Rotary atomizing head type coating machine and electrostatic coating device

Abstract

This invention relates to a rotary atomizing head type coating machine and an electrostatic coating apparatus, which can maintain the productivity of each coating machine and improve coating efficiency without changing coating conditions such as the rotation speed of the rotary atomizing head, the forming air, and the paint flow rate. The inner cylinder surface (7A) of the air forming ring (7) is formed with the same inner diameter. Based on the first forming air ejection part (8) being formed as an annular gap, its gap size (a) is set to 0.1 to 1.0 mm. The front end (7E) of the air forming ring (7) is positioned 0.1 to 10.0 mm away from the discharge end edge (6D) of the rotary atomizing head (6) on the rearward side. The radial width dimension (c) of the front end (7E) is set to 2 mm or less. The rearward-expanding cone angle (β) of the front outer cylinder surface (7B) of the air forming ring (7) is set to 25° or less relative to the axis O-O.

Description

Technical Field

[0001] This invention relates to a rotary atomizing head type coating machine and an electrostatic coating device suitable for painting automobile bodies. Background Technology

[0002] Typically, when painting car bodies, rotary atomizing head painting machines with high coating efficiency and good coating quality are used. The rotary atomizing head type coating machine includes: a pneumatic motor powered by compressed air; a hollow rotating shaft rotatably supported in a state extending along the axis of the pneumatic motor in the front-rear direction, with its front end protruding from the pneumatic motor; a feed pipe passing through the rotating shaft and extending to the front end of the rotating shaft; a rotary atomizing head mounted on the front end of the rotating shaft, having a cup-shaped outer peripheral surface, an inner peripheral surface for diffusing paint supplied from the feed pipe, and a discharge end edge located at the front end for discharging paint; a cylindrical air forming ring disposed on the outer peripheral side of the rotary atomizing head; a first forming air ejection section disposed on the outer peripheral side of the rotary atomizing head for ejecting first forming air to the paint discharged from the discharge end edge; and a second forming air ejection section located radially outward of the first forming air ejection section and arranged to surround the rotary atomizing head for ejecting second forming air to the paint discharged from the discharge end edge (Patent Document 1).

[0003] In coating processes using rotary atomizing head type coating machines, it is expected that the amount of paint used can be reduced by improving the coating efficiency on the object being coated, carbon dioxide emissions can be reduced by simplifying equipment such as the coating booth, and the maintenance costs of the coating booth can be reduced.

[0004] Furthermore, in electrostatic coating using a rotary atomizing head type coating machine, a high voltage is applied to the paint, causing charged paint particles to fly along electric field lines formed between the paint and the object being coated. In this electrostatic coating, the coating distance from the rotary atomizing head type coating machine (rotary atomizing head) to the object being coated is set considering factors such as a safety distance for high voltage. Based on this, first forming air is sprayed from the first forming air ejection section onto the paint particles emitted from the discharge edge of the rotary atomizing head, and second forming air is sprayed from the second forming air ejection section onto the paint particles. As a result, the paint particles sprayed from the rotary atomizing head are rectified and formed into a spray pattern with a uniform film thickness distribution.

[0005] However, considering the coating distance, such as the safety distance for high voltage, the mobility of paint particles based on the forming air decreases, and the electric field strength also decreases. As a result, paint particles are transported over a wide area by the airflow flowing on the surface of the object being coated without reaching the object (coating surface), thus reducing coating efficiency.

[0006] Therefore, increasing the flow rate of the forming air is considered, but in this case, the amount of paint particles flowing along the surface of the object being coated increases. As a result, the paint particles emitted from the rotating atomizing head are affected by the turbulence generated by the forming air, and are guided by the turbulent airflow, failing to reach the object being coated, thus reducing the coating efficiency.

[0007] Furthermore, as a measure to achieve high coating efficiency, there are methods to shorten the coating distance (known as very close-range coating, proximity coating, etc.). This method can improve the mobility of paint particles carried by the forming air and increase the electric field strength, thus improving coating efficiency. However, currently, some paint particles sprayed from the rotating atomizing head are ejected radially from the rotating atomizing head due to the centrifugal force caused by the rotation of the rotating atomizing head, and are also unable to reach the object being coated due to turbulence caused by the forming air ejected from behind the rotating atomizing head.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2003-236417 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] In order to significantly reduce the amount of paint particles that do not reach the coated object, which leads to a decrease in coating efficiency, while solving the above-mentioned problems, firstly, we should consider shortening the coating distance and increasing the electric field strength; secondly, we should consider changing the coating conditions (e.g., reducing the rotation speed of the atomizing head, reducing the forming air flow rate, and reducing the paint flow rate) to reduce paint particle scattering.

[0013] First, while shortening the coating distance and increasing the electric field strength improves the coating efficiency of the object being coated, a certain amount of paint particles remain and disperse around the object without reaching it due to the turbulence of the residual forming air.

[0014] Next, when coating conditions are set too low, such as insufficient rotation speed of the rotary atomizer or insufficient flow rate of the forming air, to reduce paint particle dispersion, there is a tendency for the paint particle size sprayed from the rotary atomizer to increase, resulting in a decrease in coating (film) quality. To address this, measures exist to reduce the paint viscosity to minimize the increased particle size. However, when reducing paint viscosity, the film tends to sag, making paint adjustment difficult. Furthermore, reducing paint flow rate results in a smaller spray pattern width, leading to a decrease in productivity per coating machine.

[0015] The present invention is proposed in view of the problems of the prior art. The purpose of the present invention is to provide a rotary atomizing head type coating machine and electrostatic coating device that can maintain the productivity of each coating machine and improve the coating efficiency without changing the coating conditions such as the rotation speed of the rotary atomizing head, the forming air, and the flow rate of the coating.

[0016] Methods for solving problems

[0017] The rotary atomizing head type coating machine of the present invention includes: a pneumatic motor powered by compressed air; a hollow rotating shaft rotatably supported in a forward-backward direction extending along the axis of the pneumatic motor, with its front end protruding from the pneumatic motor; a feed pipe passing through the rotating shaft and extending to the front end of the rotating shaft; a rotary atomizing head mounted on the front end of the rotating shaft, having a cup-shaped outer peripheral surface, an inner peripheral surface for diffusing paint supplied from the feed pipe, and a discharge end edge located at the front end for discharging paint; a cylindrical air forming ring disposed on the outer peripheral side of the rotary atomizing head; and a first forming air ejection section disposed on the outer peripheral side of the rotary atomizing head for ejecting first forming air onto the paint discharged from the discharge end edge. The rotary atomizing head type coating machine is characterized in that... The inner cylinder surface of the air forming ring has at least the front portion opposite to the outer peripheral surface of the rotating atomizing head having the same inner diameter. The first forming air ejection portion forms an annular gap between the outer peripheral surface of the rotating atomizing head and the inner cylinder surface of the air forming ring. The radial gap between the outer peripheral surface of the rotating atomizing head and the inner cylinder surface of the air forming ring is set to 0.1 to 1.0 mm. The front end of the air forming ring is positioned 0.1 to 10.0 mm away from the discharge edge of the rotating atomizing head. The radial width of the front end of the air forming ring is set to 2 mm or less. The conical angle of the outer cylinder surface of the air forming ring expanding from the front end of the air forming ring toward the rear is set to 25° or less relative to the axis.

[0018] Invention Effects

[0019] According to the present invention, coating conditions can be optimized without causing the rotational speed of the atomizing head to be too low or the flow rate of the forming air and coating to be too low, thereby maintaining the productivity of each coating machine and improving coating efficiency. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view showing the rotary atomizing head type coating machine according to the first embodiment of the present invention.

[0021] Figure 2 It is a cross-sectional view that shows the enlarged dimensions of each part.

[0022] Figure 3 This is an explanatory diagram showing the airflow when the width of the front end of the air forming ring is set to less than 2 mm.

[0023] Figure 4 The illustration is a comparative example of airflow when the width of the front end of the air forming ring is set to be greater than 2 mm.

[0024] Figure 5 This is a cross-sectional view showing the second shaped air ejection section of the first modified example.

[0025] Figure 6 This is a cross-sectional view showing the second shaped air ejection section of the second modified example.

[0026] Figure 7 This is a structural diagram showing the rotary atomizing head type coating machine according to the second embodiment of the present invention.

[0027] Figure 8 This is a structural diagram showing the electrostatic coating apparatus according to the third embodiment of the present invention.

[0028] Explanation of reference numerals in the attached figures

[0029] 1. 31 Rotary Atomizing Head Coating Machine

[0030] 3. Pneumatic motor

[0031] 4. Rotation axis

[0032] 4A front

[0033] 5. Feed pipe

[0034] 6. Rotary atomizing head

[0035] 6B outer periphery

[0036] 6C Inner circumferential surface

[0037] 6D emission edge

[0038] 6F Front Section

[0039] 7 Air-forming ring

[0040] 7A Inner Cylinder Surface

[0041] 7B front outer cylinder surface (outer cylinder surface)

[0042] 7E front end

[0043] 8. First forming air ejection section

[0044] 9, 11, 21 Second forming air ejection section

[0045] 34 Forming Air Control Device

[0046] 41 Electrostatic Coating Equipment

[0047] 42 High Voltage Generator

[0048] 43. Painting Robot (Painting Machine Moving Mechanism)

[0049] 44. Robot Control Device (Mobile Mechanism Control Device)

[0050] 45. Object to be painted (projected object)

[0051] 45A Coated Surface

[0052] a. Gap size

[0053] b Back dimension

[0054] c Width dimension

[0055] The angle of the front part of the α-rotary atomizing head

[0056] β-shaped angle of the outer front cylindrical surface

[0057] γ, the cone-shaped angle of the imaginary cone surface

[0058] L painting distance Detailed Implementation

[0059] Hereinafter, the rotary atomizing head type coating machine and electrostatic coating device of the present invention will be described in detail with reference to the accompanying drawings.

[0060] Figures 1 to 4 The first embodiment of the present invention is shown. Rotary atomizing head type coating machines include electrostatic coating machines that apply high voltage to the sprayed paint for coating, and non-electrostatic coating machines that do not apply high voltage to the paint for coating. In the embodiments described below, a rotary atomizing head type coating machine configured as a direct-charge electrostatic coating machine that directly applies high voltage to the paint will be used as an example. Even when applied to a non-electrostatic coating machine, the same effect can be obtained regarding the flow of forming air.

[0061] exist Figure 1 In this invention, the rotary atomizing head type coating machine 1 of the first embodiment is configured as a direct-charge electrostatic coating machine in which a high voltage is directly applied to the coating material by a high voltage generator (not shown). The rotary atomizing head type coating machine 1 is mounted on the front end of, for example, the arm (not shown) of a coating robot. The rotary atomizing head type coating machine 1 is configured to include, as described later, a housing 2, a pneumatic motor 3, a rotating shaft 4, a feed pipe 5, a rotary atomizing head 6, an air forming ring 7, a first forming air ejection section 8, and a second forming air ejection section 9.

[0062] The housing 2 is formed into a cylindrical shape and is mounted on the front end of the arm of the painting robot. A motor housing (not shown) for housing the pneumatic motor 3 within the inner circumference of the housing 2 opens towards the front. Here, the motor housing is formed by a circular stepped hole, with an axis OO extending in the front-rear direction at its center. This axis OO serves as the rotation axis (central axis) for the pneumatic motor 3, the rotating shaft 4, and the rotating atomizing head 6. Furthermore, an air-forming ring 7 is provided on the front side of the housing 2.

[0063] A pneumatic motor 3 is mounted on axis OO within the housing 2. The pneumatic motor 3 uses compressed air as a power source to rotate the rotating shaft 4 and the rotating atomizing head 6 at a high speed, for example, 3k to 150k rpm. The pneumatic motor 3 includes: a stepped cylindrical motor housing 3A, which is mounted in the motor housing section of the housing 2; a turbine, rotatably mounted on the rear side of the motor housing 3A; and an air bearing (not shown), mounted in the motor housing 3A, which rotatably supports the rotating shaft 4. The turbine's rotational speed (i.e., the rotational speed of the rotating atomizing head 6) is controlled according to the flow rate of the supplied turbine air.

[0064] The rotating shaft 4 extends coaxially with the axis OO of the pneumatic motor 3 in the front-rear direction and is rotatably supported by an air bearing. The rotating shaft 4 is formed as a hollow cylinder, with its rear end integrally mounted in the center of the turbine, and its front end 4A protruding from the motor housing 3A. A rotating atomizing head 6 is mounted on the front end 4A of the rotating shaft 4.

[0065] The feed tube 5 passes through the rotating shaft 4 and extends to the front part 4A of the rotating shaft 4. The front side of the feed tube 5 protrudes from the front part 4A of the rotating shaft 4 and extends into the rotating atomizing head 6. The rear end of the feed tube 5 is fixedly installed at the center of the housing 2.

[0066] The feed pipe 5 is formed as a coaxial double-layered pipe. The central flow path of this double-layered pipe is called the paint flow path 5A, and the outer annular flow path is called the cleaning fluid flow path 5B. Furthermore, the paint flow path 5A and the cleaning fluid flow path 5B are connected to a supply source (not shown) for paint and cleaning fluid (thinner, air, etc.). Thus, during the painting operation, the feed pipe 5 supplies paint from the paint flow path 5A to the rotary atomizing head 6. On the other hand, during the cleaning operation of adhering paint, the feed pipe 5 supplies cleaning fluid from the cleaning fluid flow path 5B towards the rotary atomizing head 6. It should be noted that the feed pipe can also be configured to switch between the paint and cleaning fluid flow paths.

[0067] The rotating atomizing head 6 atomizes and sprays the paint supplied from the feed pipe 5. The mounting part 6A on the rear side of the rotating atomizing head 6 is mounted on the front part 4A of the rotating shaft 4. The rotating atomizing head 6 rotates at high speed together with the rotating shaft 4 via the pneumatic motor 3.

[0068] The rotary atomizing head 6 includes: an outer peripheral surface 6B that expands in a cup shape from the mounting portion 6A toward the front; and an inner peripheral surface 6C, which is configured as a coating film-forming surface, expanding in a funnel shape toward the front to film and diffuse the coating supplied from the feed pipe 5. Furthermore, the front end of the inner peripheral surface 6C becomes a discharge edge 6D from which the coating diffused by the inner peripheral surface 6C is released during the rotation of the rotary atomizing head 6.

[0069] On the other hand, a circular plate-shaped hub member 6E is provided inside the rotary atomizing head 6, and this hub member 6E is located inside the inner peripheral surface 6C (near the mounting part 6A). This hub member 6E can smoothly guide the coating supplied from the feed pipe 5 to the inner peripheral surface 6C. In addition, the front portion 6F of the outer peripheral surface 6B of the rotary atomizing head 6, on the side of the discharge end edge 6D, is radially opposite to the inner cylinder surface 7A of the air forming ring 7, which will be described later.

[0070] Here, the shape of the front portion 6F of the rotating atomizing head 6 will be described in detail. For example... Figure 2 As shown, the preferred front portion 6F has a shape with the same outer diameter in the front-rear direction (a shape with a constant gap size to the inner cylinder surface 7A of the air forming ring 7). In this case, if the boundary position between the front portion 6F and the front end edge 6D is set as point P1, then the front portion 6F is preferably formed through point P1 and along a straight line A extending parallel to the axis OO. On the other hand, the front portion 6F is allowed to have a tapered inclination (conical shape) that tends to narrow towards the rear within a specified angle range. Specifically, the angle α of the straight line B (double-dotted line) that passes through point P1 and is tapered relative to the straight line A is set to within 10°. That is, the angle α of the front portion 6F from the front end edge 6D toward the rearward tapering direction is set as shown in the following mathematical formula 1.

[0071]

Mathematical Formula 1

[0072] 0 degrees ≤ α ≤ 10 degrees

[0073] The rotary atomizing head 6 supplies paint from the feed pipe 5 while rotating at high speed by the pneumatic motor 3. As a result, the rotary atomizing head 6 thins and diffuses the paint on its inner circumferential surface 6C (the paint film-forming surface), and sprays it out from the discharge edge 6D as a large number of paint particles atomized by centrifugal force.

[0074] An air-forming ring 7 is disposed on the outer periphery of the rotating atomizing head 6. The air-forming ring 7 is formed into a stepped cylindrical shape and is disposed on the front side of the housing 2 in a manner that surrounds the rotating atomizing head 6. The air-forming ring 7 has an inner cylinder surface 7A, a front outer cylinder surface 7B located on the front side, a rear outer cylinder surface 7C located on the rear side, a layer difference portion 7D between the front outer cylinder surface 7B and the rear outer cylinder surface 7C, and a front end portion 7E located at the foremost part.

[0075] The inner cylinder surface 7A has an inner diameter larger than the outer diameter of the outer peripheral surface 6B of the rotating atomizing head 6, and is formed as a cylindrical surface with the same inner diameter extending in the front-rear direction. The front portion of the inner cylinder surface 7A overlaps with the periphery of the outer peripheral surface 6B at a distance. Therefore, the first forming air ejection section 8, described later, is formed between the outer peripheral surface 6B and the inner cylinder surface 7A.

[0076] Here, refer to Figure 2 The radial clearance dimension between the outer peripheral surface 6B of the rotating atomizing head 6 and the inner cylindrical surface 7A of the air forming ring 7 is described in detail. If the corner (boundary) between the inner cylindrical surface 7A and the front end 7E is designated as point P2, then this clearance dimension can be expressed as the radial dimension a between point P2 and point P1 of the rotating atomizing head 6. This clearance dimension a is set as shown in the following mathematical formula 2.

[0077]

Mathematical Formula 2

[0078] 0.1mm≤a≤1.0mm

[0079] Therefore, the nozzle of the first forming air ejection section 8 can be reduced to a gap size a, resulting in good ejection direction and convergence of the first forming air ejected from the first forming air ejection section 8. It should be noted that the first forming air ejection section can also be formed by arranging multiple partition plates extending inward from the inner cylinder of the air forming ring at intervals in the circumferential direction, thus creating multiple slits or quadrilateral holes connected in the circumferential direction. In this case, the inner cylinder surface of the air forming ring, composed of circumferentially continuous slits or quadrilateral holes, also has the same inner diameter as the portion opposite to the outer circumferential surface of the rotating atomizing head.

[0080] Furthermore, the front end 7E of the air forming ring 7 (between points P2 and P3) is positioned at a distance b that is separated from the discharge edge 6D (point P1) of the rotating atomizing head 6 by a rearward dimension. This dimension b is set as shown in the following mathematical formula 3.

[0081]

Mathematical Expression 3

[0082] 0.1mm≤b≤10.0mm

[0083] By positioning the front end 7E of the air forming ring 7 0.1 to 10.0 mm rearward relative to the discharge edge 6D of the rotating atomizing head 6, a low-turbulence airflow can be formed near the end of the rotating atomizing head 6. This stabilizes the flow of paint particles discharged from the rotating atomizing head 6, improving coating efficiency. Furthermore, it prevents paint discharged from the discharge edge 6D of the rotating atomizing head 6 from adhering to the front end 7E.

[0084] Furthermore, if the corner (boundary) between the front outer cylinder surface 7B and the front end portion 7E is designated as point P3, then the radial width dimension of the front end portion 7E of the air forming ring 7 becomes the radial dimension c between points P2 and P3. This width dimension c is set as shown in the following mathematical formula 4.

[0085]

Mathematical Expression 4

[0086] c≤2mm

[0087] Here, if the rotating atomizing head 6 rotates, an airflow (swirling flow) is generated in the tangential direction of the outer peripheral surface of the rotating atomizing head 6. After in-depth research, the inventors of this application discovered that if a wide end face exists near the rotating atomizing head 6 due to the front end portion 7E, then... Figure 4 As shown, a portion of the swirling flow flows rearward along the outer cylindrical surface 101A of the air forming ring 101. Specifically, when the width of the front end portion 101B of the air forming ring 101 is set to be greater than 2 mm, the air near the front end portion 101B is carried away by the swirling flow. Consequently, the pressure near the front side of the front end portion 101B decreases, therefore, as... Figure 4 As indicated by the middle arrow, a portion of the swirling flow flows rearward along the outer cylindrical surface 101A of the air-forming ring 101 due to the wall adhesion effect. Figure 4 In the illustration, no shaped air is ejected.

[0088] Figure 4 The airflow during coating is opposite to the airflow that carries paint particles forward. Therefore, it is necessary to increase the flow rate of the forming air to resist the opposite airflow and supply paint particles forward. However, increasing the flow rate of the forming air affects the velocity of the airflow near the object being coated, resulting in a decrease in coating efficiency.

[0089] Therefore, when the width c of the front end portion 7E is set to 2 mm or less, as in this embodiment, no large amount of stagnant air is formed near the front side of the front end portion 7E, thus suppressing the pressure drop at the front side of the front end portion 7E. This also suppresses the flow of air to the rear along the front outer cylinder surface 7B of the air forming ring 7, such as... Figure 3 As indicated by the arrow, air flows radially (in the radial direction). That is, by suppressing the flow of paint particles in the opposite direction, the flow rate of forming air can be reduced to suppress airflow near the object being coated, thereby improving the coating efficiency of paint particles.

[0090] The front outer cylindrical surface 7B, which forms the outer cylindrical surface of the air-forming ring 7, is formed to expand from the front end 7E toward the rear (the diameter increases). Specifically, the front outer cylindrical surface 7B is formed as a conical surface with a conical angle β relative to a straight line C that passes through point P3 and extends parallel to the axis OO in the front-rear direction. The conical angle β of the front outer cylindrical surface 7B is set by the following mathematical formula 5.

[0091]

Mathematical Expression 5

[0092] β≤25 degrees

[0093] In this way, when the cone angle β of the front outer cylinder surface 7B is set to be less than 25° relative to the straight line C (axis OO), in other words, when the cone angle β of the front outer cylinder surface 7B is set to be very small and close to the axis OO, the air entrained by the swirling flow generated by the rotation of the rotating atomizing head 6 can be reduced, and the reverse flow that causes the paint particles to flow to the rear can be suppressed.

[0094] The first shaping air ejector 8 is provided on the outer periphery of the rotating atomizing head 6. The first shaping air ejector 8 ejects first shaping air into the paint discharged from the discharge end edge 6D. The first shaping air ejector 8 forms an annular gap between the outer peripheral surface 6B of the rotating atomizing head 6 and the inner cylinder surface 7A of the air shaping ring 7. As a result, the first shaping air ejector 8 is in a state where there are no obstructions in front of it, so the first shaping air can be ejected stably. The first shaping air ejector 8 is connected to a first shaping air source (not shown) via a first shaping air supply passage 8A, etc.

[0095] The inner cylinder surface 7A of the air forming ring 7 is formed with the same inner diameter, and the angle α of the front portion 6F of the outer peripheral surface 6B of the rotating atomizing head 6 is formed in the range of 0 to 10°. Therefore, the first forming air ejection section 8 is formed with the same gap in the front-rear direction. Furthermore, the gap size α of the nozzle of the first forming air ejection section 8 is reduced to 0.1 to 1.0 mm. Thus, in the first forming air ejection section 8, first forming air can be sprayed onto the coating particles in a laminar flow state, with the ejection direction and convergence meeting the requirements.

[0096] The second forming air ejection section 9 is located radially outward from the first forming air ejection section 8 and is arranged to surround the rotating atomizing head 6. The second forming air ejection section 9 ejects second forming air into the coating material discharged from the discharge end edge 6D of the rotating atomizing head 6. The second forming air ejection section 9 is formed by a plurality of holes that open side by side in the circumferential direction on the layer difference portion 7D of the air forming ring 7. The second forming air ejection section 9 is connected to a second forming air source (not shown) via a second forming air supply passage 9A, etc. It should be noted that the second forming air ejection section 9 may also be omitted, and the configuration may be configured so that forming air is ejected only from the first forming air ejection section 8.

[0097] Here, an imaginary conical surface D is provided, expanding rearward relative to a straight line C. This straight line C passes through point P3 and extends in the front-rear direction parallel to the axis OO. Furthermore, the cone angle γ of the imaginary conical surface D relative to the straight line C is set to 25°. Based on this, a second forming air ejector 9 is positioned inside the imaginary conical surface D (near the axis OO). As a result, the air around the rotating atomizing head 6 can resist the wall adhesion effect that would otherwise flow rearward along the front outer cylinder surface 7B and flow radially (in the radial direction). Therefore, the flow rate of the forming air can be reduced to suppress airflow near the object being coated, thereby improving the coating efficiency of the paint particles.

[0098] The rotary atomizing head type coating machine 1 of this embodiment has the above-described configuration. Next, the operation when using the rotary atomizing head type coating machine 1 to perform coating operations will be described.

[0099] First, turbine air is supplied to the turbine of the pneumatic motor 3, causing the rotating shaft 4 and the rotating atomizing head 6 to rotate at high speed. In this state, paint from the paint supply source is supplied to the rotating atomizing head 6 via the paint flow path 5A of the feed pipe 5. As a result, the rotating atomizing head 6 sprays the supplied paint in the form of paint particles.

[0100] In this case, a high voltage is applied to the rotating atomizing head 6 by means of a pneumatic motor 3, a rotating shaft 4, etc. As a result, the paint particles sprayed from the rotating atomizing head 6, i.e., charged paint particles, fly towards the grounded car body or other objects to be coated, and can be coated on their surfaces.

[0101] On the other hand, the paint particles emitted from the discharge end edge 6D of the rotating atomizing head 6 are shaped into a good shape by being sprayed from the rear by the first forming air sprayed from the first forming air spray section 8 and the second forming air sprayed from the second forming air spray section 9.

[0102] Here, the coating efficiency, based on the ratio of paint adhering to the coating surface to the sprayed paint, can be improved to a certain extent (around 90%). However, some of the paint particles sprayed from the rotating atomizing head 6 do not reach the coating surface of the object and instead disperse around. Therefore, it is difficult to make the coating efficiency infinitely close to 100%.

[0103] Therefore, in this embodiment, the change in coating efficiency is measured from both structural and control aspects. Structurally, the width dimension c of the front end portion 7E of the air forming ring (SA ring) 7, the cone shape angle β of the air forming ring 7, and the gap dimension a of the first forming air ejection section (first SA ejection section) 8 are adjusted. Controlling aspects include adjusting the rotational speed of the rotating atomizing head 6, the flow rate of the forming air (SA), the coating distance from the rotating atomizing head 6 to the coating surface of the object being coated, and the applied voltage. The measurement results are shown in Table 1 below and Table 2.

[0104] Table 1

[0105]

[0106] Table 2

[0107]

[0108] Table 3

[0109]

[0110] First, the adjustment to obtain the high coating efficiency (coating efficiency of 98% or more) that is the subject of this embodiment will be explained.

[0111] Around the tip of the rotating atomizing head 6, paint particles that are not directed towards the object being coated exist due to the turbulence generated by the coating particles. Additionally, paint particles that flow along the coating surface of the object but do not adhere to it exist. High coating efficiency (over 98%) can be achieved by minimizing these paint particles that are detrimental to coating.

[0112] This section describes the coating conditions and results obtained using a conventional rotary atomizing head type coating machine, as an example of the present invention. In the conventional example shown in Table 2, the width c of the front end of the air forming ring (SA ring) is set to 6-8 mm, the cone angle β of the air forming ring is set to 30-60°, and there is no first forming air ejection section (first SA ejection section). In addition, the angle α of the outer peripheral surface in the direction of the rearward diameter reduction from the discharge edge of the rotary atomizing head is set to 45°, the dimension b of the front end of the air forming ring retracting from the discharge edge of the rotary atomizing head is set to 11 mm, the rotational speed of the rotary atomizing head is set to 20-40 krpm, the flow rate of the forming air (SA) is set to 300-400 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 not directed towards the object being coated becomes "very large," and the amount of paint particles flowing along the coating surface without adhering to it becomes "very large." Consequently, the coating efficiency stops at 70-80%.

[0113] It should be noted that the amount of paint particles not directed toward the object being coated and the amount of paint particles flowing along the coated surface of the object without adhering to it are judged in four levels: "none" (trace to unmeasurable), "few", "many", and "very many".

[0114] In this embodiment, in the rotary atomizing head type coating machine 1, as shown in Table 1, the coating conditions are as follows: the width c of the front end portion 7E of the air forming ring (SA ring) 7 is set to 2 mm; the cone angle β of the air forming ring 7 is set to 22°; the gap a of the first forming air ejection portion (first SA ejection portion) 8 is set to 0.1 to 1.0 mm; the angle α of the front portion 6F (outer peripheral surface) in the direction of the rearward diameter contraction from the discharge end edge 6D of the rotary atomizing head 6 is set to 0°; and the dimension b of the retraction of the front end portion 7E of the air forming ring (SA ring) from the discharge end edge 6D of the rotary atomizing head 6 is set to 4 mm. Furthermore, the rotational speed of the rotary atomizing head 6 is set to 20 krpm; the flow rate of the forming 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. As a result, the amount of paint particles not directed towards the object being coated becomes "zero," and the amount of paint particles flowing along the coating surface of the object without adhering becomes "zero." Consequently, a coating efficiency of over 98% can be achieved.

[0115] Furthermore, in the coating conditions of the rotary atomizing head type coating machine 1 in the embodiment, when the width dimension c of the front end 7E of the air forming ring 7 is set to 2 mm or less, the angle α of the front side portion 6F (outer peripheral surface) of the rotary atomizing head 6 is set to 0 to 10°, the retraction dimension b of the air forming ring 7 is set to 0.1 to 10.0 mm, the outer cone shape angle β of the air forming ring 7 is set to 25° or less, the coating distance is set to 90 to 110 mm, and the applied voltage is set to -50 kV or more, the coating efficiency can also be 98% or more.

[0116] The reason for this is that by ejecting the first forming air from the gap between the rotating atomizing head 6 and the inner cylinder surface 7A of the air forming ring 7, i.e., the first forming air ejection part 8, a structure is formed in which there are no obstructions in front of the first forming air ejection part 8, and the front part 6F of the rotating atomizing head 6 is parallel to the inner cylinder surface 7A of the air forming ring 7 (uniform gap). Therefore, turbulence in the airflow around the rotating atomizing head 6 can be suppressed, and the forming air flow can be stabilized without increasing the flow rate of the first forming air. That is, the rebound of paint particles on the surface of the object being coated, which would occur when the flow rate of the forming air is increased, can be suppressed.

[0117] Based on this, by setting the width c of the front end 7E of the air forming ring 7 to 2 mm and the cone angle β of the air forming ring 7 to 22°, the phenomenon of paint particles flowing backward due to the wall adhesion effect can also be suppressed. In addition, by setting the gap a of the first forming air ejection part 8 to 0.1 to 1.0 mm, setting the angle α of the front part 6F of the rotating atomizing head 6 to 0°, and setting the backward dimension b of the air forming ring 7 to 4 mm, the first forming air can be stabilized, the flow rate can be increased, and the paint particles can be directed toward the object being coated.

[0118] Next, Tables 1 and 2 will be used as comparative examples 1 to 12 to illustrate the results when the coating conditions of the structural surface are changed. First, in Comparative Examples 1 and 2, the width dimension c of the front end 7E of the air-forming ring (SA ring) 7 in each of the embodiments was changed. In Comparative Example 1, where the width dimension c was changed to 4 mm, the amount of paint particles not directed towards the object being coated became "less," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency became 95%. Furthermore, in Comparative Example 2, where the width dimension c was changed to 6 mm, the amount of paint particles not directed towards the object being coated became "more," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency stopped at 90%.

[0119] In Comparative Examples 3-5, the outer cone shape angle β of the air forming ring 7 in each coating condition of the embodiment was changed. In Comparative Example 3, where the outer cone shape angle β was changed to 35°, the amount of paint particles not facing the object being coated became "few," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency became 95%. Furthermore, in Comparative Example 4, where the outer cone shape angle β was changed to 45°, the amount of paint particles not facing the object being coated became "few," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency became 93%. Moreover, in Comparative Example 5, where the outer cone shape angle β was changed to 55°, the amount of paint particles not facing the object being coated became "more," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency stopped at 90%.

[0120] In Comparative Examples 6-8, the gap size 'a' of the first forming air ejection section (first SA ejection section) 8 in each coating condition of the embodiment was changed. In Comparative Example 6, where the gap size 'a' was changed to 1.1 mm, the amount of paint particles not directed towards the object being coated became "few," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency became 95%. In Comparative Example 7, where the gap size 'a' was changed to 1.2 mm, the amount of paint particles not directed towards the object being coated became "large," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency became 92%. Furthermore, in Comparative Example 8, where the gap size 'a' was changed to 1.5 mm, the amount of paint particles not directed towards the object being coated became "very large," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency stopped at 88%.

[0121] In Comparative Examples 9 and 10, the angle α of the front portion 6F (outer peripheral surface) of the rotating atomizing head 6 in each coating condition of the embodiment was changed. In Comparative Example 9, where the angle α was changed to 10°, this 10° is within the range of angle α that can obtain high coating efficiency. By changing the angle α to 10°, the gap size a becomes 1.2 mm. Therefore, in Comparative Example 9, the amount of paint particles not facing the object being coated becomes "more", and the amount of paint particles flowing along the coating surface of the object without adhering becomes "none". As a result, the coating efficiency becomes 92%. In Comparative Example 10, where the angle α was changed to 15°, the amount of paint particles not facing the object being coated becomes "very more", and the amount of paint particles flowing along the coating surface of the object without adhering becomes "none". As a result, the coating efficiency stops at 88%.

[0122] In Comparative Examples 11 and 12, the retraction dimension b of the air-forming ring (SA ring) 7 in each coating condition of the embodiment was changed. In Comparative Example 11, where the retraction dimension b was changed to 15 mm, the amount of paint particles not facing the object being coated became "less," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency became 96%. Furthermore, in Comparative Example 12, where the retraction dimension b was changed to 20 mm, the amount of paint particles not facing the object being coated became "more," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency became 93%.

[0123] The results of comparative examples 1 to 12, which show changes in coating conditions on the structural surface, indicate that although the coating efficiency can be improved to about 95%, multiple coating conditions need to be met simultaneously in order to improve the coating efficiency to over 98%.

[0124] Next, Table 3 will be used to illustrate the results under different coating conditions. First, in Comparative Examples 13-15, the rotational speed of the rotary atomizing head 6 in each coating condition of the embodiment was changed. In Comparative Example 13, where the rotational speed was changed to 25 krpm, the amount of paint particles not directed towards the object being coated became "less," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency became 96%. In Comparative Example 14, where the rotational speed was changed to 35 krpm, the amount of paint particles not directed towards the object being coated became "more," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency became 95%. Furthermore, in Comparative Example 15, where the rotational speed was changed to 45 krpm, the amount of paint particles not directed towards the object being coated became "more," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency became 93%.

[0125] In Comparative Examples 16-18, the flow rate of the forming air (SA) in each coating condition of the embodiment was changed. In Comparative Example 16, where the flow rate of the first forming air was changed to 400 Nl / min, the amount of paint particles not directed towards the object being coated became "none," and the amount of paint particles flowing along the coating surface of the object without adhering was "few." As a result, the coating efficiency became 96%. In Comparative Example 17, where the flow rate of the first forming air was changed to 500 Nl / min, the amount of paint particles not directed towards the object being coated became "none," and the amount of paint particles flowing along the coating surface of the object without adhering was "more." As a result, the coating efficiency became 95%. Furthermore, in Comparative Example 18, where the flow rate of the first forming air was changed to 600 Nl / min, the amount of paint particles not directed towards the object being coated became "none," and the amount of paint particles flowing along the coating surface of the object without adhering was "more." As a result, the coating efficiency became 92%.

[0126] In Comparative Examples 19-21, the coating distance in each coating condition of the embodiment was changed. In Comparative Example 19, where the coating distance was changed to 130 mm, the amount of paint particles not directed towards the object being coated became "none," and the amount of paint particles flowing along the coating surface of the object without adhering was "few." As a result, the coating efficiency became 96%. Furthermore, in Comparative Example 20, where the coating distance was changed to 150 mm, the amount of paint particles not directed towards the object being coated became "none," and the amount of paint particles flowing along the coating surface of the object without adhering was "few." As a result, the coating efficiency became 94%. Moreover, in Comparative Example 21, where the coating distance was changed to 200 mm, the amount of paint particles not directed towards the object being coated became "none," and the amount of paint particles flowing along the coating surface of the object without adhering was "more." As a result, the coating efficiency stopped at 90%.

[0127] In Comparative Examples 22-24, the applied voltage in each coating condition of the embodiment was changed. In Comparative Example 22, where the applied voltage was changed to -40kV, the amount of paint particles not directed towards the object being coated became "none," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency became 97%. Furthermore, in Comparative Example 23, where the applied voltage was changed to -30kV, the amount of paint particles not directed towards the object being coated became "none," and the amount of paint particles flowing along the coating surface of the object without adhering became "none." As a result, the coating efficiency became 92%. Moreover, in Comparative Example 24, where the applied voltage was changed to 0kV (non-electrostatic), the amount of paint particles not directed towards the object being coated became "few," and the amount of paint particles flowing along the coating surface of the object without adhering became "many." As a result, the coating efficiency stopped at 85%.

[0128] Observing the results of Comparative Examples 13 to 24 regarding coating conditions for change control, it can be seen that, similar to the case of coating conditions for change in structure, the coating efficiency can be improved to about 95%, but in order to improve the coating efficiency to more than 98%, multiple coating conditions need to be met simultaneously.

[0129] Thus, according to this embodiment, the front portion of the inner cylinder surface 7A of the air forming ring 7, which faces the outer peripheral surface 6B of the rotating atomizing head 6, is formed with the same inner diameter. Furthermore, the first forming air ejection portion 8 forms an annular gap between the outer peripheral surface 6B (front portion 6F) of the rotating atomizing head 6 and the inner cylinder surface 7A of the air forming ring 7. Based on this, the radial gap dimension 'a' between the front portion 6F of the rotating atomizing head 6 and the inner cylinder surface 7A of the air forming ring 7 is set to 0.1 to 1.0 mm. The front end portion 7E of the air forming ring 7 is positioned 0.1 to 10.0 mm rearward from the discharge edge 6D of the rotating atomizing head 6. The radial width dimension 'c' of the front end portion 7E of the air forming ring 7 is set to 2 mm or less. The cone angle β of the front outer cylinder surface 7B of the air forming ring 7, which expands rearward from the front end portion 7E of the air forming ring 7, is set to 25° or less relative to the axis OO. The second forming air ejection part 9 is disposed inside the imaginary conical surface D, which expands outward from the front end 7E of the air forming ring 7 at a conical angle of 25°.

[0130] Therefore, the inner cylinder surface 7A of the air forming ring 7 is formed with the same inner diameter, and the angle α of the front portion 6F of the outer peripheral surface 6B of the rotating atomizing head 6 is formed in the range of 0 to 10°. Therefore, the first forming air ejection section 8 is formed with the same gap in the front-rear direction. In addition, since the gap size α of the nozzle of the first forming air ejection section 8 is reduced to 0.1 to 1.0 mm, it is possible to spray the first forming air, which meets the requirements of ejection direction, convergence, etc., onto the coating particles.

[0131] Furthermore, the front end 7E of the air forming ring 7 is positioned 0.1 to 10.0 mm further back than the discharge edge 6D of the rotating atomizing head 6, thus stabilizing the flow of paint particles discharged from the rotating atomizing head 6 and improving coating efficiency. In addition, it prevents paint discharged from the discharge edge 6D of the rotating atomizing head 6 from adhering to the front end 7E.

[0132] Furthermore, by setting the width c of the front end portion 7E of the air forming ring 7 to 2 mm or less, it is possible to prevent the formation of large amounts of stagnant air near the front side of the front end portion 7E. That is, by suppressing the pressure drop at the front side of the front end portion 7E, it is possible to prevent paint particles from flowing in the opposite direction towards the low-pressure area. Therefore, by reducing the flow rates of the first forming air and the second forming air, the airflow near the object being coated can be stabilized, thereby improving the coating efficiency of the paint particles.

[0133] Furthermore, the cone angle β of the front outer cylindrical surface 7B of the air forming ring 7 is set to 25° or less relative to the straight line C parallel to the axis OO, and is configured to be close to the axis OO. This reduces the amount of air entrained by the swirling flow generated by the rotation of the rotating atomizing head 6, and suppresses the reverse flow that causes paint particles to flow backward. Moreover, since paint particles flying in the air are not entrained by this reverse flow (turbulence), paint adhesion to the rotating atomizing head 6 and the air forming ring 7 is prevented.

[0134] Furthermore, the second forming air ejection section 9 is positioned inside the imaginary conical surface D (near the axis OO) with a conical angle γ set at 25° relative to the straight line C. As a result, the air around the rotating atomizing head 6 can resist the wall adhesion effect that would otherwise flow backward along the front outer cylinder surface 7B and flow radially (in the radial direction). This reduces the flow rate of the forming air, suppresses airflow near the object being coated, and improves the coating efficiency of the paint particles.

[0135] As a result, the coating efficiency of the rotary atomizing head type coating machine 1 can be improved. In addition, since it is not necessary to change the coating conditions such as the rotation speed of the rotary atomizing head 6, the forming air, and the flow rate of the coating material, productivity can be maintained and coating efficiency can be improved by maintaining the coating range of one rotary atomizing head type coating machine 1.

[0136] It should be noted that in the first embodiment, the example is given where the air forming ring 7 has a layer difference portion 7D between the front outer cylinder surface 7B and the rear outer cylinder surface 7C, and the second forming air ejection portion 9 is formed as a plurality of holes that open side by side in the circumferential direction on the layer difference portion 7D. However, the present invention is not limited to this, and may also be implemented according to... Figure 5 The configuration shown is as described in the first modification. Specifically, in the first modification, the second forming air ejection section 11 is arranged circumferentially side-by-side on the air forming ring 7, with its front end opening on the inner cylinder surface 7A around the front portion 6F of the rotating atomizing head 6. This allows the second forming air ejected from the second forming air ejection section 11 to merge with the first forming air ejected from the first forming air ejection section 8, thereby accelerating the flow rate of the forming air. As a result, even high-viscosity coatings can be atomized by the high-speed forming air, improving the finishing quality of the coating. This first modification can also be applied to the second and third embodiments described later.

[0137] Alternatively, you can follow Figure 6The second modification shown is configured such that the second forming air ejection section 21 of the second modification is formed as a slit on the inner cylinder surface 7A of the air forming ring 7, opening at the rear side of the first forming air ejection section 8. Therefore, like the second forming air ejection section 11 of the first modification, the second forming air ejection section 21 allows the second forming air to merge with the first forming air ejected from the first forming air ejection section 8, thereby accelerating the flow rate of the forming air. As a result, for the second forming air ejection section 21, it is not necessary to make the front end portion 7E of the air forming ring 7 radially thick, thus achieving both improved coating efficiency and improved finishing quality. This second modification can also be applied to the second and third embodiments described later.

[0138] Furthermore, in the first embodiment, the rotary atomizing head type coating machine 1 is described as an example of a direct-charge electrostatic coating machine 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 can also be applied to an indirect-charge rotary atomizing head type coating machine, which has an external electrode at the outer periphery of the housing for releasing a high voltage, and applies a high voltage to the paint particles sprayed from the rotary atomizing head through discharge from the external electrode. Furthermore, the present invention can also be applied to non-electrostatic coating machines that coat the paint without applying a high voltage.

[0139] Next, Figure 7 A second embodiment of the present invention is shown. The second embodiment is characterized by including a forming air control device that controls the ejection amount of a first forming air and a second forming air. The forming air control device controls the ratio of the ejection amount of the first forming air to the ejection amount of the second forming air, thereby minimizing the spray pattern of the coating material emitted from the rotating atomizing head. It should be noted that in the second embodiment, the same reference numerals are used for the same components as in the first embodiment, and their descriptions are omitted.

[0140] exist Figure 7 In the second embodiment, the rotary atomizing head type coating machine 31 is similar to the rotary atomizing head type coating machine 1 of the first embodiment, and is configured to include a housing 2, a pneumatic motor 3, a rotating shaft 4, a feed pipe 5, a rotary atomizing head 6, an air forming ring 7, a first forming air ejection section 8, and a second forming air ejection section 9. Furthermore, the rotary atomizing head type coating machine 31 of the second embodiment includes the forming air control device 34, which will be described later.

[0141] The first forming air ejector 8 is connected to the first forming air source (first SA source) 32 via the first forming air supply passage 8A, etc. The second forming air ejector 9 is connected to the second forming air source (second SA source) 33 via the second forming air supply passage 9A, etc. Furthermore, the ejection volume of forming air from the first forming air source 32 and the second forming air source 33 is controlled by the forming air control device 34.

[0142] The forming air control device 34 controls the flow rate (ejection amount) of the first forming air ejected from the first forming air ejection unit 8 and the flow rate (ejection amount) of the second forming air ejected from the second forming air ejection unit 9. Specifically, the forming air control device 34 controls the ratio of the ejection amount of the first forming air to the ejection amount of the second forming air so as to minimize the diameter of the spray pattern of the paint emitted from the rotating atomizing head 6.

[0143] Here, an example is given of the ratio of the first forming air ejection volume to the second forming air ejection volume controlled by the forming air control device 34. For example, when painting with a large spray pattern (large pattern), under the conditions that the diameter of the rotary atomizing head 6 is 70 mm, the rotation speed is 20 k rpm, and the paint spray volume is 250 cc / min, the forming air control device 34 sets the first forming air ejection volume to 300 Nl / min and the second forming air ejection volume to 50 Nl / min. That is, for large patterns, by setting the ratio of the first forming air ejection volume to the second forming air ejection volume to 6:1, the spray pattern of the paint emitted from the rotary atomizing head 6 can be made smaller.

[0144] Furthermore, when painting with a spray pattern smaller than a large pattern (small pattern), under the conditions of a 70mm diameter rotary atomizing head 6, a rotation speed of 20krpm, and a paint spray volume of 150cc / min, the forming air control device 34 sets the first forming air spray volume to 50Nl / min and the second forming air spray volume to 400Nl / min. That is, for small patterns, by setting the ratio of the first forming air spray volume to the second forming air spray volume to 1:8, the diameter of the paint spray pattern emitted from the rotary atomizing head 6 can be reduced.

[0145] Thus, in the rotary atomizing head type coating machine 31 of the second embodiment configured as described above, the same functions and effects as in the first embodiment can be obtained. In particular, the rotary atomizing head type coating machine 31 of the second embodiment can use the forming air control device 34 to control the ratio of the amount of first forming air ejected from the first forming air ejection section 8 to the amount of second forming air ejected from the second forming air ejection section 9. Therefore, the spray pattern of the paint emitted from the rotary atomizing head 6 can be minimized. As a result, the dispersion of the sprayed paint can be suppressed, and the coating efficiency can be improved.

[0146] Next, Figure 8 A third embodiment of the present invention is shown. 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 coating machine moving mechanism on which a rotary atomizing head type coating machine is mounted; and a moving mechanism control device that controls the coating machine moving mechanism to maintain a coating distance of 90–150 mm from the discharge edge to the coating surface of the object to be coated. It should be noted that in the third embodiment, the same reference numerals are used for the same components as in the first embodiment, and their descriptions are omitted.

[0147] exist Figure 8 In the third embodiment, the electrostatic coating apparatus 41 includes the rotary atomizing head type coating machine 1 of the first embodiment, the coating robot 43 (described later), and the robot control device 44. The rotary atomizing head type coating machine 1 is configured to include a housing 2, a pneumatic motor 3, a rotating shaft 4, a feed pipe 5, a rotary atomizing head 6, an air forming ring 7, a first forming air ejection section 8, a second forming air ejection section 9, and a high-voltage generator 42 (described later).

[0148] A high-voltage generator 42 is mounted on the housing 2 (shown in dashed lines). The high-voltage generator 42, for example, is constructed using a Croft circuit to boost the voltage supplied from the power supply unit (not shown) to -60 to -120 kV. Furthermore, the output side of the high-voltage generator 42 is electrically connected to, for example, a pneumatic motor 3, thereby applying a high voltage to the rotating atomizing head 6 via the rotating shaft 4, and applying a high voltage to the coating material dispensed from the rotating atomizing head 6.

[0149] The painting robot 43, serving as the moving mechanism of the painting machine, has, for example, an arm 43B that moves freely on a support platform 43A. A rotary atomizing head type painting machine 1 is mounted at the front end of the arm 43B. The painting robot 43 moves the arm 43B and the like according to control signals from a robot control device 44 (described later). Besides multi-joint robots, for example, a moving mechanism that only performs reciprocating movements can also be used as the moving mechanism of the painting machine.

[0150] The robot control device 44, acting as a mobile mechanism control unit, controls the painting robot. The robot control device 44 controls the coating distance L from the discharge edge 6D of the rotating atomizing head 6 constituting the rotating atomizing head type painting machine 1 to the coating surface 45A of the workpiece 45, thereby improving coating efficiency. Specifically, the robot control device 44 controls the painting robot 43 while applying a high voltage to the paint discharged from the rotating atomizing head 6 via the high voltage generator 42, maintaining the coating distance L at 90–150 mm. In this way, when painting is performed with the coating distance L maintained at 90–150 mm, for example, the coating efficiency can be increased to approximately 95% (when the coating distance L is not maintained at 90–150 mm, the coating efficiency is approximately 80%).

[0151] Here, when the coating distance L is greater than the upper limit of 150mm, the electric field lines formed between the coating distance L and the workpiece 45 weaken, resulting in a decrease in coating efficiency. On the other hand, when the coating distance L is less than the lower limit of 90mm, although the coating efficiency does not decrease, high voltage anomalies occur frequently due to proximity to the workpiece 45, potentially causing production line shutdowns. Therefore, the lower limit of the coating distance L is set at 90mm.

[0152] Thus, the electrostatic coating apparatus 41 of the fourth embodiment configured as described above includes: a high-voltage generator 42 that applies a high voltage to the coating material emitted from the rotating atomizing head 6; a coating robot 43 equipped with the rotating atomizing head type coating machine 1; and a robot control device 44 that controls the coating robot 43. Furthermore, the robot control device 44 controls the coating robot 43 to maintain the coating distance L from the emission edge 6D of the rotating atomizing head 6 to the coating surface 45A of the workpiece 45 at 90-150 mm. In this way, when the coating robot 43 is controlled by the robot control device 44, the coating efficiency of the coating surface 45A of the workpiece 45 can be improved.

[0153] It should be noted that in the third embodiment, the rotary atomizing head type coating machine 1 is described as an example of a direct-charge electrostatic coating machine that directly applies a high voltage to the coating material supplied to the rotary atomizing head 6. However, the present invention is not limited to this and can also be applied to an indirect-charge rotary atomizing head type coating machine, which has an external electrode at the outer periphery of the housing that discharges a high voltage, and the high voltage is applied to the coating particles sprayed from the rotary atomizing head by the discharge from the external electrode.

Claims

1. A rotary atomizing head type coating machine, comprising: Pneumatic motors use compressed air as their power source; A hollow rotating shaft is rotatably supported in a state that extends along the axis of the pneumatic motor in the front-rear direction, with its front end protruding from the pneumatic motor. A feed tube that passes through the rotating shaft and extends to the front end of the rotating shaft; A rotary atomizing head, which is mounted on the front end of the rotating shaft, has an outer peripheral surface that expands in a cup shape, an inner peripheral surface that diffuses the coating supplied from the feed pipe, and a discharge end edge located at the front end and discharging the coating. A cylindrical air-forming ring is disposed on the outer periphery of the rotating atomizing head; as well as A first shaping air ejection section is disposed on the outer periphery of the rotating atomizing head, and ejects first shaping air onto the coating material emitted from the discharge end edge. The rotary atomizing head type coating machine is characterized by the following: The inner cylindrical surface of the air forming ring, at least the front portion opposite the outer peripheral surface of the rotating atomizing head, is formed to have the same inner diameter dimension. The first shaping air ejection section forms an annular gap between the outer peripheral surface of the rotating atomizing head and the inner cylindrical surface of the air shaping ring. The radial gap between the outer peripheral surface of the rotating atomizing head and the inner cylindrical surface of the air forming ring is set to 0.1–1.0 mm. The front end of the air forming ring is positioned 0.1–10.0 mm rearward from the discharge edge of the rotating atomizing head. The radial width of the front end of the air forming ring is set to be less than 2 mm. The conical angle of the outer cylindrical surface of the air-forming ring, which expands from the front end of the air-forming ring toward the rear, is set to be less than 25° relative to the axis.

2. The rotary atomizing head coating machine according to claim 1, characterized in that, Regarding the front portion of the outer peripheral surface of the rotating atomizing head that is opposite to the inner cylinder surface of the air forming ring, the angle from the discharge end edge toward the rear diameter reduction direction is set to 0 to 10°.

3. The rotary atomizing head coating machine according to claim 1, characterized in that, The air forming ring includes a second forming air ejection section, which is located radially outward compared to the first forming air ejection section and is arranged to surround the rotating atomizing head, ejecting the second forming air onto the coating material emitted from the discharge end edge. The second forming air ejection portion is disposed on the inner side of the imaginary conical surface, wherein the cone-shaped angle of the imaginary conical surface expanding from the front end of the air forming ring toward the rear is 25°.

4. The rotary atomizing head coating machine according to claim 3, characterized in that, A forming air control device is provided for controlling the ejection volume of the first forming air and the ejection volume of the second forming air. The forming air control device controls the ratio of the first forming air ejection amount to the second forming air ejection amount, so as to minimize the spray pattern of the coating emitted from the rotating atomizing head.

5. An electrostatic coating apparatus, characterized in that, The rotary atomizing head type coating machine as described in claim 1 The electrostatic coating device includes: A high-voltage generator that applies a high voltage to the coating material emitted from the rotating atomizing head; The painting machine moving mechanism is equipped with the rotary atomizing head type painting machine; and The moving mechanism control device controls the moving mechanism of the coating machine. The moving mechanism control device controls the moving mechanism of the coating machine to maintain the coating distance from the release end edge to the coating surface of the object to be coated at 90-150mm.

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