Discharge device

Abstract

To provide a discharge device capable of reducing discharge sound.SOLUTION: A discharge device 10 includes a voltage application circuit 2 for generating discharge in a discharge electrode 41 by applying an output voltage Vo to a load 4 including the discharge electrode 41 for holding liquid 50. The voltage application circuit 2 has a function of fluctuating magnitude of an output voltage Vo, and a function of switching a discharge period that is a period for fluctuating the magnitude of the output voltage Vo to any one of a plurality of periods with the elapsed time.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a discharge device. [Background technology]

[0002] Conventionally, a discharge device including a discharge electrode and a voltage application circuit has been provided.

[0003] For example, in the discharge device of Patent Document 1, a voltage application circuit applies a voltage to a load including a discharge electrode that holds liquid, thereby generating a discharge in the discharge electrode. The voltage application circuit mechanically vibrates the liquid by periodically varying the magnitude of the voltage applied to the load at a drive frequency within a predetermined range including the resonant frequency of the liquid. Then, the liquid held in the discharge electrode is electrostatically atomized by the discharge. As a result, charged minute particle liquid containing radicals is generated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-46635 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a discharge device, a discharge sound is generated when the discharge electrode discharges, and therefore, there is a demand for the discharge device to reduce the discharge sound.

[0006] An object of the present disclosure is to provide a discharge device capable of reducing discharge noise. [Means for solving the problem]

[0007] A discharge device according to an aspect of the present disclosure includes a voltage application circuit that applies an output voltage to a load including a discharge electrode that holds a liquid, thereby generating a discharge in the discharge electrode. The voltage application circuit has a function of varying the magnitude of the output voltage and a function of setting a discharge period, which is a period during which the magnitude of the output voltage is varied, to one of a plurality of periods. Based on elapsed time and the ability to switch between them. A discharge device according to one aspect of the present disclosure includes a voltage application circuit that applies an output voltage to a load including a discharge electrode that holds a liquid, thereby generating a discharge in the discharge electrode. The voltage application circuit has a function of varying the magnitude of the output voltage and a function of switching a discharge period, which is a period for varying the magnitude of the output voltage, to one of a plurality of periods over time. The voltage application circuit switches the discharge period to one of the plurality of periods every time the discharge period is repeated a predetermined number of times. A discharge device according to one aspect of the present disclosure includes a voltage application circuit that applies an output voltage to a load including a discharge electrode that holds a liquid, thereby generating a discharge in the discharge electrode. The voltage application circuit has a function of varying the magnitude of the output voltage and a function of switching a discharge period, which is a period for varying the magnitude of the output voltage, to one of a plurality of periods over time. The voltage application circuit randomly switches the discharge period to one of the plurality of periods. Effect of the Invention

[0008] The present disclosure has an effect of reducing discharge noise. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram of a discharge device according to an embodiment. [Diagram 2] Fig. 2A is a schematic diagram showing a state in which the liquid held by the discharge electrode in the discharge device is expanded, and Fig. 2B is a schematic diagram showing a state in which the liquid held by the discharge electrode in the discharge device is contracted. [Diagram 3] Fig. 3A is a perspective view showing a specific example of a discharge electrode and a counter electrode in the discharge device of the above Fig. 3B is a cross-sectional view taken along line X1-X1 in Fig. 3A. [Figure 4] FIG. 4 is a side view showing the tip shape of the discharge electrode of the above. [Diagram 5] FIG. 5 is a circuit diagram showing an example of the discharge device of the above embodiment. [Figure 6] Fig. 6A is a graph showing the output of the discharge device of the embodiment, and Fig. 6B is a graph showing the output of a discharge device according to a comparative example. [Figure 7] FIG. 7 is a graph showing frequency characteristics of discharge sounds of the above discharge device and a discharge device according to a comparative example. [Figure 8] FIG. 8 is a graph simply showing the output of the discharge device according to the first modified example of the embodiment. [Figure 9]FIG. 9 is a graph simply showing the output of the discharge device according to the second modified example of the embodiment. [Figure 10] FIG. 10 is a graph simply showing the output of the discharge device according to the third modified example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] FIELD OF THE DISCLOSURE Embodiments relate generally to a discharge device. More particularly, embodiments relate to a discharge device that generates a discharge in a discharge electrode that holds a liquid.

[0011] Hereinafter, the discharge device according to the embodiment will be described in detail with reference to the drawings. However, each drawing described in the following embodiment is a schematic drawing, and the size and thickness ratio of each component do not necessarily reflect the actual dimensional ratio.

[0012] In addition, the embodiment described below is merely an example of an embodiment of the present disclosure. The present disclosure is not limited to the following embodiment, and various modifications are possible depending on the design, etc., as long as the effects of the present disclosure can be achieved.

[0013] (Embodiment) (1) Overview First, an overview of a discharge device 10 according to this embodiment will be described with reference to FIG.

[0014] A discharge device 10 according to this embodiment includes a voltage application device 1, a load 4, and a liquid supply unit 5, as shown in FIG.

[0015] The voltage application device 1 is a device that applies a voltage Vo to a load 4 to generate a discharge, and includes a voltage application circuit 2 and a detection circuit 3. That is, the discharge device 10 includes the voltage application circuit 2. In the following, the voltage Vo will be referred to as an output voltage Vo.

[0016] The load 4 has a discharge electrode 41 and a counter electrode 42. The counter electrode 42 is an electrode disposed so as to face the discharge electrode 41 with a gap therebetween. In other words, the discharge electrode 41 is disposed so as to face the counter electrode 42. In the load 4, a discharge is generated between the discharge electrode 41 and the counter electrode 42 by applying an output voltage Vo between the discharge electrode 41 and the counter electrode 42.

[0017] The liquid supply unit 5 has a function of supplying the liquid 50 to the discharge electrode 41 .

[0018] Thus, the discharge device 10 according to this embodiment includes, as its components, the voltage application circuit 2, the detection circuit 3, the liquid supply unit 5, the discharge electrode 41, and the counter electrode 42. However, it is sufficient for the discharge device 10 to include the voltage application circuit 2 as a minimum component, and each of the detection circuit 3, the discharge electrode 41, the counter electrode 42, the liquid supply unit 5, etc. may not be included as components of the discharge device 10.

[0019] In the discharge device 10 according to the present embodiment, in a state in which the liquid 50 is held by the discharge electrode 41, the voltage application circuit 2 applies an output voltage Vo between the discharge electrode 41 and the counter electrode 42. The state in which the liquid 50 is held by the discharge electrode 41 is, for example, a state in which the liquid 50 is attached to the surface of the discharge electrode 41. That is, the voltage application circuit 2 applies the output voltage Vo to the load 4 including the discharge electrode 41 that holds the liquid 50. As a result, a discharge occurs between the discharge electrode 41 and the counter electrode 42, and the liquid 50 held by the discharge electrode 41 is electrostatically atomized by the discharge. That is, the discharge device 10 according to the present embodiment constitutes a so-called electrostatic atomization device. In the discharge device 10, the liquid 50 held by the discharge electrode 41 is electrostatically atomized by the discharge generated between the discharge electrode 41 and the counter electrode 42. In the present embodiment, the liquid 50 held by the discharge electrode 41, that is, the liquid 50 to be electrostatically atomized, is also simply referred to as the "liquid 50".

[0020] 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 electrode (plus) of the voltage application circuit 2, and the discharge electrode 41 is electrically connected to the negative electrode (ground) of the voltage application circuit 2. The voltage application circuit 2 applies an output voltage Vo between the discharge electrode 41 and the counter electrode 42.

[0021] The voltage application circuit 2 applies the output voltage Vo to the load 4 (between the discharge electrode 41 and the counter electrode 42) to generate a discharge between the discharge electrode 41 and the counter electrode 42. In particular, in this embodiment, the voltage application circuit 2 periodically varies the magnitude of the output voltage Vo to generate a discharge intermittently. That is, the output voltage Vo alternates between a period in which the output voltage Vo rises to a high voltage and a period in which the output voltage Vo falls to a low voltage, and the periodic variation in the magnitude of the output voltage Vo generates a mechanical vibration in the liquid 50. Note that the "high voltage" referred to here may be any voltage set to generate a discharge in the discharge electrode 41, and is, for example, a voltage with a peak of about 7.0 kV. However, the voltage value of the output voltage Vo is not limited to about 7.0 kV, and is appropriately set according to, for example, the shapes of the discharge electrode 41 and the counter electrode 42, the distance W1 between the discharge electrode 41 and the counter electrode 42 (see FIG. 3B), and the like. Furthermore, the "low voltage" may be any voltage that is set so that no discharge occurs in the discharge electrode 41, and may be a voltage lower than the above-mentioned "high voltage", and may be either a voltage greater than 0 V or 0 V. In the following description, "the magnitude of the output voltage Vo fluctuates periodically" may be referred to as "the output voltage Vo fluctuates periodically".

[0022] Specifically, when the output voltage Vo is applied to the load 4, the liquid 50 held in the discharge electrode 41 forms a cone-like shape called a Taylor cone as shown in FIG. 2A during the period when the output voltage Vo is high, due to the force of the electric field. Then, the electric field is concentrated at the tip (apex) of the Taylor cone, and discharge occurs. At this time, the sharper the tip of the Taylor cone is, that is, the smaller (acute) the apex angle of the cone is, the smaller the electric field intensity required for dielectric breakdown becomes, and discharge is more likely to occur. Also, during the period when the output voltage Vo is low, the liquid 50 held in the discharge electrode 41 forms an approximately spherical shape as shown in FIG. 2B due to the reduction in the force of the electric field. Then, due to the periodic fluctuation of the output voltage Vo, the liquid 50 held in the discharge electrode 41 is deformed alternately into the shape shown in FIG. 2A and the shape shown in FIG. 2B in association with mechanical vibration. As a result, the Taylor cone as described above is formed periodically, and discharge occurs intermittently in accordance with the timing at which the Taylor cone as shown in FIG. 2A is formed. In addition, in FIG. 2A and FIG. 2B, the liquid 50 is hatched with dots so that the tip portion 411 and the liquid 50 can be easily distinguished from each other.

[0023] The discharge device 10 generates radicals by generating discharge between the discharge electrode 41 and the counter electrode 42 of the load 4, and electrostatically atomizes the liquid 50 held by the discharge electrode 41. The discharge device 10 generates nanometer-sized charged minute particle liquid (charged minute particle water) containing radicals in fine droplets of the electrostatically atomized liquid 50. That is, the discharge device 10 functions as a charged minute particle liquid generating device. The radicals are the basis for providing useful effects in various situations, including sterilization, deodorization, moisturization, freshness preservation, and virus inactivation. Hereinafter, the radicals and the charged minute particle liquid may be collectively referred to as an active ingredient. The active ingredient also includes air ions, which will be described later.

[0024] The discharge device 10 generates the charged minute particle liquid containing radicals, thereby making it possible to extend the life of the radicals compared to the case where the radicals are released into the air alone. Furthermore, since the charged minute particle liquid is, for example, nanometer-sized, the charged minute particle liquid can be suspended over a relatively wide range.

[0025] In the discharge device 10 according to this embodiment, the voltage application circuit 2 is configured to have a function for periodically varying the magnitude of the output voltage Vo applied to the load 4, and to be able to switch the discharge period, which is the period for varying the magnitude of the output voltage Vo, to one of a plurality of periods over time. In other words, the discharge device 10 has a function for switching the discharge period over time, thereby generating discharge in a plurality of periods. As a result, the discharge device 10 can reduce the discharge sound compared to when the discharge period is a single period.

[0026] (2)Details Next, details of the discharge device 10 according to this embodiment will be described with reference to FIGS.

[0027] (2.1) Overall Structure 1, 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 includes a voltage application circuit 2 and a detection circuit 3. The load 4 includes a discharge electrode 41 and a counter electrode 42. The liquid supply unit 5 supplies liquid 50 to the discharge electrode 41.

[0028] (2.1.1) Electrode As shown in FIGS. 3A and 3B, each of the discharge electrode 41 and the counter electrode 42 is held in a housing 40 made of an electrically insulating synthetic resin.

[0029] (discharge electrode) The discharge electrode 41 is a rod-shaped electrode. The discharge electrode 41 includes a shaft portion 41a and a base end portion 41b. The shaft portion 41a is formed in a rod shape with a circular cross section, and has a tip portion 411 at a first end in the longitudinal direction of the shaft portion 41a. A flat base end portion 41b is formed integrally and continuously at a second end in the longitudinal direction of the shaft portion 41a (the end portion opposite to the tip portion 411). The tip portion 411 has a tapered shape in which the cross-sectional area becomes smaller as it approaches the tip of the shaft portion 41a. In other words, the discharge electrode 41 is a needle electrode in which the tip portion 411 is formed in a tapered shape. The "tapered shape" referred to here is not limited to a shape with a sharply pointed tip, but includes a shape with a rounded tip as shown in FIG. 2A and FIG. 2B.

[0030] The shape of the tip 411 of the discharge electrode 41 will be described with reference to Fig. 4. In Fig. 4, the liquid 50 is hatched with dots so that the tip 411 and the liquid 50 can be easily distinguished from each other.

[0031] The shape of the tip 411 of the discharge electrode 41 is, for example, a shape including a cone portion. The shape of the part of the tip 411 facing the counter electrode 42 (here, the shape of the tip of the cone portion) is, for example, an R-shape. That is, the shape of the part of the tip 411 opposite to the base end 41b side (see FIG. 3B) is an R-shape. In the present disclosure, the "R-shape" may include a surface of a certain member being rounded (having a roundness). The tip surface of the tip 411 of this embodiment includes a curved surface having a convex roundness. The tip surface of the discharge electrode 41 of this embodiment has a cross-sectional shape including the central axis of the discharge electrode 41 formed in an arc shape that is continuously connected from the side surface of the tip 411, and does not include a corner. That is, the tip surface of the discharge electrode 41 is a curved surface (curved surface) as a whole. For example, the shape of the tip 411 is a hemispherical shape (or a nearly hemispherical shape).

[0032] The tip portion 411 has a first portion 4111 and a second portion 4112. The first portion 4111 is a portion of the tip portion 411 closer to the base end portion 41b than the second portion 4112, and is cylindrical and flat in the axial direction of the discharge electrode 41. The second portion 4112 is a portion of the tip portion 411 farther from the base end portion 41b than the first portion 4111, and is conical. In short, the tip portion 411 has the first portion 4111 corresponding to a cylindrical portion and the second portion 4112 corresponding to a conical portion.

[0033] Furthermore, by applying a voltage between the discharge electrode 41 and the counter electrode 42, the liquid 50 held in the discharge electrode 41 is subjected to a force due to an electric field and takes on a conical shape called a Taylor cone, as shown in Fig. 4. The shape of the Taylor cone is a cone shape that follows the conical portion of the tip 411 of the discharge electrode 41, as shown in Fig. 4. A second portion 4112 of the tip 411 of the discharge electrode 41 enters the Taylor cone-shaped liquid 50. That is, in the discharge device 10 according to this embodiment, the second portion 4112 constitutes a part of the tip 411 that enters the Taylor cone-shaped liquid 50.

[0034] (Counter electrode) As shown in FIG. 3A and FIG. 3B, the counter electrode 42 is disposed so as to face the tip 411 of the discharge electrode 41. The counter electrode 42 includes, for example, a flat support portion 422, and a first recess 421 is provided at the approximate center of the support portion 422. The first recess 421 is formed in a truncated cone shape by recessing the approximate center of the support portion 422 toward the discharge electrode 41 side. A protruding portion 423 is integrally formed at the center of the bottom wall 4211 of the first recess 421. The protruding portion 423 is formed in a truncated cone shape (dome shape) by protruding a part of the bottom wall 4211 of the first recess 421 to the opposite side to the discharge electrode 41 side. In other words, a truncated cone-shaped second recess 424 is formed in the bottom wall 4211 by recessing the center of the bottom wall 4211 in the opposite direction to the discharge electrode 41.

[0035] The direction in which the first recess 421 is recessed (the direction in which the first recess 421 is recessed) and the direction in which the protruding portion 423 protrudes (the direction in which the second recess 424 is recessed) are opposite to each other. A circular opening 4232 is formed in the center of a top wall 4231 (a bottom wall 4231 of the second recess 424) of the protruding portion 423. The opening 4232 penetrates the top wall 4231 in the thickness direction of the top wall 4231.

[0036] The above-mentioned counter electrode 42 comprises a truncated cone-shaped first recess 421 recessed toward the discharge electrode 41, a truncated cone-shaped protrusion 423 protruding away from the discharge electrode 41 at the bottom surface 4211 of the first recess 421, and an opening 4232 formed in a top wall 4231 of the protrusion 423.

[0037] Here, the thickness direction of the counter electrode 42 (the penetration direction of the opening 4232) coincides with the longitudinal direction of the discharge electrode 41. In plan view (seen from the thickness direction of the counter electrode 42), the tip 411 of the discharge electrode 41 is located near the center of the opening 4232 of the counter electrode 42. The tip 411 of the discharge electrode 41 is located outside the second recess 424 of the counter electrode 42, and is located closer to the base end 41b of the discharge electrode 41 than the bottom wall 4211 of the first recess 421. That is, a gap (space) is secured between the counter electrode 42 and the discharge electrode 41 by at least the opening 4241 of the second recess 424 of the counter electrode 42. In other words, the counter electrode 42 is disposed so as to face the discharge electrode 41 via a gap, and is spatially separated from the discharge electrode 41.

[0038] The abutment 423 (second recess 424) of the counter electrode 42 faces the discharge electrode 41, and is formed so as to have a shape axially symmetrical with respect to the shaft 41a of the discharge electrode 41 in a plan view. The periphery of the opening 4241 of the second recess 424 (the periphery of the opening 4241 facing the opening 4232 in the abutment 423) becomes an annular edge 425 that constitutes the boundary between the bottom wall 4211 and the abutment 423. In a plan view, the tip 411 of the discharge electrode 41 is located at the center of the annular edge 425. That is, the distance W1 (see FIG. 3B) between the annular edge 425 and the tip 411 is equal around the entire circumference of the edge 425.

[0039] (2.1.2)Liquid supply section The liquid supply unit 5 supplies the liquid 50 for electrostatic atomization to the discharge electrode 41. The liquid supply unit 5 is realized by using a cooling device 51 shown in FIG. 3B as an example. The cooling device 51 cools the discharge electrode 41 to generate condensed water as the liquid 50 on the discharge electrode 41. Specifically, 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 passing current through the pair of Peltier elements 511. The pair of heat sinks 512 are held by the housing 40 by a portion of each of the pair of heat sinks 512 being embedded in the housing 40. At least a portion of the pair of heat sinks 512 that holds the Peltier elements 511 is exposed from the housing 40.

[0040] The pair of Peltier elements 511 are mechanically and electrically connected to the base end 41b of the discharge electrode 41, for example, by solder. The pair of Peltier elements 511 are also mechanically and electrically connected to the pair of heat sinks 512, for example, by solder. Electric current is applied to the pair of Peltier elements 511 through the pair of heat sinks 512 and the discharge electrode 41. Therefore, the cooling device 51 constituting the liquid supply unit 5 cools the entire discharge electrode 41 through the base end 41b. As a result, moisture in the air condenses and adheres to the surface of the discharge electrode 41 as condensed water. This condensed water is held in the discharge electrode 41 as liquid 50. That is, the liquid supply unit 5 is configured to cool the discharge electrode 41 and generate condensed water as the liquid 50 on the surface of the discharge electrode 41. In this configuration, the liquid supply unit 5 can supply the liquid 50 (condensed water) to the discharge electrode 41 by utilizing the moisture in the air, so that the supply and replenishment of liquid to the discharge device 10 is not required.

[0041] (2.1.3) Voltage application circuit and detection circuit As shown in FIG. 1, the voltage application circuit 2 has a drive circuit 21 and a voltage generation circuit 22. The drive circuit 21 is a circuit that drives the voltage generation circuit 22. The voltage generation circuit 22 is a circuit that receives power from a power supply unit 6 and generates an output voltage Vo that is a voltage to be applied to the load 4. The power supply unit 6 is a power supply circuit that generates a DC voltage of, for example, several volts to several tens of volts. In the present embodiment, the power supply unit 6 is described as not being included in the components of the voltage application device 1, but the power supply unit 6 may be included in the components of the voltage application device 1. The voltage application circuit 2 periodically boosts the input voltage Vin from the power supply unit 6 to generate an output voltage Vo, and applies the output voltage Vo to the load 4.

[0042] The voltage application circuit 2 is electrically connected to the load 4 (the discharge electrode 41 and the counter electrode 42). The voltage application circuit 2 applies a periodically varying output voltage Vo to the load 4. The voltage application circuit 2 is configured to apply the output voltage Vo between the discharge electrode 41 and the counter electrode 42, with the discharge electrode 41 being the negative electrode (ground) and the counter electrode 42 being the positive electrode (plus). When the voltage application circuit 2 is applying the output voltage Vo 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 at a high potential and the discharge electrode 41 side at a low potential.

[0043] The voltage application circuit 2 operates in at least one of a first mode and a second mode. The first mode is a mode for increasing the output voltage Vo over time, leading to dielectric breakdown to start discharging, and generating an output current Io (discharge current). The second mode is a mode for cutting off the output current Io to end discharging. In other words, the voltage application circuit 2 has a first mode and a second mode as operation modes. Specifically, the drive circuit 21 drives the voltage generation circuit 22 in either the first mode or the second mode.

[0044] The detection circuit 3 detects the magnitudes of the output voltage Vo and the output current Io. The voltage application circuit 2 alternately repeats a first mode and a second mode as an operation mode based on the detection result of the detection circuit 3 during a drive period in which the voltage application device 1 is driven.

[0045] This causes the magnitude of the electrical energy acting on the liquid 50 held in the discharge electrode 41 to vary periodically, and as a result, the liquid 50 held in the discharge electrode 41 mechanically vibrates in a period that varies the output voltage Vo.

[0046] In this embodiment, the voltage application circuit 2 operates based on the object to be monitored by the detection circuit 3. The "object to be monitored" here refers to the output current Io and output voltage Vo of the voltage application circuit 2. Note that the "object to be monitored" may be at least one of the output current Io and output voltage Vo of the voltage application circuit 2.

[0047] As shown in FIG. 1, the detection circuit 3 has a voltage detection circuit 31 and a current detection circuit 32. The voltage detection circuit 31 monitors the output voltage Vo of the voltage application circuit 2 and detects the magnitude (voltage value) of the output voltage Vo. The voltage detection circuit 31 outputs a voltage detection signal Si1 including data on the magnitude of the output voltage Vo to the drive circuit 21 of the voltage application circuit 2. The current detection circuit 32 monitors the output current Io of the voltage application circuit 2 and detects the magnitude (current value) of the output current Io. The current detection circuit 32 outputs a current detection signal Si2 including data on the magnitude of the output current Io to the drive circuit 21 of the voltage application circuit 2. The drive circuit 21 drives the voltage generation circuit 22 based on the voltage detection signal Si1 and the current detection signal Si2 to control the output voltage Vo. That is, the detection circuit 3 monitors both the output current Io and the output voltage Vo of the voltage application circuit 2. The detection circuit 3 may also monitor one of the output current Io and the output voltage Vo of the voltage application circuit 2.

[0048] Since there is a correlation between the output voltage Vo (secondary side voltage) of the voltage application circuit 2 and the input voltage Vin (primary side voltage) of the voltage application circuit 2, the voltage detection circuit 31 may indirectly detect the output voltage Vo from the input voltage Vin. Similarly, there is a correlation between the output current Io (secondary side current) of the voltage application circuit 2 and the input current (primary side current) of the voltage application circuit 2, so the current detection circuit 32 may indirectly detect the output current Io from the input current.

[0049] The voltage application circuit 2 is configured to operate in the first mode if the size of the monitored object is less than a threshold value, and to operate in the second mode if the size of the monitored object is equal to or greater than the threshold value. First, the voltage application circuit 2 operates in the first mode, and when the output voltage Vo increases with time, a corona discharge is initiated in the discharge electrode 41 due to localized dielectric breakdown, and an output current Io is generated. When the size of the monitored object reaches the threshold value, the voltage application circuit 2 operates in the second mode, and the output voltage Vo decreases, and the potential difference between the discharge electrode 41 and the counter electrode 42 decreases, thereby cutting off the output current Io. That is, after the load 4 is discharged, the voltage application circuit 2 reduces the output voltage Vo to cause the output current Io to disappear (disappear). Then, the voltage application circuit 2 operates again in the first mode, and the above operation is repeated. The voltage application circuit 2 may switch the operation mode from the first mode to the second mode when a certain time has elapsed since the load 4 was discharged.

[0050] Specifically, if the output voltage Vo is less than the voltage threshold Vs1 (see FIG. 6A) and the output current Io is less than the current threshold Is1 (see FIG. 6A), the voltage application circuit 2 operates in the first mode and increases the output voltage Vo over time. If the output current Io becomes equal to or greater than the current threshold Is1 (see FIG. 6A) while operating in the first mode, the voltage application circuit 2 switches the operation mode from the first mode to the second mode and ends the discharge. Note that in FIG. 6A, the voltage application circuit 2 switches the operation mode from the first mode to the second mode when a certain time has elapsed since the output current Io became equal to or greater than the current threshold Is1.

[0051] In this way, the voltage application circuit 2 operates to alternate between the first mode and the second mode during the drive period, and periodically varies the magnitude of the output voltage Vo applied between the discharge electrode 41 and the counter electrode 42. The voltage application circuit 2 first sets the operation mode to the first mode, and generates a localized corona discharge at the tip 411 of the discharge electrode 41 that holds the liquid 50. When the discharge starts, the voltage application circuit 2 sets the operation mode to the second mode and ends the discharge. As a result, the discharge electrode 41 intermittently discharges repeatedly.

[0052] The specific circuit configurations of the drive circuit 21 and the voltage generating circuit 22 (booster circuit B1) will be described later in the section "(2.2) Circuit Configuration."

[0053] (2.2) Circuit configuration Next, a specific circuit configuration of the voltage application device 1 will be described with reference to Fig. 5. Fig. 5 is a circuit diagram that shows an example of a circuit configuration of the discharge device 10. Note that in Fig. 5, the power supply unit 6 is omitted from the illustration.

[0054] As described above, the voltage application circuit 2 includes the drive circuit 21 and the voltage generation circuit 22. In the example of FIG. 5, the voltage application circuit 2 is an insulating DC / DC converter and includes a boost circuit B1. The boost circuit B1 periodically boosts a DC input voltage Vin (e.g., 13.8 V) from the power supply unit 6 and outputs it as an output voltage Vo. Here, the voltage generation circuit 22 functions as the boost circuit B1. The output voltage Vo is applied to the load 4 (the discharge electrode 41 and the counter electrode 42) as an applied voltage. That is, the voltage application circuit 2 applies the periodically fluctuating output voltage Vo to the load 4, thereby periodically causing a discharge in the discharge electrode 41.

[0055] The voltage generating circuit 22 (booster circuit B1) has an isolation transformer 220. The isolation transformer 220 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 and magnetically coupled to the secondary winding 222. A counter electrode 42 is electrically connected to a first end of the secondary winding 222. In other words, the boost circuit B1 includes the isolation transformer 220 that boosts an input voltage Vin input to a primary side (primary winding 221 side) and outputs an output voltage Vo from a secondary side (secondary winding 222 side) electrically connected to a load 4.

[0056] The driving circuit 21 includes a transistor Q1, and is configured to supply power to a primary winding 221 of an isolation transformer 220 by a switching operation of the transistor Q1. In addition to the transistor Q1, the driving circuit 21 includes a microcomputer MC1 that drives the transistor Q1. The transistor Q1 is, for example, an npn-type bipolar transistor.

[0057] The collector of the transistor Q1 is connected to the primary winding 221, and the emitter of the transistor Q1 is connected to ground. An input voltage Vin is applied from a power supply unit 6 to a series circuit of the primary winding 221 and the transistor Q1. The base of the transistor Q1 is connected to an output port of the microcomputer MC1 via a resistor R1. The control power supply generates a control voltage Vcc (e.g., 5 V) and applies the control voltage Vcc to the drive circuit 21.

[0058] With the above configuration, the voltage application circuit 2 constitutes a separately excited converter. That is, the transistor Q1 is repeatedly turned on and off by the microcomputer MC1, and a pulse-like voltage is generated in the primary winding 221. As a result, a high voltage is induced in the secondary winding 222 of the isolation transformer 220, and the high voltage induced in the secondary winding 222 is applied to the load 4 via the discharge electrode 41 and the counter electrode 42. Through these operations, the voltage application circuit 2 generates an output voltage Vo by periodically boosting the input voltage Vin, and applies the output voltage Vo to the load 4.

[0059] The detection circuit 3 includes a voltage detection circuit 31 and a current detection circuit 32 shown in FIG.

[0060] The voltage detection circuit 31 includes a diode D11, resistors R11-R13, and a capacitor C11. The anode of the diode D11 is connected to a first end of the auxiliary winding 223. The second end of the auxiliary winding 223 is connected to ground. The cathode of the diode D11 is connected to a first end of the capacitor C11 via the resistor R11. The second end of the capacitor C11 is connected to ground. Furthermore, the first end of the capacitor C11 is connected to an input port of the microcomputer MC1 via the resistor R12, and is connected to ground via a series circuit of the resistors R12 and R13.

[0061] With the above configuration, the voltage detection circuit 31 monitors the induced voltage of the auxiliary winding 223, thereby indirectly monitoring the output voltage Vo (induced voltage of the secondary winding 222) of the voltage application circuit 2 to be monitored. Specifically, the capacitor C11 is charged by the induced voltage of the auxiliary winding 223 via the diode D11 and resistor R11. The voltage of the capacitor C11 divided by the resistors R12 and R13 is input to the input port of the microcomputer MC1 as a voltage detection signal Si1. When the output voltage Vo increases, the voltage detection signal Si1 increases, and when the output voltage Vo decreases, the voltage detection signal Si1 decreases.

[0062] The current detection circuit 32 includes resistors R21 and R22, and capacitors C21 and C22. A control voltage Vcc is applied to a first end of the resistor R21, and a first end of the capacitor C21 is connected to a second end of the resistor R21. The second end of the capacitor C21 is connected to the ground. A second end of the secondary winding 222 of the insulating transformer 220 is connected to a connection point between the resistor R21 and the capacitor C21. The second end of the secondary winding 222 is an end opposite to the first end of the secondary winding 222 to which the counter electrode 42 is connected. That is, the control voltage Vcc is applied to the counter electrode 42 via the resistor R21 and the secondary winding 222. The second end of the secondary winding 222 is connected to the ground via a series circuit of the resistor R22 and the capacitor C22. The voltage of the capacitor C22 is input to an input port of the microcomputer MC1 as a current detection signal Si2. When the output current Io increases, the current detection signal Si2 increases, and when the output current Io decreases, the current detection signal Si2 decreases.

[0063] The microcomputer MC1 monitors the output voltage Vo based on the voltage detection signal Si1 and monitors the output current Io based on the current detection signal Si2. If the output voltage Vo is less than the voltage threshold (see Vs1 in FIG. 6A) and the output current Io is less than the current threshold (see Is1 in FIG. 6A), the microcomputer MC1 sets the operation mode to the first mode and drives the transistor Q1 on and off. If the output current Io becomes equal to or greater than the current threshold while operating in the first mode, the microcomputer MC1 sets the operation mode to the second mode, stops driving the transistor Q1 on and off, and maintains the transistor Q1 in the off state. Note that in FIG. 6A, when a certain time has elapsed since the output current Io became equal to or greater than the current threshold Is1, the operation mode is set to the second mode, stops driving the transistor Q1 on and off, and maintains the transistor Q1 in the off state. In addition, when the output voltage Vo becomes equal to or greater than the voltage threshold value (see Vs1 in Figure 6A) while operating in the first mode, the microcomputer MC1 switches the operating mode to the second mode after a predetermined time has elapsed, stops turning the transistor Q1 on and off, and maintains the transistor Q1 in the off state.

[0064] (2.3) Discharge control Fig. 6A shows discharge control by the voltage application circuit 2 of this embodiment. Fig. 6A shows the waveform of the output voltage Vo and the waveform of the output current Io. In Fig. 6A, the horizontal axis represents time, the vertical axis on the left represents voltage, and the vertical axis on the right represents current.

[0065] The voltage application circuit 2 periodically varies the output voltage Vo, so that a discharge periodically occurs between the discharge electrode 41 and the counter electrode 42. In the load 4, a discharge occurs between the discharge electrode 41 and the counter electrode 42 due to a potential difference between the discharge electrode 41 and the counter electrode 42. Then, the discharge occurring between the discharge electrode 41 and the counter electrode 42 of the load 4 generates radicals, and the liquid 50 held in the discharge electrode 41 is electrostatically atomized. Thus, the discharge device 10 generates nanometer-sized charged minute particle liquid containing radicals in the fine droplets of the electrostatically atomized liquid 50. The generated charged minute particle liquid is discharged to the periphery of the discharge device 10, for example, through the opening 4232 of the counter electrode 42.

[0066] If the period during which the voltage application circuit 2 changes the output voltage Vo is defined as a discharge period, in each discharge period, the voltage application circuit 2 first operates in the first mode and increases the output voltage Vo from a minimum value Vo2 to a maximum value Vo1. Then, when the output voltage Vo reaches the maximum value Vo1, the voltage application circuit 2 maintains the output voltage Vo at the maximum value Vo1. At this time, when the output voltage Vo increases from the minimum value Vo2, a localized dielectric breakdown occurs at the tip of the liquid 50 held by the discharge electrode 41, and a micro-discharge due to a corona discharge begins. Thereafter, the output voltage Vo further increases and reaches the maximum value Vo1, and the output current Io flows.

[0067] When the voltage application circuit 2 is operating in the first mode, if the output current Io becomes equal to or greater than the current threshold Is1, the voltage application circuit 2 switches the operation mode from the first mode to the second mode and reduces the output voltage Vo to stop discharging. In FIG. 6A, the voltage application circuit 2 switches the operation mode from the first mode to the second mode and reduces the output voltage Vo to stop discharging when a certain time has elapsed since the output current Io became equal to or greater than the current threshold Is1. In other words, the waveform of the output voltage Vo is trapezoidal.

[0068] In addition, when the output voltage Vo becomes equal to or greater than the voltage threshold Vs1 while operating in the first mode, the voltage application circuit 2 switches the operation mode to the second mode after a predetermined time has elapsed, and stops discharging by switching the operation mode from the first mode to the second mode and reducing the output voltage Vo.

[0069] As described above, the output voltage Vo alternates between the maximum value Vo1 and the minimum value Vo2, and fluctuates periodically in the discharge period. That is, the magnitude of the output voltage Vo fluctuates in a range above 0V during the drive period. The maximum value Vo1 of the output voltage Vo corresponds to a discharge voltage that causes discharge. The minimum value Vo2 of the output voltage Vo is higher than 0V and lower than the maximum value Vo1. The maximum value Vo1 is, for example, about 7.0 kV. The minimum value Vo2 may be any voltage that is set so that no discharge occurs in the discharge electrode 41, and is a voltage higher than 0V and lower than the maximum value Vo1.

[0070] In Fig. 6A, when the output voltage Vo increases from the minimum value Vo2 to the maximum value Vo1, the output voltage Vo increases approximately linearly with time. When the output voltage Vo decreases from the maximum value Vo1 to the minimum value Vo2, the output voltage Vo decreases approximately linearly with time. Note that the output voltage Vo may increase or decrease nonlinearly with time.

[0071] The voltage application circuit 2 switches the discharge period, which is a period for varying the output voltage Vo, between the first period T1 and the second period T2 over time. Specifically, as shown in FIG. 6A, the voltage application circuit 2 alternately switches the discharge period between the first period T1 and the second period T2 for each discharge period. The first period T1 and the second period T2 are different discharge periods. For example, the first period T1 is 2.2 msec (frequency 455 Hz), and the second period T2 is 1.8 msec (frequency 555 Hz). That is, the voltage application circuit 2 uses two periods, the first period T1 and the second period T2, as the discharge period. The first period T1 and the second period T2 as the discharge period are set to be close to the resonance period of the liquid 50 held by the discharge electrode 41. The resonance period of the liquid 50 is a period in which the amplitude of the vibration of the liquid 50 caused by the variation of the output voltage Vo is maximized.

[0072] The resonance period of the liquid 50 depends on the volume (amount) of the liquid 50 and is expressed as [1 / a·V-0.5], where "V" is the volume of the liquid 50 held by the discharge electrode 41. "a" is a proportionality coefficient that depends on the surface tension, viscosity, etc. of the liquid 50 held by the discharge electrode 41.

[0073] For example, the volume of a Taylor cone is 0.0917 mm 3 The volume of the second portion 4112 of the tip portion 411 is 0.0650 mm 3 In this case, the volume of the liquid 50 forming the Taylor cone is 0.076 μL, and the resonance period of the liquid 50 is 0.33 msec. In this embodiment, the volume of the liquid 50 forming the Taylor cone is 0.46 μL, and the resonance period of the liquid 50 is 2 ms.

[0074] (2.4) Improvement of discharge noise The improvement of the discharge sound in the discharge device 10 according to this embodiment will be described below with reference to FIGS. 6A, 6B, and 7. FIG.

[0075] As described above, by periodically varying the magnitude of the voltage applied to the load 4, i.e., the output voltage Vo, in a discharge period, the magnitude of the electrical energy acting on the liquid 50 held in the discharge electrode 41 varies periodically. As a result, the liquid 50 mechanically vibrates in the discharge period. If the discharge period is set to the resonant period (the inverse of the resonant frequency) of the liquid 50 or close to the resonant period, the amplitude of the mechanical vibration of the liquid 50 caused by the variation in the magnitude of the output voltage Vo becomes relatively large. When the amplitude of the liquid 50 increases, the tip of the Taylor cone-shaped liquid 50 (see FIG. 4) becomes more pointed (sharp), making it easier to discharge.

[0076] However, the discharge device 10 generates a discharge sound due to mechanical vibration of the liquid 50. The larger the amplitude of the vibration of the liquid 50, the greater the sound pressure of the discharge sound. If the energy acting on the liquid 50 is suppressed, the discharge sound will be reduced, but the amount of active ingredients such as radicals and charged microparticle liquid generated by the discharge device 10 will also decrease. Therefore, there is a need to reduce the discharge sound while suppressing the decrease in the amount of active ingredients generated.

[0077] 6A, the voltage application circuit 2 of the discharge device 10 switches the discharge period, which is the period for varying the output voltage Vo, between a first period T1 and a second period T2 over time. In this embodiment, the voltage application circuit 2 uses two periods, the first period T1 and the second period T2, as the discharge period, and alternates between the discharge periods T1→T2→T1→T2→... for each discharge period. Therefore, the discharge sound of the discharge device 10 mainly includes sound components of the first period T1 and the second period T2.

[0078] Here, it is preferable that the average of the first period T1 and the second period T2 is included in a predetermined range including the resonance period of the liquid 50. In this case, the predetermined range including the resonance period of the liquid 50 may be a range in which the amount of the active ingredient generated by the discharge device 10 can be sufficiently secured. As a result, the amount of the active ingredient generated by the discharge device 10 can be made almost the same as the amount of the active ingredient generated by the comparative example of FIG. 6B described later, and the decrease of the active ingredient generated by the discharge device 10 can be suppressed. Specifically, the first period T1 is set to 2.2 msec (frequency 455 Hz) and the second period T2 is set to 1.8 msec (frequency 555 Hz) for a resonance period of 2 msec (frequency 500 Hz) of the liquid 50. That is, the average of the first period T1 and the second period T2 is equal to the resonance period of the liquid 50. Note that the closer the average of the first period T1 and the second period T2 is to the resonance period of the liquid 50, the more the amount of the active ingredient generated by the discharge device 10 can be increased.

[0079] 6B shows a discharge mode of a comparative example. In the comparative example, only one period T11 is used as the discharge period. Here, the period T11 is set to the resonance period of the liquid 50, 2 msec (frequency 500 Hz). Therefore, the discharge sound of the discharge device 10 mainly contains the sound component of the period T11.

[0080] Fig. 7 is a graph with frequency on the horizontal axis and sound pressure (magnitude) of the discharge sound on the vertical axis, and shows characteristics Y1 and Y11. Characteristic Y1 is the frequency characteristic of the discharge sound generated by the discharge device 10 operating in the discharge mode of Fig. 6A. Characteristic Y11 is the frequency characteristic of the discharge sound generated by the comparative example operating in the discharge mode of Fig. 6B.

[0081] In the characteristic Y1, the sound pressure reaches a maximum value (peak value) P1 at a frequency of 500 Hz (period of 2 msec) corresponding to the average of the first period T1 and the second period T2. In the characteristic Y11, the sound pressure reaches a maximum value (peak value) P11 at a frequency of 500 Hz (period of 2 msec) corresponding to the period T11. The maximum sound pressure P1 of the characteristic Y1 is smaller than the maximum sound pressure P11 of the characteristic Y11, and the discharge sound of the discharge device 10 is smaller than the discharge sound of the comparative example. In FIG. 7, the maximum sound pressure P1 of the characteristic Y1 is reduced by about 4 to 5 dB (about 40% reduction) than the maximum sound pressure P11 of the characteristic Y11. In other words, the discharge device 10 can reduce the discharge sound compared to the comparative example.

[0082] In the above description, the first period T1 and the second period T2 are each selected from the vicinity of the resonance period of the liquid 50 held in the discharge electrode 41, and the amount of the active ingredient generated by the discharge device 10 can be made almost the same as the amount of the active ingredient generated by the comparative example. However, if the first period T1 is 0.5 msec and the second period T2 is 3.5 msec, the average of the first period T1 and the second period T2 is 2 msec, which is the same as the resonance period, but the amount of the active ingredient generated by the discharge device 10 is significantly reduced compared to the comparative example. This is because the first period T1 and the second period T2 are each too far from the resonance period. Therefore, it is preferable that the first period T1 and the second period T2 are not too far from the resonance period. In other words, it is preferable that the first period T1 and the second period T2 as the discharge period are set to be in the vicinity of the resonance period.

[0083] Specifically, each of the first period T1 and the second period T2 is preferably equal to or less than a first value, which is the resonance period plus half the resonance period, and equal to or greater than a second value, which is the resonance period minus the half value. For example, if the resonance period is 2 msec, the half value of the resonance period is 1 msec. In this case, the first value is 3 msec (=2 msec+1 msec), and the second value is 1 msec (=2 msec-1 msec). That is, each of the first period T1 and the second period T2 is selected from the range of 1 msec or more and 3 msec or less. As a result, the reduction of the active ingredient generated by the discharge device 10 can be further suppressed.

[0084] (3) First Modification It is preferable that the voltage application circuit 2 switches the discharge period to one of a plurality of periods every time the discharge period is repeated a predetermined number of times.

[0085] In the above-described embodiment, the voltage application circuit 2 alternately switches the discharge period between the first period T1 and the second period T2, in the order of T1→T2→T1→T2→T1→..., for each discharge period (each discharge period).

[0086] Furthermore, the voltage application circuit 2 may alternately switch the discharge period between the first period T1 and the second period T2 every several periods of the discharge period (every several discharge periods). For example, in Fig. 8, the voltage application circuit 2 alternately switches the discharge period between the first period T1 and the second period T2 every two periods of the discharge period (every two discharge periods) as follows: T1→T1→T2→T2→T1→T1→T2→T2→...

[0087] (4) Second Modification The voltage application circuit 2 may switch the discharge period to one of three or more periods over time.

[0088] When three discharge periods T1, T2, and T3 are used, the voltage application circuit 2 switches the discharge period for each discharge period in the order of a first period T1, a second period T2, and a third period T3, that is, T1→T2→T3→T1→T2→T3→..., as shown in FIG. 9, for example.

[0089] Furthermore, the voltage application circuit 2 may switch the discharge period in the order of the first period T1, the second period T2, and the third period T3 every several periods of the discharge period. For example, the voltage application circuit 2 switches the discharge period in the order of T1→T1→T2→T2→T3→T3→T1... every two periods of the discharge period.

[0090] In this modified example, it is preferable that the average of the first period T1, the second period T2, and the third period T3 is equal to the resonance period of the liquid 50.

[0091] Moreover, each of the first period T1, the second period T2, and the third period T3 is preferably equal to or smaller than a first value, which is the sum of the resonance period and half the resonance period, and equal to or larger than a second value, which is the resonance period minus the half the resonance period. For example, if the resonance period is 2 msec, each of the first period T1, the second period T2, and the third period T3 is selected from the range of 1 msec or more and 3 msec or less.

[0092] It is also possible to use four or more discharge periods.

[0093] (5) Third Modification It is preferable that the voltage application circuit 2 randomly switches the discharge period to one of a plurality of periods.

[0094] 10, for example, the voltage application circuit 2 randomly switches the discharge period to any one of the first period T1, the second period T2, and the third period T3 for each discharge period. For example, the voltage application circuit 2 has a random number generator (random number generation function). The voltage application circuit 2 sets the period corresponding to the random number generated by the random number generator among the first period T1, the second period T2, and the third period T3 as the next discharge period.

[0095] In this modified example, it is preferable that the average of the first period T1, the second period T2, and the third period T3 is equal to the resonance period of the liquid 50.

[0096] Moreover, each of the first period T1, the second period T2, and the third period T3 is preferably equal to or smaller than a first value, which is the sum of the resonance period and half the resonance period, and equal to or larger than a second value, which is the resonance period minus the half the resonance period. For example, if the resonance period is 2 msec, each of the first period T1, the second period T2, and the third period T3 is selected from the range of 1 msec or more and 3 msec or less.

[0097] It is also possible to use four or more discharge periods.

[0098] (6) Fourth Modification In the above-described embodiment, the discharge caused by the discharge electrode 41 and the counter electrode 42 is a corona discharge, but the discharge caused by the discharge electrode 41 and the counter electrode 42 is not limited to a corona discharge.

[0099] For example, the discharge by the discharge electrode 41 and the counter electrode 42 may be a discharge (hereinafter referred to as a leader discharge) in which a phenomenon in which a corona discharge progresses and leads to a dielectric breakdown between the discharge electrode 41 and the counter electrode 42 is intermittently repeated. In a leader discharge, the voltage application circuit 2 operates in the first mode, the output voltage Vo increases with time, and when a local corona discharge progresses in the discharge electrode 41 and leads to a dielectric breakdown, a relatively large output current Io flows instantaneously. Immediately thereafter, the voltage application circuit 2 operates in the second mode, the output voltage Vo decreases, and the output current Io is cut off. Thereafter, the voltage application circuit 2 alternately repeats the first and second modes as the operation modes, thereby repeating a series of processes of corona discharge → dielectric breakdown → discharge current → discharge cutoff. In other words, in a leader discharge, a discharge path is intermittently formed between the discharge electrode 41 and the counter electrode 42, and a pulsed output current Io (discharge current) is repeatedly generated.

[0100] In such a leader discharge, radicals are generated with greater energy than in a corona discharge, and a large amount of radicals, about 2 to 10 times larger than in a corona discharge, are generated. The radicals generated in this way are the basis for useful effects in various situations, including sterilization, deodorization, moisturization, freshness preservation, and virus inactivation. Here, when radicals are generated by a leader discharge, ozone is also generated. However, while about 2 to 10 times more radicals are generated in a leader discharge than in a corona discharge, the amount of ozone generated is suppressed to the same level as in the case of a corona discharge. Therefore, the amount of ozone generated can be suppressed while increasing the amount of radicals generated.

[0101] Generally, when energy is applied between a pair of electrodes to generate a discharge, the discharge progresses from a corona discharge to a spark discharge, a glow discharge, and an arc discharge depending on the amount of energy applied.

[0102] A corona discharge is a discharge that occurs locally at one electrode and does not involve dielectric breakdown between a pair of electrodes (e.g., the discharge electrode 41 and the counter electrode 42). A spark discharge, a glow discharge, and an arc discharge are discharges that involve dielectric breakdown between a pair of electrodes. A spark discharge is a discharge in which a discharge path is formed instantaneously (single-shot). In a glow discharge and an arc discharge, the discharge path formed by dielectric breakdown is maintained while energy is being input between the pair of electrodes, and a discharge current is continuously generated between the pair of electrodes. If the current capacity that can be discharged per unit time from a power source (e.g., the voltage application circuit 2) between the pair of electrodes is sufficiently large, the discharge path once formed is maintained without interruption, and progresses from a corona discharge or spark discharge to a glow discharge and an arc discharge.

[0103] On the other hand, a leader discharge is accompanied by a dielectric breakdown between a pair of electrodes, but the dielectric breakdown does not occur continuously but occurs intermittently. Therefore, the discharge current occurring between the pair of electrodes occurs intermittently. In other words, as soon as the corona discharge progresses to dielectric breakdown, the voltage applied between the pair of electrodes is reduced, and the discharge path is interrupted and the discharge stops. Such occurrence and stopping of discharge is repeated, so that a discharge current flows intermittently between the pair of electrodes. In this way, a leader discharge differs from a spark discharge in which dielectric breakdown occurs instantaneously (single-shot), a glow discharge in which dielectric breakdown occurs continuously (i.e., a discharge current occurs continuously), and an arc discharge in that a state of high discharge energy and a state of low discharge energy are repeated.

[0104] In particular, by configuring the discharge electrode 41 and the counter electrode 42 as described above in (2.1.1), the point where the distance W1 (see FIG. 3B) between the tip 411 of the counter electrode 42 is shortest is the annular edge 425. Therefore, the discharge path between the discharge electrode 41 and the counter electrode 42 is easily generated between the annular edge 425 and the tip 411. That is, electric field concentration is easily generated at the annular edge 425 of the counter electrode 42. As a result, discharge (hereinafter referred to as round discharge) that forms a discharge path that spreads in a cone-like side connecting between the edge 425 of the counter electrode 42 and the tip 411 of the discharge electrode 41 is easily generated stably. In the round discharge, the discharge path between the discharge electrode 41 and the counter electrode 42 is a path from the tip 411 to the annular edge 425, that is, a path along the side of a cone that spreads from a point to a ring.

[0105] Furthermore, the discharge by the discharge electrode 41 and the counter electrode 42 may be a round discharge (hereinafter referred to as a round leader discharge) that generates dielectric breakdown intermittently. The round leader discharge has the advantages of both leader discharge and round discharge. In the round leader discharge, the discharge path is spread into a cone side shape, which prevents the electric field concentration from growing rapidly and progressing to a full-path breakdown discharge, and the partial breakdown discharge can be spread spatially. In other words, the round leader discharge can further increase the amount of active ingredients produced.

[0106] In addition, in each of the above-mentioned leader discharge, round discharge, and round leader discharge, it is preferable to form a discharge path with partial dielectric breakdown between the discharge electrode 41 and the counter electrode 42. In this case, the discharge path includes a first dielectric breakdown region generated around the discharge electrode 41 and a second dielectric breakdown region generated around the counter electrode 42. In other words, a discharge path with dielectric breakdown is formed between the discharge electrode 41 and the counter electrode 42, not entirely but partially (locally). In the present disclosure, "dielectric breakdown" means that the electrical insulation of an insulator (including gas) is broken down between conductors, and the insulating state can no longer be maintained. Dielectric breakdown of gas occurs, for example, when ionized molecules are accelerated by an electric field and collide with other gas molecules to be ionized, causing a sudden increase in ion concentration and causing a gas discharge. In short, in a discharge path with partial (local) dielectric breakdown, dielectric breakdown occurs only partially, that is, in only a part, in the gas (air) present on the path connecting the discharge electrode 41 and the counter electrode 42. That is, it is preferable that the discharge path formed between the discharge electrode 41 and the counter electrode 42 is a path that does not result in a complete breakdown but is a path that is partially broken down. Even in a discharge path where partial breakdown has occurred in this way (a part of the discharge path is not broken down), a current flows through the discharge path between the discharge electrode 41 and the counter electrode 42, and a discharge occurs. A discharge in this manner in which a discharge path with partial breakdown is formed is called a "partial breakdown discharge." In this partial breakdown discharge, it is preferable that the edge portion 425 is configured to have a shape that connects the bottom wall 4211 and the protruding portion 423 with a curved surface that has an arc-shaped cross section. By making the edge portion 425 a curved surface, partial breakdown discharge is more likely to occur.

[0107] In such partial breakdown discharge, radicals are generated with greater energy than in corona discharge, and a large amount of radicals, about 2 to 10 times larger than in corona discharge, are generated. The radicals generated in this way are useful not only for sterilization, deodorization, moisturization, freshness preservation, and virus inactivation, but also in various other situations. When radicals are generated by partial breakdown discharge, ozone is also generated. However, while the partial breakdown discharge generates about 2 to 10 times more radicals than in corona discharge, the amount of ozone generated is suppressed to the same level as in corona discharge.

[0108] In addition to the partial breakdown discharge, there is a discharge that develops from a corona discharge and forms a discharge path in which a continuous dielectric breakdown (full-path breakdown) occurs between the discharge electrode 41 and the counter electrode 42 (a discharge path in which dielectric breakdown continues from the discharge electrode 41 to the counter electrode 42). Hereinafter, this type of discharge is referred to as a "full-path breakdown discharge." In a full-path breakdown discharge, when a corona discharge develops and a full-path breakdown occurs, a relatively large output current Io (discharge current) flows instantaneously, and immediately thereafter, the output voltage Vo drops and the output current Io is cut off, and the output voltage Vo rises and dielectric breakdown occurs. This phenomenon is repeated. In a full-path breakdown discharge, radicals are generated with large energy compared to a corona discharge, as in a partial breakdown discharge, and a large amount of radicals are generated, about 2 to 10 times larger than that of a corona discharge. However, the energy of a full-path breakdown discharge is even larger than the energy of a partial breakdown discharge. Therefore, even if a large amount of radicals are generated due to the disappearance of ozone and an increase in radicals when the energy level is "medium," some of the radicals may disappear when the energy level becomes "high" in the subsequent reaction pathway.

[0109] In other words, in the case of full-path breakdown discharge, the energy involved in the discharge is too high, so that some of the active ingredients such as the generated radicals may disappear, leading to a decrease in the generation efficiency of the active ingredients. As a result, by adopting partial breakdown discharge, it is possible to improve the generation efficiency of the active ingredients compared to when full-path breakdown discharge is adopted.

[0110] As described above, in the discharge device 10, the discharge between a pair of electrodes (for example, the discharge electrode 41 and the counter electrode 42) is not limited to a corona discharge, and may be a leader discharge, a round discharge, or a round leader discharge.

[0111] The leader discharge intermittently forms a discharge path between a pair of electrodes, and generates a discharge current (output current Io) intermittently and repeatedly.

[0112] The round discharge forms a discharge path that spreads out like a cone side surface connecting a pair of electrodes.

[0113] The round leader discharge intermittently forms a discharge path that spreads out like a cone connecting a pair of electrodes, and generates a discharge current (output current Io) intermittently and repeatedly.

[0114] Furthermore, each of the leader discharge, the round discharge, and the round leader discharge may be either a partial breakdown discharge or a full-path breakdown discharge.

[0115] The partial breakdown discharge forms a discharge path with partial dielectric breakdown between a pair of electrodes.

[0116] A full-path breakdown discharge forms a discharge path in which a continuous dielectric breakdown occurs between a pair of electrodes (a discharge path in which dielectric breakdown occurs continuously from one electrode to the other electrode).

[0117] (7) Other modifications The shape of the counter electrode 42 is not limited to that of the above embodiment, and may be any shape that generates a discharge between the counter electrode 42 and the discharge electrode 41. For example, the counter electrode 42 may be configured to include a needle-shaped protrusion and to generate a dielectric breakdown region between the needle-shaped protrusion and the discharge electrode 41.

[0118] The discharge device 10 may omit the liquid supply unit 5 for generating the charged minute particle liquid. In this case, the discharge device 10 generates air ions by partial breakdown discharge occurring between the discharge electrode 41 and the counter electrode 42. In this configuration, the air ions are included in the active ingredient.

[0119] Furthermore, the liquid supply unit 5 is not limited to a configuration that cools the discharge electrode 41 to generate condensed water on the discharge electrode 41 as in the above-described embodiment. The liquid supply unit 5 may be configured to supply the liquid 50 from a tank to the discharge electrode 41 using, for example, a supply mechanism such as a capillary phenomenon or a pump. Furthermore, the liquid 50 is not limited to water (including condensed water) and may be a liquid other than water.

[0120] Furthermore, the voltage application circuit 2 may be configured to apply an output voltage Vo between the discharge electrode 41 and the counter electrode 42, with the discharge electrode 41 as a positive electrode (plus) and the counter electrode 42 as a negative electrode (ground). Furthermore, since it is sufficient that a potential difference (voltage) occurs between the discharge electrode 41 and the counter electrode 42, the voltage application circuit 2 may apply a negative voltage to the load 4 by setting the electrode on the high potential side (positive electrode) as the ground and the electrode on the low potential side (negative electrode) as a negative potential. That is, the voltage application circuit 2 may set the discharge electrode 41 as the ground and the counter electrode 42 as a negative potential, or may set the discharge electrode 41 as a negative potential and the counter electrode 42 as the ground.

[0121] The voltage application device 1 may also include a limiting resistor between the voltage application circuit 2 and the discharge electrode 41 or the counter electrode 42. The limiting resistor is a resistor for limiting the peak value of the output current Io (discharge current) that flows after dielectric breakdown in partial breakdown discharge. The limiting resistor is electrically connected, for example, between the voltage application circuit 2 and the discharge electrode 41, or between the voltage application circuit 2 and the counter electrode 42.

[0122] In addition, the specific circuit configuration of the voltage application device 1 can be changed as appropriate. For example, the voltage application circuit 2 is not limited to a separately excited converter, and may be a self-excited converter. In addition, the voltage generation circuit 22 may be realized by a transformer (piezoelectric transformer) having a piezoelectric element.

[0123] Furthermore, the waveform of the output voltage Vo that the voltage application circuit 2 applies between the discharge electrode 41 and the counter electrode 42 is not limited to the waveforms shown in Fig. 6A and Fig. 8 to Fig. 10. The output voltage Vo may have a triangular waveform that gradually increases and then immediately decreases when a discharge path is formed and the output current Io (discharge current) starts to flow.

[0124] Furthermore, the discharge device 10 may omit the counter electrode 42. In this case, the discharge occurs between the discharge electrode 41 and a member (such as a housing) present around the discharge electrode 41. Furthermore, the discharge device 10 may omit both the liquid supply unit 5 and the counter electrode 42.

[0125] Furthermore, functions similar to those of the above-described voltage application device 1 may be embodied in a control method for the voltage application circuit 2, a computer program, or a recording medium on which a computer program is recorded, etc. In other words, the functions of the voltage application circuit 2 may be embodied in a control method for the voltage application circuit 2, a computer program, or a recording medium on which a computer program is recorded, etc.

[0126] Further, the discharge device 10 may be an ion generating device or the like other than an electrostatic atomizing device.

[0127] (8) Summary The discharge device (10) of the first aspect according to the above-described embodiment includes a voltage application circuit (2) that applies an output voltage (Vo) to a load (4) including a discharge electrode (41) that holds a liquid (50) to generate a discharge in the discharge electrode (41). The voltage application circuit (2) has a function of varying the magnitude of the output voltage (Vo) and a function of switching the discharge period, which is a period for varying the magnitude of the output voltage (Vo), to one of a plurality of periods (T1, T2, T3) over time.

[0128] The above-described discharge device (10) can reduce the discharge sound.

[0129] In the discharge device (10) of the second aspect according to the above-described embodiment, in the first aspect, it is preferable that the average of the multiple periods (T1, T2, T3) is within a predetermined range including the resonance period at which the amplitude of the vibration of the liquid (50) caused by the fluctuation of the output voltage (Vo) is maximized.

[0130] The above-described discharge device (10) can reduce the discharge noise while suppressing the decrease in the amount of the active ingredient produced.

[0131] In the discharge device (10) of the third aspect according to the above-mentioned embodiment, in the first or second aspect, each of the multiple periods (T1, T2, T3) is preferably less than or equal to a first value which is the resonance period at which the amplitude of the vibration of the liquid (50) caused by the periodically fluctuating output voltage (Vo) is maximized plus half the resonance period, and is greater than or equal to a second value which is the resonance period minus the half value.

[0132] The above-described discharge device (10) can reduce the discharge noise while further suppressing the decrease in the amount of active ingredient produced.

[0133] In the fourth aspect of the discharge device (10) according to the above-described embodiment, in any one of the first to third aspects, it is preferable that the discharge device (10) further includes a liquid supply unit (5) that supplies a liquid (50) to the discharge electrode (41).

[0134] In the above-described discharge device (10), the liquid (50) is automatically supplied to the discharge electrode (41), eliminating the need for a human operator to supply the liquid (50) to the discharge electrode (41).

[0135] In the discharge device (10) of the fifth aspect according to the above-described embodiment, in any one of the first to fourth aspects, it is preferable that the liquid (50) is electrostatically atomized by discharge.

[0136] The discharge device (10) described above can generate charged minute particle liquid containing radicals. Therefore, the life of the radicals can be extended compared to when the radicals are released into the air alone. Furthermore, since the charged minute particle liquid is, for example, nanometer-sized, the charged minute particle liquid can be suspended over a relatively wide area.

[0137] In the sixth aspect of the discharge device (10) according to the above-described embodiment, in any one of the first to fifth aspects, it is preferable that the voltage application circuit (2) switches the discharge period to any one of a plurality of periods (T1, T2, T3) every time the discharge period is repeated a predetermined number of times.

[0138] The above-described discharge device (10) can reduce the discharge sound.

[0139] In the seventh aspect of the discharge device (10) according to the above-mentioned embodiment, in any one of the first to fifth aspects, it is preferable that the voltage application circuit (2) randomly switches the discharge period to any one of a plurality of periods (T1, T2, T3).

[0140] The above-described discharge device (10) can reduce the discharge sound. [Explanation of symbols]

[0141] 10 Discharge device 2. Voltage application circuit 4. Load 41 Discharge electrode 5 Liquid supply section 50 liquid Vo output voltage T1, T2, T3 period

Claims

1. A voltage application circuit applies an output voltage to a load including a discharge electrode for holding a liquid, thereby generating a discharge in the discharge electrode; The voltage application circuit includes: varying the magnitude of the output voltage; and a function of switching a discharge period, which is a period for varying the magnitude of the output voltage, to one of a plurality of periods based on an elapsed time. Discharge device.

2. The average of the multiple periods is included in a predetermined range including a resonance period in which the amplitude of the vibration of the liquid caused by the fluctuation of the output voltage is maximized. The discharge device according to claim 1.

3. Each of the multiple periods is equal to or less than a first value that is a value obtained by adding half the resonance period to a resonance period at which the amplitude of the vibration of the liquid caused by the output voltage that periodically varies is maximized, and is equal to or greater than a second value that is a value obtained by subtracting the half value from the resonance period.

3. The discharge device according to claim 1 or 2.

4. A liquid supply unit that supplies the liquid to the discharge electrode.

4. A discharge device according to claim 1.

5. The liquid is electrostatically atomized by the discharge.

5. A discharge device according to claim 1.

6. The voltage application circuit switches the discharge period to one of the plurality of periods every time the discharge period is repeated a predetermined number of times.

6. A discharge device according to claim 1.

7. The voltage application circuit randomly switches the discharge period to one of the plurality of periods.

6. A discharge device according to claim 1.

8. A liquid-holding liquid-discharging device comprising: a voltage application circuit that applies an output voltage to a load including a discharge electrode to generate a discharge in the discharge electrode; The voltage application circuit includes: varying the magnitude of the output voltage; A function of switching a discharge period, which is a period for varying the magnitude of the output voltage, to one of a plurality of periods over time, The voltage application circuit switches the discharge period to one of the plurality of periods every time the discharge period is repeated a predetermined number of times. Discharge device.

9. A voltage application circuit that applies an output voltage to a load including a discharge electrode that holds a liquid, thereby generating a discharge in the discharge electrode; The voltage application circuit includes: varying the magnitude of the output voltage; A function of switching a discharge period, which is a period for varying the magnitude of the output voltage, to one of a plurality of periods over time, The voltage application circuit randomly switches the discharge period to one of the plurality of periods. Discharge device.

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