discharge device

Abstract

The discharge device (10) includes a discharge electrode (41), a voltage application circuit (2), and a current limiting element (43). The discharge electrode (41) is arranged to face the opposite electrode (42) and is used to hold the liquid (50). The voltage application circuit (2) is electrically connected to the discharge electrode (41) and the opposite electrode (42) in such a way that the discharge electrode (41) is on the ground side. The voltage application circuit (2) applies a voltage between the discharge electrode (41) and the opposite electrode (42) to generate a discharge between the discharge electrode (41) and the opposite electrode (42). The current limiting element (43) is electrically connected to the side of the discharge electrode (41) opposite to the opposite electrode (42). The current limiting element (43) is used to limit the current flowing to the discharge electrode (41).

Description

Technical Field

[0001] The present disclosure generally relates to a discharge device, and more particularly, to a discharge device including a discharge electrode. Background Art

[0002] Patent Document 1 describes an electrostatic atomizer (discharge device) that generates water particles containing free radicals (charged water particles). The electrostatic atomizer described in Patent Document 1 includes a discharge electrode (discharge electrode), a counter electrode, and a Peltier unit (liquid supply unit). The counter electrode is positioned opposite the discharge electrode. The Peltier unit supplies water to the discharge electrode.

[0003] In the electrostatic atomizer described in Patent Document 1, a high voltage is applied between a discharge electrode and a counter electrode to generate discharge between the discharge electrode and the counter electrode, thereby atomizing water supplied to the discharge electrode to generate charged microparticle water containing radicals.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-000826 Summary of the Invention

[0007] In the field of the electrostatic atomizer described in Patent Document 1, improvement in radical generation efficiency is desired.

[0008] An object of the present disclosure is to provide a discharge device capable of improving the efficiency of generating radicals.

[0009] A discharge device according to one embodiment of the present disclosure includes a discharge electrode, a voltage application circuit, and a current limiting element. The discharge electrode is arranged to face an opposing electrode and is used to retain a liquid. The voltage application circuit is electrically connected to the discharge electrode and the opposing electrode so that the discharge electrode is on the ground side. The voltage application circuit applies a voltage between the discharge electrode and the opposing electrode to generate a discharge between the discharge electrode and the opposing electrode. The current limiting element is electrically connected to the side of the discharge electrode opposite to the opposing electrode. The current limiting element is used to limit the current flowing to the discharge electrode.

[0010] According to the discharge device according to one embodiment of the present disclosure, it is possible to improve the efficiency of generating radicals. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a block diagram of a discharge device according to an embodiment.

[0012] Figure 2 It is a perspective view of a load included in the above-mentioned discharge device.

[0013] Figure 3 The load shown above is Figure 2 X1-X1 line cross-sectional view.

[0014] Figure 4 This is a perspective view of a discharge electrode included in the above-mentioned discharge device as viewed from below.

[0015] Figure 5 : is a circuit diagram showing an example of the above-mentioned discharge device.

[0016] Figure 6 Schematic diagram showing the shape of the tip of the discharge electrode.

[0017] Figure 7A Graph schematically showing the discharge behavior of the above-mentioned discharge device.

[0018] Figure 7B This is a graph schematically showing the discharge behavior of the discharge device according to the comparative example.

[0019] Figure 8 It is a bottom view of a discharge electrode included in the discharge device according to Modification 1 of the embodiment. DETAILED DESCRIPTION

[0020] (Implementation Method)

[0021] Below, refer to Figures 1 to 8 The discharge device 10 according to this embodiment will be described.

[0022] However, the embodiments and modifications described below are merely examples of the present disclosure, and the present disclosure is not limited to the embodiments and modifications described below. Embodiments and modifications other than the embodiments and modifications described below can be modified in various ways based on design, etc., as long as they do not depart from the technical concept of the present disclosure.

[0023] In addition, each of the drawings described in the following embodiments and the like is a schematic diagram, and the ratios of the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensional ratios.

[0024] (1) Summary

[0025] First, refer to Figure 1 The outline of the discharge device 10 according to this embodiment will be described. Figure 1 It is a block diagram of the discharge device 10 according to this embodiment.

[0026] like Figure 1As shown, the discharge device 10 according to this embodiment includes a voltage application device 1, a load 4, and a liquid supply unit 5. The voltage application device 1 applies a voltage to the load 4 to generate a discharge, and includes a voltage application circuit 2 and a control circuit 3. The load 4 includes a discharge electrode 41 and a counter electrode 42. Specifically, the discharge device 10 includes the discharge electrode 41 and the voltage application circuit 2. Furthermore, the discharge device 10 includes the counter electrode 42. The counter electrode 42 is an electrode disposed so as to face the discharge electrode 41 with a gap therebetween. Specifically, the discharge electrode 41 is disposed so as to face the counter electrode 42. In the load 4, a voltage is applied between the discharge electrode 41 and the counter electrode 42, thereby generating a discharge between the two electrodes. The liquid supply unit 5 has the function of supplying a liquid 50 to the discharge electrode 41. Thus, the discharge device 10 according to this embodiment includes the voltage application circuit 2, the control circuit 3, the liquid supply unit 5, the discharge electrode 41, and the counter electrode 42. However, the discharge device 10 only needs to include the voltage application device 1 and the discharge electrode 41 as minimum components, and the counter electrode 42 and the liquid supply unit 5 may not be included in the components of the discharge device 10 .

[0027] The discharge device 10 according to this embodiment, for example, applies a voltage between the discharge electrode 41 and the counter electrode 42 while the liquid 50 is held on the discharge electrode 41 by adhering to the surface of the discharge electrode 41. This generates a discharge between the discharge electrode 41 and the counter electrode 42, and the liquid 50 held on the discharge electrode 41 is electrostatically atomized by the discharge. In other words, the discharge device 10 according to this embodiment constitutes a so-called electrostatic atomization device. In other words, the discharge device 10 electrostatically atomizes the liquid 50 held on the discharge electrode 41 by generating a discharge between the discharge electrode 41 and the counter electrode 42. In this disclosure, the liquid 50 held on the discharge electrode 41, that is, the liquid 50 to be electrostatically atomized, is simply referred to as "liquid 50."

[0028] The voltage application circuit 2 is electrically connected to the discharge electrode 41 and the counter electrode 42. Specifically, the counter electrode 42 is electrically connected to the positive terminal (positive) of the voltage application circuit 2, and the discharge electrode 41 is electrically connected to the negative terminal (ground) of the voltage application circuit 2. The voltage application circuit 2 applies a voltage between the discharge electrode 41 and the counter electrode 42. This generates a discharge in the load 4 between the discharge electrode 41 and the counter electrode 42.

[0029] Furthermore, the discharge device 10 according to the present embodiment further includes a current limiting element 43 . Figure 4This is a perspective view of the discharge electrode 41 included in the discharge device 10, viewed from below. A current limiting element 43 is electrically connected to the side of the discharge electrode 41 opposite the counter electrode 42. Specifically, the current limiting element 43 is electrically connected to a base end 412 located at one end in the longitudinal direction of the discharge electrode 41. The current limiting element 43 functions to limit the current flowing into the discharge electrode 41. This reduces the discharge energy between the discharge electrode 41 and the counter electrode 42.

[0030] In the discharge device 10 of this embodiment, free radicals are generated by generating a discharge between the discharge electrode 41 and the counter electrode 42. Free radicals not only provide the basis for sterilization, deodorization, moisture retention, freshness preservation, and bacterial inactivation, but also provide the basis for a variety of useful effects. Here, when free radicals are generated by discharge, ozone is also generated. During the discharge generated between the discharge electrode 41 and the counter electrode 42, a relatively large current may flow momentarily. Consequently, the discharge energy between the discharge electrode 41 and the counter electrode 42 increases, significantly expanding the discharge space. This promotes the reaction with atmospheric oxygen, increasing the amount of ozone generated.

[0031] As described above, in the discharge device 10 according to the present embodiment, the current (discharge current) flowing to the discharge electrode 41 is limited by the current limiting element 43. As a result, the discharge energy between the discharge electrode 41 and the counter electrode 42 can be reduced. As a result, the discharge space becomes smaller, thereby suppressing the reaction with oxygen in the atmosphere and thus suppressing the amount of ozone generated. On the other hand, the discharge space of the discharge generated between the discharge electrode 41 and the counter electrode 42 is difficult to expand, and the discharge is generated near the discharge electrode 41, thereby increasing the free radicals obtained by the reaction with water. That is, according to the discharge device 10 according to the present embodiment, the amount of free radicals generated can be increased while suppressing the amount of ozone generated, thereby achieving an improvement in the efficiency of free radical generation. In addition, the discharge energy can be reduced, so that not only the amount of ozone generated can be suppressed, but also the NO generation can be suppressed. x (For example, the amount of NO2 produced, which is a target substance for environmental standards under the Basic Environmental Law).

[0032] (2) Details

[0033] Next, refer to Figures 1 to 6 The details of the discharge device 10 according to this embodiment will be described. Figure 2 It is a perspective view of the load 4 included in the discharge device 10 . Figure 3 The load 4 is shown. Figure 2 X1-X1 line cross-sectional view. Figure 4 This is a perspective view of a discharge electrode included in the above-mentioned discharge device as viewed from below. Figure 51 is a circuit diagram showing an example of the discharge device 10 . Figure 6 Schematic diagram showing the shape of the tip of discharge electrode 41 included in discharge device 10 .

[0034] (2.1) Overall structure

[0035] like Figure 1 As shown, the discharge device 10 according to this embodiment includes a voltage applying device 1, a load 4, and a liquid supply unit 5. The voltage applying device 1 includes a voltage applying circuit 2 and a control circuit 3. The load 4 includes a discharge electrode 41 and an opposing electrode 42. The liquid supply unit 5 supplies a liquid 50 to the discharge electrode 41. Figure 1 , the shapes of the discharge electrode 41 and the counter electrode 42 are schematically shown.

[0036] The discharge electrode 41 is a rod-shaped electrode. Figure 2 and Figure 3 As shown, the discharge electrode 41 has a tip portion 411 at one end in the longitudinal direction and a base portion 412 at the other end in the longitudinal direction (the end opposite to the tip portion 411). Figure 4 As shown, the discharge electrode 41 further includes, for example, a shaft portion 413 that is continuously formed integrally with the base end portion 412 and extends toward the tip portion 411. The tip portion 411 extends in one direction (the longitudinal direction of the discharge electrode 41) relative to the base end portion 412. The discharge electrode 41 is a needle electrode in which at least the tip portion 411 is formed into a tapered shape. The so-called "tapered shape" here is not limited to a shape with a sharp tip, such as Figure 6 As shown, the shape with rounded corners at the top is also included. In addition, the shape of the top portion 411 is described in the column "(2.3) Shape of the top portion".

[0037] The counter electrode 42 is arranged to face the tip 411 of the discharge electrode 41. The counter electrode 42 is, for example, plate-shaped and has a concave portion 421 (see Figure 3The recess 421 is formed into a truncated cone shape by recessing a portion of the counter electrode 42 toward the discharge electrode 41. A boss portion 423 is integrally formed in the center of the bottom wall 4211 of the recess 421. The boss portion 423 is formed into a truncated cone shape by protruding a portion of the bottom wall 4211 of the recess 421 toward the side opposite to the discharge electrode 41. In other words, the recessed direction of the recess 421 (the direction in which the recess 421 is recessed) is opposite to the protruding direction of the boss portion 423. An opening 4232 is formed in the center of the bottom wall 4231 of the boss portion 423. The opening 4232 penetrates the bottom wall 4231 along the thickness direction of the bottom wall 4231. Here, the positional relationship between the counter electrode 42 and the discharge electrode 41 is determined so that the thickness direction of the counter electrode 42 (the direction through which the opening 4232 penetrates) is aligned with the longitudinal direction of the discharge electrode 41, and the tip 411 of the discharge electrode 41 is located near the center of the opening 4232 of the counter electrode 42. In other words, a gap (space) is ensured between the counter electrode 42 and the discharge electrode 41, at least by the opening 4232 of the protrusion 423 of the counter electrode 42. In other words, the discharge electrode 41 is positioned so as to face the counter electrode 42 across the gap, and the discharge electrode 41 and the counter electrode 42 are electrically insulated.

[0038] More specifically, as an example, the discharge electrode 41 and the counter electrode 42 are each formed as follows: Figure 2 and Figure 3 The counter electrode 42 has a shape as shown. Specifically, the counter electrode 42 includes a support portion 422 and a protrusion 423. The discharge electrode 41 and the counter electrode 42 are each held in a housing 40 made of electrically insulating synthetic resin. The support portion 422 is flat and has a concave portion 421 that is recessed in a truncated cone toward the discharge electrode 41. The bottom wall 4211 of the concave portion 421 is integrally formed with a protrusion 423 that protrudes in a truncated cone toward the side opposite the discharge electrode 41. The bottom wall 4231 of the protrusion 423 has an opening 4232 that opens in a circular shape. In this case, discharge occurs between the opening edge of the opening 4232 formed in the bottom wall 4231 of the protrusion 423 and the top end 411 of the discharge electrode 41.

[0039] like Figure 4 As shown, the base end portion 412 of the discharge electrode 41 is formed into a disk shape. The base end portion 412 has a first surface 4121 and a second surface 4122. The first surface 4121 is the surface of the base end portion 412 on the side of the tip portion 411. Figure 4 As shown, the shaft portion 413 is formed into a long cylindrical shape, and the first end portion of the shaft portion 413 (at Figure 4 The lower end portion is located at the approximate center of the first surface 4121. In addition, the second end portion of the shaft portion 413 opposite to the first end portion (in the Figure 4The middle is the upper end) through the contraction portion 4113 described later (refer to Figure 6 ) and connected to the top end 411. The second surface 4122 of the base end 412 is the surface on the side opposite to the top end 411. That is, the first surface 4121 and the second surface 4122 of the base end 412 face each other in the longitudinal direction (one direction) of the discharge electrode 41. The current limiting element 43 is formed on the second surface 4122 of the base end 412 in a manner that extends over the entire second surface 4122. Here, Figure 4 In order to easily distinguish the current limiting element 43 from the conductive member 44 described later, the current limiting element 43 is dotted with shadows. The current limiting element 43 is directly electrically connected to the base end portion 412 of the discharge electrode 41 on the side opposite to the opposing electrode 42. In more detail, the current limiting element 43 is directly electrically connected to the second surface 4122 of the base end portion 412. When viewed from the long side direction of the discharge electrode 41, the shape of the current limiting element 43 is circular. The current limiting element 43 is, for example, an insulating film made of silicon carbide oxide (SiCO). The current limiting element 43 is formed on the second surface 4122 of the base end portion 412 by, for example, chemical vapor deposition (CVD). The current limiting element 43 is, for example, a thin film with a thickness of 4 μm. In the present disclosure, "thin film" refers to a thin film with a thickness of 10 μm or less. As Figure 5 As shown, the current limiting element 43 includes a resistor 431. That is, in this embodiment, the insulating film is not used to connect the two elements (here, the discharge electrode 41 and Figure 4 The current limiting element 43 is not an electrically insulating film (a pair of Peltier elements 511 described later shown in FIG), but a film having a function as a resistor element 431 between the two elements. The resistance value of the current limiting element 43 is preferably, for example, greater than 1 MΩ and less than 900 MΩ. More preferably, the resistance value of the current limiting element 43 is preferably greater than 10 MΩ. As an example, the resistance value of the current limiting element 43 is 300 MΩ. As described above, the current limiting element 43 includes an insulating film having a function as a resistor element 431. In addition, one of the Peltier elements is grounded and connected to a high-voltage circuit.

[0040] A conductive member 44 is formed on the surface of the current limiting element 43 (the surface on the side opposite to the base end portion 412 of the discharge electrode 41) (see Figure 4When viewed from the longitudinal direction of the discharge electrode 41, the conductive member 44 has a circular shape with a diameter smaller than that of the current-limiting element 43. The conductive member 44 is, for example, a thin film. The conductive member 44 has the function of conducting a pair of Peltier elements 511, described later. In the discharge device 10 according to this embodiment, the pair of Peltier elements 511 are mechanically and electrically connected to the conductive member 44, for example, by welding. As described above, the current-limiting element 43 is a thin film. Therefore, even if the current-limiting element 43 is inserted between the discharge electrode 41 and the pair of Peltier elements 511, the cooling performance of the pair of Peltier elements 511 on the discharge electrode 41 can be maintained.

[0041] The liquid supply unit 5 supplies the electrostatic atomization liquid 50 to the discharge electrode 41. As an example, the liquid supply unit 5 is implemented using a cooling device 51, which cools the discharge electrode 41 to generate condensed water on the discharge electrode 41. Specifically, as an example, Figure 3 As shown, the cooling device 51 includes a pair of Peltier elements 511 and a pair of heat sinks 512. The pair of Peltier elements 511 are held by the pair of heat sinks 512. The cooling device 51 cools the discharge electrode 41 by energizing the pair of Peltier elements 511. The pair of heat sinks 512 are held in the housing 40 by embedding a portion of each of the pair of heat sinks 512. At least the portion of the pair of heat sinks 512 that holds the Peltier elements 511 is exposed from the housing 40 (see FIG. 1 ). Figure 3 ).

[0042] As described above, the pair of Peltier elements 511 are mechanically and electrically connected to the conductive member 44, for example, by welding. Thus, the pair of Peltier elements 511 are in contact with the discharge electrode 41 via the current limiting element 43. Furthermore, the pair of Peltier elements 511 are mechanically and electrically connected to the pair of heat sinks 512, for example, by welding. Current is supplied to the pair of Peltier elements 511 via the pair of heat sinks 512, the conductive member 44, the current limiting element 43, and the discharge electrode 41. Therefore, the cooling device 51 constituting the liquid supply unit 5 cools the entire discharge electrode 41 via the base end 412. This causes moisture in the air to condense and adhere to the surface of the discharge electrode 41 as condensed water. As a result, the liquid 50 is retained on the discharge electrode 41. In other words, the liquid supply unit 5 is configured to cool the discharge electrode 41, generating condensed water as the liquid 50 on the surface of the discharge electrode 41. With this configuration, the liquid supply unit 5 can supply the liquid 50 (condensed water) to the discharge electrode 41 using moisture in the air, and therefore, there is no need to supply and replenish the liquid to the discharge device 10 .

[0043] like Figure 1As shown, the voltage applying circuit 2 has a driving circuit 21 and a voltage generating circuit 22 that functions as a boost circuit B1. The driving circuit 21 is a circuit for driving the voltage generating circuit 22. The voltage generating circuit 22 is a circuit that receives power supply from the input unit 6 to generate a voltage (applied voltage) to be applied to the load 4. The input unit 6 is, for example, a power supply circuit that generates a DC voltage of several V to about ten V. In this embodiment, the input unit 6 is described as not being included in the components of the voltage applying device 1, but the input unit 6 may also be included in the components of the voltage applying device 1. The specific circuit structure of the driving circuit 21 and the voltage generating circuit 22 (boost circuit B1) is described in the "(2.2) Circuit structure" column.

[0044] The voltage application circuit 2 is electrically connected to the load 4 (discharge electrode 41 and counter electrode 42) (see Figure 5 ). The voltage application circuit 2 applies a high voltage to the load 4. Here, the voltage application circuit 2 is configured to use the discharge electrode 41 as the negative electrode (ground) and the counter electrode 42 as the positive electrode (positive), and to apply a high voltage between the discharge electrode 41 and the counter electrode 42. In other words, when a high voltage is applied from the voltage application circuit 2 to the load 4, a potential difference is generated between the discharge electrode 41 and the counter electrode 42, with the counter electrode 42 side being the high potential and the discharge electrode 41 side being the low potential. The so-called "high voltage" here is any voltage that is set to generate a discharge at the discharge electrode 41. As an example, it is a voltage with a peak value of about 7.0 kV. However, the high voltage applied from the voltage application circuit 2 to the load 4 is not limited to about 7.0 kV, and can be appropriately set according to, for example, the shapes of the discharge electrode 41 and the counter electrode 42, or the distance between the discharge electrode 41 and the counter electrode 42.

[0045] Here, the operating modes of the voltage application circuit 2 include two modes: a first mode and a second mode. The first mode is a mode for causing the applied voltage to increase over time and, when insulation breakdown is reached, initiates discharge to generate a discharge current. The second mode is a mode for interrupting the discharge current by, for example, controlling the control circuit 3 to terminate the discharge. In other words, the voltage application circuit 2 has two operating modes: a first mode and a second mode. The first mode is a mode for causing the applied voltage to increase over time and generate a discharge current. The second mode is a mode for interrupting the discharge current.

[0046] The control circuit 3 controls the voltage application circuit 2. During the driving period of the voltage application device 1, the control circuit 3 controls the voltage application circuit 2 so that the voltage application circuit 2 alternately repeats the first mode and the second mode. Here, the control circuit 3 switches between the first mode and the second mode according to the driving frequency so that the magnitude of the applied voltage (transformer voltage described later) applied from the voltage application circuit 2 to the load 4 periodically changes according to the driving frequency.

[0047] As a result, the magnitude of the electrical energy acting on the liquid 50 held by the discharge electrode 41 fluctuates periodically at the drive frequency, causing the liquid 50 held by the discharge electrode 41 to mechanically vibrate at the drive frequency. The voltage generating circuit 22 (boosting circuit B1) varies the magnitude of the applied voltage so that the frequency of the applied voltage fluctuation (the drive frequency) is equal to or greater than the resonant frequency (natural frequency) of the liquid 50 held by the discharge electrode 41. Furthermore, the closer the drive frequency is set to the resonant frequency of the liquid 50, the greater the amplitude of the mechanical vibration of the liquid 50 generated by the fluctuation in the magnitude of the applied voltage.

[0048] In this embodiment, the control circuit 3 controls the voltage application circuit 2 based on a monitoring target. Here, the “monitoring target” is at least one of the output current and the output voltage of the voltage application circuit 2 .

[0049] Here, as Figure 1 and Figure 5 As shown, the control circuit 3 has a voltage control circuit 31 and a current control circuit 32. The voltage control circuit 31 controls the drive circuit 21 of the voltage application circuit 2 based on the monitoring object constituted by the output voltage of the voltage application circuit 2. The control circuit 3 outputs a control signal Si1 to the drive circuit 21, and controls the drive circuit 21 through the control signal Si1. The current control circuit 32 controls the drive circuit 21 of the voltage application circuit 2 based on the monitoring object constituted by the output current of the voltage application circuit 2. That is, in this embodiment, the control circuit 3 controls the voltage application circuit 2 by monitoring both the output current and the output voltage of the voltage application circuit 2. However, there is a correlation between the output voltage (secondary side voltage) of the voltage application circuit 2 and the primary side voltage of the voltage application circuit 2, so the voltage control circuit 31 can also indirectly detect the output voltage of the voltage application circuit 2 based on the primary side voltage of the voltage application circuit 2. Similarly, there is a correlation between the output current (secondary-side current) of the voltage application circuit 2 and the input current (primary-side current) of the voltage application circuit 2. Therefore, the current control circuit 32 can also indirectly detect the output current of the voltage application circuit 2 based on the input current of the voltage application circuit 2. The specific circuit structures of the voltage control circuit 31 and the current control circuit 32 are described in the "(2.2) Circuit Structure" column.

[0050] The control circuit 3 is configured to operate the voltage application circuit 2 in the first mode if the size of the monitored object is less than a threshold value, and in the second mode if the size of the monitored object exceeds the threshold value. Specifically, before the size of the monitored object reaches the threshold value, the voltage application circuit 2 operates in the first mode, with the applied voltage increasing over time. At this point, corona discharge begins at the discharge electrode 41 due to insulation breakdown, generating a discharge current. When the size of the monitored object reaches the threshold value, the voltage application circuit 2 operates in the second mode, with the applied voltage decreasing. At this point, the potential difference between the discharge electrode 41 and the counter electrode 42 disappears, and the discharge current is interrupted by the control circuit 3 and other means. In other words, the control circuit 3 and other means detect discharge in the load 4 via the voltage application circuit 2 and eliminate (interrupt) the discharge current by decreasing the applied voltage.

[0051] Thus, during the driving period, the voltage application circuit 2 operates alternately between the first mode and the second mode, and the magnitude of the applied voltage periodically fluctuates at the driving frequency. As a result, discharge is intermittently repeated at the discharge electrode 41 .

[0052] To explain in more detail, the discharge device 10 first generates local corona discharge in the liquid 50 held at the tip 411 of the discharge electrode 41 . Immediately after the discharge starts, the discharge device 10 switches to the second mode to intermittently generate discharge between the discharge electrode 41 and the counter electrode 42 .

[0053] Figure 7A Graphs showing the discharge pattern (voltage waveform Vx1 and current waveform Ix1) of the discharge device 10 in this embodiment. Figure 7A In FIG, the horizontal axis is the time axis, the vertical axis on the left shows the output voltage of the voltage application circuit 2 (applied voltage, i.e., transformer voltage), and the vertical axis on the right shows the discharge current. The applied voltage rises and insulation breakdown occurs at the top of the liquid 50, generating a small discharge through corona discharge. When the applied voltage reaches the maximum value V1, a discharge state is formed, and then the discharge is stopped by rapidly decreasing the voltage. In addition, Figure 7B This is a graph showing a discharge behavior of a discharge device according to a comparative example, which will be described in detail later.

[0054] like Figure 7AAs shown, the magnitude of the applied voltage (transformer voltage) fluctuates periodically with a discharge cycle T1. When the drive frequency is set to "f1," the discharge cycle T1 is represented by the inverse of the drive frequency f1 (1 / f1). Furthermore, in this embodiment, for example, the magnitude of the applied voltage (transformer voltage) fluctuates within a range exceeding 0V during the drive period. Here, the minimum value V0 of the applied voltage is greater than 0V, and the magnitude of the applied voltage fluctuates between the minimum value V0 and the maximum value V1. The applied voltage increases and decreases approximately linearly over time within each discharge cycle T1.

[0055] In each discharge cycle T1, if the size of the monitored object is smaller than the threshold, that is, when the applied voltage reaches the threshold (e.g. Figure 7A The maximum value V1) and the output current reaches the threshold value (e.g. Figure 7A Before the threshold value I1 is reached, the control circuit 3 operates the voltage application circuit 2 in the first mode. Then, in each discharge cycle T1, when the magnitude of the monitored object becomes greater than the threshold value, that is, when the output current becomes greater than the threshold value, the control circuit 3 operates the voltage application circuit 2 in the second mode.

[0056] As described above, the drive frequency f1 is set to be equal to or higher than the resonant frequency fr1 (natural frequency) of the liquid 50 held on the discharge electrode 41. The resonant frequency fr1 of the liquid 50 depends on, for example, the volume (amount) of the liquid 50 and is expressed by fr1 = a × V^-0.5. "V" is the volume of the liquid 50 held on the discharge electrode 41. "a" is a proportionality factor that depends on, for example, the surface tension and viscosity of the liquid 50 held on the discharge electrode 41. Therefore, reducing the volume of the liquid 50 held on the discharge electrode 41 increases the resonant frequency fr1 of the liquid 50.

[0057] In the discharge device 10 according to this embodiment, a voltage is applied from the voltage application circuit 2 to the load 4 while liquid 50 (condensed water) is supplied to (held at) the discharge electrode 41. Consequently, a discharge occurs between the discharge electrode 41 and the counter electrode 42 in the load 4 due to the potential difference between the discharge electrode 41 and the counter electrode 42. At this time, the liquid 50 held at the discharge electrode 41 is electrostatically atomized by the discharge. As a result, a nanometer-sized charged microparticle liquid containing free radicals is generated in the discharge device 10. In other words, the discharge device 10 constitutes a so-called charged microparticle liquid generating device. The generated charged microparticle liquid is released into the surrounding area of ​​the discharge device 10 through, for example, the opening 4232 of the counter electrode 42.

[0058] (2.2) Circuit structure

[0059] Next, refer to Figure 5 A specific circuit configuration of the voltage applying device 1 will be described. Figure 5 1 is a circuit diagram schematically showing an example of the circuit configuration of the discharge device 10. Figure 5 In the figure, the input unit 6 is omitted.

[0060] The voltage applying circuit 2 includes the driving circuit 21 and the voltage generating circuit 22 as described above. Figure 5 In this example, the voltage application circuit 2 is an isolated DC / DC converter. The voltage application circuit 2 includes a boost circuit B1 that boosts the input voltage Vin (e.g., 13.8V) from the input unit 6 and outputs the boosted voltage as an output voltage. Here, the voltage generating circuit 22 functions as the boost circuit B1. The output voltage of the boost circuit B1 is applied as an applied voltage to the load 4 (the discharge electrode 41 and the counter electrode 42). Specifically, the voltage application circuit 2 applies a voltage to the load 4, causing a discharge at the discharge electrode 41.

[0061] The voltage generating circuit 22 (boosting circuit B1) includes an isolation transformer 220 (boosting transformer) having a primary coil 221, a secondary coil 222, and an auxiliary coil 223. The primary coil 221 and the auxiliary coil 223 are electrically insulated from the secondary coil 222 and magnetically coupled. One end of the secondary coil 222 is electrically connected to the counter electrode 42. Specifically, the boosting circuit B1 includes the isolation transformer (isolation transformer 220), which boosts the input voltage Vin input to the primary side (primary coil 221 side) and applies an output voltage from the secondary side (secondary coil 222 side), which is electrically connected to the load 4.

[0062] Here, the boost circuit B1 is configured to periodically vary the output voltage at a frequency greater than or equal to the resonant frequency of the liquid 50. In particular, in this embodiment, the inductance value of the secondary side (secondary coil 222 side) of the boost transformer (insulation transformer 220) is set to a magnitude that allows the output voltage to vary at a frequency greater than or equal to the resonant frequency of the liquid 50.

[0063] The "secondary-side inductance" referred to here is the effective inductance of the secondary side (secondary coil 222 side), which is obtained by multiplying the self-inductance L of secondary coil 222 by the coupling coefficient k (0-1). The value of the secondary-side inductance can be set by adjusting the core permeability, the number of turns of secondary coil 222, the length, and the cross-sectional area.

[0064] In this embodiment, the inductance of the secondary side of the step-up transformer (insulation transformer 220) is 900 mH or less. Specifically, the lower limit of the inductance of the secondary side is 50 mH or more and 900 mH or less. It is preferably 500 mH or less, and more preferably 100 mH or less.

[0065] By setting the inductance value in this manner, even when the resonant frequency of the liquid 50 is relatively high (for example, 1.5 kHz or higher), the boost circuit B1 can change the output voltage at a drive frequency higher than the resonant frequency so as to follow the resonant frequency.

[0066] Drive circuit 21 includes a transistor Q1. Drive circuit 21 is configured to supply power to primary coil 221 of isolation transformer 220 based on the switching operation of transistor Q1. In addition to transistor Q1, drive circuit 21 also includes transistors Q2 and Q3, and resistors R1 to R5. For example, transistors Q1, Q2, and Q3 are configured as npn-type bipolar transistors.

[0067] The collector of transistor Q1 is connected to primary coil 221, and the emitter of transistor Q1 is grounded via resistor R1. An input voltage Vin is applied from input unit 6 to the series circuit consisting of primary coil 221, transistor Q1, and resistor R1. The base of transistor Q1 is connected to control power supply Vcc via resistor R2. Control power supply Vcc applies a control voltage (e.g., 5.1V) to drive circuit 21.

[0068] The collectors of transistors Q2 and Q3 are connected to the base of transistor Q1. The emitters of transistors Q2 and Q3 are grounded. The base of transistor Q2 is connected to the emitter of transistor Q1 via resistor R3. The base of transistor Q1 is connected to one end of auxiliary coil 223 via a parallel circuit of resistors R4 and R5. The other end of auxiliary coil 223 is grounded. The base of transistor Q3 is connected to control circuit 3 (voltage control circuit 31 and current control circuit 32), and control signal Si1 is input to the base of transistor Q3 from control circuit 3.

[0069] With the above configuration, the voltage application circuit 2 forms a self-excited converter. Specifically, when transistor Q1 turns on, causing current to flow through the primary winding 221 of the isolation transformer 220, the voltage across resistor R1 rises, turning on transistor Q2. Consequently, the base of transistor Q1 is grounded via transistor Q2, turning off transistor Q1. When transistor Q1 turns off, the current flowing through the primary winding 221 is cut off, and the voltage across resistor R1 drops, turning off transistor Q2. Consequently, a high voltage is induced in the secondary winding 222 of the isolation transformer 220, which is applied to the load 4 as the output voltage of the voltage application circuit 2. At this time, the induced voltage generated in the secondary winding 222 also induces a voltage in the auxiliary winding 223, increasing the base-emitter voltage of transistor Q1, turning on transistor Q1. By repeating the above operation, the voltage application circuit 2 boosts the input voltage Vin and applies the output voltage to the load 4.

[0070] like Figure 5 As shown, the control circuit 3 includes a voltage control circuit 31 and a current control circuit 32 .

[0071] The voltage control circuit 31 includes a diode D1, a resistor R6, a capacitor C1, and a Zener diode ZD1. The anode of diode D1 is connected to the junction of auxiliary coil 223 and resistors R4 and R5. The cathode of diode D1 is connected to one end of capacitor C1 via resistor R6. The other end of capacitor C1 is grounded. Furthermore, the cathode of Zener diode ZD1 is connected to one end of capacitor C1 (the junction with resistor R6). The anode of Zener diode ZD1 is connected to the base of transistor Q3 as the output terminal of the voltage control circuit 31.

[0072] According to the above configuration, the voltage control circuit 31 indirectly monitors the output voltage of the voltage application circuit 2 (the induced voltage of the secondary coil 222) by monitoring the induced voltage of the auxiliary coil 223. Specifically, while the output voltage of the voltage application circuit 2 is below the threshold (maximum value V1), the Zener diode ZD1 of the voltage control circuit 31 is turned off. On the other hand, when the output voltage of the voltage application circuit 2 exceeds the threshold (maximum value V1), the Zener diode ZD1 of the voltage control circuit 31 turns on. At this time, the control signal Si1 exceeds the control threshold, applying a voltage between the base and emitter of transistor Q3, turning on transistor Q3. This causes the base current of transistor Q1 to flow to ground via transistor Q3, reducing the collector current of transistor Q1. Therefore, when the output voltage of the voltage application circuit 2 is above the threshold (maximum value V1), the voltage control circuit 31 reduces the switching energy of the driver circuit 21 of the voltage application circuit 2.

[0073] The current control circuit 32 includes an operational amplifier OP1, a reference voltage generator 321, resistors R7 to R11, and capacitors C2 and C3. One end of capacitor C2 is connected to a control power supply Vcc via resistor R7. The other end of capacitor C2 is grounded. The control power supply Vcc applies a control voltage (e.g., 5.1V) to the series circuit of resistor R7 and capacitor C2. The connection point between resistor R7 and capacitor C2 (one end of capacitor C2) is connected to the inverting input terminal of the operational amplifier OP1 via resistor R8. Furthermore, the connection point between resistor R7 and capacitor C2 (one end of capacitor C2) is connected to the end (the other end) of the secondary coil 222 of the isolation transformer 220 on the side opposite to the counter electrode 42. In other words, the control power supply Vcc is connected to the counter electrode 42 via resistor R7 and the secondary coil 222. The reference voltage generator 321 is connected to the non-inverting input terminal of the operational amplifier OP1, and the reference voltage is input from the reference voltage generator 321 to the non-inverting input terminal of the operational amplifier OP1. A series circuit of resistor R9 and capacitor C3 is connected between the inverting input terminal and the output terminal of operational amplifier OP1. One end of resistor R10 is connected to the output terminal of operational amplifier OP1. The other end of resistor R10 is grounded via resistor R11. The connection point between resistors R10 and R11 (the other end of resistor R10) serves as the output terminal of current control circuit 32 and is connected to the base of transistor Q3.

[0074] According to the above configuration, the current control circuit 32 monitors the output current (induced voltage in the secondary coil 222) of the voltage application circuit 2, which is the monitored object, by monitoring the induced current in the secondary coil 222. Specifically, while the output current of the voltage application circuit 2 is less than the threshold, the output of the operational amplifier OP1 of the current control circuit 32 is at an L level (low level). When the output current of the voltage application circuit 2 exceeds the threshold, the output of the operational amplifier OP1 of the current control circuit 32 becomes an H level (high level). At this time, the control signal Si1 exceeds the control threshold, applying a voltage between the base and emitter of transistor Q3, turning on transistor Q3. This causes the base current of transistor Q1 to flow to ground through transistor Q3, reducing the collector current of transistor Q1. Therefore, when the output current of the voltage application circuit 2 is above the threshold, the current control circuit 32 reduces the energy input from the driver circuit 21 of the voltage application circuit 2 to the voltage generating circuit 22.

[0075] (2.3) Shape of the top end

[0076] Next, refer to Figure 6 The shape of the top end portion 411 of the discharge electrode 41 will be described. Figure 6In the figure, in order to easily distinguish the tip portion 411 from the Taylor cone 501 formed at the tip portion 411 , the Taylor cone 501 is dotted.

[0077] like Figure 6 As shown, the shape of the tip portion 411 of the discharge electrode 41 is, for example, a shape including a conical portion. The shape of the portion of the tip portion 411 facing the counter electrode 42 (here, the shape of the tip of the conical portion) is, for example, an R-shape. In other words, the portion of the tip portion 411 opposite the base end 412 is R-shaped.

[0078] The tip portion 411 includes a first portion 4111 and a second portion 4112. The first portion 4111 is a portion of the tip portion 411 that is closer to the base end 412 than the second portion 4112 and has a cylindrical shape. The second portion 4112 is a portion of the tip portion 411 that is farther from the base end 412 than the first portion 4111 and has a conical shape. In short, the tip portion 411 includes the first portion 4111, which corresponds to the cylindrical portion, and the second portion 4112, which corresponds to the conical portion.

[0079] The first portion 4111 and the second portion 4112 are arranged in this order from the base end portion 412 side in the longitudinal direction of the discharge electrode 41. Figure 6 As shown, the shape of the second portion 4112 is preferably approximately conical, but is not limited thereto. The shape of the second portion 4112 may also be a curved shape such as a protrusion toward the opposing electrode 42. Specifically, it may be hemispherical or bell-shaped. In addition, in the top portion 411 of the present embodiment, the shape is obtained by combining the second portion 4112 (conical portion) with the first portion 4111 (cylindrical portion) having a shape different from that of the second portion 4112. For example, the top portion 411 may omit the first portion 4111 and be composed of only a portion of a single shape (e.g., a conical portion) as a whole.

[0080] In addition, in this embodiment, as an example, a contraction portion 4113 is provided between the top portion 411 and the shaft portion 413. That is, the top portion 411 and the shaft portion 413 are connected via the contraction portion 4113. The contraction portion 4113 is formed into a cone whose diameter becomes smaller as it approaches the shaft portion 413 from the end edge 4114 of the top portion 411. By providing the contraction portion 4113, it is possible to suppress the remaining condensed water generated on the shaft portion 413 side from merging with the condensed water (Taylor cone) on the top portion 411 side. In addition, in order to obtain the same effect of suppressing merging, an extension portion having a large diameter in a manner extending radially relative to both the top portion 411 and the shaft portion 413 may be provided between the top portion 411 and the shaft portion 413 instead of the contraction portion 4113. In addition, a step portion may be provided between the top portion 411 and the shaft portion 413 instead of the conical contraction portion 4113.

[0081] The maximum diameter of the top portion 411 including the conical portion is equal to the maximum diameter D11 of the first portion 4111 (hereinafter, the maximum diameter of the top portion 411 is also referred to as "maximum diameter D11"). The maximum diameter D11 of the top portion 411 is preferably, for example, not less than 0.35 mm and not more than 1.5 mm. As an example, the maximum diameter D11 of the top portion 411 is 0.710 mm. As an example, the top angle θ1 of the second portion 4112 is 47.580°. In addition, as an example, the total length L1 of the top portion 411 (the length dimension of the top portion 411 in the long side direction of the discharge electrode 41) is 0.830 mm. Here, as an example, Figure 6 As shown, the total length L1 of the tip portion 411 is defined as the length from the end edge 4114 on the base end 412 side of the substantially cylindrical portion having the maximum diameter D11 of the first portion 4111 as a diameter to the tip of the second portion 4112. If the first portion 4111 is omitted, the total length L1 of the tip portion 411 is the length of the second portion 4112.

[0082] Here, when the maximum diameter D11 of the tip portion 411 is 1.5 mm, the ratio of the total length L1 of the tip portion 411 to the maximum diameter D11 of the tip portion 411 is 1.6. Furthermore, when the maximum diameter D11 of the tip portion 411 is 0.35 mm, the ratio of the total length L1 of the tip portion 411 to the maximum diameter D11 of the tip portion 411 is 1.0. That is, in the discharge device 10 according to this embodiment, the ratio of the total length L1 of the tip portion 411 in one direction (the longitudinal direction of the discharge electrode 41) to the maximum diameter D11 of the tip portion 411 (hereinafter also referred to as the "first ratio") is greater than 1.0 and less than 1.6. In other words, the total length L1 of the tip portion 411 in one direction is greater than or equal to the maximum diameter D11 of the tip portion 411. For example, when the maximum diameter D11 of the tip portion 411 is 0.710 mm and the total length L1 of the tip portion 411 is 0.830 mm, the first ratio is 1.169. As described above, if the first ratio is greater than 1.0 and less than 1.6, the volume of liquid 50 forming Taylor cone 501 can be reduced, resulting in a higher resonant frequency of liquid 50. This reduces the discharge energy between discharge electrode 41 and counter electrode 42, resulting in a smaller discharge space. This suppresses reactions with atmospheric oxygen and reduces ozone generation. Furthermore, by generating the discharge between discharge electrode 41 and counter electrode 42 at a high frequency, the discharge space between discharge electrode 41 and counter electrode 42 is less likely to expand, allowing the discharge to occur near discharge electrode 41, thereby increasing the number of free radicals generated by the reaction with water. In other words, the discharge device 10 according to this embodiment can increase the amount of free radicals generated while suppressing ozone generation, thereby improving the efficiency of free radical generation.

[0083] Furthermore, by applying a voltage between the discharge electrode 41 and the counter electrode 42, a Taylor cone 501 is formed at the tip 411 of the discharge electrode 41 by the liquid 50 held in the discharge electrode 41. Figure 6 As shown, the Taylor cone 501 has a conical shape that follows the conical portion of the tip 411 of the discharge electrode 41. The second portion 4112 of the tip 411 of the discharge electrode 41 enters the Taylor cone 501. That is, in the discharge device 10 according to this embodiment, the second portion 4112 constitutes the portion of the tip 411 that enters the Taylor cone 501.

[0084] Furthermore, as described above, in order to increase the resonant frequency of the liquid 50 forming the Taylor cone 501, the ratio of the volume of the second portion 4112 of the tip 411 of the discharge electrode 41 to the volume of the Taylor cone 501 (hereinafter also referred to as the "second ratio") is preferably 0.6 or more and 0.95 or less. For example, when the volume of the Taylor cone 501 is 0.0917 mm3 And the volume of the second portion 4112 is 0.0650mm 3 , the second ratio is 0.71. For example, without the aforementioned shape, the volume of liquid 50 forming the Taylor cone 501 is 0.23 μL, and the resonant frequency of liquid 50 is 1 kHz. In contrast, with the aforementioned shape of this embodiment, the volume of liquid 50 forming the Taylor cone 501 is 0.076 μL, and the resonant frequency of liquid 50 is 3 kHz. In this way, by reducing the volume of liquid 50 forming the Taylor cone 501, the resonant frequency of liquid 50 can be increased.

[0085] In the discharge device 10 according to this embodiment, as described above, the second portion 4112 of the tip 411 of the discharge electrode 41 enters the Taylor cone 501. In this case, the outer periphery 502 of the Taylor cone 501 is preferably located between the first position and the second position. The outer periphery 502 of the Taylor cone 501 is the portion of the Taylor cone 501 that is farthest from the counter electrode 42 in the direction in which the discharge electrode 41 and the counter electrode 42 are arranged. Figure 6 In the example shown, the outer edge 502 of the Taylor cone 501 is annular when viewed from the longitudinal direction of the discharge electrode 41. The first position is a position at a distance from the tip of the tip portion 411 of 0.62 times the total length L1 of the tip portion 411. The second position is a position at a distance from the tip of the tip portion 411 of 1.00 times the total length L1 of the tip portion 411. For example, as described above, when the total length L1 of the tip portion 411 is 0.830 mm, the outer edge 502 of the Taylor cone 501 is located between a position at a distance of 0.515 mm from the tip of the tip portion 411 (the first position) and a position at a distance of 0.830 mm from the tip of the tip portion 411 (the second position).

[0086] (2.4) Improvement of discharge times

[0087] Below, refer to Figure 7A and Figure 7B The improvement in the number of discharges in the discharge device 10 according to this embodiment will be described.

[0088] As described above, by varying the magnitude of the applied voltage to the load 4, that is, the output voltage (transformer voltage), at the drive frequency (discharge frequency), the magnitude of the electrical energy acting on the liquid 50 held by the discharge electrode 41 is periodically varied at the drive frequency. As a result, the liquid 50 mechanically vibrates at the drive frequency. Furthermore, if the drive frequency is set to be higher than the resonant frequency of the liquid 50, the amplitude of the mechanical vibration of the liquid 50 generated by the variation in the magnitude of the applied voltage becomes relatively large. When the amplitude of the liquid 50 increases, the Taylor cone 501 (see FIG. 1 ) is formed. Figure 6) has a more pointed (sharp) shape, making it easier to discharge.

[0089] Furthermore, in the discharge device 10, after the discharge starts, the voltage is reduced in the second mode to stop the sustained discharge generated by the corona discharge, thereby stopping the sustained discharge that tends to generate ozone. By repeating this discharge at a high speed, that is, by increasing the driving frequency, a large amount of free radicals can be generated while suppressing the increase of ozone.

[0090] As described above, the resonant frequency of the liquid 50 depends on the volume of the liquid 50 held by the discharge electrode 41. Furthermore, by setting the shape of the tip portion 411 of the discharge electrode 41 as described above, the volume of the liquid 50 held by the discharge electrode 41 is reduced, thereby increasing the resonant frequency of the liquid 50. For example, if the resonant frequency of the liquid held by a discharge electrode without the aforementioned shape is 1 kHz, the resonant frequency of the liquid 50 held by the discharge electrode 41 with the aforementioned shape is 1.5 kHz or higher (e.g., 3 kHz). By increasing the drive frequency to 1.5 kHz or higher (e.g., if the resonant frequency is 3 kHz, the drive frequency is 3 kHz to 5 kHz) to follow the increase in the resonant frequency to 1.5 kHz or higher, the amplitude of the mechanical vibration of the liquid 50 increases, thereby improving discharge efficiency.

[0091] On the other hand, in order to increase the drive frequency in a manner that can track the resonant frequency increasing above 1.5kHz, the transformer voltage in the first mode needs to be rapidly increased to a threshold value (maximum value V1). Furthermore, when the aforementioned sustained discharge generated by corona discharge continues, it may be impossible to form a new atomizing discharge, and the next atomizing discharge must be generated after the sustained discharge is stopped. To stop the sustained discharge, the transformer voltage needs to be lowered, or the tip of the Taylor cone 501 formed by the transformer voltage needs to be softened, and the rate of reduction of the transformer voltage needs to be increased.

[0092] Therefore, in this embodiment, in order to increase the speed of rising and falling of the transformer voltage, the value of the inductance on the secondary side of the step-up transformer (insulation transformer 220 ) is set to 900 mH or less.

[0093] Figure 7B Graph showing the discharge behavior (voltage waveform Vx1 and current waveform Ix1) of the discharge device of the comparative example. Figure 7B In, also with Figure 7A Similarly, the horizontal axis represents the time axis, the left vertical axis represents the output voltage of the voltage application circuit (applied voltage, ie, transformer voltage), and the right vertical axis represents the discharge current. Figure 7B The maximum value V2 (threshold) of the transformer voltage shown in FIG is set to Figure 7AThe maximum value V1 (threshold) of the transformer voltage shown in is the same, but it can also be different from the maximum value V1. Figure 7B The discharge current threshold value I2 shown in FIG is set to Figure 7A The threshold value I1 of the discharge current shown in is the same as that of , but may be different from the threshold value I1. Figure 7A and Figure 7B The time scale of the horizontal axis is set to be the same.

[0094] In the discharge device of the comparative example, the inductance value of the secondary side of the step-up transformer is set to, for example, 3000 mH. However, the aforementioned shape of the tip portion 411 of the discharge electrode 41 is employed to increase the resonant frequency of the liquid 50. While it would have been desirable to increase the drive frequency in accordance with the increased resonant frequency, in the comparative example with the inductance value set to 3000 mH, the time taken to increase the voltage to the maximum value V2 is slow, and the time taken to decrease the voltage to the minimum value V0 is also slow, resulting in a drive frequency f2 of approximately 1 kHz. As a result, the discharge period T2 in the comparative example is longer than the discharge period T1.

[0095] On the other hand, the discharge device 10 of this embodiment, set to 900 mH or less, increases the voltage to the maximum value V1 faster than the discharge device of the comparative example, and also decreases the voltage to the minimum value V0 faster. In the illustrated example, the discharge cycle T1 is approximately half the discharge cycle T2. In other words, the number of discharges performed by the discharge device 10 within a predetermined period is approximately twice that of the discharge device of the comparative example.

[0096] As described above, the step-up transformer (insulating transformer 220) of this embodiment, in which the secondary-side inductance is set to 900 mH or less, is configured to periodically vary the output voltage at a frequency equal to or higher than the resonant frequency of the liquid 50. This increases the number of discharges by the discharge device 10, and as a result, improves the efficiency of generating free radicals.

[0097] In particular, in discharge device 10, by shortening discharge cycle T1, although the discharge energy generated per discharge is less than that generated per discharge by the discharge device of the comparative example, the number of discharges is increased, thereby achieving an increase in the amount of free radicals generated and a reduction in the amount of ozone generated. Furthermore, by reducing the discharge energy generated per discharge, it is also possible to suppress the increase in NO2 generation that would otherwise occur with an increase in discharge energy.

[0098] (2.5) Action

[0099] in the case of Figure 5 In the circuit configuration as illustrated, the discharge device 10 causes discharge with suppressed energy to occur between the discharge electrode 41 and the counter electrode 42 by operating the control circuit 3 as follows.

[0100] That is, the control circuit 3 monitors the output voltage of the voltage applying circuit 2 before the insulation breakdown occurs, and when the output voltage of the monitored object reaches a threshold value (eg Figure 7A When the maximum value V1 of the voltage application circuit 2 is exceeded, the switching energy of the drive circuit 21 is reduced by the voltage control circuit 31. On the other hand, after the insulation breakdown occurs, the control circuit 3 monitors the output current of the voltage application circuit 2. When the output current of the monitored object reaches a threshold value (for example, Figure 7A When the voltage drops to a threshold value I1 (i.e., the voltage drop), the current control circuit 32 stops the switching operation of the drive circuit 21. As a result, the voltage application circuit 2 operates in the second mode, which reduces the transformer voltage, causing the load 4 to be overloaded relative to the voltage application circuit 2 and thereby cutting off the discharge current. In other words, the operating mode of the voltage application circuit 2 switches from the first mode to the second mode.

[0101] At this point, the output voltage and output current of the voltage application circuit 2 both decrease, so the control circuit 3 restarts the switching operation of the drive circuit 21. As a result, the voltage application circuit 2 operates in the first mode, in which the applied voltage increases over time to generate discharge. In other words, the operating mode of the voltage application circuit 2 switches from the second mode to the first mode.

[0102] By repeating the above-described operation by the control circuit 3, the voltage application circuit 2 operates alternately between the first mode and the second mode. As a result, the discharge at the discharge electrode 41 is switched between on and off. Furthermore, the voltage application circuit 2 of this embodiment can achieve output voltage fluctuations at a drive frequency that is greater than the resonant frequency of the liquid 50.

[0103] (3) Modification

[0104] The above embodiment is merely one of various embodiments of the present disclosure. As long as the above embodiment can achieve the purpose of the present disclosure, various modifications can be made according to design, etc. Below, examples of modifications of the above embodiment are listed. The modifications described below can be appropriately combined and applied.

[0105] (3.1) Modification 1

[0106] Figure 8 FIG1 is a bottom view of the discharge electrode 41 included in the discharge device according to Modification 1. In the above embodiment, the conductive member 44 for conducting the pair of Peltier elements 511 is circular when viewed from the longitudinal direction of the discharge electrode 41. However, this is not limiting. For example, the conductive member 44 may be circular. Figure 8As shown in FIG. 4 , the conductive member 44B is rectangular when viewed from the longitudinal direction of the discharge electrode 41. In this case, the width dimension ( Figure 8 The vertical dimension of each Peltier element 511 is Figure 8 The conductive member 44B is preferably the same as the vertical dimension of the Peltier elements 511, but may also be larger than the width of each Peltier element 511. In this case, the conductive member 44B is preferably a thin film. Furthermore, the conductive member may have an elliptical shape, for example, when viewed from the longitudinal direction of the discharge electrode 41. In other words, the conductive member may have any shape as long as it allows for electrical conduction between the pair of Peltier elements 511.

[0107] (3.2) Modification 2

[0108] In the above embodiment, the upper limit of the maximum diameter D11 of the tip 411 of the discharge electrode 41 is 0.71 mm, but this is not limiting. The upper limit of the maximum diameter D11 of the tip 411 of the discharge electrode 41 may be, for example, 0.600 mm. In other words, the maximum diameter D11 of the tip 411 of the discharge electrode 41 may be, for example, 0.600 mm or less. Furthermore, the maximum diameter D11 of the tip 411 of the discharge electrode 41 is preferably 0.500 mm or greater, for example. In this case, the volume of the liquid 50 forming the Taylor cone 501 can be further reduced, resulting in a higher resonant frequency of the liquid 50. This further reduces the discharge energy between the discharge electrode 41 and the counter electrode 42. As a result, the discharge space is further reduced, thereby suppressing reactions with atmospheric oxygen and further reducing the amount of ozone generated. Furthermore, by generating the discharge between the discharge electrode 41 and the counter electrode 42 at a higher frequency, the number of free radicals generated by the reaction with water can be further increased. That is, the discharge device 10 according to this embodiment can further increase the amount of free radicals generated while further suppressing the amount of ozone generated, thereby further improving the efficiency of free radical generation. In this case, it is more preferable that the maximum diameter D11 of the tip 411 of the discharge electrode 41 is 0.550 mm or less. In other words, it is more preferable that the maximum diameter D11 of the tip 411 of the discharge electrode 41 is 0.500 mm or more and 0.550 mm or less.

[0109] (3.3) Other variations

[0110] The liquid supply unit 5 is not limited to a configuration that cools the discharge electrode 41 to generate condensed water. The liquid supply unit 5 may also be configured to supply the liquid 50 from a tank to the discharge electrode 41 using, for example, capillary action or a supply mechanism such as a pump. Furthermore, the liquid 50 is not limited to water (condensed water) and may be a liquid other than water.

[0111] Figure 5 This is merely an example of the circuit configuration of the discharge device 10 ; the specific circuit configuration of the voltage application device 1 can be modified as appropriate. For example, the voltage application circuit 2 is not limited to a self-excited converter; it can also be a separately excited converter. Furthermore, in the voltage application circuit 2 , the transistors Q1 , Q2 , and Q3 are not limited to bipolar transistors; for example, they can also be MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors). Furthermore, the voltage generating circuit 22 can also be implemented as a transformer (transformer) having a piezoelectric element.

[0112] The current limiting element 43 is not limited to the resistor 431 and may include a capacitor. In other words, the current limiting element 43 only needs to include at least one of the resistor 431 and the capacitor.

[0113] The current-limiting element 43 is not limited to an insulating film composed of silicon carbide oxide; for example, it may be a nickel (Ni) oxide film (NiO). In this case, the nickel oxide film of the current-limiting element 43 is formed, for example, by applying a nickel paste to the second surface 4122 of the base end portion 412 of the discharge electrode 41 and then sintering the applied nickel paste. Alternatively, the current-limiting element 43 may be an insulating film composed of diamond-like carbon (DLC). Alternatively, the current-limiting element 43 may be an insulating film composed of aluminum nitride (AlN). Alternatively, the current-limiting element 43 may be a titanium (Ti) oxide film (TiO). Alternatively, the current-limiting element 43 may be formed of a sintered material with high thermal conductivity. Alternatively, the current-limiting element 43 may be a bonded product formed by bonding two copper (Cu) sheets using epoxy resin (EP) as an adhesive, or a bonded product formed by bonding two copper sheets using aluminum oxide (AlO3 or Al2O3) as an adhesive.

[0114] In a comparison between two values, such as a monitored object and a threshold, the term "above" includes both the case where the two values ​​are equal and the case where one value exceeds the other. However, this is not limiting; "above" here can also have the same meaning as "greater than," which only includes the case where one value exceeds the other. In other words, whether or not the two values ​​are equal can be arbitrarily changed based on the setting of the threshold, etc., so there is no technical difference between "above" and "greater than." Similarly, "less than" can also have the same meaning as "below."

[0115] Alternatively, needle-shaped protrusions may be provided on the counter electrode 42, and a pilot discharge that progresses from corona discharge to strong discharge may be used to intermittently generate insulation breakdown (full-circuit breakdown). In this case, multiple needle-shaped portions may be arranged at equal intervals around the circumference of the opening 4232. Each needle-shaped portion may protrude from the inner peripheral edge of the opening 4232 toward the center of the opening 4232. Each needle-shaped portion may also protrude obliquely from the inner peripheral edge of the opening 4232 in such a manner that the closer to the tip, the shorter the distance to the discharge electrode 41 in the longitudinal direction of the discharge electrode 41. By forming each needle-shaped portion into such a shape, electric field concentration is easily generated at the tip of each needle-shaped portion. As a result, a stable discharge is easily generated between the tip of each needle-shaped portion and the tip 411 of the discharge electrode 41.

[0116] (Way)

[0117] Based on the above-described embodiment and modified examples, the following aspects are disclosed.

[0118] The discharge device (10) involved in the first embodiment includes a discharge electrode (41), a voltage application circuit (2), and a current limiting element (43). The discharge electrode (41) is arranged to face the opposite electrode (42). The voltage application circuit (2) is electrically connected to the discharge electrode (41) and the opposite electrode (42) in such a manner that the discharge electrode (41) is on the ground side. The voltage application circuit (2) applies a voltage between the discharge electrode (41) and the opposite electrode (42) to generate a discharge between the discharge electrode (41) and the opposite electrode (42). The current limiting element (43) is electrically connected to the side of the discharge electrode (41) opposite to the opposite electrode (42). The current limiting element (43) is used to limit the current flowing to the discharge electrode (41).

[0119] According to this aspect, the efficiency of generating radicals can be improved.

[0120] Regarding the discharge device (10) according to the second aspect, in the first aspect, the current limiting element (43) includes at least one of a resistance element (431) and a capacitance element.

[0121] According to this aspect, the efficiency of generating radicals can be improved.

[0122] The discharge device (10) according to the third embodiment, in the first embodiment or the second embodiment, further comprises a liquid supply unit (5). The liquid supply unit (5) supplies electrostatic atomization liquid (50) to the discharge electrode (41). The liquid supply unit (5) includes a Peltier element (511). The Peltier element (511) is thermally coupled to the discharge electrode (41) via a current limiting element (43).

[0123] According to this embodiment, the liquid (50) can be supplied to the discharge electrode (41) through the liquid supply portion (5) while achieving improvement in the efficiency of generating free radicals.

[0124] Regarding the discharge device (10) according to the fourth aspect, in the third aspect, the current limiting element (43) is a thin film.

[0125] According to this embodiment, the liquid (50) can be supplied to the discharge electrode (41) through the liquid supply portion (5) while improving the efficiency of generating free radicals through the current limiting element (43).

[0126] Regarding the discharge device (10) according to the fifth aspect, in any one of the first to fourth aspects, the resistance value of the current limiting element (43) is 1 MΩ or more.

[0127] According to this aspect, the efficiency of generating radicals can be improved.

[0128] A discharge device (10) according to a sixth aspect is, in any one of the first to fifth aspects, further comprising a counter electrode (42).

[0129] According to this embodiment, the generation efficiency of free radicals can be improved by the discharge generated between the discharge electrode (41) and the counter electrode (42).

[0130] Regarding the discharge device (10) involved in the seventh aspect, in any one of the first to sixth aspects, the liquid (50) held by the discharge electrode (41) is electrostatically atomized by the above-mentioned discharge.

[0131] According to this aspect, it is possible to generate charged fine particle water containing free radicals while achieving improvement in the generation efficiency of free radicals.

[0132] The structures involved in the second to seventh aspects are not essential structures of the discharge device (10) and can be omitted as appropriate.

[0133] Description of Reference Numerals

[0134] 2: voltage application circuit; 5: liquid supply unit; 10: discharge device; 41: discharge electrode; 42: counter electrode; 43: current limiting element; 431: resistor; 50: liquid; 511: Peltier element.

Claims

1. A discharge device comprising: a discharge electrode disposed to face the opposing electrode and configured to hold the liquid; a voltage applying circuit electrically connected to the discharge electrode and the counter electrode in such a manner that the discharge electrode is on the ground side, the voltage applying circuit applying a voltage between the discharge electrode and the counter electrode to generate a discharge between the discharge electrode and the counter electrode; a current limiting element electrically connected to a side of the discharge electrode opposite to the opposing electrode side, for limiting a current flowing to the discharge electrode; as well as a liquid supply unit for supplying liquid for electrostatic atomization to the discharge electrode; The liquid supply unit includes a Peltier element, and the Peltier element is thermally coupled to the discharge electrode via the current limiting element.

2. The discharge device according to claim 1, wherein The current limiting element includes at least one of a resistance element and a capacitance element.

3. The discharge device according to claim 1, wherein The current limiting element is a thin film.

4. The discharge device according to any one of claims 1 to 3, wherein: The resistance value of the current limiting element is 1 MΩ or more.

5. The discharge device according to any one of claims 1 to 3, wherein: The counter electrode is further provided.

6. The discharge device according to any one of claims 1 to 3, wherein: The liquid held on the discharge electrode is electrostatically atomized by the discharge.

7. The discharge device according to any one of claims 1 to 3, wherein: The current limiting element is electrically connected between a side of the discharge electrode opposite to the counter electrode and the ground.

Images