In-cabin air filter with polarization

Abstract

Gas filter (1) comprising a filter medium (20) for filtering a gas stream from an upstream-facing side (3) through the filter medium (20) to a downstream-facing side (4), wherein the filter medium (20) comprises a capacitor having a first electrode (21), a second electrode (22) and a dielectric medium (23), wherein the gas filter further comprises a first electrical contact T1 and a second electrical contact T2, which can be variably adapted in the case that the first electrical contact T1 is electrically connected to a branching point B by means of a first electrical resistor R1 and in the case that the second electrical contact T2 is electrically connected to said branching point B by means of a second electrical resistor R2. Furthermore, the first electrode (21) is preferably electrically connected to said branching point B and the second electrode (22) is preferably electrically connected to the second electrical contact T2.

Description

TECHNICAL FIELD

[0001] The present invention relates to a passenger compartment air filter, or more generally to a gas filter and a housing for the gas filter and a gas filtering system comprising at least the gas filter. BACKGROUND

[0002] Passenger compartment air filtering systems remove pollutants from ambient air and provide clean air to the interior of the passenger compartment of a vehicle. Essentially the same technology can be used in other fields, for example for building ventilation.

[0003] Generally, "filtering" refers to the removal of particulate matter from a gas stream by sieving the gas stream through a fibrous filter - a sieve. Cleaning air based on sieving alone requires a balance between the size of the smallest particles to be retained in the sieve and the pressure drop of the sieving element - the fibrous filter medium. The removal of particulate matter from a gas stream by filtration appears to be the result of a number of effects, including interception, diffusion, inertial impaction. It has been proposed to use electret filters to improve the removal of particles from a gas stream by means of electrostatic forces. However, the particle removal of these electret filters appears to weaken with increasing particle deposition on the fibres. To address this shortcoming, it has been proposed to exert an external electric field on the filter medium by positioning the filter medium as a dielectric between two air-permeable electrodes. Even sub-micron sized particles, which are not charged, can be effectively removed from a gas stream using this technology, and the technology is known as active field polarisation medium air cleaning, which is different from electrostatic precipitation and passive electrostatic filters (electret filters). In this context, active field polarisation medium air cleaners, and optionally but preferably a combination of active field polarisation medium air cleaning with gas cleaning based on gas ionisation, are highlighted.

[0004] These active field polarisation medium gas cleaners generally have a gas filter housing having a receiving portion for a gas filter and a high voltage (HV) source connected to the electrodes of the gas filter. Once the service life of the gas filter is reached, the gas filter is removed from the housing and replaced by another gas filter. Therefore, the housing has at least two electrical contacts for removably contacting corresponding electrical contacts of the gas filter, enabling the provision of an electrical connection of the gas filter to the HV source.

[0005] US 2007 / 0199450 Al proposes an air filter having two air-permeable ground electrodes and an air-permeable HV electrode between the two ground electrodes. Between each ground electrode and the HV electrode is a dielectric filter medium. The HV field polarises both the fibres and the particles of the dielectric between the electrodes.

[0006] US 2006 / 0137527 Al discloses a polarized medium air filter. The filter medium is located between a first electrode and a second electrode. The first electrode is connected to a high voltage source by means of a resistor. The second electrode is connected to another port of the high voltage source. In the figure, the resistor is located in the gap between the two electrodes, but is not connected to the two electrodes. The resistor represents a leakage resistance in case of spark occurrence. The resistivity of the electrodes is chosen to be high, whereby a voltage drop is generated on the electrodes in case of any leakage current, thereby eliminating the spark.

[0007] US 2008 / 0190772 Al discloses another polarized medium air filter having an array of filter elements. A first upstream filter element is a first conductive filter electrode grounded. Downstream of the first filter element is a second conductive filter element spaced apart from the first filter element. The second filter element is a wire ionization array coupled directly to a positive port of a high voltage power supply. The voltage is adjusted to ionize particles passing through the second filter element. Downstream of the second filter element is a third conductive filter element grounded and a fourth conductive filter element having a floating voltage. Between the third filter element and the fourth filter element is a filter material.

[0008] JP 6-91199 A proposes to determine whether a removable electrostatic precipitator is present or not, which has a first terminal connected to a first port of a high voltage source and a second terminal grounded. The second port of the high voltage device is connected to ground by means of a resistor. The voltage drop across the resistor is compared to a reference voltage. Depending on the voltage difference it is decided whether to switch on or off the high voltage supply.

[0009] While active field polarized medium air cleaners allow for efficient removal of even sub-micron particles, air ionization enables to disinfect the air and remove odors on a molecular scale. Air ionization requires a voltage of about 5 kV depending on the distance of the electrodes and - depending on the size of the air ionizer - a current of several 10 μΑ to 10 mA. Corona discharge air cleaners are an example for air ionizers. Gas ionizers of industrial scale can have correspondingly larger currents. SUMMARY

[0010] The underlying problem of the present invention is based on the observation that the thickness and the dielectric constant of a dielectric filter medium and the surface area of the electrodes have a direct influence on the voltage required to provide a predetermined electric field E in the dielectric filter medium, because (for simplicity, assume a plate capacitor), where Q = C · U is the charge, C is the capacitance, U is the voltage, A is the surface, and ε0, ε rare the electric field constant and the relative dielectric constant, respectively. In other words, once the HV source is installed, any change to the filter medium (material, active surface, thickness, etc.) can be required due to changes in the regulatory requirements for gas cleaning and / or due to user preferences for a specific cleaning level and / or to adapt the gas cleaning system to different geographical or climatic conditions, which is expensive since it also requires the replacement of the HV source or the initial installation of a HV source with an adjustable output voltage.

[0011] Therefore, the underlying problem of the present application is to reduce the costs associated with using different capacities C d and / or electrode surfaces A d of another gas filter replacing the gas filter of the first capacity C1 and electrode surface A1, while at the same time being able to verify the presence of a gas filter in the corresponding gas filter housing of the gas cleaning system.

[0012] The solution to the problem to be solved is the gas filter of claim 1 and the method of claim 12. The dependent claims relate to further improvements of the application.

[0013] The gas filter can have an upstream-facing side, a downstream-facing side, and a peripheral narrow-face side connecting the upstream-facing side and the downstream-facing side. Once installed in a gas filter housing, the upstream-facing side can generally face the gas flow, i.e. the gas flow can enter the gas filter via the upstream-facing side of the gas filter and correspondingly exit the gas filter via the downstream-facing side of the gas filter. Thus, the gas flow can at least substantially flow through a cross-section limited by the narrow-face side, but the narrow-face side does not necessarily define the area of the cross-section through which the gas flow can pass, as will become apparent in the following.

[0014] The gas filter comprises at least a filter medium for filtering, i.e. sieving, the gas flow from the upstream-facing side through the filter medium to the downstream-facing side. Preferably, the filter medium comprises a capacitor having at least a first electrode and a second electrode. A dielectric medium can be located between the first electrode and the second electrode. The first electrode and / or the second electrode and / or the dielectric medium is the filter medium. The at least one filter medium is permeable to a gas, e.g. air, but impermeable to particles above a given particle size. Thus, the filter medium can be regarded as a sieve.

[0015] In a preferred example, the first electrode is a first conductive filter layer, and / or the second electrode is preferably a second conductive filter layer, and / or the dielectric medium is an intermediate insulating filter layer, wherein the term "filter layer" implies that the respective layer is permeable to a gas, e.g. air, but impermeable to particles above a threshold diameter. The threshold diameter can be different for different filter layers.

[0016] The capacitor can be attached to the support. Preferably, the support is electrically non-conductive. For example, the portion of the surface facing away from the capacitor can be at least a portion of the narrow face side of the gas filter.

[0017] The gas filter can further comprise a first electrical contact (hereinafter referred to as “first contact”) located at a first location. The gas filter can further comprise a second electrical contact (hereinafter referred to as “second contact”) located at a second location. Preferably, the first contact and / or the second contact are attached to the support and / or integral with the support. Preferably, the first contact is configured to be removably connected to a high voltage output contact of a high voltage source. Preferably, the second contact is configured to be removably connected to a ground contact of the high voltage source. The first electrical contact and the second electrical contact can each be considered as an electrical connector or terminal. The first electrical contact and the second electrical contact can each be considered as an electrical connector and / or terminal. The contacts enable and are therefore configured to connect the filter element to corresponding first housing contacts and second housing contacts of the gas filter housing. The gas filter housing can comprise the HV source and / or the first housing contacts and the second housing contacts can be electrically connected to HV output terminals and ground terminals of the HV source. Just to avoid confusion, the location of the HV source is irrelevant, i.e. the HV source can be attached to the housing and therefore comprised in the filter housing or comprised in any other location and / or not comprised in the gas filter housing. In another example, the gas filter housing has third housing contacts and fourth housing contacts for connecting the gas filter housing with the HV source. For example, the third housing contacts can be connected with the first housing contacts and the fourth housing contacts can be connected with the second housing contacts.

[0018] In a particularly preferred example, the first electrical contact is electrically connected to the branching point by means of a first electrical resistor R1 and the second electrical contact is electrically connected to the same branching point by means of a second electrical resistor R2. Furthermore, the first electrode can also be electrically connected to the branching point. Preferably, the second electrode can be electrically connected to the second electrical contact. The corresponding first and second electrical resistors and the branching point are thereby preferably part of the gas filter. At least one of these components may, for example, be attached to the support or can be part of the support.

[0019] The gas filter allows for the adaptation of the dielectric filter medium to any requirement without altering the HV source, and thus the distance between the electrodes or electrode surfaces and the relative permittivity to any requirement. Therefore, an installed gas filter can be replaced with another gas filter having a different filter medium, avoiding the cost or installation errors of replacing or adjusting the HV source for the new filter medium. This is because, during the manufacture of the new gas filter, the electric field E' between the electrodes of the new (i.e., the replaced) gas filter (after an increase in time, i.e., t >> t0) can be adjusted, by adjusting the resistivity R1 of the first resistor and the resistivity R2 of the second resistor to the corresponding correction values ​​R1' and R2', because the voltage U across the capacitor... cap (t>>t0) by Provided. Typically, in this document, t represents time, and t0 is the point in time when the HV source has been turned on. By simply choosing reasonably sized R1'+R2', the current drawn from the HV source can be selected to be negligible. For example, voltage U HV =4kV and the accumulated resistivity R1'+R2'=80kΩ provides the current I gf The current I gf Extracted by a gas filter, only I gf =0.05mA.

[0020] Furthermore, the ability to adjust the voltage across the capacitor over a wide range allows the gas filter to be connected to the same HV source terminal, which also powers the gas ionizer. Such an optional gas ionizer can be placed in a gas conduit, preferably upstream of the first electrode, as part of the gas filter or as a separate component within the gas conduit. An example gas ionizer is described in German patent application DE 102021120127.6, the teachings of which are incorporated herein by reference as if fully disclosed.

[0021] Typical values ​​for operating gas ionizers are in the range of several kV (typically 3 to 6 kV). However, at these voltage levels, the dielectric of a typical active field-polarized dielectric gas cleaning filter can be damaged by sparks. However, the gas filter according to the claim allows for appropriate adjustment. That is, the voltage across the capacitor. It can be adjusted to any reasonable value, such as between 0.5kV and 1.5kV.

[0022] Furthermore, while the current consumed by the gas ionizer is typically in the range of 10 μΑ - 100 mA, the additional current for maintaining the electrode charge of the active field polarized medium gas cleaner is negligible as explained above: the gas filter can thus be connected in parallel to the gas ionizer of the gas cleaning system to the same HV source and thus provide the expected voltage for the first and second electrode: initially, upon energizing the HV source (at t0= 0), the voltage between the first and second electrical contact rises. The voltage U c (t) (assuming t0= 0) can accordingly be approximated as During the course of the time increase, the current I gf (t) provided by the HV source to the gas filter decreases exponentially until the current I gf (t) reaches its minimum value At the point in time where the current provided to the gas filter is at its maximum, the current provided to the gas ionizer is essentially zero because the voltage is still below the minimum voltage required for ionization to start. In other words, the maximum current Max(I HV (t)) drawn from the HV source is lower than the sum of the maximum current Max(I gs (t)) through the gas filter and the maximum current Max(I ai (c)) through the gas ionizer, i.e. Max(I HV (t)) < Max(I gf (t)) + Max(I ai (t)). Furthermore, by choosing a rather high R1+R2 (or R1'+R2', as the case can be), Max(I gf (t)) can actually be reduced to a value that is practically negligible. Thus, a single HV source can be used to power both the gas ionizer and the gas filter. Using the gas filter according to claim 1, it is even possible to retrofit an existing gas cleaning system with a gas ionizer because the voltage between the first and second electrode can be adjusted as described and because Max(I HV (t)) remains practically constant because Max(I gf (t)) « Max(I ai (t)).

[0023] In a preferred example, the gas filter comprises a third electrical contact T3 (third contact T3) at a third location, wherein the third electrical contact is electrically connected to the first contact by means of a third electrical resistance R3. This allows to electrically connect the gas ionizer to the HV source by means of the gas filter. In case the gas filter has been omitted by mistake, the gas ionizer is not connected to the HV source, the gas ionizer remains switched off. Thus, in case no gas filter is installed, the gas ionizer can be prevented from being operated, because - in case the gas treated by the gas cleaning system is an oxygen containing gas, like air - this would lead to an increased ozone (O3) concentration in the air leaving the gas filtration system. This increased ozone (O3) concentration can pose a health risk. As will be explained below, the insertion of the gas filter can also be detected by measuring the voltage and / or the current after switching on the HV source.

[0024] Alternatively or in addition, the gas filter can comprise a fourth electrical contact T4 (fourth contact T4) at a fourth location, wherein the fourth electrical contact is electrically connected to the second contact T2 by means of a fourth electrical resistance R4. This allows to electrically connect the HV terminal and the ground terminal of the optional gas ionizer to the HV source by means of the gas filter. The advantages are essentially the same as those of the third contact T3. Just to avoid misunderstandings, the term “fourth contact” does not imply that the third contact T3 is present. Thus, in an example, the gas filter comprises the first contact T1, the second contact T2 and the fourth contact T4, but not the third contact T3. In another preferred example, the gas filter comprises all four contacts T1 to T4, i.e. the first contact T1, the second contact T2, the third contact T3 and the fourth contact T4. The gas filter can also comprise the first contact T1, the second contact T2 and the third contact T3, but not the fourth contact.

[0025] In case the third electrical resistance R3 and / or the fourth electrical resistance R4 is present, the optional third electrical resistance R3 and / or the fourth electrical resistance R4 can be connected in parallel to the first electrical resistance R1 and the second electrical resistance R2, respectively. The third electrical resistance R3 and / or the fourth electrical resistance R4 can also be provided by a section of the first resistance / resistor R1 and the second resistance / resistor R2. In this case, the first electrical resistance R1 can be written as R1 = R3 + R3B, wherein R3B is the electrical resistance between the third contact R3 and the branching point B. Similarly, the fourth electrical resistance R4 can be provided by a section of the second resistance / resistor R2, and thus R2 = R4 + R4B, wherein R4B is the electrical resistance between the fourth resistance / resistor R4 and the branching point B. In yet another example, the fourth contact can be located between the second electrode and the second contact T2. All these options and alternatives can simplify the arrangement of the wiring and thus contribute to reducing the cost of the gas filter.

[0026] In a preferred example, the third resistance R3 between the first and third electrical contacts is smaller than or equal to the first and / or second resistors R1 and R2, i.e. R3 < Max({R1, R2}). It is particularly preferred that the third resistance R3 is significantly smaller than the first and / or second resistors R1 and R2, which can be written as R3 < a R • Max({R1, R2}), where a R ∈ {0.5, 0.4, 0.3, 0.25, 0.2, 0.1, 0.05, 0.01, 0.001}. By choosing a third resistance R3 that is small to negligible, the voltage drop can be minimized, and thus the power loss across R3 can be minimized.

[0027] At least one of the first, second and / or third electrical contacts can be attached to and / or located on the support. This facilitates a safe connection of the corresponding contact to a complementary contact of the gas filter housing when the gas filter is inserted into the gas filter housing.

[0028] In a preferred example, the first and / or second and / or third resistors R1, R2 and / or R3 are an electrically conductive polymer and / or an electrically conductive ceramic and / or an electrically conductive compound. Electrically conductive polymers and / or electrically conductive ceramics and / or electrically conductive compounds are not considered electronic devices in many regulations. The gas filter is thus not considered an electronic device, and the gas filter can be disposed as “normal waste” once the lifetime of the gas filter is reached, instead of as more expensive electronic waste.

[0029] The electrical contacts as well as the one or more branching points can also be made of said electrically conductive polymer and / or electrically conductive ceramic and / or electrically conductive compound, thereby reducing the number of materials required for manufacturing the gas filter - which leads to a reduced manufacturing cost - and simplifying the recycling of the used materials. In other words, the gas filter can comprise a module formed of an electrically conductive polymer, an electrically conductive ceramic or an electrically conductive compound, wherein the module comprises or consists of the first and second contacts, the branching point, the first and second resistors R1 and R2. Optionally, the third resistor R3 and the third contact can also be part of the module. In other words, preferably, all electrical components except the first and second electrodes of the capacitor are part of the module. Such a module can be manufactured as a single piece (and thus as a monolithic piece) of electrically conductive polymer and / or electrically conductive ceramic and / or electrically conductive compound. This allows for a reduced manufacturing cost as well as disposal cost of the gas filter.

[0030] For example, the electrically conductive polymer and / or electrically conductive ceramic and / or electrically conductive compound can have an outer layer with a specific resistivity pi and an inner layer or core with a core resistivity pc For the sake of linguistic simplicity only, no distinction is made between inner layer or core. This means that the core can also be a layer as long as it is surrounded by an outer layer. In a first example, the core can have a circular, polyhedral and / or elliptical cross section or any other cross section that is bounded by a single curve. This would correspond to the intuitive concept of the term "core" and can be considered as a preferred example. Alternatively, the core can have a cross section of annular shape, i.e. the core can be bounded by two closed curves, being a closed ring. In this case, the core can be located, for example, between two layers, the inner layer and the outer layer. The core can have a specific electrical resistivity p c where p c ≠ p l and / or p c < a ρ · p l and / or p c > a ρ · p l where a ρ e {0.9, 0.8, 0.75, 0.6, 0.5, 0.4, 0.3, 0.25, 0.2, 0.1}. For example, in the case of a conductive polymer or conductive ceramic that comprises conductive fibers embedded in a non-conductive polymer and / or conductive ceramic and / or conductive compound, the fibers in the core can be essentially randomly oriented and not even straight. In the vicinity of the surface of the conductive polymer and / or conductive ceramic and / or conductive compound, the conductive fibers can be aligned, for example, due to the process of extruding and / or injecting the polymer and / or slurry (ceramic precursor). This can lead to a non-uniform transition resistance along the surface of the polymer and / or ceramic.

[0031] It is preferred that the core extends through the outer layer at the first location and / or the second location and / or the third location. Thereby, the core can be contacted that has a more uniform transition resistance and thereby defined transition resistance. Thus, at the first location and / or the second location and / or the third location, the core is preferably not covered by the outer layer. This can be obtained by, for example, positioning the injection port at the respective location, whereby after removal of the injection port, the core becomes exposed. Alternatively, any subtractive process (such as, for example, milling, polishing, drilling, milling, etching, etc.) can be used to remove a portion of the outer layer and thereby expose the core.

[0032] Alternatively or in addition, the electrically conductive polymer and / or the electrically conductive ceramic can have at least one recess at the first position and / or the second position and / or the third position. The recess allows a corresponding protrusion of the gas filter housing to enter the recess. The electrically conductive blade that is optionally attached to the protrusion can thereby cut into the core and provide a reliable electrical connection of the first electrical contact, the second electrical contact and / or the third electrical contact, respectively, with the core. At the same time, the risk of injury when inserting the blade can be reduced, since the protrusion can extend onto the blade and thereby prevent a person's fingers or other parts from being injured by the blade or the voltage that can be (and jointly) applied to the blade. In other words, the gas filter housing can thus comprise at least one (preferably electrically conductive) blade that is positioned to penetrate into the electrically conductive polymer and / or the electrically conductive ceramic and / or the electrically conductive compound at the first position and / or the second position of the gas filter. The blade can be part of the first housing contact and / or the second housing contact and / or the third housing contact, or the blade is part of the first housing contact and / or the second housing contact and / or the third housing contact. In another example, the blade is located in front of the respective housing contact and thus the blade is configured to cut through the electrically conductive polymer and / or the electrically conductive ceramic and / or the electrically conductive compound, while the associated housing contact can follow the blade in a slot provided by the cutting edge and thus the blade can be configured to contact the optional core of the electrically conductive polymer and / or the electrically conductive ceramic and / or the electrically conductive compound.

[0033] Thus, the protrusion of the gas filter housing that has been mentioned can extend into a gas filter receiving portion provided by the gas filter housing. For example, the protrusion can extend from a housing wall towards an interior of the housing, i.e. towards a space that is configured to receive a gas filter. In an example, the protrusion can be positioned to extend into a recess. Alternatively or in addition, the protrusion can be or comprise a ring and / or a ring segment. The ring and / or the ring segment can be positioned to at least partially enclose an outer boundary of the first electrical contact and / or the second electrical contact and / or the third electrical contact of the gas filter.

[0034] The blade can be located inside the ring / ring segment. Alternatively or in addition, the protrusion can extend further into the gas filter receiving portion than the blade. Thus, the protrusion can protect the blade from accidental touching or contacting. Thereby, the corresponding housing contact is protected by the protrusion, while at the same time the protrusion protects a worker from the blade or a voltage that can be applied to said blade during replacement of the gas filter. In an example, at least a distal portion of the protrusion is electrically non-conductive, i.e. electrically insulating.

[0035] Preferably, the protrusion supports at least a portion of the blade. Thereby, the blade can be made particularly thin. Thereby, the force that is required for installing the gas filter, or more precisely the force that is required for driving the blade into the electrically conductive polymer and / or the electrically conductive ceramic and / or the electrically conductive compound, is low.

[0036] The gas filter can further comprise a gasket for sealing a gap between the gas filter and a wall of a gas filter receiving portion defining the gas filter housing. In a preferred example, at least a portion of the electrically conductive polymer and / or electrically conductive ceramic can be positioned between the support and the gasket. Thus, the gasket protects the polymer from mechanical stress and at the same time insulates a portion of the electrically conductive polymer and / or electrically conductive ceramic. The gasket can also attach the polymer to the support by adhesion.

[0037] In another example, at least a portion of the gasket can be made of electrically conductive polymer. The number of different components of the gas filter can be further reduced, which helps to reduce manufacturing costs.

[0038] The electrically conductive polymer and / or electrically conductive ceramic and / or a section thereof can be attached to and / or extend over a section of the first electrode and / or second electrode, wherein the insulating sheath is located between at least the section of the electrically conductive polymer and / or electrically conductive ceramic.

[0039] By the method of claim 12, it is possible to automatically detect whether a gas filter as described herein is present in a gas filtration system without the need for additional contact. Depending on the result of the determination, an optionally present gas ionizer of the corresponding gas cleaning system can be controlled. In case of correct installation, the first and second electrical contacts of the gas filter electrically contact the corresponding first and second housing contacts T11, T12. Preferably, these housing contacts are connected to an HV source.

[0040] The method can comprise providing at least a first voltage U d and determining a current through the housing contacts T11, T12. This current allows to determine whether a gas filter is present by comparing the current I h (U d ) through the housing contacts T11, T12 with a threshold current I t . t In case I h > I d (U h ), no current I d (U t ) can flow through a second resistor R2. Thus, in case I h > I d (U o , preferably, the gas ionizer is switched off and / or remains switched off. This can be provided by simply switching off the HV source and / or by controlling the HV source to provide a voltage U oThis can be accomplished using voltage. Alternatively, error messages can be symbolized, for example, displayed on a screen or simply by lighting a control light.

[0041] The comparison step provides the current I(U) through the housing contacts. d () greater than the threshold current I c In this case, it means I t <I(U) d If the condition is true, the gas ionizer can be controlled to operate because the gas filter can be expected to be installed. In other words, the voltage supplied to the gas ionizer may be higher than the gas ionizer's start voltage, because in this case, it is unlikely that the gas filter is not installed.

[0042] The current I used in the comparison step above is directly measured. h (U d As a substitute or supplement to ), any other value χ can be determined and considered, which can be represented or used as the current I. h (U) or at least I h (U d The value χ is a measure of current I. Such a value can be measured and / or calculated. Typically, the value of χ is conditional upon it being a current I. h Mapping (e.g., function), (χ=χ(I) h ), and / or it exists from the value χ to the current I h Mapping (I) h =I h (χ)). In both cases, it is preferable that the corresponding mapping is unique or even bijective, but this is not necessary. In the context of this patent, determining any of these values ​​χ should be regarded as determining the current I. h Because these values ​​χ provide information about the current I h Information such as χ. Examples of such values ​​include the power consumption of the HV source (obtainable through input power measurement), the current consumed by the HV source (obtainable through input current measurement), and controlling the voltage across terminals T11 and T12 of the housing to U. d The duty cycle of the pulse width modulation signal, the magnetic field, and the resistance between the housing terminals T11 and T12 are all considered. Clearly, for each such value χ, a corresponding threshold χ must be defined. c The threshold χ c Provide threshold current I c (of) the corresponding mapping or by the threshold current I c The corresponding mapping is provided, and the χ² must be used in the comparison step. c Depending on the mapping, the indicated relationship may need to be reversed, but this can be determined through simple testing.

[0043] Preferably, the first voltage U d complies with | U o - ΔU | ≤ U d ≤ | U o + ΔU |, wherein ΔU ∈ {2kV, 1.5kV, 1kV, 0.75kV, 0.5kV} and U o is still the starting voltage of the gas ionizer. The voltage U d is chosen in such a way that the risk of false control of the operation of the gas ionizer is reduced, since the difference between the currents is maximum in the case where the gas filter is not installed and in the case where the gas filter is installed. This measure is particularly effective when the gas ionizer is connected in parallel to the first and second contacts of the gas filter.

[0044] The terms "gas stream" and "gas flow" are used interchangeably herein. Furthermore, in the present disclosure, the term "gas" includes the term "air" as a preferred example.

[0045] An insulator has an (almost) infinite electrical resistivity, in other words, there is a band gap between the conduction band and the Fermi level. In contrast, a conductor cannot show this band gap, since the Fermi level is in the conduction band. A so-called semiconductor has a band gap ΔE of the order of magnitude of T, wherein K β T, wherein K β is the Boltzmann constant and T is the temperature (in Kelvin), a semiconductor essentially behaves like a metallic conductor at temperature T, although a semiconductor behaves like an insulator at lower temperatures (ΔE » K β T). Thus, the terms "insulator", "insulation", "conductor", "conductivity" and the like refer to electrical conductivity, not thermal properties.

[0046] In the present context, the terms "conductive polymer" and / or "conductive ceramic" encompass not only polymers and / or ceramics which are conductors or semiconductors, but also composite materials based on a matrix of a non-conductive polymer and / or non-conductive ceramic material, into which a conductive material, such as metal and / or carbon fibers and / or graphite and the like, has been integrated. The conductive compound can thus have a non-conductive matrix into which conductive fibers, which can also be filaments, particles, beads and the like, have been embedded, and the conductivity of the compound can thus be attributed to the conductive fibers, which are, for example, randomly distributed in the matrix.

[0047] The terms "first electrical contact", "second electrical contact", "third electrical contact", "n-th electrical contact" are considered in the present context as releasably contactable contacts, which can also be referred to as electrical terminals or electrical connectors. These electrical contacts can be formed, for example, by male pin-type connectors and / or corresponding female socket-type connectors and / or simple contact pads.

[0048] “n e {n1, n2,... n k}” means that n can take any value of the set {n1, n2,... n k}, e.g. n = n1or more generally n = n j and 1 ≤ j ≤ k. BRIEF DESCRIPTION OF DRAWINGS

[0049] The application will be described in the following non-limiting examples with reference to the accompanying drawings, in which:

[0050] Figure 1 A perspective view of a first example of a gas filter is shown.

[0051] Figure 2 A perspective view of a second example of a gas filter is shown.

[0052] Figure 3 A perspective view of a third example of a gas filter is shown.

[0053] Figure 4 A gas filter housing is shown.

[0054] Figure 5 A gas filter housing is shown, wherein a gas filter is partially inserted.

[0055] Figure 6 A schematic view of a filter medium is shown.

[0056] Figure 7 A current and voltage diagram is shown.

[0057] Figure 8 A detail of a gas filter housing is shown.

[0058] Figure 1 An example gas filter 1 is shown. Assuming a gas flow direction as indicated by arrow 2, the gas filter has an upstream-facing side 3 and a downstream-facing side 4. Of course, the gas flow direction can also be reversed. A narrow face side 5 connects the upstream-facing side 3 and the downstream-facing side 4.

[0059] The gas filter 1 has a filter medium 20. The filter medium 20 can comprise one or more stacked sheets, but this is only a preferred example. Other types and shapes of filter media can also be used. Preferably, the filter medium 20 can comprise at least three layers: two electrode layers 21, 22 and a dielectric layer 23 located between the electrode layers 21 and 22. Thus, each of the electrode layers 21 can be regarded as an electrode 21, 22 of a capacitor, wherein the dielectric layer 23 is the dielectric 23 of the capacitor between the two electrodes 21, 22 (see Figure 6 ). Thus, the filter medium 20 can comprise and / or form a capacitor.

[0060] The gas filter 1 can further comprise at least one support 10. In this example, the support 10 comprises a front wall 11 and a rear wall 12, preferably sealingly attached to opposite portions of the narrow sides of the filter medium 20. The gas filter 1 can also comprise side walls (not shown), but as shown, the side walls can be omitted.

[0061] The gas filter 1 can have an electrical module 30. As shown, the electrical module 30 can comprise, or preferably consist of, an electrically conductive polymer wire 30, which can also be referred to as a tube 30, a wire 30 or an electrical conduit 30. Alternatively or additionally, the module can comprise, or preferably consist of, an electrically conductive ceramic wire and / or an electrically conductive compound. For the sake of linguistic simplicity only, in this document, the term “electrically conductive polymer” is used as a general term for electrically conductive polymers and / or electrically conductive ceramics and / or electrically conductive compounds.

[0062] The electrically conductive wire can have a first electrical contact T1. In this example, preferably, the first electrical contact T1 can have a ring shape and thus form a first recess which is at least partially surrounded by the polymer wire. The ring shape is not necessarily closed and thus can form a ring segment or a ring.

[0063] The first electrical contact can be connected with the branching point B by the electrically conductive polymer 30 and thus the portion of the electrically conductive polymer 30 which forms an electrical connection between the first contact T1 and the branching point B forms a first electrical resistor R1.

[0064] The electrically conductive polymer wire can have a second electrical contact T2 which can also form a ring or a ring segment. Preferably, the second contact T2 is connected with the branching point by a portion R2 of the electrically conductive polymer wire 30. Thus, the portion of the electrically conductive polymer which connects the second contact T2 and the branching point can define a second electrical resistor R2.

[0065] Furthermore, preferably, the branching point B and the second terminal can be connected to one of the first electrode 21 and the second electrode 22, e.g. by said electrically conductive polymer 30.

[0066] Thus, for example Figure 5 As shown, the insertion of the gas filter into the gas filter housing enables to provide an electrical connection of the first electrical contact (T1) and the second electrical contact (T2) with the two poles of an HV source which can provide a voltage U HV The voltage U cap between the capacitor terminals is then approximately (for large t, i.e. t » t0). By reducing or lengthening the length of the connection between the first contact T1 and the branching point B, the voltage Ucap To match the requirements provided by the capacitor.

[0067] Figure 2 and Figure 3 Each shows a slightly different gas filter 1. Figure 1 The description of Figure 2 and Figure 3 can also be read on Figure 2 and Figure 4 The gas filter of each has a gasket 40. The gasket 40 can extend over the edge formed by the upstream facing side 3 and the narrow side 5, and the gasket 40 can cover a portion of the wire 30, thereby functioning as an adhesive for attaching the conductive polymer 30. In Figure 2 the gasket 40 covers the portion of the conductive polymer 30 that contacts the second electrode. In Figure 3 the gasket covers and thus secures the portion of the electrical conduit 30 that extends along the downstream edge of the support 10, i.e. the portion of the wire 30 that extends along the downstream edge of the support 10.

[0068] Figure 4 An example gas filter housing 100 is shown. The gas filter housing 100 can be attached to or integrated in a gas conduit, and in this sense the side walls 111 to 114 of the gas filter housing 100 can be considered as part of the gas conduit. The front side wall 111 can have an opening that enables insertion of the rear portion of the gas filter 1 of Figure 1 or Figure 2 into the gas filter housing 100, as sketched in Figure 5 . Preferably, the gas filter housing can comprise at least a first housing contact T11 and a second housing contact T12, which are configured to contact the first and second contacts T1, T2 of the gas filter 1. In a preferred example, at least one of the housing contacts T11, T12 comprises a blade that is configured to penetrate at least a portion of the polymer wire 30, thereby contacting an inner portion of the polymer wire, which can be referred to as a core portion, therefrom.

[0069] Figure 5 An example gas filter 1 of Figure 3 is shown partially inserted into the gas filter housing 100. The side wall 114 has been omitted, and the gasket 40 has been shown as transparent. As can be seen, the first contact T1 is configured to contact the first housing contact T11, and the second contact T2 is configured to contact the second housing contact T12.

[0070] Figure 6 An example gas filter housing 100 is shown that can be used for Figures 1 to 3 and Figure 4Details of the filter medium 20 in any of the examples are provided. The filter medium has a first electrode 21, a second electrode, and a dielectric medium 23 located between the first electrode 21 and the second electrode 22. T1 and T2 represent the first electrical contact and the second electrical contact, B represents the branch point, and resistors R1 and R2 represent, for example, the resistance through the corresponding connection of the polymer wire 30 as described above.

[0071] Figure 7 Three different current I(U) curves are shown, where I(U) is indicated in mA and voltage U is indicated in kV. The coarsely hatched curve depicts... Figure 6 The example shows the current flowing through electrical contacts T1 and T2. The current value was measured after the current stabilized, meaning the depicted current is essentially the current through resistor R2, defined by Ohm's law. Below 3.5kV, the thick dashed curve is identical to a continuously drawn curve and therefore cannot be distinguished optically.

[0072] The thin dashed curve depicts the current through a gas ionizer connected to the same high-voltage source in parallel with contacts T1 and T2. As can be seen, in this example, gas ionization begins at a corona initiation voltage of approximately 3.5 kV (i.e., 3.5 kV is the example corona initiation voltage U). o The corona initiation voltage U o (This can be varied, for example, by increasing or decreasing the distance between the gas ionizer electrodes), and the current increases with increasing slope. The corona initiation voltage depends on the gas ionizer and the gas, but can be easily determined by measuring the current I(U) as a function of the supply voltage.

[0073] The solid line represents the total current flowing when the gas ionizer is connected in parallel to the HV source, which supplies power to T1 and T2, the electrical conduit 30, and therefore the filter medium 20 (see [link]). Figure 6 As can be seen, based on the measurement results of the output current of the HV source, it can be determined whether gas filter 1 has been inserted into the gas filter housing: at a given voltage U d The current I(U) d (Below the threshold I) t In the case of I(U) d ) < I t In such cases, it is preferable to shut down the HV source. Therefore, the gas ionizer will not operate, and the ozone concentration in the air supplied by the corresponding gas cleaning system will be low. Health risks due to unexpectedly high ozone concentrations can be avoided.

[0074] Preferably, given voltage Ud Below the corona initiation voltage U o Or given voltage U d The corona initiation voltage U for ionizing gas using an installed gas ionizer. o Within a voltage range of ±2kV (preferably ±1kV, ±0.75kV, or ±0.5kV), the difference between the currents of the thick and thin dashed curves reaches its maximum. This reduces the risk of erroneously shutting down the HV source and erroneously operating the air ionizer.

[0075] Figure 8 Details of another gas filter housing 100 are shown. The gas filter housing 100 has a housing wall 113 with a block 120 defining the position of a gas filter 1. In this example, the gas filter 1 can be inserted from the top, and the gas filter 1 can rest on the block 120. The gas filter housing 100 may have at least one (first) protrusion 131, such as... Figure 1 , Figure 2 , Figure 3 and Figure 5 As shown, the protrusion can be positioned to engage with corresponding recesses of electrical contacts T1, T2, or T3 of conductive polymers and / or conductive ceramics and / or conductive compounds. The protrusion 131 can support a blade T11 with a cutting edge. Preferably, the cutting edge points in a direction different from the insertion direction of the gas filter, for example, towards a housing opening in the front wall 111, such as... Figure 4 As shown. When the gas filter is inserted into the housing 100, the cutting edge of the blade-shaped first housing contact T11 can penetrate into the material of the conduit 30 of the gas filter 1 (i.e., into the conductive polymer, and / or conductive ceramic and / or conductive compound), thereby making the core of the conduit 30 electrically contact the HV terminal of the HV source 141.

[0076] like Figure 8As can be seen, a further (third) protrusion (133) can be present, which is configured to be engaged into a further (third) recess of a further (third) electrical contact of the gas filter 1. Similar to the first protrusion, a blade T13 can be attached to the third protrusion. The blade can form a third housing contact T13, and the blade can be connected with an HV terminal of the gas ionizer 143. As can be seen, there is an optional gap between the first housing terminal T11 and the third housing terminal T13. Thus, the gas ionizer is only connected to the HV source 141 in case the pipe 30 electrically connects the first housing terminal 141 and the third housing terminal 143. In other words, in case the gas filter 1 is not inserted into the gas filter housing, the electrical connection between the HV source and the gas ionizer is interrupted. Thereby, it is safely avoided that harmful substances generated by the upstream gas ionizer leave the gas filter housing without passing the gas filter.

[0077] As visually apparent, the gap between the first housing contact T11 and the third housing contact T13 is too small, whereby the electrical resistance between the first housing electrode and the third housing electrode is also small. However, in practice, the large distance should be chosen reasonably to avoid ambient air in the ionization gap in case the gas filter is not inserted. Additionally or alternatively, a fourth insulating protrusion can be located between the housing contact T12 and the housing contact T13, thereby allowing the housing contact T12 and the housing contact T13 to be placed closer together, which results in a smaller electrical resistance R3 between the first contact and the third contact in case the gas filter is installed.

[0078] As apparent from the description of Figure 8 By omitting the terms "second housing electrode", "second blade" and "second protrusion", it is implied that the gas filter housing can have a second housing contact T12, which is formed by a second blade T12 and optionally attached to a second protrusion, as apparent from the description of

[0079] List of reference signs

[0080] 1 gas filter

[0081] 2 flow direction

[0082] 3 upstream-facing side

[0083] 4 outer peripheral side

[0084] 5 downstream-facing side

[0085] 10 support

[0086] 11 front wall

[0087] 12 back wall

[0088] 20 filter medium / capacitor

[0089] 21 first conductive filter layer

[0090] 22 second conductive filter layer

[0091] 23 dielectric medium

[0092] 30 electric module, which electric module optionally comprises a conductive polymer string and / or a conductive ceramic string and / or a conductive compound

[0093] 31 first recess

[0094] 32 second recess

[0095] 33 third recess

[0096] 35 outer layer

[0097] 36 core

[0098] 40 gasket (optional)

[0099] 100 gas filter housing

[0100] 111 front side wall / front wall

[0101] 112 side wall

[0102] 113 back side wall / back wall

[0103] 114 side wall

[0104] 120 block (optional)

[0105] 131 protrusion (optional)

[0106] 132 protrusion (optional)

[0107] 141 to HV source (optional)

[0108] 143 to air ionizer (optional)

[0109] R1 resistance / resistor between first electrical contact T1 and branching point

[0110] R2 resistance / resistor between branching point B and second electrical contact T2

[0111] T1 first contact (which first contact is configured to be connected to a high voltage contact of a high voltage source, for example to a high voltage contact of a high voltage source by means of an optional first housing contact T11)

[0112] T2 second contact (which second contact is configured to be connected to a ground contact of the high-voltage source, for example to a ground contact of the high-voltage source by means of an optional second housing contact T12)

[0113] T11 first housing contact, which first housing contact is configured to be connected to and / or is connected to a high-voltage contact of the high-voltage source

[0114] T12 second housing contact, which second housing contact is configured to be connected to and / or is connected to a ground contact of the high-voltage source

[0115] T13 third housing contact, which third housing contact is configured to be connected to and / or is connected to a contact of an air ionizer of the gas cleaning system

Claims

1. A gas filter (1) having an upstream-facing side (3), a downstream-facing side (4) and a peripheral narrow side (5) connecting the upstream-facing side (3) and the downstream-facing side (4), the gas filter (1) comprising at least: - a filter medium (20) for filtering a gas stream from the upstream-facing side through the filter medium (20) to the downstream-facing side (4), wherein the filter medium (20) comprises and / or forms a capacitor, and wherein the capacitor has at least a first electrode (21), a second electrode (22) and a dielectric medium (23), wherein the first electrode (21), the second electrode (22) and / or the dielectric medium (23) is a filter layer, - at least one support (10), wherein the capacitor is attached to the support (10), - a first electrical contact (T1) at a first location, - a second electrical contact (T2) at a second location, - a branching point (B), a first electrical resistance (R1) and a second electrical resistance (R2), wherein each of the first electrical contact (T1) and the second electrical contact (T2) is attached to and / or integral with the support, each of the branching point (B), the first electrical resistance (R1) and the second electrical resistance (R2) is attached to and / or part of the support, the first electrical contact (T1) is electrically connected to the branching point (B) by means of the first electrical resistance (R1), the second electrical contact (T2) is electrically connected to the branching point (B) by means of the second electrical resistance (R2), the first electrode (21) is electrically connected to the branching point (B), and the second electrode (22) is electrically connected to the second electrical contact (T2).

2. The gas filter (1) according to claim 1, characterized in that The gas filter (1) comprises a third electrical contact (T3) at a third location, wherein the third electrical contact (T3) is electrically connected to the first electrical contact (T1) by means of a third electrical resistance (R3).

3. The gas filter (1) according to claim 2, characterized in that the third electrical resistance (R3) between the first electrical contact (T1 ) and the third electrical contact (T3) is smaller than or equal to the first electrical resistance (R1 ) and / or the second electrical resistance (R2), i.e. .

4. The gas filter (1) according to claim 2 or 3, characterized in that At least one of the first electrical contact to the third electrical contact is attached to and / or located on the support.

5. The gas filter (1) according to claim 2 or 3, characterized in that The first electrical resistance (R1) and / or the second electrical resistance (R2) is an electrically conductive polymer and / or an electrically conductive ceramic, wherein at least a portion of the electrically conductive polymer and / or the electrically conductive ceramic is attached to the support (10).

6. The gas filter (1) according to claim 2 or 3, characterized in that The first electrical resistance (R1) and / or the second electrical resistance (R2) is an electrically conductive compound, wherein at least a portion of the electrically conductive compound is attached to the support (10), wherein the electrically conductive compound has a non-conductive matrix in which electrically conductive fibers are embedded.

7. The gas filter (1) according to claim 5, characterized in that The electrically conductive polymer and / or the electrically conductive ceramic has an outer layer (35) with a specific resistivity ρ l and a core (36) with a specific resistivity ρ c wherein ρ l α ρ ρ c or ρ l α ρ ρ c and α ρ ∈ {0.9, 0.8, 0.75, 0.6, 0.5, 0.4, 0.3, 0.25, 0.2, 0.1}.​​​​ 8. The gas filter (1) according to claim 6, characterized in that The electrically conductive compound has an outer layer (35) with a certain resistivity ρ l and a core (36) with a certain resistivity ρ c wherein ρ l < α ρ · ρ c or ρ l > α ρ · ρ c and α ρ ∈ {0.9, 0.8, 0.75, 0.6, 0.5, 0.4, 0.3, 0.25, 0.2,0.1}.

9. The gas filter (1) according to claim 7 or 8, characterized in that The core (36) extends through the outer layer (35) at the first location and / or the second location.

10. The gas filter (1) according to claim 5, characterized in that The electrically conductive polymer (30) and / or the electrically conductive ceramic has at least one recess (31, 32, 33) at the first location and / or the second location.

11. The gas filter (1) according to claim 6, characterized in that The electrically conductive compound has at least one recess (31, 32, 33) at the first location and / or the second location.

12. The gas filter (1) according to claim 5, characterized in that The gas filter (1) comprises a gasket (40) for sealing a gap between the gas filter (1) and a wall defining a gas filter receiving portion.

13. The gas filter (1) according to claim 12, characterized in that The electrically conductive polymer (30) and / or the electrically conductive ceramic forms at least a section of the gasket (40).

14. The gas filter (1) according to claim 6, characterized in that The gas filter (1) comprises a gasket (40) for sealing a gap between the gas filter (1) and a wall defining a gas filter receiving portion, the electrically conductive compound forming at least a section of the gasket (40).

15. The gas filter (1) according to claim 5, characterized in that The electrically conductive polymer (30) and / or the electrically conductive ceramic is attached to or extends over a section of the first electrode (21) and / or a section of the second electrode (22), wherein an electrically insulating sheath is located between the electrically conductive polymer (30) and / or the electrically conductive ceramic and at least a portion of the section.

16. The gas filter (1) according to claim 6, characterized in that The electrically conductive compound is attached to or extends over a section of the first electrode (21) and / or a section of the second electrode (22).

17. A method for determining the presence of a gas filter (1) according to any one of the preceding claims in a gas filter housing of a gas filtration system having a high-voltage source and an air ionizer, wherein The high voltage source is connected to a first housing contact (T11) and a second housing contact (T12), the first housing contact (T11) and the second housing contact (T12) being configured to contact the first electrical contact (T1) and the second electrical contact (T2), the method comprising, in case the gas filter is properly installed: providing at least a first voltage to the first housing contact (T11), to the second housing contact (T12) U d and measuring a current through the first housing contact (T11), through the second housing contact (T12) I(U d ) ; the current through the housing contact I(U d ) compared to a threshold current I t and in the case where I t > I(U d ) the air ionizer is turned off and / or remains off. The current through the housing contact I(U d ) compared to a threshold current I t and in case the comparison is true, the air ionizer is switched on and / or kept on. I t < I(U d ) the air ionizer is switched on and / or kept on.

18. The method of claim 17, wherein, the first voltage U d complying with U o - delta U | <= 0.5 kV U d <= | delta | U o + delta U |, wherein delta U e {1.5 kV, 1 kV, 0.75 KV, 0.5 KV}, and U o is a corona inception voltage of the air ionizer.

19. A gas filtering system comprising at least a high voltage source and a gas filter housing (100) having a gas filter receiving portion, the gas filter housing (100) having a first housing contact (T11) and a second housing contact (T12), the first housing contact (T11) and the second housing contact (T12) each being electrically connected to different terminals of the high voltage source, characterized in that The gas filtering system further comprises at least: The gas filter (1) according to any one of claims 1 to 16, wherein the first electrical contact (T1) and the second electrical contact (T2) are configured to electrically contact the first housing contact (T11) and the second housing contact (T12), respectively; and / or a controller configured to perform the method according to claim 17 or 18; and / or a controller configured to perform the method according to claim 17 or 18; and / or The gas filtration system further includes at least one blade having a cutting edge extending into the gas filter receiving portion, and wherein the at least one blade is the first housing contact (T11) and / or the second housing contact (T12).

20. The gas filtration system of claim 19, wherein, The gas filtration system further includes at least one blade having a cutting edge, characterized in that the at least one blade is positioned to penetrate into a conductive polymer and / or conductive ceramic at the first and / or second positions of the gas filter (1) according to any one of claims 1 to 16.

21. The gas filtration system of claim 19, wherein, The gas filtration system further includes at least one blade having a cutting edge, characterized in that the at least one blade is positioned to penetrate into a conductive compound at the first and / or second location of the gas filter (1) according to any one of claims 1 to 16.

22. The gas filtration system of any one of claims 19 to 21, wherein, The gas filter housing (100) further includes at least one protrusion extending into the gas filter receiving portion, and the at least one protrusion being positioned to extend into the recess of the gas filter (1) according to any one of claims 10 to 11, or the at least one protrusion being positioned to at least partially surround the outer boundary of the first electrical contact and / or the second electrical contact and / or the third electrical contact of the gas filter according to any one of claims 2 to 16.

23. The gas filtration system of claim 22, wherein, The protrusion extends further into the gas filter receiving section than the blade, and / or wherein the protrusion is non-conductive and / or the blade is attached to the protrusion.

24. The gas filtration system of claim 22, wherein, The protrusion forms a ring and / or annular segment, and wherein the cutting edge of the blade is at least partially surrounded by the ring and / or the annular segment.

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