JP2007203257A - Spray pattern adjustable mechanism and spray pattern adjustable method of bell-type painting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spray pattern adjustable mechanism which gives a good painting surface even if the size of a spray pattern is changed. <P>SOLUTION: A bell-type painting apparatus 1 has a bell 3 and a plurality of spray openings 13a. The bell 3 makes a paint centrifugally atomize from an edge 3a in the radial direction by rotation while the paint is supplied into a concave part 31 forming a circular edge 3a. Shaping air is ejected from a plurality of spray openings 13a towards a slope 32 formed on the outer surface opposite to the concave part 31. Rotation control of the bell 3a is carried out to change the rotation speed of the bell 3a so that the circumferential speed of the edge 3a becomes the velocity near subsonic, and thus the spray pattern being painted on the material to be painted is changeable. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrostatic spraying device that electrically charges a spray of paint. In particular, the present invention relates to a spray pattern variable mechanism and a spray pattern variable method in a so-called bell type coating apparatus having a swivel outlet or a deflecting element.

  There is electrostatic painting as a painting method called atomization painting. For example, in electrostatic coating, a centrifugal force is applied to a paint to atomize, and the atomized paint particles are charged with static electricity to coat an object to be coated. Electrostatic coating is a kind of atomization coating, in which liquid particles, air pressure, and centrifugal force are applied to charge the atomized paint particles to electrostatically coat the object to be coated (work).

  Specifically, in electrostatic coating, an object to be coated is grounded (grounded), and a rotary atomizing coating apparatus (hereinafter referred to as a bell-type coating apparatus) is made a high voltage negative electrode. By making the bell type coating apparatus side a negative electrode, the surface of the object to be coated is positively charged. As a result, an electrostatic field is formed between the object to be coated and the bell type coating apparatus. Since the paint particles sprayed from the bell-type coating device are negatively charged, they are applied toward the positively charged object. In general, such a bell-type coating apparatus is considered to have little waste of paint compared to a coating apparatus using a spray gun.

  As such a bell-type coating apparatus, an invention has been disclosed in which paint particles are reliably charged to a high voltage and charged paint particles are transported to an object to be coated to improve the coating efficiency (for example, Patent Document 1). reference).

The bell-type coating apparatus according to Patent Document 1 is provided with an electrode bar whose tip protrudes in front of a bell (rotating atomizing head). Further, an external electrode branched into four toward the front of the bell is provided at the tip of the electrode rod. As a result, the branching external electrode forms an ionization zone in front of the bell from the axial center side to the outer peripheral side, so that the paint particles passing through a wide range from the axial center side to the outer peripheral side of the bell are charged to a high voltage. Can be made. Further, by making the distance dimension L1 between the tip of the external electrode and the paint discharge edge of the bell and the distance dimension L2 between the tip of the external electrode and the object to be coated substantially equal, The electric field strength between the objects can be increased.
JP 2003-236417 A

  FIG. 7 is a front view showing a configuration of a bell-type coating apparatus according to Patent Document 1, and a part thereof is drawn in a broken state. FIG. 7 of the present application corresponds to FIG. FIG. 8 is a bottom view of the bell-type coating apparatus shown in FIG. 7 viewed from the paint spraying side. FIG. 8 of the present application corresponds to FIG. FIG. 9 is a front view showing a state where an object to be coated is applied using the bell-type coating apparatus according to Patent Document 1, and a part of the object is drawn in a broken state. FIG. 9 of the present application corresponds to FIG.

  In FIG. 7, a cover 71 is formed in a cylindrical shape using an insulating synthetic resin material, and an air motor 72 is accommodated therein. The air motor 72 includes a motor main body 72a, an air turbine, and a static pressure air bearing (all not shown). The air motor 72 rotationally drives the rotary shaft 73 by supplying high-pressure air to the air turbine.

  The bell 74 atomizes the paint supplied from the feed tube 75 while rotating by the rotating shaft 73. The bell 74 has a stepped cylindrical mounting portion 74a whose one end is screwed to the tip of the rotary shaft 73, and a cup-shaped paint spraying portion 74b whose other end is expanded outward. The front surface side of the paint spraying portion 74b is a paint smoothing surface 74c for smoothing the paint, and the front end side of the paint spraying portion 74b is a paint discharge edge for discharging the paint supplied from the paint smoothing surface 74c. 74d. On the rear side of the paint spraying part 74b, a paint receiving part 74f is formed by a stepped cylindrical part 74e. A plurality of paint outflow holes 74g reaching the paint smoothing surface 74c from the paint receiving part 74f are arranged in an annular shape in the paint spraying part 74b (see FIG. 8).

  The feed tube 75 supplies paint and thinner to the bell 74. The proximal end side of the feed tube 75 is attached to the cover 71, and the distal end side of the feed tube 75 is open to the paint receiving portion 74f. The feed tube 75 is connected to an external paint supply source (not shown). The shaping air ring 76 is formed in a cylindrical shape using an insulating resin material, and is located on the rear side of the paint discharge end edge 74d of the bell 74 and covers the paint spraying portion 74b. Further, a plurality of shaping air injection ports 77 are arranged in an annular shape along the paint discharge end edge 74d at the tip of the shaping air ring 76 (see FIG. 8). The ejection port 77 is connected to an external air source (not shown) via an air passage, and shaping air having a predetermined discharge pressure (air amount) is ejected. As a result, the shaping air forms a spray pattern of the paint sprayed from the bell 74.

  The auxiliary cover 78 covers the outer peripheral side of the shaping air ring 76 and is formed of an insulating synthetic resin material. At the tip of the auxiliary cover 78, a plurality of injection ports 79 for pushing air are arranged in an annular shape so as to be positioned between the outer peripheral surface of the shaping air ring 76 (see FIG. 8). The jet outlet 79 is located on the outer peripheral side of the shaping air injection port 77 and jets indented air from the outer peripheral side of the bell 74 toward the axial center. As a result, the paint particles sprayed from the bell 74 are squeezed forward without excessively spreading to form a spray pattern having a predetermined width.

  The electrode rod 80 is fixedly provided so as to extend in the axial direction within the rotation shaft 73. The electrode rod 80 is formed in a cylindrical shape from an insulating material, and electrically insulates the rotating shaft 73 and the bell 74. The electrode rod 80 has a protruding portion 80a whose front end protrudes forward from the bell 74, and a branched external electrode 82 is provided at the front end of the protruding portion 80a. The electrode rod 80 is provided with a disc-shaped shielding plate 80b that is located behind the protruding portion 80a and prevents the paint particles from entering the gap between the electrode rod 80 and the rotating shaft 73. .

  The high resistance 81 extends in the axial direction in the electrode rod 80 and is provided between a high voltage generator (not shown) and the external electrode 82. The external electrode 82 includes four needle-like electrodes 82a that protrude forward from the tip of the protruding portion 80a and branch toward the front of the bell 74 (see FIG. 8). Each needle electrode 82 a is connected to the tip of the high resistance 81. The external electrode 82 can form an ionization zone B that charges paint particles sprayed from the paint discharge edge 74d of the bell 74 when a high voltage is applied from a high voltage generator (see FIG. 9).

  As shown in FIG. 7 or FIG. 8, each needle electrode 82a has an angle θ of 20 ° to 70 °, preferably 45 ° with respect to the axis center of the rotating shaft 73 so that the tip side faces the outer peripheral side. Inclined. In FIG. 9, the distance dimension between the tip of the needle electrode 82a and the paint discharge edge 74d of the bell 74 is L1, and the distance dimension between the tip of the needle electrode 82a and the article T is L2. In this case, when the distance dimension L1 is 0.75 times or less (L1 ≦ 0.75 × L2) or 1.5 times or more (L1 ≧ 1.5 × L2) with respect to the distance dimension L2, the paint application efficiency Has been experimentally confirmed to be lower than, for example, about 87%.

  In FIG. 9, the needle electrode 82a has a position (0) in which the distance dimension L1 between the tip thereof and the paint discharge end edge 74d of the bell 74 is substantially equal to the distance dimension L2 between the tip and the workpiece T. .75 × L2 <L1 <1.5 × L2, preferably L1≈L2).

  In FIG. 9, the rotating shaft 73 and the bell 74 are rotated at high speed by the air motor 72, and the paint is supplied from the paint supply source to the bell 74 through the feed tube 75. The paint supplied to the bell 74 jumps out as paint particles atomized from the paint discharge end edge 74d outward in the radial direction. On the other hand, shaping air is blown around the coating material discharge end edge 74d from a plurality of injection ports 77 located behind the coating discharge edge 74d. Thus, since the atomization (atomization) of the paint is promoted, the paint particles are small when the shaping air discharge pressure is high, and the paint particles are large when the shaping air discharge pressure is low.

  Further, the spray pattern width is narrow when the shaping air discharge pressure is high, whereas the spray pattern width is wide when the shaping air discharge pressure is low. For this reason, the plurality of ejection ports 79 provided on the outer peripheral side of the plurality of ejection ports 77 eject the pushing air according to the discharge pressure of the shaping air, and keep the width of the spray pattern constant.

  In general, when a bell-type coating apparatus is used, for example, when the body of an automobile is painted metallic, the coloration state (so-called color matching) of the base coat is determined by the particle size of the paint particles, the collision speed of the paint particles, and the coating NV. (Non Volatile), and is governed by parameters such as air impact force. Moreover, the body of an automobile can efficiently apply the paint by changing the spray pattern depending on the painting site.

  However, the bell-type coating apparatus according to Patent Document 1 configured as described above has a radially outer side from the paint discharge end edge 74d of the bell 74 by changing the discharge pressure of the shaping air ejected from the plurality of ejection ports 77. The spray pattern of the paint particles atomized by centrifugal force is changed. That is, when the amount of shaping air is increased, the spray pattern is reduced in diameter. On the other hand, when the amount of shaping air is reduced, the spray pattern expands in diameter.

  Here, the pushing air ejected from the plurality of jets 79 squeezes the paint particles sprayed from the bell 74 toward the front without excessively spreading to form a spray pattern of a predetermined width. Does not change the spray pattern. In addition, by providing an external electrode that branches to the bell-type coating device, the electric field strength between the external electrode and the object to be coated can be increased, but the branched external electrode itself does not change the spray pattern. Absent.

  On the other hand, in the bell-type coating apparatus according to Patent Document 1, the atomized paint particles are small when the amount of shaping air is large, and the atomized paint particles are large when the amount of shaping air is low. Since the bell-type coating apparatus according to Patent Document 1 changes the size of the spray pattern by changing the amount of shaping air, the size of the paint particles hitting the coating surface differs depending on the size of the spray pattern. There is a problem that color matching becomes difficult.

  In addition, the bell-type coating apparatus according to Patent Document 1 has a structure in which the spray pattern is narrowed by ejecting considerably strong shaping air, so that strong air hits the clear coat surface, so a wet coating film Then, there is a problem that the solvent volatilizes, the coating NV increases locally, and the skin of the painted surface becomes rough. For example, it is possible to use a bell-type coating apparatus to apply metallic coating twice and to correct the color matching of the painted surface and the skin, but this is not preferable because it increases the stroke. It is preferable that color matching and skin matching can be performed in one stroke. These can be said to be the problems of the present invention.

  The present invention has been made in view of such problems, and in a bell-type coating apparatus in which atomized paint is sprayed from a rotating bell, even if the size of the spray pattern is changed, color matching and coating are performed. It is an object of the present invention to provide a spray pattern variable mechanism and a spray pattern variable method that provide good surface skin.

  The present inventor has found that, even if the size of the spray pattern is changed by controlling the rotational speed of the bell, the color matching and the skin of the coating surface are improved, and the following new bell type coating apparatus The inventors have invented a spray pattern variable mechanism and a spray pattern variable method.

  (1) A bell formed by centrifugally atomizing paint from the end edge in a radial direction by rotating while supplying the paint into a recess forming a circular edge, and a gradient formed on the outer surface opposite to the recess. A bell-type coating apparatus comprising: a plurality of injection ports that eject shaping air toward the rotation direction of the bell by controlling the rotation of the bell so that the peripheral speed of the edge is close to the subsonic speed. A spray pattern variable mechanism that varies the spray pattern applied to the workpiece by changing the speed.

  The bell-type coating apparatus according to the invention of (1) includes a bell and a plurality of injection ports. The bell rotates and atomizes the paint in the radial direction from the edge by rotating while the paint is supplied into the recess forming the circular edge. The plurality of injection ports eject shaping air toward a gradient formed on the outer surface opposite to the recess.

  In the bell-type coating apparatus according to the invention of (1), for example, an air motor is built in a housing as the apparatus main body, and the bell is fixed to the distal end side of the rotating shaft of the air motor. The bell has a disc-shaped bell cup on the concave side, and is formed in a circular truncated cone shape. A plurality of discharge holes for discharging paint are arranged at equal intervals on the same circumference at the boundary portion and the center portion with the bell cup.

  On the other hand, a feed pipe to which paint or cleaning liquid is supplied is provided extending in the axial direction at the central portion of the rotary shaft of the air motor. A paint nozzle is provided at the tip of the feed pipe. The tip portion of the paint nozzle faces the conical convex portion at the center position of the bell cup in a separated state with a predetermined interval. And you may make it the coating material discharged from the front-end | tip part of a coating material nozzle flow out to the recessed inner wall of a bell through several discharge holes. The paint is scattered from the center of the bell to the outer periphery by centrifugal force generated by the rotation of the bell, and is atomized in a radial direction from a circular edge.

  Here, the concave portion formed in the bell may be formed with a conical inner wall that expands in the radial direction from the center, and the inner wall of the concave portion may be formed with a curved surface having a relatively large curvature. On the other hand, the gradient formed on the outer surface opposite to the concave portion may be formed in a conical shape or a curved surface having a relatively large curvature.

  For example, a cylindrical ring block is fixed to the inner peripheral surface of the housing on the front end side, and a hat-shaped air ring is detachably fixed to the inner peripheral portion of the ring block. Then, a plurality of injection ports for ejecting the shaping air toward the gradient formed on the outer surface opposite to the concave portion can be provided at the lower edge portion of the air ring. These spouts are preferably arranged in an annular shape concentrically with a circular end edge and provided at equal intervals.

  Here, a ring-shaped air chamber is formed between the inner peripheral surface of the ring block and the outer wall surface of the cylindrical portion of the air ring, and is connected to the air chamber inside the ring block and the housing. An air passage is provided. Then, the air passage is connected to an external air source, and a predetermined amount of air is ejected from these ejection ports, so that shaping air can be formed.

  As will be described later, the axial distance between the circular edge and these injection ports is preferably considerably long, and the ejection directions of the shaping air ejected from these injection ports may cross each other. . The shaping air from these injection ports is for correcting the flying direction of the paint that is atomized by the centrifugal force from the edge of the bell and scatters in the radial direction to the direction of the object to be coated. Further, the shaping air from these injection ports can adjust the particle size of the paint particles, the collision speed of the paint particles, the coating NV, and the air impact force as the four parameters governing the coloration of the base coat.

  The spray pattern variable mechanism according to the invention of (1) controls the rotation of the bell so that the peripheral speed of the end edge is close to the subsonic speed. Then, by changing the rotation speed of the bell, the spray pattern applied to the article to be coated is varied.

  The bell of the spray pattern variable mechanism according to Patent Document 1, for example, has a rotational speed of about 30,000 revolutions / minute (rpm) and is fixed, whereas the bell of the spray pattern variable mechanism according to the present invention has a rotational speed. Is about 60,000 revolutions per minute (rpm), which is a higher speed rotation, and there is a difference in varying this rotation speed. Here, if the diameter of the edge of the bell is 50 mm, which is close to the actual condition, the peripheral speed of the edge of the bell is about 79 m / sec in Patent Document 1 and about 157 m / sec in the present invention. The subsonic speed is defined as 0.6 to 0.7 times the sound speed (340 m / sec), and the peripheral speed of the edge of the bell according to the present invention is close to the subsonic speed.

  And the spray pattern variable mechanism by patent document 1 sprayed shaping air to the coating material discharge | released from the edge of a bell, changed the discharge pressure of shaping air, and changed the width | variety of the spray pattern. The spray pattern variable mechanism by means that the bell is controlled at a rotational speed close to subsonic speed, the paint is atomized at the edge of the bell, and the spray pattern applied to the object is varied by changing the rotational speed of the bell There is a difference to do. That is, if the rotation speed of the bell is increased, the centrifugal force increases and the spray pattern expands in diameter. On the other hand, if the rotation speed of the bell is reduced, the centrifugal force is reduced and the spray pattern is reduced in diameter.

  Here, the shaping air according to Patent Document 1 is applied to the edge of the bell to assist in the atomization of the paint, whereas the shaping air according to the present invention is applied to the paint released from the edge of the bell. There is a difference that the direction of the fine particles is changed to the substrate side. Furthermore, there is a difference that the speed of flying in the radial direction is attenuated toward the object to be coated. Even though the shaping air according to the present invention assists the atomization of the paint, the atomization of the paint is not promoted unlike the shaping air according to Patent Document 1.

  The spray pattern variable mechanism according to the invention of (1) may be said to have a basic mechanism of a bell rotating at high speed, and the paint flowing in the recess of the bell is formed into a liquid string by applying an electrostatic field. Thus, the liquid-like paint is interrupted from the edge of the bell, and the atomization of the paint is promoted. The spray pattern variable mechanism according to the invention of (1) is characterized in that even if the size of the spray pattern is changed, the fine particle diameter of the paint discharged from the edge of the bell does not change greatly on the coating surface. Or, it is characterized in that the fine particles of the paint do not hit the coated surface strongly. This is because the shaping air acts to attenuate the flying speed of the fine particles of the paint.

  For example, the spray pattern variable mechanism according to the invention of (1) can reduce the amount of paint supplied by reducing the width of the spray pattern. On the other hand, the spray pattern variable mechanism according to Patent Document 1 does not change the supply amount of the paint due to the mechanism even if the spray pattern width is reduced. Paradoxically speaking, the spray pattern variable mechanism according to Patent Document 1 cannot reduce the amount of paint supplied even if the spray pattern width is reduced.

  Further, the spray pattern variable mechanism according to Patent Document 1 has a demerit that when the width of the spray pattern is reduced, the particles of the paint are crushed and the color matching of the coating surface and the skin are not good, whereas the invention of (1) Because the spray pattern variable mechanism by controlling the rotation speed of the bell does not change the particle size distribution of the paint even if the size of the spray pattern is changed, the color matching and the skin of the paint surface may be improved. confirmed.

  (2) The spray pattern variable mechanism according to (1), wherein the shaping air ejected from the plurality of ejection ports jets the coating material centrifugally atomized from the edge along the gradient without a gap.

  In the spray pattern variable mechanism according to Patent Document 1, since the shaping air is directly blown to the paint discharged from the edge of the bell, the shaping air is jetted to the paint to be centrifugally atomized from the edge without a gap. For this purpose, it is necessary to increase the number of arrangements so that a plurality of injection ports are close to each other, but it is not practical such as increasing the supply air.

  On the other hand, in the spray pattern variable mechanism according to the invention of (2), since the shaping air ejected from the plurality of injection ports flows along the gradient of the bell, the shaping air having no gap is diffused in the radial direction at the edge of the bell. It becomes. As a result, the paint particle size distribution in the radial direction of the coating surface can be made uniform.

  (3) The spray pattern variable mechanism according to (1) or (2), wherein an axial distance between the end edge and the plurality of injection ports is in a range of 20 mm to 40 mm.

  Since the spray pattern variable mechanism according to Patent Document 1 blows shaping air directly on the paint discharged from the end edge of the bell, it is preferable that the end edge of the bell and the plurality of injection ports are close to each other. In the spray pattern variable mechanism according to Patent Document 1, for example, the axial distance between the end edge and the plurality of injection ports is in the range of 7 mm to 10 mm.

  On the other hand, in the spray pattern variable mechanism according to the invention of (2), since the shaping air ejected from the plurality of ejection ports flows along the gradient of the bell, the axial distance between the edge of the bell and the plurality of ejection ports Is preferably in the range of 20 mm to 40 mm.

  (4) The jetting direction of the shaping air is inclined in a direction to cancel the rotational direction component of the paint scattered by receiving centrifugal force from the edge of the bell to the surroundings. The spray pattern variable mechanism described.

  In the spray pattern variable mechanism according to the invention of (4), the shaping air crosses so as to cancel the swirl force component by applying a shearing force to the paint particles that are swirled and scattered while being diffused in the radial direction from the bell. Then, due to the rapid expansion and shearing action, a turbulent flow suitable for realizing further atomization of the paint and high dispersibility is formed. This turbulent flow has an effect that the initial velocity is high and the velocity is gradually reduced near the coating surface.

  (5) A bell formed by centrifugally atomizing the paint from the end edge in a radial direction by rotating while the paint is supplied into the recess forming the circular edge, and a gradient formed on the outer surface opposite to the recess. A spray pattern varying method for a bell-type coating apparatus, wherein the bell is rotationally controlled so that a peripheral speed of the edge is close to a subsonic speed. A spray pattern changing method for changing a spray pattern to be applied to an object by changing a rotation speed of the bell.

  (6) The spray pattern changing method according to (5), wherein the shaping air ejected from the plurality of ejection ports is jetted along the gradient without gaps with respect to the paint that is centrifugally atomized from the edge.

  (7) The spray pattern changing method according to (5) or (6), wherein an axial distance between the end edge and the plurality of injection ports is in a range of 20 mm to 40 mm.

  (8) The ejection direction of the shaping air is inclined in a direction to cancel the rotational direction component of the paint scattered by receiving centrifugal force from the edge of the bell to the surroundings. The spray pattern variable method as described.

  According to the present invention, a bell-type coating comprising: a bell for centrifugally atomizing paint from a circular end edge in a radial direction; and a plurality of injection ports for ejecting shaping air toward a gradient formed on an outer surface of the bell. Since the spray pattern is varied by rotating the bell so that the speed is close to the subsonic speed, even if the spray pattern is changed, the color matching and the surface of the coating surface can be improved.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram showing an embodiment of a bell-type coating apparatus according to the present invention, and its main part is a longitudinal sectional view. FIG. 2 is a front view of the air ring of the bell-type coating apparatus according to the embodiment, and corresponds to a bottom view of the bell-type coating apparatus shown in FIG. 1 viewed from the paint spraying side. FIG. 3 is an enlarged front view of a main part of the air ring according to the embodiment. FIG. 4 is a longitudinal sectional view of a main part of the air ring according to the embodiment. FIG. 5 is a front view for explaining the operation of the bell-type coating apparatus according to the above-described embodiment, and only the main parts are drawn. FIG. 6 is a graph comparing the coated surface painted with the spray pattern variable mechanism of the bell type coating apparatus according to the present invention and the painted surface coated with the spray pattern variable mechanism of the bell type coating apparatus according to the prior art.

  First, the configuration of the bell type coating apparatus according to the present invention will be described. In FIG. 1, a bell type coating apparatus 1 houses an air motor 2 in a housing 11 made of a cylindrical insulator. The air motor 2 rotates the rotating shaft 21 when compressed air is supplied from the outside. The bell 3 is fixed to the tip 21a side of the rotating shaft 21. The bell 3 has a disc-shaped bell cup 4 on the concave portion 31 side, and is formed in a circular truncated cone shape. And in the boundary part and center part with the bell cup 4, the several discharge holes 4a * 4b for discharging a coating material are arranged at equal intervals on the same periphery.

  In FIG. 1, a feed pipe 5 to which a paint or cleaning liquid is supplied is provided extending in the axial direction at the central portion of the rotating shaft 21 of the air motor 2. A paint nozzle 51 is provided at the tip of the feed pipe 5. The tip 51a of the paint nozzle 51 is opposed to the conical convex portion 4c at the center position of the bell cup 4 in a separated state with a predetermined interval.

  The paint discharged from the tip 51a of the paint nozzle 51 flows out to the inner wall of the recess 31 of the bell 3 through the plurality of discharge holes 4a and 4b. The paint P is scattered from the central portion of the bell 3 to the outer periphery by centrifugal force generated by the rotation of the bell 3, and is atomized in the radial direction from the circular edge 3a (see FIG. 1). In FIG. 1, a curved surface having a relatively large curvature is formed on the inner wall of the recess 31 formed in the bell 3. On the other hand, the gradient 32 formed on the outer surface opposite to the recess 31 is formed in a conical shape.

  In FIG. 1, a cylindrical ring block 12 is fixed to the inner peripheral surface of the housing 11 on the distal end side. An air ring 13 having a hat-shaped cross section is detachably fixed to the inner periphery of the ring block 12. The lower edge portion 131 of the air ring 13 is provided with a plurality of injection ports 13 a, 13 b, and 13 c that eject shaping air toward a gradient 32 formed on the outer surface opposite to the concave portion 31.

  In FIG. 1, a ring-shaped air chamber 122 connected to a plurality of injection ports 13 a, 13 b, and 13 c is formed between the inner peripheral surface of the ring block 12 and the outer wall surface of the cylindrical portion of the air ring 13. An air passage 121 connected to the air chamber 122 is provided inside the ring block 12 and the housing 11. Then, the air passage 121 is connected to an external air source (not shown), and a predetermined amount of air is ejected from the plurality of ejection ports 13a, 13b, and 13c, thereby shaping the shaping air.

  In FIG. 1, the axial distance S2 between the circular edge 3a and the plurality of injection ports 13a, 13b, and 13c is considerably long, and the shaping air is discharged from the plurality of injection ports 13a, 13b, and 13c. The directions cross each other. In addition, the shaping air from the plurality of injection ports 13a, 13b, and 13c receives the centrifugal force from the edge 3a of the bell 3 and corrects the flight direction of the paint P that is atomized and scattered in the radial direction to the direction of the object to be coated. Is to do. Further, the shaping air of the plurality of injection ports 13a, 13b, and 13c adjusts the particle diameter of the paint particles, the collision speed of the paint particles, the coating NV, and the air impact force as four parameters that govern the color formation of the base coat. be able to.

  As shown in FIG. 2, the plurality of injection ports 13a, 13b, and 13c have different inclination angles θ1 to θ3 in the circumferential direction of the bell 3 on the circumferences R1, R2, and R3 that are concentric circles having different radii. Are drilled at equal intervals (see FIG. 3). In FIG. 4A, which is an AA cross section of FIG. 3, the inclination angle θ1 of the plurality of injection ports 13a is 30 degrees. In FIG. 4B, which is a BB cross section of FIG. 3, the inclination angle θ2 of the plurality of injection ports 13b is 15 degrees. In FIG. 4C, which is a CC cross section of FIG. 3, the inclination angle θ3 of the plurality of injection ports 13c is 30 degrees.

  Next, the operation of the spray pattern variable mechanism of the bell type coating apparatus according to the present invention will be described.

  In FIG. 1, in the spray pattern variable mechanism of the bell type coating apparatus 1, the rotation of the bell 3 is controlled so that the peripheral speed of the edge 3 a of the bell 3 is close to the subsonic speed. Then, by changing the rotation speed of the bell 3, the spray pattern applied to the article can be varied.

  In FIG. 7, the bell 74 of the spray pattern variable mechanism is fixed with, for example, a rotational speed of about 30,000 revolutions per minute (rpm), whereas the bell 3 of the spray pattern variable mechanism according to the present invention is The rotation speed is about 60,000 rotations / minute (rpm), and the rotation speed is higher, and there is a difference in varying this rotation speed. Here, the peripheral speed of the edge 3a of the bell 3 is close to the subsonic speed.

  In FIG. 7, the spray pattern variable mechanism according to Patent Document 1 sprays shaping air onto the paint released from the edge of the bell 74 and changes the discharge pressure of the shaping air to change the width of the spray pattern. In the spray pattern variable mechanism according to the present invention, the bell 3 is controlled at a rotational speed close to subsonic speed so that the paint is atomized at the edge 3a of the bell 3 and the rotational speed of the bell 3 is changed. There is a difference that the spray pattern to be painted is variable. That is, if the rotation speed of the bell 3 is increased, the centrifugal force increases and the spray pattern can be expanded in diameter. On the other hand, if the rotational speed of the bell 3 is reduced, the centrifugal force is reduced and the spray pattern can be reduced in diameter.

  The shaping air according to Patent Document 1 hits the edge of the bell 74 and assists in the atomization of the paint (see FIG. 9), whereas the shaping air according to the present invention is applied from the edge of the bell 3. There is a difference that the direction of the discharged paint fine particles is changed to the object side. Furthermore, there is a difference that the speed of flying in the radial direction is attenuated toward the object to be coated.

  The spray pattern variable mechanism according to the present invention may be said to have the basic mechanism of the bell 3 rotating at a high speed, and the paint flowing in the recess 31 of the bell 3 is formed into a liquid string by being given an electrostatic field. Thus, the liquid-like paint is interrupted from the edge 3a of the bell 3, and the atomization of the paint is promoted. The spray pattern variable mechanism according to the present invention has an advantage that the fine particle diameter of the paint discharged from the edge 3a of the bell 3 does not change greatly on the coating surface even if the size of the spray pattern is changed. Alternatively, there is an advantage that the fine particles of the paint do not hit the coating surface strongly. This is because the shaping air acts to attenuate the flying speed of the fine particles of the paint.

  The spray pattern variable mechanism according to the present invention can reduce the amount of paint supplied by reducing the width of the spray pattern. On the other hand, the spray pattern variable mechanism according to Patent Document 1 does not change the supply amount of the paint due to the mechanism even if the spray pattern width is reduced. The spray pattern variable mechanism according to Patent Document 1 cannot reduce the amount of paint supplied even if the spray pattern width is reduced.

  Further, the spray pattern variable mechanism according to Patent Document 1 has the demerits that if the width of the spray pattern is reduced, the particles of the paint are crushed and the color matching of the paint surface and the skin are not good, whereas the spray pattern according to the present invention. The variable mechanism controls the rotation speed of the bell 3 so that the particle size distribution of the paint does not change even if the size of the spray pattern is changed. As described later, the color matching and the skin of the coating surface are improved. It was confirmed.

  Furthermore, since the spray pattern variable mechanism according to Patent Document 1 blows shaping air directly on the paint discharged from the edge of the bell 74, the shaping air is spaced from the paint that is centrifugally atomized from the edge. In order to make a complete jet, it is necessary to increase the number of arrangements so that the plurality of injection ports 77 are close to each other, but it is not practical to increase the supply air (see FIG. 8).

  On the other hand, in the spray pattern variable mechanism according to the present invention, since the shaping air ejected from the plurality of ejection ports 13a, 13b, and 13c flows along the gradient 32 of the bell 3, it diffuses in the radial direction at the edge 3a of the bell 3. Therefore, the shaping air without gaps is obtained. As a result, the paint particle size distribution in the radial direction of the coating surface can be made uniform.

  For example, in the spray pattern variable mechanism according to the present invention, the axial distance S1 between the end edge 3a of the bell 3 and the plurality of injection ports 13a, 13b, 13c is in the range of 20 mm to 40 mm (see FIG. 1). On the other hand, since the spray pattern variable mechanism according to Patent Document 1 blows shaping air directly onto the paint discharged from the end edge of the bell 74, the end edge of the bell 74 and the plurality of injection ports 77 are close to each other. Is preferred. For example, the axial distance S2 between the edge of the bell 74 and the plurality of injection ports 77 is in the range of 7 mm to 10 mm (see FIG. 7).

  In the spray pattern variable mechanism according to the present invention, the shaping air ejected from the plurality of ejection ports 13a, 13b, and 13c flows along the gradient 32 of the bell 3, so that the edge 3a of the bell 3 and the plurality of ejection ports 13a and 13b -It is preferable that axial distance S1 with 13c is the range of 20 mm to 40 mm (refer FIG. 1).

  Further, in the spray pattern variable mechanism according to the present invention, the inclination direction of the plurality of injection ports 13a, 13b, and 13c is inclined in the direction to cancel the rotational direction component of the paint scattered by receiving centrifugal force from the edge of the bell 3 to the surroundings. (See FIGS. 3 and 4).

  For example, in FIG. 1, to apply a base coat using a metallic paint P, an electrostatic charge of, for example, minus 90 KV is applied to the paint side of the bell 3, while a positive electrostatic charge is charged to the object side such as the body of an automobile. Let In this state, the rotating shaft 21 of the air motor 2 is rotated at a high speed of 60000 rpm, for example, and the metallic paint P supplied from the feed pipe 5 and the paint nozzle 51 is rotated by the centrifugal force of the bell 3 rotating integrally with the rotating shaft 21. Then, it is scattered on the outer peripheral side of the bell 3 through the plurality of discharge holes 4a and 4b.

  With respect to the metallic paint P that scatters in the radial direction from the edge 3a of the bell 3, first, the metallic paint P is ejected in the reverse turning direction from the plurality of injection ports 13a located on the innermost side in the radial direction of the air ring 13. The first shaping air La with a high speed and small air volume collides, and the primary shearing force due to the collision is applied to the paint particles in the initial stage of scattering, and the centrifugal force (swirl inertial force) of the paint is slightly canceled. The paint flight direction is slightly corrected to the workpiece direction (see FIG. 5).

  Next, the metallic paint in which the shaping air Lb having a high speed and a small air volume ejected from the plurality of injection ports 13b located in the middle of the air ring 13 in the reverse direction is decelerated by the first shaping air La. Collision with P particles, secondary shearing force acting on the paint particles in the middle stage of scattering, the centrifugal force (swirl inertial force) of the paint is almost cancelled, and the paint flight direction is the direction of the object to be coated (See FIG. 5).

  Next, the high-speed small-air-volume shaping air Lc ejected from the plurality of injection ports 13c located at the outermost radial direction of the air ring 13 in the reverse turning direction is decelerated by the second shaping air Lb. Colliding with paint P particles, the third shearing force acting on the paint particles acts on the paint particles, canceling the centrifugal force (rotating inertial force) of the paint, and improving the paint flight direction in the direction of the object It is corrected (see FIG. 5).

  As described above, in the spray pattern variable mechanism according to the present invention, the shaping air crosses so as to cancel the swirl force component by applying a shearing force to the paint particles that are swirled and scattered while being diffused in the radial direction from the bell. Then, due to the rapid expansion and shearing action, a turbulent flow suitable for realizing further atomization of the paint and high dispersibility is formed. This turbulent flow has an effect that the initial velocity is high and the velocity is gradually reduced near the coating surface.

  Here, the plurality of injection ports for ejecting the shaping air toward the gradient 32 formed on the outer surface opposite to the concave portion 31 of the bell 3 may be only the plurality of injection ports 13a, and the plurality of injection ports 13b and 13c include It may be blocked. Further, a plurality of injection ports 13a for ejecting the shaping air La toward the gradient 32 formed on the outer surface opposite to the concave portion 31 of the bell 3 and the shaping air Lb acting on the paint scattered from the end edge 3a of the bell 3 are provided. A plurality of injection ports 13b for injecting may be added, and further, a plurality of injection ports 13c for injecting shaping air Lc acting on the paint scattered from the edge 3a of the bell 3 may be added.

  FIG. 6 shows a coating surface coated with the spray pattern variable mechanism of the bell type coating apparatus configured as described above, and a spray pattern variable mechanism of a bell type coating apparatus according to the prior art represented by Patent Document 1. It is the graph which compared the painted surface.

  The scale on the horizontal axis in FIG. 6 indicates the outer diameter (Pattern Width) of the spray pattern applied to the coating surface. In FIG. 6, the scale on the right side of the vertical axis indicates the finished skin of the painted surface (so-called clear coat) with the clear paint measured by the wave scan. In FIG. 6, the scale on the left side of the vertical axis indicates the color difference of the painted surface (so-called base coat) by light blue metallic coating.

  In FIG. 6, a curve obtained by connecting the circled plots with a broken line indicates the finished skin of the clear coat by the conventional painting. On the other hand, a curve obtained by connecting the circled plots with a solid line shows the finished skin of the clear coat by the coating of the present invention. A curve formed by connecting the x-marked plots with a broken line indicates the color difference of the base coat by the conventional coating. On the other hand, a curve obtained by connecting the x-marked plots with a solid line shows the color difference of the base coat by the coating of the present invention.

  As shown in the graph of FIG. 6, the characteristics of the finished skin of the clear coat and the color difference of the base coat by the conventional painting deteriorate as the diameter of the spray pattern is reduced. As discussed above, the size of the spray pattern is changed by changing the amount of shaping air, so the size of the paint particles hitting the paint surface will differ depending on the size of the spray pattern. Color matching is difficult. In addition, as the spray pattern is reduced in diameter, it has a structure that narrows the spray pattern by ejecting considerably strong shaping air, so strong air hits the clear coat surface, so a wet coating film Then, it accelerates | stimulates that a solvent volatilizes, coating NV rises locally and the skin of the coating surface is rough.

  On the other hand, as shown in the graph of FIG. 6, the finished skin of the clear coat and the color difference of the base coat by the painting of the present invention have good characteristics and are stable regardless of the diameter of the spray pattern. It has been confirmed that the spray pattern variable mechanism according to the present invention improves the color matching and the skin of the coated surface even when the size of the spray pattern is changed by controlling the rotational speed of the bell.

It is a block diagram which shows one Embodiment of the bell type coating apparatus by this invention. It is a front view of the air ring of the bell type coating apparatus by the said embodiment. It is a principal part enlarged front view of the air ring by the said embodiment. It is a principal part longitudinal cross-sectional view of the air ring by the said embodiment. It is a front view for demonstrating an effect | action of the bell type coating apparatus by the said embodiment. It is the graph which compared the coating surface painted with the spray pattern variable mechanism of the bell type coating apparatus by this invention, and the coating surface coated with the spray pattern variable mechanism of the bell type coating apparatus by a prior art. It is a front view which shows the structure of the bell type coating apparatus by a prior art. It is the bottom view which looked at the bell type painting device by the prior art from the spraying side of paint. It is a front view which shows the state which is coating the to-be-coated object using the bell type coating device by a prior art.

Explanation of symbols

1 Bell type coating equipment 2 Air motor 3 Bell 3a Edge (Bell edge)
13a, 13b, 13c Injection port 31 Concave portion 32 Gradient

Claims (8)

A bell that centrifugally atomizes the paint from the end edge in a radial direction by rotating while being supplied with the paint in a recess forming a circular edge, and shaping toward a gradient formed on the outer surface opposite to the recess. A bell-type coating apparatus comprising a plurality of ejection ports for ejecting air,
A spray pattern variable mechanism that controls the rotation of the bell so that the peripheral speed of the edge is close to the subsonic speed, and changes the spray pattern applied to the object by changing the rotation speed of the bell.   The spray pattern variable mechanism according to claim 1, wherein shaping air ejected from the plurality of ejection ports jets the coating material centrifugally atomized from the end edge along the gradient without a gap.   The spray pattern variable mechanism according to claim 1 or 2, wherein an axial distance between the end edge and the plurality of injection ports is in a range of 20 mm to 40 mm.   The spray pattern variable according to any one of claims 1 to 3, wherein the shaping air is ejected in a direction in which the rotational direction component of the paint scattered by receiving centrifugal force from the edge of the bell to the surroundings is canceled. mechanism. A bell that centrifugally atomizes the paint from the end edge in a radial direction by rotating while being supplied with the paint in a recess forming a circular edge, and shaping toward a gradient formed on the outer surface opposite to the recess. A spray pattern variable method of a bell-type coating apparatus comprising a plurality of jets for jetting air,
A spray pattern changing method for changing a spray pattern to be coated on an object by controlling rotation of the bell so that a peripheral speed of the edge is close to subsonic speed and changing a rotation speed of the bell.   The spray pattern changing method according to claim 5, wherein the shaping air ejected from the plurality of ejection ports jets the coating material centrifugally atomized from the edge along the gradient without any gap.   The spray pattern changing method according to claim 5 or 6, wherein an axial distance between the edge and the plurality of injection ports is in a range of 20 mm to 40 mm.   The spraying pattern variable according to any one of claims 5 to 7, wherein the shaping air is ejected in a direction in which the rotational direction component of the paint scattered by receiving centrifugal force from the edge of the bell to the surroundings is canceled. Method.

Images