JPH0424111B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotary atomization type coating device that can obtain various coating patterns.

[Prior art]

Conventionally, rotary atomization type painting equipment has a cylindrical or bell-shaped atomization head attached to the rotating shaft of a rotary drive device, a paint supply path is connected to the base end of the atomization head, and a paint supply path is connected to the tip of the atomization head. An air injection port is provided in an annular shape at the rear of the atomizing head to form a paint discharge part and to emit an air flow that bends the paint particles emitted from the paint discharge part forward. The coating pattern is adjusted by increasing or decreasing the flow rate of air ejected from the air injection port.

However, even if the flow rate of the ejected air is greatly increased or decreased (air flow rate: 0 to 500/min), the shape of the coating pattern remains donut-shaped, the width of the coating pattern does not change significantly, and the adjustment range of the coating pattern is limited. is narrow. Needless to say, it is impossible to obtain oval or dumbbell-shaped paint patterns.

In addition, for the purpose of controlling the shape of the coating pattern, a large number of air injection ports are provided at positions around the outer circumference of the atomization head, and air injection from the injection ports is controlled in the circumferential direction of the atomization head. An atomization type painting device was devised [Utility Model Application No. 54-25270]. This coating device controls the speed and width of the airflow formed in front of the outer periphery of the atomizing head in the circumferential direction of the atomizing head.
This is an attempt to control the dispersion of coating particles discharged from the atomizing head in the centrifugal direction. However, once the coating particles are released from the atomizing head in a centrifugal direction and are dispersed around the outside of the atomizing head, controlling the direction of dispersion of these coating particles using the air flow as described above is difficult. It is extremely difficult, inefficient, and impractical in the following ways:

Since the coating particles themselves have relatively large kinetic energy, changing their flight direction (diffusion direction) requires a high velocity or the formation of a thick airflow.

In order to cover the entire coating particles once dispersed around the outside of the atomizing head with an air flow that satisfies the above conditions, it is necessary to inject a very large amount of air.

Since the pitch circle diameter of the air injection port is large, the coating equipment becomes large and heavy.

Some of the paint particles ejected from the atomizing head adhere to the vicinity of the air injection port, causing spittle (a type of paint defect).
It causes In order to prevent this, it is necessary to arrange the air injection port at a further rear position of the atomizing head, and it becomes necessary to inject even more air to control the coating pattern.

In addition, for the purpose of obtaining an elliptical coating pattern, a large number of first air injection ports are provided in an annular shape, and a second air injection port is used to inject an air flow to distort the air flow ejected from the injection ports. A rotary atomizing coating device equipped with a spray nozzle has also been proposed [JP-A-57
-180460, Utility Model Publication No. 59-127762]. However, in all of these painting devices, another air flow collides with the annular air flow formed in front of the outer periphery of the atomization head, and the speed and width of the air flow are controlled in the circumferential direction of the atomization head. This is an attempt to control the dispersion of coating particles discharged in the centrifugal direction from the atomizing head, and its basic design concept is no different from the coating device of Utility Model Application Publication No. 54-25270. I can say that. Therefore, they have exactly the same problems and are not practical.

[Purpose of the invention]

An object of the present invention is to provide a rotary atomization coating device that can obtain oval or dumbbell-shaped coating patterns in addition to circular (including donut-shaped) coating patterns and has a wide adjustment range for coating patterns. be.

〔Viewpoints〕

The present inventors conducted extensive research on a method of controlling a coating pattern in a rotary atomization coating device, and came to the following conclusion.

In order to control the coating pattern efficiently (with a small amount of air), it is essential that the coating particles are not dispersed in the centrifugal direction from the atomizing head. This makes it easier to control the coating pattern, and at the same time eliminates paint from adhering to the coating device and eliminates spitting.

In order to prevent paint particles from dispersing in the centrifugal direction from the atomizing head, it is necessary to form an air flow with a high velocity near the paint discharge part of the atomizing head.

From at least a pair of air injection ports provided around the outer periphery of the atomizing head at approximately symmetrical positions centered on the axis of the atomizing head,
When air is injected forward toward the flat outer circumferential surface (including a tapered surface, etc.), a high-speed air flow as shown in FIGS. 1 to 3 is formed. In other words, when the air injected from the air injection port hits the outer circumferential surface of the atomizing head, it flows along the outer circumferential surface, and at an intermediate point on the outer circumferential surface, it merges with the air flow injected from the other air injection port. They collide to form a fan-shaped airflow. The key point of this is that the high-speed airflow that flows near the outer peripheral surface of the atomizing head along the outer peripheral surface and the fan-shaped high-speed airflow that is formed when the airflow collides at an intermediate point on the outer peripheral surface. be. The former air flow plays the role of preventing the coating particles released from the atomizing head by centrifugal force from spreading and transporting the coating particles to the vicinity of the intermediate point on the outer peripheral surface. Moreover, the latter air flow plays the role of spreading the coating particles conveyed near the intermediate point on the outer circumferential surface in a fan shape. As a result, the coating pattern becomes elliptical or dumbbell-shaped.

[Structure of the invention]

(1) The rotary atomizing painting device of the first invention has an atomizing head attached to the rotating shaft of the rotary drive device, a paint supply path connected to the base end of the atomizing head, and paint being discharged from the tip of the atomizing head. In a rotary atomizing coating device that forms a part and emits paint particles from a paint discharge part, the outer circumferential surface of the atomizing head is approximately symmetrical to the axis of the atomizing head. The configuration includes at least a pair of air injection ports that inject air forward toward the vehicle.

(2) Furthermore, the device of the second invention includes the above-mentioned air injection port (second air injection port) and an air injection port ( This is a configuration in which a first air injection port) is arranged.

[Operation and effects of the invention]

The device of the first invention having the above-mentioned configuration has at least one pair of air injection ports provided around the outer periphery of the atomizing head at substantially symmetrical positions with respect to the axis of the atomizing head toward the outer peripheral surface of the atomizing head. An airflow that flows near the outer circumferential surface of the atomizing head due to the air injected forward, and a fan-shaped airflow that is formed when the airflow collides at an intermediate point on the outer circumferential surface. (see Figures 1 to 3), it is possible to obtain elliptical or dumbbell-shaped coating patterns that could not be obtained with conventional rotary atomization coating equipment, and the coating pattern can be adjusted over a wide range. It has excellent practical effects.

Note that the air flow flowing along the outer circumferential surface of the atomizing head described above prevents the coating particles emitted from the atomizing head by centrifugal force from being dispersed in the centrifugal direction, and also prevents the coating particles emitted from the atomizing head from being dispersed in the centrifugal direction. It plays the role of transporting particles to collect them. In addition, the fan-shaped airflow
It plays the role of spreading the coating particles collected at the intermediate point on the outer peripheral surface in a fan shape and conveying them.

Further, in the device of the second invention having the above configuration,
An annular or circular air flow is formed by the air jetted forward from the first air injection port. The coating flow carried by this air flow is
Forms an annular or circular coating pattern.
Further, in the device of the second invention, in addition to the first air injection ports, there are at least a pair of second air injection ports provided at substantially symmetrical positions with respect to the axis of the atomizing head. By changing the flow rate of air injected from the injection port, the coating pattern can be set to a large diameter donut shape, a small diameter circle shape, an ellipse shape, or a dumbbell shape. Therefore, it has an extremely excellent practical effect in that the adjustment range of the coating pattern is wider than that of the coating apparatus having the configuration of the first invention.

Hereinafter, typical embodiments of the present invention will be described.

[First Embodiment] The rotary atomization type coating device of this embodiment shown in FIGS. 4 and 5 has a rotating shaft 2 protruding from the tip of the case of an air turbo motor 1 with a maximum rotation speed of 60,000 revolutions per minute.
A hub 3 having a disk portion 5 concentrically connected to the tip of a cylindrical portion 4 is inserted into the hub 3, and the rotation shaft of the air turbo motor is inserted into a tapered mounting hole 6 drilled in the center of the disk portion 5 of the hub. The hub 3 is attached concentrically to the rotating shaft 2 of the air turbo motor with a screw 7 passing through the center of the disk portion 5 of the hub, and a cylindrical tube is attached to the outer periphery of the hub 3. The rear half of the body 8 is fitted, the front half of the cylindrical body 8 is projected to the front position of the hub 3, and the hub 3 is attached to the hub 3 by a screw 9 screwed through the circumferential wall of the cylindrical body 8.
The hub 3 and the cylindrical body 8 are attached concentrically to the
The atomizing head is made up of: Atomization head 3,8
is connected to a DC high voltage generator (not shown) via an air turbo motor 1, and also serves as an electrode.

A paint supply passage 10 connected to a paint supply device (not shown) is attached to the tip of the case of the air turbo motor 1, and the opening at the tip of the paint supply passage 10 is placed inside the cylindrical portion 4 of the hub of the atomization head to perform atomization. A paint supply path 10 is connected to the base ends of the heads 3 and 8. A large number of paint passage holes 11 communicating with the front half of the cylindrical body 8 are provided at equal intervals on the peripheral wall of the tip of the cylindrical part 4 of the hub of the atomizing head.
The inner circumferential surface of the front half of the cylindrical body 8 is formed as a paint flow surface 12, and the inner circumferential surface of the tip end of the cylindrical body 8 is provided with a large number of paint flow dividing grooves 13 at equal intervals to prevent air from being drawn into the paint particles. It is provided along the axial direction, and the opening edge at the tip of the cylindrical body 8 serves as a paint discharge part 14.

Further, a pair of air injection members 1 are provided on the upper end surface 15 and the lower end surface 16 of the case tip of the air turbo motor 1.
8 are loosely fitted into the lower heads 3 and 8, and fixed to the upper end surface 15 and lower end surface 16 of the case tip of the air turbo motor 1 with screws 17. Each air passage 1 is provided in the air injection member 18.
9, the air passage 19 is connected to a high-pressure air supply device via a flow rate regulating valve (not shown), and the air passage 19 is connected to the front inner circumferential surface of the pair of air injection members 18 located rearward from the paint discharge part 14 of the atomizing head. , a total of four air injection ports 20, two each communicating with the air passage 19, are arranged so that the extension line of their axis intersects the outer peripheral surface of the atomization heads 3 and 8, and The holes are drilled at symmetrical positions around the axis. Each air injection member 18
Two air injection ports 20 bored in the atomization head 3,
8 is 3mm apart in the circumferential direction.

The diameter and number of the air injection ports 20 are 1.8 mm and four, and the total opening area S of the air injection ports 20 is approximately 50 mm ² for practical purposes.
In this example, it is approximately 10 ^mm2 .

Furthermore, the angle θ _p formed by the extension line of the axis of the air injection port 20 and the outer peripheral surface of the atomizing heads 3 and 8 is in the range of 0° to 90°, and in this example, it is 50°. The point where the extension line of the wick intersects with the outer peripheral surface of the atomizing heads 3 and 8 and the paint discharge part 1
The distance L _p from 4 is in the range of 0 to 50 mm, and in this example it is 10 mm.
It is. In addition, the air injection ports 20 at the upper end and the lower end
In practice, the distance D _p satisfies the relationship 4d≧D _p ,
In this example, the diameter is 50 mm, and the outer diameter d of the spray heads 3 and 8, that is, the outer diameter d of the paint discharge part, is 37 mm. In addition, the external shape of the atomizing heads 3 and 8 is thick at the tip, having the same diameter, and tapering, that is, the angle between the outer peripheral surface of the atomizing head and the axis of the atomizing head is within a range of ±45° when viewed from a longitudinal section. Preferably 0° in this example
It is.

When the rotary atomizing coating device of this example is driven, the atomizing heads 3 and 8 rotate at high speed, and the atomizing heads 3 and 8 also serve as electrodes.
A direct current high voltage is applied between the and an object to be painted (not shown) placed in front of it, high pressure air is supplied to the air passage 19, air is jetted forward from the air injection port 20, and the paint supply passage is From 10, paint is supplied into the hub 3 on the proximal side of the atomizing head. The paint supplied into the hub 3 of the rotating atomizing head passes through a large number of paint passage holes 11 into the front half of the cylindrical body 8 due to centrifugal force, and forms a thin film on the paint flow surface 12 of the cylindrical body. The liquid flows into a large number of paint distribution grooves 13, is divided into a large number of liquid threads, and is emitted from the paint discharge part 14 in the radial direction, where it is atomized into fibrous particles. At this time, the paint particles emitted from the paint discharge part 14 are
Transported by high-speed airflow along the outer circumferential surfaces of the atomizing heads 3, 8 formed by air injected forward toward the outer circumferential surfaces of the atomizing heads 3, 8 from the two pairs of upper and lower air injection ports 20. is collected near the midpoint between the outer peripheral surfaces of the atomizing heads 3 and 8, and is further formed into a fan-shaped airflow by the fan-shaped airflow formed when the high-speed airflow collides at the midpoint between the atomization heads 3 and 8. It is expanded to. The paint particles spread out in a fan shape fly to the surface of the object to be coated and apply the coating due to the force of the airflow and the electrostatic attraction that acts between the particles and the object to be coated.

In the case of the rotary atomization type coating apparatus of this example, the relationship between the air flow rate and the coating pattern is as shown in FIGS. 6 and 7. When the air flow rate is 0, the coating pattern is donut-shaped with a width of about 90 cm, but when air is injected at 500 N/min, it becomes dumbbell-shaped with a width of about 70 cm. Note that no coating particles were observed to adhere to the coating equipment at any air flow rate.

[Second Embodiment] The rotary atomization type coating device of this example shown in FIGS. 8 and 9 has a rotating shaft 2 protruding from the tip of the case of an air turbo motor 1 with a maximum rotation speed of 60,000 revolutions per minute.
A hub 3 having a disk portion 5 concentrically connected to the tip of a cylindrical portion 4 is inserted into the hub 3, and the rotation shaft of the air turbo motor is inserted into a tapered mounting hole 6 drilled in the center of the disk portion 5 of the hub. The hub 3 is attached concentrically to the rotating shaft 2 of the air turbo motor with a screw 7 passing through the center of the disk portion 5 of the hub, and a cylindrical tube is attached to the outer periphery of the hub 3. The rear half of the body 8 is fitted, the front half of the cylindrical body 8 is projected to the front position of the hub 3, and the hub 3 is attached to the hub 3 by a screw 9 screwed through the circumferential wall of the cylindrical body 8.
The hub 3 and the cylindrical body 8 are attached concentrically to the
The atomizing head is made up of: Atomization head 3,8
is connected to a DC high voltage generator (not shown) via an air turbo motor 1, and also serves as an electrode.

A paint supply passage 10 connected to a paint supply device (not shown) is attached to the tip of the case of the air turbo motor 1, and the opening at the tip of the paint supply passage 10 is placed inside the cylindrical portion 4 of the hub of the atomization head to perform atomization. A paint supply path 10 is connected to the base ends of the heads 3 and 8. A large number of paint passage holes 11 communicating with the front half of the cylinder body 8 are penetrated at equal intervals on the peripheral wall of the tip of the cylindrical part 4 of the hub of the atomizing head, and the inner peripheral surface of the front half of the cylinder body 8 is connected to the paint flow surface 12. In addition, on the inner peripheral surface of the tip of the cylindrical body 8, a large number of paint flow dividing grooves 13 are provided at equal intervals along the axial direction to prevent air from being drawn into the paint particles. The edge of the opening is used as a paint discharge part 14.

Also, at the tip of the case of the air turbo motor 1,
An annular member 51 made of an insulating material is loosely fitted and fixed to the atomizing heads 3 and 8, and a first annular air passage 52 is formed in the annular member 51 disposed around the outer circumference of the atomizing heads 3 and 8. , is connected to a high-pressure air supply device through a flow rate regulating valve (not shown) on the side of the first air passage 52, and the first air is connected to the front surface of the annular member 51 located behind the paint discharge part 14 of the atomizing head. A large number of first air injection ports 53 communicating with the passage 52 are provided at equal intervals from the axes of the atomizing heads 3 and 8.

Further, a pair of second air injection members 54 are fixed to the upper and lower ends of the annular member 51 with screws (not shown), and are inserted into the pair of second air injection members 54 arranged around the outer circumference of the annular member 51, respectively. Second air passage 5
5, the second air passage 55 is connected to a high-pressure air supply device via a flow rate regulating valve (not shown), and the second air passage 55 is connected to a high-pressure air supply device through a flow rate regulating valve (not shown). A total of four second air injection ports 56, two each communicating with the second air passage 55, are provided on the inner peripheral surface so that the extension line of the axis intersects with the outer peripheral surface of the atomizing heads 3 and 8. In addition, the holes are drilled at symmetrical positions with respect to the axes of the atomizing heads 3 and 8.

The two second air injection ports 56 formed in each second air injection member 54 are separated by 5 mm in the axial direction of the atomizing heads 3 and 8.

The diameter and number of the first air injection ports 53 are 0.6 mm and 33 pieces.
The total opening area S _S of the first air injection ports 53 is approximately 40 mm ² or less, and in this example is approximately 10 mm ² . Further, the distance l _S from the opening of the first air injection port 53 to the paint discharge part 14 of the atomizing head is 20 mm, and the extension line of the axis of the air injection port 53 and the outer peripheral surface of the atomizing head 3, 8 or the For practical reasons, the angle θ _s formed with the extension line satisfies the relationship 0°≦θ _s <90°, and is 10° in this example. Note that the center diameter of the first air injection ports 53 arranged in an annular shape concentric with the atomization heads 3 and 8
D _s is 44 mm, and the outer diameter d of the atomizing heads 3 and 8, that is, the outer diameter d of the paint discharge portion 14, is 37 mm.

Further, the diameter and number of the second air injection ports 56 are 1.4 mm.
, and the total opening area S _P of the second air injection ports 56 is approximately 6 mm ² . The angles θ P1 and θ _P2 formed by the extension of the axes of the two second air injection ports 56 at one end and the outer peripheral surfaces of the atomizing heads 3 and ₈ are both 70°, and the two second air injection ports 56 The distances L _P1 and L _P2 between the point where the extension line of the axis of the atomizing head 56 intersects with the outer peripheral surface of the atomizing heads 3 and 8 and the paint discharge portion 14 are 11 mm and 5 mm, respectively. The distance D _P between the second air injection port 56 at the upper end and the lower end of the annular member 51 is 80
mm.

When the rotating under-mist coating device of this example is driven, the atomizing heads 3 and 8 rotate at high speed, and the atomizing heads 3 and 8 also serve as electrodes.
A DC high voltage is applied between the air passages 52 and an object to be painted (not shown) placed in front of the air passages 52 and 55.
High pressure air is supplied to each air injection port 53, 5.
Air blows out forward from 6, and paint supply path 1
Paint is supplied into the hub 3 on the proximal end side of the atomizing head from zero. The paint supplied into the hub 3 of the rotating atomizing head passes through a large number of paint passage holes 11 into the front half of the cylindrical body 8 due to centrifugal force, and forms a thin film on the paint flow surface 12 of the cylindrical body. The liquid flows into a large number of paint distribution grooves 13, is divided into a large number of liquid threads, and is emitted from the paint discharge part 14 in the radial direction, where it is atomized into fibrous particles. At this time, the paint particles emitted from the paint discharge part 14 are
The particles fly to the surface of the object to be coated due to the force of the high-speed airflow that is injected forward from the air injection port 56 around the outer circumference of the paint discharge part, and the electrostatic attraction that acts between the coating particles and the object to be coated. Paint.

The action and effect of the air injected from the second air injection port are almost the same as in the first embodiment, so a description thereof will be omitted. The high-speed air flow jetted forward from the first air injection port 53 around the outer circumference of the paint discharge part 14 collects the paint emitted from the paint discharge part 14 on an extension of the axes of the atomizing heads 3 and 8. Show action.

In the case of the rotary atomization coating apparatus of this example, air is injected from the first air injection port 53 and the second air injection port 56 (referred to as first air and second air, respectively).
The relationship between the flow rate and the coating pattern is as shown in FIGS. 10 to 13. The coating pattern will be donut-shaped with a width of about 90 cm if both the first and second air are not injected, but if the first air is injected at 200 N/min, it becomes a solid circle with a width of about 40 cm. Also, the second
When only air is injected at 300N/min, the coating pattern becomes dumbbell-shaped with a width of about 60cm.
When 200N/min and the second air is injected at 300N/min, the coating pattern becomes an ellipse with a width of about 50cm.

As mentioned above, the rotary atomization coating device of this example is
It has the advantage that the coating pattern can be changed significantly by adjusting the flow rate of the first air and the flow rate of the second air. Generally, when increasing the first air flow rate,
The painting pattern approaches a narrow solid circle, and the second
As the air flow rate increases, the coating pattern approaches a wide oval or dumbbell shape.

The total opening area S _S and S _P of the first air injection port 53 and the second air injection port 56 is the average velocity of air at the opening of the injection port [=air flow rate/total opening area (S _S or S _P )] It is better to make it so that it exceeds the speed of sound. Further, it is preferable that the flow rate Q ₁ of the first air is set so that Q ₁ /d is 2.5 (N/mm·min) or more.

When two or more pairs of second air injection ports are provided, an extension of the axis of at least one pair of second air injection ports may intersect with the outer circumferential surface of the atomization head. Also θ _Pi (i=1,
2...) may not be the same value.

In this embodiment, the first air and the second air can be supplied separately, but they may be supplied integrally. Furthermore, all the air injection ports may be arranged in an annular shape, and some of the air injection ports may satisfy the following conditions. That is, an extension of the axes of at least one pair of air injection ports located at symmetrical positions with respect to the axis of the atomizing head intersects with the outer circumferential surface of the atomizing head.

(Modified example) In the case of the rotary atomization coating device of the second embodiment, the first
When the flow rates of air and secondary air are respectively switched using high-speed flow rate control devices, the coating pattern can be switched instantaneously, so it is useful as a coating device for automatic coating devices and coating robots. Furthermore, if the switching of the air flow rate and the switching of the paint discharge amount are linked, the practicality will be improved.

ΓThe present invention focuses on the shape of the atomization head, the shape of the air outlet,
The number and arrangement are not limited to those in the above embodiment. Moreover, it is not limited to electrostatic coating equipment.

The Γ coating efficiency is slightly lower than that of a conventional rotary atomization coating device, but higher than that of an air atomization coating device.

[Brief explanation of drawings]

1 to 3 are conceptual diagrams showing the state of air flow, which is the basis of the present invention, FIGS. 4 and 5 are longitudinal and transverse sectional views showing the device of the first embodiment, and FIG. 7 and 7 are schematic diagrams respectively showing the coating pattern by the apparatus of the first embodiment, FIGS. 8 and 9 are longitudinal and transverse sectional views showing the apparatus of the second embodiment, and FIGS. FIG. 13 is a schematic diagram showing coating patterns by the apparatus of the second embodiment. In the figure, 3, 8...atomization head, 10...paint supply path,
14...Paint discharge part, 19...Air passage, 20...
...Air injection port.

Claims (1)

[Scope of Claims] 1. An atomizing head is attached to the rotating shaft of the rotary drive device, a paint supply path is connected to the base end of the atomizing head, a paint discharge portion is formed at the tip of the atomization head, and a paint discharge portion is formed at the tip of the atomization head. In a rotary atomizing coating device that emits coating particles from the atomizing head, air is ejected forward toward the outer circumferential surface of the atomizing head around the outer periphery of the atomizing head at approximately symmetrical positions around the axis of the atomizing head. A rotary atomizing coating device characterized by being provided with at least one pair of air injection ports. 2. Attach the atomizing head to the rotating shaft of the rotary drive device, connect the paint supply path to the base end of the atomizing head, form a paint discharge part at the tip of the atomization head, and collect paint particles emitted from the paint discharge part. In a rotary atomizing coating device provided with a first air injection port that blows out an air flow that bends the air forward,
In addition to the first air injection ports, at least a pair of second air injection ports are provided at substantially symmetrical positions with respect to the axis of the atomization head and for injecting air forward toward the outer peripheral surface of the atomization head. This is a rotary atomization coating device that is characterized by: