Air filter unit and air filter system

Abstract

The invention relates to an air filter unit (100) for an air filter device (1) of an air conditioning system, in particular for separating particles, preferably dirt particles, from air (L). The air filter unit (100) comprises a filter element (101) with an electrically conductive layer (103). Furthermore, the air filter unit (100) comprises a housing (104) which partially surrounds an interior housing space (105) in which the filter element (101) is replaceably arranged. The air filter unit (100) also comprises a connection element (106) made of an electrically conductive material, arranged on the housing (104) and electrically contactable from outside the interior housing space (105), which is electrically connected to the electrically conductive layer (103) of the filter element (101).

Description

[0001] The present invention relates to an air filter unit for an air filter device of an air conditioning system and to an air filter device with such an air filter unit.

[0002] For pleasant and healthy air quality, the air in and supplied to a vehicle's passenger compartment must be freed from pollutants such as particulate matter, harmful gases, hydrocarbons, nitrogen oxides, and unpleasant odors. High levels of particulate matter in the outside air also prove problematic. In large cities, these levels can often exceed the prescribed daily average limit.

[0003] The removal of dust particles that enter the vehicle interior via the air conditioning system is typically achieved nowadays using a filter element through which the air to be cleaned flows. This filter element contains a fiber filter layer to separate airborne particles. This filter element is crucial for the air quality of the filtered air. Modern automotive air conditioning systems have very little installation space available for such a filter element. Therefore, these elements must have low flow resistance to minimize pressure loss in the air, ensuring that the desired volume of air can still be transported into the vehicle interior.

[0004] To achieve low flow resistance, the particle-separating filter fiber layer is usually very open-pored, which limits the filter's mechanical dust separation efficiency to relatively low values. Therefore, conventional filter elements are electrostatically charged during the filter media production process. This allows for better separation of the often also electrostatically charged particles during subsequent operation, using electrostatic deposition of the filter medium. This separation mechanism enables even very small particles with a diameter of less than 0.3 µm to be captured without significantly increasing the flow resistance of the filter element and thus the pressure drop generated in the air.

[0005] However, the electrostatic charge applied during the production process quickly becomes ineffective as the filter ages and accumulates dust during operation. The filter's electrostatic charge is therefore primarily effective only at the beginning of its life cycle. Depending on the level of ambient air pollution, a significant decrease in electrostatic charge can occur after just a few weeks or months.

[0006] It is therefore an object of the present invention to demonstrate new approaches in the development of the air filter units described above. In particular, an improved embodiment of such an air filter unit is to be created that utilizes the aforementioned operating principle of electrostatic charging and implements improved particle separation throughout the entire life cycle of the filter element.

[0007] This problem is solved by the subject matter of the independent patent claims. Preferred embodiments are the subject matter of the dependent patent claims.

[0008] The basic idea of ​​the invention is therefore to provide an air filter unit, as described above, with a filter element on which an electrically conductive layer is arranged, with the aid of which the filter element can be electrostatically recharged, i.e., reactivated. For this purpose, the invention proposes equipping the air filter unit with an electrically conductive connection element, which is electrically connected to the electrically conductive layer of the filter element and can also be electrically contacted from the outside. This allows the electrically conductive layer to be electrically connected to a high-voltage electrical source, so that the filter element can be electrostatically charged. This prevents the electrostatic charge of the filter element from only being effective at the beginning of its service life.In this way, a filter element is created that maintains a high filter efficiency throughout its entire lifespan.

[0009] Specifically, an air filter unit according to the invention comprises a filter element with a filter medium for filtering particles from air flowing through the filter element and with an electrically conductive layer. Furthermore, the air filter unit comprises a housing that partially surrounds an interior space. The filter element is arranged replaceably within the housing space. According to the invention, the air filter unit includes a connection element made of an electrically conductive material, arranged on the housing and electrically contactable from outside the housing space. This connection element is electrically connected to the electrically conductive layer of the filter element when the filter element is arranged within the housing space.

[0010] In a preferred embodiment, the filter element can, in addition to the electrically conductive layer, have at least one air-permeable filter layer for separating particles from the air. The electrically conductive layer is preferably arranged on the filter layer. Alternatively, the layer can also be arranged on a support different from the filter layer, in particular on a support layer or on a support layer. The latter variant proves advantageous if the electrically conductive layer is formed by activated carbon. In this case, the activated carbon can be attached to the support, in particular by means of an adhesive bond. Preferably, the support can be formed by a carrier fleece.

[0011] Preferably, the electrically conductive layer can form an outer surface of the filter element against which the electrical connection element rests. This facilitates and improves the electrical contact of the electrical connection element.

[0012] In another preferred embodiment, the connecting element is designed as a spring-elastic component, in particular as a leaf spring. This allows the electrical connecting element to be pre-tensioned against the filter element with the electrically conductive layer. In this way, a particularly good electrical contact between the electrical connecting element and the electrically conductive layer is achieved.

[0013] It is particularly advantageous for the electrical connection element to be pre-tensioned against the electrically conductive layer of the filter element located inside the housing. The connection element is thus designed as a pre-tensioning element. This measure also ensures particularly good electrical contact between the connection element and the electrically conductive layer.

[0014] Particularly suitable is the material of the electrical connection element or the spring-elastic component, which can be steel, especially spring steel. This option allows for a cost-effective implementation of the connection element as a spring-elastic component, as explained above.

[0015] In another preferred embodiment, the electrical connection element is attached to the housing, in particular detachably or permanently. Alternatively or additionally, in this embodiment, the electrical connection element can protrude from the housing. Alternatively or additionally, in this embodiment, the electrical connection element can at least partially close an opening formed in the housing. All of the aforementioned measures of this preferred embodiment, individually or in combination, facilitate the assembly of the air filter unit as well as the electrical contacting of the electrical connection element with the electrically conductive layer.

[0016] In another preferred embodiment, the filter element comprises a filter medium designed as a bellows with a plurality of successive folds on which the electrically conductive layer is arranged. In this further development, the connecting element rests against at least one fold, in particular at a fold apex of the bellows. Such a bellows-type filter element has a particularly large effective cross-section and thus allows for efficient filtration of particles from the air with a comparatively small pressure drop generated in the air. Therefore, in this embodiment, the advantages of the filter element associated with electrostatic charging are combined with the advantages of a filter element with a bellows-like geometric shape.

[0017] According to a further advantageous embodiment, the filter medium or a filter layer of the filter element comprises a filter material designed for the separation of particles, in particular aerosols, preferably with a particle or aerosol diameter between 50 nm and 2.5 µm. The filter material can particularly preferably be or comprise a nonwoven fabric or filter paper.

[0018] Preferably, the electrically conductive layer can comprise or consist of activated carbon. In this way, the air flowing through the filter element can be effectively freed not only from particles, but also from harmful gases and odor-causing substances. Advantageously, the activated carbon can be arranged on a substrate, in particular on a substrate layer or carrier layer, and especially bonded to it. The substrate or carrier layer or carrier layer can also be arranged between the electrically conductive layer and the connecting element. In this case, the substrate must be designed such that an electrical connection between the electrically conductive layer and the electrically conductive connecting element is ensured. This can preferably be achieved by a sufficiently small layer thickness of the substrate or carrier layer or carrier layer.

[0019] According to a further advantageous embodiment, a receiving opening for inserting the filter element into the housing interior can be provided. In this embodiment, a deflecting element is arranged inside the housing, by means of which the filter element can be deflected towards the connection element, and in particular pressed against it, when being inserted into the housing interior. This ensures that the essential electrical contact of the connection element with the electrically conductive layer remains intact even after the filter element has been replaced with a spare part.

[0020] In a further preferred embodiment, the filter element can be inserted, in particular slid in, through the receiving opening into the interior of the housing along an insertion direction. In this embodiment, the cross-sectional area of ​​the interior of the housing, measured perpendicular to the insertion direction, is reduced by means of the deflecting element. This advantageously ensures that the filter element is moved towards the connection element when inserted into the interior of the housing.

[0021] Preferably, the deflecting element can be wedge-shaped. In this configuration, the filter element is successively deflected towards the electrical connection element as it is inserted into the housing interior. This ensures that, after the filter element has been inserted into its intended position within the housing interior, the necessary electrical connection is established between the electrically conductive layer on the filter element and the electrical connection element.

[0022] Particularly advantageous is the ability to attach the deflector element to the housing or to form an integral part of the housing. This results in significant cost savings in the manufacture of the air filter unit.

[0023] It is particularly advantageous for the internal cross-section to decrease in the insertion direction along the deflection element. This allows the filter element to be deflected towards the electrical connection element as desired when inserted into the housing interior. Such a housing interior configuration can be achieved using the wedge-shaped deflection element described above.

[0024] The invention further relates to an air filter device for an air conditioning system, in particular for separating particles, preferably dirt particles, from air. The air filter unit comprises an air path through which air flows along a flow direction, and an ionizer arranged in the air path, having at least one spray electrode and at least one counter electrode for generating ions in the air path.

[0025] Furthermore, the air filter device comprises an air filter unit, as previously described and according to the invention, arranged downstream of the ionizer in the air path with respect to the flow direction. The advantages of the air filter unit according to the invention, as explained above, are therefore transferred to the air filter device according to the invention.

[0026] The air filter assembly also includes a high-voltage electrical source having an electrical pole and an electrical counter pole for generating a high voltage, in particular between 5 kV and 15 kV, between the pole and the counter pole. The pole is electrically connected to the at least one spray electrode of the ionizer. The counter pole is electrically connected to the at least one counter electrode of the ionizer and to the electrically conductive layer of the air filter assembly. Thus, the at least one spray electrode has the electrical potential of the pole. The at least one counter electrode and the electrically conductive layer have the electrical potential of the counter pole. In a simplified embodiment, the counter electrodes and the electrically conductive layer are connected to the electrical potential of the counter pole, and the spray electrodes are connected to the electrical potential of the pole.

[0027] In a preferred embodiment, at least one counter electrode comprises or is an electrode plate, which is preferably arranged between two spray electrodes. In this way, the ionization effect of the ionizer can be improved.

[0028] Particularly efficient ionization can be achieved if at least three spray electrodes and two electrode plates are arranged alternately and at a distance from each other, perpendicular to the direction of flow.

[0029] In a preferred embodiment of the air filter device according to the invention, the electrical counter-pole is connected to the electrical connection element by means of an electrical connecting line, in particular in the form of an electrical cable. In this embodiment, the electrical connecting line or cable is electrically connected to the connection element of the air filter unit by means of a material-bonded connection, in particular by means of a soldered or welded connection, or alternatively, by means of a crimp connection. This simplifies the construction of the air filter device.

[0030] Particularly advantageous is the application of a negative high-voltage voltage to at least one of the spray electrodes. In this variant, the counter electrode then forms the electrical reference potential. Preferably, a negative-polarity DC voltage is applied to generate a so-called corona discharge; this is because a negative-polarity corona discharge ensures greater stability and higher values ​​of the corona current of electrons compared to a positive-polarity corona discharge.

[0031] The spray electrode particularly preferably comprises at least one electrode rod from which at least one electrode tip, preferably needle-shaped, projects towards the second electrode, preferably opposite to the flow direction, for generating the ions. Particularly preferably, at least two, preferably more, electrode tips project from the at least one electrode rod.

[0032] Advantageously, at least one electrode tip extends in the opposite direction to the flow direction. Such a spray electrode geometry allows for the generation of an extremely high electric field with a field strength between 10 kV / mm and 40 kV / mm, which promotes the generation of numerous ions and thus the charging of the particles in the airflow. It is particularly preferred that several electrode tips are arranged at intervals along one direction of extension of the electrode rod. In this way, ions can be generated across the entire cross-section of the air path.

[0033] In a further preferred embodiment, the at least one electrode rod extends, in particular in a straight line, along a direction of extension transversely, preferably orthogonally, to the direction of flow in the air path.

[0034] Particularly preferably, at least two, preferably several, and most preferably all, electrode rods are arranged at a distance from each other measured orthogonally to the direction of extension, which is between 20 mm and 60 mm, preferably between 25 mm and 35 mm. This ensures that the pressure drop generated by the ionizer in the air remains relatively low.

[0035] Particularly preferably, at least two, preferably several, and especially preferably all, adjacent electrode tips are arranged at a distance from each other, measured along the direction of extension, which is between 1 mm and 30 mm, preferably between 5 mm and 9 mm. This allows a particularly strong ionization effect to be generated.

[0036] It is particularly advantageous to arrange the electrode tips in a grid pattern within the air path. This measure results in an improved field line distribution of the electric corona field within the air path.

[0037] According to an advantageous embodiment, at least one of the electrode tips tapers, particularly conically, and especially preferably in the opposite direction to the flow direction. This preferably applies to several of the electrode tips, and particularly preferably to all electrode tips.

[0038] The effect of the polarization exerted on the filter element by the electric field depends on the intensity of the electric field generated by the ionizer. The higher the intensity of the electric field, the greater the polarization effect. Therefore, the electrodes of the ionizer should be located as close as possible to the entrance surface of the filter element. In a further preferred embodiment, the distance between the ionizer and the filter element is therefore at most 30 mm, preferably at most 7 mm.

[0039] Particularly preferably, the material of the at least one electrode and / or the at least one counter electrode can be steel, in particular stainless steel.

[0040] According to an advantageous embodiment, an electrical switch can be arranged between the electrical connection element and the opposite pole to interrupt the electrical connection between the electrical connection element and the opposite pole. This allows the electrostatic charging of the filter element to be activated or deactivated as needed and thus controlled in a targeted manner.

[0041] Further important features and advantages of the invention will become apparent from the dependent claims, the drawings and the associated description of the figures based on the drawings.

[0042] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0043] Preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components.

[0044] They show, schematically: Fig. 1 In a rough schematic representation, an example of an air filter unit according to the invention in a longitudinal section, Fig. 2 a variant of the example of Fig. 1, Fig. 3 by way of example an air filter device according to the invention with an air filter unit according to the invention.

[0045] The Fig. Figure 1 shows a schematic and longitudinal section example of an air filter unit 100 according to the invention. The air filter unit 100 comprises a filter element 101 with a filter medium 107, on the outer surface 102 of which an electrically conductive layer 103 is arranged. Such a layer 103 can be provided on the entire outer surface 102 or only in certain areas of the outer surface 102.

[0046] The electrically conductive layer 103 can be formed from activated carbon. Furthermore, the air filter unit comprises an open housing 104, which partially surrounds an interior housing space 105 through which air L to be filtered flows along a flow direction S.

[0047] In the example of the Fig. The flow direction S is perpendicular to the plane of the drawing. The filter element 101 is arranged in a replaceable manner in the housing interior 104. For this purpose, a receiving opening 112 can be provided in the housing 104 for inserting the filter element 101 into the housing interior 105.

[0048] In the example of the Fig. 1. The filter element 101 can be inserted, in particular slid in, along an insertion direction ESR through the receiving opening 112 into the housing interior 105. Fig. Figure 1 therefore shows a longitudinal section of the air filter unit 100 along the insertion direction ESR.

[0049] According to Fig. The air filter unit 100 also includes a connecting element 106, arranged on the housing 104 and electrically contactable from outside the housing interior 105. The connecting element 106 is made of an electrically conductive material. The electrically conductive material is preferably a metal. The connecting element 106 rests against the electrically conductive layer 103 of the filter element 101 and is thus electrically connected to the electrically conductive layer 103. In this example, the connecting element 106 is designed as a spring-elastic component 114, for example, in the form of a leaf spring. The material of the connecting element 106 or the spring-elastic component 114 can be steel, preferably spring steel.

[0050] In this way, the connecting element 106 can be used as in Fig. The electrical connection element 106 is pre-tensioned against the electrically conductive layer 103 of the filter element 101 located in the interior of the housing 105, as indicated by a force arrow P. The electrical connection element 106 thus also fulfills the function of a pre-tensioning element 116.

[0051] In this example, the electrical connection element 106 is permanently attached to the housing 104, for example by means of an adhesive or screw connection, and projects both inwards into the housing interior 105 and outwards from the housing 104 into an external environment 115 of the air filter unit 100. The electrical connection element 106 can close a housing opening 111 formed in the housing 104.

[0052] Filter element 101 can be in Fig. The filter element 101 comprises a filter medium 107, schematically indicated, which is designed as a bellows 108 with a plurality of successive folds 109 on which the electrically conductive layer 103 is arranged. The connecting element 106 rests against a fold tip 118 of at least one of the folds 109 of the bellows 108. The filter medium 107 comprises a filter material 110, which is designed for the separation of particles, in particular aerosols, with a particle or aerosol diameter between 50 nm and 2.5 µm. The filter material can preferably be a nonwoven fabric or filter paper. In this example, the filter element 101 comprises a filter layer 119 on which the electrically conductive layer 103 is arranged. The electrically conductive layer 103 forms an outer surface 102 of the filter element 101, against which the electrical connecting element 106 rests.In an embodiment not shown, the electrically conductive layer 103 can also be arranged on a support layer or carrier layer different from the filter layer 119, which can be positioned between the electrically conductive layer 103 and the filter layer 109 (not shown). The electrically conductive layer 103 can contain or consist of activated carbon. In this case, the activated carbon, if present, can be bonded to said support. As shown, the electrical connection element 106 rests against the electrically conductive layer 103, which forms the outer surface 102, in the region of a fold tip 118. In an embodiment not shown, the electrically conductive layer 103 can also be arranged between the filter layer 119 and the support, so that the support forms the outer surface 102.

[0053] The Fig. 2 illustrates a further development of the example of Fig. 1. Therefore, the following will only address the differences, for example, of the Fig. 1 received. In this training course - unlike, for example, the Fig. 2 - A deflection element 113 is arranged inside the housing 105, by means of which the filter element 101, when inserted into the housing 105, is deflected towards the electrical connection element 106 and thereby pressed against it. This ensures, particularly when replacing the filter element 101 with a spare part, that the required electrical contact between the electrical connection element 106 and the electrically conductive layer 103 of the filter element 101 is reliably established when the replacement filter element 101 is inserted. Advantageously, the deflection element 113 can be attached to the housing 104 or integrally formed with the housing 104. Alternatively, the deflection element 113 can also be formed separately from the housing 104 and attached to it detachably or permanently.

[0054] Even in the example of Fig. 2. The filter element 101 can be inserted, in particular slid in, through the receiving opening 112 into the interior of the housing 105 along the insertion direction ESR. Here, the cross-sectional area Q of the interior of the housing 105, measured perpendicular to the insertion direction ESR, is reduced by means of the deflecting element 113. For this purpose, the deflecting element 113 is wedge-shaped, which means that the cross-sectional area Q decreases along the deflecting element 113 in the insertion direction ESR.

[0055] The Fig. Figure 3 shows an exemplary construction of an air filter device 1 according to the invention for an air conditioning system. The air filter device 1 comprises an air path 2 through which the air L flows along a flow direction S. The air filter device 1 also comprises an ionizer 3 arranged in the air path 2 for generating ions in the air path 2. The ionizer 2 comprises several spray electrodes 6 and several counter electrodes 7, which in this example are arranged upstream of the spray electrodes 6 in the air path.

[0056] The air filter device 1 also comprises an air filter unit 100 according to the invention arranged downstream of the ionizer 3 in the air path 2 with respect to the flow direction S.

[0057] Each spray electrode 6 comprises an electrode rod 12, from which several needle-like electrode tips 9 protrude, from which the aforementioned ions can be generated for particle charging. The spray electrodes 6 are arranged perpendicular to the flow direction S at a distance from one another. The individual electrode tips 9 extend from the respective electrode rod 12 in the opposite direction to the flow direction S.

[0058] How the representation of Fig. As illustrated in Figure 3, the electrode tips 9 can be arranged in a grid pattern in the air path 2 and taper conically away from the electrode rod 12. A steel, for example stainless steel, is a suitable material for the spray electrodes 6. The individual electrode rods 12 extend in a straight line in the air path 2 along a common direction of extension E, which is orthogonal to the flow direction S.

[0059] Finally, the air filter device 1 includes an electrical high voltage source 8, which has an electrical pole 8a and an electrical counter pole 8b for generating an electrical high voltage HV, in the example scenario between 5 kV and 15 kV, between the pole 8a and the counter pole 8b.

[0060] In the example scenario, electrical pole 8a is configured as the negative pole and the opposite pole as the positive pole of the high-voltage source 8. Alternatively, electrical pole 8a can also be configured as the positive pole and the opposite pole 8b as the negative pole of the high-voltage source 8 (not shown). In this configuration, pole 8a is electrically connected to the spray electrodes 6 of the ionizer 3 via an electrical conductor 4. The opposite pole 8b is electrically connected to the counter electrodes 7 of the ionizer and to the electrically conductive layer 103 of the air filter unit 100 via an electrical conductor 55. In one variant, the counter electrodes 7 and the electrically conductive layer 103 are connected to the electrical potential of the opposite pole 8b, and the spray electrodes 6 are connected to the electrical potential of pole 8a. The counter electrodes 7 are each formed by an electrode plate 11 arranged between two adjacent spray electrodes 6.Advantageously, the spray electrodes 6 and the electrode plates 11 can be arranged alternately one after the other transversely to the flow direction S.

[0061] In the example of the Fig. 3 The electrical opposite pole 8b is electrically connected to the electrical connection element 106 by means of an electrical connecting line 122, for example in the form of an electrical cable 123. The electrical connecting line 122 or the electrical cable 123 is in turn electrically connected to the connection element 106 of the air filter unit 100 by means of a material-bonded connection 124, in this example by means of a soldered connection. As an alternative to the soldered connection used in the example, a welded connection or a crimped connection is conceivable.

[0062] As the Fig.As can be seen from Figure 3, an electrical switch 10 can be arranged between the electrical connection element 106 and the opposite pole 8b to interrupt the electrical connection between the electrical connection element 106 and the opposite pole 8b.

Claims

[1] Air filter unit (100) for an air filter device (1) of an air conditioning system, in particular for separating particles, preferably dirt particles, from air (L), - with a filter element (101) comprising an electrically conductive layer (103) which is preferably arranged at least partially on an outer surface (102) of the filter element (101), - with a housing (104) which partially surrounds a housing interior (105) in which the filter element (101) is arranged in an interchangeable manner, - wherein the air filter unit (100) comprises a connection element (106) made of an electrically conductive material, arranged on the housing (104) and electrically contactable from outside the housing interior (105), which is electrically connected to the electrically conductive layer (103) of the filter element (101). [2] Air filter unit according to claim 1, characterized by , that - the filter element (101) has at least one filter layer (119) through which air can flow for separating particles from the air (L), - the electrically conductive layer (103) is arranged on the filter layer (119) or on a support different from the filter layer (119), in particular a support layer or support layer, of the filter element (101). [3] Air filter unit according to claim 1 or 2, characterized by , that the electrically conductive layer (103) forms an outer surface (102) of the filter element (101) to which the electrical connection element (106) is attached. [4] Air filter unit according to one of claims 1 to 3, characterized by , that the electrical connection element (106) is designed as a spring-elastic component, preferably as a leaf spring. [5] Air filter unit according to any one of the preceding claims, characterized by, that a material of the electrical connection element (106) or of the spring-elastic component is a steel, in particular a spring steel. [6] Air filter unit according to one of the preceding claims, characterized by , that the electrical connection element (106) is biased against the filter element (101). [7] Air filter unit according to one of the preceding claims, characterized by , that - the electrical connection element is attached to the housing (104): or / and that - the electrical connection element (106) protrudes from the housing (104); or / and that - the electrical connection element (106) at least partially closes a housing opening (111) formed in the housing (104); or / and that [8] Air filter unit according to one of the preceding claims, characterized by, that the filter element (101) has a filter medium (107) which is designed as a bellows (108) with a plurality of successive folds (109) on which the electrically conductive layer (103) is arranged, - the connecting element (106) is in contact with at least one fold (109), in particular a fold tip (118) of this fold (109) of the bellows (108). [9] Air filter unit according to any one of the preceding claims, characterized by , that the filter medium (107) comprises a filter material (110) designed for the separation of particles, in particular aerosols, preferably with a particle or aerosol diameter between 50 nm and 2.5 µm. [10] Air filter unit according to any one of the preceding claims, characterized by , that the electrically conductive layer (103) comprises or consists of activated carbon. [11] Air filter unit according to one of the preceding claims, characterized by , that - the housing has a receiving opening (112) for inserting the filter element into the housing interior (105), - a deflection element (113) is arranged in the interior of the housing (105), by means of which the filter element (101) is deflected towards the connection element (106) when being inserted into the interior of the housing (105), in particular pressed against it. [12] Air filter unit according to any one of the preceding claims, characterized by , that - the filter element (101) can be inserted, in particular slid in, into the housing interior (105) along an insertion direction (ESR), - the internal cross-sectional area (Q) of the housing interior (105) measured perpendicular to the insertion direction (ESR) is reduced by means of the deflecting element (113). [13] Air filter unit according to claim 10 or 11, characterized by , that the deflecting element (113) is wedge-shaped. [14] Air filter unit according to one of claims 10 to 12, characterized by, that the deflecting element (113) is attached to the housing (104) or integrally formed on the housing (104). [15] Air filter unit according to any one of claims 10 to 13, characterized by , that the interior cross-sectional area (Q) decreases in the insertion direction (ESR) along the deflection element (113). [16] Air filter device (1) for an air conditioning system, in particular for separating particles, preferably dirt particles, from air (L), - with an air path (2) through which the air (L) flows along a flow direction (S), - with an ionizer (3) arranged in the air path (2) for generating ions in the air path (2), which has at least one spray electrode (6) and at least one counter electrode (7), - with an air filter unit (100) arranged downstream of the ionizer (3) with respect to the flow direction (S) according to one of the preceding claims, - with a high-voltage source (8) having an electric pole (8a) and an electric counter-pole (8b) for generating an electric high voltage (HV), in particular between 5 kV and 15 kV, between the pole (8a) and the counter-pole (8b), - wherein the pole (8a) is electrically connected to the at least one spray electrode (6) of the ionizer (3) and the counter pole (8b) is electrically connected to at least one counter electrode (7) of the ionizer and to the electrically conductive layer (103) of the air filter unit (100). [17] Air filter device according to claim 15, characterized by , that at least three spray electrodes (6) and two electrode plates (11) are arranged alternately in succession perpendicular to the direction of flow (S). [18] Air filter device according to claim 15 or 16, characterized by , that - the electrical opposite pole (8b) is connected to the electrical connection element (106) by means of an electrical connecting line (122), in particular in the form of an electrical cable (123), - the electrical connecting line (122) or the electrical cable (123) is electrically connected to the connection element (106) of the air filter unit (100) by means of a material-bonded connection, in particular by means of a soldered or welded connection, or by means of a crimp connection. [19] Air filter device according to claim 15 or 16, characterized by , that an electrical switch (10) is arranged between the electrical connection element (106) and the opposite pole (8b) for interrupting the electrical connection between the electrical connection element (106) and the opposite pole (8b). [20] Air filter device according to one of claims 15 to 17, characterized by , that - the electrical pole (8a) is configured as the negative pole and the electrical opposite pole as the counter potential of the high voltage source (8), or that - the electrical pole (8a) is configured as the positive pole and the electrical opposite pole as the counter potential of the high voltage source (8).

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