JP7626432B2 - Electrospray nozzle and electrospray device - Google Patents

Description

Embodiments of the present invention relate to an electrospray nozzle and an electrospray device.

In recent years, electrospray has been attracting attention as a coating technique for paints and cleaning fluids. In electrospray, a high voltage is applied to coating fluids such as paints and cleaning fluids, the coating fluid flowing out of the nozzle tip is atomized by electrostatic force, and the high-voltage charged mist of coating fluid is attracted to the substrate, which serves as the opposing electrode, for coating. In electrospray, gas such as air is not used to atomize the coating fluid, i.e., to make it fine particles. In addition, the charged coating fluid is attracted to the substrate by electrostatic force and adsorbed thereon, resulting in less diffusion of the coating fluid and high coating efficiency. Therefore, compared to conventional air spray, electrospray can reduce the amount of coating fluid used and the amount of waste fluid to be disposed of, and is therefore expected to be a technology that can reduce the environmental impact.

However, because the electrospray method does not use external forces such as air pressure to atomize the coating liquid as in the conventional air spray method, the amount of coating applied per unit time is smaller than that of the conventional air spray method. For this reason, it has been difficult to apply the conventional electrospray method to applications that require a large amount of coating in a short period of time, such as painting in a production process.

JP 2020-526334 A

The present invention was made in consideration of the above circumstances, and its purpose is to provide an electrospray nozzle and an electrospray device that can increase the amount of liquid applied per unit time while performing stable atomization when applying liquid using the electrospray ionization method.

The electrospray nozzle of the embodiment is a nozzle for electrospray that sprays liquid by electrospray ionization, has a plurality of liquid flow paths formed in a groove shape and capable of flowing coating liquid supplied from the outside, and is equipped with an electrode member capable of applying a voltage supplied from the outside to the coating liquid flowing in the liquid flow paths.

The electrospray device of the embodiment includes the electrospray nozzle, a coating liquid supply device that supplies a coating liquid to the liquid flow path of the electrospray nozzle, and a voltage supply device that supplies a voltage to the electrode member of the electrospray nozzle.

FIG. 1 is a schematic diagram showing an example of the configuration of an electrospray device according to an embodiment. FIG. 1 is a perspective view showing an example of a nozzle for electrospray according to an embodiment. FIG. 1 is a cross-sectional view showing a schematic example of a nozzle for electrospray according to an embodiment. 4 is a cross-sectional view taken along line X4-X4 of FIG. 3, which is a schematic diagram showing an example of an electrospray nozzle according to an embodiment. FIG. 1 is a cross-sectional view showing an example of an electrospray nozzle according to a first modified example. FIG. 11 is a cross-sectional view showing an example of an electrospray nozzle according to a second modified example.

Several embodiments will be described below with reference to the drawings. Note that elements that are substantially the same in several embodiments will be given the same reference numerals and descriptions will be omitted.

The electrospray device 1 shown in FIG. 1 is a device that can spray coating liquid, such as paint or cleaning liquid, by the electrospray method, thereby coating the coating liquid on a coating object 90. That is, the electrospray device 1 in FIG. 1 can be applied to a coating device for coating a product with paint in a production process, for example, or a cleaning device for coating a product with cleaning liquid and cleaning it. That is, the electrospray device 1 can also be called, for example, a coating device or a cleaning device depending on its application. Note that the application of the electrospray device 1 is not limited to the above-mentioned coating device and cleaning device, and can be widely applied to devices for coating a coating liquid on a coating object.

As shown in FIG. 1, the electrospray device 1 includes a coating liquid supply device 10, a gas supply device 20, a voltage supply device 30, a control device 40, a support member 50, and an electrospray nozzle 60. In the following description, the electrospray nozzle is simply referred to as a nozzle. In this embodiment, the lower side of the paper in FIG. 1 is the side in the ejection direction of the coating liquid and corresponds to the tip side of the nozzle 60, and the upper side of the paper in FIG. 1 is the side opposite the ejection direction of the coating liquid and corresponds to the base end side of the nozzle 60.

The coating liquid supply device 10 is for supplying coating liquid such as paint or cleaning liquid to the nozzle 60. In this embodiment, the coating liquid supply device 10 has a coating liquid tank 11 and a coating liquid supply pump 12. The coating liquid tank 11 stores coating liquid such as paint or cleaning liquid. The coating liquid supply pump 12 has a function of supplying the coating liquid in the coating liquid tank 11 to the nozzle 60 at a predetermined discharge pressure.

The suction port of the coating liquid supply pump 12 is connected to the coating liquid tank 11 via the coating liquid hose 13. The discharge port of the coating liquid supply pump 12 is connected to the nozzle 60 via the coating liquid hose 13 and the support member 50. The coating liquid discharged from the coating liquid supply pump 12 is supplied to the nozzle 60 via the coating liquid hose 13 and the support member 50. In the case of this embodiment, the coating liquid hose 13 is made of, for example, a synthetic resin having electrical insulation properties. In addition, the coating liquid supply pump 12 is composed of, for example, a syringe pump, and the amount of coating liquid supplied to the nozzle 60 can be controlled with high precision. Note that the coating liquid supply pump 12 is not limited to a syringe pump.

The gas supply device 20 is for supplying gas to the nozzle 60. The gas supplied from the gas supply device 20 is an insoluble gas that does not dissolve in the coating liquid or a poorly soluble gas that is difficult to dissolve, and can be, for example, an inert gas such as compressed air or nitrogen. The gas supply device 20 can be composed of, for example, a compressor that generates compressed air, a gas cylinder filled with compressed gas, and a regulator that adjusts the outflow pressure of the gas from the gas cylinder. In this embodiment, the gas supply device 20 is composed of an air compressor.

The discharge port of the gas supply device 20 is connected to the nozzle 60 via the gas hose 21 and the support member 50. The gas discharged from the gas supply device 20 is supplied to the nozzle 60 via the gas hose 21 and the support member 50. In this embodiment, the gas hose 21 is made of an electrically insulating material, such as a synthetic resin.

The voltage supply device 30 can also be called a power supply device, and has the function of applying a high voltage of several kV to several tens of kV between the nozzle 60 and the workpiece 90. The voltage supply device 30 has a boost circuit and a rectifier circuit, and supplies the voltage required to drive the electrospray device 1, that is, the high DC voltage required to charge and atomize the coating liquid. The output side of the voltage supply device 30 is connected to the nozzle 60 via a power cable 31. In addition, the voltage supply device 30 and the workpiece 90 are grounded via an earth wire 32.

The control device 40 is configured with a microcomputer having a CPU, ROM, RAM, etc. (not shown). In this embodiment, the control device 40 is electrically connected to the coating liquid supply device 10 (in this case, the coating liquid supply pump 12), the gas supply device 20, and the voltage supply device 30, and can control the amount of coating liquid discharged from the coating liquid supply pump 12, the amount of gas discharged from the gas supply device 20, and the output voltage of the voltage supply device 30. This allows the control device 40 to automatically or semi-automatically control the amounts of coating liquid and gas supplied to the nozzle 60 and the voltage applied to the coating liquid.

The electrospray device 1 does not necessarily have to include the control device 40. If the electrospray device 1 does not include the control device 40, the user of the electrospray device 1 manually adjusts the coating liquid supply pump 12, the gas supply device 20, and the voltage supply device 30 to adjust the amount of coating liquid supplied, the amount of gas supplied, and the applied voltage.

The support member 50 supports the nozzle 60 attached thereto, and also has the function of connecting the nozzle 60 to the coating liquid hose 13 and the gas hose 21. In this embodiment, the support member 50 is made of a non-metallic material such as non-conductive plastic. In this embodiment, the nozzle 60 is configured to be detachable from the support member 50. This allows the user to easily take measures when, for example, the nozzle 60 becomes clogged with coating liquid and maintenance becomes necessary.

The nozzle 60 has the function of spraying the coating liquid supplied from the coating liquid supply device 10 by electrospray ionization. In this embodiment, the nozzle 60 has an electrode member 70 and a housing 80, as shown in Figures 2 to 4.

The electrode member 70 is made of a conductive material, such as a metal material. The electrode member 70 can be made of, for example, aluminum, iron, gold, silver, titanium, stainless steel, or chromium, but is not limited to these. The electrode member 70 has the function of contacting the coating liquid supplied from the coating liquid supply device 10 and applying the high voltage supplied from the voltage supply device 30 to the coating liquid.

In this embodiment, the electrode member 70 is formed by processing, for example, a metal plate member. The electrode member 70 has a plurality of liquid flow paths 71, as shown in Figs. 2 and 4. Each liquid flow path 71 is formed in a groove shape by digging into at least one surface of the electrode member 70 in the thickness direction. Each liquid flow path 71 extends linearly and is arranged in parallel with each other. In this embodiment, as shown in Fig. 4, the cross section of the liquid flow path 71 cut in a plane perpendicular to the extension direction of the liquid flow path 71 is formed in a semicircular shape that is open in one direction. Note that the cross section of the liquid flow path 71 cut in a plane perpendicular to the extension direction of the liquid flow path 71 may be formed in, for example, a rectangular shape.

Each liquid flow path 71 is directly or indirectly connected to the coating liquid supply device 10. In this embodiment, each liquid flow path 71 is connected to the coating liquid supply pump 12 of the coating liquid supply device 10 via the support member 50 and the coating liquid hose 13. The coating liquid discharged from the coating liquid supply pump 12 is supplied to the nozzle 60 from the support member 50 and the coating liquid hose 13, and branches into each liquid flow path 71. In each drawing, arrow A indicates the flow of the coating liquid. A voltage supplied from the outside of the nozzle 60 (in this case, the voltage supply device 30 to the electrode member 70) is applied to the coating liquid flowing through each liquid flow path 71.

In this embodiment, the electrode member 70 has a bent tip side, i.e., the downstream side of the flow of the coating liquid. The liquid flow path 71 is formed up to the tip of the electrode member 70 in the flow direction of the coating liquid. In other words, as shown in Figures 2 and 3, the liquid flow path 71 in this embodiment is configured to have a base end region 711 and a tip end region 712. The tip end region 712 is disposed at an angle with respect to the base end region 711.

In this embodiment, the base end region 711 is a portion of the liquid flow path 71 provided in the electrode member 70 that is horizontally disposed when the nozzle 60 is in use, and is provided upstream of the tip end region 712, i.e., on the base end side of the nozzle 60. The tip end region 712 is a portion of the liquid flow path 71 provided in the electrode member 70 that is inclined downward toward the workpiece 90 when the nozzle 60 is in use, and is provided downstream of the base end region 711, i.e., on the tip end side of the nozzle 60. In this embodiment, the total length of the base end region 711 is set longer than the total length of the tip end region 712 in each liquid flow path 71. As shown in Figures 2 and 3, at least a part or all of the tip end region 712 is exposed to the outside from the housing 80. Also, the tip of the tip end region 712, i.e., the tip portion of the electrode member 70, is pointed so as to taper, as shown in Figure 2.

In this case, the thickness of the electrode member 70 in the tip region 712 is preferably 100 μm or less, and more preferably 30 μm or less. In this embodiment, the thickness of the electrode member 70 in the tip region 712 is set to 20 μm or more and 100 μm or less.

The housing 80 constitutes the outer shell of the nozzle 60, houses a part of the electrode member 70, and has the function of flowing the coating liquid supplied from the coating liquid supply device 10 and the gas supplied from the gas supply device 20 inside. The housing 80 can be made of, for example, an electrically insulating resin material. The housing 80 is formed, for example, in a cylindrical shape. In this embodiment, the housing 80 is formed in a cylindrical shape with a rectangular cross section. The housing 80 has a liquid outlet 81, a gas flow path 82, a gas outlet 83, and an induction section 84. That is, in this embodiment, the housing 80 functions as a gas flow path forming member for forming the gas flow path 82.

The liquid outlet 81 is an outlet for allowing the coating liquid introduced into the housing 80 to flow out of the housing 80. The coating liquid supplied from the coating liquid supply device 10 and introduced into the housing 80 flows along the liquid flow path 71 of the electrode member 70 and flows out of the housing 80 from the liquid outlet 81.

The gas flow path 82 is formed in a space provided within the housing 80 and extends along the extension direction of the liquid flow path 71. The gas flow path 82 can be formed, for example, in a rectangular, elliptical, or oval shape with a long cross section in one direction when cut along a plane perpendicular to the extension direction of the gas flow path 82, i.e., the direction in which the gas flows. In this embodiment, the cross section of the gas flow path 82 is formed in a rectangular shape with a long cross section in the horizontal direction.

In this embodiment, in the portion of the electrode member 70 housed within the housing 80, the surface on which the liquid flow path 71 is provided is separated from the inner surface of the housing 80, and the surface opposite to the surface on which the liquid flow path 71 is provided, i.e., the surface on which the liquid flow path 71 is not provided, is in contact with the inner surface of the housing 80. The gas flow path 82 is formed by the space between the surface of the electrode member 70 on the liquid flow path 71 side and the inner surface of the housing 80.

The gas flow path 82 is directly or indirectly connected to the gas supply device 20. In this embodiment, the gas flow path 82 is connected to the gas supply device 20 via the support member 50 and the gas hose 21. The gas supplied to the gas flow path 82 from the gas supply device 20 via the gas hose 21 and the support member 50 flows through the gas flow path 82 along the extension direction of the liquid flow path 71. In each drawing, the arrow B indicates the flow of gas.

The gas outlet 83 is an outlet for allowing the gas introduced into the housing 80 to flow out of the housing 80. The guide section 84 is provided on the tip side of the liquid flow path 71 in the housing 80. The guide section 84 has the function of separating the gas flowing through the gas flow path 82 from the coating liquid flowing through the liquid flow path 71, that is, the function of guiding the gas in a direction away from the liquid flow path 71. The guide section 84 is provided between the liquid outlet 81 and the gas outlet 83, and separates the liquid outlet 81 from the gas outlet 83. The guide section 84 is formed, for example, in a flat plate shape and is inclined in the opposite direction to the inclination direction of the tip side region 712, in this case, upward.

The gas supplied from the gas supply device 20 and introduced into the housing 80 flows along the gas flow path 82 inside the housing 80, and then flows out of the housing 80 from the gas outlet 83. At this time, the gas flowing through the gas flow path 82 is guided by the guide section 84, and flows out of the gas outlet 83 in the opposite direction to the inclination direction of the tip side region 712, in this case, the upward direction. Also, in this case, the speed of the gas flowing through the gas flow path 82 can be made different from the speed of the coating liquid flowing through the liquid flow path 71.

In this configuration, the coating liquid supplied from the coating liquid supply pump 12 into the housing 80 branches into multiple liquid flow paths 71 of the electrode member 70 housed in the housing 80. The coating liquid is charged to a high voltage when it comes into contact with the liquid flow path 71 formed by the electrode member 70, and springs out from the liquid outlet 81 to the tip side region 712. The coating liquid that springs out from the liquid outlet 81 to the tip side region 712 becomes spherical due to the surface tension of the coating liquid. At this time, an electrostatic force is generated between the coating liquid that has become spherical in the tip side region 712 and the coating object 90, which serves as the opposing electrode, and the tip of the spherical coating liquid is attracted to the coating object 90. Then, as shown in FIG. 3, a conical Taylor cone T is formed.

When the electrostatic force acting on the coating liquid becomes greater than the surface tension of the coating liquid, charged droplets D charged to a high voltage are released from the tip of the Taylor cone T. These charged droplets D are gradually broken down into fine particles and atomized due to repulsion caused by electrostatic force and promotion of evaporation of the liquid. The fine droplets in the atomized state are attracted to the workpiece 90 by electrostatic force and adsorbed to the workpiece 90.

According to the embodiment described above, the nozzle 60 is an electrospray nozzle that sprays liquid by electrospray ionization, and includes an electrode member 70. The electrode member 70 has a groove shape and has a plurality of liquid flow paths 71 through which the coating liquid supplied from the coating liquid supply device 10 can flow, and a voltage supplied from the outside can be applied to the coating liquid flowing through the liquid flow paths 71. The electrospray device 1 also includes the nozzle 60, the coating liquid supply device 10 that supplies the coating liquid to the liquid flow paths 71 of the nozzle 60, and a voltage supply device 30 that supplies a voltage to the electrode member 70 of the nozzle 60.

Here, for example, a simple cylindrical shape may be adopted as the shape of the nozzle for electrospray. In this case, the electrode for applying a high voltage to the coating liquid flowing through the nozzle may be, for example, a cylindrical rod-shaped core material passing through the nozzle, or the inner surface of the nozzle may be used as an electrode. In these configurations, in order to increase the amount of coating per unit time, it is necessary to increase the diameter of the nozzle, i.e., the cross-sectional area of the nozzle.

However, in the case of the former configuration, it has been found that even if the diameter of the core material is increased, the atomization efficiency of the coating liquid does not improve in proportion to the increase in diameter. Also, in the latter configuration, the cross-sectional area of the nozzle is proportional to the square of the nozzle radius, while the circumference of the nozzle is proportional to the nozzle radius. Therefore, even if the nozzle diameter is increased in the latter configuration, the contact area of the electrode with the coating liquid does not increase in proportion to the increase in the amount of coating liquid, and the stability of the atomization of the coating liquid decreases. Therefore, in the conventional configuration, it was difficult to increase the amount of coating in a configuration that adopted the electrospray ionization method.

In contrast, in the nozzle 60 of this embodiment, the electrode member 70 has multiple liquid flow paths 71 and is configured to be able to apply a voltage supplied from the outside to the coating liquid flowing through the liquid flow paths 71. This allows the flow rate of the coating liquid to be ensured by the multiple liquid flow paths 71 while ensuring a contact area with the electrode member 70. Therefore, the electrospray device 1 using the nozzle 60 of this embodiment can increase the amount of coating per unit time while performing stable atomization. This allows the electrospray device 1 using the nozzle 60 of this embodiment to be applied to, for example, painting devices and cleaning devices that apply a large amount of coating per unit time. As a result, this embodiment can reduce the amount of coating liquid used and the amount of waste liquid treatment compared to the conventional air spray method, which can contribute to reducing the environmental load.

The liquid flow path 71 also has a base end region 711 and a tip end region 712. The base end region 711 is a region of the liquid flow path 71 that is positioned horizontally when in use. The tip end region 712 is a region that is provided downstream of the base end region 711, is bent relative to the base end region 711, and is inclined downward when in use.

In this configuration, the coating liquid supplied into the nozzle 60 first flows horizontally through the base end region 711, and then flows downward along the slope of the tip end region 712. This prevents the coating liquid flowing through the nozzle 60 from forming clumps and falling due to gravity. This prevents clumps of coating liquid from falling from the nozzle 60 onto the object to be coated, thereby improving the quality of the coating.

The nozzle 60 further includes a housing 80. In this embodiment, the housing 80 functions as a gas flow path forming member that forms a gas flow path 82 that allows gas supplied from the outside of the nozzle 60 (in this case, the gas supply device 20) to flow along the extension direction of the liquid flow path 71. The electrospray device 1 further includes a gas supply device 20 that supplies gas to the gas flow path 82 of the nozzle 60.

By passing gas through the gas flow path 82, the pressure of the gas can be used to hold the coating liquid flowing through the liquid flow path 71 within the liquid flow path 71. This prevents the coating liquid from jumping out of the liquid flow path 71, ensuring contact with the inner surface of the liquid flow path 71, i.e., the electrode member 70, and improving the stability of atomization.

Furthermore, for example, when the electrospray device 1 is used in a device for applying a non-Newtonian fluid such as paint, the gas flowing through the gas flow path 82 is a Newtonian fluid, while the paint flowing through the liquid flow path 71 is a non-Newtonian fluid. For this reason, by flowing the gas, which is a Newtonian fluid, parallel to the flow of the paint, which is a non-Newtonian fluid, vortices are easily generated in the non-Newtonian fluid flowing through the liquid flow path 71. These vortices then stir the liquid flowing through the liquid flow path 71. As a result, contact with the inner surface of the liquid flow path 71, i.e., the electrode member 70, is improved, and the stability of atomization can be further effectively improved.

Here, if the coating liquid and gas introduced into the nozzle 60 are ejected from the nozzle 60 in the same direction, the coating liquid becomes entrained in the gas ejected from the nozzle 60 and tends to diffuse, which tends to reduce the efficiency of coating on the workpiece 90.

Therefore, the nozzle 60 of this embodiment further includes a guide section 84. In this embodiment, the guide section 84 is provided in the housing 80. The guide section 84 is provided on the tip side of the liquid flow path 71 and has the function of guiding the gas flowing through the gas flow path 82 in a direction away from the liquid flow path 71. In other words, the coating liquid and gas supplied into the nozzle 60 flow in parallel in the same space within the nozzle 60, and then are separated by the guide section 84 and flow out in different directions. This makes it possible to prevent the coating liquid from being drawn into the gas discharged from the nozzle 60 and spreading, and as a result, it is possible to improve the efficiency of coating on the workpiece 90.

Next, some modified examples of this embodiment will be described with reference to Figs. 5 and 6. The modified examples shown in Figs. 5 and 6 differ from the above embodiment in the position of the gas outlet 83, i.e., the position of the induction section 84. In modified example 1 shown in Fig. 5, the gas outlet 83 and the induction section 84 are located further toward the tip of the nozzle 60 than the liquid outlet 81, i.e., the most distal end of the liquid flow path 71. That is, in the example of Fig. 5, the gas outlet 83 and the induction section 84 are provided at the most distal end of the nozzle 60. In this case, the liquid outlet 81 is located on the base end side of the nozzle 60, i.e., downstream side, relative to the gas outlet 83.

On the other hand, in the second modified example shown in FIG. 6, the gas outlet 83 and the induction section 84 are located relative to the liquid outlet 81, that is, on the base end side of the liquid flow path 71. That is, in the example of FIG. 6, the tip side region 712 of the liquid flow path 71 is provided at the most distal end of the nozzle 60. In this case, the gas outlet 83 is located on the base end side of the nozzle 60, that is, downstream side, relative to the gas outlet 83. With these, the same action and effect as the above embodiment can be obtained.

The above-described embodiments are presented as examples, and are not limited to the embodiments described above and shown in the drawings. They can be modified as appropriate without departing from the spirit of the invention.

1...electrospray device, 10...coating liquid supply device, 20...gas supply device, 30...voltage supply device, 60...electrospray nozzle, 70...electrode member, 71...liquid flow path, 80...casing (gas flow path forming member), 82...gas flow path, 84...induction section, 711...base end region, 712...tip end region

Claims (5)

A nozzle for electrospray that sprays a liquid by electrospray ionization, comprising:
an electrode member having a plurality of liquid flow paths formed in a groove shape and capable of flowing a coating liquid supplied from the outside, and capable of applying a voltage supplied from the outside to the coating liquid flowing through the liquid flow paths;
a gas flow path forming member that forms a gas flow path that allows a gas supplied from the outside to flow along the extension direction of the liquid flow path,
the coating liquid flowing through the liquid flow path is pressed into the liquid flow path by the pressure of the gas flowing through the gas flow path;
Nozzle for electrospray. A nozzle for electrospray that sprays a liquid by electrospray ionization, comprising:
a liquid flow path formed in a groove shape and capable of flowing a coating liquid supplied from an outside; and an electrode member capable of applying a voltage supplied from an outside to the coating liquid flowing through the liquid flow path;
The liquid flow path has a base end region that is disposed horizontally when in use, and a tip end region that is provided downstream of the base end region, bent with respect to the base end region, and inclined downward when in use.
Nozzle for electrospray . The liquid passage further includes a guide portion provided at a tip end side of the liquid passage and configured to guide the gas flowing through the gas passage in a direction away from the liquid passage.
The electrospray nozzle according to claim 1 . The electrospray nozzle according to claim 2 ;
a coating liquid supplying device that supplies a coating liquid to the liquid flow path of the electrospray nozzle;
a voltage supply device for supplying a voltage to the electrode member of the electrospray nozzle;
An electrospray device comprising: The electrospray nozzle according to claim 1 or 3 ;
a coating liquid supplying device that supplies a coating liquid to the liquid flow path of the electrospray nozzle;
a gas supply device that supplies a gas to the gas flow path of the electrospray nozzle;
a voltage supply device for supplying a voltage to the electrode member of the electrospray nozzle;
An electrospray device comprising:

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