JP5826662B2 - Rotary atomizing electrostatic coating machine - Google Patents

Description

  The present invention relates to a rotary atomizing electrostatic coating machine and a rotary atomizing head (bell cup).

  Electrostatic coating is a coating method using a charged paint, and a rotary atomizing electrostatic coating machine equipped with a rotary atomizing head is widely used particularly for painting automobile bodies (Patent Documents 1 to 3). A painting booth equipped with a painting robot is installed in the automobile production line, and painting is applied to the automobile body that passes through the painting booth one after another.

  Patent Document 1 proposes an improvement plan related to electrostatic coating of metallic paint including metallic pieces such as aluminum pieces and mica. When the amount of shaping air discharge is increased based on the knowledge that the brightness of the paint color increases as the speed at which the metallic paint collides with the workpiece increases, the width of the paint pattern decreases accordingly. There is a problem that unevenness of coating occurs and the quality of the finished product deteriorates. The invention proposed in Patent Document 1 aims at preventing the coating pattern width from becoming smaller even when the discharge amount of the shaping air is increased, and the shaping air toward the rotary atomizing head, that is, the outer periphery of the bell cup. It is proposed that the shaping air discharge port is directed in the forward or reverse twist direction with respect to the axis of the rotation axis of the bell cup. According to this proposal, the shaping air becomes an air flow that draws a spiral trajectory, and the coating pattern is brought inward by overcoming the suction force due to the negative pressure generated in the front area of the bell cup by the centrifugal force of this spiral air flow. It can be prevented from being drawn.

  Patent Document 2 proposes an improvement plan for this problem, citing the problems of the invention of Patent Document 1 described above. That is, according to the invention of Patent Document 1, the width of the coating pattern is widened, but with the constant width, overspray occurs when painting a narrow part of an automobile body, resulting in a loss of paint. The problem of increasing occurs. In response to this problem, the invention of Patent Document 2 proposes that control air is discharged in addition to shaping air, and the width of the coating pattern is variably controlled by this control air.

  Patent Document 3 proposes an invention aimed at improving the problem of overspray when painting a narrow part of an automobile body, as in the invention of Patent Document 2. Specifically, in the invention of Patent Document 3, the absolute value of the inclination angle of the control air discharge port is set to be larger than the inclination angle of the shaping air discharge port with respect to the shaping air that is a swirling flow and the control air that is positioned on the outer peripheral side thereof. Propose to enlarge. According to the invention of Patent Document 3, by setting the absolute value of the inclination angle of the control air discharge port to be larger than the inclination angle of the shaping air discharge port, the control air can increase the degree of turning compared to the shaping air. The width of the coating pattern can be variably controlled by relatively increasing or decreasing the amount of control air and the amount of shaping air.

JP-A-3-101858 Japanese Patent Laid-Open No. 7-24367 JP 2008-93521 A

  In order to promote the efficiency of painting automobile bodies, it is meaningful to expand the width of painting patterns. That is, even if the operating speed of the painting robot is the same, the painting time can be shortened by increasing the width of the painting pattern. In addition, the overlapping width of the coating can be set large by increasing the width of the coating pattern. This means that the moving distance of the painting robot can be set small, and the painting time can be shortened by shortening the moving distance of the painting robot.

  In addition, the improvement of the atomization of the paint is effective in improving the quality of the coating. Of course, the development of technology for atomizing paint leads to improved coating quality, but when the coating quality is the same as before, this atomization technology can be used for air used for electrostatic coating. Including the possibility of reducing the amount and the number of rotations of the rotary atomizing head.

  An object of the present invention is to provide a rotary atomizing electrostatic coating machine and a rotary atomizing head capable of expanding the width of a coating pattern.

  It is a further object of the present invention to provide a rotary atomizing electrostatic coating machine and a rotary atomizing head capable of finely atomizing a paint.

  A further object of the present invention is to provide a rotary atomizing electrostatic coating machine and a rotary atomizing head capable of improving the coating efficiency.

The above-mentioned technical problem, according to the onset Akira,
A rotary atomizing head having an inner surface composed of a recess open toward the front and a back surface with an inclined surface that gradually increases in diameter toward the front, and a rotary shaft disposed in the main body of the coating machine A rotary atomizing head attached to the tip of the
An atomizing air discharge port that is arranged in the coating machine body and discharges atomized air toward the inclined surface on the back of the rotary atomizing head;
The atomized air discharge port is directed in a direction opposite to the rotational direction of the rotary atomizing head;
The outer peripheral edge of the rotary atomizing head is configured with a sharp edge where the outer peripheral edge of the inner surface intersects with the outer peripheral edge of the back surface ,
The back surface of the rotary atomizing head has a shape in which a region extending from the portion to which the atomized air discharged from the atomized air discharge port hits to the outer peripheral edge is straightly inclined. This is accomplished by providing a rotary atomizing electrostatic coating machine.

  The effects of the present invention will become apparent from the detailed description of the following examples.

It is sectional drawing of the front part of the rotary atomization type electrostatic coating machine of an Example. It is a figure for demonstrating the setting of the shaping air discharge port (atomization air discharge port) with which the rotary atomization type electrostatic coating machine of an Example is provided. It is a front view of the coating machine main body of the rotary atomizing electrostatic coating machine of an Example. It is sectional drawing for demonstrating the shape of the outer periphery of the bell cup of an Example. It is sectional drawing for demonstrating the shape of the outer periphery part of the conventional bell cup corresponding to FIG. It is a figure which shows the measured value of the film thickness distribution of the workpiece | work coated using the rotary atomization type electrostatic coating machine of an Example. It is a figure which shows the relationship between the discharge amount of the coating material of the rotary atomization type electrostatic coating machine of an Example, and the average particle diameter of a coating material.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view of a front portion of a rotary atomizing electrostatic coating machine according to an embodiment. Referring to FIG. 1, a rotary atomizing electrostatic coating machine 1 has a rotary atomizing head 2, and this electrostatic coating machine 1 is a robot arm installed in a painting booth for painting a car body. (Not shown) or the like. Since the rotary atomizing head 2 is generally called “bell cup”, the term “bell cup” is used in the following description.

  The electrostatic coating machine 1 has a built-in air motor (not shown) at the tip of the coating machine body 4. The bell cup 2 is detachably connected to the output shaft 6 of the air motor, and the bell cup 2 rotates in one direction when the air motor operates.

  The bell cup 2 has an inner surface 2a composed of a recess opened toward the front side, and a back surface 2b constituted by an inclined outer peripheral surface whose diameter increases toward the front side. The inner surface 2a of the bell cup 2 has a spreading function for spreading the paint thinly along the inner surface 2a. A shaping air discharge port 8 is opened forward on the front end surface of the coating machine body 4.

  A plurality of the shaping air discharge ports 8 are arranged at equal intervals on a concentric circle of the motor output shaft 6. The directing direction of the shaping air discharge port 8 will be described in detail later. Liquid paint is supplied to the bell cup 2 through a paint supply pipe 10 to a paint reservoir 14 continuously extending in the circumferential direction of the central portion thereof, and the paint discharge port 12 formed in the central portion of the bell cup 2. The paint flows out to the bell cup inner surface 2a. A plurality of the paint discharge ports 12 are formed at equal intervals on a concentric circle of the axis A of the motor output shaft 6 as in the prior art. A high voltage is applied to the bell cup 2 from a high voltage generator (not shown).

  The shaping air discharge port 8 will be described with reference to FIGS. FIG. 2 is a side view of the tip portion (bell cup 2) of the electrostatic coating machine 1, and FIG. With reference to FIG. 2, the directing direction of the shaping air discharge port 8 is directed to the back surface 2 b of the bell cup 2 along a straight line SL parallel to the axis A of the motor output shaft 6 when viewed from the side. .

  2 and 3, when the shaping air discharge port 8 is viewed from the front, each shaping air discharge port 8 has a rotation direction R of the bell cup 2 with respect to a straight line SL passing therethrough. In the opposite direction, the angle of inclination β, that is, the motor output shaft 6 is directed in the twist direction opposite to the rotation direction R. Here, the straight line SL is parallel to the axis A of the motor output shaft 6.

  As described above, as is apparent from FIG. 3, a plurality of shaping air discharge ports 8 are arranged at equal intervals on a concentric circle of the axis A of the motor output shaft 6 when the bell cup 2 is viewed from the front. Yes. The shaping air SA discharged from the plurality of shaping air discharge ports 8 is directed in the direction opposite to the rotation direction of the bell cup 2 and directed toward the bell cup back surface 2b.

  Referring again to FIG. 1, the bell cup 2 has a back surface 2 b which is linearly inclined to the outer peripheral edge 2 c of the bell cup 2 at an inclination angle of γ with respect to a vertical line VLa perpendicular to the axis A of the motor output shaft 6. The back surface 2b has an inclination angle γ of 55 ° (γ = 55 °). The region (symbol L in FIG. 2) that extends straight to the outer peripheral edge 2c at the inclination angle γ of 55 ° includes at least a portion P where the shaping air SA hits the back surface 2b (FIG. 2). That is, on the back surface 2b of the bell cup 2, at least a region from the portion P (FIG. 2) where the shaping air SA hits to the outer peripheral edge 2c extends straight at an inclination angle γ of 55 °. On the other hand, the shape of the bell cup back surface 2b on the inner peripheral side with respect to the portion P where the shaping air SA collides is arbitrary. Here, in this embodiment, the diameter of the bell cup 2 was 77 mm, and the distance L from the portion P where the shaping air SA hits to the outer peripheral edge 2c was 6 mm. The distance L from the portion P where the shaping air SA hits to the outer peripheral edge 2c is 2 to 70 mm, preferably 3 to 20 mm, and most preferably 4 to 10 mm. The shaping air SA is placed at a position close to the outer peripheral edge 2c of the bell cup 2. It is easier to smash and atomize the paint with a smaller amount of air than to apply the shaping air SA to a position far away from the outer peripheral edge 2c, and contribute to the efficiency of the paint adhering to the workpiece, that is, the application efficiency. Can do. In other words, the greater the distance L from the position P where the shaping air SA hits the bell cup back surface 2b to the bell cup outer periphery 2c, the lower the force (momentum) of air that divides the paint at the bell cup outer periphery 2c. Therefore, it is necessary to increase the amount of shaping air SA.

  Since the inclination angle γ of the bell cup back surface 2b is set to 55 ° and the directing direction of the shaping air discharge port 8 is set in parallel with the axis A of the motor output shaft 6 in a side view, as shown in FIG. The incident angle α of the shaping air SA with respect to the bell cup back surface 2b is 55 ° (α = 55 °). In order to prevent diffusion of the shaping air SA and amplify kinetic energy, the incident angle α of the shaping air SA with respect to the bell cup back surface 2b is preferably 20 ° to 70 ° when viewed from the side.

  The incident angle α of the shaping air SA can be set by the inclination angle γ of the bell cup back surface 2b and the angle with respect to the axis SL (FIG. 2) of the shaping air discharge port 8 when viewed from the side. Regarding the coating pattern width of the electrostatic coating machine 1, a desired coating pattern width can be set by adjusting the inclination angle γ of the bell cup back surface 2b. In order to set the optimal incident angle α of the shaping air SA when the inclination angle γ of the bell cup back surface 2b that is convenient for obtaining the desired coating pattern width is set, the desired incident angle α of the shaping air SA is What is necessary is just to set the discharge direction of the shaping air discharge port 8 so that it may be implement | achieved.

  As in the embodiment, the shaping air SA is applied to the rotational direction R of the bell cup 2 with respect to the paint that is atomized while being scattered radially outward from the outer peripheral edge of the bell cup 2 and in the rotational direction R of the bell cup 2. By directing the shaping air SA to the bell cup back surface 2b in the opposite direction, the shaping air SA collides with the paint in a state intersecting with the paint scattering direction, thereby further promoting the atomization of the paint. it can.

  FIG. 4 is an explanatory view partially showing the outer peripheral edge portion of the bell cup 2 of the embodiment, and FIG. 5 is an explanatory view partially showing the outer peripheral edge portion of the conventional bell cup 20. The conventional bell cup 20 has a flat surface 22 whose outer peripheral edge 20c is parallel to the axis of the motor output shaft, and the outer peripheral edge of the inner surface 20a of the bell cup 20 and the outer peripheral edge of the back surface 20b are the flat surfaces. 22 are connected to each other. On the other hand, the outer peripheral edge 2c of the bell cup 2 of the embodiment is configured by an edge where the outer peripheral edge of the inner surface 2a and the outer peripheral edge of the back surface 2b intersect each other, and preferably by a sharp edge. The crossing angle between the inner surface 2a and the rear surface 2b of the bell cup 2 is preferably 5 ° to 60 °.

  Since the bell cup 2 of the embodiment has the sharp outer peripheral edge 2c, the shaping air SA that collides with the rear face 2b of the bell cup 2 flows along the rear face 2b of the bell cup 2, and this flow flows along the sharp outer peripheral edge 2c. It is maintained even if it passes (FIG. 4).

  On the other hand, even if the shaping air SA is applied to the back surface 20b of the conventional bell cup 20, the Coanda effect occurs on the flat surface 22 that intersects the outer peripheral edge of the back surface 20b. When moving away from the outer peripheral edge of the bell cup 20, a radially inward air flow is generated along the flat surface 22 constituting the outer peripheral edge of the bell cup 20, so that the shaping air SA leaving the bell cup 20 is dispersed in the radial direction. (Fig. 5). Along with this, the paint pattern formed by the bell cup 20 becomes a blurred pattern in which the outer peripheral edge is poorly cut.

  According to the experiment, in the bell cup 2 of the example, the coating pattern tended to converge inward due to the central negative pressure of the bell cup 2 at a rotational speed of 20,000 rpm or less. When the rotational speed of the bell cup 2 was increased to 20,000 rpm or more, the coating pattern tended to spread. On the other hand, in the conventional bell cup 20 in which the outer peripheral edge 20c is constituted by the flat surface 22, the coating pattern tends to converge inward due to the central negative pressure of the bell cup 2 at a rotational speed of 20,000 rpm or less. Is the same as that of the example, but in the conventional example, even if the rotation speed of the bell cup 2 is increased, the width of the coating pattern is smaller than that of the example. It has been found that the peripheral edge 2c is effective in expanding the width of the coating pattern.

  Accordingly, when the use purpose of the bell cup 2 of the embodiment provided with the outer peripheral edge 2c having a sharp edge shape in which the outer peripheral edge of the inner surface 2a intersects with the outer peripheral edge of the back surface 2b is set to enlarge the width of the coating pattern, Since the overlapping width of painting can be set large, the painting time can be shortened by setting the moving distance of the painting robot small.

  The film thickness of the paint when the bell cup 2 of the example and the conventional bell cup 20 were coated under the same conditions was measured. The coating conditions are as follows, and the measurement results are shown in FIG.

Painting conditions :
(1) Bell cup rotation speed: 25,000 rpm;
(2) Shaping air SA discharge speed: 375 Nl / min.
(3) Discharge rate of paint: 300cc / min.
(4) Voltage applied to bell cup: -90kV
(5) Separation distance (HTD) between bell cup and workpiece: 300mm

  Referring to FIG. 6 showing the measurement results, the horizontal axis of FIG. 6 represents the horizontal distance (mm) from the center of the workpiece that intersects the axis of the bell cup, and the vertical axis represents the coating film thickness (μm). The black marks in FIG. 6 are conventional examples, and the white marks are examples. The paint used was a solid solid paint that is not a metallic paint containing metallic pieces such as aluminum pieces and mica, but may be a metallic paint.

  In the conventional example, the film thickness decreases abruptly when the distance from the center of the workpiece exceeds 120 mm. On the other hand, in the embodiment, a substantially uniform film thickness can be maintained from the center of the workpiece to 200 mm. This also shows that the sharp outer peripheral edge 2c of the bell cup 2 of the embodiment is effective for enlarging the coating pattern.

  FIG. 7 shows data obtained by measuring the relationship between the discharge amount of the paint and the average particle diameter of the paint. Referring to FIG. 7, in the painting line of an automobile, the current painting conditions are as follows: (1) Discharge amount of paint is about 300 cc / min. And (2) Average particle diameter of paint is about 20 μm. . According to the electrostatic coating machine 1 of the example implemented on the same conditions, it should be noted that the average particle size of the paint is 20 μm or less in the range of the discharge amount of the paint of 300 to 600 cc / min. In other words, this means that the amount of paint discharged can be doubled compared to the current painting line. In other words, it can be said that the electrostatic coating machine 1 of the embodiment has the ability to maintain the quality of the coating even when the work conveying speed of the coating line of the automobile body is doubled. That is, it can be said that the electrostatic coating machine 1 of an Example is equipped with the capability which can improve the coating efficiency of a motor vehicle body greatly.

  In the bell cup 2 of the embodiment, the outer peripheral edge 2c is preferably provided with a sharply sharp edge (FIGS. 3 and 4), and the shaping air SA collides with the bell cup back surface 2b and the shaping air SA is bell. As described above, a sharp coating pattern and atomization can be realized by directing in the direction opposite to the rotation direction of the cup 2. This can reduce the discharge amount of the shaping air SA, that is, the amount of air used, when the coating quality and the coating pattern width are set to be the same as the conventional one.

  The coating conditions of the current electrostatic coating machine using the conventional bell cup 20 described with reference to FIG. 5 and using the well-known straight type shaping air that discharges the shaping air parallel to the axis of the motor output shaft are as follows: It is as follows.

Coating conditions for electrostatic coating machines currently used in car body painting lines :
(1) Paint pattern width: 330mm
(2) Average particle diameter of paint: 15.8 μm
The air pressure for shaping air was 0.15 MPa, and the distance to the workpiece (gun distance) was 300 mm.

The coating conditions when the electrostatic coating machine 1 of the example was operated in conformity with the above-described current coating conditions were as follows.
(1) Air pressure for shaping air SA: 0.03 MPa
(2) Paint pattern width: 390mm
(3) Average particle diameter of paint: 14.6 μm
(4) Distance to work (gun distance): 300mm
The paint used is a solid paint that is not a metallic paint containing metallic pieces such as aluminum pieces and mica, but may be a metallic paint.

  What should be noted here is that the coating efficiency of the current electrostatic coating machine is 87.0%, whereas the coating efficiency of the electrostatic coating machine 1 of the example is 92.5%. . That is, it was confirmed that the electrostatic coating machine 1 of the example can improve the coating efficiency by 5.5%.

  In the electrostatic coating machine 1 of the example, although the air pressure for shaping air (0.03 MPa) is lower than the conventional pressure (0.15 MPa), atomization of the paint can be realized. Moreover, it has succeeded in improving the coating efficiency by 5.5%. Incidentally, in the above experimental example, the distance to the workpiece is set to 300 mm, which is the same as the current painting line for painting the automobile body. However, in the electrostatic coating machine 1 of the embodiment, as the air pressure for shaping air, it is conventionally Since a significantly lower pressure can be set, the distance (gun distance) between the electrostatic coating machine 1 and the workpiece can be set to 200 mm, for example. A person skilled in the art can easily understand that further improvement of the coating efficiency can be expected by setting the gun distance small.

  As a modification of the bell cup 2 included in the embodiment shown in FIG. 1, a prototype (in which the incident angle α of the shaping air SA is 45 °) with the inclination angle γ of the bell cup back surface 2b set to 45 ° is described above. When various tests were performed, the result was substantially the same as or slightly inferior to that of the bell cup 2 (γ = 55 °) included in the above-described example. From this, it can be inferred from the experiment that a better result is obtained as the inclination angle γ of the bell cup back surface 2b becomes larger. Further, it is considered that the shaping air SA collided with the bell cup back surface 2b, thereby eliminating the diffusion of the shaping air SA and aggregating the kinetic energy of the shaping air SA, thereby contributing to the atomization of the paint more effectively. . And it can be inferred that the ability of atomization is improved more effectively and the above-described excellent effects are obtained by configuring the outer peripheral edge 2c of the bell cup with an edge where the inner surface 2a and the back surface 2b intersect.

  Since the bell cup 2 included in the embodiment is configured by an edge where the inner surface 2a and the back surface 2b intersect, as described above, the width of the coating pattern of the electrostatic coating machine 1 is the inclination angle of the bell cup back surface 2b. It can be defined by γ. Therefore, a desired coating pattern width can be obtained by adjusting the inclination angle γ of the bell cup back surface 2b.

  As described above, the preferred embodiment of the present invention has been described. In addition to the shaping air SA applied to the back surface 2b of the bell cup 2, an additional air discharge port is provided on the outer side in the radial direction, and discharge is performed from the additional air discharge port. You may make it perform control which narrows the width | variety of a coating pattern with the air to perform. In this way, when adopting a form that discharges air internally and externally, if the air discharged from the additional air discharge port is called `` control air '', by controlling the amount of this control air, The width can be variably controlled. In this electrostatic coating machine that discharges air inside and outside, when the air applied to the bell cup back surface 2b is called "atomization air" and the outside air is called "control air", the control air is not included. In order to make the terminology common to the shaping air SA of the electrostatic coating machine 1 of the example, the air applied to the bell cup back surface 2b can be collectively referred to as a term “atomization air”. The “shaping air discharge port” used in the description of the embodiments can be collectively referred to as “atomization air discharge port”.

1 Rotating Atomizing Electrostatic Coating Machine 2 Bell Cup (Rotating Atomizing Head)
2a Bell cup inner surface 2b Bell cup back surface 2c Bell cup outer periphery 4 Coating machine body 6 Output shaft of air motor 8 Shaping air discharge port (atomization air discharge port)
10 Paint Supply Pipe 14 Paint Reservoir 12 Paint Discharge Port SA Shaping Air (Atomization Air)
A Axis of motor output shaft α Incident angle of shaping air β Twist angle of shaping air discharge port
(Reverse direction of bell cup rotation)
γ Bell cup back tilt angle

Claims (6)

A rotary atomizing head having an inner surface composed of a recess open toward the front and a back surface with an inclined surface that gradually increases in diameter toward the front, and a rotary shaft disposed in the main body of the coating machine A rotary atomizing head attached to the tip of the
An atomizing air discharge port that is arranged in the coating machine body and discharges atomized air toward the inclined surface on the back of the rotary atomizing head;
The atomized air discharge port is directed in a direction opposite to the rotational direction of the rotary atomizing head;
The outer peripheral edge of the rotary atomizing head is configured with a sharp edge where the outer peripheral edge of the inner surface intersects with the outer peripheral edge of the back surface ,
In the back surface of the rotary atomizing head, a region from the portion where the atomized air discharged from the atomized air discharge port collides to the outer peripheral edge of the back surface has a straight inclined shape. A rotary atomizing electrostatic coating machine that is characterized. A plurality of the atomized air discharge ports are formed on the front end surface of the coating machine body,
The rotary atomizing electrostatic coating machine according to claim 1, wherein the plurality of atomized air discharge ports are arranged at equal intervals on a concentric circle with the axis of the rotary shaft. When viewed from the side of the rotary atomizing head, the incident angle of the atomization air for the back of the rotary atomizing head is 20 ° to 70 °, rotary atomizing type electrostatic according to claim 1 or 2 Painting machine. The rotary atomization according to any one of claims 1 to 3 , wherein a distance between a portion where the atomized air collides with the rotary atomizing head and an outer peripheral edge of the rotary atomizing head is 2 to 70 mm. Type electrostatic coating machine. The rotary atomization type | formula as described in any one of Claims 1-3 whose distance of the site | part with which the said atomization air collides with the said rotary atomization head and the outer periphery of the said rotary atomization head is 3-20 mm. Electrostatic coating machine. The rotary atomization type according to any one of claims 1 to 3, wherein a distance between a portion where the atomized air collides with the rotary atomizing head and an outer peripheral edge of the rotary atomizing head is 4 to 10 mm. Electrostatic coating machine.

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