EP4087684A1

EP4087684A1 - Electrostatic filter unit and air-cleaning device

Info

Publication number: EP4087684A1
Application number: EP20824514.2A
Authority: EP
Inventors: Georg Hepperle; Daniel Vollmar; Barbara John; Holger Eich
Original assignee: BSH Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2020-01-07
Filing date: 2020-12-10
Publication date: 2022-11-16
Also published as: WO2021139957A1; DE102020200074A1

Abstract

The present invention relates to an ionising filter unit for an air-cleaning device, the filter unit (2) having a mechanical particle filter (7) and an odour filter (8). The ionising filter unit (2) is characterised in that the odour filter (8) is a plasma filter (8) which is connected immediately downstream of the mechanical particle filter (7) in the flow direction, and at least the mechanical particle filter (7) and the odour filter (8) are held in a common filter frame (40). The invention also relates to an air-cleaning device (1) having at least one such ionising filter unit (2).

Description

Electrostatic filter unit and air cleaning device

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 are mainly used in practice for circulating air operation Activated charcoal filters and zeolite filters (also known as recirculating air filters in practice for extractor hoods) are used.

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 free the sucked in air flow from volatile organic compounds, or VOC's (Volatile Organic Compounds) for short.

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 filters 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 which 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 can ensure 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 Us _cheiteiwe n> = 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 n> = 500V and a period T> = 1s is 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 is connected to the electrical counter-potential so that a changing electrical voltage difference AU 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 are preferably perpendicular to the direction of flow. This alignment of the electrodes can, on the one hand, reduce the area of the electrodes generated plasma wall can be maximized without the depth of the filter unit, that is, its dimensions in the flow direction must 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 AU 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, enter into chemical compounds with unpleasant odor molecules and other volatile organic compounds (VOC's), 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 an electrical surface insulation (a dielectric) in order to prevent electrical flashovers and short circuits between the two electrodes and the 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, painting or rubber coating of the electrode (s) are possible.

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 ok

High-voltage electrodes or only the counter electrodes consist of such a material and the other electrodes 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 purifying device may 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 the fume hood or along the air flow guide between the inlet and outlet area of the fume hood. 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.

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

FIG. 1: a schematic perspective view of an embodiment of the air cleaning unit according to the invention;

FIG. 2: a schematic, perspective exploded view of an embodiment of the filter unit according to the invention;

FIG. 3: a schematic, perspective rear view of the embodiment of the filter unit according to FIG. 2;

FIG. 4: a schematic perspective view of an embodiment of the electrodes of the odor filter; Figures 5 to 9: schematic representations of embodiments of the

Electrode geometry of the odor filter of the filter unit according to the invention;

FIG. 10: a schematic block diagram of an embodiment of a

High voltage transformer; and

FIGS. 11a and 11b: schematic representation of possible voltage profiles of the voltage for the odor filter of the filter unit according to the invention.

An embodiment of an air cleaning device 1 is shown in FIG. In the embodiment shown, the air cleaning device 1 is an extractor hood. The air cleaning device 1 has a housing 10, in the front side of which a suction opening is formed. A fan (not shown) is accommodated in the housing 10, by means of which air is sucked into the air cleaning device 1. In the embodiment shown, an air outlet connector 3 is provided on the top of the housing 10, via which purified air can be output. In the embodiment shown, three ionizing filter units 2 according to the invention are introduced into the suction opening. Because the filter units 2 are arranged in the suction area, in particular in the suction opening of the fume hood, the components of the fume hood behind it remain free of contamination caused by cooking fumes / vapors drawn in. Although a vertical arrangement of the filter units 2 is shown in FIG. 1, depending on the design, shape and geometry of the air cleaning device 1, the arrangement can be horizontal or at a defined angle cp for 0 ° <cp <90 °.

An exploded view of an embodiment of the filter unit 2 according to the invention is shown in FIG. In the embodiment shown, the ionizing filter unit has a mechanical aerosol filter 7 for particle filtration, an odor filter formed by an air-permeable plasma filter 8 for odor reduction or odor reduction, and an ozone filter element 6 for ozone neutralization. Both the aerosol filter 7 and the plasma filter 8 are located in a common, preferably electrically conductive or electrically antistatic filter frame 40. In the embodiment shown, the filter frame 40 consists of a front frame part 4 and a rear frame part 5. As soon as the frame parts 4, 5 together are connected, the aerosol filter 7 and the plasma filter 8 are held in this. In the embodiment shown, the frame parts 4, 5 each represent half of the filter frame 40.

The plasma filter 8 has an electrode package 81, of which only one electrode can be seen in FIG. The electrode package 81 is held in a frame 80. As shown in FIG. 2, the filter unit 2 also has a high-voltage transformer 82 on which electrical contacts 83 are provided. A recess is provided in the rear frame part 5 through which contact can be made with the electrical contacts 83 from outside the filter unit 2.

In addition, a holder 50 for the ozone filter element 6 is provided on the rear frame part 5. In the embodiment shown, the bracket 50 consists 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. The ozone filter 6 can be pushed into this holder 50 from above. The ozone filter 6 lies behind the filter frame 40 in the direction of flow.

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

The components aerosol filter 7, plasma filter 8 and the high-voltage transformer 82, which can also be referred to as a high-voltage power supply unit, are housed in the filter frame 40.

The high-voltage transformer 82 is electrically connected to the plasma filter 8 via contacts. The electrical voltage supply of the filter unit 2 takes place by means of the electrical contacts 83. The filter unit 2 is placed in the fume cupboard is used, then by means of this electrical contact point / coupling 83, an electrical voltage supply is generated between the extractor hood and the filter unit 2. 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 8 consists of at least one (n> 1) high-voltage electrode 811, at least one (n> 1) air-permeable counter-electrode 810 and a frame 80 which mechanically holds the electrodes 810, 811 together. In the embodiment of the electrode arrangement 81 according to FIG. 3, the air-permeable high-voltage electrode 811 is arranged between two counter-electrodes 810.

With regard to the sequence, the counter electrodes 810 and the high-voltage electrodes 811 are arranged alternately with one another. The first and last electrodes of the plasma filter 8 in the flow direction can alternatively be both a counter-electrode 810 and an air-permeable high-voltage electrode 811.

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. The multiple layers of the counter-electrode 810 and / or the high-voltage electrode 811 can promote the mechanical filter function in addition to the aerosol filter 7.

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 rest against one another.

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

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

With regard to a possible perforated plate geometries, in addition to the circular perforated plates shown in FIG. 5, polygonal hole geometries are also possible, preferably hexagonal geometries (see FIG. 6). 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 plate geometry.

As an alternative to the above-mentioned embodiment, the individual electrodes 810, 811 can have a pleated or corrugated structure, which is shown in FIGS. 8 and 9. This measure serves on the one hand to reduce the pressure loss Dr [Pa] when flowing through the plasma filter 8 and 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 shown in FIG. 7, that the high-voltage electrode 811 represents a flat electrode and the counter-electrode 810 has a meander shape and thus surrounds the high-voltage electrode 811.

If plastic media are used as the material for the electrodes 810, 811, these must be electrically conductive or antistatic with a surface resistance R <10 ¹¹ ohms 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 at least one insulator (dielectric) is present between the high-voltage electrode 811 and the counter-electrode 810. For this reason, at least one of the two electrodes 810, 811 preferably has an electrical surface insulation (not shown) to prevent electrical flashovers and short circuits between the electrodes and to ensure the function of the plasma filter 8. The high-voltage electrode 811 is preferably designed to be electrically insulating. Alternatively, the counter electrode 810 can be made electrically insulating or both electrodes 810, 811 each have an electrical insulation on their surface. This at least one electrical insulator, which serves as a dielectric, is designed, for example, as an electrical ionization coating (sheathing) of the at least one electrode 810, 811, preferably the high-voltage electrode 811.

For example, functional powder or ceramic surface coatings, fluidized bed processes, sol-gel processes, dip coating, enamelling, painting or rubber coating of the electrode (s) 810, 811 come into consideration as coating processes for the electrical insulation of the electrodes 810, 811.

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 connection or contact between the high-voltage transformer 82 and the individual electrodes 810, 811 of the plasma filter 8 is shown in FIG. On the primary side, the high-voltage transformer 82 is supplied with electrical voltage via the electrical contacts 83, which are connected to the air cleaning device 1.

On the secondary side, the at least one air-permeable high-voltage electrode 811 is connected to the high-voltage transformer 82 via the high-voltage supply line 84. In the embodiment shown, the at least one counter electrode 810 is connected to the high-voltage transformer 82 via the grounded return line 85.

_{With regard to the voltage shape,} a pulsed voltage with Us cheiteiwe n> = 500 V (see FIG. 11a) and a period T <= 1s can be used for the air-permeable high-voltage electrode 811. The pulsed voltage can be act positive or negative voltage type. Alternatively, an alternating voltage with U _{rms value} _t > = 500V (see FIG. 11b) and a period T> = 1s is 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 AU between the high-voltage electrode 811 and the counter-electrode 810 can be ensured.

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

According to the concept of dielectrically impeded 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 Uzun _dspa nn _u ng . 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), as a result of which 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.

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

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 cleaning device

10 housing

2 filter unit

3 Air outlet nozzle from air cleaning device

40 filter frames

4 filter frames front frame part

5 filter frame rear frame part

50 bracket

6 ozone filters

7 aerosol filters

8 plasma filters

80 frames

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

PATENT CLAIMS

1. Ionizing filter unit for an air purification device, wherein the filter unit (2) has a mechanical particle filter (7) and an odor filter (8), characterized in that the odor filter (8) is a plasma filter (8) which corresponds to the mechanical particle filter (7 ) is immediately downstream 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).

2. Ionizing filter unit according to 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.

3. Ionizing filter unit according to claim 2, wherein at least one air-permeable high-voltage electrode (811) is arranged between two air-permeable counter-electrodes (810).

4. Ionizing filter unit according to one of 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 flow direction.

5. Ionizing filter unit according to claim 4, wherein the ozone filter (6) is releasably held on the filter frame (40).

6. Ionizing filter unit according to one of claims 2 to 5, wherein the electrodes (810, 811) of the odor filter are held in a frame (80).

7. Ionizing filter unit according to one of claims 2 to 6, wherein the electrodes (810, 811) of the odor filter (8) are arranged in a direction which is inclined to the flow direction.

8. Ionizing filter unit according to one of claims 2 to 7, wherein at least one of the electrodes (810, 811) of the odor filter (8) has an insulation coating on at least one surface.

9. Ionizing filter unit according to one of claims 2 to 8, wherein at least one high-voltage electrode (811) and / or at least one counter electrode (810) is constructed in multiple layers.

10. Ionizing filter unit according to one of 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.

11. Ionizing filter unit according to one of 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 metals, sintered material and / or foam.

12. Ionizing filter unit according to one of claims 2 to 11, wherein at least one high-voltage electrode (811) or a counter electrode (810) is designed in a meandering shape and surrounds the other electrode (810, 811).

13. Ionizing filter unit according to one of claims 2 to 12, wherein the odor filter (8) has a high-voltage transformer (82) through which a time-changing high voltage for the high-voltage electrode (811) of the odor filter (8) can be generated.

14. Ionizing filter unit according to claim 13, wherein the high-voltage transformer (82) is implemented in the filter unit (2).

15. Air cleaning device, characterized in that the

Air cleaning device has at least one ionizing filter unit (2) according to one of claims 1 to 14.

16. Air cleaning device according to claim 15, characterized in that the

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.