JPH04166252A - Metallic coating method - Google Patents

Abstract

PURPOSE:To eliminate the uneven coating, and also, to secure the coating efficiency by coating with a metallic base paint by heightening discharge pressure of shaping air from a rotary atomization electrostatic coating machine, and lowering the pressure of the shaping air at the time of coating with a clear paint. CONSTITUTION:At the time of coating with a metallic base paint, pressure of shaping air discharged from a rotary atomization electrostatic coating machine M is set to high pressure for increasing the collision speed of metallic base coating grains onto an object W to be coated. Also, in order that a pitch in a reciprocating locus of the rotary atomization electrostatic coating machine M becomes a value set in advance, its reciprocating speed is controlled, based on the speed of the conveyor (b). Subsequently, at the time of coating with a clear paint, pressure of the shaping air is set to a value being lower than the value set at the time of coating with the metallic base paint. As a result, at the time of applying the rotary atomization electrostatic coating machine for metallic coating, uneven coating is not generated, and also, it contributes to resources saving and prevention of environmental pollution.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method of applying metallic paint to an object to be coated conveyed by a conveyor using a rotary atomizing electrostatic coating machine.

(Prior art) Rotary atomizing electrostatic atomizers can achieve higher coating efficiency than air atomizing electrostatic painting and airless atomizing electrostatic II painting, so they have recently been used for painting vehicle bodies, etc. It is becoming widely used. Fig. 8 shows a rotary atomizing electrostatic coating machine that has been commonly used in the past.A rotary shaft 3 is disposed inside the main body 1 and supported by an air bearing 2, and extends to the outside of the main body 1. An atomizing head 4 is fixed to the tip of the rotating shaft 3, and a head member 5 fixed to the tip of the main body 1 is provided with a large number of air outlets 6 for blowing out shaping air toward the outer peripheral edge of the atomizing head 4. Furthermore, a paint supply pipe 7 is disposed at the axial center in a non-contact state with the rotating shaft 3. In such a rotary atomizing electrostatic coating machine, the atomizing head 4 is now rotated at high speed by the driving means (path shown), and a high voltage is applied to the atomizing head 4, and paint is supplied from the S paint supply pipe 7. Then, the paint flows out from the hole 4a provided in the atomizing head 4 to the front surface, travels along the front surface to the outer peripheral edge, becomes π due to centrifugal force, and is charged at the same time, and is directed toward the object to be painted. fly and apply. At this time, the shaping air blown out from the air outlet 6 forms a coating pattern in a desired shape.

By the way, metallic painting consists of a step of applying a metallic base paint containing aluminum pieces and mica pieces to the first step, and a step of applying a transparent rear paint to ensure quality such as gloss following the above step. However, it is known that when a metallic base paint is applied with the above-mentioned rotary atomizing electrostatic coating machine, the finished appearance becomes significantly darker than when it is applied with an air atomizing coating machine. This is because the paint particles adhere to the surface to be painted mainly by electrostatic force, so the speed of the paint particles colliding with the surface to be painted is lower than that in air atomized electrostatic painting, and aluminum pieces and mica pieces are coated. For painted surfaces.

This is thought to be because it is difficult to arrange them in parallel.

Therefore, for example, Japanese Utility Model Application Publication No. 62-13557 or Japanese Patent Application Publication No. 1-315361 K discloses that the pressure of shaping air is increased to increase the collision speed of coating particles on the surface of the object to be coated, thereby reducing the brightness of the metallic coating surface. A coating method has been proposed that increases the quality of the paint, and has achieved some degree of effectiveness.

On the other hand, when painting objects that have a wide coating area, such as vehicle bodies, in order to improve coating efficiency (productivity), it is usually necessary to The paint sprayer is moved in reciprocating motion in a direction perpendicular to the direction. Therefore, even when applying metallic coating to objects with a wide coating area using the rotary atomizing electrostatic coating machine, it is a matter of course that the coating machine must be moved in a reciprocating motion. becomes.

(Problems to be Solved by the Invention) However, according to the coating methods disclosed in the above-mentioned publications, as a result of increasing the pressure of the shaping air, negative pressure is generated in the front region of the atomizing head. Paint particles were attracted to the negative pressure area, resulting in a narrow coating pattern width. In other words, this reduction in coating pattern width means that the coating efficiency of the paint is improved, and the above-mentioned coating method If you apply S reciprocating paint directly to paint a metallic base paint, the boundaries of the paint pattern will clearly appear due to slight fluctuations in conveyor speed, making it easy to cause so-called paint unevenness. On the other hand, when applying the clear paint following the application of the metallic base paint, there is no restriction on the shaping air pressure, so a rotary atomizing electrostatic atomizer is not required. However, since the application of both types of paint is carried out consecutively in the same painting booth, using different paint machines for different paints would be troublesome in terms of equipment layout or equipment management. In order to unify paint machines, we had no choice but to rely on air atomizing electrostatic atomizers for painting.In other words, conventional metallic painting generally had to rely on air atomizing electrostatic atomizers. In this case, since the coating efficiency is lower than when using a rotary atomizing electrostatic coating machine, not only is an increase in the amount of paint used unavoidable, but also pollution caused by the diffusion of organic solvents due to the increased amount of paint used. Countermeasures were needed, and there were many problems.

The present invention was made with the aim of solving the above-mentioned conventional problems, and its purpose is to prevent coating unevenness and save resources when applying two rotary atomizing electrostatic coating machines to metallic coatings. The object of the present invention is to provide a coating method that contributes to the prevention of pollution.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention reciprocates a coating machine by moving a rotary atomizing section in a direction perpendicular to the conveying direction of the object being conveyed by a conveyor. In a metallic painting method in which a metallic base paint is applied first and then a clear paint is applied, when applying the metallic base paint, the pressure of shaping air discharged from the rotary atomizing electrostatic coating machine is applied to the object to be painted. setting a high pressure to increase the collision speed of the metallic base coating particles, and controlling the reciprocating speed based on the conveyor speed so that the pitch in the reciprocating trajectory of the rotary atomizing electrostatic coating machine becomes a preset value, The present invention is characterized in that, when applying the clear paint, the pressure of the shaping air is set to a lower value than the value set when applying the metallic base paint.

(In the metallic coating method configured as above,
When applying metallic base paints, by setting the pressure of the shaping air discharged from the rotary atomizing electrostatic coating machine to a high pressure that provides the desired brightness of the painted surface, the collision speed of the paint particles on the surface of the object to be painted is increased. The brightness of the painted surface will increase. Similarly, when applying metallic base paint, the reciprocating speed of the rotary atomizing electrostatic coating machine is controlled based on the conveyor speed so that the reciprocating locus and pitch of the rotary atomizing electrostatic coating machine become a preset value. Even when painting is performed under conditions where the pressure is increased and the width of the coating pattern is narrowed, the occurrence of uneven coating can be suppressed. Moreover, since the pressure of shaping air is lowered when applying the clear paint, the width of the painting pattern can be expanded as much as possible, making it possible to perform painting with high efficiency.

(Example) Hereinafter, an example of the present invention will be described based on the accompanying drawings.

Figure 1.2 shows a schematic configuration of equipment for carrying out the coating method of the present invention. In Figure 1.2, a represents a painting booth, and b represents a conveyor for conveying the automobile body W. In the one shown in Figure 1, station A for painting metallic base paint and clear paint are placed in painting booth a. Stations B for painting are provided at appropriate intervals, and in the case shown in Figure 2, a station C for painting the metallic base paint and the painting of the clear paint is placed at one location in the painting booth a. is provided. Each station A to C includes a horizontal surface coating device C for painting horizontal surfaces such as the hood and roof of the automobile body W;
A vertical surface coating device d is provided for painting the side surfaces of side members, doors, etc. Each coating device c, d is a rotary atomizing electrostatic coating machine (hereinafter referred to as
(simply referred to as a coating machine) M, and this coating machine M
It has a function of being able to move in a direction perpendicular to the transport direction of the automobile body W.

The equipment shown in Fig. 1 is applied to mass production, and first, a metallic base paint is applied to an automobile body W conveyed at a predetermined speed by a conveyor b at a station A using coating devices c and d. Then, at station B, clear paint is applied by separate coating devices c and d. On the other hand, the equipment shown in Fig. 2 is applied to small-volume production, and first the car body W is passed through station C by conveyor b, and then the car body W is sent for painting! Coating with metallic base paint is performed by units c and d, and then the conveyor b is reversed to cause the automobile body W to pass through station C again, where it is coated with clear paint by the same coating units c and d.

According to the coating equipment shown in FIG. 2, the coating equipment c
, d can be shared, reducing equipment investment costs.

Therefore, when applying the metallic base paint, the pressure of the shaping air discharged from the coating machine M is set to a high pressure that increases the collision speed of the metallic base paint particles against the object to be painted and obtains the desired brightness of the painted surface. At the same time, the reciprocating speed of the coating machine M is controlled based on the speed of the conveyor b so that the pitch in the reciprocating locus of the coating machine M becomes a preset value. is set to a lower value than the value set when applying the metallic base paint. By performing metallic coating in this way, when applying the metallic base paint, the collision speed of the metallic base coating particles on the surface of the object to be coated increases, and the alignment of the coating particles becomes parallel and even, so the brightness of the painted surface increases. is increased, and the pitch in the reciprocating locus of the atomizer M becomes a preset value, so even if the pressure of the shaping air is increased and the coating pattern width is narrowed, uneven coating is less likely to occur. Moreover, when applying the clear paint, the pressure of the shaping air is lowered, so the width of the painting pattern is expanded as much as possible, and efficient painting can be performed.

Hereinafter, specific embodiments of the present invention will be described based on FIGS. 3 to 7.

3 and 4 show the specific structure of the horizontal surface coating apparatus C. In both figures, reference numeral 11 denotes a first reciprocator for reciprocating the two coating mms arranged in a direction perpendicular to the conveyance direction of the automobile body W in the same direction. This first reciprocator 11 is supported by two cylinders 13 provided on a frame 12 installed on the ceiling, and is movable in the vertical direction. The first reciprocator 11 includes a support member 14 that supports the two paint sprayers M, a guide member 16 that horizontally slides and guides a slide member 15 extending upward from the support member 14, and a slide member 16. Rotating cam mechanism 1 that drives I5
It consists of 7. The rotating cam mechanism 17 includes a motor 18
The plate cam 19 is provided with a disc-shaped plate cam 19 that is rotationally driven by the plate cam 19, and the slide member 15 is attached to an eccentric portion of the plate cam 19.
One end of the link 20 is pivotally attached to the link 20, and the other end of the link 20 is pivotably attached to the link 20.

When the plate cam 19 rotates, the rotation is transmitted to the slide member 15 via the link 20, and the slide member 15
move along the guide member 16, and the support member 14, that is, the two paint machines M, come to perform reciprocating motion in a direction perpendicular to the conveyance direction of the automobile body W. When the paint sprayer M is reciprocated in accordance with the movement of the automobile body W, the reciprocating locus of the center of the atomization head (indicated by reference numeral 4 in Figure 8) of the paint sprayer M is as shown in Figure 6. It becomes a waveform (actually a sine curve shape). In this embodiment, in order to control the pitch S in this reciprocating trajectory (hereinafter referred to as reciprocating pitch) to a preset value, a sensor 21 that detects the conveyance speed of the automobile body W, that is, the speed of the conveyor b, A control device 22 is separately installed which receives signals from the sensor 21 and outputs signals for controlling the rotation speed of the motor 18.

On the other hand, the vertical surface coating device d includes a second reciprocator for reciprocating the two coating machines M arranged in the conveyance direction of the automobile body W in a direction perpendicular to the conveyance direction, as shown in FIG. It is equipped with 31. The second reciprocator 31 includes a support member 32 that supports the two atomizers M so that their atomizing heads face the side surface of the automobile body W;
It has a chain 33 that drives this support member 32 in the vertical direction. The chain 33 is wound around a pair of sprockets 34 and 34 arranged in the vertical direction, and one of the sprockets is driven by a motor 35 to rotate the chain 33 to the left or to the right. The support member 32
is connected to one side of this chain 33 so as to face in the horizontal direction, and when the chain 33 is rotated to the left or right by the operation of the motor 35, this connection part moves arbitrarily in the vertical direction and follows this movement. Painting machine M is used for car body W
reciprocating motion in the direction perpendicular to the transport direction. The atomizer M is connected via a link 38 to a movable body 37 that moves along a guide rail 36 that is curved to follow the curved shape of the side surface of the automobile body W, and is atomized during the reciprocating movement. The posture of the head is controlled so that it always faces the side surface of the automobile body W.

Then, when the coating machine M is moved in a reciprocating manner in accordance with the movement of the automobile body W, the two coating machines M (Ml, M
The reciprocating trajectories centered on the atomizing head of z) come to overlap each other as shown in FIG. In this embodiment, in order to control the pitch S' in the shiburo trajectory to a preset value, a signal from the sensor 21 that detects the speed of the conveyor b is inputted to the motor 35.
A control device 22 that outputs a signal for controlling the rotation speed of the
' is installed separately.

Hereinafter, the metallic coating method of the present invention using the above-mentioned coating equipment will be explained separately for the case using the horizontal coating device C and the case using the vertical coating device d.

When applying a metallic base paint using the horizontal surface coating device C, the pressure of the shaping air discharged from the coating device M is set high so as to obtain the desired brightness of the painted surface.
Ideal reciprocating pitch S (6th
) is determined in advance through experiments, and this value is stored in the control device 22. During painting, the speed K of the conveyor b is input from the sensor 21 to the control device 22, and the control device 22 uses the formula R=
Painted according to /S $14 reciprocating speed R (
The number of times/m1n) is calculated, and a control signal corresponding to this reciprocating speed R is output to control the rotation speed of the motor 22 (FIG. 3) of the first reciprocator 11. As a result, the coating machine M performs a reciprocating motion on the automobile body W conveyed by the conveyor b at a reciprocating speed R that is a preset reciprocating pitch S, and under this condition,
If the metallic base paint is supplied to the coating machine M, the overlapping of the coating patterns on the upper surface of the automobile body W will be proper, and uneven coating will not occur.

On the other hand, when applying a metallic base paint using the vertical surface coating device d, the pressure of the shaping air discharged from the coating device M was set high so as to obtain the desired brightness of the painted surface, and the coating was performed under these conditions. The ideal reciprocating pitch S' (FIG. 7) is determined in advance through experiments, and this value is stored in the control device 22'. When painting, the speed K (cm/m
1n) is taken into the control device 22', and the control device 22' adjusts the reciprocating pitch S' to this conveyor speed.
(cm), calculate the reciprocating speed R' (number of times/m1n). At this time, two coating machines M arranged in the transport direction of the automobile body W1. When the interval P of M2 is set to three times the reciprocating pitch S'(P=33'), the reciprocating speed R' is determined according to the formula R'=3/2P. The control device 22' outputs a control signal corresponding to the calculated reciprocating speed R' to control the rotation speed of the motor 35 (FIG. 5) of the second reciprocator 31. As a result, the coating machine M (M, , M,) performs reciprocating motion on the automobile body W conveyed by the conveyor b at a reciprocating speed R' that is a preset reciprocating pitch S', and in this state. If the metallic base paint is supplied to the paint machine M, the overlapping of the paint patterns on the side surfaces of the automobile body W will be proper, and uneven painting will not occur.

When applying the clear paint subsequent to the application of the metallic base paint, the pressure of the shaping air discharged from the coating machine M is set to a lower value than the value set during the application of the metallic base paint. As a result, the width of the coating pattern can be expanded as much as possible, and efficient coating can be performed.

(Effects of the Invention) As described above in detail, according to the metallic coating method of the present invention, the discharge pressure of shaping air from the rotary atomizing electrostatic coating machine is increased to coat the metallic base paint. This makes it possible to suppress the occurrence of uneven coating even when the shaping air pressure is increased, and together with the improvement in the brightness of the painted surface due to the increased shaping air pressure, the desired coating quality can be ensured. Moreover, when applying clear paint, the pressure of shaping air can be lowered to ensure the desired painting efficiency, which increases the adaptability of rotary atomizing electrostatic atomizers to metallic painting, resulting in resource savings and pollution prevention. It is possible to establish a metallic coating method that greatly contributes.

[Brief explanation of drawings]

Figures 1 and 2 are side views of the coating method according to the present invention;
The figure is a schematic diagram showing the reciprocating mechanism of the flat surface coating device, and FIG. 5 is a front view of the flat surface coating device constituting the coating equipment.
6 and 7 are diagrams showing the reciprocating locus of the atomizer, and FIG. 8 is a partially opened perspective view of the structure of a general rotary atomizing atomizer. a ... Painting booth b ... - Conveyor C ... Horizontal surface coating device d ... Vertical surface coating device M ... Rotating atomizing static 'W coating machine W ... Object to be painted (automobile body) 11 .31...
・ Reciprocator 18.35... Motor 21... Conveyor speed detection sensor 22, 2
2...Control device Fig. 1 Fig. 2 Fig. 3 Fig. 5 Fig. 6 Off view

Claims (1)

[Claims] (1) A rotary atomizing electrostatic coating machine is moved in a reciprocating direction perpendicular to the direction of conveyance to the object to be coated, which is conveyed by a conveyor, and the metallic base paint is applied first, and then the clear paint is applied. In the coating method, when applying the metallic base paint, the pressure of the shaping air discharged from the rotary atomizing electrostatic coating machine is set to a high pressure that increases the collision speed of the metallic base paint particles against the object to be coated, and The reciprocating speed of the rotary atomizing electrostatic coating machine is controlled based on the conveyor speed so that the pitch in the reciprocating locus becomes a preset value, and when applying the clear paint, the pressure of the shaping air is adjusted to the metallic base paint. A metallic painting method characterized by setting a value lower than the value set when painting.