Air filter system

Abstract

The invention relates to an air filter device (1) for filtering an airflow (2), preferably for introducing it into a vehicle interior (3), comprising a housing (4) having a channel (5) for guiding the airflow (2), an ionization device (6) for ionizing particles carried in the airflow (2), which has an electrode (7) electrically connected to a first electrical potential (I) and a counter electrode (8) electrically connected to a second electrical potential (II) for generating a corona discharge (9), and a particle filter element (11) replaceably inserted into the channel (5), which has an electrical contact surface (12) and a filter material (13) comprising a particle filter layer (14) and an electrically conductive layer (15) electrically connected to the respective contact surface (12).wherein the housing (4) has a contact device (16) for electrically connecting the electrically conductive layer (15) to the second potential (II), which has a contact element (17) electrically connected to the second potential (II) and which rests against the contact surface (12). The functional reliability can be improved by having the respective contact element (17) rest against the contact surface (12) transversely to a mounting direction (18) of the particle filter element (11), wherein the respective contact element (17) rests against the respective contact surface (12) under preload.

Description

[0001] The present invention relates to an air filter device for filtering an airflow, preferably for introduction into an interior space, in particular of a motor vehicle.

[0002] Air filtration devices of this type are configured to remove contaminants from an airflow and are preferably used in air conditioning or HVAC systems of motor vehicles, which can cool, heat, and dehumidify an airflow as needed before supplying it to the vehicle's interior. Typically, such an air filtration device has a housing with a channel for guiding the airflow to be filtered. A replaceable particle filter element can be arranged in the channel to separate particles from the airflow. The housing can already be an integral part of the HVAC system, where HVAC, in the usual sense, stands for Heating, Ventilation, and Air Conditioning.

[0003] To improve particle separation, it is known to use particle filter elements whose filter material is electrostatically charged. Ionized particles carried in the airflow adhere to the filter material as it passes through, even if the particles are smaller than a pore size of the filter material. Modern air filtration systems can be equipped with an ionization device for the active ionization of particles carried in the airflow. This device has at least one electrode electrically connected to a first potential and at least one counter electrode electrically connected to a second potential to generate a corona discharge. In this way, a corona discharge field can be generated in the duct through which the airflow passes, thereby ionizing the entrained particles.Such air filter devices with ionization device are known, for example, from EP 3 056 364 B1, from EP 3 488 933 A1, from KR 102 205 159 B1, from US 2021 / 0 021 107 A1, from WO 2020 / 263171 A1 and from WO 2021 / 226639 A2.

[0004] However, it has been shown that the electrostatic charge of the filter material decreases relatively quickly with increasing particle loading.

[0005] One approach to solving this problem is to equip the filter material with an electrically conductive layer that is electrically connected to the second potential. This allows the electrostatic charge of the filter material to be regenerated permanently, periodically, or as needed, thereby maintaining the electrostatic filtration effect continuously.

[0006] In air filtration systems of this type, the electrical contact between the respective conductive layer of the filter material and the secondary potential is problematic with regard to the replaceability of the particulate filter element. Electrical contacts are provided on the housing and the particulate filter element for this purpose; these contacts interact when the particulate filter element is inserted into the duct. When replacing the particulate filter element, it must be moved relative to the housing, generating forces that can damage the contacts. Reliable plug contacts are often too expensive for such particulate filter elements. Inexpensive solutions are typically not very robust and can be permanently damaged during particulate filter element replacement, thus jeopardizing the electrical contact between the conductive layer of the particulate filter element and the secondary potential.

[0007] The present invention addresses the problem of providing an improved or at least a different embodiment of an air filter device of the type described above, which is characterized in particular by a simple design and a reliable functioning.

[0008] This problem is solved according to the invention by the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims.

[0009] The invention is based on the general concept of configuring a contact device for electrically connecting the electrically conductive filter layer to the second potential such that the electrical contact is made transversely to the mounting direction with which the particle filter element is inserted into the duct. This largely decouples the contact device from forces acting parallel to the mounting direction when replacing the particle filter element, thereby significantly reducing the mechanical stress on the contact device. This simplifies reliable and durable operation while simultaneously enabling a comparatively inexpensive solution.

[0010] In the present context, a “configuration” corresponds to a “design” and / or a “setup”, so that the phrase “configured so that” is synonymous with the phrase “designed so that” and / or “set up so that”.

[0011] In detail, the invention proposes an air filter device for filtering an airflow, comprising a housing having a channel for guiding the airflow, an ionization device for ionizing particles carried in the airflow, which has at least one electrode that is electrically connectable or connected to a first electrical potential and at least one counter electrode that is electrically connectable or connected to a second electrical potential for generating a corona discharge, and a particle filter element replaceably inserted into the channel for separating the particles from the airflow, wherein the particle filter element has at least one electrical contact surface and a multilayer filter material through which the airflow flows, comprising at least one particle filter layer and at least one electrically conductive layer that is electrically connected to the respective contact surface.According to the invention, the housing also has a contact device for electrically connecting the respective electrically conductive layer to the second potential, which has at least one contact element electrically connected to the second potential and which rests against the respective contact surface when the particle filter element is inserted into the channel. The respective contact element and the respective contact surface are configured such that the respective contact element rests against the contact surface transversely to the mounting direction in which the particle filter element is inserted into the channel. Furthermore, according to the invention, the respective contact element is designed as a spring element that rests against the respective contact surface under preload.

[0012] According to an advantageous embodiment, the contact device can include an electrical switch arranged in the electrical connection between the second potential and the contact element, and configured to switch the connection. The switch allows the electrical connection of the electrically conductive layer to the second potential to be controlled, and in particular, the regeneration of the electrically conductive layer to be carried out as needed.

[0013] According to an advantageous embodiment, the respective contact element can be adjustable between a contact position, in which it rests against the respective contact surface with a preload when the particle filter element is inserted into the channel, and a non-contact position, in which it is spaced away from the respective contact surface when the particle filter element is inserted into the channel. Furthermore, the contact device for the respective contact element can have an actuating mechanism with which the respective contact element can be adjusted between the contact position and the non-contact position. In this embodiment, any interaction between the respective contact element and the particle filter element, which could lead to mechanical stress and damage to the respective contact element or the particle filter element when the particle filter element is changed, can be avoided in the non-contact position of the respective contact element.This ensures reliable, long-term functionality for the contact device and the particle filter element.

[0014] According to an advantageous embodiment, the actuating mechanism can include an actuating element coupled to the respective contact element. Actuating this element causes the contact element to move between the contact and non-contact positions. Using this actuating element, it is possible to selectively move the contact element between these positions. This makes it particularly possible to move the contact element to the non-contact position before changing the particulate filter element, thus decoupling it from mechanical interaction with the element. After the particulate filter element has been changed, the contact element can then be selectively moved back to the contact position without any risk of damage.

[0015] The housing can advantageously include a shaft arranged in the duct to receive the particle filter element, an insertion opening through which the particle filter element can be inserted into the shaft, and a cover for opening and closing the insertion opening. This makes it particularly easy to insert and remove the particle filter element from the duct, thus facilitating easy replacement of the particle filter element during maintenance.

[0016] According to an advantageous embodiment, the actuating element can be coupled to the cover such that opening the cover causes the respective contact element to move from the contact position to the non-contact position, and closing the cover causes the respective contact element to move from the non-contact position to the contact position. In this way, the adjustment of the respective contact element occurs automatically when the cover is actuated and therefore cannot be forgotten when changing the particulate filter element. This ensures a high level of operational reliability.

[0017] In an alternative embodiment, the actuating element in the shaft can be arranged in such a way that it interacts with the particle filter element, such that at the end of an insertion process, in which the particle filter element is inserted into the shaft in the assembly direction, the particle filter element actuates the actuating element to adjust the respective contact element from the non-contact position to the contact position, and that at the beginning of a removal process, in which the particle filter element is pulled out of the shaft against the assembly direction, the particle filter element actuates the actuating element to adjust the respective contact element from the contact position to the non-contact position.This measure also ensures that removing and inserting the particle filter element inevitably leads to an adjustment of the respective contact element, so that essentially no mechanical interaction takes place between the particle filter element and the respective contact element. In particular, it can be provided that the respective actuating element is arranged opposite the insertion opening in the shaft with respect to the mounting direction, in order to avoid interactions with the airflow in the duct.

[0018] In another embodiment, the actuating element can be arranged and configured so that it can be manually actuated and thus switched between an actuated and an unactuated state. When the actuating element is actuated to switch from the unactuated to the actuated state, it causes the respective contact element to move from the contact position to the non-contact position. In the actuated state, the respective contact element is held in the non-contact position. When the actuating element is actuated to switch from the actuated to the unactuated state, it causes the respective contact element to move from the non-contact position to the contact position. In the unactuated state, the respective contact element is held in the contact position.In this embodiment, the actuating element can be positioned virtually anywhere on the housing, such that it is easily accessible for manual operation. Preferably, the actuating element can be arranged on the outside of the housing and be easily accessible by hand.

[0019] In particular, according to one embodiment, the contact element configured as a spring element can have a preload section which is elastically deformed and thereby tensioned when moved into the contact position, thus generating the preload during the contact position.

[0020] In another embodiment, the actuating mechanism can be configured such that, when the respective contact element is moved from the non-contact position to the contact position, the actuating element generates a preload that causes the respective contact element to bear against the respective contact surface in the contact position. In other words, the contact element, configured as a spring element, is tensioned by the actuating element when moved into the contact position, i.e., it is elastically deformed to generate the preload.

[0021] In another embodiment, the respective contact element can have a driver that interacts with the actuating element and generates the preload when the actuating element is actuated to move the respective contact element into the contact position. This selectively generates the desired elastic deformation within the contact element to achieve the preload.

[0022] In another embodiment, the actuating element can include a joint that connects two sections of the actuating element. When the respective contact element is deformed, the joint allows relative movement between the two sections of the actuating element. This enables a simple and low-wear kinematic design in the actuating mechanism.

[0023] In particular, in one embodiment, the contact element configured as a spring element can have a return section which, when moved into the contact position, is elastically deformed and thereby tensioned, generating a return force that drives the contact element into the non-contact position. This assists in moving the contact element into the non-contact position.

[0024] A particularly advantageous embodiment is one in which the respective contact element is also configured to be pre-tensioned in the non-contact position when in contact. This can be especially beneficial for adjusting the contact element to the non-contact position in embodiments where the actuating element permanently holds the respective contact element in contact. In particular, the spring-induced restoring force can then simplify the adjustment to the non-contact position. The contact position is maintained for a comparatively long period during normal operation of the particulate filter element, so that, due to unavoidable contamination, the contact element may stick to the respective contact surface. The pre-tensioning in the non-contact position easily overcomes these undesirable holding forces.This ensures proper functioning, while simultaneously reducing the risk of damage to the actuation mechanism or contact device.

[0025] According to an advantageous embodiment, the electrically conductive layer of the particle filter element can, for example, be formed by an adsorption filter layer equipped with activated carbon particles.

[0026] 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.

[0027] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention. Components of a higher-level unit, such as a device, apparatus, or arrangement, mentioned above and those to be mentioned below, which are designated separately, can form separate parts or components of this unit or be integral areas or sections of this unit, even if this is depicted differently in the drawings.

[0028] 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.

[0029] They show, schematically, Fig. 1. A highly simplified, circuit diagram-like schematic representation of an air filter device, Fig. 2 a highly simplified schematic representation of the air filter device in the area of ​​a contact device with a contact element in a non-contact position, Fig. 3 a view as in Fig. 2, however with the contact element in a contact position, Fig. 4 a view like in Fig. 2, however, in another embodiment with the contact elements in the non-contact position, Fig. 5 a view like in Fig. 3, however, in the embodiment of the Fig. 4 with the contact element in the contact position.

[0030] Accordingly Fig. 1 comprises an air filter device 1, which serves to filter an airflow 2, which is supplied in particular to an interior 3 of a motor vehicle (not otherwise shown), and a housing 4, which has a channel 5 for guiding the airflow 2. The airflow 2 is in Fig. Figure 1 is indicated by arrows and is purely illustrative, oriented from left to right. The air filter unit 1 can be part of an air conditioning system, which also serves to cool and / or heat and / or dehumidify the airflow 2. The housing 4 can form part of the air conditioning system's housing.

[0031] The air filter device 1 is equipped with an ionization device 6 for ionizing particles carried in the airflow 2, which has at least one electrode 7 and at least one counter electrode 8, which interact during operation to generate a corona discharge 9. Fig. Figure 1 shows only a single electrode 7, representing several electrodes 7. Similarly, only a single counter electrode 8 is shown, representing several counter electrodes 8. The electrode 7 can, for example, have several needles 10, which are particularly suitable for generating a corona discharge 9. The electrode 7 and the counter electrode 8 are configured to allow airflow 2 to flow around and through them, respectively. During operation of the ionization device 6, the respective electrode 7 is electrically connected to a first electrical potential I, while the counter electrode 8 is electrically connected to a second electrical potential II. A high voltage of several kV typically exists between the two potentials I and II to generate the corona discharge 9. The second potential II represents a counter-potential to the first potential I.A preferred configuration is one in which the first potential I is negative, while the second potential II is positive or neutral.

[0032] The air filter device 1 also includes a particle filter element 11 for separating particles from the airflow 2, which is replaceably inserted into the duct 5. The particle filter element 11 is equipped with at least one electrical contact surface 12 and comprises a multi-layered filter material 13 through which the airflow 2 can pass. The multi-layered filter material 13 can have at least one particle filter layer 14 and at least one electrically conductive layer 15. The electrically conductive layer 15 can, in particular, be formed by an adsorption filter layer containing activated carbon particles. Advantageously, the electrically conductive layer 15 extends over the entire cross-sectional area through which the airflow passes through the particle filter element 11. If the particle filter layer 14 is pleated, the electrically conductive layer 15 can also be pleated. Likewise, the electrically conductive layer 15 can be unfolded.This electrically conductive layer 15 is electrically connected to the respective contact surface 12 in a suitable manner. In particular, the contact surface 12 can be formed by a section of the electrically conductive layer 15. Preferably, however, the contact surface can be located on a frame of the particle filter element 11, which surrounds the filter material 13.

[0033] The housing 4 is equipped with a contact device 16 for electrically connecting the respective electrically conductive layer 15 directly or indirectly to the second potential II. This allows the electrically conductive layer 15 to be electrically connected to the same electrical potential, namely the second potential II or the counter potential, to which the respective counter electrode 8 is also electrically connected.

[0034] The electrical connection 35 thus established can be made via a suitable electrical conductor. Optionally, an electrical switch 36 can be integrated into the connection 35. This switch 36 can be used to control the connection 35, i.e., to open or close it. Without the switch 36, the connection 35 can be implemented directly and permanently. With the switch 36, the connection 35 can be implemented in a switchable and indirect manner.

[0035] The contact device 16 has at least one contact element 17 which is electrically connected to the second potential II via the connection 35. When the particle filter element 11 is inserted into the channel 5, the contact element 17 rests against the contact surface 12, whereby the electrically conductive layer 15 is electrically connected to the potential of the counter electrode 8, or can be connected when the switch 36 is used.

[0036] The respective contact element 17 and the respective contact surface 12 are configured such that the respective contact element 17 rests against the contact surface 12 transversely to an assembly direction 18, which is symbolized by an arrow in the figures and with which the particle filter element 11 is inserted into the channel 5. The respective contact element 17 is configured as a spring element that rests against the respective contact surface 12 under preload. Fig. 1, Fig. 3 and Fig. 5 is a preload 19 with which the contact element 17 rests on the contact surface 12 transversely to the mounting direction 18, indicated by an arrow 19.

[0037] The housing 4 can have a shaft 20 arranged in the channel 5. The housing 4 can also have an insertion opening 21 through which the particle filter element 13 can be inserted into the shaft 20. Furthermore, the housing 4 can have a cover 22 for opening and closing the insertion opening 21.

[0038] The following will be based on the Fig. Sections 2 to 5 went into more detail about contact facility 16. According to the Fig. The respective contact element 17 can be positioned between 2 and 5 in the Fig. 3 and Fig. 5 shown contact position KS and one in the Fig. 2 and Fig. The non-contact position NS shown in Figure 4 can be adjusted. In the contact position KS, the contact element 17 rests against the respective contact surface 12 when the particle filter element 11 is inserted into the channel 5. In the non-contact position NS, the contact element 17 is, however, spaced away from the respective contact surface 12 when the particle filter element 11 is inserted into the channel 5. Fig. 2 and Fig. Figure 4 shows a corresponding distance A between the contact element 17 and the contact surface 12. The contact device 16 is equipped with an actuating mechanism 23, which is assigned to the respective contact element 17, such that the actuating mechanism 23 allows the respective contact element 17 to be adjusted between the contact position KS and the non-contact position NS. Advantageously, the actuating mechanism 23 can have an actuating element 24, which is coupled to the respective contact element 17 and which, when actuated, causes the respective contact element 17 to be adjusted between the contact position KS and the non-contact position NS.

[0039] During the Fig. 2 and Fig. In the first embodiment shown in Figure 3, the actuating element 24 is coupled to the cover 22 such that opening the cover 22 causes the contact element 17 to move from the contact position KS to the non-contact position NS. Conversely, closing the cover 22 causes the respective contact element 17 to move from the non-contact position NS to the contact position KS. Fig. 2. The cover 22 is open, allowing the particle filter element 11 to be inserted into or removed from the shaft 20 through the insertion opening 21. With the cover 22 open, the actuating element 24 can, for example, move outwards, away from the channel 5, through a base 25 of the contact element 17 attached to the housing 4, i.e., through an opening formed in the base element 25 (not visible here). This moves the contact element 17 into the Fig. The non-contact position NS shown in Figure 2 is adjusted, whereby the distance A is formed between the contact element 17 and the contact surface 12. The outward adjustment movement of the actuating element 24 is in Fig. 2 is indicated by an arrow 26. However, according to Fig. 3. When the cover 22 is closed to seal the insertion opening 21, the cover 22 interacts with the actuating element 24 such that an actuating force 27, which is in Fig. 3, indicated by an arrow, acts on the actuating element 24 and drives it inwards through the base 25, i.e., into the channel 5. In doing so, the contact element 17 is moved towards the contact surface 12 into the contact position KS. The actuating element 24 can be rod-shaped and interact with a driver 26 formed on the contact element 17.

[0040] During the Fig. 4 and Fig. In the second embodiment shown in Figure 5, the actuating element 24 is arranged in the shaft 20, in particular opposite to the insertion opening 21 with respect to the mounting direction 18, which is located in the Fig. 4 and Fig. 5 is not apparent. In any case, the actuating element 24 is arranged such that it can interact with the particle filter element 11 when the particle filter element 11 is inserted into the shaft 20 or when the particle filter element 11 is removed from the shaft 20. The interaction between the particle filter element 11 and the actuating element 24 is such that, at the end of an insertion process in which the particle filter element 11 is inserted into the shaft 20 in the mounting direction 18, the actuating element 24 is actuated by the particle filter element 11 to adjust the respective contact element 17 from the non-contact position NS to the contact position KS.In contrast, at the beginning of a removal process, in which the particle filter element 11 is pulled out of the shaft 20 against the mounting direction 18, the actuating element 24 is used to adjust the respective contact element 17 from the contact position KS to the non-contact position NS. Fig. Figure 4 depicts a state in which the particle filter element 11, with its end face leading when inserted into the shaft 20, contacts a stop 28 formed on the actuating element 24. From this state onward, during the insertion process, the movement of the particle filter element 11 in the mounting direction 18 drives the actuating element 24 via the stop 28 and adjusts it in the mounting direction 18. The actuating element 24, which is connected to the contact element 17, carries a portion of the contact element 17 with it, causing the contact element 17 to deform elastically. Due to this elastic deformation, the contact element 17 approaches the contact surface 12 transversely to the mounting direction 18 until it reaches the Fig. In the end position shown in Figure 5, the particle filter element 11 reaches the contact position KS and rests against the contact surface 12 with the preload 19, perpendicular to the mounting direction 18. During the removal process, the contact element 17 moves away and takes the actuating element 24 with it, allowing the stop 28 to initially follow the particle filter element 11 against the mounting direction 18, until the state in Fig. Position 4 is reached. From this point, the particle filter element 11 detaches from the stop 28, preventing it from moving or adjusting further. The contact element 17 has already reached its non-contact position NS.

[0041] In the Fig. 4 and Fig. In the example shown in Figure 5, the actuating element 24 is essentially U-shaped and is also guided through a base 25 of the contact element 17 attached to the housing 4, or through an opening formed in the base 25. A joint 29 is formed on the actuating element 24 in this area, allowing the actuating element 24 to better follow the deformation movement of the contact element 17. This is also the case in the example of Fig. 4 and Fig. 5 the actuating element 24 interacts with a driver 26 of the contact element 17.

[0042] In the embodiments of the Fig. In sections 2 to 5, the actuating mechanism 23 is configured such that, when the respective contact element 17 is moved from the non-contact position NS to the contact position KS, the actuating element 24 generates the preload 19 by spring-elastic deformation of the contact element 17, which is designed as a spring element. This preload causes the respective contact element 17 to bear against the respective contact surface 12 in the contact position KS. The preloaded contact with the contact surface 12 with the preload 19 is described in the Fig. 3 and Fig. 5 indicated.

[0043] When the actuating element 24 is actuated to adjust the respective contact element 17 into the contact position KS, the driver 26 generates an elastic deformation of the contact element 17. The elastic deformation is, in the example of the Fig. 2 and Fig. 3. This is recognizable by the fact that an angle 30° between the base 25 and a section of the contact element 17 projecting from it is increased when moving from the non-contact position NS to the contact position KS. In contrast, the elastic deformation occurs in the Fig. 4 and Fig. In the example shown in Figure 5, an angle 31 is formed between the base 25 and a section of the contact element 17 projecting from it. In this example, the angle 31 decreases when the contact element 17 is moved from the non-contact position NS to the contact position KS. This elastic deformation generates a restoring force 32 in the contact element 17, which drives the contact element 17, moved from the contact position KS to the non-contact position NS. This restoring force 32 is in the Fig. 3 and Fig. 5 is indicated by an arrow pointing away from the contact surface.

[0044] The restoring force 32 assists the adjustment movement of the contact element 17 from the contact position KS to the non-contact position NS. Through the coupling between the actuating element 25 and the contact element 17, the actuating element 24 is also driven.

[0045] The contact element 17, configured as a spring element, can therefore have a preload section 33 which is elastically deformed and thus tensioned when moved into the contact position KS, thereby generating the preload 19 in the contact position KS. In the examples shown here, the preload section 33 is formed in a section of the contact element 17 that connects to the driver 26 on a side facing away from the base 25.

[0046] The contact element 17, configured as a spring element, can additionally or alternatively have a return section 34 which is elastically deformed when moved into the contact position KS and is thereby tensioned, generating the return force 32 that drives the contact element 17 into the non-contact position NS. In the examples shown here, the return section 34 is formed in a section of the contact element 17 that contains the respective angle 30 or 31, which is used to generate the return force 32 in the example of Fig. 2 and Fig. 3 enlarged and in the example of the Fig. 4 and Fig. 5 is reduced in size. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 3 056 364 B1

[0003] EP 3 488 933 A1

[0003] KR 102 205 159 B1

[0003] US 2021 / 0 021 107 A1

[0003] WO 2020 / 263171 A1

[0003] WO 2021 / 226639 A2

[0003]

Claims

[1] Air filter device (1) for filtering an airflow (2), preferably for introduction into an interior space (3), in particular a motor vehicle, - with a housing (4) which has a channel (5) for guiding the airflow (2), - with an ionization device (6) for ionizing particles carried in the air stream (2), which has at least one electrode (7) that is electrically connectable or connected to an electrical first potential (I) and at least one counter electrode (8) that is electrically connectable or connected to an electrical second potential (II) for generating a corona discharge (9), - with a particle filter element (11) interchangeably inserted into the channel (5) for separating the particles from the airflow (2), which has at least one electrical contact surface (12) and a multilayer filter material (13) through which the airflow (2) can flow, which has at least one particle filter layer (14) and at least one electrically conductive layer (15) which is electrically connected to the respective contact surface (12), - wherein the housing (4) has a contact device (16) for electrically connecting the respective electrically conductive layer (15) to the second potential (II), which has at least one contact element (17) electrically connected to the second potential (II), which rests against the respective contact surface (12) when the particle filter element (11) is inserted into the channel (5), - wherein the respective contact element (17) and the respective contact surface (12) are configured such that the respective contact element (17) rests against the contact surface (12) transversely to a mounting direction (18) with which the particle filter element (11) is inserted into the channel (5), - wherein the respective contact element (17) is designed as a spring element which is pre-tensioned against the respective contact surface (12). [2] Air filter device (1) according to claim 1, characterized by , - that the contact device (16) has an electrical switch (36) which is arranged in the electrical connection (35) between the second potential (II) and the contact element (17) and is configured to switch the connection (35). [3] Air filter device (1) according to claim 1 or 2, characterized by , - that the respective contact element (17) is adjustable between a contact position (KS), in which it is pre-tensioned against the respective contact surface (12) when the particle filter element (11) is inserted into the channel (5), and a non-contact position (NS), in which it is spaced away from the respective contact surface (12) when the particle filter element (11) is inserted into the channel (5), - that the contact device (16) for the respective contact element (17) has an actuating mechanism (23) with which the respective contact element (17) can be adjusted between the contact position (KS) and the non-contact position (NS). [4] Air filter device (1) according to claim 3, characterized by , - that the actuating mechanism (23) has an actuating element (24) which is coupled to the respective contact element (17) and which, when actuated, causes the respective contact element (17) to be adjusted between the contact position (KS) and the non-contact position (NS). [5] Air filter device (1) according to one of the preceding claims, characterized by , - that the housing (4) has a shaft (20) arranged in the channel (5) for receiving the particle filter element (11), an insertion opening (21) through which the particle filter element (11) can be inserted into the shaft (20), and a cover (22) for opening and closing the insertion opening (21). [6] Air filter device (1) according to claims 4 and 5, characterized by , - that the actuating element (24) is coupled to the cover (22) in such a way that opening the cover (22) causes the respective contact element (17) to be moved from the contact position (KS) to the non-contact position (NS), and that closing the cover (22) causes the respective contact element (17) to be moved from the non-contact position (NS) to the contact position (KS). [7] Air filter device (1) according to claims 4 and 5, characterized by , - that the actuating element (24) is arranged in the shaft (20) such that it interacts with the particle filter element (11) in such a way that at the end of an insertion process in which the particle filter element (11) is inserted into the shaft (20) in the assembly direction (18), the particle filter element (11) actuates the actuating element (24) to adjust the respective contact element (17) from the non-contact position (NS) to the contact position (KS), and that at the beginning of a removal process in which the particle filter element (11) is pulled out of the shaft (20) against the assembly direction (18), the particle filter element (11) actuates the actuating element (24) to adjust the respective contact element (17) from the contact position (KS) to the non-contact position (NS). [8] Air filter device (1) according to one of claims 4, 6 and 7, characterized by , - that the actuating mechanism (23) is configured such that the actuating element (24) generates a preload (19) when adjusting the respective contact element (17) from the non-contact position (NS) to the contact position (KS), with which the respective contact element (17) rests against the respective contact surface (12) in the contact position (KS). [9] Air filter device (1) according to claim 8, characterized by , - that the respective contact element (17) has a driver (26) that interacts with the actuating element (24) and which, when the actuating element (24) is actuated to adjust the respective contact element (17) into the contact position (KS), causes an elastic deformation of the respective contact element (17). [10] Air filter device (1) according to claim 8 or 9, characterized by , - that the actuating element (24) contains a joint (29) which, when the respective contact element (17) is deformed, allows relative movements between two sections of the actuating element (24) connected to each other via the joint (29). [11] Air filter device (1) according to any one of the preceding claims, characterized by , - that the respective contact element (17) is also configured such that it is pre-tensioned in the contact position (KS) to the non-contact position (NS). [12] Air filter device (1) according to claim 3 or according to claim 3 and one of claims 4 to 11, characterized by , - that the respective contact element (17) has a preload section (33) which is elastically deformed and thereby tensioned when the respective contact element (17) is moved into the contact position (KS), thus generating the preload (19) with which the respective contact element (17) rests against the respective contact surface (12) in the contact position (KS). [13] Air filter device (1) according to claim 3 or according to claim 3 and one of claims 4 to 12, characterized by , - that the respective contact element (17) has a restoring section (34) which is elastically deformed when the respective contact element (17) is moved into the contact position (KS) and thereby generates a restoring force (32) which drives the respective contact element (17) moved into the contact position (KS) into the non-contact position (NS).

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