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) and the counter electrode (42) are arranged facing each other and are filled with liquid (50). The voltage application circuit (2) is electrically connected to the discharge electrode (41) and the counter electrode (42) in such a way that the discharge electrode (41) is grounded. The voltage application circuit (2) generates a discharge between the discharge electrode (41) and the counter electrode (42) by applying a voltage between them. The current limiting element (43) is electrically connected to the side of the discharge electrode (41) opposite to the side of the counter electrode (42). The current limiting element (43) limits the current flowing to the discharge electrode (41).

Description

Technical Field

[0001] This disclosure generally relates to a discharge device, and more specifically to a discharge device having discharge electrodes. Prior Technology

[0002] Background Technology

[0003] Patent Document 1 describes an electrostatic atomizing device (discharge device) that generates water microparticles containing free radicals (charged water microparticles). The electrostatic atomizing device described in Patent Document 1 includes a discharge electrode, a counter electrode, and a Peltier unit (liquid supply unit). The counter electrode is located opposite the discharge electrode. The Peltier unit supplies water to the discharge electrode.

[0004] In the electrostatic atomization device described in Patent Document 1, a discharge is generated by applying a high voltage between the discharge electrode and the counter electrode, which atomizes the water supplied to the discharge electrode and produces charged microparticle water containing free radicals. [Preliminary Technology Documents]

[0005] [Patent Literature] Patent Document 1: Japanese Patent Application Publication No. 2006-000826 Summary of the Invention

[0006] Invention Summary

[0007] In the field of electrostatic atomization devices described in Patent Document 1, there is a desire to improve the efficiency of free radical generation.

[0008] The purpose of this disclosure is to provide a discharge device that can improve the efficiency of free radical generation.

[0009] The disclosed discharge device includes a discharge electrode, a voltage application circuit, and a current limiting element. The discharge electrode is disposed opposite to a counter electrode and is held in liquid. The voltage application circuit is electrically connected to both the discharge electrode and the counter electrode in such a way that the discharge electrode is grounded. The voltage application circuit generates a discharge between the discharge electrode and the counter electrode by applying a voltage between them. The current limiting element is electrically connected to the side of the discharge electrode opposite to the counter electrode side. The current limiting element limits the current flowing through the discharge electrode.

[0010] According to the discharge device disclosed herein, the efficiency of free radical generation can be improved. Simple Explanation of the Diagram

[0011] Figure 1 is a block diagram of the discharge device in an embodiment.

[0012] Figure 2 is a perspective view of the load provided by the same discharge device as above.

[0013] Figure 3 is a cross-sectional view along line X1-X1 of Figure 2 showing the same load as above.

[0014] Figure 4 is a perspective view of the discharge electrodes of the same discharge device as above, viewed from below.

[0015] Figure 5 is a circuit diagram showing one example of the discharge device described above.

[0016] Figure 6 is a schematic diagram showing the shape of the front end of the discharge electrode as described above.

[0017] Figure 7A is a diagram that schematically shows the discharge pattern of the same discharge device as above.

[0018] Figure 7B is a diagram that schematically shows the discharge pattern of the discharge device of the comparative example.

[0019] Figure 8 is a bottom view of the discharge electrodes of the discharge device in Modified Example 1 of the embodiment. Implementation

[0020] (Implementation Mode)

[0021] The discharge device 10 of this embodiment will be described below with reference to Figures 1 to 8.

[0022] However, the embodiments and modifications described below are merely examples of this disclosure, and the present invention is not limited to the embodiments and modifications described below. Even in addition to the embodiments and modifications described below, various changes can be made according to design and other factors as long as they do not depart from the technical concept of this disclosure.

[0023] Furthermore, the figures described in the following embodiments are all schematic diagrams, and the proportions of the size and thickness of each component in each figure are not limited and may not reflect the actual size ratios. (1) Summary

[0024] First, the general outline of the discharge device 10 of this embodiment will be described with reference to FIG1. ​​FIG1 is a block diagram of the discharge device 10 of this embodiment.

[0025] As shown in Figure 1, the discharge device 10 of this embodiment includes a voltage application device 1, a load 4, and a liquid supply unit 5. The voltage application device 1 is a device that 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 has a discharge electrode 41 and a counter electrode 42. That is, the discharge device 10 includes a discharge electrode 41 and a voltage application circuit 2. Furthermore, the discharge device 10 also includes a counter electrode 42. The counter electrode 42 is an electrode arranged facing the discharge electrode 41 with a gap between them. In other words, the discharge electrode 41 is arranged facing the counter electrode 42. A voltage is applied to the load 4 between the discharge electrode 41 and the counter electrode 42, thereby generating a discharge between the discharge electrode 41 and the counter electrode 42. The liquid supply unit 5 has the function of supplying liquid 50 to the discharge electrode 41. Thus, the discharge device 10 of this embodiment includes a voltage application circuit 2, a control circuit 3, a liquid supply unit 5, a discharge electrode 41, and a counter electrode 42 as constituent elements. However, the discharge device 10 may also include only the voltage application device 1 and the discharge electrode 41 as the minimum components, and the opposing electrode 42 and the liquid supply unit 5 may not be included in the components of the discharge device 10.

[0026] In this embodiment of the discharge device 10, for example, liquid 50 is attached to the surface of the discharge electrode 41 to keep the liquid 50 on the discharge electrode 41. In this state, a voltage is applied from the voltage application circuit 2 between the discharge electrode 41 and the counter electrode 42. 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. That is, the discharge device 10 of 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 means of the discharge generated 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 that becomes the object of electrostatic atomization, can also be simply referred to as "liquid 50".

[0027] Voltage application circuit 2 is electrically connected to discharge electrode 41 and counter electrode 42. Specifically, counter electrode 42 is electrically connected to the positive terminal (plus) of voltage application circuit 2, and discharge electrode 41 is electrically connected to the negative terminal (ground) of voltage application circuit 2. Voltage application circuit 2 applies a voltage between discharge electrode 41 and counter electrode 42. This generates a discharge between discharge electrode 41 and counter electrode 42 on load 4.

[0028] Furthermore, the discharge device 10 of this embodiment also includes a current limiting element 43. Figure 4 is a perspective view of the discharge electrode 41 of the discharge device 10 from below. The current limiting element 43 is electrically connected to the side of the discharge electrode 41 opposite to the side of the opposing electrode 42. Specifically, the current limiting element 43 is electrically connected to the base end 412 located at one end of the discharge electrode 41 in the long side direction. The current limiting element 43 has the function of limiting the current flowing to the discharge electrode 41. In this way, the discharge energy between the discharge electrode 41 and the opposing electrode 42 can be reduced.

[0029] 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 are fundamental to various applications, including sterilization, deodorization, humidification, preservation, and inactivation of viruses, and exhibit useful effects in a wide range of situations. Ozone is also generated during the discharge of free radicals. During the discharge between the discharge electrode 41 and the counter electrode 42, there may be a momentary, relatively large current flow. Therefore, the discharge energy between the discharge electrode 41 and the counter electrode 42 increases, and the discharge space expands, thus promoting the reaction with atmospheric oxygen and increasing the amount of ozone generated.

[0030] In the discharge device 10 of this embodiment, as described above, the current flowing to the discharge electrode 41 (discharge current) is limited by the current limiting element 43. This reduces the discharge energy between the discharge electrode 41 and the counter electrode 42, resulting in a smaller discharge space. Consequently, the reaction with atmospheric oxygen is restricted, thus suppressing ozone generation. On the other hand, the discharge space generated between the discharge electrode 41 and the counter electrode 42 is difficult to expand, and the discharge occurs near the discharge electrode 41, thereby increasing the amount of free radicals generated through the reaction with water. In other words, the discharge device 10 of this embodiment can suppress ozone generation while increasing free radical generation, thereby improving the efficiency of free radical generation. Furthermore, because the discharge energy can be reduced, not only ozone but also the generation of NOx (such as NO2, an object of environmental standards under the Basic Environmental Law of Japan) can be suppressed. (2) Detailed explanation

[0031] Next, referring to Figures 1 to 6, the discharge device 10 of this embodiment will be described in detail. Figure 2 is a perspective view of the load 4 included in the discharge device 10. Figure 3 is a cross-sectional view of the load 4 along line X1-X1 of Figure 2, showing the load 4. Figure 4 is a perspective view of the discharge electrode included in the same discharge device from below. Figure 5 is a circuit diagram showing an example of the discharge device 10. Figure 6 is a schematic diagram showing the front end shape of the discharge electrode 41 included in the discharge device 10. (2.1) Overall Composition

[0032] As shown in Figure 1, the discharge device 10 of this embodiment includes a voltage application device 1, a load 4, and a liquid supply unit 5. The voltage application device 1 has a voltage application circuit 2 and a control circuit 3. The load 4 has a discharge electrode 41 and a counter electrode 42. The liquid supply unit 5 supplies liquid 50 to the discharge electrode 41. The shapes of the discharge electrode 41 and the counter electrode 42 are schematically shown in Figure 1.

[0033] The discharge electrode 41 is a rod-shaped electrode. As shown in Figures 2 and 3, the discharge electrode 41 has a front end portion 411 at one end along its long side and a base end portion 412 at the other end along its long side (the end opposite to the front end portion 411). Furthermore, as shown in Figure 4, the discharge electrode 41 also has a shaft portion 413, which is formed integrally with the base end portion 412 and extends toward the front end portion 411. The front end portion 411 extends in one direction (the long side direction of the discharge electrode 41) relative to the base end portion 412. The discharge electrode 41 is a needle-shaped electrode with at least the front end portion 411 having a narrow front end shape. The term "narrow front end shape" here is not limited to a sharp front end shape, as shown in Figure 6, but also includes a rounded front end shape. Furthermore, the shape of the front end portion 411 will be described in the column "(2.3) Shape of the front end portion".

[0034] The counter electrode 42 is configured to face the front end 411 of the discharge electrode 41. The counter electrode 42 is, for example, plate-shaped, with a recess 421 in the center (refer to FIG. 3). The recess 421 is formed by recessing a portion of the counter electrode 42 toward the discharge electrode 41, thereby forming a truncated cone shape. A protrusion 423 is integrally formed in the center of the bottom wall 4211 of the recess 421. The protrusion 423 is formed by protruding a portion of the bottom wall 4211 of the recess 421 toward the side opposite to the discharge electrode 41, thereby forming a truncated cone shape. That is, the recessed direction of the recess 421 (the direction in which the recess 421 is recessed) is opposite to the protruding direction of the protrusion 423. An opening 4232 is formed in the center of the bottom wall 4231 of the protrusion 423. The opening 4232 penetrates the bottom wall 4231 in the thickness direction. Here, the positional relationship between the counter electrode 42 and the discharge electrode 41 is determined such that the thickness direction of the counter electrode 42 (the through direction of the opening 4232) is aligned with the long side direction of the discharge electrode 41, and the front end portion 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 through the opening 4232 of the protrusion 423 of the counter electrode 42. In other words, the discharge electrode 41 is configured to face the counter electrode 42 across the gap and is electrically insulated from the counter electrode 42.

[0035] More specifically, the discharge electrode 41 and the counter electrode 42, for example, are formed in the shapes shown in Figures 2 and 3, respectively. That is, the counter electrode 42 has a support portion 422 and a protrusion portion 423. The discharge electrode 41 and the counter electrode 42 are respectively held in a housing 40 made of electrically insulating synthetic resin. The support portion 422 is flat and has a recess 421 that is recessed into a truncated cone shape toward the discharge electrode 41 side. A protrusion portion 423 that is protruded into a truncated cone shape toward the side opposite to the discharge electrode 41 side is integrally formed on the bottom wall 4211 of the recess 421. An opening portion 4232 with a circular opening is formed on the bottom wall 4231 of the protrusion portion 423. In this case, a discharge occurs between the opening edge of the opening portion 4232 formed on the bottom wall 4231 of the protrusion portion 423 and the front end portion 411 of the discharge electrode 41.

[0036] As shown in Figure 4, the base end portion 412 of the discharge electrode 41 is formed in the shape of a circular plate. The base end portion 412 has a first surface 4121 and a second surface 4122. The first surface 4121 is the surface on the side of the front end portion 411 of the base end portion 412. As shown in Figure 4, the shaft portion 413 is formed in the shape of a long cylindrical strip, and its first end portion (the lower end portion in Figure 4) is disposed at the slightly central portion of the first surface 4121. Furthermore, the second end portion (the upper end portion in Figure 4) on the opposite side of the first end portion of the shaft portion 413 is connected to the front end portion 411 through the necked neck 4113 (refer to Figure 6). The second surface 4122 of the base end portion 412 is the surface on the side opposite to the front end portion 411. That is, the first surface 4121 and the second surface 4122 of the base end portion 412 face each other in the long side direction (one direction) of the discharge electrode 41. A current limiting element 43 is formed on the second surface 4122 of the base end portion 412, covering the entire area of ​​the second surface 4122. Here, in FIG. 4, to easily distinguish the current limiting element 43 from the conductive member 44 described later, dot hatching is applied to the current limiting element 43. The current limiting element 43 is directly and electrically connected to the base end portion 412 of the discharge electrode 41 on the side opposite to the opposing electrode 42. More specifically, the current limiting element 43 is directly and electrically connected to the second surface 4122 of the base end portion 412. The shape of the current limiting element 43 is circular when viewed from the long side of the discharge electrode 41. The current limiting element 43 is, for example, an insulating film made of silicon carbide (SiCO). The current limiting element 43 is formed on the second surface 4122 of the base end portion 412, for example, by chemical vapor deposition (CVD). The current limiting element 43 is, for example, a thin film with a thickness of 4 μm. In this disclosure, "thin film" means a thin film with a thickness of 10 μm or less. As shown in FIG5, the current limiting element 43 includes a resistive element 431. That is, in this embodiment, the insulating film is not a film that electrically insulates the two elements (here, the discharge electrode 41 and one of the Peltier elements 511 shown later in FIG4), but a film that functions as a resistive element 431 between the two elements. The resistance value of the current limiting element 43 is preferably, for example, 1 MΩ or more and 900 MΩ or less. More preferably, the resistance value of the current limiting element 43 is preferably 10 MΩ or more. 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 that functions as a resistive element 431. Furthermore, one of the Peltier elements is connected to ground and connected to a high-voltage circuit.

[0037] A conductive member 44 is formed on the surface of the current limiting element 43 (the side opposite to the base end 412 of the discharge electrode 41) (refer to FIG. 4). Viewed from the long side direction of the discharge electrode 41, the conductive member 44 is a circle 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 functions to conduct the pair of Peltier elements 511 described later. In the discharge device 10 of this embodiment, the pair of Peltier elements 511 are mechanically and electrically connected to the conductive member 44, for example, by solder. Here, as mentioned above, the current limiting element 43 is a thin film. Therefore, even though the current limiting element 43 is located between the discharge electrode 41 and the pair of Peltier elements 511, the cooling performance of the discharge electrode 41 provided by the pair of Peltier elements 511 can be maintained.

[0038] The liquid supply unit 5 supplies liquid 50 for electrostatic atomization 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 induce condensation. Specifically, as shown in FIG3, 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 in place 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 place in the housing 40 by embedding a portion of each heat sink 512 into the housing 40. At least the portion of the heat sink 512 holding the Peltier elements 511 is exposed from the housing 40 (see FIG3).

[0039] As described above, a pair of Peltier elements 511 are mechanically and electrically connected to the conductive member 44, for example, by solder. Therefore, the pair of Peltier elements 511 are connected to the discharge electrode 41 via the current limiting element 43. Furthermore, the pair of Peltier elements 511 are mechanically and electrically connected to a pair of heat sinks 512, for example, by solder. Energizing the pair of Peltier elements 511 is achieved through the 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 section 5 cools the discharge electrode 41 as a whole via the base end 412. This causes moisture in the air to condense and adhere to the surface of the discharge electrode 41 as condensation. As a result, liquid 50 is retained on the discharge electrode 41. That is, the liquid supply section 5 is configured to cool the discharge electrode 41, and condensation as liquid 50 is generated on the surface of the discharge electrode 41. In this configuration, the liquid supply unit 5 can use the moisture in the air to supply liquid 50 (condensation) to the discharge electrode 41, so there is no need to supply and replenish the liquid to the discharge device 10.

[0040] As shown in Figure 1, the voltage application circuit 2 includes a drive circuit 21 and a voltage generation circuit 22 that functions as a boost circuit B1. The drive circuit 21 drives the voltage generation circuit 22. The voltage generation circuit 22 receives power from the input unit 6 and generates a voltage (application voltage) 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 tens of V. In this embodiment, the input unit 6 is described as not being included in the components of the voltage application device 1, but the input unit 6 may also be included in the components of the voltage application device 1. The specific circuit configuration of the drive circuit 21 and the voltage generation circuit 22 (boost circuit B1) will be described in the "(2.2) Circuit Configuration" section.

[0041] The voltage application circuit 2 is electrically connected to the load 4 (discharge electrode 41 and counter electrode 42) (refer to Figure 5). The voltage application circuit 2 applies a high voltage to the load 4. Here, the voltage application circuit 2 is configured to apply a high voltage between the discharge electrode 41 and the counter electrode 42, with the discharge electrode 41 as the negative terminal (ground) and the counter electrode 42 as the positive terminal (plus). In other words, when a high voltage is applied to the load 4 from the voltage application circuit 2, a potential difference is generated between the discharge electrode 41 and the counter electrode 42, resulting in a high voltage on the counter electrode 42 side and a low potential on the discharge electrode 41 side. The "high voltage" referred to here is simply a voltage that can generate discharge at the discharge electrode 41; for example, it is a voltage with a peak value of around 7.0 kV. However, the high voltage applied to the load 4 from the voltage application circuit 2 is not limited to 7.0 kV; it can be appropriately set, for example, according to the shape of the discharge electrode 41 and the counter electrode 42, or the distance between the discharge electrode 41 and the counter electrode 42.

[0042] Here, the voltage application circuit 2 has two operating modes: a first mode and a second mode. The first mode is used to increase the applied voltage over time, causing insulation breakdown, initiating discharge, and generating a discharge current. The second mode is used to interrupt the discharge current via the control circuit 3, etc., to end the discharge. In other words, the voltage application circuit 2 has both a first mode and a second mode as its operating modes. The first mode is used to increase the applied voltage over time, generating a discharge current. The second mode is used to interrupt the discharge current.

[0043] Control circuit 3 controls voltage application circuit 2. During the driving period when voltage application device 1 is driven, control circuit 3 controls voltage application circuit 2 to alternately repeat mode 1 and mode 2. Here, control circuit 3 switches between mode 1 and mode 2 by periodically varying the magnitude of the applied voltage (transformer voltage described later) from voltage application circuit 2 to load 4 at the driving frequency.

[0044] This causes the magnitude of the electrical energy acting on the liquid 50 held at the discharge electrode 41 to vary periodically with the driving frequency, resulting in the liquid 50 held at the discharge electrode 41 mechanically vibrating at the driving frequency. Here, the voltage generating circuit 22 (boost circuit B1) varies the magnitude of the applied voltage in such a way that the frequency of the applied voltage variation (driving frequency) is above the resonant frequency (natural frequency) of the liquid 50 held at the discharge electrode 41. Furthermore, the closer the driving frequency is set to a value near the resonant frequency of the liquid 50, the greater the amplitude of the mechanical vibration of the liquid 50 accompanying the variation in the magnitude of the applied voltage.

[0045] In this embodiment, the control circuit 3 controls the voltage application circuit 2 according to the monitored object. The so-called "monitored object" is at least one of the output current and output voltage of the voltage application circuit 2.

[0046] Here, as shown in Figures 1 and 5, the control circuit 3 includes 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 a monitoring object formed by the output voltage of the voltage application circuit 2. The control circuit 3 outputs a control signal Si1 to the drive circuit 21, thereby controlling the drive circuit 21. The current control circuit 32 controls the drive circuit 21 of the voltage application circuit 2 based on a monitoring object formed by the output current of the voltage application circuit 2. That is, in this embodiment, the control circuit 3 uses both the output current and output voltage of the voltage application circuit 2 as monitoring objects to control the voltage application circuit 2. However, because there is a correlation between the output voltage (secondary voltage) and the primary voltage of the voltage application circuit 2, the voltage control circuit 31 can also indirectly detect the output voltage of the voltage application circuit 2 from the primary voltage of the voltage application circuit 2. Similarly, there is a correlation between the output current (secondary current) of the voltage application circuit 2 and the input current (primary 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 from the input current of the voltage application circuit 2. The specific circuit configuration of the voltage control circuit 31 and the current control circuit 32 will be described in the "(2.2) Circuit Configuration" section.

[0047] The control circuit 3 is configured such that if the size of the monitored object is less than a threshold, the voltage application circuit 2 operates in mode 1; and if the size of the monitored object exceeds the threshold, the voltage application circuit 2 operates in mode 2. That is, until the size of the monitored object reaches the threshold, the voltage application circuit 2 operates in mode 1, and the applied voltage increases over time. During this time, corona discharge begins in the discharge electrode 41 due to insulation failure, generating a discharge current. When the size of the monitored object reaches the threshold, the voltage application circuit 2 operates in mode 2, and the applied voltage decreases. At this time, the potential difference between the discharge electrode 41 and the opposing electrode 42 is lost, and the discharge current is interrupted by the control circuit 3. In other words, the control circuit 3 detects the discharge of the load 4 through the voltage application circuit 2, reduces the applied voltage, and extinguishes the discharge current.

[0048] Therefore, during the driving period, the voltage application circuit 2 alternately operates in the first mode and the second mode, and the magnitude of the applied voltage varies periodically with the driving frequency. As a result, the discharge electrode 41 will intermittently discharge repeatedly.

[0049] Furthermore, it is explained in detail that the discharge device 10 first generates a local corona discharge in the liquid 50 held at the front end 411 of the discharge electrode 41, but immediately switches to the second mode after the discharge begins, intermittently generating discharge between the discharge electrode 41 and the opposing electrode 42.

[0050] Figure 7A is a graph showing the discharge state (voltage waveform Vx1 and current waveform Ix1) of the discharge device 10 in this embodiment. In Figure 7A, the horizontal axis is the time axis, the left vertical axis represents the output voltage of the voltage application circuit 2 (application voltage, i.e., transformer voltage), and the right vertical axis represents the discharge current. As the applied voltage rises, insulation breakdown occurs at the front end of the liquid 50, generating a small discharge through corona discharge. When the applied voltage reaches its maximum value V1, a discharge state is formed, and then the voltage is rapidly reduced, thereby stopping the discharge. Figure 7B is a graph showing the discharge state of the discharge device of the comparative example, the details of which will be described later.

[0051] As shown in Figure 7A, the magnitude of the applied voltage (transformer voltage) varies periodically with the discharge cycle T1. When the driving frequency is set to "f1", the discharge cycle T1 can be expressed as the reciprocal of the driving frequency f1 (1 / f1). Furthermore, in this embodiment, for example, the magnitude of the applied voltage (transformer voltage) varies within a range exceeding 0V during the driving period. Here, the minimum applied voltage V0 is greater than 0V, and the magnitude of the applied voltage varies between the minimum value V0 and the maximum value V1. The applied voltage increases in a slightly linear manner with the passage of time in each discharge cycle T1, and then decreases in a slightly linear manner.

[0052] In each discharge cycle T1, if the size of the monitored object is less than a threshold, that is, until the applied voltage reaches a threshold (e.g., the maximum value V1 in Figure 7A) and the output current reaches a threshold (e.g., the threshold I1 in Figure 7A), the control circuit 3 causes the voltage application circuit 2 to operate in mode 1. Then, in each discharge cycle T1, when the size of the monitored object becomes above the threshold, that is, when the output current becomes above the threshold value, the control circuit 3 causes the voltage application circuit 2 to operate in mode 2.

[0053] Incidentally, as mentioned above, the driving frequency f1 is set to be above the resonant frequency fr1 (natural frequency) of the liquid 50 in the discharge electrode 41. The resonant frequency fr1 of the liquid 50 depends, for example, on 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 in the discharge electrode 41. "a" is a proportionality coefficient depending on the surface tension and viscosity of the liquid 50 held in the discharge electrode 41. Therefore, by reducing the volume of the liquid 50 held in the discharge electrode 41, the resonant frequency fr1 of the liquid 50 will increase.

[0054] In this embodiment, the discharge device 10 applies a voltage to the load 4 from the voltage application circuit 2 while liquid 50 (condensation) is supplied (held) to the discharge electrode 41. This causes a discharge to occur between the discharge electrode 41 and the counter electrode 42 in the load 4 due to the potential difference between them. At this time, the liquid 50 held at the discharge electrode 41 is electrostatically atomized by the discharge. As a result, nano-sized charged microparticles containing free radicals are generated in the discharge device 10. In other words, the discharge device 10 constitutes a so-called charged microparticle liquid generation device. The generated charged microparticle liquid is released around the discharge device 10 through, for example, the opening 4232 of the counter electrode 42. (2.2) Circuit configuration

[0055] Next, the specific circuit configuration of the voltage application device 1 will be described with reference to FIG5. FIG5 is a circuit diagram that schematically shows an example of the circuit configuration of the discharge device 10. In FIG5, the input unit 6 is omitted.

[0056] The voltage application circuit 2, as described above, includes a drive circuit 21 and a voltage generation circuit 22. In the example of FIG. 5, the voltage application circuit 2 is an isolated DC / DC converter. The voltage application circuit 2 has a boost circuit B1, which boosts the input voltage Vin (e.g., 13.8V) from the input section 6 and outputs the boosted voltage as the output voltage. Here, the voltage generation circuit 22 functions as the boost circuit B1. The output voltage of the boost circuit B1 is applied as the applied voltage to the load 4 (discharge electrode 41 and counter electrode 42). That is, the voltage application circuit 2 applies a voltage to the load 4, thereby causing the discharge electrode 41 to discharge.

[0057] The voltage generating circuit 22 (boost circuit B1) has an insulation transformer 220 (boost transformer), which includes a primary winding 221, a secondary winding 222, and an auxiliary winding 223. The primary winding 221 and the auxiliary winding 223 are electrically insulated from the secondary winding 222 and magnetically coupled. A counter electrode 42 is electrically connected to one end of the secondary winding 222. In other words, the boost circuit B1 includes a boost transformer (insulation transformer 220) that boosts the input voltage Vin input to the primary side (primary winding 221 side) and applies an output voltage from the secondary side (secondary winding 222 side) electrically connected to the load 4.

[0058] Here, the boost circuit B1 is configured to periodically change the output voltage at a frequency higher than or equal to the resonant frequency of the liquid 50. In particular, in this embodiment, the inductance value of the secondary side (secondary winding 222 side) of the boost transformer (insulation transformer 220) is set to be such that the output voltage can be changed at a frequency higher than or equal to the resonant frequency of the liquid 50.

[0059] The so-called "secondary-side inductance" refers to the effective inductance of the secondary side (secondary winding 222 side), which is the self-inductance L of the secondary winding 222 side multiplied by the coupling coefficient k (0~1). The value of the secondary-side inductance can be set by adjusting the permeability of the magnetic core, the number of turns of the secondary winding 222, its length, or its cross-sectional area.

[0060] 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 secondary side inductance is 50 mH or more and 900 mH or less. Preferably, it is 500 mH or less, and more preferably, it is 100 mH or less.

[0061] By setting the inductor value in this way, even when the resonant frequency of the liquid 50 is relatively high (e.g., above 1.5kHz), the boost circuit B1 can still change the output voltage at a driving frequency above the resonant frequency in a way that follows its resonant frequency.

[0062] The drive circuit 21 includes a transistor Q1, configured to supply power to the primary winding 221 of the insulation transformer 220 by switching the transistor Q1. In addition to transistor Q1, the drive circuit 21 also includes transistors Q2 and Q3, and resistors R1 to R5. Transistors Q1, Q2, and Q3, as an example, are composed of npn-type bipolar transistors.

[0063] The collector of transistor Q1 is connected to the primary winding 221, and the emitter of transistor Q1 is connected to ground through resistor R1. An input voltage Vin is applied from the input section 6 to the series circuit of the primary winding 221, transistor Q1, and resistor R1. The base of transistor Q1 is connected to the control power supply Vcc through resistor R2. The control power supply Vcc applies a control voltage (e.g., 5.1V) to the drive circuit 21.

[0064] The collectors of transistors Q2 and Q3 are connected to the base of transistor Q1. The emitters of transistors Q2 and Q3 are connected to ground. The base of transistor Q2 is connected to the emitter of transistor Q1 through resistor R3. The base of transistor Q1 is connected to one end of auxiliary winding 223 through a parallel circuit of resistors R4 and R5. The other end of auxiliary winding 223 is connected to ground. A control circuit 3 (voltage control circuit 31 and current control circuit 32) is connected to the base of transistor Q3, and a control signal Si1 is input from the control circuit 3.

[0065] With the above configuration, voltage application circuit 2 constitutes a self-excited converter. That is, when transistor Q1 is turned on, current flows to the primary winding 221 of the insulation transformer 220, causing the voltage across resistor R1 to rise, and transistor Q2 will turn on. Since the base of transistor Q1 is connected to ground through transistor Q2, transistor Q1 will turn off. When transistor Q1 turns off, the current flowing through the primary winding 221 is interrupted, the voltage across resistor R1 decreases, and transistor Q2 will turn off. This induces a high voltage in the secondary winding 222 of the insulation transformer 220, which becomes the output voltage of voltage application circuit 2 and is applied to load 4. At this time, the induced voltage in the secondary winding 222 also induces a voltage in the auxiliary winding 223, causing the voltage between the base and emitter of transistor Q1 to rise, and transistor Q1 will turn on. Voltage application circuit 2, by repeating the above operation, boosts the input voltage Vin and applies an output voltage to load 4.

[0066] As shown in Figure 5, the control circuit 3 has a voltage control circuit 31 and a current control circuit 32.

[0067] 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 the auxiliary winding 223 and resistors R4 and R5. The cathode of diode D1 is connected to one end of capacitor C1 through resistor R6. The other end of capacitor C1 is connected to ground. 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 serves as the output terminal of the voltage control circuit 31 and is connected to the base of transistor Q3.

[0068] Based on the above configuration, the voltage control circuit 31 monitors the induced voltage of the auxiliary winding 223, thereby indirectly monitoring the output voltage (induced voltage of the secondary winding 222) of the voltage application circuit 2, which is the object of monitoring. That is, when the output voltage of the voltage application circuit 2 is less than the threshold (maximum value V1), the Zener diode ZD1 of the voltage control circuit 31 is off. On the other hand, if the output voltage of the voltage application circuit 2 is above the threshold (maximum value V1), the Zener diode ZD1 of the voltage control circuit 31 is turned on. At this time, the control signal Si1 exceeds the control threshold, and a voltage is applied between the base and emitter of the transistor Q3, causing the transistor Q3 to turn on. Consequently, the base current of transistor Q1 flows to ground through transistor Q3, thus reducing the collector current of transistor Q1. Therefore, if 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 drive circuit 21 of the voltage application circuit 2.

[0069] The current control circuit 32 includes an operational amplifier OP1, a reference voltage generator 321, resistors R7-R11, and capacitors C2 and C3. One end of capacitor C2 is connected to the control power supply Vcc through resistor R7. The other end of capacitor C2 is connected to ground. 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 of resistor R7 and capacitor C2 (one end of capacitor C2) is connected to the inverting input terminal of operational amplifier OP1 through resistor R8. Furthermore, at the connection point of resistor R7 and capacitor C2 (one end of capacitor C2), an end opposite to the opposing electrode 42 in the secondary winding 222 of the insulating transformer 220 is connected (the other end). In other words, the control power supply Vcc is connected to the opposing electrode 42 via resistor R7 and the secondary winding 222. The reference voltage generator 321 is connected to the non-inverting input terminal of operational amplifier OP1, and a reference voltage is input from the reference voltage generator 321. 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 connected to ground through resistor R11. The junction of 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.

[0070] Based on the above configuration, the current control circuit 32 monitors the induced current of the secondary winding 222 to monitor the output current (induced voltage of the secondary winding 222) of the voltage application circuit 2, which is the object of monitoring. That is, when the output current of the voltage application circuit 2 is less than a threshold, the output of the operational amplifier OP1 of the current control circuit 32 is at the 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 at the H level (High Level). At this time, the control signal Si1 exceeds the control threshold, and a voltage is applied between the base and emitter of the transistor Q3, turning the transistor Q3 on. As a result, the base current of transistor Q1 flows to ground through transistor Q3, thus reducing the collector current of transistor Q1. Therefore, if the output current of the voltage application circuit 2 is above the threshold, the current control circuit 32 reduces the energy input from the drive circuit 21 of the voltage application circuit 2 to the voltage generation circuit 22. (2.3) Shape of the front end

[0071] Next, the shape of the front end portion 411 of the discharge electrode 41 will be explained with reference to FIG6. In FIG6, in order to easily distinguish the front end portion 411 from the Taylor cone 501 formed on the front end portion 411, dotted lines are applied to the Taylor cone 501.

[0072] The shape of the front end portion 411 of the discharge electrode 41, as shown in FIG6, is, for example, a shape including a conical portion. The shape of the portion of the front end portion 411 facing the opposing electrode 42 (here, the shape of the conical front end) is, for example, an R (rounded corner) shape. That is, the shape of the portion opposite to the base end portion 412 side of the front end portion 411 is an R shape.

[0073] The front end portion 411 has a first portion 4111 and a second portion 4112. The first portion 4111 is the part of the front end portion 411 that is closer to the base end portion 412 than the second portion 4112, and is cylindrical. The second portion 4112 is the part of the front end portion 411 that is farther from the base end portion 412 than the first portion 4111, and is conical. In short, the front end portion 411 has a first portion 4111 corresponding to a cylindrical portion and a second portion 4112 corresponding to a conical portion.

[0074] Part 1 4111 and Part 2 4112 are arranged in the order of Part 1 4111 and Part 2 4112, starting from the base end 412 side along the long side of the discharge electrode 41. Furthermore, the shape of Part 2 4112, as shown in FIG6, is preferably slightly conical, but is not limited to this. The shape of Part 2 4112 can also be a convex curved surface towards the opposing electrode 42; specifically, it can be hemispherical or bell-shaped. In this embodiment, the front end 411 is configured as a combination of Part 2 4112 (conical portion) and Part 1 4111 (cylindrical portion), which has a different shape. The front end 411 can also, for example, omit Part 1 4111 and consist entirely of a single-shaped portion (e.g., a conical portion).

[0075] Furthermore, in this embodiment, as an example, a neck 4113 is provided between the front end portion 411 and the shaft portion 413. That is, the front end portion 411 and the shaft portion 413 are connected by the neck 4113. The neck 4113 is formed into a conical shape whose diameter decreases from the end edge 4114 of the front end portion 411 towards the shaft portion 413. By providing the neck 4113, the merging of residual condensate on the shaft portion 413 side with the condensate (Taylor cone) on the front end portion 411 side can be suppressed. Alternatively, to obtain the same merging suppression effect, a protrusion may be provided between the front end portion 411 and the shaft portion 413 instead of the neck 4113. This protrusion has a larger diameter, protruding radially more than both the front end portion 411 and the shaft portion 413. Alternatively, a step portion may be provided between the front end portion 411 and the shaft portion 413 instead of the conical neck 4113.

[0076] The maximum diameter of the front end portion 411, including the conical portion, is equal to the maximum diameter D11 of the first portion 4111 (hereinafter, the maximum diameter of the front end portion 411 is also referred to as "maximum diameter D11"). The maximum diameter D11 of the front end portion 411 is preferably, for example, 0.35 mm or more and 1.5 mm or less. For example, the maximum diameter D11 of the front end portion 411 is 0.710 mm. For example, the apex angle θ1 of the second portion 4112 is 47.580°. Furthermore, the total length L1 of the front end portion 411 (the length dimension of the front end portion 411 in the long side direction of the discharge electrode 41) is, for example, 0.830 mm. Here, as an example, the total length L1 of the front end portion 411, as shown in FIG6, is set to be the length from the end edge 4114 on the base end portion 412 side of the cylindrical portion to the front end of the second portion 4112, with the maximum diameter D11 of the first portion 4111 being slightly less than the diameter. Alternatively, if the first part 4111 is omitted, the total length L1 of the front end 411 becomes the length of the second part 4112.

[0077] Here, when the maximum diameter D11 of the front end portion 411 is 1.5 mm, the ratio of the total length L1 of the front end portion 411 to the maximum diameter D11 of the front end portion 411 is 1.6. Furthermore, when the maximum diameter D11 of the front end portion 411 is 0.35 mm, the ratio of the total length L1 of the front end portion 411 to the maximum diameter D11 of the front end portion 411 is 1.0. That is, in the discharge device 10 of this embodiment, in one direction (the direction of the long side of the discharge electrode 41), the ratio of the total length L1 of the front end portion 411 to the maximum diameter D11 of the front end portion 411 (hereinafter also referred to as the "first ratio") is 1.0 or more and 1.6 or less. In other words, in one direction, the total length L1 of the front end portion 411 is a length greater than or equal to the maximum diameter D11 of the front end portion 411. For example, when the maximum diameter D11 of the front end 411 is 0.710 mm and the total length L1 of the front end 411 is 0.830 mm, the first ratio is 1.169. Therefore, if the first ratio is 1.0 or higher and 1.6 or lower, the volume of the liquid 50 forming the Taylor cone 501 can be reduced, resulting in an increase in the resonant frequency of the liquid 50. This reduces the discharge energy between the discharge electrode 41 and the counter electrode 42, resulting in a smaller discharge space, thus suppressing the reaction with atmospheric oxygen and inhibiting ozone formation. On the other hand, by generating the discharge between the discharge electrode 41 and the counter electrode 42 at a high frequency, the discharge space created by the discharge between the discharge electrode 41 and the counter electrode 42 is difficult to expand, becoming generated near the discharge electrode 41, and increasing the amount of free radicals obtained from the reaction with water. That is, the discharge device 10 according to this embodiment can suppress the amount of ozone generated and increase the amount of free radicals generated, thereby improving the efficiency of free radical generation.

[0078] Incidentally, by applying a voltage between the discharge electrode 41 and the counter electrode 42, the liquid 50 held in the discharge electrode 41 forms a Taylor cone 501 at the front end 411 of the discharge electrode 41. The shape of the Taylor cone 501, as shown in FIG6, is a cone shape along the conical portion of the front end 411 of the discharge electrode 41. A second portion 4112 of the front end 411 of the discharge electrode 41 enters the Taylor cone 501. That is, in the discharge device 10 of this embodiment, the second portion 4112 constitutes a part of the front end 411 that enters the Taylor cone 501.

[0079] 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 front end 411 of the discharge electrode 41 to the volume of the Taylor cone 501 (hereinafter also referred to as the "second ratio") should preferably be 0.6 or more and 0.95 or less. As an example, when the volume of the Taylor cone 501 is 0.0917 mm³ and the volume of the second portion 4112 is 0.0650 mm³, the second ratio is 0.71. For example, without the above-described shape, the volume of the liquid 50 forming the Taylor cone 501 is 0.23 μL, and the resonant frequency of the liquid 50 is 1 kHz. In contrast, in the present embodiment with the above-described shape, the volume of the liquid 50 forming the Taylor cone 501 is 0.076 μL, and the resonant frequency of the liquid 50 is 3 kHz. In this way, by reducing the volume of the liquid 50 forming the Taylor cone 501, the resonant frequency of the liquid 50 can be increased.

[0080] In the discharge device 10 of this embodiment, as described above, the second portion 4112 of the front end portion 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 furthest from the counter electrode 42 in the direction in which the discharge electrode 41 and the counter electrode 42 are arranged. In the example of FIG. 6, the shape of the outer periphery 502 of the Taylor cone 501 is annular when viewed from the long side direction of the discharge electrode 41. The first position is a position where the distance from the front end portion 411 is 0.62 times the total length L1 of the front end portion 411. The second position is a position where the distance from the front end portion 411 is 1.00 times the total length L1 of the front end portion 411. For example, as described above, when the total length L1 of the front end 411 is 0.830 mm, the outer periphery 502 of the Taylor cone 501 is located between a position 0.515 mm (first position) and a position 0.830 mm (second position) from the front end of the front end 411. (2.4) Improvement in the number of discharges

[0081] The following explanation focuses on improving the discharge count of the discharge device 10 in this embodiment, with reference to Figures 7A and 7B.

[0082] As explained above, the voltage applied to the load 4, i.e., the output voltage (transformer voltage) is varied by the driving frequency (discharge frequency), thereby causing the electrical energy acting on the liquid 50 held at the discharge electrode 41 to vary periodically with its driving frequency. As a result, the liquid 50 vibrates mechanically by the driving frequency. Then, when the driving frequency is set above the resonant frequency of the liquid 50, the amplitude of the mechanical vibration of the liquid 50 with the variation of the applied voltage becomes larger. As the amplitude of the liquid 50 increases, the tip of the Taylor cone 501 (refer to Figure 6) becomes a sharper shape, making it easier to discharge.

[0083] Incidentally, in the discharge device 10, after the discharge begins, the voltage is reduced in the second mode, thereby stopping the continuous discharge generated by corona discharge and stopping the continuous discharge that easily generates ozone. By repeating this discharge at high speed, that is, by increasing the driving frequency, the increase of ozone can be suppressed and a large number of free radicals can be generated.

[0084] Here, as explained above, the resonant frequency of the liquid 50 depends on the volume of the liquid 50 held in the discharge electrode 41. Furthermore, the shape of the front end 411 of the discharge electrode 41 is set as described above, thereby reducing the volume of the liquid 50 held in the discharge electrode 41 and increasing the resonant frequency of the liquid 50. If the resonant frequency of the liquid held in the discharge electrode without the aforementioned shape is set to, for example, 1 kHz, the resonant frequency of the liquid 50 held in the discharge electrode 41 with the aforementioned shape becomes 1.5 kHz or higher (for example, 3 kHz). By following the resonant frequency which has increased to 1.5 kHz or higher, the driving frequency is also increased to 1.5 kHz or higher (for example, 3 kHz to 5 kHz if the resonant frequency is 3 kHz). As a result, the amplitude of the mechanical vibration of the liquid 50 increases, and the discharge efficiency is improved.

[0085] On the other hand, in order to increase the driving frequency to be able to follow the resonant frequency that has increased to over 1.5kHz, it is necessary to rapidly boost the transformer voltage in mode 1 to the threshold (maximum value V1). Furthermore, if the continuous discharge generated by the aforementioned corona discharge continues, there is a possibility that a new atomized discharge cannot be formed; therefore, it is necessary to stop the continuous discharge before generating the next atomized discharge. Regarding stopping the continuous discharge, it is necessary to reduce the transformer voltage, or to smooth the tip of the Taylor cone 501 formed by the transformer voltage, and it is necessary to increase the rate of voltage reduction.

[0086] In this embodiment, in order to increase the speed of voltage rise and fall of the transformer, the inductance value of the secondary side of the step-up transformer (insulation transformer 220) is set to 900mH or less.

[0087] Figure 7B is a graph showing the discharge characteristics (voltage waveform Vx1 and current waveform Ix1) of the discharge device in the comparative example. In Figure 7B, similar to Figure 7A, the horizontal axis is set as the time axis. The vertical axis on the left represents the output voltage of the voltage application circuit (the applied voltage, i.e., the transformer voltage), and the vertical axis on the right represents the discharge current. The maximum value V2 (threshold) of the transformer voltage shown in Figure 7B is set to be the same as the maximum value V1 (threshold) of the transformer voltage shown in Figure 7A, but it can also be different from the maximum value V1. Similarly, the threshold I2 of the discharge current shown in Figure 7B is set to be the same as the threshold I1 of the discharge current shown in Figure 7A, but it can also be different from the threshold I1. The time scale of the horizontal axis in Figures 7A and 7B is the same.

[0088] In the comparative example discharge device, the inductance value of the secondary side of the step-up transformer was set to, for example, 3000mH. However, the shape of the front end 411 of the discharge electrode 41 was adopted to increase the resonant frequency of the liquid 50. Originally, it was hoped that the driving frequency would also be increased to follow the increased resonant frequency. However, in the comparative example set to 3000mH, the time to boost to the maximum value V2 was slow, and the time to depress to the minimum value V0 was also slow. The driving frequency f2 was around 1kHz. As a result, the discharge period T2 in the comparative example was longer than the discharge period T1.

[0089] On the other hand, in the discharge device 10 of this embodiment, which is set to 900mH or less, the time to rise to the maximum value V1 and the time to drop to the minimum value V0 are faster compared to the discharge device of the comparative example. In the example shown, the discharge period T1 is approximately half of the discharge period T2. That is, the number of discharges of the discharge device 10 within the predetermined period is approximately twice that of the discharge device of the comparative example.

[0090] In this way, the step-up transformer (insulation transformer 220) of this embodiment, with the inductance value set to 900mH or less, is configured to periodically change the output voltage at a frequency higher than the resonant frequency of the liquid 50. Therefore, the number of discharges of the discharge device 10 increases, resulting in an improvement in the efficiency of free radical generation.

[0091] In particular, in the discharge device 10, by shortening the discharge cycle T1, although the discharge energy obtained from a single discharge is smaller than that of the discharge device in the comparative example, the number of discharges is increased, thereby increasing the amount of free radicals generated and suppressing the amount of ozone generated. Furthermore, by suppressing the discharge energy obtained from a single discharge, the amount of NO2 generated, which increases depending on the increase in discharge energy, can also be suppressed. (2.5) Actions

[0092] If the circuit is configured as shown in Figure 5, the discharge device 10 will generate a suppressed discharge between the discharge electrode 41 and the counter electrode 42 by means of the control circuit 3.

[0093] That is, during the period until insulation failure occurs, the control circuit 3 monitors the output voltage of the voltage application circuit 2. When the monitored output voltage reaches or exceeds a threshold (e.g., the maximum value V1 in Figure 7A), the voltage control circuit 31 reduces the switching energy of the drive circuit 21. On the other hand, after insulation failure occurs, the control circuit 3 monitors the output current of the voltage application circuit 2. If the monitored output current reaches or exceeds a threshold (e.g., the threshold I1 in Figure 7A), the current control circuit 32 stops the switching operation of the drive circuit 21. In this way, the voltage application circuit 2 is operated in the second mode, where the transformer voltage is reduced and the load 4 is overloaded by the voltage application circuit 2 to interrupt the discharge current. In other words, the operating mode of the voltage application circuit 2 switches from the first mode to the second mode.

[0094] At this time, both the output voltage and output current of voltage application circuit 2 decrease together, so control circuit 3 will start the switching operation of drive circuit 21 again. Thus, in the first mode where the applied voltage rises over time to trigger discharge, voltage application circuit 2 is activated. In other words, the operating mode of voltage application circuit 2 switches from the second mode to the first mode.

[0095] By repeating the above-described operation through control circuit 3, voltage application circuit 2 operates in a manner that alternately repeats the first mode and the second mode. As a result, the discharge electrode 41 switches between ON and OFF states. Subsequently, voltage application circuit 2 of this embodiment can achieve output voltage variation by using a driving frequency higher than the resonant frequency of liquid 50. (3) Variations

[0096] The above-described embodiments are merely one of the various embodiments disclosed herein. If the above-described embodiments achieve the purpose of this disclosure, various changes can be made to accommodate design modifications, etc. The following are examples of variations of the above-described embodiments. The variations described below can be appropriately combined and applied. (3.1) Variation Example 1

[0097] Figure 8 is a bottom view of the discharge electrode 41 of the discharge device in Modified Example 1. In the above embodiment, the shape of the conducting member 44 that conducts the pair of Peltier elements 511 is circular when viewed from the long side of the discharge electrode 41. However, it is not limited to this. For example, the conducting member 44B shown in Figure 8 may be rectangular when viewed from the long side of the discharge electrode 41. In this case, the width dimension of the conducting member 44B (the dimension in the vertical direction of Figure 8) should preferably be the same as the width dimension of each Peltier element 511 (the dimension in the vertical direction of Figure 8), but it may also be larger than the width dimension of each Peltier element 511. In this case, the conducting member 44B is preferably a thin film. Furthermore, the shape of the conducting member may also be, for example, elliptical when viewed from the long side of the discharge electrode 41. That is to say, the shape of the conducting member is acceptable as long as it is a shape that can conduct the pair of Peltier elements 511. (3.2) Variation Example 2

[0098] In the above-described embodiment, the maximum diameter D11 of the front end portion 411 of the discharge electrode 41 is 0.71 mm, but it is not limited to this. The maximum diameter D11 of the front end portion 411 of the discharge electrode 41 can also be, for example, 0.600 mm. That is, the maximum diameter D11 of the front end portion 411 of the discharge electrode 41 can also be, for example, 0.600 mm or less. Furthermore, the maximum diameter D11 of the front end portion 411 of the discharge electrode 41 is preferably, for example, 0.500 mm or more. In this case, the volume of the liquid 50 forming the Taylor cone 501 can be made smaller, 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 smaller, thus suppressing the reaction with atmospheric oxygen and further suppressing ozone formation. On the other hand, by generating the discharge between the discharge electrode 41 and the counter electrode 42 at a high frequency, the free radicals obtained through the reaction with water can be further increased. That is, the discharge device 10 according to this embodiment can further suppress the generation of ozone and increase the generation of free radicals, thereby further improving the efficiency of free radical generation. In this case, it is even more preferable that the maximum diameter D11 of the front end portion 411 of the discharge electrode 41 is 0.550 mm or less. That is, the maximum diameter D11 of the front end portion 411 of the discharge electrode 41 is 0.500 mm or more, and 0.550 mm or less is more preferable. (3.3) Other variations

[0099] The liquid supply unit 5 is not limited to a configuration that cools the discharge electrode 41 to generate condensation on the discharge electrode 41. The liquid supply unit 5 may also be a configuration that uses a supply mechanism such as a capillary effect or a pump to supply liquid 50 to the discharge electrode 41 from a storage tank. Furthermore, the liquid 50 is not limited to water (condensation water) and may be a liquid other than water.

[0100] Figure 5 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 appropriately modified. For example, the voltage application circuit 2 is not limited to a self-excited converter, but can also be an externally excited converter. Furthermore, in the voltage application circuit 2, the transistors Q1, Q2, and Q3 are not limited to bipolar transistors, but can also be, for example, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). Moreover, the voltage generation circuit 22 can also be implemented in a transformer (transformer) with piezoelectric elements.

[0101] The current limiting element 43 is not limited to the resistive element 431, but may also include a capacitive element. That is, the current limiting element 43 only needs to include at least one of the resistive element 431 and the capacitive element.

[0102] The current limiting element 43 is not limited to an insulating film composed of silicon carbide oxide, but can also be, for example, a nickel oxide film (NiO). In this case, the current limiting element 43 is formed, for example, by sintering the nickel paste after coating the second surface 4122 of the base end 412 of the discharge electrode 41 with nickel paste. Alternatively, the current limiting element 43 can also be an insulating film composed of, for example, diamond-like carbon (DLC). Furthermore, the current limiting element 43 can also be an insulating film composed of, for example, aluminum nitride (AlN). Additionally, the current limiting element 43 can also be, for example, a titanium oxide film (TiO). Furthermore, the current limiting element 43 can also be formed, for example, by using a sintering material with high thermal conductivity. Furthermore, for example, epoxy resin (EP) can be used as an adhesive to bond two copper (Cu) pieces together, or aluminum oxide (AlO3 or Al2O3) can be used as an adhesive to bond two copper pieces together.

[0103] In comparisons between two values, such as the monitored object and a threshold, the condition set to "above" includes both cases where the two values ​​are equal and cases where one value exceeds the other. However, it is not limited to these two cases; "above" here can also mean the same as "greater than," which only includes cases where one value exceeds the other. In other words, whether or not the case of equal values ​​is included can be arbitrarily changed according to the setting of the threshold, etc., so there is no technical difference between "above" and "greater than." Similarly, "less than" can also mean the same as "below."

[0104] Alternatively, needle-shaped protrusions can be provided on the opposing electrode 42, and a leader discharge can be used. The aforementioned leader discharge progresses from corona discharge to strong discharge, intermittently causing insulation failure (complete circuit failure). In this case, a plurality of needle-shaped portions can also be arranged at equal intervals in the circumferential direction of the opening 4232. Each needle-shaped portion can also protrude from the inner periphery of the opening 4232 toward the center of the opening 4232. Each needle-shaped portion can also protrude obliquely from the inner periphery of the opening 4232 in such a way that the distance to the discharge electrode 41 in the long side direction of the discharge electrode 41 is shorter as it gets closer to its front end. The needle-shaped portions are formed in such a shape that it is easy to generate electric field concentration at the front end of each needle-shaped portion. As a result, it is easy to stably generate discharge between the front end of each needle-shaped portion and the front end 411 of the discharge electrode 41. (State / Appearance)

[0105] The following forms are revealed from the above-described implementation forms and variations.

[0106] The discharge device (10) of the first state includes a discharge electrode (41), a voltage application circuit (2), and a current limiting element (43). The discharge electrode (41) and the counter electrode (42) are arranged facing each other. The voltage application circuit (2) is electrically connected to the discharge electrode (41) and the counter electrode (42) in such a way that the discharge electrode (41) is grounded. The voltage application circuit (2) generates a discharge between the discharge electrode (41) and the counter electrode (42) by applying a voltage between them. The current limiting element (43) is electrically connected to the side opposite to the counter electrode (42) side of the discharge electrode (41). The current limiting element (43) limits the current flowing to the discharge electrode (41).

[0107] By following this approach, we can seek to improve the efficiency of free radical generation.

[0108] Regarding the discharge device (10) of the second state, in the first state, the current limiting element (43) includes at least one of a resistive element (431) and a capacitive element.

[0109] By following this approach, we can seek to improve the efficiency of free radical generation.

[0110] The discharge device (10) of the third state sample further includes a liquid supply unit (5) compared to the first or second state sample. The liquid supply unit (5) supplies liquid (50) for electrostatic atomization 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) through a current limiting element (43).

[0111] In this way, it is possible to improve the efficiency of free radical generation while supplying liquid (50) to the discharge electrode (41) through the liquid supply section (5).

[0112] The discharge device (10) of the fourth state sample is a thin film in the third state sample where the current limiting element (43) is a thin film.

[0113] In this case, by means of the current limiting element (43), the efficiency of free radical generation can be improved, and by means of the liquid supply part (5), liquid (50) can be supplied to the discharge electrode (41).

[0114] Regarding the discharge device (10) of the fifth state, in any of the states from the first to the fourth state, the resistance value of the current limiting element (43) is 1 MΩ or more.

[0115] By following this approach, we can improve the efficiency of free radical generation.

[0116] The discharge device (10) of the sixth state sample is further equipped with opposing (42) electrodes in any of the first to fifth state samples.

[0117] In this way, the efficiency of free radical generation can be improved by the discharge generated between the discharge electrode (41) and the counter electrode (42).

[0118] The discharge device (10) of the 7th state is used in any of the 1st to 6th states to electrostatically atomize the liquid (50) held at the discharge electrode (41) by the above discharge.

[0119] In this way, we can simultaneously improve the efficiency of free radical generation and generate charged microparticle water containing free radicals.

[0120] The configuration of the second to seventh states is not a necessary configuration for the discharge device (10) and can be omitted appropriately.

[0121] 1: Voltage application device 10: Discharge device 2: Voltage application circuit 21: Drive Circuit 22: Voltage generation circuit 220: Insulating Transformer 221: Primary winding 222: Secondary winding 223: Auxiliary winding 3: Control Circuit 31: Voltage control circuit 32: Current control circuit 321: Reference Voltage Generation Unit 4: Load 40: Casing 41: Discharge electrode 411: Front end 4111: Part 1 4112: Part 2 4113: Neck retraction 4114: End Edge 412: Base end 4121: Page 1 4122: Page 2 413: Shaft 42: Opposing electrode 421: concave part 4211: Bottom wall 422: Support Department 423: Protruding Platform 4231: Bottom wall 4232: Opening 43: Current Limiting Elements 431: Resistive element 44, 44B: Conducting components 5: Liquid Supply Department 50: Liquid 501: Taylor Cone 502: Peripheral edge 51: Cooling device 511: Peltier element 512: Heat sink 6: Input Section B1: Boost circuit C1~C3: Capacitors D1: Dipolar D11: Maximum diameter f1, f2: Driving frequency I1, I2: Thresholds Ix1: Current waveform L1: Total Length OP1: Operational Amplifier Q1~Q3: Transistors R1~R11: Resistors Si1: Control signal T: Time T1, T2: Discharge cycle V0: Minimum value V1, V2: Maximum value Vcc: Control power supply Vin: Input voltage Vx1: Voltage waveform X1-X1: Line ZD1: Zener Diode θ1: Vertex angle

Claims

1. A discharge device comprising: a discharge electrode disposed opposite to a counter electrode and holding a liquid thereon; a voltage application circuit electrically connected to the discharge electrode and the counter electrode such that the discharge electrode is grounded, thereby generating a discharge between the discharge electrode and the counter electrode by applying a voltage between the discharge electrode and the counter electrode; a current limiting element electrically connected to the side of the discharge electrode opposite to the counter electrode side, limiting the current flowing to the discharge electrode; and a liquid supply unit supplying liquid for electrostatic atomization to the discharge electrode, the liquid supply unit including a Peltier element thermally coupled to the discharge electrode through the current limiting element.

2. The discharge device of claim 1, wherein the aforementioned current limiting element includes at least one of a resistive element and a capacitive element.

3. The discharge device as claimed in claim 1, wherein the aforementioned 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 aforementioned current limiting element is 1 MΩ or more.

5. The discharge device according to any one of claims 1 to 3 further comprises the aforementioned opposing electrode.

6. The discharge device of any one of claims 1 to 3, which electrostatically atomizes the liquid held at the aforementioned discharge electrode by means of the aforementioned discharge.

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

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