Air filter unit and use of air filter unit in motor vehicle

Abstract

The invention relates to an air filter unit having at least one ionization unit and at least one filter medium, the at least one ionization unit having at least one injection electrode, at least one counter electrode and at least one voltage source, and the filter medium having at least one filter medium. The at least one filter medium is located downstream of the ionization unit and, viewed from the inflow side in the direction of the outflow side, has first at least one electret stack, next at least one mechanical separation stack and next at least one electrically conductive stack. The invention further relates to the use of such an air filter unit in a motor vehicle.

Description

Field of the Invention

[0001] The present invention relates to an air filter unit, in particular for a motor vehicle. In addition, the present invention relates to the use of such an air filter unit in a motor vehicle. Background Art

[0002] In order to achieve a high and comfortable air quality in the passenger compartment of a motor vehicle, it is necessary to remove particles (such as fine dust particles) and harmful gases (such as volatile hydrocarbons, nitrogen oxides, ammonia, ozone or hydrogen sulfide) from the fresh air fed in from the outside. Especially in urban areas, a high fine dust load often occurs in the outside air. In terms of daily average values, the fine dust load in big cities can often be greater than the PM2.5 daily average value of 15 μg / m3 specified by the WHO. This can pose a significant health hazard.

[0003] In the prior art, the separation of dust is usually achieved by means of a filter element, which would otherwise enter the passenger compartment via, for example, an air-conditioning device. The filter element is, for example, installed in the air-conditioning device and has a fibrous filter layer for separating particles. However, the space available for use in such an air-conditioning device is limited. At the same time, minimum safety requirements, such as for avoiding fogging of the glass panes, need to be observed, which presupposes an adequate air supply. In order to ensure an adequate air flow, a low flow resistance or a low pressure loss of the filter element is required. This results in the following disadvantage: typically, the filter fiber laminate used for particle separation needs to be implemented very open-pored. As a result, the mechanical dust separation degree usually appears very low.

[0004] To circumvent this problem, in the prior art, it is generally proposed to use a filter medium that attracts electrostatically charged particles. For this purpose, the filter medium is electrostatically charged, for example, during the production process, or a filter medium that also shows a certain electrostatic charge without a special charging method during the production process is used. This results in the fact that usually also electrostatically charged dust particles, even very small particles with a diameter of <0.3 μm, can be separated well during operation by means of the electrostatically charged filter medium. In this way, it is not necessary to increase the flow resistance of the filter. For example, EP3056364A1 describes the use of a dielectric material (such as polypropylene) as a filter medium.

[0005] However, during driving operation, the electrostatic charge applied, for example, during the production process, decreases rapidly as the filter medium ages and the dust load increases. This means that the electrostatic attraction of the filter medium is only effective at the beginning of the filter's life cycle and, depending on the degree of external air pollution, a significant reduction in the electrostatic attraction usually occurs after a few weeks or months. As a result, passengers are already exposed to a significantly increased particle concentration at a time well before the filter medium replacement interval. Summary of the invention

[0006] The invention addresses the problem of specifying a filter system for cleaning external air fed into a passenger compartment, by means of which a sufficient filtering effect can be achieved even with large air flows and over a longer period of use.

[0007] 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.

[0008] According to the invention, an air filter unit is provided with at least one ionization unit and at least one filter medium, wherein the at least one ionization unit has at least one ejection electrode, at least one counter electrode and at least one voltage source, and wherein the at least one filter medium is located downstream of the ionization unit and, viewed from the inlet side in the direction of the outlet side, first has at least one electret layer, then has at least one mechanical separation layer and then has at least one conductive layer.

[0009] Compared to the prior art, the air filter unit according to the invention having the features of independent patent claim 1 has the following important advantage: a high degree of particle separation is achieved over the entire service life of the filter medium. This is mainly because the electrostatic separation effect of the air filter unit can be maintained during the service life of the filter medium.

[0010] This results in the following additional important advantage: the air filter unit can provide a good separation rate with low pressure loss over the entire service life of the filter medium, and the passengers are thus exposed to a significantly lower particle load. At the same time, the flow resistance of the system is similar to that of a conventional cabin interior air filter, which has a significantly lower particle separation rate.

[0011] This is achieved in particular by the proposed combination of at least one ionization unit and at least one filter medium, wherein, viewed from the inlet side in the direction of the outlet side, the at least one filter medium first has at least one electret layer, then at least one mechanical separation layer and then at least one electrically conductive layer.

[0012] Next, the air filter unit according to the present invention will be described in more detail.

[0013] The present invention is based on the general concept that at least one filter medium configured to clean air guided from the outside into the passenger space is combined with at least one ionization unit such that the supplied air can be efficiently cleaned.

[0014] Accordingly, an air filter unit is proposed, for example, an air filter unit for a vehicle air conditioning device, a vehicle ventilation system, a vehicle heating system, or a combined heating, ventilation, and air conditioning system (HVAC system), through which a flow path of an air flow passes. The air flow is an air flow by means of which air is guided from the outside into the vehicle interior, in particular into the passenger space. Accordingly, the inflow side is understood to be the side from which the air flow is supplied from the outside. The air filter unit has at least one ionization unit and at least one filter medium, the at least one ionization unit being arranged in the flow path, and the at least one filter medium being arranged downstream of the ionization unit in the flow path.

[0015] This means that the air filter unit can have one ionization unit and one filter medium, the ionization unit being arranged in the flow path, and the filter medium being arranged downstream of the ionization unit in the flow path. However, alternatively, it is also conceivable that the air filter unit has two or more ionization units and two or more filter mediums, the two or more ionization units being arranged in the flow path, and the two or more filter mediums being arranged downstream of the respective ionization unit in the flow path. It has proven to be particularly advantageous that the air filter unit has one ionization unit and one filter medium, the ionization unit being arranged in the flow path, and the filter medium being arranged downstream of the ionization unit in the flow path.

[0016] At least one ionization unit is used to ionize at least a part of the particles contained in the particles in the air supplied from the outside. In principle, all ionization units known to those skilled in the art that are suitable for this purpose can be considered. For example, the ionization units described in US2021 / 0021107A1 and EP3056364A1.

[0017] At least one ionization unit has at least one counter electrode. For example, it can be considered that at least one counter electrode is first located on the inflow side in the air path. For example, at least one counter electrode can be configured as a grid structure made of a conductive material, which is located in the air path and can be flowed through by air. For example, such a grid structure can include steel, especially stainless steel. In addition, at least one ionization unit has at least one injection electrode. This means that the ionization unit has one or more injection electrodes. It should be understood that at least one counter electrode is arranged electrically separated from one or more injection electrodes. One or more injection electrodes can be located at different positions in the air path. For example, the one or more injection electrodes are located downstream of at least one counter electrode in the air path and can be configured as electrode rods, for example.

[0018] Furthermore, it has proven to be advantageous that at least one counter electrode located on the inflow side in the air path is arranged at a distance of at least approximately 15 mm to at most approximately 50 mm from the one or more injection electrodes. In addition, the ionization unit has a voltage source, especially a high-voltage source, to which at least one counter electrode and one or more injection electrodes are conductively connected.

[0019] For example, an electric field is generated between one or more injection electrodes and at least one counter electrode in the air path. It is appropriate that, during operation of the air filter unit, a first electric potential is applied or can be applied to one or more injection electrodes, and a second electric potential, which is different from the first electric potential, is applied or can be applied to at least one counter electrode. For example, it can be considered that the first electric potential is the supply potential and the second electric potential is the counter potential. For example, the counter potential can be obtained by grounding at least one counter electrode. For example, the counter potential can be zero potential. It is appropriate that, during operation of the air filter unit, a negative or positive potential difference is applied or can be applied between at least one counter electrode and one or more injection electrodes. For example, a negative potential difference in the range of at least approximately -5 kV to at most approximately -15 kV can be applied. In this case, a negative corona discharge can be achieved on one or more injection electrodes.

[0020] Thus, by means of one or more injection electrodes, a negative or positive corona discharge can be generated and thereby the gas separation ionization from the air can be achieved. In principle, it is conceivable to generate a DC, AC or pulsed corona discharge by means of an ionization unit. In principle, a potential with a negative polarity or a potential with a positive polarity can be applied to the one or more injection electrodes. It has proven to be particularly advantageous to apply a DC voltage with a negative polarity to the one or more injection electrodes to generate a corona discharge. Thereby, more ions are generated compared to the positive polarity. The obtained ionized gas molecules can accumulate on the surface of the particles contained in the air supplied from the outside, whereby the particles acquire a charge.

[0021] It is also conceivable that, additionally, one or more further counter electrodes are arranged downstream of the injection electrodes. For example, such a further counter electrode can be conductively connected to a conductive surface filtration layer of at least one filtration medium, in particular at least one conductive laminate. This will be discussed in more detail later.

[0022] After the air stream is ionized in at least one ionization unit, the ionized air stream flows onto at least one filtration medium. It should be understood that in this context, the ionized air stream only refers to the electrostatic charging of at least a part of the gas molecules in the air of the air stream and at least a part of the particles carried in the air stream. For example, it is conceivable that at least one filtration medium is arranged at a distance of at least about 1 mm to at most about 50 mm, preferably at least about 5 mm to at most about 20 mm from at least one ionization unit.

[0023] At least one filtration medium according to the invention has at least one electret laminate on the inflow side. In this context, the inflow side is understood to mean that the air stream supplied from the outside, which is first ionized by the ionization unit, then first flows onto the electret laminate of the filtration medium. A person skilled in the art understands an electret as an electrically insulating material that contains quasi-permanently stored charges or quasi-permanently oriented electric dipoles and thus generates a quasi-permanent electric field in the environment of the electrically insulating material or inside the electrically insulating material. The electret laminate can be made, for example, of polymer fibers, for example of fibers made of polypropylene or polyethylene terephthalate. At least one electret laminate has an electrostatic charging. Thus, the particle separation on at least one electret laminate is mainly based on the electrostatic separation effect. The function of at least one electret laminate is to receive larger dust particles.

[0024] On the outflow side of at least one electret laminate, at least one mechanical separation laminate is arranged. It should be understood that in this context, the outflow side of at least one electret laminate is understood as the side where the ionized air flow supplied from the outside first flows onto the electret laminate, where at least a part of the electrostatically charged particles are separated, and the air flow without these already separated particles flows out on the opposite side of the electret laminate and flows onto at least one mechanical separation laminate there. At least one mechanical separation laminate is protected by at least one electret laminate located in front of it in the following respect: Most of the larger particles are intercepted in at least one electret laminate, whereby an incorporation into and the resulting increase in the flow resistance of at least one mechanical separation laminate can be avoided to the greatest extent or at least strongly delayed. For example, at least one mechanical separation laminate can be a nonwoven fabric made of nanofibers, wherein the separation effect is based on the fact that at least one mechanical separation laminate has intermediate spaces, and the number and diameter of such intermediate spaces are configured such that the inflowing air can pass through at least one mechanical separation laminate while the particles therein are intercepted to the greatest extent. Thus, at least one mechanical separation laminate is used to ensure a high mechanical separation degree of fine dust. Thereby, compared to at least one electret laminate, this at least one mechanical separation laminate shows a slightly higher flow resistance.

[0025] Furthermore, at least one conductive laminate is arranged on the outflow side of at least one mechanical separation laminate. For example, this can be a mesh made of metal, for example made of stainless steel. Alternatively, this can be, for example, a laminate having at least one activated carbon layer.

[0026] At least one electret laminate, at least one mechanical separation laminate and optionally at least one conductive laminate can be stacked, pressed and glued on top of each other, or, for example, additionally connected or bonded to each other linearly at the cutting edges and dotwise in the plane by means of ultrasonic welding or thermal welding. This also applies mutatis mutandis to further laminates and layers still to be explained in more detail in this application.

[0027] In the context of this application, a "laminate (Lage)" is understood as a coherent unit that has a thickness extending in the flow direction. In this context, such a laminate can consist of a single layer. However, alternatively, it is also possible that such a laminate has a plurality, i.e., at least two, consecutive layers, where such layers are different from each other, for example, different in their material composition.

[0028] For example, it is also possible to consider placing at least one filter medium into the frame contained in the air filter unit. Thereby, better stability of this construction can be achieved. All frames known to those skilled in the art are suitable for the filter medium. Such a frame can be made of, for example, metal or plastic. For example, the frame can be made of a thermoplastic, a thermosetting plastic or an elastomer. Suitably, the frame is made of a thermoplastic. For example, the frame is constructed from PA6, PA6.6, polypropylene, polyethylene, polystyrene, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate or polyetheretherketone. It should be understood that the frame can contain additional auxiliary materials, such as adhesives, crosslinking agents and additives. Particularly suitably, the frame is reinforced with proportional fibers. For example, the frame can be made of PA6.6 GF30. In addition, it should be understood that it is also possible to consider placing a sealing element between the filter medium and the frame.

[0029] It has proven to be advantageous for at least the conductive laminate to be in electrical contact with the counter electrode of the ionization unit. It should be understood that the electrical contact of at least one conductive laminate with the counter electrode of the ionization unit is advantageously achieved via a conductive surface layer, for example a surface layer having or consisting of activated carbon is suitable for this. This electrical contact is particularly advantageous because it enables the reactivation of the filter medium with respect to the electret laminate function of the filter medium. Advantageously, this in turn results in a significantly increased separation power with respect to fine dust or other particles.

[0030] In the present context, "electrical contact" should be understood to mean all situations in which an electrical path extends between the conductive laminate and the counter electrode.

[0031] For example, the electrical contact can be achieved by means of an electrical line that extends between the conductive laminate and the counter electrode.

[0032] Alternatively or additionally, the electrical contact can be achieved by electrically connecting the conductive laminate and the counter electrode at the same electrical potential.

[0033] For example, it has proven to be suitable that, during operation of the air filter unit, on the one hand a first electrical potential is applied or can be applied to one or more injection electrodes, and on the other hand a second electrical potential, which is different from the first electrical potential, is applied or can be applied to at least one counter electrode and at least one conductive laminate. Regarding the configuration of the first electrical potential and the second electrical potential different from the first electrical potential, reference is made to the above-described embodiments.

[0034] For a preferred case where negative corona discharge should be carried out on one or more injection electrodes, when the air filter unit is operating, suitably, a negative potential difference is applied or can be applied between, on the one hand, one or more injection electrodes and, on the other hand, at least one counter electrode and at least one conductive laminate. Thereby, at least partially negative polarization is imparted to the particles in the air stream supplied from the outside, and the particles are separated in at least one electret laminate. Thereby, a polarization effect can in turn be formed between at least one electret laminate loaded with particles having negative polarization and at least one conductive laminate. However, alternatively, it is also possible to consider that the air filter unit is set up and operated such that positive corona discharge occurs on one or more injection electrodes.

[0035] Furthermore, it has proven to be advantageous that the electrical contact between at least one conductive laminate and the counter electrode of the ionization unit can be controlled in time such that at least one conductive laminate is electrically separated from the counter electrode after a predetermined polarization time and is electrically connected to the counter electrode again after a predetermined depolarization time. For example, the controllability can be achieved by means of at least one electrical switch. Electrical switches for time-controllable separation and contact are known to those skilled in the art. For example, an electromechanical relay can be used for this purpose. Alternatively, the switching can be achieved purely electrically, for example. For this purpose, a bipolar transistor with an insulated gate electrode (IGBT) or a metal oxide semiconductor field effect transistor (MOSFET) can be used.

[0036] This means that preferably at least one conductive laminate is only connected to the counter potential within a predetermined polarization time. It should be understood that this predetermined polarization time is related to the desired polarization value. This measure is based on the recognition that after the polarization of at least one conductive laminate, especially when at least one conductive laminate is a laminate containing activated carbon, the separation power of the filter medium only slowly decreases again, so that the power consumption can be saved by the time-controlled electrical separation of at least one conductive laminate.

[0037] After a predetermined depolarization time, at least one conductive laminate can be reconnected to the counter potential, that is, to the counter electrode of the ionization unit. The polarization time and the depolarization time are related to the application situation and the configuration of the air filter unit, for example, related to the size of the filter medium and the amount of air to be filtered.

[0038] Advantageously, the electrical connection and separation of the conductive laminate and the counter electrode mean the corresponding connection and separation in the electrical contact part or in the circuit path.

[0039] The control of the electrical connection and separation, especially of at least one electrical switch, is advantageously carried out by means of a control device with a corresponding configuration.

[0040] Alternatively or additionally, it may be possible to arrange at least one resistor in the electrical contact, in particular in the circuit path. As a result, a reduced flow of charge to the conductive laminate occurs. Thus, in particular, the temporal control of the electrical contact can be dispensed with or at least reduced. The air filter unit is accordingly constructed simply and cost-effectively.

[0041] Furthermore, it has proven to be advantageous for at least one filter medium to additionally have a carrier laminate on the outflow side of at least one conductive laminate. This contributes to the stability of the filter medium. For example, it has proven to be advantageous for the carrier laminate to have polyester fibers, for example fibers made of polyethylene terephthalate. For example, the carrier laminate can be a non-woven fabric made of a spunbond non-woven fabric, where the non-woven fabric has, for example, polyester fibers.

[0042] For example, it is also conceivable that the carrier laminate is a spunbond non-woven fabric made of polymer fibers, where the fibers are made of two polymers, namely so-called "BiCo" fibers. For example, those skilled in the art refer to these "BiCo" fibers as -BiCo technology. For BiCo fibers, typically, a polymer material different from the polymer material of the shell of the fiber is used in the core of the fiber. Typically, these BiCo fibers are produced as continuous fibers (Endlosfaser), whereby non-woven fabrics can in turn be manufactured. For example, it is conceivable that the fibers have a core made of polyethylene terephthalate and a shell made of dibutyl terephthalate.

[0043] Spunbond non-woven fabrics are known to those skilled in the art. Typically, such spunbond non-woven fabrics are obtained by pulling the polymer into fine continuous fibers after extrusion, and the continuous fibers are laid irregularly (ablegen) on a backing. Preferably, the spunbond non-woven fabric used has a grammage of approximately at least 25 g / m 2 to approximately at most 100 g / m 2 and more preferably, the spunbond non-woven fabric used has a grammage of approximately at least 45 g / m 2 to approximately at most 75 g / m 2 Preferably, additionally, the spunbond non-woven fabric used has a breathability (LD) of at least approximately 3500 l / (m 2 s) to at most approximately 10000 l / (m 2 s) at 200 Pa, and more preferably, the spunbond non-woven fabric used additionally has a breathability (LD) of at least approximately 5500 l / (m 2 s) to at most approximately 6500 l / (m 2 s) at 200 Pa. The breathability can be determined according to DIN EN 9237:1995.

[0044] In addition, the spunbond nonwoven fabric used has the following fibers: the fibers have a fiber thickness of approximately at least 20 μm to a maximum of approximately 80 μm.

[0045] Of course, it can be considered that the carrier laminate contains additional auxiliary materials such as adhesives, crosslinking agents, and additives. Examples of adhesives are acrylates and melamine formaldehyde. An example of an additive is polyurethane. For example, the carrier laminate contains a low weight percentage of additional auxiliary materials, in particular, the respective auxiliary materials contained in the carrier laminate are each less than two percent by weight (2 Gew-%).

[0046] Typically, the carrier laminate has a thickness of at least approximately 80 μm to a maximum of approximately 2 mm, preferably, the carrier laminate has a thickness of 300 μm to a maximum of approximately 1 mm.

[0047] The determination of the thickness of such a laminate is known to those skilled in the art and can be determined, for example, according to DIN EN ISO 9073-02:1997.

[0048] In addition, it has proven to be advantageous that the filter medium has a covering nonwoven fabric in front of at least one electret laminate on the inflow side. Advantageously, the covering nonwoven fabric is configured as a light, open covering nonwoven fabric, which has a grammage of less than approximately 50 g / m 2 and, particularly preferably, approximately 16 g / m 2 and is used to intercept the largest dust particles and thereby relieve the load on the subsequent laminate without significantly increasing the flow resistance. In addition, the covering nonwoven fabric prevents fibers from shedding from the subsequent layer. For example, the covering nonwoven fabric can be configured from the following polypropylene fibers: the polypropylene fibers have a grammage of less than approximately 50 g / m 2 and, particularly preferably, approximately 16 g / m 2 of grammage.

[0049] Regarding the auxiliary materials that may optionally be included in the covering nonwoven fabric, such as adhesives, crosslinking agents, and additives, refer to the content described previously in the context of the carrier laminate as appropriate.

[0050] In addition, it has proven to be suitable that at least one electret laminate has at least two layers. This means that, preferably, the electret laminate has two layers or alternatively three or more layers. Preferably, the at least two layers have fibers and the diameter of the fibers in the layers decreases in the flow direction. Alternatively, it can also be considered that the diameter of the fibers in the layers remains substantially the same. The at least one mechanical separation laminate is effectively protected from the incorporation of dust particles by at least one electret laminate.

[0051] In principle, all of the following non-woven fabrics, textiles, knitted fabrics or woven fabrics can be used for at least two layers of the electret laminate: the non-woven fabric, textile, knitted fabric or woven fabric has electrostatic charging or can be electrostatically charged. For example, the corresponding layers of the electret laminate can have melt-blown or spun-bond continuous polymer fibers, which are processed, for example, in the form of a non-woven fabric. Melt-blown fibers can be obtained by the following method: pressing a molten polymer through an extruder with small capillaries, blowing the fibers emerging from the capillaries in one direction with hot air, stretching the fibers in length and then thermally connecting the fibers. An example of such a layer for an electret laminate is a melt-blown polypropylene non-woven fabric. Additionally, it is possible to consider using melt-blown fibers or spun-bond fibers made of polyester (such as polyethylene terephthalate), made of polycarbonate or made of polyamide. Alternatively, it is also possible to consider using charged short fibers or electrostatically charged short fibers. For example, it is possible to consider short fibers made of polyester (such as polyethylene terephthalate), made of polycarbonate or made of polyamide.

[0052] It is possible to consider that the fibers have a polymer material, but it is also possible to consider that the fibers have two or more polymer materials. An example of a polymer fiber made of two polymers is the so-called "BiCo" fiber, as described above, which those skilled in the art would refer to, for example, as -BiCo technology.

[0053] Regarding the auxiliary materials that may optionally be included in the at least one electret laminate, reference is made, in terms of meaning, to what was previously described in the context of the carrier laminate.

[0054] It has proven to be advantageous for the electret laminate to have two layers, wherein the first layer located upstream is made of a non-woven fabric containing polypropylene fibers and polycarbonate fibers, more preferably made of a non-woven fabric containing polypropylene fibers and polycarbonate fibers, having a grammage of approximately at least 20 g / m 2 and approximately at most 40 g / m 2 and particularly preferably made of a non-woven fabric containing polypropylene fibers and polycarbonate fibers, having a grammage of approximately 30 g / m 2 and the second layer oriented downstream of the first layer is made of a non-woven fabric containing polypropylene fibers, more preferably made of a non-woven fabric containing polypropylene fibers, having a grammage of approximately at least 10 g / m 2 and approximately at most 30 g / m 2 and particularly preferably made of a non-woven fabric containing polypropylene fibers, having a grammage of approximately 20 g / m 2It is made of non-woven fabric with a grammage. With such an arrangement, the subsequent mechanical separation laminate can be effectively protected from large particles.

[0055] Alternatively, it has been proven advantageous that the electret laminate has three layers, which are respectively made of the following non-woven fabrics: the non-woven fabric is made of melt-blown thermoplastic polymer fibers, especially polypropylene fibers. Here, for example, the first layer, i.e., the upstream-oriented layer, is composed of a non-woven fabric with a grammage of approximately 20 g / m 2 The second layer following this first layer downstream is composed of a non-woven fabric with a grammage of approximately 15 g / m 2 The third layer following this second layer downstream is composed of a non-woven fabric with a grammage of approximately 15 g / m 2 The grammage of the non-woven fabric.

[0056] Typically, at least one electret laminate has a thickness of at least approximately 300 μm to at most approximately 5 mm. In addition, at least one electret laminate is configured to have an intermediate space. It should be understood that typically, the intermediate space is configured as an open intermediate space (even if it does not exclude that at least one electret laminate additionally includes a closed intermediate space for production reasons) to ensure the penetrability of the air to be cleaned. Preferably, additionally, at least one electret laminate has a gas permeability (LD) of at least approximately 300 l / (m 2 s) to at most approximately 1500 l / (m 2 s) at 200 Pa.

[0057] It can be considered that the diameter of the intermediate space is constantly distributed over the entire thickness of at least one electret laminate. However, it has been proven particularly advantageous that the intermediate space first has a slightly larger diameter on the side facing the incoming air flow and further has a slightly smaller diameter in the direction of the side facing away from the incoming air flow. This can be achieved by the following method: the fibers are compressed more tightly on the side facing away from the incoming air flow than on the side facing the air flow. Additionally, it has been proven particularly advantageous that the diameter of the fibers is first slightly larger on the side facing the incoming air flow and further slightly smaller in the direction of the side facing away from the incoming air flow. For example, the diameter of the fibers in the first layer facing the air flow can be at least approximately 8 μm to at most approximately 50 μm, and the diameter of the fibers in the second layer arranged after the first layer can be at least approximately 1 μm to at most approximately 10 μm. Thus, it can be achieved that the largest dust particles are separated first, and then smaller dust particles are further separated inside the layer. This results in the maximization of the service life and filtration power of the filter medium.

[0058] As described above, suitably, the following electret laminate is used: The electret laminate can in turn have one or more layers. However, alternatively, it is also conceivable to use, for example, two or more laminates of at least one electret laminate stacked one on top of the other. The two or more laminates of at least one electret laminate can in turn have one or more layers. However, preferably, one electret laminate is used.

[0059] In addition, in principle, at least one mechanical separation laminate can have one or more layers. It has proven to be advantageous for at least one mechanical separation laminate to have one layer, as this leads to particularly good results not only in terms of separation but also in terms of flow resistance. In addition, in principle, all of the following non-wovens, textiles, woven fabrics or knitted fabrics can be used for one or more layers of at least one mechanical separation laminate: The non-wovens, textiles, woven fabrics or knitted fabrics are capable of achieving mechanical separation of particles.

[0060] However, it has proven to be particularly advantageous for at least one mechanical separation laminate to have nanofibers, wherein the diameter of the nanofibers is at least approximately 10 nm to at most approximately 800 nm, preferably, the diameter of the nanofibers is at least approximately 90 nm to at most approximately 500 nm. In particular, it has proven to be advantageous for the diameter of the nanofibers to be at least approximately 90 nm to at most approximately 120 nm.

[0061] This means that for the case where at least one mechanical separation laminate has one layer, this layer preferably has nanofibers. This means that for the case where at least one mechanical separation laminate has multiple layers, preferably, at least one of these layers has nanofibers.

[0062] In addition, it has proven to be advantageous to obtain nanofibers by electrospinning a polymer material. The electrospinning process itself is known to those skilled in the art. Typically, a polymer solution is metered onto an electrode, where the polymer solution is accelerated away from the electrode due to an electric field. Thereby, continuous fibers are formed, and the continuous fibers are laid as a non-woven fabric on the counter electrode.

[0063] It is further preferred that one or more layers of the mechanical separation laminate each have a grammage of at least approximately 0.5 g / m2 to at most approximately 2 g / m2, preferably approximately 1 g / m2.

[0064] Preferably, one or more layers of the mechanical separation laminate are each composed of the following non-woven fabrics: the non-woven fabric is made of polyamide fibers (especially fibers made of PA6.6 fibers), made of polypropylene fibers, made of polyester fibers (such as fibers made of polyethylene terephthalate), or made of polyvinyl alcohol. Here, it can be considered that different stacked layers are made of the same material. Similarly, it can be considered that at least one mechanical separation laminate has two or more layers made of different non-woven materials. For example, one layer is made of a polypropylene non-woven fabric, and another layer is made of a polyamide non-woven fabric.

[0065] Regarding the auxiliary materials that may optionally be included in the at least one mechanical separation laminate, refer to the content described previously in the context of the carrier laminate for meaning.

[0066] Typically, at least one mechanical separation laminate has a thickness of at least approximately 1 μm to at most approximately 0.5 mm. In addition, at least one mechanical separation laminate is configured to have an intermediate space. It should be understood that typically, the intermediate space is configured as an open intermediate space (even if it does not exclude that at least one mechanical separation laminate additionally includes a closed intermediate space for production reasons) to ensure the penetrability of the air to be cleaned.

[0067] For example, in the case where at least one mechanical laminate is composed of one layer made of a polypropylene non-woven fabric and another layer made of a polyamide non-woven fabric, the at least one mechanical laminate preferably additionally has a minimum of approximately 200 l / (m 2 s) to a maximum of approximately 600 l / (m 2 s) air permeability (LD) at 200 Pa.

[0068] It can be considered that the diameter of the intermediate space is constantly distributed throughout the entire thickness of the at least one mechanical separation laminate. However, it has been proven to be particularly advantageous that the intermediate space first has a slightly larger diameter on the side facing the incoming air flow and further has a slightly smaller diameter in the direction of the side facing away from the incoming air flow. This is advantageous if at least one mechanical separation laminate has a total thickness of approximately 0.5 mm and includes a layer made of nanofibers, which is in turn applied to a layer made of a polypropylene non-woven fabric or a polyamide non-woven fabric. This helps to maximize the service life and filtration power of the filter medium.

[0069] As described above, suitably, a mechanical separation laminate is used: the mechanical separation laminate can in turn have one or more layers. However, alternatively, it can also be considered that, for example, two or more laminates of at least one mechanical separation laminate are used stacked one on top of the other. These two or more laminates of at least one mechanical separation laminate can in turn have one or more layers. However, it is particularly advantageous to use one mechanical separation laminate.

[0070] Furthermore, it has proven to be advantageous for at least one of the conductive laminates to additionally be a laminate for gas adsorption. This means that at least one of the conductive laminates comprises or consists of a material capable of enabling gas adsorption, such as activated carbon.

[0071] Furthermore, it has proven to be advantageous for at least one of the conductive laminates to have at least two layers, where at least one of the layers has activated carbon. It is also conceivable for at least one of the conductive laminates to have two or more layers, each of which in turn has activated carbon.

[0072] Alternatively, it has proven to be advantageous for at least one of the conductive laminates to have at least two layers, where at least one of the layers consists of activated carbon. It is also conceivable for at least one of the conductive laminates to have two or more layers, each of which in turn consists of activated carbon.

[0073] For example, such a layer consisting of or having activated carbon can consist of or have granular activated carbon. Alternatively, such a layer consisting of or having activated carbon can also consist of or have fibrous activated carbon. Additionally, such a layer consisting of or having activated carbon can consist of or have so-called spherical carbon. As a further alternative, such a layer consisting of or having activated carbon can consist of not only granular activated carbon but also fibrous activated carbon, or can have not only granular activated carbon but also fibrous activated carbon. Furthermore, alternatively, such a layer consisting of or having activated carbon can consist of not only spherical carbon but also fibrous activated carbon, or can have not only spherical carbon but also fibrous activated carbon.

[0074] In addition, preferably, such a layer consisting of or having activated carbon has a grammage of at least approximately 100 g / m 2 up to a maximum of approximately 750 g / m 2 and, more preferably, such a layer consisting of or having activated carbon has a grammage of at least approximately 300 g / m 2 up to a maximum of approximately 400 g / m 2 and, most preferably, such a layer consisting of or having activated carbon has a grammage of approximately 350 g / m 2 .

[0075] Furthermore, it has proven to be advantageous that at least one electrically conductive laminate has at least two layers, wherein at least one of the two layers has an ion exchanger. Alternatively, it has proven to be advantageous that at least one electrically conductive laminate has at least two layers, wherein at least one of the two layers has an ion exchanger and activated carbon. Likewise, it is of course conceivable that at least one electrically conductive laminate comprises two layers, wherein one of the two layers comprises activated carbon and the other of the two layers comprises an ion exchanger. For example, it is conceivable that at least one electrically conductive laminate comprises a layer comprising a granular material consisting of a mixture of activated carbon and ion exchanger. Alternatively, it is also conceivable that at least one electrically conductive laminate comprises a layer comprising a fiber mixture consisting of activated carbon fibers and ion exchanger fibers.

[0076] For example, it is conceivable that at least one electrically conductive laminate comprises two layers, wherein one of the two layers comprises activated carbon granules and has a carbon content of at least approximately 100 g / m 2 Up to about 600g / m 2 The other of the two layers comprises an ion exchanger particulate material and has a grammage of at least about 100 g / m 2 Up to about 390g / m 2 It is particularly preferred that at least one conductive laminate comprises two layers, wherein one of the two layers comprises activated carbon granular material and has a grammage of about 300 g / m 2 The other of the two layers comprises an ion exchanger particulate material and has a grammage of at least about 220 g / m 2 Weight.

[0077] Alternatively, it is conceivable, for example, that at least one electrically conductive laminate first comprises a conductive layer having a thickness of at least approximately 160 g / m 2 The first layer of the grammage of at least about 160 g / m 2 and immediately comprising a second layer having a grammage of at least about 250 g / m 2 The first layer comprises granular activated carbon, and the second layer comprises fibrous activated carbon.

[0078] The ion exchanger can contain a cation exchanger and an anion exchanger or can contain a mixed bed ion exchanger. However, it is also conceivable that the ion exchanger contains only anion exchangers or only cation exchangers. Preferably, the ion exchanger contains a cation exchanger.

[0079] Anion exchangers and cation exchangers are known per se to those skilled in the art. For example, an anion exchanger can be a material having a secondary amine compound or a tertiary amine compound or a quaternary ammonium group compound. For example, a suitable anion exchanger is based on polymer (polystyrene - co - divinylbenzene) beads functionalized with quaternary ammonium groups.

[0080] For example, a cation exchanger can be a material having a sulfonic acid group or a carboxyl group. For example, such a cation exchanger is a plastic resin which is based on, for example, polystyrene and is based on sulfonic acid groups firmly bonded to the resin. For example, a suitable anion exchanger is based on polymer (polystyrene - co - divinylbenzene) beads functionalized with sulfonic acid groups.

[0081] Furthermore, it has proven to be advantageous for at least one conductive laminate to have at least two layers, wherein one of the two layers has activated carbon and one of the two layers has activated carbon and an ion exchanger.

[0082] Furthermore, it is appropriate to fix the activated carbon in the layer having activated carbon, to fix the ion exchanger in the layer having the ion exchanger, or to fix the activated carbon and the ion exchanger in the layer having activated carbon and the ion exchanger by means of an adhesive material.

[0083] All common adhesive material systems can be used for bonding.

[0084] For example, a physically hardened adhesive material system can be selected from the group consisting of: polyamide resins, saturated polyesters, ethylene - vinyl acetate copolymers, polyolefins, styrene - butadiene - styrene block copolymers, styrene - isoprene - styrene block copolymers, and polyimides, or a chemically hardened adhesive material system can be selected from the group consisting of: epoxy resins, polyurethanes, phenolic resins, silicones, and cyanoacrylates. It has proven to be advantageous to use an adhesive material system selected from the group of polyolefins or to use an adhesive material system selected from the group of epoxy resins or polyurethanes. In particular, it has proven to be particularly advantageous to use a physically hardened adhesive material system made of polypropylene. Typically, such a system can be obtained as hot - melt polypropylene.

[0085] Furthermore, preferably, the layer containing the ion exchanger has a grammage of approximately at least 100 g / m 2 and approximately at most 390 g / m 2 and more preferably, such a layer containing the ion exchanger has a grammage of approximately 220 g / m 2 of grammage.

[0086] Preferably, at least one conductive laminate has a thickness of at least about 500 μm to at most about 5 mm, more preferably, at least one conductive laminate has a thickness of at least about 800 μm to at most about 3 mm. Particularly preferably, at least one conductive laminate has a thickness of about 2 mm.

[0087] As described above, suitably, the following conductive laminates are used, in particular those containing activated carbon: the conductive laminate can in turn have one or more layers. However, alternatively, it is also possible to consider, for example, using two or more laminates of at least one conductive laminate stacked one on top of the other. The two or more laminates in at least one conductive laminate can in turn have one or more layers. However, it is particularly advantageous to use one conductive laminate.

[0088] Furthermore, it has proven to be advantageous to additionally arrange at least one intermediate laminate between at least one mechanical separation laminate and at least one conductive laminate. This mainly contributes to the mechanical stability of at least one mechanical separation laminate.

[0089] Advantageously, at least one intermediate laminate is configured as a light, open non-woven fabric having a grammage of less than about 50 g / m 2 and particularly preferably about 16 g / m 2 . For example, the non-woven fabric can be configured from the following polypropylene fibers: the polypropylene fibers have a grammage of less than about 50 g / m 2 and particularly preferably about 16 g / m 2 .

[0090] Regarding the auxiliary materials that may optionally be included in the at least one intermediate laminate, reference is made, mutatis mutandis, to what was previously described in the context of the carrier laminate.

[0091] Furthermore, it has proven to be advantageous for the filter medium to be configured in a pleated manner, i.e., the filter medium is laid in the form of pleats. Thereby, a larger filter area can be provided without significantly increasing the flow resistance.

[0092] Furthermore, the present invention is additionally based on the following general concept: providing the air filter unit as described above for use in a motor vehicle. In particular, the proposed air filter unit is suitable for use in a vehicle air conditioning device, a vehicle ventilation system, a vehicle heating system, or a combined heating, ventilation, and air conditioning system (HVAC system).

[0093] Other important features and advantages of the invention result from the dependent claims, the drawings, and the associated description of the drawings.

[0094] It should be understood that the features mentioned above and to be described below can be used not only in the respective given combinations but also in other combinations or individually, without departing from the framework of the invention. Brief Description of the Drawings

[0095] The drawings schematically show respectively:

[0096] Figure 1 A simplified perspective view showing a preferred air filter unit having an ionization unit and a filter medium,

[0097] Figure 2 A simplified view showing the filter medium,

[0098] Figure 3 A simplified view showing a filter medium having multiple layers according to a preferred embodiment,

[0099] Figure 4 A graphical view showing the separation efficiency of dust in the filter medium in the new state compared to an aged filter medium, and a graphical view of the corresponding effect caused by the proposed combination of the filter medium with the ionization unit and an additional polarization effect. Detailed Description of the Invention

[0100] Figure 1 A preferred air filter unit 100 is shown in a greatly simplified perspective view. The air filter unit is preferably installed in a housing 105 of a vehicle air-conditioning device (not shown). In addition, Figure 1 the air flow of the air supplied from the outside in the inflow direction 103 and the air outflow flow 102 after passing through the ionization unit 101 and the filter medium 102 are schematically marked. It should be understood that the air supplied from the outside is outside air, which especially carries dust in an urban environment, and this dust should be separated by the air filter unit 100. Next, the thus purified air is especially supplied to Figure 1 a passenger interior space (not shown). Preferably, the air supplied from the outside completely flows through the air filter unit. At least part of the gas molecules contained in this air flow are ionized by the ionization unit 101, which is marked in a greatly simplified view in Figure 1 . By accumulating the ionized gas molecules on the surfaces of the particles contained in the air, these particles gain charges again. Thereby, an improved particle separation rate in the filter medium 102 can be achieved. The structure of the filter medium 102 is discussed in more detail in Figure 2 and 3 . The ionization unit 101 shown in Figure 1 has a plurality of electrodes 108 located in a plane. The electrodes are used to generate corona discharge and are configured as so-called injection electrodes, which are made of stainless steel, for example. In Figure 1These electrodes are indicated by small triangles in the figure. The ejection electrodes 108 are electrically conductively connected to a high voltage power supply 107 via an electrical conductor 106. In addition, the ionization unit 101 has a counter electrode 109, Figure 1 In the embodiment shown, the counter electrodes are designed as hollow cylindrical counter electrode bodies, through which air can flow. Figure 1 The filter medium 102 is schematically shown in a pleated configuration, but can alternatively also be configured flat. Figure 1 The conductive stack not shown in the figure can be electrically contacted with the counter electrode via another conductor 110. Now, when the air filter unit 100 is in operation, the injection electrode 108 can be loaded with a first potential by the high-voltage power supply 107, and a second potential different from the first potential is applied to the counter electrode 109 and optionally to the conductive stack of the filter medium 102.

[0101] Figure 2 The basic form of the filter medium 102 is shown, which has an electret layer 201 with a thickness d , a mechanical separation layer 202 and a conductive layer 203 in the flow direction 204 of the air. 201 , the mechanically separated laminate has a thickness d 202 , the conductive stack has a thickness d 203 .

[0102] exist Figure 3 1 shows a preferred embodiment of a filter medium 102. The filter medium first has a cover nonwoven 301 in the flow direction of the air 204. Next, in the flow direction, the electret laminate 201 follows, which has two layers 304 and 305. Next, the mechanical separation laminate 202 follows. The mechanical separation laminate is separated from the subsequent conductive laminate 203 by an intermediate laminate 302, which has two layers 306 and 307. Next, the carrier laminate 303 follows, which has a thickness d 303 .

[0103] Figure 4 Plot the filter media in a new state compared to the aged state. Figure 3 The particle separation efficiency of the filter medium plotted in FIG. 1 and the corresponding effect achieved by the proposed combination of the filter medium with the ionization unit and the additional polarization effect.

[0104] An additional polarization effect is obtained based on the favorable electrical contact between at least one conductive laminate and the counter electrode of the ionization unit. It can be clearly seen that in the case of an unloaded filter medium (new state), the separation efficiency for fine dust is initially high, and the increase in this separation achieved through the additional polarization effect is relatively low at first. However, as the filter medium ages continuously, the separation on the filter medium decreases accordingly. Nevertheless, through the additional polarization effect, the separation efficiency of the unloaded filter medium can be approximately maintained. In order to obtain an aged filter medium, on the one hand, it can be considered to first use the filter medium in real driving operation. Alternatively, as in the case of Figure 4 , the filter medium can be artificially aged to simulate driving operation. This is achieved by exposing the filter medium to isopropanol vapor in a closed chamber for 48 hours.

[0105] List of reference numerals

[0106] 100 Air filter unit

[0107] 101 Ionization unit

[0108] 102 Filter medium

[0109] 103 Air flow in the inflow direction

[0110] 104 Air outflow

[0111] 105 Housing

[0112] 106 Electrical conductor for supplying the injection electrode

[0113] 107 High-voltage power supply

[0114] 108 Injection electrode

[0115] 109 Counter electrode

[0116] 110 Another electrical conductor, which is connected to another counter electrode and has a conductive filter laminate

[0117] 201 Electret laminate

[0118] 202 Mechanical separation laminate

[0119] 203 Conductive laminate

[0120] d 201 Thickness of the electret laminate

[0121] d 202 Thickness of the mechanical separation laminate

[0122] d 203 Thickness of the conductive laminate

[0123] Flow direction of the 204 air flow

[0124] 301 Cover non-woven fabric

[0125] 302 Intermediate laminate

[0126] 303 Carrier laminate

[0127] 304 First electret layer

[0128] 305 Second electret layer

[0129] 306 First layer of the conductive laminate

[0130] 307 Second layer of the conductive laminate

[0131] d 303 Thickness of the carrier laminate.

Claims

1. Air filter unit (100), The air filter unit comprises at least one ionization unit (101) and at least one filter medium (102), wherein: The at least one ionization unit has at least one ejection electrode (108), at least one counter electrode (109) and at least one voltage source (107), and wherein The at least one filter medium (102) is located downstream of the ionization unit and, viewed from the inlet side in the direction of the outlet side, first has at least one electret layer (201), then at least one mechanical separation layer (202) and then at least one conductive layer (203).

2. The air filter unit (100) according to claim 1, characterized in that The at least one conductive stack (203) is in electrical contact with a counter electrode of the ionization unit (101).

3. The air filter unit (100) according to any one of claims 1 or 2, characterized in that: The electrical contact of the at least one conductive stack (203) with the counter electrode of the ionization unit (101) can be controlled in time such that the at least one conductive stack (203) is electrically separated from the counter electrode after a predetermined polarization time and is electrically connected to the counter electrode again after a predetermined depolarization time.

4. The air filter unit (100) according to claim 2 or 3, characterized in that: At least one resistor is arranged in the electrical contact portion between the at least one conductive stack (203) and the counter electrode of the ionization unit (101).

5. The air filter unit (100) according to any one of the preceding claims, It is characterized in that The at least one filter medium (102) further comprises a carrier laminate (303) on the outflow side of the at least one electrically conductive laminate (203).

6. The air filter unit (100) according to any one of the preceding claims, It is characterized in that The at least one filter medium (102) further comprises a covering nonwoven (301) on the inflow side in front of the at least one electret layer (201).

7. The air filter unit (100) according to any one of the preceding claims, It is characterized in that The at least one electret stack (201) has at least two layers, Preferably, the at least two layers comprise fibers and the diameter of the fibers in the layers decreases in the flow direction.

8. The air filter unit (100) according to any one of the preceding claims, It is characterized in that The at least one mechanical separation layer (202) comprises nanofibers, The diameter of the nanofibers ranges from about 10 nm at the minimum to about 800 nm at the maximum. Preferably, the nanofibers have a diameter of a minimum of about 90 nm up to a maximum of about 500 nm.

9. The air filter unit (100) according to any one of the preceding claims, characterized in that The at least one electrically conductive stack (203) is additionally a stack for gas adsorption.

10. The air filter unit (100) according to any one of the preceding claims, It is characterized in that The at least one conductive stack (203) has at least two layers, wherein at least one of the two layers comprises activated carbon.

11. The air filter unit (100) according to any one of the preceding claims, It is characterized in that The at least one electrically conductive stack (203) has at least two layers, wherein at least one of the two layers comprises an ion exchanger or an ion exchanger and activated carbon.

12. The air filter unit (100) according to any one of the preceding claims, It is characterized in that At least one intermediate laminate (302) is additionally arranged between the at least one mechanically separating laminate (202) and the at least one electrically conductive laminate (203).

13. The air filter unit (100) according to any one of the preceding claims, characterized in that The filter medium (102) is configured in a pleated manner.

14. Use of an air filter unit (100) according to any one of the preceding claims in a motor vehicle.

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