Method for diagnosing an air filter device comprising an ionizer and an air filter unit for separating particles from air passed through the air filter unit

Abstract

The invention relates to a method for diagnosing an air filter device (1) for separating particles (P) from air (L) passed through the air filter unit (20), which has an ionizer (3) with at least one spray electrode (17) and with at least one counter electrode (5) and also an air filter unit (20) with a filter element (21) having an electrically conductive layer (22), wherein the electrically conductive layer (22) is electrically connected to the counter electrode (5), - according to which an electrical potential difference or high voltage (HV) is generated between the spray electrode (17) and the counter electrode (5) by means of an electrical high-voltage source (8) which is electrically connected to at least one spray electrode (17) and to at least one counter electrode (5) of the ionizer (3), which causes an electric corona current from electrical charges, in particular electrons, emerging from the at least one spray electrode (17), - according to which electrical supply current (I0) is supplied to the electrical high-voltage source (8) for the generation of the electrical corona current, which depends on the electrical corona current, - according to which this electrical supply current (I0) is determined and, depending on this, a conclusion is drawn about a current operating state of the filter element (21) and / or about a filter type of the filter element (21).

Description

[0001] The present invention relates to a method for diagnosing an air filter device comprising an ionizer and an air filter unit for separating particles from air passed through the air filter unit. The invention further relates to a method that is set up / programmed for carrying out this method.

[0002] For pleasant and healthy air quality, the air introduced into a vehicle interior 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 of the vehicle prove to be particularly problematic.

[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 element often incorporates a filter layer to separate the particles contained in the air. This filter element is crucial for the air quality of the filtered air. However, modern automotive air conditioning systems offer limited installation space for such a filter element. Therefore, this filter element must have low flow resistance to minimize pressure loss in the air, ensuring that the desired volume of air can be transported into the vehicle interior.

[0004] To achieve low flow resistance, the particle-separating filter layer of the filter element is usually very open-pored, which means the mechanical dust separation efficiency of the filter can only reach comparatively low values. Therefore, the filter media of conventional filter elements are electrostatically charged during the production process. This allows electrostatically charged particles to be more effectively separated in the filter medium during subsequent operation using electrostatic deposition.

[0005] The mechanism of electrostatic charging of particles is also utilized by a so-called ionizer. This device electrostatically charges particles contained in the air path by emitting charged particles, particularly electrons, during a corona discharge. Furthermore, the ions introduced into the air can also at least partially recharge the filter element. Thanks to the separation mechanism described above, even very small particles with a diameter of less than 0.3 µm can be separated from the electrostatically charged filter element without significantly increasing the flow resistance of the filter element and thus the resulting pressure drop.

[0006] The filter element in question is usually arranged in a filter housing so that it can be replaced with a spare part when a maximum load of particles separated from the air is reached.

[0007] However, for the proper functioning of the air filter system, it is important that the filter element, designed as a replacement part, is always positioned in the air path during operation of the air filter system.

[0008] To achieve optimal dust separation performance throughout the entire service life of the filter element, it is also important that the filter element is subjected to the intended flow direction of the air to be filtered.

[0009] It is therefore an object of the present invention to provide an improved diagnostic method for an air filter device with a filter element as described above, which takes into account the problem described above.

[0010] This problem is solved by the subject matter of the independent patent claims. Preferred embodiments are the subject matter of the dependent claims.

[0011] The basic idea of ​​the invention is therefore to use an analysis of the electrical supply current required to generate an electrical corona discharge from a high-voltage source in a system consisting of an ionizer and an electrostatically chargeable filter element to determine the current operating state and – alternatively or additionally – the filter type of the filter element used. This method exploits the fact that the electrical current depends on the current operating state of the filter element and also on the filter type used. Thus, by measuring and analyzing the electrical supply current, it can be determined whether the electrical connection between the filter element and the high-voltage electrical source, necessary for the proper functioning of the air filter system, exists or not.From this, it can be deduced whether the filter element is positioned in the air path in the receptacle provided for the filter element and, if so, whether it is positioned there with the correct orientation.

[0012] The magnitude of the corona current, and therefore the electrical supply current required to power the high-voltage source, depends on the structure and condition of the filter medium, and in particular on whether the filter element has an electrically conductive layer. If the filter medium is activated carbon, the magnitude depends on its composition and the amount or density of activated carbon it contains. Since the required electrical supply current also depends on the airflow and the number of particles, air volume and particle concentration can be additionally measured using a PM2.5 sensor. Other factors that can influence the current include humidity, temperature, and gaseous air pollutants.

[0013] Following the above inventive concept, the method according to the invention serves to diagnose an air filter device for separating particles from air passed through the air filter unit. The air filter device comprises an ionizer with at least one spray electrode and at least one counter electrode, and also an air filter unit with a filter element having an electrically conductive layer.

[0014] In a negative corona discharge, electrons are emitted from the spray electrode, which can be shaped like pointed spikes, and are accelerated to high speeds, particularly in the electric field near the electrode. These electrons collide with gas molecules, causing them to lose an electron and become positively ionized. This results in one positively charged gas molecule and two electrons. This effect occurs primarily at very high field strengths and close to the spray electrode. At greater distances from the electrode, the faster-moving electrons predominantly attach themselves to gas molecules, forming negative gas ions. A negative corona discharge produces more gas ions than a positive corona discharge because electrons, due to their lower mass, move faster.This promotes the electrostatic charging of the particles and thus also their deposition in the filter element located downstream of the ionizer in the air path.

[0015] To carry out the method according to the invention, the electrically conductive layer is electrically connected to the counter electrode. This electrical connection can be realized by means of a low-resistance electrical conduction path and, in this case, be designed to be low-resistance. Alternatively, an electrical resistance element, in particular an ohmic resistor, can also be arranged in the electrical connection or electrical conduction path, across which an electrical voltage can drop when an electric current flows through the resistance element. According to the method, an electrical potential difference or high voltage is generated between the spray electrode and the counter electrode by means of an electrical high-voltage source, which is electrically connected to at least one spray electrode and to at least one counter electrode of the ionizer.This generates an electric corona current from electrical charges, particularly electrons, emanating from at least one spray electrode. An electrical supply current, dependent on the electric corona current, is fed to the high-voltage electrical source to generate this current.

[0016] According to the invention, this electrical supply current is now determined, and depending on the determined value, a conclusion is drawn about a current functional state of the filter element and / or about a filter type of the filter element.

[0017] In a particularly preferred embodiment of the method according to the invention, the functional state or filter type of the filter element is determined by comparing the measured electric current with at least one stored reference value. Such a comparison makes it easy to verify whether the actual measured value of the electric current corresponds to an expected value, meaning that the filter element is in a nominal state. It can also be detected if this is not the case. In such cases, appropriate countermeasures can then be initiated.

[0018] According to an advantageous embodiment, the measured electrical supply current is used to determine whether the filter element is positioned within the fixture or not. This method exploits the fact that when the filter element is positioned within the fixture and there is an electrical connection between the electrically conductive layer of the filter element and the high-voltage source—compared to a scenario where the filter element is not positioned within the fixture and consequently there is no electrical connection between the electrically conductive layer and the high-voltage source—an additional electrical current can flow from the layer to the high-voltage source, which also affects the electrical supply current. Therefore, the magnitude of the electrical supply current differs when the filter element is positioned within the fixture compared to when it is not.Thus, using the procedure described above, it can be determined whether the filter element is included in the recording or not.

[0019] A (first) error signal can be generated particularly preferably when it has been determined that the filter element is not located in the recording. This facilitates the initiation of suitable countermeasures if it has been determined by the method according to the invention that the filter element is not arranged in the recording. Such a (first) error signal can be a processable electrical signal. However, the (first) error signal can also be output in optical and / or acoustic and / or haptic form and thus be perceived directly by a user.

[0020] According to a further preferred embodiment, the measured electrical current is used to determine whether the filter element is arranged with the correct orientation in the air path or in the receptacle provided for the filter element in the air path. This method exploits the fact that the electrical corona current, and thus also the electrical supply current, depends on the orientation of the filter element in the receptacle.

[0021] A (second) error signal can be generated particularly advantageously if—especially as described above—it is determined that a filter element with the wrong orientation is present in the recording. This facilitates the initiation of appropriate countermeasures. Such a (second) error signal can be a processable electrical signal. However, the (second) error signal can also be output in optical, acoustic, and / or haptic form and thus be perceived directly by a user.

[0022] According to an advantageous embodiment of the method according to the invention, the electrically conductive layer of the filter element can be selectively electrically disconnected from or connected to the high-voltage electrical source by means of an electrical switch. In this embodiment, the filter condition or filter type is determined by comparing the electrical supply current when the layer is electrically connected to the high-voltage source with the electrical supply current when the layer is electrically disconnected from the high-voltage source. For this purpose, a difference, in particular a differential, between the two electrical supply currents can be determined.This variant takes advantage of the fact that, with an existing electrical connection between the electrically conductive layer and the high-voltage source, an increased corona current flows compared to an interrupted electrical connection, which also results in an increased electrical supply current.

[0023] In another preferred embodiment, a deviation, particularly by calculating the difference, can be determined from the measured electric current and the stored reference value for the electric current. In this embodiment, it is determined, depending on the calculated deviation or difference, whether the filter element is arranged in the correct orientation in the receptacle. This utilizes the fact that, when the filter element is arranged in the receptacle with an incorrect orientation, the electrical connection generated between the electrically conductive layer provided on the filter element and the high-voltage electrical source differs in terms of electrical conductivity or electrical resistance from that when the filter element is arranged in the correct orientation in the receptacle.

[0024] According to another preferred embodiment, in addition to the electric current, the amount of air striking the filter element and the concentration of particles present in the air can also be measured. These two measured quantities are taken into account when determining the functional state of the filter element. By measuring the aforementioned air volume or airflow rate and the aforementioned particle concentration, the electric current expected when the filter element is functioning properly can be determined. This allows the current functional state of the filter element to be determined independently of the amount of air flowing through it and independent of the particle concentration in that air.

[0025] According to a further advantageous development, the determined airflow rate and the measured particle concentration in the air can also be used to ascertain whether the filter element is correctly oriented in the housing. This takes into account that the electrical current can also depend on the aforementioned airflow rate and particle concentration. It is therefore conceivable, in particular, that individual reference values ​​could be stored for different airflow rates and particle concentrations, for example, in the form of a comparison table or a so-called "lookup table." Thus, the corresponding reference value can be selected, or at least determined or calculated, for different airflow rates or particle concentrations.

[0026] The invention further relates to an air filter device for an air conditioning system, in particular for separating particles, preferably dirt particles, from air passed through the air filter device. The air filter device comprises a high-voltage source having an electrical pole and an electrical counter pole for generating a high electrical voltage or potential difference, in particular between 5 kV and 15 kV, between the pole and the counter pole. The air filter device further comprises an air path through which air flows along a flow direction. An electrically energized ionizer of the air filter device is arranged in the air path for generating electrical charges, in particular electrons, exiting the air path. The ionizer has at least one, and more preferably several, spray electrode(s).Likewise, the ionizer has at least one, and preferably several, counter electrode(s) arranged at a distance from the at least one spray electrode.

[0027] Preferably, the counter electrode(s) is / are arranged upstream of the spray electrode(s) in the air path. Equally preferably, a counter electrode can also be arranged between two spray electrodes, or a spray electrode can be arranged between two counter electrodes. A further variant (also not shown) is considered particularly preferred, in which at least two, preferably more, counter electrodes and at least two, preferably more, spray electrodes are provided, wherein the counter electrodes and the spray electrodes are particularly preferably arranged alternately in succession in the air path.

[0028] Furthermore, the air filtration system includes an air filter unit arranged downstream of the ionizer in the air path with respect to the airflow direction. This unit comprises a filter element through which the air flows to separate the particles from the air. An electrically conductive layer is arranged on the filter element, which can be, or is, electrically connected to the counter electrode of the ionizer. The layer can have the same electrical potential as the counter electrode, particularly by providing a low-resistance connection between the layer and the counter electrode. This electrically conductive layer allows the filter element to be electrostatically recharged, i.e., reactivated, when its filtering capacity is exhausted. This prevents the electrostatic charge of the filter element from only being effective at the beginning of its service life.This ensures that the filter element maintains high filtration efficiency throughout its entire service life. The electrically conductive layer can be advantageously positioned facing away from the ionizer in the air path.

[0029] In the air filter device according to the invention, the pole of the high-voltage source is electrically connected to the at least one spray electrode of the ionizer. The opposite pole of the high-voltage source is electrically connected to the at least one counter electrode of the ionizer. Furthermore, the opposite pole is electrically connected to the electrically conductive layer of the filter element. Advantageously, the counter electrode and the electrically conductive layer can then have the same electrical potential, in particular by providing a low-resistance electrical connection between the layer and the opposite pole.

[0030] Furthermore, the air filter device includes an electrical current measuring device for determining an electrical supply current that serves to supply the electrical high voltage source with electrical energy.

[0031] Furthermore, the air filter device comprises an evaluation unit that interacts with the current measuring device and is configured and / or programmed to carry out the aforementioned inventive method. The advantages of the inventive method explained above are therefore transferred to the inventive air filter device.

[0032] In a preferred embodiment of the air filter device according to the invention, the air filter device can include an electrical or electronic, in particular controllable, switch by means of which the electrical connection between the electrically conductive layer of the filter element and the counter electrode can be interrupted. For this purpose, the switch can be toggled between an open state, in which the switch interrupts said electrical connection between the layer and the counter electrode or the high-voltage source, and a closed state, in which this interruption is lifted. In the case of an electrical switch, it can be an electromechanical switch. If an electronic switch is preferred, a semiconductor switch, preferably in the form of a transistor, is particularly suitable.

[0033] According to a further preferred embodiment of the air filter device according to the invention, the air filter device can comprise a sensor device arranged in the air path for determining the amount of air hitting the filter element and / or passing through the filter element, as well as for determining the concentration of particles in this air.

[0034] In another preferred embodiment, the air filter unit can have a receptacle arranged in the air path in which the filter element is arranged in a replaceable manner.

[0035] 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.

[0036] 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 on their own, without leaving the scope of the present invention.

[0037] 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.

[0038] They show, schematically: Fig. 1 by way of example the construction of an air filter device according to the invention, Fig. 2 a flowchart illustrating the method according to the invention.

[0039] The Fig. Figure 1 illustrates an air filter device 1 for an air conditioning system, in particular for separating particles P, preferably dirt particles, from air L passed through the air filter device 1. The air filter device 1 comprises a high-voltage source 8 having an electrical pole 11a and an electrical counter-pole 11b for generating an electrical high voltage HV, in particular between 5 kV and 15 kV, between the pole 11a and the counter-pole 11b.

[0040] The high-voltage source 8 can have a high-voltage transformer 14 with a low-voltage side 14a having a primary coil and a high-voltage side 14b having a secondary coil, which are inductively coupled to each other. The low-voltage side 14a can be electrically connected to a low-voltage voltage source 40, which is located in the Fig. 1 is only schematically indicated and provides a low-voltage direct current (LV) electrical voltage. The low-voltage voltage source 40 can, for example, be a 12V voltage source, which consequently provides a 12V DC voltage. This DC voltage can be converted into a low-voltage alternating current (AC) voltage, or 12V AC voltage, by means of a DC-AC converter. The low-voltage AC voltage can be transformed into the aforementioned high voltage, which is initially an AC voltage, by means of the high-voltage transformer 14. This AC voltage can be converted into a high-voltage direct current (HV) voltage by means of an AC-DC converter (not shown). Furthermore, the air filter assembly 1 includes an electrical current measuring device 15 for determining an electrical supply current I0 for supplying the electrical high-voltage source 8 with electrical energy.

[0041] The electrical current measuring device 15 can include an electrical current sensor 41, which can measure the electrical supply current I0 from the low-voltage voltage source 40 to the low-voltage side 14a of the high-voltage transformer 14 of the high-voltage source 8. For this purpose, the current sensor 41 can be arranged in an electrical conductor path 44, which electrically connects the low-voltage voltage source 40 to the primary side 14a of the high-voltage transformer 14. The low-voltage voltage source 14 can be part of the air filter device 1 or, alternatively, it can be designed separately from it, i.e., not be part of the air filter device 1.

[0042] Furthermore, the air filter device 1 comprises an air path 2 through which the air L flows along a flow direction S. In the air path 2, an ionizer 3 of the air filter device 1, which can be electrically powered by means of the high voltage source 8, is arranged to generate electrical charges, in this example electrons, exiting into the air path 2.

[0043] The ionizer 3 in this example has several spray electrodes 17 for generating ions. The spray electrodes 17 are arranged at intervals from each other in the air path 2. Each spray electrode 17 comprises an electrode rod 12, from which several needle-like electrode tips 13 extend towards the second electrode 5b, from which the aforementioned ions can be generated for particle charging. The electrode tips 13 extend from the respective electrode rod 12 in the opposite direction to the flow direction S.

[0044] In a variant not shown, the electrode tips 13 can also be aligned with the flow direction S of the respective electrode rod 12. As shown in the illustration of the Fig. As illustrated in Figure 1, the electrode tips 13 can be arranged in a grid pattern in the air path 2 and taper conically. The material for the ionizer 3, the spray electrodes 17, and their electrode rods 12 can be steel, for example, stainless steel. The individual electrode rods 12 extend in a straight line in the air path 2 along a common direction of extension E, which is perpendicular to the flow direction S.

[0045] Furthermore, the ionizer 3 comprises a counter electrode 5, which in the example is arranged upstream of the spray electrodes 17 in the air path 2. The counter electrode 5 can be designed in the form of an electrode plate. In a variant not shown, the counter electrode can also be arranged between two spray electrodes. Another variant (also not shown) is conceivable in which several counter electrodes 5 are provided, such that, particularly preferably, these counter electrodes 6 and the spray electrodes 17 are arranged alternately in succession in the air path 2.

[0046] Furthermore, the air filter device 11 comprises an air filter unit 20 arranged downstream of the ionizer 3 in the air path 2 with respect to the flow direction S. This air filter unit 20, in turn, has a filter element 21 through which the air L flows to separate the particles P from the air L. An electrically conductive layer 22 is arranged on the filter element 21. The electrically conductive layer 22 can be formed from activated carbon. To generate ions or an electric corona current by means of the ionizer 3, the pole 11a of the high-voltage source 8 is electrically connected to the spray electrodes 17, and the counter pole 11b of the high-voltage source 8 is electrically connected to the counter electrode 5. The counter electrode 5 is also electrically connected to the electrically conductive layer 22 of the filter element 21 via an electrical conduction path 43. The electrical conduction path 43 can be designed with low resistance so that the counter electrode 5 and the layer 22 have the same electrical potential.Alternatively, in the electrical connection between counter electrode 5 and layer 22, i.e. in the electrical conduction path 43, as in . Fig. 1 indicates an electrical resistance element 47, for example in the form of an ohmic resistor R, may be arranged.

[0047] Furthermore, the air filter unit 20 according to the example comprises an open housing 23, which partially surrounds an interior chamber 24 through which air L to be filtered flows along a flow direction S. The filter element 21 is arranged in the interior chamber 24 in a replaceable manner. For this purpose, a receiving opening 25 for inserting the filter element 21 into the interior chamber 24 can be provided in the housing 23. The interior chamber 24 thus forms a receptacle 18 for the filter element 21.

[0048] According to Fig. 1 The air filter unit 20 also includes an electrical connection element 26 made of an electrically conductive material, arranged on the housing 23 and electrically contactable from outside the housing interior 24. In this example, the electrically conductive material is a metal. The connection element 26 rests against the electrically conductive layer 22 of the filter element 21 and is thus electrically connected to the electrically conductive layer 22. In this example, the connection element 26 is designed as a spring-elastic component 27, for example, in the form of a leaf spring. For this purpose, the material of the connection element 26 or the spring-elastic component 27 can be steel, preferably spring steel. In this way, the connection element 26 can be designed as in Fig. The electrical connection element 26 is pre-tensioned against the electrically conductive layer 22 of the filter element 21 arranged in the housing interior 24. The electrical connection element 26 thus also fulfills the function of a pre-tensioning element 116. In this example, the electrical connection element 26 is permanently attached to the housing 23, for example by means of an adhesive or screw connection, and projects both inwards into the housing interior 24 and outwards from the housing 23 into an external environment 28 of the air filter unit 20.

[0049] Filter element 21 can be in Fig. 1. A schematically indicated filter medium 29 comprises a bellows 30 with a plurality of successive folds, on which the electrically conductive layer 22 is arranged. The filter medium 29 can comprise a filter material designed for the separation of particles, in particular aerosols, with a particle or aerosol diameter between 50 nm and 2.5 µm.

[0050] Finally, the air filter device 1 comprises an evaluation device 16 that interacts with the current measuring device 15 and is designed to control the high voltage source 8 and is set up / programmed to carry out the method according to the invention.

[0051] In the example scenario, the air filter device 1 includes an electrical or electronic switch 45 arranged in the electrical conduction path 46 and electrically controllable by the evaluation device 16. This switch interrupts the electrical connection between the electrically conductive layer 22 of the filter element 21 and the counter electrode 5 or the counter pole 11b of the high-voltage source 8. The switch 45 can be combined with the resistor element 47, as shown. However, variants are also possible in which either the resistor element 47 or the switch 45 is provided. In a particularly simple variant, the resistor element 47 and the switch 45 can be omitted.

[0052] The following is an explanation of the flowchart of the Fig. 2 The method according to the invention is explained by way of example. The method serves to diagnose the air filter device 1 of the Fig. 1.

[0053] To carry out the method according to the invention, the electrically conductive layer 22 is electrically connected to the counter electrode 5.

[0054] According to the method, in a first step a) an electrical potential difference or high voltage is generated between the spray electrodes 17 and the counter electrode 5 by means of an electrical high-voltage source 8, which is electrically connected to the spray electrodes 17 and to the counter electrode of the ionizer 3. This generates an electrical corona current from electrical charges in the form of electrons emerging from the spray electrodes 17.

[0055] To generate the electrical corona current Ic, an electrical supply current I0 is fed to the electrical high-voltage source 8, which depends on the electrical corona current.

[0056] In a second step b) of the inventive method, this electrical supply current I0 is now determined by means of the electrical measuring device 15 or the electrical current sensor 41, and a conclusion is drawn about the current operating state of the filter element 21 and the filter type used for the filter element 21 based on this. This takes advantage of the fact that the electrical supply current I0 depends on both the current operating state and the filter type of the filter element 21.

[0057] The functional state or filter type of filter element 21 can be determined by comparing the measured electrical supply current I0 with a stored reference value. Such a comparison can be used to determine whether the filter element 21 is functioning as shown in the recording 18 (see figure). Fig. 1) or is located outside the receptacle 18, or whether this is not the case. The electrical reference current can correspond to a state of the filter element 21 that is located in the receptacle 18 or not located in the receptacle 18.

[0058] Does the electric air filter unit 1 include as shown in Fig.Figure 1 shows the switch 45 described above for electrically isolating layer 22 from the high-voltage source 8. By comparing the electrical supply current I0 when layer 22 is electrically connected to the high-voltage source 8 with the electrical supply current I0 when layer 22 is electrically disconnected from the high-voltage source 8, the filter state or filter type can be determined. To electrically isolate layer 22 from the high-voltage source 8, the electrical switch 45 can be switched to the open position. To electrically connect the high-voltage source 8 to the electrically conductive layer 22, the switch can be switched to the closed position. Consequently, the electrical supply current I0 is determined, preferably consecutively, with the switch 45 open and closed.

[0059] By evaluating the measured electrical supply current I0, it can also be determined, as described above, whether the filter element 21 is arranged in the correct orientation in the receptacle 18. Similarly, a second error signal F2 can be generated if it is determined that a filter element 21 is installed in the receptacle 18 with an incorrect orientation.

Claims

[1] Method for diagnosing an air filter device (1) for separating particles (P) from air (L) passed through the air filter unit (20), which has an ionizer (3) with at least one spray electrode (17) and with at least one counter electrode (5) and also an air filter unit (20) with a filter element (21) having an electrically conductive layer (22), wherein the electrically conductive layer (22) is electrically connected to the counter electrode (5), - according to which an electrical potential difference or high voltage (HV) is generated between the spray electrode (17) and the counter electrode (5) by means of an electrical high-voltage source (8) which is electrically connected to at least one spray electrode (17) and to at least one counter electrode (5) of the ionizer (3), which causes an electric corona current from electrical charges, in particular electrons, emerging from the at least one spray electrode (17), - according to which electrical supply current (I0) is supplied to the electrical high-voltage source (8) for the generation of the electrical corona current, which depends on the electrical corona current, - according to which this electrical supply current (I0) is determined and, depending on this, a conclusion is drawn about a current operating state of the filter element (21) and / or about a filter type of the filter element (21). [2] Method according to claim 1, characterized by , that the functional state (Z) or the filter type of the filter element (21) is determined by comparing the measured electric current (I) with at least one stored reference value. [3] Method according to any one of the preceding claims, characterized by, that by evaluating the measured electrical supply current (I0) it is determined whether the filter element (21) is arranged in a receptacle (18) of the air filter device (1) for receiving the filter element (21) or not. [4] Method according to claim 3, characterized by , that a (first) error signal (F1) is generated when it is determined that the filter element (21) is not in the recording (18). [5] Method according to claim 3 or 4, by evaluating the measured electrical supply current (I0) it is determined whether the filter element (21) is arranged with the correct orientation in the receptacle (18). [6] Method according to claim 5, characterized by , that a (second) error signal (F2) is generated if it is detected that a filter element (21) with an incorrect orientation is recorded in the recording (18). [7] Method according to any one of the preceding claims, characterized by , that - the electrically conductive layer (22) of the filter element (21) can be selectively electrically disconnected from or connected to the electrical high-voltage source (8) by means of an electrical switch (45), - by comparing the electrical supply current (I0) of the layer electrically connected to the high voltage source (8) with the electrical supply current (I0) of the layer (22) electrically separated from the high voltage source (8), the filter condition or filter type can be determined. [8] Air filter device (1) for an air conditioning system, in particular for separating particles (P), preferably dirt particles, from air (L) passed through the air filter device (1), - with a high-voltage source (8) having an electric pole (11a) and an electric counter-pole (11b) for generating an electric high voltage (HV) or potential difference, in particular between 5 kV and 15 kV, between the pole (11a) and the counter-pole (11b), - 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) and comprising at least one spray electrode (17) and at least one counter electrode (5), and which can be electrically powered by means of the high voltage source (8) for generating electrical charges, in particular electrons, emerging into the air path (2), - with an air filter unit (20) arranged downstream of the ionizer (3) in the air path (2) with respect to the flow direction (S), which comprises a filter element (21) through which the air (L) can flow for separating the particles (P) from the air (L), on which an electrically conductive layer (22) is arranged, - wherein the pole (11a) is electrically connected to at least one spray electrode (3) and the counter pole (11b) is electrically connected to at least one counter electrode (5), - wherein the electrically conductive layer (22) of the filter element (21) is electrically connected to the counter electrode (5), - with an electrical current measuring device (15) for determining an electrical supply current (I0) for supplying the electrical high-voltage source (8) with electrical energy, - with an electrical evaluation device (16) cooperating with the current measuring device (15), which is set up / programmed to carry out the method according to one of the preceding claims. [9] Air filter device according to claim 8, characterized by , that the air filter device (1) includes an electrical or electronic switch (45) by means of which the electrical connection of the electrically conductive layer (22) of the filter element (22) with the counter electrode (5) can be interrupted.

Images