JPS6210700B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic coating method that prevents malfunction of a high voltage interrupting device.

In electrostatic painting, charged paint discharged from a paint sprayer is applied to the object to be coated, which has a potential difference with respect to the charged paint, but since the painting is performed in a high-voltage atmosphere, safety precautions must be taken. From the point of view, there is a built-in safety device in the high-voltage generator, ie a high-voltage cut-off device in case of an emergency.

This high-voltage cutoff device is designed to prevent people from entering a high-voltage atmosphere.
It is designed to be activated when a change that occurs when an object or the like enters is detected, and is normally activated depending on the magnitude of the current change.

By the way, when electrostatically painting a fairly large object such as a car body, the total area to be coated is large, so the object to be coated must be moved relative to the coating machine while the object is being painted. The surface is painted in small sections one by one. When painting in this way, there are small parts of the object that do not require painting at all (for example, wheel housing parts of a car body). Conventionally, when such a small part that does not require painting is located within the painting range of the paint sprayer, the discharge of charged paint from the paint sprayer is temporarily stopped (paint off), and the part that requires painting is moved according to the relative movement. When the paint was located within the painting range, the paint was again sprayed with charged paint from the paint sprayer.

However, according to the conventional method as described above, when the discharge of charged paint from the paint sprayer is temporarily stopped, a large current change occurs similar to the case in an emergency as described above, and the high voltage interrupt device malfunctions. , that is, high voltage is cut off at high speed,
A situation where the subsequent painting process had to be temporarily interrupted was likely to occur.

The present invention solves the above-mentioned problems, and when a part that does not require painting is located within the coating range of the paint sprayer, the paint sprayer discharges a very small amount of charged paint without temporarily stopping the discharge. By this,
To provide an electrostatic coating method that prevents large current changes from occurring during normal coating work and prevents malfunction of a high voltage interrupting device.

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes an automobile body as an object to be coated, and the body 1 is conveyed and moved in the direction of the arrow in the figure by a conveyance device (not shown). On the sides of this conveyance device, a pair of left and right electrostatic coating machines 2 are installed either fixedly or in the vertical direction (vertical direction in Fig. 2) in order to electrostatically coat the left and right side surfaces of the body 1.
It is arranged so that it can freely reciprocate by a certain amount. Although not shown, an electrostatic coating machine for coating the upper surface of the body 1 is also arranged.

As shown in FIG. 3, the electrostatic atomizer 2 is equipped with a so-called bell-shaped rotary atomizing head 2a, which has an electrostatic paint reservoir connected to it via an electrostatic paint supply hose 3. Tank 4 is connected. In addition, a power source 6 such as a commercial power source is connected to the rotary atomizing head 2a through a high voltage generator 5 having a built-in high voltage cutoff device (safety device) 5a for cutting off high voltage at high speed. There is. Here, the high voltage generator 5 receives a voltage (for example, 100V) from the power supply 6.
is boosted to a negative high voltage (for example, -90 Kv), and this high voltage is applied to the rotary atomizing head 2a. Further, the high voltage cutoff device 5a detects a change in current between the object to be coated 1 and the rotating atomizing head 2a of the coating machine 2, and cuts off the applied voltage from the high voltage generator 5 if there is an abnormality. This high-voltage cutoff device 5a is designed to operate when a person, object, etc. enters the high-voltage atmosphere, or when the coating machine 2 approaches the object 1 to be coated abnormally. It is known (for example, Special Publication No. 55-35988). During electrostatic coating, by applying a high voltage to the rotating atomizing head 2a of the coating machine 2, the electrostatic coating discharged from the rotating atomizing head 2a is negatively charged and the body is charged. 1 is grounded, and a high voltage potential difference is applied between the two.

In the above configuration, the atomizing head 2a is rotationally driven.
When the electrostatic paint is supplied from the pump 7, the charged electrostatic paint is atomized and applied to the body 1 by suction. Therefore, while the body 1 is being moved, it is electrostatically coated sequentially from the left side to the right side in FIGS. 1 and 2.

As is clear from FIG. 2, in the side surface portion of the body 1, the front wheel housing portion 1a and the rear wheel housing portion 1b are essentially unnecessary parts that do not require painting, and the remaining portion 1c is the unpainted portion. This is a part that requires painting. The action of the coating machine 2 on the parts requiring painting 1c and the parts not needing painting 1a, 1b are different as shown in FIG.
In other words, when the area to be painted 1c is located in front of the coating machine 2 (painting range), an extremely high potential difference of, for example, 90 kV is applied between the electrostatic paint and the body 1, and at the same time, the voltage from the coating machine 2 is The discharge amount of the charged paint is large, and the areas 1c that require painting are subjected to normal electrostatic painting.

When the unnecessary parts 1a and 1b are located in front of the paint sprayer 2, a predetermined high voltage difference is maintained between the electrostatic paint and the body 1, and the amount of charged paint discharged from the paint sprayer 2 is small. be done. The amount of paint to be discharged at this time is set to an extremely low amount that does not interfere with painting, that is, a level that does not cause dripping of paint on the edge portions of the wheel housing portions 1a and 1b.
The actual value of this low discharge amount varies depending on the painting distance between the sprayer 2 and the body 1, but for example, if the painting distance is 300mm, the actual value is 100mm.
cc/min or less (of course, it is not considered zero). By the way, the discharge amount when painting the area 1c that requires painting is, for example, 400 mm at the above painting distance of 300 mm.
cc/min.

When electrostatic painting was carried out as described above, a large current change occurred during the painting from the left end to the right end of the body 1 in Figure 1, unless a foreign object such as a human body entered the high voltage atmosphere. Therefore, it is possible to completely prevent malfunction of the high voltage interrupting device 5a. Of course, if a foreign object such as a human body enters the high voltage atmosphere, the high voltage cutoff device 5a will operate normally.
Application of high voltage is cut off.

In addition, in the example, the case where one object to be coated has a part that requires painting and a part that does not need to be painted is explained.
All the objects to be coated require painting, and if the next object to be coated follows at a short interval, the space between the objects to be coated should be treated as an unnecessary part and painted as described above. Good too. Also,
In the embodiment, an electrostatic coating machine 2 is used for an automobile body 1.
Although the electrostatic coating machine 2 has been described as being moved, the electrostatic coating machine 2 may be moved while the automobile body 1 is stopped; in short, it is sufficient if the object to be coated moves relative to the coating machine.

As is clear from the above description, the present invention allows a very small amount of paint to be discharged from the paint sprayer without stopping the paint discharge when the paint sprayer is relatively displaced to a position corresponding to an area that does not require painting. By doing so, the following effects can be achieved.

For example, when painting an object to be coated, such as an automobile body, that is transported by a conveyor or other conveyor, a very small amount of paint is discharged without temporarily stopping the discharge of charged paint as in conventional technology. This prevents the high voltage generator from malfunctioning due to large current changes during normal painting work.

As a result of the above, the lines of electric force between the coating machine and the object may be lost during the painting process, causing the paint to fly to areas other than the object and causing uneven coating on the object. There is no risk of this happening, and staining inside the painting booth can be prevented. Therefore, there is no waste of paint.

Furthermore, there is no possibility that a malfunction of the high-voltage generator would force the conveyance device to stop, thereby causing a drop in coating efficiency, such as temporarily interrupting the subsequent coating process.

[Brief explanation of the drawing]

FIG. 1 is a top view showing an example of electrostatic painting of an automobile body, FIG. 2 is a side view of FIG. 1, and a diagram showing a time chart of electrostatic painting.
FIG. 3 is a diagram showing an example in which a high voltage interrupting device is connected to an electrostatic coating machine. 1... Automobile body, 2... Electrostatic coating machine, 5a
...High voltage cutoff device.

Claims (1)

[Claims] 1. A coating machine that discharges paint from a paint source toward an object to be coated, a high voltage generator that applies a high voltage to the coating machine in order to charge the paint discharged from the coating machine, and the high voltage generator. A high voltage cutoff device is built in the device and detects a change in current between the object to be coated and the coating machine, and cuts off the high voltage generated by the high voltage generator when there is an abnormality. In an electrostatic coating method in which an object to be coated that has a potential difference with respect to the charged paint being discharged is coated while being moved relative to the coating machine, when the coating machine is relatively displaced to a position corresponding to an area that does not need to be coated. , an electrostatic coating characterized in that the high voltage generator continues to apply a predetermined high voltage, and the paint sprayer continues to discharge a very small amount of paint without stopping the paint discharge. Method.