Electrospray device

Abstract

To provide an electrospray device that enables imaging of a liquid spraying state with reduced installation space.SOLUTION: An electrospray device includes a nozzle that sprays a liquid by an electrospray method, a mirror that reflects the liquid sprayed from the nozzle, and an imaging unit that is provided on a base end side relative to a tip end of the nozzle and captures an image of the liquid reflected in the mirror.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to an electrospray device. [Background technology]

[0002] Conventionally, electrostatic atomization devices that scatter charged water particles by applying a strong electric field to water have been known. Patent Document 1 discloses a technology in which an imaging device is provided facing a head portion, which is the tip of an atomization electrode, in order to automate testing to determine whether charged water particles are normally generated. The imaging device then captures images of condensed water adhering to the head portion, thereby automating various tests. In addition, in the field of electrostatic atomization, an electrospray method is used to form a film of a liquid agent on a surface to be applied. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-150845 Summary of the Invention [Problem to be solved by the invention]

[0004] In the electrospray method, if an imaging device is provided facing a nozzle that ejects a liquid agent, there is a risk that droplets ejected from the nozzle will be attracted toward the imaging device made of a conductive material. In this case, it is possible to make the imaging device retractable from the nozzle, but this would require securing a large space, which poses a layout problem. For this reason, the conventional configuration leaves room for improvement in terms of capturing an image of the liquid spray state while saving space.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrospray device that is space-saving and capable of capturing an image of the spray state of a liquid. [Means for solving the problem]

[0006] The electrospray device of the embodiment includes a nozzle that sprays a liquid by electrospraying, a mirror that reflects the liquid sprayed from the nozzle, and an imaging unit that is provided closer to the base end than the tip of the nozzle and captures an image of the liquid reflected in the mirror. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an electrospray device according to one embodiment. [Figure 2] FIG. 1 is a block diagram showing an example of the electrical configuration of an electrospray device according to one embodiment. [Figure 3] FIG. 1 is a diagram showing a circuit configuration including a voltage dividing resistor provided between the nozzle and the imaging side mirror in an electrospray device according to one embodiment. [Figure 4] FIG. 10 shows an example of test results for examining the relationship between the voltage applied to the imaging mirror and the reference voltage of the nozzle for an electrospray device according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that in each drawing, for the sake of convenience, the dimensions of each component may be enlarged as necessary, and the dimensional ratios between the components may not necessarily be the same as in reality.

[0009] The electrospray device 1 shown in FIG. 1 is an apparatus that can spray a liquid, such as a chemical solution or paint, by electrospraying, thereby depositing the liquid on a counter electrode 90, which serves as a substrate, to form a film. The electrospray device 1 includes a liquid supply unit 10, a power supply unit 20, a support member 30, a nozzle 40, an imaging mechanism 50, a light source mechanism 60, and a control unit 70. Here, the electrospray method is a technology in which a high voltage is applied between the nozzle 40 and the counter electrode 90, thereby applying a high voltage between the counter electrode 90 and a liquid pool at the tip of the nozzle 40, converting the liquid into fine droplets carrying an excess electric charge, which are sprayed toward the counter electrode 90 and attracted to and adhere to the counter electrode 90. Note that in this embodiment, the lower side of the paper in FIG. 1 is the side in the direction of liquid ejection, which corresponds to the tip side of the nozzle 40, and the upper side of the paper in FIG. 1 is the side opposite the direction of liquid ejection, which corresponds to the base end side of the nozzle 40. Furthermore, the electrospray device 1 can be configured so that its position relative to the counter electrode 90 can be changed by a movement mechanism (not shown).

[0010] The liquid supply unit 10 is for supplying a liquid such as a chemical solution or paint to the nozzle 40. The liquid supply unit 10 has a liquid tank 11 and a liquid supply pump 12. The liquid tank 11 is configured to be able to store a liquid. The liquid supply pump 12 is for supplying the liquid in the liquid tank 11 to the nozzle 40 at a predetermined discharge pressure. The liquid supply pump 12 is configured, for example, as a syringe pump, and can control the amount of liquid supplied to the nozzle 40 with high precision. However, the liquid supply pump 12 is not limited to a syringe pump. The suction port of the liquid supply pump 12 is connected to the liquid tank 11 via a liquid hose 13. The discharge port of the liquid supply pump 12 is connected to the nozzle 40 via the liquid hose 13 and a support member 30.

[0011] The power supply unit 20 applies a high voltage of, for example, several kV to several tens of kV between the nozzle 40 and the counter electrode 90. The power supply unit 20 has a booster circuit, a rectifier circuit, etc., and supplies the power necessary to drive the electrospray device 1, that is, the high DC voltage necessary to charge and atomize the liquid. The output side of the power supply unit 20 is connected to the nozzle 40 via a power cable 21, etc. Furthermore, the power supply unit 20 and the counter electrode 90 are grounded via a ground wire 22.

[0012] Support member 30 supports nozzle 40, to which nozzle 40 is attached, and also connects liquid hose 13 and nozzle 40. Support member 30 is made of, for example, an electrically insulating resin material. Support member 30 is configured, for example, to be detachable from nozzle 40. This allows the user to easily take action when, for example, nozzle 40 becomes clogged with liquid and maintenance becomes necessary.

[0013] The nozzle 40 is formed, for example, in a cylindrical shape, with both axial ends open. The nozzle 40 is provided facing vertically downward. The distance between the nozzle 40 and the counter electrode 90 is set, for example, to approximately several tens of millimeters. The nozzle 40 functions to spray the liquid supplied from the liquid supply unit 10 by an electrospray method. The nozzle 40 is made of a conductive material, for example, a metal material. The nozzle 40 can be made of, for example, aluminum, iron, gold, silver, titanium, stainless steel, or chromium, but is not limited to these. The nozzle 40 also functions to apply a high voltage supplied from the power supply unit 20 to the liquid supplied from the liquid supply unit 10. The nozzle 40 is electrically connected to the power supply unit 20 via a power cable 21 or the like.

[0014] In this configuration, the liquid supplied from the liquid supply unit 10 to the nozzle 40 moves along the inner circumferential surface of the nozzle 40 and reaches the tip 401 of the nozzle 40. Due to the wettability of the liquid with the inner surface of the tip 401, the liquid leaks out from the end face of the tip 401 toward the tip, forming a puddle. This puddle receives an excess charge from the tip 401, and the excess charge concentrates on the surface of the puddle due to the strong electric field between the tip 401 and the counter electrode 90. This forms a conical Taylor cone T.

[0015] When the excess charge concentrated on the liquid surface exceeds the surface tension of the liquid, fine charged droplets D are released from the tip of the Taylor cone T. These fine charged droplets D are further atomized into a fine mist by a so-called Coulomb explosion and the promotion of evaporation of the liquid. These fine mist are attracted to the counter electrode 90 by their own charges and adsorbed to the counter electrode 90. The state of the Taylor cone T and the charged droplets D is an important factor in, for example, evaluating the quality of the film formation. In other words, observing the Taylor cone T and the charged droplets D is effective in, for example, improving the quality of the film formation.

[0016] The imaging mechanism 50 and the light source mechanism 60 are connected to the support member 30 via the connecting member 31, and are thereby integrally attached to the nozzle 40. In other words, the imaging mechanism 50 and the light source mechanism 60 are supported by the connecting member 31. The connecting member 31 is formed, for example, by combining plate-like members. The imaging mechanism 50 captures an image of the spray state of the liquid, including the state of the Taylor cone T generated at the tip 401 of the nozzle 40. As shown in FIG. 1 , the imaging mechanism 50 has an imaging unit 51 and an imaging side mirror 52. The imaging unit 51 is, for example, a camera that captures still images or videos. The imaging unit 51 has an outer shell formed of a conductive member, for example, a metal member.

[0017] Here, when attempting to capture an image of the area around the tip 401 of the nozzle 40 using the imaging unit 51, it is conceivable to place the imaging unit 51 to the side of the tip 401 of the nozzle 40, but there is a risk that charged droplets sprayed from the nozzle 40 will be attracted to the imaging unit 51 and cause contamination. If an attempt is made to secure a retractable space for the imaging unit 51 to avoid this, the working area will become larger, causing layout problems. Therefore, the imaging unit 51 is provided closer to the base end than the tip 401 of the nozzle 40. In this case, the imaging unit 51 is aligned parallel to the nozzle 40 in the vertical direction.

[0018] An imaging-side mirror 52 is provided at a position facing the tip 401 of the nozzle 40. In this case, at least a portion of the imaging-side mirror 52 is located between the tip 401 of the nozzle 40 and the counter electrode 90 in the extension direction of the nozzle 40. The imaging-side mirror 52 reflects the liquid sprayed from the nozzle 40. The imaging unit 51 then images the liquid reflected on the imaging-side mirror 52, as indicated by the black arrow A in FIG. 1 . This makes it possible to image the Taylor cone T and the charged droplets D while suppressing attraction of charged droplets to the imaging unit 51. Furthermore, since the imaging unit 51 can be located at a distance of approximately several tens of millimeters from the nozzle 40, a compact layout can be achieved. The imaging-side mirror 52 functions as a mirror.

[0019] The light source mechanism 60 is capable of irradiating light, in this case visible light, around the liquid sprayed from the nozzle 40. The irradiation area of ​​the visible light irradiated by the light source mechanism 60 is set so that the Taylor cone T and at least a portion of the charged droplets D are contained therein. The light source mechanism 60 has a light source unit 61 and a light source side mirror 62. The light source unit 61 is configured to include, for example, a light-emitting element capable of emitting visible light and an electric circuit for controlling the operation of the light-emitting element. Note that the light source unit 61 may also be configured to emit invisible light. The light source unit 61 has an outer shell made of a conductive material, for example, a metal material.

[0020] As shown by the black arrow B in FIG. 1 , the light source-side mirror 62 guides light emitted from the light source unit 61 to the periphery of the liquid sprayed from the nozzle 40. In this case, the light beam emitted from the light source unit 61 is guided to the light source-side mirror 62 via a light guide unit (not shown). The light source-side mirror 62 is positioned opposite the imaging-side mirror 52 across the nozzle 40. By adjusting the installation position of the light source-side mirror 62, the light emitted from the light source unit 61 can be directed to a desired area. For example, if the liquid to be applied has high transparency or is easily reflective, the installation position of the light source-side mirror 62 is set so that light directly hits the Taylor cone T and the charged droplets D. On the other hand, if the liquid to be applied has low transparency or is not easily reflective, the installation position of the light source-side mirror 62 is set so that light is directed to the background of the Taylor cone T and the charged droplets D rather than directly hitting the Taylor cone T and the charged droplets D. This makes it easier for the imaging mechanism 50 to capture images of the Taylor cone T and the charged droplets D. The light source mechanism 60 is not limited to being positioned opposite the imaging unit side mirror 52 across the nozzle 40, and all or part of the light source mechanism 60 may be positioned on the same side of the nozzle 40 as the imaging unit side mirror 52.

[0021] The control unit 70 is mainly composed of a microcomputer having storage areas such as a CPU, ROM, and RAM (not shown). The control unit 70 controls the overall operation of the electrospray device 1. The storage area of ​​the control unit 70 stores a control program for controlling the electrospray device 1 to, for example, perform film formation. Each process of the control unit 70 is realized by the CPU executing the control program. As shown in FIG. 2, the control unit 70 is electrically connected to the liquid supply pump 12, power supply unit 20, imaging mechanism 50, and light source unit 61, and controls the operation of these components.

[0022] Images captured by imaging unit 51 of imaging mechanism 50 are stored, for example, in a memory area of ​​control unit 70. Control unit 70 can also control the discharge rate of liquid supply pump 12 and the output voltage of power supply unit 20. This allows control unit 70 to automatically or semi-automatically control the amount of liquid supplied to nozzle 40 and the voltage applied to the liquid. Note that adjustment of the amount of liquid supplied by liquid supply pump 12 and adjustment of the voltage applied to the liquid may be performed manually by a user manually changing control parameters of liquid supply pump 12 and power supply unit 20 while visually checking the spray state of the liquid, etc.

[0023] As described above, a portion of the imaging side mirror 52 is located between the tip 401 of the nozzle 40 and the counter electrode 90 in the extension direction of the nozzle 40. Therefore, unless some countermeasure is taken, the charged droplets sprayed from the nozzle 40 will be attracted to the imaging side mirror 52, not only soiling the imaging side mirror 52 but also adversely affecting the adhesion of the liquid to the counter electrode 90, and changing the voltage at which atomization of the liquid ejected from the nozzle 40 begins. After extensive research, the inventors of the present application have discovered that in order to control the generation of an electric field in the imaging side mirror 52, a voltage can be applied to the imaging side mirror 52.

[0024] Therefore, the imaging-side mirror 52 includes a layer on its surface made of a material capable of controlling voltage. Examples of materials capable of controlling voltage include metals, conductive polymer materials, and carbon thin films. In this embodiment, the imaging-side mirror 52 is a so-called surface reflector with a metal layer formed on its surface. In other words, the imaging-side mirror 52 is configured so that a voltage can be applied directly to the mirror surface. This makes it possible to effectively prevent the liquid sprayed from the nozzle 40 from being attracted toward the imaging-side mirror 52 by applying a voltage to the surface of the imaging-side mirror 52.

[0025] The voltage applied to the imaging-side mirror 52 needs to be set within a range that suppresses the generation of an electric field on the imaging-side mirror 52 while not affecting the properties of the charged droplets D. In this embodiment, as shown in FIG. 3 , the electrospray device 1 includes a voltage-dividing resistor 80. The voltage-dividing resistor 80 is connected between the nozzle 40 and the imaging-side mirror 52 and divides the reference voltage applied to the nozzle 40. The reference voltage is a voltage equivalent to the atomization voltage. The atomization voltage refers to the voltage at which atomization of the liquid ejected from the nozzle 40 begins. The voltage-dividing resistor 80 has a resistance ratio that maintains a constant ratio of the voltage applied to the imaging-side mirror 52 to the reference voltage of the nozzle 40. Note that the electrospray device 1 may be configured without the voltage-dividing resistor 80, and may instead apply a voltage to the imaging-side mirror 52 from a separately provided power source or the like.

[0026] FIG. 4 shows an example of test results examining the relationship between the voltage applied to the imaging-side mirror 52 and the reference voltage of the nozzle 40. The vertical axis represents the reference voltage of the nozzle 40, and the horizontal axis represents the voltage applied to the imaging-side mirror 52. These test results were obtained, for example, by setting the nozzle 40, counter electrode 90, and imaging-side mirror 52 at a fixed distance, and the conditions were the same except for the changes in the voltage applied to the imaging-side mirror 52 and the reference voltage of the nozzle 40. In FIG. 4, the reference voltage of the nozzle 40 corresponding to the voltage applied to the imaging-side mirror 52 is represented by a black circle. When no voltage is applied to the imaging-side mirror 52, V0, the electric field strength at the tip 401 of the nozzle 40 is stronger than when the imaging-side mirror 52 is not present, and therefore the reference voltage shows a low value. When a voltage is gradually applied to the imaging-side mirror 52 from voltage V0, an electric field is generated in the imaging-side mirror 52, and the reference voltage tends to decrease until voltage V1 is reached.

[0027] Furthermore, within the range of voltages V1 to V2, a reference voltage close to the reference voltage Va in the absence of the imaging-side mirror 52 was confirmed. Furthermore, when the voltage applied to the imaging-side mirror 52 exceeded voltage V2, the reference voltage of the nozzle 40 tended to increase. This is because an increase in the voltage applied to the imaging-side mirror 52 inhibits the generation of an electric field that would be present around the imaging-side mirror 52 in the absence of the imaging-side mirror 52, resulting in a weakened electric field strength at the tip 401 of the nozzle 40. Furthermore, near voltage V2, no droplets were observed to adhere to the imaging-side mirror 52. In other words, applying voltage V2 to the imaging-side mirror 52 can suppress droplets from adhering to the imaging-side mirror 52 without affecting the reference voltage of the nozzle 40. In this case, an electric field of the same magnitude is generated between the nozzle 40 and the imaging-side mirror 52 as when only the nozzle 40 and the counter electrode 90 are present.

[0028] According to the embodiment described above, the electrospray device 1 includes the nozzle 40, the imaging side mirror 52, and the imaging unit 51. The nozzle 40 sprays a liquid by electrospraying. The imaging side mirror 52 reflects the liquid sprayed from the nozzle 40. The imaging unit 51 is provided closer to the base end than the tip 401 of the nozzle 40, and captures an image of the liquid reflected on the imaging side mirror 52. This allows for space saving while capturing an image of the spray state of the liquid, including the state of the Taylor cone T formed at the tip 401 of the nozzle 40.

[0029] The electrospray device 1 further includes a light source mechanism 60. The light source mechanism 60 irradiates light onto the periphery of the liquid sprayed from the nozzle 40. This allows a clear image of the liquid sprayed from the nozzle 40 to be captured, making it possible to properly identify the state of the Taylor cone T, for example.

[0030] The imaging side mirror 52 includes a layer formed of a material capable of controlling voltage on its surface side. This allows voltage to be applied to the surface side of the imaging side mirror 52, thereby preventing the sprayed liquid from adhering to the imaging side mirror 52. This prevents the imaging side mirror 52 from becoming soiled, thereby improving the reliability of the electrospray device 1.

[0031] Furthermore, the electrospray device 1 further includes a voltage dividing resistor 80. The voltage dividing resistor 80 is connected between the nozzle 40 and the imaging side mirror 52, and divides the reference voltage applied to the nozzle 40. This allows an appropriate voltage to be applied to the imaging side mirror 52. This allows stable imaging of the liquid spray state.

[0032] The above-described embodiments are presented as examples, and are not limited to the embodiments described above and shown in the drawings, but can be modified as appropriate within the scope of the gist of the invention. [Explanation of symbols]

[0033] 1...electrospray device, 40...nozzle, 51...imaging unit, 52...imaging side mirror (mirror)

Claims

1. a nozzle for spraying a liquid by an electrospray method; a mirror that reflects the liquid sprayed from the nozzle; an imaging unit that is provided closer to the base end than the tip end of the nozzle and captures an image of the liquid reflected in the mirror, Electrospray apparatus.

2. The liquid spraying device further includes a light source mechanism that irradiates light around the liquid sprayed from the nozzle.

10. The electrospray device of claim 1.

3. The mirror includes a layer formed of a voltage-controllable material on the front surface side.

10. The electrospray device of claim 1.

4. a voltage dividing resistor connected between the nozzle and the mirror, which divides a reference voltage applied to the nozzle; 10. The electrospray device of claim 1.

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