JP2023155757A - dust collector - Google Patents

Abstract

To provide a dust collector with reduced energy consumption.SOLUTION: A dust collector includes: an ion generating part that is disposed upstream from an air passage and generates ions through the application of pulse voltage; a power supply circuit that outputs the pulse voltage to the ion generating part; and a dust collecting part disposed downstream of the air passage. The power supply circuit is a resonant pulse power supply circuit that outputs unipolar pulse voltage.SELECTED DRAWING: Figure 1

Description

The technology disclosed in this specification relates to a dust collector.

Patent Document 1 discloses a dust collector equipped with an ion generating element. Such a dust collector can efficiently remove dust by charging the dust with positive ions or negative ions generated by the ion generating element.

Japanese Patent Application Publication No. 2005-211746

The pulse voltage applied to the ion generating element of Patent Document 1 is a pulse voltage with a positive voltage of +2.7 kV and a negative voltage of -2.7 kV, a sine wave frequency of 20 kHz, and a pulse wave repetition period of 60 Hz. has been done. Due to these pulse voltage conditions, the power supply circuit connected to the ion generating element of Patent Document 1 is a bipolar pulse generating circuit, such as an inductive energy storage (IES) system using a transformer. This is considered to be a power supply circuit. When such a power supply circuit is used, there is a problem in that it consumes a large amount of energy. The present specification provides a dust collector that consumes less energy.

The dust collector disclosed in this specification includes an ion generating section that is arranged on the upstream side of an air flow path and is configured to generate ions by applying a pulse voltage, and an ion generating section that is configured to generate ions by applying a pulse voltage to the ion generating section. The air conditioner may include a power supply circuit configured to output an output, and a dust collection section disposed on the downstream side of the air flow path. The power supply circuit is a resonant pulse power supply circuit that outputs a unipolar pulse voltage. Such a resonant pulse power supply circuit may be, for example, a leakage inductance resonance (LIR) power supply circuit that outputs a unipolar pulse voltage, or an inductive energy storage circuit that outputs a unipolar pulse voltage. It may be an inductive energy storage (IES) power supply circuit. The pulse width of the unipolar pulse voltage outputted by such a resonant pulse power supply circuit is short. Therefore, in the dust collector disclosed in this specification, the ion generating section is driven by a pulse voltage with a short pulse width, so that energy consumption can be suppressed.

An outline of the configuration of the dust collector is shown. A power supply circuit that outputs a unipolar pulse voltage to the ion generator is shown. 3 shows an equivalent circuit converted on the secondary side of the power supply circuit shown in FIG. 2. FIG. 3 shows voltage and current for one cycle output by the power supply circuit shown in FIG. 2. 3 shows voltage and current waveforms and energy consumption of the power supply circuit shown in FIG. 2. 3 shows voltage and current waveforms and energy consumption of an inductive energy storage (IES) power supply circuit that outputs a bipolar pulse voltage as a comparative example. The results of calculating the dust collection efficiency when the polarity of the unipolar short pulse voltage is positive and negative are shown. A simple structure of the ion generator is shown. The plasma generation situation is shown when a comparative example power supply circuit using an inductive energy storage system (IES) is used. This figure shows how plasma is generated when a leakage inductance resonance (LIR) type power supply circuit is used. A modification of the power supply circuit that outputs a unipolar pulse voltage to the ion generator is shown. 9 shows voltage and current waveforms and energy consumption of the power supply circuit shown in FIG. 8. The results of calculating the dust collection efficiency when DC voltage is applied are shown. The results of calculating the dust collection efficiency when changing the pulse frequency are shown.

The dust collector disclosed in this specification can include an ion generator, a power supply circuit, and a dust collector. The ion generating section is arranged on the upstream side of the air flow path, and is configured to generate ions by applying a pulse voltage. The power supply circuit is a resonant pulse power supply circuit, and is configured to output a unipolar pulse voltage to the ion generating section. The dust collection section is arranged on the downstream side of the air flow path.

The power supply circuit may include a DC power supply, a transformer including a primary winding and a secondary winding, and a switch element. In the transformer, a primary winding is connected to a DC power source, and a secondary winding is connected to an ion generator. The switch element is connected in series with the primary winding of the transformer. The power supply circuit generates a unipolar pulse voltage based on the resonance phenomenon between the leakage inductance of the primary winding and the secondary winding and the stray capacitance of the secondary circuit when the switch element is turned on. is configured to print. In this way, the power supply circuit may be a leakage inductance resonance (LIR) power supply circuit that outputs a unipolar pulse voltage.

The power supply circuit may include a DC power supply, a transformer including a primary winding and a secondary winding, and a switch element. In the transformer, a primary winding is connected to a DC power source, and a secondary winding is connected to an ion generator. The switch element is connected in series with the primary winding of the transformer. In a power supply circuit, when the switch element is turned on, energy is accumulated in the primary winding, and when the switch element is turned off, the excitation inductance of the secondary winding and the stray capacitance of the secondary circuit are accumulated. The device is configured to output a unipolar pulse voltage based on a resonance phenomenon between . In this way, the power supply circuit may be an inductive energy storage (IES) power supply circuit that outputs a unipolar pulse voltage.

The power supply circuit may be configured to output the DC voltage after outputting the unipolar pulse voltage. In this case, the power supply circuit may further include a capacitor connected in parallel to the ion generator. Further, the power supply circuit may be configured to maintain output of the DC voltage from after application of the unipolar pulse voltage until before application of the next unipolar pulse voltage. A dust collector equipped with such a power supply circuit can have high dust collection efficiency.

The power supply circuit may be configured to output a negative unipolar pulse voltage. A dust collector equipped with such a power supply circuit can have high dust collection efficiency.

As shown in FIG. 1, the dust collector 1 includes a housing 10, an ion generator 20, a dust collector 30, a blower fan 40, and a controller 50.

The housing 10 has an intake port 12 through which air flows in, and an exhaust port 14 through which air flows out. The housing 10 accommodates an ion generating section 20, a dust collecting section 30, and a blowing fan 40 in an air flow path that connects an intake port 12 and an exhaust port 14. Note that the arrow in the figure indicates the direction in which air flows.

The ion generator 20 is disposed upstream of the air flow path of the housing 10 than the dust collector 30, and is configured to generate ions by applying a pulse voltage. The ion generating section 20 is not particularly limited, but may be an ion generating element using corona discharge, barrier discharge, or creeping discharge, for example. In this example, the ion generating section 20 has a positive electrode and a negative electrode, and when the pulse voltage applied between the positive electrode and the negative electrode becomes equal to or higher than the discharge start voltage, the positive electrode and the negative electrode It is configured to generate ions by the discharge during the period. Specifically, the ion generating section 20 may be configured with a thin metal wire so as to perform line-to-line discharge, for example. The ion generator 20 can generate negative ions or positive ions depending on the polarity of the pulse voltage. Since this type of ion generating element is well known, a detailed description of its configuration will be omitted.

The dust collecting section 30 is disposed downstream of the ion generating section 20 in the air flow path of the housing 10, and is designed to collect various dust including biological contaminants such as mold, viruses, and pollen. It is composed of The dust collector 30 is not particularly limited, but may be, for example, an electric dust collector. In this example, the dust collection unit 30 is configured such that flat dust collection electrodes and flat counter electrodes are arranged alternately at a predetermined distance. The dust collecting section 30 is used by having a counter electrode grounded and applying a negative or positive DC high voltage to the dust collecting electrode depending on the ion species (positive ions or negative ions) generated in the ion generating section 20 . Specifically, when a negative pulse voltage is applied to the ion generating section 20, a positive DC high voltage is applied to the dust collection electrode of the dust collection section 30. When a positive pulse voltage is applied to the ion generating section 20, a negative DC high voltage is applied to the dust collection electrode of the dust collection section 30. The dust collection unit 30 is configured to draw charged dust toward the dust collection electrode and collect it with a filter. Since this type of electrostatic precipitator is well known, a detailed description of its configuration will be omitted.

The blower fan 40 is arranged in the air flow path of the housing 10 and sucks air from outside the housing 10 through the intake port 12 and exhausts air to the outside of the housing 10 through the exhaust port 14. is configured to do so. In this example, the blower fan 40 is arranged on the downstream side of the air flow path of the housing 10 than the ion generator 20 and the dust collector 30, and is configured to adjust the inside of the housing 10 to negative pressure. ing. Instead of this example, the blower fan 40 is arranged on the upstream side of the air flow path of the housing 10 than the ion generating section 20 and the dust collecting section 30, and is configured to adjust the inside of the housing 10 to a positive pressure. You can leave it there.

The control unit 50 has a power supply circuit, outputs an appropriate voltage to each of the ion generation unit 20 , the dust collection unit 30 , and the ventilation fan 40 , and controls the ion generation unit 20 , the dust collection unit 30 , and the ventilation fan 40 . It is configured to drive each. The control unit 50 outputs a unipolar short pulse voltage to the ion generation unit 20, as described later. Here, the unipolar short pulse voltage refers to a nanosecond pulse voltage with a steep voltage rise. The control unit 50 further outputs an appropriately adjusted DC voltage to each of the dust collection unit 30 and the blower fan 40. The control unit 50 may be mounted integrally with the housing 10 or may be provided separately from the housing 10. The power supply circuit of the control unit 50 that outputs a unipolar short pulse voltage will be described in detail below.

FIG. 2 shows a power supply circuit 52 included in the control section 50. The power supply circuit 52 is a leakage inductance resonance (LIR) power supply circuit configured to output a unipolar short pulse voltage to the ion generator 20, and includes a DC power supply V1 and an input capacitor C1. , a transformer T1, a switch element SW1, and a gate drive circuit 54.

Input capacitor C1 is connected in parallel to DC power supply V1. The transformer T1 has a primary winding L1 and a secondary winding L2, the primary winding L1 is connected between the positive and negative poles of the DC power supply V1, and the secondary winding L2 is connected between the positive and negative electrodes of the ion generating section 20. The winding ratio between the primary winding L1 and the secondary winding L2 is 1:n. A magnetic reset diode D1 is connected in antiparallel between both ends of the primary winding L1. The switch element SW1 is, for example, an N-channel MOSFET, although it is not particularly limited, and is connected in series with the primary winding L1 of the transformer T1 between the positive and negative electrodes of the DC power supply V1. ing. Therefore, depending on whether the switch element SW1 is turned on or off, energization to the primary winding of the transformer T1 can be controlled on or off. Note that the switch element SW1 may be connected between the positive electrode of the DC power supply V1 and the switch element SW1. Switch element SW1 is a high frequency switch element made of a wide bandgap semiconductor such as silicon carbide, gallium nitride, or gallium oxide. The gate drive circuit 54 is connected to the gate of the switch element SW1, and controls on/off of the switch element SW1.

FIG. 3 shows an equivalent circuit obtained by converting the power supply circuit 52 to the secondary side of the transformer T1. Here, "l" is the leakage inductance of transformer T1, "M" is the mutual inductance of transformer T1, and "c" is the stray capacitance of the secondary circuit (the capacitance between the windings of transformer T1 and the ion generation 20), and "r" is the on-resistance of the switch element SW1. When the switch element SW1 is turned on, if M>>1, r=0, and ω=1/√lc, the voltage v _c (t) that charges the stray capacitance and the stray capacitance due to the resonance phenomenon of the leakage inductance and the stray capacitance. The current i _c (t) flowing through is expressed by the following equations 1 and 2. FIG. 4 shows waveforms for one period of voltage v _c (t) and current i _c (t).

In this manner, when the switch element SW1 is turned on, the power supply circuit 52 can output a pulse voltage that is twice as much as the voltage boosted by the turns ratio n of the transformer T1 due to the resonance phenomenon of the leakage inductance and the floating capacitance. The pulse width becomes narrower as the product of leakage inductance and stray capacitance decreases, and ranges from several ns to several tens of ns (nanoseconds).

FIG. 5 shows simulation results of the waveforms of the voltage (Voltage) and current (Current) of the short pulse voltage output by the power supply circuit 52 of this embodiment, and the consumption energy (Consumption energy). As a comparative example, FIG. 6 shows simulation results of the voltage and current waveforms of the pulse voltage output by the inductive energy storage system (IES) and the energy consumption. Note that the pulse frequency and load resistance are the same.

In this example, the pulse width of the short pulse voltage of the present example shown in FIG. 5 is 30 ns, and the pulse width of the pulse voltage of the comparative example shown in FIG. 6 is 150 ns. In this way, the pulse width of the short pulse voltage of the present example is narrower than that of the pulse voltage of the comparative example. As a result, the energy consumption of the present example shown in FIG. 5 is about 0.41 mJ per pulse, and the energy consumption of the comparative example shown in FIG. 6 is about 0.92 mJ per pulse. In this way, the power supply circuit 52 of this embodiment can output a short pulse voltage with a narrow pulse width, so that energy consumption can be suppressed. Further, the LIR type power supply circuit 52 of this embodiment has a shorter turn-on time than the IES type power supply circuit of the comparative example. Therefore, the conduction loss in the switch element SW1 is also small, so that the power supply circuit 52 of this embodiment consumes little energy in this respect as well. Further, the power supply circuit 52 can be configured to be small and lightweight. Therefore, the power supply circuit 52 has high efficiency and can be made into an extremely small and lightweight power supply device.

Furthermore, as shown in FIG. 5, the short pulse voltage output by the power supply circuit 52 of this embodiment is a unipolar pulse wave. Therefore, the power supply circuit 52 of this embodiment can apply a short pulse voltage of either positive polarity or negative polarity to the ion generating section 20.

FIG. 7 shows test results of dust collection efficiency when the polarity of the short pulse voltage is positive and negative. Note that the pulse frequency of the short pulse voltage is fixed at 960 pps, and the maximum value is varied within ±0 to 9 kV. The dust collection voltage of the dust collection unit 30 is controlled so that ±2.0 kV, which is opposite in polarity to the short pulse voltage, is applied. The diameter of the collected dust particles is 0.3 μm to 0.5 μm. The air flow rate is 5 L/min. The length of the dust collecting electrode is 10 mm in the air flow direction. As shown in FIG. 7, regardless of the maximum value of the short pulse voltage, the negative polarity short pulse voltage has higher dust collection efficiency than the positive polarity short pulse voltage. As described above, the power supply circuit 52 can output a unipolar short pulse voltage. Therefore, the dust collector 1 including the power supply circuit 52 can have high dust collection efficiency.

As described above, the dust collector 1 of this embodiment has high dust collection efficiency. One reason for such high dust collection efficiency is thought to be the formation of widely uniform plasma in the ion generating section 20. The results of verifying this will be explained below.

FIG. 8 shows an example of a simple structure of the ion generating section 20. The ion generating section 20 is configured to perform line-to-line discharge, and includes a pair of fixed stands 22 and 24, a high-voltage metal wire 26, and a ground metal wire 28. The first fixed base 22 and the second fixed base 24 are placed apart by a distance d1 and define a plasma discharge area therebetween. In this example, the distance d1 is 40 mm. The high-voltage metal wire 26 is, for example, a stainless steel metal wire with a diameter of 0.05 mm, and one end is fixed to the first fixing base 22 and the other end is fixed to the second fixing base 24. Further, the high voltage metal wire 26 is connected to the LIR type power supply circuit 52 of this embodiment described above. The ground metal wire 28 is, for example, a stainless steel metal wire with a diameter of 0.05 mm, and one end is fixed to the first fixed base 22 and the other end is fixed to the second fixed base 24. The distance d2 between the high voltage metal wire 26 and the ground metal wire 28 is 4 mm in this example.

FIG. 9 is an image of plasma discharge formed in the ion generating section 20 when an IES system power supply circuit of a comparative example is used in place of the LIR system power supply circuit 52 of the present embodiment. In the comparative example, non-uniform plasma discharge is generated only in the vicinity of the high-voltage metal wire 26.

FIG. 10 is an image of plasma discharge formed in the ion generating section 20 when the LIR type power supply circuit 52 of this embodiment is used. In this embodiment, a wide and uniform plasma discharge is generated between the high voltage metal line 26 and the ground metal line 28. Therefore, the ion generating section 20 of this embodiment has high charging efficiency and high radical efficiency. In this way, when the LIR type power supply circuit 52 that outputs a unipolar short pulse voltage is used, the electric field strength in the discharge space increases in the ion generation unit 20, and the energy input from the power supply circuit 52 is efficiently converted into electronic energy. As a result, it becomes possible to generate a widely uniform plasma discharge with high efficiency. Therefore, the dust collector 1 including the power supply circuit 52 can have high dust collection efficiency.

(Modified example)
FIG. 11 shows a modification of the power supply circuit 52. This power supply circuit 52 is characterized in that it further includes a reverse current blocking diode D2 and an output capacitor C2 provided in the secondary circuit. The backflow blocking diode D2 is connected between the secondary winding L2 of the transformer T1 and the ion generating section 20, and is in the forward direction from the secondary winding L2 of the transformer T1 toward the ion generating section 20. are connected like this. The output capacitor C2 is connected in parallel to the ion generator 20, with one end connected between the backflow blocking diode D2 and the ion generator 20, and the other end connected to the secondary winding L2 of the transformer. and the ion generating section 20.

FIG. 12 shows a voltage waveform output by the power supply circuit 52 of the modified example. After the voltage of the output capacitor C2 sharply increases due to the output of the short pulse voltage, the voltage decreases. During this voltage drop, current flows in the reverse direction through the reverse blocking diode D2 and the output capacitor C2 is discharged. As the voltage drop progresses, the current passing through the reverse blocking diode D2 stops, the discharge of the output capacitor C2 also stops, and a DC voltage is output to the ion generating section 20. In this example, a DC voltage of about 2.0 kV having the same polarity as the short pulse voltage is output. In this way, the power supply circuit 52 of the modified example can output a DC voltage to the ion generation section 20 after outputting a short pulse voltage. Note that the magnitude of the DC voltage output by the power supply circuit 52 can be adjusted based on the capacitance value of the output capacitor C2 and the junction capacitance (C3) of the reverse current blocking diode D2.

FIG. 13 shows the test results of dust collection efficiency when DC voltage was applied. The test conditions are the same as those described with reference to FIG. Note that the polarity of the short pulse voltage is negative. As shown in FIG. 13, when a DC voltage is applied after applying a short pulse voltage, the dust collection efficiency is improved. Furthermore, as the DC voltage increases, the dust collection efficiency also improves. This is thought to be because the application of the DC voltage increased the amount of ions generated in the ion generating section 20, and as a result, the amount of charge on the dust increased. Here, a case where the dust collection efficiency is 99% or more is evaluated as passing. In this case, although the test was rejected when a short pulse voltage of 5.0 kV was applied alone, the test was passed when a DC voltage was applied in combination. Taking the case of a short pulse voltage of 5.0 kV as an example, even if the DC voltage is less than 80% ((4 kV/5 kV) x 100) of the short pulse voltage, it is recognized that it is effective in improving a reject product to a pass product. It will be done. More preferably, the DC voltage is 50% ((2.5kV/5kV)×100) or more of the short pulse voltage.

For example, by adjusting the pulse frequency, the power supply circuit 52 can maintain the output of the DC voltage from after application of a short pulse voltage until before application of the next short pulse voltage. In this case, dust collection efficiency can be improved. Note that improving the dust collection efficiency can also be said to mean that the maximum value of the short pulse voltage can be reduced while maintaining the dust collection efficiency. It can also be said that the power supply circuit 52 can suppress energy consumption while maintaining dust collection efficiency.

FIG. 14 shows the test results of the dust collection efficiency when the pulse frequency was changed in the case where a short pulse voltage of 8.0 kV was applied alone. In all cases where the pulse frequency is 50 pps or more, the dust collection efficiency exceeds 99%. From this result, when determining the relationship between air volume and pulse frequency, it can be considered that dust collection efficiency exceeds 99% if it is 0.1 L/min/pps or less.

In this way, the dust collector 1 of this embodiment has the maximum value and pulse frequency of the short pulse voltage generated by the ion generator 20, the polarity and voltage value of the dust collection voltage of the dust collector 30, and the blower fan 40. By appropriately adjusting the air volume, high dust collection efficiency can be achieved while reducing energy consumption.

(Other variations)
In the above embodiment, the leakage inductance resonance (LIR) power supply circuit 52 that outputs a unipolar pulse voltage has been described. Instead of this example, an inductive energy storage (IES) power supply circuit that outputs a unipolar pulse voltage may be used. The specific circuit configuration is the one in which the magnetic reset diode D1 of the power supply circuit 52 shown in FIG. 2 is removed. This power supply circuit stores energy in the primary winding L1 when the switch element SW1 is turned on, and then stores energy in the secondary winding L2 and the secondary winding L1 when the switch element SW1 turns off. A unipolar pulse voltage can be output based on the resonance phenomenon between the stray capacitance of the circuit and the floating capacitance of the circuit. Even if an inductive energy storage type power supply circuit that outputs such a unipolar pulse voltage is used in the dust collector 1, the same effects as in the above embodiment can be achieved.

In the above embodiment, control was described in which a negative pulse voltage was applied to the ion generating section 20 and a positive DC high voltage was applied to the dust collection electrode of the dust collection section 30. However, the polarity of the pulse voltage applied to the ion generation section 20 and the polarity of the DC high voltage applied to the dust collection electrode of the dust collection section 30 are not limited to this example, and various combinations are possible. For example, when a positive pulse voltage is applied to the ion generating section 20, a negative DC high voltage may be applied to the dust collection electrode of the dust collection section 30. Furthermore, a positive pulse voltage may be applied to the ion generating section 20, a positive DC high voltage may be applied to the dust collecting electrode of the dust collecting section 30, and a negative pulse voltage may be applied to the ion generating section 20. Then, a negative DC high voltage may be applied to the dust collection electrode of the dust collection unit 30. Even if the pulse voltage and the DC high voltage are combined in this way, the same effects as in the above embodiment can be achieved.

Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The techniques described in the claims include various modifications and changes to the specific examples illustrated above. Further, the technical elements described in this specification or the drawings exhibit technical usefulness singly or in various combinations, and are not limited to the combinations described in the claims as filed. Furthermore, the techniques illustrated in this specification or the drawings can achieve multiple objectives simultaneously, and achieving one of the objectives has technical utility in itself.

1: Dust collector 10: Housing 20: Ion generator 30: Dust collector 40: Blower fan 50: Control unit 52: Power supply circuit 54: Gate drive circuit V1: DC power supply T1: Transformer L1: Primary winding L2: Secondary winding SW1: Switch element

Claims (7)

A dust collector,
an ion generator disposed on the upstream side of the air flow path and configured to generate ions by applying a pulse voltage;
a power supply circuit configured to output the pulse voltage to the ion generator;
a dust collecting section disposed on the downstream side of the air flow path,
A dust collector, wherein the power supply circuit is a resonant pulse power supply circuit that outputs a unipolar pulse voltage. The power supply circuit is
DC power supply and
a transformer including a primary winding connected to the DC power supply and a secondary winding connected to the ion generating section;
a switch element connected in series to the primary winding of the transformer,
The power supply circuit is based on a resonance phenomenon between the leakage inductance of the primary winding and the secondary winding and the stray capacitance of the secondary circuit when the switch element is turned on. The dust collector according to claim 1, configured to output the unipolar pulse voltage. The power supply circuit is
DC power supply and
a transformer including a primary winding connected to the DC power supply and a secondary winding connected to the ion generating section;
a switch element connected in series to the primary winding of the transformer,
The power supply circuit stores energy in the primary winding when the switch element is turned on, and stores energy in the excitation inductance of the secondary winding and the secondary winding when the switch element is turned off. The dust collector according to claim 1, wherein the dust collector is configured to output the unipolar pulse voltage based on a resonance phenomenon between a stray capacitance of a side circuit. The dust collector according to any one of claims 1 to 3, wherein the power supply circuit is configured to output a DC voltage after outputting the unipolar pulse voltage. The dust collector according to claim 4, wherein the power supply circuit further includes a capacitor connected in parallel to the ion generating section. The dust collector according to claim 4, wherein the power supply circuit is configured to maintain the output of the DC voltage from after application of the unipolar pulse voltage until before application of the next unipolar pulse voltage. . The dust collector according to any one of claims 1 to 3, wherein the power supply circuit is configured to output the unipolar pulse voltage of negative polarity to the ion generating section.

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