JP2006181556A - Bell cup for rotary atomizing type coating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bell cup for a rotary atomizing coating apparatus capable of achieving highly fine atomization even if the cut is turned at a high speed. <P>SOLUTION: A bell cup 1 is used in the rotary atomizing type coating apparatus having a rotation shaft 3 and the bell cup 1 which is installed on the rotation shaft and on the surface of which a coating is supplied, and the surface of the bell cup 2 has a surface roughness Ra of not lower than 5μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bell cup of a rotary atomizing coating apparatus.

  Rotating atomizing coating equipment has better coating efficiency than air atomizing coating equipment (spray coating equipment), so it can be used for intermediate coating and top coating (solid paint, metallic base paint and clear paint). Widely used.

  By the way, when painting a metallic base paint, in order to reproduce a desired hue, it is known that it is effective to make the paint particles collide with the paint surface at a high speed. When coating a metallic paint using, it is necessary to increase the flow velocity of shaping air in order for the paint particles to collide with the paint surface at high speed. However, when the flow velocity of the shaping air exceeds a certain value, there is a problem that the coating efficiency is lowered.

  Therefore, the rotational speed of the bell cup of the rotary atomizing coating device is rotated at a high speed to about 70,000 rpm to reduce the particle size of the paint, and the metallic paint luster material is applied to the coating surface without increasing the shaping air flow rate. It has been confirmed that they can be oriented in parallel.

  In the rotary atomizing coating equipment, when paint is supplied to the center of the bell cup rotating at high speed, the paint becomes a thin liquid film due to the centrifugal force of the bell cup and spreads over the entire surface of the bell cup. Scattered in the tangential direction. The paint particles scattered radially are guided to the paint surface by shaping air supplied to the outer periphery of the bell cup. In order to promote atomization of the paint, a cut groove or the like is formed on the edge of the bell cup (see Patent Document 1).

  However, even if the rotation speed of the bell cup is increased to about 70,000 rpm in order to improve atomization of the paint, the liquid film formed on the surface of the bell cup is not sufficiently thin depending on the discharge amount of the paint. The thickness of the liquid film is biased by sliding. This unevenness of the liquid film thickness affects the edge of the bell cup, and as a result of atomization with a non-uniform liquid film thickness, the problem that the desired high atomization cannot be achieved has been confirmed. If the desired atomization cannot be achieved, there is no way to stabilize the hue of the metallic base paint in addition to increasing the flow rate of shaping air and colliding with the paint surface at high speed. End up.

In particular, in the water-based metallic base paint using water as a solvent, the surface tension of water is higher than that of the organic solvent, so that the wettability on the surface of the bell cup is lower than that of the organic solvent-based metallic base, and the above-mentioned problems become remarkable. .
Japanese Utility Model Publication No. 58-174263

An object of this invention is to provide the bell cup of the rotary atomization type coating apparatus which can achieve high atomization even if it rotates at high speed.
In order to achieve the above object, a bell cup of a rotary atomizing coating apparatus according to the present invention has a rotary shaft, and a rotary atomizing type having a rotary cup and a bell cup attached to the rotary shaft and supplied with paint on the surface thereof. In the coating apparatus, the surface roughness Ra of the surface of the bell cup is 5 μm or more.

  In the present invention, since the surface roughness Ra is set to 5 μm or more by forming irregularities on the surface of the bell cup to which the paint is supplied, the wettability of the supplied paint is improved and the liquid film slips. As a result, a liquid film having a uniform thickness can be formed.

  This improves the atomization of the paint particles released from the edge of the bell cup, so even when applying a metallic base paint that requires a predetermined hue, the predetermined hue is not increased without increasing the flow rate of shaping air. Can be secured.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a first embodiment of a bell cup according to the present invention, and FIG. 2 is a front view (X arrow view). The figure shows the entire bell cup and the tip of the rotary atomizing coating device to which the bell cup is attached. In addition, the rotary atomizing coating device has an air motor for rotating the rotating shaft at high speed. , A voltage application device for applying a DC high voltage to the bell cup, a paint tube for supplying paint, cleaning liquid and cleaning air to the bell cup, an air tube for supplying shaping air around the bell cup, etc. It has been.

  The bell cup 1 of the present example is formed in a bell shape as schematically shown in the figure, and the surface 2 of the concave bell cup 1 serves as a paint supply surface. The bell cup 1 is fixed to the tip of the rotating shaft 3 via a hub 4 and rotates at a high speed as the rotating shaft 3 rotates. On the side surface of the hub 4 protruding from the center of the surface of the bell cup 1, paint supply holes or paint supply slits (typically indicated by 5) are formed at uniform intervals over the entire circumference, and the paint pipe 6 shown in FIG. The coating material supplied from the front end is discharged onto the surface 2 of the bell cup 1 through the coating material supply hole or the coating material supply slit 5 of the hub 4.

  In the outermost peripheral portion of the surface 2 of the bell cup 1, fine cut grooves 7 for atomizing the liquid film-like paint sent from the surface 2 of the bell cup 1 by centrifugal force are uniformly formed over the entire circumference. Has been.

  An outer cylinder member 8 for supplying shaping air is provided outside the bell cup 1, and the outer cylinder member 8 has an air passage 9, an annular air passage 10 communicating with the air passage 9, and an annular air An air outlet 11 formed at a predetermined interval from the passage 10 toward the back surface of the bell cup 1 is provided. Thereby, when spraying the paint, the shaping air having a predetermined flow rate is supplied from the back surface thereof, so that the paint particles can be conveyed in the direction of the object to be coated.

  In particular, the bell cup 1 of the present example is subjected to uneven treatment on the entire surface 2 to which the paint is supplied, and the surface roughness (surface roughness) Ra is 5 μm or more, 50 μm or 60 μm or less, and the surface roughness The maximum height Ry is 20 μm or more, 180 μm or 200 μm or less. It is desirable that the unevenness treatment range be at least a range in which the paint discharged from the paint supply hole of the hub 4 or the paint supply slit 5 forms a thin liquid film as the bell cup 1 rotates. That is, it is desirable to make the range shown by x in FIG. 1 and the hatched area in FIG. 2, but it is not necessary to perform uneven processing on the outermost peripheral portion of the bell cup 1 in which the cut groove 7 is formed.

  The unevenness treatment of this example is not limited to the treatment method as long as the surface roughness Ra and the maximum height Ry are the values described above. For example, sandblasting, shot blasting, thermal spraying, rolling, etc. Can be used.

  The unevenness treatment applied to the surface 2 of the bell cup 1 does not have to be a uniform pattern in a strict sense. However, as will be described later, the unevenness treatment improves the wettability of the paint with respect to the bell cup surface 2, and the uniform film Since the ability to form a thick liquid film is the reason why it is possible to achieve high atomization, it is desirable that the entire surface 2 of the bell cup 1 be subjected to a concavo-convex process that is as uniform as possible.

  The upper limit of the surface roughness Ra and the maximum height Ry of the surface 2 of the bell cup 1 described above, that is, the surface roughness Ra is 50 μm or 60 μm or less, the maximum height Ry is 180 μm or 200 μm or less, and there are two upper limit values. However, this is due to the following reasons.

  In other words, currently used metallic base paints include water-based metallic base paints that use water as a solvent and organic solvent-based metallic base paints that use an organic solvent as a solvent, but the surface tension of water is higher than that of organic solvents. Therefore, the wettability of the water-based metallic base paint on the bell cup surface is lower than that of the organic solvent-based metallic base. This is because the wettability of the paint has a problem that it takes time to clean the surface 2 of the bell cup 1 using a cleaning solvent after the paint is applied. That is, when the water-based metallic base paint is used, the surface roughness Ra of the surface 2 of the bell cup 1 is 50 μm or less, the maximum height Ry is 180 μm or less, and the surface roughness Ra when using the organic solvent-based metallic base paint = It is desirable to make it smaller than 60 μm or less and the maximum height Ry = 200 μm or less. However, if the cleaning time is not a problem, the larger the surface roughness Ra and the maximum height Ry, the smaller the average atomization diameter. Therefore, when priority is given to atomization, it is necessary to regulate the upper limit. There is no.

  When the surface 2 of the bell cup 1 is subjected to unevenness treatment, the wettability of the paint supplied from the paint supply hole of the hub 4 or the paint supply slit 5 is improved over the entire surface 2 of the bell cup 1, thereby As a result of preventing slippage, a liquid film having a uniform thickness is formed over the entire surface 2 of the bell cup 1.

  Therefore, the atomization of the paint particles discharged from the edge of the bell cup 1 is improved, and even when a metallic base paint requiring a predetermined hue is applied, the predetermined hue is not increased without increasing the flow rate of shaping air. Can be secured.

  In the embodiment shown in FIG. 1 and FIG. 2, the uneven surface treatment with a predetermined surface roughness and maximum height was applied to the entire surface 2 of the bell cup 1, but considering the above-described wettability improvement of the paint, Even if the unevenness treatment is applied to a part of the surface 2 of the bell cup 1, the same effect is exhibited.

  3 and 4 are front views of a bell cup 1 showing another embodiment according to the present invention, and a range shown by hatching is a portion subjected to uneven processing. In the bell cup 1 shown in FIG. 3, the unevenness processing is performed only on the outer peripheral range of the bell cup 1, and the unevenness processing is not performed on the central portion. In contrast, in the bell cup 1 shown in FIG. 4, concavity and convexity processing is performed only on the center portion of the bell cup 1, and the concavity and convexity processing is not performed on the outer periphery.

  In this way, even if the unevenness treatment is applied to a part of the surface 2 of the bell cup 1, the wettability of the paint is improved, so the degree of atomization is slightly inferior to the embodiment shown in FIG. 1 and FIG. The average atomization diameter is smaller than that of the bell cup 1 that is not subjected to the uneven treatment.

  However, it is desirable that the unevenness treatment is performed in the area ratio of at least 10% or more with respect to the surface 2 of the bell cup 1. This is because if it is less than 10%, it does not differ greatly from the average atomized diameter of the bell cup that is not subjected to the uneven treatment.

  Moreover, as shown in FIG. 3, the surface of the bell cup 1 that has been subjected to the unevenness treatment on the outer peripheral side of the surface 2 is compared to the surface of the bell cup 1 that has been subjected to the unevenness treatment as shown in FIG. It has been confirmed that the average atomization diameter is improved. As shown in FIG. 3, when the unevenness is applied to the outer peripheral side, the thickness of the liquid film immediately before being discharged from the edge of the bell cup 1 becomes uniform. .

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  Hereinafter, the present invention will be described more specifically.

Example 1
The entire surface of the bell cup (manufactured by Nissan Motor Co., Ltd., with a surface roughness of less than 5 μm) is subjected to uneven treatment with a surface roughness Ra of 5 μm and a maximum height Ry of 20 μm. Attached to.

  A water-based metallic base paint (Silver, Aqua BC-3 manufactured by Nippon Oil & Fats BASF Coatings Co., Ltd.) is discharged using this rotary atomizing coating device, with a discharge rate of 200 cc / min, a bell rotation speed of 70,000 rpm, and a shaping air flow rate of 280 NL / min. The average atomization diameter (μm) at this time was measured. Moreover, after discharging this metallic base coating material, the bell cup was automatically cleaned using cleaning water, and the surface cleaning property (easiness of cleaning) at that time was evaluated. This surface cleanability was evaluated as ◯ when the bell cup surface was cleaned by the cleaning process within 2 seconds, and Δ when it took 3 seconds or more to clean the bell cup surface.

  Further, using the rotary atomizing type coating apparatus equipped with the bell cup, the above-mentioned metallic base paint is applied to the test piece on which the intermediate coating film is formed, the discharge amount is 200 cc / min, the bell rotation number is 70,000 rpm, After coating with a shaping air flow rate of 280 NL / min so that the film thickness is 15 to 20 μm, and subsequently applying a clear paint on the metallic base coating film by wet-on-wet with a film thickness of 20 to 25 μm, These metallic base coating and clear coating were baked at 140 ° C. for 20 minutes.

  The obtained top coat film was measured for a color difference ΔL with the hue standard plate (hue standard contrast shade side lightness difference, NISSAN COLOR ANALYZER), and the results are shown in Table 1.

Example 2
The average atomization diameter (μm), color difference ΔL, and surface cleanability under the same conditions as in Example 1 except that the entire surface of the bell cup was subjected to unevenness treatment with a surface roughness Ra of 20 μm and a maximum height Ry of 100 μm. Measurement and evaluation. The results are shown in Table 1.

Example 3
The average atomization diameter (μm), color difference ΔL, and surface cleanability under the same conditions as in Example 1 except that the entire surface of the bell cup was subjected to unevenness treatment with a surface roughness Ra of 50 μm and a maximum height Ry of 180 μm. Measurement and evaluation. The results are shown in Table 1.

Example 4
The average atomization diameter (μm), color difference ΔL, and surface cleanability under the same conditions as in Example 1 except that the entire surface of the bell cup was subjected to unevenness treatment with a surface roughness Ra of 60 μm and a maximum height Ry of 200 μm. Measurement and evaluation. The results are shown in Table 1.

Example 5
The average atomization diameter (μm), color difference ΔL, and surface cleanability under the same conditions as in Example 1 except that the entire surface of the bell cup was subjected to unevenness treatment with a surface roughness Ra of 70 μm and a maximum height Ry of 220 μm. Measurement and evaluation. The results are shown in Table 1.

<< Comparative Example 1 >>
As a comparative example of Examples 1 to 5, the average atomization diameter (μm) and color difference under the same conditions as in Example 1 except that the entire surface of the bell cup was not subjected to unevenness treatment and the surface roughness was kept below 5 μm. ΔL and surface cleanability were measured and evaluated. The results are shown in Table 1.

Example 6
Examples 1 to 5 and Comparative Example 1 used a water-based metallic base paint, while Example 6 used an organic solvent-based metallic base paint (Silver, Bell Coat 6010 manufactured by Nippon Oil & Fats BASF Coatings). Measured and evaluated the average atomization diameter (μm), color difference ΔL, and surface cleanability under the same conditions as in Example 1. The results are shown in Table 1.

Example 7
The average atomization diameter (μm), color difference ΔL, and surface cleanability under the same conditions as in Example 6 except that the entire surface of the bell cup was subjected to unevenness treatment with a surface roughness Ra of 20 μm and a maximum height Ry of 100 μm. Measurement and evaluation. The results are shown in Table 1.

Example 8
The average atomization diameter (μm), color difference ΔL, and surface cleanability were the same as in Example 6 except that the entire surface of the bell cup was subjected to unevenness treatment with a surface roughness Ra of 50 μm and a maximum height Ry of 180 μm. Measurement and evaluation. The results are shown in Table 1.

Example 9
The average atomization diameter (μm), color difference ΔL, and surface cleanability were the same as in Example 6 except that the entire surface of the bell cup was subjected to unevenness treatment with a surface roughness Ra of 60 μm and a maximum height Ry of 200 μm. Measurement and evaluation. The results are shown in Table 1.

Example 10
The average atomization diameter (μm), color difference ΔL, and surface cleanability were the same as in Example 6 except that the entire surface of the bell cup was subjected to unevenness treatment with a surface roughness Ra of 70 μm and a maximum height Ry of 220 μm. Measurement and evaluation. The results are shown in Table 1.

<< Comparative Example 2 >>
As a comparative example of Examples 6 to 10, the average atomization diameter (μm) and color difference were the same as in Example 1 except that the entire surface of the bell cup was not subjected to unevenness treatment and the surface roughness was kept below 5 μm. ΔL and surface cleanability were measured and evaluated. The results are shown in Table 1.

  From the results of Example 1 and Comparative Example 1, Example 6 and Comparative Example 2, when the surface roughness Ra of the bell cup surface is 5 μm or more and the maximum height Ry is 20 μm or more, both water-based paints and organic solvent-based paints are used. It is understood that the average atomization diameter is reduced, the color difference from the hue standard plate is reduced, and the surface cleanability is not a problem.

  In addition, from the results of Examples 1 to 5 and Examples 6 to 10, as the surface roughness Ra and the maximum height Ry of the bell cup surface are increased, the average atomization of both water-based paints and organic solvent-based paints is increased. It is understood that the diameter is reduced and the color difference from the hue standard plate is also reduced.

  However, from the results of Examples 3 to 5, when the water-based paint is applied, when the surface roughness of the surface of the bell cup is 60 μm or more, the surface cleanability of the bell cup is lowered. From these results, it is understood that when the organic solvent-based paint is applied, the surface cleanability of the bell cup is lowered when the surface roughness of the bell cup surface is 70 μm or more.

It is sectional drawing which shows 1st Embodiment of the bell cup which concerns on this invention. It is a front view which shows 1st Embodiment of the bell cup which concerns on this invention. It is a front view which shows 2nd Embodiment of the bell cup which concerns on this invention. It is a front view which shows 3rd Embodiment of the bell cup which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Bell cup 2 ... Bell cup surface 3 ... Rotating shaft 4 ... Hub 5 ... Paint supply hole, paint supply slit 6 ... Paint pipe 7 ... Cut groove 8 ... Outer cylinder member 9, 10 ... Air passage 11 ... Air outlet

Claims (9)

In a rotary atomizing coating apparatus having a rotating shaft and a bell cup attached to the rotating shaft and supplied with paint on the surface thereof, the surface roughness Ra of the surface of the bell cup is 5 μm or more. The bell cup of the rotary atomizing type coating equipment. The bell cup of the rotary atomizing coating apparatus according to claim 1, wherein the maximum height Ry of the surface of the bell cup is 20 µm or more. The bell cup of the rotary atomizing coating apparatus according to claim 1 or 2, wherein the surface roughness Ra of the surface of the bell cup is 50 µm or less. The bell cup of the rotary atomizing coating apparatus according to claim 3, wherein the maximum height Ry of the surface of the bell cup is 180 µm or more. The bell cup of the rotary atomizing coating apparatus according to claim 1 or 2, wherein the surface roughness Ra of the surface of the bell cup is 60 µm or less. The bell cup of the rotary atomizing coating apparatus according to claim 5, wherein the surface roughness Ra of the surface of the bell cup is 200 μm or less. Of the surface of the bell cup to which the paint is supplied, the area ratio in the range where the surface roughness Ra is 5 μm or more is 10% or more, and the surface roughness Ra in the other range is less than 5 μm. A bell cup of the rotary atomizing coating apparatus according to any one of claims 1 to 6. The bell cup of the rotary atomizing coating apparatus according to claim 7, wherein the range where the surface roughness Ra is 5 µm or more is formed outside the surface of the bell cup. The bell cup of the rotary atomizing coating apparatus according to any one of claims 1 to 8, wherein the surface roughness Ra is 5 µm or more by forming irregularities on the surface of the bell cup.

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