Electrostatic atomizing coating apparatus and coating method

Patent metadata

Field	Value
Publication number	US-10688526-B2
Application number	US-201615235543-A
Country	US
Kind code	B2
Filing date	Aug 12, 2016
Priority date	Aug 28, 2015
Publication date	Jun 23, 2020
Grant date	Jun 23, 2020

Abstract

An electrostatic atomizing coating apparatus and method incorporate a rotary head having a base portion, an open end and a plurality of grooves formed radially on an inner peripheral surface of the open end, an inside diameter of the rotary head increasing from the base portion toward the open end, and a motor configured to rotate the rotary head to discharge a thread-shaped paint. A voltage is applied to the rotary head so as to form an electrostatic field between the open end of the rotary head and an earthed coating target and to electrostatically atomize the thread-shaped paint discharged from the open end. Voltage output from the generator is controlled so as to adjust an intensity of the electrostatic field and to control a particle diameter of the electrostatically atomized thread-shaped paint.

First claim

What is claimed is:

1. An electrostatic atomizing coating apparatus comprising:
at least one rotary head having a base portion, an open end and a plurality of grooves formed radially on an inner peripheral surface of the open end, an inside diameter of the rotary head increasing from the base portion toward the open end;
a motor configured to rotate the at least one rotary head to discharge a thread-shaped paint from the open end;
a generator configured to provide a voltage to the at least one rotary head so as to form an electrostatic field between the open end and a grounded coating target and electrostatically atomize the thread-shaped paint discharged from the open end;
a measurement circuit configured to measure a distance between the rotary head and the grounded coating target; and
a controller configured to control a voltage output from the generator based on the measurement from the measurement circuit so as to provide a constant current flow between the rotary head and the grounded coating target to control a particle diameter of the electrostatically atomized thread-shaped paint,
wherein the thread-shaped paint discharged from the open end of the rotary head is electrostatically atomized by an electrostatic force in the electrostatic field without shaping air, and
the controller controls the voltage output while the distance between the rotary head and the grounded coating target changes in order to maintain the constant current flow, the change in distance being based on a change in shape of the grounded coating target.

2. The electrostatic atomizing coating apparatus according to claim 1 , further comprising an outer ring configured to surround an outer peripheral surface of the at least one rotary head,
wherein the voltage output from the generator is provided to the outer ring.

3. The electrostatic atomizing coating apparatus according to claim 2 , wherein the outer ring comprises a base and a front end.

4. The electrostatic atomizing coating apparatus according to claim 3 , wherein a sectional area of the outer ring perpendicular to an axial direction of the outer ring decreases from the base of the outer ring toward the front end.

5. The electrostatic atomizing coating apparatus according to claim 4 , wherein a thickness of the front end is in the range of 0.3 mm to 1 mm.

6. The electrostatic atomizing coating apparatus according to claim 3 , wherein a plurality of grooves are formed on an outer peripheral surface of the front end along the axial direction of the outer ring.

7. The electrostatic atomizing coating apparatus according to claim 3 , wherein the outer ring further comprises a plurality of protruding portions projecting from the front end along the axial direction of the outer ring.

8. The electrostatic atomizing coating apparatus according to claim 1 , wherein the apparatus comprises a plurality of rotary heads, and
the plurality of rotary heads are provided in parallel with each other.

9. The electrostatic atomizing coating apparatus according to claim 1 , wherein an outside diameter of the at least one rotary head is in the range of 20 mm to 50 mm.

10. The electrostatic atomizing coating apparatus according to claim 1 , wherein a number of the plurality of grooves is in the range of 600 to 1,000.

11. The electrostatic atomizing coating apparatus according to claim 1 , wherein the controller is configured to control the particle diameter of the electrostatically atomized thread-shaped paint when the particle diameter of the electrostatically atomized thread-shaped paint is in the range of 20 μm to 30 μm in terms of Sauter Mean Diameter.

12. The electrostatic atomizing coating apparatus according to claim 1 , wherein the motor rotates the at least one rotary head at a speed in the range of 500 mm/s to 1,200 mm/s.

13. The electrostatic atomizing coating apparatus according to claim 1 , wherein a glow discharge is generated from the open end of the rotary head.

14. The electrostatic atomizing coating apparatus according to claim 1 , wherein an outer peripheral surface of the at least one rotary head has a circular column shape.

15. An electrostatic atomizing coating method comprising:
providing the electrostatic atomizing coating apparatus according to claim 1 ;
discharging the thread-shaped paint from the open end of the rotary head by rotating the rotary head;
electrostatically atomizing the thread-shaped paint discharged from the open end by forming the electrostatic field between the open end and the coating target;
measuring the distance between the rotary head and the grounded coating target; and
controlling a current flowing between the rotary head and the grounded coating target based on the measurement to provide the constant current flow between the rotary head and the grounded coating target to control the particle diameter of the electrostatically atomized thread-shaped paint.

16. The electrostatic atomizing coating method according to claim 15 , wherein an outer peripheral surface of the rotary head has a circular column shape.

17. An electrostatic atomizing coating apparatus comprising:
at least one rotary head having a base portion, an open end and a plurality of grooves formed radially on an inner peripheral surface of the open end, an inside diameter of the rotary head increasing from the base portion toward the open end;
a motor configured to rotate the at least one rotary head to discharge a thread-shaped paint from the open end;
a generator configured to provide a voltage to the at least one rotary head so as to form an electrostatic field between the open end and a grounded coating target and electrostatically atomize the thread-shaped paint discharged from the open end;
a measurement circuit configured to measure a distance between the rotary head and the grounded coating target; and
a controller configured to control a voltage output from the generator based on the measurement from the measurement circuit so as to provide a constant current flow between the rotary head and the grounded coating target to control a particle diameter of the electrostatically atomized thread-shaped paint,
wherein the thread-shaped paint discharged from the open end of the rotary head is electrostatically atomized by an electrostatic force in the electrostatic field without shaping air,
the controller controls the voltage output while the distance between the rotary head and the grounded coating target changes in order to maintain the constant current flow, the change in distance being based on a change in shape of the grounded coating target, and
a distance between the rotary head and the coating target is in a range of 50 to 100 mm.

Assignees

• Toyota Motor Co Ltd

Inventors

• Tani Shinji
• Nabeshima Astuo
• Kondo Takahito

Classifications

• B05D1/06

  Applying particulate materials · CPC title

• B05B5/0533

  Electrodes specially adapted therefor; Arrangements of electrodes · CPC title

• B05B5/0411 Primary

  with individual passages at its periphery · CPC title

• B05B5/005

  the high voltage supplied to an electrostatic spraying apparatus being adjustable during spraying operation, e.g. for modifying spray width, droplet size · CPC title

• B05B5/043

  using induction-charging · CPC title