Air filter system and motor vehicle

Abstract

The invention relates to an electrostatic air filter device (6), in particular for a motor vehicle (1), with a flow channel (7) for guiding an airflow (5), with an ionization device (9) for ionizing particles carried in the airflow (5), which has at least one spray electrode (10) and at least one counter electrode (11) in the flow channel (7), and with a filter element (8) for filtering out the particles from the airflow (5), which is arranged in the flow channel (7) downstream of the ionization device (9) and which has a multi-layered filter body (13) with at least one particle filter layer (14) and at least one electrically conductive layer (15). The separation efficiency of the air filter device (9) can be improved, especially in the long term, by electrically connecting the at least one electrically conductive layer (15) to the at least one counter electrode (11) via an electrical resistor (16).

Description

[0001] The present invention relates to an electrostatic air filter device, preferably of a motor vehicle, according to the preamble of claim 1. The invention further relates to a motor vehicle equipped with such an air filter device.

[0002] For pleasant and healthy air quality, the air contained within and supplied to a vehicle's interior or passenger compartment must be purified of pollutants such as particulate matter, harmful gases such as hydrocarbons and nitrogen oxides, and unpleasant odors such as ammonia, trimethylamine, hydrogen sulfide, and similar substances. A major problem, particularly in urban areas of Asia, is the high concentration of particulate matter in the ambient air. In large cities, the daily average levels often exceed the PM2.5 limit or daily average of 15 µg / m³ recommended by the WHO.The removal of dust particles entering the vehicle interior via a fresh air system is nowadays usually achieved using a filter element within a filter unit located in the fresh air system. This filter element can be designed as a particle filter, a hybrid filter, or a combination filter with both a particle filter and an activated carbon filter. The particle filter typically incorporates a fiber filter layer for removing the particles. This filter element is crucial for the air quality inside the vehicle.

[0003] In the fresh air system, which typically also includes an air conditioning system, there is very little installation space available for the filter element. Often, the air conditioning system and the filter unit are combined in a single housing. Therefore, these filter elements must have low flow resistance and / or pressure drop so that the required airflow can still be transported into the vehicle interior, thus ensuring compliance with safety requirements such as preventing window fogging. This has the disadvantage that a particle-separating filter layer is usually very open-pored, resulting in a very low mechanical dust separation efficiency of the filter element. Many filter media and / or filter fiber layer manufacturers therefore ensure that the filter media are electrostatically charged during the production process.This allows for better separation of the often electrostatically charged particles during subsequent operation, thanks to the electrostatic deposition of the filter medium. This separation mechanism enables even very small particles (< 0.3 µm) to be captured without increasing the flow resistance and / or pressure drop of the filter element. However, the electrostatic charge applied during the manufacturing process quickly becomes ineffective as the filter element ages and accumulates dust during operation. The electrostatic charge of the filter element is therefore primarily effective only at the beginning of its life cycle. A significant drop in electrostatic charge can occur after just a few weeks or months, depending on the level of ambient air pollution.

[0004] Ionizers or ionization devices utilize the mechanism of electrostatic charging of particles. Positioned upstream of the filter element with respect to the airflow, these devices charge the particles contained in the airflow. Furthermore, the ions introduced into the air also slightly recharge the filter element. This results in an increase in the filter element's efficiency, in addition to its purely mechanical filtration capacity, through electrostatic particle separation maintained over a longer period.

[0005] The ionization devices used for particle charging often feature a negative transmitting or spraying electrode to generate a corona discharge. During a negative corona discharge, electrons are generated at a spraying electrode, which frequently has a series of sharp contours, such as very sharp spikes or needles. These electrons are then strongly accelerated, particularly in the electric field near the electrode. The electrons subsequently collide with gas molecules, causing them to lose an electron and become positively ionized. This results in one positively charged gas molecule or gas ion and two electrons. This effect occurs primarily at very high field strengths and close to the spraying electrode. At greater distances from the electrode, the rapidly moving electrons predominantly attach to gas molecules, forming negatively charged gas ions.Negative corona discharges produce more gas ions than positive corona discharges because electrons, due to their smaller size, migrate faster. This promotes the charging of the particles and thus their deposition in the subsequent filter element.

[0006] This results in the formation of positive and negative ions in the gas or air stream, which in turn attach themselves to the particles. However, the net charge of a negative corona discharge is always negative, since electrons are introduced into the air stream.

[0007] The electrostatic charge of the filter element decreases with increasing load or operating time, because the electrostatics or electrostatic charge of the filter element is also lost due to the dust layer on the filter element.

[0008] An electrostatic air filter device of this type is known, for example, from US 5,403,383 A. It operates with a flow channel for guiding an airflow and includes an ionization device for ionizing particles carried in the airflow, which comprises a spray electrode and a counter electrode in the flow channel. Furthermore, a particle filter element is provided for filtering the particles from the airflow. This element is arranged in the flow channel downstream of the ionization device and comprises a multi-layered filter body with a particle filter layer and an electrically conductive layer. In the known air filter device, the counter electrode and the electrically conductive layer are each electrically connected to an electrical ground.

[0009] The present invention addresses the problem of providing an improved embodiment for an ionization device of the type described above, or for an air filter device equipped therewith, or for a motor vehicle equipped therewith, which is characterized in particular by a high separation efficiency for particles even in an aged state of the filter element.

[0010] 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.

[0011] The invention is based on the general concept of electrically connecting each electrically conductive layer of the filter element to its respective counter electrode via an electrical resistor. This ensures that each electrically conductive layer is at the same electrical potential as its counter electrode. As a result, the electrostatic charge of the particle filter element can be continuously regenerated. However, the invention also significantly reduces the electrical current flowing to the particle filter element. Excessive current flow results in too much current reaching the filter element, thus reducing the ionization necessary to charge the particles. The resistor therefore achieves an optimal balance between ionization and regeneration of the filter element, thereby ensuring optimal, long-term filter separation performance with the aid of the ionization device.At the same time, this reduces the possibility of unwanted ozone formation within the air filter system. Furthermore, with the same power consumption, more electrical energy is available for the ionization process, which can also improve the separation or filtration efficiency of the air filter system.

[0012] Specifically, an electrostatic air filter device is proposed, comprising a flow channel for guiding an airflow, an ionization device for ionizing particles carried in the airflow, and a filter element for filtering the particles out of the airflow. The ionization device includes at least one spray electrode and at least one counter electrode in the flow channel. The filter element is arranged downstream of the ionization device in the flow channel and comprises a multi-layered filter body with at least one particle filter layer and at least one electrically conductive layer. A key aspect of the invention is that the at least one electrically conductive layer is electrically connected to the at least one counter electrode via an electrical resistor, preferably an ohmic resistor.

[0013] Since the filter element is located downstream of the ionization device in the flow channel, all electrodes of the ionization device are located upstream of the filter element.

[0014] The filter element can be designed as a particle filter, meaning it has at least one particle filter layer. Preferably, however, the filter element is a hybrid filter or combination filter that has both at least one particle filter layer and at least one activated carbon filter layer.

[0015] The respective resistance can be formed by a single resistive element or by several resistive elements, which can be connected in series or in parallel.

[0016] The respective particle filter layer can be suitably electrically insulating and, in particular, dielectrically configured.

[0017] According to an advantageous embodiment, the resistor can be a high-resistance resistor. By designing the resistor as a high-resistance resistor, the current flow to the electrically conductive layer of the filter element is significantly reduced, thereby making considerably more electrical energy available for particle ionization, which improves the filtration efficiency of the air filter device.

[0018] In this context, an ohmic resistor is considered high-resistance if its resistance value is at least 500 times greater than the electrical voltage applied to the system or network. In this case, the respective high-resistance value can therefore be at least 500 times greater than the high voltage used in the ionization device. At a high voltage of, for example, 10 kV, the high-resistance resistor would thus have a resistance value of at least 5 MΩ.

[0019] According to an advantageous embodiment, the resistor can be arranged in an electrical connection that directly connects the at least one electrically conductive layer to the at least one counter electrode. In other words, it is proposed here to connect the respective electrically conductive layer from an electrical contact point formed on the filter element to the electrical connection and, via the high-resistance resistor, to the respective counter electrode. The electrical connection can be a connecting wire, a cable, a printed circuit board, or the like.

[0020] In an advantageous embodiment, the resistor can have a resistance value in the range of 10 MOhm to 100 MOhm.

[0021] The resistor may expediently have a resistance of at least 10 MOhm, or at least 15 MOhm, or at least 20 MOhm, or at least 25 MOhm.

[0022] Additionally or alternatively, the resistor may in particular have a resistance value of at most 100 MOhm, or at most 90 MOhm, or at most 40 MOhm, or at most 35 MOhm.

[0023] A particularly advantageous embodiment has been found in which the resistor has a resistance value of approximately 30 MOhm, i.e., a resistance value of 30 MOhm ± 10 %, so that it lies particularly in a range of 27 MOhm to 33 MOhm.

[0024] In another advantageous embodiment, the resistor may have a resistance value at least 500 times greater than the high electrical voltage applied to the at least one spray electrode during operation of the ionization device. At a high voltage of 10 kV, the resistance value of the resistor is therefore at least 5 MΩ.

[0025] The ionization device can be advantageously configured to generate a corona discharge at the respective spray electrode and / or to apply a high electrical voltage to the spray electrode, wherein the high voltage is at least 5 kV or at least 6 kV or at least 10 kV or at least 15 kV.

[0026] In the present context, a “configuration” is synonymous with a “design” and / or “setup” and / or “programming”, so that the phrase “configured so that” is synonymous with the phrase “designed and / or set up and / or programmed so that”.

[0027] The ionization device can be equipped with a high-voltage generator for generating high electrical voltage, to which the respective spray electrode and counter electrode are electrically connected. Preferably, each spray electrode and each counter electrode is electrically connected to the high-voltage generator.

[0028] A motor vehicle according to the invention comprises a vehicle interior and an air conditioning system for conditioning an airflow supplied to the vehicle interior. The air conditioning system is equipped with an air filter device of the type described above.

[0029] Further important features and advantages of the invention will become apparent from the dependent claims, the drawing and the associated description of the figures based on the drawing.

[0030] 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 as defined by the claims. 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 drawing.

[0031] Preferred embodiments of the invention are shown in the drawing and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components.

[0032] The only Fig. Figure 1 shows a highly simplified, circuit diagram-like schematic representation of a motor vehicle in the area of ​​an air filter system.

[0033] Accordingly Fig. Figure 1 comprises a motor vehicle 1 (only partially depicted), a vehicle interior 2, and an air conditioning system 3, which is configured such that fresh air originating from the vehicle's environment 4 and / or from the vehicle interior 2 can be supplied to the vehicle interior 2 by means of the air conditioning system 3. This creates an airflow 5 which is Fig. 1 is indicated by an arrow. The air conditioning system 3 contains an electrostatic air filter device 6, which has a flow channel 7 that is in Fig. 1 is bounded above and below by broken lines. The air filter unit 6 is integrated into the air conditioning system 3 in such a way that the airflow 5 also flows through the flow channel 7.

[0034] The electrostatic air filter device 6 comprises the flow channel 7 for guiding the airflow 5 and a filter element 8, which is arranged in the flow channel 7 such that the airflow 5 passes through the filter element 8. The air filter device 6 is also equipped with an ionization device 9, which ionizes particles carried in the airflow 5 to improve particle adhesion to the filter element 8. The filter element 8 can, in particular, be electrostatically charged to further enhance the adhesion of the ionized particles.

[0035] The air conditioning system 3 serves to condition the airflow 5 and can be equipped in the usual manner with a cooler (not shown here) and / or a heater (not shown here) so that the airflow 5 can be cooled or heated as required and, if necessary, dried. Advantageously, the air conditioning system 3 is configured such that the conditioning of the airflow 5 takes place with respect to the airflow direction downstream of the filter unit 6. Advantageously, the air filter unit 6 is installed in a housing of the air conditioning system 3, which is not shown here.

[0036] The ionization device 9 has at least one spray electrode 10 and at least one counter electrode 11 in the flow channel 7 upstream of the filter element 8. In the example of the Fig. Figure 1 shows, purely by way of example, two spray electrodes 10 interacting with two counter electrodes 11. Each spray electrode 10 and each counter electrode 11 are arranged in the flow channel 7 upstream of the filter element 8. When multiple spray electrodes 10 and multiple counter electrodes 11 are used, it is advantageous to arrange all spray electrodes 10 and all counter electrodes 11 upstream of the filter element 8 in the flow channel 7.

[0037] The respective spray electrode 10 and the respective counter electrode 11 are arranged in the flow channel 7 such that they are exposed to the airflow 5. During operation of the ionization device 9, the spray electrode 10 and the counter electrode 11 generate an electric field 12, which propagates between the respective spray electrode 10 and the respective counter electrode 11 and in Fig. 1 is indicated by broken lines. Particles that pass through this field 12 in the airflow 5 are thereby ionized.

[0038] The filter element 8 comprises a multi-layered filter body 13, which includes at least one particle filter layer 14 and at least one electrically conductive layer 15. The layers 14 and 15 can be folded to increase the available filtration area in the usual manner. The electrically conductive layer 15 can be formed by electrically conductive fibers or wires and laid on top of the respective particle filter layer 14. It is also conceivable that the electrically conductive layer 15 is configured as an activated carbon layer containing activated carbon particles and is preferably arranged or formed downstream of the particle filter layer 14. In this case, the filter element 8 is designed as a hybrid filter. In a hybrid or combination filter, it is also possible to provide the electrically conductive layer 15 in addition to the particle filter layer 14 and the activated carbon layer.

[0039] According to Fig. 1. The respective electrically conductive layer 15 is electrically connected to the respective counter electrode 11 via an electrical resistor 16. The resistor 16 is preferably configured as an ohmic resistor 16. Advantageously, the resistor 16 is a high-resistance resistor 16. In the example of the Fig. In this case, the resistor 16 is arranged in an electrical connection 17 that directly connects the respective electrically conductive layer 15 to the respective counter electrode 11. Thus, the respective electrically conductive layer 15 is neither directly grounded nor directly connected to an electrical ground. It is clear that the electrical connection 17 is preferably electrically connected to an electrical contact point formed on the filter element 8, which is suitably connected within the filter element 8 to the respective electrically conductive layer 15.

[0040] The resistor 16 can have a resistance value of at least 10 MΩ, at least 15 MΩ, at least 20 MΩ, or at least 25 MΩ. Additionally or alternatively, the resistor 16 can also have a resistance value of at most 50 MΩ, at most 45 MΩ, at most 40 MΩ, or at most 35 MΩ. Thus, the resistance value of the resistor 16 can, in particular, lie in a range of 10 MΩ to 100 MΩ, or in a range of 15 MΩ to 45 MΩ, or in a range of 20 MΩ to 40 MΩ, or in a range of 25 MΩ to 35 MΩ, with the narrower ranges being increasingly preferred over the wider ranges. It has proven particularly advantageous if the resistance value of the resistor 16 lies in a range of 27 MΩ to 33 MΩ, i.e., at 30 MΩ ± 10%, and especially at 30 MΩ.

[0041] The ionization device 9 operates with a high electrical voltage, which is applied to the respective spray electrode 10 during operation. For this purpose, the ionization device 9 can be equipped with a high-voltage generator 18, which is electrically connected to the respective spray electrode 10 on one side and to the respective counter electrode 11 on the other. The ionization device 9 can be configured to apply a high electrical voltage of at least 5 kV, 6 kV, 10 kV, 12 kV, 13 kV, or 15 kV. In particular, the ionization device 9 can be configured to generate a corona discharge at the respective spray electrode 10. During the corona discharge, the field 12 is generated, which can also be referred to as the corona field 12, discharge field 12, or corona discharge field 12.

[0042] According to a preferred design, the resistor 16 can have a resistance value at least 500 times greater than the high electrical voltage applied to the respective spray electrode 10 during operation of the ionization device 9. At a high voltage of 15 kV, the resistance value is therefore at least 10 MΩ. Reference symbol list 1 motor vehicle 2 Vehicle interior 3 Air conditioning system 4 Environment 5 Airflow 6 Air filter system 7 Flow channel 8 filter elements 9 Ionization device 10 Spray electrode 11 Counter electrode 12 field 13 filter bodies 14 particle filter layer 15 electrically conductive layer 16 Resistance 17 electrical connection 18 High-voltage generator 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] US 5 403 383 A

[0008]

Claims

[1] Electrostatic air filter device (6), in particular for a motor vehicle (1), - with a flow channel (7) for guiding an airflow (5), - with an ionization device (9) for ionizing particles carried in the airflow (5), which has at least one spray electrode (10) and at least one counter electrode (11) in the flow channel (7), - with a filter element (8) for filtering out the particles from the airflow (5), which is arranged in the flow channel (7) downstream of the ionization device (9) and which has a multi-layered filter body (13) with at least one particle filter layer (14) and at least one electrically conductive layer (15), characterized by , - that the at least one electrically conductive layer (15) is electrically connected to the at least one counter electrode (11) via an electrical resistance (16). [2] Air filter device (6) according to claim 1, characterized by , - that the resistor (16) is a high-resistance resistor (16). [3] Air filter device (6) according to one of the preceding claims, characterized by , - that the resistor (16) is arranged in an electrical connection (17) which directly connects the at least one electrically conductive layer (15) to the at least one counter electrode (11). [4] Air filter device (6) according to one of the preceding claims, characterized by , - that the resistor (16) has a resistance value in the range of 10 MOhm to 50 MOhm, or - that the resistor (16) has a resistance value in the range of 15 MOhm to 45 MOhm, or - that the resistor (16) has a resistance value in the range of 20 MOhm to 40 MOhm, or - that the resistor (16) has a resistance value in the range of 25 MOhm to 35 MOhm. [5] Air filter device (6) according to one of the preceding claims, characterized by , - that the resistor (16) has a resistance value of at least 10 MOhm, or - that the resistor (16) has a resistance value of at least 15 MOhm, or - that the resistor (16) has a resistance value of at least 20 MOhm, or - that the resistor (16) has a resistance value of at least 25 MOhm. [6] Air filter device (6) according to one of the preceding claims, characterized by , - that the resistor (16) has a resistance value of at most 100 MOhm, or - that the resistor (16) has a resistance value of at most 90 MOhm, or - that the resistor (16) has a resistance value of at most 80 MOhm, or - that the resistor (16) has a resistance value of at most 70 MOhm. [7] Air filter device (6) according to one of the preceding claims, characterized by , - that the resistor (16) has a resistance value of 30 MOhm. [8] Air filter device (6) according to one of the preceding claims, characterized by , - that the resistor (16) has a resistance value that is at least 500 times greater than an electrical high voltage that is applied to the at least one spray electrode (10) during the operation of the ionization device (9). [9] Air filter device (6) according to any one of the preceding claims, characterized by , - that the ionization device (9) is configured to generate a corona discharge at the respective spray electrode (10) and / or to apply a high electrical voltage to the spray electrode (10) of at least 5 kV. [10] Motor vehicle (1), - with a vehicle interior (2), - with an air conditioning system (3) for conditioning an airflow (5) to be supplied to the vehicle interior (2), - wherein the air conditioning system (3) is equipped with an air filter device (6) according to one of the preceding claims.

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