Method for controlling an electrostatic precipitator for the interior of a motor vehicle

Abstract

Method for controlling an electric air filter (2) for a vehicle interior of a motor vehicle, wherein a filter layer (6) is alternately charged with a first voltage (U1) and with a second voltage (U2) having a polarity different from the first voltage (U1), wherein the filter layer (6) can be selectively connected to either the first voltage source (10) or the second voltage source (11) by switching from a first voltage source (10) providing the first voltage (U1) to a second voltage source (11) providing the second voltage (U2) and vice versa, or wherein a voltage source for providing the first voltage (U1) and the second voltage (U2) is reversed in such a way that the filter layer (6) is charged at a time when the first filter layer is not charged, and vice versa.

Description

[0001] The invention relates to a method for controlling an electric air filter for a vehicle interior of a motor vehicle.

[0002] Modern motor vehicles are equipped with a ventilation system that allows, for example, fresh air to be drawn into the vehicle interior from outside. The ventilation system can be designed as an air conditioning system, i.e., it can also include an air conditioning unit. In order to supply the cleanest possible air, a filter device is provided that separates particles contained in the air as far as possible. Combination filters are known that separate pollen, for example, and have an activated carbon layer and an anti-allergen layer. Electric air filters are also known, which have a high-voltage electrode, past which the air to be cleaned flows. The electrode, which is, for example, strongly negatively charged, emits electrons that migrate to a second electrode, which is, for example, grounded. On their path, the electrons encounter gas atoms, which ionize them, i.e.When the electrons accelerate towards the second electrode hit, further electrons are split off from the gas molecules, or the electrons emitted by the first electrode attach themselves to the gas atoms. In the first case, new free electrons and positive gas ions are created, while in the second case, negatively charged gas ions are created. Positively charged gas ions attach themselves to the negatively charged first electrode, which can also be referred to as the spray grid, and are neutralized there, while the negatively charged particles, i.e. the free electrons and the negatively charged gas ions, migrate to the second electrode, attach themselves there, and are neutralized.

[0003] The first electrode is charged with a high voltage of several kV. This creates a correspondingly strong electric field towards the second electrode, within which the electrons and gas ions migrate. Since the air to be cleaned flows past the electrodes and this migration is more or less perpendicular to the direction of air flow, it can happen that charged particles also migrate out of the electrode area and settle elsewhere in the downstream area of ​​the ventilation device. This sometimes leads to static charging in the area of ​​the electrodes and in downstream areas. If, for example, the first electrode is strongly negatively charged, the surrounding area primarily becomes negatively charged. This static charging is undesirable.

[0004] The invention is therefore based on the problem of providing a correspondingly improved method for controlling an electric air filter.

[0005] To solve the problem, the invention provides a method for controlling an electrostatic precipitator for a vehicle interior of a motor vehicle, which is characterized in that a filter layer is alternately charged with a first voltage and with a second voltage having a different polarity than the first voltage, wherein the filter layer can be selectively connected to the first voltage source or the second voltage source either by switching from a first voltage source providing the first voltage to a second voltage source providing the second voltage and vice versa, or wherein the polarity of a voltage source for providing the first voltage and the second voltage is reversed such that the filter layer is charged at a time when the first filter layer is not charged, and vice versa.

[0006] The electric air filter used has a filter layer, which can be designed, for example, in the form of a conductive metal mesh and / or metal needles. The filter layer is alternately charged with high voltages of different polarities—i.e., in a first mode with a negative high voltage and in a second mode with a positive high voltage.

[0007] In the first mode, the actual ionization process that cleans the air takes place, as described in the introduction. This is the actual "cleaning mode." The second mode, in contrast, is essentially the "neutralization mode." This is switched on alternately with the first mode. While in the first mode, for example, the filter layer is strongly negatively charged and emits electrons as described above, when switching to the second mode the filter layer is positively charged. It then no longer emits electrons. Instead, due to the changed voltage polarity, a large number of positively charged particles form in the area around the filter layer. These particles attach themselves to corresponding surfaces in the area around the electrode arrangement or arrangement of filter layers and neutralize the negative charges present there, thus neutralizing any static charges.By switching the voltage polarity, a targeted discharge of statically charged environmental areas is achieved at defined times through the emission of oppositely charged particles, so that the static charge can be reduced.

[0008] With regard to the specific control, different variants are conceivable. For example, the filter layer can be charged via a constant first voltage that is applied during a first time interval, while the filter layer is charged via a constant second voltage that is applied during a second time interval that follows the first time interval. Thus, constant direct voltages in the range of several kV are applied to the filter layer, but at different times or over different time intervals. During regular cleaning operation, the filter layer is operated in the first mode, i.e. a constant, e.g. negative high voltage in the range of several kV is applied to it over a first time interval, for example for 5 minutes. After the time interval has elapsed, the filter layer is discharged, the voltage drops to zero, after which the voltage with the opposite sign is applied and the filter layer, e.g.positively charged, also with a corresponding high voltage in the range of several kV. This is applied for a second time interval, lasting, for example, 1 minute. After this time interval has elapsed, the voltage is reduced again and the first negative high voltage is recharged. Thus, an intermittent alternation takes place.

[0009] The first time interval is preferably longer than the second time interval. As described, the actual cleaning effect occurs via the filter layer in the first mode, while neutralization or discharge occurs via the filter layer in the second mode. It is sufficient to carry out the neutralization or discharge over a shorter period of time, since the static charge builds up quite slowly and does not become excessively high when the method according to the invention is carried out continuously, allowing the electric air cleaner to operate in cleaning mode most of the time. The first time interval should be between 2 and 10 minutes, and the second time interval between 0.5 and 2 minutes.

[0010] According to an alternative control variant, first voltage pulses can be applied to the filter layer as the first voltage and second voltage pulses can be applied to the filter layer as the second voltage, with the first and second voltage pulses being applied with a time offset. In this case, true pulsed operation takes place in which there is a permanent change in terms of the operating mode or voltages. The voltage pulses are only applied for a few seconds, i.e. there is a higher frequency alternation between the negative charging and discharging of the filter layer and the positive charging and discharging of the filter layer. Here, too, the first voltage pulses can generally be somewhat longer than the second voltage pulses. For example, the first voltage pulses can be applied for 5 seconds, while the second voltage pulses only for 1 second.

[0011] Preferably, the first and second voltage pulses are rectangular pulses, i.e. pulses with steep edges and constant high voltage levels.

[0012] Alternatively, the first and second voltages can be sinusoidal or trapezoidal voltages. With this control variant, the charging and discharging processes occur according to a common sinusoidal or trapezoidal curve, meaning the voltage continuously fluctuates between a positive and a negative maximum. With each zero crossing, the filter layer is discharged and can be strongly recharged with the high voltage of the other polarity. Each partial voltage is defined by the respective negative or positive half-waves of the sinusoidal or trapezoidal voltage.

[0013] The half-waves of the second voltage can be shorter than those of the first voltage. This means that the second voltage is only applied for a short time, while the first voltage, which actually serves to purify the air, is applied for a longer time.

[0014] The level of the first and / or second voltage can further be varied depending on at least one environmental parameter and / or at least one operating voltage of a fan connected to a ventilation duct operated via the electric air filter. Such an environmental parameter can be, for example, the outside air temperature or the temperature of the air passed through the electric air filter. The higher the outside temperature or the air temperature, the lower the positive and negative high voltage of the filter layer can be. Another environmental parameter can be the outside air humidity or the humidity of the air passed through the electric air filter. The higher the air humidity, the lower the high voltage of the first and second filter layers can be. The current operating voltage of a fan conveying the air, which is indicative of the air throughput, can also be used as a parameter.

[0015] As described, the filter layer is charged with a high voltage of different polarity. Generally, the first voltage should be higher than the second voltage in terms of magnitude. The first voltage should be in the range of 5-10 kV, and the second voltage should be in the range of 1-4 kV.

[0016] Preferably the first voltage is negative and the second voltage is positive, but the polarity can be reversed if necessary.

[0017] In addition to the method, the invention further relates to an electrostatic precipitator device, comprising an electric air filter with a filter layer, either a first voltage source via which the filter layer can be charged with a first voltage, and a second voltage source via which the filter layer can be charged with a second voltage having a different polarity than the first voltage, or a reversible voltage source via which the first and second voltages can be supplied, as well as a control device, configured to control the two voltage sources or the one voltage source according to the method described above.

[0018] Finally, the invention also relates to a motor vehicle comprising at least one electrostatic precipitator device of the type described above.

[0019] Further advantages and details of the present invention will become apparent from the exemplary embodiments described below and from the drawings. In the drawings: Fig. 1 a schematic diagram of a filter device of a motor vehicle comprising an electric air filter, Fig. 2 a schematic diagram of the electric air filter, Fig. 3 a schematic diagram of a diagram showing the course of the high voltage at both filter layers according to a first embodiment, Fig. 4 a schematic diagram of a diagram showing the course of the high voltage at both filter layers according to a second embodiment, Fig. 5 is a schematic diagram of a diagram showing the high voltage profile at both filter layers according to a third embodiment, and Fig. 6 a schematic diagram of a diagram showing the course of the high voltage at both filter layers according to a fourth embodiment.

[0020] Fig. Figure 1 shows a schematic diagram of a filter device 1 according to the invention, which is part of a ventilation system of a motor vehicle. The filter device 1 comprises an electric air filter device including an electric air filter 2, downstream of which is a standard air filter 3, for example, a combination filter with a pollen filter, an activated carbon filter, and the like. The electric air filter 2 and the air filter 3 are accommodated, for example, in a pipe 4, which is part of the ventilation system. An air stream 5 flows through this pipe 4, which is to be cleaned via the electric air filter 2 and the air filter 3.

[0021] The electric air filter 2 comprises a filter layer 6, which is arranged in the pipe 4, which is at ground potential 7, via corresponding insulators 8. The filter layer 6 can be separately supplied with high voltage of different polarity via separate voltage sources. A basic circuit diagram for this is shown in Fig. 2 shown.

[0022] Fig. Figure 2, which shows a pure schematic circuit by means of which the basic functional principle can be explained, shows the filter layer 6, which is formed, for example, as a metal grid or using metal needles. It is integrated into an electrical circuit 9, via which it can be separately charged with high voltages of different polarities. The electrical circuit 9 comprises a first voltage source 10, which provides a first, for example, negative high voltage. Also integrated into the circuit 9 is a second voltage source 11, which is connected in parallel to the first voltage source and provides the high voltage with a different polarity, here as a positive high voltage. Each voltage source 10, 11 is assigned a switching means 12, 13, via which the electrical circuit 9 can be closed by switching on either the first voltage source 10 or the second voltage source 11.Such switching means are not required, for example, in modulated control systems and the like, which directly control voltage sources 10, 11. A capacitor 14 is also provided, by way of example, across which the high voltage drops.

[0023] Also shown is a control device 15, which, by way of example, controls the two switching devices 12, 13, but can of course also directly control the voltage sources 10, 11 accordingly, for example, when controlling sine or trapezoidal curves. At least one sensor 16 is assigned to the control device 15, via which, for example, the air temperature or humidity can be measured, which environmental information can be incorporated into the control operation, such as the level of the respective high voltage applied, or the durations or frequencies of the respective high voltage.

[0024] The control device 15 is now able to control the two voltage sources 10, 11 or the switching devices 12, 13 differently, so that the filter layer is alternately charged with high voltages of different polarities. The charging operation is therefore alternating, so that the filter layer 6 is alternately charged with strong negative and positive high voltages. The first negative high voltage is present in the first mode, i.e., the cleaning mode, while the second positive high voltage is present in the second mode, i.e., the discharging mode. The actual cleaning operation takes place via the filter layer 6 when it is sufficiently highly charged, preferably strongly negatively charged, so that it emits electrons that attach to the gas molecules in the air and charge them negatively, or remove electrons from the gas molecules, so that the molecules become positively charged. The charged molecules, in turn, attach to air particles such as dust particles or pollen, etc.which are charged via this, allowing them to deposit on a downstream separation electrode or the pipeline, which is at ground potential. Since this deposition movement occurs virtually perpendicularly or at least with a perpendicular movement component relative to the direction of air flow, it can happen that charged particles are carried along with the air flow and adhere to locations that are distant from the actual desired deposition position, so that the described static charge occurs in these areas. This can now be counteracted by intermittently charging the filter layer 6 with positive high voltage, since this opposite high-voltage charge creates oppositely charged particles, which can also deposit at these locations and neutralize the statically charged particles.

[0025] Fig. Figure 3 shows a first diagram illustrating a first voltage curve at filter layer 6. The time t in minutes is plotted along the abscissa, and the voltage U in kV is plotted along the ordinate. The curve sections above the abscissa represent the charging voltage of the second filter layer 7, while the curve sections below represent the charging voltage of the first filter layer 6.

[0026] Fig. 3 shows corresponding square-wave voltages, i.e. the filter layer 6 is constantly negatively charged via a constant first voltage U1 during a first time interval, while the second voltage U2 shown is the constant voltage with which the filter layer 6 is constantly positively charged during a second time interval. It is evident that the first time interval is significantly longer than the second time interval. It is, for example, between 2 and 10 minutes, while the second time interval is between 0.5 and 2 minutes. The voltage U1 is, for example, 6 to 10 kV, while the voltage U2 is, for example, 2 to 4 kV. The control device 15 controls the circuit 9 or the switching means 12, 13 or, if appropriate, directly the two voltage sources 10, 11 according to this square-wave diagram. The intended cleaning takes place in the first time interval, and the neutralization of any static charge takes place in the second.

[0027] Fig. Figure 4 shows a schematic diagram of a second voltage curve at the filter layer 6, with the time in seconds being plotted along the abscissa and the voltage U in kV along the ordinate. Again, a rectangular voltage is provided here, with the voltages U1 and U2, which in turn represent the voltages already Fig. 3. However, the time intervals here are significantly shorter and are in the range of seconds. Thus, a higher-frequency, rapid pulse sequence is present. For example, a time interval in which voltage U1 is applied lasts 5 seconds, and a time interval in which voltage U2 is applied lasts 1 second.

[0028] Fig. Figure 5 shows a schematic diagram of a third voltage curve at filter layer 6. Time is again plotted in seconds along the abscissa, and voltage U in kV is plotted along the ordinate. Here, the voltage is shown as a common sinusoidal voltage, again with voltage U1 as the negative voltage (defined by the negative half-waves of the sine curve) and voltage U2 as the positive voltage (defined by the positive half-waves of the sine curve). Voltage U1 is significantly higher in magnitude than voltage U2, and it also lasts significantly longer.

[0029] Fig. 6 finally shows a schematic diagram of a fourth voltage curve at the filter layer 6. Instead of a sinusoidal curve as in Fig. 5 is according to Fig. 6, a common trapezoidal voltage is applied, again comprising the negative voltage U1 (defined by the negative half-waves of the trapezoidal curve) and the positive voltage U2 (defined by the positive half-waves of the trapezoidal curve). Again, the magnitude of the negative voltage U1 is significantly greater than the magnitude of the positive voltage U2. The voltage U1 is also applied for a significantly longer time than the voltage U2.

[0030] Also in the Fig. 4 and Fig. 5, the amounts of the respective positive and negative high voltages are in the above-specified ranges of 6 - 10 kV for the negative high voltage U1 and of 2 - 4 kV for the positive high voltage U2.

[0031] Direct control of the two voltage sources 10,11 is particularly useful for controlling the sinusoidal and trapezoidal voltages.

[0032] Instead of integrating two high-voltage sources 10, 11, it is also conceivable to provide only one voltage source whose polarity can be reversed via the control device 15, i.e., it can be used to apply both the negative voltage U1 and the positive voltage U2. This single voltage source, as well as the two voltage sources 10, 11, can be controlled, for example, via pulse-width modulation, particularly for controlling any sinusoidal or trapezoidal voltages.

[0033] The Fig. The voltage curves shown in 3 - 6 are merely exemplary in nature, they are not restrictive, other control voltage curves are also conceivable.

Claims

[1] Method for controlling an electric air filter (2) for a vehicle interior of a motor vehicle, characterized by in that a filter layer (6) is charged alternately with a first voltage (U1) and with a second voltage (U2) having a different polarity than the first voltage (U1), wherein the filter layer (6) can be selectively connected to the first voltage source (10) or the second voltage source (11) either by switching from a first voltage source (10) providing the first voltage (U1) to a second voltage source (11) providing the second voltage (U2) and vice versa, or wherein the polarity of a voltage source for providing the first voltage (U1) and the second voltage (U2) is reversed in such a way that the filter layer (6) is charged at a time when the first filter layer is not charged, and vice versa. [2] Method according to claim 1, characterized bythat the filter layer (6) is charged via a constant first voltage (U1) which is applied during a first time interval, while the filter layer (6) is charged via a constant second voltage (U2) which is applied during a second time interval which follows the first time interval. [3] Method according to claim 2, characterized by that the first time interval is between 2 - 10 min and the second time interval is between 0.5 - 2 min. [4] Method according to claim 1, characterized by that first voltage pulses are applied to the filter layer (6) as the first voltage (U1) and second voltage pulses are applied to the filter layer (6) as the second voltage (U2). [5] Method according to claim 4, characterized by that the first and second voltage pulses are rectangular pulses. [6] Method according to claim 4 or 5, characterized by that the first voltage pulses are longer than the second voltage pulses. [7] Method according to claim 1, characterized by that the first voltage (U1) and the second voltage (U2) are given as a sinusoidal voltage or trapezoidal voltage. [8] Method according to claim 7, characterized by that the half-waves of the second voltage (U2) are shorter than those of the first voltage (U1). [9] Method according to one of the preceding claims, characterized by that the level of the first and the second voltage (U1, U2) is varied depending on at least one environmental parameter and / or at least one operating voltage of a fan which is connected to a ventilation duct operated via the electric air filter (2). [10] Method according to claim 9, an environmental parameter is the outside temperature or temperature of the air passed through the electric air filter (2) or outside air humidity or the humidity of the air passed through the electric filter (2). [11] Method according to one of the preceding claims, characterized bythat the first voltage (U1) is in the range between 5 - 10 kV and the second voltage (U2) is in the range between 1 - 4 kV. [12] Method according to one of the preceding claims, characterized by that the first voltage (U1) is negative and the second voltage (U2) is positive. [13] Electrostatic precipitator device, comprising an electric air filter (2) with a filter layer (6), either a first voltage source (10) via which the filter layer (6) can be charged with a first voltage (U1), and a second voltage source (11) via which the filter layer (6) can be charged with a second voltage (U2) having a different polarity than the first voltage (U1), or a reversible voltage source via which the first and the second voltage (U1, U2) can be given, and a control device (15) set up to control the two voltage sources (10, 11) or the one voltage source according to the method according to one of the preceding claims. [14] Motor vehicle comprising at least one electrostatic precipitator device according to claim 13.

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