JPH0531408A - Spark preventing device in electrostatic painting - Google Patents

Abstract

PURPOSE:To prevent in advance a spark generated between an object to be painted and a painting equipment by detecting surely a fact that the object to be painted approaches abnormally a grounded painting equipment, at the time of applying a high voltage to the object to be painted and executing electrostatic painting by grounding a painting machine. CONSTITUTION:On the peripheral surface of a painting equipment 2 having a fear that an object W to be painted approaches abnormally, an electrode 14 whose capacitance is small to the painting equipment 2 is attached in an insulating state, and also, the electrode 14 is connected to a ground 13 through a ground circuit 16, and an abnormal current detector 17 for detecting a fact that an abnormal current flows to the ground circuit 16, and a controller 18 for dropping a current and a voltage supplied to the object W to be painted, based on its detecting signal are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a coating machine, a top machine, a side machine, a coating robot, etc., when a high voltage is applied to a coating object and the coating machine is grounded for electrostatic coating. The present invention relates to a spark prevention device for electrostatic coating, which prevents sparks caused by abnormal proximity to grounded coating equipment.

[0002]

2. Description of the Related Art For example, when an automobile body is electrostatically coated by using a non-conductive paint, a coating machine is applied with 80 to 120 KV.
In addition to applying a high voltage, the automobile body to be coated is grounded and the distance between the coating machine and the automobile body is kept constant to form a coating film with uniform coating quality.

However, for example, when transporting an automobile body, the vehicle may be transported without forgetting to close the hood, trunk lid, hatchback door, and entry / exit doors, or due to a computer input error when painting a large vehicle model. If an instruction is given to paint a small car model, the painter and the object to be coated may be abnormally close to each other, causing not only poor painting but also a risk of sparking.

Therefore, conventionally, the supply current flowing through the high-voltage supply circuit for electrically connecting the high-voltage generator and the object to be coated is monitored, and an overcurrent which may cause a spark flows in the circuit. At the same time, the high voltage supply circuit is cut off, and the paint supply is stopped to interrupt the coating. By doing so, when the object to be coated and the coating machine are abnormally close to each other and an overcurrent flows, the supply of high voltage to the coating machine is stopped, so that the occurrence of sparks can be prevented in advance. .

[0005]

By the way, when a conductive paint such as a water-based paint is used, even if a high voltage is applied to the paint machine, the paint machine is grounded through the paint. Electrostatic coating may be performed by applying a high voltage and grounding the coating machine. In this case, most of the coating equipment in the coating booth is also grounded, so that the current supplied by the object such as the car body being transported to and away from the coating equipment other than the coating machine is fluctuate.

[0006] Usually, the electrostatic capacity of the object to be coated such as an automobile body is large, and the total electrostatic capacity of the coating equipment installed in the coating zone is also very large. Therefore, the object to be coated is transported near the coating equipment. A relatively large current flows between the two just by doing so. Then, the object to be coated is electrostatically coated while being conveyed by a conveyor or the like while approaching one coating facility or moving away from another coating facility, so that the current supplied to the object is in a considerably large range. Fluctuates with.

Therefore, the supply current constantly fluctuates even during normal electrostatic coating, and even if the fluctuation of the supply current from the high-voltage generator is monitored, the fluctuation leads to the generation of sparks. There is a problem that it is not possible to distinguish whether it is a thing or not, and it is not possible to prevent sparks in advance.

Therefore, according to the present invention, when a high voltage is applied to an object to be coated and a coating machine or other coating equipment is grounded for electrostatic coating, the object to be coated abnormally approaches the grounded coating equipment. It is an object of the present invention to reliably detect such a thing and prevent a spark occurring between them from occurring.

[0009]

In order to solve this problem, the present invention provides a grounded coating facility when a high voltage is applied to an object to be coated and the coating machine is grounded for electrostatic coating. It is a spark prevention device in electrostatic coating that prevents sparks caused by abnormally approaching an object to be coated. An electrode with a small capacitance is attached in an insulated state, and the electrode is connected to the earth via a ground circuit, and an abnormal current that may cause a spark between the object to be coated and the electrode flows in the ground circuit. An abnormal current detector that detects that the current is detected, and based on the detection signal, a control device that reduces the current or voltage supplied to the object to a safe current or voltage that does not cause sparking is provided. Characterized by

[0010]

[Function] On the peripheral surface of the grounded coating equipment, an electrode having a small electrostatic capacity is attached to the coating equipment in an insulated state, and since it is connected to the ground through a grounding circuit, the opposite pole When the tinged object approaches, a current will flow in the ground circuit. At this time, the electrostatic capacitance of the electrodes is small, a constant interval is maintained as long as the object to be coated is conveyed normally, and the current flowing through each electrode is small.

When the object to be coated abnormally approaches the electrode attached to the peripheral surface of the coating facility, regardless of whether or not the current supplied to the object to be coated fluctuates, an overcurrent or the like is generated in each ground circuit of the electrode that has abnormally approached. Since the abnormal current flows in, the abnormal current detector detects the abnormal current, and thus it can be reliably detected that the object to be coated abnormally approaches the coating equipment. When an abnormal current is detected, a detection signal is output from the abnormal current detector to the control device, and the voltage or current supplied to the object to be coated is reduced to a safe value that does not cause sparks. The occurrence of sparks between the object and the object to be coated is prevented in advance.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on the embodiments shown in the drawings. FIG. 1 is a flow sheet showing an example of a spark prevention device in electrostatic coating according to the present invention, and FIG. 2 is a perspective view thereof. In the figure, 1 is a conveyer for applying a high voltage to convey an article W, and a side machine 3 for painting the upper surface and the side surface of the article W along the conveyor 1.
And the top machine 3 is installed.

The conveyor 1 is supported in an insulated state from the installation surface 4 and is connected to a high voltage generator 6 via a high voltage supply circuit 5 to apply a high voltage to the article W to be coated via the conveyor 1. It is made to apply. Top machine 2
Is provided with an elevating stand 8 to which the coating machines 7, 7 are attached so as to be movable up and down along columns 9, 9 installed on both sides of the conveyor 1. Further, in the side machine 3, the coating machine 10 is attached to a pillar 11 arranged along the conveyor 1 so as to be vertically reciprocally movable. Each coating machine 7 and 1
0 is connected to the ground 13 through the grounding circuit 12 and is configured to coat conductive paint such as water-based paint by the electrostatic field formed between the coating machines 7 and 10 and the object W to be coated. The top machine 2 and the side machine 3 are also connected to the ground 13, respectively.

These top machine 2 and side machine 3
On the peripheral surface of the lifting platform 8, pillars 9 and 11 of the coating equipment such as
A large number of electrodes 1 with a small electrostatic capacity for the coating equipment
4, 14 are attached in an insulated state. Each electrode 14
Is formed of, for example, a metal rod, both end portions of which are supported by the columns 9 and 11 via the insulator 15, and
Each is connected to the ground 13 via the ground circuit 16.

The ground circuits 12 and 16 monitor the current flowing in the circuits and detect abnormalities which may cause sparks between the coating equipment such as the top machine 2 and the side machine 3 and the object W to be coated. An abnormal current detector 17 that detects that a current has flown is provided. This abnormal current detector 1
A predetermined current value smaller than a critical current value that may cause sparks between the coating machines 7 and 10 and the object W to be coated is set as a dangerous current value in the grounding circuit 12 and 1 in FIG.
When the current flowing through 6 exceeds the dangerous current value, it is determined that an abnormal current has flowed and a detection signal is output. Further, the time change of the current is monitored, and when there is a rapid current increase with a large rising slope, it is judged that an abnormal current has flowed and a detection signal is output.

A control device 18 lowers the voltage / current applied from the high voltage generator 6 to the article W to a safe voltage / current which does not cause sparks when the detection signal is input. In this example, the switch circuit 1 that shuts off the high voltage supply circuit 5 when the detection signal is input.
8a and a grounding circuit 19 for connecting the object W to the earth 13
The switch circuit 18b for conducting the power is used.

Therefore, the object to be coated W and the coating machines 7 and 10 are
Is abnormally approached and the detected current reaches a dangerous current, the high-voltage supply circuit 5 is cut off by the switch circuit 18a and the supply voltage / current becomes 0, and at the same time, the switch circuit 18b remains on the object W to be coated. The charge is grounded and sparks are reliably prevented.

The above is an example of the configuration of the present invention, and its operation will be described below. First, when an object W to be coated such as an automobile body is conveyed by the conveyor 1 and at the same time a high voltage of 80 to 120 KV is applied to the object W to be coated via the conveyor 1, the coating machines 7, 10 and the object W to be coated are applied. An electrostatic field is formed between and. In this state, according to the shape of the article W to be conveyed by the conveyor 1, the lifting platform 8 of the top machine 2
Up and down, or the coating machine 10 of the side machine 3
When the paint is discharged from each of the coating machines 7 and 10 while reciprocating vertically, the upper surface and the side surface of the article W to be coated are coated.

While the object W to be coated is normally coated, the gap between the object W to be coated and the electrode 14 is maintained at a certain value or more, so that an abnormal current flows in the ground circuit 16 of each electrode 14. Not here. Here, for example, a hood or the like opened by transporting the bonnet or trunk lid of the object to be coated close to the columns 9 and 11 abnormally, or due to a setting mistake of the vehicle type, the lifting platform 8 of the top machine 2
When the pillar 11 of the side machine 3 abnormally approaches the object W to be coated, the object W to be abnormally approaches the electrode 14 and the current flowing through the ground circuit 16 increases.

This current is monitored by the abnormal current detector 17, and when the current flowing through the ground circuit 16 exceeds the dangerous current value due to the abnormal proximity of the coating machines 7, 10 and the object W to be coated, the abnormal current detector 17 A detection signal is output from the switch circuit 18a and the high voltage supply circuit 5 is cut off by the switch circuit 18a. At the same time, the switch circuit 18b connects the ground circuit 19 to connect the article W to the ground 13 and the coating machine. The supply of paint to 7 and 10 is also stopped. Therefore,
The coating is interrupted and the voltage / current supplied to the object W is 0
At the same time, the residual charge is released to the ground 13 through the grounding circuit 19 to prevent the occurrence of sparks, so that the coating failure due to the sparks and the damage to the electronic circuit of the coating equipment will not occur.

Although the case where the rod-shaped electrode is used as the electrode 14 has been described, the present invention is not limited to this, and the shape thereof is arbitrary as long as the capacitance is smaller than that of the coating equipment. Further, as the control device 18, a variable resistance device capable of switching between high resistance and low resistance is interposed in the high voltage supply circuit 5, and is set to high resistance when a detection signal is input from the abnormal current detector 17. Alternatively, a voltage drop may be generated to reduce the potential difference between the object W to be coated and the electrode 14 to prevent sparking. Further, as the control device 18, a voltage control device for adjusting the output voltage is provided in the high voltage generator 6, and the abnormal current detector 1
The output voltage may be lowered when the detection signal is input from 7.

In the description of the embodiment, the top machine 2 and the side machine 3 are described as an example of the coating equipment, but the present invention is not limited to this, and the coating equipment installed in the coating booth by being grounded. If so, for example, it can be applied to arbitrary equipment such as a painting robot. Furthermore, as long as a high voltage is applied to the object W to be coated and the coating machines 7 and 10 are connected to the ground 13 for electrostatic coating, the conductive coating is not limited to the non-conductive coating. Of course, it can be applied when used.

[0023]

As described above, according to the present invention, an electrode having a small electrostatic capacity is attached to the peripheral surface of the coating equipment, and the object to be coated becomes abnormal due to the current flowing through the electrode to the ground circuit. Since it is possible to reliably detect the approach, it is possible to reliably detect that the object to be coated and the coating equipment have approached abnormally without being affected by the change in current caused by approaching or moving away from other coating equipment. It is possible to prevent the spark generated between the coating machine and the object to be coated, which is a very excellent effect.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an example of the device of the present invention.

FIG. 2 is a perspective view thereof.

[Explanation of symbols]

W ... Substrate 1 ... Conveyor 2 ... Top machine 3 ... Side machine 5 ... High voltage supply circuit 6 ... High voltage generator 7 ... Coating machine 8 ... Elevating stand 9 ... Support 10 ... Coating machine 11 ... Support 12 ... Ground circuit 13 ... Ground 14 ... Electrode 15 ... Insulator 16 ... Ground circuit 17 ... Abnormal current detector 18 ... Control device 18a, 18b ... Switch circuit 19 ... Ground circuit

Claims (3)

[Claims] 1. A spark which is produced when a grounded coating facility and an object to be coated (W) are abnormally close to each other when a high voltage is applied to the object to be coated (W) to electrostatically coat a coating machine. A spark preventive device in electrostatic coating for preventing
An electrode (14) having a small capacitance is attached to the peripheral surface of the coating equipment (2, 3) where the object (W) may approach abnormally in an insulated state with respect to the coating equipment (2, 3). At the same time, the electrode (14) is connected to the ground (13) through the ground circuit (16), and the ground circuit (16) is provided with a spark between the object to be coated (W) and the electrode (14). An abnormal current detector (17) for detecting the flow of an abnormal current that may occur is provided, and it is safe to prevent the current or voltage supplied to the object from being sparked based on the detection signal. A spark prevention device in electrostatic coating, comprising a control device (18) for reducing the current or voltage. 2. A large number of the electrodes (14) are attached so as to cover a peripheral surface portion of a coating facility (2, 3) where an object to be coated may approach abnormally, and each electrode (14) is grounded. The spark prevention device for electrostatic coating according to claim 1, wherein (16) is formed and an abnormal current detector (17) is individually provided for each ground circuit (16). 3. A high voltage for the control device (18) to electrically connect the article to be coated (W) and the high voltage generator (6) based on the detection signal of the abnormal current detector (17). The electrostatic coating according to claim 1, further comprising: a switch circuit (18a, 18b) for interrupting the supply circuit (5) and at the same time conducting a ground circuit (19) for connecting the object (W) to the ground. Spark prevention device.