JP3353513B2 - Painting gun and painting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating gun and a coating method using the same, and more particularly to a technique for suppressing the scattering of atomized paint ejected from the coating gun and improving the coating efficiency. is there.

[0002]

2. Description of the Related Art The spray coating method of atomizing a paint to apply it to an object to be coated is of good industrial workability and beautiful finish. Is the most widely used.

[0003] As is well known, this spray coating method is an air spray coating method in which a compressed air flow impinges on a paint flow and is dispersed by a paint atomization method, and a spray is applied from a nozzle by applying high pressure to the paint. The high-speed paint flow is divided into the airless spray coating method in which the high-speed paint flow is dispersed by receiving the resistance of air while traveling in the air.In these air spray coating methods or airless spray coating methods, paint particles are charged and electrostatically charged. 2. Description of the Related Art An electrostatic coating method for improving the coating efficiency by attracting to an object to be coated by an attractive force is known.

Conventionally, as a coating gun used in these spray coating methods, those having various configurations according to the type of coating and the like have been developed, but as shown in FIG. The spray pattern of the finely-divided paint particles M discharged and directed to the workpiece B has an axis C at the center.
In the vicinity of the object to be coated, as shown in FIG. 7, the pressure is high at the center and the pressure at the periphery is low, so that air flowing from the center to the side of the object is A flow is formed, and the paint particles M also flow to the side upon receiving the drag F _R from the air, and there is a problem that the coating efficiency is low.

[0005] Conventionally, in an air spray type coating gun, an air outlet, which is referred to as an air curtain and shares an air chamber for supplying atomized air in an air cap, is provided in the vicinity of the atomized air jet port. There is also known one having a mechanism for rectifying a spray pattern by an air flow ejected from a mouth.

[0006] However, the air outlet for the air curtain is close to the atomized air outlet, and the air chamber for supplying air to the air outlet is common to the one for supplying atomized air. Because the internal pressure is high and the air ejected from the air outlet is a diffusion flow, the spray pattern and the air curtain are integrated before reaching the vicinity of the object to be coated. Therefore, a predetermined rectifying effect as an air curtain cannot be expected.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a coating gun and a coating method with improved coating efficiency. Another object of the present invention is to provide a coating gun and a coating method that suppress the lateral spray of the atomized paint ejected from the coating gun in the vicinity of the object and improve the coating efficiency. is there.

[0008]

To solve the above problems SUMMARY OF THE INVENTION The present invention is a paint atomized in the gun head portion, a spray gun for forming atomized coating material flow toward to a coating object, the
An air flow forming means provided independently of the atomizing paint flow forming means of the coating gun ;
Air that is provided on the tip side of the mounting gun and that is arranged in a ring around the central axis of the atomized paint flow and at a position separated by a predetermined distance in a radial direction from the central axis so as not to interfere with the atomized paint flow.
An air outlet, which is located on the side of the coating gun base and is continuous from an air inlet having a small cross-sectional area connected to an air supply source to the air outlet having a large cross-sectional area, and is pressure-fed from the air supply source. A pipe having a length sufficient to reduce the internal pressure in the vicinity of the air outlet to approximately the same level as the external atmospheric pressure, and having a rectifying function,
The air outlet arranged in the
The pipes are coaxially multiplexed around the central axis of the atomized paint flow.
And the air flowing out of the multiple pipes
Flow rates are different from each other and flow out from the air outlet.
The flow velocity distribution of the air flowing in the radial direction from the central axis
The coating gun is characterized in that it is formed so as to become gradually smaller .

[0009] In the coating gun of the present invention, the pipe in the air flow forming means, which is continuous from the air inlet to the air outlet, is at least a predetermined length from the air outlet side. Desirably, it has a cross section substantially equal to the outlet and is extended in a direction substantially parallel to the central axis of the atomized paint flow to form a straightening portion.

Further, in the coating gun according to the present invention, it is preferable that the air outlet of the air flow forming means is located behind or at substantially the same position as the tip of the gun head.

[0011]

In a preferred embodiment of the coating gun of the present invention, an electrostatic coating type coating gun can be used.

Further, according to the present invention, there is provided a spray gun in which a paint is atomized at a gun head portion of a coating gun to form an atomized paint stream toward an object to be coated. Forming a low-diffusion air curtain flow having an annular cross section at a position radially away from the center axis of the paint flow in the radial direction toward the object to be coated ;
Flow is the velocity distribution in the axial direction of the air curtain flow.
Is gradually reduced from the inner circumference to the outer circumference.
A coating method characterized by being formed .

[0014]

[0015]

As described above, the coating gun of the present invention has an air flow forming means independently of the atomized paint flow forming means. Since the conduit connecting the small cross-section air inlet connected to the supply source to the large cross-section air outlet located on the tip side of the coating gun has a sufficient length, the air supply The air that is pressure-fed from the source and flows into the pipeline from the air inlet and is accelerated is reduced to almost the same pressure as the outside atmospheric pressure before reaching the vicinity of the air outlet. It is hardly diffused even after being discharged to the outside, and reaches the object to be coated while keeping the flow at the air outlet . In addition, the air outlet is annularly formed around a central axis of the atomized paint flow formed by the atomized paint flow forming means of the coating gun and does not interfere with the atomized paint flow radially from the central axis. Since the air is discharged at a distance from the air outlet, the air discharged from the air outlet forms a portion having a high pressure distribution on the outer periphery of the atomized paint flow. Accordingly, the amount of the paint particles flowing to the side of the object to be coated in the vicinity of the object to be coated is reduced, and it is desired to improve the coating efficiency. In the coating gun of the present invention, the above d.
The air outlets arranged in an annular shape of
A pipe communicating with the atomizing paint flow is coaxial about a central axis of the atomized paint flow.
, The outer periphery of the atomized paint flow
Can be formed more reliably.
Further, air flowing out of the multiplexed pipes
Flow rates are different from each other and flow out from the air outlet.
The flow velocity distribution of the air flowing in the radial direction from the central axis
Radially
Flow velocity drop can be smoothed.

Further, in the coating gun according to the present invention, the pipe continuous from the air inlet to the air outlet of the air flow forming means has a length at least a predetermined length from the air outlet side. If the air outlet has a cross section substantially equal to that of the air outlet and extends in a direction substantially parallel to the central axis of the atomized paint flow, air passes through this portion and is exposed to external atmospheric pressure. Since the pressure is reduced to substantially the same level and the flow is sufficiently rectified to form an air flow (laminar flow) having more excellent straightness after flowing out from the air outlet, it surrounds the outer periphery of the atomized paint flow. The air flow shielding effect is more reliable.

Further, in the coating gun according to the present invention, if the air outlet of the air flow forming means is located behind or substantially at the same position as the tip of the gun head, the air flows out from the air outlet. The predetermined spray pattern can be obtained without the air adversely affecting the formation of the atomized paint flow at the gun head portion.

[0018]

Further, when the coating gun of the present invention is an electrostatic coating type coating gun, by forming such an air flow, a particularly good improvement in coating efficiency can be expected.

Further, the present invention uses a coating gun having the above-described structure, atomizes the paint at the gun head portion, and forms an atomized paint flow toward the object to be coated.
A low-diffusive air curtain flow having an annular cross section toward the object to be coated having an annular cross section around the atomized paint flow and at a position spaced apart from the central axis of the atomized paint flow by the predetermined distance in the radial direction. Since coating is performed after forming, good coating efficiency can be expected, paint loss during coating can be reduced, and raw material cost can be reduced.

In the coating method of the present invention, as described above, the air curtain flow is formed such that the flow velocity distribution in the axial direction of the air curtain flow gradually decreases from the inner peripheral side to the outer peripheral side. By smoothing the flow velocity drop, the generation of the vortex is reduced, and better coating efficiency can be obtained.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram schematically showing the main structure of an embodiment of a coating gun according to the present invention, together with a flow of air or fine paint particles formed in front of the coating gun during coating. FIG. 3 is a diagram showing a pressure distribution in a cross section taken along the line aa in FIG. 1; FIG. 3 is a perspective view schematically showing a main part of the embodiment; FIG. 4 is another embodiment of a coating gun according to the present invention; FIG. 5 is a diagram schematically showing an example of the flow rate of an air flow formed in front of the coating gun when the coating gun of the embodiment is used.

As shown in FIG. 1, the coating gun of this embodiment is an air spray type coating gun. As is well known, a paint nozzle and an air cap are disposed at the tip thereof, and thereby, A paint passage 11 communicating with a paint supply source (not shown) is located near the tip of the gun, at the center along the axis of the barrel 10 of the gun, and is reduced in diameter at its tip to open (the tip of the paint nozzle). On the other hand, an air passage 13 communicating with a paint atomizing compressed air supply source (not shown) is opened near the paint nozzle tip opening 12 at the tip of the gun. Main air hole 14
And the paint nozzle tip opening 12 and the main air hole 1
A common air chamber portion 16 is located on the outer peripheral side of the nozzle 4 and communicates with a side hole 15 having an extension line extending from the paint nozzle tip opening and having an extension line intersecting in front of the gun. Branch through. In FIG. 1, reference numeral 17 denotes a needle for adjusting the paint discharge amount.

Accordingly, in the coating gun of this embodiment, the paint discharged from the paint nozzle tip opening 12 through the paint passage 11 to the outside is compressed by the compressed air which is blown out from the main air hole 14 located on the immediate periphery. The atomized paint is conveyed by the high-speed air stream, moves forward, and forms an atomized paint stream having a center axis C coinciding with the axis of the paint nozzle tip opening 12 and toward the workpiece. . If necessary, compressed air can be ejected from the side holes 15 to change the spray pattern from a round shape to an elliptical shape.

However, in the coating gun of the present invention, the configuration of the atomized paint flow forming means for forming such an atomized paint stream is as long as the atomized paint stream has a spray pattern having an axis C at the center. The present invention is not limited to an air spray gun having an external mixing type nozzle as described above, and may be, for example, an air spray gun having an internal mixing type nozzle, or atomization of paint. Various airless spray guns, which blow out from nozzles by applying high pressure to paint without using compressed air
Furthermore, various modes such as an electrostatic coating air spray gun, an electrostatic coating airless spray gun, and a bell type coating gun can be adopted.

According to the coating gun of the present invention, an air curtain generating device for forming an air curtain flow around the atomized paint flow is provided with the atomizing paint flow forming means of the coating gun as described above. Are independently possessed. As shown in FIGS. 1 and 3, the air curtain generator 20 in the above-described embodiment moves the barrel 10 of the coating gun along its axis (to be exact, the center axis C of the atomized paint flow that matches this axis). A predetermined distance (r)
At a distance from each other in an annular manner, and
Pipes 21a, 21b, 21c of a predetermined length (L) arranged to have axes parallel to the central axis of
.. Are formed. Each of the ends of the tube bodies 21a, 21b, 21c... On the rear end side of the gun is air-tightly inserted and fixed into an insertion hole provided on one disk surface of the flat cylindrical box-shaped air release chamber 23. Are connected to the internal space of the air release chamber 23. The pipes 21a, 21b, 21c,. further,
At the approximate center of the other disk surface of the air release chamber 23,
An air inlet 25 for connecting a compressed air supply pipe 24 connected to a compressed air supply source (not shown) is provided. On the other hand, the respective ends of the pipes 21a, 21b, 21c... On the tip side of the gun have substantially the same cross-sectional area as their internal cross-sections, and are opened to form air outlets 26. In this embodiment, the air outlet 26 is located at substantially the same cross section as the paint nozzle tip opening 12 at the paint gun tip.

Therefore, the air outlet 26 is annularly formed around the central axis C of the atomized paint flow, and is spaced apart from the central axis by a predetermined distance (r) which does not interfere with the atomized paint flow. It will be arranged in.

In the air curtain generator 20 having such a configuration, the compressed air having the pressure (p ₀ ) and the flow velocity (v ₀ ) supplied from the compressed air supply pipe 23 connected to the compressed air supply source is cut off. The pressure energy is converted into velocity energy by flowing from the compressed air supply pipe 24 or the air introduction port 25 having a small area into the air opening chamber part 23 having a larger cross-sectional area, and further has a predetermined length (L). The air is rectified while passing through the rectifying pipe section 22 and the air outlet 26 is formed.
To reach. Accordingly, the internal pressure (p ₁ ) of the air passing through the vicinity of the air outlet 26 is reduced to substantially the same level as the external atmospheric pressure (p), and is rectified. It is difficult to be diffused even after being discharged from the outlet 26, and as shown in FIG.
.. Reach the object B while maintaining the air flow along the axes 21b, 21c. As described above, the air outlet 26
Are arranged in a ring around the central axis C of the atomized paint flow and at a position spaced apart from the central axis by a predetermined distance (r) that does not interfere with the atomized paint flow. The high-speed air curtain flow discharged from the outlet 26 is
Between the tip of the coating gun and the object B, the atomized paint flow flows independently of the atomized paint flow while wrapping the atomized paint flow in a tubular shape. Therefore, in the air pressure distribution near the article to be coated, as shown in FIG. 2, a high pressure portion is formed on the outer periphery of the atomized paint flow by the air curtain flow. For this reason, in the pressure distribution in the vicinity of the object to be coated, portions having a lower pressure than these portions are generated between the vicinity of the central axis C of the atomized paint flow and the outer peripheral portion where the air curtain flow flows. As shown in FIG.
Instead of the flow escaping from the vicinity of the central axis C of the atomized paint flow to the side as it is, the circulation between the central axis C of the atomized paint flow (and the outer peripheral portion where the air curtain flow flows) and this low-pressure portion Flow occurs. Therefore, the paint particles M in the flow of the atomized paint receive the drag F _R received from the air in the vicinity of the workpiece B.
Is small. In this way, a stagnant layer of the paint is provided inside the air curtain, and the paint is applied to the object by the cloning force F _C during the stay.

When the flow of the atomized paint is surrounded by the air curtain in this way, the streamline of the atomized paint flows from the tip of the coating gun to the vicinity of the object B, and the central axis of the atomized paint flows. A flow which is almost parallel to C and has a bend with a remarkably large curvature in the vicinity of the object to be coated is obtained, and the function of increasing the inertia force F _I of the paint particles in the vicinity of the object to be coated and contributing to the improvement of coating efficiency is also obtained. is there.

Here, the distance (r) between the air outlet 26 and the center axis C of the atomized paint flow may be any distance as long as it does not interfere with the atomized paint flow. The size of the spray pattern of the atomized paint flow differs depending on the size of the sprayed paint.
It is about 00 mm. If the distance (r) is extremely small, the air flow ejected from the air outlet 26 collides with the atomized paint flow before reaching the vicinity of the object to be scattered, and the paint particles are scattered. If the diameter is extremely large, even if an air curtain flow is formed, the coating particles are already diffused inside the air curtain flow, and it is not possible to expect an improvement in coating efficiency due to a shielding effect. Further, in FIG. 1, the air outlet 26 is arranged in a circle around the central axis C of the atomized paint flow, but if the spray pattern is something other than a circle, for example, Of course, it is also possible to arrange them in an elliptical shape or the like. In this embodiment, the air outlet 26 is located in substantially the same cross section as the paint nozzle tip opening 12 at the tip of the coating gun. As long as there is no risk of adversely affecting the formation of the flow, it is also possible to arrange it behind the tip of the coating gun to obtain a predetermined spray pattern,
Preferably, it is desirable to set the position substantially equal to or behind the tip position of the gun head, for example, within a range of about 20 mm from the tip position of the gun head.

The length (L) of the straightening pipe section 22 is reduced by reducing the pressure of the compressed air introduced into the pipe section from the air supply source through the air introduction port, and substantially equal to the external atmospheric pressure. The length is not particularly limited as long as the length is sufficient to reduce the pressure to the same extent and a length that exhibits a sufficient rectifying function. For example, the length is desirably about 50 to 200 mm. Further, in this embodiment, the flow straightening pipe portion is formed by a plurality of pipes 21a, 21b, 21c.
However, as long as a sufficiently rectified air flow can be supplied to the air outlet, the shape of the conduit is arbitrary. Thus, for example, a single continuous pipe formed between the inner pipe and the outer pipe arranged coaxially may be used.

The width (d) of the air inlet may be any width as long as a sufficient thickness of the air curtain ejected from the air inlet can be obtained. For example, about 5 to 20 mm is desirable.

FIG. 4 schematically shows the construction of an air curtain generator in another embodiment of the coating gun according to the present invention. As shown in FIG. 4, the air curtain generator of this embodiment has an air outlet 26 arranged in an annular shape and a rectifying pipe portion 22 communicating with the air outlet 26, which is coaxial about the central axis C of the atomized paint flow. (Hereinafter, referred to as a coaxial multi-tube configuration). With such a coaxial multi-tube configuration, the air flow surrounding the outer periphery of the atomized paint flow can be more reliably formed.

Further, in the case of such a coaxial multi-pipe configuration, the air curtain flow to be formed is such that the flow velocity distribution in the axial direction of the air curtain flow gradually decreases from the inner peripheral side to the outer peripheral side. It is desirable to form and paint. For example, in the configuration of the embodiment shown in FIG. 4, as shown in FIG. 5, v _p is the flow rate of the atomized paint flow surrounded by the air curtain flow, and v _{a1 to} v _a5 are respectively discharged from the air outlet 26. Assuming the flow velocity of the air to be performed, the air flow velocity v _a1 on the innermost side is almost the same as the flow velocity v _p of the atomized paint flow, and the flow velocity decreases as the distance to the outside increases
That is, v _p > v _a1 > v _a2 > v _a3 > v _a4 > v _a5 is set. In this way, by making the flow velocity drop in the radial direction smooth, vortex generation is reduced and better coating efficiency is obtained.

Table 1 shows that the actual coating efficiency (n = 5) in the case where the coating was actually performed using the coating gun provided with the air curtain generating unit according to the present invention, This is a comparison with the average coating efficiency (n = 4) when using a coating gun of exactly the same configuration except that no coating gun was provided. The coating conditions were as follows: the distance between the object to be coated and the tip of the coating gun was 30 cm, the size of the object to be coated was 90 cm × 12.
The coating efficiency was measured in a range of 30 cm × 60 cm on the object to be coated.

[0037]

[Table 1]

As shown in Table 1, when the coating gun according to the present invention was used, good coating efficiency was obtained with both the air spray gun and the electrostatic spray gun. For, a remarkable improvement in the coating efficiency was observed.

[0039]

As described above, according to the coating gun of the present invention, the amount of the paint particles flowing to the side of the object in the vicinity of the object is reduced, and the coating efficiency can be improved. It is.

[0040] In the coating gun of the present invention, the pipe continuous from the air inlet to the air outlet of the air flow forming means may be at least a predetermined length from the air outlet side. When having a cross section substantially equal to the air outlet and extending in a direction substantially parallel to the central axis of the atomized paint flow, the air flow surrounding the outer periphery of the atomized paint flow is The shielding action is more reliable.

Further, in the coating gun according to the present invention, if the air outlet of the air flow forming means is located forward or substantially at the same position as the tip position of the gun head, the atomized paint flow at the gun head portion is obtained. A predetermined spray pattern can be obtained without adversely affecting the formation of the spray.

Further, in the coating gun of the present invention, the air outlet formed in the annular shape of the air flow forming means and the conduit communicating therewith are provided in a coaxial multiple around the central axis of the atomized paint flow. Thus, the air flow surrounding the outer periphery of the atomized paint flow can be formed as a more reliable and stable flow.

Further, when the coating gun of the present invention is a coating gun of an electrostatic coating system, particularly good improvement in coating efficiency can be expected.

In the coating method of the present invention, by using the coating gun having the above-described configuration, good coating efficiency can be expected, paint loss during coating can be reduced, and raw material cost can be reduced. It is.

In the coating method of the present invention, as described above, the air curtain flow is formed such that the flow velocity distribution in the axial direction of the air curtain flow becomes gradually smaller from the inner peripheral side to the outer peripheral side, and is formed in the radial direction. By smoothing the flow velocity drop, the generation of vortex is reduced, and a better coating efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a main structure of an embodiment of a coating gun according to the present invention, together with a flow of air or fine paint particles formed in front of the coating gun during coating.

FIG. 2 is a diagram showing a pressure distribution in a cross section taken along line aa of FIG. 1;

FIG. 3 is a perspective view schematically showing a configuration of a main part of the embodiment;

FIG. 4 is a perspective view schematically showing a main part configuration of another embodiment of the coating gun according to the present invention;

FIG. 5 is a view showing an example of a flow velocity of an air flow formed in front of the coating gun when the coating gun of the embodiment is used;

FIG. 6 is a diagram schematically showing a main part structure of one embodiment of a conventional coating gun together with a flow of air or fine paint particles formed in front of the coating gun during coating;

FIG. 7 is a view showing a pressure distribution in a cross section taken along the line bb of FIG. 6;

[Explanation of symbols]

Reference Signs List 11 paint passage 12 paint nozzle tip opening, 13 paint compressed air passage, 14 main air hole, 15 side hole, 20 air curtain generator section, 21a, 21b, 21c ... tubular body, 22 rectifying pipe section, 23 air release chamber, 24 compressed air supply pipe, 25 an air inlet, the central axis of 26 the air outlet 26, C atomized paint flow, M paint particles, B article to be coated, drag F _R paint particles are subjected from the air , F _C clone force, F _I inertia force.

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tatsuya Fukushima 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Nissan Motor Co., Ltd. (56) References JP-A-2-211266 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B05B 1/28 B05D 1/02 B05D 7/14

Claims (5)

(57) [Claims] 1. A coating gun for atomizing paint at a gun head portion and forming an atomized paint flow toward an object to be coated, wherein the paint gun is provided independently of the atomized paint flow forming means of the coating gun. Air flow forming means is provided on the tip side of the coating gun , and the air flow forming means is provided in an annular shape around the central axis of the atomized paint flow and radially from the central axis. It is placed at a predetermined distance away from
Air outlet, which is located on the side of the coating gun base , is continuous from the air inlet having a small cross-sectional area connected to the air supply source to the air outlet having a large cross-sectional area, and is pressure-fed from the air supply source. that the pressure in the air outlet near the air, has a sufficient length to the pressure drop to approximately equivalent to that of the external atmospheric pressure
And a conduit having a rectification function, and communicates with the air outlet arranged in an annular shape and the air outlet.
The conduit is multiplexed coaxially about a central axis of the atomized paint flow.
And the flow velocity of the air flowing out of the multiple pipes
Are different from each other, and
A) The flow velocity distribution gradually increases in the radial direction from the central axis.
A coating gun characterized by being formed as a smaller one . 2. The air flow forming means, wherein the conduit continuing from the air inlet to the air outlet is substantially equal to the air outlet at least a predetermined length from the air outlet side. 2. The coating gun according to claim 1, wherein the coating gun has a cross section equal to that of the spray gun and extends in a direction substantially parallel to a central axis of the atomized paint flow to form a rectifying portion. 3. The coating gun according to claim 1, wherein the air outlet of the air flow forming means is located behind or substantially at the same position as the tip position of the gun head. Wherein said coating gun is spray gun according to claim 1 which is spray gun of an electrostatic coating method. 5. A paint at a gun head portion of a paint gun.
Is atomized to form an atomized paint flow toward the object to be coated , and around the atomized paint flow and from the center axis of the atomized paint flow.
An annular cross section is provided at a position separated by a predetermined distance in the radial direction.
To form a low-diffusive air curtain flow toward the substrate.
And the air curtain flow is in the axial direction of the air curtain flow.
Flow velocity distribution gradually decreases from the inner circumference to the outer circumference
Characterized in that it is formed as
Mounting method.