INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2018-180709 filed on Sep. 26, 2018 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The disclosure relates to a coating device.

2. Description of Related Art

A coating device having a rotary head is known (for example, see Japanese Unexamined Patent Application Publication No. 2017-42749 (JP 2017-42749 A)).

The coating device described in JP 2017-42749 A is configured so as to discharge a thread-shaped coating material from the rotary head, and electrostatically atomize the thread-shaped coating material so that coating material particles are formed and a workpiece is coated with the coating material. In the coating device, a high voltage is applied to the rotary head by a voltage generator, and the workpiece is grounded. Therefore, an electric field is formed between the rotary head and the workpiece. In the coating device, since an output voltage of the voltage generator is adjusted in accordance with a distance between the rotary head and the workpiece, fluctuations of electric field strength are restrained, and fluctuations of a discharge current discharged from the rotary head towards the workpiece are restrained. Thus, the electrostatic atomization is stabilized.

SUMMARY

The thread-shaped coating material discharged from the rotary head is split by repulsive force caused by an electrified charge. Therefore, stabilization of a discharge current is desired in order to stabilize the electrostatic atomization. This means that, in order to appropriately control the atomization of the coating material, it is desired to appropriately control a discharge current.

However, in the coating device described above, only the distance between the rotary head and the workpiece is considered as a factor that causes fluctuations of a discharge current at the time of coating, and there is room for improvement. For example, it is considered that a discharge current may fluctuate due to changes of a state of the workpiece because of the coating, changes in a leak current in the coating device, and so on.

The disclosure provides a coating device that is able to appropriately control a discharge current.

A coating device according to an aspect of the disclosure includes a rotary head, a drive part, a coating material supply pipe, a power supply part, and a control part. The drive part rotates the rotary head. The coating material supply pipe supplies a coating material to the rotary head. The power supply part applies a voltage to the rotary head, and the control part controls the power supply part. The rotary head includes a diffusion surface and a plurality of groove portions. On the diffusion surface, the coating material is diffused by centrifugal force to an outer edge portion, and the groove portions are provided in the outer edge portion. The rotary head is configured so that the thread-shaped coating material is discharged from the groove portions, and that the thread-shaped coating material is electrostatically atomized. The control part is configured so as to calculate a discharge current based on a total current and a leak current and control the power supply part based on the discharge current. The total current flows from the power supply part to the rotary head, and the leak current leaks from the rotary head through the coating material supply pipe. The discharge current is discharged from the rotary head towards a workpiece that is grounded.

As described above, as the discharge current is calculated based on the total current and the leak current, it is possible to estimate the discharge current that is difficult to measure directly. Then, as the power supply part is controlled based on the calculated discharge current, it is possible to appropriately control the discharge current.

In the coating device described above, the control part may be configured so as to control an output voltage of the power supply part so that the discharge current reaches a given target value.

With this configuration, as the output voltage of the power supply part is controlled, it is possible to adjust the discharge current to the given target value.

In the foregoing coating device, a moving part may be provided that moves the rotary head and the workpiece relative to each other. The moving part may be configured so as to prohibit the rotary head and the workpiece from moving closer to each other when an absolute value of the output voltage of the power supply part is smaller than a given value.

With such a configuration, it is possible to restrain the rotary head and the workpiece from coming into contact with each other.

With the coating device according to the aspect of the disclosure, it is possible to appropriately control the discharge current.

