DE102020200074A1 - Electrostatic filter unit and air cleaning device - Google Patents

Abstract

The present invention relates to an ionizing filter unit for an air cleaning device, the filter unit (2) having a mechanical particle filter (7) and an odor filter (8). The ionizing filter unit (2) is characterized in that the odor filter (8) is a plasma filter (8) which is connected directly downstream of the mechanical particle filter (7) in the direction of flow, and at least the mechanical particle filter (7) and the odor filter (8) are held in a common filter frame (40). In addition, an air cleaning device (1) with at least one such ionizing filter unit (2) is described.

Description

The present invention relates to a filter unit for an air cleaning device and an air cleaning device.

Especially in the case of extractor hoods in recirculation mode, the filter efficiency of the built-in filter media is largely responsible for the extent to which the vapor air produced during the cooking process, interspersed with the finest particles and cooking odors, is filtered. This is relevant insofar as the vapor air sucked in by the extractor is not conveyed to the outside into the open environment, but is recirculated in the closed space (living room, kitchen, etc.). If the filter media installed in the extractor have a low or unsatisfactory filter efficiency, the cooking fumes remain in the closed living room air, consisting of an aerosol and olfactory unpleasant volatile organic compounds. In this context, the filter media installed in the fume cupboard are subject to high demands in terms of filter efficiency. The purpose of the invention is to keep the air clean in interiors such as living rooms, lounges and offices, but also in passenger cabins, e.g. in the automotive sector.

In fume hoods, mechanical filters are used to filter aerosols (solid and liquid particles), which are preferably arranged in the air intake area of the fume hood. These are expanded metal filters, perforated plate filters, baffle filters, fleeces (fiber material), edge suction filters, sintered plastics and other porous media or the like. All of these mentioned filter media filter according to mechanical separation mechanisms such as the diffusion effect, the blocking effect and, most importantly, the inertia effect. When separating according to the inertia effect, the particle cannot follow the streamline of the gas (air) around the individual filter fibers, expanded metal layers, porous media or the like due to its mass inertia and as a result collides with them.

With regard to the odor filtration of cooking odors and other organic, volatile compounds VOCs, mainly activated charcoal filters and zeolite filters (in practice for fume cupboards also referred to as circulating air filters) are used for circulating air operation.

In addition to these adsorbents mentioned, plasma filters are also used in practice, which are used as a system for reducing odors that is separate from the extractor hood. These systems, mostly intended as purchased parts, are installed as an attachment on the exhaust socket (behind the fan) of the extractor. As a rule, these plasma filters have a cylindrical design in order to be applied to the air outlet nozzle of the fan housing.

What is essential for these systems described is the fact that the grease filter and the odor filter or the separate system for odor reduction (plasma filter) are spatially separated from one another along the air flow guide. Another disadvantage of the plasma filters currently available is the fact that they require a relatively large amount of space and cannot be combined with every type of extractor. Furthermore, neither the adsorber (activated carbon filter) nor the plasma filter are normally cleanable systems. Systems that can be regenerated are occasionally offered on the market. The service life of these odor filters or systems for odor reduction (plasma filters) is shorter than that of a conventional extractor hood.

The invention is therefore based on the object of creating a solution by means of which sufficient filter efficiency can be reliably ensured with little space requirement.

According to a first aspect, the invention therefore relates to an ionizing filter unit for an air cleaning device, the filter unit having a mechanical particle filter and an odor filter. The ionizing filter unit is characterized in that the odor filter is a plasma filter which is connected directly downstream of the mechanical particle filter in the direction of flow, and at least the mechanical particle filter and the odor filter are held in a common filter frame.

The ionizing filter unit is also referred to below as a filter unit, filter module or filter cassette. The air cleaning device in which the ionizing filter unit can be used can be a fume extractor or a fume hood or other vapor extraction device or an air cleaner for interiors or for passenger cabins in the automotive sector.

The particle filter can also be referred to as an aerosol filter or, in the case of extractor hoods, also as a grease filter. A mechanical particle filter is a particle filter that filters particles out of the air according to mechanical separation mechanisms such as the diffusion effect, barrier effect and, to a large extent, the inertia effect. The mechanical particle filter is also referred to simply as a particle filter in the following. The particle filter can
be an expanded metal filter, perforated plate filter, baffle filter, porous sintered plastic, groove filter or surface filter.

The odor filter for odor reduction is also referred to below as a plasma filter, plasma unit or plasma module. The plasma filter is used to remove volatile organic compounds, or VOCs (Volatile Organic Compounds), from the air flow that is sucked in.

According to the invention, the odor filter represents a plasma filter and is also referred to as such in the following. A plasma filter is a filter in which the odor reduction or reduction takes place by means of ionization. In particular, the operating mechanism of the plasma filter is based on the dielectrically impeded barrier discharge.

According to the invention, the odor filter is connected directly downstream of the mechanical particle filter in the direction of flow. The direction of flow is the direction in which air flows through the filter unit during operation of an air cleaning device in which the at least one ionizing filter unit is provided. In particular, the flow direction therefore denotes the direction from the suction side of the filter unit to the clean air side of the filter unit. An arrangement of the mechanical particle filter and the odor filter in which no further filter elements are provided between the two filters is referred to as immediately downstream. The mechanical particle filter can rest against the odor filter or be provided at a certain distance from it.

Finally, at least the mechanical particle filter and the odor filter are held in a common filter frame. The filter frame can be constructed in one piece or in several pieces. In particular, the filter frame can consist of a front and a rear frame part. The front frame part faces the upstream side of the filter unit and the rear frame part faces the clean air side of the filter unit. In addition to the mechanical particle filter and the odor filter, the filter frame can also accommodate components that are used to supply power to the odor filter. The filter frame is preferably designed to be electrically conductive or electrically antistatic.

In that, in the ionizing filter unit according to the invention, a mechanical particle filter and an odor filter, which represents a plasma filter, are held directly one behind the other in a common frame, a number of advantages can be achieved. On the one hand, a filter unit can be created by means of which any type of contamination from the air can be reduced. In addition, the filter unit is a compact unit that can be easily introduced into or attached to an air cleaning device. The compactness of the filter unit results in particular from the fact that, apart from the mechanical particle filter and the odor filter, no further filters, such as electrostatic separation filters, are provided. Nevertheless, a high filter efficiency is achieved with the filter unit according to the invention, since the odor filter is designed as a plasma filter. Since the filters of the filter unit are held in a common frame, they can also be easily removed from the air cleaning device in order to clean it, for example.

According to a preferred embodiment, the odor filter comprises at least one flat, air-permeable high-voltage electrode and at least one flat, air-permeable counter-electrode and the at least one air-permeable high-voltage electrode and the at least one air-permeable counter-electrode are arranged one behind the other in the direction of flow.

The electrodes of the odor filter are flat electrodes and are also referred to below as flat elements. The at least one air-permeable high-voltage electrode and the at least one air-permeable counter-electrode are arranged one behind the other in the direction of flow. The shape of the high-voltage electrode and the counter-electrode, that is to say the surface elements, can be a flat surface. Alternatively, however, the surface element can also have a meandering, arched, corrugated or pleated shape, for example. The electrodes of the odor filter are preferably parallel to one another. In the case of electrodes that represent a surface element deviating from a flat surface, the shape of the high-voltage electrode (s) and the counter electrode (s) is the same, i.e. their curvature, curvature of the individual waves or the pitch of the pleated tips is preferably the same. This ensures that the distance between the electrodes is the same over the area of the electrodes. When the filter unit is in operation, a plasma is generated between the high-voltage electrode and the counter-electrode.

With regard to the form of voltage applied to the electrodes of the odor filter, either a pulsed voltage, for example with U _{peak value} > = 500 V and a period T <= 1s, is used for the air-permeable high-voltage electrode. The pulsed voltage can be a positive or negative type of voltage. Alternatively, an alternating voltage with, for example, U _{rms value} > = 500V and a period T> = 1s is possible. Various voltage forms are possible for the alternating voltage and the pulsed voltage. For example, a sinusoidal, rectangular, triangular or sawtooth voltage waveform application. The air-permeable counter-electrode is connected to the electrical counter-potential so that a changing electrical voltage difference ΔU between the high-voltage electrode and the counter-electrode can be ensured. Alternatively, the air-permeable counter electrode can be grounded. For this application, the air-permeable counter electrode is electrically connected to the protective conductor PE (protective earth).

Since the electrodes each represent a surface element, a plasma wall is formed in the distance between the electrodes, through which the air to be cleaned passes and is cleaned there.

Since the high-voltage electrode and the counter-electrode are air-permeable and are arranged one behind the other in the direction of flow, a number of advantages can be achieved. In particular, great efficiency in terms of odor reduction can be achieved. This is due to the fact that by means of the at least one air-permeable high-voltage electrode and the at least one air-permeable counter-electrode, a plasma wall is built up during operation, through which the air laden with odor molecules flows. When the odor molecules in the air flow through this ionization area, which is referred to as the “plasma wall”, there is a sustained chemical reaction of these odor molecules with the reactive species. In other words, there is a complete mixing of odor molecules with reactive oxygen species (ROS) and reactive nitrogen species (RNS).

According to one embodiment, at least one air-permeable high-voltage electrode is arranged between two air-permeable counter electrodes. As will be described further below, it is also possible here for only one air-permeable counter-electrode to surround a high-voltage electrode, in that the counter-electrode has a suitable shape. The advantage of arranging the high-voltage electrode between counter-electrodes is that the high-voltage electrode that carries the voltage-carrying electrode or the electrode that carries the higher voltage is located in a Faraday cage, which is formed in particular by the counter-electrodes. The counterelectrode or electrodes are therefore preferably grounded counterelectrodes.

In addition, when the high-voltage electrode is arranged between counter-electrodes, all voltage-carrying components can be oriented into the interior of the filter unit. The filter frame, the particle filter and the air-permeable counter-electrode can spatially and electrically shield the live electrode from the "outside". This means, more precisely, that the high-voltage electrode is protected during operation when the electrical voltage is switched on and that there is no electrical hazard for the user with this arrangement. In this embodiment, the filter frame is preferably designed to be electrically conductive or at least antistatic.

According to one embodiment, the filter unit has at least one ozone filter, which is connected downstream of the odor filter in the direction of flow. The ozone filter can also be referred to as an ozone filter element. The ozone filter is used for ozone neutralization, which is generated in the odor filter, i.e. the plasma filter, during the ionization. So that the ozone (O ₃ ) cannot leave the filter unit, the ozone filter is arranged behind the plasma filter in the air flow direction. The ozone filter element can, for example, be a filter made from an adsorbing material such as activated carbon or zeolite. Alternatively, ozone catalysts can also be used, which can also be referred to as ozone destroyers. The ozone catalysts can consist of a support structure that is coated with catalytically active material, or consist entirely of the catalytically active material.

According to a preferred embodiment, the ozone filter is detachably held on the filter frame. For this purpose, a holder can be provided on the filter frame, in particular on the clean air side of the filter frame, into which the ozone filter can be pushed, for example. Since the ozone filter can be detached from the filter frame, it can be removed from the filter unit. This is particularly advantageous for cleaning the filter unit. As a rule, the materials of the ozone filter, such as activated carbon, zeolite or ozone catalyst, are not suitable for cleaning with water or even cleaning agents. Since the ozone filter can be removed, the filter unit can be cleaned without the ozone filter and, for example, cleaned in a dishwasher.

According to one embodiment, the electrodes of the odor filter are held in a frame. The frame is a separate frame from the filter frame. Since the odor filter preferably consists of a plurality of electrodes, the mutual relative position of the electrodes can be adjusted and maintained by providing a frame for the odor filter.

According to a preferred embodiment, the electrodes of the odor filter are arranged in a direction which is inclined to the direction of flow. The electrodes of the Odor filter perpendicular to the direction of flow. This alignment of the electrodes enables, on the one hand, the area of the plasma wall generated by the electrodes to be maximized without the depth of the filter unit, that is to say its dimensions in the direction of flow, having to be increased. On the other hand, with this orientation, the air to be cleaned can flow through the air-permeable electrodes and thus the mixing of the air can be guaranteed, whereby a more efficient breakdown of odor molecules and other VOCs is guaranteed even with lower energy input.

According to one embodiment, at least one of the electrodes of the odor filter has an insulation coating on at least one surface.

According to the invention, the mechanism of action of the odor filter for eliminating odors is the concept of dielectric barrier discharge (DBE). The insulation coating provided on at least one electrode of the odor filter can therefore function as a dielectric between the high-voltage electrode and the counter-electrode.

The capacitive odor filter arrangement, consisting of at least two electrodes (high-voltage electrode, counter-electrode) with different electrical voltage potentials from one another and at least one dielectric between these two electrodes. Using a time-changing electrical voltage difference ΔU between these two electrodes, this leads to an electrical displacement current I, which in turn causes ionization of the air by ionization processes. Through this ionization process in the ionization area (plasma area) reactive species are formed by impact ionization processes, so-called reactive oxygen species (ROS) and reactive nitrogen species (RNS). These reactive species are energetically highly reactive molecules which, among other things, form chemical compounds with unpleasant odor molecules and other volatile organic compounds (VOCs), whereby these unpleasant odor molecules are chemically converted into other chemical compounds. As a result of chemical processes between the odor molecules and the reactive species, there is consequently a reduction in odor down to odor reduction below the odor threshold value.

For this reason, at least one of the two electrodes of the odor filter preferably has electrical surface insulation (a dielectric) in order to prevent electrical flashovers and short circuits between the two electrodes and to ensure the functioning of the plasma unit. Ideally, the air-permeable high-voltage electrode is designed to be electrically insulating. Alternatively, the air-permeable counter-electrode can be designed to be electrically insulating, or all electrodes have electrical insulation on their surface.

As a coating process for electrical insulation of the electrode (s) of the odor filter, for example, functional powder and ceramic coatings, fluidized bed sintering processes, sol-gel processes, dip coating, enamelling, lacquering or rubber coating of the electrode (s) come into consideration.

The electrodes of the odor filter are preferably arranged alternately with one another. This means that in each case an air-permeable high-voltage electrode is arranged in relation to an air-permeable counter-electrode. The first and last electrodes in the direction of flow can either be an air-permeable counter-electrode or an air-permeable high-voltage electrode.

According to one embodiment, at least one high-voltage electrode and / or at least one counter electrode is constructed in multiple layers. In this embodiment, the respective electrode consists of several air-permeable layers (n> = 1).

According to the invention, the electrodes of the odor filter are air-permeable. According to one embodiment, the at least one high-voltage electrode and the at least one counter electrode consist of air-permeable material. In this embodiment, the electrodes are also referred to as porous electrodes. The electrodes can all consist of the same air-permeable material. However, it is also within the scope of the invention that different electrodes consist of different materials. The advantage of using air-permeable material for the electrodes of the odor filter is that, on the one hand, the production of the odor filter is facilitated, since the required air permeability is provided by the material itself.

According to a further embodiment, the electrodes of the odor filter consist of an air-impermeable material with at least one air passage opening. It is also possible that only some of the electrodes, for example only the high-voltage electrodes or only the counter electrodes, consist of such a material and the other electrodes in each case consist of air-permeable material.

Regardless of whether the electrodes of the odor filter are made of an air-permeable material or of air-impermeable material with air passage openings, the material of the electrodes is chosen so that it is electrically conductive or antistatic.

The electrodes of the odor filter can, for example, be perforated sheets, e.g. perforated sheets, welded grids, woven wire grids, expanded metals, sintered materials and foams.

The electrodes of the odor filter are preferably arranged offset to one another in order to ensure optimal ionization of the air flowing through, which is laden with odor molecules, which in turn leads to an optimal reduction of the odor molecules. A staggered arrangement is an arrangement in which the openings in one electrode do not coincide with the openings in an adjacent electrode.

According to one embodiment, a high-voltage electrode and a counter-electrode are arranged with respect to one another in such a way that their structure lies rotated about an axis in the plane of the respective electrode. This means that the individual electrodes in the plane of the respective electrode are offset around an axis of rotation which is perpendicular to the plane of the electrode by an angle of 0 to 360 ° when installed.

According to one embodiment, at least one high-voltage electrode or one counter-electrode is designed in a meandering shape and surrounds the other electrode. The total number of electrodes can be reduced by at least one electrode having a meandering shape. In this case, the air-permeable counter-electrode is preferably arranged in a meandering shape between high-voltage electrodes. For example, only one counter electrode is required here. The same is possible for the high-voltage electrode. Another advantage of this constructive measure is the fact that with a meander shape only one counter electrode and / or one high voltage electrode is required and the areas in which, for example, the high voltage electrode lies between areas of the counter electrode are already electrically connected to one another. In this case, there is no separate contacting of individual electrodes.

According to one embodiment, the odor filter has a high-voltage transformer, by means of which a high voltage that changes over time can be generated for the electrodes, in particular the high-voltage electrode, of the odor filter. As a result, the electrodes of the odor filter can be subjected to a high voltage that changes over time. The high voltage can be, for example, alternating voltage or a pulsed voltage. The high-voltage transformer is used to generate or generate the necessary electrical high voltage. The high-voltage transformer can also be referred to as a high-voltage generator or high-voltage power supply unit. This high-voltage transformer supplies the electrodes of the odor filter, in particular the at least one high-voltage electrode and at least one counter-electrode, with electrical high voltage or with electrical energy on the secondary side via the connecting lines. On the primary side, the high-voltage transformer is supplied with electrical power via a connection or a connection line for lower voltage. This lower voltage on the primary side of the high-voltage transformer can be a direct voltage of <= 1500 V DC or an alternating voltage of <= 1000 V AC.

According to a further aspect, the present invention relates to an air cleaning device which has at least one ionizing filter unit according to the invention.

Advantages and features that are described with respect to the ionizing filter unit apply - if applicable - correspondingly to the air cleaning device and vice versa.

The air cleaning device can be, for example, an air cleaner for filtering room air, a device for filtering air sucked into a passenger cabin in the automotive sector, or an extractor hood for kitchens. The air cleaning device can have several ionizing filter units according to the invention. The at least one filter unit is preferably arranged on the suction side of the air cleaning device. However, it is also within the scope of the invention to additionally or alternatively provide at least one filter unit on the air outlet side of the air cleaning device.

According to a preferred embodiment, the air cleaning device is an extractor hood and the at least one ionizing filter unit is arranged in front of the fan of the extractor device.

In relation to the fume hood, the filter unit according to the invention is preferably arranged in the air intake area of the fume hood in order not to contaminate the components located behind it with cooking vapors / aerosols / dirt. However, such a filter unit can optionally also be arranged in the air outlet area in a vapor suit or along the air flow guide between the inlet and outlet areas the extractor. The geometric dimensions (length, width and height) of the filter unit vary depending on the installation location or the type and geometry of the extractor hood.

• 1: eine schematische Perspektivansicht einer Ausführungsform der erfindungsgemäßen Luftreinigungseinheit;
• 2: eine schematische, perspektivische Explosionsansicht einer Ausführungsform der erfindungsgemäßen Filtereinheit;
• 3: eine schematische, perspektivische Rückansicht der Ausführungsform der Filtereinheit nach 2;
• 4: eine schematische Perspektivansicht einer Ausführungsform der Elektroden des Geruchsfilters;
• 5 bis 9: schematische Darstellungen von Ausführungsformen der Elektrodengeometrie des Geruchsfilters der erfindungsgemäßen Filtereinheit;
• 10: eine schematische Blockdarstellung einer Ausführungsform eines Hochspannungsübertragers; und
• 11a und 11b: schematische Darstellung möglicher Spannungsverläufe der Spannung für den Geruchsfilters der erfindungsgemäßen Filtereinheit.

The invention is described again in more detail below with reference to the accompanying figures. Show it:

• 1 : a schematic perspective view of an embodiment of the air cleaning unit according to the invention;
• 2 : a schematic, perspective exploded view of an embodiment of the filter unit according to the invention;
• 3 : a schematic, perspective rear view of the embodiment of the filter unit according to FIG 2 ;
• 4th : a schematic perspective view of an embodiment of the electrodes of the odor filter;
• 5 to 9 : schematic representations of embodiments of the electrode geometry of the odor filter of the filter unit according to the invention;
• 10 : a schematic block diagram of an embodiment of a high-voltage transformer; and
• 11a and 11b : Schematic representation of possible voltage curves of the voltage for the odor filter of the filter unit according to the invention.

In 1 is one embodiment of an air cleaning device 1 shown. In the illustrated embodiment, the air cleaning device 1 an extractor hood. The air cleaning device 1 has a housing 10 on, in the front of which a suction port is formed. In the case 10 A fan (not shown) is included through which air enters the air cleaning device 1 is sucked in. In the embodiment shown is on top of the housing 10 an air outlet nozzle 3 provided through which purified air can be output. In the embodiment shown, there are three ionizing filter units in the suction opening 2 introduced according to the invention. By the filter units 2 Are arranged in the suction area, in particular in the suction opening of the extractor hood, the components of the extractor hood located behind it remain free of impurities caused by cooking vapors / vapors that are sucked in. Although in 1 a vertical arrangement of the filter units 2 however, the arrangement may depend on the design, shape and geometry of the air cleaning device 1 lie in the horizontal or at a defined angle φ for 0 ° ≤ φ ≤ 90 °.

In the 2 Figure 3 is an exploded view of one embodiment of the filter unit of the present invention 2 shown. In the embodiment shown, the ionizing filter unit has a mechanical aerosol filter 7th for particle filtration, an odor filter that passes through an air-permeable plasma filter 8th is formed for odor reduction or odor reduction, and an ozone filter element 6th for ozone neutralization.

Both the aerosol filter 7th as well as the plasma filter 8th are located in a common, preferably electrically conductive or electrically antistatic filter frame 40 . In the embodiment shown, there is the filter frame 40 from a front frame part 4th and a rear frame part 5 . Once the frame parts 4th , 5 are connected to each other, the aerosol filter 7th and the plasma filter 8th kept in this. In the embodiment shown, the frame parts 4th , 5 half of the filter frame 40 represent.

The plasma filter 8th has an electrode package 81 from which in 2 only one electrode can be seen. The electrode package 81 will be in a frame 80 held. Like in the 2 is shown, has the filter unit 2 also a high voltage transformer 82 on where electrical contacts 83 are provided. In the rear part of the frame 5 a recess is provided through which the electrical contacts 83 from outside the filter unit 2 can be contacted.

In addition, is on the rear frame part 5 a bracket 50 for the ozone filter element 6th intended. In the embodiment shown, there is a bracket 50 made of rails that extend over part of the height of the filter frame 40 and along part of the lower part of the filter frame 40 extend. In this bracket 50 can the ozone filter 6th can be inserted from above. The ozone filter 6th lies behind the filter frame in the direction of flow 40 .

This arrangement of the ozone filter 6th is in the 3 which is a rear perspective view of the filter unit 2 shows, visible.

In the filter frame 40 the components are aerosol filters 7th , Plasma filter 8th and the high voltage transformer 82 , which can also be called high-voltage power supply, high-voltage supplier houses.

The high voltage transformer 82 is electrical with the plasma filter 8th connected via contacts. By means of the electrical contacts 83 the filter unit is supplied with electrical power 2 . Will the filter unit 2 inserted into the extractor hood, this electrical contact point / coupling 83 an electric Power supply between extractor and filter unit 2 generated. A low voltage (≤ 50V AC, ≤ 120V DC) or low voltage (≤ 1,000V AC, ≤ 1,500V DC) is preferably provided for the electrical power supply.

The plasma filter 8th consists of at least one (n ≥ 1) high voltage electrode 811 , at least one (n ≥ 1) air-permeable counter electrode 810 as well as a frame 80 holding the electrodes 810 , 811 holds together mechanically. In the embodiment of the electrode arrangement 81 to 3 is the air-permeable high-voltage electrode 811 between two counter electrodes 810 arranged.

In terms of order, the counter electrodes are 810 and the high voltage electrodes 811 arranged alternately to one another. At the first and last electrode of the plasma filter in the direction of flow 8th Alternatively, it can be both a counter-electrode 810 as well as an air-permeable high-voltage electrode 811 act.

There is also the possibility that the counter electrode 810 is composed of individual air-permeable electrode layers (n ≥ 1). The same principle also applies to the air-permeable high-voltage electrode 811 . Due to the multiple layers of the counter electrode 810 and / or high voltage electrode 811 can perform the mechanical filter function in addition to the aerosol filter 7th be favored.

The electrodes 810 , 811 are preferably arranged at a small distance from one another. The distance can, for example, be in a range from 0 to 10 mm, preferably from 0 to 6 mm, 0 to 4 mm or 0 to 2 mm. The electrodes 810 , 811 can lie against each other.

With the electrodes 810 , 811 In principle, it can be any material / medium that is air-permeable and electrically conductive or antistatic, so that an electric field is created between the electrodes 810 , 811 can build.

The material of the at least one electrode 810 , 811 can for example be perforated sheet metal (perforated sheet), wire mesh, in particular welded mesh or expanded metal.

Alternatively, the material of the at least one electrode can be used 810 , 811 also wire mesh, sintered materials, fiber materials or foams. Preferably is for the high voltage electrode 811 to use a welding grid or perforated plate and for the counter electrode 810 Wire mesh or expanded metal. Alternatively, the electrodes 810 , 811 of the electrode package 81 be constructed from an identical air-permeable geometry.

With regard to possible perforated sheet geometries, in addition to those in 5 The circular perforated sheets shown here also consider polygonal hole geometries, preferably hexagonal geometries (see Sect. 6th ). One advantage of polygonal geometries (for example triangular or square perforations) is the resulting larger opening area of the air-permeable electrodes 810 , 811 in contrast to a circular perforated sheet geometry.

The individual electrodes 810 , 811 can alternatively to the embodiment mentioned above have a pleated or corrugated structure, which in the 8th and 9 are shown. On the one hand, this measure serves to reduce the pressure loss Δp [Pa] when flowing through the plasma filter 8th as well as to increase the efficiency in terms of odor reduction with otherwise constant boundary conditions. The aim of this measure is, in particular, to enlarge the electrode area.

Additionally or alternatively, it is also possible, as in 7th shown the high voltage electrode 811 represents a flat electrode and the counter electrode 810 has a meander shape and so does the high-voltage electrode 811 surrounds.

Are plastic media used as the material for the electrodes 810 , 811 used, they must be electrically conductive or antistatic with a surface resistance R ≤ 10 ¹¹ Ohm with regard to their specific properties.

According to the invention, the mechanism of action for eliminating odors by means of ionization is based on the dielectrically impeded barrier discharge. This assumes that there is at least one insulator (dielectric) between the high voltage electrode 811 and the counter electrode 810 is available. For this reason, at least one of the two electrodes preferably has 810 , 811 an electrical surface insulation (not shown) to prevent electrical flashovers and short circuits between the electrodes and the function of the plasma filter 8th to guarantee. Preferably the high voltage electrode is 811 procure electrically insulating. Alternatively, the counter electrode 810 be made electrically insulating or both electrodes 810 , 811 each have electrical insulation on their surface. This at least one electrical insulator, which serves as a dielectric, is used, for example, as an electrical ionization coating (sheathing) of the at least one electrode 810 , 811 executed, preferably the high voltage electrode 811 .

As a coating process for the electrical insulation of the electrodes 810 , 811 For example, functional powder or ceramic surface coatings, fluidized bed sintering processes, sol- Gel process, dip coating, enamelling, painting or rubber coating of the electrode (s) 810, 811 are possible.

In the air cleaning device according to the invention, a low voltage is transmitted in the air cleaning device 1 to the filter unit 2 . The transformation of a low voltage into high voltage takes place preferably within the filter unit by means of the high voltage transformer 82 .

The electrical interconnection or contact between the high-voltage transformer 82 and the individual electrodes 810 , 811 of the plasma filter 8th is in 10 shown. The electrical power supply of the high-voltage transformer takes place on the primary side 82 via the electrical contacts 83 that came with the air purifier 1 are connected.

The at least one air-permeable high-voltage electrode is on the secondary side 811 via the high-voltage supply line 84 with the high voltage transformer 82 connected. The at least one counter electrode 810 is in the embodiment shown via the grounded return line 85 with the high voltage transformer 82 connected.

Regarding the voltage shape, for the air-permeable high-voltage electrode 811 a pulsed voltage with U _{peak value} > = 500 V (see 11a) and a period T <= 1s can be used. The pulsed voltage can be a positive or negative type of voltage. Alternatively, an alternating voltage with U _{rms value} > = 500V (see 11b) and a period T> = 1s possible. Various voltage forms are possible for the alternating voltage and the pulsed voltage. A sinusoidal, rectangular, triangular or sawtooth-shaped voltage form is used here, for example. The air-permeable counter electrode 810 can be connected to the electrical counter potential, so that a changing electrical voltage difference ΔU between the high-voltage electrode 811 and the counter electrode 810 can be guaranteed.

According to one embodiment, as in 10 the air-permeable counter electrode 810 grounded. The air-permeable counter-electrode is used for this application 810 electrically connected to the protective conductor PE (protective earth).

According to the concept of dielectrically hindered barrier discharge (DBE), there is an electrical displacement current I between two electrodes with at least one dielectric if an electrical voltage U that changes over time is applied between these two electrodes under ambient conditions, the so-called ignition voltage U _{ignition voltage} . The amount of ignition voltage depends on many factors, such as the electrode geometry, the insulation material, the gap width, the voltage shape, the gas composition, etc. This displacement current causes the air to ionize between the two electrodes (ionized air = plasma). Through this ionization process in the ionization area (plasma area) reactive species are formed by impact ionization processes, so-called reactive oxygen species (ROS) and reactive nitrogen species (RNS). These reactive species are energetically highly reactive molecules which, among other things, form chemical compounds with unpleasant odor molecules and other volatile organic compounds (VOCs), whereby these unpleasant odor molecules are chemically converted into other chemical compounds. As a result of chemical processes between the odor molecules and the reactive species, the odor is reduced to below the odor threshold.

Based on this process or this mode of operation, electrodes are used in the plasma filter, which ionize the air between the electrodes according to the principle of dielectrically hindered barrier discharge.

This ionization of the air in the ionization area (plasma formation) leads to the reduction of olfactory unpleasant odor molecules below the odor threshold and oxidation of other volatile chemical compounds (VOCs).

The present invention has a number of advantages.

The present invention provides a compact, self-sufficient filter unit which can reduce both particles and olfactory unpleasant odor molecules from the air.

Due to its concept with the air-permeable electrodes for odor reduction, the filter unit requires significantly less space than the plasma filters currently available on the market.

The plasma filter used preferably consists only of air-permeable electrodes arranged one behind the other through which the air flows. This simple and odor-reducing invention makes the plasma unit cost effective in terms of material and manufacturing costs.

The plasma filter used, consisting of porous or air-permeable electrodes arranged one behind the other, has, in contrast to other plasma filters, a far greater efficiency in terms of odor reduction. This is due to the fact that a plasma wall builds up during operation by means of the porous electrodes, and the odor molecules in the air through this ionization area “plasma wall” lead to a sustained chemical reaction of these odor molecules with the reactive species. In other words, there is a complete mixing of odor molecules and other VOCs in the air with the reactive species (more precisely: the so-called reactive oxygen species (ROS) and reactive nitrogen species (RNS). The air-permeable electrodes of the plasma filter lead to better results due to their geometric properties Mixing of the air flowing through.

Due to the more efficient mixing of the air and the resulting more efficient breakdown of odor molecules and other VOCs, in contrast to the existing plasma systems, less electrical power (energy input) is required with the same filter efficiency.

The filter unit can be cleaned in the dishwasher or by hand using cleaning substances and water. As a result, the service life of such a filter unit is unlimited. The electrodes for odor reduction can be washed out of dirt and impurities under water. The currently available plasma filters are not suitable for cleaning purposes or, according to the manufacturer, are not intended. This is especially true for cleaning purposes in private household use.

The filter unit of the present invention has no restrictions due to its concept and compact design.

List of reference symbols

1

Air purifier

10

casing

2

Filter unit

3

Air outlet nozzle from air cleaning device

40

Filter frame

4th

Filter frame front frame part

5

Filter frame rear frame part

50

bracket

6th

Ozone filter

7th

Aerosol filters

8th

Plasma filter

80

frame

81

Electrode package

810

Counter electrode

811

High voltage electrode

82

High voltage transformer

83

electrical contacts

84

high-voltage supply line

85

grounded return line

Claims (16)

Ionizing filter unit for an air cleaning device, the filter unit (2) having a mechanical particle filter (7) and an odor filter (8), characterized in that the odor filter (8) is a plasma filter (8) which is attached to the mechanical particle filter (7) Flow direction is immediately downstream, and at least the mechanical particle filter (7) and the odor filter (8) are held in a common filter frame (40). Ionizing filter unit after Claim 1 , wherein the odor filter (8) comprises at least one flat, air-permeable high-voltage electrode (811) and at least one flat, air-permeable counter-electrode (810) and the at least one air-permeable high-voltage electrode (811) and the at least one air-permeable counter-electrode (810) are arranged one behind the other in the direction of flow . Ionizing filter unit after Claim 2 , wherein at least one air-permeable high-voltage electrode (811) is arranged between two air-permeable counter-electrodes (810). Ionizing filter unit after one of the Claims 1 to 3 , wherein the filter unit (2) has at least one ozone filter (6) which is connected downstream of the odor filter (8) in the direction of flow. Ionizing filter unit after Claim 4 , wherein the ozone filter (6) is releasably held on the filter frame (40). Ionizing filter unit after one of the Claims 2 to 5 , wherein the electrodes (810, 811) of the odor filter are held in a frame (80). Ionizing filter unit after one of the Claims 2 to 6th wherein the electrodes (810, 811) of the odor filter (8) are arranged in a direction inclined to the flow direction. Ionizing filter unit after one of the Claims 2 to 7th wherein at least one of the electrodes (810, 811) of the odor filter (8) has an insulation coating on at least one surface. Ionizing filter unit after one of the Claims 2 to 8th , wherein at least one high-voltage electrode (811) and / or at least one counter electrode (810) is constructed in multiple layers. Ionizing filter unit after one of the Claims 2 to 9 , wherein the at least one high-voltage electrode (811) and the at least one counter electrode (810) consist of air-permeable material or consist of an air-impermeable material with at least one air passage opening. Ionizing filter unit after one of the Claims 2 to 10 , wherein at least one high-voltage electrode (811) and / or at least one counter electrode (810) consists of perforated sheet metal, welded mesh, woven wire mesh, expanded metal, sintered material and / or foam. Ionizing filter unit after one of the Claims 2 to 11 wherein at least one high-voltage electrode (811) or one counter-electrode (810) is designed in a meandering shape and surrounds the respective other electrode (810, 811). Ionizing filter unit after one of the Claims 2 to 12th wherein the odor filter (8) has a high-voltage transformer (82) by means of which a high voltage that changes over time can be generated for the high-voltage electrode (811) of the odor filter (8). Ionizing filter unit after Claim 13 , wherein the high-voltage transformer (82) is implemented in the filter unit (2). Air cleaning device, characterized in that the air cleaning device has at least one ionizing filter unit (2) according to one of the Claims 1 to 14th having. Air purification device according to Claim 15 , characterized in that the air cleaning device (1) is an extractor device and the ionizing filter unit (2) is arranged in front of the fan of the extractor device.

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