JP7546398B2 - Coating device and coating method - Google Patents

Description

This disclosure relates to a coating device and a coating method.

Conventionally, there is a painting device that paints an object with paint. The painting gun (nozzle) of the painting device sprays paint toward the surface of the object facing the painting gun. This forms a coating on the surface of the object.

One example of the above coating device is the coating device described in JP 2019-155324 A (Patent Document 1). The coating device described in this publication includes a nozzle, a mounting table, and an electrode. The workpiece is placed on the mounting surface of the mounting table. The electrode is disposed between the nozzle and the workpiece along the direction in which the nozzle and the mounting table face each other. A voltage is applied to the electrode, forming an electric field between the nozzle and the workpiece. The nozzle sprays the charged paint toward the workpiece. The charged paint passes through the electric field formed between the nozzle and the workpiece. The behavior of the charged paint passing through the electric field is controlled by the electric field. This controls the film thickness distribution of the paint applied to the workpiece.

JP 2019-155324 A

In the coating device described in the above publication, the mounting surface of the mounting table has a flat plate shape. In addition, the back surface of the object to be coated that is placed on the mounting surface has a flat plate shape. Therefore, the back surface of the object to be coated has a shape that matches the mounting surface of the mounting table. Therefore, when the mounting surface has a flat plate shape, there is no gap between the back surface of the object to be coated and the mounting surface. However, wear and deformation due to aging of the mounting table can cause a gap to form between the mounting surface and the object to be coated. If a gap forms between the mounting surface and the object to be coated, paint passes through the gap and is applied to the back surface of the object to be coated.

This disclosure has been made in consideration of the above problems, and its purpose is to provide a coating device and coating method that can prevent paint from being applied to the back surface of the object to be coated.

The coating device disclosed herein is a coating device for coating an object with paint. The object includes a front surface and a back surface. The back surface faces the front surface. The coating device includes a holding unit, a nozzle, and an electrode. The holding unit is configured to hold the object. The nozzle is configured to charge the paint. The nozzle is configured to spray the charged paint toward the surface of the object held in the holding unit. The electrode is configured to apply a voltage of a polarity opposite to the potential at which the paint is charged by the nozzle. The electrode is disposed on the back surface side. The electrode has a portion disposed inside the outer shape of the object when the electrode is viewed from the opposite side of the object in the direction in which the object and the electrode face each other.

According to the coating device disclosed herein, the electrode is disposed on the back side. The electrode has a portion that is disposed inside the outer shape of the object to be coated when the electrode is viewed from the opposite side of the object to be coated in the direction in which the object to be coated and the electrode face each other. Therefore, the electrode can adsorb paint that has wrapped around to the back side of the object to be coated. This makes it possible to prevent paint from being applied to the back side of the object to be coated.

1 is a cross-sectional view showing a schematic configuration of a coating device according to a first embodiment; 1 is a perspective view showing a schematic configuration of an object to be coated according to a first embodiment; FIG. 2 is a top view illustrating a schematic configuration of an electrode according to the first embodiment. FIG. 2 is a side view illustrating a schematic configuration of an electrode according to the first embodiment. 1 is a side view showing a schematic configuration of a mass-production painting line according to a first embodiment; 1 is a cross-sectional view showing a schematic configuration of one of a plurality of coating devices in a mass-production coating line according to a first embodiment, electric wires, a robot arm, a voltage supply device, and a transport unit. 1 is a flowchart illustrating a coating method according to a first embodiment. FIG. 2 is a schematic diagram illustrating the conditions of a simulation of the coating device according to the first embodiment. 4 is a graph roughly showing a result of a first simulation according to the first embodiment; 11 is a graph roughly showing a result of a second simulation according to the first embodiment; FIG. 11 is a cross-sectional view showing a schematic configuration of a coating device according to a second embodiment. FIG. 11 is a schematic diagram illustrating the conditions of a simulation of a coating device according to a second embodiment. FIG. 11 is a cross-sectional view showing a schematic configuration of a coating device according to a third embodiment. FIG. 11 is a cross-sectional view showing another configuration of the coating device according to the third embodiment. FIG. 11 is a perspective view illustrating a schematic configuration of an electrode according to a third embodiment. FIG. 11 is a schematic diagram illustrating the conditions of a simulation of a coating device according to a third embodiment. FIG. 11 is a cross-sectional view showing a schematic configuration of a coating device according to a fourth embodiment. FIG. 13 is a perspective view illustrating a schematic configuration of an electrode according to a fourth embodiment. FIG. 13 is a schematic diagram illustrating the conditions of a simulation of a coating device according to a fourth embodiment. FIG. 13 is a cross-sectional view showing a schematic configuration of a coating device according to a fifth embodiment.

The following describes the embodiment with reference to the drawings. Note that, in the following, the same or corresponding parts are given the same reference numerals, and redundant explanations will not be repeated.

Embodiment 1.
As shown in FIG. 1, the coating apparatus 100 is a coating apparatus for coating an object W with paint. In this embodiment, the paint is a powder paint. The object W includes a front surface S1 and a back surface S2. The back surface S2 faces the front surface S1. The front surface S1 is coated with the paint. Therefore, a coating film is formed on the front surface S1. The back surface S2 is exposed from the paint. Desirably, a coating film is not formed on the back surface S2.

As shown in Figures 1 and 2, the workpiece W according to this embodiment has an internal space IS. The workpiece W is formed, for example, by processing such as pressing or casting. In this embodiment, the workpiece W is curved. The curved workpiece W surrounds the internal space IS. The internal space IS of the workpiece W is connected to the outside of the workpiece W by an opening OP. The workpiece W may also have a flat plate shape. Therefore, each of the front surface S1 and the back surface S2 may have a planar shape.

In this embodiment, the first direction DR1 is a direction that intersects with the direction in which the workpiece W and the electrode 3 face each other. The second direction DR2 is a direction in which the workpiece W and the electrode 3 face each other. The second direction DR2 intersects with the first direction DR1. In this embodiment, the second direction DR2 is perpendicular to the first direction DR1. The surface S1 has a portion that is aligned with the first direction DR1. The surface S1 has a portion that faces the back surface S2 along the second direction DR2.

As shown in FIG. 1, the coating device 100 includes a nozzle 1, a holding portion 2, an electrode 3, and an electrode-side voltage application device 42.

The nozzle 1 is configured to charge the paint. Methods by which the nozzle 1 charges the paint include, for example, corona charging and tribocharging. The charging potential of the paint differs between the corona charging and tribocharging methods. In the corona charging method, a negative potential is applied to the nozzle 1. In the corona charging method, the paint is negatively charged by corona discharge. In the tribocharging method, the paint is positively charged inside the nozzle 1 due to friction between the paint and the inner wall surface of the nozzle 1.

The nozzle 1 is configured to spray electrically charged paint toward the surface S1 of the workpiece W held in the holding portion 2. The nozzle 1 includes a spray nozzle 11. The spray nozzle 11 is disposed at the tip of the nozzle 1. The nozzle 1 is configured to spray electrically charged paint from the spray nozzle 11 toward the surface S1 of the workpiece W. The nozzle 1 is configured to spray the paint along a direction intersecting the surface S1. Preferably, the nozzle 1 is configured to spray the paint along a direction perpendicular to the surface S1. The workpiece W is disposed between the nozzle 1 and the electrode 3.

The holding portion 2 is configured to hold the workpiece W. The holding portion 2 is configured to hold the workpiece W so that it does not move from the holding portion 2. The holding portion 2 is electrically connected to the earth 5. Therefore, the holding portion 2 is grounded. The workpiece W is electrically connected to the holding portion 2. The workpiece W is grounded via the holding portion 2. This creates a potential difference between the grounded workpiece W and the charged paint. Due to the potential difference between the grounded workpiece W and the charged paint, the charged paint is adsorbed to the surface S1 of the workpiece W.

The holding part 2 includes a first part 21, a second part 22, and a third part 23. The first part 21 is configured to hold the workpiece W. The first part 21 is inserted into the through hole TH of the workpiece W. In this way, the first part 21 holds the workpiece W. The first part 21 is connected to the second part 22 at an upward inclination in the direction of gravity. The first part 21 extends along the second direction DR2. The first part 21 is grounded via the second part 22.

The first part 21 is connected to the second part 22. The second part 22 extends along the direction of gravity DRG. The second part 22 may extend at an angle to the direction of gravity DRG. The second part 22 is electrically connected to the earth 5. Therefore, the second part 22 is grounded.

The electrode 3 is fixed to the third part 23. Therefore, the electrode 3 is fixed to the holding part 2. The third part 23 is connected to the first part 21. The third part 23 is not connected to the second part 22. In FIG. 1, the third part 23 extends upward on the paper, but the position and shape of the third part 23 may be appropriately determined as long as the electrode 3 is fixed to the holding part 2. In addition, the third part 23 is an insulator. Therefore, the electrode 3 is electrically insulated from the earth 5.

The electrode 3 is configured so that a voltage of the opposite polarity to the potential to which the paint is charged by the nozzle 1 is applied. If the paint is negatively charged, a positive potential is applied to the electrode 3. If the paint is positively charged, a negative potential is applied to the electrode 3. This causes the charged paint to be attracted to the electrode 3.

The electrode 3 is disposed on the back surface S2 side. The back surface S2 side is the opposite side of the nozzle 1 with respect to the workpiece W. Therefore, the electrode 3 is disposed on the opposite side of the nozzle 1 with respect to the workpiece W. The electrode 3 is disposed on the back surface S2 side as a whole. Also, the front surface S1 side is the opposite side of the electrode 3 with respect to the workpiece W.

The electrode 3 has a portion that is positioned inside the outer shape of the workpiece W when the electrode 3 is viewed from the opposite side of the workpiece W relative to the electrode 3 in the direction in which the workpiece W and the electrode 3 face each other (second direction DR2). In this embodiment, the electrode 3 is positioned inside the outer shape of the workpiece W when the electrode 3 is viewed from the opposite side of the workpiece W relative to the electrode 3 in the direction in which the workpiece W and the electrode 3 face each other (second direction DR2).

The electrode 3 is configured to form an electric field when a voltage is applied. The electric field is formed in the electric field region R. The electric field region R blocks the opening OP of the workpiece W. Therefore, the internal space IS of the workpiece W is closed by the electric field region R. The charged paint is captured by the electric field. For ease of explanation, a gap is provided between the electric field region R and the opening OP in FIG. 1, but the electric field region R may be in contact with the opening OP.

As shown in Figures 1, 3 and 4, the electrode 3 in this embodiment has a ring shape. As shown in Figure 1, the electrode 3 is arranged along the entire circumference of the outer peripheral edge of the workpiece W. The electrode 3 is arranged along the first direction DR1. The cross-sectional shape of the electrode 3 along the second direction DR2 is, for example, circular. Since the outer peripheral edge of the workpiece W in this embodiment is circular, the electrode 3 having a ring shape can follow the shape of the workpiece W. Note that if the outer peripheral edge of the workpiece W is polygonal, it is preferable that the electrode 3 also has a polygonal shape.

The electrode side voltage application device 42 is electrically connected to the electrode 3. The electrode side voltage application device 42 is configured to apply a voltage to the electrode 3.

The object to be painted W is, for example, the housing of a motor. Surface S1 is, for example, the front surface of the housing. Back surface S2 is, for example, the back surface of the housing. The front surface of the housing is the area that is visible to the human eye when the housing is in use. For this reason, the front surface of the housing is required to have design quality. The front surface of the housing is also exposed to the external environment. For this reason, the front surface of the housing is required to have corrosion resistance. Therefore, it is necessary to improve the design quality and durability of front surface S1 by painting with paint.

For example, a motor shaft is placed inside the housing. For this reason, the clearance between the shaft and the housing is important. Also, when the positional accuracy of a part placed inside the housing, such as a motor, is ensured by the fit between the housing and the motor, etc., the dimensional accuracy of the rear surface of the housing is important. If a coating is formed on the rear surface of the housing, the dimensional accuracy of the rear surface of the housing will decrease.

From the above, it is required that a coating film be formed on the surface S1 of the workpiece W, and that a coating film not be formed on the back surface S2. The coating device 100 is a coating device for coating the workpiece W, which includes the surface S1 on which a coating film is required to be formed and the back surface S2 on which a coating film is not required to be formed.

Next, the configuration of the mass-production painting line 200 according to the first embodiment will be described with reference to Figures 5 and 6.

As shown in FIG. 5, the painting device 100 is used in a mass production painting line 200. The mass production painting line 200 includes a plurality of painting devices 100, a plurality of electric wires 6, a plurality of robot arms 7, a voltage supply unit 8, and a transport unit 9. Each of the holding units 2 of the plurality of painting devices 100 is connected to the voltage supply unit 8 via each of the plurality of electric wires 6. The transport unit 9 is configured to transport the plurality of painting devices 100 continuously. The transport direction of the transport unit 9 is indicated by a white arrow. The holding unit 2 is configured to be transported along the mass production line in the transport direction by the driving force of the transport unit 9. Each of the plurality of robot arms 7 is connected to each of the plurality of nozzles 1.

The transport unit 9 is configured to transport the painting device 100 from outside the painting booth (not shown) through the interior of the painting booth (not shown) and the interior of the drying furnace (not shown) to the outside of the drying furnace (not shown). The painting device 100 is configured to spray paint onto the workpiece W inside the painting booth. The drying furnace is configured to dry the workpiece W by baking the workpiece W sprayed with paint at a high temperature.

As shown in FIG. 6, the electric wire 6 is arranged along the holding part 2. Specifically, the electric wire 6 is arranged so as to be wound around the second part 22 of the holding part 2. For ease of explanation, the outline of the electric wire 6 arranged on the front side of the paper is shown by a solid line. The outline of the electric wire 6 arranged on the back side of the paper is shown by a dashed line. The electric wire 6 includes a conductor 61 and an insulating coating 62. The conductor 61 is covered with the insulating coating 62. Therefore, the holding part 2 and the electrode 3 are not electrically connected via the conductor 61 of the electric wire 6. The first end of the electric wire 6 is electrically connected to the electrode 3. The second end of the electric wire 6 is electrically connected to the voltage supply unit 8. As a result, the electrode 3 is electrically connected to the voltage supply unit 8 via the electric wire 6.

The voltage supply unit 8 is electrically connected to the electrode side voltage application device 42. The electrode side voltage application device 42 and the voltage supply unit 8 are not arranged in the drying furnace process, but are installed in the painting booth process. In the painting booth process, the voltage supply unit 8 and the electrode side voltage application device 42 are installed outside the painting booth, and are configured so that the powder paint sprayed from the nozzle 1 does not adhere to them. The voltage supply unit 8 and the electrode side voltage application device 42 are fixed (do not move), and when the holding unit 2, which is moved by the conveying unit 9, comes into the painting booth area, the electric wire 6 physically comes into contact with the voltage supply unit 8, which is fixed in position, and conducts electricity, and a voltage is applied to the electrode 3.

Next, the painting method according to the first embodiment will be explained using Figures 7 and 6.

The coating method according to this embodiment is a coating method for coating an object W with paint. As shown in FIG. 7, the coating method includes a holding step S101 and a spraying step S102. As shown in FIG. 6, a nozzle 1, a holding unit 2, and an electrode 3 are prepared. The holding unit 2 is connected to a transport unit 9.

Then, the workpiece W is held in the holding unit 2 so that the electrode 3 is positioned on the back surface S2 side. In the direction in which the workpiece W and the electrode 3 face each other (second direction DR2), the workpiece W is held in the holding unit 2 so that the electrode 3 is positioned inside the outer shape of the workpiece W when the electrode 3 is viewed from the opposite side of the workpiece W. The workpiece W is placed on the holding unit 2, which is connected to the transport unit 9. The holding unit 2 with the workpiece W placed on it is transported by the transport unit 9 into the interior of the transport booth.

Then, the workpiece W is painted inside the transport booth. The paint is charged by the nozzle 1, and a voltage of the opposite polarity to the potential to which the paint is charged is applied to the electrode 3. The charged paint is then sprayed by the nozzle 1 onto the surface S1 of the workpiece W held by the holding part 2.

Then, the holding part 2, the electrode 3, and the workpiece W onto which the paint has been sprayed are each transported to a drying furnace. The holding part 2, the electrode 3, and the workpiece W are each exposed to a high-temperature environment in the drying furnace. This causes the paint to harden. Thus, a coating is formed on the workpiece W.

Then, the workpiece W is removed from the holding part 2. Through the above steps, the workpiece W coated with paint is obtained.

Next, we will explain the effects of this embodiment.

According to the coating device 100 of the first embodiment, as shown in FIG. 1, the electrode 3 is disposed on the back surface S2 side. Therefore, the electrode 3 can adsorb the paint that has wrapped around from the front surface S1 side to the back surface S2 side. In addition, the electrode 3 has a portion that is disposed inside the outer shape of the workpiece W when the electrode 3 is viewed from the opposite side of the workpiece W with respect to the electrode 3 in the direction in which the workpiece W and the electrode 3 face each other (second direction DR2). Therefore, an electric field region R is formed so as to block the opening OP of the workpiece W. Therefore, the paint that has wrapped around to the back surface S2 side of the workpiece W can be captured on the electrode 3 by the electric field. Therefore, it is possible to prevent the paint from being applied to the back surface S2 of the workpiece W.

Next, the effects of this embodiment will be described in detail using a simulation of the behavior of the paint. A simulation of the behavior of the paint according to embodiment 1 will be described using Figures 8 to 10. As shown in Figure 8, in the simulation, the nozzle 1 sprays paint toward the surface S1 from a direction perpendicular to the workpiece W. In the simulation, the electric field generated in each of the multiple meshes is calculated. The size of one mesh is the same as the cross-sectional size of the electrode 3, which has a ring shape. For ease of explanation, the shapes of the nozzle 1, the electrode 3, and the workpiece W are shown by hatching. For ease of explanation, the holder 2 (see Figure 1) is not shown in Figure 8.

In the simulation, the nozzle 1 is set as an anode. The electrode 3 and the workpiece W are set as cathodes. In order to qualitatively confirm the effective area according to the position of the electrode 3, the potential of the workpiece W and the potential of the electrode 3 are set to be the same. Note that, if different potentials can be applied to the electrode 3 and the workpiece W, the voltage applied to the electrode 3 may be lower than the voltage applied to the workpiece W. This provides an even greater effect.

In the simulation, the amount of paint that wraps around to the back surface S2 is calculated according to the intensity distribution of the electric field formed by the nozzle 1, the electrode 3, and the workpiece W. This allows the ratio of paint that has been applied to the back surface S2 out of the paint that has been applied to the workpiece W to be calculated. In this embodiment, the ratio of paint that has been applied to the back surface S2 out of the paint that has been applied to the workpiece W is called the back surface coating rate.

In this embodiment, the coating rate on the back side is calculated under three conditions: a first simulation, a second simulation, and a third simulation. In each of the first and second simulations, the position of electrode 3 shown in FIG. 8 is the origin 0. In the third simulation, electrode 3 is not positioned. Therefore, the third simulation is a comparative example.

In the first simulation, the radius of the ring-shaped electrode 3 is changed by one mesh along the first direction DR1. Therefore, the coating rate on the back side of the electrode 3 shown in FIG. 8, the coating rate on the back side of the electrode 3 having a larger radius than the electrode 3 shown in FIG. 8, and the coating rate on the back side of the electrode 3 having a smaller radius than the electrode 3 shown in FIG. 8 are calculated.

In the second simulation, the position of the electrode 3 is changed by one mesh at a time along the second direction DR2. Therefore, the coating rate on the back side by the electrode 3 shown in FIG. 8, the coating rate on the back side by the electrode 3 arranged on the front surface S1 side of the electrode 3 shown in FIG. 8, and the coating rate on the back side by the electrode 3 arranged on the back surface S2 side of the electrode 3 shown in FIG. 8 are calculated.

Figure 9 is a graph showing the results of the first simulation. As shown in Figure 9, the results of the first simulation show that the smaller the radius of the electrode 3, the lower the coating rate on the back side. Therefore, the closer the electrode 3 is positioned to the center of the workpiece W, the lower the coating rate on the back side. Therefore, the closer the electrode 3 is positioned to the center of the workpiece W, the more the paint is prevented from being applied to the back side S2 of the workpiece W. The minimum coating rate on the back side is 2%.

Figure 10 is a graph showing the results of the second simulation. As shown in Figure 10, in the results of the second simulation, the coating rate on the back side is approximately constant regardless of whether the electrode 3 is placed on the front side S1 side or the back side S2 side. The coating rate on the back side is 4% or more and 5% or less. However, when the electrode 3 is placed on the front side S1 side, the workpiece W and the electrode 3 may come into contact when the workpiece W is held by the holding part 2. Therefore, the position of the electrode 3 may fluctuate due to damage or deformation of the electrode 3. This may cause the position of the electrode 3 to fluctuate. Therefore, there is a possibility that the coating of the paint on the back side S2 side will not be suppressed. For the above reasons, it is desirable to place the electrode 3 on the back side S2 side.

In the results of the third simulation, the coating rate on the back side is 16.7%. Therefore, when electrode 3 is not placed, the coating rate on the back side is higher than when electrode 3 is placed. Also, the coating efficiency on the front surface S1 side is 60%. Therefore, the coating efficiency on the front surface S1 side is low. Also, when electrode 3 is not placed, for example, a coating film having a thickness of 40 μm is formed on front surface S1, and a coating film having a thickness of 11.1 μm is formed on back surface S2. Note that, when electrode 3 is placed, for example, a coating film having a thickness of 40 μm is formed on front surface S1, and a coating film having a thickness of 1.3 μm is formed on back surface S2.

As described above, by arranging the electrode 3 on the back surface S2 side and by arranging the electrode 3 so that, in the direction in which the workpiece W and the electrode 3 face each other (second direction DR2), the electrode 3 has a portion that is positioned inside the outer shape of the workpiece W when the electrode 3 is viewed from the opposite side of the workpiece W, it is possible to prevent paint from being applied to the back surface S2.

In addition, if the workpiece W is covered with a masking member to form an unpainted surface, the dimensions of the masking member will become smaller due to wear and deformation caused by aging. As a result, the masking member will no longer be able to completely cover the unpainted surface, and paint will be applied to the unpainted surface. In addition, if the masking member is deformed, a gap will be created between the workpiece W and the masking member, and paint will pass through the gap and be applied to the unpainted surface.

In addition, if an unpainted surface is formed by covering the workpiece W with a masking member, as described above, the unpainted surface will no longer be formed due to deterioration of the masking member over time. For this reason, it is necessary to check that the masking member has not deteriorated over time before using the masking member. In addition, if the masking member has deteriorated over time, it is necessary to replace the deteriorated masking member with a masking member that has not deteriorated over time. This increases the painting cost.

In addition, if the workpiece W is covered with a masking material, forming an unpainted surface, the quality of the paint job may decline if deterioration of the masking material over time goes unnoticed. This creates a risk of a decline in the quality of the paint job.

In addition, if the workpiece W is covered with a masking member to form an unpainted surface, an electrode is electrically connected to the masking member. The optimal shape of the electrode varies depending on the shape of the masking member. Therefore, if the shape of the masking member is changed, the shape of the electrode must also be changed.

According to this embodiment, as shown in FIG. 1, the electrode 3 is configured to be applied with a voltage of the opposite polarity to the potential to which the paint is charged by the nozzle 1. Therefore, the paint is attracted to the electrode 3. Therefore, it is not necessary to cover the workpiece W with a masking member. Therefore, the above-mentioned problems caused by the masking member do not occur. Therefore, it is possible to suppress an increase in painting costs. In addition, it is possible to reduce the risk of deterioration in the quality of the paint. Moreover, a common electrode can be used regardless of the shape of the non-painted surface. Also, high positional accuracy is not required as with the masking member.

As shown in FIG. 1, the electrode 3 is configured to apply a voltage of the opposite polarity to the potential to which the paint is charged by the nozzle 1. Therefore, there is no need to cover the holding part 2 by bringing a part of the coating device 100, such as the holding part 2, into contact with the entire surface of the back surface S2 of the workpiece W. Therefore, the shape of the back surface S2 of the workpiece W is not limited by the shape of the holding part 2, etc. In other words, the shape of the back surface S2 of the workpiece W is not limited by the shape of the coating device 100. Therefore, even if the back surface S2 of the workpiece W has a shape that does not match the shape of the holding part 2, it is possible to prevent the paint from being applied to the back surface S2.

As shown in FIG. 1, the electrode 3 is disposed on the back surface S2 side. This makes it possible to suppress a decrease in the paint application efficiency on the surface S1 on which a coating film is to be formed, compared to when the electrode 3 is disposed between the nozzle 1 and the workpiece W along the direction in which the workpiece W and the electrode 3 face each other (the second direction DR2).

As shown in FIG. 1, the electrode 3 is positioned generally inward from the outer diameter of the workpiece W when viewed from the opposite side of the workpiece W relative to the electrode 3 in the direction in which the workpiece W and the electrode 3 face each other (second direction DR2). This further prevents paint from being applied to the back surface S2.

As shown in FIG. 1, the electrode 3 is fixed to the holding part 2. The third part 23 is configured to hold the electrode 3. The third part 23 is connected to the first part 21 and is not connected to the second part 22. Therefore, even if the second part 22 of the holding part 2 is deformed due to aging, the relative position between the workpiece W and the electrode 3 can be prevented from changing. This reduces the frequency of maintenance of the coating device 100.

As shown in FIG. 1, the first part 21 is connected to the second part 22 at an upward inclination in the direction of gravity. This prevents the workpiece W from falling off the first part 21.

As shown in FIG. 1, the electrode 3 is disposed along the entire circumference of the outer periphery of the workpiece W. This makes it possible to prevent paint from being applied to the back surface S2 more effectively than if the electrode 3 were disposed along only a portion of the outer periphery of the workpiece W.

The electrode-side voltage application device 42 and the voltage supply unit 8 are not disposed in the drying oven process, but are installed in the painting booth process. In the painting booth process, the voltage supply unit 8 and the electrode-side voltage application device 42 are installed outside the painting booth, and are configured so that the powder paint sprayed from the nozzle does not adhere to them. The voltage supply unit 8 and the electrode-side voltage application device 42 are fixed (do not move), and when the holding unit 2, which is moved by the conveying unit 9, comes into the painting booth area, the electric wire 6 physically comes into contact with the voltage supply unit 8, thereby establishing electrical conduction, and a voltage is applied to the electrode 3. Therefore, the electrode-side voltage application device 42 is not installed inside the drying oven, and deterioration due to the high temperature environment inside the drying oven can be suppressed.

According to the coating method of embodiment 1, as shown in FIG. 6, the electrode 3 is arranged on the back surface S2 side, and in the direction in which the workpiece W and the electrode 3 face each other (second direction DR2), the workpiece W is held by the holding portion 2 so that the electrode 3 is arranged inside the outer shape of the workpiece W when viewed from the opposite side of the electrode 3 to the workpiece W. Therefore, when paint is sprayed onto the workpiece W, the electrode 3 is arranged on the back surface S2 side and inside the outer shape of the workpiece W. This makes it possible to prevent paint from being applied to the back surface S2.

Embodiment 2.
Next, the configuration of a coating apparatus 100 according to a second embodiment will be described with reference to Fig. 11. Unless otherwise specified, the second embodiment has the same configuration and effects as the first embodiment. Therefore, the same components as those in the first embodiment are given the same reference numerals and will not be described repeatedly.

As shown in FIG. 11, the electrode 3 in this embodiment includes a first electrode portion 31 and a second electrode portion 32. The first electrode portion 31 is configured to be applied with a voltage different from that applied to the second electrode portion 32. In FIG. 11, the electrode 3 has two electrode portions, but the number of electrode portions may be appropriately determined depending on the quality required for the coating and the shape of the workpiece W.

The first electrode section 31 and the second electrode section 32 each have a ring shape. The second electrode section 32 surrounds the first electrode section 31. The second electrode section 32 surrounds the first electrode section 31 at a distance from the first electrode section 31. The electrode side voltage application device 42 includes a first application device 421 and a second application device 422. The first application device 421 is configured to apply a voltage to the first electrode section 31. The second application device 422 is configured to apply a voltage to the second electrode section 32.

Next, we will explain the effects of this embodiment.

According to the coating device 100 of the second embodiment, as shown in FIG. 11, the electrode 3 includes a first electrode portion 31 and a second electrode portion 32. Therefore, the coating device 100 can form a more complex electric field than when there is only one electrode 3. Therefore, it is possible to prevent paint from being applied to the back surface S2 more than when there is only one electrode 3.

As shown in FIG. 11, the first electrode unit 31 is configured to be applied with a voltage different from that applied to the second electrode unit 32. Therefore, the coating device 100 can form a more complex electric field than when the same voltage is applied to the first electrode unit 31 and the second electrode unit 32. Therefore, it is possible to prevent paint from being applied to the back surface S2 more effectively than when the same voltage is applied to the first electrode unit 31 and the second electrode unit 32.

More specifically, according to the results of the fourth simulation shown in FIG. 12, the coating rate on the back side is 1.18%. Therefore, the coating rate on the back side is lower than when there is only one electrode 3. Other conditions of the fourth simulation for the configuration of the electrode 3 are the same as those of the first simulation.

As shown in FIG. 11, the electrode 3 includes a first electrode portion 31 and a second electrode portion 32. Therefore, even if the dimension of the workpiece W in the first direction DR1 is large, the entire back surface S2 of the workpiece W can be covered by an electric field more easily than if there was only a single electrode 3. Therefore, even if the dimension of the workpiece W in the first direction DR1 is large, it is possible to prevent paint from being applied to the back surface S2.

Embodiment 3.
Next, the configuration of a coating apparatus 100 according to a third embodiment will be described with reference to Figures 13 to 16. Unless otherwise specified, the third embodiment has the same configuration and effects as the first embodiment. Therefore, the same components as those in the first embodiment are given the same reference numerals and will not be described repeatedly.

As shown in FIG. 13, the electrode 3 in this embodiment includes a first end E1 and a second end E2. The first end E1 is located inside the outer shape of the workpiece W when the electrode 3 is viewed from the opposite side of the workpiece W relative to the electrode 3 in the direction in which the workpiece W and the electrode 3 face each other (second direction DR2). The second end E2 is located on the opposite side of the workpiece W relative to the first end E1. Each of the first end E1 and the second end E2 is located on the back surface S2 side. Each of the first end E1 and the second end E2 is located outside the internal space IS of the workpiece W.

The outer edge of the electrode 3 is configured to become larger from the first end E1 toward the second end E2. The outer edge of the electrode 3 is configured to become larger in the radial direction of the electrode 3 from the first end E1 toward the second end E2. The electrode 3 is configured in a trumpet shape. The electrode 3 is configured in a tapered shape. The electrode 3 is configured such that the outer edge of the electrode 3 becomes larger as the electrode 3 moves away from the workpiece W. The electrode 3 surrounds the first portion 21 of the holding portion 2.

In FIG. 13, the second end E2 is positioned outside the outer shape of the workpiece W when the electrode 3 is viewed from the opposite side of the workpiece W relative to the electrode 3 in the direction in which the workpiece W and the electrode 3 face each other (second direction DR2). As shown in FIG. 14, the second end E2 may be positioned inside the outer shape of the workpiece W when the electrode 3 is viewed from the opposite side of the workpiece W relative to the electrode 3 in the direction in which the workpiece W and the electrode 3 face each other (second direction DR2).

As shown in FIG. 15, the electrode 3 is in the shape of a truncated cone. Therefore, the cross-sectional shape of the electrode 3 in a direction perpendicular to the direction from the first end E1 to the second end E2 is in the shape of a ring. The electrode 3 is configured so that the outer diameter of the ring increases along the direction from the first end E1 to the second end E2. The electrode 3 may also be in the shape of a truncated pyramid.

Next, we will explain the effects of this embodiment.

According to the coating device 100 of the third embodiment, as shown in FIG. 13, the outer edge of the electrode 3 is configured to become larger from the first end E1 toward the second end E2. Therefore, the area of the electrode 3 of this embodiment facing the opening OP is larger than that of a ring-shaped electrode 3 having the same surface area. Therefore, the electrode 3 of this embodiment can adsorb more paint than a ring-shaped electrode 3 having the same surface area. Therefore, it is possible to further prevent paint from being applied to the back surface S2.

More specifically, according to the results of the fifth simulation shown in FIG. 16, the coating rate on the back side is 0.79%. Therefore, the coating rate on the back side is lower than when the electrode 3 has a ring shape. Other conditions of the fifth simulation for the configuration of the electrode 3 are the same as those of the first simulation.

Embodiment 4.
Next, the configuration of a coating apparatus 100 according to embodiment 4 will be described with reference to Figures 17 to 19. Unless otherwise specified, embodiment 4 has the same configuration and effects as embodiment 1. Therefore, the same components as embodiment 1 are denoted by the same reference numerals and will not be described repeatedly.

As shown in Figs. 17 and 18, the electrode 3 according to this embodiment includes a cylindrical portion 33 and a flat portion 34. As shown in Fig. 17, the cylindrical portion 33 is configured to surround the first portion 21 of the holding portion 2. The cylindrical portion 33 is disposed along the second direction DR2.

The cylindrical portion 33 includes a first cylindrical end CE1 and a second cylindrical end CE2. The second cylindrical end CE2 is disposed on the opposite side of the workpiece W from the first cylindrical end CE1. The first cylindrical end CE1 and the second cylindrical end CE2 are disposed on the back surface S2 side. The first cylindrical end CE1 and the second cylindrical end CE2 are disposed inside the outer shape of the workpiece W when the electrode 3 is viewed from the opposite side of the workpiece W with respect to the electrode 3 in the direction in which the workpiece W and the electrode 3 face each other (second direction DR2). The first cylindrical end CE1 and the second cylindrical end CE2 are disposed outside the internal space IS of the workpiece W.

The flat plate portion 34 is connected to the second cylinder side end CE2. The flat plate portion 34 protrudes from the second cylinder side end CE2 of the cylindrical portion 33. Therefore, the outer shape of the flat plate portion 34 is larger than the outer shape of the cylindrical portion 33. The flat plate portion 34 protrudes from the second cylinder side end CE2 along the radial direction of the cylindrical portion 33. The flat plate portion 34 is perpendicular to the second cylinder side end CE2. The flat plate portion 34 is arranged along the first direction DR1.

Next, we will explain the effects of this embodiment.

According to the coating device 100 of the fourth embodiment, as shown in FIG. 17, the flat portion 34 protrudes from the second cylindrical end CE2 of the cylindrical portion 33. Therefore, the area of the electrode 3 of this embodiment facing the opening OP is larger than that of a ring-shaped electrode 3 having the same surface area. Therefore, the electrode 3 of this embodiment can adsorb more paint than a ring-shaped electrode 3 having the same surface area. Therefore, it is possible to further prevent paint from being applied to the back surface S2.

More specifically, according to the results of the sixth simulation shown in FIG. 19, the coating rate on the back side is 0.76%. Therefore, the coating rate on the back side is lower than when the electrode 3 is ring-shaped. Other conditions of the sixth simulation for the configuration of the electrode 3 are the same as those of the first simulation.

Embodiment 5.
Next, the configuration of a coating apparatus 100 according to a fifth embodiment will be described with reference to Fig. 20. Unless otherwise specified, the fifth embodiment has the same configuration and effects as the first embodiment. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

As shown in FIG. 20, the coating device 100 according to this embodiment further includes a blow unit 90, a first pipe 92, a second pipe 93, and a connection unit 94. The blow unit 90 is configured to blow gas toward the electrode 3. The gas is, for example, compressed air. The gas is blown out from an outlet 91 of the blow unit 90. In FIG. 20, the direction of the gas blown out by the blow unit 90 toward the electrode 3 is indicated by an arrow.

The blow unit 90 is held by the holding unit 2. In this embodiment, the blow unit 90 includes a first nozzle unit 9a and a second nozzle unit 9b. Each of the first nozzle unit 9a and the second nozzle unit 9b is held by the holding unit 2.

A first end of the first pipe 92 is connected to the blow section 90. The first pipe 92 is a rigid body. Therefore, the first pipe 92 is configured not to deform. The first pipe 92 is fixed to the holding section 2. A second end of the first pipe 92 is connected to a first end of the second pipe 93.

The second pipe 93 is configured to be deformable. The second end of the second pipe 93 is connected to the connection part 94.

The connection part 94 is connected to the second pipe 93, which is configured to be deformable. Therefore, the connection part 94 can move within a range in which the second pipe 93 can elastically deform. The connection part 94 is, for example, a coupler or the like. The connection part 94 is configured to supply gas supplied from the outside to the blow part 90. The outside is, for example, a cylinder or the like on the building side, not shown. The connection part 94 is configured to supply gas, such as compressed air, from the building side, not shown. The connection part 94 is configured to be connected to the building, for example, by a pipe. The connection part 94 and the second pipe 93 may be connected manually by an operator or automatically by a robot or the like. The blow part 90, the first pipe 92, the second pipe 93, and the connection part 94 are connected in sequence.

Next, the painting method according to embodiment 5 will be explained using FIG.

As shown in FIG. 20, paint is sprayed onto the workpiece W inside a painting booth (not shown), so that the paint is applied to the electrode 3 and the workpiece W. In the painting method according to this embodiment, after the paint is sprayed onto the workpiece W and before the workpiece W is carried into the drying furnace, the blow unit 90 blows gas toward the electrode 3. This blows off the paint that has been applied to the electrode 3. Next, the holding unit 2 and the workpiece W are placed into the drying furnace, so that the paint on the workpiece W hardens.

Next, we will explain the effects of this embodiment.

According to the coating device 100 of the fifth embodiment, the blow unit 90 is configured to blow gas toward the electrode 3. Therefore, the paint applied to the electrode 3 is removed by being blown away by the gas. This makes it possible to prevent a coating film from being formed on the electrode 3.

If the paint applied to the electrode 3 is not removed before it dries, the electrode 3 will be brought into the drying oven with the paint still applied to it, and the coating will adhere to the surface of the electrode 3. The coating is an insulator. This inhibits the formation of an electric field by the electrode 3. As a result, the coating of the paint to the back surface S2 is not suppressed by the electric field. Therefore, if the paint applied to the electrode 3 is not removed before it dries, the coating that has adhered to the electrode 3 must be periodically peeled off in order to suppress the coating of the paint to the back surface S2.

According to this embodiment, since the paint applied to the electrode 3 is removed, there is no need to peel off the coating film adhered to the electrode 3. Therefore, the functionality of the coating device 100 is maintained for a long period of time without the need to peel off the coating film adhered to the electrode 3.

In addition, if a painted area and a non-painted area are adjacent to each other on one surface of the workpiece W, and the non-painted area is covered by a masking member, the paint in the painted area will also be removed by blowing gas onto the masking member. For this reason, it is not possible to remove the paint applied to the masking member in a limited manner. According to this embodiment, since the front surface S1 is the painted area and the back surface S2 is the non-painted area, unnecessary paint can be removed by blowing gas onto the electrode 3 in a limited manner.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope of the claims.

1 nozzle, 2 holding part, 3 electrode, 21 first part, 22 second part, 31 first electrode part, 32 second electrode part, 33 cylindrical part, 34 flat part, 90 blow part, 100 coating device, CE1 first end part of cylindrical part, CE2 second end part of cylindrical part, DRG gravity direction, E1 first end part, E2 second end part, S1 front surface, S2 back surface, W workpiece.

Claims (10)

A coating device for coating a coating object having a front surface and a back surface opposite to the front surface with a paint,
The object to be coated has an internal space,
A holding portion including a columnar first portion configured to hold the back surface side ;
a nozzle configured to charge the paint and spray the charged paint toward the surface of the workpiece held by the holder;
an electrode configured to apply a voltage of a polarity opposite to the potential to which the paint is charged by the nozzle;
The electrode is disposed on the back surface side by the first portion ,
the electrode has a portion that is disposed inside an outer shape of the object to be coated when the electrode is viewed from the opposite side of the object to be coated in a direction in which the object to be coated and the electrode face each other ,
the holding portion includes a second portion to which the first portion is connected,
A coating device , wherein the first section is connected to the second section and inclined upward in a direction of gravity . A coating device for coating a coating object having a front surface and a back surface opposite to the front surface with a paint,
The object to be coated has an internal space,
A holding portion including a columnar first portion configured to hold the back surface side ;
a nozzle configured to charge the paint and spray the charged paint toward the surface of the workpiece held by the holder;
an electrode configured to apply a voltage of a polarity opposite to the potential to which the paint is charged by the nozzle;
The electrode is disposed on the back surface side by the first portion ,
the electrode has a portion that is disposed inside an outer shape of the object to be coated when the electrode is viewed from the opposite side of the object to be coated in a direction in which the object to be coated and the electrode face each other ,
The electrode includes a first electrode portion and a second electrode portion,
A coating device , wherein the first electrode portion is configured to be applied with a voltage different from that applied to the second electrode portion . A coating device for coating a coating object having a front surface and a back surface opposite to the front surface with a paint,
The object to be coated has an internal space,
A holding portion including a columnar first portion configured to hold the back surface side ;
a nozzle configured to charge the paint and spray the charged paint toward the surface of the workpiece held by the holder;
an electrode configured to apply a voltage of a polarity opposite to the potential to which the paint is charged by the nozzle;
The electrode is disposed on the back surface side by the first portion ,
the electrode has a portion that is disposed inside an outer shape of the object to be coated when the electrode is viewed from the opposite side of the object to be coated in a direction in which the object to be coated and the electrode face each other ,
A coating device , wherein the electrode has a ring shape and is arranged along the entire outer periphery of the outer periphery of the object to be coated . A coating device for coating a coating object having a front surface and a back surface opposite to the front surface with a paint,
The object to be coated has an internal space,
A holding portion including a columnar first portion configured to hold the back surface side ;
a nozzle configured to charge the paint and spray the charged paint toward the surface of the workpiece held by the holder;
an electrode configured to apply a voltage of a polarity opposite to the potential to which the paint is charged by the nozzle;
The electrode is disposed on the back surface side by the first portion ,
the electrode has a portion that is located inside an outer shape of the object to be coated when the electrode is viewed from the opposite side of the object to be coated in a direction in which the object to be coated and the electrode face each other ,
the electrode includes a first end portion located inside an outer shape of the object to be coated when the electrode is viewed from the opposite side of the object to be coated relative to the electrode in a direction in which the object to be coated and the electrode face each other, and a second end portion located on the opposite side of the object to be coated relative to the first end portion,
The outer edge of the electrode is configured to increase in size from the first end to the second end. A coating device for coating a coating object having a front surface and a back surface opposite to the front surface with a paint,
The object to be coated has an internal space,
A holding portion including a columnar first portion configured to hold the back surface side ;
a nozzle configured to charge the paint and spray the charged paint toward the surface of the workpiece held by the holder;
an electrode configured to apply a voltage of a polarity opposite to the potential to which the paint is charged by the nozzle;
The electrode is disposed on the back surface side by the first portion ,
the electrode has a portion that is disposed inside an outer shape of the object to be coated when the electrode is viewed from the opposite side of the object to be coated in a direction in which the object to be coated and the electrode face each other ,
the electrode includes a cylindrical portion having a cylindrical first end and a cylindrical second end disposed on the opposite side of the workpiece from the cylindrical first end, and a flat portion connected to the cylindrical second end,
The flat portion protrudes from the second cylindrical end of the cylindrical portion . A coating device for coating a coating object having a front surface and a back surface opposite to the front surface with a paint,
The object to be coated has an internal space,
A holding portion including a columnar first portion configured to hold the back surface side ;
a nozzle configured to charge the paint and spray the charged paint toward the surface of the workpiece held by the holder;
an electrode configured to apply a voltage of a polarity opposite to the potential to which the paint is charged by the nozzle;
The electrode is disposed on the back surface side by the first portion ,
the electrode has a portion that is disposed inside an outer shape of the object to be coated when the electrode is viewed from the opposite side of the object to be coated in a direction in which the object to be coated and the electrode face each other ,
Further comprising a blow section;
The coating device , wherein the blow unit is configured to blow gas toward the electrode . The coating device according to any one of claims 1 to 6, wherein the electrode is positioned overall inward from an outer shape of the object to be coated when the electrode is viewed from the opposite side of the object to be coated in a direction in which the object to be coated and the electrode face each other . The coating device according to claim 1 , wherein the electrode is fixed to the holding portion. the holding portion includes a second portion to which the first portion is connected,
The coating device according to claim 2 , wherein the first section is connected to the second section while being inclined upward in a direction of gravity. A coating method for coating a coating object including a front surface and a back surface opposite to the front surface with a paint, comprising:
a step of holding the back side of the electrode in a columnar first portion included in a holding portion such that the electrode is positioned inside the outer shape of the object to be coated when the electrode is viewed from the opposite side of the object to be coated in a direction in which the object to be coated and the electrode face each other;
a step of spraying the electrically charged paint by the nozzle toward the surface of the workpiece held by the holding part while a voltage of a polarity opposite to the potential to which the paint is charged is applied to the electrode ;
The object to be coated has an internal space,
the holding portion includes a second portion to which the first portion is connected,
A coating method, wherein the first part is connected to the second part while inclining upward in the direction of gravity .

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