JP2009034577A - Washing process of rotation atomization electrostatic coating machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the washing process of a rotation atomization electrostatic coating machine which is capable of effectively controlling the wear of the rotation spraying head even if the coating including a pigment with high hardness is used. <P>SOLUTION: In the washing process which washes the residual coating in a coating pathway by alternately supplying washing air and washing solution in this order or opposite order to the coating pathway through which the coating is supplied to the rotation spraying head, the supply time for supplying the washing solution to the coating pathway at first (B pattern) is lengthened more than that of the standard (A pattern) or the pressure of the washing air supplied to the coating pathway at first is reduced more (C pattern) than that of the standard when the hardness of the pigment included in the coating to be washed is high. The wear of the center cone is controlled by reducing the amount of the remaining coating at the coating pathway in the case of B pattern, and by reducing the speed of the coating at which the washing air impinges to the center cone in the case of C pattern. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of cleaning a rotary atomizing electrostatic coating machine that rotates a rotary atomizing head at high speed to atomize a paint.

  2. Description of the Related Art In an automobile body painting line, it is common to perform so-called multicolor coating by switching paints supplied to a single rotary atomizing electrostatic coating machine (hereinafter simply referred to as a coating machine). In this case, the paint is switched (color change) to the paint machine automatically by the valve operation of the color change valve device connected to the paint machine, but the color of the previous color remaining in the paint path in the paint machine is changed at each color change. Since the paint needs to be washed, the color change valve device is also provided with a valve for supplying washing air and liquid (thinner).

Conventionally, when changing colors as described above, it is necessary to completely remove the previous color from the paint path in the coating machine, so a cleaning pattern in which cleaning air and cleaning liquid are alternately supplied to the coating machine is used multiple times. Is done. In this case, a cleaning pattern is generally adopted in which the supply of high-pressure cleaning air is preceded and the supply of the cleaning liquid is continued (see, for example, Patent Document 1), but in some cases, the supply of the cleaning liquid is preceded. In addition, a cleaning pattern in which the supply of cleaning air is continued is also employed (see, for example, Patent Document 2).
JP-A-8-155349 JP-A-10-216567

  By the way, the paint supplied from the color change valve device to the coating machine is discharged to the inner bottom of the rotary atomizing head through a paint feed tube inserted into the hollow rotary shaft of a motor (usually an air motor) that rotates the rotary atomizing head. It has become so. A paint chamber is defined by a flat hub at the inner bottom of the bell-shaped rotary atomizing head, and the paint discharged from the paint feed tube is applied to a center cone formed in the center of the back of the hub. It collides and diffuses in the paint chamber to the periphery, passes through the paint discharge hole provided around the hub, and is supplied to the inner surface of the cup of the rotary atomizing head.

  On the other hand, recently, the painting using a paint containing a bright pigment is increasing in the painting of automobile bodies. As a brilliant pigment, mica (pearl mica) has been conventionally known, but recently, artificial mica has been mainly used in place of natural mica (natural mica). However, with the increase in the use of this artificial mica, the progress of wear of the rotary atomizing head (mainly the center cone) has been accelerated. When the center cone is worn, the cleaning liquid (aqueous) rebounds so much that the rotary atomizing head is not sufficiently cleaned. In some cases, the cleaning liquid leaks to the ground side (robot side) through the air passage in the coating machine. Then, troubles such as subsequent electrostatic coating became impossible, and countermeasures were desired. As a result of intensive studies by the present inventors, the Mohs hardness of the artificial mica is about 8.5 to 9.0, which is extremely higher than the Mohs hardness of 2.5 of the natural mica. It came to the conclusion that it is.

  That is, when the coating machine is first cleaned with a general cleaning pattern that supplies high-pressure cleaning air to the paint path, the paint containing the hard mica (pre-color) has a high speed (10 m / sec or more). Collides with the center cone of the rotary atomizing head. On the other hand, the rotary atomizing head is generally made of an aluminum-based material, and its Mohs hardness is about 2.7. Thus, a high-hardness artificial mica is added to the rotary atomizing head of low hardness. It is presumed that the progress of wear of the center cone was accelerated as a result of the collision of the contained paint at a high speed. Further, when the cleaning pattern for supplying the cleaning liquid to the paint path first is employed, the collision speed of the paint against the center cone of the rotary atomizing head becomes small, so that it is considered that the wear of the center cone can be suppressed to some extent. However, in this case, since a large amount of paint remains in the paint path only by supplying the first cleaning liquid, the remaining paint collides with the center cone at a high speed as described above by supplying the next high-pressure cleaning air. Is insufficient.

  The present invention has been made in view of the technical background described above, and the problem is to effectively suppress the wear of the rotary atomizing head even when using a paint containing a pigment having a high hardness. It is providing the washing | cleaning method of the rotary atomization electrostatic coating machine which can do.

  In order to solve the above problem, the present invention supplies cleaning air and cleaning liquid alternately in this order or in the reverse order to a paint path for supplying paint to the rotary atomizing head, and remains in the paint path. In the cleaning method of the rotary atomizing coating machine for cleaning the paint to be cleaned, the supply condition of the cleaning air or cleaning liquid supplied to the paint path first is changed according to the type of the paint to be cleaned.

In the cleaning method of the rotary atomizing coating machine performed in this way, the optimal supply condition of the cleaning air or the cleaning liquid supplied to the coating path first is set in advance according to the type of the coating to be cleaned. It is possible to perform the cleaning under the optimum conditions according to the type, and it is possible to suppress the wear of the rotary atomizing head.
In the following, some aspects of the present invention will be illustrated and described in terms of items.

  (1) Rotating atomization in which cleaning air and cleaning liquid are alternately supplied in this order or in reverse order to a paint path for supplying paint to the rotary atomizing head to wash the paint remaining in the paint path. In the cleaning method of the coating machine, when the hardness of the pigment contained in the paint to be cleaned is equal to or higher than a predetermined value, the supply condition of the cleaning air or the cleaning liquid to be supplied to the paint path first is suppressed to prevent wear of the rotary atomizing head. A cleaning method for a rotary atomizing electrostatic coating machine, characterized in that the condition is changed to a condition capable of performing

  In the cleaning method of the rotary atomizing coating machine described in the item (1), the optimum supply condition of the cleaning air or the cleaning liquid supplied to the paint path first is previously determined according to the hardness of the pigment contained in the paint to be cleaned. By setting this, it is possible to perform cleaning under optimum conditions corresponding to the hardness of the pigment contained in the paint, and it is possible to suppress the wear of the rotary atomizing head.

  (2) In the item (1), when the Mohs hardness of the pigment contained in the paint to be cleaned is 2.7 or more, the supply condition of the cleaning air or the cleaning liquid supplied to the paint path is changed first. The cleaning method of the rotary atomizing electrostatic coating machine as described.

  The rotary atomizing head is generally often made of an aluminum material, but the Mohs hardness of the aluminum material is about 2.7. Therefore, when the Mohs hardness of the pigment contained in the paint is 2.7 or more as described in the item (2), the supply condition of the cleaning air or the cleaning liquid to the paint path is changed, so that the rotary atomizing head made of aluminum is changed. It becomes possible to suppress the wear of.

  (3) When the Mohs hardness of the pigment contained in the paint to be cleaned is 2.7 or higher, the cleaning air first supplied to the paint path so that the flow velocity of the fluid flowing through the paint path is 10 m / sec or less. The method for cleaning a rotary atomizing electrostatic coating machine according to the item (2), wherein the pressure is set.

  When cleaning the coating machine with a general cleaning pattern that supplies high-pressure cleaning air to the paint path first, the pressure of the cleaning air supplied to the paint path first is the standard pressure as described in (3). By making it lower, the speed of the paint which is pushed out by the cleaning air and collides with the hub (center cone) of the rotary atomizing head is lowered. In this case, even if the Mohs hardness of the pigment contained in the paint is 2.7 or more, the pressure of the cleaning air supplied to the paint path is first set so that the fluid flow rate is 10 m / sec or less. It becomes possible to suppress the wear of the atomizing head.

  (4) When the Mohs hardness of the pigment contained in the paint to be cleaned is 2.7 or higher, the paint path is first supplied to the paint path so that the degree of contamination of the paint path after the initial cleaning is 50% or higher. The cleaning method for the rotary atomizing electrostatic coating machine according to the item (2), wherein a supply time and / or a supply flow rate of the cleaning liquid is set.

  When the coating machine is first cleaned with a cleaning pattern in which the cleaning liquid is supplied to the paint path, the supply time of the cleaning liquid first supplied to the paint path is set longer than the standard supply time or the cleaning liquid as described in (4). By increasing the supply flow rate from the standard, the amount of paint pushed out by the cleaning liquid increases, and the amount of paint remaining in the paint path decreases. As a result, the hub of the rotary atomizer head ( The amount of paint that collides with the center cone is also reduced. In this case, the Mohs hardness of the pigment contained in the paint is 2.7 or more by setting the supply time and / or the supply flow rate of the cleaning liquid so that the degree of contamination of the paint path after the initial cleaning is 50% or more. Even in this case, it becomes possible to suppress the wear of the rotary atomizing head.

  According to the cleaning method of the rotary atomizing electrostatic coating machine according to the present invention, the wear of the rotary atomizing head can be effectively suppressed even when a paint containing a pigment with high hardness is used. There is an effect that greatly contributes to improvement of durability and reliability.

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

  FIG. 1 shows the structure of a main part of a rotary atomizing electrostatic coating machine which is an object of the cleaning method according to the present invention. A rotary atomizing electrostatic coating machine 1 (hereinafter simply referred to as a coating machine 1) includes a bell-shaped rotary atomizing head 2 made of aluminum alloy, an air motor 3 that rotationally drives the rotary atomizing head 2, and a rotary atomization. A paint feed tube 4 for supplying paint to the head 2 and a high voltage generator (not shown) for generating a high voltage to be applied to the air motor 3 are provided. The air motor 3, the paint feed tube 4 and the high voltage generator are provided. Are collectively stored in an insulating coating machine main body 5 having a mounting portion for the coating robot at the rear end. The coating machine 1 also includes a ring member 6 having a plurality of air discharge ports 6a for discharging shaping air from behind the rotary atomizing head 2 toward the periphery thereof. 5 is connected to the front end.

  The rotating shaft 7 of the air motor 3 has a hollow structure, and one end thereof is drawn forward from the motor casing 8. A screw portion is formed at one end portion of the hollow rotating shaft 7, and the rotary atomizing head 2 is screwed to one end portion of the rotating shaft 7 using this screw portion. The motor casing 8 is made of metal, and is supplied with an electrostatic high voltage (as an example, -90 kV) from the high voltage generator via an internal cable. On the other hand, the shaping air discharge ring member 6 is made of metal here and is disposed in contact with the motor casing 8. Thereby, an electrostatic high voltage is also applied to the ring member 6 via the motor casing 8, and thus the ring member 6 is an electrostatic high voltage portion in the coating machine 1. The type of motor that rotates the rotary atomizing head 2 is arbitrary, and a hydraulic motor, an electric motor, or the like can be used instead of the air motor 3 described above.

  The coating material feed tube 4 is extended through the hollow rotary shaft 7 of the air motor 3, and its tip is inserted into the inner bottom of the rotary atomizing head 2. The paint feed tube 4 is supplied with a paint having a predetermined paint color from a color change valve device 20 described later via a hose and a paint passage in the main body 5 (here, they are integrated and shown as a connection passage 9). The paint is supplied from the paint feed tube 4 to the rotary atomizing head 2.

  A paint chamber 11 is defined by a disc-shaped hub 10 at the inner bottom of the rotary atomizing head 2, and the tip of the paint feed tube 4 is introduced into the paint chamber 11 partitioned by the hub 10. ing. The hub 10 is provided with a center cone 12 at the center of the back surface thereof, and is provided with a large number of paint discharge holes 13 that are equally distributed in the circumferential direction at a portion connected to the inner surface of the rotary atomizing head 2. The paint supplied from the paint feed tube 4 to the rotary atomizing head 2 collides with the center cone 12 on the back surface of the hub 10, diffuses in the paint chamber 11 to the periphery, passes through the paint discharge hole 13, and rotates. It is supplied to the cup inner surface on the front side of the chemical head 2.

  The color change valve device 20 includes a plurality of (here, six) paint valves 21 that supply each coating color (here, six colors), a liquid valve 22 that supplies a cleaning liquid (thinner), and a cleaning air (compressed air). ) Is provided. A paint source corresponding to the paint color is connected to each paint valve 21, a cleaning liquid source is connected to the liquid valve 22, and an air source is connected to the air valve 23. The valves 21, 22, and 23 in the color change valve device 20 are controlled to be opened and closed by a control device (not shown), and at the time of painting, the paint valve 21 having a predetermined paint color is selectively selected by the control device. And the paint of a predetermined paint color is supplied to the rotary atomizing head 2. At the time of cleaning, the liquid valve 22 and the air valve 23 are alternately opened by the control device, and the cleaning liquid and the cleaning air are alternately supplied to the rotary atomizing head 2.

  When electrostatic coating is performed using the coating machine 1, the rotary atomizing head 2 is rotated at high speed by the air motor 3 while applying the electrostatic high voltage generated by the high voltage generator to the motor casing 8 of the air motor 3. At the same time, shaping air is discharged from the ring member 6, and a coating material of a predetermined color is supplied from the color change valve device 20 to the rotary atomizing head 2. Then, the paint collides with the center cone 12 on the back surface of the hub 10, diffuses in the paint chamber 11 to the periphery, passes through the paint discharge hole 13, and is supplied to the cup inner surface on the front side of the rotary atomizing head 2. . Since the centrifugal force is acting on the paint supplied to the inner surface of the cup due to the high speed rotation of the rotary atomizing head 2, the paint is directed toward the tip (paint discharge end) of the rotary atomizing head 2 along the cup inner surface. And is discharged in a mist form from the tip. At this time, since the ring member 6 as an electrostatic high voltage portion is disposed around the rotary atomizing head 2, the paint atomized by the rotary atomizing head 2 is negatively charged, and the ring member 6 It flies toward the object by the discharged shaping air, and adheres to the object set on the anode by electrostatic force.

  At the time of color change, the paint of the previous color remaining in a series of paint paths from the color change valve device 20 through the connection passage 9 and the feed tube 4 to the rotary atomizing head 9 is washed. This cleaning is performed with a cleaning pattern in which the liquid valve 22 and the air valve 23 in the color change valve device 20 are operated to alternately supply the cleaning liquid and the cleaning air to the paint path. In this embodiment, when the Mohs hardness is lower than 2.7 according to the hardness of the pigment contained in the paint, the pattern A shown in FIG. 2 is selected for cleaning, and the Mohs hardness is 2.7. In the above case, the cleaning is performed by selecting the B pattern or the C pattern shown in FIG. Examples of the pigment having a Mohs hardness of 2.7 or more include artificial mica (Mohs hardness 8.5 to 9.0).

  More details. The A pattern is a standard pattern that is generally used in the past, and the cycle of supplying cleaning air first and continuing to supply the cleaning solution is repeated a plurality of times (here, three times) every predetermined time T1. Finally, cleaning air is supplied for a relatively long time T2. In the B pattern, the cleaning liquid is first supplied for a relatively long time T2, and then the supply of the cleaning air and the supply of the cleaning liquid are repeated a plurality of times (here, twice) every predetermined time T1, and finally the cleaning is performed. Air is supplied for a relatively long time T2. Furthermore, in the C pattern, low-pressure cleaning air is first supplied for a predetermined time T1, and then the supply of the cleaning liquid and the supply of cleaning air are repeated a plurality of times (here, three times) every predetermined time T1, and finally The cleaning air is supplied to T2 for a relatively long time. However, in the present embodiment, the total time T required for cleaning is constant regardless of the patterns A to C. Here, the high-pressure cleaning air used in the C pattern is the same as the cleaning air used in the A or B pattern, and has a value of about 0.4 to 0.6 MPa as an example. On the other hand, the low-pressure cleaning air used in the C pattern is, for example, about 0.005 to 0.01 MPa. In the illustrated example, the supply times T1 and T2 are the same regardless of the A to C patterns for the sake of convenience. However, these may be changed between the A to C patterns.

  When cleaning with the standard A pattern, the high pressure cleaning air is first supplied to the paint path to remove most of the paint remaining in the paint path, and then the cleaning liquid is supplied and the cleaning air is supplied. By repeating this supply, the paint of the previous color is completely washed away from the paint path. Further, by finally supplying the cleaning air for a relatively long time (T2), moisture is completely removed from the inside of the paint path, and the paint of the next color is not diluted with the cleaning liquid.

  When cleaning is performed using the B pattern, the amount of paint extruded by the cleaning liquid is increased by increasing the supply time of the cleaning liquid supplied to the paint path first (T2) longer than the standard supply time (T1). The amount of paint remaining on the surface is reduced. As a result, the amount of paint that collides with the center cone 12 (FIG. 1) of the rotary atomizing head 2 is reduced by the supply of the next cleaning air, and the wear of the center cone 12 is suppressed accordingly. In this case, it is desirable to set the supply time of the cleaning liquid so that the degree of contamination of the paint path after the initial cleaning is 50% or more. When the Mohs hardness of the pigment contained in the paint is 2.7 or more However, it is possible to reliably suppress the wear of the rotary atomizing head. As a deformation pattern of the B pattern, the supply flow rate of the cleaning liquid supplied to the paint path first may be set so that the degree of contamination of the paint path after the initial cleaning is 50% or more. Also, the same effect as the B pattern can be obtained.

  When cleaning is performed using the C pattern, the speed of the paint that is pushed out by the cleaning air and collides with the hub 12 of the rotary atomizing head 1 by first lowering the pressure of the cleaning air supplied to the paint path from the standard pressure. As a result, wear of the center cone 12 is suppressed. In this case, even if the Mohs hardness of the pigment contained in the paint is 2.7 or more, the pressure of the cleaning air supplied to the paint path is first set so that the fluid flow rate is 10 m / sec or less. It becomes possible to suppress the wear of the atomizing head.

   After applying electrostatic coating using # 209 paint containing artificial mica using the coating machine 1 shown in FIG. 1, the flow rate and supply time (on time) of the cleaning liquid (thinner) supplied to the paint path first As shown in Table 1, initial cleaning was performed in various ways. After this initial cleaning, fresh thinner is again supplied to the paint path to collect the spray liquid from the rotary atomizing head 2 and measure the turbidity with a turbidimeter, and the center cone of the rotary atomizing head 2 The degree of wear was judged by visually observing 12 wear situations. In Table 1, the measurement result by the turbidimeter and the determination result of the wear state are shown together.

  Test No. shown in Table 1 From the comparison of 3, 4, 5, and 6, it is clear that when the cleaning liquid supply flow rate is set to the standard (900 ml), the turbidity increases as the cleaning liquid supply time becomes longer than the standard (0.7 sec). It is. In addition, test No. From the comparison between 4 and 7, when the supply time of the cleaning liquid is the same (1.0 sec), the turbidity increases as the supply flow rate of the cleaning liquid is increased (900 → 1200 ml / min). Furthermore, test no. From the comparison between 1 and 6, when the supply time of the cleaning liquid is the same (1.6 sec), the turbidity decreases as the supply flow rate of the cleaning liquid decreases (900 → 800 ml / min).

  On the other hand, when the turbidity and the wear state of the center cone 12 are compared, a branch point of evaluation is recognized around 50% of the turbidity, and in order to suppress the wear of the center cone 12 as much as possible, the degree of contamination of the paint path after the initial cleaning. It can be seen that it is desirable to set the supply time and / or supply flow rate of the cleaning liquid supplied to the paint path first so that the turbidity becomes 50% or more.

It is sectional drawing which shows the principal part structure of the rotary atomization electrostatic coating machine which is the implementation object of the cleaning method which concerns on this invention. It is a time chart which shows typically the washing pattern adopted by the present invention.

Explanation of symbols

1 Rotating Atomizing Electrostatic Coating Machine 2 Rotating Atomizing Head 3 Air Motor 4 Paint Feed Tube (Paint Path)
6 Shaping air discharge ring member 9 Connection passage (paint path)
10 Hub 12 Center cone 20 Paint switching valve device 22 Liquid valve for cleaning liquid 23 Air valve for cleaning air

Claims (4)

  Rotating atomizing electrostatic coating for cleaning paint remaining in the paint path by alternately supplying cleaning air and cleaning liquid in this order or in reverse order to the paint path for supplying paint to the rotary atomizing head In the cleaning method of the machine, when the hardness of the pigment contained in the paint to be cleaned is equal to or higher than a predetermined value, the supply condition of the cleaning air or the cleaning liquid to be supplied to the paint path first is set to suppress wear of the rotary atomizing head. A cleaning method for a rotary atomizing electrostatic coating machine, characterized in that it is changed to a condition that can be performed.   The rotating mist according to claim 1, wherein when the Mohs hardness of the pigment contained in the paint to be cleaned is 2.7 or more, the supply condition of the cleaning air or the cleaning liquid supplied to the paint path is changed first. Cleaning method of the electrostatic coating machine.   When the Mohs hardness of the pigment contained in the paint to be cleaned is 2.7 or higher, the pressure of the cleaning air first supplied to the paint path is set so that the flow velocity of fluid flowing through the paint path is 10 m / sec or less. The cleaning method for a rotary atomizing electrostatic coating machine according to claim 2, wherein the cleaning method is set.   Supply of the cleaning liquid first supplied to the paint path so that the degree of contamination of the paint path after the initial cleaning is 50% or more when the Mohs hardness of the pigment contained in the paint to be cleaned is 2.7 or more The cleaning method for a rotary atomizing electrostatic coating machine according to claim 2, wherein time and / or supply flow rate is set.

Images