JPH0641647Y2 - Rotary atomizing coating equipment - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention sprays paint from a rotary atomizing head that is rotationally driven by a drive source, and forms between the rotary atomizing head and an object to be coated. The present invention relates to a rotary atomizing coating device that electrostatically adsorbs a coating material on an object to be coated according to the applied potential difference.

[Conventional technology]

Conventionally, for example, as shown in Japanese Utility Model Laid-Open No. 60-54754,
While rotating the rotary atomizing head at high speed, the paint is sprayed from the tip of the rotary atomizing head to atomize the paint by centrifugal force to diffuse it, and a high voltage is applied to the rotary atomizing head to apply the coating. There is known a rotary atomizing coating apparatus that forms a predetermined potential difference with an object and electrostatically adsorbs the paint to an object to be coated according to the potential difference.

In the rotary atomizer, the centrifugal force acting according to the rotation of the rotary atomizing head causes the paint to diffuse into a donut shape, so that as shown in FIG. As shown in FIG. 15, when the thickness of the central portion of the film T is reduced, when a coating material H having a straight line portion G is coated with a coating material, a portion protruding from the straight line portion G, that is, a diagonal line There is a problem that the paint in the range I shown in is wastefully consumed. Therefore, in the above-mentioned conventional apparatus, a pattern-deformation ring that ejects air for pattern-deformation that regulates the spray direction of the paint is provided to prevent the paint from diffusing by the air and to make the thickness of the coating film uniform. , I try to suppress the waste of paint.

[Problems to be solved by the device]

As described above, by supplying air for coating pattern deformation that regulates the injection direction of the paint, the sprayed paint is moved toward the central portion side to make the thickness of the coating film uniform, Since the coating pattern is defined according to the arrangement of the air blowout holes formed in the pattern deforming ring, there is a problem that it is difficult to properly set the coating pattern corresponding to the shape of the object to be coated. is there. Further, in the case where the above-described air is used to control the injection direction of the paint, the injection direction of the paint cannot be effectively controlled unless a large amount of air is supplied, and the air supply amount becomes excessive. In that case, there is a problem that the direction in which the paint is ejected varies.

Incidentally, in place of the above configuration, a needle-shaped electrode for pattern deformation is installed in the peripheral portion of the rotary spray head, and a high voltage is applied to the electrode for pattern deformation to generate a potential difference,
It is conceivable that the spraying direction of the paint that is atomized and charged during spraying is regulated by the electric force generated according to the potential difference. For example, as shown by the phantom line in FIG. 15, by forming the coating pattern in a square shape corresponding to the shape of the object H to be coated, it is possible to prevent wasteful spraying of the coating material.

However, in the case of using the above-mentioned needle-shaped pattern-changing electrode, when the distance between the tip of this electrode and the object to be coated is small, the tip of the electrode is covered by the potential difference formed between them. There has been a problem that an overcurrent flows toward the coated object and a spark is generated due to the discharge phenomenon.

The present invention has been made in order to solve the above problems, and rotary atomization coating capable of accurately and easily changing a coating pattern according to the shape of an object to be coated without causing a discharge phenomenon. The purpose is to provide a device.

[Means for Solving the Problems]

The present invention sprays paint from a rotary atomizing head that is rotationally driven by a drive unit, and electrostatically applies the paint to the object to be coated according to the potential difference formed between the rotary atomizing head and the object to be coated. In the rotary atomizing coating device for adsorbing, a rectangular ring-shaped electrode is arranged around the rotary atomizing head, and a pin is projected from the corner portion of the ring-shaped electrode to the front end thereof. A ball-shaped electrode is provided and the same voltage is applied to the rotary atomizing head, the ring-shaped electrode and the ball-shaped electrode.

[Operation] According to the present invention having the above-described configuration, the spray direction of the paint is regulated by the voltage applied to the rotary atomizing head, the ring-shaped electrode, and the ball-shaped electrode, and the spray pattern of the paint has a straight portion. In addition to being formed in a shape corresponding to the object, the electrode facing the object to be coated is formed into a ball shape, so that the occurrence of a discharge phenomenon in which an overcurrent flows from this electrode toward the object to be coated is effectively prevented. To be done.

〔Example〕

FIG. 1 shows an embodiment of a rotary atomizing coating device according to the present invention. This rotary atomization coating apparatus includes a rotary drive unit 1 composed of an air motor or an electric motor (not shown), a bell type rotary atomization head 2 which is rotationally driven by the rotary drive unit 1 at a high speed of about 25000 rpm, and A ring-shaped electrode 5 is provided around a casing 3 of the drive unit 1 via a bracket 4, a pin 6 is provided so as to project forward from the ring-shaped electrode 5, and a pin 6 is provided at the tip of the pin 6. The ball-shaped electrode 7 and the casing 3 of the drive unit 1 have -70 to -100k.
And a high voltage cable 8 for applying a high voltage of V.

The rotary atomizing head 2 diffuses and sprays the paint supplied from a paint supply pipe (not shown) by a centrifugal force that acts according to the rotation of the rotary atomizing head 2, and at the same time, the high-voltage cable 8
Is configured to be anionized by the high voltage applied to the casing 3 of the drive unit 1. Further, an air supply pipe (not shown) for supplying air for regulating the coating pattern is connected to the casing 3 of the drive unit 1,
Air of a predetermined pressure is supplied from an air outlet hole formed at the tip of the casing 3 toward the peripheral portion of the rotary atomizing head 2.

As shown in FIG. 2, the ring-shaped electrode 5 is formed in a square surrounding the rotary atomizing head 2, and the electrode 5 is connected to the drive unit 1 via a lead wire provided in the bracket 4.
Is connected to the casing 3 or is connected to a high-voltage cable branched from the high-voltage cable 8 so that the voltage of the same polarity as that of the rotary atomizing head 2, that is, the voltage of the cathode is applied. The ball-shaped electrode 7 and the pin 6 are respectively arranged at the corners of the ring-shaped electrode 5 formed in a square shape, and the same voltage as that of the ring-shaped electrode 5 is applied via the pin 6. .

In order to apply the paint by spraying with the rotary atomizing coating device having the above-mentioned configuration, the high pressure cable 8 and the casing 3 of the drive unit 1 are transferred to the rotary atomizing head 2, the ring-shaped electrode 5 and the ball-shaped electrode 7. While applying a high voltage and supplying air for deforming the coating pattern around the rotary atomizing head 2 from the air supply pipe, the rotary atomizing head 2 is rotated to spray the paint. The sprayed paint is subjected to a centrifugal force acting according to the rotation of the rotary atomizing head 2 and the ring-shaped electrode 5 and the ball-shaped electrode 7 while the coating range is regulated by the air for deforming the coating pattern. And an electric force that acts according to the potential difference formed between the object and the object to be coated, fly in the direction of the resultant force, and adhere to the object to be coated.

That is, the above-mentioned paint is atomized when sprayed from the rotary atomizing head 2 and is negatively charged according to the voltage applied to the rotary atomizing head 2. Therefore, as shown in FIG.
Lines of electric force A formed between the rotary atomizing head 2 and the object H to be coated, and lines of electric force formed between the ring-shaped electrode 5 and the ball-shaped electrode 7 and the object H to be coated. It will be affected by B and will fly. The electric force E1 of the electric force line A and the electric force E2 of the electric force line B have the values shown in the following expressions.

E1 = Q1 × a ₁ / 2πε (a ₁ + X1) ^3/2 E2 = Q2 × a ₂ / 2πε (a ₂ + X2) ^{3/2 In} this formula, Q1 and Q2 are the charges given to electrodes 5 and 7, ε
Is the relative permittivity, X1 and X2 are the horizontal distances in the drawing from the installation position of the rotary atomizing head 2 and the electrodes 5 and 7 to the measurement point, a ₁ ,
a ₂ is the distance from the installation position of the rotary atomizing head 2 and the electrodes 5 and 7 to the object H to be coated.

When the distance l between the rotary atomizing head 2 and the electrodes 5 and 7 is set to 325 mm, the electric forces E1 and E2 and the electric lines of force of these are set.
The electric force E of the electric line of force formed by combining A and B is distributed as shown in FIG. Further, the combined electric force E becomes equal to the sum of the electric forces E1 and E2, and it is assumed that when the distance 1 is changed, the width of the electric field and the strength of the electric force E change. Therefore, by setting the distance 1 to an appropriate value, the centrifugal force generated according to the rotation of the rotary atomizing head 2 and the inertial force acting on the paint according to the air for deforming the paint putter and the electric force line A , B, the balance with the electric forces E1, E2 acting on the paint is adjusted, whereby the spread of the coating pattern can be regulated and the coating efficiency can be improved.

A first experimental example performed for confirming a change in the coating state according to the balance between the inertial force and the electric forces E1 and E2 will be described below. That is, the discharge rate is 200 cc / sec, the rotation speed is 25000 rpm, and the discharge pressure of the pattern deformation air is 2.0 kgf / cm ^2.
With the rotary atomizing head 2 set to No. 4 at a distance of 300mm from the object to be coated, viscosity # 4 FC21 ″ / 20 ℃ melamine alkyd paint (Scatter the paint with a NO.4 Ford cup to 20 ℃ The paint with a viscosity that requires 21 seconds to discharge at the temperature of 3) is sprayed at a booth wind speed of 0.3 to 0.35 m / sec for about 5 seconds, and the distance 1 between the rotary atomizing head 2 and the ring-shaped electrode 5 is increased. When the coating pattern width and the coating efficiency were measured with various changes, the coating pattern width data α and the coating efficiency data β were obtained as shown in Fig. 5. In the first experimental example, , The ring-shaped electrode 5
In order to observe the change in the coating state due to the application of a high voltage to the electrodes, the ring-shaped electrode 5 ′ formed in a circular shape as shown in FIGS. 6 and 7 was provided without providing the ball-shaped electrode 7. Was set up and the experiment was conducted.

From the above experimental data, when the distance 1 between the rotary atomizing head 2 and the ring-shaped electrode 5'is 150 mm or less, the coating pattern width decreases and the coating efficiency increases as the distance 1 increases. In the range where the distance l exceeds 150 mm, the coating pattern width increases as the distance l increases and the coating efficiency decreases, so that the distance l between the rotary atomizing head 2 and the ring-shaped electrode 5'is reduced. It was confirmed that the coating efficiency showed the maximum value when it was set to 150 mm. This is because the ring-shaped electrode 5'is provided when the distance l is 150 mm or less.
Electric force acting on the paint by applying high voltage to the paint
Since the effect of centrifugal force acting on the paint according to the rotation of the rotary atomizing head 2 is greater than the effect of E2, it is shown that the effect of regulating the spreading of the coating pattern by the electric force E2 is insufficient. There is.

Next, in order to confirm the change in the coating state when the supply pressure of the pattern deforming air is changed, the distance l is set to 15
When the second experiment was performed to measure the coating pattern width and the coating efficiency by changing the supply pressure of the pattern-deforming air variously in the state of setting to 0 mm, the data α and β as shown in FIG. 8 were obtained. Was given. From this experimental data, it was confirmed that the lower the air supply pressure is, the higher the coating efficiency is, the more the width of the coating pattern is increased, and the better the adhesion state of the coating is. This is because, in a rotary atomizing coating device provided with a ring-shaped electrode 5'for controlling the flight direction of the paint, when the above air is excessively supplied, the flight direction of the paint is disturbed due to the influence of the air and the adhered state of the paint On the contrary, it shows that it becomes defective. Therefore, as described above, the ring-shaped electrode 5,
It was confirmed that when 5'is provided, the air for pattern deformation, which was conventionally required to prevent the diffusion of the paint, is not required so much.

Further, as described above, the ring-shaped electrode 5 and the rotary atomizing head 2
Since the width of the coating pattern changes according to the distance l between
For example, as shown in FIG. 9, the ring-shaped electrode 5 is formed in a square shape, and the distance l between the rotary atomizing head 2 and the ring-shaped electrode 5 is increased.
Between the maximum value 1 and the minimum value l2 The shape of the coating pattern can be changed by, for example, arranging so as to produce a double difference. Then, a third experiment was carried out to confirm the shape of the coating pattern formed by changing the length of one side of the square ring electrode 5 variously, and the following experimental data were obtained.

That is, the length of one side of the electrode 5 is 150 mm, 200 mm, 30
When changed to 0 mm and 400 mm, the major axis value, minor axis value and square case of the formed coating pattern are 100
The value of the rate of change of the major axis and the minor axis in% was changed as shown below.

Major axis: 700mm, 650mm, 600mm, 600mm.

Minor axis: 640mm, 600mm, 560mm, 560mm.

Rate of change: 29.3%, 26.3%, 22.8%, 22.8%.

Thus, it was confirmed that the change rate of the coating pattern was extremely low and the square coating pattern could not be formed only by changing the shape of the ring-shaped electrode 5.

Next, as shown in FIG. 10, corona pins 9 are projected toward the object to be coated at the corners of the square ring-shaped electrode 5 having a side length of 300 mm, and the charges are concentratedly applied. When a fourth experiment was performed to confirm the shape of the coating pattern in the case of being, the major axis length of the coating pattern was 750 mm, the minor axis length was 560 mm, and the rate of change was 86.5%. It was confirmed that However, when the corona pin 9 has a small diameter and a large protrusion amount, an overcurrent may flow from the tip of the corona pin 9 toward the object to be coated, and a discharge phenomenon may occur. Therefore, when the diameter and the amount of protrusion of the corona pin 9 were set to various values and a fifth experiment for confirming the presence or absence of the discharge phenomenon by measuring the current value (μA) being energized was performed, the results are shown in the table below. Data was obtained.

From the above experimental data, the ratio of the protrusion amount of the corona pin 9 to the diameter is
It was confirmed that in the case of 1: 1 or when the shape of the corona pin 9 was formed into a shape close to a sphere, overcurrent did not flow and the discharge phenomenon did not occur.

Next, in the structure shown in FIG. 1 and FIG. 2, the ring-shaped electrode 5 is arranged 55 mm above the tip of the rotary atomizing head 2 and the pin of the corner of the ring-shaped electrode 5 is pinned. 6
6th experimental example carried out to confirm the generation state of the discharge phenomenon and the coating state when the ball-shaped electrode 7 corresponding to the spherical corona pin is installed at the tip of this pin 6 Will be described. That is, when the amount L of projection of the ball-shaped electrode 7 and the diameter D are variously changed and the state of occurrence of overcurrent is confirmed,
As shown in the drawing, when the diameter D of the ball-shaped electrode 7 is 5 mm and 10 mm, overcurrent occurs in all regions, and when the diameter D is 20 mm, the protrusion amount L is 60 mm or less. It was confirmed that no overcurrent occurred in the area.

In addition, when a seventh experiment was performed in which the projection amount L of the ball-shaped electrode 7 having a diameter of 20 mm was variously changed and the shape of the formed coating pattern was confirmed, the data shown in FIG. 12 were obtained. That is, the protrusion amount L is 30 mm, 40 mm, 50 mm, 60 m
When changed to m, 70 mm, and 90 mm, the difference between the major axis and the minor axis of the coating pattern, that is, the rate of change between the major axis and the minor axis became the following percentages for an ideal square.

Rate of change: 16.2%, 36.5%, 57.4%, 80.8%, 100%, 110
%.

Therefore, the projection amount L of the ball-shaped electrode 7 is set to about 60 mm, and the position of this electrode 7 and the position of the tip of the rotary atomizing head 2 are set to substantially the same position, which is ideal. It is possible to form a coating pattern having a shape close to a square. Moreover, the protrusion amount L of the ball-shaped electrode 7 is 70 mm.
In the following cases, it was confirmed that no stain was caused by the paint adhering to the electrode 7.

Next, the case where the paint is applied by the rotary atomization coating apparatus according to the embodiment of the present invention shown in FIGS. 1 and 2 and the rotary atomization coating apparatus used in the first experimental example, that is, the diameter of 150 mm An eighth experimental example for measuring the thickness of the coating film when the coating material is applied by a coating device having the ring-shaped electrode 5'is described. That is, three rotary atomizing coating devices were arranged at 550 mm intervals, respectively, and an experiment was conducted in which the objects to be coated having a width of 1500 mm were coated while reciprocating with a stroke of 420 mm. In this case, as shown by the solid line in FIG. 13, it was confirmed that the thickness of the coating film on the coated portion was thicker than that by the device of the first experimental example shown by the broken line.

Therefore, as described above, around the rotary atomizing head 2, a square ring-shaped electrode 5 to which a voltage having the same polarity as that of the rotary atomizing head 2 is applied and a ball-shaped electrode 7 protruding forward from the corner portion thereof. In the case of arranging, the coating pattern can be changed into an arbitrary shape without causing a discharge phenomenon in which an overcurrent flows from the electrodes 5 and 7 to the object to be coated, and the coating efficiency is effectively increased. Can be improved.

That is, the coating range of the paint in the installation portion of the electrode 7 is regulated by the electric force acting according to the voltage applied to the ball-shaped electrode 7, and the ball-shaped electrodes adjacent to each other are regulated by the regulation of the coating range. The fact that the coating range of the paint in the middle part of 7, 7 expands as shown by the broken line I ′ in FIG. 16 is restricted by the electric force acting according to the voltage applied to the ring-shaped electrode 5. As shown by the solid line I, the coating range of the paint is set to a state close to a square.

Since the shape of the coating pattern can be arbitrarily changed according to the shape of the object to be coated, the mounting position of the bracket 4 supporting the ring-shaped electrode 5 and the ball-shaped electrode 7 can be adjusted. By changing the distance between the ball-shaped electrode 7 and the object to be coated, or by changing the distance 1 between the ball-shaped electrode 7 and the rotary atomizing head 2, the magnitude of the electric force E2 is changed. It is desirable to be able to adjust.

[Effect of device]

As described above, according to the present invention, the rectangular ring-shaped electrode is arranged around the rotary atomizing head, and the pin is projected from the corner of the ring-shaped electrode to the front end. Since a ball-shaped electrode is provided and the same voltage is applied to the rotary atomizing head, the ring-shaped electrode and the ball-shaped electrode, respectively, the paint can be diffused and the central portion of the coating pattern can be covered with a simple structure. It is possible to prevent the thickness of the product from becoming thin, and by controlling the coating pattern according to the shape of the object to be coated that has a straight portion,
There are advantages such as preventing wasteful spraying of the paint. Further, it is possible to effectively prevent an overcurrent from flowing from the ball-shaped electrode to the object to be coated, and to reliably prevent the occurrence of a discharge phenomenon.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a rotary atomizing coating apparatus according to the present invention, FIG. 2 is a bottom view of the coating apparatus, FIG. 3 is an explanatory view showing a state of forming electric lines of force, and FIG. Is a graph showing the magnitude of electric force, FIG. 5 is a graph showing experimental data of the first experimental example conducted to confirm the effect of the present invention, and FIG. 6 is a graph showing the apparatus used in the first experimental example. Front view, FIG. 7 is a bottom view of the device used in the first experimental example, FIG. 8 is a graph showing experimental data of the second experimental example, and FIG. 9 is a bottom view of the device used in the third experimental example. , FIG. 10 is a front view of the apparatus used in the fourth experimental example, FIG. 11 is a graph showing experimental data of the fourth experimental example, FIG. 12 is a graph showing experimental data of the seventh experimental example, and FIG. The figure is a graph showing the experimental data of the eighth experimental example.
FIG. 14 is a cross-sectional view showing a coating pattern of a conventional device, FIG. 15 is an explanatory diagram showing a coating state by the conventional device, and FIG. 16 is an explanatory diagram showing a coating pattern of paint. 1 ... driving part, 2 ... rotary atomizing head, 5 ... ring-shaped electrode, 6 ... pin, 7 ... ball-shaped electrode, H ... painted object.

Claims (1)

[Scope of utility model registration request] 1. A paint is sprayed from a rotary atomizing head which is rotationally driven by a drive unit, and the paint is statically applied to the object to be coated according to a potential difference formed between the rotary atomizing head and the object to be coated. In a rotary atomizing coating device for electroadsorption, a rectangular ring-shaped electrode is arranged around the rotary atomizing head, and a pin is provided so as to project from a corner portion of the ring-shaped electrode to the front side. A rotary atomization coating apparatus, wherein a ball-shaped electrode is provided in the rotary atomization head, and the same voltage is applied to the rotary atomization head, the ring-shaped electrode, and the ball-shaped electrode, respectively.