetrical structure.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).Filter insert (10) according to claim 4, characterised in that the two contact fields (20a, 20b, 22a, 22b) arranged on opposite sides of the filter insert (10) have opposite alignments and / or a single mirror-symmetrical construction.Filter insert (10) according to one of the preceding claims, characterized in that the contact pads (20a, 20b, 22a, 22b) each have at least one contact point (24a, 24b) for making electrical contact with a counter contact point of the predetermined counter contact pad, wherein - the longitudinal distance (L1, L2) between a contact point (24a, 24b) of a first contact pad (20a, 22a) and a first longitudinal termination (28a) of the filter insert (10) and the longitudinal distance (L1, L2) between a contact point (24a, 24b) of a second contact pad (20b, 22b) and a second longitudinal termination (28b) of the filter insert (10) coincide; and / or - the height distance (H1, H2) between a contacting point (24a, 24b) of a first contacting field (20a, 22a) and a first height termination (30a) of the filter insert (10) and the height distance (H1, H2) between a contacting point (24a, 24b) of a second contacting field (20b, 22b) and a second height termination (30b) of the filter insert (10) coincide.Filter insert (10) according to one of the preceding claims, characterized in that the contact pads (20a, 20b, 22a, 22b) each have two contact pads (24a, 24b) spaced apart from one another for the electrical contact with two counter contact pads of the predetermined counter contact pad spaced apart from one another.Filter insert (10) according to claim 7, characterised in that - the longitudinal distance (L1) between a first contacting point (24a) of a first contacting area (20a, 22a) and a first longitudinal termination (28a) of the filter insert (10) and the longitudinal distance (L1) between a first contacting point (24a) of a second contacting area (20b, 22b) and a second longitudinal termination (28b) of the filter insert (10) coincide; and / or - the longitudinal distance (L2) between a second contacting point (24b) of the first contacting area (20a, 22a) and a first longitudinal termination (28a) of the filter insert (10) and the longitudinal distance (L2) between a second contacting point (24b) of the second contacting area (20b, 22b) and the second longitudinal termination (28b) of the filter insert (10) coincide; and / or - the height distance (H1) between a first contacting point (24a) of a first contacting area (20a, 22a) and a first height termination (30a) of the filter insert (10) and the height distance (H1) between a first contacting point (24a) of a second contacting area (20b, 22b) and a second height termination (30b) of the filter insert (10) coincide; and / or - the height distance (H2) between a second contacting point (24b) of the first contacting area (20a, 22a) and a first height termination (30a) of the filter insert (10) and the height distance (H2) between a second contacting point (24b) of the second contacting area (20b, 22b) and the second height termination (30b) of the filter insert (10) coincide.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).Filter insert (10) according to one of the preceding claims, characterized in that the contact fields (20a, 20b, 22a, 22b) are formed at least in sections by a contact foil applied, in particular glued, to a surface of the filter insert (10) or by a contact label applied, in particular glued, to a surface of the filter insert (10).Filter insert (10) according to one of the preceding claims, characterized in that the contact fields (20a, 20b, 22a, 22b) and / or the electrical conduction paths (32) of the contact fields (20a, 20b, 22a, 22b) are at least partially printed on.Filter insert (10) according to one of the preceding claims, characterized in that the polarization element (16a, 16b) is designed as a polarization layer.Filter insert (10) according to one of the preceding claims, characterized in that two electrically conductive polarization elements (16a, 16b), each formed as polarization layers, are separated from one another by the electrically insulating filter material (14).Filter insert (10) according to claim 13, characterised in that the two electrically conductive polarising elements (16a, 16b) formed as polarising layers are connected to the contacting arrangement.Filter unit, having - a filter insert (10); - an electrical supply device; - an insert receiving region, into which the filter insert (10) can be inserted in a plurality of insert alignments; and - a countercontact field, which is connected to the electrical supply device and arranged on the insert receiving region, 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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