HK1131761B - Electrostatic atomizer - Google Patents

Description

Electrostatic atomization device

Technical Field

The present invention relates to an electrostatic atomization device for producing nano-scale droplets.

Background

There is known an electrostatic atomizing device which, when a liquid such as water is supplied to a discharge electrode, applies a high voltage between the discharge electrode and a counter electrode (counter electrode) to cause an electric discharge therebetween, thereby generating nanometer-sized charged fine water droplets (i.e., nanometer-sized mist droplets) by Rayleigh breakup (Rayleigh break-up) generated in the liquid atomizing the liquid held on the discharge electrode.

The charged fine water droplets have a characteristic of containing radicals (radials) and having a relatively long duration of mist state, thereby being capable of diffusing in a target space in a large amount to effectively act on malodor substances attached to, for example, wall surfaces, clothes and curtains in a room, and exert a deodorizing effect.

In the electrostatic atomizer in which water stored in a water tank is supplied to a discharge electrode by a capillary phenomenon, a user must fill the water tank with water again each time the water tank becomes empty. As an electrostatic atomization device that does not require the above-described refill operation, there is known an electrostatic atomization device provided with a heat exchange portion for cooling air to generate water, the water (i.e., condensed water) generated by the heat exchanger being supplied to a charging electrode. In this type of electrostatic atomizer, a relatively long time of at least about several minutes is required to send the condensed water produced by the heat exchanger to the discharge electrode.

The applicant of the present application proposes an electrostatic atomization device comprising: a cooler for cooling the discharge electrode to generate condensed water on a surface of the charge electrode based on moisture in the air; and a controller for detecting a discharge current flowing between the discharge electrode and the counter electrode and controlling the cooler so as to maintain the discharge current at a predetermined value (see patent document 1 below).

As a method for enabling this type of electrostatic atomization device to stably generate mist droplets, it is conceivable that the mist generation can be performed by stabilizing the output of a high-voltage output circuit. It is considered that the concept can be realized by directly detecting a high voltage applied between the discharge electrode and the counter electrode and adjusting the output of the high voltage output circuit based on the detected voltage so that the output of the high voltage output circuit is equal to a target value. However, for such a technique of directly detecting the output voltage of the high-voltage output circuit to adjustably stabilize the output voltage of the high-voltage output circuit, it is essential to configure the detection circuit using circuit elements capable of withstanding a high voltage (i.e., high-voltage withstanding circuit components). This complicates the circuit configuration, resulting in an increase in the cost and volume of the electrostatic atomization device.

[ patent document 1] Japanese unexamined patent publication No. 2006-122819

Disclosure of Invention

In view of the above problems in the prior art, an object of the present invention is to provide an electrostatic atomizer capable of stably generating nano-sized droplets and simplifying a circuit configuration.

In order to achieve the above object, an electrostatic atomizer according to an aspect of the present invention comprises: a high voltage generating section that applies a high voltage to a discharge electrode supplied with a liquid to be electrostatically atomized to cause discharge; and an output stabilizing section for stabilizing an output voltage of the high voltage generating section. In the electrostatic atomizer, the high voltage generating section includes a self-oscillation type DC/DC converter provided with: a transformer having a primary winding, a secondary winding, and a control winding; and a switching element interposed between the positive and negative electrodes of the primary winding, connected in series to a DC power source, and to which an induced voltage generated in the control winding is applied through a control terminal. The self-oscillation type DC/DC converter outputs an induced voltage generated in the secondary winding in accordance with a switching operation of the switching element to the discharge electrode. The output stabilizer adjusts a time period during which the switching element is in the on state based on a voltage induced in the control winding during the switching element is in the on state.

In the electrostatic atomizer, the output stabilizing section adjusts a time period during which the switching element is in the on state based on a voltage induced in the control winding during the period during which the switching element is in the on state, thereby stabilizing the output voltage of the high voltage generating section. Therefore, compared to the above-described prior art in which the output voltage of the high voltage generation circuit is detected to adjust and stabilize the output voltage of the high voltage generation circuit, the output voltage of the high voltage generation section can be stabilized using a circuit element having a relatively low withstand voltage, and there is no need to electrically insulate the primary side and the secondary side of the high voltage generation section (transformer). Thereby stably generating nano-scale droplets and simplifying a circuit structure.

Drawings

Fig. 1 is a circuit diagram showing a specific circuit configuration of an electrostatic atomization device according to a first embodiment of the present invention.

Fig. 2 is a block diagram of the electrostatic atomization device of fig. 1.

Fig. 3 is a block diagram of an electrostatic atomization device according to a second embodiment of the present invention.

Fig. 4 is a circuit diagram showing a specific circuit configuration of the electrostatic atomization device in fig. 3.

Detailed Description

The present invention will be specifically explained based on embodiments of the present invention with reference to the drawings.

First embodiment

As shown in fig. 2, an electrostatic atomizing apparatus according to a first embodiment of the present invention includes: a discharge electrode 1; a counter electrode 2 disposed opposite to a distal end (digital end) of the discharge electrode 1 at a given distance, the counter electrode 2 having a circular inner edge as a substantial electrode (substential electrode); a high voltage generating circuit 3 for applying a high voltage between the discharge electrode and the counter electrodes 1, 2 to cause a discharge therebetween; and an output stabilization circuit 6 for stabilizing the output voltage of the high voltage generation circuit 3. In the first embodiment, the counter electrode 2 provided in the electrostatic atomizer is grounded. During the discharge, a high negative or positive voltage (e.g., a negative voltage of several kilovolts) is applied to the discharge electrode 1. Meanwhile, a liquid (e.g., water) is supplied to the discharge electrode 1 through an existing supplier (e.g., a water tank or a cooler described in "background art", not shown).

In the case where water (e.g., condensed water) is attached to the discharge electrode 1, when a discharge voltage is applied between the discharge electrode 1 and the counter electrode 2, the water on the discharge electrode 1 is drawn toward the counter electrode 2 to have a shape called "taylor cone" TC (taylor cone), and is formed into nanometer-sized charged fine water droplets by rayleigh breakup occurring at the tip of the taylor cone TC, thereby achieving atomization of the liquid (water). In this process, if the discharge voltage (i.e., the output voltage of the high voltage generating circuit 3) fluctuates, the number of the generated charged fine water droplets will unstably increase or decrease. Therefore, stabilizing the output voltage of the high voltage generation circuit 3 is necessary for stabilizing the number of the generated charged minute water droplets. In order to meet this demand, the electrostatic atomization device according to the first embodiment is provided with the output stabilization circuit 6 for stabilizing the output voltage of the high-voltage generation circuit 3.

Fig. 1 is a circuit diagram showing a specific circuit configuration of an electrostatic atomization device of a first embodiment.

The high-voltage generation circuit 3 includes a conventional ringing choke converter (ringing choke converter)3A and a multistage (3-stage in the illustrated embodiment) voltage-doubler rectification circuit 3B. The ringing choke converter 3A includes: a transformer T having a primary winding L1, a secondary winding L2 magnetically coupled to the primary winding L1, and a control winding L3; the DC power supply is formed of a primary winding L1 of the transformer T, a switching element Q1 including an NPN-type bipolar transistor, and a resistor R4, and is connected to a series circuit of positive and negative electrodes (open poles) of a DC power supply (smoothing capacitor C0). The voltage doubler rectifier circuit 3B has three diodes D11, D12, D13 and three capacitors C11, C12, C13, and is connected to the secondary winding L2 of the ringing choke converter 3A. In the ringing choke converter 3A, one terminal of the control winding L3 of the transformer T is connected to the control terminal (base) of the switching element Q1 through a series circuit formed by a capacitor C1 and a resistor R2. The ringing choke converter 3A further includes: a resistor R1 inserted between the positive terminal (i.e., the positive electrode) of the smoothing capacitor C0 and the base of the switching element Q1; and a switching element Q2 including an NPN-type bipolar transistor having a base connected to the emitter of the switching element Q1 through a resistor R3, a collector connected to the base of the switching element Q1, and an emitter connected to a connection point of the connecting resistor R4 and the control winding L3.

The basic operation of the high voltage generating circuit 3 is briefly described below. When a DC voltage across (across) the smoothing capacitor C0 serving as a DC power supply is generated, a drive current is supplied to the base of the switching element Q1 through the resistor R1 to switch the switching element Q1 to a conducting state (ON state) so as to start supplying a current to the primary winding L1 of the transformer T through the switching element Q1 (in this state, the secondary winding L2 has a polarity opposite to that of the primary winding L1, so that magnetic energy is accumulated in the primary winding L1). Then, when the voltage across the resistor R4 increases to a predetermined value with an increase in current, the switching element Q2 is switched to a conductive state. Accordingly, the base of the switching element Q1 is grounded through the switching element Q2, whereby the switching element Q1 is switched to an off state. In response to the switching element Q1 being switched to the off state, the switching element Q2 is switched to the off state due to interruption of the current supplied to the resistor R4, and a back electromotive force is generated in the primary winding L1 to cause the magnetic energy accumulated in the primary winding L1 to be released to the secondary winding L2, thereby generating an induced voltage in the secondary winding L2. The magnetic energy accumulated in the primary winding L1 is also discharged to the control winding L3 to generate an induced voltage in the control winding L3, so that a drive current is supplied to the base of the switching element Q1 to switch the switching element Q1 to a conductive state. The self-oscillation operation will be repeated in this manner. The induced voltage generated in the secondary winding L2 during the off state of the switching element Q1 is rectified and boosted by the voltage doubler rectifier circuit 3B, and then applied between the discharge electrode 1 and the counter electrode 2 as the output voltage of the high voltage generation circuit 3. In the above operation, the more delayed the time at which the switching element Q1 is switched to the off state (i.e., the time at which the switching element Q2 is switched to the on state), the higher the voltage induced in the secondary winding L2; the earlier the time at which the switching element Q1 is switched to the off state (i.e., the time at which the switching element Q2 is switched to the on state), the lower the voltage induced in the secondary winding L2. That is, the output voltage of the high voltage generation circuit 3 can be adjusted by controlling the switching time (i.e., the time period of the on state) of the switching element Q1.

The output stabilization circuit 6 is specifically described below. The output stabilization circuit 6 includes a diode D1 serving as a rectifying element, a smoothing capacitor C2, a transistor Q3 serving as a control switching element Q3, two voltage-dividing resistors R6, R7, and a zener diode ZD. The cathode of the diode D1 is connected to the connection point of the control winding L3 and the capacitor C1, and the smoothing capacitor C2 is inserted between the anode of the diode D1 and the ground. The transistor Q3 is a NPN-type bipolar transistor, and has a collector connected to the base of the switching element Q1, an emitter connected to the anode of the diode D1, and a base connected to the anode of the zener diode ZD. The voltage dividing resistor R6 is interposed between the cathode of the zener diode ZD and the ground, and the voltage dividing resistor R7 is interposed between the cathode of the zener diode ZD and the emitter of the transistor Q3. Thus, when a voltage (as a reference voltage) obtained by dividing the voltage across the smoothing capacitor C2 by the voltage dividing resistors R6, R7 is larger than a resultant voltage (as a threshold voltage) obtained by adding the zener voltage of the zener diode ZD and the base-emitter voltage of the transistor Q3, the transistor Q3 is switched to the on state, and the base voltage of the switching element Q1 is lowered so that the switching element Q1 is switched to the off state.

The operation of the output stabilization circuit 6 is explained in more detail below. As described above, when the switching element Q1 is switched to the off state during the self-oscillation of the ringing choke converter 3A, a counter electromotive force is generated in the primary winding L1 in the direction indicated by the solid arrow in fig. 1, so that an induced voltage having the same polarity as the counter electromotive force is generated in the control winding L3 to supply a drive current to the switching element Q1 through the capacitance C1 and the resistor R2, thereby switching the switching element Q1 to the on state. In this process, the diode D1 remains in a non-conducting state to prevent current flow through the output stabilization circuit 6. Thus, no reference voltage is generated.

In contrast, when the switching element Q1 is in the on state, the polarity of the induced voltage generated in the control winding L3 is reversed, so that the diode D1 is placed in the on state. Thus, the induced voltage of the control winding L3 is applied to the series circuit formed by the voltage dividing resistors R6, R7 through the smoothing capacitor C2, and rectified by the diode D1 to be formed as a reference voltage. In this process, since the ground side electrode of the smoothing capacitor C2 has a high potential, the reference voltage is formed as a negative voltage without exception. The reference voltage is proportional to the induced voltage generated in the secondary winding L2. Specifically, the reference voltage increases with an increase in the induced voltage generated in the secondary winding L2 (i.e., an increase in the output voltage generated in the high-voltage generation circuit 3), and decreases with a decrease in the induced voltage generated in the secondary winding L2 (i.e., a decrease in the output voltage generated in the high-voltage generation circuit 3). That is, when the output voltage generated in the high voltage generation circuit 3 rises, the rate of increase of the reference voltage becomes higher, thereby advancing the timing at which the switching element Q3 is switched to the on state. Thereby, the time period in which the switching element Q1 is in the on state is shortened, so that the output voltage generated in the high voltage generation circuit 3 is reduced. Conversely, when the output voltage generated by the high voltage generation circuit 3 decreases, the rate of increase of the reference voltage becomes lower to delay the time at which the switching element Q3 is switched to the on state. Thereby, the period of time during which the switching element Q1 is in the ON state is prolonged, so that the output voltage generated in the high-voltage generation circuit 3 is raised. In this way, the output voltage of the high voltage generation circuit 3 can be adjusted and stabilized based on the feedback control of the output stabilization circuit 6 described above.

In the conventional electrostatic atomizer not including the output stabilization circuit 6, the time period during which the switching element Q1 is in the on state is adjusted by the switching element Q2. In this case, the switching time of the switching element Q2 depends on the base voltage of the switching element Q2, and thus there is a large fluctuation due to a temperature change, which causes a fluctuation in the output voltage of the high voltage generating circuit 3 resulting from the temperature change. In addition, since the time period during which the switching element Q1 is in the on state is adjusted based on the emitter current of the switching element Q1 (the current flowing through the primary winding L1 of the transformer T), it is difficult to sufficiently respond to load fluctuations.

In contrast, according to the electrostatic atomizer having the output stabilization circuit 6 of the first embodiment, the time period of the on state of the switching element Q1 is adjusted based on the reference voltage induced in the control winding L3 during the on state of the switching element Q1 to stabilize the output voltage of the high voltage generation circuit 3. Thus, compared with the related art that detects the output voltage of the high voltage generation circuit 3, the output voltage of the high voltage generation circuit 3 can be stabilized using circuit elements of a relatively low withstand voltage without the need to electrically insulate the primary side and the secondary side of the high voltage generation circuit 3 (transformer T). Thereby simplifying the circuit structure and stably generating nano-scale droplets. In addition, the polarity of the reference voltage is opposite to the induced voltage generated by the control winding L3 during the off state of the switching element Q1. Thus, the adjustable range of the control voltage (base voltage) applied to the control terminal (base) of the switching element Q1 can be expanded as compared with the reference voltage (i.e., positive polarity) in which the polarity of the induced voltage generated by the control winding L3 during the off state of the switching element Q1 is the same. This has an advantage that the time period of the on state of the switching element Q1 can be easily and stably adjusted. In addition, the output stabilization circuit 6 can be composed of a transistor, a resistor, a diode, and a capacitor, which is advantageous in simplifying the circuit configuration compared to a circuit configuration using a microcomputer and/or an a/D converter.

Second embodiment

As shown in fig. 3, the electrostatic atomizing device of the second embodiment of the present invention includes a discharge electrode 1, a counter electrode 2, a high voltage generating circuit 3, and an output stabilizing circuit 6, as with the electrostatic atomizing device of the first embodiment. The electrostatic atomizing device of the second embodiment is characterized by further comprising: a discharge current detection circuit 4 that detects a discharge current flowing between the discharge electrode and the counter electrodes 1, 2 via the counter electrode 2; and a control circuit 5 that controls the output of the high voltage generation circuit 3 in such a manner as to maintain a required discharge state based on the detection result of the discharge current detection circuit 4, wherein the operating power (operating power) of the control circuit 5 is obtained from a reference voltage.

Fig. 4 is a circuit diagram showing a specific circuit configuration of the electrostatic atomizing device of the second embodiment. In fig. 4, the high voltage generation circuit 3 and the output stabilization circuit 6 of the first and second embodiments are the same. Thus, the same elements or components are given the same reference numerals, and the description thereof is omitted. The control circuit 5 performs feedback control including comparing the detection voltage output (i.e., a DC voltage proportional to the discharge current) of the discharge current detection circuit 4 with a predetermined reference voltage, and adjusting the discharge current such that when the detection voltage is greater than the reference value, the switching element Q2 is switched to the on state to shorten the time period of the on state of the switching element Q1, thereby reducing the discharge current, and, when the detection voltage is equal to or less than the reference value, the switching element Q2 is switched to the off state to lengthen the time period of the on state of the switching element Q1, thereby enhancing the discharge current. The smoothing capacitor C2 of the output stabilization circuit 6 is connected to the control circuit 5, so that an induced current generated in the control current L3 of the transformer T is rectified by the diode D1, so that a direct current (reference voltage) is supplied to the control circuit 5 through the smoothing capacitor C2 and is used as operating power.

In the second embodiment, the operation power of the control circuit 5 is obtained from the reference voltage. Therefore, a power supply circuit does not need to be separately provided for the control circuit 5, which is advantageous for cost reduction.

As described above, the electrostatic atomization device of the present invention includes: a discharge electrode provided with a liquid to be electrostatically atomized; a counter electrode disposed opposite to the discharge electrode; a high voltage generating part for applying a high voltage between the discharge electrode and the counter electrode; and an output stabilizing section for stabilizing an output voltage of the high voltage generating section. In the electrostatic atomizer, the high voltage generator includes a self-oscillation type DC/DC converter provided with: a transformer having a primary winding, a secondary winding, and a control winding; and a switching element interposed between the positive and negative electrodes of the primary winding, connected in series to the DC power supply, and to which an induced voltage generated in the control winding is applied through a control terminal. The self-oscillation type DC/DC converter outputs an induced voltage generated in the secondary winding in accordance with a switching operation of the switching element to the discharge electrode. The output stabilizer adjusts a time period during which the switching element is in the on state based on a voltage induced in the control winding during the switching element is in the on state.

In the electrostatic atomizer, the output stabilizer adjusts a time period during which the switching element is in the on state based on a reference voltage induced in the control winding during which the switching element is in the on state. Therefore, compared to the prior art in which the output voltage of the high voltage generating circuit is detected to adjust and stabilize the output voltage of the high voltage generating circuit, the output voltage of the high voltage generating section can be stabilized using a circuit element of a relatively low withstand voltage without electrically insulating the primary side and the secondary side of the high voltage generating section (transformer). This enables stable generation of nano-sized droplets and simplification of the circuit structure.

Preferably, in the electrostatic atomizer, the output stabilizer compares a reference voltage induced in the control winding with a predetermined threshold voltage, and switches the switching element to the off state in response to a change in a magnitude relationship between the reference voltage and the threshold voltage. According to this feature, the output stabilizing section can be realized with a simplified circuit configuration not including a microcomputer or the like.

Preferably, the reference voltage has a polarity opposite to a polarity of a voltage induced in the control winding during the off state of the switching element. According to this feature, the polarity of the reference voltage can be set to be opposite to the polarity of the induced voltage generated by the control winding during the off state of the switching element. Therefore, in the switching operation of the control switching element, the adjustable range of the voltage (control voltage) applied to the control terminal of the switching element can be expanded as compared with the reference voltage having the same polarity of the induced voltage generated in the control winding while the switching element is in the off state. This enables easy and stable adjustment of the time period during which the switching element is in the on-state. In addition, the output stabilization circuit 6 can be composed of a transistor, a resistor, a diode, and a capacitor, which is advantageous in simplifying the circuit configuration compared to a circuit configuration using a microcomputer and/or an a/D converter.

Preferably, the output stabilizing section includes: a series circuit formed of a rectifying element and a smoothing capacitor and connected between opposite terminals of the control winding; and a control switching element that is switched to a conducting state when a voltage across the smoothing capacitor is greater than a predetermined threshold voltage, wherein the control terminal of the switching element, and one terminal of the series circuit formed by the rectifying element and the smoothing capacitor are connected to one of the terminals of the control winding, the control switching element being interposed between the control terminal of the switching element and a connection point connecting the rectifying element and the smoothing capacitor. According to this feature, the time period during which the switching element is in the on state can be easily and stably adjusted in a simplified structure.

Preferably, any circuit in the electrostatic atomizer other than the output stabilizer obtains an operating voltage from the reference voltage. According to this feature, the operating voltage of any circuit in the electrostatic atomizer, except for the output stabilizer, can be obtained from the reference voltage, so that the power supply circuit can be minimized, contributing to cost reduction.

In the present specification, an element or component described in the form of a means for performing a function is not limited to a specific structure, configuration, or arrangement disclosed in the present specification for performing the function, and may include any other suitable structure, configuration, or arrangement, such as a unit, mechanism, or component, capable of performing the function.

Industrial applicability of the invention

According to an aspect of the present invention, in a period in which a high voltage is applied from a high voltage generating portion to a discharge electrode supplied with a liquid to be electrostatically atomized, an output voltage of the high voltage generating portion is stabilized by an output stabilizing portion to cause a discharge to electrostatically atomize the liquid. The high voltage generating section includes a self-oscillation type DC/DC converter having a transformer and a switching element; and an output stabilizer that adjusts a time period during which the switching element is in the on state, based on a voltage induced in the control winding during the switching element is in the on state. The electrostatic atomization device can stably generate nanoscale droplets and simplify a circuit structure.

Claims (5)

1. An electrostatic atomizing apparatus, characterized by comprising:

a high voltage generating section that applies a high voltage to a discharge electrode supplied with a liquid to be electrostatically atomized to cause discharge; and

an output stabilizing section for stabilizing an output voltage of the high voltage generating section, wherein,

the high voltage generation section includes a self-oscillation type DC/DC converter provided with: a transformer having a primary winding, a secondary winding, and a control winding; and a switching element connected in series with the primary winding between positive and negative poles of a DC power supply and to which an induced voltage generated in the control winding is applied through a control terminal, the self-oscillation type DC/DC converter outputting to the discharge electrode an induced voltage generated in the secondary winding in response to a switching operation of the switching element; and

the output stabilizer adjusts a time period during which the switching element is in the on state based on a voltage induced in the control winding during the switching element is in the on state.

2. An electrostatically atomizing device as set forth in claim 1, wherein: the output stabilizing section compares a reference voltage induced in the control winding with a predetermined threshold voltage, and switches the switching element to an off state in response to a change in a magnitude relationship between the reference voltage and the threshold voltage.

3. An electrostatically atomizing device as set forth in claim 2, wherein: the reference voltage has a polarity opposite to a polarity of a voltage induced in the control winding during the off state of the switching element.

4. The electrostatic atomizing device according to claim 3, wherein the output stabilizing portion includes:

a series circuit formed of a rectifying element and a smoothing capacitor and connected between opposite terminals of the control winding; and

a control switching element switched to a conducting state when a voltage across the smoothing capacitor is greater than a predetermined threshold voltage, wherein,

the control terminal of the switching element and one terminal of the series circuit formed by the rectifying element and the smoothing capacitor are connected to one of the terminals of the control winding; and

the control switching element is interposed between the control terminal of the switching element and a connection point connecting the rectifying element and the smoothing capacitor.

5. The electrostatic atomizing device according to any one of claims 2 to 4, characterized in that: any circuit other than the output stabilization part obtains an operating voltage from the reference voltage.