JP4911926B2 - Electrostatic coating system and electrostatic coating method - Google Patents

Description

  The present invention relates to a directly charged electrostatic coating system and an electrostatic coating method used for coating an object such as an automobile body while changing the color.

  In general, electrostatic painting is used for painting a body such as an automobile or an object to be coated such as a bumper. The electrostatic coating method is a method in which a high voltage is applied to a water-based paint or an organic solvent-based paint to coat an object to be charged with a charge opposite to that of the paint. As a coating apparatus used for such an electrostatic coating method, a rotary atomizing head type coating apparatus (bell type coating apparatus) is widely used. In recent years, it has been desired for coating apparatuses to reduce the amount of paint and solvent that are discarded during a color change operation that changes the coating color of a body, a bumper, etc., and to be able to cope with many coating colors.

  For example, Patent Document 1 discloses a bell-type electrostatic paint gun to which a voltage is applied, a paint pipe for guiding paint to the paint gun, and a paint color change operation provided in the middle of the paint pipe. A color change valve unit and a piston capable of sliding in a watertight manner inside the paint piping and the manifold of the color change valve unit, and applying pressure to the piston with compressed air, which is an insulating fluid, A coating apparatus is described in which the paint is moved to guide the paint to the paint gun and spray the paint from the paint gun. As a result, all the paint in the paint pipe is pushed out, so that the portion that needs to be cleaned at the time of color change is remarkably reduced.

  Moreover, what was described in patent document 2 is known as a rotary atomizing head type coating apparatus corresponding to the waste paint, the reduction of a solvent, and the increase in coating color, for example. The rotary atomizing electrostatic coating apparatus of Patent Document 2 has a configuration in which a cartridge including a paint nozzle and a paint tank filled with a paint for each color is replaced and attached to a housing provided in the coating machine. In such a rotary atomizing electrostatic coating apparatus, a color cartridge to be used for coating is selected from the cartridges of each color, and this cartridge is attached to the cartridge mounting portion of the housing. Then, by appropriately supplying air (air), which is an insulating fluid, to the extruded air storage chamber of the cartridge, the paint in the paint storage chamber of the cartridge flows out from the feed tube toward the rotary atomizing head to which a voltage is applied, The paint is sprayed from the rotary atomizing head toward the object to be coated. In addition, when changing colors, it is not necessary to wash away the remaining paint in the paint supply path including the paint nozzle and wash it with a cleaning solvent such as thinner, simply by replacing the cartridge with another color cartridge. Can be replaced.

  Patent Document 3 discloses a cartridge type in which an organic solvent such as thinner, which is an insulating liquid, is used as a liquid for extruding paint to displace a piston and supply the paint toward a rotary atomizing head to which a voltage is applied. A rotary atomizing head type coating device is described.

JP 2001-327897 A JP-A-8-229446 JP 11-262699 A

  However, in the coating apparatus described in Patent Documents 1 and 2, extruded air is used to displace the piston. However, since air is an insulative fluid but a compressive fluid, it is supplied to the extruded air storage chamber. Sometimes volume fluctuations are likely to occur. For this reason, the paint cannot be supplied stably and accurately during painting. Therefore, in order to accurately supply the paint at the time of painting, it is necessary to provide a separate flow meter, various control valves, etc., and there is a problem that the coating apparatus is increased in size and costs are increased.

  In order to solve this problem, Patent Document 3 proposes to use an organic solvent, which is an insulative and incompressible liquid, as the extrusion liquid instead of the extrusion air. However, when an organic solvent such as thinner is used as an extrusion liquid as in Patent Document 3, the organic solvent volatilizes from the joint between the cartridge and the coating apparatus main body into the atmosphere, causing environmental pollution. It becomes. Also, when the piston of the cartridge tank slides, the paint in the paint storage chamber gradually mixes into the thinner storage chamber, and the electrical resistance value of the insulating organic solvent, which is the extrusion liquid, decreases, and the insulation function Therefore, it was necessary to maintain the insulating function by frequently replacing the insulating organic solvent. However, the organic solvent is relatively expensive and causes an increase in cost. In addition, disposal of organic solvents is a factor that causes environmental pollution.

The present invention is a direct charging electrostatic coating system that sprays paint by applying a high voltage to the paint supplied from the paint tank to the atomizing head of the coating apparatus, comprising a pure water supply device and the pure water An extrusion liquid supply means for controlling the amount of pure water supplied by the supply device and supplying it as an extrusion liquid, a coating material tank defined by an easily-moving material and an extrusion liquid chamber, and a mist And a coating device that atomizes after applying a high voltage to the paint, and the electrical resistance value of the pure water is 1 MΩ · cm or more, and the coating device supplies pure water. An amount of current flowing in the pure water in the pure water supply path is 30 μA or less, and the pure water supply path is composed mainly of a resin that does not substantially contain a plasticizer, When pure water is supplied to the extrusion liquid chamber as an extrusion liquid, The printing material is pushed and the paint contained in the paint chamber is supplied to the coating apparatus.

The present invention also relates to a direct charging electrostatic coating system that sprays paint by applying a high voltage to the paint supplied from the paint tank to the atomizing head of the coating apparatus, the water supply device, and the water An extrusion liquid supply means for controlling the amount of water supplied by the supply apparatus and supplying it as an extrusion liquid, a pure water production apparatus for purifying the extrusion liquid, and a composition material that easily moves. A paint tank having a paint chamber and an extrusion liquid chamber; and a coating device having an atomizing head and atomizing after applying a high voltage to the paint. The electric resistance value of the pure water is 1 MΩ · cm or more, the coating apparatus has a pure water supply path, an amount of current flowing in the pure water in the pure water supply path is 30 μA or less, and the pure water supply path substantially contains a plasticizer. It is composed of a resin that does not contain as a main component, Is supplied to the extrusion liquid chamber, the paint is pushed and the paint contained in the paint chamber is supplied to the coating apparatus.

  In this way, the present invention relates to direct charging electrostatic coating in which a high voltage is applied to the paint supplied from the paint tank to the atomizing head of the coating apparatus to spray the paint, and the paint in the paint tank is Pure water having a high insulating property is used as an extrusion liquid for control for quantitatively supplying toward the atomizing head.

  In the present invention, in the direct charging electrostatic coating in which a high voltage is applied to the paint supplied from the paint tank to the atomizing head of the coating apparatus to spray the paint, the paint in the paint tank is directed toward the atomizing head. By using pure water having a high electric resistance value as a control extrusion liquid for quantitative supply, it is possible to stably coat with a simple configuration.

  Embodiments of the present invention will be described below.

  An outline of an example of a coating system according to the present embodiment is shown in FIG. 1 and the configuration thereof will be described. The painting system 1 includes a painting robot 10, a painting gun 12, a pure water supply device 13, pipes 15 a and 15 b, and a discharge amount control device 16 that is an extrusion liquid supply means.

  More specifically, in the coating system 1 of FIG. 1, the pure water supply device 13 outside the painting booth is connected to the discharge amount control device 16 inside the painting booth by a pipe 15a, and the discharge amount control device 16 is connected to the piping. The paint gun 12 attached to the painting robot 10 is connected by 15b. The painting gun 12 is held on the wrist portion 26 of the painting robot 10 at the site of the painting gun body 32.

  In the present embodiment, the pure water supply device 13 may be divided into a water supply device 14 and a pure water production device 18 to have the configuration shown in FIG. In FIG. 2, a painting system 3 includes a painting robot 10, a painting gun 12, a water supply device 14, pipes 15a, 15b, and 15c, a discharge amount control device 16 that is an extrusion liquid supply means, and a pure water production device. 18.

  More specifically, in the coating system 3 of FIG. 2, the water supply device 14 outside the painting booth is connected to the discharge amount control device 16 inside the painting booth by a pipe 15a, and the discharge amount control device 16 is connected to the pipe 15b. Is connected to the pure water production apparatus 18, and the pure water production apparatus 18 is connected to the painting gun 12 attached to the painting robot 10 by a pipe 15 c.

  The pure water supply device 13 in FIG. 1 is a device that supplies pure water used as a liquid for extruding paint in the coating gun 12. As a method for producing pure water in the pure water supply device 13, a microfiltration membrane method, an ultrafiltration membrane method, a reverse osmosis membrane method, an ion exchange method using an ion exchange resin, an ion exchange membrane, an ion exchange membrane, Examples thereof include an ion regeneration resin and the like, and an electric regeneration method (EDI) in which the ion exchange resin is continuously regenerated by using a direct current, a distillation method, and the like, and combinations thereof.

  When the pure water supply device is divided into the water supply device 14 and the pure water production device 18 as shown in FIG. 2, the pure water supply device 14 supplies water to be used as a paint extrusion liquid in the coating gun 12. It is. The water supplied from the water supply device 14 may be any of tap water, industrial water, pure water, ultrapure water, etc., but in order to reduce the load in pure water by the pure water production device 18, Pure water and ultrapure water having a high electric resistance value are preferred. As a method for producing pure water in the water supply device 14, a microfiltration membrane method, an ultrafiltration membrane method, a reverse osmosis membrane method, an ion exchange method using an ion exchange resin, an ion exchange membrane, an ion exchange membrane, and an ion Examples include an electric regeneration system (EDI), a distillation system, and the like, which are composed of an exchange resin and continuously regenerate the ion exchange resin using a direct current.

  The pure water supply device 13 or the water supply device 14 may be equipped for the coating system according to the present embodiment. For example, existing equipment such as a pure water supply device and a water supply device in a painting factory such as a body of an automobile. The cost can be reduced by using existing equipment.

  The pure water production apparatus 18 of FIG. 2 is installed to maintain and improve the electrical resistance value of the pure water supplied to the coating gun 12. Installed downstream. As a method for producing pure water in the pure water production apparatus 18, a microfiltration membrane method, an ultrafiltration membrane method, a reverse osmosis membrane method, an ion exchange method using an ion exchange resin, an ion exchange membrane, an ion exchange membrane, Examples thereof include an ion regeneration resin and the like, and an electric regeneration method (EDI), a distillation method, and the like that continuously regenerate the ion exchange resin using a direct current, and combinations thereof. The ion exchange method is preferable from the viewpoints of being inexpensive, simple and easy to maintain, and more preferably a cartridge type ion exchange method in which the exchange of the ion exchange resin is easy. Examples of the ion exchange resin include known anion exchange resins, cation exchange resins, mixed beds thereof, and the like, and combinations thereof may be used.

  The pure water used as a liquid for extruding the paint must have a high electric resistance value because the present coating systems 1 and 3 are used for electrostatic coating, and preferably has an electric resistance value of 1 MΩ · cm or more, More preferably, the electric resistance value is 3 MΩ · cm or more, and further preferably 5 MΩ · cm or more. If the electrical resistance value of pure water is less than 1 MΩ · cm, high voltage may leak from the high voltage portion of the coating gun 12 through the extrusion liquid.

  Since pure water has a strong tendency to react with many substances, when supplying pure water to the coating gun 12, it is necessary to maintain the state of pure water by shortening the supply path as much as possible. When the pure water supply device 13 is configured integrally as shown in FIG. 1, there may be restrictions on the position where the device is installed, but it is divided into a water supply device 14 and a pure water production device 18 as shown in FIG. 2. In this case, the pure water production apparatus 18 can be installed at a position close to the coating gun 12. For this reason, it becomes possible to supply pure water to the coating gun 12 while maintaining high purity. Therefore, the structure divided into the water supply apparatus 14 and the pure water manufacturing apparatus 18 as shown in FIG. 2 is preferable. In order to maintain a high resistance value of pure water, the length of the pipes 15a and 15b connecting the pure water supply device 13 and the coating gun 12 in FIG. 1 or the pure water production device 18 and the coating gun 12 in FIG. The length of the pipe 15c connecting the two is preferably as short as possible. Moreover, it is preferable to always monitor the electrical resistance value of pure water supplied from the pure water supply device 13 or the pure water production device 18 using a conductivity meter or the like.

  The pure water supply capability of the pure water supply device 13 or the pure water production device 18 may be ensured at least to the extent that the paint discharge amount of one paint gun is exceeded. For example, when the paint discharge rate per coating gun is 100 cc / min (maximum), the pure water supply device 13 or the pure water production device 18 may have a pure water supply capacity exceeding 100 cc / min. . The water supply device 14 may supply water to the plurality of pure water producing devices 18, and the supply amount may be determined according to the number of coating guns 12 used.

  Resin or the like can be used as the material constituting the pipes 15a, 15b, and 15c, but in order to maintain the electrical resistance value of pure water supplied to the coating gun 12, in particular, as the material constituting the pipe 15c, It is preferable to use a resin that does not substantially contain a plasticizer. Examples of such a resin include fluorine-based resins such as polytetrafluoroethylene (PTFE) resin having flexibility even when substantially containing no plasticizer, polyethylene resin, and the like, and PTFE resin is more preferable.

  Moreover, although resin etc. can be used as a material which comprises the piping 15a, 15b, 15c, in order to maintain the electrical resistance value of the pure water supplied to the coating gun 12, especially about the piping 15c, piping The inner surface may be covered with a fluorine resin or the like.

  The discharge amount control device 16 is a device that controls the amount of pure water supplied to the coating gun 12, and the method is not particularly limited, but a pump method with high quantitative accuracy such as a positive displacement gear pump can be used.

  The painting robot 10 is a painting robot that serves as a painting work machine. The painting robot 10 is a base 20, a vertical arm 22 that is rotatably and swingably provided on the base 20, and a swing at the tip of the vertical arm 22. The horizontal arm 24 is provided so as to be movable, and a wrist portion 26 is provided at the tip of the horizontal arm 24. The painting gun 12 is attached to the wrist portion 26 of the painting robot 10.

  For example, as shown in FIG. 3, the coating gun 12 is a cartridge type composed of two parts that are separable from each other. One of the two parts is a coating gun body 32 which is a coating device provided with a bell head (atomizing head) 28 and an air motor 30, and the other is a coating nozzle 34 shown in FIG. The paint tank unit 38 includes a paint tank 36. The paint nozzle 34 may be provided in the paint gun main body 32. The painting gun 12 may be a painting device in which the painting gun main body 32, the paint nozzle 34, and the paint tank 36 are integrated. Here, FIG. 3 shows an example (corresponding to the coating system 3 in FIG. 2) in which the water supply device 14, the discharge amount control device 16, and the pure water production device 18 are connected to the coating gun 12. The water supply device 13 and the discharge amount control device 16 may be connected to the coating gun 12 (corresponding to the coating system 1 in FIG. 1).

  As shown in FIGS. 3 and 4, the paint tank unit 38 is configured as a cartridge type and is detachably attached to the paint gun main body 32. A paint tank unit 38 is prepared for each paint color, and the paint tank unit 38 is replaced when changing colors. The paint tank unit 38 includes a paint nozzle 34 and a paint tank 36, and the paint tank 36 is provided with a paint quantitative supply means 40 and a cartridge trigger valve 47. The paint nozzle 34 is provided in the paint tank unit 38 so that the paint nozzle shaft core is positioned on the extension of the shaft core of the bell head 28 when the paint tank unit 38 is attached to the paint gun body 32.

  The paint constant supply means 40 of the paint tank 36 includes a paint chamber 42 having a predetermined volume for containing paint, a piston 44, and an extrusion liquid chamber 46. A chamber 42 and an extrusion liquid chamber 46 are defined. The piston 44 is pushed by the extruding liquid supplied to the extruding liquid chamber 46 and the paint in the paint chamber 42 is pushed out to the paint nozzle 34 via the cartridge trigger valve 47.

  The coating gun main body 32 is provided with a pure water supply path 48a and a valve 50, and the paint tank unit 38 is provided with a pure water supply path 48b. The pure water supply port of the pure water production apparatus 18 and the pure water supply path 48a are connected via a pipe 15c, and further connected to the pure water supply path 48b of the paint tank unit 38 via a valve 50 to supply pure water. The path 48 b is connected to the extrusion liquid chamber 46 of the paint quantitative supply means 40. The cartridge trigger valve 47 and the valve 50 are opened, and the water discharged in a desired amount by the discharge amount control device 16 is converted into pure water by the pure water production device 18, and the pure water is converted into the pipe 15 c and the pure water. When the piston 44 is supplied to the extrusion liquid chamber 46 through the supply passages 48a and 48b and is moved in the direction in which the paint chamber 42 is contracted, the paint is pushed out from the paint chamber 42 to the paint nozzle 34 and supplied to the bell head 28 in a fixed amount. .

  The coating gun main body 32 incorporates an air motor 30, and a bell head 28 is attached to the tip of the air motor 30. In the bell head 28 rotated at high speed by the air motor 30, a high voltage is applied to the paint supplied from the paint tank unit 38 via the paint nozzle 34, and the paint atomized by centrifugal atomization by the bell head 28 is charged to a high voltage. Sprayed as charged paint particles. The coating pattern of the atomized paint is controlled by the shaping air discharged from the shaping air discharge portion 51 provided around the bell head 28.

  The bell head 28 is composed mainly of an electrostatically semiconductive material (resistance is about 10 to 1000 MΩ) in order to prevent the occurrence of electrostatic spark even during malfunction. The outer peripheral portion 52 of the air motor 30 of the coating gun main body 32 is mainly composed of an electrically insulating resin such as polyacetal. A high voltage generator 54 is built in the outer peripheral portion 52 of the insulating resin, and a high voltage of about 30 to 100 KV is applied to the air motor 30 and the bell head 28 via the high voltage cable 56. Electric power is sent to the high voltage generator 54 via a low voltage cable 60 from a controller 58 having a low voltage power supply (0 to 24 V).

  A high voltage supplied from the high voltage generator 54 is supplied to the paint through the air motor 30 and the bell head 28. Since the paint in the paint chamber 42 is also charged to a high voltage via the paint in the paint nozzle 34, insulation can be ensured by using pure water as the extrusion liquid as in this embodiment.

  The air motor 30 includes a rotating shaft connected to the bell head 28, a radial air bearing portion that rotatably supports the rotating shaft, a turbine portion that rotationally drives the rotating shaft, and the like. The rotation controller 62 includes a rotation control unit and an electropneumatic converter. In the electropneumatic converter, the air supplied from the pressurized air supply source is set to an air pressure corresponding to the current value based on the current value corresponding to the desired rotation number instructed by the rotation control unit, and the air Is supplied to the air motor 30 via the air tube 66. Further, the air motor 30 is provided with a rotation pulse generation mechanism by light reflection or the like in its rotating body, and the rotation pulse is fed back to the rotation control unit via the cable 64. The rotation control unit converts the rotation pulse into a current value, and controls to maintain a desired number of rotations by comparing with the desired current value.

  The paint is sucked into the paint chamber 42 by removing the paint tank unit 38 from the paint gun body 32. The paint tank unit 38 removed from the paint gun body 32 is placed on a placement table of a paint filling device (not shown), and the paint tank units having different paint colors are filled with the paint of each color. Is done.

  The paint used in the present embodiment can be used without particular limitation as long as it is a paint having a low electrical resistance value, such as a water-based paint or an organic solvent-based paint, but a water-based paint is particularly preferred.

  Further, in order to prevent a decrease in electrical resistance value due to the dissolution of carbon dioxide in the air into the pure water, the pipe 15c between the pure water production apparatus 18 and the extrusion liquid chamber 46 of the paint tank unit 38, the pure water The water supply passages 48a and 48b are preferably sealed. Similarly, the pipes 15a and 15b and the pure water supply paths 48a and 48b between the pure water supply device 13 and the extrusion liquid chamber 46 of the paint tank unit 38 are preferably sealed.

  In order to prevent the high voltage portion of the coating gun 12, that is, the high voltage from the bell head 28 from leaking through the extrusion liquid, the ground leakage is caused from the high voltage portion of the coating gun 12 to the ground side through the pure water supply paths 48 b and 48 a. The amount of current, that is, the amount of current flowing in the pure water in the pure water supply channels 48a and 48b is preferably 30 μA or less, and more preferably 10 μA or less. In order to reduce the current flowing in the pure water in the pure water supply paths 48a and 48b, it is preferable to take sufficient length of the pure water supply paths 48a and 48b.

For example, when the electrical resistance value ρ of pure water is 5 MΩ · cm and the applied voltage to the bell head 28 is −90 kV at the maximum, the pure water supply path has an inner diameter of 2 mm (0.2 cm) and a length L = 5 m (500 cm). If you use the hose
Cross-sectional area in the hose S = (0.1 cm) ² × π = 0.0314 cm ²
Resistance value R = ρL / S = (5 × 10 ⁶ ) × 500 / 0.0314 = 79.618 GΩ
The theoretical current value flowing in the hose is 90 kV / 79.618 GΩ = 1.13 μA.
And 30 μA or less. Similarly, when the electrical resistance value ρ of pure water is 1 MΩ · cm and the applied voltage to the bell head 28 is −90 kV at the maximum,
Resistance value R = ρL / S = (1 × 10 ⁶ ) × 500 / 0.0314 = 15.924 GΩ
The theoretical current value flowing in the hose is 90 kV / 15.924 GΩ = 5.65 μA.
And 30 μA or less.

  Resin or the like can be used as the material constituting the pure water supply paths 48a and 48b inside the coating gun 12, but it is substantially the same as the pipes 15a, 15b and 15c in order to maintain the electrical resistance value of pure water. It is preferable to use a resin that does not contain a plasticizer, and a resin that has flexibility without containing a plasticizer substantially, such as a fluororesin such as polytetrafluoroethylene (PTFE) resin, a polyethylene resin, etc. It is preferable to do. And in order to ensure the length of the pure water supply channels 48a and 48b sufficiently as described above, it is preferable that a tube made of a material such as PTFE is wound in a coil shape, for example. As shown in FIG. 5, the pure water supply path 48a is coiled and housed inside the coating gun body 32, so that the length of the pure water supply path 48a is longer than when the pure water supply path is linear. It can be stored compactly inside the coating gun 12 while ensuring sufficient thickness.

  Further, in the coating gun 12, a cartridge fixing suction circuit may be provided so that the paint tank unit 38 does not fall off from the coating gun main body 32. That is, a negative pressure space defined between the cartridge mounting portion of the coating gun 12 and the paint tank unit 38 in FIG. 3 is provided, and an air suction passage that opens to the negative pressure space is provided in the cartridge mounting portion of the coating gun 12. 70 is provided, and the paint tank unit 38 can be fixed to the paint gun 12 by sucking the air in the negative pressure space via the air suction passage 70 by the eductor 68. Further, when removing the paint tank unit 38, by supplying air into the negative pressure space, the negative pressure state can be released and the paint tank unit 38 can be removed from the cartridge mounting portion of the paint gun 12.

  Next, the operation of the electrostatic coating method and the electrostatic coating system 3 according to this embodiment will be described with reference to FIGS. The supply amount of water supplied by the water supply device 14 is controlled by the discharge amount control device 16 according to the amount of paint discharged from the coating gun 12 through the pipe 15a. The water adjusted to the predetermined supply amount passes through the pipe 15b and is purified by the ion exchange resin or the like in the pure water production apparatus 18 to obtain a high electric resistance value. The pure water having the high electrical resistance value is supplied in a fixed amount toward the painting gun 12 of the painting robot 10 through the pipe 15c and the pure water supply paths 48a and 48b. When this pure water flows into the extrusion liquid chamber 46 of the coating material quantitative supply means 40, the piston 44 is pushed, and the coating material stored in the coating material chamber 42 is supplied toward the bell head 28 and atomized.

  The pure water used for controlling the discharge amount is allowed to flow in one direction so that fresh pure water maintaining a high electrical resistance value is always supplied to the coating gun 12. For this reason, even if a very small amount of metal ions or the like may be mixed in the pure water coming out of the discharge amount control device 16 during the painting operation, the pure water production device 18 removes the contaminants such as metal ions. The electric resistance value of pure water is maintained.

  The pure water that has pushed out the paint remains in the extrusion liquid chamber 46 of the paint tank unit 38, and is removed from the paint gun 12 together with the paint tank unit 38 after the painting is finished, and returned to the paint filling device (not shown). . The pure water remaining in the extrusion liquid chamber 46 is collected when the paint is refilled. The recovered pure water may be returned to the water supply device 14 for reuse, or returned to the painting booth and used as circulating water for booth washing, or may be discarded as it is. In order to improve the life of the pure water production apparatus 18, it is preferable that the recovered pure water is returned to the water supply apparatus 14 and not reused. Thereafter, another paint tank unit 38 is attached to the painting gun 12, and water is supplied by the water supply device 14 in accordance with the painting operation.

  In the coating system according to this embodiment, pure water, which is an insulating liquid, is used as the extrusion liquid for the coating material, so that the coating material can be supplied more accurately at the time of coating than when conventional air is used. In addition, when an organic solvent such as thinner is used as an extrusion liquid as in the past, when the cartridge and the coating machine main body are attached and detached, the organic solvent volatilizes from the coupling portion into the atmosphere, causing environmental pollution. However, if pure water is used as the extrusion liquid as in this embodiment, there is almost no possibility of environmental pollution. Also, when the piston of the paint tank unit slides, the paint in the paint chamber gradually gets mixed into the thinner storage chamber, and the electrical resistance value of the extruded liquid decreases. However, since pure water is cheaper than organic solvents, the cost can be reduced. In addition, in the case of water, the possibility of causing environmental pollution is low compared to the disposal of organic solvents.

  Further, in the coating system according to the present embodiment, the pure water supply path of the coating gun is made of, for example, a coiled tube made of a material such as PTFE, so that the length of the pure water supply path is sufficiently ensured from the bell head. Since the amount of current leaking to the ground side through the pure water supply path can be further reduced, and the load on the high voltage generator can be reduced, the life of the high voltage generator can be extended.

  Further, in the coating system according to the present embodiment, since it is possible to adopt a simple configuration in which a pure water production apparatus is simply installed in the supply path for the extrusion liquid, it is not necessary to add a significant improvement to the conventional coating system. Furthermore, when this coating system is used in a painting factory such as an automobile body equipped with a device that uses a large amount of pure water, it can be easily used by simply connecting the pure water supply pipe of the painting factory to the discharge amount control device. Therefore, it is not necessary to newly equip a pure water production apparatus. The painting system can be sufficiently operated with pure water that can be manufactured and managed in a painting factory such as an automobile body.

  Conventionally, when a water-based paint is used as a paint and an organic solvent is used as a liquid for extruding the paint, the organic solvent is mixed in the water-based paint and a coating defect due to coating flaws has occurred. In such a coating system, pure water is used, so that occurrence of such coating defects can be prevented.

  In addition, in the coating system according to the present embodiment, when a water-based paint is used, it is not necessary to use the anti-sparking safety function of the electrostatic high-voltage generator, the cost can be reduced, and the painting line can be stopped. Generation can be reduced.

  The coating system which concerns on this embodiment can be used suitably for the electrostatic coating which paints by applying a high voltage directly to what is called a conductive coating material which has a low electrical resistance value, for example. Moreover, the coating system which concerns on this embodiment is applicable also to an air atomization type coating device etc. besides a rotary atomizing head type coating device (bell type coating device).

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

Example 1
The automobile body was painted using the painting system 3 shown in FIG. 2 and the painting gun 12 shown in FIGS. 3 and 4. A water-based paint was used as the paint. The water supply device 14 used was a water supply device in an automobile body painting factory, and the electric resistance value of the supplied water was 1 MΩ · cm. The amount of pure water supplied by the water supply device 14 was 400 L / hr. As the pipes 15a, 15b, 15c, tubes made of polytetrafluoroethylene (PTFE) resin (pipes 15a, 15b: inner diameter 8 mm, pipe 15c: inner diameter 4 mm) were used. The discharge amount control device 16 used a gear pump system. As the pure water production apparatus 18, an ion exchange system apparatus (G-5C type ion exchange resin system manufactured by Organo Corporation) was used. The electric resistance value of pure water discharged from the pure water production apparatus 18 was maintained at 1 MΩ · cm to 5 MΩ · cm. A piston method was used as an extrusion method for the coating gun 12, and a voltage applied to the bell head 28 was set to -90 kV. Tubes made of polytetrafluoroethylene (PTFE) resin (inner diameter 2 mm × length 5 m) are used for the pure water supply paths 48 a and 48 b connecting the high voltage portion (bell head 28) and the ground portion inside the coating gun 12. The pure water supply path 48a was coiled as shown in FIG. The amount of pure water that can be supplied into the paint constant quantity supply means 40 of one paint tank unit 38 was 500 cc. In order to prevent a decrease in electrical resistance value due to the dissolution of carbon dioxide in the air into pure water, the pure water production apparatus 18 and later, that is, the coating gun 12, the pure water production apparatus 18, and the pure water production apparatus 18 and coating are applied. The pipe 15 connecting the gun 12 has a sealed structure.

(Comparative Example 1)
The automobile body was painted in the same manner as in Example 1 except that the water supply device 14 and the pure water production device 18 were not used, and thinner was used as the paint extrusion liquid.

  When the automobile body was painted using the coating system of Example 1, high voltage leakage current was lower than that of Comparative Example 1 because pure water was used as the extrusion liquid. Moreover, since pure water was used as the extrusion liquid, the maintenance cost was reduced as compared with the case where an organic solvent was used as in Comparative Example 1. Further, in the case of Example 1, even if the extrusion liquid in the extrusion liquid chamber enters the coating chamber and is mixed into the coating material to some extent, the occurrence of coating flaws that cause the coating failure of the coating surface of the object to be coated occurs. There wasn't.

It is a figure which shows the outline of an example of the coating system which concerns on embodiment of this invention. It is a figure which shows the outline of the other example of the coating system which concerns on embodiment of this invention. It is a figure which shows the outline of an example of the coating gun in the coating system which concerns on embodiment of this invention. It is a figure which shows the outline of an example of the paint tank unit of the coating gun in the coating system which concerns on embodiment of this invention. It is a figure which shows the outline of an example of the pure water supply path of the coating gun in the coating system which concerns on embodiment of this invention.

Explanation of symbols

  1,3 painting system, 10 painting robot, 12 painting gun, 13 pure water supply device, 14 water supply device, 15a, 15b, 15c piping, 16 discharge amount control device, 18 pure water production device, 20 base, 22 Vertical arm, 24 Horizontal arm, 26 Wrist, 28 Bell head, 30 Air motor, 32 Paint gun body, 34 Paint nozzle, 36 Paint tank, 38 Paint tank unit, 40 Paint metering means, 42 Paint chamber, 44 Piston, 46 Extrusion Liquid chamber, 47 Cartridge trigger valve, 48a, 48b Pure water supply path, 50 valve, 51 Shaping air discharge part, 52 Outer part, 54 High voltage generator, 56 High voltage cable, 58 Low voltage power supply, 60 Low voltage cable, 62 Rotation controller, 64 cable, 66 Air tube, 68 Eductor, 70 Air suction passage.

Claims (3)

A directly charged electrostatic coating system that sprays paint by applying a high voltage to the paint supplied from the paint tank to the atomizing head of the coating device,
A pure water supply device;
Extrusion liquid supply means for controlling the amount of pure water supplied by the pure water supply apparatus and supplying it as an extrusion liquid,
A paint tank having a paint chamber and an extrusion liquid chamber defined by an easily pushable composition material;
A coating device that has an atomizing head and that atomizes after applying a high voltage to the paint;
Have
The electric resistance value of the pure water is 1 MΩ · cm or more,
The coating apparatus has a pure water supply path, and an amount of current flowing in the pure water in the pure water supply path is 30 μA or less,
The pure water supply path is composed mainly of a resin that does not substantially contain a plasticizer,
The pure water is supplied as an extruding liquid to the extruding liquid chamber, whereby the composition material is pushed and the coating material stored in the coating chamber is supplied to the coating apparatus. system. A directly charged electrostatic coating system that sprays paint by applying a high voltage to the paint supplied from the paint tank to the atomizing head of the coating device,
A water supply device;
An extrusion liquid supply means for controlling the amount of water supplied by the water supply device and supplying it as an extrusion liquid;
A pure water production device for purifying the extrusion liquid;
A paint tank having a paint chamber and an extrusion liquid chamber defined by an easily pushable composition material;
A coating device that has an atomizing head and that atomizes after applying a high voltage to the paint;
Have
The electric resistance value of the pure water is 1 MΩ · cm or more,
The coating apparatus has a pure water supply path, and an amount of current flowing in the pure water in the pure water supply path is 30 μA or less,
The pure water supply path is composed mainly of a resin that does not substantially contain a plasticizer,
The dehydrated extrusion liquid is supplied to the extrusion liquid chamber, whereby the composition material is pushed and the paint contained in the paint chamber is supplied to the coating apparatus. Electropainting system. A direct charging electrostatic coating method in which a high voltage is applied to the paint supplied from the paint tank to the atomizing head of the coating apparatus to spray the paint,
An electrostatic coating method using the electrostatic coating system according to claim 1 .

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