JPH08294661A - Painting method - Google Patents

Abstract

PURPOSE: To continuously form a base coating film and a clear coating film on the surface of an article to be painted by applying aq. metallic paint to the article to be painted while performing its slat conveyance in a work voltage applying painting region by impressing high voltage, drying and solidifying the painted article in a flash-off region and forming a clear coating film on the dried article in an electrostatic painting area. CONSTITUTION: A slat conveyor 1 is operated to feed an article 29 to be painted in the direction shown by an arrow and coated with aq. metallic paint by a current supply painting method using a side reciprocating painting apparatus 23 and a top receprocating painting apparatus 24. Next, the base coating film is dried and solidified in a flash-off region B by the radiation heat by a radiation panel 27 and the hot air from a hot air blowoff port 28. Continuously, the coated article is sent to an electrostatic painting region (c) to spray solvent type clear paint by electrostatic painting by a side reciprocating painting apparatus 37 and a top reciprocating painting apparatus 38 to perform painting. By this constitution, a base coating film of aq. metallic paint and solvent clear paint clear painting film can be continuously formed by one process and high efficient productivity and high coating quality can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms a base coating film of a water-based metallic coating on the surface of an article to be coated such as an automobile body, and, after flash-off, further coating,
The present invention relates to a coating method for forming a clear coating film with a solvent-based clear coating material.

[0002]

2. Description of the Related Art Conventionally, the coating of an automobile body is performed by a procedure of applying an undercoat by electrodeposition coating or the like, and then applying a middle coating and a top coating according to an electrostatic coating method using a color coating or a metallic coating. ing. The electrostatic coating method in this case is generally a method in which a high voltage of −60 to −150 kV is applied to the electrostatic coating machine to atomize and spray the insulating coating toward the grounded automobile body. there were.

However, the insulating coating used in this coating method contains a lot of harmful organic solvents such as thinner. In recent years, the movement to protect the environment has increased worldwide, and regulations on the use of organic solvents in the industrial world have been screaming. In response to this, in the coating industry, paints containing a small amount of organic solvents, that is, water-based paints. It is recommended to perform electrostatic coating with (water-soluble paint and water-based paint in a narrow sense).

However, since the water-based paint has conductivity, when it is atomized or sprayed by an electrostatic coating machine,
It is necessary to insulate the entire paint supply system so that the high-voltage current applied to the coating machine does not leak through the paint. Currently, in paint facilities for automobile bodies, multicolor paints are usually applied using dozens of colors of paint, so it is not possible to insulate the paint pipes and paint tanks for each color. It is very complicated work,
In addition, since the insulation treatment is accompanied by the attachment of an explosion-proof chamber and the like, the coating equipment becomes very complicated and large.

Therefore, conventionally, there have been proposed some coating systems capable of performing electrostatic coating using a conductive coating without subjecting the coating piping system to insulation treatment (Japanese Utility Model Publication No. 3-105948). , Japanese Utility Model Publication No. 4-16796, etc.). In this coating system, generally, an electrode attachment is mounted on a carriage of a conveyor device via an insulator, and a current collecting rail to which high-voltage current is supplied is provided near the conveyor device along the conveyance direction of the carriage. When an object to be coated, such as a car body, is placed on the electrode attachment and transported by the conveyor device, the contactor of the electrode attachment slides on the current collecting rail to apply a high voltage to the object to be coated. By doing so,
This is a system in which the water-based paint atomizes and sprays onto the object to be coated.

However, in the above coating system, the surfaces of these contacts gradually melt due to the heat of the spark generated by the contact between the contactor and the current collecting rail, and irregularities are eventually formed. The rail has a drawback that it needs to be replaced frequently, and that the current collecting rail is apt to be coated with paint, which requires frequent cleaning processing. Proposal for eliminating this drawback (Japanese Patent Laid-Open No. 4-61944)
It's been done, but it's not enough.

Further, when the article to be coated is transferred to the entrance of the high voltage application area, the article to be coated is transferred from the ordinary conveyor to the insulating conveyor, and then a high voltage is applied to the article to be coated to cause electrostatic discharge. A method has also been conventionally proposed in which coating is performed, and then the object to be coated is transferred from the insulating conveyor to a normal conveyor at the exit of the high voltage application region (JP-A-3-224651 and JP-A-4-225857). etc). However, in this method, in order to prevent the occurrence of sparks when transferring from a conveyor to another conveyor, it is necessary to provide a zone for controlling the elevation of the voltage at the entrance and exit of the high voltage application area. The equipment becomes large-scale. Further, the voltage raising / lowering control is generally troublesome.

Some of the above-mentioned coating methods are coating methods in which a coating machine is kept grounded and a high voltage is applied to an object to be coated to electrostatically coat it with a water-based coating. This coating method corresponds to electrostatic coating in a broad sense, but it is a method of applying a high voltage to the conventional general electrostatic coating method in which the paint is atomized / sprayed by applying a high voltage to the coating machine. Is basically different. In this specification,
For the sake of convenience, the above-mentioned new coating method will be referred to as a work electrification coating method.

However, the conventional work electrification coating method has various drawbacks as described above.
Therefore, in the painting of automobile bodies, the above-mentioned drawbacks such as the occurrence of sparks and the enlargement of equipment do not occur,
Further, it has been a serious technical problem to develop a new coating system capable of surely performing electrostatic coating with a water-based coating material by applying a high voltage to an automobile body.

The inventors of the present invention have conducted extensive research, and as a result, have reached the stage where they can propose and develop a novel work electrification coating system that can solve this problem. The work electrification coating system, as disclosed in Japanese Patent Application No. 7-61809 and Japanese Patent Application No. 7-61810, has a coating machine installed near the endless slat conveyor and serves as a primary circuit for electromagnetic induction. The guide path is installed in the conveying direction of the slat conveyor, and a pickup coil serving as an electromagnetic induction secondary circuit is attached to the conveyor slat so as to face the guide path in a non-contact manner, and an electrode attachment is attached to the slat. It is a system that is installed on top in an insulated state and further equipped with a high voltage generator on the slat, boosting the electromotive force generated by electromagnetic induction of the induction path and the pickup coil,
By supplying it to the electrode attachment, the required high voltage is applied to the mounted object to be coated, and at the same time, the water-based paint is discharged or sprayed from the coating machine to perform electrostatic coating. It is a thing.

[0011]

However, when actually introducing the above-mentioned work electrification coating system into an automobile factory, not a test plant, for painting an automobile body, a high quality coating film is formed. Therefore, it is necessary to thoroughly study the properties and performance of the water-based paint used for painting.
That is, the suitability for coating of water-based paint has emerged as the next issue. Among the water-based paints, metallic paints and the like can form sufficiently high-quality coating films, but clear paints for forming topcoats are of sufficiently high quality at the current technical level known to the inventor. There are no water-based paints that can form coatings. Among the clear paints, water-based powder paints have been developed, but the paint film quality thereof has not yet fully met the quality conditions required for paint films of automobile bodies. Therefore, at present, solvent-based clear paints are used for top coats of automobile bodies. The application of such clear paint has to be continued for the time being. In addition, it is more preferable that the base coating film and the clear coating film are continuously formed in the top coating (metallic) coating of an automobile body.

Therefore, the present invention has been made in view of the above circumstances, and its purpose is to apply a work electrification coating method and to apply a base to the surface of an object to be coated such as an automobile body. It is to provide a coating method capable of continuously forming a coating film and a clear coating film.

[0013]

The present invention utilizes the equipment of a newly proposed work electrification coating system to provide work electrification painting using an aqueous metallic paint, flash-off, and solvent-based clear paint. The present invention relates to a coating method in which the usual electrostatic coating used is sequentially performed in a series of processes.

Specifically, the coating method according to the present invention is a coating system having three consecutive zones, namely a work electrification coating zone, a flash-off zone and an electrostatic coating zone,
An endless slat conveyor installed substantially horizontally from the work-applied coating area to the electrostatic coating area, and an insulator standing upright on the slat surface of the conveyor and having an electrode attachment mounted thereon. A support means capable of mounting an object to be coated or a trolley thereof on the object to be energized; a grounded coating machine arranged near the slat conveyor in the workpiece electrification coating area; and the flash-off A flash-off facility for radiating and / or hot-air heating an object to be coated mounted on the slat conveyor, which is provided in the area, and an electrostatic coating machine arranged near the slat conveyor in the electrostatic coating area. , Between the upper and lower slat rows of the slat conveyor, a guideway formed along the transport direction, and on the back surface of the slat of the conveyor. A pickup coil mounted so as to face the induction path in a non-contact manner, and an electromotive force generated by electromagnetic induction of the induction path and the pickup coil, which is provided on the slat of the conveyor, are converted into a required high voltage current. A high voltage generator for supplying it to the electrode attachment based on the operation of a controller, and a ground switch provided on the slat of the conveyor and capable of short-circuiting a high voltage output part of the high voltage generator and a ground part. And controlling the spraying operation of the paint from the grounded coating machine and the on / off operation of high voltage application to the object to be coated, and controlling the spraying operation of the paint from the electrostatic coating machine, and When an object to be coated is mounted on the slat conveyor and conveyed by using a coating system including an automatic control device for controlling the operation of the ground switch. Moni, by way of the following steps (a) to step (c), relates to a method for coating the object to be coated. (a) In the work electrification coating area, keep the grounding switch operative when necessary, and apply a high voltage to the object to direct the aqueous metallic paint from the grounded coating machine to the object to be coated. To form a base coating film on the surface of the object to be coated by spraying by spraying (b) Next, in the flash-off area, the surface of the object to be coated is radiated and / or heated with hot air without applying a high voltage. By doing so, the step of drying and solidifying the base coating film is performed. (C) After that, in the electrostatic coating area, the ground switch is always kept in the operating state, and a high voltage is applied to the electrostatic coating machine to clear the solvent system. Forming a clear coating film on the base coating film of the work by spraying the paint from the electrostatic coating machine toward the grounded work

A coating system for using the coating method of the present invention is a coating system having three consecutive zones, namely, a work electrification coating zone, a flash-off zone and an electrostatic coating zone, which is an endless slat conveyor. Is installed substantially horizontally from the work electrification coating area to the electrostatic coating area, and the object to be coated or its carriage is mounted on the conveyor by the supporting means so that the object to be coated can be energized. In addition to making it possible to convey in the vertical direction, in the work electrification coating area, in addition to a coating device equipped with a coating machine, equipment for electrification of the work such as a high voltage generator on the conveyor is provided. In the flash-off area, equipment for flash-off such as radiant panel and hot air outlet is installed.
Further, in the electrostatic coating area, the coating system is provided with equipment for electrostatic coating such as a coating device equipped with an electrostatic coating machine.

The endless slat conveyor is a conveyor for transporting an object to be coated and is installed substantially horizontally in the coating booth. The structure is a general slat consisting of two (or three or more) parallel endless chains, sprockets on both ends of each chain, and a large number of slats stretched between the chains. A conveyor structure is sufficient. As a more preferable aspect, a jet of pressurized water (or pressurized air) is attached to the lower side of the slat conveyor, and the jetting of pressurized water or the like toward the insulator on the slat makes it possible to wash them. A certain configuration is adopted. As the slats, blind plate slats are usually used, but if they can support the insulator, each component of the high voltage generator, the wireless transceiver, etc., a part or the whole of the slats. May be finished into a structure similar to a perforated plate, a lattice plate or a punching metal plate, and a part of the slats may be cut out.

The supporting means is a means for mounting and supporting an object to be coated (or a dolly on which it is mounted) such as an automobile body, and mounting them so that the object to be coated can be energized. , Insulator and electrode attachment. The insulator has, for example, a pillar shape, and is erected on the slat surface of the slat conveyor, usually one or two in the front and rear in the case of an automobile body. The electrode attachment is a conductive (metal) jig that is mounted on the insulator and is configured so that it can be energized when an object to be coated such as an automobile body is mounted. There is. Therefore, since the electrode attachment is mounted on the slat conveyor in an insulated state, even if a high voltage is applied to the electrode attachment, current does not leak to the surface of the slat conveyor. In addition, an appropriate number of sets of insulators and electrode attachments corresponding to one object to be coated are provided on the slat surface of the slat conveyor according to the length of the object to be coated and the total length of the slat conveyor.

Next, the equipment in the work electrification coating area will be described in more detail. The equipment is Japanese Patent Application No. 7-61809,
It may be a modification of the coating system shown in Japanese Patent Application No. 7-61810 and the like, and a typical work electrification coating system is, in addition to the above slat conveyor and supporting means,
A grounded coating machine arranged near the slat conveyor, and a guideway formed along the transport direction between the upper and lower slat rows of the conveyor at least in the work electrification coating area, and the conveyor. A pickup coil mounted on the back surface of the slat so as to face the induction path in a non-contact manner, and an electromotive force generated by electromagnetic induction of the induction path and the pickup coil, which is provided on the slat of the conveyor, are set to a required high level. A high voltage generator for converting the voltage into a current and supplying it to the electrode attachment based on the operation of the controller; and a high voltage output part and a ground portion of the high voltage generator provided on the slat of the conveyor. A grounding switch that can be short-circuited, a spraying operation of the paint from the painting machine, and a high-voltage mark on the object to be painted, which are arranged outside the painting booth. And an automatic controller for controlling the on / off operation of the conveyor, and more preferably, one transceiver is mounted on the slat of the conveyor, and the other transceiver is connected to the automatic controller outside the coating booth. ,
Performing electrostatic coating with water-based paint by applying high voltage to the object to be coated, which comprises two sets of wireless transceivers that enable bidirectional communication between the controller of the high-voltage generator and the automatic controller It is a painting system.

Further, each element used in this work electrification coating system will be described in sequence. The coating machine is appropriately placed near the slat conveyor in the coating booth and kept grounded. This coating machine includes a top reciprocating coating apparatus, a side reciprocating coating apparatus, and a built-in coating robot. The coating machine used in the present invention uses a water-based metallic coating as a coating, and is used in a state where the coating machine itself is grounded.
As the coating machine, either an electrostatic coating machine or a non-electrostatic coating machine can be used.

The guide path serves as a primary circuit for electromagnetic induction, and is formed along the conveying direction between the upper and lower slat rows of the slat conveyor in at least the work-applied coating area. The guideway is, for example, a structure in which an appropriate number of columns are arranged at intervals, and a multicore cable is supported and erected on the columns along the transport direction (usually in parallel). Often, the pickup coil is supplied with low power (e.g., single-phase AC 300V to 600V, 10kHz in the case of painting automobile bodies) to the extent that the electromotive force required as the primary power source of the high-voltage generator is generated by electromagnetic induction. The configuration may be more supplied. Therefore, since a strong electrostatic field is not formed between the taxiway and the coating machine, and since there is a slat between them, it is considered that the paint mist from the painting machine is not electrostatically applied to the taxiway. To be

The pickup coil serves as a secondary circuit for electromagnetic induction, and is arranged on the back surface of the slat of the slat conveyor, for example, at a position between the front and rear insulators, and so as to face the guide path in a non-contact manner. Mounted. Therefore, the pickup coil runs along with the slat by the operation of the slat conveyor, and at this time, the electromotive force is generated by electromagnetic induction with the guideway (in the case of painting the car body, for example, single-phase AC 50V-100V, 10kHz). Results in
This current is output to the high voltage generator. This system has a structure in which the guide path and the pickup coil are opposed to each other in a non-contact manner, so that the electromotive force generated by electromagnetic induction is always stable and high voltage while the pickup coil is opposed to the guide path. It can be supplied to the generator. Therefore, it is possible to automatically apply and stop the high voltage to the object to be coated by the on / off operation of the high voltage generator without performing the conventional voltage raising / lowering control in the entrance / exit zone of the high voltage applying region. it can.

The high-voltage generator uses the electromotive force generated by the electromagnetic induction of the induction path and the pickup coil as a primary power source, boosts this to convert it into a required high-voltage current, and uses this as the above-mentioned electrode attachment. The feeding device is installed on the slat surface of the slat conveyor or on the back surface of the slat. This generator is generally composed of a transformer unit, a controller and a high voltage generator. Also, usually several sets of high voltage generators are assembled on one slat conveyor so that simultaneous electrostatic painting is possible.

The substation unit is a device for adjusting the electromotive force current from the pickup coil to a current suitable for the primary power source to the controller (usually a low frequency current of 60 Hz or 50 Hz). For example, the electromotive force from the pickup coil is adjusted. It consists of a terminal block that collects current, a power receiving box that performs AC / DC conversion, and an inverter.

The controller is a control device connected between the substation unit and the high voltage generator for performing on / off control of high voltage application, and a predetermined control signal (for example, 1
2V or 24V DC signal) is sent to the high voltage generator, and the applied voltage / current and leakage current are monitored. Therefore, the controller generally includes an on / off control circuit for applying a high voltage, a monitor circuit for the applied voltage / current, and the like. Since the high-voltage generator is a high-voltage generator, it is more preferable to take appropriate explosion-proof measures for it. Therefore, more preferably,
The high voltage generator, in particular the controller and the transformer unit (inverter etc.) is housed in an explosion proof casing.

The high voltage generator includes a high frequency pulse oscillator, a transformer, a voltage doubler rectifier circuit (cock croft circuit), etc., and receives a voltage signal from the controller to obtain a required high voltage current (in the case of painting an automobile body, a high voltage current). , For example, -60
kV to -150 kV (or +60 kV to +150 kV), 40
It is a device that generates 0 μA). It should be noted that whether to apply a positive high voltage or a negative high voltage to an object to be coated such as an automobile body should be appropriately selected according to the shape of the object to be coated, the installation condition of the coating device, etc. You can
Also, more preferably, the high voltage generator is mounted inside the insulator on the slat such that its connection terminal is connected to the electrode attachment. In particular, it is more preferable that the high voltage generator is loaded inside the insulator, and at the same time, the connection terminal is directly (without a wiring cord) electrically connected to the electrode attachment. The loading method is not particularly limited, but as the method, for example, (a) a bore having an appropriate capacity is formed inside the insulator, and the miniaturized high voltage generator is housed in the bore. , A method of filling the gap between the high voltage generator and the peripheral wall of the bore with insulating oil, (b) filling the bore with an insulating resin,
Further, a method of embedding a high voltage generator in the resin, (c)
A method of accommodating a high voltage generator in a protective casing and accommodating it in an insulator, and (d) embedding the high voltage generator circuit of the high voltage generator inside the insulator,
There is a method of omitting the loading of the housing of the high voltage generator.

The grounding switch is a device that can be turned on or off to short-circuit the high-voltage output section (high-voltage generator) and the grounding part to lower the applied voltage to the grounding voltage. To ensure system safety,
Provided on the conveyor slats with a high voltage generator. As the grounding switch, a mechanical grounding switch including a solenoid or the like, a recent electronic switch, or a combination thereof is used. The ground switch used in the present invention may also be referred to as a high voltage cutoff switch. In particular, in the coating method of the present invention, the grounding switch can be turned on (or off) when necessary in the work electrification coating area so that the high voltage generator and the ground portion can be short-circuited. In addition to being configured, the electrostatic coating area is always on (or off) in an operating state, and the object to be coated is always kept at the ground voltage state. The flash-off area may be either a structure capable of being operated when necessary in the work electrification coating area or a structure of being constantly operating in the electrostatic coating area. When it is necessary to operate the grounding switch in the work electrification coating area, for example, when the leakage current from the electrode attachment to the slat increases, or when a grounded coating machine, etc. This is when an abnormal voltage is generated due to an abnormal approach, or when the required high voltage is not applied for some reason.

Further preferably, the ground switch is
Inside the insulator on the slat, its connecting terminal is loaded so as to connect with the electrode attachment. In particular, it is more preferable that the ground switch is loaded inside the insulator and the connection terminal is directly (not via the wiring cord) and electrically connected to the electrode attachment. The loading method is not particularly limited, and examples thereof include (a) a bore having an appropriate capacity is formed inside the insulator, and a small grounding switch is housed in the bore, and a grounding switch is provided. And (b) filling the insulating resin in the bore and then burying the grounding switch in the resin, (c) grounding switch Housed in a protective casing,
There are a method of putting this in an insulator, and a method of (d) embedding the switch circuit of the earthing switch inside the insulator so as to omit loading of the housing of the earthing switch and the like.

The automatic control device is usually a control device incorporated in a computer, and relates to the overall control of the operation of the system, for example, the operation of the slat conveyor and the power supply to the guide path, and the application of a high voltage to the object to be coated. This is an apparatus for automatically controlling the on / off operation and the operation of each coating machine related to spraying the paint, and the operation of the electrostatic coating machine in the following electrostatic coating area and the operation of a coating apparatus including the same. The automatic control device may be a single-system control device, but may be separately provided with an automatic control device for various controls in the work electrification coating area and an automatic control device for various controls in the electrostatic coating area. . Further, the automatic controller may incorporate a controller for radiant heating and / or hot air heating in the flash-off zone. Since the high voltage is applied in the coating area, the automatic control device is more preferably arranged outside the coating booth.
The automatic control device includes, for example, a means for sensing the mounting of the object to be coated (for example, a set of a light projector and a light receiving sensor), and a mechanism (a pulse oscillator etc.) for generating a pulse having a pulse number proportional to the traveling distance of the slat conveyor. Each of them is connected to each other, and more preferably, the automatic control device for various controls in the work electrification coating area is capable of bidirectional communication with the controller on the slat conveyor via the following wireless transceiver. Composed.

Further, one of the two sets of radio transceivers is
It is mounted on the slats of the slat conveyor and is connected to the controller of the high voltage generator. The other wireless transceiver is connected to an automatic control device outside the coating booth. As a result, the present coating system is configured to enable two-way communication between the controller on the slat and the automatic control device outside the coating booth via these two sets of radio transceivers. That is, an on / off signal for high voltage application (or an operation signal for the ground switch), etc. is transmitted from the automatic control device outside the coating booth, and the controller on the slat conveyor receives these signals, while the slat conveyor receives the signals. From the controller above,
Each monitor signal such as the voltage / current value (and leakage current value) that is actually applied is transmitted, and the automatic control device outside the coating booth receives these signals. The automatic control regarding the application can be performed.

As a radio transmitter / receiver, one device can simultaneously (digital or analog) transmit / receive (duplex system)
A wireless device may be used, but a wireless device dedicated to transmission and a wireless device dedicated to reception may be used in combination. In addition, as the communication means, in addition to radio wave (frequency of 3000 GHz or less, more preferably electromagnetic wave of 30 kHz to 30 MHz) communication, microwave communication, optical communication (for example, using visible light or infrared light), or sound wave communication (for example, Ultrasonic waves) may be used. Optical communication is more preferable than radio communication in that it is less likely to suffer electromagnetic interference and that the explosion-proof structure is easier. In the case of radio communication, a general radio equipped with an antenna and an electric circuit for radio communication is used, and in the case of microwave communication, a radio equipped with a waveguide or a cavity resonator in a transmission / reception circuit. Is used,
Further, in the case of optical communication, a radio having a combination of a light emitter (beam emitter) and a light receiver (beam light receiver) is used.

Next, the flash-off equipment will be described. The equipment comprises a radiant panel capable of radiant heating, a hot air outlet capable of hot air heating, a hot air supply mechanism, and the like.
Any material can be used as long as it can flash off by evaporating water from the coating film of the water-based metallic coating material formed by the work electrification coating. More preferable equipment is such that, at the entrance side of the flash-off area, a radiant panel is arranged around the object to be coated mounted on the slat conveyor, and radiant heat from the panel is applied to the surface of the object to be coated. And, on the exit side of the flash-off area, a hot air outlet is provided toward the object to be coated on the conveyor, and the hot air supply mechanism is operated so that the hot air blows against the surface of the object to be coated. Is a facility capable of first radiantly heating the surface of the coated object and then hot air heating. Further, since the flash-off area is a high temperature area, the equipment such as the high-voltage generator, the insulator and the electrode attachment on the slat conveyor may be malfunctioned or damaged by heat. Therefore, more preferably, a heat shield member such as an aluminum reflector is disposed so as to be interposed between the equipment on the slat conveyor and the radiation panel and the hot air outlet.

Finally, the equipment for electrostatic coating will be described. The equipment places the electrostatic coating machine near the slat conveyor toward the object to be coated which is carried on it, and the high voltage is applied. By applying to the electrostatic coating machine, the solvent-based clear paint is discharged from the electrostatic coating machine toward the object to be coated,
Any equipment capable of spraying may be used, and any equipment conventionally used for electrostatic coating, such as a top reciprocating coating apparatus, a side reciprocating coating apparatus, or a coating robot, is used for the method of the present invention. be able to.
In the electrostatic coating area, as described above, the object to be coated is always kept grounded by the operation of the ground switch.

[0033]

In the method of the present invention, electrostatic coating is performed by the following process. The operation of the endless slat conveyor causes the slat to travel, and an object to be coated such as an automobile body mounted on the slat is conveyed in the length direction of the conveyor. Then, during the transfer of the object to be coated, at the first stage, by applying a high voltage to the object to be coated according to the work electrification coating method,
The water-based metallic paint is sprayed toward the object to be coated from a grounded coating machine, and a base coating film is formed on the surface of the object to be coated. At this stage, that is, while the object to be coated is in the work electrification coating area, the grounding switch is kept operable when necessary. Then, by flash-off, the surface of the coated object is radiated and / or heated with hot air, and the base coating film is dried and solidified. The heating in this case is performed under the condition that a high voltage is not applied. Then, in the subsequent steps, by applying a high voltage to the electrostatic coating machine, the solvent-based clear coating is sprayed from the electrostatic coating machine to the grounded object according to a general electrostatic coating method. Therefore, a clear coating film is formed on the base coating film of the object to be coated. At this stage, that is, while the object to be coated is in the electrostatic coating area, the ground switch is always kept in the operating state (grounding state).

[0034]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are views showing the whole of a coating system suitable for using the coating method of the present embodiment, and FIGS. 3 to 5 are main parts of a work electrification coating facility in the coating system. Indicates. FIG. 6 and FIG. 7 are cross-sectional views showing the insulator and its surroundings of this work electrification coating facility.
FIG. 8 shows the inside of the radiant heating furnace of the flash-off equipment of the coating system.

The above coating system is an electrostatic coating system for automobile bodies, and as shown in FIGS.
The coating booth 10 is divided into three areas: a work electrification coating area A, a flash-off area B, and an electrostatic coating area C. At the lower part of the long coating booth 10, one endless slat conveyor 1 is installed substantially horizontally over the above three areas A, B and C, and the conveyor slat conveyor 1 was mounted on the conveyor slat conveyor 1 by the operation of the conveyor 1. The automobile body 20 is conveyed (in the direction of arrow P in the figure). The endless slat conveyor 1 has two parallel endless chains 9 and 9 with sprockets 17 and 1, respectively.
7 (FIG. 1), and a large number of slats 2 ... Are stretched between the two chains 9 and 9 (see FIG. 4). Therefore, slat rows 3 and 3 are formed vertically. (Fig. 1).

Further, as shown in detail in FIGS. 3 to 5, on the surface of the slat 2 of the slat conveyor 1, insulators 4a and 4b are erected as support means, and
Electrode attachments 5 are mounted on them. These members are means that can support the trolley 21 on which the automobile body 20 is mounted, and at that time, enable electric conduction from the electrode attachment 5 to the automobile body 20. An appropriate number of sets of the insulators 4a and 4b and the electrode attachments 5 are provided so as to correspond to each automobile body 20 to be coated. Insulator 4
Each of a and 4b has a pillar shape, and is provided on the surface of the slat 2, ... Also, the electrode attachment 5
Is an electrode member (made of metal) mounted on the insulators 4a and 4b, and is a carriage 21 on which the vehicle body 20 is mounted.
When is mounted on it, it can be energized. Therefore, since the electrode attachment 5 is mounted on the slat conveyor 1 in an insulated state, even if a high voltage is applied to the electrode attachment 5, current does not leak to the surface of the slat conveyor 1.

Next, the peculiar equipment of the work electrification coating area A will be described. As shown in FIGS. 1 and 2, a coating robot 22, a side reciprocating coating device 23, and a top reciprocating coating device 24 are sequentially installed near the slat conveyor 1 along the conveying direction. Each of these coating devices is constructed by incorporating a bell-type coating machine (not shown), and each coating machine is kept in a grounded state. Water-based metallic paint is supplied to all of the coating machines, and spraying (discharging) is possible. In these figures, 34
Is a turntable for loading the car body into the painting booth, and 35 is pressurized water (or pressurized air).
Shows a washer 28 that can be sprayed towards the surface of the slat 2 (outer surface of the conveyor).

Further, as shown in FIGS. 1 and 2, in the work electrification coating area, the electromagnetic induction as shown in FIGS. 3 to 5 is provided between the upper and lower slat rows 3 and 3 of the slat conveyor 1. The guide path 6 serving as a primary circuit is formed in a predetermined length along the transport direction. In this guide path 6, from the power supply, through the high frequency composite multi-core cable,
For example, a single-phase AC of 600 V and a low power of 10 kHz (power enough to generate the electromotive force required as the primary power source of a high-voltage generator in the pickup coil by electromagnetic induction) are supplied. Therefore, since a strong electrostatic field is not formed between the guideway 6 and the coating machine and is shielded by the slats 2 ..., The paint mist is less likely to be electrostatically applied to the guideway 6. .

On the back surface of the slat 2 of the slat conveyor 1, as clearly shown in FIG. 5, a pickup coil 7 serving as an electromagnetic induction secondary circuit is attached so as to face the guide path 6 in a non-contact manner. ing. Pickup coil 7
Is the front two insulators 4 as shown in FIGS. 3 and 4.
Between the a and 4a and the rear two insulators 4b and 4b, two pieces are provided side by side in the front and rear at a position near the rear insulator 4b. Therefore, the pickup coils 7 and 7 travel with the slat 2 by the operation of the slat conveyor 1,
At this time, since it opposes the induction path 6 in a non-contact manner, an electromotive current of, for example, a single-phase alternating current of 100 V and 10 kHz is generated by electromagnetic induction, and this can be output to the high voltage generator 8 described below.

As described above, in the work-apparatus coating system, the primary circuit and the secondary circuit of the electromagnetic induction are opposed to each other in a non-contact manner. While traveling oppositely (i.e., in the work electrification coating area), it is always stably output to the high voltage generator 8 described below.

The slat conveyor 1 is equipped with a high voltage generator 8 shown in FIGS. 3, 4 and 6.
The generator 8 generates an electromotive force generated by electromagnetic induction of the induction path 6 and the pickup coil 7 at a required high voltage current (-90
Boost conversion to kV (or +90 kV), 400 μA,
This is a device that supplies this to the electrode attachment 5 under the control of the controller 14, and includes a terminal block 11, a power receiving box 12, and an inverter 13 as a substation unit, and further includes a controller 14 and a high voltage generator 15
It is equipped with. Among these parts, the terminal block 11, the power receiving box 12, the inverter 13 and the controller 14 are
It is mounted on the surface of the slat 2 (FIGS. 3 and 4), while the high voltage generator 15 includes two front insulators 4
a, 4a, inside one of them, the connection terminal 4
1 is mounted so as to connect with the electrode attachment 5 (see FIG. 6). Several high voltage generators 8 are assembled on the slat conveyor 1, and simultaneous electrostatic coating is possible.

The terminal block 11 is a component that is connected to the two pickup coils 7, 7 and collects electromotive force from them. The power receiving box 12 is a component that is connected to the terminal block 11 and converts the collected electromotive force (AC) into DC.
Further, the inverter 13 is a component that is connected to the power receiving box 12 and that converts the converted DC current into AC again and modulates it. Thus, the electromotive force current from the pickup coils 7 and 7 is, for example, a low frequency current of 60 Hz,
The current is adjusted to match the primary power supply to the controller 14. The controller 14 is a control device connected between the inverter 13 and the high voltage generator 15 for on / off control of high voltage application, and has a predetermined control signal (for example, 12 V or 24 V DC). The signal) is sent to the high voltage generator 15, and the applied voltage value (or current value at that time) and the leak current value are monitored. The power receiving box 12, the inverter 13, and the controller 14 are all housed in an explosion-proof casing as an explosion-proof measure against a high-voltage generation source.

The high voltage generator 15 is a device including a high frequency pulse oscillator, a transformer, a voltage doubler rectifier circuit, etc., and receives a control signal from the controller 14 and is required for painting the automobile body 20. -60 kV to -150 kV
(Or +60 kV to +150 kV), for example, a high voltage current of 400 μA is generated, and this is output to the electrode attachment 5. This high voltage generator 15
As shown in FIG. 6, the upper surface is provided with a connection terminal 41 to which a high voltage current is output, and the lower surface is fixed with a terminal plate 42, which penetrates the inside of the insulator 4a. Housed in a cylindrical bore 40 formed by
It is fixed by a fixture 43 interposed between the inner peripheral wall of the insulator 4a and the terminal plate 42. Insulation oil 44 is filled in the space between the high voltage generator 15 and the inner peripheral wall of the insulator 4a in order to prevent current leakage. The insulator 4a
Are erected on a substrate 45 fixed to the surface of the slat 2. A connecting shaft 46, which is a round shaft with a flange, is fitted on the upper portion of the bore 40 of the insulator 4 a and is connected to the electrode attachment 5. Therefore, the high voltage generator 15
When is loaded in the insulator 4a, the connection terminal 41 is electrically connected to the electrode attachment 5 via the connecting shaft 46. A wiring cord 39 is connected to the terminal plate 42, which extends through the back side of the slat 2 and then passes through the slat 2 and is connected to the controller 14 on the front side, as shown in FIG. .

Further, as shown in FIG. 2, the present work electrification coating equipment is provided with an automatic control device 18 with a built-in computer outside the coating booth 10. This controller 18
In addition to operating the slat conveyor 1 and supplying power to the taxiway 6, the coating robot 22, the side reciprocating coating device 23
And the automatic control of the operation of the top reciprocating coating device 24 and the spraying (discharging) operation of the water-based metallic paint from each of the bell type coating machines incorporated therein, and the high voltage application on / off of the automobile body 20. It is a device that also performs automatic control of operations.

Further, in the present coating equipment, in order to control the operation of the high voltage generator 8, that is, to control the application of the high voltage to the automobile body 20, as shown in FIGS. 3 and 4, the wireless transmitter 30 and the wireless transmitter 30 are used. A receiver 31 is mounted on the surface of the slat 2 of the conveyor 1 in connection with the controller 14, while a wireless transmitter 32 and a wireless receiver 33, which are in communication therewith, are connected to the automatic controller 18 as shown in FIG. Then, it is installed in the same device. The transmitter 32 and the receiver 33
Is incorporated in the automatic control device 18 in the present embodiment, it may be provided in the explosion-proof case in the coating booth 10 and connected to the automatic control device 18.
Each of the wireless devices 30 to 33 is a communication device for radio waves having a frequency of 30 kHz to 30 MHz, which includes an antenna, a wireless communication circuit, and the like. Both the transmitter 30 and the receiver 31 on the surface of the slat 2 are operated by being supplied with power from the inverter 13, and the transmitter 30 operates with the monitor signal from the controller 14 (the voltage value / current value actually applied and The leak current value is wirelessly transmitted to the receiver 33 in the automatic control device 18, while the receiver 31 controls the control signal from the transmitter 32 in the automatic control device 18 (high voltage application ON / OFF signal or The operation signal of the ground switch) is sent to the controller 14. Therefore, this enables automatic control regarding application of a high voltage to the vehicle body 20. In the present coating system, the bidirectional multiple communication system is adopted so that the automatic control device 18 and the controllers 14 on the slat conveyor 1 can simultaneously transmit and receive.

Therefore, in the area A for applying electric power to the work, painting is performed by the following process. When the slat conveyor 1 is in operation, the slats 2 are moved, and the automobile bodies 20 are mounted on the electrode attachments 5 on the slats 2 in succession, which are continuously indicated by the arrow P.
Transport in the direction. At this time, an electromotive force is generated by the electromagnetic induction between the pickup coil 7 on the back side of the slat 2 and the guide path 6, and then this is generated by the high voltage generator 8 on the slat 2.
It is converted into a required high voltage current by the (high voltage generator 15) and is applied to the vehicle body 20 via the electrode attachment 5 under the control of the controller 14.
By applying this high voltage, the water-based metallic paint is atomized and sprayed toward the automobile body 20 from the coating machine (grounded) near the conveyor, whereby the base coating film of the water-based metallic paint is applied to each automobile body. It is formed on the surface of 20.

Next, the equipment in the flash-off area B will be described. As shown in FIGS. 1 and 2, the equipment is provided with a radiant heating furnace 25 on the inlet side and a hot air heating furnace 26 on the outlet side. Become. The radiant heating furnace 25, as shown in FIG.
.. are arranged so as to surround the automobile body 20 on the slat conveyor 1, and the radiant heat from the panel 27 is applied to the surface of the automobile body 20. The hot air heating furnace 26 is shown in FIGS.
, The hot air outlets 28 ... Are provided toward the automobile body 20 on the slat conveyor 1 so that the hot air from the outlet 28 hits the surface of the automobile body 20 by the operation of the hot air supply mechanism (not shown). It is configured. Therefore, in the flash-off area B, the work body electrified and coated on the automobile body 20 is conveyed by the slat conveyor 1, and at the same time, the surface of the body 20 is first radiantly heated and then hot air heated. There is. In addition,
In order to prevent malfunction and damage of the high voltage generator 8 and the like on the conveyor 1 due to high heat, the heat shield plate 29 made of an aluminum reflection plate is provided with the high voltage generator 8 and the radiant panel 27 or the hot air outlet. It is provided so as to intervene with 28.

Further, the equipment of the electrostatic coating area C will be described.
As shown in FIGS. 1 and 2, a coating robot 36, a side reciprocating coating device 37, and a top reciprocating coating device 38 are sequentially installed near the slat conveyor 1 along the conveying direction thereof. Each of these coating devices is equipped with a bell-type electrostatic coating machine (not shown), and solvent-based clear coating material is supplied to each coating machine to enable spraying (discharging). . Further, as shown in FIG. 2, an automatic control device 19 with a built-in computer is provided outside the coating booth 10. This control device 19
Relates to the operation of the coating robot 36, the side reciprocating coating device 37, and the top reciprocating coating device 38, and the paint spraying operation from each of the built-in electrostatic coating machines, that is, the running of the slat 2 of the slat conveyor 1. Then, the required high voltage is applied to each electrostatic coating machine to automatically control the operation of atomizing and spraying the solvent-based clear paint.

Further, in the present coating system, a grounding switch 16 is provided on the slat conveyor 1 to ensure safety. The ground switch 16 is the high voltage generator 8
This is a component that lowers the applied voltage to the ground voltage by short-circuiting the high voltage output part and the ground part. As shown in FIG. 7, the insulator 4a (the side on which the high voltage generator 15 is not loaded) is erected on the substrate 45 fixed to the surface of the slat 2, and the cylindrical bore 40 is provided therein. Are formed so as to penetrate therethrough. The ground switch 16 has the cylindrical bore 4
0, and the upper surface of which is provided with a protruding connecting terminal 41, while the lower surface of which is fixed with a terminal plate 42. A fixture 43 is interposed between the terminal plate 42 and the inner peripheral wall of the insulator 4a, whereby the ground switch 16 is fixed. In addition, in the gap between the ground switch 16 and the inner peripheral wall of the insulator 4a, insulating oil 44
Are filled. A connecting shaft 46, which is a round shaft with a flange, is fitted on the upper portion of the bore 40 of the insulator 4 a and is connected to the electrode attachment 5. Therefore, when the ground switch 16 is loaded inside the insulator 4 a, the connection terminal 41 is electrically connected to the electrode attachment 5 via the connecting shaft 46. A wiring cord 39 communicating with the high voltage generator 15 is connected to the terminal plate 42.

The ground switch 16 is composed of a combination of a mechanical ground switch including a solenoid and the like and an electronic switch.
In the work-applied coating area A, it is in an operable state when necessary, and when it receives a control signal from the controller 14, it operates and short-circuits the circuit of the high-voltage generator 15 to bring the applied voltage to the ground voltage. In the flash-off area B and the electrostatic coating area C, the vehicle body 20 is always operated and the vehicle body 20 is always kept at the ground voltage. The control signal from the controller 14 is issued when the leakage current from the electrode attachment 5 onto the slat 2 is increased, or when the coating machine approaches the automobile body 20 abnormally.

Therefore, in the above coating system, electrostatic coating is performed in the following process. The slat 2 runs by the operation of the slat conveyor 1, and the automobile body 20 mounted on the slat 2 is conveyed in the direction of arrow P.
Then, during this transportation, first, in the work electric-charging area A, a required high voltage is generated through the electrode attachment 5 by the operation of the high voltage generator 8 or the like.
Is applied to the surface of the automobile body 20 by atomizing and spraying the aqueous metallic paint toward the automobile body 20 from a grounded coating machine, and then a flash paint is formed on the surface of the automobile body 20. Off B
In the area, the painted car body 20 first receives radiant heat from the radiant panel 27 and subsequently the outlet 28.
The base coating film on the surface of the automobile body 20 is rapidly dried and solidified by being exposed to the hot air from, and then in the electrostatic coating area C, a predetermined high voltage is applied to the electrostatic coating machine to clear the solvent system. The clear coating film is formed on the base coating film of the automobile body 20 by atomizing and spraying the paint toward the automobile body 20. Therefore, the electrostatic coating can be performed very efficiently, and the coating film quality of the obtained coated product is sufficiently satisfactory.

[0052]

As described above, according to the coating method of the present invention, the work electrification coating method and the conventional electrostatic coating method are used in combination, on the surface of an object to be coated such as an automobile body, The base coating film of water-based metallic paint and the clear coating film of solvent-based clear paint can be continuously formed on it in one process. Therefore, highly efficient productivity and satisfactory coating film quality of coated products can be achieved. The effect that and are achieved is obtained.

[Brief description of drawings]

FIG. 1 is an overall view of a coating system suitable for using a coating method according to an embodiment of the present invention.

FIG. 2 is a view of the entire coating system shown in FIG. 1 viewed from above.

FIG. 3 is a front view showing a main part of a work electrification coating facility of the coating system shown in FIG. 1.

FIG. 4 is a plan view showing a main part of a work electrification coating facility of the coating system shown in FIG. 1.

5 is a side view of the main part of the work electrification coating facility shown in FIGS. 3 and 4. FIG.

FIG. 6 is a cross-sectional view showing one insulator and its surroundings of the work electrification coating facility shown in FIGS. 3 and 4.

7 is a cross-sectional view showing another insulator and its surroundings of the work electrification coating facility shown in FIGS. 3 and 4. FIG.

8 is a cross-sectional view showing the inside of a radiant heating furnace of the flash-off equipment of the coating system shown in FIG.

[Explanation of symbols]

 A Work electrification coating area B Flash-off area C Electrostatic coating area P Transfer direction 1 Slat conveyor 2 Slat 3 Slat row 4a 4b Insulator 5 Electrode attachment 6 Induction path 7 Pickup coil 8 High voltage generator 10 Coating booth 11 Terminal block 12 Power receiving box 13 Inverter 14 Controller 15 High voltage generator 16 Grounding switch 18 Automatic control device 19 Automatic control device 20 Automobile body (object to be coated) 21 Car body 22 Painting robot 23 Side reciprocating coating device 24 Top reciprocating coating device 25 Radiant heating furnace 26 hot air heating furnace 27 radiant panel 28 hot air outlet 30 wireless transmitter 31 wireless receiver 32 wireless transmitter 33 wireless receiver 36 painting robot 37 side reciprocating coating device 38 top reciprocating coating device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeki Fujiwara 1-9 Kakimoto-cho, Toyota-shi, Aichi Trinity Industry Co., Ltd.

Claims (1)

[Claims] 1. A coating system having three consecutive zones, namely, a work electrification coating zone, a flash-off zone and an electrostatic painting zone, which is substantially from the work electrification coating zone to the electrostatic coating zone. An endless slat conveyor installed horizontally, an insulator standing on the slat surface of the conveyor, and an electrode attachment mounted on the insulator, so that the object to be coated or its carriage can be energized to the object to be coated. Support means that can be mounted, a grounded coating machine that is arranged near the slat conveyor in the work electrification coating area, and an object that is mounted on the slat conveyor that is arranged in the flash-off area A flash-off facility capable of radiating and / or heating with hot air, and an electrostatic coating device disposed near the slat conveyor in the electrostatic coating area. Machine, a guide path formed between the upper and lower slat rows of the slat conveyor along the transport direction, and a pickup coil mounted on the back surface of the slat of the conveyor so as to face the guide path in a non-contact manner. And converting the electromotive force generated by electromagnetic induction of the induction path and the pickup coil provided on the slat of the conveyor into a required high voltage current, and supplying this to the electrode attachment based on the operation of the controller. A high-voltage generator, a grounding switch provided on the slat of the conveyor and capable of short-circuiting a high-voltage output part of the high-voltage generator and a ground part, and a spraying operation of the paint from the grounded coating machine, Controls on / off operation of high voltage application to an object to be coated, and controls spraying operation of paint from the electrostatic coating machine, and
A coating system comprising an automatic control device for controlling the operation of the ground switch is used to load and convey an object to be coated on the slat conveyor, and the next step
A method of coating an object to be coated by way of steps (a) to (c). (a) In the work electrification coating area, keep the grounding switch operative when necessary, and apply a high voltage to the object to direct the aqueous metallic paint from the grounded coating machine to the object to be coated. To form a base coating film on the surface of the object to be coated by spraying by spraying (b) Next, in the flash-off area, the surface of the object to be coated is radiated and / or heated with hot air without applying a high voltage. By doing so, the step of drying and solidifying the base coating film is performed. (C) After that, in the electrostatic coating area, the ground switch is always kept in the operating state, and a high voltage is applied to the electrostatic coating machine to clear the solvent system. Forming a clear coating film on the base coating film of the work by spraying the paint from the electrostatic coating machine toward the grounded work