Electrostatic coating device

Abstract

To provide an electrostatic coating device that can control discharge modes of two fluids independently from each other.SOLUTION: An electrostatic coating device 100 comprises: a nozzle 1 having a discharge port 10, a conductive first shell 11 having a first flow channel 16 that is a flow channel for a first fluid F1 and extends to the discharge hole 10, and a conductive second shell 12 having a second flow channel 17 that is a flow channel for a second fluid F2 and extends to the discharge hole 10; a counter electrode 2 which is so positioned as to face the discharge port 10; and a voltage control part 51 which can apply a first drive voltage between the first shell 11 and the counter electrode 2, and can apply a second drive voltage different from the first drive voltage between the second shell 12 and the counter electrode 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrostatic coating device. [Background technology]

[0002] An electrostatic spraying device disclosed in Patent Document 1 is known.

[0003] The electrostatic spraying device includes a spray head having multiple channels and a device for applying an electric potential to the spray head, and the liquids passing through the channels and exiting the spray head are mixed and move toward and coat an article positioned below the spray head, which is held at ground potential. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-290179 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the device of Patent Document 1, it is difficult to control the outflow pattern of fluids from each channel, for example, to coat a target so that multiple fluids form layers without mixing them. [Means for solving the problem]

[0006] In order to solve the above problem, an electrostatic coating device according to one aspect of the present invention includes a nozzle having a discharge hole, a conductive first tubular body having a first flow path for a first fluid that leads to the discharge hole, and a conductive second tubular body having a second flow path for a second fluid that leads to the discharge hole; a counter electrode positioned opposite the discharge hole; and a voltage control unit capable of applying a first drive voltage between the first tubular body and the counter electrode, and capable of applying a second drive voltage different from the first drive voltage between the second tubular body and the counter electrode.

[0007] This configuration makes it possible to differentiate the speed and ejection timing of the first fluid drawn toward the counter electrode by electrostatic force from the speed and ejection timing of the second fluid drawn toward the counter electrode by a different electrostatic force, thereby differentiating the timing at which the first fluid adheres to the counter electrode from the timing at which the second fluid adheres to the counter electrode, and thereby controlling the ejection modes of the two fluids independently of each other. [Effects of the Invention]

[0008] The present invention has the advantage that the ejection modes of the first fluid and the second fluid can be controlled independently of each other. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing an example of the configuration of an electrostatic coating device according to a first embodiment. [Figure 2] 2 is a diagram showing an operation example 1 of the electrostatic coating device of FIG. 1. FIG. [Figure 3] 1. FIG. 4 is a diagram showing a second example of operation of the electrostatic coating device of FIG. [Figure 4] FIG. 10 is a cross-sectional view showing an example of the configuration of an electrostatic coating device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments. In addition, the same or corresponding elements will be denoted by the same reference numerals throughout the drawings, and redundant description will be omitted.

[0011] The functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuitry. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and processor.

[0012] (Embodiment 1) FIG. 1 is a cross-sectional view showing an example of the configuration of an electrostatic coating device 100 according to the first embodiment.

[0013] As shown in FIG. 1, the electrostatic coating device 100 includes a nozzle 1, a counter electrode 2, a voltage control unit 51, and a control device 50.

[0014] The nozzle 1 is capable of ejecting a plurality of fluids, for example, two types of fluids: a first fluid F1 which is a liquid, and a second fluid F2 which is a liquid different from the first fluid F1.

[0015] The nozzle 1 is, for example, a tubular body extending in the vertical direction, and has a discharge hole 10 at its lower end through which the first fluid F1 and the second fluid F2 are discharged. That is, the discharge hole 10 is provided so as to face downward. The nozzle 1 includes a first tubular body 11 and a second tubular body 12 which are conductive cylindrical tubular bodies, and an insulating part 13 which has insulating properties.

[0016] The first pipe 11 has an internal space that forms a first flow path 16. The first flow path 16 is a flow path for the first fluid F1 and leads to the discharge hole 10. An insulating portion 13 is provided to cover the entire outer peripheral surface of the first pipe 11. The second pipe 12 is a tubular body with a larger diameter than the first pipe 11. The first pipe 11, whose outer peripheral surface is covered by the insulating portion 13, is nested inside the second pipe 12. The first pipe 11 and the second pipe 12 are concentrically arranged, and the nozzle 1 has a double-pipe structure. The space between the second pipe 12 and the insulating portion 13 forms a second flow path 17. The second flow path 17 is a flow path for the second fluid F2 and leads to the discharge hole 10. In this way, the insulating portion 13 is located between the second flow path 17 and the first pipe 11, electrically isolating the first flow path 16 and the second flow path 17.

[0017] The counter electrode 2 is a conductive plate-like body, and is a discharge receiving medium to be coated. The upper surface of the counter electrode 2 is positioned opposite the discharge holes 10. The counter electrode 2 is connected to the ground (GND) by a wiring 61.

[0018] The counter electrode 2 is supported by a stage 3. The stage 3 is driven by a stage drive unit 4. As a result, the counter electrode 2 moves in the in-plane direction of the upper surface of the counter electrode 2 while maintaining a constant distance from the ejection holes 10 of the nozzle 1. Note that, although the counter electrode 2 itself is the coating target here, this is not limiting, and the discharge-receiving medium to be coated may be supported on the counter electrode 2.

[0019] The voltage control unit 51 includes a DC power supply and a waveform generating circuit that can supply a plurality of different voltages. The voltage control unit 51 is connected to the first tubular body 11 by a wiring 62, and is further connected to the counter electrode 2 by a wiring 63. The voltage control unit 51 can apply a first drive voltage between the first tubular body 11 and the counter electrode 2 via the wirings 62 and 63. The voltage control unit 51 is also connected to the second tubular body 12 by a wiring 64, and is connected to the counter electrode 2 by a wiring 65. The voltage control unit 51 can apply a second drive voltage, different from the first drive voltage, between the second tubular body 12 and the counter electrode 2 via the wirings 64 and 65.

[0020] The control device 50 generates waveforms of the first drive voltage and the second drive voltage to be applied to the first tube 11 and the second tube 12, and controls the voltage control unit 51 so that the drive voltages are applied to the first tube 11 and the second tube 12 in accordance with the generated waveforms. The control device 50 also controls the stage drive unit 4 to move the stage 3 and the counter electrode 2. The control device 50 includes a control unit having a computing unit such as a CPU, and a storage unit having memories such as ROM and RAM. The control device 50 may be configured as a single controller that performs centralized control, or may be configured as a plurality of controllers that cooperate with each other to perform distributed control.

[0021] Next, an example of the operation of the electrostatic coating device 100 will be described below.

[0022] [Example 1] FIG. 2 is a diagram showing waveforms of the first driving voltage applied to the first tubular body 11 and the second driving voltage applied to the second tubular body 12 by the control device 50 in the first operation example.

[0023] In this operation example, the control device 50 applies a voltage to the nozzle 1 as shown in FIG. 2 while moving the stage 3 and the counter electrode 2 in the direction D. Specifically, the control device 50 applies a first driving voltage having a first waveform W11 to the first tubular body 11. By applying the first driving voltage to the first tubular body 11, the first driving voltage is applied to the first fluid F1 in the first flow path 16. Furthermore, the control device 50 applies a second driving voltage having a second waveform W2 to the second tubular body 12. By applying the second driving voltage to the second tubular body 12, the second driving voltage is applied to the second fluid F2 in the second flow path 17. The first waveform W11 and the second waveform W12 are pulse voltage waveforms in which high-voltage pulse waves are arranged along the time axis. The maximum voltage (peak voltage) of the pulse wave of the first waveform W11 is voltage V1. Furthermore, the second waveform W12 is a waveform synchronized with the first waveform W11. That is, the timing of the rise (start of voltage application) and fall (end of voltage application) of the pulse waves of the first waveform W11 and the second waveform W12 is the same. The maximum voltage V2 of the pulse wave of the second waveform W12 is different from the maximum voltage V1 of the first waveform W11. In this embodiment, the maximum voltage V1 is set to a value greater than the maximum voltage V2, but this is not limited to this. Note that, since the first flow path 16 and the second flow path 17 are electrically independent due to the insulating section 13, it is possible to effectively make the voltages applied to the first fluid F1 and the second fluid F2 different.

[0024] When the first driving voltage is applied to the first tubular body 11, the first fluid F1 is charged at the timing when the pulse wave rises, and an electrostatic field is formed between the first fluid F1 and the counter electrode 2, which is maintained at GND potential. As a result, an electrostatic force acts on the first fluid F1 toward the counter electrode 2, and the first fluid F1 is discharged from the discharge hole 10. The first fluid F1 discharged from the discharge hole 10 turns into droplets, moves toward the counter electrode 2, and adheres to the counter electrode 2.

[0025] Furthermore, when the second driving voltage is applied to the second tubular body 12, an electrostatic force acts on the second fluid F2 toward the counter electrode 2, causing the second fluid F2 to be discharged from the discharge hole 10, just as when the first driving voltage is applied to the first tubular body 11. Because the first waveform W11 and the second waveform W12 are synchronized waveforms, the first fluid F1 and the second fluid F2 are discharged from the discharge hole 10 at approximately the same timing. On the other hand, because the voltage V2 applied to the second fluid F2 is smaller than the voltage V1 applied to the first fluid F1, the electrostatic force acting on the second fluid F2 is smaller than the electrostatic force acting on the first fluid F1, and the speed of the second fluid F2 toward the counter electrode 2 is slower than the speed of F1 toward the counter electrode 2. Therefore, the second fluid F2 adheres to the counter electrode 2 later than the first fluid F1. The second fluid F2 can be deposited at a position different from the first fluid F1 by the movement of the counter electrode 2 during the period from when the first fluid F1 adheres to the counter electrode 2 until when the second fluid F2 adheres to the counter electrode 2. In this way, the electrostatic coating device 100 can individually control the speeds of the first fluid F1 and the second fluid F2 toward the counter electrode 2, and by utilizing this speed difference, the first fluid F1 and the second fluid F2 can be deposited at different positions on the counter electrode 2.

[0026] In some cases, the first fluid F1 and the second fluid F2 are simultaneously deposited at the same position on the counter electrode 2, and the first fluid F1 and the second fluid F2 are mixed on the counter electrode 2. However, if the first fluid F1 and the second fluid F2 have different dielectric constants, there may be a difference in the speed at which the first fluid F1 and the second fluid F2 move toward the counter electrode 2, even if the same voltage is applied. The electrostatic coating device 100 can apply different voltages to the first fluid F1 and the second fluid F2 depending on the dielectric constant, thereby making it possible to equalize the speed at which the first fluid F1 and the second fluid F2 move toward the counter electrode 2. This allows the first fluid F1 and the second fluid F2 to be deposited simultaneously on the counter electrode 2.

[0027] [Example 2] FIG. 3 is a diagram showing waveforms of the first driving voltage applied to the first tubular body 11 and the second driving voltage applied to the second tubular body 12 by the control device 50 in the second operation example.

[0028] In Operation Example 2, the first waveform W21 of the first driving voltage applied by the control device 50 to the first tubular body 11 is the same waveform as the first waveform W11 in Operation Example 1. On the other hand, the second waveform W22 of the second driving voltage applied by the control device 50 to the second tubular body 12 is a waveform that rises at a timing different from the timing at which the first waveform W21 rises and has a maximum voltage V2. In this Operation Example, the second waveform W22 rises with a delay from the rising timing of the first waveform W21 and falls with a delay from the falling timing of the first waveform W21.

[0029] When the second drive voltage is applied to the second tubular body 12, the second waveform W22 rises with a delay from the rise of the first waveform W21, and the second fluid F2 is therefore discharged from the discharge hole 10 with a delay from the first fluid F1. As a result, the second fluid F2 adheres to the counter electrode 2 with a delay from the first fluid F1. The second fluid F2 can be deposited at a position different from the first fluid F1 by the movement of the counter electrode 2 between the time when the first fluid F1 adheres to the counter electrode 2 and the time when the second fluid F2 adheres to the counter electrode 2. In this way, the electrostatic coating device 100 can individually control the timing at which the first fluid F1 and the second fluid F2 are discharged from the discharge hole 10 and the velocities of the first fluid F1 and the second fluid F2 toward the counter electrode 2. By utilizing this timing difference and speed difference, the first fluid F1 and the second fluid F2 can be deposited at different positions on the counter electrode 2.

[0030] The control device 50 controls the voltage control unit 51 and the stage driving unit 4 in cooperation with each other, thereby allowing the first fluid F1 and the second fluid F2 to adhere to any position on the upper surface of the counter electrode 2. In this way, the electrostatic coating device 100 can apply the first fluid F1 and the second fluid F2 to the counter electrode 2.

[0031] As described above, the electrostatic coating device 100 can differentiate the speed and ejection timing of the first fluid F1 that is attracted toward the counter electrode 2 by electrostatic force from the speed and ejection timing of the second fluid F2 that is attracted toward the counter electrode 2 by a different electrostatic force. This makes it possible to differentiate the timing at which the first fluid F1 adheres to the counter electrode 2 from the timing at which the second fluid F2 adheres to the counter electrode 2, and to control the ejection modes of the first fluid F1 and the second fluid F2 independently of each other.

[0032] (Embodiment 2) FIG. 4 is a cross-sectional view showing an example of the configuration of an electrostatic coating device 100 according to the second embodiment.

[0033] In the first embodiment, the nozzle 1 has a double-tube structure. In the present embodiment, on the other hand, as shown in FIG. 4 , the nozzle 101 has a triple-tube structure and further includes a third tube 113 and an insulating portion 114. The third tube 113 is a tubular body having a larger diameter than the second tube 12 and is arranged concentrically with the first tube 11 and the second tube 12. The outer circumferential surface of the second tube 12 is covered with the insulating portion 114, and the first tube 11 and the second tube 12 are nested inside the third tube 113. The space between the third tube 113 and the insulating portion 114 forms a third flow path 115. The third flow path 115 is a flow path for the third fluid F3 and leads to the discharge hole 10.

[0034] The voltage control unit 51 is connected to the third tubular body 113 by a wiring 166, and is connected to the counter electrode 2 by a wiring 167. The voltage control unit 51 is capable of applying a third drive voltage, which is different from the first drive voltage and the second drive voltage, between the third tubular body 113 and the counter electrode 2 via the wirings 166 and 167.

[0035] The control device 50 controls the voltage control section 51, so that the timing and speed at which the first fluid F1 to the third fluid F3 are discharged from the discharge holes 10 can be varied.

[0036] (Embodiment 3) In the first and second embodiments, the nozzle 1 has a double-pipe structure or a triple-pipe structure, but is not limited to this. Alternatively, the nozzle 1 may have a quadruple or more multi-pipe structure.

[0037] (Fourth embodiment) In the first to third embodiments, the nozzle 1 has a multi-tube structure of two or more layers, but the present invention is not limited to this. Instead, the nozzle 1 may have a structure in which a plurality of tubes are bundled together.

[0038] From the above description, many modifications and other embodiments of the present invention will be apparent to those skilled in the art. Therefore, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure and / or function thereof may be substantially changed without departing from the spirit of the present invention. [Explanation of symbols]

[0039] F1 1st fluid F2 2nd fluid 1 nozzle 2 Counter electrode 10 Discharge hole 11 First pipe 12 Second pipe 13 Insulation section 16 First Flow Path 17 Second Flow Path 50 Control device 51 Voltage control section 100 Electrostatic coating device

Claims

1. a nozzle having a discharge hole, a conductive first tubular body having a first flow path for a first fluid that leads to the discharge hole, and a conductive second tubular body having a second flow path for a second fluid that leads to the discharge hole; a counter electrode positioned opposite the ejection hole; a voltage control unit capable of applying a first drive voltage between the first tube and the opposing electrode, and a second drive voltage different from the first drive voltage between the second tube and the opposing electrode.

2. The electrostatic coating device according to claim 1 , wherein the first flow path and the second flow path are electrically independent of each other.

3. The electrostatic coating device according to claim 1 , further comprising an insulating portion that electrically isolates the first flow path and the second flow path.

4. The first tube is located inside the second tube, The electrostatic coating device according to claim 3 , wherein the insulating portion is located between the second flow path and the first pipe body.

5. Further, a control device for controlling the voltage control unit is provided. the control device applies the first driving voltage having a first waveform to the first tubular body and applies the second driving voltage having a second waveform to the second tubular body; The electrostatic coating device according to claim 1 , wherein the second waveform is synchronized with the first waveform and has a maximum voltage different from that of the first waveform.

6. Further, a control device for controlling the voltage control unit is provided. the control device applies the first driving voltage having a first waveform to the first tubular body and applies the second driving voltage having a second waveform to the second tubular body; The electrostatic coating device according to claim 1 , wherein the second waveform rises at a timing different from a timing at which the first waveform rises and has a maximum voltage different from a maximum voltage of the first waveform.

7. The electrostatic coating device according to claim 5 , wherein the first waveform and the second waveform are pulse voltage waveforms.

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