ELECTROSTATIC FILTER UNIT FOR AN AIR-PURIFICATION DEVICE AND AIR-PURIFICATION DEVICE

Abstract

An electrostatic filter unit for an air-purification device, the filter unit comprising an ionization unit and a separation unit with at least one voltage-carrying collecting electrode and at least one grounded collecting electrode, characterized in that the at least two collecting electrodes are air-permeable.

Claims

1-11. (canceled)

12. An electrostatic filter unit for an air-purification device, said filter unit comprising: an ionization unit; and a separation unit arranged downstream of the ionization unit in a flow direction of air, said separation unit including a voltage-carrying collecting electrode and a grounded collecting electrode, with the voltage-carrying collecting electrode and the grounded collecting electrode being air-permeable.

13. The electrostatic filter unit of claim 12, wherein the flow direction of the air toward the collecting electrodes lies at an angle α in the region of 0≤α≤90° in relation to a surface of the collecting electrodes.

14. The electrostatic filter unit of claim 12, wherein the flow direction of the air toward the collecting electrodes lies at an angle α in the region of 45° or 90° in relation to a surface of the collecting electrodes.

15. The electrostatic filter unit of claim 12, wherein the voltage-carrying collecting electrode and the grounded collecting electrode are placed adjacent to one another at a distance in a range of 0 to 20 mm.

16. The electrostatic filter unit of claim 12, wherein the voltage-carrying collecting electrode and the grounded collecting electrode are placed adjacent from one another at a distance in a range of 0 to 2 mm.

17. The electrostatic filter unit of claim 12, wherein the separation unit includes at least two of said voltage-carrying collecting electrode arranged adjacent to one another or at least two of said grounded collecting electrode arranged adjacent to one another.

18. The electrostatic filter unit of claim 12, wherein at least one of the voltage-carrying collecting electrode and the grounded collecting electrode has an electrical insulation coating.

19. The electrostatic filter unit of claim 12, wherein the voltage-carrying collecting electrode has an electrical insulation coating.

20. The electrostatic filter unit of claim 12, wherein the voltage-carrying collecting electrode and the grounded collecting electrode are made of air-permeable material.

21. The electrostatic filter unit of claim 12, wherein the voltage-carrying collecting electrode and the grounded collecting electrode are made of an air-impermeable material with at least one air discharge opening.

22. The electrostatic filter unit of claim 12, wherein at least one of the voltage-carrying collecting electrode and the grounded collecting electrode is made of expanded metal, wire mesh, wire gauze, fiber material, nonwoven material, perforated sheet, sintered plastic or foam.

23. The electrostatic filter unit of claim 12, wherein the voltage-carrying collecting electrode and the grounded collecting electrode are arranged relative to one another so that their structure lies rotated about an axis in a plane of the voltage-carrying collecting electrode or the grounded collecting electrode.

24. An air-purification device, comprising an electrostatic filter unit, said electrostatic filter unit comprising an ionization unit, and a separation unit arranged downstream of the ionization unit in a flow direction of air, said separation unit including a voltage-carrying collecting electrode and a grounded collecting electrode, with the voltage-carrying collecting electrode and the grounded collecting electrode being air-permeable.

25. The air-purification device of claim 24, wherein the air-purification device is embodied as an extractor hood, said filter unit being arranged on an air inlet opening of the extractor hood.

Description

[0034] The invention is described in more detail below again with reference to the appended figures, in which:

[0035] FIG. 1: shows a schematic perspective view of an embodiment of the inventive electrostatic filter unit;

[0036] FIG. 2: shows a schematic perspective view of a further embodiment of the inventive electrostatic filter unit;

[0037] FIG. 3: shows a schematic perspective view of a further embodiment of the inventive electrostatic filter unit;

[0038] FIG. 4: shows a schematic perspective detailed view of the embodiment according to FIG. 1;

[0039] FIG. 5: shows a schematic detailed view of the collecting electrodes of a further embodiment of the electrostatic filter unit;

[0040] FIG. 6: shows a schematic sectional view of an embodiment of the inventive electrostatic filter unit;

[0041] FIG. 7: shows a schematic sectional view of a further embodiment of the inventive electrostatic filter unit;

[0042] FIG. 8: shows a schematic sectional view of a further embodiment of the inventive electrostatic filter unit; and

[0043] FIG. 9: shows a schematic representation of the incident flow of two collecting electrodes.

[0044] FIG. 1 shows an embodiment of an inventive, electrostatic filter unit 1 in a perspective view. The filter unit 1 preferably has a housing, which is not shown in the Figures, however.

[0045] The filter unit 1 consists of an ionization unit 2 and a separation unit 3. The separation unit 3 is arranged downstream of the ionization unit 2 in the flow direction S. The ionization unit 2 has ionization electrodes 20 and counter electrodes 21. In the embodiment shown, the ionization unit 2 has three ionization electrodes 20 and four counter electrodes 21. The number of respective electrodes 20, 21 is however not restricted to the number shown. More or fewer electrodes 20, 21 can however also be provided.

[0046] The ionization electrode 20 is shown as a wire. The ionization electrode 20 can also represent a tooth profile, for instance. In this case, the ionization electrode 20 can also be referred to as discharge electrode. The counter electrode 21 represents a plate. The counter electrodes 21 are arranged parallel to one another. In particular, the counter electrodes 21 are aligned so that they lie in or parallel to the flow direction S, in which air flows toward the filter unit 1. An ionization electrode 20 is arranged in each case between two counter electrodes 21.

[0047] The separation unit 3 consists of collecting electrodes 30, 31. The collecting electrodes 30 represent collecting electrodes which are applied with positive of negative high voltage and are therefore also referred to below as voltage-carrying collecting electrodes. The collecting electrodes 31 represent collecting electrodes, which on the electrical mass lie at or on the protective earth (PE) and are therefore also referred to below as grounded collecting electrodes. The collecting electrodes 30, 31 are air-permeable in each case. The collecting electrodes 30, 31 represent planar electrodes, which are aligned parallel to one another and rest against one another in the embodiment shown. Moreover, the collecting electrodes 30, 31 lie at right angles to the alignment of the counter electrodes 21 of the ionization unit 2 and therefore at right angles to the flow direction S of the air.

[0048] Four collecting electrodes 30, 31 are provided in FIG. 1. These are present alternately in the separation unit 3. In FIG. 1, the first, in other words the collecting electrode 30 facing the ionization unit 2, is a voltage-carrying collecting electrode 30.

[0049] A further embodiment of the electrostatic filter unit 1 is shown in FIG. 2. This differs from the embodiment according to FIG. 1 only on account of the number and arrangement of the collecting electrodes 30, 31 in the separation unit. The further design of the electrostatic filter unit 1 corresponds to the design of the embodiment according to FIG. 1. Five collecting electrodes 30, 31 are provided in FIG. 2. The collecting electrodes 30, 31 are arranged alternately in the separation unit 3. In this embodiment, the first collecting electrode 31 is a grounded collecting electrode 31.

[0050] In FIG. 3, a further embodiment of the electrostatic filter unit 1 is shown. This differs from the embodiment according to FIG. 1 only on account of the number and arrangement of collecting electrodes 30, 31 in the separation unit. The further design of the electrostatic filter unit 1 corresponds to the design of the embodiment according to FIG. 1. Five collecting electrodes 30, 31 are provided in FIG. 3. In this embodiment, the first collecting electrode 31 is a voltage-carrying collecting electrode 30. Two grounded collecting electrodes 31, a further voltage-carrying electrode 30 and a last grounded collecting electrode 31 follow this first collecting electrode 31. With this embodiment, two grounded collecting electrodes 31 are arranged between two voltage-carrying collecting electrodes 30.

[0051] FIG. 4 shows a schematic representation in detail of the design of the separation unit 3. To this end, the individual collecting electrodes 30, 31 are shown in each case only partially in order to allow the respective other collecting electrodes 30, 31 to be viewed. In the embodiment shown, the collecting electrodes 30, 31 have a mesh structure. In the embodiment according to FIGS. 1 and 4, the air discharge openings formed by the mesh strips are aligned in the same direction. The collecting electrodes 30, 31 are arranged however so that the air through openings of the one layer are offset in relation to the next layer.

[0052] In the embodiment according to FIG. 5, the collecting electrodes 30, 31 are moreover rotated in the plane in relation to one another so that the air discharge openings are rotated at an angle of 45° in relation to one another.

[0053] The electrical fields, which are formed in the ionization unit 2 and the separation unit 3 are indicated schematically in FIGS. 6, 7 and 8.

[0054] FIG. 6 shows the collecting electrodes made from a mesh material, as shown in FIGS. 4 and 5. In FIG. 7, the collecting electrodes 30, 31 consists of perforated sheet and in FIG. 8 from expanded metal.

[0055] FIG. 9 shows a schematic representation of the incident flow of two collecting electrodes 31, 30. The air here flows onto the upper collecting electrode 31, so that the vector of the partial air flow, which specifies the air flow direction L, lies at an angle α in relation to the surface of the respective collecting electrode 31, 30. The partial air flow through the electrode arrangement can flow through at right angles to the surface of the collecting electrode 31. It is also possible, however, as shown in FIG. 9, for the air flow direction L to strike the collecting electrode 31 at an angle α which is smaller than 90°. The angle α can lie in a range of 0 to 90°. Moreover, the angle β under the one vector of the partial air flow, which strikes the collecting electrode 31 at an angle α of less than 90°, can be any angle between 0° and 360°. The angles α and β and thus the air flow direction L depend on the installation position of the filter unit in the air-purification device.

[0056] In particular, in the embodiment according to FIG. 8, an increase in the electrical field strength takes place on account of the sharp edges of the expanded metal. In these regions, the electrical fields are very inhomogeneous, which results in the homogenous electrical field strength multiplying. As a result, the charged particle is exposed to a higher field strength, in relative terms, and is separated more efficiently onto the respective collecting electrodes 30, 31.

[0057] The electrostatic force effect F onto the particle between the collecting electrodes is determined according to the equation:

F[N]=E[V/m]X q [C]

[0058] Here E represents the electrical field strength and q the electrical charge of the particle.

[0059] A combination of mechanical separation effect and electrostatic separation effect is used with the present invention. To this end, air-permeable collecting electrodes are used.

[0060] The invention is now described again in particular with respect to the used effects. The inventive electrostatic filter unit, which can also be referred to as filter module or filter cassette, can be used, for instance, in vents, air purifiers or in order to filter the air flow drawn into passenger compartment in the automotive sector. In order to enable an electrostatic separation of particles which are located in the air, these must firstly be charged (ionized) electrostatically. For the ionization of air particles, and also their separation, an electrical high voltage of several thousand volts is required. Here both the positive high voltage and also the negative high voltage can be used. A high voltage transmitter, which can also be referred to as high voltage generator or high voltage main supply, is used to generate this necessary electrical high voltage. This high voltage transmitter supplies the ionization unit, which can also be referred to as ionization region, and the separation region, which can also be referred to as separation unit, with electrical high voltage or electrical energy. The high voltage transmitter is preferably implemented into the filter module here. The electrostatic filter module is preferably arranged in the air intake region of the air-purification device, in order not to contaminate the components arranged therebehind with cooking vapors/aerosols/dirt, for instance. However, the filter unit can optionally also be arranged in the air blow-out region in the air-purification device or along the air flow guide between the inlet and outlet region of the air-purification device.

[0061] With the separation according to the inertia effect, on account of its mass inertia, the particle is not able to follow the flow line of the gas (air) about the individual filter fibers, expanded metal layers, porous media or suchlike and as a result collides herewith. The probability of a particle striking the individual filter fibers of the filter medium, which ultimately corresponds to the filter separation efficiency overall, on the basis of the inertia effect increases inter alia with an increasing particle speed, increasing particle diameter, increasing filter packing density and filter thicknesses in the flow direction and decreasing filter fiber diameters of the filter medium. If on account of its electrical charge the particle has an electrical potential in relation to the filter medium, the particle is therefore pulled from the filter medium or the smallest possible filter fiber by means of the electrostatic force of attraction. By additionally overlaying the electrostatic filter effect/filter mechanism in relation to the already available mechanical filter mechanisms (diffusion effect, blocking effect, mass inertia effect), a higher filter separation efficiency can be reached with the present invention, particularly for smaller particle diameters and with low air flow speeds.

[0062] The inventive filter unit represents a combination of mechanical filter according to the already mentioned filter mechanisms and the electrostatic filter mechanism. The filter unit consists of an ionization region and a separation region. In the ionization region the particles (fixed and solid) located in the air are charged electrically by means of a corona discharge. This is carried out for instance by means of a wire ionization electrode, which is arranged between two counter electrodes. This is necessary since in their original state the particles generally have no electrical charge or an electrical charge which is inadequate for an efficient electrostatic separation. The aim of the ionization unit is the electrical particle charge of each individual particle up to a maximum electrical saturation charge. The particle then flows through the separation region which consists of individual air-permeable collecting electrodes arranged one on top of the other and is separated / filtered hereon. These individual air-permeable media (voltage-carrying or grounded collecting electrodes) are alternately under electrical high voltage and as a result develop an electrical field with one another. The extent/amount of the electrical strength is decisive here as a function of the electrical potential (of the amount of the voltage in kV), the distance of the voltage-carrying and grounded collecting electrode in relation to one another and the geometric shape of the individual media of the collecting electrodes.

[0063] The inventively used collecting electrodes can essentially be any material/medium, which is air-permeable. Examples considered here are wire mesh, fiber material and nonwoven material, perforated sheet, expanded metals, sintered plastics and foam. If porous plastic media are used, these must be electrically conductive or electrically deriving in respect of their specific properties, so that an electrical field can develop between the individual layers. The collecting electrodes are preferably to rest one on top of the other (in order to efficiently utilize the mechanical and electrostatic filter mechanism and to save on installation space), but can also be arranged at any distance from one another in the flow direction.

[0064] With respect to the sequence, the first collecting electrode arranged in the flow direction can either represent a voltage-carrying collecting electrode or a grounded collecting electrode. The number of collecting electrodes, which can also be referred to as filter layers, is >2 and depends on the required filter efficiency. The electrical field lines always leave or enter a surface orthogonally. If a charged particle flows through the separation region, this is separated onto the voltage-carrying or grounded collecting electrodes by means of mechanical and electrostatic separation mechanisms as a function of its polarity. Positively charged particles are separated onto the grounded collecting electrode and negatively charged particles are separated onto the voltage-carrying collecting electrode. The amount of electrical voltage difference between the voltage-carrying and grounded collecting electrode typically lies at <=1 kilovolt (kV). The grounded collecting electrodes are connected to one another by way of contact points and typically lie on ground/earth. The voltage-carrying collecting electrodes lie one on top of the other preferably likewise on the same electrical potential and are connected electrically with one another by way of contact points and with the high voltage generator which supplies the high voltage.

[0065] The ionization unit and the separation unit are preferably arranged in a housing. However, a housing is not absolutely necessary. The ionization unit and the separation unit can be accommodated in a shared housing. Optionally, the ionization unit and the separation unit can be spatially separated from one another in housings separated spatially from one another or without a housing.

[0066] Furthermore, in order to achieve a high filter efficiency, a number of collecting electrodes or filter layers >=1 can optionally be used one behind the other as a homopolar poled collecting electrode. The number of grounded collecting electrodes between two voltage-carrying collecting electrodes can be >=1. The same also applies conversely, in other words the number of voltage-carrying collecting electrodes between two grounded collecting electrodes can be >=1.

[0067] The present invention has a series of advantages.

[0068] In particular, a drop in complexity is achieved with the invention. As a result of the simple design of the separation unit, viewed relatively, cost advantages result in relation to electrostatic filters with plate and tube separators, which generally required higher material and manufacturing expenditures.

[0069] With conventional electrostatic filters with plate or tube separation, the solid and liquid particles are separated onto the plates or tube walls. On account of the smooth surface property of these plates/tubes, the oil flows in the direction of the gravity pull. With these systems, an oil collection container or a collecting channel is to be provided since these separation plates or separation tubes are not able to store the oil on their surfaces. With the present invention, by contrast, no additional oil collection containers or collection channels are required. The particle filtered/separated between the individual air-permeable collecting electrodes remains suspended herebetween on account of capillarity. The inventive separation region is able to store this particle.

LIST OF REFERENCE CHARACTERS

[0070] 1 filter unit

[0071] 2 ionization unit

[0072] 20 ionization electrode

[0073] 21 counter electrode

[0074] 3 separation unit

[0075] 30 voltage-carrying collecting electrode

[0076] 31 grounded collecting electrode

[0077] 32 air discharge opening

[0078] L air flow direction