Electrostatic coating device and system

Abstract

PROBLEM TO BE SOLVED: To evolve a spark discharge preventing effect of an electrostatic coating device. SOLUTION: One coating robot has an arm equipped with a plurality of electrostatic coating devices 100 close to each other and the plurality of the electrostatic coating devices 100 is connected in parallel with each other to one high-voltage generator 102. A hollow rotary shaft 108 driven by an air motor 104 is disposed with nine plate-shaped resistors 120 arranged circumferentially at intervals. The nine plate-shaped resistors 120 are connected in series and a high voltage is applied via the resistors 120 to a rotary atomization head 110. The rotary atomization head 110 is made of a semiconductive resin.

Claims

1. An electrostatic coating system having an electrostatic coating device configured to charge coating particles by applying to a discharge electrode a voltage generated by a voltage generator controlled by a controller, the electrostatic coating system comprising: a first resistance; a second resistance; and an air motor made of a conductive material between the first resistance and the second resistance, the first and second resistances and the air motor making up a voltage application path between the voltage generator and the discharge electrode; a rotary shaft configured to transmit a rotating force of the air motor, wherein the rotary shaft is made of an electrically insulating materials, and wherein the second resistance couples directly to the rotary shaft; wherein the first resistance and the second resistance are connected in series; wherein the first resistance is between the voltage generator and the second resistance along the voltage application path; wherein the second resistance is between the discharge electrode and the first resistance along the voltage application path; and wherein a resistance value of the second resistance is larger than a resistance value of the first resistance.

2. The electrostatic coating system of claim 1, wherein the electrostatic coating device is a rotary atomization type electrostatic coating device, and wherein the discharge electrode is a rotary atomization head of the rotary atomization type electrostatic coating device.

3. The electrostatic coating system of claim 2, wherein the rotary shaft is configured to transmit the rotating force of the air motor to the rotary atomization head.

4. The electrostatic coating system of claim 3, wherein the second resistance is made up of a plurality of resistors connected in series to each other, and wherein the plurality of resistors is arranged in a circumferential direction of the rotary shaft at regular intervals.

5. The electrostatic coating system of claim 4, wherein each of the plurality of resistors is plate-shaped, wherein each of the plurality of plate-shaped resistors is fit into a groove formed on an outer circumferential surface of the rotary shaft, and wherein each of the plurality of plate-shaped resistors is disposed on the rotary shaft in a standing state from the outer circumferential surface of the rotary shaft.

6. The electrostatic coating system of claim 5, wherein the rotary atomization head is made of a semiconductive material.

7. The electrostatic coating system of claim 6, wherein the rotary shaft is made up of a hollow rotary shaft made of the electrically insulating material, wherein a feed tube is disposed inside the hollow rotary shaft, and wherein a coating material is supplied through the feed tube to the rotary atomization head.

8. The electrostatic coating system of claim 1, wherein the voltage generator is incorporated in the electrostatic coating device.

9. The electrostatic coating system of claim 1, wherein the voltage generator is disposed outside the electrostatic coating device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a diagram for explaining an example according to a principle of the present invention.

(2) FIG. 2 shows a diagram for explaining another example according to the principle of the present invention.

(3) FIG. 3 shows a diagram for exemplarily explaining a specific example of a second high resistance shown in FIGS. 1 and 2.

(4) FIG. 4 shows a diagram for explaining an example of a typical method of use of an electrostatic coating device according to the present invention.

(5) FIG. 5 shows a diagram of a cross section of a front end portion of a rotary atomization type electrostatic coating device of an embodiment according to the present invention.

(6) FIG. 6 shows a side view for explaining a main portion of a hollow rotary shaft included in the rotary atomization type electrostatic coating device of the example.

(7) FIG. 7 shows a perspective view for explaining the main portion of the hollow rotary shaft included in the rotary atomization type electrostatic coating device of the embodiment as shown in FIG. 6.

(8) FIG. 8 shows a perspective view for explaining the main portion of the hollow rotary shaft included in the rotary atomization type electrostatic coating device of the embodiment viewed from the air motor side.

(9) FIG. 9 shows a diagram of Japanese Laid-Open Patent Publication No. 2000-117155 corresponding to FIG. 2.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

(10) FIG. 5 shows a rotary atomization type electrostatic coating device 100 of an embodiment according to the present invention. The electrostatic coating device 100 is a coating device of the cascade-less type (FIG. 2) described above. In FIG. 5, reference numeral 102 denotes a cascade. The one cascade (high-voltage generator) 102 is incorporated in a coating robot, for example. The one coating robot has an arm equipped with the multiple electrostatic coating devices 100 close to each other, and the multiple electrostatic coating devices 100 are connected in parallel with each other to the one cascade (high-voltage generator) 102.

(11) The rotary atomization type electrostatic coating device 100 is controlled by the high-voltage controller 2 as described with reference to FIG. 4 and is secured in safety by the safety circuit 4 as described above with reference to FIGS. 1, 2, and 4.

(12) As described above with reference to FIG. 4, when multiple second electrostatic coating devices of the cascade-less type are adjacently arranged, the safety circuit 4 uses the current limit (CL) function as a backup and mainly provides the constant current control CB (current buffer) function. As described above, constant current control function is a function of reducing the high voltage output by the cascade 102 to keep the high-voltage current i.sub.1 constant when the high-voltage current i.sub.1 equal to or greater than a predetermined current is about to flow.

(13) Preferably, the first high resistance 10 (FIG. 2) described above is incorporated in the cascade 102. The high voltage generated by the one cascade 102 is supplied to the multiple electrostatic coating devices 100. The first resistance value R1 of the first high resistance 10 (FIG. 2) is typically 80 M, and the first resistance value R1 of the first high resistance 10 (FIG. 2) of the currently available cascade 102 is 60 to 120 M, preferably 80 to 100 M.

(14) Reference numeral 104 denotes an air motor. The air motor 104 is made of a conductive metal as in the conventional case. The high voltage generated by the cascade 102 is supplied via a high-voltage conductor 106 to the air motor 104. Reference numeral 108 denotes a hollow rotary shaft. The output of the air motor 104 is transmitted via the hollow rotary shaft 108 to the rotary atomization head 110.

(15) The rotary atomization head 110 is smaller than conventional ones. The diameter of the rotary atomization head 110 is, for example, 30 mm, and may be 50 mm or less, preferably 30 to 40 mm. A feed tube 112 is disposed inside the hollow rotary shaft 108 and a liquid coating material is supplied through the feed tube 112 to the center portion of the rotary atomization head 110.

(16) The rotary atomization head 110 is made of a semiconductive resin. A shaping air ring 114 is made of an insulating resin. The shaping air ring 114 and a motor support case 116 are connected via a relay case 118. The motor support case 116 and the relay case 118 are both made of a resin having electrically insulating characteristics.

(17) The hollow rotary shaft 108 is made of a PEEK resin (polyether ether ketone resin). The PEEK resin is excellent in electric insulation and formability. FIGS. 6 to 8 are diagrams for explaining the hollow rotary shaft 108.

(18) FIG. 6 is a side view of a main portion of the hollow rotary shaft 108 incorporated in the air motor 104. FIG. 7 is a perspective view. FIG. 8 is a perspective view of the hollow rotary shaft 108 viewed from the air motor 104. In FIGS. 6 to 8, reference numeral 120 denotes plate-shaped resistors. The hollow rotary shaft 108 has nine grooves 122 (FIG. 8) formed on an outer circumferential surface thereof. The grooves 122 axially extend. The nine grooves 122 are circumferentially arranged at regular intervals.

(19) The plate-shaped resistors 120 are partially fit and fixed into the respective grooves 122. The plate-shaped resistors 120 extend outward from the outer circumferential surface of the hollow rotary shaft 108. In particular, the plate-shaped resistors 120 are disposed in an obliquely standing state from the hollow rotary shaft 108. The two adjacent plate-shaped resistors 120 are connected to each other by an intermediate conducting wire 124 so that the nine plate-shaped resistors 120 are serially connected. A resistance value r of the plate-shaped resistor 120 is 20 M, for example. The nine plate-shaped resistors 120 make up the second high resistance 12 (FIGS. 1 and 2) described above and the second resistance value R2 of the second high resistance 12 (FIGS. 1 and 2) is 180 M.

(20) Although nine plate-shaped resistors 120 are used in the embodiment, if the first resistance value R1 of the first high resistance 10 is 60 to 120 M, the second resistance value R2 of the second high resistance 12 (FIG. 1) may be 100 to 200 M. If the first resistance value R1 of the first high resistance 10 is 80 to 100 M, the second resistance value R2 of the second high resistance 12 may be 120 to 180 M. If the first resistance value R1 of the first high resistance 10 is 80 to 100 M, the second resistance value R2 of the second high resistance 12 may preferably be 140 to 160 M. The resistance value (R1+R2) acquired by summing the resistance values of the first and second high resistances 10, 12 may be 220 to 260 M.

(21) The first plate-shaped resistor 120 (No. 1) on the input side of the nine plate-shaped resistors 120 is always connected via and input-side conducting wire 126 to the air motor 104. The ninth plate-shaped resistor 120 (No. 9) located outermost on the output side is connected via an output-side conducting wire 128 to a rear end portion of the rotary atomization head 110.

(22) A high-voltage application path from the cascade 102 to the rotary atomization head 110 is made up of the conductive air motor 104, the input-side conducting wire 126, the nine serially-connected plate-shaped resistors 120, the output-side conducting wire 128, and the rotary atomization head 110 made of a semiconductive material.

(23) Returning to FIG. 5, a portion 118a surrounding the plate-shaped resistor 120 in the relay case 118 may be made by vacuum molding from a two-component epoxy resin with high electric insulation. 1 electrostatic coating system according to the present invention 6 electrostatic coating device according to the present invention 6A cascade built-in type electrostatic coating device 6B cascade-less type electrostatic coating device 8 high-voltage generator 10 first high resistance (first resistance value R1) 12 second high resistance (second resistance value R2) 14 discharge electrode 16 coating device component(s) made of conductive material 18 resistor 100 electrostatic coating device of embodiment 102 cascade 104 air motor 108 hollow rotary shaft 110 rotary atomization head of semiconductive material 120 plate-shaped resistor 122 groove 124 intermediate conducting wire 126 input-side conducting wire 128 output-side conducting wire