Rotary atomizing head type painting machine and electrostatic painting device

Abstract

To improve coating efficiency.SOLUTION: An inner cylindrical surface 7A of a shaping air ring 7 is formed with a uniform inner diameter. A first shaping air ejection part 8 is formed as an annular gap, and the gap dimension a thereof is set to 0.1 to 1.0 mm. A front end part 7E of the shaping air ring 7 is arranged at a position of 0.1 to 10.0 mm rearward from a discharge end edge 6D of a rotary atomizing head 6. The width dimension c in the radial direction of the front end part 7E is set to 2 mm or less. A front outer cylindrical surface 7B of the shaping air ring 7 is set such that a tapered angle β enlarged toward the rear side is set to equal to or less than 25° relative to the axis O-O.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a rotary atomizing head type coating machine and an electrostatic coating device that are preferably used for coating the bodies of automobiles, for example. [Background technology]

[0002] Generally, when painting the bodies of automobiles, a rotary atomizing head type paint coater is used, which has good paint transfer efficiency and produces a good painted finish. This rotary atomizing head type coating machine includes an air motor powered by compressed air, a hollow rotating shaft supported for rotation while extending in the front-rear direction along the axis of the air motor, with its front end protruding from the air motor, a feed tube extending through the inside of the rotating shaft to the front end of the rotating shaft, a rotary atomizing head attached to the front end of the rotating shaft and having an outer circumferential surface that expands into a cup shape, an inner circumferential surface that diffuses paint supplied from the feed tube, and a discharge edge located at the front end for discharging the paint, a cylindrical shaping air ring provided on the outer circumferential side of the rotary atomizing head, a first shaping air jetting section provided on the outer circumferential side of the rotary atomizing head and jetting a first shaping air toward the paint discharged from the discharge edge, and a second shaping air jetting section located radially outward of the first shaping air jetting section and surrounding the rotary atomizing head, jetting a second shaping air toward the paint discharged from the discharge edge (Patent Document 1).

[0003] Painting using a rotary atomizing head type paint coater is expected to have the following benefits: reducing the amount of paint used by improving the efficiency of paint transfer onto the object being painted, reducing carbon dioxide emissions by simplifying equipment such as paint booths, and reducing the maintenance costs of paint booths. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-236417 A Summary of the Invention [Problem to be solved by the invention]

[0005] In coating with a rotary atomizing head type coating machine, the first shaping air is blown out from the first shaping air blowing part and the second shaping air is blown out from the second shaping air blowing part toward the paint particles discharged from the discharge edge of the rotary atomizing head. As a result, the paint particles sprayed from the rotary atomizing head are rectified and shaped into a spray pattern that provides a uniform film thickness distribution.

[0006] However, the coating distance from the rotary atomizing head type coater (rotary atomizing head) to the object to be coated is set with consideration given to preventing contact between the rotary atomizing head and the object to be coated and preventing contamination of the coater. At such a coating distance, the paint particles tend to move less straight due to the shaping air. As a result, the paint particles are carried over a wide area by the air flow flowing over the surface of the object to be coated and do not reach the object to be coated (the surface to be coated), resulting in a decrease in coating efficiency.

[0007] One possible solution is to increase the flow rate of the shaping air, but this would result in an increase in the number of paint particles flowing along the surface of the workpiece. As a result, the paint particles released from the rotary atomizing head are affected by the turbulence caused by the shaping air, and are guided by the turbulent flow and fail to reach the workpiece, resulting in a decrease in coating efficiency.

[0008] Furthermore, there is a method of shortening the coating distance (called close-distance coating or proximity coating) as a measure to obtain high coating efficiency. This method can increase the straightness of the paint particles transported by the shaping air, and therefore improve coating efficiency. However, the current situation is that some of the paint particles sprayed from the rotary atomizing head do not reach the object to be coated due to the influence of centrifugal force caused by the rotation of the rotary atomizing head, being ejected in the radial direction of the rotary atomizing head, or being caught up in the turbulence of the shaping air ejected from the rear of the rotary atomizing head.

[0009] Considering the above-mentioned issues, possible ways to significantly reduce the amount of paint particles that do not reach the workpiece, which reduces coating efficiency, are, first, to shorten the coating distance to increase the straightness of the paint particles, and, second, to change the coating conditions to reduce the scattering of paint particles (for example, by reducing the rotation speed of the rotary atomizing head, reducing the shaping air flow rate, or reducing the paint flow rate).

[0010] First, when the coating distance is shortened, the coating efficiency on the workpiece is improved, but because turbulence in the shaping air remains, there is the problem that a certain amount of paint particles will scatter around and not reach the workpiece.

[0011] Next, if the painting conditions are changed to reduce the scattering of paint particles, for example, by lowering the rotation speed of the rotary atomizing head too much or by reducing the flow rate of the shaping air too much, the particle size of the paint sprayed from the rotary atomizing head tends to become large, resulting in a decrease in the quality of the paint (coat). In response to this, one method of reducing the size of large paint particles is to lower the viscosity of the paint. However, if the viscosity of the paint is lowered, the paint film becomes more likely to drip, making it very difficult to adjust the paint. In addition, if the paint flow rate is reduced, the width of the paint spray pattern becomes narrower, resulting in a problem of reduced productivity per paint sprayer.

[0012] The present invention has been made in consideration of the above-mentioned problems in the prior art, and an object of the present invention is to provide a rotary atomizing head type coater and an electrostatic coating device which are capable of improving coating efficiency. [Means for solving the problem]

[0013] The present invention relates to a rotary atomizing head type coating machine comprising an air motor using compressed air as a power source, a hollow rotating shaft supported rotatably while extending in the front-rear direction along the axis of the air motor, with a front end protruding from the air motor, a feed tube extending through the inside of the rotating shaft to the front end of the rotating shaft, a rotary atomizing head attached to the front end of the rotating shaft and having an outer circumferential surface expanding into a cup shape, an inner circumferential surface for diffusing paint supplied from the feed tube, and a discharge edge located at the front end for discharging the paint, a cylindrical shaping air ring provided on the outer circumferential side of the rotary atomizing head, and a first shaping air ejection section provided on the outer circumferential side of the rotary atomizing head for ejecting a first shaping air toward the paint ejected from the discharge edge, wherein the inner cylindrical surface of the shaping air ring is At least a front portion facing the outer circumferential surface of the rotary atomizing head is formed to have a uniform inner diameter dimension, the first shaping air ejection part is formed as an annular gap between the outer circumferential surface of the rotary atomizing head and the inner cylindrical surface of the shaping air ring, the radial gap dimension between the outer circumferential surface of the rotary atomizing head and the inner cylindrical surface of the shaping air ring is set to 0.1 to 1.0 mm, the front end of the shaping air ring is disposed at a position 0.1 to 10.0 mm rearward from the discharge edge of the rotary atomizing head, the radial width dimension of the front end of the shaping air ring is set to 2 mm or less, and the taper angle of the outer cylindrical surface of the shaping air ring expanding from the front end of the shaping air ring toward the rear is set to 25° or less with respect to the axis. Effect of the Invention

[0014] According to the present invention, the coating efficiency can be improved. [Brief description of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view showing a rotary atomizing head type coating machine according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing the dimensions of each part in an enlarged manner. [Diagram 3]FIG. 11 is an explanatory diagram showing the air flow when the width dimension of the front end of the shaping air ring is set to 2 mm or less. [Figure 4] FIG. 13 is an explanatory diagram showing, as a comparative example, the air flow when the width dimension of the front end portion of the shaping air ring is set to be greater than 2 mm. [Diagram 5] FIG. 11 is a cross-sectional view showing a second shaping air jetting part according to a first modified example. [Figure 6] FIG. 11 is a cross-sectional view showing a second shaping air jetting part according to a second modified example. [Figure 7] FIG. 4 is a configuration diagram showing a rotary atomizing head type coating machine according to a second embodiment of the present invention. [Figure 8] FIG. 11 is a configuration diagram showing an electrostatic coating device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rotary atomizing head type coating machine and an electrostatic coating device according to embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0017] 1 to 4 show a first embodiment of the present invention. There are two types of rotary atomizing head type sprayers: electrostatic sprayers that apply a high voltage to the paint to be sprayed, and non-electrostatic sprayers that apply a high voltage to the paint. In the embodiment described below, a rotary atomizing head type sprayer configured as a direct charging type electrostatic sprayer that directly applies a high voltage to the paint will be taken as an example. Even when applied to a non-electrostatic sprayer, the same effect can be obtained with respect to the flow of shaping air.

[0018] In Fig. 1, the rotary atomizing head type coater 1 according to the first embodiment of the present invention is configured as a direct charging type electrostatic coater that applies a high voltage directly to paint by a high voltage generator (not shown). The rotary atomizing head type coater 1 is attached to the tip of an arm (not shown) of a painting robot, for example. The rotary atomizing head type coater 1 includes a housing 2, an air motor 3, a rotating shaft 4, a feed tube 5, a rotary atomizing head 6, a shaping air ring 7, a first shaping air ejection part 8, and a second shaping air ejection part 9, which will be described later.

[0019] The housing 2 is formed as a cylindrical body, and is attached to the tip of the arm of a painting robot. A motor housing section (not shown) for housing the air motor 3 is open toward the front on the inner circumferential side of the housing 2. Here, the motor housing section is made of a circular stepped hole, and has an axis OO extending in the front-rear direction at its center. This axis OO is the rotation axis (center axis) of the air motor 3, the rotary shaft 4, and the rotary atomizing head 6. Furthermore, a shaping air ring 7 is provided on the front side of the housing 2.

[0020] The air motor 3 is provided on the axis OO in the housing 2. The air motor 3 uses compressed air as a power source to rotate the rotary shaft 4 and the rotary atomizing head 6 at a high speed of, for example, 3k to 100k rpm. The air motor 3 includes a stepped cylindrical motor case 3A attached to the motor accommodating portion of the housing 2, a turbine rotatably provided on the rear side of the motor case 3A, and an air bearing (none of which are shown) provided on the motor case 3A and rotatably supporting the rotary shaft 4. The rotation speed of the turbine, i.e., the rotation speed of the rotary atomizing head 6, is controlled according to the flow rate of the turbine air supplied.

[0021] The rotating shaft 4 is rotatably supported via an air bearing, extending in the front-rear direction coaxially with the axis OO of the air motor 3. The rotating shaft 4 is formed as a hollow cylinder, with its rear part integrally attached to the center of the turbine and its front part 4A protruding from the motor case 3A. A rotary atomizing head 6 is attached to the front part 4A of the rotating shaft 4.

[0022] The feed tube 5 passes through the rotary shaft 4 and extends to the front part 4A of the rotary shaft 4. The front side of the feed tube 5 protrudes from the front part 4A of the rotary shaft 4 and extends into the rotary atomizing head 6. The rear end side of the feed tube 5 is fixedly attached to the center position of the housing 2.

[0023] The feed tube 5 is formed as a double pipe arranged coaxially. The central flow path of this double pipe is the paint flow path 5A, and the outer annular flow path is the cleaning fluid flow path 5B. The paint flow path 5A and the cleaning fluid flow path 5B are connected to supply sources (not shown) of paint and cleaning fluid (thinner, air, etc.), respectively. Thus, the feed tube 5 supplies paint from the paint flow path 5A toward the rotary atomizing head 6 when performing a painting operation. On the other hand, the feed tube 5 supplies cleaning fluid from the cleaning fluid flow path 5B toward the rotary atomizing head 6 when performing a cleaning operation of adhering paint. The feed tube may be configured to use one flow path by switching between both paint and cleaning fluid.

[0024] The rotary atomizing head 6 atomizes and sprays the paint supplied from the feed tube 5. The rotary atomizing head 6 has a rear mounting part 6A attached to the front part 4A of the rotary shaft 4. The rotary atomizing head 6 is rotated at high speed together with the rotary shaft 4 by the air motor 3.

[0025] The rotary atomizing head 6 has an outer peripheral surface 6B that expands from the mounting portion 6A toward the front in a cup shape, and an inner peripheral surface 6C that expands toward the front in a funnel shape to form a paint thinning surface that spreads the paint supplied from the feed tube 5 while thinning it. The front end of the inner peripheral surface 6C forms a discharge edge 6D that discharges the paint diffused by the inner peripheral surface 6C when the rotary atomizing head 6 rotates.

[0026] Meanwhile, a disk-shaped hub member 6E is provided at the back (near the mounting portion 6A) of the inner peripheral surface 6C inside the rotary atomizing head 6. This hub member 6E can smoothly guide the paint supplied from the feed tube 5 to the inner peripheral surface 6C. Furthermore, a front portion 6F of the outer peripheral surface 6B of the rotary atomizing head 6 on the discharge edge 6D side faces an inner cylindrical surface 7A of a shaping air ring 7 described later in the radial direction.

[0027] Here, the shape of the front part 6F of the rotary atomizing head 6 will be described in detail. As shown in FIG. 2, the front part 6F is preferably shaped to have a uniform outer diameter in the front-rear direction (a shape in which the gap dimension between the front part 6F and the inner cylindrical surface 7A of the shaping air ring 7 is constant). In this case, if the boundary position between the front part 6F and the discharge edge 6D, which is the front end of the front part 6F, is set to point P1, the front part 6F is preferably formed along a straight line A that passes through this point P1 and extends parallel to the axis OO. On the other hand, the front part 6F is allowed to be inclined (tapered) in a direction in which the diameter decreases toward the rear side within a predetermined angle range. Specifically, the angle α of the straight line B (two-dot chain line) that passes through point P1 and is inclined with respect to the straight line A is set to within 10°. That is, the angle α of the front part 6F in the direction in which the diameter decreases from the discharge edge 6D toward the rear side is set as shown in the following formula 1.

[0028]

number

[0029] The rotary atomizing head 6 is rotated at high speed by the air motor 3 and receives paint from the feed tube 5. As a result, the rotary atomizing head 6 spreads the paint while thinning it on the inner circumferential surface 6C (paint thinning surface), and sprays it as countless paint particles atomized by centrifugal force from the discharge edge 6D.

[0030] The shaping air ring 7 is provided on the outer periphery of the rotary atomizing head 6. The shaping air ring 7 is formed in a stepped cylindrical shape and is provided on the front side of the housing 2 so as to surround the rotary atomizing head 6. The shaping air ring 7 has an inner cylindrical surface 7A, a front outer cylindrical surface 7B located on the front side, a rear outer cylindrical surface 7C located on the rear side, a step portion 7D between the front outer cylindrical surface 7B and the rear outer cylindrical surface 7C, and a front end portion 7E located at the forefront.

[0031] The inner cylindrical surface 7A has an inner diameter larger than the outer diameter of the outer peripheral surface 6B of the rotary atomizing head 6, and is formed as a cylindrical surface with an equal inner diameter extending in the front-rear direction with this inner diameter. The front portion of the inner cylindrical surface 7A overlaps the periphery of the outer peripheral surface 6B with a gap therebetween. Therefore, a first shaping air ejection part 8, which will be described later, is formed between the outer peripheral surface 6B and the inner cylindrical surface 7A.

[0032] 2, the radial gap dimension between the front portion 6F of the outer circumferential surface 6B of the rotary atomizing head 6 and the inner cylindrical surface 7A of the shaping air ring 7 will be described in detail. If the corner (boundary) between the inner cylindrical surface 7A and the front end portion 7E is defined as point P2, this gap dimension can be expressed as the radial dimension a between point P2 and point P1 of the rotary atomizing head 6. This gap dimension a is set as shown in the following formula 2.

[0033]

number

[0034] This allows the nozzle opening of the first shaping air jetting part 8 to be narrowed to the gap dimension a, improving the jetting direction, convergence, etc. of the first shaping air jetted from the first shaping air jetting part 8. The first shaping air jetting part can also be formed as a number of circumferentially continuous slits or square holes by providing a number of partition plates extending inward from the inner cylindrical surface of the shaping air ring at intervals in the circumferential direction. Even in this case, the inner cylindrical surface of the shaping air ring consisting of circumferentially continuous slits or square holes is formed with a uniform inner diameter dimension in the portion facing the outer circumferential surface of the rotary atomizing head.

[0035] Further, the front end 7E (between point P2 and point P3) of the shaping air ring 7 is disposed at a position a dimension b behind the discharge edge 6D (point P1) of the rotary atomizing head 6. This dimension b is set as shown in the following formula 3.

[0036]

number

[0037] In this way, by locating the front end 7E of the shaping air ring 7 0.1 to 10.0 mm behind the discharge edge 6D of the rotary atomizing head 6, it is possible to create an air flow with less turbulence near the end of the rotary atomizing head 6. This makes it possible to stabilize the flow of paint particles discharged from the rotary atomizing head 6, improving the coating efficiency. In addition, it is possible to prevent the paint discharged from the discharge edge 6D of the rotary atomizing head 6 from adhering to the front end 7E.

[0038] Furthermore, the radial width dimension of the front end 7E of the shaping air ring 7 is the radial dimension c between points P2 and P3, assuming that the corner (boundary) between the front outer cylindrical surface 7B and the front end 7E is point P3. This width dimension c is set as shown in the following equation 4. The lower limit of the width dimension c is determined by the machining accuracy, mechanical rigidity, etc. of the front end 7E of the shaping air ring 7.

[0039]

number

[0040] When the rotary atomizing head 6 rotates, an air flow (swirl flow) is generated in the tangential direction of the outer peripheral surface of the rotary atomizing head 6. As a result of intensive research by the inventors of the present application, it was found that when a wide end surface is present due to the front end 7E near the rotary atomizing head 6, as shown in FIG. 4, a part of the swirl flow flows backward along the outer cylindrical surface 101A of the shaping air ring 101. To be more specific, when the width dimension of the front end 101B of the shaping air ring 101 is set to be larger than 2 mm, the air near the front end 101B is carried away by the swirl flow. As a result, the pressure near the front side of the front end 101B decreases, and as shown by the arrow in FIG. 4, a part of the swirl flow flows backward along the outer cylindrical surface 101A side of the shaping air ring 101 due to the Coanda effect. In the explanatory diagram of FIG. 4, shaping air is not ejected.

[0041] The air flow in Figure 4 is opposite to the flow during painting, which transports paint particles forward. Therefore, it is necessary to increase the flow rate of the shaping air so that the paint particles can be supplied forward against the reverse air flow. However, if the flow rate of the shaping air is increased, it affects the flow rate of the air flow near the workpiece, resulting in a decrease in coating efficiency.

[0042] In contrast, when the width dimension c of the front end 7E is set to 2 mm or less as in this embodiment, a large air pool is not formed near the front side of the front end 7E, so that the pressure drop in front of the front end 7E can be suppressed. This suppresses the flow of air toward the rear side along the front outer cylinder surface 7B side of the shaping air ring 7, and allows air to flow in the radial direction (radial direction) as shown by the arrow in FIG. 3. In other words, since the flow of paint particles in the reverse direction can be suppressed, the flow rate of the shaping air can be reduced to suppress the air flow near the object to be coated, and the coating efficiency of the paint particles can be improved. In order to suppress the air pool near the front side of the front end 7E, it is preferable that the width dimension c of the front end 7E is as small as possible. On the other hand, in consideration of the mechanical strength of the front end 7E, it is preferable that the width dimension c of the front end 7E is a large value within the range of 2 mm or less. The width dimension c of the front end 7E is appropriately set within the range of 2 mm or less, taking into account both of these characteristics.

[0043] The front outer cylindrical surface 7B, which is the outer cylindrical surface of the shaping air ring 7, is formed to widen (so that the diameter dimension becomes larger) from the front end portion 7E toward the rear side. Specifically, the front outer cylindrical surface 7B is formed as a tapered surface having a taper angle β with respect to a straight line C that passes through point P3 and extends in the front-rear direction so as to be parallel to the axis OO. The taper angle β of the front outer cylindrical surface 7B is set as shown in the following formula 5.

[0044]

number

[0045] In this way, when the taper angle β of the front external cylinder surface 7B is set to 25° or less with respect to the straight line C (axis OO), in other words, when the taper angle β of the front external cylinder surface 7B is made small and close to the axis OO, the amount of air entrained by the swirling flow generated by the rotation of the rotary atomizing head 6 can be reduced, and the reverse flow that causes the paint particles to flow backward can be suppressed. For this reason, the taper angle β may be 25° or less, for example, 0°. However, as the taper angle β becomes smaller, the thickness of the front external cylinder surface 7B becomes thinner overall, and the mechanical strength decreases. The taper angle β of the front external cylinder surface 7B is appropriately set within a range of 25° or less, taking into consideration both of these characteristics.

[0046] The first shaping air ejection part 8 is provided on the outer periphery of the rotary atomizing head 6. The first shaping air ejection part 8 ejects the first shaping air toward the paint ejected from the ejection edge 6D. The first shaping air ejection part 8 is formed as an annular gap between the outer periphery 6B of the rotary atomizing head 6 and the inner cylindrical surface 7A of the shaping air ring 7. This ensures that there are no obstacles in front of the first shaping air ejection part 8, so that the first shaping air can be ejected stably. The first shaping air ejection part 8 is connected to a first shaping air source (not shown) via a first shaping air supply passage 8A or the like.

[0047] The inner cylindrical surface 7A of the shaping air ring 7 is formed with a uniform inner diameter. Meanwhile, the angle α of the front portion 6F of the outer circumferential surface 6B of the rotary atomizing head 6 is formed in the range of 0 to 10°. The first shaping air ejection part 8 is formed with a roughly uniform gap in the front-rear direction. Also, the gap dimension a of the ejection port of the first shaping air ejection part 8 is narrowed to 0.1 to 1.0 mm. As a result, the air flows in a laminar state in the first shaping air ejection part 8, and the first shaping air with a uniform ejection direction, convergence, etc. can be ejected to the paint particles.

[0048] The second shaping air ejection section 9 is located radially outward of the first shaping air ejection section 8 and is disposed surrounding the rotary atomizing head 6. The second shaping air ejection section 9 ejects the second shaping air toward the paint discharged from the discharge edge 6D of the rotary atomizing head 6. The second shaping air ejection section 9 is formed by a number of holes that are opened in a line in the circumferential direction in the step section 7D of the shaping air ring 7. The second shaping air ejection section 9 is connected to a second shaping air source (not shown) via a second shaping air supply passage 9A or the like. The second shaping air ejection section 9 may be eliminated and the shaping air may be ejected only from the first shaping air ejection section 8.

[0049] Here, an imaginary tapered surface D is provided that spreads out toward the rear side with respect to a straight line C that passes through point P3 and extends in the front-rear direction so as to be parallel to the axis OO. The imaginary tapered surface D has a taper angle γ of 25° with respect to the straight line C. In addition, the second shaping air jetting part 9 is disposed inside the imaginary tapered surface D (at a position close to the axis OO). This allows the air around the rotary atomizing head 6 to flow in the radial direction (radial direction) against the Coanda effect that tries to flow rearward along the front outer cylinder surface 7B, so that the flow rate of the shaping air can be reduced to suppress the air flow near the workpiece, and the coating efficiency of the paint particles can be improved.

[0050] The rotary atomizing head type coater 1 according to this embodiment has the above-mentioned configuration, and next, the operation of this rotary atomizing head type coater 1 when performing a coating operation will be described.

[0051] First, turbine air is supplied to the turbine of the air motor 3, which rotates the rotary shaft 4 and the rotary atomizing head 6 at high speed. In this state, paint from a paint supply source is supplied to the rotary atomizing head 6 through the paint flow path 5A of the feed tube 5. As a result, the rotary atomizing head 6 sprays the supplied paint as paint particles.

[0052] In this case, the rotary atomizing head 6 is connected to a high voltage generator via the air motor 3, the rotary shaft 4, etc., so that a high voltage is applied to the paint flowing on the surface of the rotary atomizing head 6. As a result, the paint particles sprayed from the rotary atomizing head 6, i.e., the charged paint particles, fly toward the object to be painted, such as the body of an automobile, which is connected to the earth, and are applied to the painted surface.

[0053] On the other hand, the paint particles discharged from the discharge edge 6D of the rotary atomizing head 6 are sprayed from the rear by the first shaping air ejected from the first shaping air ejection port 8 and the second shaping air ejected from the second shaping air ejection port 9, thereby enabling the spray pattern to be well shaped.

[0054] Here, the coating efficiency is the ratio of the paint that adheres to the coating surface to the sprayed paint. Even when using the rotary atomizing head type coater disclosed in Patent Document 1, the coating efficiency can be increased to a certain extent by appropriately setting various coating conditions. For example, as shown in Conventional Example 1 in Table 2, when electrostatic coating is performed with a rotary atomizing head type coater of the prior art, the coating efficiency can be increased to, for example, about 70 to 80%. On the other hand, as shown in Conventional Example 2 in Table 4, when non-electrostatic coating is performed with a rotary atomizing head type coater of the prior art, the coating efficiency is lower than that of electrostatic coating, for example, 66%. However, some of the paint particles sprayed from the rotary atomizing head 6 scatter around without reaching the coating surface of the object to be coated. For this reason, it was difficult to further increase the coating efficiency with the rotary atomizing head type coaters of Conventional Examples 1 and 2.

[0055] Therefore, the inventors of the present application have studied the change in coating efficiency from the structural aspects of rotary atomizing head type coaters. The structural aspects of rotary atomizing head type coaters are, for example, the width dimension c of the front end 7E of the shaping air ring (SA ring) 7, the external taper angle β of the shaping air ring 7, and the gap dimension a of the first shaping air jetting part (first SA jetting part) 8. The inventors of the present application have measured the coating efficiency of several rotary atomizing head type coaters with different structural conditions. The measurement results are shown in Tables 1 and 2 below.

[0056] [Table 1]

[0057] [Table 2]

[0058] [Table 3]

[0059] [Table 4]

[0060] With reference to Tables 1 and 2, the structural conditions of the rotary atomizing head type coater 1 required for increasing the coating efficiency, which is the subject of the present invention, will be described.

[0061] Around the tip of the rotary atomizing head 6, paint particles become disorganized, resulting in some paint particles not moving toward the object to be coated. Also, on the surface of the object to be coated, there are paint particles that flow along the surface and do not adhere to it. By minimizing these paint particles that do not contribute to coating, the coating efficiency can be increased.

[0062] The coating conditions of the current rotary atomizing head type coating machine shown as Conventional Example 1 and the results obtained under these coating conditions are explained. In Conventional Example 1 shown in Table 2, the width dimension c of the front end of the shaping air ring (SA ring) is set to 6 to 8 mm, the outer taper angle β of the shaping air ring is set to 30 to 60°, and the first shaping air jetting part (first SA jetting part) does not exist. In addition, the angle α of the outer peripheral surface in the direction of decreasing diameter from the discharge edge of the rotary atomizing head toward the rear side is set to 45°, the dimension b of the front end of the shaping air ring retreated from the discharge edge of the rotary atomizing head is set to 11 mm, the rotation speed of the rotary atomizing head is set to 20 to 40 krpm, the flow rate of the shaping air (SA) is set to 300 to 400 Nl / min, the coating distance is set to 200 mm, and the applied voltage is set to -80 kV. As a result, the amount of paint particles that do not move toward the object to be coated is "very large", and the amount of paint particles that flow along the coated surface of the object to be coated and do not adhere is "very large". As a result, coating efficiency remains at 70-80%.

[0063] The amount of paint particles that do not head toward the object being painted, and the amount of paint particles that flow along the painted surface of the object being painted and do not adhere to it, are judged on a four-point scale: "none" (too small to be measured), "small," "large," and "very large."

[0064] In contrast, in the rotary atomizing head type coater 1 of the embodiment 1 of the present invention, the coating conditions are as follows: width dimension c of the front end 7E of the shaping air ring (SA ring) 7 is 2 mm, outer taper angle β of the shaping air ring 7 is 22°, gap dimension a of the first shaping air ejection part (first SA ejection part) 8 is 0.1 to 1.0 mm, angle α of the front part 6F (outer peripheral surface) in the direction of decreasing diameter from the discharge edge 6D of the rotary atomizing head 6 toward the rear is 0°, and dimension b of the front end 7E of the shaping air ring (SA ring) 7 retreating from the discharge edge 6D of the rotary atomizing head 6 is 4 mm, as shown in Table 1. In addition, the rotation speed of the rotary atomizing head 6 is set to 20 krpm, the flow rate of the shaping air (SA) is set to 100 to 300 Nl / min, the coating distance is set to 100 mm, and the applied voltage is set to -60 kV. At this time, the amount of paint particles that do not move toward the workpiece is "none," and the amount of paint particles that flow along the coating surface of the workpiece and do not adhere to it is "none." As a result, in Example 1, the coating efficiency can be increased by 10% or more compared to Conventional Example 1, and the coating efficiency can be increased to, for example, 98% or more.

[0065] Table 1 lists only the coating efficiency when the coating conditions are set to those of Example 1. The present invention is not limited thereto, and even when the coating conditions of the rotary atomizing head type coater 1 are set to the width dimension c of the front end portion 7E of the shaping air ring 7 being 2 mm or less, the angle α of the front portion 6F (outer peripheral surface) of the rotary atomizing head 6 being 0 to 10°, the recession dimension b of the shaping air ring 7 being 0.1 to 10.0 mm, the outer taper angle β of the shaping air ring 7 being 25° or less, the coating distance being 90 to 110 mm, and the applied voltage being -50 kV or more, the coating efficiency can be increased in the same manner as in Example 1, and for example, the coating efficiency can be made 98% or more.

[0066] The reason for this is that the first shaping air is ejected from the first shaping air ejection part 8 in the gap between the rotary atomizing head 6 and the inner cylindrical surface 7A of the shaping air ring 7, so that there is no obstacle in front of the first shaping air ejection part 8, and the front part 6F of the rotary atomizing head 6 is parallel to the inner cylindrical surface 7A of the shaping air ring 7 (uniform gap). This suppresses turbulence of the air flow around the rotary atomizing head 6, and the flow of the shaping air can be stabilized without increasing the flow rate of the first shaping air. In other words, when the flow rate of the shaping air is increased, it is possible to suppress non-application of paint particles caused by the air flow flowing over the surface of the workpiece.

[0067] Furthermore, by setting the width dimension c of the front end 7E of the shaping air ring 7 to 2mm and the external taper angle β of the shaping air ring 7 to 22°, it is possible to suppress the phenomenon in which paint particles flow backward due to the Coanda effect. Also, by setting the gap dimension a of the first shaping air jetting part 8 to 0.1 to 1.0 mm, the angle α of the front part 6F of the rotary atomizing head 6 to 0°, and the setback dimension b of the shaping air ring 7 to 4 mm, it is possible to stabilize the first shaping air while accelerating the flow rate and directing the paint particles toward the workpiece.

[0068] Next, the inventors of the present application investigated the coating efficiency when the values ​​of the width dimension c of the front end 7E of the shaping air ring 7, the angle α of the front part 6F (outer peripheral surface) of the rotary atomizing head 6, the recession dimension b of the shaping air ring 7, and the outer taper angle β of the shaping air ring 7 were changed. The results are shown in Comparative Examples 1 to 12 in Tables 1 and 2. First, in Comparative Examples 1 and 2, the width dimension c of the front end 7E of the shaping air ring (SA ring) 7 was changed among the coating conditions of Example 1. In the case of Comparative Example 1 in which the width dimension c was changed to 4 mm, the amount of paint particles that do not move toward the object to be coated is "small," and the amount of paint particles that do not flow along the coated surface of the object to be coated and do not adhere is "none." As a result, the coating efficiency is lower than that of Example 1, for example, 95%. In addition, in the case of Comparative Example 2 in which the width dimension c was changed to 6 mm, the amount of paint particles that do not move toward the object to be coated is "large," and the amount of paint particles that do not flow along the coated surface of the object to be coated and do not adhere is "none." As a result, the coating efficiency is lower than that in Example 1, for example, 90%.

[0069] In Comparative Examples 3 to 5, the outer taper angle β of the shaping air ring 7 is changed among the coating conditions of Example 1. In Comparative Example 3, in which the outer taper angle β is changed to 35°, the amount of paint particles not directed toward the workpiece is "small", and the amount of paint particles that do not flow along the coated surface of the workpiece and adhere to the workpiece is "none". As a result, the coating efficiency is lower than that of Example 1, for example, 95%. In Comparative Example 4, in which the outer taper angle β is changed to 45°, the amount of paint particles not directed toward the workpiece is "small", and the amount of paint particles that do not flow along the coated surface of the workpiece and adhere to the workpiece is "none". As a result, the coating efficiency is lower than that of Example 1, for example, 93%. In Comparative Example 5, in which the outer taper angle β is changed to 55°, the amount of paint particles not directed toward the workpiece is "large", and the amount of paint particles that do not flow along the coated surface of the workpiece and adhere to the workpiece is "none". As a result, the coating efficiency is lower than that of Example 1, for example, 90%.

[0070] In Comparative Examples 6 to 8, the gap dimension a of the first shaping air jetting part (first SA jetting part) 8 is changed among the coating conditions of Example 1. In Comparative Example 6, in which the gap dimension a is changed to 1.1 mm, the amount of paint particles not directed toward the object to be coated is "small", and the amount of paint particles that do not flow along the coated surface of the object to be coated and do not adhere is "none". As a result, the coating efficiency is lower than that of Example 1, for example, 95%. In Comparative Example 7, in which the gap dimension a is changed to 1.2 mm, the amount of paint particles not directed toward the object to be coated is "large", and the amount of paint particles that do not flow along the coated surface of the object to be coated and do not adhere is "none". As a result, the coating efficiency is lower than that of Example 1, for example, 92%. In Comparative Example 8, in which the gap dimension a is changed to 1.5 mm, the amount of paint particles not directed toward the object to be coated is "very large", and the amount of paint particles that do not flow along the coated surface of the object to be coated and do not adhere is "none". As a result, the coating efficiency is lower than that of Example 1, for example, 88%.

[0071] In Comparative Examples 9 and 10, the angle α of the front portion 6F (outer peripheral surface) of the rotary atomizing head 6 is changed among the coating conditions of Example 1. In Comparative Example 9, where the angle α is changed to 10°, this 10° is within the range of the angle α that can obtain high coating efficiency, but by changing the angle α to 10°, the gap dimension a is 1.2 mm. For this reason, in Comparative Example 9, the amount of paint particles that do not move toward the object to be coated is "large", and the amount of paint particles that do not flow along the coated surface of the object to be coated and do not adhere is "none". As a result, the coating efficiency is lower than that of Example 1, for example, 92%. In Comparative Example 10, where the angle α is changed to 15°, the amount of paint particles that do not move toward the object to be coated is "very large", and the amount of paint particles that do not flow along the coated surface of the object to be coated and do not adhere is "none". As a result, the coating efficiency is lower than that of Example 1, for example, 88%.

[0072] In Comparative Examples 11 and 12, the recession dimension b of the shaping air ring (SA ring) 7 is changed from the coating conditions in Example 1. In Comparative Example 11, where the recession dimension b is changed to 15 mm, the amount of paint particles not directed toward the workpiece is "small," and the amount of paint particles that do not flow along the coated surface of the workpiece and adhere to it is "none." As a result, the coating efficiency is lower than that in Example 1, for example, 96%. In Comparative Example 12, where the recession dimension b is changed to 20 mm, the amount of paint particles not directed toward the workpiece is "large," and the amount of paint particles that do not flow along the coated surface of the workpiece and adhere to it is "none." As a result, the coating efficiency is lower than that in Example 1, for example, 93%.

[0073] Looking at the results of Comparative Examples 1 to 12, in which the coating conditions for the structural surface were changed, it is possible to increase the coating efficiency to a certain extent (for example, about 95%). However, in Comparative Examples 1 to 12, the coating efficiency is lower than in Example 1. This shows that when many of the coating conditions shown in Example 1 are satisfied simultaneously, the coating efficiency can be increased compared to when any of the coating conditions are not satisfied.

[0074] Next, the coating efficiency was investigated when the rotary atomizing head type coater 1 of the present invention was used with the coating conditions of the control surface changed. The results are shown in Examples 2 to 13 in Table 3. In this case, the control surface of the rotary atomizing head type coater 1 is, for example, the rotation speed of the rotary atomizing head 6, the flow rate of the shaping air (SA), the coating distance from the rotary atomizing head 6 to the coating surface of the object to be coated, and the applied voltage. First, in Examples 2 to 4, the rotation speed of the rotary atomizing head 6 is changed among the coating conditions of Example 1. In the case of Example 2 in which the rotation speed is changed to 25 krpm, the amount of paint particles that do not move toward the object to be coated is "small", and the amount of paint particles that flow along the coating surface of the object to be coated and do not adhere is "none". As a result, the coating efficiency is 96%. In addition, in the case of Example 3 in which the rotation speed is changed to 35 krpm, the amount of paint particles that do not move toward the object to be coated is "large", and the amount of paint particles that flow along the coating surface of the object to be coated and do not adhere is "none". As a result, the coating efficiency is 95%. Furthermore, in the case of Example 4, where the rotation speed was changed to 45 krpm, the amount of paint particles that did not move toward the workpiece was "large," and the amount of paint particles that flowed along the paint surface of the workpiece and did not adhere to it was "none." As a result, the coating efficiency was 93%.

[0075] In Examples 5 to 7, the flow rate of the shaping air (SA) is changed from the coating conditions in Example 1. In Example 5, where the flow rate of the first shaping air is changed to 400 Nl / min, the amount of paint particles not directed toward the workpiece is "none", and the amount of paint particles that do not flow along the coated surface of the workpiece and adhere to the workpiece is "small". As a result, the coating efficiency is 96%. In Example 6, where the flow rate of the first shaping air is changed to 500 Nl / min, the amount of paint particles not directed toward the workpiece is "none", and the amount of paint particles that do not flow along the coated surface of the workpiece and adhere to the workpiece is "large". As a result, the coating efficiency is 95%. In Example 7, where the flow rate of the first shaping air is changed to 600 Nl / min, the amount of paint particles not directed toward the workpiece is "none", and the amount of paint particles that do not flow along the coated surface of the workpiece and adhere to the workpiece is "large". As a result, the coating efficiency is 92%.

[0076] In Examples 8 to 10, the coating distance is changed from the coating conditions in Example 1. In Example 8, where the coating distance is changed to 130 mm, the amount of paint particles not directed toward the object to be coated is "none", and the amount of paint particles that do not flow along the coated surface of the object to be coated and do not adhere is "small". As a result, the coating efficiency is 96%. In Example 9, where the coating distance is changed to 150 mm, the amount of paint particles not directed toward the object to be coated is "none", and the amount of paint particles that do not flow along the coated surface of the object to be coated and do not adhere is "small". As a result, the coating efficiency is 94%. In Example 10, where the coating distance is changed to 200 mm, the amount of paint particles not directed toward the object to be coated is "none", and the amount of paint particles that do not flow along the coated surface of the object to be coated and do not adhere is "large". As a result, the coating efficiency is 90%.

[0077] In Examples 11 to 13, the applied voltage is changed from the coating conditions in Example 1. In Example 11, the applied voltage is changed to -40 kV, and the amount of paint particles not directed toward the workpiece is "none", and the amount of paint particles that do not flow along the coated surface of the workpiece and adhere to the workpiece is "none". As a result, the coating efficiency is 97%. In Example 12, the applied voltage is changed to -30 kV, and the amount of paint particles not directed toward the workpiece is "small", and the amount of paint particles that do not flow along the coated surface of the workpiece and adhere to the workpiece is "none". As a result, the coating efficiency is 92%. In Example 13, the applied voltage is changed to 0 kV (non-electrostatic), and the amount of paint particles not directed toward the workpiece is "small", and the amount of paint particles that do not flow along the coated surface of the workpiece and adhere to the workpiece is "large". As a result, the coating efficiency is 85%.

[0078] Looking at the results of Examples 2 to 13 in which the coating conditions of the control surface were changed, in Examples 2 to 12 in which electrostatic coating was performed, the coating efficiency was 90% or more. Therefore, it can be seen that in Examples 2 to 12 in which electrostatic coating was performed, the coating efficiency can be increased by, for example, 10% or more compared to Conventional Example 1 in which electrostatic coating was performed. Also, in Example 13 in which non-electrostatic coating was performed, the coating efficiency can be increased compared to the case where non-electrostatic coating was performed with the coater of Conventional Example 2. Therefore, even if the coating conditions of the control surface are different from those of Example 1, for example, depending on the viscosity of the paint used or the shape of the object to be coated, when the rotary atomizing head type coater 1 of Examples 1 to 13 is used, the coating efficiency can be increased compared to the case where the coaters of Conventional Examples 1 and 2 are used. That is, it can be seen that by setting the coating conditions of the structural surface to a predetermined value, as in the rotary atomizing head type coater 1 of Example 1, the coating efficiency can be improved compared to the case where a coater having a structure other than that is used.

[0079] Next, the coating efficiency was examined when non-electrostatic coating was performed using the rotary atomizing head type coater 1 of the present invention. The results are shown in Examples 14 and 15 in Table 4. Here, in the rotary atomizing head type coater 1 of Examples 14 and 15 of the present invention, the coating conditions of the structural surface were the same as those of Example 1. In addition, in the rotary atomizing head type coater of Conventional Example 2, the coating conditions of the structural surface were the same as those of Conventional Example 1. As other coating conditions, in Examples 14 and 15, the rotation speed of the rotary atomizing head 6 was 20 krpm, the flow rate of the first shaping air (SA) was 100 Nl / min, and the flow rate of the second shaping air (SA) was 500 Nl / min. In addition, in Conventional Example 2, the flow rate of the first shaping air (SA) was 300 Nl / min, and the flow rate of the second shaping air (SA) was 100 Nl / min. The other coating conditions were the same as those of Example 14. In Examples 14 and 15 and Conventional Example 2, the paint discharge rate was 300 cc / min and the paint sprayer movement speed (robot speed) was 500 mm / sec. In Examples 14 and 15 and Conventional Example 2, the applied voltage was set to 0 kV, and the results shown are for non-electrostatic painting.

[0080] In Example 14 and Conventional Example 2, the coating distance is set to 100 mm. In Conventional Example 2, the coating efficiency is, for example, 66%. In contrast, in Example 14, the coating efficiency can be increased by 10% or more compared to Conventional Example 2, and the coating efficiency can be, for example, 83%. In Example 15, the coating distance is set shorter than that of Example 14, and the coating distance is set to 60 mm. In Example 15, the coating efficiency is higher than that of Example 14, and the coating efficiency is, for example, 86%. As shown by these results, even in the case of performing non-electrostatic coating like the rotary atomizing head type coater 1 of Examples 14 and 15, it is found that the coating efficiency can be increased by setting the coating conditions of the structural surface to a predetermined value compared to the case of using the coater of Conventional Example 2 having a different structure.

[0081] Thus, according to this embodiment, the inner cylindrical surface 7A of the shaping air ring 7 is formed with a uniform inner diameter dimension at the front portion facing the outer peripheral surface 6B of the rotary atomizing head 6. The first shaping air ejection portion 8 is formed as an annular gap between the outer peripheral surface 6B (front portion 6F) of the rotary atomizing head 6 and the inner cylindrical surface 7A of the shaping air ring 7. In addition, the radial gap dimension a between the front portion 6F of the rotary atomizing head 6 and the inner cylindrical surface 7A of the shaping air ring 7 is set to 0.1 to 1.0 mm. The front end portion 7E of the shaping air ring 7 is disposed at a position 0.1 to 10.0 mm rearward from the discharge edge 6D of the rotary atomizing head 6. The radial width dimension c of the front end portion 7E of the shaping air ring 7 is set to 2 mm or less. The front outer cylindrical surface 7B of the shaping air ring 7 has a taper angle β expanding from the front end portion 7E of the shaping air ring 7 toward the rear side, which is set to 25° or less with respect to the axis OO. The second shaping air jetting portion 9 is disposed inside an imaginary tapered surface D that expands from the front end portion 7E of the shaping air ring 7 toward the rear side and has a taper angle of 25°.

[0082] Therefore, the inner cylindrical surface 7A of the shaping air ring 7 is formed with a uniform inner diameter, and the angle α of the front portion 6F of the outer circumferential surface 6B of the rotary atomizing head 6 is formed in the range of 0 to 10°, so the first shaping air jetting portion 8 is formed with a uniform gap in the front-rear direction. Also, the gap dimension a of the jet outlet of the first shaping air jetting portion 8 is narrowed to 0.1 to 1.0 mm, so the first shaping air can be jetted to the paint particles with the jet direction, convergence, etc., adjusted.

[0083] In addition, since the front end 7E of the shaping air ring 7 is located 0.1 to 10.0 mm behind the discharge edge 6D of the rotary atomizing head 6, the flow of paint particles discharged from the rotary atomizing head 6 can be stabilized, improving the coating efficiency. Furthermore, the paint discharged from the discharge edge 6D of the rotary atomizing head 6 can be prevented from adhering to the front end 7E.

[0084] Furthermore, because the width dimension c of the front end 7E of the shaping air ring 7 is set to 2 mm or less, it is possible to prevent the formation of a large air pocket near the front side of the front end 7E. In other words, by suppressing the pressure drop in front of the front end 7E, it is possible to prevent paint particles from flowing backward toward the low pressure area. As a result, by reducing the flow rate of the first shaping air and the second shaping air, it is possible to stabilize the air flow near the workpiece and improve the coating efficiency of the paint particles.

[0085] In addition, the taper angle β of the front outer cylinder surface 7B of the shaping air ring 7 is set to 25° or less with respect to a straight line C parallel to the axis OO, and is configured to be close to the axis OO. This makes it possible to reduce the amount of air that is sucked in by the swirling flow generated by the rotation of the rotary atomizing head 6, and suppresses the reverse flow that carries the paint particles backward. Moreover, since the paint particles suspended in the air are not sucked in by this reverse flow (turbulent flow), it is possible to prevent the paint from adhering to the rotary atomizing head 6 or the shaping air ring 7.

[0086] Furthermore, the second shaping air jetting part 9 is disposed inside (close to the axis OO) of the imaginary tapered surface D, which has a taper angle γ set to 25° with respect to the straight line C. This allows the air around the rotary atomizing head 6 to flow in the radial direction (radial direction) against the Coanda effect, which causes the air to flow rearward along the front external cylinder surface 7B, so the flow rate of the shaping air can be reduced to suppress the air flow near the object to be coated, improving the coating efficiency of the paint particles.

[0087] As a result, it is possible to improve the coating efficiency of the rotary atomizing head type coater 1. Also, since there is no need to change coating conditions such as the rotation speed of the rotary atomizing head 6 or the flow rates of the shaping air and paint, it is possible to improve the coating efficiency while maintaining the productivity by maintaining the coating area of ​​one rotary atomizing head type coater 1.

[0088] In the first embodiment, the shaping air ring 7 has a step portion 7D between the front outer cylinder surface 7B and the rear outer cylinder surface 7C, and the second shaping air ejection portion 9 is formed as a number of holes that are aligned in the circumferential direction on the step portion 7D. However, the present invention is not limited to this, and may be configured as in the first modified example shown in FIG. 5. That is, the second shaping air ejection portions 11 according to the first modified example are aligned in the circumferential direction on the shaping air ring 7, and their tips open on the inner cylinder surface 7A around the front portion 6F of the rotary atomizing head 6. This allows the second shaping air ejected from the second shaping air ejection portion 11 to merge with the first shaping air ejected from the first shaping air ejection portion 8, and the flow speed of the shaping air can be increased. As a result, even paint with a high viscosity can be atomized by the high-speed shaping air, and the finish quality of the paint can be improved. This first modified example can be similarly applied to the second and third embodiments described later.

[0089] Also, it may be configured as in the second modified example shown in Fig. 6. That is, the second shaping air ejection part 21 according to the second modified example is formed as a slit that opens to the rear side of the first shaping air ejection part 8 on the inner cylindrical surface 7A of the shaping air ring 7. As a result, the second shaping air ejection part 21 can merge the second shaping air with the first shaping air ejected from the first shaping air ejection part 8, similar to the second shaping air ejection part 11 according to the first modified example, and can increase the flow rate of the shaping air. As a result, the second shaping air ejection part 21 can be provided without making the front end part 7E of the shaping air ring 7 thick in the radial direction, so that both improvement in coating efficiency and improvement in the finish quality of the coating can be achieved. Furthermore, as shown in Examples 16 and 17 in Table 5, when the second shaping air jetting part 21 extends to the vicinity of the outlet of the first shaping air jetting part 8, the angle α of the front part 6F of the outer circumferential surface 6B of the rotary atomizing head 6 may be a value larger than 10°. In other words, as long as air flows out of the first shaping air jetting part 8 in a laminar flow state, the angle α may be larger than 10°. This second modified example can be similarly applied to the second and third embodiments described later.

[0090] [Table 5]

[0091] Furthermore, in the first embodiment, the rotary atomizing head type coater 1 has been described as being a direct charging type electrostatic coater that directly applies a high voltage to the paint supplied to the rotary atomizing head 6. However, the present invention is not limited to this, and may be applied to an indirect charging type rotary atomizing head type coater that has an external electrode that discharges a high voltage at the outer periphery of the housing, and applies a high voltage to the paint particles sprayed from the rotary atomizing head by discharging from this external electrode. Furthermore, the present invention can also be applied to a non-electrostatic coater that coats paint without applying a high voltage to the paint.

[0092] Next, Fig. 7 shows a second embodiment of the present invention. The second embodiment is characterized in that it includes a shaping air control device that controls the amount of first shaping air and the amount of second shaping air, and the shaping air control device controls the ratio between the amount of first shaping air and the amount of second shaping air so that the spray pattern of the paint discharged from the rotary atomizing head becomes smaller in diameter. In the second embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and their description will be omitted.

[0093] 7, the rotary atomizing head type coater 31 according to the second embodiment, like the rotary atomizing head type coater 1 according to the first embodiment, is configured to include a housing 2, an air motor 3, a rotary shaft 4, a feed tube 5, a rotary atomizing head 6, a shaping air ring 7, a first shaping air ejection section 8, and a second shaping air ejection section 9. In addition, the rotary atomizing head type coater 31 according to the second embodiment is equipped with a shaping air control device 34 described later.

[0094] The first shaping air jetting section 8 is connected to a first shaping air source (first SA source) 32 via a first shaping air supply path 8A, etc. The second shaping air jetting section 9 is connected to a second shaping air source (second SA source) 33 via a second shaping air supply path 9A, etc. The amount of shaping air jetted from the first shaping air source 32 and the second shaping air source 33 is controlled by a shaping air control device 34.

[0095] The shaping air control device 34 controls the flow rate (ejection amount) of the first shaping air ejected from the first shaping air ejection portion 8 and the flow rate (ejection amount) of the second shaping air ejected from the second shaping air ejection portion 9. Specifically, the shaping air control device 34 controls the ratio between the ejection amount of the first shaping air and the ejection amount of the second shaping air so that the spray pattern of the paint ejected from the rotary atomizing head 6 becomes smaller in diameter.

[0096] Here, an example of the ratio when the shaping air control device 34 controls the ejection amount of the first shaping air and the ejection amount of the second shaping air will be described. For example, when painting with a large spray pattern (large pattern), the shaping air control device 34 sets the ejection amount of the first shaping air to 300 Nl / min and the ejection amount of the second shaping air to 50 Nl / min under the conditions that the diameter dimension of the rotary atomizing head 6 is 70 mm, the rotation speed is 20 krpm, and the paint spray amount is 250 cc / min. That is, in the large pattern, by setting the ratio of the ejection amount of the first shaping air to the ejection amount of the second shaping air to 6:1, the spray pattern of the paint discharged from the rotary atomizing head 6 can be made small in diameter.

[0097] When painting with a spray pattern (small pattern) smaller than the large pattern, the shaping air control device 34 sets the first shaping air ejection rate to 50 Nl / min and the second shaping air ejection rate to 400 Nl / min under the conditions of a diameter of the rotary atomizing head 6 of 70 mm, a rotation speed of 20 krpm, and a paint spray rate of 150 cc / min. That is, in the small pattern, by setting the ratio of the ejection rate of the first shaping air to the ejection rate of the second shaping air to 1:8, the diameter of the spray pattern of the paint discharged from the rotary atomizing head 6 can be made smaller.

[0098] Thus, the rotary atomizing head type coater 31 according to the second embodiment configured as described above can achieve the same actions and effects as those of the first embodiment. In particular, the rotary atomizing head type coater 31 according to the second embodiment can control the ratio between the amount of first shaping air ejected from the first shaping air ejection portion 8 and the amount of second shaping air ejected from the second shaping air ejection portion 9 by the shaping air control device 34. This makes it possible to reduce the diameter of the spray pattern of the paint ejected from the rotary atomizing head 6. This makes it possible to prevent the sprayed paint from scattering around, thereby improving the coating efficiency.

[0099] Next, Fig. 8 shows a third embodiment of the present invention. The third embodiment is characterized by comprising a high voltage generator that applies a high voltage to the paint discharged from the rotary atomizing head, a coater moving means to which a rotary atomizing head type coater is attached, and a moving means control device that controls the coater moving means, and the moving means control device controls the coater moving means so that the coating distance from the discharge edge to the coating surface of the coating target is maintained at 90 to 150 mm. In the third embodiment, the same components as those in the first embodiment described above are given the same reference numerals, and their explanations will be omitted.

[0100] 8, an electrostatic coating device 41 according to the third embodiment includes the rotary atomizing head type coater 1 according to the first embodiment, a coating robot 43, and a robot control device 44, which will be described later. The rotary atomizing head type coater 1 includes a housing 2, an air motor 3, a rotating shaft 4, a feed tube 5, a rotary atomizing head 6, a shaping air ring 7, a first shaping air jetting section 8, a second shaping air jetting section 9, and a high voltage generator 42, which will be described later.

[0101] The high voltage generator 42 is provided in the housing 2 (shown by a dotted line). The high voltage generator 42 is, for example, configured with a Cockcroft circuit, and boosts the voltage supplied from a power supply device (not shown) to -60 to -120 kV. The output side of the high voltage generator 42 is electrically connected, for example, to the air motor 3, so that the high voltage generator 42 applies a high voltage to the rotary atomizing head 6 via the rotating shaft 4, and applies the high voltage to the paint discharged from the rotary atomizing head 6.

[0102] The coating robot 43 serving as the coater moving means has, for example, an arm 43B that moves freely on a support stand 43A. The rotary atomizing head type coater 1 is attached to the tip of the arm 43B. The coating robot 43 operates the arm 43B and the like in accordance with control signals from a robot control device 44, which will be described later. As the coater moving means, other than a multi-jointed robot, for example, a moving means that only performs reciprocating motion, etc., can also be used.

[0103] The robot control device 44, which serves as a moving means control device, controls the painting robot. The robot control device 44 controls the painting distance L from the discharge edge 6D of the rotary atomizing head 6 constituting the rotary atomizing head type paint sprayer 1 to the coating surface 45A of the workpiece 45 to be painted, and improves the coating efficiency. Specifically, the robot control device 44 controls the painting robot 43 so that the painting distance L is kept at 90 to 150 mm while applying a high voltage to the paint discharged from the rotary atomizing head 6 by the high voltage generator 42. In this way, when painting is performed with the painting distance L kept at 90 to 150 mm, the coating efficiency can be improved to about 95%, for example.

[0104] Here, if the coating distance L is greater than the upper limit of 150 mm, the electric field lines formed between the coating object 45 will be weakened, resulting in a decrease in coating efficiency (for example, the coating efficiency will be approximately 80%). On the other hand, if the coating distance L is less than the lower limit of 90 mm, there will be no decrease in coating efficiency, but there is a risk that high voltage abnormalities will occur frequently due to the proximity to the coating object 45, causing the line to stop. For this reason, the lower limit of the coating distance L is set to 90 mm.

[0105] Thus, the electrostatic coating device 41 according to the third embodiment thus configured includes a high voltage generator 42 that applies a high voltage to the paint discharged from the rotary atomizing head 6, a coating robot 43 to which the rotary atomizing head type coating machine 1 is attached, and a robot control device 44 that controls the coating robot 43. The robot control device 44 is configured to control the coating robot 43 so that the coating distance L from the discharge edge 6D of the rotary atomizing head 6 to the coating surface 45A of the workpiece 45 is kept within a range of 90 to 150 mm. When the coating robot 43 is controlled by the robot control device 44 in this manner, the coating efficiency for the coating surface 45A of the workpiece 45 can be improved.

[0106] In the third embodiment, the rotary atomizing head type coater 1 has been described as being a direct charging type electrostatic coater that directly applies a high voltage to the paint supplied to the rotary atomizing head 6. However, the present invention is not limited to this, and may be configured to be applied to an indirect charging type rotary atomizing head type coater that has an external electrode that discharges a high voltage on the outer periphery of the housing, and applies a high voltage to the paint particles sprayed from the rotary atomizing head by discharging from this external electrode. [Explanation of symbols]

[0107] 1,31 Rotary atomizing head type coating machine 3 Air motor 4 Rotation Axis 4A Front 5 Feed Tube 6 rotating atomization head 6B Outer surface 6C Inner surface 6D Emission Edge 6F front part 7 Shaping Air Ring 7A Inner cylinder surface 7B Front outer cylinder surface (outer cylinder surface) 7E Front end 8 First shaping air outlet 9, 11, 21 Second shaping air outlet 34 Shaping air control device 41 Electrostatic painting equipment 42 High Voltage Generator 43 Painting robot (means for moving the paint machine) 44 Robot control device (mobility control device) 45 Painted object (painting target) 45A Painted surface a Gap dimension b Setback dimension c Width dimension α Angle of the front part of the outer periphery of the rotary atomizing head β Taper angle of front outer cylinder surface γ Taper angle of virtual taper surface L Paint Distance

Claims

1. An air motor powered by compressed air; a hollow rotating shaft that is rotatably supported in a state in which it extends in a front-rear direction along an axis of the air motor and has a front end protruding from the air motor; a feed tube extending through the shaft to the front end of the shaft; a rotary atomizing head attached to the front end of the rotary shaft and having an outer circumferential surface expanding into a cup shape, an inner circumferential surface for diffusing the paint supplied from the feed tube, and a discharge edge located at the front end for discharging the paint; a cylindrical shaping air ring provided on the outer periphery of the rotary atomizing head; a first shaping air ejection section provided on an outer circumferential side of the rotary atomizing head and ejecting a first shaping air toward the paint ejected from the ejection edge; In a rotary atomizing head type coating machine comprising: the inner cylindrical surface of the shaping air ring is formed to have a uniform inner diameter at least in a front portion thereof facing the outer circumferential surface of the rotary atomizing head; the first shaping air ejection portion is formed as an annular gap between the outer circumferential surface of the rotary atomizing head and the inner cylindrical surface of the shaping air ring, a radial gap dimension between the outer circumferential surface of the rotary atomizing head and the inner cylindrical surface of the shaping air ring is set to 0.1 to 1.0 mm; a front end of the shaping air ring is disposed at a position 0.1 to 10.0 mm rearward from the discharge edge of the rotary atomizing head; The radial width dimension of the front end portion of the shaping air ring is set to 2 mm or less, a taper angle of an outer cylindrical surface of said shaping air ring expanding from said front end portion toward said rear end is set to be 25° or less with respect to said axis line of said rotary atomizing head type coater.

2. 2. The rotary atomizing head type coating machine according to claim 1, a front portion of the outer circumferential surface of the rotary atomizing head, which faces the inner cylindrical surface of the shaping air ring, has an angle of 0 to 10 degrees in a direction in which the diameter of the front portion of the outer circumferential surface of the rotary atomizing head decreases from the discharge edge toward the rear side.

3. 2. The rotary atomizing head type coating machine according to claim 1, the shaping air ring is disposed radially outward of the first shaping air ejection portion and surrounding the rotary atomizing head, and includes a second shaping air ejection portion that ejects second shaping air toward the paint ejected from the ejection edge, the second shaping air jetting portion is disposed inside an imaginary tapered surface that expands from the front end portion of the shaping air ring toward the rear side and has a taper angle of 25°.

4. 4. The rotary atomizing head type coating machine according to claim 3, A shaping air control device is provided that controls the ejection amount of the first shaping air and the ejection amount of the second shaping air, a shaping air control device that controls a ratio between an amount of the first shaping air and an amount of the second shaping air ejected so that a spray pattern of the paint ejected from the rotary atomizing head is reduced in diameter.

5. An electrostatic coating apparatus comprising the rotary atomizing head type coating machine according to any one of claims 1 to 4, a high voltage generator for applying a high voltage to the paint discharged from the rotary atomizing head; a coating machine moving means to which the rotary atomizing head type coating machine is attached; A moving means control device that controls the coating machine moving means; Equipped with The electrostatic coating device is characterized in that the moving means control device controls the coating machine moving means so that the coating distance from the discharge edge to the coating surface of the coating target is maintained at 90 to 150 mm.

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