JP3012694B2 - Electrostatic coating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic coating method in which a high voltage is applied directly to a water-based coating to perform electrostatic coating.

[0002]

2. Description of the Related Art Conventionally, as a technique of applying a high voltage to a water-based paint to apply an electrostatic coating to an object to be coated such as an automobile body,
For example, a paint color changing system disclosed in Japanese Patent Application Laid-Open No. 2-2885 is known.

In this prior art, after a water-based paint is once introduced from a water-based paint supply source into an intermediate storage tank (reservoir) via an insulating tube, the insulating tube is washed and dried to be electrically insulated. (Voltage block) is configured so that the current is prevented from leaking to the water-based paint supply source side, the water-based paint is supplied from the intermediate storage tank to the coating gun, and the object to be coated is subjected to electrostatic coating. Is being done.

[0004]

By the way, in the above-mentioned prior art, deionized water is used to cut off the electric current when cleaning the insulating tube body. It is impossible to interrupt the current, and if deionized water remains in a thin film in the insulating tube, a current leaks. For this reason, a high voltage cannot be applied to the water-based paint unless the deionized water used in the cleaning operation is completely dried, and thus it takes a considerable time to form a voltage block, and the paint is applied. There is a disadvantage that the efficiency of the entire operation is not achieved.

The present invention solves this kind of problem. In particular, the drying time of deionized water can be effectively shortened, and the efficiency of the entire coating operation can be easily achieved. It is an object to provide a possible electrostatic coating method.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for supplying a predetermined amount of water from a grounded aqueous paint supply to an intermediate supply through a supply passage having at least a part of an insulating part. Supplying water-based paint, washing at least the insulating portion with warm water that is deionized water , and after the washing, using a dry air having a lower temperature than the deionized water to insulate the insulating portion. Removing the deionized water in the unit and electrically insulating the aqueous paint supply source and the intermediate supply unit from each other; and supplying the aqueous paint from the intermediate supply unit to the coating gun in the insulated state to perform a coating operation. And performing the following.

[0007]

In the above-described electrostatic coating method according to the present invention, after a predetermined amount of aqueous paint is supplied to the intermediate supply section from the grounded aqueous paint supply source via the supply path, at least a part of the supply path is supplied. Is washed with warm water, which is deionized water , and then deionized water in the insulating part is removed by dry air at a lower temperature than deionized water. At that time, Me <br/> deionized water specific conductivity becomes low temperature was low Kunar, an insulating portion and a water-based paint supply and intermediate supply portion in a state the deionized water without Tei completely dry Are electrically insulated. Thereby, the drying operation of the deionized water becomes unnecessary, and the voltage block can be formed only by the removing operation, so that the efficiency of the entire coating operation is improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrostatic coating method according to the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 denotes a coating apparatus for performing the electrostatic coating method according to the present embodiment.
The coating apparatus 10 includes a color change valve mechanism (water-based paint supply source) 12 that is grounded. The color change valve mechanism 12 includes air (A), deionized water (W), and a cleaning liquid (S). A first cleaning valve 14 for controlling the supply and a plurality of paint valves 16a to 16c capable of supplying different water-based paints are provided. The color changing valve mechanism 12 includes at least a part of an electrically insulating pipe (insulating portion) 17 made of resin such as polytetrafluoroethylene (PTFE), and a block valve mechanism 18 including the electrically insulating pipe 17. Supply path 2 where
0 is connected.

The block valve mechanism 18 includes a switching valve 22
a, 22b, and the color change valve mechanism 12, air (A), deionized water (W) by the switching valve 22a on the inlet side.
Cleaning valve 24 for controlling the supply of cleaning liquid (S) and the like
And is connected to the intermediate storage tank (intermediate supply unit) 26 via the supply path 20. This intermediate storage tank 26
A first cylinder chamber 30 for injecting a water-based paint and a cleaning liquid divided through a piston 28 and a second cylinder chamber 32 for supplying air are provided. In the second cylinder chamber 32, an air supply source 34 is provided with a flow control valve. 36, and communicate via an on-off valve 38. The air supply source 34 is connected via a booster 40 to a water-based paint flow controller 42 for adjusting the air pressure, and the flow controller 42 controls the discharge amount of the water-based paint. The switching valve 22b is connected to a waste liquid tank 46 via a discharge path 44.

A coating gun 52 is connected to the first cylinder chamber 30 of the intermediate storage tank 26 via a delivery path 48. The coating gun 52 includes a dump valve 54 and a trigger valve 56, It is connected to voltage application means.

Next, the coating apparatus 10 constructed as described above will be described.
Will be described in relation to the electrostatic coating method according to the present embodiment.

First, an aqueous paint of a predetermined color is pressure-fed from the paint valve 16 a of the color changing valve mechanism 12, filled into the first cylinder chamber 30 of the intermediate storage tank 26 via the supply path 20, and further passed through the delivery path 48. Then, it is filled up to the coating gun 52. During this filling, the trigger valve 56 is closed, while the dump valve 54 is opened, and after filling, the dump valve 54 is closed.

Therefore, the switching valve 22 of the block valve mechanism 18
When the switching operations a and 22b are performed, the block valve mechanism 18 is washed under the driving action of the second washing valve 24, and the washing liquid and deionized water used for this washing are discharged to the discharge path 4
The waste liquid is discharged to the waste liquid tank 46 via the drain tank 4. Then, the block valve mechanism 18 is dried, so that the color changing valve mechanism 12 and the intermediate storage tank 26 are electrically insulated.

Next, a flow control valve 36 is supplied from an air supply source 34.
Driving air is supplied to the second cylinder chamber 32 of the intermediate storage tank 26 via the opening and closing valve 38, and the piston 28
The water-based paint is applied to a work (not shown) while being displaced to the cylinder chamber 30 side and under the action of opening the trigger valve 56 in a state where a high voltage is applied.

In this case, in this embodiment, the electrically insulating conduit 17 provided in the block valve mechanism 18 is washed with deionized water having a specific conductivity smaller than a predetermined specific conductivity through the second washing valve 24. Therefore, there is an effect that the drying operation (removal operation) of the deionized water is performed at once in a short time.

That is, under the conditions that the applied voltage is −60 kV, the inner diameter is 6 mm and the length is 20 cm, and the electrically insulating conduit 17 is used, and the drying is performed by dry air at 20 ° C. (dew point is −20 ° C.) An experiment was performed to measure the time required for the voltage block by changing the specific conductivity of deionized water. At that time, deionized water and dry air were alternately supplied as shown in the pattern of FIG.

As a result, when deionized water having a specific conductivity of 1.0 μs (Siemens) is used, the drying operation is performed for 12 hours.
A voltage block was formed by performing for a second. This was a state where the inside of the electrically insulating conduit 17 was completely dried. On the other hand, when deionized water having a specific conductivity of 0.1 μs is used, the drying operation is performed for 4 seconds, and when deionized water having a specific conductivity of 0.03 μs is used, the drying operation is performed. In 3 seconds, good voltage blocks were formed. Here, the inside of the electrically insulating conduit 17 was not completely dried, but deionized water remained in the form of a thin film. For this reason, it has been demonstrated that the use of deionized water having a small specific conductivity has an effect that a voltage block can be formed in a short drying time.

Further, as shown in FIGS. 3 and 4, the specific conductivity of the deionized water changes depending on the temperature. As the temperature of the deionized water increases, the specific conductivity increases. The drying time becomes longer. For this reason, it is necessary to keep the temperature of the deionized water as low as possible in consideration of insulation properties, but it is desirable to make the temperature relatively high in consideration of cleaning properties. Thus, the use of deionized water consisting of warm water of 35 ° C. or more as the cleaning liquid and the use of dry air at a low temperature, preferably 20 ° C. or less, provide an effect of being excellent in cleanability and insulating properties. As a result, the voltage block can be formed in a short time, and the efficiency of the entire painting operation can be easily improved.

[0020]

According to the electrostatic coating method of the present invention, the following effects can be obtained.

[0021] After a predetermined amount of water-based paint in an intermediate supply unit through the supply path from an aqueous coating material source that is grounded is supplied, the insulating portion provided in at least part of the supply passage, de Lee <br /> After being washed with warm water, which is
Because the said deionized water is removed by A, state where the deionized water from the insulating portion is not completely dry, i.e. said aqueous coating supply and intermediate supply section only in removal work in electrically insulated Become. Accordingly, the operation of forming the voltage block can be performed in a short time, and the efficiency of the entire coating operation can be easily achieved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a coating apparatus that performs an electrostatic coating method according to the present invention.

FIG. 2 is a timing chart of a cleaning and drying pattern in the electrostatic coating method.

FIG. 3 is a diagram showing the relationship between the temperature of deionized water, specific conductivity, and drying time.

FIG. 4 is a diagram showing the relationship between the temperature of deionized water and the specific conductivity.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Coating apparatus 12 ... Color change valve mechanism 17 ... Electrically insulating pipe line 18 ... Block valve mechanism 20 ... Supply path 24 ... Washing valve 26 ... Intermediate storage tank 48 ... Delivery path 52 ... Painting gun

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B05D 1/00-7/26 B05B 5/08

Claims (1)

(57) [Claims] From 1. A water-based paint supply source that is grounded, and the step of supplying a predetermined amount of water-based paint in an intermediate supply unit via a supply path having a at least a portion insulating portion, at least the insulating part, deionized Washing with hot water that is water , after the washing , removing the deionized water in the insulating portion using dry air lower in temperature than the deionized water, and electrically connecting the aqueous paint supply source and the intermediate supply portion with each other. A process of supplying a water-based paint from the intermediate supply unit to the coating gun to perform a painting operation in the insulated state.